Laser-Plasma Accelerators Workshop

13 Apr 2025, 16:00 → 19 Apr 2025, 13:00 Europe/Rome

Hotel Continental, Ischia Island (Naples, Italy)

Massimo Ferrario (Istituto Nazionale di Fisica Nucleare)

REMINDER: 23 March, deadline for meals confirmation and shuttle reservation.

The Laser-Plasma Accelerators Workshop 2025 (LPAW 2025) will be held at Hotel Continental Ischia, in the Ischia Island (Naples, Italy), from Monday 14 to Friday 18 April 2025.

The Laser-Plasma Accelerators Workshop (LPAW) series is one of the leading workshops in the field of plasma-based acceleration and radiation generation. It started in the 1990s, with the first edition held in Kardamili, Greece.

The latest editions were held in Algarve, Portugal (2023); Split, Croatia (2019); Jeju, Korea (2017); Guadeloupe, French Caribbean (2015); Goa, India (2013); and Wuzhen, China (2011). As is traditional in the LPAW series, the 2025 edition will be in a friendly and relaxed environment with plenty of time for discussions.

The following scientific topics will be the main focus of the conference:

• Electron Acceleration
• Ion Acceleration
• Secondary Radiation Sources 
• Applications
• Plasma Sources
• Theory and Simulations
• Diagnostics
• Machine Learning
• Laser Technology
• Facilities

 

John Dawson Thesis Prize

“John Dawson Thesis Prize” is awarded on a biannual basis to the best PhD thesis in the area of plasma accelerators driven by laser or particle beams. The prize will be awarded for fundamental (theoretical or experimental) or applied aspects.

Each prize winner will receive a certificate of merit and a stipend of 500€.

 

Arrivals are expected on Sunday April 13th.

Departures are expected on Saturday April 19th.

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Continental_reservation_form_LPAW - 2025.pdf

NEW Agenda LPAW25_3.pdf

Privacy Policy.pdf

Sunday, 13 April

16:00 Arrivals and Registration

19:30 Welcome Cocktail

Monday, 14 April

1 Opening remarks

Plenary Session: Electron Acceleration

2 Matched Guiding and Controlled Injection in Dark-Current-Free, 10-GeV-Class, Channel-Guided Laser Plasma Accelerators

A pre-formed plasma channel can be used to maintain laser pulse intensity over the full dephasing/pump depletion length of a laser plasma accelerator and maximize electron beam energy for a given drive laser. In this talk we present recent results[1] that show high quality guiding of ~0.5PW (20J) laser pulses in a 30cm-long, hydrodynamic optical-field-ionized (HOFI) plasma channel. By varying the length of the plasma channel, we observed the transport of higher-order modes, quasimatched propagation, and the dark-current-free transfer of laser energy to the wake. By introducing a localized region of nitrogen dopant, electron beams were generated with energy up to ~10GeV.

[1] Picksley et al., Phys. Rev. Lett., 133, 255001 (2024).

Speaker: Josh Stackhouse (Lawrence Berkeley National Laboratory)

3 ELI NP status and challenges for the LPAW community

The dual 10 PW lasers at ELI NP, surrounded by well-equipped experimental areas, provide the user community with privileged access to a versatile laser system capable of delivering up to 250 J of energy over 25 fs or longer pulse durations. This enables target intensities of approximately 10²³ W/cm², with a repetition rate of one shot per minute. This unique European facility has been designed to support groundbreaking discoveries in nuclear physics, high-field physics, and plasma science, as well as applications in medicine, biology, and security.
I will briefly present the current status of ELI NP, detailing its transition from the commissioning of the laser and experimental areas to its opening to the user community. I will highlight the recent breakthroughs it has enabled, with particular emphasis on its contributions to the laser wakefield community. This will be followed by a discussion of the scientific direction for the next two years, focusing on new opportunities in particle acceleration and the exploration of strong-field quantum electrodynamics (SF QED).

Speaker: Prof. Victor Malka (Weizmann Institute of Science and ELI-NP (Extreme Light Infrastructure- Nuclear Physics))

4 High charge laser acceleration of electrons to 10 GeV

Recent demonstrations of all-optical multi-GeV laser wakefield acceleration (LWFA) have been enabled by the development of low-density meter-scale plasma waveguides produced above supersonic gas jets. This talk reviews recent advances at the University of Maryland which have enabled these results, focusing on the development of elongated supersonic gas jets, experimental and simulation studies of plasma waveguide formation, and a new three-stage model for relativistic pulse propagation dynamics in these waveguides. We will then present the culmination of these efforts, focusing on results from recent LWFA experiments demonstrating high charge, low divergence electron bunches to ~10 GeV, with laser-to-electron beam efficiency of at least ~30%. Finally, we will discuss recent demonstrations for further improving this accelerator, including longitudinally tailored plasma waveguides for optimizing laser coupling efficiency and electron acceleration.

This work was supported by the U.S. DOE (DE-SC0015516, LaserNetUS DE-SC0019076/ FWP#SCW1668, and DE-SC0011375), and the Defense Advanced Research Projects Agency (DARPA) under the Muons for Science and Security Program. E. Rockafellow is supported by NSF GRFP (Grant No. DGE 1840340).

Speaker: Ela Rockafellow (University of Maryland)

10:40 Coffee Break

Plenary Session: Ion Acceleration

5 Ion acceleration with gaussian and vortex laser beam

Developing compact ‘all-optical’ ion accelerators using high-power lasers has attracted significant interest due to their broad applicative potential in science, industry, and healthcare. Most research on ion acceleration has focused on the Target Normal Sheath Acceleration (TNSA) and the Radiation Pressure Acceleration (RPA) mechanisms using the typical Gaussian laser beam TEM00. Although the Gaussian beam provides the highest peak intensity, its intensity profile generates a ponderomotive force that pushes charged particles outwards, increasing the ion beam divergence, thus reducing the density. Laguerre-Gaussian (LG) laser beams are an interesting alternative to the Gaussian beam. Such beams exhibit a doughnut-intensity shape that has a component of the ponderomotive force pushing inwards, along with a helical phase that generates an orbital angular momentum (OAM). The properties of the LG beams have been theoretically investigated for decades, but experiments with such laser beams have been happening only recently as creating vortex beams, especially with high topological OAM orders, is challenging. A novel method for generating a high-order LG pulse with a PW-class laser beam and the latest experimental results on ion acceleration will be presented. Additionally, 3D PIC simulations will be compared with the experimental results.

Speaker: Dr Domenico DORIA (ELI-NP, HH-IFIN)

6 Efficient proton acceleration in the near critical density regime

Laser plasma-based particle accelerators attract great interest in fields where conventional accelerators reach limits based on size, cost or beam parameters. However, laser accelerators have not yet reached their full potential in producing high-radiation doses at high particle energies. The quest to fully leverage the available laser pulse energies is guided by first principles simulations predicting efficient ion acceleration mechanisms at near critical plasma densities. The most stringent limitation for accessing this regime is the lack of a system that provides a high degree of control of the plasma density conditions at high-repetition rates.
In this talk I will outline our approach for overcoming these challenges using a novel cryogenic hydrogen target in combination with petwawatt-class lasers. Controlled pre-expansion of the initially solid target by low intensity pre-pulses allows for tailored density scans from the overdense to the underdense regime transitioning between different acceleration mechanisms. Under ideal conditions, the near-critical density produces proton energies of 80 MeV representing a boost in maximum energy by a factor of more than two compared to the solid jet case. Furthermore, recent investigations provide the basis for transferring the high single-shot performance into a reproducible, robust and, above all, highly repetitive operation mode.

Speaker: Martin Rehwald (Helmholtz-Zentrum Dresden-Rossendorf)

7 Stable laser-acceleration of high-flux proton beams with plasma collimation

Laser-plasma acceleration has enormous potential to provide compact sources of ultra-short ion beams. Several factors, such as the low shot-to-shot stability, large beam divergence and the difficulty of high-repetition rate operation, hamper their wider adoption. Recent work demonstrates an approach for overcoming these challenges using a novel liquid sheet target, developed at the SLAC National Accelerator Laboratory. These experiments, at the GEMINI TA2 laser facility (10 TW, 5 Hz), demonstrated stable acceleration of few MeV proton beams via target normal sheath acceleration with beam exhibiting high flux and low-divergence in comparison to proton beams from typical thin foil targets [1]. Supporting PIC simulations indicate that the presence of the low-density background vapour which surrounded the target plays an important role in the observed collimation of the proton beam through the generation of azimuthal magnetic fields which act to focus the proton beam. The measured proton beams are already suitable for applications requiring high proton flux and the platform can be extended to kHz repetition rates or higher laser energies extending the utility of the source to a wide range of applications.
[1] Streeter et al., Nat. Comms 16, 1004 (2025)

Speaker: Charlotte Palmer (Queen's University Belfast)

12:40 Lunch Break

Parallel Session: Electron Acceleration

8 Experimental and Simulation Study on Direct Acceleration of Electron Beams Driven by Vortex Lasers

Recent developments in relativistic Laguerre–Gaussian (LG) lasers have sparked physical research into petawatt (PW) laser facilities. It has been observed that LG lasers not only produce hollow laser intensity but also generate novel structured electric fields for different LG modes. In the case of left circularly polarized LG lasers, the longitudinal electric field, combined with the hollow intensity around the axis, enables stable direct acceleration of electrons. Compared to traditional Gaussian lasers, this configuration allows for stable concentration of electrons at the center, resulting in the generation of high-flux beams. Recently, the longitudinal vortex laser (LG) has been further extended to the transverse vortex laser (STOV), introducing time dimension modulation for the electron beam. This advancement has achieved isolated attosecond electron acceleration and corresponding attosecond γ-ray generation. This report discusses the recent development of PW vortex lasers at the SULF laser facility, along with considerations for electron acceleration driven by LG and STOV lasers and their applications in γ-ray generation.

Speaker: Mr Wenpeng Wang (Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences)

9 Progress in electron acceleration at CALA

This contribution will present recent progress and limitations of the electron acceleration program at CALA. We are working on several programmatic goals:
1. providing monoenergetic multi-GeV beams for our planned Breit-Wheeler experiment.
2. expanding the hybrid LWFA-PWFA scheme towards ultra-low emittance and high transformer ratios, while characterizing the hybrid LWFA-PWFA plasma wave morphology in dependence of electron beam parameters.
3. work towards the realization of the Plasma-Modulated Plasma Acceleration (P-MoPA) scheme towards kHz electron acceleration.
As all the performance of all these projects is currently limited by shot-to-shot fluctuations, I will not only give an overview of the insights from and the status of these projects, but also discuss recent finding on the origin of these fluctuations in a PW laser system.

Speaker: Prof. Stefan Karsch (LMU München)

10 Laser Wavefront-based Classification of successful Injection in LWFA

We present an in-depth analysis of Laser Wakefield Acceleration (LWFA) experiments performed at the ATLAS-3000 system at CALA in Garching, achieving GeV-scale electron energies with a slit-nozzle target. Through simultaneous monitoring of laser and electron diagnostics for about 2000 shots performed at a 0.25 Hz repetition rate, we identify the laser wavefront as the primary factor influencing electron energy. Notably, fluctuations in the defocus and astigmatism coefficients exhibit strong correlation with electron energy variations, closely mirroring their dynamics that fluctuates on a timescale of minutes. This correlation enables classification of successful injection into the first plasma bubble based solely on wavefront properties, underscoring the predictive value of wavefront diagnostics for LWFA performance.
Additionally, we investigate the origin of defocus fluctuations by comparing them to temperature variations within the main amplifier crystal and other possible sources. By enhancing cooling systems and reducing crystal temperature, we could demonstrate first improvements in wavefront stability.

Speaker: Johannes Zirkelbach

11 Progress towards high-repetition-rate GeV-scale plasma-modulated plasma accelerators

We describe recent results from our programme to develop high-repetition-rate, GeV-scale plasma-modulated plasma accelerators (P-MoPAs), which seeks to take advantage of advanced thin-disk lasers (TDLs) that can deliver joule-scale, picosecond-duration pulses, at kHz repetition rates.

A P-MoPA has three stages: (i) a modulator, in which a TDL pulse is guided in a hydrodynamic optical-field-ionized (HOFI) plasma channel and is spectrally modulated by the wake driven by a short, low-energy pulse; (ii) a compressor, which converts the spectrally-modulated drive pulse to a train of short pulses; and (iii) a resonantly-driven accelerator stage.

We present simulations that establish the operating regime of P-MoPAs and demonstrate acceleration to $\sim 2.5\,\mathrm{GeV}$ with a 5 J drive pulse. This analysis shows that a P-MoPA can drive larger amplitude wakefields than a plasma beat-wave accelerator with the same total laser energy.

We also present the results of experiments that demonstrate resonant wakefield excitation by a train of $\sim 10$ pulses, of total energy $\sim 1\,\mathrm{J}$, in a 110 mm long HOFI channel. Measurements of the spectral shift of the pulse train suggest a wake amplitude in the range $3 – 10\,\mathrm{GV\,m}^{-1}$, corresponding to an accelerator stage energy gain of order $1\,\mathrm{GeV}$.

Speaker: Simon Hooker (University of Oxford)

12 Increasing the energy of high-quality electron bunches from a hybrid L-PWFA

Hybrid laser and electron beam-driven plasma accelerators (L-PWFA) have been a growing focus in recent years, combining the strengths of laser wakefield acceleration (LWFA) and particle beam-driven plasma wakefield acceleration (PWFA). In this approach, an LWFA stage generates a high-current electron bunch, which drives a subsequent PWFA stage where a witness bunch is internally injected and accelerated. This hybrid design leverages the accessibility of LWFA with the stability and beam quality achievable in PWFA.
Our earlier experiments demonstrated witness beams with reduced energy spread and divergence, leading to higher spatial and spectral particle densities—crucial for producing brilliant X-rays and enabling advanced applications. However, energy gain in these witness beams was previously limited, resulting in a transformer ratio below unity.
In this contribution, I will present our latest experimental results, where the witness beam energy equals the average driver energy through optimized plasma density profiles in the PWFA stage. Additionally, ongoing efforts to tailor the drive beam current profile aim to achieve much higher transformer ratios in upcoming campaigns, further enhancing the potential of L-PWFA for future applications.

Speaker: Moritz Foerster (LMU Munich)

Parallel Session: Ion Acceleration

13 20-dimension Bayesian Optimization of maximum proton energy in the Target Normal Sheath Acceleration regime using dynamic wavefront shaping on a short focal length off-axis parabola system

To optimize proton maximum energy, we adjusted the deformable mirror’s actuators, which directly influence the laser spot size and shape (measured by a wavefront analyzer). Starting with all voltages set to 0V, we aimed to find the optimal configuration to maximize proton energy. Utilizing the ALLS 150 TW laser’s high-repetition rate and a multi-target holder, we collected a dataset of approximately 200 samples. Bayesian Optimization (BO) was then employed to guide the process by creating a surrogate model of the objective function, enabling efficient parameter space exploration.

By controlling 20 out of 48 actuators, we identified configurations that significantly improved proton energy while minimizing experimental iterations (200 data points). This adaptive approach integrates data-driven optimization with precise wavefront control, achieving enhanced ion acceleration. Our method challenges the notion that Gaussian beams are optimal for Target Normal Sheath Acceleration and provides a robust strategy for facilities lacking terawatt/petawatt attenuators to visualize the full-power laser spot. This demonstrates the potential of combining advanced optical control with optimization algorithms to enhance high-intensity laser-driven ion acceleration systems.

Speaker: Elias Catrix (Institut national de la recherche scientifique)

14 Ultra-efficient proton acceleration from planar cryogenic hydrogen jets at 1 Hz repetition rate

Laser plasma-based ion accelerators have not yet reached their full potential in producing high radiation doses at high particle energies, mainly due to the lack of a suitable high-repetition-rate targets that also provide adequate control of the plasma conditions. Cryogenic, solid gas jet targets are being developed to fill this gap, as they combine many favourable properties for studying advanced laser ion acceleration regimes, such as low solid density, single ion species composition and ease of probing in experiments, with repetition-rated operation capability by being self-replenishing and completely debris-free.
In this talk, we present first results from an ongoing experiment using planar, sheet-like cryogenic hydrogen jet targets to accelerate proton bunches at 1 Hz repetition rate. Using the Draco PW laser at intrinsic contrast and significantly reduced laser energy, we report stable, continuous acceleration of ion beams over thousands of consecutive shots. Despite the low laser energy of only 1.6 J, maximum proton energies of up to 40 MeV are observed, indicating an extremely high acceleration efficiency. This combination of tens of MeV proton energies with very modest laser parameters marks a significant step forward towards developing laser driven ion sources for scientific and industrial applications.

Speaker: Stefan Assenbaum (Helmholtz-Zentrum Dresden-Rossendorf)

15 The contribution of collisional ionization to energetic highly charged Au ions by high-intensity high-contrast laser pulses in a relativistic transparency regime

The acceleration of heavy ions with mass number of ~200-class by high intensity femtosecond laser pulse is still challenging because of the too small knowledge of the ionization mechanisms which strongly couple to the dynamics of the plasma and determine the acceleration efficiency especially at the relativistically induced transparency (RIT) phase where efficient acceleration takes place. The issue arises from the fact that the information of dominant ionization mechanism in the plasma is always clarified by state-of-the-art PIC simulations which are backed up by a limited set of experimental investigations.
Aiming at improving the situation, we carried out both simultaneous measurements of accelerated ions, transmitted laser energy, and plasma parameters by X-ray spectroscopy, by scanning the gold target thickness to cover a wide range of plasma densities which includes the transition phase to RIT and demonstrated over 10 MeV/u gold ions with ~70+ charge at the RIT phase. State-of-the-art simulations, which make use of the measured temporal pulse conditions and are backed up by a large set of diagnostics, demonstrate that the collisional ionization process cannot be neglected for the generation of high-energy highly charged gold ions through a large range of plasma parameters even within the RIT phase.

Speaker: Mamiko Nishiuchi (National Institutes for Quantum Science and Technology(QST))

16 Experimental and computational evaluation of Alpha particle production from Laser-driven proton-boron nuclear reaction in hole-boring scheme

Most of the previous studies [1,2,3] on laser-driven proton-boron nuclear reactions are based on the measurement of α-particles with Solid-State Nuclear Track Detectors (CR-39). However, the interpretation of CR-39 results is difficult due to the presence of several other accelerated particles, which can bias the analysis [4]. Furthermore, in some laser irradiation geometries, cross-checking measurements are almost impossible. In this context, numerical simulations may play an important role in guiding the analysis of experimental results.

In this study, we analyze the data from the same experimental campaign, exploiting different laser irradiation schemes (pitcher-catcher and direct irradiation) but the same laser parameters. Different mechanisms are responsible for the acceleration of protons: TNSA in the case of the pitcher-catcher, and hole boring in the case of direct irradiation. Numerical simulations, validated in the pitcher-catcher geometry, have allowed us to obtain conclusive results on laser-driven proton-boron reactions also in the direct-irradiation geometry.

References
[1] D. Margarone, et al., Applied Sciences, 12, 1444 (2022)
[2] J. Bonvalet, et al., Physical Review E, 103, 053202 (2021)
[3] A. Picciotto, et al., Physical Review X, 4, 031030 (2014)
[4] F. Consoli, et al., Frontier in Physics, 8 (2020)

Speaker: Marine Huault (celia)

17 Diagnosing the onset of relativistically induced transparency in high-energy laser-driven proton acceleration experiments

Ion acceleration via compact laser-plasma sources holds great potential for applications from radiation therapy research to fusion research. Achieving the desired beam quality requires a deep understanding and precise control of laser-plasma interactions. Our collaborative research at the DRACO PW (HZDR) and J-KAREN-P (KPSI) laser systems investigates the promising regime of Relativistically Induced Transparency (RIT).
Previous studies [1] achieved high-performance proton beams (>60 MeV) in an expanded foil configuration, identifying an optimum at target transparency onset. Later experiments recorded proton energies over 100 MeV [2], emphasizing transparency onset timing in optimizing beam parameters. Using particle and laser diagnostics, we explore the correlation between transparency onset and acceleration performance.
This contribution details our recent investigations into spectral components of transmission and emission from laser-plasma interactions. Building on established methodologies [3], we apply spectral interferometry, using the unperturbed laser beam as a reference, and correlate findings with proton acceleration. Our results suggest a promising direction for analyzing spectral and spatial distribution, offering deeper insights into laser-plasma interactions and optimizing beam quality parameters.

[1] Dover, N.P. et al.: Light Sci. Appl. (2023).
[2] Ziegler, T. et al.: Nat. Phys. (2024).
[3] Williamson, S.D.R. et al.: Phys. Rev. Appl. (2020).

Speaker: Karl Zeil (Helmholtz-Zentrum Dresden-Rossendorf)

16:40 Coffee Break

Poster Session

18 Development of a Plasma Cell Target for Higher Repetition Rates in Laser-Plasma Accelerators

This poster presents the development of an advanced plasma target designed for laser-plasma injectors and accelerators. It specifically focuses on gas cell targets with spatial confinement of a nitrogen/helium mixture. This design ensures controlled localized ionization injection, leading to high-quality electron beam production.

We compare fluid dynamics simulations with experimental measurements to assess dopant confinement and electron density in the cell. The impact of these characterizations on beam properties is further explored through numerical optimization using the fast PIC simulations carried out with the SMILEI code using envelope approximation and azimuthal mode decomposition of the laser pulse.

Additionally, we will discuss the thermal loads associated with operating at high repetition rates, analyzing the increased power dissipation from the laser in the gas cell.

Speaker: Jana Serhal

19 “Preliminary Study of the X-ray Betatron Radiation Source in the EuAPS Project”

X-rays radiation produced by electrons oscillating in a plasma in the Laser WakeField Acceleration (LWFA) process is called betatron radiation.
When an ultra-short, high-intensity laser pulse interacts with a supersonic gas jet, it simultaneously ionizes the gas, creating a plasma, and injects and accelerates electrons into the plasma wave, leading to the emission of this radiation.

As part of the EuPRAXIA project, EuAPS (EuPRAXIA Advanced Photon Source) will be the first user dedicated betatron radiation source developed at INFN Frascati. This source has significant potential for applications in fields such as materials science, medical imaging and biological research.
The facility is designed to produce 1-10 keV photons using a compact laser-driven plasma accelerator operating at 1 Hz, in the self-injection regime under highly nonlinear laser-plasma interaction conditions.

This contribution presents the expected parameters of the radiation source and the results of several experimental campaigns conducted within the EuAPS project to characterize the acceleration process and the X-ray radiation source.

Speaker: Federica Stocchi (Istituto Nazionale di Fisica Nucleare)

20 Analytic solutions for plasma expansion into vacuum

We investigate a simple hydrodynamic plasma expansion model
which contains the coupled continuity, Euler and Poisson equations
with the reduction technique applying the self-similar and the traveling wave trial functions and present analytic results.

Speaker: Dr Imre Ferenc Barna (Wigner Research Center for Physics)

21 AWAKE: Towards high-energy electrons for particle physics experiments

The Advanced Wakefield Experiment, AWAKE, at CERN is an accelerator R&D experiment, which moved from a proof-of-concept experiment to a facility that develops the proton-driven plasma wakefield acceleration technology to be ready for proposing first particle physics applications in the 2030’s. The AWAKE program aims to accelerate electrons to energies of 10 to 100 GeV in a single plasma source, while controlling the beam quality and demonstrating the scalability of the process.
This talk gives a summary of the recent results of the self-modulator experiments for the long proton drive bunch and presents the program, experimental layout and challenges of the electron acceleration experiment where a 150 MeV, 100pC charge, 200fs long electron bunch is externally injected into a 10m -long accelerator plasma source. In addition the development of scalable discharge and helicon plasma sources to hundreds of meters length, necessary to reach high energies, is shown.

Speaker: Edda Gschwendtner

22 Beam-loaded plasma photocathode beams for XFEL application to the water-window and beyond

X-ray free-electron lasers currently rely on kilometre-scale linear accelerators to produce very high quality electron beams with GeV energies. Plasma-based accelerators are a highly compact alternative with a drastically higher accelerating gradient and smaller footprint. Here, we show in simulation how beams from a plasma wakefield accelerator (PWFA) could drive a robust and tunable compact soft XFEL using the plasma photocathode injection method. Operating in a beam-loaded regime, single low-energy injected bunches produce sub-millijoule energy radiation pulses in the water-window from 2.3-4.4 nm. Furthermore the FEL output is resilient to large drive-beam charge jitter and can be maintained over a large range of witness beam working points. Additionally, we investigate how such beams could be created at the possible future UK-XFEL facility using realistic drive beams from the linac, and how these beams may be used to reach very hard X-ray energies.

Speaker: Lily Berman (University of Strathclyde)

23 Compact High-Energy Electron Spectroscopy via Nuclear-Static-Field Deflection

The measurement of electron energy spectra can be understood as distinguishing high-energy and low-energy electrons by electromagnetic deflection at varying angles. When the deflection distance is constrained, the deflection force determines the upper energy limit of the measurement. Given that static magnetic fields in the macroscopic world are limited to ~10 T, magnets ~1 m in length are typically required to measure electron spectra above 10 GeV. However, utilizing the static electric fields near atomic nuclei could enable stronger deflection forces, facilitating high-energy electron spectrum measurements. In our experiment, a 0.86 mm Sn foil scattered electrons with a peak energy of ~2 GeV. By analyzing the angular distribution of scattered electrons via Molière theory and gradient descent optimization, we successfully reconstructed the electron energy spectrum. The results were cross-verified against magnetic spectrometer measurements, confirming the method’s validity. Extensive GEANT4 simulations further suggest this approach may extend to measuring electron spectra at 10 GeV or even 100 GeV scales. This work demonstrates a compact, high-efficiency alternative to conventional magnetic spectrometers for ultra-high-energy electron detection.

Speaker: Xiantao Cheng (Shanghai Jiaotong Unversity)

24 Electron acceleration by Laguerre-Gaussian beams from a high-density dual-staged plasma nozzle

Laser wakefield acceleration (LWFA) of electrons is predominantly achieved using gas targets. In recent years, the development of high-repetition-rate, high-intensity lasers has driven research into employing high-density gas targets to generate very high-energy electrons (VHEE) beams, which hold potential for medical applications. Laguerre-Gaussian (LG) laser beams differ from Gaussian beams by their azimuthal phase structure, imparting orbital angular momentum (OAM), and a donut-shaped intensity profile with a central minimum. These features, combined with advanced gas nozzle setups, enable new possibilities for optimising electron acceleration. This research explores the LWFA of electrons driven by LG beams in a dual-stage gas nozzle setup. The method offers precise control over the plasma density profile, facilitating improved electron injection and acceleration. To assess the effectiveness of this configuration, Fourier–Bessel Particle-In-Cell (FBPIC) simulations are performed using hydrogen and hydrogen-nitrogen (H₂ + 1% N₂) gas mixtures within the bubble regime over a 1 mm acceleration distance. Simulation results indicate that combining vortex beams, such as LG beams, with optimised dual-stage gas nozzles is an effective technique for producing VHEE beams and controlling energy spread.

Speaker: Dr Vidmantas Tomkus (FTMC-Center for Physical Science and Technology)

25 ELIMAIA User Beamline: Dedicated Platform for Applications Using Laser-Driven Ion Beams

Laser-driven ion sources are emerging as a compact and complementary alternative to conventional accelerators due to their unique features, including ultra-short bunch duration, ultrahigh dose rate, and low emittance. Over the past decade, research efforts have focused on optimizing key beam parameters (energy, flux, divergence, and shot-to-shot stability) to meet application demands.

The Extreme Light Infrastructure (ELI) ERIC is a pan-European research consortium dedicated to multidisciplinary applications of ultra-intense, ultra-short laser pulses. The ELI Beamlines Facility hosts various secondary particle and radiation sources, including an ion acceleration beamline, available to international users.

The ELIMAIA Beamline uses the L3-HAPLS laser system, achieving relativistic intensities up to $5\cdot10^{21}\,W/cm^2$. Commissioning experiments with solid foil targets have demonstrated proton fluxes above $10^{11}\,protons/shot/sr$ and cut-off energies exceeding $40\,MeV$. ELIMAIA supports research on ion acceleration mechanisms, high-repetition-rate targets, machine learning, nuclear reactions, and electromagnetic pulse studies.

The ELIMED Beamline, an end-station connected to ELIMAIA, provides controlled sample irradiation with a magnetic optics system for beam transport and energy selection. It is designed to deliver tailored ion beams for medical research (e.g. cancer therapy), radiobiology, radiation testing of electronics, material science, and cultural heritage studies, particularly in the ultra-high dose rate regime.

Speaker: M. Tryus (ELI Beamlines Facility, The Extreme Light Infrastructure ERIC)

26 Enabling energy-doubling at CLARA FEBE: High-quality beam generation in plasma wakefield acceleration

Plasma-wakefield acceleration (PWFA) has gained global attention for the achievable ultra-high accelerating gradients, which will drastically reduce the price, footprint, and carbon load of accelerators to be used for medical applications, free electron lasers (FEL), and future high-energy physics experiments. The Compact Linear Accelerator for Research and Applications (CLARA) at the Daresbury Laboratory is a state-of-the-art electron accelerator for a future FEL test facility, capable of producing 250-MeV electron bunches. Recently, a new beamline attached to CLARA, the Full Energy Beam Exploitation (FEBE) facility, has been designed to provide ultra-short and low-emittance electron bunches. Here, by employing the Fourier-Bessel particle-in-cell (FBPIC) code, we investigate PWFA with a two-bunch configuration at FEBE to double the energy of the externally injected witness bunch while maintaining incoming beam quality as much as possible. Simulation results indicate that the driver's trailing portion is tightly focused by the transverse wakefield, leading to a surging beam density and a transition from the linear to the non-linear regime. A flattened wakefield due to beam loading is achieved with appropriate tailoring of the witness bunch's longitudinal current profile. Tolerance analysis for bunch parameters is presented. Moreover, we explore the impacts of plasma-density profiles on beam quality.

Speaker: Hossein Saberi (University of Manchester)

27 Experiment Concepts of Heavy-Ion Driven Plasma Acceleration with Muon Beams at the HIAF

The muon beams decay quickly at low energy. Therefore, it is important to rapidly accelerate the muon beams to higher energy to ensure sufficient lifetime for beam manipulations or further acceleration. Plasma acceleration offers higher acceleration gradients compared to conventional RF cavities. It is the most promising acceleration method for muon research projects at the HIAF facility. The HIAF can provide multiple proton or heavy ion beams at the same time, which can be utilized to produce muon beams by hitting targets and drive the plasma oscillations to provide acceleration fields. Preliminary simulation studies indicate that employing heavy ion beams in the HIAF to drive plasma oscillations, or wakes, through self-modulation instabilities can accelerate the muon beams from 800 MeV to 1.95 GeV within a length of 0.6 m. Ongoing research on plasma acceleration of muon beams at the HIAF will focus on introducing the generation and cooling simulation results to refine the existing plasma acceleration scheme based on self-modulation instabilities, and finding a way to enhance the energy gain of the muon beams in this scheme. Additionally, new plasma acceleration mechanisms will be explored to efficiently utilize the energy carried by the high intensity heavy ion beams.

Speaker: Jie Liu (Institute of Modern Physics, Chinese Academy of Sciences)

28 Heavy-ion-driven plasma wakefield acceleration

This paper pioneers the first study on heavy-ion-driven plasma wakefield acceleration, highlighting potential of heavy ions (higher beam charge density, heavier particle mass and higher kinetic energy) to plasma-based acceleration techniques. Our investigation aims to identify an optimal regime for achieving high-amplitude wakefields excited by heavy ion beams. Among various drivers in HIAF, the Bismuth beam with an rms beam radius of 0.1 mm and an energy of 9.58 GeV/u in HIAF, due to its high beam charge intensity and energy, can rapidly develop self-modulation instability after 0.14 m, exciting a wakefield with a maximum amplitude of 6 GV/m. However, the phase slippage caused by differences in relativistic velocities limits further acceleration. By introducing a plasma density gradient, we ensure that the accelerated beam remains in the accelerating and focusing phase of the wakefield throughout the process, enabling electrons to be accelerated up to 562 MeV within 0.26 m. Then, an extremely narrow and short electron bunch is employed as a witness beam. With plasma density gradients, after propagating a distance of 0.92 m in the plasma, electrons can be accelerated from 16 MeV up to 626 MeV, resulting in an acceptable energy spread of 0.8 %.

Speaker: Mr Jiangdong Li (Institute of Modern Physics, Chinese Academy of Sciences)

29 High electron charge accelerated in the SM-LWFA regime with the LMJ-PETAL laser

Energetic electron sources generated by ultra-intense lasers can serve for various applications in many research fields. In this presentation, we will report on recent numerical and experimental results on electron acceleration with the ~ 0.3 kJ, 0.7 ps, 5×10^18 W/cm^2 LMJ-PETAL laser system. Due to the long pulse duration, the interaction of the PETAL beam with a gas jet accelerates electrons in the self-modulated laser wakefield acceleration (SM-LWFA) regime. Energies up to 150 MeV have been experimentally obtained, with an exponentially decreasing spectrum and a large divergence (~100 mrad), as expected in the SM-LWFA regime. However, due to the high laser energy, a very high charge, close to the µC range, is measured, which open encouraging perspectives for new applications. Multidimensional particle-in-cell (PIC) simulations, run with the codes CALDER and Osiris, are able to reproduce these findings. The laser self-focusing and self-modulation is observed in the simulation, as well as electron acceleration in the wakefield. The simulation shows that direct laser acceleration (DLA) can also occur, but it doesn’t seem to be the dominant mechanism in this setup.

Speaker: Xavier Davoine (CEA DAM DIF)

30 High quality electron beams for plasma based light sources.

Plasma-based accelerators provide a compact and efficient means of generating ultra-relativistic particles [1], making them strong candidates for next-generation light sources. These X-ray sources are inherently ultrafast, highly-collimated, and energetic, with applications in many fields.

One of the most well-established mechanisms for X-ray generation in plasma accelerators is nonlinear Thomson-scattering [2]. While these sources are compact, tunable and cost-effective, their main limitation is the lack of temporal-coherence. Achieving coherence and superradiance would enable plasma-based X-ray sources to rival the brightness of modern X-ray free-electron lasers (FELs). However, this requires electron beams with low energy spread and divergence.

This work presents simulations using PIC code OSIRIS for a LWFA designed for a potential EuPRAXIA facility at Rutherford Appleton Laboratory known as EPAC. The accelerated electrons satisfy the stringent demands of next-generation light sources. By investigating nonlinear Thomson-scattering with these beams, we explore generalised superradiance [3] and collective effects, potentially identifying new coherent emission regimes that could enhance X-ray brightness and benefit multiple scientific fields.

References
[1] T. Tajima and J. M. Dawson, Phys. Rev. Lett. 43, 267 (1979).
[2] E. Esarey et al., Phys. Rev. E 48, 3003 (1993).
[3] J. Vieira et al., Nature Physics 17, pages 99–104 (2021).

Speaker: Bhushan Thakur (Instituto Superior Tecnico, Lisbon)

31 High-Energy OPCPA at Lund Laser Centre and its Application to LWFA

A state-of-the-art high-energy short-pulse laser system was commissioned last year at Lund Laser Centre. This dual-output Optical Parametric Chirped Pulse Amplification (OPCPA) system delivers sub-10 fs pulses at 10 Hz and 100 Hz repetition rates, generating independent output channels of up to 30 TW and 6 TW, respectively. Operating at a central wavelength of 850 nm with a broad bandwidth of 300 nm, the system features both passive and active feedback stabilization of the carrier-envelope phase (CEP), achieving a CEP stability of 250 mrad, as measured using an f-2f interferometer.

Spectral phase errors are precisely managed using a Dazzler in combination with dispersion scan (D-scan) measurements. The 10 Hz beamline undergoes pulse compression via 16 broadband chirped mirrors, achieving a Fourier-limited 9 fs pulse, verified through D-scan diagnostics. Spatio-temporal couplings (STC) are minimal, enabling near-ideal focusing, as characterized using INSIGHT and IMPALA techniques. To correct wavefront distortions, an adaptive feedback loop integrates a deformable mirror and a wavefront sensor.

The laser attains focused intensities exceeding 10¹⁹ W/cm², driving plasma wakefields with field gradients reaching hundreds of GV/m. Recently, the system successfully demonstrated laser wakefield acceleration (LWFA) of electrons up to 100 MeV, showing its potential for advanced plasma-based acceleration research.

Speaker: Andrea Angella

32 Hybrid accelerator to deliver therapeutic electron beams at high energies

Very High Energy Electrons (VHEE) are emerging as a cancer treatment commodity. Compared to protons, VHEE is less sensitive to inhomogeneities within the human body. This means they are less damaging to healthy tissue when treating dynamic organs such as the lungs, liver, and kidneys. VHEE have a range of penetration depth depending upon the energy, often ranging from 50 MeV to 250 MeV. Such beams can be generated using radiofrequency photoinjectors followed by tens of meters long copper-based booster linacs. We are envisaging a hybrid approach where high-brightness electron beams are generated using a copper photoinjector radiofrequency gun and injected into a plasma module for further acceleration. The end goal is proof of a compact VHEE radiotherapy machine. In this contribution, we will review therapeutic electron beams and discuss the layout of the hybrid VHEE machine and a technique developed to match the conventional electron source and the plasma accelerator.

Speaker: Oznur Apsimon (The University of Manchester)

33 Laser Acceleration of Protons in Hydrogen Gas Targets using 2 TW laser

In this study, the acceleration of proton beams from gas targets, formed by converging shock nozzles and utilising a 1 Hz laser with limited pulse energy, has been demonstrated.

Energetic ion beams are routinely generated in laser-driven ion acceleration experiments in PW-class laser-foil experiments but are limited by slow repetition rate of these laser systems. New opportunities of developing more compact ion sources are offered by emerging multi-terawatt high-repetition rate lasers and utilisation of liquid leaf targets. However, there is still a demand for easy-to-handle and debris-free laser-driven ion acceleration. Therefore, high density gas targets have attracted great attention in recent years.

The proton acceleration experiments were performed using a few-cycle 12 fs SEA laser at ELI-ALPS with 8 mJ of pulse energy focused at a spot of 2.9 μm x 2.1 μm FWHM on the target. The high-density region of the 9×10^19 cm^-3 hydrogen gas target was formed by intersecting shock waves of a supersonic nozzle manufactured using hybrid 3D laser machining technology from fused silica. 4 x10^5 protons per 1000 shots, with an energy of tens keV were registered on CR-39 plates, within the angle of 70 degrees in the propagation direction of the laser beam.

Speaker: Vidmantas Tomkus (FTMC - Center for Physical Sciences and Technology)

34 MACRO Tools for Real-time Analysis of Laser-driven Experiments at ELI-NP

Swift macro-tools can be useful when real-time analysis is key, such as fast image capturing and processing, for instance, when studying multi-parametric phenomena such as LWFA.
During tight beamtime schedules, such an approach is central to quickly optimizing physical outputs via fast diagnostics. In LWFA investigation, where high repetition rate shots can be carried out, fast processing can help achieve desirable results such as high-quality laser-plasma interaction, suitable plasma parameters, and stable quasi-monoenergetic electron beams with high cut-off energy. During the commissioning activities of the ELI-NP 10 PW experimental area, we have developed and begun applying such real-time analysis tools. In this work, we will present some of our experimental results and illustrate the codes employed during the experimental runs. Generally, ELI-NP is also currently working on developing machine learning tools and AI algorithms to be used by the Users during the experimental campaigns.

Speaker: Mx Diana Catana (ELI-NP)

35 Non-destructive charge monitoring in a harsh laser-plasma environment for medical applications

The ability of laser plasma accelerators (LPA) to produce quasimonoenergetic electron beams with energies ranging from tens of MeV to tens of GeV in just a few millimeters to centimeters brought LPA to the attention of many scientific and industry fields. Arguably the most important of them is medicine, in a newly developed, so-called FLASH radiotherapy. In this regard, generating high-quality beams in terms of energy, pointing stability, and charge is crucial, and therefore their monitoring is essential. However, the electrical devices used for diagnostics can be directly or indirectly affected by transient electromagnetic pulses (EMPs) with a large frequency range normally occurring during laser-plasma interaction. In the case of charge measurements, overestimation by integrating current transformers (ICTs) has been previously reported and linked with the EMP influence. For this reason, experimental studies have been conducted at the ILIL, INO-CNR, in which electron beam charge has been directly measured by the integrating current transformer (ICT). The results have been compared with charge measurements retrieved from irradiated radiochromic films. At the same time, ICT charge measurements have been put into a correlation with the Lanex screen emission signal.

Speaker: David Gregocki (Consiglio Nazionale delle Ricerche - Istituto Nazionale di Ottica)

Poster_LPAW25_Gregocki_A0.pdf

36 Numerical study of the target geometry on the proton-boron fusion yield under direct laser illumination

The α-particle sources present many applications and may be produced through nuclear reactions thanks to laser-driven protons [V. S. Belyaev, A. P. Matafonov, V. I. Vinogradov, V. P. Krainov, V. S. Lisitsa, A. S. Roussetski, G. N. Ignatyev, and V. P. Andrianov, Phys. Rev. E 72, 026406 (2005)]. In this numerical study, the effect of the target geometry, planar or spherical, is investigated and the different particle acceleration processes, responsible for the source of α-particles, analyzed. Thanks to the implementation of nuclear reactions in the particle in cell code SMILEI [J. Derouillat, A.Beck, F. Perez, T. Vinci, M. Chiaramello, A. Grassi, M. Fle, G. Bouchard, I. Plotnikov, N. Aunai, J. Dargent, C. Riconda and M. Grech, Comput. Phys. Comm. 222, 351 (2018)], the spatial and temporal locations of the α-particle sources are presented and highlight the benefit of using a spherical target. Specifically, effects of electric and magnetic fields on ion acceleration are analyzed and show, in spherical geometry, succession of two different acceleration processes leading to an increase of nuclear reactions

Speaker: Philippe Nicolai (Centre Lasers Intenses et Applications (CELIA), university of Bordeaux, FRANCE)

37 Observation of Monoenergetic Electrons from Two-Pulse Ionization Injection in Quasilinear Laser Wakefields

The generation of low emittance electron beams from laser-driven wakefields is crucial for the development of compact x-ray sources. Here, we show new results for the injection and acceleration of quasimonoenergetic electron beams in low amplitude wakefields experimentally and using simulations. This is achieved by using two laser pulses decoupling the wakefield generation from the electron trapping via ionization injection. The injection duration, which affects the beam charge and energy spread, is found to be tunable by adjusting the relative pulse delay. By changing the polarization of the injector pulse, reducing the ionization volume, the electron spectra of the accelerated electron bunches are improved.

Speaker: Marko von der Leyen (University of Oxford)

38 Optimization of Laser Wakefield Acceleration for High-Quality Electron Beams: Simulations and Experimental Results in Collaboration with HZDR

Laser Wakefield acceleration (LWFA) has been demonstrated as a mechanism to accelerate electrons to very high energies over a few millimeters. A high-intensity laser ionizes the atoms in a gas mixture, and excites plasma waves with accelerating gradients reaching up to 100 GV/m – far exceeding those in conventional accelerators. Enhancing the electron beam charge and energy while minimizing its divergence and energy spread are fundamental objectives and ongoing challenges in advancing these accelerators for various applications, including radiation therapy, free electron lasers, and future compact colliders.
In the context of LWFA experiments at Helmholtz-Zentrum Dresden-Rossendorf (HZDR), we are developing tailored plasma density profiles, and utilizing the ionization injection method to efficiently trap, and accelerate electrons. To refine our approach, numerical Particle-in-Cell (PIC) simulations are conducted using SMILEI to optimize the laser and plasma parameters for the experiment.
The primary goal is to develop a high-quality electron source suitable for advanced applications, such as free-electron lasers and compact accelerators. This poster illustrates the role of key mechanisms through the comparison of experimental results and numerical simulations with SMILEI.

Speaker: Mohamad Masckala

39 Plasma Mirror Operation for Staging Applications

A plasma mirror reflected pulse was evaluated for staging applications. The Gemini north beam was focused just after a Kapton tape. On-tape intensities of $10^{19}-10^{21} Wm^{−2}$ generated a plasma mirror. The reflected pulse was used to drive a injection and acceleration in a gas cell.

The plasma mirror was operated with a reflectivity exceeding 70%, this fell for on-tape intensities nearing $3×10^{21} Wm^{−2}$. Reducing the spot area on the tape improved the reflected spot quality, increasing energy in FWHM for comparative intensities. These results are indicative of some pre-plasma formation and surface distortion. The plasma mirror reflected spot was used to drive an accelerator stage to ionisation injection. Ionisation injection was demonstrated with spots containing up to 0.4 ± 0.1 J in their FWHM at densities exceeding $2.7 ± 0.4 × 10^{24} m^{−3}$. Electrons were accelerated in a cell of $6.7 ± 0.8 × 10^{24} m^{−3}$ to energies up to 455 ± 28 MeV. At densities between $0.5 × 10^{24} m^{−3}$ and $2 × 10^{24} m^{−3}$, closer to ideal staging regimes, guiding and complete blue-shifting of the transmitted spot was observed.

These results inform our understanding of plasma mirrors operated at high intensity and indicate their utility for staging applications.

Speaker: Jasmin Hills (Imperial)

40 Prediction of laser-induced breakdown in sub-micron-thick dielectric targets for laser-ion acceleration

In laser-ion acceleration experiments, the rising flank of a high power laser pulse can cause target pre-ionization and subsequent pre-expansion long before the arrival of the main laser peak. Exact knowledge of this target pre-expansion is required in order to understand laser-plasma acceleration mechanisms with the help of numerical simulations. For dielectric targets, the start of target pre-expansion is characterized by the point in time at which the target undergoes laser-induced breakdown (LIB).
In this contribution, we present a recently published method to determine the time of LIB in sub-micron-thick Formvar targets during interaction with a specific high-power laser pulse [1]. The required pulse-duration-dependent LIB threshold of Formvar is measured in a dedicated experiment. A comparison of LIB threshold to previously published data facilitates an empirical LIB scaling for other wide-band-gap dielectric materials used as targets in laser-ion acceleration experiments.

[1] S. Assenbaum et al 2025 Plasma Phys. Control. Fusion 67 015032

Speaker: Stefan Assenbaum (Helmholtz-Zentrum Dresden-Rossendorf)

41 Realization of plasma photocathode injection in a compact plasma accelerator powered by laser-accelerated electron beams

Ultrashort high-peak current electron beams generated from laser wakefield acceleration (LWFA) are capable to drive high accelerating gradient plasma wakefield accelerators (PWFAs) operating in high plasma density regime. Implementation of advanced cold-injection schemes in this hybrid platform promises the generation of high brightness electron beams with unprecedented low emittance and energy spread.
Here we report on the realization of plasma photocathode injection using 90 degree geometry in such a compact plasma accelerator consisting of a mixture of hydrogen and helium gas. Electrons from the highest ionization level of helium are released into the wakefield by a carefully tuned low intensity laser pulse. Scanning of the laser arrival time shows that the injection only occurs within the first cavity, characterizing this injection scheme.
In this proof-of-concept experiment, witness beams with an absolute energy bandwidth as low as 2 MeV (full-width at half-maximum) peaked at 140 MeV can be generated at divergence of only 0.4 mrad (root-mean-square). Further post-acceleration of such a witness beam, i.e elongating the PWFA stage close to the depletion distance of the driver in future work, would result to relative energy spread in per mille level required for beam-quality-demanding light source applications.

Speaker: Patrick Ufer (Helmholtz-Zentrum Dresden-Rossendorf)

42 Simulation studies in preparation for AWAKE Run 2c

AWAKE is a plasma wakefield acceleration experiment where the wakefields are driven by a highly energetic, long proton bunch that undergoes the self-modulation instability. The objectives of Run 2c, due to start in 2029, are to demonstrate emittance preservation of the accelerated electron bunch.

In contrast with the 10-meter-long plasma setup used thus far, in Run 2c the witness electron bunch will be injected between two plasma sections, after the proton bunch has become fully self-modulated in the first section. It is therefore crucial to obtain as much information as possible about the parameters achievable with the new layout and the challenges it poses before actual commissioning begins.

In this work we use particle-in-cell simulations to provide an expectation for the wakefield amplitude and energy gain in the second plasma section. We also simulate, with particle-tracking code RF-Track [1], possible emittance increase of the injected electron bunch for the case of an injection region that contains rubidium vapour. These results inform the planning of AWAKE Run 2c but could also be relevant for other facilities that are building plasma-based accelerators.

[1]: Latina, A. (2024). RF-Track Reference Manual. Zenodo.

Speaker: Mariana Moreira (CERN)

43 Single-shot spectrometer with pointing angle correction for laser-driven electron beams featuring moderate pointing instability and transverse inhomogeneity

Electron beams produced via Laser Wakefield Acceleration are notorious for their non-negligible pointing instability. This makes the retrieval of the energy spectrum via magnetic spectrometers particularly prone to energy miscalculations. As such, various spectrometer configurations have already been suggested to correct spectra for the pointing angle. Here, we experimentally demonstrate an improved scheme of a previously published concept employing two scintillating screens and a magnetic dipole in between. The first screen, providing the pointing angle, is placed at the exit of the vacuum chamber, and the second one behind the dipole. A collimator is coupled with the dipole, allowing a portion of the beam to be detected, resulting in an improved energy resolution. For the electrons entering the collimator, a numerical procedure is laid out to retrieve the exact pointing angle of each transverse beamlet on the dipole, which in turn allows a weighted sum procedure to be carried out to retrieve the final spectrum. We note that the first scintillator screen used in our setup causes significant electron scattering, effectively acting as an energy dependent attenuator. For this reason, we performed Monte Carlo simulations to measure this effect and back projected the observed spectrum to retrieve correct one.

Speaker: Simon Vlachos (CNR-INO)

44 Snapshot Hyperspectral Imaging of low-order chirped harmonics at GEMINI

High-Harmonic Generation (HHG) from laser-solid interactions is a process whereby harmonics of the incident driving pulse are generated; a phenomenon which is paving the way to the generation of attosecond pulses and the emission of coherent extreme ultraviolet (XUV) and soft X-ray radiation. Chirped harmonics can be produced by varying the chirp of the driving beam as shown by simulations using the Smilei PIC code. Chirped pulses allow the bridge between Snapshot Hyperspectral Imaging (SHI) and Video Compressive Sensing (VCS) to be made, and hyperspectral images can then be converted into videos with extremely high temporal resolution. This motivated the design of the Low-Order Boosted Spatio-Temporal Encoder of Radiation (LOBSTER) which was optimised, through ray-tracing, for the capture of high spectral and spatial resolution images of low-order harmonics from laser-solid interactions and the study of the effects of a chirped driving beam on the interaction. This setup was used in an experiment at GEMINI TA3 in November 2024 where hyperspectral imaging of low-order chirped harmonics was carried out. I present the design of a SHI setup, the reconstruction method as well as results from the experiment.

Speaker: Elliott Denis (Univerity of Oxford)

45 Ultra-Short Laser Pulses: A Parameter Study for Laser Wakefield Acceleration

The overarching goal of EuPRAXIA is to pioneer the development of next-generation compact particle accelerators using advanced plasma-based technology. Among the most promising methods for achieving this vision is laser wakefield acceleration (LWFA), which enables the generation of high-energy electron beams within a compact setup.

This work explores the effect of ultrashort laser pulses and tailored plasma density profiles on the injector parameter space, with the aim of optimizing electron injection and acceleration, a step toward meeting EuPRAXIA’s requirements.

The study focuses on leveraging a new high-energy, short-pulse laser system developed at the Lund Laser Center. This system, based on Optical Parametric Chirped Pulse Amplification (OPCPA), features dual outputs capable of simultaneous operation at 100 Hz and 10 Hz, delivering peak powers of 6 TW and 30 TW, respectively. The 10 Hz, 250 mJ laser arm, with its ultrashort pulse duration of 9 fs, is particularly suited for exploring LWFA.

These exceptional parameters open new possibilities to study how laser pulse properties influence key factors such as acceleration length and electron energy gain. Using the Fourier-Bessel Particle-in-Cell (FBPIC) code, this work examines the interplay between laser and plasma parameters, comparing the results against established scaling laws, and proposing experimental configurations.

Speaker: Mr Flanish D'Souza (Lund University)

20:30 Dinner

Tuesday, 15 April

Plenary Session: Secondary Radiation Sources

46 Experimental results on all optical Compton source with GeV photon at ELI-NP

The Compton scattering between a GeV electron beam and a relativistic laser pulse is a promising scheme for studies including radiation reaction in strong-field quantum electrodynamics (QED), in-suit laser intensity measurement, and brilliant gamma-ray generation. Instead of using the routine method with an individual scattering laser, we applied the self-aligned single-laser Compton scattering setup at the ELI-NP and Apollon multi-PW laser facilities. GeV photons were measured after the Compton scattering of a 2- to 5-GeV electron beam and a laser pulse reflected by a plasma mirror with $a_0$ of the order of 5, corresponding to a quantum nonlinearity parameter of χ ≈ 0.3. Benefiting from the automatic alignment and synchronization provided by the plasma mirror, nonlinear Compton scattering was probed with a collision success rate of approximately 100%, free from the misalignment errors and fluctuations of usual multibeam approaches. The distance between the gas nozzle and the plasma mirror was scanned to investigate the dependence of photon energy, photon divergence, and change of electron divergence during scattering on the laser intensity. The dynamics of electrons passing through the overlapped region of the forward and the reflected laser pulses were also explored with the help of PIC simulations.

Speaker: Dr Yinren Shou (Department of Physics of Complex Systems, Weizmann Institute of Science)

47 All-optical Nonlinear Compton Scattering: Strong Field QED Experiment

All-optical nonlinear Compton scattering (NCS) experiment has been carried out with a multi-PW laser at Center for Relativistic Laser Science (CoReLS). CoReLS finished the construction of a 20 fs, 4 PW Ti:Sapphire laser in 2017 and achieved the record high laser intensity of 10^23 W/cm^2 in 2021. By applying the laser wakefield electron acceleration scheme, mono-energetic multi-GeV electrons were produced by applying PW laser pulses to a He gas medium. In the all-optical NCS demonstration a multi-GeV electron scatters off hundreds of laser photons and converts them into a single gamma-ray photon with energy well over the cutoff energy of linear Compton scattering, i.e. NCS occurs. Along with quantum electrodynamics (QED) simulations and analytic calculations, our experimental measurement of gamma-ray spectra verifies the occurrence of Compton scattering in the strongly nonlinear regime. Our results may help understand the physics associated with QED processes occurring in extreme astrophysical objects such as neutron stars and black holes.

Speaker: Prof. Chang Hee Nam (CoReLS, Institute for Basic Science & Gwangju Institute of Science and Technology)

48 Characterization of a laser-plasma betatron source for high resolution x-ray imaging

Betatron radiation from laser-plasma accelerators has distinctive features: bright[1,2] broadband, micron scale source size, and ultrashort pulse duration of the order of femtoseconds. Betatron radiation has been successfully used for X-ray imaging, including single[3] shot phase contrast imaging[4] and multimodal imaging[5].
Pushing betatron-based imaging to higher and higher resolution depends on the source properties as well as on the versatility and robustness of the imaging technique adopted. Here we review the key parameters of the betatron source and their characterization as a function of the imaging modality. We present the current status and future prospective of betatron imaging, towards nanoscopy at the femtosecond.
[1] Kneip, S. et al. (2010), Nat. Phys. 6 (980-983).
[2] Cipiccia, S. et al., (2011), Nat. Phys. 7 (867-871).
[3] Wood, J. et al. (2018) Sci Rep. 8(1).
[4] Fourmaux, S. et al. (2011). Opt. Lett. 36 (2426).
[5] Doherty, A et al.(2023). Commun Phys 6, 288 .

Speaker: Silvia Cipiccia (University College London)

10:40 Coffee Break

Plenary Session: Applications

49 The status of research on the FLASH effect using laser-driven protons

The recent observation of a normal tissue protecting effect of ultra-high dose rate (UHDR) radiation at unchanged tumor treatment efficacy, the FLASH effect, promises great benefits for radiotherapy patients. Since the first description of the FLASH effect, preclinical studies have confirmed the effect for electrons, photons, protons, and carbon ions in various tumor and normal tissue models. Yet, two fundamental questions remain to be answered: Firstly, what are the mechanisms causing the FLASH effect, and secondly, what are the dose application parameters, e.g. peak and mean dose rate, required for triggering FLASH?
In this context, laser-driven plasma accelerators (LPAs) for protons offer unique research capabilities by providing proton pulses with multi-10 MeV energies at unprecedented dose rates of 10^9 Gy/s. Yet, to make these beam parameters available for the FLASH research community, a research environment supporting radiobiological experiments at LPAs needs to be established, including beam transport and radiation field formation to provide pre-defined dose distributions at an in-air irradiation site, beam monitoring, as well as dosimetry and infrastructure to handle biological samples.
In this talk, the current status of FLASH research at LPA sources as well as the challenges for a wider implementation of radiobiological studies will be discussed.

Speaker: Josefine Metzkes-Ng

50 Generation and characterization of directional muon beams using Laser Plasma Acceleration

Muons and their applications in tomography of large objects have recently gained significant interest within the accelerator physics community. However, the lack of portable muon sources has limited muon tomography to relying on cosmic rays, which are characterized by a low and non-directional flux. This restricts muon tomography to objects that remain immobile for extended periods. Laser-Plasma Accelerators (LPAs) have demonstrated production of multi-GeV-class electron beams over compact accelerating lengths. When a converter target is placed in front of the generated electron beam, a substantial number of muon pairs are produced via the Bethe-Heitler process. Therefore, an LPA can serve as a compact high-flux muon source. In this talk, we present recent experimental results at the BELLA Center, where muon production from LPA-produced, multi-GeV electron beams was demonstrated. Simulations show that the interaction of the beam with the electron beam dump produces a collimated cone of muon pairs, which were detected on the other side of the wall using scintillating paddles.

This work was supported by DARPA and the U.S. Department of Energy Office of Science, Office of High Energy Physics under Contract No. DE-AC02-05CH11231, and used the computational facilities at NERSC.

Speaker: Davide Terzani (Lawrence Berkeley National Laboratory)

51 First lasing with the free electron laser driven by a laser plasma accelerator at BELLA

Laser plasma accelerators (LPAs) have emerged as a viable alternative to traditional accelerators for various applications, thanks to their capability to generate high-brightness beams and much higher accelerating gradients. This enables more compact designs for future light sources, such as free electron lasers (FELs). FEL technology leveraging LPA sources is progressing swiftly, with several key milestones achieved in recent years. However, significant work remains to be done to move from proof-of-concept experiments to the dependable operation of LPA-driven FELs. Recent initiatives at the BELLA center's Hundred Terawatt Undulator beamline, which includes an electron beam transport section leading to a 4-meter-long, strong focusing undulator, have successfully demonstrated the consistent operation of a high-gain FEL in the SASE regime. SASE gain is detectable on 90% of shots with measured SASE gain in excess of 1000.

Speaker: Sam Barber (LBNL)

12:40 Lunch

Parallel Session: Electron Acceleration

52 A parametric approach to plasma wakefield acceleration at CLARA

The Compact Linear Accelerator for Research and Applications (CLARA) at Daresbury Laboratory in the UK is a state-of-the-art facility that provides mid-energy range, high-brightness electron beams for exploring innovative concepts in accelerator science and technology. An exciting upcoming development is the integration of the Full Energy Beam Exploitation (FEBE) beamline, specifically designed for applications requiring the full beam energy of 250 MeV at CLARA. This integration will transform CLARA into an advanced testbed for proof-of-principle novel acceleration applications. Notably, a plasma wakefield acceleration (PWFA) experiment is potentially feasible with the CLARA FEBE. In this context, we present particle-in-cell simulation studies to explore a potential two-beam PWFA experiment at CLARA FEBE. A parametric approach will be employed to systematically determine the initial parameters of the plasma, driver, and witness beams by varying these parameters methodically. The study aims to double the energy of the witness beam while maintaining its low energy spread. We will identify the acceleration regime and the parameters that best suit a PWFA experiment at CLARA.

Speaker: Hossein Saberi (University of Manchester and Cockcroft Institute)

53 Impact of the gas species and optical ionization effects in kHz laser-wakefield acceleration

Laser-wakefield acceleration (LWFA) of electrons at a kHz repetition rate holds significant promise for medical and industrial applications. Until recently, kHz laser systems have been limited to few-mJ pulses, necessitating sharp focusing and strong temporal compression to achieve relativistic intensities [Guénot 2017]. Continuous operation of a kHz laser-plasma accelerator requires specialized target systems capable of sustaining a continuous gas flow, previously demonstrated only in N2 [Rovige 2020]. However, recent studies indicate that lighter gases, such as H2, promise superior performance [Salehi 2021].
We present our latest study on optical ionization effects in kHz LWFA with few-mJ, few-cycle pulses [Monzac 2024]. We confirm and elucidate the improved performance of H2 compared to other gases, including He: the ionization effects significantly distort the laser pulse, negatively impacting the accelerator performance. These effects are minimal in hydrogen plasma, thereby enhancing beam quality. Utilizing 4 fs pulses with 2.5 mJ on-target energies at the Salle Noire facility (LOA), we achieved low-divergence electron beams with narrow spectra peaking around 5-10 MeV. These beams exhibited remarkable shot-to-shot stability in beam pointing, charge and energy spectrum. To achieve these results, we implemented a differential pumping scheme enabling continuous operation at kHz repetition rates in light gases.

Speaker: Joséphine MONZAC

54 How are CEP effects affected by the injection mechanism in a Laser Wakefield Accelerator driven by near single-cycle laser pulses

Our group has developed a laser wakefield accelerator (LWFA) based on a near-single-cycle laser driver, producing up to 10 MeV electron beams at kHz repetition rates [1]. For near-single-cycle laser pulses, the ponderomotive approximation breaks down and the plasma response becomes sensitive to the waveform of the laser field so that the carrier-envelope phase (CEP) can affect electron injection in the wake. In previous work, we showed that the CEP modifies the dynamics of self-injection by triggering a transversely oscillating plasma bubble, resulting in CEP dependent electron beam pointing [2]. In contrast, this talk will focus on very recent experimental results where electrons are injected by ionization injection. Ionization injection directly depends on the amplitude and phase of the laser field and is, therefore, particularly sensitive to the CEP. In this regime, we show that the electron beam undergoes an angular CEP dependent splitting in 2 sub-beams, reflecting the dynamics of ionization injection at the sub-cycle level. Finally, we also show experimentally that CEP effects can be strongly mitigated by relying on density down-ramp injection instead of self-injection of ionization injection.

[1] Monzac et al., PRR 6, 043099 (2024)
[2] Huijts et al., PRX 12, 011036 (2022)

Speaker: Jerome Faure (Laboratoire d'Optique Appliquée)

55 Injection dynamics in hybrid LWFA-PWFA plasma photocathodes

Plasma photocathodes, also known as Trojan Horse injectors, utilise a comparatively low-intensity laser pulse to ionise and release electrons at defined locations directly inside a plasma wakefield. Provided a sufficiently strong wakefield, these electrons are initially compressed, trapped and subsequently accelerated. The trapped bunch characteristics are thereby largely determined by the initial electron release locations, which are in turn defined and tunable via the injector laser parameters, its position and delay with respect to the wake, as well as the injector geometry. Trojan Horse scenarios, typically realised in particle-driven plasma wakefield accelerators (PWFAs), promise to deliver electron beams with exceptionally high (slice) brightness. High peak-current electron drivers generating wakefields with adequate plasma photocathode trapping conditions can be provided by laser-driven wakefield accelerators (LWFAs) in a compact setup. Such hybrid LWFA-PWFA plasma photocathodes offer unique operating modes at high plasma densities. Based on simulations, aspects of plasma photocathode injection dynamics under different injector geometries and their implementation in hybrid LWFA-PWFA scenarios are discussed.

Speaker: Thomas Heinemann (Heinrich-Heine-University Düsseldorf)

56 Plasma electron acceleration driven by a long-wave-infrared laser

We report self-injecting LWFA driven by CPA-CO2 laser pulses of wavelength ~10 micrometers at Brookhaven's Accelerator Test Facility [1]. Long-wave IR pulses open opportunities to drive large wakes in low-density plasma more efficiently than near-IR pulses, potentially enabling higher-quality accelerated bunches. In experiments, 0.5-TW, 4-ps laser pulses generated no electrons, but drove self-modulated wakes characterized by optical scattering in plasma of density down to 4e17 cm-3, when peak power exceeded the critical power for relativistic self-focusing. 2-ps pulses with power up to 5-TW captured and accelerated electrons to relativistic energy in plasma of density as low as 3e16 cm-3. The shortest, most powerful pulses generated up to 0.4 nC total charge, including a collimated quasi-monoenergetic peak at ~10-MeV, along with a low-energy background. This marked the onset of a transition from self-modulated to the bubble regime. 3D Particle-in-cell simulations accurately predicted the thresholds for wake excitation and for self-injection, and other key details. The results portend future accelerators in which yet shorter, more powerful CO2 pulses drive plasma bubbles of ~300-micron radius, that can preserve the low emittance and energy spread of electron bunches injected externally from a synchronized low-energy linac.

Speaker: Michael Downer

Parallel Session: Ion Acceleration

57 New designs of helical coil targets for laser-driven proton, carbon and alpha acceleration

Helical coil targets [1] are commonly used to focus, collimate, bunch, and accelerate protons via the Target Normal Sheath Acceleration (TNSA) process, producing highly focused and collimated beams [2]. However, acceleration and bunching remain limited by current dispersion along the helix. To overcome this, we introduced a tube around the helix, reducing dispersion and enhancing bunching [3]. To increase the post-acceleration, a new electromagnetic model with variable pitch and diameter was then developed to synchronize proton propagation with the current pulse over longer helices [4]. Our recent experiments at the ALLS facility confirmed effects on both protons and carbon ions [5]. Building on this, new helical targets were designed to accelerate alpha particles for scandium radioisotope production. Simulations predict a 10–3000-fold increase in radioisotope yield [6].

References
[1] S. Kar et al., Nature Com. 7, 10792 (2016)
[2] M. Bardon et al., Plasma Phys. Control. Fusion 62, 125019 (2020)
[3] A. Hirsch-Passicos et al., Phys. Rev. E 109, 025211 (2024)
[4] C.L.C. Lacoste et al, Matter Radiat. Extremes 9, 067201 (2024)
[5] C.L.C. Lacoste et al, submitted to Matter Radiat. Extremes (January 2025)
[6] C.L.C. Lacoste et al, submitted to Phys. Rev. Appl. (January 2025)

Speaker: Matthieu Bardon (CELIA)

58 Transforming Laser-Driven Proton Beams into Application-Ready Sources

Laser-plasma acceleration (LPA) generates ion beams with extraordinary properties. The inherently high number of accelerated ions, delivered in ultrashort bunches, makes LPA ion sources ideal for high-dose-rate applications such as radiobiology. However, these bunches exhibit high divergence and broad energy spectra, necessitating spatial and spectral shaping before utilization.

To address these challenges, we introduce the pulsed power technology platform ALBUS – Advanced Laser-driven Beamlines for User-specific Studies. ALBUS uses pulsed magnets, adapted from high-field laboratories, as tunable beam optics with large apertures and short focal lengths, enabling efficient beam capture, transport, and energy selection.

We demonstrate its capability using the two-solenoid beamline ALBUS-2S as an example. Designed to shape LPA proton beams for homogeneous dose delivery to volumetric radiobiological samples, it has been implemented at the DRACO PW laser, where we performed the world’s first controlled tumor irradiations in a dedicated mouse model using LPA protons.

Looking ahead, we outline our plans to further advance the unique combination of pulsed power technology and LPA by developing high-repetition-rate beamline magnets alongside targetry capable of similarly high repetition rates. Coupled with advanced real-time diagnostics and automated feedback systems, these developments will pave the way for application-ready LPA proton sources.

Speaker: Florian Kroll (Helmholtz-Zentrum Dresden-Rossendorf)

59 Quasi monochromatic Carbon beams acceleration in the peeler setup

In the peeler scheme the laser pulse is incident on the narrow edge of a tape-like target. The generated surface plasma wave accelerates the electrons peeled from the lateral surface of the target, thus generating an high-charge electron bunch that creates a large amplitude accelerating field for positive ions residing the in the target rear, allowing for the generation of quasi-mochromatic proton beams [1,2].

In this study, we discuss the applicability of the peeler scheme for a quasi-monochromatic acceleration of ions such as carbon, too. So far, the application of the peeler scheme for the acceleration of ions from carbon layers resulted in an exponentially decreasing spectrum [2]. In the new proposed scheme, an engineered carbon structure with tuned spatial extent and density is placed at the target rear. By using 3D-PIC simulations which employ a realistic multi-PW laser pulses like the ones available at ELI-NP, we demonstrate that quasi monochromatic C-beams with 10% FWHM energy spread and about $10^9$ ions can be obtained [3]. Finally, an experimental demonstration of the scheme with the granted beamtime at ELI-NP/1PW in September will be discussed.

[1] Phys.Rev.X 11, 041002(2021)
[2] PPCF 65, 034005 (2023).
[3] B. Corobean et al., TBS

Speaker: Paolo Tomassini (ELI-NP and CNR-INO)

60 Cascading Acceleration Regimes in the Relativistically Induced Transparency Regime Driven by Ultra-Intense PW Lasers

Laser-driven ion accelerators offer multi-MeV beams with high-peak currents, enabling applications in radiotherapy, neutron generation, and fast ignition in inertial confinement fusion. However, transitioning from complex experiments to reliable particle sources requires advances in beam quality, robustness, and high-repetition-rate scalability.

Recent studies have identified the Relativistically Induced Transparency (RIT) regime as a promising pathway for enhanced ion acceleration, achieved by precisely synchronizing the laser pulse arrival with the onset of target transparency. Using the DRACO-PW and J-KAREN-P laser systems, we systematically investigated laser and target parameters to optimize acceleration performance in this regime. Our results show record proton energies of up to 150 MeV at only 22 J of laser energy. The generated proton beam featured a high-energy, low-divergence component that was both spectrally and spatially distinct. Target transparency proved to be a simple yet powerful control parameter, highly sensitive to subtle laser–target variations.

Start-to-end simulations validate these findings, revealing the influence of preceding laser light in pre-expanding the target and detailing the acceleration dynamics during the main pulse interaction. These results offer critical insights into the role of ultrashort pulse duration and laser contrast, marking a substantial step toward controlled and efficient ion acceleration in the RIT regime.

Speaker: Tim Ziegler (Helmholtz-Zentrum Dresden-Rossendorf)

61 Laser-Driven Proton Sources for Efficient Radiation Testing

High radiation environments are present in many fields, such as fusion facilities, nuclear reactors, high-luminosity accelerators, space and defense sector. The employed materials, e.g. plasma facing materials, and devices, e.g. Commercial Off-The-Shelf (COTS) semiconductor components, need to withstand excessive stressful radiation levels. Quick and adequate qualification tests against radiation effects on the materials and components are thus required to guarantee the performances in an operational environment and quick production. A study of the radiation-induced damage and of its effect on materials and electronic devices used in harsh environment was carried out employing different types of radiation sources (including conventionally accelerated protons, laser-accelerated protons, 60 Co gamma radiation, neutrons, convention stress testing facilities) and different characterization methods.
In this talk we compare the results obtained by the study and show that in our conditions, laser-accelerated protons have the advantage of being much more efficient for stress testing materials and components than other methods.

Speaker: Prof. Patrizio Antici (INRS)

16:40 Coffee Break

Poster Session

62 Controlled Acceleration of Unstable Particles in Laser-Plasma Wakefields Using Structured Light

Plasma-based accelerators achieve accelerating fields of 10-100 GV/m. While plasma wakefields naturally accelerate electrons due to their near-light-speed motion [1,2], heavier particles like muons [3] and pions, with lifetimes from microseconds to nanoseconds, struggle to be trapped due to velocity mismatch with the wake.

We use spatio-temporal spectral shaping [4,5,6] to control the group velocity of drive pulses, generating subluminal wakes suitable for slower particles. PIC simulations with OSIRIS [7] show non-relativistic particles accelerating to relativistic speeds. By tailoring the plasma density profile, we can extend the dephasing length, which sustains the acceleration process.
This method enables plasma-based acceleration of unstable particles, with applications in cooled muon injection and enhanced muon yield via pion acceleration and decay.

[1] T. Tajima and J. M. Dawson, Physical Review Letters 43, 267 (1979).
[2] C. Joshi, Physics Today 56 (6), 47 (1993).
[3] K.R. Long, et al., Nature Physics 17, 289–292 (2021).
[4] A. Sainte-Marie et al., Optica 4, 1298-1304 (2017).
[5] Froula, D.H., Turnbull, D., Davies, A.S. et al., Nature Photonics 12, 262–265 (2018).
[6] H. Kondakci, Y. F. Abouraddy, Nature Communications 10, 929 (2019).
[7] R.A. Fonseca et al., Phys. Plasmas Control. Fusion 55, 124011 (2013).

Speaker: Chiara Badiali (GoLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico)

63 Updates to the Xopt/Badger Ecosystem for Advanced\\Optimization and Online Control

The Xopt/Badger ecosystem offers a versatile suite of tools designed to address the growing needs of advanced optimization and online control in scientific applications. The goal of these tools is to standardize the implementation and use of advanced optimization algorithms at arbitrary scientific facilities for the benefit of the wider accelerator community. In this work, we provide a summary of updates to Xopt and Badger that enable new capabilities and improve ease of use. This includes new developments in trust-region approaches to Bayesian optimization and GUI-based online visualization of surrogate models. Finally, we discuss the implementation of generator standards established between Xopt, libensemble, and optimus packages to allow for future interoperability, enabling robust usage of advanced optimization algorithms in both experiment and at high performance computing clusters.

Speaker: Ryan Roussel (University of California Los Angeles)

64 A generalized parallelization algorithm for Particle-In-Cell Simulations

Particle-in-cell (PIC) codes have been a cornerstone of plasma-based accelerator development. However, these work at the most fundamental, microscopic level, making few physics approximations, which makes them some of the most computationally expensive models in plasma physics, requiring efficient use of even the most modern HPC systems.

In this paper, we present a generalized parallelization algorithm for PIC simulations that is shown to work across all of the main architectures available today, including both CPUs (x86 / Arm) and GPUs (NVIDIA, AMD, Intel). The algorithm is based on a micro-spatial domain decomposition, with a high-performance particle manager to move particles between domains. Each domain is then assigned to a different thread (CPU) or thread block (GPU), achieving good parallel load balancing even for realistic simulation scenarios. The implementation is done using different programming models for different architectures, namely OpenMP (CPU), CUDA, ROCm (GPU), and SYCL (CPU/GPU/FPGA). While the implementations are effectively different code bases, given that the overall algorithm is the same, there are great similarities between all the implementations, making porting between them relatively straightforward. We present a performance comparison between different architectures/programming models for a test 2D problem, demonstrating very high performance for the architectures explored.

Speaker: Ricardo Fonseca (Instituto Superior Técnico, Universidade de Lisboa)

65 Advancing LWFA Beams for FEL Operation Using Synergies between Experiment, Simulation and Automation

The first FEL light from LWFA beams has recently been demonstrated. However, achieving shorter wavelengths requires stable and optimized beams, which remains a challenge due to the nonlinear nature of cavity formation and injection, and because many critical parameters are not directly accessible in experiments, making it difficult to fully characterize the 6D phase space.

We present a simulation-driven approach to study the stability of LWFA sources using automated parameter scans in the self-truncated ionization-injection (STII) regime. Using PIConGPU, we generate stability maps for laser and gas parameters and compare them with recent LWFA FEL experimental data. These simulations reveal the conditions that maximize beam quality and clarify the regime where STII does not produce optimal beams. By analyzing the ionization-injection dynamics, we uncover a transition between different beam quality regimes and manifests itself in substructures of the bunches that could be studied experimentally with Coherent Transition Radiation (CTR).

In addition, we explore other synthetic diagnostics - such as few-cycle shadowgraphy and far-field radiation - to validate our findings. We also discuss the limitations of electron spectrometer optimization for FEL drivers, highlighting the need for an integrated approach combining simulation and experimental diagnostics.

Speaker: Richard Pausch (Helmholtz-Zentrum Dresden - Rossendorf)

66 An Analysis of Electromagnetic Wave Propagation in a Conducting Cylinder with a Small Aperture

This study investigates the propagation and reflection of electromagnetic waves in a conducting cylindrical cavity with a small aperture, analyzing the effects of boundary conditions on wave transmission and diffraction. Using a Green’s function approach, we derive exact solutions for the electromagnetic potentials in the Lorentz gauge, incorporating the influence of conducting boundaries and image charges. The field distribution inside the cavity is expressed in terms of eigenmode expansions involving Bessel functions, satisfying Maxwell’s equations and the cavity’s boundary conditions. The presence of a small hole introduces diffraction effects, which are analyzed using Bethe’s small-aperture theory and mode-matching techniques to quantify the transmitted field. For large apertures, the wave leakage is modeled through cylindrical waveguide modes, while for small apertures, the diffraction pattern follows a dipole-like radiation structure. Additionally, we examine the wakefields induced by a charged particle beam inside the cavity, illustrating their interaction with reflected and transmitted waves. The study provides a rigorous framework for understanding space-charge fields in accelerator structures and wave leakage in confined conducting environments, with applications in beam physics and electromagnetic field modeling.

Speaker: Chong Shik Park (Korea University, Sejong)

67 Boosted Frame Simulations of Free-electron Lasers

A free electron laser (FEL) is a revolutionary light source capable of producing femtosecond-duration hard X-rays. These properties make FELs ideal for probing rapidly evolving phenomena, such as shock waves in metals, and for imaging dense materials, like in bone tomography. However, modeling FELs is challenging due to their extremely short radiation wavelengths and the large physical size of the devices, which can span several kilometers.

Here, we demonstrate the use of boosted frame particle-in-cell (PIC) simulations to efficiently model FEL radiation and interactions. The Doppler redshift and length contraction in the boosted frame yield a significant computational speedup, scaling as 𝛾^2. Simulations that would take over a month in the lab frame can now be completed within hours in the boosted frame. PIC simulations accurately capture critical effects such as emittance and space-charge dynamics. Additionally, the flexibility of the PIC framework allows seamless integration of additional physics through modular extensions, enabling a comprehensive approach to studying FELs.

Speaker: Runfeng Luo (Imperial College London)

68 Computational modelling of the semi-classical quantum vacuum in 3D

The commissioning of multi-Petawatt laser systems is gathering pace around the world, promising unparalleled access to ultra-high electromagnetic fields for fundamental Physics studies. Here, we present the first real-time three-dimensional simulation results of two quantum vacuum effects using a semi-classical numerical solver for the Heisenberg-Euler Lagrangian. The simulation model is benchmarked against vacuum birefringence analytical results using counter-propagating probe and pump pulses. Simulations of both plane-wave and Gaussian pulses show results consistent with theoretical predictions. The solver is then applied to four-wave mixing using three Gaussian pulses with real-time information on the output pulse for the first time. Results of the polarisation and power of the output pulse and the number of photons obtained from the interaction are obtained and compared with analytical theory based on the plane-wave model. The solver delivers key quantities such as asymmetry in the signal and near-focus field strengths that analytical predictions are unable to resolve. The output power and polarisation dependence on input polarisation is also investigated, and found to be consistent with the theoretical predictions.

Speaker: Ms Zixin Zhang (University of Oxford)

69 First ML-Based Start-to-End Simulation of a Plasma Acceleration Facility integrated into Geant4: PALLAS - laser-plasma accelerator test facility

Plasma acceleration is a groundbreaking technology with applications in accelerator and light source facilities, medical and nuclear physics, and beyond. However, their development and optimization rely on computationally intensive Particle-in-Cell (PIC) simulations, requiring specialized expertise and multiple simulation tools, significantly limiting broader adoption.

Geant4 [1] is a widely used Monte Carlo (MC) simulation toolkit for modeling particle interactions with matter in high-energy, nuclear, accelerator, medical physics and space science. Many Geant4 applications are adaptable for plasma acceleration, which is currently missing in this toolkit.

We present the first integration of a Machine Learning (ML)-based surrogate model [2-3], trained on PIC simulations, into Geant4 as a particle source. This enables the generation and tracking of plasma-accelerated beams within complete experimental setups, unifying plasma acceleration and MC-based simulations. Our implementation focuses on the PALLAS laser-plasma accelerator test facility [4], integrating its full experimental setup into Geant4. We describe the ML model, its integration into Geant4, and key simulation results, demonstrating the feasibility of start-to-end simulations of plasma acceleration applications within a unified framework.

[1] S. Agostinelli et al., NIMA 506, 250-303 (2003).
[2] G. Kane et al. arXiv2408.15845 (2024).
[3] P. Drobniak et al., PRAB 26, 091302 (2023)
[4] https://pallas.ijclab.in2p3.fr/

Speaker: Alexei Sytov (Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara)

70 Laser experimental profiles initialization in PIC simulations

The study of laser-plasma interactions deeply relies on Particle-in-cell (PIC) simulations due to the complexity and the high non-linearity of the physics involved. In this regard, PIC simulations are a powerful instrument in modeling and predicting the outcomes of a Laser Plasma Accelerator experiment. However, the results of this kind of simulations can be profoundly different from the experimental reality because of the initialization of highly idealized laser fields not accounting for the effects of phase aberrations.

In this work, we present the development of a numerical tool to retrieve the phase and rebuild the transverse profile of laser fields from Near Field (NF) and Far Field (FF) fluence measurements to be then automatically initialized in a FBPIC simulation through a properly customized interface
The phase retrieval is based on the Gerchberg-Saxton algorithm, where the reconstruction of fields is obtained with a Fourier-based Fresnel propagator. Main features of Laser Pulse reconstructor For Particle In Cell simulations (LP4PIC) will be shown with some examples and comparisons, also in terms of PIC simulation results.

Speaker: Federico Avella (Istituto Nazionale di Ottica - CNR)

71 Laser-driven very high energy electrons for radiotherapy: beam characterization and radiobiological evaluation

Laser-Plasma Accelerators (LPAs) are emerging as versatile sources for generating ultra-high dose rate beams for radiotherapy research. With ultrashort pulse durations from femtoseconds to nanoseconds, they enable instantaneous dose rates exceeding 10⁹ Gy/s. Their acceleration gradients, surpassing 100 GV/m, allow for the generation of Very High Energy Electron (VHEE) beams (>50 MeV) in a compact setup, overcoming the limitations of conventional linear accelerators. These beams are investigated as a novel radiotherapy modality, offering clinical advantages over photons and protons.

We characterized the LPA at the Laboratoire d’Optique Appliquée, optimizing acceleration conditions for stable VHEE beam delivery (50-100 MeV, 350 mGy/shot, 10 Gy/min average dose rate). To assess the biological effects of LPA-driven VHEE beams, we performed a comparative study against Conventionally Accelerated Electrons (CAE, 7 MeV) across multiple assays: i) in vitro survival of U87 human glioblastoma cells, ii) ex vivo quantification of dividing cells in mouse lung slices, and iii) in vivo growth monitoring of zebrafish embryos post-irradiation.

Results demonstrated that LPA-driven VHEE beams exhibit comparable antitumoral efficacy and toxicity to CAE, supporting their feasibility for radiobiological applications. This work establishes laser-driven VHEE beams as a promising platform for preclinical studies and a viable alternative to conventional electron therapy.

Speaker: Camilla Giaccaglia (Laboratoire d'Optique Appliquée, CNRS, Ecole Polytechnique, Institute Polytechnique de Paris, 921120 Palaiseau, France)

72 Machine Learning techniques for betatron diagnostics in AWAKE Run 2

Following the successful experimental demonstration of proton-driven plasma wakefield acceleration in AWAKE Run 1 (2016-2018), the subsequent Run 2 (2022-) experiment aims to achieve high-quality electron beam acceleration to several-GeV energies, applicable for high-energy physics experiments. Non-invasive betatron diagnostics could play a crucial role in determining key witness beam parameters, such as emittance and beam profile. Betatron radiation (BR) in AWAKE Run 2 has been investigated through simulation studies, demonstrating a synchrotron-like broadband spectrum spanning from UV to X-ray ranges. Here, advanced machine learning (ML) techniques are being explored to reconstruct witness beam parameters from the associated BR. To achieve this, we will generate the dataset using particle-in-cell simulations, conducting a systematic parametric study of the AWAKE configuration by methodically varying the parameters. The witness beam acceleration and its betatron emission are investigated over a 10-meter-long plasma acceleration using the AWAKE baseline parameters. ML models are then trained, validated, and tested for their prediction of beam parameters. Particularly, they will be utilized to explore energy, emittance, and beam profile of the witness beam.

Speaker: Hossein Saberi (University of Manchester)

73 Mid-Infrared Laser Development for High Intensity Experiments

Here we present progress on the high-intensity, short-pulse, multibeam mid-infrared (MIR) OPCPA laser system named Chimera, based at Imperial College London. With a primary beam in the MIR spectral range (centred at 3.7 µm), the system lends itself to an abundance of potential high-field applications and experiments. Largely as a result of the lack of available gain media with the bandwidth to support an ultra-short pulse, Chimera uses a cascaded series of non-linear stages to generate and then amplify MIR light using parametric processes. This system is unique in the UK, and is, at present, one of only a few such systems worldwide.

Now entering into a commissioning and optimisation phase for experimental use, we present preliminary results of its first use in solid high harmonic generation experiments, as well as the plans for a MIR laser wakefield acceleration (LWFA) experiment.

This poster will be highlighting the laser technology, and can be complimented by a talk (if accepted) describing the results of a simulation campaign to plan and understand a future MIR LWFA experiment

Speaker: Annabel Gunn

74 Modeling of axion and electromagnetic fields interaction in particle-in-cell simulations

Axion, a theoretically well-motivated particle, has been searched extensively worldwide via its hypothetical interaction with ordinary matter and fields. Recently, a new axion detection approach has been considered utilizing the ultra-intense electromagnetic (EM) fields produced by laser-plasma interactions. However, a detailed simulation tool is missing in current studies to understand the axion-coupled laser-plasma interactions in such a complex environment. In this paper, we report a custom-developed particle-in-cell (PIC) simulation to incorporate the axion field, the electromagnetic fields, and their interactions. The axion field equation and modified Maxwell's equations are numerically solved, where the axion-induced modulation to the electromagnetic field is treated as the first-order perturbations in order to handle the huge orders of magnitude difference between the two type fields. The simulation has been benchmarked with well-studied effects such as the axion-photon conversion and the propagation of an extremely weak laser pulse in a magnetized plasma. Such an extended PIC simulation provides a powerful tool to study axions under ultra-intense electromagnetic fields in the laboratory or astrophysical processes.

Speaker: Xiangyan An (Tsung-Dao Lee Institute, Shanghai Jiao Tong University, China)

75 Modeling of the electron beam dynamics in an electron beam transport for a laser-plasma accelerator based free-electron laser

Achieving high-quality electron beam is crucial for the next generation Free Electron Laser (FEL) operating in the extreme ultraviolet (EUV) range of the radiation spectrum. In order to transport the laser-plasma-accelerator-based electron bunch without significant degradation in beam quality, the capture block of the electron beamline can be designed using either a set of quadrupole magnets or plasma-based focusing element, known as active plasma lens (APL). In the frame of this presentation, we compare the evolution of the electron bunch for both cases. The initial particle distribution was obtained from laser-plasma interaction code and serves as input for a start-to-end simulation. The obtained results demonstrate the active plasma lens as a suitable device for electron beam capture. Furthermore, the outcomes of the start-to-end simulations will be discussed in order to develop the entire electron beam transport suitable for a compact laser-plasma FEL, which will be developed at ELI-ERIC (ELI Beamlines).

Speaker: Mihail MICESKI

76 Plasma wakefield acceleration of light

Bright, coherent extreme ultraviolet (XUV) light has many important applications across the sciences. Frequency upshifting of an optical laser pulse in the co-moving refractive index gradient of a relativistic phase-velocity plasma wave is one method for producing short wavelengths at high intensity. In particular, beam-driven plasma wakefields can generate arbitrarily high frequency-upshifts of `relativistically intense' light pulses and preserve their spatio-polarization structure. We present some recent theoretical advancements in understanding photon kinetics in plasma wakes. Ab-initio quasi-3D, boosted-frame electromagnetic particle-in-cell simulations show the formation of attosecond duration XUV light with 30-nm wavelengths, nearly flat phase fronts and high pulse-energy. Using only weak focusing with a plasma lens, it may be possible to achieve $10^{23}$ Wcm$^{-2}$ intensities. The use of such XUV laser light in laser-beam collisions at 50 GeV energies would enable studies of the most extreme regimes of strong field QED at the onset of the fully non-perturbative regime. Beam-driven wakefield acceleration of light may provide new applications for intermediate level (~100 GeV) plasma accelerators.

Speaker: Alec Thomas (University of Michigan)

77 Production of C-11 for PET imaging using a HRR laser-driven proton source

In recent years, laser-driven ion accelerators have gained significant interest as an alternative to conventional accelerators. A promising application is the production of radionuclides for medical theragnostics, such as ¹¹C for PET imaging. Currently, these radionuclides are produced in cyclotrons, limiting availability to isotopes with longer lifetime. In this context, compact laser-driven accelerators offer an attractive option for in-situ generation of short-lived isotopes. Although the activities required for PET (>MBq) exceed those achievable from a single laser shot (~kBq), high-power, high-repetition-rate lasers enable continuous production if a suitable target system is developed.
Here, a target assembly based on a rotating wheel and automatic alignment has been designed and commissioned, achieving stable MeV proton acceleration at rates of up to 10 Hz using a 45 TW laser system. Moreover, continuous ¹¹C production via the ¹¹B(p,n)¹¹C reaction was recently demonstrated using the 1 Hz, 1 PW VEGA-3 system (CLPU, Spain), reaching activation levels above 4 MBq. The only current bottleneck to achieving pre-clinical (~10 MBq) PET activities is laser-induced optic heating. Scalability to next-generation laser systems is being explored to assess the feasibility of producing clinical-level (~200 MBq) activities.

Speaker: Alicia Reija (Galician Institute of High Energy Physics (IGFAE))

78 Relativistic Laser-Driven, Highly Collimated MeV Gamma-Ray and Electron Beam Generation in Plasma Cone Channels.

Recent advancements in high-intensity lasers have made all-optical Compton scattering a promising method for generating ultrashort, brilliant $\gamma$-rays in compact systems. However, existing Compton $\gamma$-ray sources are limited by low conversion efficiency and spectral intensity. In this study, we explore overdense electron acceleration and $\gamma$-ray emission through 2D and 3D Particle-In-Cell (PIC) simulations using two setups: one with a hollow-cone plasma channel and one with a standard channel. The hollow cone channel improves laser focusing, resulting in enhanced electron acceleration. Our simulations show a tenfold increase in intensity and a 13$\%$ improvement in the electron conversion efficiency when we used the hollow cone setup instead of the standard channel. This is due to the increase in laser intensity when it is focused using the hollow cone plasma channel, compared to the standard channel setup, where intensity is lower because of the lack of focusing. Additionally, 3D PIC simulations reveal a 8$\%$ improvement in laser-to-electron conversion efficiency with the cone plasma setup. These findings suggest that the hollow cone plasma can serve as an effective optical element to boost laser intensity in petawatt (PW) laser facilities, enabling efficient $\gamma$-ray sources with broad applications.

Speaker: Sachin Chintalwad (William and Mary University , VA, USA)

79 Self-triggered strong-field QED collisions in laser-plasma interaction

Recent progress in laser technology opens new possibilities in high-field science, notably to investigate the largely unexplored strong-field quantum electrodynamics (SFQED) regime where electron-positron pairs can be created directly from light-light or even light-vacuum interactions. Here we propose a new strategy where a single laser pulse is first used to accelerate electrons to high energy using standard LWFA, is self-focused in a high density gas jet, increasing the laser pulse amplitude a0 from 4 to 40 and is then reflected on a plasma mirror eventually colliding with the electrons just behind. This original concept with a plasma-mirror based ICS source and laser intensity booster could be a game changer allowing to reach deep SFQED regime with a simple experimental setup using a single laser and guaranteeing automatic spatial and temporal overlap. We show a start-to-end PIC simulation of this scheme in the case of a laser with 100 J of energy on target and show the strong potential of this scheme, allowing to probe SFQED at chi > 5.

Speaker: Aimé Matheron

80 Synthetic Optical Imaging for Investigating Injection Radiation in Hybrid LPWFAs

We present a synthetic optical imaging plugin for PIConGPU, that enables self-consistent imaging of plasma structures in laser-plasma accelerators. By integrating electromagnetic fields from the PIC simulation and propagating them via Fourier methods onto a virtual screen, we generate synthetic images that resemble experimental measurements. This approach allows direct comparison with experiments, providing insights into plasma dynamics and laser-plasma interactions.

A key focus of the study is an unexplained radiation signal in hybrid LPWFAs employing photo cathode injection. While experimentally observed and significant for timing calibration, its underlying physics remains elusive. Using our synthetic diagnostic, we reproduce this signal in simulations for the first time, linking it to plasma structures and cavity dynamics. By analyzing the images alongside 3D, time-resolved density distributions, we trace the formation of distinct scattering patterns, offering new perspectives on plasma dynamics.

These results highlight the potential of synthetic optical imaging to improve experimental diagnostics in laser-plasma accelerators, such as shadowgraphy, and to deepen our understanding of scattering processes in wakefield acceleration.

Speaker: Finn-Ole Carstens (Helmholtz-Zentrum Dresden - Rossendorf e. V.)

81 Time-resolved betatron imaging of pulsed discharges in water

Liquid-plasma interactions are vital to advancing applications such as plasma water treatment, nanoparticle production, and biomedicine. However, many open questions remain in understanding breakdown mechanisms in liquids, particularly the formation and evolution of plasma structures. Here, we optimized a laser betatron source for single-shot x-ray imaging of nanosecond pulsed discharges in liquids. Nanosecond time-resolved measurements enabled analysis of the size, density and evolution of plasma channels, as well as the formation of instabilities, not observable using conventional optical diagnostics. These measurements provide new insight on electrical breakdown processes in liquids, and highlight the unique capabilities of laser-driven x-rays for dynamic imaging.

Speaker: Amina Hussein

82 Transversely pumped laser driven particle accelerator

We present a new acceleration scheme capable of accelerating electrons and ions in an underdense plasma. Transversely Pumped Acceleration (TPA) uses multiple arrays of counter-propagating laser beamlets that focus onto a central acceleration axis. Tuning the injection timing and the spacing between the adjacent beamlets allows for precise control over the position and velocity of the intersection point of the counter-propagating beam arrays, resulting in an accelerating structure that propagates orthogonal to the direction of laser propagation. We present the theory that sets the injection timing of the incoming pulses to accelerate electrons and ions with a tunable phase velocity plasma wave. Simulation results are also presented which demonstrate 1.2 GeV proton beams accelerated in 3.6 mm of plasma and electron acceleration gradients on the order of 1 TeV/m in a scheme that circumvents dephasing. This work has potential applications as a compact accelerator for medical physics and high energy physics colliders.

Speaker: Tanner Nutting (University of Michigan)

83 Versatile, compact and highly stable OPCPA seeder for modern LPA laser drivers

Laser Wakefield Acceleration is a very promising technology opening new opportunities in modern electron accelerators worldwide. However, this highly nonlinear process requires highly stable laser drivers in order to reach the expected performances to be used in synchrotrons or Free-Electron Lasers. Among the different parameters one has to pay attention to, the temporal and spectral characteristics are one of the critical parameters identified in the community.
We present here a solution based on a unique architecture, providing high performances together with a broad spectral versatility to be used either for TiSa, Yb or OPCPA technologies.
The optical seeder is based on a patented method, using a continuum generation in a dielectric crystal driven by an industrial ultrafast fiber laser followed by a DFG step, followed by a two-stage optical parametric amplifier to reach the µJ energy level, including a SHG to access the 0.7-1.3 µm spectral range.
The measurement at the output of the OPCPA shows a spectrum compatible with 15.8fs, with a central wavelength stability of 0.27nm rms over 16 hours.
This ultra-stable seeder is ready to be integrated in state-of-the-art high intensity lasers used for modern laser-based accelerators.

Speaker: Antoine Courjaud

84 X-Ray Sources for Fast 3D Tomography Using Laser-Plasma Acceleration

The MULTISCAN3D project aims to provide a technical solution to create 3D tomography systems capable of detecting threats invisible with current 2D technology. Laser-plasma acceleration appears to be a promising method to achieve this goal. Indeed, the laser allows generating multiple X-ray sources at low cost in order to perform 3D cargo scanning. Furthermore, laser-plasma acceleration can produce highly charged, low-energy, and highly divergent electron beams, generating X-rays of interest for cargo screening.

For such X-ray sources to be implemented in industrial systems, several challenges need to be overcome. One major issue is the high divergence of the electron beams. While it is an advantage to illuminate large objects, it can also become a drawback when it is too large, as it tends to increase the X-ray source size and reduce image resolution. To address this, we propose using a train of laser pulses instead of a single pulse. Each laser pulse will accelerate electrons in its wake, producing a train of electron bunches that achieve the same overall charge with smaller divergence. We present here the principle of this technique as well as the first results obtained within the framework of the MULTISCAN3D project.

Speaker: Guillaume Chapelant (Thales & LOA)

20:30 Dinner

Wednesday, 16 April

Plenary Session: Plasma Sources

85 Overview of advanced plasma sources for plasma-based particle accelerators

Recent achievements in Laser and Plasma Wakefield Acceleration experiments are driving interest in the scientific community towards the realization of compact and cost-effective plasma-based particle accelerators and light sources.
Research in this field is focused in the optimization of the plasma acceleration mechanism, aimed at improving the quality and stability of accelerated particle beams.
A key role in the efficiency of the acceleration process is played by the plasma source, generating and confining the plasma channels in which the laser or particle driver beams excite strong GV/m-range wakefields, which in turn accelerate the electron witness bunches.
R&D on plasma sources is devoted to the improvement of the plasma stability, uniformity and reproducibility and the realization of m-scale devices able to sustain long-term high repetition rate operation, such as to meet the requirements of light sources and other accelerator applications.
In addition, plasma sources are employed for applications other than particle acceleration, including particle beam focusing and guiding, performed with the so-called Active Plasma Lenses, and guiding of high intensity laser pulses.
This talk presents a summary overview of current solutions and future perspectives about advanced plasma sources for plasma-based particle accelerators.

Speaker: Lucio Crincoli (Istituto Nazionale di Fisica Nucleare)

86 Development of long plasma sources for PWFAs

Plasma wakefield acceleration (PWFA) offers accelerating fields up to two orders of magnitude higher than conventional RF cavities. Achieving TeV-scale electron energies for high-energy physics experiments, however, requires multiple acceleration stages in laser- and electron-driven PWFA schemes.
The AWAKE experiment at CERN explores a proton-driven approach, utilizing the kJ-level energy of proton bunches from the Super Proton Synchrotron (SPS), for single-stage acceleration. A key challenge in scaling this technology is the development of long, highly uniform plasma sources—capable of maintaining electron density uniformity better than 0.25%—to extend acceleration lengths from tens to hundreds of meters.
This talk presents the development and characterization of long plasma sources for PWFA applications. We present results from a 10-meter pulsed-DC discharge plasma source (DPS), designed for scalability, achieving electron densities of 1–30 × 10$^{14}$ cm$^{-3}$ in argon, xenon, and helium. The DPS's performance was assessed in the AWAKE experiment by propagating the 400 GeV proton bunch through the plasma and observing the induced bunch self-modulation, necessary for resonant excitation of a wakefield in the plasma. These results highlight the potential of scalable plasma sources to meet the demands of future plasma wakefield acceleration applications.

Speaker: Carolina Amoedo (CERN)

87 Recent results and R&D opportunities at SCAPA

The Scottish Centre for the Applications of Plasma-based Accelerators (SCAPA) is a state-of-the art research centre dedicated in providing high energy particle beams and next-generation radiation sources for users across all scientific and engineering disciplines. SCAPA, an £8M+ worth of investment of University of Strathclyde and SUPA (Scottish Universities Physics Alliance), houses two high-power (TW level) laser systems and four radiation beamlines. The centre aims to promote collaboration between academia and industry and to provide an avenue for world-class long term research projects. In this talk, I will give an overview of the facility and showcase the capabilities and recent results of each beamline. I will also go through the research and development opportunities for the upcoming new projects of SCAPA.

Speaker: Grace Manahan (SCAPA, University of Strathclyde)

10:40 Coffee Break

Plenary Session: Theory and Simulations

88 Detecting Unruh radiation with full inverse Compton scattering performed at plasma accelerators

The availability of high brightness GeV-class electron beams at EupraXia@LNF makes it the ideal laboratory to explore the Full Inverse Compton Scattering (FICS) process, that has been theoretically predicted but still never experimentally observed. FICS occurs when relativistic electrons of any energy are impinged by photons of 255 keV of energy.
Electrons transfer all their kinetic energy to photons, leading to the most extreme levels of deceleration in the (present) universe, up to 10^30 m/s2. The effect is also related to Unruh radiation photon energies in the MeV range. Thanks to the high brightness of the electron beams available at EupraXia@LNF, the FICS collision luminosity can achieve levels adequate for the generation of a significant rate of FICS events, allowing to possibly detect MeV-class Unruh photons generated in the interaction, together with electron-positron pairs popping out of Dirac's vacuum due to the trespassing of the Schwinger's field limit (10^18 V/m). The modeling of a possible experiment at EupraXia will be presented, aiming at showing the large potentialities of a FICS experiment in addressing strategic and
advanced scientific subjects in fundamental physics.

Speaker: Vittoria Petrillo (Università degli Studi di Milano)

89 Laser and plasma-based compression for mega-amp, ultrashort electron bunches at FACET-II

High-brightness, ultra-high peak current electron beams are of significant interest to applications including high-energy colliders, strong field quantum electrodynamics, and laboratory astrophysics. Despite such interest, compressing tightly-focused electron beams to attosecond pulse durations and mega-amp peak currents while preserving beam quality remains a challenge. In this work, we examine the feasibility and challenges involved in generating such extreme beams using plasma-based compression and laser shaping techniques.

Using simulations, we demonstrate that plasma wakefields enable orders-of-magnitude greater compression than conventional radiofrequency techniques, offering a pathway to achieving unprecedented beam parameters. We examine the scaling of beam properties with accelerator and plasma parameters, identifying the limits on achievable beam brightness and the optimal conditions for different applications. Complementary to these studies, we report on the experimental generation of beams with petawatt peak power at FACET-II, shaped using a laser heater. We demonstrate the on-demand manipulation of the beam’s current profile for triggerable beam-induced ionization in gas targets. Together, these techniques pave the way for the next-generation of high-brightness electron beams.

Speaker: Kelly Swanson (SLAC National Accelerator Laboratory)

90 General theory of the bubble regime

We present the energy-conserving theory of plasma wakefields in the strongly nonlinear "bubble" or "blowout" regime. In this theory, we derive an equation for the bubble boundary based on the energy conservation law. Compared to previous models, this equation precisely characterizes the bubble boundary and the accelerating field across a broad spectrum of driver parameters, including those with small transverse bubble sizes, without relying on fitting parameters. Additionally, our model converges with existing models in cases where the bubble size is sufficiently large. We establish a self-consistent method for describing bubble excitation by both electron drivers and laser drivers based on setting the initial conditions from the analytically calculated quasi-linear solution at the front of the driver. The model’s predictions are validated through 3D PIC simulations, showing excellent agreement.

Speaker: Dr Anton Golovanov (Weizmann Institute of Science)

12:40 Lunch

15:30 Castello Aragonese - Guided tour

19:30 Aperitivo Dinner

Thursday, 17 April

Plenary Session: Diagnostics

91 New methods for reconstructing 3D e-beams structure

Plasma-wakefield accelerators use tabletop equipment to produce relativistic femtosecond electron bunches. Optical and x-ray diagnostics have established that their charge concentrates within a micron-sized volume, but its sub-micron internal distribution, which critically influences gain in free-electron lasers or particle yield in colliders, has proven elusive to characterize. Here, by simultaneously imaging different wavelengths or collecting spectra of coherent optical transition radiation (COTR) that a laser-wakefield-accelerated e-bunch generated when exiting a metal foil, we reveal the structure of the coherently-radiating component of bunch charge. Key features of the images are shown to correlate uniquely with how plasma electrons injected into the wake by either a plasma-density discontinuity, by ionizing high-Z gas-target dopants, or by uncontrolled laser-plasma dynamics. With additional input from electron spectra, spatially-averaged COTR spectra, and particle-in-cell simulations, we reconstruct coherent 3D charge structures. The results demonstrate essential metrology for next-generation compact X-ray free-electron lasers driven by plasma-based accelerators.

Speaker: Dr Maxwell LaBerge (Helmholtz-Zentrum Dresden-Rossendorf)

92 Spectrally resolved wavefront measurement of ultrashort laser pulses

We present a novel and experimentally simple method for measuring the multispectral wavefronts of ultrashort laser pulses. IMPALA, or Iterative Multispectral Phase Analysis for LAsers, relies on only standard optical elements and a pinhole mask, allowing for the extraction and retrieval of multiple monochromatic wavefronts from a single polychromatic intensity image [1]. By algorithmically isolating the contribution of different colors to the measured speckle pattern, IMPALA enables the user to forgo expensive optics and convoluted experimental setups while probing the spatio-spectral behavior of the beam in a single shot. Additional rotations of the mask can be used to improve the spatial resolution of the wavefronts. We conducted proof-of-principle experiments at the Laboratoire d’Optique Appliquée (LOA) using a 30 fs laser. We successfully retrieved the correct amount of pulse front tilt (PFT) introduced in a controlled way by misaligning the compressor. In another experiment, we retrieved the pulse-front curvature (PFC) induced by a lens. With its mask modifications, IMPALA can be optimized for a wide array of ultrashort, high-intensity laser systems. A number of the world’s most powerful and sophisticated laser facilities are working to implement IMPALA as a new diagnostic.
[1] S. Smartsev et al, Opt. Lett. 49, 1900-1903 (2024)

Speaker: Slava Smartsev (Laboratoire d'Optique Appliquée (LOA))

93 All-optical source size and emittance measurements of laser-accelerated electron beams

Recent developments in ultra-low emittance electron beam generation offer compact, high-quality particle sources for future high-energy physics and free-electron laser applications. Measuring such excellent emittances poses a significant challenge.

Here we present a new, laser-based technique which modulates the electron phase-space ponderomotively, achieving sub-0.1 mm mrad emittance resolution. We report the first experimental validation of this approach using a laser wakefield accelerator. Our results are in agreement with emittance and source size values of prior studies using different methods such as quadrupole scans. Additionally, we demonstrate that the "laser-grating" method provides upper limits on emittance and source size, even under conditions of low signal-to-noise ratio and uncertainties in laser-grating parameters.

Speaker: Felipe Salgado (Helmholtz Institute Jena / FSU Jena)

10:40 Coffee Break

Plenary Session: Machine Learning

94 Bayesian approaches to measurement and optimization

This work explores the application of Bayesian methods to enhance measurement and optimization in experimental physics, with a focus on laser-plasma interactions. Bayesian updates enable the integration of prior knowledge with new data, facilitating refined parameter estimation and uncertainty quantification. These methods have been employed to achieve the first single-shot measurement of complete spatio-temporal vector fields, providing a comprehensive characterization of petawatt laser pulses. Additionally, Bayesian Autocorrelation Spectroscopy (BAS) is introduced as an innovative technique for spectral measurements, leveraging prior information for rapid convergence. Finally, Bayesian optimization demonstrates exceptional efficiency in tuning laser wakefield accelerators, enabling precise control over electron beam properties through systematic exploration of parameter space.

Speaker: Andreas Döpp

95 6D phase space reconstruction with generative machine learning

Next-generation accelerator concepts, which hinge on the precise shaping of beam distributions, demand equally precise diagnostic methods capable of reconstructing beam distributions within 6-dimensional phase spaces. However, the characterization of intricate features within 6-dimensional beam distributions using conventional diagnostic techniques necessitates hundreds of measurements, using many hours of valuable beam time. Novel diagnostic techniques are needed to substantially reduce the number of measurements required to reconstruct detailed, high dimensional beam features as feedback in precision beam shaping applications. In this study, we present an approach to analyzing experimental measurements using generative machine learning models of 6-dimensional beam distributions and differentiable beam dynamics simulations. We demonstrate in simulation and experiment that using our analysis technique, conventional beam manipulations and diagnostics can be used to reconstruct detailed 6-dimensional phase space distributions using as few as 20 beam measurements with no prior training or data collection. These developments enable detailed, high dimensional phase space information as online feedback for precision control of beam distributions in advanced accelerator applications and can be used to improve our understanding of complex accelerator beam dynamics.

Speaker: Ryan Roussel (University of California Los Angeles)

96 Short-lived particle acceleration in laser plasma accelerators

Plasma-based accelerators achieve accelerating fields of 10-100 GV/m. While plasma wakefields naturally accelerate electrons due to their near-light-speed motion [1], heavier particles like muons [2] and pions, with lifetimes from microseconds to nanoseconds, struggle to be trapped due to velocity mismatch with the wake.

We use spatio-temporal spectral shaping [3,4,5] to control the group velocity of drive pulses, generating subluminal wakes suitable for slower particles. PIC simulations with OSIRIS [6] show non-relativistic particles accelerating to relativistic speeds. We can extend the dephasing length by tailoring the plasma density profile, which sustains the acceleration process.
This method enables plasma-based acceleration of unstable particles, with applications in cooled muon injection and enhanced muon yield via pion acceleration and decay.

[1] T. Tajima and J. M. Dawson, Physical Review Letters 43, 267 (1979).
[3] K.R. Long, et al., Nature Physics 17, 289–292 (2021).
[4] A. Sainte-Marie et al., Optica 4, 1298-1304 (2017).
[5] Froula, D.H., Turnbull, D., Davies, A.S. et al., Nature Photonics 12, 262–265 (2018).
[6] H. Kondakci, Y. F. Abouraddy, Nature Communications 10, 929 (2019).
[7] R.A. Fonseca et al., Phys. Plasmas Control. Fusion 55, 124011 (2013).

Speaker: Chiara Badiali

12:40 Lunch

Parallel Session: Applications

97 Exploring deep in‑vivo application of laser-driven very-high, energy, wide spectrum electrons

Laser-driven electron acceleration schemes can be easily and reliably used to accelerate electrons in the energy band between 20 MeV and 200 MeV, termed Very-High Energy electrons (VHEE) in medical physics. Such radiation quality is regarded as a candidate for novel radiation therapy schemes, owing to a favorable depth-dose deposition profile and the possibility of reaching very-high dose-rates required by FLASH therapy schemes.
We present the application of a laser-driven VHEE source to systematic irradiation of in-vitro, ex-vivo and in-vivo biological targets, aiming at explore the effects of the laser-driven temporal irradiation modality, calles fast-fractionation. Properties of the laser-driven electron beam (charge, spectrum, stability) will be discussed with an eye on dosimetry and beam caracterization best practices. Relaxation of spectral conditions enable reaching doses as high as 350mGy/shot over 1cm2 target diamter, and a uniform penetration up to 5cm.
The application to in vivo deep irradiation will be presented for the case of whole-thorax irradiation in mice. Passive beam expansion and shaping are used to conform the deposited dose to the target volume, while protecting at-risk organs. Perspectives of laser-driven sources as a tool for exploring the differential toxicity between conventional, FLASH and laser-driven irradiation modalities will be discussed.

Speaker: Alessandro Flacco (LOA/ENSTA)

98 Laser-driven Particle Induced X-Ray Emission for Rapid Real-Time Analysis of Aerosols

We developed a laser-driven Particle Induced X-ray Emission (laser-PIXE) system utilizing compact and high-intensity particle sources to achieve rapid real-time elemental analysis of aerosols. Conventional PIXE techniques rely on large accelerators, limiting their use in on-site and real-time applications. Our study addresses this limitation by leveraging advancements in laser-driven particle acceleration to enable a portable diagnostic tool for environmental monitoring.

We focused on detecting harmful elements in aerosols by directing laser-driven particle beams onto collected samples. Using optimized laser parameters and a compact setup, we analyzed the elemental composition of aerosols in real time without the need for post-collection processing. This approach minimizes delays and logistical challenges associated with traditional methods.

Our results demonstrate significant improvements in the speed and accessibility of PIXE analysis, showcasing its potential as a transformative tool for environmental sciences. This method not only provides rapid diagnostics but also introduces a scalable solution for real-time monitoring of emission gases and aerosols in diverse settings. By integrating advanced laser technology with elemental analysis, we offer a robust strategy to address current challenges in aerosol diagnostics and environmental monitoring.

Speaker: Ms Canan Yağmur Boynukara (Sapienza University of Rome)

99 The E332 experiment at FACET-II: first experimental demonstration of beam self-focusing in electron beam - multifoil collisions

When an electron bunch passes through a conducting foil, its self-fields are reflected at the foil surface, also known as Near-Field Coherent Transition Radiation (NF-CTR) resulting in a focusing effect for the electron beam. Passing through multiple foils may allow to focus the electron beam down to solid densities and generate collimated gamma-rays with micrometer source sizes and conversion efficiencies exceeding 10% [Sampath et al., PRL 126, 064801 (2021)]. The possibility offered by this scheme to self-focus high-energy beams and generate extremely dense gamma-ray beams calls for an experimental demonstration.
For the first time we show experimental results of this very strong focusing effect on the electron beam passing through a “multi-foil” target. The unprecedented beam parameters available at the FACET-II accelerator facility allows for high statistics data taking and high precision measurements. We show the experimental results of the beam focusing effect when varying the number of foils, the beam waist position, looking at the beam size and divergence and comparing with PIC simulations of realistic electron beam passing through the multifoil target. Eventually we present the first experimental results of this new focusing process using a laser-plasma accelerated electron beam at the APOLLON laser facility.

Speaker: Aimé Matheron

100 Bright solid high harmonic generation on GEMINI PW: unlocking a pathway to SF-QED

For over twenty years high harmonic generation from the interaction between a relativistic laser pulse and solid target (SHHG) has been heralded as a realistic route to the Schwinger limit, the electromagnetic field intensity at which SF-QED effects can be probed in vacuum. Despite extensive simulation campaigns and the development of theoretical models of increasing sophistication, experimental evidence has been plagued by poor conversion efficiencies, typically producing XUV beams of micro-Joules of energy with no successful SHHG experiments on fs PW class lasers until now. Here we present our recent results from the PW class Gemini laser system, demonstrating bright harmonic production in the XUV range. Through analysis of numerical simulation and experimental data, evidence for why it worked is presented and to highlight the key parameters requiring attention to unlock this pathway in extreme field physics.

Speaker: Robin Timmis (University of Oxford)

Parallel Session: Secondary Radiation Source

101 Laser plasma wakefield based axion generation and detection

Axion and axion-like particle are the candidates of dark matter. In the current theoretical frame, they can couple with the electromagetic fields and convert to photons and vice versa. We proprosed a scheme to generate axions in a plasma bubble structure driven by two intense laser pulses. One pulse drives a nonlinear bubble wake in a plasma and the other propagates inside the bubble. The axions are generated through during the interaction between the trailor pulse and the wakefields. The axions can also generate perturbative electromagenetic fields at the same time. By analyzing the output EM fields, we give an evaluation of the axion-photon coupling strength. We use an axion inculded particle-in-cell code to study the process. The code will be introduced in another talk during this conference.

Speaker: Prof. Min Chen (Shanghai Jiao Tong university)

102 Commissioning results of the hard X-ray betatron source at ELI Beamlines

We present the results achieved during the commissioning of the ELI Gammatron beamline, a femtosecond hard X-ray betatron source based on laser wakefield acceleration driven by the petawatt-class L3 laser system (10 J, 27 fs, 3.3 Hz) at ELI Beamlines. Leveraging the small pointing and energy fluctuations of the laser system, we have successfully demonstrated laser wakefield acceleration of shot-to-shot reproducible quasi-monoenergetic electron beams exceeding 1 GeV. Adjusting the position of the gas jet, we have found a regime of strong transverse electron oscillations and a stable betatron X-ray signal. A broadband synchrotron-like energy spectrum was measured using Ross filter pairs and a single-photon counting CCD, with approximately $10^{10}$ photons per shot at critical energy of 14 keV, with beam divergence of about 15 mrad. Finally, we demonstrated the viability of the X-ray source for applications through phase-contrast imaging of polymer samples and a biological specimen, at large contrast-to-noise ratios.

Speaker: Marcel Lamač (ELI Beamlines)

103 Ultrashort pulse X-ray absorption spectroscopy using laser-plasma accelerators

Laser-plasma accelerators now regularly achieve GeV electron energies in laboratory-scale facilities, enabling new research opportunities. One significant application is the generation of ultrashort (few femtoseconds) X-rays through betatron electron oscillations. These broadband pulses are ideal for X-ray absorption spectroscopy (XAS), particularly XANES (X-ray Absorption Near Edge Structure) and EXAFS (Extended X-ray Absorption Fine Structure) spectroscopy, which provide valuable insights into the temperature and structure of a samples electronic and ionic distributions simultaneously.
Current multi-100 TW laser systems can achieve single-shot XAS measurements, with $>10^6$ photons/eV per shot [1], in the few to 10 keV range. It is predicted that PW class systems will increase this flux by an order of magnitude, and the photon energies to >100 keV, allowing high-Z elements to be probed. Given that these high-flux, broadband, femtosecond X-ray sources can be synchronised with other high-power lasers, this offers new possibilities for studying ultrafast energetic processes. Moreover, increasing repetition rate demonstrates the potential for developing high-quality laboratory-scale XAS facilities, reducing dependence on large-scale synchrotrons.

[1] B. Kettle et al. Communications Physics 7, 247 (2024).

Speaker: Brendan Kettle (Imperial College London)

104 Thomson scattering for producing spatiotemporal optical vortices

Accurate representation of electromagnetic wave packets in particle-in-cell simulations is crucial for ensuring that the outcomes closely align with experimental results. Conventional methods for laser injection rely on the paraxial and envelope approximations, effective for beams that are both long and wide with respect to the laser's wavelength. However, new laser systems are advancing towards shorter pulse durations (down to single-cycle) and more focused spot sizes (near or at the diffraction limit), enabling higher intensities. Under these new conditions, the assumptions underlying the said approximations break.

Here, we propose an exact injection method tailored for arbitrarily shaped lasers in particle-in-cell codes that exactly satisfies Maxwell’s equations without any approximation. It allows injecting pulses based on the outputs of standard experimental diagnostics (e.g., spectrum and spectral phase measurements), and is ideal to inject structured light pulses with spatiotemporal couplings.

We employ this novel technique to show that the interaction of electron bunches with intense structured lasers in nonlinear Thomson scattering can be used to control the spatiotemporal structure of the resulting radiation. As an example, we use this approach to convert orbital angular momentum (OAM) into transverse optical angular momentum (TOAM), thereby creating spatiotemporal optical vortices (STOV) in nonlinear Thomson scattering.

Speaker: Rafael Almeida (GoLP / Instituto de Plasmas e Fusão Nuclear Instituto Superior Técnico, Lisbon, Portugal)

105 Plasma Density Shaping for Enhanced Electron Beam Control and Brilliant X-ray Generation in Laser Wakefield Acceleration

Energy gain in laser wakefield accelerators is limited by dephasing, and the resulting electron beams often exhibit high divergence, posing challenges for transport and applications. We experimentally demonstrate that tailoring the plasma density profile can mitigate both limitations. Using shock-assisted ionization injection, we generate quasi-monoenergetic 100 MeV electron bunches. A subsequent, independently tunable plasma density region enables controlled energy enhancement or divergence reduction, yielding a 25% energy boost and 40% divergence reduction. Furthermore, electron bunches focused within a dense, passive plasma lens emit X-ray pulses with divergences approaching the incoherent limit. This facilitates the development of highly collimated, brilliant, few-femtosecond X-ray sources for ultrafast science.

Speaker: Olle Lundh (Lund University)

16:40 Coffee Break

Parallel Session: Diagnostics and Plasma Sources

106 Development of gas targets for various laser-plasma experiments

Various laser-plasma experiments, including those in laboratory astrophysics, particle acceleration, plasma physics, and X-ray generation, require advanced gas target technology—a system capable of delivering gas with a precisely defined density profile within a high-vacuum environment. The performance of particle beams and radiation in these experiments is highly sensitive to the optimal density profile established in the gas target. In this work, we present the development of supersonic gas jet targets designed for high-intensity, ultra-short laser pulses operating at high repetition rates (3.3 Hz at GeV, 1 kHz at 10s MeV)[1]. Hydrodynamic simulations of neutral gas flow were employed to build the design of these targets. The density profiles were characterized through tomography[2] before the experiment and ultra-fast post-compressed probe diagnostics during the experiment[3]. We explore conical and slit supersonic nozzles, along with multi-stage target configurations, tailored for specific experimental needs. Additionally, we introduce a novel supersonic gas jet catcher, developed for differential pumping in laser-plasma interaction experiments. To enhance the stability and reproducibility of the laser-plasma interactions, the targets are optimized for continuous-flow operation.

[1] Lazzarini et al., Phys Plasmas 2024, https://doi.org/10.1063/5.0189051
[2] Karatodorov et al., Sci Rep 2021, https://doi.org/10.1038/s41598-021-94436-6
[3] Lorenz et al., HPLSE 2024, https://doi.org/10.1017/hpl.2024.29

Speaker: Dr Sebastian Lorenz (The Extreme Light Infrastructure ERIC)

107 Development of a High-Sensitivity Wavefront Sensor for KALDERA

At DESY, we are developing KALDERA, a high-repetition-rate laser system designed to enable active stabilization of laser-plasma acceleration through fast feedback systems. A critical step in this process is accurately measuring how variations in laser parameters affect the electron beam properties, with particular emphasis on the wavefront due to its significant influence on the acceleration process. However, commercially available wavefront sensors typically lack the sensitivity and acquisition rates required for our application. To address this limitation, we have developed a custom Shack-Hartmann wavefront sensor capable of measuring rapid wavefront variations with high precision. In this talk, we will review our design and implementation process, highlight development challenges, and present first measurements with the new sensor.

Speaker: Luisa Niggemeier (DESY)

108 Characterization and recent results of the LWFA driven COXINEL FEL

This presentation summarizes recent progress made by the HZDR-Soleil collaboration on seeded free-electron-laser performance with the COXINEL line operated at HZDR's laser plasma electron accelerator.
Following the first demonstration of lasing [1], tuning range and output spectrum were studied [2], while a careful analysis of the shape of the interference pattern of seed and FEL light revealed novel insight into the FEL process.
Progress in the control of the LWFA stage in particular in increasing the spectral charge density to 10 pC/MeV (350 pC FWHM at ~200 MeV) recently enabled to boost FEL output to pulse energies of up to 50 nJ, close to expectations for the given undulator geometry, encouraging future scaling to shorter wavelength.
[1] M. Labat, et al., Nature Photonics 17, 150 (2023)
[1] M. Labat, et al., PRAB in press (2025)

Speaker: Ulrich Schramm (Helmholtz-Zentrum Dresden-Rossendorf)

109 Diagnosing a metre-scale plasma discharge for plasma wakefield acceleration

In order to reach higher energies, next generation plasma accelerators will use multi-meter plasma technology. Many applications will also require high repetition rates to obtain high average fluxes comparable to conventional radiofrequency accelerators. These long-scale plasmas are not trivial to produce due to the very high power requirements for gas ionisation.

We present the construction and diagnosis of a 1 m argon discharge plasma cell designed as a source for plasma wakefield accelerator experiments. By implementing an all solid-state high voltage power supply and switch, an arc discharge plasma with currents up to 350 A was produced using voltages up to 9 kV at repetition rates up to 2 Hz. The plasma was diagnosed using plasma emission spectroscopy and temporally-resolved longitudinal interferometry. The source achieved plasma densities in the range 10^20 – 10^21 m^-3, which are suitable for PWFA applications.

Speaker: Claudia Cobo (Imperial College London)

110 Compact high-resolution multi-GeV electron spectrometer for PW-laser-driven plasma accelerators

We report the design and performance of a compact magnetic spectrometer tailored to unique characteristics of quasi-monoenergetic, multi-GeV electron bunches from petawatt-laser-driven wakefield accelerators: mrad-level shot-to-shot pointing fluctuations, co-generation of betatron X-rays and of background electrons with a broad energy spectrum. The spectrometer replaces the first screen of a standard two-screen spectrometer with an array of thin, precisely-located, high-Z wires distributed throughout, and perpendicular to, the magnet’s dispersion plane. The thin, sharply-bounded shadows that they cast on betatron X-ray and electron signals enable determination of > 10 GeV electron energies and launch angles with few-% precision using a ∼ 1 T dipole magnetic field of ∼ 10 cm dimensions. Perturbations to the electron signals caused by hybrid acceleration mechanisms or inserted foils are also shown to be resolvable.

Speaker: Xiantao Cheng (Shanghai Jiaotong Unversity)

Parallel Session: Machine Learning, Theory and Simulations

111 Exascale simulations of laser plasma accelerators with PIConGPU

Exascale simulation capabalities are now available for studying laser plasma accelerators using realistic laser and plasma descriptions and providing quantitative predictions. We present recent advances in modeling LPA at large scales for both electron and ion acceleration. We specifically discuss workflows for comparison to experiments and evaluate predictive capabilities. The role of reliable simulation data for the community and its use to ease modeling using machine learning will be discussed.

Speaker: Richard Pausch (Helmholtz-Zentrum Dresden - Rossendorf)

112 e-e+ plasma generation and dynamics in laser interaction with solid-state target

New laser facilities will reach intensities of 1023 Wcm−2. In these setups with extreme fields, quantum electrodynamic (QED) effects become important. We study high-intensity lasers grazing the surface of a solid-state target by two-dimensional particle-in-cell simulations with QED effects included. The two laser beams collide at the target surface at a grazing angle. Due to the fields near the target surface, electrons are extracted and accelerated. Finally, the extracted electrons collide with the counter-propagating laser, which triggers many QED effects and leads to a QED cascade under a sufficient laser intensity. Here, the processes are studied for various laser intensities and angle of incidence and finally compared with a seeded vacuum cascade. Our results show that the proposed target can yield many orders of magnitude more secondary particles and develop a QED cascade at lower laser intensities than the seeded vacuum alone [1].
At even higher laser intensities, 1024 Wcm−2, the created e-e+ plasma may reach solid densities and exhibit collective behavior [2].

[1] M. Filipovic and A. Pukhov Eur. Phys. J. D (2022) 76:187 (2022)
[2] A. Samsonov and A. Pukhov, https://arxiv.org/pdf/2409.09131 (2024)

Speaker: Prof. Alexander Pukhov (uni duesseldorf)

113 Data-Driven Control and Optimization of High Repetition Rate Laser-Plasma Accelerators

The emergence of high-power laser systems approaching kilohertz repetition rates presents both a challenge and an opportunity for the next generation of laser-plasma accelerators (LPAs). The vast amount of data generated at these high repetition rates opens the door to novel, data-driven approaches for improving stability, beam quality, and reliability—critical steps toward making LPAs viable for real-world applications.

In this talk, we present recent developments at DESY’s Kaldera project, focusing on real-time data acquisition and processing strategies tailored for high-rep-rate operation. We explore how this data forms the foundation for advanced optimization techniques, enabling closed-loop feedback control and providing deeper insights into the complex dynamics of laser-plasma acceleration. By leveraging machine learning, real-time diagnostics, and intelligent control systems, we outline a path toward more robust and efficient laser-plasma acceleration.

Speaker: Sören Jalas

114 Simulating relativistic beam-plasma instabilities with the quasistatic PIC code QuaSSis

Quasistatic particle-in-cell (QSPIC) codes[1] are increasingly used to study laser or plasma wakefield accelerators. QSPIC codes decouple the slow evolution of a beam from the fast response of a plasma, which reduces the computational cost by several orders of magnitude compared with conventional PIC codes. In this presentation, we demonstrate the potential of the QSPIC method to investigate relativistic beam-plasma instabilities[2].

QuaSSis, a new QSPIC code, is first employed to simulate the oblique two-stream instability (OTSI) arising during the propagation of μm-scale, 10 GeV electron beams through a collisionless plasma. Its predictions are validated against the PIC code CALDER[3]. We then describe a new numerical scheme adapted to periodic transverse boundary conditions, which simulates transversely infinite beams, the results of which can be compared with an analytical spatiotemporal model for the OTSI[4]. Finally, we discuss how the initial noise, intrinsic to the PIC method can be controlled in QSPIC simulations to ensure reliable predictions of instability growth rates and saturation levels.

[1]P. Mora et al., Phys. Plasmas 4, 217 (1997).
[2]A. Bret et al, Phys. Plasmas 17, 120501 (2010).
[3]E. Lefebvre et al., Nucl. Fusion 43, 629 (2003).
[4]P. San Miguel Claveria et al., Phys. Rev. Res. 4, 023085 (2022).

Speaker: Quentin Labro (CEA/DAM/DIF)

115 Muon beams with plasma accelerators: challenges and applications

We discuss generation and acceleration of muon beams in the 500 GeV - 1 TeV energy range via staged plasma accelerators, in view of a relevant example concerning geological investigations, with request on beam intensity and phase space quality very adapt to a pilot experiment with a hybrid plasma accelerator à la EupraXia@LNF. Unlike muon beams for muon colliders, the applications foreseen in the geo-science sector are much less demanding in terms of beam performances, making it and ideal opportunity for compact plasma accelerators, with sizes and costs significantly smaller than conventional ones for the energy range under discussion.

Speaker: Luca Serafini (Istituto Nazionale di Fisica Nucleare)

20:30 Social Dinner

Friday, 18 April

Plenary Session: Laser Technology

116 The road map towards high repetition rate laser systems

The road map towards high repetition rate laser systems

Speaker: Leonida Antonio Gizzi (Consiglio Nazionale delle Ricerche - Istituto Nazionale di Ottica)

117 Coherent combination of high-power fiber lasers for laser-plasma-based collider applications

Laser-plasma accelerators have great potential to be compact and economic to enable future colliders up to 10 TeV. Such colliders couple many plasma accelerator stages, each requiring a ultrafast laser driver with multi-Joule pulse energy and tens-of-kHz rep-rate, i.e., hundred-kW-class average power. Tens-of-percent wall-plug efficiency is also required. Current ultrashort laser technologies, e.g., Ti:Sapphire systems with pulse energies up to 100-Joule class and rep-rates up to a few Hertz, are limited by thermal handling and wall-plug efficiency and do not scale to the collider driver parameters.

Fiber lasers are the most efficient high-average power laser technology demonstrated to date, and novel coherently-combined (in space, time, and spectrum) fiber lasers are considered one of the most promising solutions that are energy/power scalable to the collider laser driver parameters. Tremendous progress has been made on demonstrating the principles and sub-scale systems of the scalable, coherently-combined, ultrafast fiber laser technology. In the near- to mid-term, tens of kW systems will be available to drive laser-plasma accelerators, and an R&D path has been identified to achieve hundreds of kW laser driver systems for colliders.

This work is a collaboration between LBNL, Univ. of Michigan, and LLNL, supported by DOE, DARPA, and Moore Foundation.

Speaker: Tong Zhou (Lawrence Berkeley National Laboratory)

118 Plasma Transmission Gratings for Compression of High-Intensity Laser Pulses

Future laser-driven plasma accelerators will require femtosecond-pulsed lasers that can deliver high peak powers at high repetition rates, posing significant challenges for current laser technology. Replacing key components in high-power lasers with plasma alternatives allows the manipulation of high-intensity beams and the construction of compact and damage-resistant laser systems. Here we discuss methods for building chirped-pulse-amplification lasers using plasma gratings and diffractive optics. We present experimental measurements of plasma grating performance and optical properties, including dispersion and diffraction efficiency, and show the constraints that achievable plasma optic properties place on the design of next-generation lasers.

Speaker: Matthew Edwards (Stanford University)

10:40 Coffee Break

Plenary Session: Facilities

119 Staus of the EuPRAXIA project

The EuPRAXIA project (European Plasma Research Accelerator with Excellence in Applications) aims to develop advanced plasma-based accelerator technologies to create compact, high-performance particle accelerators. The EuPRAXIA@SPARC_LAB facility is the beam driven pillar of the EuPRAXIA project which is expected to provide by the end of 2029 the first European Research Infrastructure dedicated to demonstrating usability of plasma accelerators delivering high brightness beams up to 1-5 GeV for users.

One of the primary goals of EuPRAXIA@SPARC_LAB is to develop a short-wavelength Free Electron Laser (FEL) that can generate radiation in the "water window" of the electromagnetic spectrum, which is useful for biophysical research. Additionally, an X-ray radiation source based on betatron radiation is set to be implemented by the end of 2025 as part of the PNRR initiatives. The production of high-quality electron beams, essential for driving an FEL, is also expected to play a crucial role in advancing the development of a plasma-driven future Linear Collider (LC).

In this presentation, we highlight the progress of the EuPRAXIA collaboration, with a particular focus on the EuPRAXIA@SPARC_LAB pillar, for which we are in the process of drafting the Technical Design Report.

Speaker: Anna Giribono (Istituto Nazionale di Fisica Nucleare)

120 The Extreme Photonics Applications Centre (EPAC)

Over the past decade, laser systems capable of delivering extremely high power at high repetition rates have been developed. These developments now enable acceleration of charged particles to near-light speeds in a very compact plasma channel – a few centimetres as opposed to kilometres required in a conventional accelerator. This technology is now considered "mature enough" for driving super-bright energetic radiation and particle sources for applications cutting across a multitude of areas in society; facilities are being designed and constructed based on this technology. I will talk about a new facility coming up in the UK based on this – the Extreme Photonics Applications Centre (EPAC). EPAC will host a Petawatt laser running at 10Hz, driving plasma accelerators producing high-energy particle and x-ray beams for fundamental science and applications in a multitude of areas – from industry, biology & medicine to security and defence. We will give an overview of the facility, describing the latest developments and future directions of EPAC.

Speaker: Rajeev Pattathil (Rutherford Appleton Laboratory)

121 The ELI Beamlines Scientific Programme

The ELI Beamlines Facility is a key pillar of the Extreme Light Infrastructure (ELI) ERIC. ELI Beamlines has developed and operates four state-of-the-art femtosecond laser systems, delivering both high peak and high average power. The facility provides a unique combination of primary (lasers) and secondary (high-energy particle and X-ray) sources.
Laser-driven particle accelerators have gained significant interest due to their cost-effectiveness, versatility and innovative characteristics. This has driven the development of beamlines that allow users to harness the unique parameters of laser-driven particle accelerators—such as ultrashort bunch duration and ultrahigh dose rates—as well as laser-driven photon sources for a broad spectrum of applications.
The presentation will provide an overview of the current performance of particle and photon sources available at the ELI Beamlines user facility, along with their applications in multidisciplinary research. This also includes the combination of optical, X-ray, and particle beams for high-energy-density physics experiments, including research related to inertial confinement fusion. The unique capabilities of laser beam will also be discussed. Furthermore, the high repetition-rate capabilities of both primary and secondary sources will be highlighted, in conjunction with advanced target delivery solutions and diagnostics designed for extreme laser-plasma conditions (>10²¹ W/cm² at >1 Hz).

Speaker: Dr Daniele Margarone (The Extreme Light Infrastructure ERIC - ELI Beamlines Facility)

12:40 Lunch

Plenary Session: Facilities

122 The Plasma Injector for PETRA IV: Conceptual Design Report

We present the conceptual design of an alternative injector system based on laser-plasma accelerator technology, to deliver high-quality electron bunches to PETRA IV – the future 4th generation synchrotron light source at DESY. The design consists of a laser-plasma accelerator to produce electron bunches at 6 GeV with state-of-the-art energy spread and stability (∼1%), and an X-band energy compressor beamline to further reduce the overall beam energy deviations down to a sub-permille level, thus maximizing the charge injection throughput into the PETRA IV storage ring. Driven by the Petawatt upgrade of DESY’s new flagship laser KALDERA, the plasma injector system can be used to top up the PETRA IV storage ring, significantly lowering the load on the RF injector chain. Ultimately, upon further development of high-efficiency, high-power laser drivers that operate at high repetition rates, the plasma injector could replace the RF-based system in the future to reduce the spatial footprint and energetic cost of the whole injector complex.

Speaker: Alberto Martinez de la Ossa (DESY)

123 Energy Compression of a Laser-Plasma Accelerator

Laser-Plasma accelerators (LPAs) promise a compact alternative to modern RF-technology, and support orders of magnitude higher electric fields. GeV-energy LPA electron beams from cm-scale sources have been demonstrated. The intrinsically short scale of the accelerating structure features femtosecond-long beams with kA peak current, but at the same time makes precise control of the beam properties a challenge. In particular, the central energy jitter and energy spread, both on the percent-level, have so far prevented LPAs to drive real-world applications.

Here, we present active energy compression of a laser-plasma accelerated electron beam.
At the LUX experiment at DESY, a dipole chicane stretches the beams in time and thereby imprints an energy-time correlation (a chirp), which is subsequently removed inside a RF cavity. Our setup reduces the fluctuation in central energy as well as the energy spread of the beams by more than an order of magnitude down to the permille-level.
The achieved performance-level – so far only attributed to modern RF based accelerators – opens the door for a variety of applications, such as compact plasma-based injectors for synchrotron storage rings.

Speaker: Paul Winkler (DESY)

Parallel Session: Facilities

124 Laser-plasma accelerator-based free-electron laser program at ELI Beamlines (ELI ERIC)

The laser-plasma accelerator-based Free Electron Laser development program at ELI-ERIC (ELI Beamlines, Czech Republic) aims to utilize the unique properties of plasma accelerators to create compact FELs with exceptional performance regarding brightness, coherence, and pulse duration. The program is based on the advanced high-power, high-repetition-rate L2-DUHA laser system developed at ELI Beamlines. This program involves extending the LUIS experimental setup to test and validate the performance of the laser-plasma accelerator-based extreme ultraviolet (EUV) free electron laser (FEL), integrating high-power laser, plasma source, and electron beam transport line with relevant diagnostics to create a comprehensive test bed for the EuPRAXIA LPA-based soft X-ray FEL development. The mitigation of the main challenges will be discussed in the framework of this report. The potential integration of the LPA-based soft X-ray FEL setup into the existing infrastructure of the ELI Beamlines Facility will be presented. The laser-plasma accelerator-based FEL development program at ELI Beamlines represents an innovative effort to enhance the capabilities of ELI Beamlines as a user-oriented European Facility, thereby opening new possibilities for scientific research and industrial applications.

Speaker: Dr Alexander Molodozhentsev (ELI-Beamlines)

125 Laser Wakefield Acceleration Experiments on the ZEUS Facility

The Zettawatt Equivalent Ultrashort Pulse Laser System (ZEUS) is a user facility funded by the National Science Foundation and located at the University of Michigan in the US. ZEUS consists of a repetitive dual-beamline 3 PW laser system, a programmable multi-nanosecond pulse driver capable of delivering 100 J of energy, and three experimental areas with radiation shielding. It offers unique capabilities for studying fields such as nonlinear quantum electrodynamics, relativistic plasmas, particle acceleration, extreme laboratory astrophysics, and nuclear photonics. This presentation will provide an update on the progress of the ZEUS facility's performance, including the laser, target areas, and radiation shielding. It will also discuss the results of the initial commissioning experiments on multi-GeV laser wakefield electron acceleration and betatron radiation generation at the 1 PW level.

Speaker: Karl Krushelnick (University of Michigan/Laboratoire d'Optique Appliquee)

126 Lifetime of beam-driven wakes at FACET-II

The time for stationary plasma to recover its original state after a wake is excited determines repetition rate and luminosity of plasma-based colliders. Recent measurements at DESY [1] showed that an argon plasma of density ne≈$10^{16}$cm$^{−3}$ in which a 0.5J(0.5nC,1GeV) e-bunch excited a first wake supported excitation of a second wake at the same location with indistinguishable beam properties within 60ns; in [2] a similar study was carried out in hydrogen plasmas. We report 2024 results at SLAC's FACET-II facility where 20J(2nC,10GeV) e-bunches excited meter-long nonlinear wakes in stationary lithium, hydrogen, and argon plasmas of density ne≈10$^{16}$cm$^{−3}$. Shallow angle optical probing (~100fs, ~1˚) was used to study wakefield remnants at delays 1ns≲∆t≲10$\mu$s. In lithium plasma, probe scatter remained visible out to ∆t≈2$\mu$s. Probe signal persisted up to ∆t≈100ns and ∆t≈300 ns, in hydrogen and argon plasmas, respectively. Bessel beam interferometry revealed nonzero phase shift out to (and possibly beyond) ∆t≈10$\mu$s in argon wakes. The results will be discussed considering findings of experiment E-224 [3], which showed that ion motion dominated energy transport out of the beam-excited region for ∆t≳0.3ns.

[1]R.D’Arcy et al., Nature 603, 58-62(2022).
[2]R.Pompili et al., Commun Phys 7, 241(2024).
[3]R.Zgadzaj et al., Nat Commun 11, 4753(2020).

Speaker: Jason Brooks (The University of Texas at Austin)

127 Fully synchronized high repetition rate Petawatt laser driver for betatron beamline on EuPRAXIA@SparcLab machine

Precise synchronization plays a major role in the stability of an accelerator-based light source, or for ultrafast dynamics studies. We will present our strategy and recent achievements applied to synchronize a kHz Ti:Sa ultrafast laser to a Terawatt Yb ultrafast laser. We report on the synchronization at few fs rms level, both on short-term and long-term.
We first synchronize the slave oscillator (Yb) to the master oscillator (TiSa) using an optical cross-correlator. The fast actuator in the slave oscillator compensates for the fast and slow timing fluctuations, leading to 5fs rms relative timing jitter.
Additionally, we implement a second optical cross-correlator placed at the outputs of both amplifiers, measuring the relative jitter and drift between the 2 amplification. A motorized fibered optical delay line is used to compensate for the slow drift between both amplifiers, with a long-term stability of 16fs rms over 8 hours.
We will discuss on the limitations and improvement perspectives of such solution, and identify how this technique can be applied to a high repetition rate Petawatt laser driver of the betatron beamline installed on Eupraxia@SparcLab machine.

Speaker: Antoine Courjaud

Parallel Session: Laser Technology

128 Status of the KALDERA drive-laser development for a next generation high repetition rate laser plasma accelerator

During recent years DESY has strengthened its effort to evolve laser plasma acceleration technology from demonstration experiments towards reliably running machines. In this framework we develop the Ti:Sapphire based drive-laser KALDERA which is supposed to deliver up to kHz repetition rates at more than 100 TW of peak power in its final phase. Since current drive-lasers operate at the low Hz-level, this new system finally supports fast active stabilization which is key to also directly improve the LPA’s electron stability that is required to run a facility.
In this presentation we will report on the completion of our first development phase: our laser is currently generating 750 mJ of pulse energy at 100 Hz repetition rate and has been operated over weeks. We will discuss crucial technological challenges that had to be mastered during the development and highlight special features of this unique laser system. Moreover, we will show the latest results from the pulse compression campaign where an MLD-grating compressor based on an out-of-plane geometry is utilized to reach down to the 30 fs-regime. Finally, we will comment on the next development phases and status to further scale the average power of the KALDERA laser towards the kW-range.

Speaker: Dr Guido Palmer (Deutsches Elektronen-Synchrotron DESY)

129 High average power laser plasma acceleration at DESY

Laser-plasma acceleration (LPA) is a promising technology for future compact accelerators. However, the low repetition rate (typically few Hz) of today’s high-power laser systems prevents reaching the average power required by applications and hinders the implementation of fast feedback systems to mitigate beam instabilities. To this end, DESY has established a dedicated research program on high-average power LPA. Our flagship project KALDERA pursues the development of a new laser tailored to plasma acceleration. Based on Ti:Sa technology, the system will deliver pulses at 100 TW peak power at up to 1 kHz repetition rate and by that enable the application of active stabilisation techniques to enhance LPA performance. Here, we report on the development of MAGMA, the first LPA that will be powered by KALDERA. We also introduce the BEETLE project which explores the use of post-compressed Yb-lasers as future alternative to scale the average power of LPA even further.

Speaker: Dr Manuel Kirchen (Deutsches Elektronen-Synchrotron)

130 Development of the L2-DUHA dual output front end at ELI-ERIC

The 100 TW DPSSL-OPCPA L2-DUHA laser system is under development at ELI-ERIC, with the goal of being the driver for the Laser Plasma Accelerator (LPA) of the LUIS-beamline, an incoherent Extreme Ultraviolet (EUV) radiation setup under development at ELI-ERIC, aiming to produce the high-quality electron beam required for a LPA-based Free Electron Laser (FEL).

The L2-DUHA broadband front-end is based on a 2kHz Yb:YAG thin disk regenerative amplifier-pumped OPCPA seeded by a supercontinuum. It will provide a 1mJ near Infrared (NIR) beam for seeding a high energy OPCPA chain, which will be used as the driver for the laser-plasma accelerator in the LUIS-beamline. In addition, a multi-mJ, synchronized mid IR auxiliary beam for high harmonic generation is under development. Both outputs are generated via supercontinuum in YAG crystals and are passing through pre-amplification OPA stages using Barium Borate (BBO) crystals.

In this presentation, we present the first characterization of the dual output L2-DUHA broadband front-end.

Speaker: Alex Johannes Whitehead (ELI-Beamlines)

131 High repetition rate TiSa lasers for laser plasma acceleration

There is a growing interest of using Laser Plasma Acceleration (LPA) for societal applications provided that particle flux is large enough to fulfill the needs of those applications. This calls for the use of lasers with higher pulse repetition rate than the lasers used up to now in laser plasma acceleration research. In this talk, we present the achievements and the technology roadmap related to 100 Hz Titanium Sapphire Chirped Pulse Amplifiers. In particular we present initial results obtained from a full system delivering 200 mJ compressed pulses and results from main technology developments regarding the significant increase of average power obtained from TiSa based laser system which will be based on disk active mirror amplifiers strongly reducing lensing effects at room temperature and actively cooled gratings compressors. These technical breakthroughs will be used for 1 J – 100 Hz lasers currently under construction for LAPLACE HC project in France and EuAPPS project in Italy, the latter aiming specifically to the investigation of LPA potential use for cancer therapy using VHEE (Very High Energy Electrons). Beyond that, this is also paving the way for developments needed to build the laser system of laser-driven machine for EuPRAXIA project.

Speaker: Vincent Leroux (Thales LAS France)

16:50 Coffee Break

Plenary Session: Facilities

132 Sub 1% energy spread and sub 5 micron emittance, high current electron beams with energies up to 26 GeV with a transformer ratio of greater than 2.

Next-generation free-electron laser-based coherent light sources and future particle colliders at the energy frontier demand high brightness, high energy electron beams that must have a sub-one percent energy spread and low emittance. Realizing such beams in practice using an ultrahigh gradient plasma accelerator remains a vexing challenge. Here we report the results of a Plasma Wakefield Accelerator campaign, at the newly commissioned FACET-II facility at SLAC National Accelerator Laboratory, that self-generates a much lower-emittance trailing bunch with energies of up to 26 GeV and sub-1% energy spread and less than 5 micron normalized transverse emittance by utilizing a novel yet simple plasma platform that utilizes down ramp self-injection in the wake followed by acceleration in a >1 m long plasma wake created in a lower density hydrogen gas. During the wakefield acceleration process the much of the charge in the 10 GeV drive is fully energy depleted while the injected bunch containing up to 25 pC charge is accelerated from rest to more than twice the initial energy of the drive beam. This places a lower bound on the transformer ratio of greater than 2.6. PIC simulations indicate that the nonlinear wake was underloaded and that there is room for

Speakers: Chan Joshi, Chandrashekhar Joshi (UCLA)

Dawson Prize

20:30 Dinner

Saturday, 19 April

09:00 Departure