7th international workshop on new Photon-Detectors (PD2025)

2 Dec 2025, 16:00 → 6 Dec 2025, 19:00 Europe/Rome

Auditorium Enzo Biagi (Bologna, Italy)

Luigi Pio Rignanese (Istituto Nazionale di Fisica Nucleare), Roberto Preghenella (Istituto Nazionale di Fisica Nucleare)

Overview

The 7th international workshop on new Photon-Detectors (PD2025) is jointly organised by the Bologna division of the Italian National Institute for Nuclear Physics (INFN Bologna, Italy) and the Department of Physics and Astronomy of the University of Bologna (DIFA UniBo, Italy). The workshop will focus on recent progress and developments in photosensor technologies, including SiPMs, MCPs, APDs, PMTs, hybrid PMTs, digital photosensors and new materials. It will also explore the broad range of applications for these devices in fields such as particle and astroparticle physics, nuclear physics, nuclear medicine, astronomy, and related instrumentation. The programme will feature plenary sessions with both invited and contributed talks, as well as a dedicated poster session.

Scientific Program

The PD2025 Workshop will cover a broad range of topics reflecting the latest developments and challenges in photon-detector science. The scientific programme is structured around three main thematic areas

• Application Areas — showcasing the diverse fields where photon detectors play a key role, from fundamental physics to societal impact.
• Photosensor Technologies — focusing on the design, development, and characterisation of current and emerging photodetector types.
• Enabling Technologies and Related Topics — highlighting cross-disciplinary innovations that support performance, integration, and future advances.

These represent the core themes of the workshop and outline the scope of discussions and presentations that will shape PD2025.

The scientific programme will consist of plenary sessions featuring both invited and contributed talks, as well as a dedicated exhibitor’s session and a poster session designed to foster interaction and collaboration, particularly among young researchers.

The workshop proceedings will be published on JINST.

 

Invited Speakers

• Florian Brunbauer, CERN (Switzerland)
• Edoardo Charbon, EPFL (Switzerland)
• Serge Charlebois, University of Sherbrooke (Canada)

• Gianfranca De Rosa, INFN Napoli (Italy)

• Silvia Gambetta, University of Edinburgh (UK)
• Erika Garutti, University of Hamburg (Germany)
• Inés Gil Botella, CIEMAT (Spain)
• Alberto Gola, FBK (Italy)
• Alexander Kiselev, BNL (USA)
• Boris Korzh, University of Geneva (Switzerland)
• Jon Lapington, University of Leicester (UK)
• Albert Lehmann, University of Erlangen-Nürnberg (Germany)
• Werner Riegler, CERN (Switerland)
• Angelo Rivetti, INFN Torino (Italy)
• Dennis R. Schaart, TU Delft (Netherlands)
• Paul Sellin, University of Surrey (UK)

Exhibitors

• Giuseppe Brizi, Hamamatsu Photonics Italia (Italy)
• Alexey Lyashenko, Incom Inc. (USA)
• Dmitry Orlov, Photonis Netherlands (Netherlands)
• Alessandro Cortopassi, CAEN Spa (Italy)

Programme Overview

Sponsors and exhibitors

Organised by

First Bulletin

Poster

Preliminary Agenda

Scientific Tracks

Second Bulletin

Tuesday 2 December

17:00 → 18:00 Visit to INFN Laboratories

18:00 → 19:00 Aperitivo at INFN Laboratories

Wednesday 3 December

08:00 → 09:00 Registration

09:00 → 09:30 Opening Session

09:00 Welcome from the Workshop Organisers

Speaker: Roberto Preghenella (Istituto Nazionale di Fisica Nucleare)

09:05 Welcome from the Director of the INFN Division of Bologna

Speaker: Eugenio Scapparone (Istituto Nazionale di Fisica Nucleare)

09:10 Welcome from the Director of the Department of Physics and Astronomy of the University of Bologna

Speaker: Andrea Cimatti

09:15 Workshop Organisation Details

Speaker: Luigi Pio Rignanese (Istituto Nazionale di Fisica Nucleare)

09:30 → 10:30 Plenary Session

Convener: Ezio Torassa (Istituto Nazionale di Fisica Nucleare)

09:30 Radiation damage in Silicon Photomultipliers

Speaker: Erika Garutti

09:55 Radiation damage studies of silicon photomultipliers for the CMS MIP Timing Detector

Recently developed 15 um, 20 um, 25 um and 30 um cell size Hamamatsu were irradiated with reactor neutrons at JSI (Ljubljana) up to 2×1014 n/cm^2 (1 MeV equivalent). The parameters of new and irradiated SiPMs were studied using pulsed light illumination. The effects of the neutron radiation on breakdown voltage, signal amplitude, dark current and noise for these devices are shown and discussed.

Speaker: Yuri Musienko (University of Notre Dame (US))

10:13 Effect of Increased DCR on the Detection of Minimum Ionizing Particles with SiPMs

Radiation damage to a silicon photomultiplier (SiPM), as occurs during the lifetime of the planned HGCAL detector, increases the dark current and degrades the signal to noise (S/N) separation and thus the minimum ionizing particles (MIP) detection efficiency. To investigate this, a system consisting of a plastic scintillator tile directly coupled to a SiPM is used to detect the MIP from a $^{90}\mathrm{Sr}$ source. The design of the single channel is similar to the tiles for the CMS HGCAL calorimeter upgrade. A key novelty of this study lies in the comparative approach to emulate radiation damage. In particular, the effects of true radiation-induced damage were compared with a method that increases the dark count rate ($\mathit{DCR}$) exclusively through DC light illumination. Crucially, this second approach does not induce any physical structural damage or introduce trapping centers relevant for after pulse. These properties are inherently absent in the purely optical method. This allows the isolation of the effect of increased $\mathit{DCR}$ as the primary factor degrading the SiPM response. Our results show that an increase in the $\mathit{DCR}$, regardless of whether it was induced by irradiation or DC illumination, leads to an identical reduction in the MIP response and the S/N ratio. This confirms that the dominant factor for the performance degradation is the increased $\mathit{DCR}$ value itself and not additional damage or defects introduced in the silicon. The $\mathit{DCR}$ range investigated in this study extends from $\sim 10\,\text{kHz}$ before irradiation to $\sim 10\,\text{GHz}$ for the highest fluence of $5\times10^{13}\,\text{cm}^{-2}$ at an overvoltage of $2-4\,\text{V}$ and a temperature of $-20\,^\circ\text{C}$. This corresponds to a reduction of the signal down to $\sim 1-2\,\%$ of the initial response and an increase of the noise by a factor $\sim 20-25$ for the maximum fluence. The same results are obtained in SiPMs irradiated using reactor neutrons and fresh SiPMs illuminated by DC triggered LED light. This study highlights a significant insight: the primary consequence of radiation damage on SiPMs can be effectively mimicked under laboratory settings using optical illumination to increase the $\mathit{DCR}$. Such an approach enables accurate assessment of performance degradation and thus offers a powerful tool for the characterization of SiPMs and strategies for mitigating radiation damage.

Speaker: Katjana Neumann (Universitaet Hamburg)

10:30 → 11:00 Coffee Break

11:00 → 12:45 Plenary Session

Convener: Roberta Cardinale (Istituto Nazionale di Fisica Nucleare)

11:00 Radiation Hardness Chacterisation of Silicon Photomultipliers for Next-Generation Particle Identification Detectors

Background:
Ring Imaging Cherenkov (RICH) detectors are indispensable for particle identification in experiments such as LHCb and Belle II, including their planned high-luminosity upgrades. These systems require photon sensors that combine high detection efficiency, precise timing, and robustness in magnetic fields. Silicon photomultipliers (SiPMs) meet these criteria due to their compactness, high gain, and sub-100 ps single-photon time resolution. Their main limitation, however, is sensitivity to neutron irradiation, which alters device properties and leads to sharply increased dark count rates (DCR), thereby threatening long-term stability in harsh radiation environments.
Methods:
A broad set of SiPMs from multiple manufacturers — including SensL, Hamamatsu, Ketek, FBK, Advansid, and Broadcom — were irradiated at the TRIGA nuclear reactor of the Jožef Stefan Institute to fluences between 10⁹ and 10¹³ neq/cm², covering the range expected in future RICH detectors. Characterisation was carried out before and after irradiation using:
• current–voltage (I–V) and capacitance–voltage (C–V) scans,
• dark count rate (DCR) measurements,
• single-photon timing resolution (SPTR) studies, and
• determination of full depletion voltage from C–V curves.
Measurements were performed across a wide temperature range (+20 °C to −180 °C) with a stabilised cryogenic setup. Post-irradiation annealing at elevated temperatures was also conducted to assess the potential recovery of performance.
Results:
The presentation will cover:
• Design of the irradiation and characterisation campaign,
• Experimental results for multiple SiPMs, including I–V, C–V, DCR, depletion voltage, and SPTR performance across fluences.
Neutron irradiation shifted the depletion voltage and altered the internal electric field, impacting key operating parameters. Breakdown voltage increased, leakage currents rose, and the DCR degraded significantly. Despite these effects, timing performance was robust: whenever single photons could be resolved, the SPTR remained ~90 ps FWHM, even after exposure up to 10¹³ neq/cm².
Room-temperature operation became unfeasible beyond 10¹⁰ neq/cm², but cooling successfully mitigated radiation-induced degradation. At 10¹² neq/cm², stable operation was possible around −140 °C, while at 10¹³ neq/cm², functionality was only recovered at liquid-nitrogen temperature. Annealing partially reduced leakage currents and DCR, typically lowering the cooling requirement by ~20 °C, but did not restore room-temperature performance or further improve timing.
Conclusions:
This study provides essential benchmarks for the integration of SiPMs into next-generation RICH detectors at the HL-LHC and Belle II upgrades. It demonstrates that neutron damage alters electric field and operating parameters — increasing breakdown voltage, shifting depletion voltage, and raising DCR — yet excellent timing precision is preserved with appropriate cooling. By testing devices from various major manufacturers, this work highlights both the common challenges and the feasibility of using SiPMs as fast photon detectors in high-radiation environments.

Speaker: Boris Gardinovački (Institute Jožef Stefan)

11:18 Photon detectors at the frontiers of particle identification

Speaker: Silvia Gambetta (University of Edinburgh)

11:43 The ALICE 3 RICH detector: prototype beam test results

In the context of the ALICE 3 upgrade planned for LHC Run 5, a proximity-focusing Ring-Imaging Cherenkov (RICH) detector for charged particle identification is foreseen. It uses aerogel with a refractive index of 1.03 as the Cherenkov radiator and a photodetector surface based on Silicon Photomultiplier (SiPM) arrays. To improve charged-particle timing, the integration of a thin, high-refractive-index window is being explored. This window, which is glued directly onto the SiPM arrays, acts as a secondary Cherenkov radiator resulting in a localized cluster of fired SiPMs around the particle's impact point.
Starting from 2022, we assembled various prototypes mounting 2 cm thick aerogel tiles and instrumented with various Hamamatsu SiPM array sensors, coupled with various window materials. The readout chain with the front-end electronics was based on both Petiroc 2A and Radioroc 2 complemented by a picoTDC ASIC. With this configuration, we measured π/K separation power better than 3σ up to 10 GeV, with a single-photon angular resolution below 4 mrad at Cherenkov angle saturation and more than 20 photoelectrons per ring over the full acceptance. In addition, we measured a charged-particle timing resolution better than 70 ps with a detection efficiency larger than 99%.
This contribution focuses on the current R&D status of the ALICE 3 RICH detector and the beam test results obtained with the latest prototype.

Speaker: Mario Nicola Mazziotta (Istituto Nazionale di Fisica Nucleare)

12:01 Photodetectors in the EIC instrumentation strategy

Speaker: Alexander Kiselev (Brookhaven National Laboratory)

12:26 Ultra-Fast Small-Angle Calorimeter for Photon Detection at KOTO II

The next-generation KOTO II experiment at J-PARC will operate at significantly higher beam intensities than its predecessor, requiring detector upgrades to maintain the stringent background suppression necessary for the search for ultra-rare $K_L \to \pi^0 \nu \bar{\nu}$ decay. One of the most critical components is the beam-hole photon veto (BHPV), which must efficiently detect the two photons from the $\pi^0$ emitted at small angles while maintaining high discrimination power against accidental coincidences from beam-induced backgrounds. The lead–aerogel Cherenkov counter previously employed in KOTO has demonstrated excellent performance; however, its timing capabilities and radiation hardness represent limiting factors for the demanding KOTO II conditions [1]
To address these challenges, we developed a novel, compact small-angle calorimeter (SAC) featuring fine granularity, excellent timing resolution, and robust radiation tolerance. The calorimeter is based on ultrafast lead tungstate (PWO-UF) crystals, complemented by radiation-hard photomultipliers optimized for operation in a high-rate and high-radiation environment. The use of PWO-UF crystals provides several key advantages: fast scintillation response, high density for compact shower containment, and intrinsic radiation resistance [2]. Moreover, the high segmentation of the SAC design enhances spatial resolution and allows effective neutron–photon discrimination, reducing false vetoes and improving overall detection efficiency.
Extensive R&D has been carried out on crystal properties and readout technologies, and dedicated test campaigns with both PWO-UF and PbF₂ samples have confirmed high photoelectron yields and sub-nanosecond timing performance, making them suitable candidates for the fast response required in the KOTO II beam environment [3].
In August 2025, we carried out a dedicated beam test of the SAC prototype at CERN T9, which included arrays of full-size PWO-UF crystals read out with different types of fast photomultipliers. In particular, we tested Hamamatsu R9880 and R14755 miniature metal-channel PMTs, which demonstrated excellent timing capabilities. Complementary to the beam campaign, the crystals were characterized at the University of Ferrara using X-ray diffraction (XRD). This allowed us to determine their crystallographic orientation with respect to the beam axis and to exploit coherent effects of charged particles traversing aligned crystals [4]. The resulting measurements provided valuable insights into both the energy response and the timing characteristics of the SAC under conditions where coherent effects may influence light production, improving the timing performance.
This contribution presents an overview of the prototype R&D and the first beam-test results obtained with oriented PWO-UF crystals and advanced ultra-fast PMTs.

[1] J.Fry, et. al., Proposal of the KOTO II experiment, arXiv:2501.14827
[2] M. Korzhik et al., NIMA, 1034 (2022) 166781
[3] D.Paesani, et. al., Front. Phys. 11:1223183.
[4] L.Bandiera, et. al., NIMA 936 (2019) 124–126

Speaker: Pierluigi Fedeli (Istituto Nazionale di Fisica Nucleare)

12:45 → 14:00 Lunch Break

14:00 → 16:00 Plenary Session

14:00 Photodector and Scintillator Development for the LHCb PicoCal

To operate at Run-5 luminosities $(\,1.5 × 10^{34}\,\,\mathrm{cm}^{−2} \,\mathrm{s}^{−1}\,)$, the LHCb electromagnetic calorimeter is being upgraded to PicoCal, which requires radiation-tolerant materials and fast timing to mitigate pile-up and spillover. The inner regions of the PicoCal will adopt a Spaghetti Calorimeter (SpaCal) design, based on scintillating fibres (polystyrene or garnet crystals) embedded in dense absorbers (lead or tungsten). Current R\&D focuses on the joint selection of suitable fibres and fast photomultiplier tubes (PMTs). Organic fibres must combine fast scintillation kinetics (decay time $\tau_d \lesssim 8$ ns, rise time $\tau_r \lesssim 1$ ns), light yields exceeding 6000 photons/MeV, and radiation tolerance up to at least 200 kGy. PMTs' integrity and characteristics, especially window transparency, must not be degraded under radiation up to 1 MGy.

We report on a coordinated R&D programme that encompasses photomultiplier-tube (PMT) performance studies and the characterisation of plastic-scintillator samples produced by the Institute for Scintillation Materials (ISMA, Ukraine) within the Eurizon Fellowship Programme.

On the photodetector side, we conducted extended ageing studies of fast PMTs for the tungsten SpaCal readout, focusing on the Hamamatsu R9880U-20 and R14744U-100, and carried out an irradiation campaign at CERN IRRAD that also included the R7600. These campaigns quantify the evolution of PMT gain and photocathode quantum efficiency under high integrated anode charge (up to ≈1000 C). Complementary test-beam measurements with SpaCal prototypes at the CERN SPS and at DESY confirm that the considered PMTs are suitable to meet the design timing requirements.

In parallel, we screened and characterised plastic-scintillator samples from ISMA for fast rise/decay kinetics, high light yield, transmission, emission and absorption spectra, and spectral compatibility with PMT photocathodes. Following high-dose proton irradiation at CERN IRRAD, the samples exhibited promising optical and timing performance, supporting fibre production for further characterisation.

Speaker: Julie Delenne (CERN)

14:18 Requirements for Digital SiPMs in fibre sampling dual-readout calorimeter at future lepton colliders

Dual-readout calorimetry is one of the technologies of interest for the next generation of leptonic colliders such as FCC-ee. By simultaneously detecting scintillation and Cherenkov signals, it promises a jet energy resolution of ≈3–4% at 90 GeV and represents the baseline solution within the IDEA detector concept. The HiDRa (Highly Granular Dual-Readout Calorimeter) demonstrator represents an important step towards a modular and cost-effective solution designed to meet the stringent 4π geometry requirements of collider experiments. Part of the demonstrator has been instrumented with Silicon Photomultipliers (SiPMs) enabling fine transversal segmentation. This approach offers improved calorimetric performance along with compatibility with particle-flow-like algorithms.

Extensive simulations, supported by several beam tests at the CERN SPS have demonstrated encouraging results. At the same time, they underlined the importance of the equalization and calibration of the readout chain in the highly granular modules (nearly 10,000 SiPMs to be equalized). This aspect may represent a potential bottleneck when scaling to the more than 50 million channels foreseen in a full detector geometry.

To address these challenges, a dedicated R&D program has been launched to design a custom SPAD array in 110 nm CMOS technology (ASPIDES), specifically tailored to the requirements of the fibre-sampling dual-readout calorimeter. The project aims to go beyond the SiPM by providing digital outputs (i.e. number of cells fired and timing information) capable to guarantee the performance required by the detector. In this respect, it is crucial to investigate the impact of the spurious effects (i.e. dark counts and cross talks) which are expected to be more pronounced than those observed with SiPMs.

This contribution will review the readout and calibration strategies developed for the HiDRa prototype, summarize the lessons learned from recent beam tests, and define the key requirements that the next generation of digital SiPMs will need to meet. Finally, we will illustrate how these requirements are being implemented in the ASPIDES development, paving the way for a scalable solution for dual-readout calorimetry at future lepton colliders.

Speaker: Romualdo Santoro (Istituto Nazionale di Fisica Nucleare)

14:36 Pushing analog SiPM performance: innovations and custom solutions

Speaker: Alberto Giacomo Gola (Istituto Nazionale di Fisica Nucleare)

15:01 3D-integrated SPAD-CMOS detector systems

Speaker: Serge Charlebois (Université de Sherbrooke)

15:26 First Application of Photon-to-Digital Counters to Particle Physics

Photon-to-Digital Converters (PDCs), or digital SiPMs, are a new generation of single-photon sensors that overcome the intrinsic limitations of conventional analog SiPMs. By digitizing the output of individual SPADs directly on-chip, PDCs eliminate the need for amplification chains and external ADCs, while providing excellent timing resolution, wide dynamic range, simplified data processing, and channel masking to disable noisy SPADs, reducing baseline noise. We report on the first application of PDC technology to particle physics applications, with proof-of-concept studies in calorimetry and tracking. Using realistic detector conditions, we evaluate the potential of PDCs to improve performance compared to traditional SiPM-based readout. These results demonstrate how these vertical-integrated PDCs can address key challenges in large-scale instrumentation and pave the way for their integration in next-generation high-energy physics experiments.

Speaker: Brais Palmeiro Pazos (University of Manchester)

15:44 Advanced Single Photon Detectors by 3D-Integration of ultra-low noise SPADs

Single Avalanche Photo Diodes (SPADs) have gained significant traction across diverse fields such as medical imaging, quantum communication, and time-of-flight measurements, including LiDAR (Light Detection and Ranging). This naturally extends to applications in fundamental research, where single photon detection, low noise characteristics, and superior timing resolution are key.
An optimized design and process flow was developed in a specialized 350 nm CMOS technology, yielding SPADs with extremely low Dark Count Rates [1].
Combining this with a novel technology for 3D integration using direct bonding of 8” wafers and customized through-silicon vias, we can achieve a highly compact and integrated combination of low-noise, backside-illuminated (BSI) SPADs with circuits fabricated in standard CMOS technologies. This was successfully demonstrated for applications in LiDAR and quantum imaging [2].
With this BSI approach, we demonstrate how additional techniques in post-CMOS processing can be leveraged to enhance the detection probability and efficiency in application specific spectral regions and thus optimize the performance for various applications in photon detection.

[1] S. Grosse, S. Dreiner, J. Hauser, D. Weiler, M. Ligges, P. vom Stein, S. Weyers : Ultra-low noise SPADs in 350 nm CMOS technology for Cherenkov radiation detection in particle and astrophysics In: XI International Workshop on Ring Imaging Cherenkov Detectors
[2] Grosse, Simon; Steuer, Andrei; Vom Stein, Peter; Zeidler, Christopher; Haase, Jan F.: A 64 x 48 BSI SPAD sensor based on 8‘‘ wafer 3D stacking technology. In: Sensor and Measurement Science International (SMSI) 2021. Wunstorf: AMA Service GmbH, 2021, B10.1: pp.167 - 168.

Speaker: Mr Peter vom Stein (Fraunhofer IMS)

16:00 → 16:30 Tea Break

16:30 → 17:30 Plenary Session

Convener: Prof. Peter Fischer (Heidelberg University)

16:30 CMOS SPADs and digital single-photon imaging sensors

Speaker: Edoardo Charbon

16:55 When will digital SiPMs become available for physics?

17:30 → 19:00 Exhibitors Talks

19:00 → 20:30 Poster Session

19:00 → 20:30 Welcome Reception

Thursday 4 December

08:30 → 10:30 Plenary Session

Convener: Rok Pestotnik

08:30 Microlense enhanced SiPMs

Our group performs R&D to improve the scintillating fibre tracker technology
(SciFi tracker) in general with the goal of transferring the technology to
large-scale projects, for example, the LHCb Upgrade II SciFi
Tracker. One of the key elements are the silicon photomultiplier
(SiPM) photodetectors. In order to overcome the challenges imposed by radiation
and low material budget, we are constantly evaluating and improving the
photodetectors. We found that the enhancement of the SiPM with pixel-level
microlenses significantly improves the effective photon-detection efficiency as
well as the single-photon time resolution. The external crosstalk is aligned
with the expectations from the geometry of the optical system.
The choice of the ideal SiPM pixel size for the SciFi Tracker is a compromise
between the high geometrical fill factor (GFF) and the resulting high photon
detection efficiency (PDE) for large pixels and the manifold disadvantages
resulting from the large pixel size, such as high gain and therefore higher
correlated noise, longer recovery time, lower dynamic range, and higher bias
current. Adding the radiation environment as an additional criterion, a low
excess bias voltage (overvoltage, $\Delta V$) is preferred to reduce the effect
of increasing the dark count rate (DCR) and correlated noise, as low DCR and low
correlated noise allow low noise rejection thresholds. In summary, small pixel
size and low $\Delta V$ are advantageous in all aspects except PDE.
In the presentation we will present an update on our current understanding of
the very promising development.

Speaker: Guido Haefeli (EPFL)

08:48 Innovative Back-Side Illuminated SiPMs (BSI-SiPMs): first results from the IBIS project

INFN, in collaboration with FBK (Fondazione Bruno Kessler), is developing a novel type of Silicon Photomultiplier (SiPM) — the Back-Side Illuminated (BSI) SiPM — within the framework of the IBIS and IBIS_NEXT projects (Innovative Back-Side Illuminated SiPMs). This new sensor architecture introduces a clear separation between the charge collection and multiplication regions of the device, enabling the implementation of a charge-focusing mechanism. This approach offers several key advantages: a near-100% fill factor even for devices with small microcells, significantly enhanced sensitivity down to vacuum ultraviolet (VUV) wavelengths through optimised surface treatments, improved radiation hardness thanks to a reduced high-field region, and simplified integration with readout electronics via bump bonding, as all electrical contacts are located on the same side of the sensor.

The BSI SiPM technology is particularly well suited for experiments employing the Cherenkov technique — such as the ePIC experiment at the EIC — and for future upgrades of ALICE 3 and LHCb. It is also highly promising for noble liquid detectors — such as DUNE — and paves the way towards high resolution imaging with SiPMs in several other applications.

We present the first results from characterisation studies of prototype sensors from the IBIS RUN 1, fabricated by FBK with single-photon avalanche diode (SPAD) pitches ranging from 15 μm to 35 μm. Detailed preliminary measurements of key performance parameters — carried out in dark conditions, within a climatic chamber, and at cryogenic temperatures (77 K) — will be reported.

Speaker: Priyanka Kachru (FBK)

09:06 Development of UV-Sensitive GaN Single Photon Geiger-Mode avalanche diodes

Silicon photomultipliers (SiPMs) had a transformational impact on experiments in high-energy and astrophysics. However, the SiPM is intrinsically limited in its response below 300 nm, a critical wavelength range for liquid noble scintillation detectors. We investigate AlGaN and GaN semiconductors, which have a tunable band gap and better sensitivity in the UV. With the availability of clean enough substrates, we successfully fabricated single GaN photodiodes and demonstrated UV sensitivity and Geiger-mode operation. I will give a status update and present results from our latest devices fabricated this year.

Speaker: Nepomuk Otte (Georgia Institute of Technology)

09:24 A Digital SiPM for Photon Multiplicity Measurement operated with a Compact USB Readout

We present a Digital SiPM sensor chip which measures photon multiplicities at a rate of $\gtrsim10\mathrm{\,MHz}$, which has been fabricated using the $350\mathrm{\,nm}$ technology of the Fraunhofer IMS (Duisburg, Germany). The demonstrator chip contains a matrix of $27\times24$ pixels with SPADs of $\approx2400\mathrm{\,mm}^2$ size. Photon hits in the SPADs occurring during an externally controlled accumulation time window are transferred to shift registers at the end of the interval. They are clocked out from the pixel matrix and counted digitally in the chip periphery while a new accumulation takes place. The digital counts are transferred off-chip serially with the possibility to daisy chain multiple chips, so that larger modules can be build with no increase in the number of required digital signals. A possible application of this chip is photon detection in the NEXT experiment which searches for neutrinoless double-beta decays.
A very compact USB interface has been developed to control and read out this and similar chips in test environments. A PCB of only $3\times 6\mathrm{\,cm}^2$ size contains a Hi-Speed USB interface, an FPGA and the programmable generation of two supply voltages and of the SPAD bias voltage, including current monitoring. All voltages are derived from the power delivered by the USB-C
connector, so that no further equipment is required. The Digital SiPM chip is connected to the interface via a single high speed flat cable containing 8 fast differential signals, 7 CMOS signals, 2 programmable supply voltages (for the chip and auxiliary circuity) and the SPAD bias. All digital signals can be programmed as output or input in the FPGA.
We will describe the chip architecture, the compact USB readout and present measurements taken with this setup.

Speaker: Prof. Peter Fischer (Heidelberg University)

09:42 Time resolution and efficiency of SPADs and SiPMs

Speaker: Werner Riegler (CERN)

10:07 Enabling photon detection: the role of ASICs

Speaker: Angelo Rivetti (Istituto Nazionale di Fisica Nucleare)

10:30 → 11:00 Coffee Break

11:00 → 12:45 Plenary Session

Convener: Angelo Rivetti (Istituto Nazionale di Fisica Nucleare)

11:00 ALCOR, a mixed-signal ASIC for SiPM readout of the ePIC-dRICH detector at the EIC

ALCOR is a mixed-signal ASIC developed for the readout of silicon photomultiplier (SiPM) sensors in the ePIC dual-radiator RICH (dRICH) detector at the future Electron-Ion Collider (EIC). The current design integrates 32 channels in an 8x4 pixel array, providing high-precision timestamping with single-photon sensitivity, data-push architecture and fully digital output. Each channel features an analog front-end compatible with both signal polarities, comprising a low-impedance input stage, four selectable gain settings, and two leading-edge discriminators with independent 6-bit DAC thresholds. Precise timing is achieved by quad-buffered, low-power TDCs with analog interpolation and 25–50 ps time bin. Additional operating modes, including time-over-threshold and slew-rate, provide indirect amplitude measurements and effective time-walk correction. The power consumption of the full channel is 12 mW with default settings.

Fabricated in 110 nm CMOS technology, ALCOR has been thoroughly validated in standalone operation and coupled with multiple SiPM models. Laboratory tests using single-photon laser pulses and HPK S13360 devices demonstrated an overall time resolution below 150 ps RMS. Two beam test campaigns at CERN-PS in 2023 and 2024, employing a dRICH prototype instrumented with 2048 3x3 mm$^{2}$ SiPMs read out by ALCOR, confirmed its suitability for ring-imaging and particle-identification. A new version of the ASIC, named ALCOR-64, was designed and submitted for fabrication in April 2025. This version doubles the channel count to 64, integrates the ASIC in a ball grid array package and addresses specific EIC-driven requirements, including a programmable-width hardware shutter to inhibit events digitization and thus suppress the SiPM out-of-time DCR-induced background.

The presentation will describe the main building blocks and features of ALCOR, highlight the key performance results from electrical characterization and beam tests, and discuss the new functionalities implemented in the novel version specifically designed for the ePIC dRICH detector.

Speaker: Fabio Cossio (Istituto Nazionale di Fisica Nucleare)

11:18 A first photon detector module based on the FastRICH ASIC

The FastRICH is a novel front-end ASIC developed for single-photon detectors in future RICH systems and targeting the upgrades of the LHCb experiment. With 24.4 ps TDC time bins, the ASIC allows for precise time-of-arrival measurements of photons in order to improve particle identification, especially in the high-multiplicity environment of the High-Luminosity LHC. The 16-channel FastRICH includes constant-fraction discrimination, on-chip time gating to suppress background, and a data-driven output format. It supports configurable data rates from 320 Mb/s to 5.12 Gb/s, addressing non-uniform hit rates across the detector. A wide input dynamic range allows coupling to various photon sensors, such as SiPMs and vacuum-based devices. The power consumption is measured to be around 12 mW/channel at 1.2 V. Fabricated in 65 nm CMOS, it includes triplication of sensitive logic for radiation tolerance. A prototype compact single-photon detector module has been assembled, integrating the FastRICH with the CERN lpGBT and VTRx+ optical link chipset. Beam tests with Cherenkov photons are foreseen at the CERN PS/SPS charged particle beam facility in autumn 2025. Initial performance results will be presented, along with details of the module integration and its role in the upgrades of the LHCb RICH system.

Speaker: Floris Keizer (CERN)

11:36 FastIC+ ASIC, a high-performance scalable solution for fast-timing applications

Silicon photomultipliers (SiPMs), with their compact form factor, high gain, and fast response, are enabling a new generation of fast-timing detectors across several fields and applications. Scaling up these systems requires readout electronics that combine high performance, low power consumption and dense integration. We present FastIC+, a custom ASIC developed for fast-timing applications, capable of processing and digitizing signals from SiPMs or other high-gain photodetectors (e.g., photomultiplier tubes, microchannel plates) with a power consumption of ~12 mW/channel. FastIC+ integrates a Time-to-Digital Converter (TDC) with 25 ps binning and achieves a time jitter of ~30 ps FWHM.

We evaluated FastIC+ performance in two different applications: Positron Emission Tomography (PET) and Time-of-Flight Mass Spectrometry (TOFMS). In PET, we reported—for the first time—a coincidence time resolution below 100 ps using full-ASIC readout. Modular readout solutions for 64 and 256 channels are under development to enable their use in next-generation PET systems. In TOFMS, we presented the first successful use of SiPM arrays read out by individual TDCs to acquire mass spectra from known samples. We show that a detector based on SiPMs and FastIC+ can achieve sub-100 ps time resolution, outperforming current state-of-the-art TOFMS detectors. These results illustrate the potential of FastIC+ as a versatile technology for high-precision timing applications across multiple domains.

Speaker: Dr Daniel Guberman (Insitut de Ciencies del Cosmos, Universitat de Barcelona (ICCUB))

11:54 Photodetectors in medical applications

Speaker: Dennis Schaart (Delft University of Technology)

12:19 High-Performance Planar TOF-PET Imager

Background:
Positron emission tomography (PET) is one of the most powerful tools in modern medical imaging, enabling accurate diagnosis and monitoring of a wide range of diseases. However, current PET systems are limited by high costs, complex mechanical designs, and reliance on large amounts of scintillator material. As healthcare increasingly shifts toward early detection and personalised treatment, there is a strong demand for next-generation PET technologies that combine superior sensitivity, improved resolution, and more flexible, scalable system architectures.
Methods:
We introduce a modular PET detector design optimised for high-resolution time-of-flight (TOF) performance. The system architecture integrates fast silicon photomultipliers with compact, low-power, high-speed readout electronics, aiming to achieve coincidence timing resolutions (CTR) below 100 ps FWHM. A key innovation is the use of flat-panel detector modules, which can be assembled into reconfigurable geometries. This approach significantly reduces scintillator requirements while maintaining image quality, thereby lowering manufacturing costs and simplifying overall system design.
The work is being carried out within the Horizon Europe EIC Pathfinder project PetVision, a consortium of eight partners representing technology developers, academic research groups, and clinical end-users. This broad collaboration ensures that the system is developed from the component level through to a prototype demonstrator that will be evaluated and verified in clinical environments.
Results:
In this presentation, we will detail the design strategies underpinning the PetVision imager and discuss results from feasibility simulations that establish the system’s capability to match or exceed the performance of current PET scanners. We will also present experimental results of CTR measurements obtained with different tested scintillators, demonstrating progress toward the project’s ambitious timing goals. These findings provide strong evidence for the feasibility of achieving sub-100 ps CTR with a significantly reduced scintillator load.
Conclusions:
The PetVision project is advancing toward the realisation of a high-performance planar TOF-PET prototype. By combining innovative detector modules, cutting-edge electronics, and clinically informed system design, the consortium aims to deliver an adaptable and cost-effective imaging solution. The presentation will highlight not only the technical design, but also simulation-based feasibility studies and experimental validation of scintillator timing performance. The resulting system is expected to enable scalable PET configurations, from conventional clinical scanners to compact, mobile, and point-of-care applications, ultimately broadening access to advanced molecular imaging and supporting the delivery of personalised healthcare.

Speaker: Rok Pestotnik

12:45 → 14:00 Lunch Break

14:00 → 16:00 Plenary Session

Convener: Marco Guarise (Istituto Nazionale di Fisica Nucleare)

14:00 Wearable, Lightweight, and Flexible Dosimeters for Real-Time Monitoring

The development of detectors for high-energy photons has long been a key research topic, not only for fundamental studies but also for radiation monitoring in harsh environments – such as in hospitals during medical treatments and in outer space exploration. Recently, there is a rapidly growing interest in novels, high-performance, radiation hard, thin, and flexible sensors capable of real-time ionizing radiation detection at affordable cost. This is driven by the limitations of current technologies, which still lack in meeting requirements such as large-area coverage, conformability, portability, low weight, and low-power operation.
Recent significant progresses in the field of perovskites have demonstrated their great potential for direct X-ray detection, coupled to unique advantages including solution-processability, cost-effective fabrication and scalability to large area systems. However, they are limited by low bulk resistivity, high trap states density and significant ion migration effects leading to large dark current drift. Among the lead-halide perovskites, X-ray detectors based on polycrystalline low-dimensional (2D layered) lead-halide perovskites have emerged as promising semiconducting materials thanks to their high atomic number, excellent optoelectronic properties, combined with high resistivity, reduced ion migration, and enhanced environmental stability. We present recent developments in X-ray detectors based on low dimensional perovskite films directly deposited onto pixelated flexible substrate. We also report on a fully wearable detector specifically designed for in-situ dose monitor in medical radiotherapy.

Speaker: Andrea Ciavatti

14:18 Advances in MCP-PMTs: performance, challenges and beyond

Speaker: Mr Albert Lehmann (Universität Erlangen-Nürnberg)

14:43 The prototype of MCP-PMT with a novel photocathode design

The photomultiplier tube (PMT) based on microchannel plates (MCP) is one of the fastest types of the single photon detectors. When coupled with a Cherenkov radiator it allows the time of a charged particle to be measured with an accuracy of order of 10 ps. Such a time resolution may be of interest for future high-energy physics experiments.
One of the main limitations of MCP-PMTs is the short photocathode lifetime resulted from the feedback ions flow. Despite the recent significant reduction of the photocathode ageing in MCP-PMT due to the use of MCPs manufactured using ALD technology, the MCP-PMT lifetime is still an order of magnitude less than that of traditional PMTs with metal dynodes. This limits the application of MCP-PMTs in high rate environments like in future experiments at high luminosity LHC.
We study the possibility of using a new configuration of the photocathode in an MCP-based detector for precise time measurement of charged particle. This configuration is expected to reduce the effect of feedback ions going from MCPs and improve the photocathode lifetime. The idea is tested using ultraviolet CsI photocathodes prepared in the vacuum evaporation setup in Bologna. For testing we use in-house customised prototype equipped with a magnesium fluoride crystal as a Cherenkov radiator and the photocathode, followed by a pair of MCPs. The prototype has been repeatedly tested with particle beam at CERN and LNF (Frascati), routinely obtaining time resolution of 17 ps for single charged particle. The time resolution for semitransparent CsI photocathode deposited on MgF$_2$ Cherenkov radiator has been measured as well.
To check the advantage of the new design in terms of lifetime, we started an ageing test which compares its degradation rate with that of semitransparent photocathode, operating the two devices in the same conditions.
In the present contribution the experimental setup and the results of the various beam tests are presented and discussed, together with the status of the ongoing ageing test.

Speaker: Mikhail Barnyakov (Istituto Nazionale di Fisica Nucleare)

15:01 Preparation status of the Hyper-Kamiokande 50 cm photomultiplier tubes

The Hyper-Kamiokande (HK) is a next-generation water Cherenkov detector aiming to study a wide range of physics targets such as neutrino oscillations, neutrino astronomy, and nucleon decays. HK is under construction and is scheduled to start operation in 2028.

Approximately 20,000 newly designed 50 cm diameter PMTs manufactured by Hamamatsu Photonics K.K., R12860, will cover the inner surface of the HK inner detector with 20% photo-coverage to detect the Cherenkov photons emitted in the inner detector.
The PMT has excellent characteristics in photon detection efficiency, charge and time resolutions, hydrostatic pressure tolerance, etc.
It is important for HK that the PMTs installed in the detector exhibit high and uniform performance, as well as maintain long-term stability.

The mass production of the HK PMTs started in 2020, and more than three-quarters of the total 20,000 units have been delivered as of September 2025.
A series of measurements has been conducted to ensure the quality of the delivered PMTs by evaluating their performance, including the response against the injected photons and the dark count rates, and their stabilities.

In this talk, our overall strategy of PMT quality assurance and the results of the measurements will be reported.

Speaker: Kota Nakagiri (Kamioka Observatory, ICRR, The University of Tokyo)

15:19 Mechanism for reduction of the afterpulsing rate of PMTs

Photomultiplier tubes (PMTs) are used in Imaging Atmospheric Cherenkov Telescopes (IACTs), to detect Cherenkov light produced by air showers induced by gamma rays. In the PMTs, accelerated photoelectrons occasionally collide with residual gas inside the tube, producing positive ions that strike the photocathode and generate additional electrons. This ion feedback produces afterpulses, which may cause a hindrance to observation. The afterpulsing rate of the PMTs for the Large-Sized Telescopes (LSTs) of the Cherenkov Telescope Array Observatory, which is a next-generation IACT, has been found to increase in PMTs that were kept unused in storage, likely due to an increase of residual gas. In contrast, PMTs that had been operated in the first LST showed a slight decrease in afterpulsing rate. This decrease was considered to result from a reduction of residual gas caused by ion feedback, but the details had not been clear until this study. In this study, to investigate factors responsible for the change in the afterpulsing rate, we operated several PMTs under different high voltage conditions, with some were illuminated by LED light while the others were not. We kept the PMTs under this condition for three weeks repeating an afterpulse measurement every day. As its result, we confirmed that the reduction of afterpulses requires both illumination of the photocathode and application of high voltage to PMTs. Remarkably, the reduction strongly depends on the applied high voltage and is closely correlated with the integrated anode current, which is proportional to the number of the multiplied secondary electrons at the last stage. Therefore, we conclude that the reduction of residual gas is mainly caused by ionization occurring at later dynodes of the PMTs, with the ions adhering to the dynodes, establishing a key mechanism for the afterpulse reduction. We thus establish a key mechanism for the afterpulse reduction of PMTs.

Speaker: Kai Morita (ICRR, U. Tokyo)

15:37 PICMIC concept

The PICosecond subMICron (PICMIC) is a new detection concept that intends to simultaneously exploit the remarkable intrinsic spatial and time precision of the MicroChannel Plate (MCP) detectors. The concept is itself made of two new ones. The first is an extension to 2-dimension of the delay line technique and allows, with a limited number of electronic channels, a precise measurement of the arrival time of particles crossing the MCP. The second, conceived to measure the position of these particles, uses pixels which pitch is smaller than the MCP tubes diameter and that are interconnected in an original way. The new scheme leads to an excellent granularity without suffering from the usual ambiguity encountered in the X-Y strip-based readout systems and still operated with a much smaller number of electronic channels with respect to a pixel-based readout one.

Spatial and time measurement systems based on the two concepts have been designed and produced. Both were individually tested and validated. The two systems were then assembled together to read out the signal produced by alpha source placed on a stack of two MCP placed in a vacuum setup in order to validate the whole concept.
In this paper the PICMIC concept, the realization of the to two measurement systems as well as the first results obtained with the prototype are presented.

Development of new generation of MCP using nanotechnologies will also be presented and the expected performances of these new detectors called NanoChannel Plate (NCP) will be discussed and the steps towards such detectors will be enumerated.

Speaker: Imad Laktineh (ipnl)

16:00 → 16:30 Tea Break

16:30 → 18:45 Plenary Session

Convener: Imad Laktineh (ipnl)

16:30 Comprehensive characterization of LAPPD and HRPPD photodetectors

Many experiments require the detection of single photons over a large, but finely segmented sensitive area with sub-nanosecond time resolution. To this end, Large Area Picosecond Photon Detectors (LAPPDs) and High Rate Picosecond Photon Detectors (HRPPDs) were recently developed by Incom in collaboration with academy. These detectors are based on Micro-Channel Plate-PMTs and have a size of 10 or 20 cm and a few mm segmentation. They feature a high time resolution and a low intrinsic noise rate. Their characteristics and relatively low cost per unit area make them ideal candidates for use as photodetectors in the pfRICH and hpDIRC of the electron-Proton/Ion Collider (ePIC) experiment at Elecron Ion Collider (EIC).

In this contribution, we will present a comprehensive of LAPPD/HRPPD characterization campaign undertaken by the INFN sections of Trieste and Genova in collaboration with BNL and JLab. This campaign included measurements of the time resolution of single photons in a test beam at CERN, magnetic field measurements and ageing studies. Overall the expected performances of LAPPD/HRPPDs were confirmed. In particular we observed a single-photon time resolution of 87 ps RMS for the LAPPD. The LAPPD’s gain drops in a magnetic field, but can be partially recovered by applying a higher bias voltage. Additionally, ageing measurements demonstrated photocathode stability of over a significant time interval.

Speaker: Dr Mikhail Osipenko (GE)

16:48 Systematic evaluation of series-produced Microchannel-Plate PMTs

Since the recent success in solving the long-standing aging issues of Microchannel Plate Photomultiplier Tubes (MCP-PMTs) by applying atomic layer deposition (ALD) technology to the MCP pores, these fast and B-field-tolerant devices have become very attractive sensors for future experiments. Given the harsh radiation environment and the placement of the photosensors in magnetic fields of $\sim$1 Tesla, MCP-PMTs were selected as sensors for the DIRC detectors of the PANDA experiment at FAIR. The chosen XP85112-S-BA sensors from PHOTONIS have an active area of 2$\times$2 inches, a grid of 8$\times$8 anode pixels, and MCPs with a pore diameter of 10 $\mu$m. A minimum performance of 16% detective quantum efficiency and 500 kHz/cm$^{2}$ rate capability is requested. To meet the experiment’s lifetime requirement of $\sim$5 C/cm$^{2}$ integrated anode charge over a period of ten years, all MCPs were treated with two ALD coatings of Al$_{2}$O$_{3}$ and MgO to improve their lifetime.

A comprehensive and systematic quality control program was carried out at the University of Erlangen. It includes a wavelength scan of the quantum efficiency (QE) and measurement of the gain curve, as well as scans of the spatial homogeneity of QE and gain. In addition, collection efficiency, time resolution, and rate capability are measured. Using GSI's DiRICH/TRB DAQ system, additional parameters such as dark count rate (DCR), afterpulse probability (AP) and its time-of-flight (TOF) distribution, and crosstalk as a function of the active area are assessed. The large number of MCP-PMTs tested provides insights into production quality and issues and produces a high statistics sample of the various performance parameters.

Although the complex process of ALD coating extends the lifetime of MCP-PMTs, it also introduces undesirable side effects with regard to some key parameters in some of the sensors. A few MCP-PMTs exhibit characteristic peaks in AP-TOF spectra, most likely corresponding to Mg and Al ions, suggesting that many AP ions originate from the ALD layers. Furthermore, a subset of tubes shows a phenomenon referred to as “escalation”, in which massive photon rates are emitted from inside the MCP. In some cases, escalation occurs only in local areas of the sensor. Tubes with higher DCR and AP values tend to enter escalation at lower gains, suggesting a correlation between ALD-induced impurities and this behavior.

Despite the issues observed, the large data set of more than 100 tested sensors allows a detailed analysis of the correlations between some sensor parameters. For example, tubes with lower MCP resistance generally perform better under high-rate conditions and maintain stable gain at photon rates of up to $>$10$^{6}$ photoelectrons/s/cm$^{2}$. However, no direct correlation was found between MCP resistance and the occurrence of escalation.

In this talk, we will present the setups and analysis techniques used to measure the various performance parameters. The results of a systematic evaluation of $>$100 series-produced MCP-PMTs will be discussed and compared, and any problems encountered will be highlighted.

• Supported by BMBF and GSI -

Speaker: Katja Gumbert

17:06 Simulation and characterisation of a 16-by-96 multi-anode MCP-PMT

Owing to their single photon sensitivity and fast rise time, micro-channel-plate photomultipliers (MCP-PMTs) make good candidates as photon detectors for the Time Of Internally Reflected Cherenkov light detector (TORCH) that is proposed as part of the phase two upgrade of the LHCb experiment.
The TORCH detector has a target time resolution per photon of approximately 70ps, required to achieve an approximately three standard deviation separation of pions and kaons at 10 GeV/c from their time-of-flight over a 10m flight distance.
A new high-granularity 16-by-96 channel MCP-PMT with a directly coupled anode has been developed in conjunction with Photek Ltd.
This device is designed to decrease the pixel pitch to 0.55\,mm, giving improved spatial resolution and importantly lower per-pixel occupancies.
This talk will cover cross-talk characterisation studies, used to determine the spatial resolution of the device. The experimental results are compared with simulation studies. The simulation is performed using CST studio, a finite element method solver that models the field and propagation of electrons in the device. Capacitive effects in the anode are simulated using a LT-Spice model. Overall, the simulation results demonstrate minimal effects of cross-talk on the device's output

Speaker: Alexander Davidson (University of Warwick)

17:24 Understanding the timing and charge sharing in MCP PMTs

This study presents a comprehensive effort to understand the timing and charge sharing in MCP PMTs. While we have investigated in detail - through on-the-bench tests and by modeling the response - the Large Area Picosecond Photodetectors (LAPPD) of Generation II, developed by Incom Inc., we have also compared our model predictions with our past studies of Burle/Photonis and Photek MCP PMTs.

The investigation centered on the effects of capacitive coupling between the monolithic resistive ground-plane anode and the external readout pads in the LAPPD, particularly examining how signal spread and timing performance depend on geometrical factors and pad segmentation. Using a pulsed diode laser system, spatial and timing characteristics were probed with fine granularity. Measurements confirm that signal distribution is dominantly governed by induced charge spread rather than electron diffusion, with signal confinement significantly affected by pad size and MCP-to-anode and anode-to-pad distances. A model was used to understand the observed signal spread and to find optimal system parameters.

Time resolution analyses show a primary timing peak (σ ≈ 27 ps) and secondary structures consistent with back-scattering effects, with resolution improving with increased photocathode-to-MCP potential, all in agreement with a simple model. The study also evaluates integration with two readout systems: PETSYS TOFPET2 ASIC, which showed effective photon detection and spatial clustering, and FastIC ASIC, which delivered excellent timing precision with low-power consumption and integrated TDC/ADC features.

Speaker: Samo Korpar (University of Maribor)

17:42 Precision timing with photon detectors

Speaker: Jon Lapington (University of Leicester)

18:07 Precision timing with the CMS Barrel Timing Layer

For the High-Luminosity phase of the LHC (HL-LHC), the Compact Muon Solenoid (CMS) experiment is undergoing an upgrade with the addition of the new MIP Timing Detector (MTD), designed to measure the arrival time of charged particles with a precision of 30-60 ps. The time information from the MTD will help handle the expected ~200 concurrent interactions per bunch crossing (pileup) to preserve the present event reconstruction performance. Furthermore, it will introduce new capabilities to the CMS detector by enabling particle identification and expanding the physics reach in searches for long-lived unstable particles. The central part of the MTD, the Barrel Timing Layer (BTL), is made of about 166,000 scintillating LYSO:Ce crystal bars with double-ended SiPM readout. Following its design optimisation and successful performance validation through dedicated test beam campaigns on prototypes, the BTL is now in the construction phase. This contribution will provide an overview of the key design features of the BTL, present recent large-scale system tests and the progress on the BTL assembly, and discuss recent developments in 4D vertex reconstruction and pileup rejection introduced by the MTD.

Speaker: Martina Malberti (Istituto Nazionale di Fisica Nucleare)

18:25 Direct charged particle detection with SiPMs for the ALICE 3 timing layer

Silicon Photomultipliers (SiPMs) are under consideration for the outer timing layer of ALICE 3, the next-generation heavy-ion experiment at the LHC, which will replace the present ALICE experiment for LS4 (2034-2035) and beyond. While SiPMs are traditionally coupled to external scintillators or Cherenkov radiators, recent studies have shown that they can directly detect charged particles through Cherenkov light emitted in the few-hundred-micron-thick protective layer deposited on top of the device. A SiPM with such a protective layer on top can therefore combine the benefits of an external photon generator, producing a large number of photons, with a high level of simplicity and compactness, opening new possibilities for standalone charged-particle detection.
Beam tests were performed at the CERN PS using FBK SiPMs of different area (~3×3 mm² and 1×1 mm²) and protection layer thicknesses (450-2450 μm). The analog waveforms were recorded with an oscilloscope, and the effect of the resin layer was clearly observed as a transition from single-SPAD to multi-SPAD (Single Photon Avalanche Diode) signals per particle. In this contribution, we present an overview of these measurements, focusing on efficiency, time resolution, and noise rejection.
Efficiencies above 99% were achieved, far beyond expectations from the device fill factor. The high photon yield also enabled strong noise suppression: applying a threshold equivalent to 2-3 times the single-SPAD signal effectively rejected dark counts (DC) while preserving >99% of true signals. Time resolutions better than 20 ps were obtained, with performance improving as more SPADs were fired.
These results demonstrate the feasibility of exploiting SiPMs as efficient, low-noise, and ultra-fast particle detectors without the need for an external radiator. This novel operating mode opens the possibility to realize compact TOF systems for high energy and space applications or combined TOF+RICH system using a single SiPM-based technology or providing timing layers in next generation calorimetry to improve the shower identification. However, these applications would imply that radiation tolerance aspects of SiPM must be better investigated looking also to new technologies.

Speaker: Francesca Carnesecchi

20:00 → 22:30 Social Dinner

Friday 5 December

08:30 → 10:15 Plenary Session

Convener: Francesca Di Lodovico (King's College London)

08:30 Light detection in dark matter and neutrino detectors

Speaker: Gianfranca De Rosa (Istituto Nazionale di Fisica Nucleare)

08:55 PLATON: high-resolution 3D photographs of particles interacting in a monolithic scintillating volume

High-spatial resolution scintillator detectors can achieve very precise particle tracking capability, when owing to a very fine segmentation down to a few hundred micrometers.
However, the required granularity comes with the price of additional complexity in the detector manufacturing and construction that can make the scaling up to large volumes and masses rather prohibitive.
Moreover, traditional photosensor systems would lead to a too large number of readout channels, further increasing complexity and cost.

As a solution, we propose a change of paradigm in scintillation detection systems, applying 3D imaging techniques to particle interactions in an unsegmented monolithic volume of organic scintillator, capable of high-resolution tracking. This is achieved by combining the concept of plenoptic imaging with a Single-Photon Avalanche Diode (SPAD) array imaging sensor.

This report will include the operation and performance of the first SPAD-based plenoptic camera for particle tracking.
We discuss both analytical and artificial intelligence-driven reconstruction algorithms capable of event imaging.
Results are presented from a controlled optical setup based on two-photon absorption, which enables localized, point-like light emission within the scintillator volume, simulating energy depositions from particle interactions.

A case study focused on accelerator neutrino detection demonstrates the unique potential of this approach, achieving full event reconstruction with a spatial resolution on the order of one hundred micrometres.
The extrapolation to tonne-scale volumes will also be discussed.

Our work sets the path forward for new detection systems for high-precision particle tracking in dense active volumes, with applications that can range from neutrino detection to particle calorimetry.

Speaker: Till Dieminger (ETH Zurich)

09:13 Overview of the TAO photo-detector and recent progress

The Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) is a satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). Its central detector is equipped with 4024 customized silicon photomultiplier (SiPM) tiles, each featuring a dimension of 5cm * 5cm, covering nearly 10 m$^2$ of spherical surface area. Operated at -50 $^\circ$C with low-temperature liquid scintillator, the detector is designed to achieve unprecedented energy resolution of 2% at 1 MeV for precise measurements of the reactor neutrino energy spectrum. The installation of the TAO detector is completed and commissioning work is on-going, with data-taking expected to begin soon. I will give a talk of TAO experiment on behalf of the JUNO collaboration. This talk will present an overview of recent progress on the TAO detector, and results from the mass characterization of the SiPMs and performance of the photo-detector.

Speaker: Hanwen Wang (Institute of High Energy Physics (IHEP))

09:31 Gaseous photon detectors: applications and perspectives

Speaker: Florian Brunbauer (CERN)

09:56 The CYGNO experiment: a gaseous TPC with optical readout for rare events searches

The CYGNO/INITIUM collaboration is developing a novel strategy for directional Dark Matter searches based on a gaseous Time Projection Chamber (TPC). The detector is optimized for the exploration of light (0.5–50 GeV) WIMPs-like particles and employs a He/CF₄ gas mixture at atmospheric pressure, sensitive to both spin-dependent and spin-independent interactions.
A key feature of the project is its optical readout, which relies on photon detection rather than charge collection.
In CYGNO detectors, electrons released by ionizing tracks drift toward an amplification stage of three Gas Electron Multipliers (GEMs). The electron avalanches generate scintillation light that is captured by scientific CMOS (sCMOS) cameras for high-resolution two-dimensional imaging and by Photomultiplier Tubes (PMTs) that provide a precise time profile along the drift direction. This allows a 3D event reconstruction, detailed energy deposition mapping, and effective topology and head-to-tail discrimination.
Building on the achievements of the 50 L prototype (LIME), which successfully operated underground at LNGS, the next step is the deployment of a 0.4 m³ demonstrator, CYGNO-04, to be completed in 2026. The demonstrator will validate scalability and confirm the advantages of the proposed technique.
Recent results from LIME highlight strong progress in 3D tracking and particle identification. The current status of CYGNO-04 and its role in advancing the program will be presented as well.

Speaker: Prof. Fabrizio Petrucci (Istituto Nazionale di Fisica Nucleare)

10:15 → 10:45 Coffee Break

10:45 → 12:45 Plenary Session

Convener: Elisabetta Bissaldi (Istituto Nazionale di Fisica Nucleare)

10:45 The focal plane cameras of the ASTRI Mini-Array air-Cherenkov telescopes for gamma ray astronomy

This work presents the design, development, and calibration of the engineering Cherenkov camera developed for the nine innovative dual-mirror imaging atmospheric telescopes of the ASTRI Mini-Array. This international project, led by the Italian National Institute for Astrophysics (INAF), is dedicated to ground-based gamma-ray astronomy. Located at the Observatorio del Teide in Tenerife, Spain, the ASTRI Mini-Array will perform high-sensitivity and high-angular-resolution observations of the gamma-ray universe in the 1–200 TeV energy band. The cameras adopted in the ASTRI Mini-Array represent the final evolution of the prototype system tested at the ASTRI-Horn telescope pathfinder since 2016, on the slopes of Mount Etna in Sicily, Italy. This prototype provided valuable experience in gamma-ray observations using the atmospheric Cherenkov technique with dual-mirror optics and cameras based on multipixel Silicon Photo Multiplier (SiPM) photodetectors. The new ASTRI cameras incorporate SiPM-based technology, employing fast-acquisition peak detectors with low power consumption thanks to the custom ASIC Citiroc, developed jointly by INAF and the French company WEEROC. Since the initial design phases, the camera has adopted advanced and elegant engineering solutions that enhance its performance and effectiveness. Embedded within the structure, the thermal control system (which requires no external cooling liquids) and calibration subsystems of the focal plane ensure operational efficiency, reliability, and ease of installation—critical factors for maintaining a fully functional array with multiple telescopes. The first Cherenkov camera was installed on the ASTRI 1 telescope in late August 2024, and the installation of the other cameras is currently ongoing. The results regarding the performance of the cameras will be presented and discussed.

Speaker: Giuseppe Sottile

11:03 Pushing the Frontiers of Space UV Detection: The SiSMUV project

The SiSMUV project (SiPM-based Space Monitor for UV-light) is devoted to the development of a compact, modular UV detector employing SiPM technology for space telescopes, designed to measure fluorescence and Cherenkov emissions generated by Ultra-High Energy Cosmic Rays (UHECRs).
SiSMUV incorporates state-of-the-art Hamamatsu SiPM matrices, low-power front-end electronics, and local intelligence into a monolithic photo-detection block. The system integrates RADIOROC ASICs, providing channel-by-channel bias tuning, sub-photoelectron triggering, dual-gain energy measurement, and excellent linearity up to 2000 p.e., combined with an Artix-7 FPGA and a CAEN bias supply.
We present the design and functional characterization of the prototype, including gain, PDE, crosstalk, afterpulses, and timing performance, using an integrating sphere with laser/LED sources and a calibrated PMT. The setup allows scanning of individual SiPMs under controlled conditions inside a dark box.
Beyond its technological development goals, the SiSMUV detector unit is envisioned as a building block for next-generation spaceborne Cherenkov cameras, such as the PoEMMA Balloon with Radio (PBR) mission, featuring a 2048-pixel focal plane, bi-focal optics for background reduction, and nanosecond-scale time resolution.

Speaker: Marco Mese (Istituto Nazionale di Fisica Nucleare)

11:21 Photon Detectors at Cryogenic temperatures

Speaker: Inés Gil-Botella (CIEMAT)

11:46 Production and Characterisation of SiPM-Based Photo Detection Units for the DarkSide-20k Experiment

The DarkSide-20k experiment, a next-generation direct dark matter search using a dual-phase liquid argon time projection chamber, requires highly sensitive and radiopure light detection systems. This talk will present the production workflow and quality assurance procedures for the SiPM-based photo detection units (PDUs), developed specifically for DarkSide-20k. Each PDU is composed of 16 tiles, which are assembled and tested in a dedicated facility. We will discuss the PDU assembly process, characterisation techniques, and key performance metrics achieved during the cryogenic tests. The talk will also address the challenges of scaling up production to meet the demands of a 20-tonne active mass detector while ensuring uniform performance and long-term stability of the photodetector modules.

Speaker: Dmitrii Rudik (Istituto Nazionale di Fisica Nucleare)

12:04 The DUNE Far Detector Photon Detection System

The Deep Underground Neutrino Experiment (DUNE) is a next-generation long-baseline experiment for neutrino physics currently under construction in the US, aiming to measure neutrino oscillation parameters, search for beyond standard model physics and detect supernova neutrinos. DUNE will include a Near Detector (ND) and a Far Detector (FD), located 1300 km away from the ND and 1.5 km underground. The FD will consist of four 17-kton Liquid Argon Time Projection Chambers (LArTPCs). In Phase I, two FD modules implementing horizontal (HD) and vertical (VD) drift technologies will be used. To test these technologies, two 750-ton LArTPCs (ProtoDUNEs) were built at CERN and were operated over the past two years.

In particular, the FD Photon Detection System (PDS) is critical for the DUNE physics program. The topology of a neutrino interaction in the LArTPC is reconstructed from the tracks of secondary charged particles, which produce scintillation light and ionization charge carriers during their propagation in LAr. The reference time of the event is provided by the scintillation light, detected by X-ARAPUCA modules, i.e. photon traps consisting of a box with highly reflective internal walls instrumented with an array of Silicon PhotoMultipliers (SiPMs).

In this talk, the designs of the DUNE PDS and first results about ProtoDUNE-HD and ProtoDUNE-VD PDS operation are presented. The preliminary results demonstrate the successful operation of the PDS, marking a crucial step toward validating the horizontal and vertical drift designs for the first FD modules.

Speaker: Anna Balboni (Istituto Nazionale di Fisica Nucleare)

12:22 A New Window into Noble Elements: VUV-Sensitive Amorphous Selenium Photodetectors for Cryogenic Applications

Detecting the deep VUV scintillation light from noble elements such as argon (128 nm) and xenon (178 nm) remains a major challenge in fully realizing the physics potential of modern dark matter and neutrino detectors. Existing direct detection technologies (cryo VUV SiPMs and PMTs) typically achieve efficiencies below 20%. In this talk, we present the first comprehensive characterization of windowless, laterally structured amorphous selenium (a-Se) photodetectors engineered for direct VUV sensitivity and stable operation at cryogenic temperatures.

We demonstrate that these devices exhibit remarkable stability and sensitivity across a wide temperature range (77–290 K) and electric fields approaching avalanche conditions.The detectors achieved single-shot detection efficiencies approaching 65% with as few as 100 field-effective 401 nm photons at 165 K, illustrating their sensitivity to such low-level optical excitation. At 87 K, the prototypes maintained a similar functional behavior under direct VUV illumination at 130 nm, showing for the first time that the avalanche response mechanism remains active at cryogenic temperature and across excitation wavelengths relevant to noble elements scintillation. Complementary studies with tellurium-doped a-Se (a-SeTe) reveal avalanche onset at reduced fields and enhanced gain, pointing to a powerful direction for future optimization.

Our new photosensors prototypes offers a compelling combination of cryogenic compatibility, wide dynamic range, low-photon sensitivity, and VUV response—paving the way for scalable, high-field-compatible photodetection systems in next-generation dark matter and neutrino detectors.

Speaker: Elena Gramellini (University of Manchester)

12:45 → 14:00 Lunch Break

14:00 → 16:30 Plenary Session

Convener: Andrea Ciavatti

14:00 LiquidO: A Revolutionary Approach to Particle Imaging and Detection Exploiting Opaqueness.

Moving beyond the conventional paradigm of transparency in detection, the LiquidO collaboration proposes an innovative approach to particle detection. Developed in 2012 and unveiled at CERN in 2019, LiquidO introduces an opaque medium with a short scattering length that stochastically confines light to within centimetres of the point of energy deposition. This light—arising from Cherenkov radiation and, when desired, scintillation—is collected by a dense lattice of optical fibres (wavelength-shifting or scintillating) and read out by fast, high-efficiency single-photon sensors such as SiPMs, together with fast electronics, to provide both static and dynamic topological information. This approach, known as energy flow imaging, allows LiquidO to deliver highly efficient imaging along with the capability to distinguish between charged and neutral elementary particles. At low MeV energies, it provides, for the first time, event-by-event topological discrimination of positrons, electrons, and gamma rays.
LiquidO is an enabling platform that opens new opportinities in neutrino physics, rare-decay searches—specifically double-beta (ββ) and proton decay—and broader applications across fundamental science and innovation.
During its development, we pioneered an ‘opaque scintillation’ approach that removes the need for optical transparency and thus permits high concentrations of metal dopants, expanding the capabilities of the LiquidO detector.
This presentation will showcase results from our most recent prototypes, concluding LiquidO’s first ‘demonstration’ R&D phase. The imaging principle has now been validated, and further investigations are in progress.

Speaker: Stefano Dusini (Istituto Nazionale di Fisica Nucleare)

14:18 Quantum technologies for photon detectors

Speaker: Boris Korzh (University of Geneva)

14:43 Development of drop-cast PbS QD detectors – from X-ray photoresistors to proton detection

The use of solution processable materials in direct ionising radiation photodetectors is currently an active research quest that is achieving exciting results. Devices based on Perovskites, Organic Semiconductors, Metal Organic Frameworks and Colloidal Quantum Dots have been demonstrated as efficient, inexpensive and easily processable sensing materials for Gamma, X-rays, Protons or Alpha particles. Perovskite-based detectors typically show the highest sensitivity values among solution processed devices and have been demonstrated for proton detection as well. Organic detectors are generally considered to be tissue-equivalent and have shown photon and proton detection capabilities. Colloidal Quantum Dots have recently started to be employed in direct and indirect ionising radiation detectors. QDs optoelectronic properties depend on their size, surface and core chemistry, and all these properties can be controlled synthesis. In the last few years, direct detectors based on QDs have shown promising sensitivities to x-ray and gamma radiation. QD of High-Z materials like PbS, CdTe and perovskites have much higher photoabsorption coefficients than organics, while photodetectors based on PbS show prolonged (months) stability in ambient air, while often perovskites’ performance is worsened by exposition to humidity and oxygen. In this work, we will initially briefly recap our results on the development of drop-cast PbS QDs X-ray photodetectors on silicon. We will then present our most recent results on PbS on PEN flexible X-ray detectors, highlighting the differences and similarities between the two devices. A preliminary experiment with the PbS on PEN devices also showed a repeatable response to proton beam irradiation, proportional to the proton beam current. These findings suggest that PbS QDs are a promising candidate as efficient, stable and highly optimizable x-ray sensing solution-processable material, with early results suggesting proton detection capabilities as well.

Speaker: Marco Ruggieri (Istituto Nazionale di Fisica Nucleare)

15:01 Perovskite single-photon counting detectors

Speaker: Paul Sellin (University of Surrey)

15:26 Development of Inorganic perovskite thin-film photo-detectors

CsPbCl3/Br3 inorganic perovskite are attracting an increasing interest in ultraviolet and visible photo-detection due to their superior intrinsic optoelectronic properties. In this study, a novel one-step magnetron sputtering technique was applied for fabricating CsPbCl3/Br3 polycrystalline films on flexible and glass substrates with interdigitated contacts. The photoconductive response of 100 nm to 1 um thick films to pulsed light with variable frequency and intensity have been tested. The experimental study allowed to evaluate relevant material properties as well as the detector responsivity, signal stability and reproducibility, detectivity, light dynamic range and dark current noise in case of pulsed UV-VIS light.

Speaker: Mara Bruzzi (Istituto Nazionale di Fisica Nucleare)

15:44 Vapor-processed Perovskite Thin-Film Photodetectors

Metal halide perovskites combine high optical absorption coefficient, bandgap tunability, and the use of heavy atoms, making them attractive for photodetectors across the visible and X-ray range. However, most demonstrations rely on solution processing, which presents challenges in terms of reproducibility, substrate compatibility, and large-area uniformity. Vapor-based methods provide a scalable and controllable alternative, already established in the optoelectronics industry.

Here we report the fabrication of perovskite photodetectors by thermal co-evaporation of the halide precursors. This approach enables precise control of film thickness, stoichiometry, and morphology, yielding uniform, pinhole-free layers across centimeter-scale substrates. The process operates at low substrate temperature, allowing deposition of perovskites on temperature-sensitive substrates.

Devices based on co-evaporated perovskites show low dark and noise currents. In the visible range, they reach external quantum efficiency above 90%, and specific detectivity up to $5 \times 10^{12}$ Jones. Under X-ray irradiation, sensitivities exceed $33 \pm 4~\mu\text{C}\,\text{Gy}^{-1}\,\text{cm}^{-2}$ with a limit of detection of $2.0 \pm 1.6~\mu\text{Gy}\,\text{s}^{-1}$. Compared to solution-processed analogues, the vapor-grown devices exhibit enhanced reproducibility and stable operation under reverse bias. Examples of broadband detectors covering the visible spectrum, as well as narrowband selective detectors, will be presented to illustrate the versatility of the method.

In summary, co-evaporation provides a simple, scalable, and uniform route for preparing thin-film perovskite photodetectors. The combination of visible and X-ray sensitivity, tunable spectral selectivity, and robust performance highlights its potential for emerging imaging and sensing technologies.

Speaker: Michele Sessolo (University of Valencia)

16:02 Solution-processed Mn-doped 2D perovskite wavelength shifters for noble-liquid photon detection

Wavelength-shifting photon detection systems (PDS) are critical components in noble-liquid detectors for high-energy physics and dark-matter searches. The vacuum ultraviolet (VUV) scintillation from liquid argon (LAr, ~128 nm) and liquid xenon (LXe, ~175 nm) must be shifted to longer wavelengths to enable efficient detection with state-of-the-art photodetectors such as photomultiplier tubes (PMTs) and silicon photomultipliers (SiPMs). Organic wavelength shifters, most notably 1,1,4,4-tetraphenyl butadiene (TPB), suffer from photodegradation, self-absorption, and long-term reliability issues, motivating hybrid alternatives. Colloidal quantum-dot approaches (e.g., CsPbBr₃) have shown promise but face challenges with re-absorption from small Stokes shifts, environmental/binder compatibility, and cryogenic robustness.

In this study, we demonstrate Mn-doped phenethylammonium lead bromide (Mn:PEA₂PbBr₄) two dimensional perovskite thin films as highly efficient wavelength shifters. The key mechanism is host to dopant energy transfer: whereas undoped PEA₂PbBr₄ exhibits a small Stokes shift and therefore re-absorbs part of its own emission, Mn²⁺ incorporation converts this loss channel into a benefit by funneling re-absorbed energy to Mn centers and re-emitting at longer wavelength. The resulting large effective Stokes shift suppresses self-absorption, improves out-coupling, relaxes thickness constraints, and aligns the output with the peak quantum efficiency region of PMTs/SiPMs.

We fabricate uniform, large-area films by low-cost, scalable solution processing (spin and bar coating) on UV grade quartz substrates, enabling meter-scale PDS manufacturing without vacuum tooling. Solution processing further allows precise control of thickness and dopant loading, conformal coverage on complex geometries, and straightforward re-work/encapsulation when needed. We report absorption, transmittance and photoluminescence (PL) characterization and demonstrate stable operation at cryogenic temperatures relevant to LAr/LXe, with repeated cool-down and warm-up cycles confirming mechanical integrity (no visible cracking/delamination) and preserved emission.

These results establish Mn-doped 2D perovskite thin films as a process-friendly, cryo-compatible, and spectrally optimized wavelength-shifting platform, offering a clear pathway to scalable, meter-class PDS and broader wavelength-shifting applications in next generation noble-liquid detectors.

This project is funded by the European Union - Next Generation EU thorugh grant MUR PRIN 2022KJZSYB, CUP J53D23001780006.

Speaker: Elisabetta Colantoni (DIFA-UNIBO)

16:30 → 17:00 Closing Session

16:30 Awards Ceremony

16:35 A word from the DRD4 Collaboration Spokesperson

Speaker: Massimiliano Fiorini (INFN and University of Ferrara)

16:45 A word from the International Advisory Committee Chairperson

Speaker: Fabrice Retiere (TRIUMF)

16:55 Future Workshops and Farewell

Speaker: Roberto Preghenella (Istituto Nazionale di Fisica Nucleare)

17:30 → 18:30 Visit to INFN Laboratories

18:30 → 19:30 Aperitivo at INFN Laboratories

Saturday 6 December

10:30 → 12:00 Guided City Tour Excursion

14:30 → 18:30 Satellite event: "da dove vengono i colori?"