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

Dec 2, 2025, 4:00 PM → Dec 6, 2025, 7:00 PM Europe/Rome

Auditorium Enzo Biagi (Biblioteca Salaborsa)

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)
• Michele Penna, Fondazione Bruno Kessler (Italy)

Programme Overview

Sponsors and exhibitors

Organised by

First Bulletin

Group Photo

instructions_for_docx.pdf

Plenary Session Booklet

Poster

Poster Session Booklet

Scientific Tracks

Second Bulletin

Third Bulletin

Tue, December 2

5:00 PM → 7:00 PM Social Events: Visit to INFN Bologna Labotatories

Auditorium Enzo Biagi

Excursion Meeting Point

INFN Laboratories

Ristorante Donatello

5:00 PM Visit to INFN Bologna Laboratories

6:00 PM Aperitivo at INFN Bologna

Wed, December 3

8:00 AM → 9:00 AM Registration

Auditorium Enzo Biagi

Dummy Badge

Wireless Connection

9:00 AM → 9:30 AM Opening Session

Convener: Roberto Preghenella (Istituto Nazionale di Fisica Nucleare)

9:00 AM Welcome from the Workshop Organisers

Speaker: Roberto Preghenella (Istituto Nazionale di Fisica Nucleare)

ps2025_intro.pdf

9:05 AM Welcome from the Director of the INFN Division of Bologna

Speaker: Eugenio Scapparone (Istituto Nazionale di Fisica Nucleare)

9:10 AM Welcome from the Director of the Department of Physics and Astronomy of the University of Bologna

Speaker: Andrea Cimatti

9:15 AM Workshop Organisation Details

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

organization details.pdf

9:30 AM → 10:30 AM Plenary Session

Convener: Ezio Torassa (Istituto Nazionale di Fisica Nucleare)

9:30 AM Invited | Radiation damage in Silicon Photomultipliers

Speaker: Erika Garutti

EG-SiPM-RadHard-PD2025-V3.pdf

9:55 AM 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))

PD25-talk-v4.pdf

10:13 AM 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)

PD2025_effects_of_DCR_on_MIP_detection_with_SiPMs_KN.pdf

10:30 AM → 11:00 AM Coffee Break

11:00 AM → 12:45 PM Plenary Session

Convener: Roberta Cardinale (Istituto Nazionale di Fisica Nucleare)

11:00 AM 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)

BGardinovacki_PD2025.pdf

11:18 AM Invited | Photon detectors at the frontiers of particle identification

Speaker: Silvia Gambetta (University of Edinburgh)

PhotonDetectors_PID_PD2025_sg.pdf

11:43 AM 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)

NicolaMazziotta_PD25_v2.pdf

12:01 PM 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)

PD2025 - KOTO2 SAC_fedeli.pdf

12:19 PM 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)

PresentationPD2025_JDelenne.pdf

12:45 PM → 2:15 PM Lunch Break

2:15 PM → 4:00 PM Plenary Session

Convener: Prof. Peter Fischer (Heidelberg University)

2:15 PM 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)

santoro_PD25.pdf

2:33 PM Invited | Pushing analog SiPM performance: innovations and custom solutions

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

2025-12-03 - Alberto Gola - PD25 - v1 - share.pdf

2025-12-03 - Alberto Gola - PD25 - v1.pptx

2:58 PM Invited | 3D-integrated SPAD-CMOS detector systems

Speaker: Serge Charlebois (Université de Sherbrooke)

202512 PD2025 - Charlebois.pdf

202512 PD2025 - Charlebois.pptx

3:23 PM 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)

First Application of Photon-to-Digital converters to particle physics

3:41 PM 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)

20251203_PD2025_Fraunhofer IMS.pdf

4:00 PM → 4:30 PM Tea Break

4:30 PM → 5:30 PM Plenary Session

Convener: Fabrice Retiere (TRIUMF)

4:30 PM Invited | CMOS SPADs and digital single-photon imaging sensors

Speaker: Edoardo Charbon

EdoardoCharbon_Bologna_v2_released.pdf

4:55 PM Topical discussion | When will digital SiPMs become available for physics?

5:30 PM → 7:00 PM Exhibitors Talks

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

5:30 PM Hamamatsu

Speaker: Giuseppe Brizi

5:48 PM INCOM: Recent advances in large area MCP-PMTs based on lead-free MCPs

Speaker: Alexey Lyashenko (Incom Inc.)

Advances in the Large Area Picosecond Photo-Detector (LAPPD): 8" x 8" MCP-PMT with Capacitively Coupled Readout

HRPPD photosensors for RICH detectors with a high resolution timing capability

Latest feasibility studies of LAPPD as a timing layer for the LHCb Upgrade 2 ECAL

lyashenko_incom_pd2025_final.pdf

6:06 PM CAEN: Comprehensive Solutions for Advanced Data Readout

Speaker: Camilla Maggio (CAEN SpA)

CAEN_ComprehensiveSolutions_for_AdvancedDataReadout_PD2025.pdf

6:24 PM Photonis-Exosens: Fast-timing Single Photon Counting and Imaging with vacuum based detectors

Speakers: Dmitry Orlov (Photonis Netherlands), Emilie Kernen

PD2025 03-12-2025 SPD EK-DO to present F.pdf

6:42 PM FBK-SD: R&D for photodetectors technology

Speaker: Michele Penna (Fondazione Bruno Kessler (FBK))

FBK_exhibitor_PD_2025.pdf

7:00 PM → 8:30 PM Poster Session

7:00 PM A new computed tomography system based on a Timepix4 sensor with CdTe for cultural heritage analysis applications: preliminary results

In the framework of a 2022 PRIN Project a new system for computed tomography based on a Timepix4 sensor coupled with CdTe semiconductor has been developed in collaboration between the Department of Physics of the University of Ferrara and the Department of Physics and Astronomy of the Univesity of Bologna.
A small area sensor with 512x448 pixels of 55 micron size each onstitutes an array of photosensitive detector with spectrometric capability. Acquisitions with conventional low power laboratory microfocus X-ray tubes may undergo to photon energy thresholding or binning for selective CT reconstructions and specific materials characterization in the object under analisys. Promising achievements require fine calibration work, detector imaging performace characterization, data processing workflow development in order to be reached. The present work shows how the system has been designed and built and the first tests with X-rays made in Bologna.

Speaker: Matteo Bettuzzi (Istituto Nazionale di Fisica Nucleare)

Poster Bettuzzi.pdf

7:01 PM 3-inch PMTs for the Hyper-K outer detector

Hyper-Kamiokande will deploy about 3,600 3-inch PMTs in its outer detector to veto cosmic-ray backgrounds and improve event classification. Each PMT will be paired with a wavelength-shifting plate to increase the active photon-collection area. Two candidate designs, both with waterproof casings, are currently being evaluated through coordinated measurements across several laboratories. This talk will present the status of these studies, the selection process, and the quality control and deployment plans for the outer detector PMTs.

Speaker: Robert Kralik (King's College Londond)

PD2025_3InPMTsForHyperKOD_RobertKralik_v2.pdf

7:02 PM Performance of the fiber tracker of the Zirè detector onboard NUSES satellite

Plastic scintillating fiber trackers read out by Silicon Photomultipliers (SiPMs) are a promising alternative to silicon trackers for space experiments. This technology combines the compactness and low power consumption of SiPMs with the low material budget of plastic scintillators.
NUSES is a satellite mission, currently under construction, aiming to test innovative observational and technological approaches to study cosmic radiation. The Zirè payload on board NUSES will be equipped with three XY fiber tracker modules (FTK), designed for effective tracking of cosmic rays below a few hundred MeV. In addition, the FTK will be able to trigger events from low-energy charged particles, and to contribute to particle identification.
In this contribution the design and the performance of Zirè FTK will be presented, with studies in dedicated beam test campaigns at the CERN PS and SPS accelerator facilities. Finally, the effects of the radiation environment on the SiPM arrays and its impact on the overall performance of the FTK in space will also be discussed.

Speaker: Antonio Liguori (Istituto Nazionale di Fisica Nucleare)

poster_pd25_v4.pdf

7:03 PM Preliminary characterization of the 64-channel MIZAR ASIC for Cherenkov light detection

This work presents the implementation and the preliminary tests of the Multi-channel Integrated Zone-sampling Analogue-memory based Readout (MIZAR) ASIC. Developed using commercial 65 nm CMOS technology, the MIZAR ASIC is designed as part of the Cherenkov camera for the POEMMA Balloon with Radio (PBR) mission. The goal of the Cherenkov camera is to detect direct Cherenkov signals produced by Extensive Air Showers (EASs) pointing towards the detector. The broader objective of the PBR mission is the detection of Ultra-High Energy Cosmic Rays (UHECRs) and tau-induced air showers resulting from the interaction of Cosmic Neutrinos with the Earth's crust. In the MIZAR ASIC, a single channel is segmented into 256 acquisition cells and each one includes a capacitor, a Wilkinson Analog-to-Digital Converter (ADC) and a digital memory. This full waveform sampling system operates with an integration time of 5 ns and the data are converted on chip at the same frequency. MIZAR is designed to send out a 64-bit hitmap to use as first-level trigger to recognize patterns of interest. Each channel can be programmed to reduce the sampling window to 32 or 64 cells and the resolution can be set within the interval 8-12 bits. MIZAR was delivered in March 2025 and it has undergone laboratory testing in recent months.

Speaker: Andrea Di Salvo (Istituto Nazionale di Fisica Nucleare)

poster_Andrea_Di_Salvo.pdf

7:04 PM DENEB: a 1024-Channel Mixed-Signal ASIC for SiPM Readout with sub-100 ps Timing and Photon Counting Operating from 77 K to 300 K

DENEB is a 1024-channel mixed-signal ASIC under development at INFN in 110 nm CMOS technology for the readout of SiPM matrices across a wide temperature range (77–300 K). It is designed for GRAIN, a sub-detector of SAND at the Deep Underground Neutrino Experiment (DUNE) Near Detector facility (FNAL, USA). GRAIN is an active target consisting of a liquid-argon cryostat instrumented with cameras based on 32 × 32 SiPM arrays read out by the ASIC, enabling neutrino track reconstruction through scintillation light detection.
Each channel integrates a current conveyor, a transimpedance amplifier, two discriminators for double-threshold measurements, and four Time-to-Digital Converters (TDCs). The TDCs employ analog interpolation with Time-to-Analog Converters (TACs) and digitization via SAR or Wilkinson ADCs. The front end achieves Single-Photon Time Resolution (SPTR) below 100 ps, with time-walk correction using slew-rate or Time-over-Threshold (ToT) methods. A second branch enables charge measurement (photon counting) through a discrete-time current-to-frequency converter with real-time digitization. This provides a dynamic range exceeding 100 photoelectrons (PEs) and up to 50 simultaneous PEs, with sensitivity below 0.5 PE.
Each channel is implemented as a 500 μm-pitch square pixel. To mitigate TDC deadtime, four TDCs per pixel provide event derandomization, supporting event rates up to 10 MHz/pixel in ToT mode and about half in slew-rate mode. On-pixel logic buffers timing, charge, ToT, and ancillary data into two 64-bit event words, which are transferred via a daisy-chain bus to the end-of-column logic. Bandwidth can be doubled by disabling the second word and transmitting only timing data.
At the periphery, the end-of-column logic is equipped with SRAM capable of hosting up to 1024 (128-bit) or 2048 (64-bit) words per column, then transmits data through 32 SLVS/LVDS transceivers. Each operates at 320 Mbps (SDR) or 640 Mbps (DDR), yielding an aggregate bandwidth up to 32 × 640 Mbps using time-division multiplexing across parallel differential lines.
The chip occupies about 2 × 2.3 cm². A 44 × 36 grid of I/O pads on a 500 μm pitch covers the die. The 32 × 32 pixel matrix interfaces directly with the SiPM array through dedicated analog inputs, while supply and ground pads form a ring around the analog island to mitigate IR drop. At the bottom, 32 differential outputs serve the transceivers, supported by dedicated power pads.
Packaging development is ongoing with an external vendor, based on Fan-Out Wafer-Level Packaging (FOWLP). Cu-pillars grown on the pads connect to a silicon substrate that routes signals to a Ball Grid Array (BGA). The BGA maintains an identical pinout at a relaxed pitch for PCB compatibility. The package is optimized to minimize CTE mismatch, ensuring reliability from 300 K down to 77 K. A first engineering run and package production are scheduled for mid-2026. A second engineering run is planned for 2027.
At the conference, details on the ASIC floorplan, architecture, design trade-offs, key block features, and packaging technology challenges will be presented.

Speaker: Stefano Durando (Istituto Nazionale di Fisica Nucleare)

POSTER_PD_Bologna_11_2025.pdf

7:05 PM The ICECAL65: an Energy Measurement ASIC for the Upgrade II in the LHCb Calorimeter Detector

The core electronics in the LHCb Calorimeter Detector are intended to measure the energy and time of arrival (ToA) of particles using two different ASICs (ICECAL65 and SPIDER, respectively). The expected radiation levels inside the detector have arisen the need to upgrade the design to a high-radiation resilient technology, such as TSMC65. This work presents the analog design of the ICECAL6, a 4-channel ASIC developed in a 65-nm CMOS technology for the continuous readout of Photomultiplier Tubes (PMTs).
The reduced voltage supply in this technology (1.2V) toughens up to achieve the required resolution of 12-bit resolution. Hence, a two-gain scheme has been adopted using a Low-Gain (LG) path with 11 bits of precision and a High-Gain (HG) path that increases this resolution by 1 additional bit against low-amplitude input signals. Following the design in the ICECAL ASIC already installed in the LHCb calorimeter, both paths are based on two time-interleaved subchannels that guarantee the continuous readout of the input samples arriving every 25 ns. This is accurately achieved by adding a Phase Locked Loop (PLL) that generates the necessary clocks for all the internal switched blocks individually per channel with a phase step configuration below 1 ns.
Each of these subchannels is based on a processing chain comprised of (1) a voltage preamplifier, (2) a configurable pole-zero cancellation circuit to mitigate the effect of the spillover generated by the different detector technologies (Shashlink, SPACAL-W, and SPACAL-Pb scintillators), (3) an integrator with tunable time constant τ, and (4) a high-slew-rate track-and-hold (T&H) based on the bottom plate sampling technique. All these blocks are built with a fully-differential rail-to-rail (RTR) amplifier with high-performance specifications which has been particularly designed for this ASIC with: (1) an equalized RTR input stage loaded with a folded cascode to achieve constant GBW along the whole common-mode (CM) input range (~ 500 MHz) and a high open-loop gain (Av0 ~ 85 dB); (2) a class-AB output to maintain the RTR swing at the output; (3) a common-mode feedback amplifier (CMFB) that ensures a minimum deviation from the CM output level. The analog processing chain is followed by an output buffer to cope with the pads' parasitics and the load of the external ADC in charge of digitizing the measurement.
Regarding the generation of the clocks inside the system, a PLL has been included to generate the 20 MHz integrator and T&H clocks individually per channel, and the 40 MHz clocks required by the external ADCs. It comprises a Phase and Frequency Detector (PFD), a charge pump followed by a loop filter, and a Voltage-Controlled Ring Oscillator (VCO) that generates a low-jitter clock of 1.28 GHz. This clock is processed by a digital clock manager to obtain the 20 MHz and 40 MHz required clocks.
The ICECAL65 ASIC has been already sent for manufacturing, and it is expected to be tested and verified in early 2026.

Speaker: Alberto López Guillén (ICCUB)

PosterPICOCAL.pdf

7:06 PM Multi-anode Photomultiplier Tubes: review of characterisation and operations at the LHCb RICH detectors

The LHCb RICH system comprises two detectors, delivering excellent charged-hadron discrimination across the momentum ranges 2.6-60 GeV and 20-100 GeV respectively. Following its 2022 upgrade, the system employs more than 3000 Multi-anode Photomultiplier Tubes (MaPMTs) and operates at the full 40 MHz LHC bunch-crossing rate. Each of the 64 anodes of an MaPMT is digitised by a CLARO channel, giving $2\times10^5$ pixels that require careful gain and threshold calibration. With a recovery time below 25ns per channel, the RICH maintains peak pixel occupancies below ~30%, even in its busiest regions. This contribution details the characterisation and performance of the MaPMT technology after three years of operations in the LHCb experiment. Dedicated quality-assurance studies have fully characterised the signal-induced noise (SIN) of the MaPMTs, leading to HV and timing profiles that define the configurations and time-gating strategies used to mitigate SIN. Regular calibration scans further counteract ageing effects from the high-photocurrent environment by reconfiguring gain and threshold on a per-channel basis. In addition, detailed surveys have characterised the relative detection efficiency across the RICH surfaces using the full luminosity integrated by LHCb. The results of these efforts, and more, are described herein. Furthermore, the MaPMTs have allowed the RICH system to provide a new measurement of instantaneous luminosity to operate LHCb: the details of such technique will be presented as well.

Speaker: Michael Kane (University of Edinburgh)

Michael_Kane_PD2025.pdf

7:07 PM The ARC compact RICH detector concept: design, simulations and prototype development

Particle Identification (PID) will be crucial in Future Circular Colliders (FCC-ee) experiments for precision studies involving heavy-flavour particles in Z decays, as well as jet flavour tagging in the decays of Higgs, W, and top particles.
In this context, a novel Ring Imaging Cherenkov (RICH) detector concept, named ARC (Array of RICH Cells), has been proposed.
The ARC detector is designed to provide charged hadron separation over a momentum range of 1-40 GeV, using both $C_4F_{10}$ gas (or an environmentally friendly alternative) and aerogel as radiators.
The ARC detector features a modular design composed of identical cells, each equipped with the two radiators, a spherical mirror, and a Silicon PhotoMultiplier (SiPM) photodetection plane. Simulations demonstrate excellent hadron separation capabilities across the target momentum range.
Current work focuses on implementing sophisticated pattern recognition techniques and developing a robust simulation framework that includes magnetic field effects for accurate performance evaluation.
To validate the concept, a prototype ARC cell is currently under construction for laboratory and beam tests. The prototype includes a radiator and an SiPM-based photodetection module with integrated cooling to minimize dark count noise.
Additionally, a prototype cooling plate, which will be necessary for the SiPM photodetectors, is currently being tested to evaluate its thermal management performance. The design has progressed from initial plastic prototypes to an aluminum version, up to the final ceramic prototype.\
The latest simulation results, prototype developments, and performance assessments of the ARC detector will be presented, highlighting its potential for high-precision PID at FCC-ee.

Speaker: Serena Pezzulo (Istituto Nazionale di Fisica Nucleare)

ARC_PD2025.pdf

7:08 PM TCSPC Setup with SiPM Readout for Volatile Organic Compound Identification

Volatile organic compounds (VOC) detection in gas mixtures is crucial for air pollution monitoring as well as gaseous contaminants identification. A compact system able to quickly analyze the presence of such compounds could be deployed in a wide variety of environments. By exploiting gas fluorescence lifetime it enables applications such as sub-ppb gas quality monitoring.
An effective and innovative approach for gas analysis involves Time Correlated Single Photon Counting (TCSPC) technique, where the time-resolved fluorescence decay of the gas is acquired following pulsed excitation. The detector of a successful TCSPC setup must have a high detection efficiency to the emitted photons. Typical VOC fluorescence peaks occur in the near-UV (NUV) spectrum, where traditional photosensors have low quantum efficiency. This parameter is fundamental for single-photon detection in processes such as TCSPC.
This technique measures the time of arrival of the first emitted photon, which for VOCs such as Xylene is on the nanosecond scale, statistically reconstructing the fluorescence time decay histogram. For this reason, a detector with sub-nanosecond time resolution is required.
Silicon Photomultipliers (SiPM) are a good candidate for this task, thanks to their single-photon sensitivity and fast time response. At Fondazione Bruno Kessler, we developed a SiPM technology with enhanced sensitivity in the NUV range with compact footprint. The metal-in-trench (MT) process, developed at LFoundry, drastically suppresses the correlated noise. Consequently, a larger area can be instrumented with an overall reduction in exposure time.
This device will be deployed in a setup where a sub-nanosecond pulsed LED (265nm) will excite a selectable gas sample (or mixture), and its fluorescence will be detected by the SiPM after passing through a band-pass filter to limit the stray light from the primary source.
Thanks to the modularity of the system, in a second phase, the filter/SiPM stack can be substituted by a dispersive grating coupled to an array of 16 SiPMs (pixels) read out by an in-house custom designed ASIC equipped with 16 time-to-digital-converters (TDC) reprogrammable as photon counters. The fully digital readout chain allows for a fast data stream to enable even higher excitation rates. With this upgrade, the setup will spectroscopically separate the different peaks present in the VOCs, acquiring in parallel their time-resolved fluorescence spectra, hence enabling the detection of multiple molecules using the same gas sample with a reduced measurement time.
A production run of MT-filled NUV-sensitive SiPM has been successfully completed, the characterization of the device with its electrical and optical functional measurements will be reported, along with its integration in the assembled TCSPC setup and some preliminary measurement.

Speaker: Jacopo Dalmasson

20251122_pd2025_poster_jd.pdf

7:09 PM Characterization of a GAGG/Si-PM Gamma Camera Prototype for Ag-111 Imaging Apllications

Targeted Radionuclide Therapy combined with diagnostic imaging (“theranostics”) requires radionuclides that can provide both therapeutic and imaging capabilities. The isotope of Silver (Ag-111), with its beta emission for therapy and gamma emission at 245 keV and 342 keV, represents a promising candidate for imaging applications. Its relatively high photon energies are outside conventional range for SPECT systems, motivating the development of dedicated detection devices.
Within the ISOLPHARM-ADMIRAL project, we designed and characterized a compact gamma camera prototype optimized for Ag-111 imaging. The system consists of a tungsten collimator (with septa of 1 mm), a Cerium-doped Gadolinium Aluminum Gallium Garnet (GAGG:Ce) scintillator matrix 23 x 23 elements (1 × 1 × 17 mm3), a Hamamatsu 8×8 silicon photomultiplier (Si-PM) array (each pixel 3.0 × 3.0 mm2), and a commercial readout electronics (CAEN-FERS). SiPMs provide compactness, robustness, high timing performance and magnetic field immunity compared to conventional photomultiplier tubes.
Laboratory characterisation was carried out using an optical laser and gamma-emitting sources, including Ba-133 and Ag-111, to evaluate spatial resolution, and system linearity.
Particular attention was given to spatial resolution and the assessment of imaging feasibility.
First results indicate that SiPM-based detectors coupled with GAGG crystals provide a feasible approach for high-energy SPECT imaging, within a modular system specifically optimized for Ag-111 theranostic applications.

Speaker: Edoardo Borciani (Istituto Nazionale di Fisica Nucleare)

ADMIRAL A0_Poster.pdf

7:10 PM Zero-Dimension Cs3Cu2I5 Perovskite-Inspired Scintillators for Next-Generation Nuclear Medicine-based Medical Imaging

The demand for efficient, cost-effective, and stable scintillators drives the search for new materials. Halide Perovskite-inspired materials have recently gained significant interest. They are considered promising scintillators in medical and high-energy physics due to their excellent theoretical light yield, energy, and time resolution. They demonstrate good structural and environmental stability when exposed to γ-rays, which promises advances over their halide Perovskite counterpart. These materials are also more chemically flexible in terms of doping and cation changes at the A- and B-sites. Smaller elements, such as lithium doping, can be employed for both gamma and neutron scintillators, allowing for highly effective neutron-gamma discrimination. These types of copper-based single crystals (SCs) can typically be grown in two phases, and the combination of these two phases, Cs3Cu2I5(0D) and CsCu2I3 (1D), emits blue and yellow light upon radiation. The max phase emits a white light with a broad spectrum from 400 to 700 nm. Moreover, these SCs can be useful in both types of radiation detectors, conventional and direct detectors, by employing charge transport layers for the band alignment with the cathode and anode. In this work, Cs3Cu2I5 PVK-inspired SCs were grown using a cost-effective solution method with larger size and transparency using chemical additives. Initially, the SCs were studied through various physical characterization techniques, including optical and structural analysis through UV-visible spectroscopy, luminescence measurements, and X-ray diffraction (XRD). For the final application, the custom-made system was coupled with a multi-anode PMT and dedicated electronics. The preliminary γ-ray testing using an imaging device shows the potential of Cs3Cu2I5 as an efficient and affordable choice for traditional halide scintillators like NaI and CsI for nuclear medicine-based imaging devices. Currently, centimeter scales and real-time characterization are possible; however, the upscaling still hinders these scintillators from being utilized commercially for large-sized application devices, and more research is required. This study marks a step toward replacing current scintillators in next-generation nuclear medicine imaging.

Speaker: Mr Ibrar Ahmad (sapienza university of rome)

AHMAD_IBRAR PD2025 POSTER_v2.pdf

7:11 PM Single-Pulse Spectroscopy with 2D Perovskites: from Single Crystals to Thin Films

Two-dimensional (2D) perovskite thin films have recently emerged as efficient direct photocurrent detectors, owing to their strong light absorption, fast charge separation, and intrinsically low dark currents. When integrated onto planar interdigitated pixel electrodes, flexible PEA₂PbBr₄ films exhibit stable operation and extremely low noise (~10 pA at 4 kV/mm), enabling sensitive photocurrent measurements across a broad spectral range, including ultraviolet, X-ray, and clinically relevant γ photons. To further validate their potential, we extend their operation to single-particle detection: alpha particle signals (²⁴¹Am, 5.5 MeV) are resolved down to single-pulse events, serving as a proof of principle toward single-photon sensitivity. Comparative analysis with single-crystal counterparts yields mobility–lifetime products of μτ ≈ 10⁻⁶ cm²/V for thin films versus ≈10⁻⁵ cm²/V for single crystals, consistent with literature benchmarks. These results highlight the versatility of 2D perovskite thin films, validating their operation as direct photocurrent detectors from ultraviolet photons to energetic particles, and positioning them as scalable platforms capable of advancing toward single-photon sensitive detection.

Speaker: Lorenzo Margotti (UNIBO)

PD_Bologna_Poster_LM.pdf

7:12 PM Status of the SiPM camera upgrade for the prototype Schwarzschild-Couder Telescope

Very-high-energy gamma-ray astrophysics will experience a substantial enhancement in sensitivity through the capabilities of the Cherenkov Telescope Array Observatory (CTAO), which will operate from two sites providing full-sky coverage. One candidate for the medium-sized telescope (MST) of CTAO southern site (CTAO-South) is the Schwarzschild-Couder Telescope (SCT). The innovative design of SCT consists of dual-mirror optics and a high-resolution silicon photomultipliers (SiPM) camera. A prototype telescope (pSCT) was installed at the Fred Lawrence Whipple Observatory in Arizona, USA, and with a partially instrumented 2.7° camera, it successfully detected the Crab Nebula with a statistical significance of 8.6 standard deviations in 2020. A major upgrade of the focal plane is currently underway to fully equip the camera with 11328 improved SiPMs, expanding the field of view from 2.7° to 8° and enabling exceptional performance in terms of angular resolution and background rejection. Additionally, upgraded low-noise front-end electronics will allow for a reduced trigger threshold and improved event reconstruction. This contribution presents an overview of the pSCT project, recent results, and the status and expected performance of the camera upgrade.

Speaker: Serena Loporchio (University and INFN Bari)

Poster_PD_SCT_Loporchio_V0.pdf

7:13 PM Characterization of afterpulse in SiPMs with single-cell readout as a function of bias voltage and fluence

We present a detailed investigation of the afterpulse effect in silicon photomultipliers (SiPMs), using a dedicated structure with single-cell readout, which enables direct measurement of intrinsic device properties and observation of individual pulses also after irradiation.

Three independent analysis methods to quantify afterpulse induced events were developed and validated by Monte Carlo simulations.

The first method is based on charge integration, while the other two methods use multiple linear regression to reconstruct transient waveforms and accurately identify individual pulse positions. These pulse positions are then used either as direct event counts or to construct time interval distributions, enabling comprehensive characterization of the afterpulse probability and providing insights into the dynamics of trapping in silicon.

Using this framework, we measured three SiPM samples with single-cell readout: one fresh reference device and two irradiated devices that were exposed to neutron fluences of 2x10¹² and 1x10¹³ neq/cm².

We report systematic measurements of the afterpulse probability and time constant as functions of bias voltage and irradiation fluence. For overvoltages in the range of 3–5 V above breakdown, the afterpulse time constant is found to be below 10 ns and the afterpulse probability below 5%. Both quantities show no significant dependence on irradiation fluence.

Speaker: Pavel Parygin (University of Hamburg)

Parygin_PD25_SingleCellSiPM.pdf

7:14 PM A novel single photon detector based on MCP-PMT with embedded Timepix4 ASIC

High-rate single-photon detection with excellent spatial and temporal precision is a critical requirement for next-generation imaging and particle physics experiments. To meet this demand, a novel detector has been developed based on a vacuum tube architecture that integrates a photocathode, a microchannel plate (MCP), and a Timepix4 CMOS ASIC as the readout anode. The system supports detection rates up to $10^9$ photons per second over a 7~cm$^2$ active area, achieving spatial resolutions of $5–10$ $\mu$m and timing resolutions better than 100 ps. The Timepix4 ASIC, comprising approximately 230 thousand pixels with integrated analog and digital front-end electronics, can operate in data-driven or frame-based acquisition mode and sustains data transmission rates up to $160$ Gb/s. Control and readout are provided by FPGA-based external electronics.
Validation with a prototype coupled to a $100$ $\mu$m thick n-on-p silicon sensor and illuminated by a pulsed infrared picosecond laser demonstrated a timing resolution of about 110~ps per pixel hit, improving to below 50~ps when exploiting cluster information and accounting for other contributions.
Six prototype detectors produced by Hamamatsu Photonics, with varying MCP stack configurations and end-spoiling depths, have been characterized in terms of gain, dark count rate, spatial and timing resolutions, both under laboratory conditions and at CERN's SPS test beam facility. These preliminary results will be discussed, along with plans for the future.

Speaker: Dario Fornaro (Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara and University of Ferrara, Physics and Earth Sciences Department)

PD2025_4DPHOTON_POSTER.pdf

7:15 PM Multi-Photomultiplier Detectors in the Water Cherenkov Test Experiment

The Water Cherenkov Test Experiment (WCTE) at CERN is designed to test various technologies and techniques related to water Cherenkov detectors, which may later be implemented in the Hyper-Kamiokande experiment. WCTE consists of 97 multi-PMT photosensors placed in a water tank (˜3.8 m in diameter, ˜3.6 m in height, total water mass ˜41 tonnes). Each multi-PMT contains nineteen 3” PMTs and associated front-end electronics, all enclosed in a watertight pressure vessel. Most of the WCTE mPMTs use the same mPMT design, with improvements, which will be used in the IWCD (Intermediate Water Cherenkov Detector). A small number of WCTE mPMTs use a similar design—capable of withstanding higher pressure and featuring lower power consumption will be deployed in the Far Detector of Hyper-Kamiokande. In this talk, we will focus on the design and production of the mPMT detectors for WCTE, describing quality assurance measures, assembly procedures, and initial testing. We will also present the methods used to evaluate the electronics performance and the parameters of the 3-inch PMTs. Finally, the results of data analysis from the gain and timing calibrations will be described, and examples of particle identification capability will be provided with modules installed in the WCTE detector.

Speaker: Bartosz Piotrowski (Warsaw University of Technology)

poster_PD2025_BP_FV.pdf

7:16 PM Design and characterization of the SiPM-based tracker-calorimeter system for space astrophysics

The Advanced Particle Astrophysics Telescope (APT) is a proposed space-based gamma-ray observatory for the MeV–TeV range. To validate its detector technologies, the Antarctic Demonstrator for APT (ADAPT) is being developed for a balloon flight during the 2026–2027 Antarctic summer. Its core consists of an Imaging CsI Calorimeter (ICC) and a four-layer scintillating fiber tracker (Hodoscope).
The ICC is built from 3x3 arrays of CsI(Na) tiles, each coupled to orthogonal WLS fiber planes read out by SiPMs, enabling fine x–y energy reconstruction. An innovative feature of ADAPT is the addition of edge-mounted SiPM arrays, which collect escaping scintillation photons and enhance both light yield and localization. The Hodoscope complements the ICC with four crossed fiber layers providing precise trajectory information.
Both detectors rely on a large number of optical channels, with each fiber individually coupled to SiPMs. To meet the compactness and low-power constraints of a space application, a multiplexing scheme is adopted together with the 16-channel SMART (SiPM Multichannel ASIC for high Resolution Cherenkov Telescopes) ASIC for SiPM readout. Edge-detector information compensates for multiplexing-induced ambiguities, preserving reconstruction accuracy.
This contribution presents the design and performance characterization of the multichannel SiPM readout for ADAPT, marking one of the first implementations of a highly segmented SiPM-based tracker–calorimeter system for space astrophysics.

Speaker: Gaia De Palma (Istituto Nazionale di Fisica Nucleare)

Poster_De_Palma_PD.pdf

7:17 PM Revealing the Impact of Phase Transition on n = 1 2D Perovskite Photodetectors with Intrinsically Tunable Narrowband Detection

n=1 two-dimensional (2D) perovskites display narrow absorption due to their excitonic nature and quantum-confined structure. They offer a compelling route to filter-free, narrowband photodetection compared with broadband 3D counterparts. While halide mixing provides spectral tunability, it introduces severe phase segregation and energetic disorder. Current understanding of this phenomenon is derived mainly from static material characterisation, leaving its dynamic impact in operational devices unexplored. Herein, we bridge this gap by integrating n = 1 (PEA)2PbBrxI4-x into photoconductors, achieving tunable response from 402 to 516 nm, with the highest specific detectivity (D) of 2.11×10^11 Jones at 20V. We demonstrate that halide immiscibility significantly reduces D. We reveal how crystal packing drives phase segregation with DFT calculations and applied spectroscopies to understand the energetic disordering. Chloride additives are found to suppress macroscopic segregation and improve crystallinity, however, electronic disorder is simultaneously worsened, introducing traps that quench photocurrent. Directly visualised via photocurrent mapping and kelvin probe force microscopy. Consequently, the additive enhances the out-of-plane orientation, disrupting in-plane transport in photoconductors, while improving performance in vertical photodiodes. This work provides the first device-level insight into halide immiscibility in n=1 2D perovskites, revealing that overcoming the performance limitations in these systems requires balancing long-range structural order with short-range electronic integrity.

Speaker: Ding Ding (Imperial College London)

Ding poster printing PD 2025.pdf

7:18 PM New generation of TSV-enabled SiPM technologies for medical imaging and industrial applications

Silicon Photomultipliers (SiPMs) have become essential photodetectors in a wide range of applications—from medical imaging to high-energy physics (HEP)—thanks to their excellent timing capabilities, compact form factor, and ease of integration. These demanding fields require continuous innovation, particularly in the development of next-generation photodetectors and advanced system integration techniques. FBK is actively addressing these challenges by developing new SiPM technologies with customized Through-Silicon Via (TSV) solutions, enabling 2.5D and 3D integration with readout electronics. This architecture allows for high-density interconnections and fine detector segmentation, reducing output capacitance per channel, preserving signal integrity, and enhancing timing performance. Two projects adopting this approach are PETVision, focused on high-resolution Time-of-Flight PET for medical imaging, and COSMOPORT, which aims to develop next-generation scanner systems for cargo inspection using Muon Transmission Tomography (MTT). These advancements will support the ongoing improvement of FBK SiPM technology, enabling enhanced performance across diverse fields—from medical imaging to large-scale physics research—with meaningful societal impact.

Speaker: Carina Trippl (Fondazione Bruno Kessler (FBK))

2025 - Poster_TSVatFBK_Penna_Trippl.pdf

7:19 PM Near-infrared CMOS imaging for large-area SiPM-based photodetectors diagnostics

Solid state photodetectors are broadly used in many areas of research, from high energy physics at colliders to low energy one for solid state studies. The DarkSide collaboration is going to explore a new direction by using large arrays of Silicon Photo Multipliers (SiPMs) for direct dark matter search, where Photo Multiplier Tubes (PMTs) have been used until now. The DarkSide-20k (DS-20k) experiment, currently in construction at Laboratori Nazionali del Gran Sasso (LNGS), will feature a 50 tonnes (20 fiducial) argon-based double-phase TPC (Time Projection Chamber) to probe WIMP-nucleon cross section down to 10$^{-48}$ cm$^2$. The top and the bottom planes of the TPC will be tessellated by 21 m$^2$ (10.5 m$^2$ each) of low-noise SiPM-based detectors with quantum efficiency greater than 40% at 420 nm designed to work at cryogenic temperatures. They will measure the light emitted by scintillation and ionization processes in the two phases of the TPC after a conversion from 128 nm to 420 nm operated by a TPB wavelength shifter. A great effort was carried out by the collaboration to reach an excellent single-photon resolution by selecting radiopure materials whose specific activities reach values down to few mBq/kg. The SiPMs themselves were custom developed for DS-20k by Fondazione Bruno Kessler (FBK) in Trento and produced by LFoundry in Avezzano, both of them located in Italy.
The mass production of 528 20 $\times$ 20 cm$^2$ Photo Detection Units (PDUs), composed by 16 $ 5 \times 5 $ cm$^2$ SiPM tiles each, is ongoing in Nuova Officina Assergi (NOA), an ISO-6 cleanroom built at LNGS equipped with production and testing facilities for large-area SiPM matrices. The DS-20k tiles, composed by 24 SiPMs read-out by a single trans impedance preamplifier, are the smallest self-consistent photodetector modules assembled in NOA and their production (more than 10000 tiles in total) represents an unprecedented effort for the INFN research center. The set up of a near-infrared CMOS camera, recently introduced in the NOA facility, enables a much deeper comprehension of our detectors, with the identification of the defective ones. The measurement of the light emission of a biased tile imaged by our CMOS camera demonstrated to be a powerful tool to identify SiPMs with high current leakages. Therefore they can be replaced, allowing the tiles to recover their full functionality. This process sensitively increases NOA’s tile production yield. A further study is ongoing to find a correlation between the light emission properties of SiPMs and the dark count rate of the tiles measured in liquid nitrogen.

Speaker: Andrea Marasciulli (Istituto Nazionale di Fisica Nucleare)

Poster_Marasciulli_PD25.pdf

7:20 PM First observation of minimum ionising particle tracks in the RIPTIDE detector

RIPTIDE is a novel fast-neutron detector concept designed to determine both the energy and the direction of incident neutrons through indirect detection via neutron-proton elastic scattering. The converter medium consists of a cubic plastic scintillator (BC408, 60 × 60 × 60 mm³), where neutron-proton scattering events can generate recoil protons that produce scintillation light. This light is collected through a lens system and an image intensifier (MCP with a phosphor screen) and subsequently recorded by a fast CMOS camera, yielding a digital image of the event.
We present the first study of an experimental apparatus in which different cubic scintillators (BC408, CsI(Tl), and GAGG) are tested to investigate the possibility of detecting minimum ionizing particles, whose light yield in scintillators is significantly lower compared to protons. To increase the available information, two faces of the scintillator cube can be imaged simultaneously using a mirror. In this first setup, we successfully observe muon scintillation tracks in the CsI(Tl) crystal and obtain the first images showing two projections of a single track.
In parallel, a Monte Carlo simulation is performed, and a comparison between simulated and experimental data is presented. Finally, we report the first preliminary results on the three-dimensional reconstruction of muon tracks inside the scintillator.

Speaker: Samuele Lanzi (Istituto Nazionale di Fisica Nucleare)

lanzi_pd2025.pdf

7:21 PM Cherenkov detectors in the extreme LHC environment: LUCID PMTs and fibers.

The LUCID-2 detector is the main luminometer of the ATLAS experiment and the only one able to provide a reliable luminosity determination in all beam configurations, luminosity ranges and at bunch-crossing level. The detector works through the production and detection of Cherenkov light in unusual ways: within the fused silica (quartz) window of the photomultipliers (PMTs) and in the core of dedicated fused-silica optical fibers. Since the PMTs and the fibers are positioned in the forward region, LUCID puts to the test these detectors in some of the most extreme environments in particle physics. To keep the detectors stable in these condition, an innovative gain monitoring system based on Bi207 source deposition of the PMT window was developed. The environment will get even more challenging with the upgrade to the High Luminosity LHC (HL-LHC), where the average number of interactions per bunch crossing will go from 60 to 140 and then 200. Prototypes of the photomultiplier and the fiber detectors are currently installed in ATLAS in order to understand their performance and the characteristics of their signals in a real environment. The analysis of these detectors will be presented, together with the laboratory, irradiation and test-beam results obtained during the characterization of the prototypes. These will also be compared with alternative PMTs and fiber lab and irradiation results.

Speaker: Davide Cremonini (Istituto Nazionale di Fisica Nucleare)

photon poster.pdf

7:22 PM Preamplifier Readout Electronics for Summing SiPMs Enhanced Circuit (PRESSEC) for Advanced SiPM camera

The next generation of IACT cameras is moving towards SiPMs for their stability, robustness, and higher sensitivity compared to PMTs. The Advanced SiPM Camera (AdvCam) is based on Silicon Photo-Multipliers (SiPMs) as photosensors and aims to deliver fully digital images downstream. It is designed to offer improved sensitivity, extended sensor durability, and intelligent data processing to more efficiently suppress background noise close to the detector level.

A 32-input channel ASIC is being designed using 65 nm CMOS technology. This ASIC, referred to as PRESSEC (Preamplifier Readout Electronics for Summing SiPMs Enhanced Circuit), has been proposed for the readout of large-area sensors. Its primary function is to provide an analog output by summing the signals from multiple sensors. An external ADC operating at 1 Gbps will be used for digitization. The PRESSEC provides accurate energy measurement by summing signals from four SiPMs into a differential output, thereby reducing the ASIC to 8 output channels. A pole-zero cancellation circuit is included to reduce the Full Width at Half Maximum (FWHM) of the pulse, minimizing pile-up effects from subsequent events. Additionally, a Night Sky Background (NSB) monitoring circuit measures unwanted events caused by moonlight or other ambient light sources. This circuit integrates detected events and can measure NSB rates from 1 MHz to 1 GHz, with a time constant ranging from 1 to 10 ms. To accommodate the large dynamic range required for NSB rate measurements, the ASIC employs a dual-gain structure with automatic switching controlled by comparators. Lastly, a trigger signal is provided at the output as the sum of all input signals for early event identification.

Several blocks are already complete at the schematic level, with layout implementation expected in early 2026. The energy readout achieves a signal-to-noise ratio (SNR) of at least 5 (linear), a dynamic range of up to 300 photons, a pulse width of 3–4 ns at FWHM, and a linearity error below 3% when tested with a Hamamatsu S13360-3075CS-UVE SiPM. Power consumption per input channel is expected to be below 10 mW. In addition, the NSB measurement circuit can accurately measure NSB fluxes up to 1 GHz with a linearity error below 2%.

Speaker: Daniel David Marín Medina (Institut de Ciències del Cosmos - Universitat de Barcelona)

Poster_CTA_PD25.pdf

7:23 PM A SiPM-based readout for high-resolution electromagnetic calorimetry

A high-resolution electromagnetic calorimeter typically consists of an array of inorganic scintillators in crystalline form (cells), read out by Photo-Multiplier Tubes (PMTs) or Avalanche Photo-Diodes (APDs). An energy resolution of $\simeq 2\%$ at 1 GeV is considered excellent performance.

When a particle hits the scintillator, it loses energy through Bremsstrahlung and $e^+e^-$ pair production, generating an electromagnetic cascade that spreads from the main cell (seed) to several adjacent scintillators. For a particle in the 1-10 GeV range, most of the energy is released in the seed (up to $\simeq 6$ GeV). To reconstruct the total energy of the particle, the deposited energy in the neighboring cells must be measured down to a few MeV. This is necessary to reduce the uncertainty to a value comparable with the statistical fluctuations of the electromagnetic cascade. PMTs and APDs are well-known technologies, with readout chains developed and optimized over many years. Nevertheless, they have some limitations: high cost and complexity, sensitivity to magnetic fields (PMTs), and the need for complex high-gain signal amplification (APDs). The commercial development of a new, cheaper, high-performance photo-sensor, the Silicon Photo-Multiplier (SiPM), opens the possibility of a new readout approach. The SiPM is a solid-state sensor consisting of a matrix of micrometer-size APDs (pixels). Its appealing features include high quantum efficiency, low bias voltage, and high gain, but some limitations arise in calorimetry applications: the saturation effect impacts energy resolution if more than 10-15\% of pixels are activated; the gain depends on external factors such as temperature and bias voltage; and the active area of a single photo-sensor is limited.

A matrix of SiPMs with asymmetric segmentation can address these issues: it consists of two sub-matrices optimized for low- and high-energy signals, with an overlap region allowing cross-calibration. One proposal is to develop a 9-photo-sensor matrix composed of 2 SiPMs with large (50-75 $\mu$m) pixels, optimized for signals in the range 5-200 MeV, and 7 SiPMs with small (10-25 $\mu$m) pixels, optimized for signals in the range 20 MeV-6 GeV. This design will provide a large dynamic range ($\sim 1000$), allowing continuous single-photoelectron measurements to monitor sensor gain, while minimizing saturation. The poster will show the idea, the simulation and the preliminary study performed at INFN Genova.

Speaker: Simone Vallarino (Istituto Nazionale di Fisica Nucleare)

Poster_PD2025.pdf

7:24 PM Probing Radiation Damage in SiPMs with Emission Microscopy

Silicon sensors are widely employed in modern physics experiments for their excellent spatial resolution, fast response, and scalability, which makes them indispensable in both tracking detectors and photodetection systems. Silicon photomultipliers (SiPMs) are increasingly adopted for their excellent photon detection efficiency, fast timing, scalability, and insensitivity to magnetic fields, making them attractive for applications ranging from calorimetry to Cherenkov light detection. However, their long-term performance is challenged by radiation damage arising from the high particle fluxes typical of collider environments. Ionizing and non-ionizing radiation introduce defects in the silicon lattice, which manifest as increased dark count rate, afterpulsing, and reduced photon detection efficiency, ultimately degrading single-photon sensitivity.

As radiation-induced defects act as generation-recombination centres in the silicon lattice, light is emitted from these defects and can be spotted taking pictures of the device with a high-performance camera. Previous studies of radiation damage in SiPMs have been limited to electrical characterization. We complement these traditional approaches with an optical characterization of the sensors, using emission microscopy to directly visualize radiation-induced defects in the silicon lattice. This combined methodology provides deeper insight into the nature and localization of the damage, offering a more comprehensive understanding of its impact on SiPM performance.

In this poster, the microscope setup and the first results will be presented. Pictures taken before and after irradiation with protons at a fluence of ~$10^9$ $\rm n_{eq}/cm^2$, and after annealing cycles, show the evolution of the defects in the Hamamatsu SiPM sensors under study.

Speaker: Tommaso Marinelli (Istituto Nazionale di Fisica Nucleare)

PD POSTER.pdf

7:25 PM Recent GasPM advances: photon-feedback mitigation and LaB6 photocathode studies

We report the results of recent developments and tests with beams and cosmic rays of the gaseous photomultiplier (GasPM). The GasPM is a photosensor that combines a photocathode with the avalanche-multiplication mechanism of a resistive-plate chamber and offers excellent time resolution and cost-effective scalability. In addition, the GasPM can provide precise and efficient, Cherenkov-based, charged-particle identification if combined with a radiator. The GasPM can find applications in many HEP experiments. Our primary use case would be in an upgrade of the Belle II detector to suppress off-collision-time beam-induced background photons that degrade the performance of the electromagnetic calorimeter. In 2022 we achieved a promising single-photon time-resolution of 25 ps at 3.3 × 10$^6$ gain using a picosecond-pulse laser and a lanthanum hexaboride (LaB$_6$) photocathode. However, a 2023 beam test with electrons impinging on a MgF$_2$ window attached to a CsI photocathode showed a worsening to 70 ps.

This contribution addresses the principal causes of the time-resolution degradation. We primarily target ultraviolet-photon emission during excitation and de-excitation of the gas molecules, which leads to a secondary signal that overlaps the primary signal, spoiling time resolution (photon feedback). To this end, we designed and executed an improved beam test that, along with several GasPM configuration changes, introduces a new 10 GSPS sampling-frequency digitizer to better discriminate primary from secondary signals thus suppressing photon feedback. We also conduct a cosmic-ray test using a LaB₆ photocathode, which is known to have higher than CsI's resistance to ions drifting backwards onto the photocathode and to air exposure, to probe quantum efficiency in view of an upcoming beam test.

Speaker: Simone Garnero (UNIBO)

PD2025_GasPM.pdf

7:26 PM Fully-Digital 110 nm CMOS SiPM for Ultra-Fast Amplitude, Time-of-Arrival, and Time-over-Threshold Measurements

A monolithic silicon photo-multiplier, including 1024 micro-cells with a 30 $\mu$m pitch and a fill-factor of 50% and covering an overall area of about 1 mm$^2$, has been designed in a 110 nm CMOS image sensor technology. The SiPM, targeting applications with light detection in dual-readout (DR) calorimetry, takes advantage of an asynchronous, parallel counter to compute the number of hit pixels. It provides the count in digital form with a worst-case (slow-slow process corner, full scale signal) latency time of 15~ns, which can compete with conventional analog processing-based solutions. Time-of-arrival of the first photon and duration of the signal are measured by means of two 12-bit time to digital converters with a sub-100 ps resolution. The careful design of a fast NAND/NOR tree (NNt), which preserves the symmetry of the signal path as much as possible, minimizes fixed pattern jitter, thus ensuring an uncertainty in the arrival time of the first photon of less than 30 ps (after parasitic extraction). Noise mitigation is accomplished both by individually disabling hot micro-cells and by selecting a suitable thresholding mode from three available options. The first one relies on the measurement of the NNt output signal duration to detect signals exceeding one single photon. The second option enables data readout when at least two photons are read out in coincidence from any two adjacent double-rows (each double-row including 64 cells). The third one, similar to the second option, is based on the coincidence readout of at least three photons from any three adjacent double-rows. The prototype of the proposed digital SiPM is also instrumented for a full characterization of the SiPM from the standpoint of uncorrelated (dark count rate) and correlated (after-pulsing, cross-talk) noise. The conference paper will present a detailed discussion of the main features of the detector, together with results from post-layout circuit simulations, highlighting its advantages with respect to established analog SiPM solutions.

Speaker: Tommaso Maria Floris (Istituto Nazionale di Fisica Nucleare)

poster_v2.pdf

7:27 PM Development of a Thin-Layer Scintillation-Based Dosimeter for Surface Dose Measurement in Radiotherapy

Non-melanoma skin cancers (NMSC) account for nearly 96% of the worldwide diagnosed skin cancers and are often surgically removed. However, when surgery is not feasible, radiotherapy is a valid alternative treatment. In radiotherapy, patient-specific quality assurance (PSQA) relies on dose distribution measurements. Today the state-of-art technologies do not assure accurate measurements of the dose deposited in the superficial layers of the skin. The first few millimeters of skin are especially sensitive to ionizing radiation, and understanding dose distribution at these depths is essential to minimize adverse effects and to optimize the treatment effectiveness. In order to address this challenge, medical physicists frequently use a “bolus”, a semi-rigid material placed over the tumor to mimic tissue. Yet, as the tumor shrinks, air gaps may appear between fractions, leading to an underdosage of the prescribed treatment. To evaluate the air gap effect, a prototype detector (DQX) was designed and tested at the LPC[1] and CFB[2]. Based on a 100 μm thick plastic scintillator connected to wavelength shifting fibers, this device aims to measure radiation doses in the superficial layers of tissue, with a target relative measurement error below 1% for a 2 Gy photon dose, down to 70 μm below the skin surface.
In this presentation, an overview of the studies conducted on the DQX detector prototype is presented, describing in detail the experiments carried out and the preliminary results obtained. We also explore the detector design, its performance, limitations, and advantages, as well as perspectives for future developments in this field.

1 Laboratoire de Physique Corpusculaire de Caen, France
2 Centre François Baclesse, Caen, France

Speaker: Giulia Tosetti (Université de Caen Normandie, ENSICAEN, CNRS/IN2P3, LPC Caen UMR6534, F-14000 Caen, France)

Poster_DQX_PD2025.pptx

7:28 PM Evaluating Position Dependency of Detection Performance for 50-cm Hyper-Kamiokande Photomultiplier Tube

Hyper-Kamiokande, the successor to Super-Kamiokande, is a next-generation water Cherenkov detector scheduled to begin operation in 2028. It aims to measure neutrino oscillation parameters, such as the CP phase and mass ordering, with much higher precision benefiting from a fiducial volume 8.4 times larger than that of Super-Kamiokande. The newly developed 50-cm photomultiplier tube (PMT), R12860, manufactured by Hamamatsu Photonics K.K., provides two times higher resolution for both charge and timing measurements, as well as twice the detection efficiency. However, possible non-uniform response across its large photosensitive area may serve as a source of systematic uncertainty. To reduce and quantify this uncertainty, it is necessary to evaluate the PMT response uniformity under realistic conditions, including different high-voltage (HV) settings and ambient magnetic fields.
To evaluate the PMT uniformity, the PMT response was measured at more than 1,000 photon incident positions. At each position, various PMT properties were measured, including the single photoelectron charge distribution (from which gain was obtained), cathode transit time difference (CTTD), transit time spread (TTS), and relative detection efficiency. The photon incident position was controlled by a robotic arm, with the light source kept at a constant distance and oriented perpendicularly to the PMT surface so that the laser beam spot size and reflectivity remained unchanged. These uniformity measurements were repeated under different HV settings and magnetic fields, the latter controlled by a Helmholtz coil.
In a 0 mG environment, variations in response depending on the photon incident position were observed, appearing to correspond to the shape of the dynode. The influence of high-voltage differences had a larger impact on the response than the dependence on the photon incident position. However, the effect on uniformity could be compensated by a constant factor that did not depend on the position. Regardless of the HV, the gain ratio varied by less than 4%, and the detection efficiency ratio by less than 10%, except at the very edge of the PMT. A magnetic field was found to affect the uniformity response, introducing an asymmetric dependence on the azimuthal angle of the PMT position. For instance, in a 100 mG environment, the CTTD shifted by about ±2 ns depending on the direction of the magnetic field and the photon incident position. These uniformity results were parametrized in a model function of the photon incident position, HV, and magnetic field, which can be incorporated into event reconstruction and simulation programs, and applied to correct the PMT response for variations in the operational conditions in Hyper-Kamiokande.
In conclusion, the uniformity study of the 50-cm PMTs has clarified the key dependencies more comprehensively than previous studies, and this has enabled us to establish a PMT response model. This model will be utilized to suppress systematic uncertainties, thereby contributing to the precise determination of oscillation parameters.

Speaker: Shogo Horiuchi (Keio University)

Horiuchi_PD2025.pdf

7:29 PM Studies of Silicon Photo-Multipliers for the LHCb Upgrade II in Genova

The Upgrade II of the LHCb experiment poses new challenges for the Ring Imaging Cherenkov (RICH) detectors in terms of high radiation levels and increased photon density during the High-Lumi LHC phase. It will therefore be essential to redesign the optical layout of the detector, improving the resolution of the reconstructed Cherenkov angle, increasing spatial granularity, and introducing photon timing information.

In this context, the Silicon PhotoMultiplier (SiPM) is one of the most promising photosensor candidates: it offers high efficiency in single-photon detection, remarkable time resolution, good granularity, and relatively low costs. However, it suffers from a high noise rate (due to dark counts and correlated noise), which worsens under radiation exposure. This makes the development of radiation-hard SiPMs indispensable; to this end, a campaign is underway to study critical parameters such as dark count rate, photon detection efficiency, and time resolution as a function of temperature, including concepts for the cooling of the sensors in order to mitigate the dark counts.

This talk aims to present an overview of the technical and scientific challenges related to the upgrade of the RICH detectors, highlighting future perspectives and possible developments of SiPM technology in the High-Luminosity LHC era.

Speaker: Simon Ghizzo (Istituto Nazionale di Fisica Nucleare)

Poster_PD2025.pdf

7:30 PM Radio Frequency Photo Multiplier Tube with different photocathodes

Abstract. Recently we developed an advanced radio frequency timer of keV energy electrons. It is based on a helical deflector, which performs circular sweep of keV electrons, by a means of 500 MHz radio frequency field. By converting a time distribution of incident electrons to a hit position distribution on a circle, this device achieves extremely precise timing. Streak Cameras, based on similar principles, routinely operate in the ps and sub-ps time domain but have substantial dead time associated with the readout system. Here, the position sensor, consisting of microchannel plates and a delay-line anode, produces ~ns duration pulses. The dead time of the device in this case is determined by the propagation time of signals in a delay-line, which are around 20 ns duration. A possible application of this new timing technique is in the Radio Frequency Photo Multiplier Tube. Measurements made with different photocathodes and sub-ps duration laser pulses, synchronized to the radio frequency power, produced a timing resolution of less than 10 ps. Also, it is demonstrated that the essence of this technique allows for the performance of absolute and precise calibration of its time scale. This technique has potential applications in a large variety of scientific devices, where ultra-high precision time measurement is a crucial factor.

Speaker: Dr Sergey Abrahamyan (A. Alikhanyan National Laboratory)

PD2025_new1.pdf

7:31 PM Modular Wavelength-Shifting Photon Detector with SiPM Readout for Large-Area Applications

Wavelength-shifting (WLS) materials offer a scalable and affordable
approach to large-area photon detection. They absorb ultraviolet photons
and re-emit them at longer wavelengths, enabling efficient light
trapping by total internal reflection.

We present a compact detector module based on WLS tiles coupled to
silicon photomultipliers (SiPMs). The design exploits the geometry of
elongated photodetectors placed along the tile edges to maximize photon
collection without requiring large sensor surfaces. Particular attention
was given to matching the spectral response of the WLS material and the
SiPMs to the Cherenkov emission peak, as well as optimizing the decay
time for fast timing performance. A dedicated readout system preserves
timing resolution in high-rate environments.

Laboratory tests with a pulsed UV laser demonstrate that the module
achieves adequate timing resolution and detection efficiency, consistent
with its cost-effective design. While the absolute efficiency is lower
than conventional solutions, the modularity and scalability of the
system enable enhanced spatial resolution and robust
signal-to-background discrimination when deployed in arrays.

This concept combines mechanical simplicity, timing capability, and low
cost, making it a promising building block for next-generation
large-area photon detectors in neutrino and cosmic-ray, gamma-ray
experiments, as well as medical and industrial applications.

Speaker: Cornelia Hanna Esther Arcaro (Istituto Nazionale di Fisica Nucleare)

PosterArcaroPD2025_CTA+online_version.pdf

7:32 PM Development and Beam-Test Results of the SiPM-Based Readout Plane for the ePIC-dRICH Photodetector at the EIC

The dual-radiator Ring-Imaging Cherenkov (dRICH) detector of the ePIC experiment at the future Electron–Ion Collider (EIC) will employ silicon photomultipliers (SiPMs) to detect Cherenkov photons. The photodetector plane will span about 3 m2 with 3x3 mm2 pixels, providing more than 300 000 readout channels—representing the first use of SiPMs for single-photon detection in a collider environment. SiPMs were selected for their high photon-detection efficiency and competitive cost, as well as for their insensitivity to the strong magnetic field at the dRICH location (~1 T).
Because SiPMs are not inherently radiation-hard, maintaining their single-photon performance and controlling the dark count rate (DCR) over the lifetime of ePIC requires dedicated mitigation strategies. These include operating at low temperature, periodic high-temperature annealing to recover radiation damage, and exploiting precise timing with fast TDC electronics to suppress DCR-induced background and improve the signal-to-noise ratio.
This contribution presents an overview of the ePIC-dRICH photodetector system and highlights results from the R&D programme for SiPM operation in ePIC. Particular emphasis is placed on the development and beam-test performance of a large-area prototype readout plane comprising up to 2048 3x3 mm2 SiPM sensors. The modular prototype is based on a novel EIC-driven photodetection unit (PDU) developed by INFN, integrating 256 SiPM pixels, cooling, and TDC electronics in a compact 5x5x14 cm³ volume. Several PDU modules have been assembled and successfully tested with particle beams at the CERN PS in October 2023 and May 2024, using a complete readout chain based on the ALCOR front-end chip developed by INFN Torino.

Speaker: Nicola Rubini (Istituto Nazionale di Fisica Nucleare)

[2025-12-04][PD25][P].pdf

7:00 PM → 8:30 PM Social Events: Welcome Reception

Auditorium Enzo Biagi

Excursion Meeting Point

INFN Laboratories

Ristorante Donatello

Thu, December 4

8:30 AM → 10:30 AM Plenary Session

Convener: Rok Pestotnik

8:30 AM 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)

PD2025_uLens_GH.pdf

8:48 AM 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)

2025-12-04 - PKachru_PD2025_Bologna.pdf

9:06 AM 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)

OttePD2025.pdf

9:24 AM Invited | Time resolution and efficiency of SPADs and SiPMs

Speaker: Werner Riegler (CERN)

photon_workshop_bologna_2025_riegler.pptx

9:49 AM Invited | Enabling photon detection: the role of ASICs

Speaker: Angelo Rivetti (Istituto Nazionale di Fisica Nucleare)

PD_ASIC_Rivetti.pdf

10:14 AM 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)

2025_Fischer_Bologna.pdf

10:30 AM → 11:00 AM Coffee Break

11:00 AM → 12:45 PM Plenary Session

Convener: Andrea Fabbri (Istituto Nazionale di Fisica Nucleare)

11:00 AM 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)

[20251204] PD2025_ALCOR.pdf

11:18 AM 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)

FastRICH-Keizer-PD2025.pdf

11:36 AM 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))

20251204_PD_Guberman.pdf

11:54 AM Invited | Photodetectors in medical applications

Speaker: Dennis Schaart (Delft University of Technology)

DR Schaart_PD2025_final.pdf

12:19 PM 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

2025-PD25-PetVision-Pestotnik.pdf

12:45 PM → 1:00 PM Group Photo

1:00 PM → 2:15 PM Lunch Break

2:15 PM → 4:15 PM Plenary Session

Convener: Marco Guarise (Istituto Nazionale di Fisica Nucleare)

2:15 PM 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

Ciavatti_PD25_Bologna.pdf

2:33 PM Invited | Advances in MCP-PMTs: performance, challenges and beyond

Speaker: Mr Albert Lehmann (Universität Erlangen-Nürnberg)

Lehmann_PD2025_Dec2025_final.pdf

2:58 PM 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)

PD2025_barnyakov.pdf

3:16 PM 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)

Nakagiri_20251204_PD2025.pdf

3:34 PM 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)

KaiMorita_PD25.pdf

3:52 PM 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)

PICMIC-PD2025.pptx

4:15 PM → 4:45 PM Tea Break

4:45 PM → 7:00 PM Plenary Session

Convener: Imad Laktineh (ipnl)

4:45 PM 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)

pd2025_osipenko_hrppd.pdf

5:03 PM 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

PD_2025_Gumbert.pdf

5:21 PM 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)

PD-2025-16-by-96 multi-anode -1.pdf

5:39 PM 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)

PD2025-Korpar.pdf

5:57 PM Invited | Precision timing with photon detectors

Speaker: Jon Lapington (University of Leicester)

Lapington_PD2025_Precision timing with photon detectors.pdf

6:22 PM 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)

PD2025_Malberti.pdf

6:40 PM 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

20251204_PD2025_Carnesecchi.pdf

8:00 PM → 10:30 PM Social Events: Gala Dinner

Auditorium Enzo Biagi

Excursion Meeting Point

INFN Laboratories

Ristorante Donatello

Fri, December 5

8:30 AM → 10:15 AM Plenary Session

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

8:30 AM Invited | Light detection in dark matter and neutrino detectors

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

PD2025_GDR.pdf

8:55 AM 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)

TD_PD25_SPADNeutrinoDetectors_Share.pdf

9:13 AM 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))

TAO_PD2025.pdf

9:31 AM Invited | Gaseous photon detectors: applications and perspectives

Speaker: Florian Brunbauer (CERN)

Gaseous Photon Detectors 2025.pdf

9:56 AM 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)

PD2025_CYGNO_Petrucci.pdf

10:15 AM → 10:45 AM Coffee Break

10:45 AM → 12:45 PM Plenary Session

Convener: Elisabetta Bissaldi (Istituto Nazionale di Fisica Nucleare)

10:45 AM 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

7th_PD_Bologna_ASTRI_Presentation_GSottile_rev2.pdf

11:03 AM 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)

SiSMUV_PD2025.pdf

11:21 AM Invited | Photon Detectors at Cryogenic temperatures

Speaker: Inés Gil-Botella (CIEMAT)

CryoPD_Ines-Gil-Botella_PD-Dec25.pdf

11:46 AM 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)

20251205_PD2025_Rudik-2.pdf

12:04 PM 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)

Balboni_DUNE.pdf

12:22 PM 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)

A New Window into Noble Elements: VUV-Sensitive A-Se Photodetectors for Cryogenic Applications

12:45 PM → 2:00 PM Lunch Break

2:00 PM → 4:30 PM Plenary Session

Convener: Andrea Ciavatti

2:00 PM 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)

StefanoDusini_PD2025_LiquidO.pdf

2:18 PM Invited | Quantum technologies for photon detectors

Speaker: Boris Korzh (University of Geneva)

20251205_SuperconductingNanowireDetectors_PD2025_Korzh.pptx

2:43 PM 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)

PDConf_Ruggieri.pptx

3:01 PM Invited | Perovskite single-photon counting detectors

Speaker: Paul Sellin (University of Surrey)

3:26 PM 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)

2025-12-05 - PD2025 Bologna - Sessolo 15 min - thin film PDs.pdf

3:44 PM 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)

PD2025_Colantoni.pptx

4:02 PM 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)

PD2025_Bruzzi.pdf

4:30 PM → 5:00 PM Closing Session

Convener: Roberto Preghenella (Istituto Nazionale di Fisica Nucleare)

4:30 PM Awards Ceremony

4:35 PM A word from the DRD4 Collaboration Spokesperson

Speaker: Massimiliano Fiorini (INFN and University of Ferrara)

2025_12_05 - DRD4 - PD2025.pdf

4:45 PM A word from the International Advisory Committee Chairperson

Speaker: Fabrice Retiere (TRIUMF)

4:55 PM Future Workshops and Farewell

Speaker: Roberto Preghenella (Istituto Nazionale di Fisica Nucleare)

future_and_farewell.pdf

5:30 PM → 7:30 PM Social Events: Visit to INFN Bologna Laboratories

Auditorium Enzo Biagi

Excursion Meeting Point

INFN Laboratories

Ristorante Donatello

5:30 PM Visit to INFN Bologna Laboratories

6:30 PM Aperitivo at INFN Bologna

Sat, December 6

10:30 AM → 12:00 PM Social Events: Guided City Tour Excursion

Auditorium Enzo Biagi

Excursion Meeting Point

INFN Laboratories

Ristorante Donatello

2:30 PM → 6:30 PM Satellite event: "da dove vengono i colori?"