IWORID 2025

6 Jul 2025, 17:00 → 10 Jul 2025, 16:30 Europe/Zurich

Bratislava, Slovakia

Andrea Sagatova (Slovak University of Technology in Bratislava)

                                             Sponsors

 

 

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Workshop topics

Sunday 6 July

Social events: Conference Reception

Monday 7 July

Detector Systems: Opening, Session 1

Christer Fröjdh

Convener: Christer Froejd (Mittuniversitetet (SE))

1 IWORID 2025 opening

The 26th Workshop on Radiation Imaging Detectors, the IWORID 2025, will be opened.

Speakers: Andrea Sagatova (Slovak University of Technology in Bratislava), Christer Froejd (Mittuniversitetet (SE))

PresentationBratislavaIWORIDopeningN.pdf

2 Detector Developments for the for the Swiss Light Source Upgrade

The Swiss Light Source is nearing the completion of its upgrade to a fourth-generation synchrotron, significantly enhancing its brilliance. This leads to a higher photon flux, while improving the coherence of the beam across the entire energy spectrum, from extreme ultraviolet to 80 keV hard X-rays.

To support the increased photon rates, we are developing the MATTERHORN detector, a single-photon counting pixel detector with a 75 µm pitch. It features faster shaping and utilizes multiple comparators and counters to achieve a count rate of up to 20 MHz per pixel with 90% efficiency. The novel digital readout architecture allows for a frame rate of up to 10 kHz with a single counter per pixel in 16-bit mode.
This fast readout technology can also be combined with on-chip digitization in our charge-integrating detectors, enabling the handling of extreme photon rates using dynamic gain switching. The planned upgrade of JUNGFRAU will allow to reach up to 100 million photons per pixel per second at a 10 kHz frame rate.
Additionally, we are developing a 1 Megapixel MÖNCH detector with a 25 µm pitch, offering noise levels below 20 e- rms ENC and 2 kHz frame rate. This will improve performance in photon-starved applications like Resonant Inelastic X-ray Scattering (RIXS) and fluorescence emission imaging, where higher brilliance enables greater sensitivity.

To extend the energy range of our detectors, we are improving sensor technologies beyond standard silicon.
For hard X-rays, we are testing and characterizing high-Z sensors, primarily GaAs and CdZnTe, to build large-area single-photon counting detectors for hard X-ray diffraction.
For soft X-rays below 2 keV, we collaborate with FBK to develop LGAD sensors optimized for soft X-ray detection, enabling single-photon counting down to 500 eV for the first time. The possibility of interpolating using LGAD sensors allows a resolution of approximately 1um and opens the possibility to develop a new hybrid detector technology for RIXS.
These advancements will significantly contribute to the experiments at SLS2.0, paving the way for exciting new scientific discoveries.

Speaker: Anna Bergamaschi

IWORID2025_Bergamaschi.pdf

IWORID2025_Bergamaschi.pdf

IWORID2025_Bergamaschi.pptx

3 Characterization and Performance Evaluation of ITk Pixel Production Modules for the ATLAS Upgrade

The ATLAS Inner Detector will be entirely replaced with a state-of-the-art all-silicon tracking detector (ITk) during the 2026–2028 upgrade, designed to withstand the demanding conditions of the High Luminosity LHC (HL-LHC). The pixel detector, positioned at the core of ITk, will feature 3D sensor technology in the innermost layer (L0), where the expected particle fluence reaches up to 2 × 10¹⁶ neq/cm², while the outer layers (L1–L4) will utilize n-in-p planar hybrid modules with sensor thicknesses of 150 μm and 100 μm.
As part of the ATLAS Upgrade UK's contribution to the ITk project, the UK cluster is responsible for the production, assembly, and quality control of endcap pixel QUAD modules. Each quad module consists of four 2 cm × 2 cm ITkPixV2 readout chips bump-bonded to a single 4 cm × 4 cm planar pixel sensor. The first batch of production modules has now been fabricated and subjected to an extensive characterization campaign. Electrical performance was assessed before and after parylene coating under both warm (+20°C) and cold (-15°C) conditions. Mechanical robustness was evaluated through thermal cycling between high (+45°C) and low (-45°C and -55°C) temperatures, while long-term stability was verified by operating the module under continuous bias for 48 hours. Throughout these procedures, key parameters such as temperature, humidity, low voltage, and high voltage were continuously monitored, with an interlock system ensuring operational safety.
To validate tracking performance, one of the characterized modules underwent a beam test at CERN using a 120 GeV pion beam, demonstrating high signal efficiency. This presentation will provide an overview of the endcap pixel module production process, focusing on key characterization results and performance evaluations at various stages.

Speaker: Md Arif Abdulla Samy (University of Glasgow (GB))

Characterization and Performance Evaluation of ITk Pixel Production Modules for the ATLAS Upgrade.pdf

Characterization and Performance Evaluation of ITk Pixel Production Modules for the ATLAS Upgrade.pptx

iworid 2025_abstract_Glasgow.pdf

4 ITS3 - A truly cylindrical tracker for ALICE

ITS3 - A truly cylindrical tracker for ALICE
Anna Villani on behalf of the ALICE Collaboration

The ALICE experiment at the CERN Large Hadron Collider (LHC) is optimized for the study of the strongly interacting state of matter arising in high-energy heavy-ion collisions through the tracking of particles at high multiplicities resulting from the collisions. The ALICE Inner Tracking System (ITS) is responsible for primary and secondary vertex reconstruction and particle tracking in the vicinity of the interaction point.

The ALICE ITS will be upgraded during LHC Long Shutdown 3 (2026-2030). The three innermost layers of the current ITS2 will be replaced by a truly cylindrical tracker, the ITS3. Such a vertex detector will comprise three layers, each composed of two self-supporting, ultra-thin (≤50 µm) flexible and bent Monolithic Active Pixel silicon Sensors (MAPS) covering a large area (O(10×27 cm$^2$)). The radius of the first layer of 19 mm and the unprecedented low material budget of 0.09 %X/X0 per layer will strongly improve the pointing resolution especially for low-momentum particles. An improvement of a factor of 2 is foreseen for particles with a p$_T$ lower than 1 GeV/c , thus allowing for the increase in the precision of measurements in the heavy-flavour sector and bringing another set of fundamental observables into reach: the measurement of B$^0_s$ and Λ$^0_b$ at low transverse momenta and of non-prompt D$^+_s$ and Ξ$^+_c$ decays in heavy-ion collisions will be possible.

The final sensor for the ITS3 will be a stitched wafer-scale MAPS sensor realised using a 65 nm CMOS imaging process. The sensor technology has been validated through characterisation both in the laboratory and with in-beam measurements of pixel test structures. First stitched prototypes called MOnolithic Stitched Sensor (MOSS) and MOnolithic Stitched sensor with Timing (MOST) were produced to prove the stitching principle, assess the yield and the performance of wafer-scale sensors. The design of the final full-function sensor prototype (MOSAIX) is underway.

Mechanical and electrical properties of prototypes, which were bent to the ITS3 required radii, were demonstrated to be maintained after bending. Cooling efficiency and mechanical stability of engineering models employing dummy silicon and heating elements were verified under an airflow of 8 m/s, demonstrating a large margin with respect to the requirements. The development of the readout system and the services is well advanced.

This contribution will provide an overview of the ITS3 upgrade project and the results from the qualification campaign on sensor prototypes, mechanics design and detector integration.

Speaker: Anna Villani (Universita e INFN Trieste (IT))

abstract_IWORID_2025_anna_villani.pdf

IWORID2025_its3_anna_villani_V2.pdf

10:30 Coffee Break + Group photo of participants

Detector Systems: Session 2

Christer Fröjdh

Convener: Ralf Hendrik Menk (Elettra Sincrotrone Trieste)

5 ATLAS Inner Tracker Upgrade Pixel Detector

In the high-luminosity era of the Large Hadron Collider, the instantaneous luminosity is expected to reach unprecedented values, resulting in up to 200 proton-proton interactions in a typical bunch crossing. To cope with the resulting increase in occupancy, bandwidth and radiation damage, the ATLAS Inner Detector will be replaced by an all-silicon system, the Inner Tracker (ITk). The innermost part of the ITk will consist of a pixel detector, with an active area of about 13 m^2. To deal with the changing requirements in terms of radiation hardness, power dissipation and production yield, several silicon sensor technologies will be employed in the five barrel and endcap layers. As a timeline, it is facing to production of components, sensor, building modules, mechanical structures and services. The pixel modules assembled with RD53B readout chips have been built to evaluate their production rate. Irradiation campaigns were done to evaluate their thermal and electrical performance before and after irradiation. A new powering scheme – serial – will be employed in the ITk pixel detector, helping to reduce the material budget of the detector as well as power dissipation. This contribution presents the status of the ITk-pixel project focusing on the lessons learned and the biggest challenges towards production, from sensors and mechanics structures, and it will summarize the latest results on closest-to-real demonstrators built using module, electric and cooling services prototypes.

Speaker: Umberto Molinatti

IWORID2025 ATLAS.pdf

6 Performance, calibration and optics robustness of the ATLAS Tile Calorimeter

The Tile Calorimeter (TileCal) is a sampling hadronic calorimeter covering the central region of the ATLAS experiment, operating at the Large Hadron Collider (LHC) at CERN. TileCal is made of steel as absorber and plastic scintillators as active medium. The scintillators are read-out by wavelength shifting fibres coupled to photomultiplier tubes (PMTs). The analogue signals from the PMTs are amplified, shaped, digitized by sampling the signal every 25 ns and stored on detector until a trigger decision is received. The TileCal front-end electronics reads out the signals produced by about 10000 channels measuring energies ranging from about 30 MeV to about 2 TeV. During LHC runs, high-momentum isolated muons have been used to study and validate the electromagnetic scale, while hadronic response has been probed with isolated hadrons. The calorimeter time resolution has been studied with multi-jet events. Besides, the integrated cells signals from minimum bias events provide auxiliary information on the response stability from the whole detector during proton-proton collisions. The calibration systems are used to estimate the radiation damage suffered by the active media of the detector, the scintillators and the wavelengths shifting optical fibres that collect the light into the photodetectors readout. First results using early LHC Run-3 data will be shown. A summary of the performance results, including the calibration, stability, absolute energy scale, uniformity, time resolution and the plastic scintillators light output loss due to integrated dose will be presented.

Speaker: Tibor Zenis (Comenius University (SK))

Zenis_Perf_Cal_Rob_TilCal.pdf

7 Performance of the Timepix3 Detector Network in ATLAS for Relative Luminosity Measurement in Run-3

The Timepix detector network inside the ATLAS cavern has proven to be effective in measuring luminosity and the radiation field composition during LHC Run-2 operation [1]. First tests of Timepix3 in this radiation environment provided promising results so that for Run-3, the network has been upgraded to a two-layer detector stack relying fully on the Timepix3 technology. Each two-layer Timepix3 detectors is equipped with neutron converters (${}^{6}$LiF and polyethylene) for spectrum resolved neutron detection. These detectors were installed at different locations within the ATLAS experiment where they provide a continuous measurement of the radiation levels and the radiation field composition. All devices are synchronized with the LHC orbit clock allowing for bunch-resolved luminosity determination.

Within the present work we will provide an overview of the capabilities of the installed detector network with a focus on evaluating its performance for relative luminosity measurement. We present an assessment of observed noise patterns which were identified by statistical methods (single-pixel noise) and by comparison of the signal of different detectors with each other (full-matrix noise).

Luminosity measurement is performed with the different units inside the network. Each unit provides a set of different algorithms. In cluster counting the overall cluster rate is used. Hereby, by using the continuous measurement of the noise corrected radiation levels during and after collision periods, the relative contribution of induced radioactivity to the overall count rate is estimated to be 3-10$\%$ depending on the location within ATLAS. We further evaluate neutron and MIP counting algorithm, which provide activation-independent measurement by utilizing only traces of shapes which are rarely produced by gamma-rays.

Within this contribution we compare the different algorithms and different units with each other to assess systematic uncertainties, the sensitivity to luminosity according to the location and properties inside the cavern and present a short-term and long-term stability. For the innermost detectors we evaluate the capability to perform a bunch-by-bunch analysis.

Figure: Long-term analysis of the main detectors using the cluster counting algorithm comparing to their average for the LHC fills between April 30th to October 16th of 2024

References:

[1] B. Bergmann et al., “Characterization of the Radiation Field in the ATLAS Experiment with Timepix Detectors”, in IEEE Transactions on Nuclear Science 66, no. 7, pp. 1861-1869 (2019) \url{https://ieeexplore.ieee.org/abstract/document/8720202}

[2] P. Burian et al. “Timepix3 detector network at ATLAS experiment” JINST 13 C11024 (2018) \url{https://iopscience.iop.org/article/10.1088/1748-0221/13/11/C11024/meta}

[3] B. Bergmann et al., “Relative luminosity measurement with Timepix3 in ATLAS” JINST 15 C01039 (2020). \url{https://iopscience.iop.org/article/10.1088/1748-0221/15/01/C01039/meta}

Speaker: Catalina Lesmes Ramirez (Institute of Experimental and Applied Physics, Czech Technical University in Prague)

ATLAS_TPX3_Run_3_Analysis___iWoRiD.pdf

long_term_internal_clusters_avg.pdf

8 Deploying Timepix3 in Low-Radioactivity Natural Settings: Integrated Workflow for Charged Particle Detection and Imaging

Naturally occurring radionuclides such as potassium (K), uranium (U), and thorium (Th) are primary sources of ionizing radiation (α, β, and γ) contributing to the radiation dose received by quartz and feldspar mineral grains used in luminescence dosimetry/dating. The heterogeneous distribution of radionuclides within or adjacent to individual mineral grains can lead to significant variations in the absorbed dose, a phenomenon referred to as micro-dosimetry. Understanding and quantifying these micro-scale dose variations are crucial for accurate dose reconstruction at the level of single grains. Yet, this aspect remains poorly constrained due to a lack of suitable experimental techniques and the complexities involved in studying natural samples, which often contain a mixture of diverse components. While gamma-ray spectrometry is commonly used to quantify natural radionuclides, it provides only bulk-averaged values and offers no spatial mapping of the sources or origin within a sample [1, 2].

In this work, we present an integrated workflow to configure and apply the Timepix3 detector (silicon-based, 14 × 14 mm² active area, 256 × 256 pixels, 300 µm thickness [3]) for high-sensitivity imaging of α- and β-particles in low-radioactivity natural settings with the goal of enabling its use in micro-dosimetric investigations. The workflow includes particle track reconstruction, charged particle identification, background suppression, energy calibration using calibration standards, including x-rays, and pixel-level filtering. Due to the low interaction probability of γ-rays in 300 µm-thick silicon, high-energy photons (>100 keV) are largely undetectable using such a detector thickness; thus, our focus is restricted to α and β detection. The developed methodology enables spatially resolved imaging of charged particle emissions from natural sample surfaces (e.g., rock), allowing the investigation of dose variations at the scale of individual mineral grains. Our results demonstrate the capability of Timepix3 to support micro-dosimetric investigations and particle-specific mapping in weak radioactive natural materials.

References

1. Nathan, R.P., Thomas, P.J., Jain, M., Murray, A.S. and Rhodes, E.J. 2003. Environmental dose rate heterogeneity of beta radiation and its implications for luminescence dating: Monte Carlo modelling and experimental validation. Radiation Measurements, 37: 305-313.
2. Fu, X., Romanyukha, A.A., Li, B., Jankowski, N.R., Lachlan, T.J., Jacobs, Z., George, S.P., Rosenfeld, A.B. and Roberts, R.G., 2022. Beta dose heterogeneity in sediment samples measured using a Timepix pixelated detector and its implications for optical dating of individual mineral grains. Quaternary Geochronology, 68: 101254.
3. Poikela, T., Plosila, J., Westerlund, T., Campbell, M., De Gaspari, M., Llopart, X., ... & Kruth, A. (2014). Timepix3: a 65K channel hybrid pixel readout chip with simultaneous ToA/ToT and sparse readout. Journal of instrumentation, 9(05), C05013.

Speaker: Dr Raju Kumar (University of Ghent)

Kumar_IWORID2025_talk.docx

Talk_Raju Kumar_07 July.pdf

9 New results from fast timing iLGAD sensors on Timepix4

With the High-Luminosity Large Hadron Collider (HL-LHC) the number of events per bunch crossing increases. To cope with these high rates in the pixel trackers, per-pixel time measurements are required, which implies the need for fast sensors. The Inverted Low-Gain Avalanche Detector (iLGAD) is one of the options that is being investigated. This presentation will show the results of an inverse Low-Gain Avalanche Detector (iLGAD) with a pitch of 55 μm, a thickness of 250 μm and a large-area (2 cm2), bump bonded to a Timepix4 ASIC. Timepix4 has 195 ps time binning on each pixel and therefore an ideal ASIC to test the sensor. The sensor is characterised with laser and radio-active source measurement in the lab and during beam test at the CERN SPS North Area H8 beamline, where the timepix4 telescope was used. The telescope consists of four 100 µm thick sensors for temporal resolution and four 300 µm thick sensors for spatial resolution. Downstream of the telescope there are two MCPs used as time reference, giving a temporal resolution of 12 ps. The iLGAD is placed in the centre of the telescope as DUT, where the telescope has a pointing resolution of 2.3 ± 0.1 μm.

The iLGAD shows an almost uniform gain of around 4 and an efficiency of 99.6±0.1%. Without any corrections the obtained time resolution is about 750 ps. After timewalk and clock corrections the time resolution becomes 358 ps. To understand the details of the time resolution also grazing angle measurements are done, which allow to measure the time-resolution as function of depth of the charge deposition in the sensor. This provides more insight for the perpendicular time resolution.

Speaker: Daan Jasper Oppenhuis (Nikhef National institute for subatomic physics (NL))

iLGAD_on_TPX4_IWORID2025.pdf

12:40 Lunch break Lunch 13.00

Detector Systems: Session 3

Christer Fröjdh

Convener: Heinz Graafsma

10 Large-Area CdTe Detector for X-ray Imaging and Overcoming Crystal Imperfections in CdTe Sensors

Hybrid semiconductor detectors with CdTe sensor chips find wide applications in medical and industrial X-ray radiography. These detectors enable direct radiation detection through their ability to effectively convert ionizing radiation into electrical signals. The design provides excellent detection sensitivity and eliminates analog noise. However, CdTe sensor chips are known to have crystal imperfections, which can affect detection stability and the quality of the recorded images. These effects are time-dependent and can be effectively addressed through hardware solutions, such as pulsed bias voltage modulation, and software solutions. In this contribution, we will show that using image correction approaches lead to an improvement in the polarization stability of the CdTe sensor and thus to a multiple enhancement in the homogeneity of the image and it represents a significant step forward in improving image quality and resolution.
The use of image correction methods we will demonstrate on the WidePIX MPX3 5x5 detector, utilizing MediPIX chips developed by the Medipix collaboration at CERN. It is an innovative solution for imaging larger objects because it features a CdTe sensor area of 7x7 cm and a resolution of 1280 x 1280 pixels. Due to MediPIX3 technology it is allowing the acquisition of X-ray images with high contrast and wide dynamic range. This means that even low-contrast structures, such as soft tissues or plastics, are easily detectable. Also it includes energy discrimination, the system enables spectral X-ray imaging, allowing the creation of multichannel "color" X-ray images where different materials are identified and displayed in different colors. The combination of image correction methods and a large sensor area opens up broad possibilities for the further development of radiographic imaging technologies.

Speaker: Dr Zuzana Melníková (ADVACAM s.r.o.)

iWorid 2025_presentation_ZM.pdf

11 First characterization of a GaAs-based Timepix4 detector assembly for X-ray imaging applications

Timepix4 is the most recent application-specific integrated circuit (ASIC) developed by the Medipix4 international collaboration at CERN. It features a 448×512 pixel matrix with a 55 μm pitch. Its design supports integration with diverse semiconductor sensors, enabling its use in multiple domains such as X-ray spectroscopy, high-energy particle detection, and medical imaging [1].

Designed for compatibility with Through-Silicon-Via (TSV) technology, Timepix4 can be tiled seamlessly on all four sides, enabling coverage of large detection areas with negligible dead zones and achieving sub-200 ps timing resolution [1]. The architecture supports two readout modes: frame-based and data-driven. In frame-based mode, events exceeding a programmable threshold are counted at the pixel level, and the matrix is read out synchronously via the core clock. In data-driven mode, a pixel transmits a data packet after detecting a hit, capturing both Time-of-Arrival (ToA) and Time-over-Threshold (ToT) values. This mode extends the photon-counting capability with additional temporal and energy information. With support for hit rates up to 5.0×10⁹ hits/mm²/s and data transfer speeds up to 160 Gbit/s, it offers high-performance capabilities for demanding applications [1,2].

Since 2020, INFN has been a member of the Medipix4 collaboration. Within this framework, two INFN-CSN5-funded projects (MEDIPIX4 (2021–2024) and TIMEPIX4 (2025–2027)) have been launched to explore the applicability of readout chips in diverse domains, ranging from X-ray spectral imaging to nuclear medicine and radiation dosimetry. Ongoing work at INFN involves the characterization of Timepix4 assemblies coupled to different sensor materials, including silicon (Si), cadmium telluride (CdTe), and gallium arsenide (GaAs).

This presentation summarizes experimental work performed with a recently acquired 700 μm-thick GaAs detector assembly. Due to its higher atomic number and electron mobility than Si and lower fluorescence photon emission energy (<12 keV) compared to CdTe (<30 keV), GaAs provides superior detection efficiency (better than 70%) for X-ray energies up to 50 keV, making it well suited for mid-energy X-ray imaging applications.

At INFN Ferrara, the detector was extensively characterized under both frame-based and data-driven readout conditions. For frame-based operation, the setup includes an X-ray mammography tube with a tungsten anode. The Timepix4 assembly is positioned one meter from the source, aligned along the beam direction, and mounted on a dedicated holder equipped with a copper heat exchanger. Temperature regulation is provided by circulating chilled water (15 °C) through the exchanger via an external chiller. In data-driven mode, an X-ray fluorescence (XRF) setup is used. In this configuration, the Timepix4 detector is positioned perpendicular to the primary beam, which is directed onto target materials placed at a 45-degree angle along the beam path. Readout in both configurations is performed using the SPIDR4 electronics, with system control and data acquisition managed via DATAPIX4 [3], an in-house software developed at INFN Ferrara.

For energy calibration in data-driven mode, the XRF setup allows the conversion of ToT signals into the corresponding collected charge and, subsequently, into the energy of the incident X-ray [2]. Five different target materials were selected for this measurement, producing characteristic X-ray fluorescence photons with energies ranging from 9.89 keV (Ge) to 24.21 keV (In). This approach reduced the energy discrepancy from 32%, observed when relying solely on internal test pulses, to 6% (see left panel of Figure 1). Additionally, this readout mode enabled the investigation of charge-sharing effects across the pixel matrix as a function of photon energy, offering insights that support the interpretation of data acquired in frame-based mode. Right panel of Figure 1 shows the fraction of clusters with different sizes generated in the sensor as a function of photon energy. As the energy increases, the fraction of single-pixel (size-1) clusters decreases significantly, with a reduction of approximately 25% across the investigated energy range. However, analysis of the energy distribution of size-1 clusters (see left panel of Figure 1) reveals that 40% of the counts correspond to energies below half of the expected value, which is consistent with photon interactions occurring near pixel borders. This indicates a pronounced charge-loss effect that needs to be investigated.

The frame-based mode, optimized for high-rate acquisition, is particularly suitable for applications such as medical diagnostics. In this context, flat-field response uniformity is a key performance metric. Over a continuous 5-hour acquisition period, multiple flat-field images were acquired under identical conditions and compared, revealing relative variations smaller than 1% over the entire period for 99.4% of the pixels. A first radiography corrected for the flat-field and for defective pixels can be seen in Figure 2a-b, showing the quality of the GaAs assembly. The image was acquired at the LARIX-A laboratory of INFN Ferrara and University of Ferrara using a 700 μm GaAs sensor coupled to a Timepix4 chip, operated in frame-based mode (16-bit, 0.01 s frame duration) with a bias voltage of –350 V and a threshold of 3.36 keV. The X-ray tube was set to 25 kVp and 60 mA, resulting in a hit rate of approximately 15,000 hits/pixel/s over a 6 s exposure. The spatial resolution was evaluated using the slanted-edge technique at two different mean energies, 17 keV and 27 keV, by calculating the Line Spread Function (LSF) and the Modulation Transfer Function (MTF). For the higher energy acquisition, the full width at half maximum (FWHM) of the LSF is approximately 70 μm (see Figure 2c). In addition, a resolution test phantom (star pattern) was acquired, as shown in Figure 2d, where the lines are clearly distinguishable up to the Nyquist frequency (9.1 mm⁻¹). The results of preliminary tests on response linearity as a function of photon rate and detector efficiency, will also be presented and discussed.

[1] X. Llopart et al., Timepix4, a large area pixel detector readout chip which can be tiled on 4 sides providing sub-200 ps timestamp binning, Journal of Instrumentation, 17 (2022) C01044.
[2] A. Feruglio et al., Timepix4 Calibration and Energy Resolution Evaluation with Fluorescence Photons, Il Nuovo Cimento C, 47 (2024).
[3] V. Cavallini et al., DataPix4 A C++ framework for Timepix4 configuration and read-out, arXiv preprint 2503.01609 (2025).

Speaker: Simone Velardita

SimoneVelardita_iWorid.pdf

12 The influence of temperature changes on the spectrometric behavior of Timepix3 detectors with different sensors

Timepix3 is an advanced hybrid pixel detector designed for precise particle tracking and energy measurement over a wide range of ionizing radiation [1]. Currently, Timepix3 detectors are equipped with a variety of semiconductor sensors, including silicon (Si), silicon carbide (4H-SiC), gallium arsenide (GaAs), and cadmium telluride (CdTe), each offering specific advantages depending on application requirements. Si is known for its excellent energy resolution, although its efficiency declines at higher photon energies. CdTe and GaAs offer higher absorption coefficient, making them more suitable for high-energy γ-ray detection, while SiC stands out for its robustness in demanding radiation and high temperature environments.
The ability to record individual interactions with precise timing and energy information, combined with a compact design, low power consumption and overall versatility, has led to its adoption in a wide range of applications. Timepix3 detectors have found applications in areas such as medicine [2], high energy and nuclear physics [3], neutron detection [4, 5] and space instrumentation [6], where robust performance and accurate radiation measurement are key requirements. In applications situated in harsh environments, detectors are expected to operate reliably under varying temperature conditions and prolonged exposure to different types of ionizing radiation. Temperature fluctuations are considered a possible factor that could influence detector performance and the accuracy of the acquired spectrometric data. Consequently, it is important to investigate the temperature dependence of such detectors, particularly with regard to their energy resolution and photopeak position.
To determine this, Timepix3-based detectors equipped with all four available sensor types - Si, 4H-SiC, GaAs and CdTe - were systematically studied. The detectors were thermally stabilized and irradiated using characteristic X-rays and a Am-241 source across an energy range of approximately 8 to 60 keV. Measurements were performed over a temperature interval from 10 ℃ to 80 ℃, with calibration set at 40 ℃. The objective of the present study was to assess the impact of temperature fluctuations on the spectrometric characteristics of the sensors, in terms of energy resolution and photopeak position.
The results obtained demonstrated a consistent trend across all sensor types. As the temperature increased, the photopeak position gradually shifted to lower energies, causing a reduction in measurement accuracy. This shift became more noticeable at temperatures above 60 °C and was more pronounced at higher photon energies. While the deviation from the calibrated peak position remained within 0-5% at lower temperatures for all detectors regardless of the sensor type, it increased to 3-10% for the detector with a silicon sensor, 5-14% for the 4H-SiC sensor, and reached approximately 6% for the GaAs-based detector at 60 °C. However, at temperatures above 60 °C, the electronic noise in GaAs and CdTe detectors became too high to enable reliable spectrometric analysis. These findings indicate that the temperature dependence of the spectrometric response is primarily influenced by the Timepix3 readout chip, with some contribution from the sensor material itself. In order to ensure accurate measurements across a broader temperature range without the need for active cooling or repeated calibrations at each operating condition, it is beneficial to implement a compensation method that corrects temperature-induced shifts in the spectral data.

[1] T. Poikela, et al., JINST 9 (2014), C05013
[2] D. Turecek, et al., Nucl. Instrum. Methods Phys. Res. A 895 (2018), 84-89
[3] B. Bergmann, et al., Nucl. Instrum. Methods Phys. Res. A 978 (2020) 164401
[4] C. Granja, et al., JINST 18 (2023) P01003
[5] C. Oancea, et al., Phys. Med. Biol. 68 (2023) 185017
[6] C. Granja, et al., JINST 17 (2022) C03019

The authors acknowledge funding from the Slovak Research and Development Agency (Research Projects APVV-18-0273 and APVV-18-0243).

Speaker: Nikola Kurucová (Institute of Nuclear and Physical Engineering, Faculty of Electrical Engineering and Information Technology, Slovak University of Technology in Bratislava)

IWORID2025_abstract.png

13 A 1M charge integrating hybrid pixel detector for electron diffraction

Electrons have emerged as an important complement to X-rays in crystallography, particularly for compounds that present challenges in growing crystals sufficiently large for synchrotron radiation (5–10 μm) or laboratory diffractometers (~50 μm). Given the nature of electron-matter interactions, electron diffraction (ED) provides a way to experimentally determine the electrostatic potential of compounds, offering insights beyond electron density maps. To fully harness the power of ED, we have integrated a fast, low-noise and radiation-hard 1 megapixel JUNGFRAU detector with a modern JEOL microscope. JUNGFRAU is a charge-integrating hybrid pixel detector, with a dynamic range of 120 MeV/pixel/frame, i.e. $10^{4}$ 12 keV photons and a maximum frame rate of 2.2 kHz in continuous mode. It effectively detects up to 1.3 million 200 keV electrons per pixel per second before saturation.

To handle the resulting 5 GB/s raw data stream (fiberoptic; 4 x 10 Gbit/s), our system features an FPGA-based backend, Jungfraujoch, which converts raw ADC values into deposited energy and enables on-the-fly frame summation. Additionally, we developed a software package with an intuitive graphical user interface that integrates detector and microscope control. This solution provides partly automated data acquisition and post-processing, with data stored in compressed HDF5 files with comprehensive metadata.

This work assesses the performance of JUNGFRAU across multiple electron energies by analyzing energy deposition and pixel spread. The complete data pipeline—from detector to user interface—is validated through an ED experiment yielding structural insights, with future improvements also discussed.

Speaker: Khalil Daniel Ferjaoui

A 1M charge integrating hybrid pixel detector for ED_Khalil_FERJAOUI.pptx

Abstract_iworid_2025_khalil.docx

15:20 Coffee Break

Poster: Session 1

Convener: Andrea Sagatova (Slovak University of Technology in Bratislava)

14 Experimental validation of Geant4 simulation model for backscatter X-ray security scanner

The Customs Service performs X-ray security screening to prevent illicit articles from entering the country. The primary contraband products that are illegally distributed include unspecified forms of narcotics, explosives, and seeds. The challenge in detecting these contraband items using a conventional transmission X-ray inspection system alone stems from their tendency to be concealed as thin layers in luggage, in addition to their low atomic number and density. However, backscatter X-ray imaging, based on Compton scattering, has been shown to provide superior image contrast compared with transmission imaging for these materials [1]. Because of these advantages, backscatter imaging has been widely adopted for detecting contraband in baggage, vehicles, and port containers. In our previous study, the Geant4 (Geometry and Tracking4) simulation toolkit was employed to optimize the design of a backscatter X-ray scanner and to obtain the backscatter images for performance estimation [2]. In the present study, the reliability of the Geant4 simulation model for the backscatter X-ray security scanner was experimentally validated. This validation was conducted by employing two gamma sources (i.e., Am-241 and Co-57) and a radiation generator operating at 100 kV and 3 mA. For the gamma sources, the energy spectrum of a large-area monolithic PVT detector was measured at 30, 40, and 50 cm from the detector. To obtain the backscatter X-ray images, the object was scanned by the collimated pencil-beam (i.e., flying spot) while moving at 5 cm/s on a conveyor belt. In the simulation, the X-ray source term was obtained by monoenergetic-electron-beam bombardment onto the target. Also, the scanning pencil-beam and moving object were simulated by using G4Messenger. To validate the simulation model, a comparison was made between the simulated and measured image profiles, as well as the energy spectra of the PVT detector. The percent differences between the simulated and measured energy spectra and the image profiles were all found to be within 5%. Consequently, it was determined that the simulation model for the backscatter X-ray scanner can be relied upon.

[1] S Huang et al., Opt. Express, 27 (2019), 337-349
[2] G An et al., JINST, 18 (2023), C01004

The authors acknowledge funding from the National Research Foundation of Korea (NRF) funded by the Korea Customs Service and Ministry of Science and ICT (NRF-2021M3I1A1097913).

Speaker: Geunyoung An (Jeonbuk National University)

15 Performance Evaluation of Dual-Energy X-ray Screening System

X-ray security screening is essential in high-security facilities such as airports and harbors. It can detect prohibited items and hazardous materials concealed in baggage. This screening process is critical to ensuring public safety. It enables the early detection and interception of dangerous items. Screening images taken with standardized test kits are commonly used to evaluate the performance of X-ray security scanners [1].
The Ministry of Land, Infrastructure, and Transport issues guidelines for the performance evaluation of X-ray security scanners in the Republic of Korea [2]. The TSA (Transportation Security Administration) ASTM test kit and the ECAC (European Civil Aviation Conference) STP test piece are used following these guidelines. Key evaluation metrics include ‘Wire Display’ and ‘Spatial Resolution’. Performance is evaluated under the standard operating conditions as specified by the equipment manufacturer.
In this study, the performance of a newly developed X-ray security scanner in terms of wire display and spatial resolution was experimentally evaluated using the ASTM F792-HP test kit (Fig. 1). These results were then compared and analyzed with the simulation results obtained by using a Geant4-based simulation model. The wire display evaluates the scanner's ability to detect sinusoidal wires placed in the test kit (Test 1). The quantitative criteria, as required by the Ministry’s guidelines, is based on the detection of wires as small as 30 AWG (0.254 mm). The test kit contains wires of different diameters (24, 30, 34, 38, and 42 AWG), allowing a comprehensive performance evaluation. A statistical algorithm was used to quantify wire display performance to increase objectivity and accuracy [3]. Both the experimental results and the simulation model confirmed that the scanner could detect wires of up to 34 AWG (0.160 mm).
Spatial resolution (Test 3 of the ASTM test kit) refers to the ability to distinguish between adjacent objects in the security screening image. The phantom consists of four bar patterns, each consisting of four bars of identical thickness, ranging from 0.5 mm to 2.0 mm (0.5, 1.0, 1.5, and 2.0 mm). The spacing between the bars in each pattern is equal to the bar thickness; for example, the 0.5 mm pattern has four bars, each 0.5 mm wide, spaced 0.5 mm apart. Spatial resolution performance is defined as the smallest distinguishable bar pattern that can be resolved in the security image [4]. Both experimental and simulation results confirmed that the scanner was able to resolve the 1.0 mm pattern, but not the 0.5 mm pattern. A refined phantom was implemented by the Geant4 model to further investigate the spatial resolution limit. Analysis of the refined phantom resulted in a final spatial resolution assessment of 0.8 mm, with a clear separation of the four peaks at 0.8 mm and no clear separation at 0.7 mm.
The results showed that the developed scanner met the domestic performance requirements. The simulation model accurately reflected the performance of the system. These results validate the reliability of the simulation model and provide a basis for its application in future performance evaluation and system optimization processes.

[1] Y. A. Yoon et al., 2021. Improving imaging quality assessment of cabinet X-ray security systems, J. Korean Soc. Qual. Manage. 49(1), 47-60
[2] Ministry of Land, Infrastructure and Transport, 2010. Aviation Security Act. Republic of Korea
[3] J. L. Glover and L. T. Hudson, 2016. An objectively-analyzed method for measuring the useful penetration of x-ray imaging systems, Meas. Sci. Technol. 27(6), 065402
[4] J. L. Glover et al., 2018. Testing the image quality of cabinet x-ray systems for security screening: The revised ASTM F792 standard, J. Test. Eval. 46(4), 1468-1477

Speaker: Junsung Park (Jeonbuk National University)

Fig. 1. ASTM F792-HP test kit.png

16 Noise behavior in filtered backprojection for robot CT with arbitrary scan paths

Signal, noise, and their correlations– in space are fundamental for determining image quality. These can be characterized by modulation-transfer function (MTF) and noise-power spectrum (NPS), which are both Fourier metrics. The ratio of the squared MTF and the NPS is termed noise-equivalent quanta (NEQ) or detective quantum efficiency (DQE), commonly used to describe the performance of an imaging system.

The cascaded-systems analysis (CSA) approach has been used to parameterize the signal and noise characteristics of 2D radiographic systems in terms of operational and design parameters, such as incident photon fluence, quantum efficiency, Swank factor, electronic noise, and pixel fill factor [1]. These parameters, explicitly expressed in the CSA formula, are implicitly related to the factors like the dose used for imaging, detector thickness, dark current, amplifier noise, and more. Consequently, CSA can identify parameters that degrade system performance, offering pathways for system improvement or optimization.

CSA can also be applied to computed tomography (CT). The CSA for cone-beam CT (CBCT) using flat-panel detectors requires additional filtering and backprojection processes. While the mathematical 3D image reconstruction process is deterministic, it has been shown to be irreversible due to sampling processes [2]. As a result, acquisition and reconstruction parameters, such as the number of projection views and reconstruction filters, significantly influence the 3D noise characteristics (e.g., NEQ or DQE). Therefore, developing a theoretical model to describe the 3D imaging chain in CBCT is essential for optimizing system parameters based on specific applications.

In this study, we apply CSA to CBCT using robotic arms, instead of the conventional circular gantry. In the filtered backprojection algorithm, one-directional filtering (i.e., filtering parallel to the scan direction) leads to a 3D NPS that is asymmetric between the axial and longitudinal directions, as shown in Fig. 1. The backprojection of projections obtained from arbitrary scan trajectories may further degrade the 3D NPS, an effect that is explored in this study. We examine the noise properties of robot CT with arbitrary scan paths for various operations and design parameters using the CSA model, comparing the results with measurements. The developed model can be used to determine the optimal scan path for robot CT.

Reference
[1] H. K. Kim, Ch. 7 in Radiation Detection Systems, Boca Raton, FL, CRC Press (2021) 163-224
[2] D. J. Tward and J. H. Siewerdsen, Med. Phys. 35(12), 5510-5529 (2008)

Acknowledgement
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. 2021R1A2C1010161 and RS-2024-00340520).

Speaker: Seungjun Yoo (Computational X-ray Imaging Laboratory, School of Mechanical Engineering, Pusan National University)

17 Dual-energy subtraction efficiency of different X-ray detector designs

Chest radiography is a widely used imaging modality for diagnosing and monitoring thoracic diseases due to its accessibility, cost-effectiveness, and relatively low radiation dose. However, conventional chest radiographs often struggle to differentiate overlapping anatomical structures, such as bones and soft tissues, which can obscure important pathological findings. To address these limitations, dual energy imaging (DEI) has emerged as a key advancement in chest radiography [1]. DEI utilizes two distinct X-ray energy levels to acquire separate image sets, enabling material decomposition based on their unique attenuation characteristics. By selectively reducing the contrast of non-relevant regions and background structures, DEI enhances the visibility of the material contrast of interest [2].

The performance of DEI can be influenced by various factors, such as imaging techniques (e.g., low and high kVp settings and dose allocation between them) and detector designs (e.g., materials like CsI or a-Se, thickness, and pixel pitch). Recently, the International Electrotechnical Commission (IEC) introduced the concept of DE subtraction efficiency (DSE) to characterize DEI systems [3]. DSE represents the contrast-to-noise ratio (DE contrast or DEC, as defined by the IEC) at the exposure level K_a used for imaging. The IEC also provides a standard phantom design made of aluminum (Al, representing hard tissue) and acrylic (Ac, representing soft tissue) with various thicknesses, as shown in Fig. 1(a), for the objective evaluation of DSE.

In this study, we evaluate the DSE performance of various detector designs by incorporating the IEC phantom into a Monte Carlo (MC) simulation framework. We use the commercial MCNP code (Version 5, RSICC, Oak Ridge, TN) and conduct the simulations using the pTrac function. An example MC image from a 0.5-mm-thick CsI detector for the IEC phantom is shown in Fig. 1(b). Fig. 2 illustrates the DSE performance of soft-tissue-subtracted images obtained from the CsI detector, where DE reconstruction was performed using weighted log-subtraction for a 6-mm-thick Ac feature, as suggested by the IEC. Different plots correspond to low-energy settings of 60, 70, and 80 kVp, with a fixed high-energy setting of 120 kVp.

The MC simulation results are being analyzed to determine the DSE as a function of detector materials (CsI, a-Se, CdTe), thicknesses, and pixel pitches. The simulation framework will be validated through experimental measurements of two different designs of CsI-coupled flat-panel detectors.

Reference
[1] J. E. Kuhlman, J. Collins, G. N. Brooks, D. R. Yandow, and L. S. Broderick, “Dual-energy subtraction chest radiography: what to look for beyond calcified nodules”, Radiographics, Vol. 26, No. 1, pp. 79-92, 2006.
[2] H. Shin, S. Yoo, S. Oh, J. Lee, and H. K. Kim, “Detective quantum efficiency of a double-layered detector for dual-energy x-ray imaging”, Journal of Instrumentation, Vol. 18, No. 11, pp. C11005, 2023.
[3] IEC, “Medical electrical equipment – Characteristics of digital X-ray imaging devices – Part 2-1: Determination of dual-energy subtraction efficiency – Detectors used for dual-energy radiographic imaging; IEC 62220-2-1”, International Electrotechnical Commission, 2023.

Acknowledgement
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (RS-2024-00340520). J. Lee was supported by the 'Human Resources Program in Energy Technology' of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), which was funded by the Ministry of Trade, Industry & Energy (MOTIE, Korea) (No. RS-2024-00398425).

Speaker: Junho Lee (Computational X-ray Imaging Laboratory, School of Mechanical Engineering, Pusan National University)

18 IN-VIVO CARBON-ION RADIOTHERAPY MONITORING USING HIGH RESOLUTION SECONDARY PARTICLE TRACKER

The radiotherapeutic method of cancer treatment using precise beam of energetic carbon ions has many advantagescompared to the conventional X-ray radiotherapy. More precise dose delivery to the tumor spares the surrounding healthytissue which makes this method especially suitable for brain cancer treatment. However, this comes with an increasedsensitivity to deformations and displacements of the tissue within the patient body. Since the whole therapeutic process isdivided into sequence of treatment sessions lasting several weeks, the above mentioned changes in the patinet body are ratherprobable to happen due to various reasons including therapy induced healing processeses. This problem is addressedirradiating the tumor with certaing marging of surronding tissue to cover position uncertainty. The other option would beperforming complete treatment replanning after each session which requires repeated diagnostics including CT scans. Thisapproach is inpracticle, expensive and and also risky due to high accumulated dignostic dose.
The aim of this work is to develop method and instrument for online radiation treatment monitoring sensitive to potentialmorphological changes in the patient body affecting the dose delivery precission.

Our team has developed a non-invasive in-vivo treatment monitoring method based on the tracking of charged nuclearfragments produced by interactions of the carbon ions with nuclei of the patient’s body. The measured tracks allow thereconstruction of fragment origins, whose distributions can be compared between different treatment fractions. In thiscomparison, interfractional changes of the patient’s morphology or positioning may be uncovered indicating need fortreatment replanning.
A novel high resolution particle tracking detector system has been developed, calibrated and successfully tested. The detectorconsists of 28 Timepix3 pixel detectors organized in seven units. Each unit consists of two layers (telescope) of two Timepix3chips with single monolithic silicon sensor. All units are synchronized with nanosecond precision. The subpixel resolution ofparticle tracks registered in each layer allows for very precise back projection reconstruction with resolution better than 300μm. This work presents the detector design and its performance testing including the system calibration.

Speaker: Carlos Granja (ADVACAM)

19 Removing constraints of 4D STEM with a framework for event-driven acquisition and processing

Removing constraints of 4D STEM with a framework for event-driven acquisition and processing
Arno Annys1,2*, Hoelen L. Lalandec Robert1,2, Saleh Gholam1,2, Joke Hadermann1,2 and Jo Verbeeck1,2

1Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
2NANOlight Center of Excellence, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
* Corresponding author: arno.annys@uantwerpen.be

Electron microscopy is a powerful and versatile tool for characterizing a wide range of samples in the fields of materials science and life sciences. In scanning transmission electron microscopy (STEM), a nanometer to picometer sized electron probe is raster scanned over a specimen, typically with microsecond dwell times. The most commonly used detection technique for transmitted electrons in STEM involves a single-pixel annular dark field detector, producing image contrast that scales with mass and thickness. However, this approach results in the loss of significant amounts of information, both from undetected electrons and from the limited information content per detected electron.

Recent advancements in detector technology, particularly the development of fast hybrid pixel array direct electron detectors, have revolutionized STEM by enabling the recording of the full scattering distribution at each probe position during a scan. This typically results in a 2D diffraction pattern for each point in the 2D scan grid, so that the technique is referred to as 4D STEM by the community. 4D STEM enables a wide range of information retrieval methods for various applications, including e.g. dose-efficient high-resolution imaging with ptychography and strain, orientation, and phase mapping in nano-beam electron diffraction.

The maximum frame rate of frame-based HPAD in STEM is generally still a factor 10-100 times slower than the megahertz regime usually desired. More importantly, because the number of electrons used in a single probe position is often much smaller than the number of detector pixels required, frame-based measuring becomes increasingly inefficient in terms of both data and computation as the detector speeds approach the desired rates. These limitations on speed and data size, among others, put stringent practical constraints on 4D STEM, making it still considered an off-line expert technique.
The sparse and continuous operation mode of event-driven HPADs, such as those based on Timepix3 and Timepix4, has been shown to mitigate some of the practical challenges in 4D STEM [1]. However, fully leveraging the benefits of event-driven detection requires redesigning the entire acquisition and processing pipeline, optimizing for sparse operation. To address this, we introduce a framework designed to bridge the gap between event-driven detection and the 4D STEM community, tackling key challenges in synchronization and processing efficiency. By redesigning current workflows to operate on individual electron events, we eliminate the need for expensive dense 4D arrays. We introduce a new algorithm that enables analytical electron ptychography to be performed directly on the raw event stream, achieving reconstruction rates that exceed maximum acquisition speeds on a standard consumer computer. This paves the way towards routinely driving experiments on the live feedback from 4D STEM measurements.
We compare the scaling laws of data size and computational requirements for event-driven and frame-based operation across various scenarios, demonstrating the benefits of event-driven workflows across a broad range of techniques. Eliminating detector speed limitations facilitates the investigation of beam-sensitive materials at extremely low doses. The advantages of high detector resolution without added data size are shown in nanobeam electron diffraction. Additionally, increasing scan resolution without penalty allows for large fields of view with sufficient sampling, which is especially important for techniques like ptychography. Finally, we illustrate how dividing a measurement into multiple scans without additional cost provides direct insights into sample dynamics, such as beam damage effects or responses to external stimuli.
References:
1. D. Jannis et al. Ultramicroscopy. 233, 113423 (2022)
2. This work received funding from the Horizon Europe framework program for research and innovation under grant agreement n. 101094299 (IMPRESS), the European Union’s Horizon 2020 research and innovation program under grant agreement n. 101017720 (FET-Proactive EBEAM) and an SBO FWO national project under grant agreement n. S000121N (AutomatED)

Speaker: Arno Annys (Electron Microscopy for Materials Science (EMAT), University of Antwerp, NANOlight Center of Excellence, University of Antwerp)

20 Utilization of the fully spectral transmision X-Ray Diffraction in non-destructive testing of welds

X-Ray Diffraction (XRD) in transmission mode is a powerful non-destructive technique for assessing the internal structure and residual stress in metallic components, with important applications in nuclear, aerospace, and petrochemical industries. Unlike conventional reflection mode, transmission XRD probes through the full material thickness, making it particularly valuable for evaluating stainless steel welds where subsurface stresses, phase changes, and microstructural transformations can affect long-term performance.
Traditionally, bulk analysis has required high-energy X-rays from synchrotron sources due to strong absorption in metals. However, with the development of spectral-sensitive detectors, transmission mode can now be performed using conventional X-ray sources—greatly increasing accessibility.
Recent advances in Timepix-family detectors, have significantly enhanced transmission XRD. These pixelated detectors offer ultra-high dynamic range, allowing accurate capture of both strong and weak diffraction signals in a single measurement. Their high sensitivity and spatial resolution open new possibilities for in-situ and real-time weld inspection—an area where transmission XRD has seen limited use until now.
This method is especially effective in the detection of critical phases like delta ferrite and sigma phase, and provides detailed information on residual stress, lattice strain, and texture—key indicators of weld quality. This approach supports robust quality control, failure prevention, and predictive maintenance strategies for critical stainless steel structures. In this presentation, we will highlight the advantages of Timepix3-based detectors for transmission XRD by comparing results across several materials.

Speaker: Roman Nebel

21 CZT based spectrometers for environmental radiation measurements

Balloon-borne Instrument for Spectral Scanning of high-altitude Environments (BISSE) is a lightweight gamma-ray measurement setup that can be placed in standard weather balloons and can be retrieved after the flight [1]. The design allows multiple flights with a relatively small cost. The BISSE setup records automatically spectral information of radiation at different altitudes throughout its flight. The sensor is cadmium zinc telluride (CZT) with crystal dimension of 1 cm cubed. This allows good spectral resolution with relatively small weight. The setup also consists of various sensors which allow various additional measurements during the flight, such as temperature and pressure sensors.

Light-weight Aranda-borne Gamma-ray and Environmental Radiation detector (LAGER) is a modification of the BISSE setup that is developed for underwater measurements. The watertight container we used required to pack the sensors in more compact manner. The main sensor for spectral measurements is also a 1 cm cubed sized CZT crystal. In addition, the same complementary sensors are included to monitor the detector measurement environment during the ascent and when reaching the bottom.

In this contribution we discuss the BISSE and LAGER designs and the latest improvements to both systems. The BISSE setup is also studied as a payload for a rotary-wing UAV which allowed us to make crucial modifications to the system for future flights. The balloon flight and the undersea measurements are also addressed with series of Geant4 simulations.

[1] T. Hildén, M. Kalliokoski, A.-P. Leppänen, J. Paatero, J. Sorri & R. Turpeinen (2025). ”CZT detector based spectrometer for drone and balloon borne measurements”. Journal of Instrumentation, 20(1), C01035.

Speaker: Dr Matti Kalliokoski (Helsinki Institute of Physics (FI))

22 Comparative study of YSO, GaGG, and BGO scintillators coupled to a SiPM array for gamma-ray spectroscopy

This study presents a novel gamma-ray detector module based on a 16-element MPPC-13360-3050 matrix (Hamamatsu) coupled with YSO, GaGG, and BGO scintillators, evaluating its performance across a 60 keV – 2500 keV energy range. Each 3×3 mm² SiPM element features a 1440 pixels/mm² density, 40% photon detection efficiency (at 470 nm), and operates at 55.5 V. The detector was characterized using gamma-ray sources (Am-243, Co-60, Cs-137, Na-22, Th-228).
The GaGG and YSO-coupled detectors exhibited a perfectly linear response between signal amplitude and gamma-ray energy (26.3 keV – 1.33 MeV). The BGO scintillator demonstrated an extended linearity up to >1 MeV but showed reduced sensitivity below 300 keV. At 662 keV, the measured energy resolutions were 8.17% (GaGG), 9.3% (YSO), and 10.2% (BGO). These results highlight the module’s versatility for spectroscopic applications across a broad energy range.

Speaker: Mr Sabuhi Nuruyev (Institute of Radiation Problems, Azerbaijan, & JINR)

23 Demonstrator detector for neutron imaging applications

To support the development and testing of detectors for Boron Neutron Capture Therapy (BNCT) and neutron imaging, we have constructed a compact neutron irradiation beamline at the Helsinki Accelerator Laboratory. The beamline includes a movable moderator/reflector assembly made of Teflon, aluminium and lead, which allows shaping the neutron spectrum to enhance specific energy ranges, such as the epithermal energy range suitable for BNCT-relevant studies. Neutrons are produced by irradiating a natural LiF target with protons. The resulting neutron spectra for various proton energies, ranging from 2.0 to 5.0 MeV, and different moderator configurations have been modelled with Monte Carlo simulations using MCNP6, FLUKA and Geant4. The neutron energy spectrum has also been measured with a "single moderator neutron spectrometer", employing spectral unfolding technique, to validate the simulated spectra.

To demonstrate the applicability of the beamline for detector development, we tested a prototype position-sensitive CMOS panel detector designed for neutron detection. The detector features two scintillator sheets based on two different neutron converters, one utilizing Lithium (6Li) and the other Gadolinium (Gd). The efficiency and characteristics of the detector are investigated, and the detector’s suitability for neutron imaging applications is presented.

Speaker: Mila Myllymäki (Helsinki Institution of Physics (FI))

24 Timepix4 Based Detection System with 1 mm CdTe Sensor: Calibration and Preliminary Spectral Imaging Application

Timepix4 is an Application-Specific Integrated Circuit (ASIC) developed by the Medipix4 Collaboration. It features a 448×512 pixel matrix, which can be bump-bonded pixel by pixel to pixelated semiconductor sensors of various materials and thicknesses, with a pixel pitch of 55 \textmu m. In ToA-ToT data-driven mode, data packets are generated only when the charge collected in a pixel exceeds a fixed threshold, providing information on both the Time of Arrival (ToA) of the hits and the Time over Threshold (ToT) of the signal. During charge collection, charge sharing can occur between neighboring pixels and the detection of a single particle may produce multiple hits. By combining the spatial location of these hits with their ToA, it is possible to cluster the events and reconstruct the correct information about the detected photons. Furthermore, after proper calibration, the ToT can be used to measure the energy of the acquired events. The ability to correct charge-sharing effects and measure particles energy over a continuous spectrum makes Timepix4-based detection systems highly promising for spectral imaging applications. Since these applications require a high X-ray detection efficiency in an energy range up to 100 keV, thick sensors made of high-Z materials are required. \
The results of the analysis of some preliminary spectral images, acquired with a Timepix4 bump-bonded to a 1 mm CdTe sensor, are here presented. Since an optimal spectral response is fundamental for spectral imaging applications, particular attention was dedicated to the energy calibration of the detector. The calibration was initially performed pixel-by-pixel with test-pulses internally generated by the ASIC to correct differences in the ToT response of the pixels. Fluorescence photons emitted by various materials in the energy range 15.8 keV - 48.7 keV were then acquired to verify and eventually correct the test-pulses calibration results. In particular, different correction factors were calculated, as a function of the energy, for different cluster size events. The energy resolution of the detection system, after completing this two-step calibration procedure, was finally evaluated as a function of the energy (see Fig. 1); a $\Delta E$/E = 11$\%$ was measured at 40 keV. \
After the calibration, spectral images were acquired in a 2D-geometry. The phantom was composed of six vials filled with $H_2O$, iodine solutions in different concentrations and a gadolinium solution. A small box filled with water was placed in front of the detection system, where the phantom was dipped during the acquisitions. A Hamamatsu micro-focus tube operating at 75 kVp - 5 \textmu A was used as X-ray source. A 600 s phantom image ($I$) and a 600 s flat-field image ($I_0$) were acquired. In the analysis, photons were separated in 1 keV energy bins, transitioning from the conventional radiographic image to a stack of quasi-monochromatic images. By using the Lambert-Beer law, the \textmu (E)x maps were calculated for each energy bin: \

\begin{equation}
\label{eq:bll}
I = I_0 \cdot e^{-\mu x} \rightarrow \mu x = ln(\frac{I_0}{I})
\end{equation}

\noindent By selecting a specific region within the various vials, and by measuring the \textmu x mean value as a function of the energy, the k-edge of iodine (33.2 keV) is clearly displayed (see Fig. 2). Furthermore, the amplitude of the signal is proportional to the solute concentration. Hence, the possibility of examining quasi-monochromatic images at selected energies allows for quantitative imaging, in which different elements and their concentrations can be identified. \
These preliminary results are very promising. Additional acquisitions in 2D geometry and further studies will be crucial for optimizing the setup and analysis procedure before transitioning to the 3D geometry used in Computed Tomography Spectral Imaging.

Speaker: Mr Alessandro Feruglio (INFN)

Fig_1.png

Fig_2.png

25 Thickness-dependent characteristics of silicon-based Medipix3RX detectors at Sirius beamlines

X-Ray imaging and diffraction techniques at Sirius [1], the fourth-generation synchrotron light source operated by the Brazilian Synchrotron Light Laboratory (LNLS) which is part of Brazilian Center for Research in Energy and Materials (CNPEM), frequently utilize hybrid pixel detectors. They consist of photon-counting devices encompassing a photo-active semiconductor sensor integrated with a pulse processing Application Specific Integrated Circuit (ASIC) capable of performing input pulse counting across a pixelated array. This work discuss characterization results based on the PIMEGA detectors [2], large area hybrid assemblies using Medipix3RX [3] ASIC, with a 55 x 55 µm2 pixel size. We compare the physical responses of 300 and 675 µm thick silicon sensors. For this contribution, we have performed the slanted edge technique for measuring the Modulation Transfer Function (MTF) [4,5] and pixel response linearity for high photon-rate conditions [6].
The MTF experiment explored the thickness dependence of the detector’s spatial resolution and was conducted under 5.9 keV incident energy ($E_0$), for equivalent energy threshold values of 0.5 and 0.7$E_0$ , as shown in Figure 1. Our work demonstrates that, even though thicker sensors present higher absorption efficiencies, the MTF values decrease along the entire spatial frequency domain. Moreover, higher threshold settings yield larger MTF values for both probed thicknesses. These observations are a consequence of the charge diffusion lengths within the thickness of the semiconductors, this leads to more pronounced charge sharing effects in thicker sensors, which are inversely proportional to the threshold settings.
The count rate linearity experiment was conducted to investigate and characterize the electronic effect of pile-up and pixel electronics paralyzable effect under high-flux incident conditions. This experiment was simultaneously conducted at two beamlines, in which we were able to vary the incident flux in the detectors by controlling the current in the Sirius storage ring.
Two detectors with Silicon sensors with thicknesses of 300 and 675 microns were studied in this experiment, with varying energies applied in accordance with the beamline and their experimental capabilities. Consequently, the CATERETE beamline [7] employs the thinner Silicon sensor for 6 keV and EMA beamline [8] employs the thicker sensor for 25 keV photon energy.
For each set ring current value, the detector was subjected to direct beam irradiation. This method enables a direct correlation between the current levels and the incident flux by analyzing the count-rate observed under low flux conditions. Numerical adjustments based on the paralyzable model [6] demonstrated the value of μ=0.66 ± 0.08 μs, which resulted in a loss of linearity under 1.58 $10^5$ photons/px.s for 675 microns sensors. The μ value demonstrated is equal to those found for 300 microns Si sensors under 6 keV μ=0.66 ± 0.01 μs and loss of linearity under 1.60 $10^5$ photons/px.s.
Our results suggest a compromise between sensor absorption efficiency and spatial resolution. Given the fair energy resolution, excellent MTF performance and despite currently unavoidable spectral distortions due to charge sharing and pile up effect, these Silicon sensor detectors constitute a very attractive technological platform for imaging and diffraction applications, especially from the tender X-ray energy range to initial hard X-ray energies.

[1] ALVES, Murilo et al. Simulation of Sirius booster commissioning. In: 10th International Particle Accelerator Conference, 2019
[2] CAMPANELLI, R. B. et al. Large area hybrid detectors based on Medipix3RX: Commissioning and characterization at Sirius beamlines. Journal of Instrumentation, v. 18, n. 02, p. C02008, 2023.
[3] BALLABRIGA, Rafael et al. The Medipix3RX: A high resolution, zero dead-time pixel detectorreadout chip allowing spectroscopic imaging. Journal of Instrumentation, v. 8, n. 02, p. C02016, 2013.
[4] BOONE, John M.; SEIBERT, J. Anthony. An analytical edge spread function model for computer fitting and subsequent calculation of the LSF and MTF. Medical physics, v. 21, n. 10, p. 1541-1545, 1994.
[5] KOENIG, Thomas et al. How spectroscopic x-ray imaging benefits from inter-pixel communication. Physics in Medicine & Biology, v. 59, n. 20, p. 6195, 2014.
[6] FROJDH, Erik et al. Count rate linearity and spectral response of the Medipix3RX chip coupled to a 300μm silicon sensor under high flux conditions. Journal of Instrumentation, v. 9, n. 04, p. C04028, 2014.
[7] MENEAU, F. et al. Cateretê: The Coherent X-ray Scattering Beamline at the 4th generation synchrotron facility SIRIUS. Acta Crystallogr. Sect. A Found. Adv, v. 77, p. C283, 2021.
[8] DOS REIS, Ricardo D. et al. Preliminary overview of the extreme condition beamline (EMA) at the new Brazilian synchrotron source (Sirius). In: Journal of Physics: Conference Series. IOP Publishing, 2020.

The authors acknowledge funding from the Brazilian Ministry of Science, Technology, and Innovation.

Speaker: Luana Santos Araujo (LNLS)

Figures Abstract.pdf

26 Projection-based Metal Artifact Reduction in Spectral Photon-Counting Dental CBCT

While cone-beam computed tomography (CBCT) is the dominant modality in dentomaxillofacial radiology due to its balance of spatial resolution, cost, and radiation dose, it remains suboptimal for visualizing fine orofacial structures and is particularly prone to metal artifacts from implants and crowns. These limitations motivate the integration of photon-counting detectors (PCDs), which offer spectral data for improved image quality and material decomposition.

In this study, we present a projection-domain metal artifact reduction method for a dental photon-counting CBCT system. The system comprises a state-of-the-art PCD (XC-Thor FX40) from Varex Imaging Corporation (Salt Lake City, USA) with two adjustable energy thresholds (set to 10 keV and 65 keV), a 750 µm thick CdTe sensor and a pixel size of 100 µm. CT scans were performed at 130 kVp with an anthropomorphic head phantom from Quart GmbH (Zorneding, Germany), in which tooth repairs in the form of dental onlays and crowns are included. Our approach employs a material separation algorithm to decompose the projection data into material-equivalent thicknesses. Via adaptive thresholding, a Boolean mask is generated to locate metal regions within each projection. Prior to reconstruction, these regions are refined through iterative steps of binary dilation and erosion to reduce false-positive and false-negative detections. Subsequently, the regions are interpolated across neighboring non-metal pixels in both spatial directions, and the projections are then reconstructed using filtered backprojection.

Applied to virtual monochromatic and material-selective images of the anthropomorphic head phantom, the algorithm demonstrates a reduction in metal streaks and beam starvation artifacts, with improvements in contrast-to-noise ratios and the preservation of visibility of larger-scale structures.

Speaker: Benjamin Berger

27 First CT Evaluation of a Novel Photon-Counting Detector Module for Clinical CTs

Background:
Photon-counting computed tomography (PCCT) is a rapidly emerging imaging modality that offers significant advantages over conventional energy-integrating detectors (EIDs)-based CTs, such as improved image quality, spectral imaging, and dose and noise reduction. Developing a new photon-counting detector with four-side buttable technology and six energy bins enables CT systems that provide high resolution, enhanced tissue differentiation, and multi-energy imaging in a single acquisition and represents a significant step toward advancing the development of PCCT systems with the potential to set new milestones in medical imaging and clinical applications.
Objective:
This study presents the first CT evaluation of a novel prototype photon-counting detector module developed by Varex Imaging, designed to advance PCCT technology for clinical applications. A first detector version was tested on a tabletop CT setup to assess its performance, particularly regarding resolution and tissue characterization. An anthropomorphic hand phantom from QUART GmbH (Zorneding, Germany) and a 3D-printed phantom were used as test objects.
Materials & Methods:
The prototype module consists of 2x3 active tiles, each with 128x128 pixels and 0.15mm^2 in pixel size. For CT scans of the samples at 120kVp, three energy thresholds (20keV, 50keV, 80keV) were set to enable multi-energy data acquisition, spectral separation, and tissue characterization. CT scans were performed on a 3D-printed phantom and an anthropomorphic hand phantom mimicking bone and soft tissue contrast. The acquired data were compared to reference scans from conventional clinical CT systems (with an energy-integrating detector (EID)) to assess image quality, resolution, and noise.
Results & Outlook:
The results indicate that the Varex photon-counting detector provides a significant advantage over conventional EID-based clinical CT systems in terms of image quality, particularly in high-contrast imaging of bone and soft tissues. Although tested on a table-top setup, these first evaluation results indicate its usefulness in clinical applications requiring high-resolution, multi-energy imaging for high-detail anatomical studies. Further research will focus on CT system integration, assessing clinical
feasibility, and validation in real-world medical imaging scenarios.

Speaker: Lisa Marie Petzold (TUM - Chair of Biomedical Physics)

iworid2025-LMP.pdf

28 Spectral CT Imaging of a Lithium-Ion Battery Using Photon-Counting and Dual-Layer Detectors: A Comparative Study

Spectral imaging in industrial CT offers significant benefits for materials analysis and artifact reduction. In this study, we demonstrate that dual-layer energy-integrating detectors (DL EIDs) provide substantial improvements over conventional flat panel detectors (FPDs) in the spectral imaging of a commercial 18650 lithium-ion battery. Using a prototype dual-layer detector (XRD4343RF-DL, Varex Imaging Corporation, Salt Lake City, USA), we reconstruct virtual monoenergetic images from energy-selective data acquired by the two scintillator layers. Compared to conventional single-layer reconstructions, these spectral images show markedly reduced beam hardening artifacts and enhanced material contrast - demonstrating the clear added value of the dual-layer approach for industrial CT.

To further assess the performance limits, the DL detector was compared with a high-resolution photon-counting detector (Thor-FX40, Varex Imaging Corporation). While the photon-counting detector (PCD) delivers superior spatial resolution and energy discriminating capabilities, it also presents significant limitations in terms of detector area (≤ 50 × 200 mm² in current systems), higher cost, and often the need for active liquid cooling. In contrast, the DL detector offers a substantially larger field of view (432 × 432 mm²), simpler system integration (passive cooling), and more accessible deployment.

Both systems successfully enabled spectral CT imaging and monoenergetic reconstruction. The PCD excels in resolution-critical applications, but the DL detector emerges as a practical and cost-efficient alternative for scenarios requiring spectral information without the technical and economic overhead of photon-counting technology. These findings highlight the dual-layer detector as a strong candidate for extending spectral imaging capabilities into broader industrial use cases.

Speaker: Daniel Berthe (Technische Universität München, Chair of Biomedical Physics)

29 Development of Prompt Gamma-ray Imaging Detector for Boron Neutron Capture Therapy

Boron Neutron Capture Therapy (BNCT) uses a nuclear reaction between boron atoms (10B) and neutrons to selectively destroy cancer cells from the inside. To estimate the treatment effect in real-time, the use of prompt gamma rays (478 keV) emitted by the 10B(n,α)7Li reaction has been proposed using a collimator. Although the collimator is able to detect the direction of incident gamma rays, background events increase due to scattering by the collimator itself. Therefore, we have developed a novel detector consisting of a scintillator, optical fiber and photomultiplier tube without the collimator.
On the other hand, single photon counting method is not available for the high counting rate and the detection of the direction for the gamma rays without the collimator. Here, if energy discrimination is not needed, the imaging is expected using center-of-gravity calculations from current mode measurement with multiple photosensors. Thus, we demonstrate a BNCT-simulated experiment and verified the adaptability of the new detection method.
Using the developed detector consisting of a novel scintillator crystal, optical fiber and photomultiplier tube, we measured gamma rays of 478 keV produced by the nuclear reaction between 10B and thermal neutrons. The boron position was successfully imaged from the current values obtained at several channels. We report on the details of our detector and imaging results.

Speaker: Mr Yusuke Urano (Tohoku University)

30 Toward Reconstruction-Free PET: Progress in Direct Positron Emission Imaging (dPEI)

Three-dimensional biomedical imaging techniques, such as X-ray computed tomography (CT), single-photon emission computed tomography (SPECT), and positron emission tomography (PET), acquire one- or two-dimensional projections of the object of interest. These projections are subsequently reconstructed into cross-sectional or volumetric images using analytic computed tomography algorithms. In all these modalities, each measured data point does not correspond directly to a specific point in image space; instead, the spatial distribution of the signal must be inferred through a reconstruction process. Furthermore, accurate tomographic reconstruction requires adequate angular sampling of the data. Positron-emitting radiotracers used in PET have the unique property of producing a pair of 511-keV annihilation photons that travel in opposite directions after each radioactive decay. This property allows for the possibility of obtaining cross-sectional or volumetric images of the radiotracer distribution directly, by measuring the difference in arrival times of the two photons—without the need for an image reconstruction step. The first demonstration of this reconstruction-free approach, referred to as direct positron emission imaging (dPEI), was accomplished using two gamma-ray detectors with ultrahigh timing resolution in combination with convolutional neural networks. By eliminating the constraints imposed by conventional tomographic sampling, dPEI creates new opportunities for innovative imaging system designs. This presentation will focus on the current progress and technological roadmap for developing dPEI scanner systems.

Speaker: Dr Sun Il Kwon (University of California, Davis)

31 High frame rate RIXS spectroscopy using a JUNGFRAU detector with an iLGAD sensor

Several experimental techniques make use of soft X-rays as a probe, commonly focusing on the energy range between a few hundred eV up to approximately 1 keV. This range is particularly relevant for the study of transition metals and light elements such as C, N and O, which are fundamental components of a large number of materials with intriguing electronic and magnetic properties, from biological matter to superconductors. One such technique is resonant inelastic X-ray scattering (RIXS), a photon-in/photon-out method in which the incident photon energy is tuned to match the absorption edge of the sample. This resonance condition greatly enhances the inelastic scattering cross-section of the system, providing a unique way of accessing information about the intrinsic excitations by measuring the change in energy, momentum, and polarization of the scattered photon [1].
The Spectroscopy and Coherent Scattering (SCS) instrument at the European XFEL is equipped with the Heisenberg-RIXS spectrometer (hRIXS), capable of performing RIXS measurements in the time domain, with time and energy resolution approaching the Heisenberg limit imposed by the uncertainty relations [2]. The unique pulse delivery structure of the European XFEL allows for bursts of pulses within a bunch train to be delivered up to $\mathrm{MHz}$ rates, which is beyond the frame rate capability of most detectors. Combining this with the additional requirements of high spatial resolution and large sensitive area, finding a detector capable of fully exploiting the potential of the hRIXS spectrometer becomes a significant challenge. So far, commercial CCD and CMOS cameras with small pixels have been used, providing a satisfactory spatial resolution. However, their limited readout speed allows only for the integration of entire XFEL trains. A faster detector, capable of resolving intra-train pulses, would greatly benefit pump-probe laser experiments, by enabling the use of alternating pumped and unpumped pulses for more reliable data normalization.
In recent years, a collaboration between the Paul Scherrer Institute (PSI) and Fondazione Bruno Kessler (FBK) has materialized into the first prototypes of X-ray-sensitive Inverse Low Gain Avalanche Diodes (iLGADs) sensors compatible with the readout chips of the widely adopted charge-integrating detectors developed by PSI, such as the JUNGFRAU [3, 4]. This detector, already used at several hard X-ray instruments at the European XFEL, is capable of storing up to 16 images in analogue memory cells, offering a maximum acquisition rate of $\sim200~\mathrm{kHz}$ in bursts. Additionally, its $75\times75~\mathrm{\mu m^2}$ pixels can be easily segmented and reorganized into narrow rectangular pixels of $25\times225~\mathrm{\mu m^2}$ (or narrower), increasing spatial resolution along the energy dispersion axis in spectroscopic experiments. This resolution can be further enhanced by leveraging charge sharing across pixels, through position interpolation methods.
In a recent beamtime, a JUNGFRAU detector equipped with an iLGAD sensor was tested at the hRIXS spectrometer, with positive outcomes. In this work, we present the main findings regarding detector performance, highlighting the spatial resolution achieved using reference solid samples, and comparing it to the previously used commercial cameras. Additionally, we present the first RIXS spectra acquired at multi-$\mathrm{kHz}$ rate in combination with pump-probe laser excitation, and analyse how the intense FEL pulses may affect the sample’s response to the incoming photons.

[1] Van den Brink, Jeroen. "Resonant inelastic x-ray scattering on elementary excitations." Rev. Mod. Phys 83 (2011): 705.
[2] Schlappa, Justine, et al. "The Heisenberg-RIXS instrument at the European XFEL." Synchrotron Radiation 32.1 (2025).
[3] Mozzanica, A., et al. "The JUNGFRAU detector for applications at synchrotron light sources and XFELs." Synchrotron Radiation News 31.6 (2018): 16-20.
[4] Hinger, Viktoria, et al. "Resolving soft X-ray photons with a high-rate hybrid pixel detector." Frontiers in Physics 12 (2024): 1352134.

Speaker: Marco Ramilli (European X-ray Free Electron Laser)

2025_Duarte_iWoRiD.pdf

32 Precise evaluation of energy dispersive X-ray diffraction data measured by Timepix3 detector for observation of dynamic phase transition in steel

X-ray diffraction (XRD) is a versatile non-destructive analytical technique used to analyze crystalline properties of various materials. This technique requires collimated monochromatic X-ray beam that reflects at certain angles from the crystals within the sample. The reflection angles are specific for given crystal type and its orientation. A composition of materials containing multiple crystalline phases can be analyzed this way. XRD analysis is an important tool for metallurgy, as crystalline microstructure directly affects the mechanical properties of alloys used in industry.
Current XRD systems utilize relatively low-energy monochromatic X-ray beam (5-20 keV) which can only penetrate shallow layer close to the sample surface. Therefore, the thick metallic parts cannot be analyzed through their entire volume. The only option is to use the synchrotron sources, which are not practical for industrial applications.
In this contribution we evaluate performance of the fast energy dispersive XRD system with polychromatic X-ray beam and spectrally sensitive imaging detector Timepix3. The results of pilot measurement demonstrate ability to sense the controlled recrystallization within volume of the 1.5 mm thick steel plate.
During the experiment the temperature of the sample changed from 25 to 750°C and back within five minutes, while its crystalline composition was monitored by dynamic XRD measurement. The sample was transmitted by a polychromatic collimated X-ray beam generated by a tungsten X-ray tube operating at 90 kV. The fully spectral imaging data recorded behind the sample by Timepix3 detector captured diffraction patterns corresponding to the actual microstructure of the sample. A comprehensive mathematical model describing the response of the experimental system was created. By comparing the model predictions with measured data, it was possible to perform data analysis with unexpectedly high precision. The timeline of dynamically changing ratio between the two significant crystalline phases of the steel (ferrite and austenite) was measured with standard deviation of 0.7%.
The experiment shows that it is possible to observe and possibly even control the metallurgic processes thanks to the novel technology of the spectrally sensitive imaging detectors.

Speaker: Jan Jakůbek (ADVACAM s.r.o.)

33 Aberration effects inherent in planar integrating detectors and their influence on imaging quality in diffraction experiments

Diffraction experiments using coherent X-ray radiation from light sources, such as X-ray free- electron lasers (XFELs), are essential for investigating the structural and functional properties of materials at the nanoscale. These sources deliver highly coherent, high-brilliance, pulsed X-ray beams that enable the detailed study of physical, chemical and iological systems. A key requirement for such experiments is the accurate detection of diffraction patterns. For this purpose, large-area planar integrating pixel detectors with a high dynamic range across the full q-range are typically employed. This simulation study investigates how aberration and charge-sharing effects inherent to a planar detector with a 500 μm-thick silicon sensor affect the achievable spatial resolution and image quality across a range of pixel sizes (from 50 μm × 50 μm to 200 μm × 200 μm). We characterize and quantify these effects using our generalized point spread function (PSF) model [1, 2], which describes the spatial distribution of detected photon signals as a function of photon energy and diffraction angle. We also analyze the effect of the PSF on the achievable signal-to-noise ratio, considering its dependence on photon energy, angle of incidence or equivalent q, image contrast and spatial resolution. Spatial resolution is assessed uantitatively through the modulation transfer function (MTF), providing a comprehensive understanding of detector performance under varying experimental conditions. Our study provides valuable insights into the design and optimization of future detector systems, particularly in terms of achieving maximum contrast, signal-to-noise and position resolution in high-resolution diffraction experiments.
[1] Kuster, M., Hartmann, R., Hauf, S et al. (2024) On the Influence of Parallax Effects in Thick Silicon Sensors in Coherent Diffraction Imaging, In Journal of Physics – Conference Series (JPCS), arXiv:2410.14474, accepted for publication, in press

Speaker: Markus Kuster (Data Department, European XFEL GmbH, Holzkoppel 4, Schenefeld, Germany)

Kuster-Aberration Effects-iWorid 2025-Abstract.pdf

34 Bayesian Deep Prior Denoising of XRF Maps Acquired Under Low Dose Constraints

Low-energy X-ray fluorescence (XRF) mapping at synchrotron radiation facilities [1, 2] is often limited by acquisition time and dose constraints [3], especially for sensitive samples such as biological specimens or cultural heritage objects. Compressive sensing strategies [3] offer a way to mitigate these limitations by enabling spatial undersampling or by triggering dynamical decisional mechanisms [3]. Still, reconstructions from these regimes are challenged by high noise, low photon counts, and incomplete data.
Traditional denoising, inpainting and reconstruction algorithms often fail under such low-count conditions, and iterative reconstruction pipelines require carefully tuned, handcrafted regularizers [4]. On the other hand, supervised deep learning methods - while powerful - pose risks of hallucinating details learned during training, which is especially problematic when ground truth is unavailable [5].
In this work, we propose a Bayesian Deep Image Prior (BDIP) framework for denoising and restoring XRF maps acquired at short dwell times [6, 7]. This method belongs to the class of unsupervised deep priors [5], requiring no pre-training, thus reducing the risk of introducing artificial features [7]. The approach [5] treats the reconstruction as an iterative optimisation problem, where a modified U-Net [8] fed with noise learns to generate a denoised image by progressively estimating the task-specific high-frequency content. Unlike conventional handcrafted priors that act as fixed filters or sparsity enforcers, the network learns a complex task-specific prior directly from the data.
A key advantage of the Bayesian formulation [7, 6] is its ability to estimate both epistemic uncertainty (reducible with more data) and aleatoric uncertainty (intrinsic to the noise) [9] via a variational method and Monte Carlo dropout [7, 10]. This results in pixel-wise uncertainty maps, providing insights into the reliability of the reconstructed signal [7]. Nonetheless, even if not fully immune to overfitting, BDIP provides more controlled convergence than conventional Deep Image Prior approaches [7].
We evaluated our method on XRF spectral maps measured at the TwinMic spectro-microscopy beamline [2] of the Elettra Synchrotron facility (Trieste) acquired from a 1 mm-thick sandstone sample treated with a nano-protective product [3, 11]. Due to the sample’s opacity, localisation was guided using only visible light and back-scattering images. Dwell times of 3 s and 0.1 s were used to simulate high and low-count scenarios. From the detected emission lines (Na, Si, and Al), Na, the weakest emitter, posed the most significant denoising challenge. Comparative benchmarks were performed using state-of-the-art methods such as calibrated [12] non-local-means [13], total variation [14], and wavelet [15] denoisers under a j-invariant framework [12]. Our method consistently achieved the highest SSIM scores [16], particularly in recovering fine details in the noisy Na map. Pixelwise uncertainty maps further highlighted regions of reconstruction instability, aiding interpretation.

References:
[1] Jenkins, R., Gould, R. W. & Gedcke, D. (1995). Quantitative X-ray Spectrometry. New York: M. Dekker.
[2] Gianoncelli, A., Kourousias, G., Merolle, L., Altissimo, M. & Bianco, A. (2016), Current status of the TwinMic beamline at Elettra: a soft X-ray transmission and emission microscopy station, J. Synchrotron Rad. 23, 1526-1537.
[3] Kourousias G, Billè F, Guzzi F, Ippoliti M, Bonanni V, et al. (2023) Advances in sparse dynamic scanning in spectromicroscopy through compressive sensing. PLOS ONE 18(11): e0285057.
[4] A. Levin, Y. Weiss, F. Durand and W. T. Freeman, "Understanding and evaluating blind deconvolution algorithms," 2009 IEEE Conference on Computer Vision and Pattern Recognition, Miami, FL, USA, 2009, pp. 1964-1971
[5] V. Lempitsky, A. Vedaldi and D. Ulyanov, "Deep Image Prior," (2018), IEEE/CVF Conference on Computer Vision and Pattern Recognition, Salt Lake City, UT, USA, 2018, pp. 9446-9454
[6] Z. Cheng, M. Gadelha, S. Maji and D. Sheldon, "A Bayesian Perspective on the Deep Image Prior," in 2019 IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), Long Beach, CA, USA, 2019, pp. 5438-5446
[7] Laves, MH., Tölle, M., Ortmaier, T. (2020). Uncertainty Estimation in Medical Image Denoising with Bayesian Deep Image Prior. In: Sudre, C.H., et al. Uncertainty for Safe Utilization of Machine Learning in Medical Imaging, and Graphs in Biomedical Image Analysis. UNSURE GRAIL 2020 2020. Lecture Notes in Computer Science(), vol 12443. Springer, Cham.
[8] Ronneberger, O., Fischer, P., Brox, T. (2015). U-Net: Convolutional Networks for Biomedical Image Segmentation. In: Navab, N., Hornegger, J., Wells, W., Frangi, A. (eds) Medical Image Computing and Computer-Assisted Intervention – MICCAI 2015. MICCAI 2015. Lecture Notes in Computer Science, vol 9351. Springer, Cham.
[9] Alex Kendall and Yarin Gal. 2017. What uncertainties do we need in Bayesian deep learning for computer vision? In Proceedings of the 31st International Conference on Neural Information Processing Systems (NIPS'17). Curran Associates Inc., Red Hook, NY, USA, 5580–5590.
[10] Yarin Gal, Zoubin Ghahramani, Dropout as a Bayesian Approximation: Representing Model Uncertainty in Deep Learning, Proceedings of The 33rd International Conference on Machine Learning, PMLR 48:1050-1059, 2016.
[11] Raneri S, Giannoncelli A, Mascha E, Toniolo L, Roveri M, Lazzeri A, et al. Inspecting adhesion and cohesion of protectives and consolidants in sandstones of architectural heritage by X-ray microscopy methods. Materials Characterization. 2019; 156: 109853.
[12] J. Batson & L. Royer. Noise2Self: Blind Denoising by Self-Supervision, International Conference on Machine Learning, p. 524-533 (2019).
[13] A. Buades, B. Coll, & J-M. Morel. Non-Local Means Denoising. Image Processing On Line, 2011, vol. 1, pp. 208-212.
[14] A. Chambolle, An algorithm for total variation minimization and applications, Journal of Mathematical Imaging and Vision, Springer, 2004, 20, 89-97.
[15] Chang, S. Grace, Bin Yu, and Martin Vetterli. “Adaptive wavelet thresholding for image denoising and compression.” Image Processing, IEEE Transactions on 9.9 (2000): 1532-1546.
[16] Wang, Z., Bovik, A. C., Sheikh, H. R., & Simoncelli, E. P. (2004). Image quality assessment: From error visibility to structural similarity. IEEE Transactions on Image Processing, 13, 600-612.

Speaker: Dr Francesco Guzzi (Elettra Sincrotrone Trieste)

35 In-vivo double photon emission coincidence imaging of tumor-targeted polymeric micelles

We report a proof-of-concept study applying double-photon emission coincidence imaging (DPECI) to visualize polymeric micelle-based nanocarriers in a tumor-bearing mouse model. The micelles, formed via self-assembly of block copolymers, had an average diameter of approximately 30 nm. They were radiolabeled with DOTA-conjugated ¹¹¹In and administered intravenously, enabling passive tumor accumulation via the enhanced permeability and retention (EPR) effect.

The DPECI system consisted of 12 high-resolution GAGG(Ce) scintillator arrays with a pixel size of 2.5 × 2.5 × 4 mm³ and a pitch of 3.2 mm, arranged in an 8 × 8 matrix. Those arrays were optically coupled to a matching 8 × 8 silicon photomultiplier (SiPM) array. A hybrid collimator configuration was employed, comprising a 15 mm-thick parallel-hole collimator (hole diameter: 2 mm, hole pitch: 3.2 mm) and a 15 mm-thick slat collimator (slat pitch: 3.2 mm). Cascade gamma photons at 171 keV and 245 keV emitted from ¹¹¹In were detected in coincidence and localize the position by intersection of a defined plane by slat collimator and a defined line by parallel hole collimator. SiPM output signals were processed using a dynamic time-over-threshold (dToT) approach, and the time stamp, ToT length, and channel number of each event were simultaneously recorded in a parallelized data acquisition (DAQ) system.

Micelle accumulation was clearly visualized at the tumor region, with distinct separation from background signals and spatial consistency. This study represents the first in vivo application of DPECI to track polymeric nanocarriers with 111In cascade nuclides, highlighting its potential as a reconstruction-free imaging platform for small-animal biodistribution assessment.

Speaker: Mr Boyu Feng (The University of Tokyo)

36 Characterization of a High Frame Rate Direct Electron Camera and Its Applications in CryoEM

The paper presents characterization of the EMPIX (Electron Microscopy PIXel) [1] camera and its applications in cryoEM，including STEM, diffraction and ptychography. The camera consists of a hybrid silicon pixel detector, TEC and water cooling and the high bandwidth DAQ (data acquisition system) up to 82.5 Gbps. The detector consists of 128 x 128 array and the pixel size is 150 um x 150 um. Each pixel works at integration mode and the dynamic range of 24 bit is implemented by combining the counts of charge injection and digitized residual charge with Wilkinson-type ADCs. Thanks to the on-chip digitization and high readout bandwidth, the frame rate of up to 100 kfps can be achieved for full size.
The camera was installed in a field emission 200 kV S/TEM (FEI Tecnai F20) and was carefully calibrated before characterization. The coefficients for one count of injected charge and the ADC bin was estimated by linear interpolation with flat field irradiation data. Single electron response was measured with low beam current. The signal to noise ratio is only 7 @ 200 kV, which is much lower than expectation and is due to some circuit design problem. But the peak of the single electron can be clearly separated from the noise floor. The MTF was measured using the edge of the beam stop and then the DQE was estimated as shown in Figure 1. The DQE(0) is measured to be 0.92, which is comparable to other hybrid pixel detectors.
The beam scanning signal generator has been also developed and the beam positions was integrated into the imaging data for each frame. Various STEM images can ben synthesized in real time, e.g., HAADF, BF and iCOM. Figure 2 shows some example images of negatively stained proteasome sample using 512 x 512 scan. Figure 3 shows a reconstructed 4D STEM image of the proteasome sample. More imaging applications in cryoEM are undergoing and the detailed results will be present at the workshop in July.

Reference:
[1] T. Wei et al Design and evaluation of EMPIX2, a 100 kfps, high dynamic range pixel detector readout ASIC for electron microscopy, 2023 JINST 18 C12007

Figures are shown in attached pdf.

Speaker: Prof. Zhi Deng

figures.pdf

37 Searching for Alternative Gases in RPC Detectors: Performance Studies of Eco-Friendly Gas Mixtures

Resistive Plate Chamber (RPC) detectors used in CERN’s LHC experiments traditionally operate with a gas mixture containing C2H2F4 (R134a) and SF6, both of which are greenhouse gases with high Global Warming Potential (GWP). In Europe, the production of these fluorinated gases is being phased out, making the identification of environmentally friendly alternatives increasingly urgent.
This study evaluates the performance of RPC detectors when R134a or SF6 are replaced with candidate gases featuring a lower GWP. The investigation also extends to Multigap RPC detectors, where SF6 concentrations can reach up to 10%. Detector tests are first conducted in a controlled laboratory environment using cosmic muons, followed by beam tests at the CERN Gamma Irradiation Facility. There, a muon beam is combined with background irradiation from a 14 TBq 137Cs source to emulate LHC-like conditions.
Key detector parameters under investigation include efficiency, dark current, streamer probability, mean prompt charge, cluster size, and time resolution. The results aim to provide an initial selection of promising eco-friendly gas mixtures, paving the way for future long-term ageing tests to assess their durability and operational stability.
This work presents the results obtained with these alternative gas mixtures, focusing on how changes in composition affect detector performance compared to the standard RPC gas mixture.

Speaker: Mattia Verzeroli (Universite Claude Bernard Lyon I (FR))

Poster_IWORID_new.pdf

38 First Demonstration of the Three-Photon Absorption Transient Current Technique (3PA-TCT) for Timing studies in Irradiated and Non-Irradiated Double-Sided Column 3D Silicon Sensors

We demonstrate the application of the Three-Photon Absorption Transient Current Technique (3PA-TCT) for the characterization of 3D silicon column device, with an active thickness of 285 µm and pitch of 55 um, manufactured at IMB-CNM through the RD50 Common Project. The work presented in this contribution is done within the framework of the CERN DRD3 and CERN Rd50 Collaborations. To our best knowledge, this technique is not utilized yet on the 3D sensors, and our work presented here is the first one. The characterization was performed at the EU laser facility ELI ERIC, ELI Beamlines in Prague, utilizing advanced nonlinear optical techniques to achieve localized charge generation with high spatial resolution while at the same time preventing the contribution from the Single Photon Absorption (SPA) which is present in significant amount in the Two Photon Absorption (TPA) when irradiated samples are studied (affecting this way the precision of the timing measurements) which is even more serious as radiation fluency and thus the amount of radiation defects increase. The 3PA technique as a novel 3D timing characterisation tool for the 3D Si irradiated sensors was tested on both single and large multiple 3D Hexagon and Square structures irradiated at the neutron fluency of 10e16 neq/cm2 at the TRIGA Reactor of the Jozef Stefan Institute in Ljubljana, exploiting this way both radiation hardness and timing under the extreme radiation conditions.

Speaker: Prof. Gordana Lastovicka-Medin (Faculty of Natural Sciences and Mathemayics, University of Montenegro (ME))

39 Advancements In LGAD Technology For Space Experiments: Insights From Recent Lab Measurements

Low Gain Avalanche Diodes (LGADs) constitute the state-of-the-art in Minimum Ionizing Particles (MIP) timing measurements in High Energy Physics (HEP), providing a time resolution of about 30 ps. These detectors feature an active area of about a few mm$^2$ on a 50~$\mu$m thick silicon and are capable of withstanding fluence up to a few 10$^{15}$ n$_{eq}$/cm$^2$. Due to their exceptional timing capability, LGADs are becoming highly attractive for 4D tracking and time-of-flight systems in astroparticle physics experiments. However, the power consumption constraints and low hit rates of space-based experiments result in larger channel sizes compared to HEP.

In recent years, LGAD technology has been produced with channel sizes up to 1~cm$^2$ to mimic the typical channel size of the silicon microstrip sensors used in many space missions. Measurements from the first production of these 1~cm$^2$ LGADs, with a gain value of 40, indicate a jitter of about 80 ps and a timing resolution of about 150 ps with a radioactive source ($^{90}$Sr). The performance of these detectors was limited by the gain as increasing the bias further would lead the LGAD to breakdown.

To improve the gain and timing resolution of these detectors, a new batch of sensors has been produced. Various design choices have been made to study the non-uniformity in signal shapes and their impact on the timing resolution of large-channel LGAD sensors. This work will present the first electrical characterization, and timing resolution results for the latest production of LGADs for space experiments.

Speaker: Ashish Bisht (Fondazione Bruno Kessler (FBK))

posterIWORID2025_BISHT.pdf

40 Up-to-date test beam results of ATLAS ITk Pixel sensors and modules

The ATLAS Inner Detector will be entirely replaced with a new all-silicon tracking detector (ITk) in 2026–2028 to meet the demands of the High Luminosity LHC (HL-LHC). The innermost region of ITk will be instrumented with 3D sensor technology at Layer 0 (L0), where the expected fluence reaches up to 2×1016 neq/cm², while the outer layers (L1–L4) will feature n-in-p planar hybrid modules with sensor thicknesses of 100 µm and 150 µm.
Beam tests play a critical role in assessing the performance and operational characteristics of these sensors and modules, both before and after irradiation at HL-LHC-relevant fluences. Over the past few years, multiple sensor designs from different vendors have undergone systematic testing. The 2024 test beam campaign introduced novel sensor types produced using enhanced fabrication techniques, along with modules incorporating the latest version of the ITk readout chip. Thick planar sensors from Micron have been evaluated before and after irradiation as part of several test beam campaigns conducted throughout 2024.
Furthermore, the final iteration of the ITkPixV2 readout chip was submitted in March 2023, and the first modules assembled with this chip were successfully tested in summer 2024. The 2025 testing phase marks an important milestone, with the introduction of new triplet-configured 3D sensors and quad-configured planar sensors, now undergoing irradiation studies. This ongoing test beam program provides valuable insights into sensor performance under operational conditions, ensuring the readiness of ITk pixel detectors for HL-LHC physics.
This presentation will provide a comprehensive overview of ITk pixel sensor and module qualification efforts through test beams, incorporating the latest results from the 2024 and 2025 campaigns.

Speaker: Md Arif Abdulla Samy (University of Glasgow (GB))

iworid2025_abstract.pdf

strnad_itk-pixel-testbeam.pdf

41 Dose rate dependence of TID Damage in front-end electronics for SLS 2.0

The Swiss Light Source (SLS) is currently in the final stages of upgrading to
a diffraction-limited storage ring configuration, SLS 2.0. This upgrade will
significantly enhance the brilliance by up to two orders of magnitude. However,
it introduces new challenges for silicon detectors due to increased radiation
damage. A primary concern is the higher accumulated dose received by the
front-end electronics, which may lead to performance degradation over time due
to total ionizing dose (TID) effects [1].
To investigate these effects, we studied test structures developed in 110 nm
technology. These structures were irradiated at different dose rates at room
temperature using an in-house X-ray source. We evaluated the analog and digital
functionalities of these structures to assess the impact of TID under different
irradiation conditions, with particular focus on dose rate dependence. We also
examined the annealing dynamics to understand the potential for recovery or
further degradation following irradiation.
References
[1] J. S. George. An overview of radiation effects in electronics. In 25th
International Conference on the Application of Accelerators in Research and
Industry, volume 2160, page 060002, 2019.

Speaker: Viveka Gautam (PSI)

Abstract_iworid_viveka-1.pdf

42 A large area gas proportional scintillation counter with a ring-shaped anode for x- and gamma-ray spectroscopy

Gas Proportional Scintillation Counters (GPSCs) are noble gas detectors in which the primary ionization charge generated by radiation interactions is amplified via electroluminescence (EL) in the gas. Under an external electric field, the primary electrons drift into a region where the field exceeds the gas scintillation threshold—known as the scintillation region. Compared to charge amplification via electron avalanches, EL amplification provides higher gain with improved signal-to-noise ratio, no space charge effects, and better immunity to radiofrequency noise and electrical discharges.
GPSCs have been widely used in applications such as X-ray fluorescence analysis, X- and γ-ray astrophysics, and planetary and asteroid exploration. Their high resistance to radiation damage, wide operational temperature range, simple yet flexible design, and large-area detection capability are notable advantages. However, the solid angle subtended by the photosensor varies with the EL emission position, causing the detected signal to depend on the radiation interaction location. This limits the size of the detector’s radiation window relative to the photosensor.
Several compensation techniques have been proposed to mitigate this effect—at the cost of increased detector complexity. Examples include electrostatic focusing of primary electrons toward the photosensor axis and radial modulation of the electric field in the scintillation region to counteract the radial variation in solid angle.
To overcome these limitations, we recently proposed a novel and simple GPSC design that ensures a constant solid angle across the scintillation region. In this configuration, a single annular anode electrode, centered on the photosensor axis and held at high voltage, defines a localized scintillation region near its surface. As a result, the entire region maintains a fixed solid angle with respect to the photosensor, making the EL signal independent of the interaction position. This design enables a large window-to-photosensor size ratio while maintaining uniform response.
Previously, we developed a comprehensive simulation tool incorporating radiation absorption, electron drift, EL emission, and light detection, which was validated against an annular-anode GPSC prototype. The simulations showed good agreement with experimental results.
In this work, we use the simulation tool to explore the optimal geometrical parameters of the annular-anode GPSC, aiming to balance energy resolution and the anode-to-photosensor radius ratio. We also investigate the effect of the anode bias voltage on detector performance.

Speaker: Joaquim Marques Ferreira Dos Santos (Universidade de Coimbra (PT))

abstract_IWORID25_PEDRO_SILVA.docx

43 DQE analysis of CdTe and Si sensor Timepix3 detectors

In this study, the Detective Quantum Efficiency (DQE) was measured by calculating the DQE at zero- frequency, the modulation transfer function (MTF), and the noise power spectrum (NPS) for Timepix3 detectors equipped with 500 μm silicon (Si) sensor (biased to 200 V and threshold equal to 3 keV) and 1mm Cadmium Telluride (CdTe) sensor (bias equal to -300V and threshold set to 5 keV). By comparing these parameters, the impact of sensor material on spatial resolution and noise characteristics was assessed. The MTF, NPS and DQE parameters were calculated with datasets using two different acquisition modes; counting mode, where the particle hits are not clustered and Time of Arrival (ΤοΑ) and Time over Threshold (ΤοΤ) mode, where the particle hits are clustered and their center of mass (c.m) is calculated. It was concluded that the c.m dataset provided better MTF and NPS values leading to an improved DQE estimation. It was also possible to correct the charge sharing caused by fluorescence events in the CdTe by identifying the clusters, reconstructing the energy of the initial particle and assigning this energy to the position of the initial hit which generated the fluorescent particle. It was shown that the CdTe sensor offer an overall better detector performance than the Si sensor for high-resolution imaging applications. Systems with higher DQE can produce images with better contrast and lower noise, making them ideal for dose-sensitive applications like medical imaging.

Speaker: Pinelopi Christodoulou

Abstract for IWORID.docx

44 Study of temperature influence on Timepix2 energy measurements

Timepix2 [1] is a hybrid pixel detector developed by the Medipix2 collaboration as the successor to Timepix [2]. Its introduction brought significant advancements, including the simultaneous measurement of Time-over-Threshold (ToT) and Time-of-Arrival (ToA), as well as new capabilities such as adaptive gain mode and pixel disabling to reduce power consumption. These features, combined with the detector’s compact size and occupancy trigger, make Timepix2 well-suited for space dosimetry applications. In such environments, high-energy heavy ions—such as Galactic Cosmic Rays—can deposit substantial radiation doses in both biological tissue and electronics, potentially leading to functional upsets. The enhanced pixel-level energy measurement capabilities of Timepix2 also enable a more accurate dE/dX spectroscopy in space. However, temperature variations can impact the absolute energy calibration and degrade the energy resolution of the Timepix2 detector.

In this contribution, we present a study of the temperature dependence of a Timepix2 (v1) detector (256 × 256 pixels, 55 μm pixel pitch) coupled to a 500 μm thick silicon sensor. Measurements were performed using X-rays (up to 60 keV) and alpha particles (5.5 MeV) in both air and vacuum across a range of stabilized temperatures from 10°C to 80°C. The separation of the readout electronics from the readout chip minimizes the influence of temperature-dependent variations in the clock frequency generator, thereby allowing to investigate the stability of the Timepix2 itself.

In normal gain mode, the detector demonstrated excellent stability in energy measurements using the ToT mode, achieving absolute energy determination within ±0.2 keV for temperatures from 10 to 70°C. At the same time, the threshold level increased by approximately 2 keV as the temperature rose from 30°C to 80°C. Measurements of the DAC voltages revealed a significant temperature dependence of the Ikrum DAC, which compensates for the threshold shift and enables accurate ToT measurements. In adaptive gain mode, a systematic shift in the absolute ToT measurement accuracy of approximately 0.6% per 10°C temperature increase was observed. A mitigation technique for this behavior was identified and will be presented.

References:
[1] W.S. Wong et al., 2020 Radiat. Meas. 131 106230.
[2] X. Llopart et al., NIM A 581 (2007) 485–494.

Acknowledgements:
B.B. and P.S. acknowledge funding from the Czech Science Foundation (GACR) under Grant No. GM23-04869M.

Speaker: Dr Petr Smolyanskiy (Czech Technical University in Prague (CZ))

iworid2025_timepix2_figures.pdf

45 ATLAS Inner Tracker Upgrade Strip Detector

The inner detector of the present ATLAS experiment has been designed and developed to function in the environment of the present Large Hadron Collider (LHC). For the next LHC upgrade to High Luminosity, the particle densities and radiation levels will exceed the current levels by a factor of ten. The instantaneous luminosity is expected to reach unprecedented values, resulting in up to 200 proton-proton interactions in a typical bunch crossing, corresponding to an instantaneous luminosity of 7 × 1034 s−1 cm−2. For these reasons, the new detectors must be faster and more highly segmented. The sensors need to be far more resistant to radiation and have a much greater power delivery to the front-end (FE) systems. At the same time, they cannot introduce excess material that could undermine the tracking performance. For this upgrade, the ATLAS detector will replace its existing inner detector with a full silicon and larger Inner Tracker (ITk).

The new ITk detector consists of several layers of silicon particle detectors: the innermost parts are pixel detectors, and a strip detector surrounds them. This poster focuses on the strip region. The ITk-Strip detector contains four layers in the barrel and six in each of the two endcaps, covering pseudorapidity (𝜂) range of |𝜂| < 2.7. The silicon sensors along with application specific integrated circuits (ASICs) and the high and low voltage power controls for the sensors are integrated in a module. These modules are placed on staves in the barrel and petals in the end-caps, providing mechanical support for the modules and host the common electrical, optical and cooling services. The FE of the ITk-Strip detector, the ABCStar chip, is an ASIC with 256 channels that read outs the hit information collected on each silicon strip. The production of modules and the structures that support them is now well underway, with the testing and integration setups for final assembly being finalised. This poster gives a general overview of the future ITk strip detector, presenting its structures, final designs and detecting technologies. Current status, performance results and future plans are discussed.

Speaker: Marta Baselga (Technische Universitaet Dortmund (DE))

46 Optimization of Timepix2 Power Consumption and Spectroscopic Performance for Space Applications

Low-mass, low-power radiation detectors are needed to monitor and predict space weather conditions for future crewed and autonomous space missions. The Compact Electron Proton Spectrometer (CEPS) combines Timepix2 ASIC technology with CdTe chips to form a small, portable, hybrid-pixel detector package capable of differentiating particle types and energies over a wide dynamic range in a mixed-radiation environment. In this work, we investigate the performance of a Timepix2 for different operating voltages, internal DAC settings, and clock frequencies. The impact on analog and digital power consumption is characterized for different settings while utilizing a 500 µm thick Si sensor. The results of these studies will inform parameter tuning and device settings for the CEPS CdTe hybrid-pixel detector.

Speaker: Jace Beavers (Los Alamos National Laboratory)

IWORID_2025_Abstract.pdf

47 Enhanced time resolution with a room-temperature energy dispersive X-ray PIN photodiode detector for improved EDX-EELS coincidence measurements in an electron microscope

Although energy dispersive X-ray spectroscopy (EDX) and energy electron loss spectroscopy (EELS) can be acquired simultaneously with a transmission electron microscope (TEM), it is not a common practise. Most users do one at the time despite that the two data streams complement each other very well allowing to have both the high selectivity of EDX with the high energy resolution of EELS. By time correlating simultaneously acquired X-ray events to electron events one can distinguish actual scattering-process correlated electron-X-ray events from unrelated background events [1]. This is extremely useful to improve sensitivity of EELS to trace elements in a matrix (e.g. nitrogen vacancies in diamond) as the subtle edges of the trace elements are otherwise buried in the background noise.

Currently coincidence measurements in a TEM are however limited to low signal to noise ratios by the limited time resolution of the commercial silicon drift detectors (SDDs) used to detect the X-rays [2]. Those are column-mounted and evolved to large sizes to maximise collection efficiencies at the cost of time resolution due to long unsystematic drift times of the signal charge carriers created upon X-ray detection [3]. In order to improve this we are building a proof-of-concept detector for this application. Our approach consists of having a small fully-depleted Si-PIN photodiode detector mounted on the sample holder itself. Its small size ensures neglectable drift times, low capacitance and therefore high acquisition rates and high temporal resolution. Lastly having the sample close to the photodiode preserves collection efficiency.

So far several prototypes have been made and tested in a scanning electron microscope (SEM). Over the different iterations the signal amplifying electronics, noise levels and form factor have been improved. The latest version (see picture) has a low-noise charge-sensitive amplifier circuit with a reverse biased, low capacitance Si-PIN photodiode that is commercially available and inexpensive to replace. The front end has already physical dimensions that would later fit a TEM holder. A theoretical noise analysis has been made and matches nicely to corresponding experimental measurements. Due to relatively high thermal energy of the photodiode, a dc leakage current is formed that substantially increases the dead time of the detector due to an increased reset rate of the charge-sensitive preamplifier. In order to solve this while preventing tedious cooling (cryogenic or peltier cooling) a precisely controlled compensating current is used that proved to work well without elevating noise levels. When irradiating with Cu X-rays the measured pulses exhibit sub-50ns rise times suggesting already a tenfold improvement in time resolution. Initial EDX spectra show an energy resolution of around 1,6keV at 8,05keV (Cu K-α) which we are now trying to improve further to be useful for EDX.

In conclusion, we present the development of an in-house build room-temperature PIN photodiode X-ray detector to improve time resolution and allow for advancements in EDX and EELS coincidence experiments in electron microscopes that so far have been hampered by the slow drift mechanism in SDD setups.

This work received funding from the Horizon 2020 research and innovation programme (European Union), under grant agreement No 101017720 (FET-Proactive EBEAM).

[1] P. Kruit et al. ; Ultramicroscopy, 13 (1984)
[2] G. F. Knoll, Radiation Detection and Measurement, 2010
[3] D. Jannis et al. ; Appl. Sci. 11, 9058 (2021)

Speaker: Luca Serafini (EMAT)

final figure 2.png

48 PIXCORE, a RISC-V microprocessor with an HPD management instruction set

Hybrid Pixel Detectors (HPD) are commonly used for X-ray imaging in both industry and medicine [1-2]. To this day, many approaches have been developed for managing such devices, such as the use of personal computers or FPGAs. Currently, one of the most interesting ones is the integration of the readout electronics for an HPD with the RISC-V microprocessor on the same silicon substrates.

In this article, we present PIXCORE, which is the application-specific integrated circuit block built of a RISC-V microprocessor with an HPD-managing extension, dedicated pixel matrix controller, memories, and some commonly used peripherals such as UART and GPIO. The designed device is the successor to HPSD [3] and is developed for manufacturing in a 16 nm CMOS process with an area of 410 x 210 µm.

Integration of a pixel matrix (PM) with a RISC-V microprocessor can significantly increase detector performance and improve its functionality. It allows the device to work without external assistive devices and execute many algorithms, such as discriminators offset calibration on the chip [4]. The predecessor of the presented solution (HPSD) implemented CPU-PM communication through the dedicated peripheral named pixel matrix controller (PMC) connected to the microprocessor data bus. It enabled fast inter-device communication but required an additional programmable unit named pixel matrix controller coprocessor (PMCC) executing programs written in a custom machine code. This solution required the implementation of synchronization mechanisms between the CPU and PMCC based on the PMCC status monitoring, which affected the overall performance of the device.

PIXCORE eliminates these restrictions through the implementation of the dedicated coprocessor tightly coupled to the RISC-V microprocessor. The CPU-coprocessor interaction is performed through the set of dedicated instructions allowing to manage the PM, such as pixels config setting or acquisition channels enabling. Additionally, usage of the more advanced semiconductor process enables the potential modification of the PM architecture and the replacement of long shift registers connecting neighboring pixels with independently addressed ones.

[1] M. Garcia-Sciveres and N. Wermes, A review of advances in pixel detectors for experiments with high rate and radiation, Reports Prog. Phys., vol. 81, no. 6, p. 066101, Jun. 2018.

[2] R. Ballabriga et al., Review of hybrid pixel detector readout ASICs for spectroscopic X-ray imaging, J. Instrum., vol. 11, no. 1, p. P01007, Jan. 2016.

[3] P. Skrzypiec and R. Szczygieł, Readout chip with RISC-V microprocessor for hybrid pixel detectors, Journal of Instrumentation, vol. 18, no. 1, C01030, Jan. 2023.

[4] P. Skrzypiec and R. Szczygieł, Development of On-Chip Calibration for Hybrid Pixel Detectors, 2021 24th International Symposium on Design and Diagnostics of Electronic Circuits & Systems (DDECS), April 2021.

Speaker: Pawel Skrzypiec

49 Performance of triple-GEM detectors for the ME0 system of the CMS Phase-2 Upgrade

The High-Luminosity LHC will deliver proton-proton collisions at 5-7.5 times the nominal LHC luminosity, with an expected number of 140-200 pp-interactions per bunch crossing. To maintain the performance of muon triggering and reconstruction under high-rate background, the forward part of the Muon spectrometer of the CMS experiment will be upgraded with Gas Electron Multiplier (GEM) detectors. The ME0 station will consist of stacks of six triple-GEM detectors, designed to extend the muon system pseudo-rapidity coverage up to $|\eta| < 2.8$. The operating environment for ME0 will be characterized by extremely high rates, estimated from simulation studies to reach approximately 150 kHz/cm^2. To ensure the ME0 system performs effectively in this challenging environment, a detailed study of its rate capability and timing performance is critical. This talk provides an overview of the ME0 project and its current status. In particular, we present the integration of a final-design prototype for a six-layer ME0 stack, along with performance measurements for muon segment reconstruction efficiency and timing. We report on measurements conducted using cosmic rays as well as rate capability tests under high-rate gamma background conditions at the CERN Gamma Irradiation Facility (GIF++). Our results confirm that the ME0 design meets the Phase-2 CMS muon system upgrade requirements.

Speaker: Felice Nenna (Universita e INFN, Bari (IT))

50 Muon shower tagging in the barrel muon system of the CMS experiment

For the HL-LHC era, the Phase-2 CMS upgrade will involve a complete replacement of the trigger and data acquisition system. The readout electronics will be enhanced to support a maximum Level-1 (L1) accept rate of 750 kHz with a latency of 12.5 µs. The muon trigger operates as a multi-layer system, designed to reconstruct and measure muon momenta by correlating data from muon chambers within specialized muon track finders. This process relies on advanced pattern recognition algorithms executed on FPGA processors. Regarding the barrel muon system, the stub building process occurs in two stages, the first one builds stubs using local information from the different muon stations while the second stage concentrates, refines and correlates the information of multiple chambers before sending the information to the track finders.
This work focuses on a muon shower tagging algorithm that will efficiently detect and reconstruct muon showers and that could be potentially used in the barrel muon system of the CMS experiment. This algorithm clusters hits to detect and identify the shower and matches those clusters to muon stubs in adjacent stations, this will be of particular importance to recover the efficiency loss that arises when a high momentum muon radiates when crossing the detector.

Speaker: Javier Prado Pico (Universidad de Oviedo (ES))

Muon shower tagging in the barrel muon system of the CMS experiment.pdf

51 Characterization of an IGZO flat-panel detector for image-guided CBCT radiotherapy

Introduction
Indium Gallium Zinc Oxide (IGZO) thin-film transistor (TFT) flat panel detectors (FPDs) have the potential to overcome limitation of a-Si:H TFT detectors by avoiding the cost increase of CMOS technology [1-3]. Main advantages of IGZO-TFT FPDs when compared to a-Si:H TFT FPDs reside in the higher electrons (≥ 10cm2∕Vs vs. ≤ 1cm2∕Vs) and holes (~0.1 cm2∕Vs vs. ~0.0005 cm2∕Vs) mobility, higher pixel infill factor, smaller pixel size and improved noise and spatial resolutions [2]. These characteristics determine improvements in image quality, especially in those applications requiring low exposure dose, high spatial resolution and high frame rate. On the other hand, the technology for manufacturing IGZO-TFT FPDs is quite mature and allows to reduce the detector cost up to 4 times lower than CMOS FPDs one.
The use of IGZO-TFT FPDs is spreading in x-ray medical applications, but there is still lack of literature related to characterization at exposure technique factors typical in cone-beam computed tomography (CBCT) scanners. The aim of this work is to characterize the AXIOS-3030 IGZO-TFT FPD produced by Teledyne Dalsa (Teledyne Technology Inc, CA – USA) for spectra and beam intensity of common use in CBCT for image-guided radiotherapy treatments.

Material and methods
The characterized AXIOS-3030 IGZO-TFT FPD consists of an active area of 299 mm × 299 mm with native pixel pitch of 146 µm, that can operate either in 1×1 or 2×2 binning mode with maximum frame rate in continuous mode of 44 fps and 88 fps, respectively. It is coupled with a CsI scintillator layer and can operate in two gain modes: a low gain mode with a saturation dose of 55 µGy and a high gain one with a saturation dose of 3 µGy (RQA5 beam quality).
The detector was characterized for spectra used in the CBCT mounted on the TrueBeam Radiotherapy system (Varian Medical System Inc) at three different tube voltages: 80 kV, 100 kV and 120 kV. The Ti flat-filter was used (no-bow tie) with resulting beam half value layers (HVL) of 3.034 mmAl, 3.804 mmAl and 4.562 mmAl measured at the central axis of the emitted cone beam. The detector was placed with the upper surface at 93 cm from the focal spot and 15 cm spacers were adopted for reducing the impact of the backscatter from the patient support. It was operated in low gain mode both for 1×1 and 2×2 pixel binning and an acquisition period of 50 ms was set. Characterizations included the evaluation of the detector response curve (i.e. the pixel value as function of the incident air kerma at the detector surface), the noise, evaluated as the pixel standard deviation by varying of the expected pixel value, the modulation transfer function (MTF) and the detector lag. For the detector-response curve evaluation, the incident air kerma at the detector surface was measured with a solid-state multiparameter back-shielded sensor (AGMS-D+) connected to an Accu-gold+ digitizer module (Radcal Corp). Average pixel size and standard deviation were evaluated over a region of interest (ROI) of 156 × 156 pixels for binning 1×1, and 88 × 88 pixel for binning 2 × 2. The same ROIs have been used for the evaluation of the detector lag, investigated using the behavior of the average pixel value for continuous detector irradiation. The presampled detector MTF was measured by using a 25 µm slit test object, by sampling profiles both in vertical and horizontal directions.

Results
Figure 1 shows the detector response curve for 1 × 1 (fig. 1a) and 2 × 2 (fig. 1b) pixel binning. In both cases and for the used spectra, the detector saturated at about 45 µGy. Red lines represent linear fits of the curves, obtained with the exclusion of measurements beyond the saturation points. The R2 fitting coefficients are > 0.9995 in all cases, demonstrating a linear behavior of the detector. The pixel standard deviation as function of the incident air kerma and for 1 × 1 pixel binning is reported in fig. 2.
The study, conducted at 10 mA, showed that the pixel value reaches a plateau after a few seconds of continuous exposition, with an increase lower than 1% (fig. 3).
The MTF curves reached 10% value (MTF10%) for spatial frequency of 3.1 mm-1 for 1 × 1 pixel binning (fig. 4a) and of 2.3 mm-1 for 2 × 2 pixel binning (fig. 4b). No impact of the spectra on the detector spatial resolution can be outlined by the MTF analysis, nor on the direction of the evaluation.

Conclusions
We characterized an IGZO TFT flat panel detector for spectra and operation mode typically adopted in CBCT for image guided radiotherapy. The detector showed a linear response curve, with a saturation level at about 45 µGy of incident air kerma. The detector presented a signal lag that increases the pixel value, which growths up to a plateau of no more than 1% after 3 s of continuous exposition. The spatial resolution of the detector, evaluated as the MTF10%, resulted 3.1 mm-1 for 1 × 1 pixel binning and of 2.3 mm-1 for 2 × 2 pixel binning.

References
[1] Zhao C and Kanickiv J 2014 Med Phys 41.9: 091902. DOI: 10.1118/1.4892382
[2] Sheth NM et al 2022 Medi Phys 49(5):3053-3066. DOI: 10.1002/mp.15605
[3] Oh S et al 2023 JINST 18(10), C10016. DOI: 10.1088/1748-0221/18/10/C10016

Speaker: Dr Francesca Saveria Maddaloni (Università degli studi di Milano, Milano (Italy))

Figures.pdf

52 Improving X-ray Detection Sensitivity Using Hybrid Active Layers of PBDB-T:ITIC and CdSe Core 2D Nanoplatelets

Jaewon Son1, Chanyeol Lee1, Yeongbin Song1, Junmo Yang1, Jungwon Kang1, 2, *
1. Department of Foundry Engineering, Dankook University, Yongin-Si, 16890, Gyeonggi-Do, Republic of Korea
2. Department of Convergence Semiconductor Engineering, Dankook University, Yongin-Si, 16890, Gyeonggi-Do, Republic of Korea
* Corresponding author: jkang@dankook.ac.kr

In recent semiconductor scaling, encountering its physical limits, 2D materials are gaining attention. Among them, nanoplatelets represent quantum confinement effects in the z-axis direction, allowing bandgap tuning and achieving high efficiency, making them a highly researched 2D material. We used hybrid active layer composed of PBDB-T, ITIC organic materials and cadmium selenide nanoplatelets (CdSe NPLs) inorganic materials. Figure 1 show Emission and absorbance properties and TEM of CdSe NPLs. Figure 2 shows the energy levels of the proposed X-ray detector and the charge collection process. To conduct experiments on the mixing ratio of organic materials, PBDB-T:ITIC was prepared at different ratios of 1:1/1:2/1:3/2:1. Figure 3a shows J-V curve of the proposed X-ray detector, and Figure 3b shows radiation parameter of the proposed X-ray detector (CCD — DCD, sensitivity). A low series resistance (R_s) and high current density (Jsc) were achieved with a 1:1 ratio, enabling optimization, and a sensitivity of 1.37 mA/Gycm² was achieved. Subsequently, CdSe NPLs were blended into the active layer along with the optimized organic material ratio to enhance performance. The CdSe NPLs were prepared in amounts of 0.5 mg, 1 mg, 1.5 mg, and 2 mg. Figure 4 shows Radiation parameters of PBDB-T:ITIC with different amount of CdSe NPLs. Using 1.5 mg of NPLs, PCE of 6.75%, Jsc of 18.61 mA/cm², and R_s of 494.87 Ω were achieved. The radiation parameters represent a trend similar to that of Jsc, with a sensitivity of 1.72 mA/Gycm². It was 25.54% higher than the sensitivity of the PBDB-T:ITIC with pristine. By enhancing electrical carrier generation and transport characteristics through NPLs and adding physical and chemical stability, the detector demonstrated improved sensitivity and electron mobility compared to conventional detectors.

Figure 1. (a) Emission and absorbance properties of 5ML CdSe Nanoplatelets, (b) the TEM image of 5ML CdSe Nanoplatelets

Figure 2. The energy band diagram of the indirect X-ray detector

Figure 3. (a) J-V curve of PBDB-T:ITIC detector with different ratio, (b) radiation parameters of PBDB-T:ITIC detector with different ratio

Table1. Photovolatic parameters with different CdSe NPLs Concentration

Figure 4. Radiation parameters of PBDB-T:ITIC detector with different amount of CdSe NPLs

Speaker: Mr Yeongbin Song (Department of Foundry Engineering, Dankook University)

Improving X-ray Detection Sensitivity Using Hybrid Active Layers of PBDB-T, ITIC and CdSe Core 2D Nanoplatelets.pdf

53 Numerical modelling of space-charge accumulation in gaseous detectors

Accumulation of space-charge in gaseous ionization detectors is a well-known phenomenon. Various signatures of its effects are observed experimentally in all sorts of gaseous detectors, starting from wire chambers, RPCs to MPGDs [1,2,3,4,5]. It is also known to have important consequences influencing avalanche to streamer transition [6], loss of efficiency and response uniformity [7] in many of these detectors. As a result, study of space-charge accumulation is a topic of great interest since long. However, since the process occurs very gradually with little effect in the initial phases, it is difficult to track the evolution of the space-charge accumulation by experimental means [8]. Numerical modelling using particle models faces insurmountable problems due to the fact that the charge accumulation occurs over a large number of events and incorporation of space charge effects through all these events becomes computationally intensive [9,10]. Fluid modelling such as those pursued in [11,12], on the other hand, does not seem to have explored the possibility of simulating multiple events to any great extent.
Since suitably large computational resources necessary to carry out relevant particle model simulations may be beyond the reach of the average user [13,14], we have worked with fluid models to investigate the problem at hand. In this presentation, we report results on space-charge accumulation and its effects in several gaseous detectors (RPC, THGEM) by carrying out multiple-event simulations based on fluid models.
As a representative result, in Figure 1, we have shown the progress of a sequence of primary electrons towards the readout anode of a THGEM detector using Ar-CO2 gas mixture in volumetric ratio of 90:10. The primaries have been generated assuming the application of a 55Fe radioactive isotope. Moreover, for this computation, the geometry of the detector has been considered axisymmetric.
References:
[1] D.D. Ryutov, S. Hau-Riege, R.M. Bionta, Space-charge effects in a gas detector, SLAC-TN-10-043, September 28, 2007
[2] Christian Lippmann, Werner Riegler, Space charge effects in Resistive Plate Chambers, Nucl. Instr. And Meth. in Phys. Res. A, Volume 517, Pages 54-76, 21 January 2004
[3] Maximilien Alexandre Chefdeville, Development of Micromegas-like gaseous detectors using a pixel readout chip as collecting anode, Ph. D. thesis, University of Amsterdam and University of Paris Sud, 2009.
[4] Purba Bhattacharya, Experimental and Numerical Investigation on Micro-Pattern Gas Detectors, Ph. D. thesis, University of Calcutta, 2014.
[5] Antonio Bianchi, R&D studies on ageing and on environment-friendly gas mixtures for the Resistive Plate Chambers of the ALICE muon system, Ph. D. thesis, Università degli Studi di Torino, 2020.
[6] J.T.Kennedy, Study of the avalanche to streamer transition in insulating gase, Phd Thesis, Technische Universiteit Eindhoven, 1995.
[7] L Shekhtman, Micro-pattern gaseous detectors, Nucl. Instr. And Meth. in Phys. Res. A, Volume 494, Pages 128-141, 21 November 2002.
[8] P. Abratenko et al, Measurement of space charge effects in the MicroBooNE LArTPC using cosmic muons, JINST, 15, P12037, 2020.
[9] Promita Roy, Prasant Kumar Rout, Jaydeep Datta, Purba Bhattacharya, Supratik Mukhopadhyay, Nayana Majumdar, Sandip Sarkar, Study of space charge phenomena in GEM-based detectors, Nucl. Instr. And Meth. in Phys. Res. A, Volume 1047, 167838, February 2023.
[10] Tanay Dey, Purba Bhattacharya, Supratik Mukhopadhyay, Nayana Majumdar, Abhishek Seal, Subhasis Chattopadhyay, Parallelization of Garfield++ and neBEM to simulate space-charge effects in RPCs, Computer Physics Communications, Volume 294, 108944, January 2024
[11] P.K. Rout, R. Kanishka, J. Datta, P. Roy, P. Bhattacharya, S. Mukhopadhyay, N. Majumdar and S. Sarkar, Numerical estimation of discharge probability in GEM-based detectors, JINST, 16, P09001, 2021.
[12] Purba Bhattacharya, Rishabh Gupta, Shounok Guha, Prasant Kumar Rout, Jaydeep Datta, Nayana Majumdar and Supratik Mukhopadhyay, Study of charge dynamics in THGEM-based detectors — a numerical approach, JINST, 20, C04019, 2025.
[13] O. Bouhali, A. Sheharyar, and T. Mohamed, Accelerating avalanche simulation in gas based charged particle detectors, Nucl. Instr. and Meth. in Phys. Res. A, 901, 92-98, 2018.
[14] Shubhabrata Dutta, Purba Bhattacharya, Tanay Dey, Nayana Majumdar, Supratik Mukhopadhyay, Numerical simulation of space charge effects in MPGDs, presented in MPGD 2024 and under review in JINST.

Speaker: Abhijit Pal (Department of Physics, School of Basic and Applied Sciences, Adamas University, Barasat, WB, India)

Picture-IWORID2025-PurbaBhattacharya.pdf

54 Studies of the scintillation yield emitted from GEM avalanches in He-40%CF4 admixtures with few percent of ethane or propane

An optical Time-Projection Chamber (TPC) using a He-40%CF4 gas mixture has been proposed for directional Dark Matter (DM) searches. The motion of the Earth around the Sun results in an anisotropic angular distribution of the WIMP relative to the gas target and, thus, relative to the nuclear recoils induced by WIMP collisions with nuclei which, together with the Earth rotation, enables an unambiguous DM signal identification. The He light nuclei allow for long track lengths, resulting in improved determination of their direction and enables high sensitivity to the WIMP masses in the GeV and sub-GeV range.
In optical TPCs the primary ionization produced by the radiation interaction, e.g. nuclear recoils due to WIMP collisions, is amplified promoting in the gas target secondary scintillation produced by electron impact, e.g. promoting electron avalanches in GEMs. CF4 presents a high scintillation yield, both in the UV and in the visible regions, and its scintillation emission is well known. The 2D readout of the GEM scintillation by a pixelized photosensor, together with the time-profile of the arrival of the ionization electrons at the GEM plane, allows for the determination of the 3D ionization track topology.
The addition of lighter nuclei, hydrogen, would further improve the sensitivity for low mass WIMPs and will result in longer track lengths, increasing the directional sensitivity and particle identification, through dE/dx, thus improving background discrimination. The impact of adding few percent of isobutane or methane to He-40%CF4 on the mixture secondary scintillation, produced in electron avalanches, have been investigated.
For isobutane, the average number of photons per avalanche electron is reduced by 90% as the concentration increases from 0 to 5%, due to quenching of the excited state species from He and CF4 excitations. Nevertheless, the average total number of photons produced in the avalanches only decreases by 35%, due to the simultaneous presence of Penning transfer from He excited atoms to isobutane molecules and to the reduction of the gas w-value, which increases the number of electrons in the avalanches and, thus, the total number of photons. This latter effect is present because the energy of the He excited states is higher than that of CF4 ionization. Methane addition does not present a strong quenching, but it also does not present Penning transfer. In overall, the addition of methane to the He-40%CF4 mixture results in improved electrical stability, allowing for higher GEM bias voltages, resulting in an increase in the maximum scintillation output.
In this work, we extend the studies to the addition of ethane and propane to the He-40%CF4 mixture, in an attempt that one of these molecules presents the advantages of both methane and isobutane: a weak quenching effect, as in methane mixtures, and the presence of Penning transfer, as in isobutane mixtures. Experimental results for the total scintillation yield produced in the electron avalanches and the yield per avalanche electron will be presented and discussed.

Speaker: Dr Cristina M. Bernardes Monteiro (LIBPhys-UC, LA-REAL, Department of Physics, University of Coimbra, PORTUGAL)

55 Feasibility Study on Ultra-high spatial-resolution X-ray Imaging using STED Technique

Observation of the dynamics for cell and its inside is required to reveal the mechanism of life activities; For example, how virus invade host cell, how liquid–liquid phase separation in the cell became to disorder. To observe such dynamics, high spatial-resolution of less than 50 nm is required, and X-ray is available for the in vivo imaging or Non-destructive Testing. To realize such high resolution against diffraction limit, we have focused on the Stimulated Emission Depletion Microscopy (STED) technique. In the visible region, STED camera have already developed, while not yet in the X-ray region. Thus, we have developed soft-X-rays STED devices consisting of a scintillation material using soft X-rays.
The soft X-rays imaging with STED technique was demonstrated as the first feasibility study in this time. We used the synchrotron radiation light (beamline BL11D, Photon Factory, KEK) with an energy of 800 eV as the soft X-ray source, and also laser photons with energies of 1.97 eV (630 nm) to 2.58 eV (480 nm) as the STED light. Ce-doped Lu₂SiO₅ (Ce:LSO) scintillatior was irradiated with such photons (X-ray and STED light), and we succeeded in observation of the STED phenomenon and its imaging. Moreover, we have developed suitable scintillation material for this STED applications.
In this presentation, we show the mechanism the STED technique with soft X-ray, the above results and the future plan.

Speaker: Shunsuke Kurosawa (Tohoku Univ. & Osaka Univ.)

56 Silicon photomultipliers: new structures for improved radiation hardness

Silicon Photomultipliers (SiPMs) are single-photon sensitive detectors that continue to attract increasing interest in several industrial and scientific applications that require fast detection speed, high sensitivity, compactness, insensitivity to magnetic fields and low bias voltages. In particular, the SiPMs are used in high-energy physics (HEP) experiments, and for the readout of scintillators in gamma-ray detectors for space experiments. In such applications they receive a significant dose of radiation (e.g. protons, electrons, neutrons, …) which degrades their performance.
During the last years, at FBK (Trento, Italy) we have been developing many different technologies for SiPMs and SPADs, optimized for different applications. We also studied extensively the effects of ionizing energy loss (IEL) effects and non-ionizing energy loss (NIEL) effects (i.e. bulk displacement damage) on many different SPAD and SiPM technologies. These highlighted the important role of electric-field enhancement on the primary noise generation, especially from the defects created by bulk damage during irradiation. As well we seen an important effect of IEL increasing charges in the dielectrics, which in turn create spurious electric field peaks in the devices, thus increasing the primary and the correlated noise.
Based on such results, we started specific technological improvements aimed at improving the radiation hardness of novel SiPMs technologies. We are currently working on several directions. Among the most promising: i) we are exploiting the reduction of the high-field active area, with a novel SiPM structure based on charge-focusing mechanisms, and ii) we are working on active control and draining of radiation-induced charge in the dielectrics. We performed TCAD simulations, and we obtained preliminary results from irradiations with protons and X-rays showing potentiality of such novel structure in reducing the radiation degradation effects on SiPMs structures.

Speaker: Fabio Acerbi

57 Development of optical-guiding Tl:Cs3Cu2I5 crystal scintillator plates for high-resolution and high-sensitivity radiation imaging

Scintillator-based radiation detectors are widely used to detect alpha, beta, gamma, X-rays, and neutrons for high-energy physics, non-destructive inspection, homeland security, resource exploration, and medical imaging applications. X-ray imaging, in particular, has been utilized in product inspection and developing battery materials, aircraft parts, and more. This has driven a strong demand for detectors with higher resolution and sensitivity. This detector’s performance depends on a scintillator material that absorbs the X-rays and converts them into visible light. Our research group has proposed GdAlO3/Al2O3 eutectic [1] and Optical-guiding Crystal Scintillator (OCS) [2-4] as structured scintillators that simultaneously achieve high resolution and sensitivity. The OCS consists of a low refractive index glass cladding and a high refractive index scintillator core, and the scintillator light is guided like in a bundled optical fiber. Therefore, the selection of the core material and the precise control of the core diameter are crucial for device performance.
In this research, OCS plates composed of Tl-doped Cs3Cu2I5 scintillator core and glass cladding were fabricated. Tl:Cs3Cu2I5 crystals were grown from the melt in the glass cladding under an inert gas atmosphere. The 5 x 5 mm² size OCS plates were fabricated with a Tl:Cs3Cu2I5 core diameter ranging from several to 10 μm. With this structure, the OCS can work as both an optical fiber and a scintillator. The X-ray excited emission peaking within the range of 400-500 nm was observed consistent with previously reported results for Tl:Cs3Cu2I5 single crystals [5]. Imaging tests were conducted using microfocus X-ray tubes and commercially available X-ray test charts. The resolution was evaluated by calculating the contrast transfer function (CTF). CTF of the Tl:Cs3Cu2I5 OCS was higher than that of commercially available CsI whiskers. In our presentation, the detailed fabrication process, results of EBSD, radiation response, and imaging test will be shown.

[1] K. Kamada, A. Yoshikawa, et al., Jpn. J. Appl. Phys. 60 (2021) SBBK04
[2] R. Yajima, A. Yoshikawa, et al., Appl. Phys. Express 16 (2023) 025505
[3] R. Yajima, A. Yoshikawa, et al., Ceramics International 49 (2023) 41259-41263
[4] R. Yajima, A. Yoshikawa, et al., Jpn. J. Appl. Phys. 62 (2023) SC1064
[5] L. Stand, et al., Nuclear Inst. And Methods in Physics Research, A 991 (2021) 164963

Speaker: Mr Yuhei Nakata (Graduation School of Engineering, Tohoku University)

58 In-situ Radiation Damage Study of Silicon Carbide Detectors subjected to Clinical Proton Beams

4H-silicon carbide (4H-SiC) is an emerging wide bandgap detector material in high-energy physics due to its superior temperature stability and low dark current compared to silicon detectors. The wide bandgap of 4H-SiC makes it suitable for high-temperature applications and allows operation at room temperature even after irradiation.
These features, combined with SiC being insensitive to visible light, make it an ideal candidate for applications in medical physics, such as beam monitoring or dosimetry.

Critical to the performance of SiC detectors and electronics is their response to radiation damage induced defects. There exists a significant amount of literature showing the compensation of lightly doped intrinsic layers and the loss of forward conduction after neutron irradiation to fluences of around $5\times10^{14} \text{n}_{\text{eq}}/\text{cm}^2$. However, only few data exist on these processes in detail, as most studies aim at higher irradiation fluences, where these processes have already taken course. We therefore aim at a radiation study involving lower irradiation fluences and an in-situ measurement method, allowing for the characterization of the same sample at different fluences throughout the irradiation.

We present an irradiation study of a $3\times 3 \:\text{mm}^2$ SiC PiN detector performed at an ion therapy center. Proton beams with an energy of $252\:\text{MeV}$ were used with clinical beam intensities, for a total irradiation fluence in the range of $10^{14}\:\text{p}^{+}/\text{cm}^2$.
Current-voltage and capacitance-voltage characteristics were measured several times during the irradiation, along with the charge collection efficiency (CCE) before and after the irradiation. These results provide a unique perspective on the gradual manifestation of radiation damage induced effects in SiC detectors. Compared to more traditional irradiation campaigns, where multiple samples are irradiated to different fluences, these measurements allowed for a characterization of different radiation damage levels with the same sample.
Additionally, this study gives an insight to the expected lifetime of SiC detector in medical applications.

Speaker: Daniel Radmanovac (Austrian Academy of Sciences (AT))

poster_radmanovac_iWoRiD2025.pdf

59 Radiation Damage Studies of 4H-SiC LGADs

Low-Gain Avalanche Detectors (LGADs) based on 4H-SiC are emerging as a promising technology for high-radiation environments due to their intrinsic radiation hardness, wide bandgap, and high breakdown field. In this work, we present results from a systematic study of radiation-induced degradation in 4H-SiC LGADs subjected to 24 GeV/c proton irradiation at the CERN IRRAD facility, with fluences up to $6×10^{15} n_{eq}​/cm^2$.
The devices were characterized before and after irradiation through I-V, C-V, and charge collection measurements under laser stimulation, focusing on the evolution of gain, leakage current, breakdown voltage, and depletion characteristics. Despite the high fluence, the devices retained measurable gain, and the charge collection remained functional, indicating a high degree of resilience compared to their silicon counterparts.
Our findings highlight the potential of SiC LGADs for future applications in harsh radiation environments such as high-luminosity collider detectors or space-based instrumentation. The study also provides insight into defect-related performance degradation and guides the ongoing optimization of SiC-based avalanche detector designs.

Speaker: Maria Marcisovska (Czech Technical University in Prague (CZ))

svihra_sic-radiation-damage_final.pdf

60 Chromium compensated gallium arsenide sensor evaluation using photon counting readout electronics

Gallium arsenide is extensively studied for about seven decades as an excellent material for semiconductor lasers, LEDs, and microwave electronics. GaAs has noticeable advantages over silicon and Cd(Zn)Te for radiation detectors. Particularly GaAs has higher electron mobility compared to Si and Cd(Zn)Te; higher average atomic number compared to Si; and lower probability and energy of the fluorescence photons compared to the Cd(Zn)Te. These advantages result in a fast charge collection, good absorption efficiency up to 80 keV and a better uniformity compared to Cd(Zn)Te. Applications for the GaAs are foreseen in medical computed tomography (CT), mammography, small animal imaging, electron microscopy, synchrotrons, XFELs and non-destructive testing of composite materials.

In frame of Eurostar GoNDT project [2], Advafab has developed radiation detectors by chromium compensation [3] of commercially available 3” n-type Liquid Encapsulated Czochralski (LEC) GaAs wafers. Wafers were annealed in quartz reactor; processed by polishing and CMP; and were patterned, metallized, and diced.

We have demonstrated a wafer-level processing of GaAs on varied thicknesses ranging from 220 um to 1 mm. Pixelized sensors with designs compatible with different readout ASICs have been fabricated. Individual diced sensors were flip-chip bonded to Timepix2, Timepix3, Medipix3, and Timepix4 ASICs. Assemblies were evaluated to study the uniformity; sensor stability; energy resolution; charge transport properties and high X-ray flux operation.

The presentation summarises the GaAs performance results received from the contributing authors. It presents an analytical evaluation of charge transport properties of different thicknesses of GaAs and their spectral response to Alpha and Gamma radiation. The pixel detector results represent sensor uniformity, spectral resolution, and high-flux operation in different applications.

The high photon flux operation has been evaluated using a medical CT X-ray tube in an open beam. It has been demonstrated that Advafab’s GaAs can tolerate and operate stably in extreme X-ray beam fluxes up to 1,200 Mcnt/s/mm2.

The presentation concludes that it is feasible to manufacture radiation sensors of chromium-compensated GaAs of different thicknesses for the photon counting applications with high uniformity and a good energy resolution that can operate at high X-ray fluxes.

Speaker: Dr Juha Kalliopuska (Advafab Oy)

IWORID2025_abstract_GaAs_evaluation.pdf

61 Characterization and X-ray imaging of metal halide perovskite scintillator films for digital flat-panel detector

Digital flat-panel detectors with indirect method typically uses amorphous silicon TFT (thin film transistor) or silicon CMOS (complementary metal oxide semiconductor) matrix arrays integrated with various scintillators for many medical diagnosis, security and nondestructive examination. Scintillator material is an indispensable component of indirect X-ray detector, which converts high-energy ionizing radiation (X-rays or γ-rays) into visible light. Over the past decades, tremendous efforts have been continued to exploring excellent scintillators for radiation detection and many kinds of scintillators have been commercialized. However, it is still necessary to develop novel scintillator materials with low-cost, high light yields and short decay time to satisfy the high-speed radiation detection technology.
In recent years, metal halide perovskite nanocrystals (NCs) have been reported as a promising scintillator for X-ray detection and imaging. In this work, high efficient scintillating films such as granular type metal halide perovksite materials with different thickness film(50-200um) were designed for high luminescent and spatial resolution in digital X-ray imaging detectors. The high-resolution dynaminc CMOS flat panel detectors as light sensing backplane in this experiment are consisted of silicon photodiode array with 50μm pixel pitch(theoretical resolution limit: 10lp/mm) and 100μm pixel pitch (theoretical resolution limit: 5lp/mm) respectively.
The microstructures and scintillation properties uch as emission spectrum and light intensity by X-ray luminescence(XL) were measured and characterized. Their X-ray imaging of CMOS flat panel imagers in combination with metal halide perovskite scintillation screens were investigated in terms of the relative light response to given X-ray irradiation, modulation transfer function (MTF), noise power spectrum and X-ray imaging with various phantom. We expect that these results will show potential for high speed and spatial resolution in digital X-ray imaging such as medical and industrial fields.

Speaker: 보경 차

iworid 2025_perovskite scintillator.docx

62 Neutron and gamma radiation discrimination performance of novel eutectic scintillators

In recent years, scintillation detectors using inorganic solid scintillators containing 6Li have been increasingly employed owing to their ease of handling and radiation resistivity. In the past decade, inorganic solid scintillators containing Li, such as Ce or Eu:LiCaAlF6 (LiCAF) [1] and Ce:Cs2LiYCl6 (CLYC) [2], have been developed in addition to the traditional Li-glass scintillator for thermal neutron detection. To achieve neutron detectors with excellent performance, it is necessary to develop scintillators with high Li content, low density, high light yield and fast decay time. In compound crystals, the Li content is limited by the chemical composition. On the other hand, the Li content can be increased in the eutectic according to the phase diagram. Up to now, fluorides such LiF/LiGdF4, LiF/BaCl2,　LiF/CaF2/LiBaF3, chlorides such LiCl/Li2SrCl4, LiCl/BaCl2, bromides such LiBr/CeBr3, LiBr/LaBr3 [3], etc. have been reported. Eutectics are composed of neutron-capturing phases containing 6Li and scintillator phases. The 6Li-containing phase converts n-rays into α-rays and 3H, which are absorbed by the scintillator phase and converted into light.
In this study, eutectics with good n/γ-ray discrimination performance were systematically investigated under the material design guideline of combining the γ-ray scintillator phases, which has good α/γ-ray discrimination performance. Tl:CsI/LiBr, Tl:NaI/LiBr, LaBr3/LiBr (pure, Ce and Sr co-doped), and LaCl3/LiCl (pure, Ce doped) were selected as materials meeting the material design guidelines. And for NaI-LiBr, which has not been reported, a state diagram was prepared. In the presentation, details of eutectic growth, structure, and scintillator characterization will be reported. We will also report on the correlation between n/γ-ray discrimination performance and scintillator properties, which is expected from the α/γ-ray discrimination performance of the γ-ray scintillator phases.

[1] Yoshikawa, et al., IEEE Trans. Nucl. Sci. 56 (2009) 3796–3799,
[2] J. Glodo, et al., J. Cryst. Growth, 379 (2013) 73–78,
[3] Y. Takizawa, K. Kamada et al,Nucl. Instr. Method A 1028 (2022), 166384

Speaker: Kei kamada

fig1.png

63 Performance Assessment of PbI₂ and PbO-Based Semiconductor Dosimeters in Ir-192 HDR Brachytherapy: Measurement and Simulation

High-dose-rate (HDR) brachytherapy using Iridium-192 (Ir-192) sources is widely adopted in the treatment of various cancers due to its ability to deliver concentrated radiation doses with high spatial precision. Accurate dose verification is essential in this modality to ensure both treatment efficacy and patient safety. In this study, we investigate the feasibility and performance of polycrystalline semiconductor dosimeters (PSDs) fabricated with lead (Ⅱ) iodide (PbI₂) and lead oxide (PbO) materials for use in HDR brachytherapy dosimetry. Specifically, we evaluated the distance and angular dependence of these PSDs when exposed to an Ir-192 source, and validated the results through comprehensive Monte Carlo (MC) simulations using the GATE v9.1 toolkit.
The PbI₂ and PbO materials were fabricated with dimensions of 0.2 cm x 0.2 cm through a polymer mixture, and gold electrodes were formed to construct the detector. Experimental measurements were performed to assess the PSDs’ responses at source-to-surface distances (SSD) ranging from 1 cm to 8 cm and at incident angles from 0° to 60°. In parallel, MC simulations replicated these conditions to model radiation interactions and validate the experimental results.
For distance dependence, both PSD types showed signal attenuation consistent with the inverse-square law, with power-law exponents of approximately -1.9 for PbI₂ and -1.8 for PbO, in both measurements and simulations. High coefficients of determination (R² > 0.98) confirmed the strong correlation between distance and signal intensity. Additionally, the D50 values, representing the distance at which the normalized signal dropped by 50%, were closely matched between measurement and simulation, with discrepancies less than 0.01 cm for both PSD types. In evaluating angular dependence, both PSDs demonstrated a gradual decline in normalized signal intensity as the irradiation angle increased. The maximum signal reduction at 60° was approximately 25%, indicating significant angular sensitivity. The difference between experimental and simulation data remained within 5% for all angles, with the PbI₂-based PSD exhibiting slightly better agreement than the PbO counterpart. These findings highlight the reproducibility and reliability of the fabricated PSDs and their potential for accurate dosimetry. The use of PbI₂ and PbO as photoconductive materials is particularly promising due to their high atomic numbers and favorable charge transport properties, contributing to efficient photon absorption and stable signal generation. This study is among the first to report on the fabrication of PbI₂ and PbO-based PSDs and their comprehensive characterization under HDR Ir-192 irradiation through both experimental and simulated approaches. Compared to prior works that utilized TlBr or CsPbBr₃ without simulation validation, our dual-method approach enhances confidence in the clinical applicability of these PSDs.
In conclusion, PbI₂ and PbO-based PSDs demonstrated reliable and predictable responses to Ir-192 irradiation in both distance and angular dependence measurements. The consistency with MC simulations supports the robustness of the fabrication and evaluation methodology. However, the observed angular sensitivity suggests that implementing angular correction factors would be necessary for clinical dosimetry applications. Future studies should focus on optimizing the PSD design for real-time monitoring and incorporating correction algorithms to enhance accuracy in complex treatment geometries.

Speaker: Dr MOO JAE HAN (Seoul National University Bundang Hospital)

64 A Plugin-Based Architecture for Onboard Data Processing in Katherine Readout Systems for Timepix Detectors

The Katherine readout system for Timepix3 (and to a smaller extent, Timepix2) is widely used within the scientific Medipix community. Timepix3, in particular, is a popular readout chip offering a resolution of 256×256 pixels with a 55 µm pitch, capable of measuring both energy and timestamps (with 1.56 ns time binning) simultaneously. It has already demonstrated excellent performance and brought significant benefits to numerous projects [2, 3, 4]. For example, it has been employed as a radiation monitor in the ATLAS Experiment at CERN [5, 6], and its efficient operation in various low-power modes has also been shown [7].
Recently, the Katherine readout for the new Timepix4 chip has been finished and introduced to Medipix scientific community. Timepix4 [8] represents another leap forward in the capabilities of Timepix-class detectors. It features a resolution of 512×448 pixels, superior time binning (195 ps), and supports extremely high hit rates—up to 2.5 Ghits/s per chip.
All Katherine devices implement on-the-fly raw data decoding, which minimizes the need for data processing in the control software. However, since their architecture is based on SoC FPGA devices, there remains an opportunity to utilize this computational power in even more effective ways.
For this reason, we present a software plugin architecture designed for Katherine readout devices, enabling onboard data processing directly on the device’s CPU. The goal of this work is to provide users with a C++ framework that supports the development of custom plugins or the use of pre-defined ones. The presented approach makes it possible to implement data-processing routines—previously handled by the acquisition software—directly in the hardware of the readout system. This capability can be used, for example, for data clustering, noisy pixel detection, or real-time processing for imaging applications.
The system has been successfully implemented on the Katherine readout platform for Timepix3 Gen2, based on the Cyclone V SoC, as well as on the new generation Katherine readout system for Timepix4, which utilizes the Arria 10 SoC. To demonstrate the capabilities and performance of the architecture, we present example plugins running on both Timepix3 and Timepix4 detectors. Additionally, we provide simple examples and documentation to guide users in developing and integrating their own custom plugins.
References:
[1] T. Poikela et al., 2014 JINST 9 C05013.
[2] X. Wu et al., Advances in Space Research, 63 (2019), Issue 8, pp 2672-2682.
[3] Bergmann, B., Jelínek, J.: Measurement of the 212Po, 214Po and 212Pb half-life time with Timepix3. Eur. Phys. J. A 58, 106 (2022). https://doi.org/10.1140/epja/s10050-022-00757-z
[4] P. Burian et al., 2018 JINST 13 C01002.
[5] P. Burian et al., 2018 JINST 13 C11024.
[6] B. Bergmann et al., 2020 JINST 15 C01039.
[8] Llopart, Xavier, et al. "Timepix4, a large area pixel detector readout chip which can be tiled on 4 sides providing sub-200 ps timestamp binning." Journal of Instrumentation 17.01 (2022): C01044.

Speaker: Martin Farkas (University of West Bohemia (CZ))

65 Development of the CoRDIA pixel detector ASIC for high-speed X-ray experiments

CoRDIA is a pixel detector being developed for X-ray experiments at future synchrotron light sources such as PETRA-IV. The extreme brilliance of these sources will enable new experiments scanning the structure of complex objects on length scales from macroscopic down to single atoms. To enable these experiments, CoRDIA is being designed to perform continuous image taking at 150.000 frames/s while achieving a large dynamic range and a pixel size of 110um. Its key building blocks consist of a per-pixel adaptive gain amplifier for high dynamic range, Analog-to-Digital Converters distributed throughout the pixel matrix for rapid digitization, and high-speed gigabit transmitters for high speed data transfer to the DAQ system. Thus far, ASIC test structures have been produced in a 65nm CMOS process to test the individual building blocks and small arrays of 16 pixels. These have confirmed the expected pixel performance in terms of noise, linearity and adaptive gain operation. Some cross-talk issues have been identified, and an updated shielded layout was designed to solve them.

Speaker: David Pennicard

DPennicard_CoRDIA_IWORID2025_v2.pdf

66 Design of Distributed Multi-level Real-time Matching Algorithm for In-beam PET Readout System

Heavy ion therapy is an advanced radiation treatment , and In-Beam Positron Emission Tomography (In-Beam PET, ib PET) is a non-invasive method for monitoring heavy ion tumor therapy. It provides rapid and accurate imaging of beam positioning and dose by identifying and sorting coincidence events of positron-electron annihilation in the irradiated area. This work presents a timestamp-based distributed real-time pipeline coincidence algorithm. The algorithm distributes coincidence event tasks across multiple edge modules and a central module, forming a two-level pipeline. The increased data volume from additional detectors is managed by distributing it across edge modules, enabling channel expansion with existing hardware. This algorithm ensures stable operation under high event rates, ensuring that coincidence events are accurately selected and imaging. The algorithm has been validated on the In-beam PET prototype developed independently by the Chinese Academy of Sciences. Joint testing with the detector included background irradiation and 22Na radioactive source tests. The results show an average energy resolution of 14% at 511 keV, a time resolution of 1.63 ns full width at half maximum (FWHM), and real-time event processing capability of up to 8.5 Mcps. Furthermore, in clinical beam tests at the Heavy Ion Medical Machine (HIMM) treatment terminal, the system accurately identified the Bragg peak position within 30 seconds, with a spatial resolution of 2 mm along the beam direction. The positron activity peaks in the vertical (Y) direction less than 0.5 mm error relative to the carbon ion beam position, enabling accurate localization of the carbon ion beam in the Y direction. These results demonstrate that the algorithm provides rapid, accurate, and real-time monitoring of beam distribution and dose, offering reliable dose feedback and ensuring treatment safety in heavy ion beam therapy.

Speaker: Junwei Yan

Design of Distributed Multi-level Real-time Matching Algorithm for Bundle PET Readout System.pdf

67 Testing of a 28 nm CMOS charge sensitive amplifier exposed to 1 Grad TID

This work describes the design and the testing of a charge-sensitive amplifier (CSA) mainly conceived for the readout of hybrid pixel detectors in extreme radiation environments, as in the high-luminosity upgrades of the LHC or in future experiments at the FCC. Developed in a 28 nm CMOS process, the CSA features a feedback network to compensate for detector leakage current and operates at a typical current close to 4 μA, with a nominal supply voltage of 0.9 V. The core amplifier of the CSA is implemented by means of a regulated cascode structure followed by an NMOS-input source follower stage. A metal-oxide-metal (MoM) capacitor, whose nominal value is around 4.5 fF, is integrated into the CSA feedback loop for charge-to-voltage conversion of the signal delivered by the sensor. A narrow channel NMOS transistor, in parallel with the feedback capacitance and operated in deep-subthreshold, is exploited to restore the CSA baseline upon signal arrival.
The CSA has been integrated into a prototype ASIC (in a mini@sic run) with additional circuitry to emulate the detector capacitance and leakage current. In particular, three MoM capacitors (0, 25 fF, and 50 fF) can be connected to the CSA input through different CMOS switches. On the other hand, the presence of an NMOS transistor, with the drain connected to the CSA input and the source tied to ground, can be exploited to emulate the detector leakage current by adjusting the voltage at its gate terminal. A charge injection circuit is also integrated in the prototype chip, which makes it possible to provide a test charge up to around 30000 electrons at the front-end input. The output of the CSA is fed into a two-stage source follower, which drives a PAD wire-bonded to a carrier board. This board is mounted on a mother board that includes biasing circuits for the CSA, as well as an additional buffer stage for the preamplifier output. The signal is then sensed by a digital oscilloscope for off-line analysis.
The prototype chip has been characterized before and after irradiation up to a total ionizing dose (TID) of 1 Grad, with a 10 keV X-ray source (Seifert RP149).
Experimental results show that the CSA can be operated properly in the presence of a detector leakage current up to 10 nA (which is the maximum that can be achieved in the test setup used for the prototype characterization), with a marginal increase in equivalent noise charge (ENC). Before irradiation, the measured ENC is close to 70 electrons RMS for a detector emulating capacitance of 50 fF, with an increase around 12% observed at 1 Grad. The Time-over-Threshold (ToT) performance of the CSA was evaluated by leveraging the digital scope, where the preamplifier signal was compared against a fixed threshold (500 electrons). The maximum integral non-linearity for the ToT characteristics was found to be close to 3.8%. A significant variation of the current discharging the CSA feedback capacitance was observed after irradiation. To restore a ToT behavior similar to the one achieved for the unirradiated device, a fine-tuning of the voltage controlling the feedback NMOS transistor was needed.
The details on the design and on the characterization of the charge sensitive amplifier will be given in the conference paper.

Speaker: Luigi Gaioni (University of Bergamo and INFN (IT))

68 Characterization of the ColorPix-2 ASIC Hybrid Pixel Readout Chip with CZT Sensors

In this contribution we present the first measurements of the characterization of the ColorPix-2 ASIC communicating with the UniCorn readout interface. ColorPix-2 is the ASIC consisting of 32x32 pixel matrix with the pixel pitch of 70 um. It is designed for high-resolution, position and color sensitive X-ray imaging. A 2 mm-thick CZT layer is bump-bonded and used as the sensing material, providing a higher gamma-ray detection efficiency compared to the commonly used silicon. The ASIC acquires data in terms of hit counting across 10 settable energy levels. Due to the device tolerance, several DACs are needed to be tuned prior to measurements.

We describe the equalization procedure, including threshold scanning or pixel offset compensation, energy level calibration, and measurement under the X-rays exposure. The measurements validated the intended functionality of the chip. The charge sharing effect among pixels is demonstrated. Finally, we summarize the implications for the upcoming ColorPix-3 revision.

Speaker: Jan Broulim (Czech Technical University in Prague (CZ))

JB_CAPADS_poster_imaging_CP2_rev2char.pdf

69 ColorPix3 ASIC: Design of a Hybrid Pixel Readout Chip for High-Resolution Spectroscopic Imaging with CZT Sensors

The ColorPix3 ASIC represents an advanced hybrid pixel detector design tailored explicitly for high-resolution, color-sensitive X-ray imaging. Developed using a 65-nm CMOS process, this ASIC integrates a pixel matrix comprising of 32×32 pixels, each sized at 70×70 µm², covering a sensitive area of 0.05 cm². In this technology demonstrator, the digital part of the readout system is being evaluated, which is capable of serving a 256×256 pixel matrix. The future enlarged version of the chip is therefore able to cover a sensitive area of 3.21 cm².

The ColorPix3 ASIC features inter-pixel communication and implements a sophisticated Winner-Leader-Follower (WLF) summation algorithm, adjustable for clusters of either 3×3 or 5×5 pixels. Each pixel in the matrix is equipped with ten independently controlled 12-bit counters with configurable equidistant thresholds, supporting multi-color, custom-color, and monochromatic imaging modes. The ASIC further boasts a high-speed data readout capability of up to 3.2 Gb/s, safety low power mode, integrated current references, and on-chip debugging functionalities. Specifically engineered for bonding to a 2 mm thick Cadmium Zinc Telluride (CZT) sensor, the ASIC design significantly enhances performance in energy-sensitive photon detection applications.

Speaker: Zdenko Janoska (Czech Technical University in Prague (CZ))

ColorPix3_poster_iworid2025_janoska.pdf

70 New photon-counting high energy resolution ASIC for laboratory diffraction

We are glad to present one of the latest developments of the R&D at DECTRIS: the novel ASIC ERMINE, a photon counting chip that is specifically designed for laboratory X-Ray Diffraction (XRD) applications.
ERMINE is a 192 x 256 pixels array with an active area of 14.4 mm x 19.2 mm and a pixel pitch of 75 µm. The ASIC’s two-side buttable design allows for larger sensitive areas with wider angular coverage. The readout electronics allows for both positive and negative signal polarity, making it compatible with standard silicon sensors (hole collection) and most high-z sensors (electron collection).
The signal readout is a typical design in terms of photon counting detectors. It includes an analog signal chain with a charge sensitive amplifier and a shaper, followed by a comparator stage with two 12-bit counters that can be operated independently, allowing for dead-time-free operation. ERMINE is optimized for excellent energy resolution while still providing high count rates at low power consumption. It achieves better than 600eV (FWHM) energy resolution at 8keV while providing >1Mcts/px/s and consuming <1.2W of power.
The chip can be fully operated using simple serial protocols. All needed analog bias current and voltages are generated on chip. Available readout modes include single threshold and windowing between two thresholds, both at a framerate of at least 400 frames per second in continuous readout.
In this contribution, we will describe the design of the ASIC and present the first extensive experimental characterization carried out in our X-ray laboratory, covering spectral performance, temperature stability and count rate capability for different sensor materials.

Speaker: Mr Giuseppe Montemurro (DECTRIS AG)

IWORID 2025.pdf

71 Modular High-Speed Digitizer Platform for Precision Timing and High-Rate Signal Capture

To meet the stringent demands of signal digitization in high-energy physics experiments, a universal high-speed digitizer module has been developed for precise acquisition of fast analog signals from various detector technologies. The system supports sampling rates of up to 20 GS/s in single-channel mode and 10 GS/s in dual-channel mode, offering 9 GHz analog bandwidth and 12-bit vertical resolution. It is optimized for use with fast-response detectors such as silicon sensors and photomultiplier tubes, where accurate time-resolved signal capture is essential. Multi-module synchronization enables scalable architectures for multi-channel acquisition or increased temporal resolution via interleaved mode, where two modules are phase-shifted to achieve an effective sampling rate of up to 40 GS/s. Data interfaces include USB 3.0 and optical link; in the latter case, an FPGA-based PCIe interface card installed in the data acquisition PC handles the optical-to-PCIe protocol conversion. The digitizer is supported by a modular DAQ software suite featuring desktop (window), console, and web-based control applications, and is fully integrable into complex distributed DAQ systems. The architecture supports flexible triggering, acquisition length control (signal-based or time-based), optional on-board preprocessing, and a design optimized for radiation tolerance. The device provides a robust and versatile solution for high-rate signal digitization in front-end electronics for modern detector systems.

Speaker: Tomas Kulhanek (University of West Bohemia (CZ))

72 Comparison of Two CMOS readout chains for a 330x330µm² pixel aiming at spectral CT medical applications

Spectral Computed Tomography (CT) based on Photon-Counting Detectors (PCDs) is an emerging technology [1] that provides 3D images on multiple energy channels (typically between 2 and 8 energy bands). The main challenge for PCDs is to achieve good spectral accuracy while maintaining reliable performance at high-count rate.

The classic architecture of a PCD utilizes a CdTe crystal hybridized to a CMOS readout ASIC. Each pixel readout chain contains an analog front-end that transforms the incoming charge into a voltage pulse whose amplitude is an image of the detected photon energy. This amplitude is digitally converted at the pixel level thanks to several comparators, each comparator having its own threshold and feeding its own counter.

This paper focuses on the comparison between 2 readout chains that can be implemented in a 330x330µm² CMOS pixel.

Two types of analog front-end are considered: one with our previously described Capacitive Transimpedance Amplifier (CTIA) with a “hard-reset” [2] and one with a Resistive Transimpedance Amplifier (RTIA). We will give a performance comparison of the front-end circuit variants, and discuss the impact of the choice of amplifier type on the remaining blocks of the readout chain, such as the leakage current compensation technique (BaseLine Holder or BaseLine Restoration) and the charge sharing correction (Analog Summing or Digital Summing). Moreover, thanks to a test-chip using the TSMC 0.13µm process, some experimental results are given. A good performance of the circuit in terms of speed and low power consumption is obtained. For a steady equivalent flux of 20Mcps, we evaluated the power consumption at 2.8mW/mm² and a deadtime of 26ns (CTIA) and 23ns (RTIA) for an input capacitance in the order of 200fF.
Given these positive results, we plan to connect the circuit to a CdTe crystal sensor and characterize the detector under X-ray condition.

References
[1] R. Ballabriga et al., “Photon Counting Detectors for X-Ray Imaging With Emphasis on CT,” IEEE Trans. Radiat. Plasma Med. Sci., Jul. 2021, doi: 10.1109/TRPMS.2020.3002949.
[2] D. Tran, A. Peizerat, and A. Brambilla, “A CMOS Readout Pixel Circuitry for Spectral-CT Applications,” in 2024 19th Conference on Ph.D Research in Microelectronics and Electronics (PRIME), Jun. 2024, doi: 10.1109/PRIME61930.2024.10559715.

Speaker: Daniel TRAN (CEA-Leti)

Abstract_IWORID.pdf

73 Designing 3-channel Solid-State Particles Detector for Multiple Radiation Sources

Novel applications of fundamental particle detectors often require that the final device has a compact and lightweight design that offers more than one sensing mechanism covering a wide energy range. Radiation emitted from different radioactive sources often consists of various types of radiation (alpha, beta, gamma).

This article describes the design of an amplification and biasing circuit for a 3-channel solid-state particle detector for multiple radiation sources. The TINA-TI V9 [1] and LTSpice [2] simulation tools were used in this study to verify and fine-tune the parameters of the selected components. In particular, the size of the feedback capacitor CF and resistor RF significantly influences the bandwidth of the charge-sensitive preamplifier.

Speaker: Ahti Elias Karjalainen (Lappeenranta-Lahti University of Technology (LUT), School of Engineering Science, Physics)

IWORIDI2025__ABSTRACT__v1.pdf

74 Development of a HV-CMOS pixel sensor prototype in 55nm process for the LHCb Upgrade II Upstream Tracker

The LHCb Upgrade II, proposed for implementation during Long Shutdown 4 (LS4) of the LHC, aims to operate the detector at a maximum luminosity of 1.5 × 10³⁴ cm⁻²s⁻¹. This necessitates the Upstream Pixel tracker (UP) to achieve a detection efficiency exceeding 99% under extreme hit densities of up to 100 MHz, provide nanosecond-level timing resolution to precisely tag collisions occurring at 25 ns intervals in the LHC, and maintain an average power density below 200 mW/cm². To address these requirements, we propose a monolithic pixel sensors designed in 55 nm HV-CMOS technology. Building on the initial validation of the COFFEE2 prototype, the COFFEE3 chip prototype was designed and submitted for fabrication in early 2025, with delivery expected by late April 2025 for preliminary testing.
The COFFEE3 prototype features two distinct pixel array architectures. This contribution will detail the design innovations, including circuit-level optimizations for timing precision, power management strategies, and architectural trade-offs. Also, the preliminary test results will be reported. The outcomes of this work aim to establish a robust foundation for next-generation radiation-hard, low-power pixel sensors tailored for high-luminosity collider experiments.

Speaker: Dr Yang Zhou (Institute of High Energy Physics, CAS, Beijing, China)

2025_iworid_COFFEE3_POSTER.pdf

75 Characterisation of a mixed-signal readout channel for x-ray science applications at fourth-generation synchrotrons

The advent of fourth-generation synchrotron light sources carries both novel and compelling scientific opportunities, as well as new requirements for the instrumentation employed in detectors within such a framework. To address this challenge, a collaboration between Argonne National Laboratory, University of Pavia, and University of Bergamo devised a prototype readout to be utilised in x-ray science detectors leveraging continuous-wave light sources. The circuit has been developed in a commercial 65 nm CMOS technology and integrated in a pixelated ASIC, named pFREYA16 (prototype Fast Readout for ptYchography Applications with 16 channels). It includes a matrix of 16 pixels to verify the compliance of the designed channel with the detector requirements: a frame rate of 1 MHz, single-photon resolution with an ENC of 250 e- rms in four different modes (5, 9, 18, or 25 keV), linearity over the whole input dynamic range of 256 photons for all modes, and a power consumption of 220 uW per pixel. Each pixel integrates a semi-Gaussian unipolar RC-CR shaper with four selectable peaking times, a differential comparator chain to enable zero-suppression, an A/D chain with a differential S/H and a differential 10-bit SAR ADC, and some basic digital backend. The results of the characterisation of the mixed-signal readout channel, including noise measurements, will be the focus of the conference contribution. The data will provide insight into the steps to be taken for the expansion of the array to experiment-grade dimensions.

Speaker: Mr Paolo Lazzaroni (University of Bergamo & INFN Pavia)

IWORID2025_abstract_Lazzaroni.pdf

76 CZT Detector Readout Electronics Design Prototype in Solar X-ray Observation Mission

The X-ray Imaging Telescope (XIT) is one of the scientific payloads of the Solar Polar Observatory (SPO). It is primarily responsible for solar X-ray observations, enabling the monitoring of full-disk eruptive events and the acquisition of X-ray spectra for small-scale activities. The X-ray Imaging Telescope (XIT) plans to employ CdZnTe (CZT) detectors as the sensitive elements due to the lightweight nature of CdZnTe crystals and their high average atomic number, which results in a large interaction cross-section with photons.This paper presents the design and implementation of a prototype readout electronics system for CZT detectors, which can be used for the prototype validation of XIT. The system employs the Application-Specific Integrated Circuit (ASIC) VATA461.3 chip to acquire and process signals from the CZT detectors. It includes the hardware design of the detector readout electronics, the development of FPGA firmware, and the implementation of the host computer software, all aimed at prototype validation of the calorimeter section of XIT. Experimental tests show that the equivalent noise charge (ENC) of the system ranges from 201 to 154 𝑒−, and the integral non-linearity (INL) of the 32 channels is better than 4.33%. The energy resolution of large pixels and small pixels is 6.63%@59.5 keV and 5.28%@59.5 keV, respectively, which meet the technical index 4keV@59.5

Speaker: Shen Wang (Purple Mountain Observatory)

77 Flash X-Ray Imaging in Impact Dynamics: A Comparison of TimePix Detector with Photodiode and High-Speed Camera Systems

This study investigates the imaging performance of the TimePix3 chip for high-speed X-ray imaging, with a focus on its potential application in impact dynamics, specifically in gas-gun experiments combined with a flash X-ray system. The flash X-ray system used is the MAT 300-4C (Scandiflash, Sweden), which generates four discrete X-ray bursts with an exposure time of 20 ns, within a voltage range of 100-300 kV and a discharge current of 10 kA. To evaluate the TimePix chip’s performance, we compare its capabilities with those of traditional detection methods, including signals from a scintillation panel captured by high-speed photodiodes and a high-speed camera. The photodiode signal acts as a high-speed reference for the study, while the high-speed camera is used for capturing the representative X-ray images. The TimePix photon counting detector, with its high spatial resolution and particle detection and traction, represents the primary system under evaluation for its suitability in capturing fast, dynamic X-ray events during high-speed impacts. We assess key performance factors, including detection capabilities, overexposure shielding, temporal resolution, signal fidelity, decay characteristics, and spatial accuracy. This comparison aims to determine the viability of the TimePix chip for high-speed X-ray imaging in the context of impact dynamics and provide insights into its potential for future applications in real-time X-ray imaging of penetration or ballistic events.

Speaker: Tomas Fila (Czech Technical University in Prague, Faculty of Transportation Sciences)

fila_iworid2025_abstract.pdf

78 Development and Validation of an Improved Optical Fiber-Based Verification System for Spent Fuel Inspection in CANDU Reactors

ABSTRACT
At the Wolsong CANDU (CANada Deuterium Uranium) nuclear power plant in the Republic of Korea, 37-element CANDU fuel assemblies using natural uranium are employed. Due to the short burnup cycle of natural uranium, a relatively large amount of spent nuclear fuel is produced, necessitating safe management and timely verification of spent fuel inventories. To address this need, the Korea Institute of Nuclear nonproliferation And Control (KINAC) developed the Optical Fiber Probe System (OFPS), which is currently used for the Physical Inventory Verification (PIV) of CANDU spent fuel bundles.
In this study, an Improved Optical fiber-based VErification System (IOVES) was developed to enhance the technical capabilities and performance of the OFPS. Radiation profile measurements were conducted using the upgraded system, and Monte Carlo simulations were performed to model the wet storage pool and spent fuel bundles. The simulated radiation profiles were compared with the experimental data to validate the IOVES’s performance.
The IOVES consists of a 2.5 × 2.5 × 10 mm³ p-terphenyl scintillator optically coupled to a photomultiplier tube (H10720-110, Hamamatsu) via a 15-meter-long optical fiber cable. Radiation profiles were measured as the probe moved between spent fuel bundles at a speed of 30 mm/s. The radioactivity of the spent fuel bundles was calculated using the Oak Ridge Isotope GENeration and depletion code (ORIGEN), incorporating actual burnup and cooling time data. The wet storage pool environment was modeled using the GEometry ANd Tracking (GEANT4) toolkit, with the ORIGEN-derived source term.
The comparison between simulated and experimental radiation profiles showed similar patterns, confirming the reliability of the newly developed IOVES. These results suggest that the proposed system can be effectively applied to future PIV activities and contribute to the safe and efficient verification of spent nuclear fuel inventories.

ACKNOWLEDGEMENTS
This work was supported by the Nuclear Safety Research Program through the Korea Foundation Of Nuclear Safety (KoFONS) using financial resources granted by the Nuclear Safety and Security Commission (NSSC) of the Republic of Korea (No. RS-2024-00405144), the Korea Institute of Energy Technology Evaluation and Planning(KETEP) and the Ministry of Trade, Industry & Energy(MOTIE) of the Republic of Korea (No. 20214000000070). and Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (RS-2024-00412342).

Speaker: Prof. Yong Hyun Chung (Department of Radiation Convergence Engineering, Yonsei University, Republic of Korea)

IWORID_abstract_Development and Validation of an Improved Optical Fiber-Based Verification System for Spent Fuel Inspection in CANDU Reactors.docx

Social events: Boat trip on Danube river

Tuesday 8 July

Sensor Materials: Session 4

Convener: Seppo Nenonen

79 Diamond and SiC as perspective materials for semiconductor radiation detectors

Detectors based on wide bandgap semiconductors and with high radiation hardness are very promising for many applications. The commercial availability of high-quality crystalline material is required for the preparation of high-grade radiation detectors. The 4H-SiC and diamonds are good candidates in term of harsh environment operation. Detectors based on SiC and diamond can operate at higher temperatures and have very high radiation hardness.
We have tested and developed detectors based on low doped 4H-SiC epitaxial layers and single crystal diamond substrates. We have prepared single detector as well as pixeled structures. As SiC and diamond are wide bandgap materials, tested structures show very low current (only few pA) at several hundreds of volts. Prepared detectors were tested using low energy X-rays and gamma rays and alpha particles from 241Am, were they showed high resolution spectroscopy below 20 keV for the energy of 5.5 MeV. In case of X-ray resolution spectroscopy, the main limitation was not due to the detectors but with the noise of used electronics. Detector structures were tested also at increased temperatures where 4H-SiC detectors showed a good energy resolution of 42 keV for 5.5 MeV alpha particles at 500 °C. Furthermore, we tested SiC and diamond detectors for fast neutron detection in the neutron energy range from 300 keV up to 18 MeV. Mainly diamond detectors showed very high resolution and detection efficiency for fast neutrons. Both detector types clearly show two typical ways of interaction between neutrons and detector materials, elastic scattering and nuclear reaction which produce mainly alpha particles and protons. Due to this, for good neutron detectors the high resolution for alpha-particle detection is needed. Finally, in case of 4H-SiC we have prepared pixelated sensor structures for Timepix3 readout chip. Developed prototype of MiniPIX TPX3 radiation camera had 256×256 pixels. The radiation camera was tested with various types of ionizing radiation like X-ray, gamma rays, protons and neutrons. Also X-ray imaging performance we tested which shows high contrast resolution comparable to commercially available silicon radiation cameras.

Speaker: Dr Bohumir Zatko (Institute of Electrical Engineering, Slovak Academy of Sciences)

80 High-flux CdZnTe Sensor Characterization at the European XFEL

The European X-ray Free-Electron Laser (European XFEL) [1] is an international user research facility located in Schenefeld, in the Hamburg area. It currently features three undulators, providing spatially coherent X-rays for seven experimental stations in the energy range of 260 eV to 25 keV. Using superconducting cavities, the facility can provide up to 2700 pulses of up to 10¹⁴ photons and fs-length with a repetition rate of up to 4.5 MHz in 10 equidistant X-ray pulse trains per second. Future upgrades will enhance accessibility to photon energies in the 25-50 keV range.
Within the framework of the development of new detectors, the European XFEL has recently started an effort to build in-house knowledge regarding high-Z sensor materials, which would offer enhanced quantum efficiencies and protection of the sensitive detector electronics behind them at energies above 20 keV with respect to the currently used silicon sensors. One of the main goals is the qualification of the performance of these alternative sensor materials against the operational requirements dictated by experimental conditions at the facility: while single photon sensitivity as well as high dynamic range of 10³ to 10⁴ photons/pixel are both needed, the sensor’s response must be compatible with MHz operation. Additionally, the user community expressed interest in an enhanced spatial sampling rate capability, therefore the development is setting its target towards an imager featuring a pixel pitch in the order of 100 µm.
To work towards this goal, the already fruitful collaborations with partners at Deutsches Elektronen-Synchrotron (DESY), the Paul Scherrer Institute (PSI), and the Science and Technology Facilities Council (STFC) have been expanded to include tests with high-Z hybrid assemblies. Versions of the Large Pixel Detector [2] (STFC), the JUNGFRAU [3] (PSI), and the Adaptive Gain Integrating Pixel Detector [4] (DESY) were equipped with high-flux CdZnTe sensors produced by REDLEN Technologies, which have improved charge carrier dynamics with respect to their spectroscopic counterpart and respectively reduced polarization effects caused by the large amount of charge generated by intense light pulses. While CdZnTe has been studied extensively at synchrotrons and also showed promising results at low repetition FELs, we have for the first time investigated its compatibility with intense pulses with a repetition rate in the MHz range.
The response of the high-flux CdZnTe sensors shows good linearity within the achieved range of up to about 4×10⁵ 18 keV photons/mm²/pulse and the residual signal after 400 ns was well below 1% of the respective initial signal caused by the photon pulse. Although the physically brittle sensors exhibit noticeable charge sharing due to their increased thickness and further investigations are required to fully deconvolute the sensor’s response from electronic effects, CdZnTe is a promising candidate to be used as high-Z sensor material at high repetition FELs.
References:
[1] W. Decking et al., Nature Photonics 14 (2020)
[2] M.C. Veale et al., J. Phys. D: Appl. Phys. 52 (2019)
[3] A. Mozzanica et al., JINST 9 C05010 (2014)
[4] A. Allahgholi et al., Nuclear Inst. and Methods in Physics Research, A 942 (2019)
Acknowledgments:
K.A. Paton gratefully acknowledges funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 884104 (PSI-FELLOW-III-3i).

Speaker: Steffen Palutke (European XFEL)

IWORID2025_Session4_HiZ at XFEL_Palutke.pdf

IWORID2025_Session4_HiZ at XFEL_Palutke.pptx

81 CdZnTe (CZT) as a Material for Detecting Hard X-rays at Synchrotrons and FELs

The first electrons have circled the newly upgraded Swiss Light Source (SLS) 2.0, a fourth generation synchrotron. Photons with energies > 20 keV will be available at an increased flux compared to the third-generation synchrotron which has been replaced. Specifically, the brilliance will increase by two orders of magnitude. In these energy ranges, Silicon is no longer efficient as a detection material. High-Z (atomic number) semiconductors are required, with GaAs:Cr, CdTe, and CdZnTe (CZT) being suitable candidates. CZT sensors, supplied by Redlen Technologies, have shown the most promising properties with a low leakage current and minimal afterglow transients.

Single sensors ((2×2) cm2) made up of 256×256 pixels with a 75 μm pitch have been bump-bonded to the JUNGFRAU readout ASIC. Developed at PSI, JUNGFRAU is a charge-integrating readout chip with three gain levels and dynamic gain switching. In this talk, we will present and overview of the basic characterisation of Redlen CZT sensors using JUNGFRAU. We will discuss leakage current maps, μ×τ measurements and noise as well as the spectral resolution at 60 keV. A comparison to GaAs:Cr and CdTe will help to provide insight into the advantages of CZT. Finally, we will discuss the future of CZT, including full modules ((8 × 4) cm2) with JUNGFRAU. We will also discuss integration with the new Matterhorn photon-counting readout ASIC (also developed at PSI), which is optimised for electron and hole collection at a high count rate (20 MHz/Pixel).

K.A.P gratefully acknowledges funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 884104 (PSI-FELLOW-III-3i)

Speaker: Jonathan Mulvey (Paul Scherrer Insitute)

20250708_JMulvey - CdZnTe (CZT) as a Material for Detecting Hard X-rays at Synchrotrons and FELs .pptx

82 Characterization of the JUNGFRAU 1.2 readout ASIC

JUNGFRAU is a state-of-the-art charge integrating hybrid pixel detector developed for photon science applications at X-ray free-electron lasers (FELs) and synchrotrons. JUNGFRAU features three automatically switching gains per pixel, which allows both detection of individual 2 keV photons and a high dynamic range up to 10⁴ 12.4 keV photons at a frame rate up to 2.2 kHz. A JUNGFRAU single module consists of 8 readout chips, each containing 256 x 256 pixels with a 75 µm pitch. Arranged in a 2 x 4 array, they are typically bump bonded to a 320 µm thick silicon sensor, resulting in an active area of about 4 x 8 cm² with 0.5M pixels. Currently, the newest version of the JUNGFRAU readout chip, JUNGFRAU 1.2, is undergoing characterization at the Paul Scherrer Institute. This updated ASIC version further optimizes the design of the pixel circuit and analog readout chain compared to its predecessors. The modifications are expected to improve the noise and output linearity. In this contribution, the results of the laboratory characterization as well as a full dynamic range scan with an X-ray beam at the SwissFEL Cristallina endstation will be presented.

Speaker: Vadym Kedych (Paul Scherrer Institute)

IWORID25_Kedych.pdf

10:30 Coffee Break

Sensor Materials: Session 5

Convener: Gian-Franco Dalla Betta (INFN and University of Trento)

83 Characterisation of inverse LGADs in the soft X-ray energy range

Hybrid detectors are the state-of-the-art technology widely used in imaging experiments using hard X-rays. They are also highly attractive for soft X-ray experiments (200 eV – 2 keV) due to their high frame rate, large area coverage, and strong radiation tolerance. However, in the soft X-ray energy range, their performance is limited by the low quantum efficiency of silicon sensors, which are typically used in hard X-ray domain, and by a low signal-to-noise ratio. To overcome these limitations, inverse Low-Gain Avalanche Diodes (iLGADs) with a thin entrance window are being developed at the Paul Scherrer Institute in collaboration with Fondazione Bruno Kessler.

iLGAD sensors, bump-bonded to 25 µm pitch charge-integrating Mönch chips, have been characterized using soft X-rays at the 4th-generation synchrotron radiation source MAX IV in Sweden. We will present the results of these measurements, including the spectral response of iLGADs with different gain layer designs at various temperatures and X-ray energies. The spectrum produced by iLGADs features a two-peak structure: a hole-initiated multiplication peak and an electron-initiated multiplication peak, corresponding to photon absorption before and after the gain layer, respectively. We will demonstrate the relationship between photon absorption depth and the proportion of hole- and electron-initiated multiplication at different X-ray energies. Based on this relationship, we are able to determine the thicknesses of the n+ layer beneath the entrance window and of the gain layer.

Additionally, we have observed a decrease in signal amplitude at X-ray energies above the Silicon K-edge, and an additional peak just below the electron-initiated multiplication peak. Through detailed spectral analysis, we will explore the relationship between signal amplitude reduction, iLGAD gain, and photon absorption depth. Finally, we will discuss the possible causes of the additional peak and the signal amplitude reduction, along with plans for further testing and improvements of iLGADs for soft X-ray detection.

Speaker: Shuqi Li

iworid2025_light.pdf

84 nLGAD detector gain performance in the deep and near-ultraviolet (UV) spectral range

Low Gain Avalanche Detectors (LGADs) are silicon detectors produced in a specialized way, such that they possess an internal charge multiplication effect (gain) that amplifies the output signal and allows for a good signal-to-noise ratio. Their stable and controlled moderate gain of up to 50, along with exceptional timing resolution, justifies their role as a baseline for HEP experiments. This enables particle tracking, which is important for collider experiments (CERN-LHC). Originally developed at CNM [1], this technology has since diversified, with various “flavours” emerging, each intended for different detection applications. In this work, we show the potential of the nLGAD, which is particularly aimed at low-penetration radiation (penetration depth around ≲ 1 µm). This is due to the nature of the charge transport dynamics in n-type semiconductor and its correlation with the specially designed doping profile, which enhances sensitivity to low penetration – particularly important in fields like soft X-ray imaging of biological samples in the water window (282 eV to 533 eV). The first simulations and gain response measurements of such devices, characterised with 404 nm (blue), 660 nm (red), 1064 nm (infrared light), 15 keV X-rays, and 600 keV protons can be found in [2-4]. These results show that the nLGAD maintains high gain at shorter wavelengths and lower penetration, confirming the consistency of the low penetration, high gain relationship. The results confirmed the viability of the nLGAD and have motivated the optimisation of this technology at CNM. In this study, we extend the characterization of this technology, presenting the gain measurements in the deep and near-ultraviolet (UV) 250-390 nm wavelength range performed at The Extreme Light Infrastructure (ELI ERIC) facility (Prague, Czech Republic). We focus the discussion on the effects of fabrication refinements such as variations in doping profile for the entrance window optimization. Findings in this work demonstrate that making the dead layer (low electric field region) thinner improves deep UV detection, and that our technology is still able to detect wavelength down to 250 nm with a gain of 2-3. However, this study strongly suggests the need for an ultra-shallow junction in the future, which will be a new benchmark for nLGAD for detecting low-penetration radiation. Our results also show that optimizing the entrance window is crucial, not only due to its thickness but also because of the significant variation in the reflectance coefficient across the deep and near UV range. This implies that antireflective coatings are mandatory for passivating nLGADs, especially for possible applications in VUV optics (10 nm – 200 nm), where challenges with shallow penetration would be even more pronounced.

Speaker: Milos Manojlovic (Consejo Superior de Investigaciones Cientificas (CSIC) (ES))

iWorid2025_abstract_CNM.pdf

nLGAD detector gain performance in the deep and near-ultraviolet (UV) spectral range.pdf

nLGAD detector gain performance in the deep and near-ultraviolet (UV) spectral range.pdf

nLGAD detector gain performance in the deep and near-ultraviolet (UV) spectral range.pptx

85 Evaluation of detector-grade GaAs via alpha and X-ray spectrometry

Although GaAs has been tested as a material for X-ray detectors for more than 50 years, practically significant results have only been achieved in the last decade, when semi-insulating, chromium-compensated single crystals have been employed [1]. This is particularly true for imaging sensors developed for Medipix/Timepix readout ASICs [1, 2].

We demonstrated imaging sensors fabricated by pixel-pattern processing of 500 µm-thick GaAs wafers compensated by post-growth doping with Cr [2]. The sensor parameters depend on the structural and electrical properties, which are determined by the characteristics of the initial commercial n-type wafers grown by the Liquid Encapsulated Czochralski method, as well as the conditions of thermal annealing of Cr-coated wafers, polishing, surface treatment, and subsequent pixel contact deposition. To evaluate the obtained detector-grade Cr-compensated GaAs and study the effect of crystal thickness on sensor spectroscopic properties, the voltage dependences of the alpha (α) particle and X-ray spectra were measured using a 241Am source at room temperature, since it is an efficient commonly used efficient technique for GaAs characterization [3, 4].

Samples with an area of 5 × 5 mm2 and a thickness of 220 µm, 380 µm, and 480 µm were diced from the double-side polished GaAs wafers, which were pretreated with bulk chemical etching for the corresponding thinning. Thin (~20 nm) Cr electrodes were deposited onto the opposite faces of GaAs samples by sputtering using a metal mask with dimensions of 4 × 4 mm2. The fabricated planar Cr/GaAs/Cr structures with symmetrical contacts exhibited low dark currents of approximately 3 µA, 4 µA, and 9 µA at bias voltage of 500 V for the different crystal thicknesses, respectively. The Cr/GaAs/Cr structures were connected to a measurement holder using clamping contacts with conductive rubber and placed inside a shielding box. A portable ultra-high count rate spectrometer was used. The spectra were acquired without charge-loss correction or rise time discrimination electronics. The spectrum acquisition time was 5 min. The 5.5 MeV α particles from the noncollimated 241Am source, positioned at front of the sample, had to pass through 20 mm of air and the contact metallization to reach the GaAs. The crystal margins were also affected. Certainly, the detected α particle kinetic energy was lower than its nominal one. The X-ray spectra of 241Am (59.5 keV) were measured using a sheet of paper to stop the α particles.

Cr/GaAs/Cr sensors resolved the full energy spectrum for a 241Am radiation source, clearly demonstrating both the dominant high-energy α particles in the high channel-number range and the accompanying low-energy X-ray peak in the low channel range. The α-peak was well distinguished when the sensor front side was negatively biased, while the X-ray peak appeared at both the polarities, however higher detection efficiency was observed with a positively biased front contact. The Cr/GaAs/Cr sensors were capable of clearly resolving α peak under low biasing conditions: 5 V, 20 V, and 40 V for 220 µm, 380 µm, and 480 µm thick GaAs crystals, respectively. The thinnest sensor showed the highest detection efficiency and energy resolution (FWHM ~ 3%). However, these α-peak parameters did not differ significantly among the samples of different thicknesses, contrary to other studies [3, 4]. Certainly, the highest values were achieved at lower bias voltages for thinner sensors: 300 V, 400 V, and 700 V for thicknesses of 220 µm, 380 µm, and 480 µm, respectively. The features of the voltage dependences of α spectra measured by all three sensor thicknesses over a wide voltage range (up to 1200 V) were analyzed. A typical shift of the peak toward larger channel numbers with increasing bias voltage was observed, and this effect was most pronounced for the thinner sensors. The peak reached the largest channel number, corresponding to the most efficient charge collection, and consequently resulted in the highest peak height and energy resolution [3].

Based on the bias voltage dependences of electrical and spectrometric characteristics, derived from I-V and α particle spectrum measurements of the planar radiation sensors, fabricated using semi-insulating Cr-compensated GaAs crystals with symmetric Cr contacts, the charge transport parameters of the semiconductor were estimated. The α particle response, observed over a wide bias voltage range with high energy resolution at the optimal biases for Cr/GaAs/Cr sensors of different thicknesses, has demonstrated the excellent suitability of the material for imaging detector applications [2]. The consistently high α spectrometric performance across all sensor thicknesses has evidenced the efficient Cr doping of GaAs wafers during thermal annealing, leading to uniformly Cr-compensated detector-grade material.

Acknowledgements:
The research project has been supported by the Shanghai (China) - Finland Industrial Innovation Cooperative Program.

References:
[1] M. Fiederle et al., Cryst. Res. Technol. 55 (9) (2020) 2000021-1-6.
[2] J. Kalliopuska, et al., IWoRID 2024, Book of Abstracts (2024) 9-10.
[3] A. Šagátová et al., EPJ Web of Conf. 288 (2023) 10013-1-4.
[4] A. Šagátová et al., JINST 20 (2) (2025) C02040-1-8.

Speaker: Dr Dmytro Nalyvaiko (Advafab Oy)

Dmytro Nalyvaiko, IWORID 2025 08.07.2025 v1.2.pdf

IWORID2025_abstract_GaAs_spectra.docx

IWORID2025_abstract_GaAs_spectra.pdf

86 MATRIX: Simulation and Experimental Study of GaN Proton Detectors

The MATRIX project explores advancements in proton therapy by developing durable detectors for improved real-time beam and dose monitoring. Proton irradiation enables precise tumor targeting while minimizing damage to healthy tissue. Current detection methods, including ionization chambers, scintillators, and silicon-based detectors, face limitations, particularly the degradation of silicon under prolonged exposure to high-energy protons (65–230 MeV) or lack of linearity and even saturation for scintillators.
To address this, MATRIX investigates the use of gallium nitride (GaN) semiconductor, which offers higher radiation resistance than silicon. Proton detection is achieved by measuring the current induced in pin GaN diodes. GaN, widely used in LED technology, is cost-effective, can be grown on large-size wafers (up to 300 mm), and enables the development of long-lasting detector arrays. Combined with silicon-based electronics placed outside the irradiation field, this approach shall enhance system stability and performance.
MATRIX has developed a GaN-based detector prototype, including linear diode arrays with 128 elements and two-dimensional arrays up to 11×11, covering 1 cm² with up to 500 µm spatial resolution. Smaller diode sizes and thus higher resolutions are obtainable thanks to the utilized microelectronic processes.
To evaluate the performance of these GaN-based detectors and understand the detector’s response to primary and secondary particles, Monte Carlo simulations were conducted using the Gate 10.0 platform to model the proton beam line. The simulation results were compared with experimental data from proton irradiation experiments performed at the Cyrcé platform of the Institut Pluridisciplinaire Hubert Curien in Strasbourg, using proton beams with energies around 20 MeV and proton currents around 2 nA.
Comparing experimental data and Monte Carlo calculations, we will present the performances of the MATRIX GaN detector under different irradiation conditions, e.g., with higher proton energies of different facilities. This comparison also allows us to assess the simulations' accuracy and validate the experimental setup. Based on high-dose measurements, we will discuss radiation tolerance. The results give insight into potential applications of the MATRIX detector in beam and dose monitoring for proton therapy systems.

Speaker: Nico Brosda (Ruhr-Universität Bochum)

IWORID_Brosda_PDFBackup.pdf

IWORID_Brosda.pptx

87 Performance of DC resistive read-out silicon sensors for future 4D tracking

In recent years, the innovative concept of low internal gain avalanche detector (LGAD) coupled with the resistive read-out (RSD) has significantly changed the performance of silicon detectors. By increasing the ratio signal-to-noise by a factor of around 20, the LGAD mechanism led to unprecedented time resolution, on the order of 30 ps for a 50 um active sensor thickness. The resistive read-out allows
instead to share the collected charge between several electrodes, achieving an excellent spatial resolution, order of 5% of the pixel pitch. These two concepts combined enable 4D tracking with silicon sensors.

This contribution presents the latest silicon sensor design based on these two concepts: a thin LGAD with a DC-coupled resistive read-out, the DC-coupled Resistive Silicon Detector (DC-RSD). This design aims at achieving controlled signal sharing through the implementation of isolating trenches (TI technology) amongst the electrodes that define the pixel.

Various structures are implemented in the wafer layout, manufactured at FBK as part of the 4DSHARE project.
A subset of sensors have been characterised with a laser TCT system, equipped with a 5-um spot, to estimate the ultimate spatial resolution as a function of the pitch. Measurements at the TCT are also performed to evaluate how different values of the resistive layer impact the signal sharing. The spatial and temporal resolutions of sensors tested at DESY with an electron beam will also be presented.
This study will provide significant feedback on the capabilities and reliability of the DC-RSD design.

Speaker: Giulio Bardelli (Universita e INFN, Firenze (IT))

Iworid2025_bardelli_4dshare.pdf

12:40 Lunch break Lunch 13.00

Detector Systems: Session 6

Christer Fröjdh

Convener: Cinzia Da Via (The University of Manchester (GB))

88 An overview of HEXITEC and HEXITEC MHz and its applications

The High Energy X-ray Imaging TECHnology (HEXITEC) and the recently developed HEXITEC MHz technologies, developed by the UK’s Science and Technology Facilities Council (STFC), represent significant advancements in spectroscopic X-ray imaging applications. These ASICs are designed for high-resolution, energy-resolved detection of X-rays and gamma rays, and have been optimized for use with compound semiconductor detectors such as CdTe and CZT. The original HEXITEC ASIC offers fine spatial resolution (250 µm pitch) and spectroscopic capabilities across a broad energy range (2–600 keV), while the HEXITEC MHz variant introduces high-speed readout capabilities, operating at frame rates up to 1 MHz, greatly enhancing temporal resolution and data throughput.
These technologies have demonstrated strong potential across various industrial and scientific domains. In transmission imaging, HEXITEC enables material discrimination and enhanced contrast through energy-resolved imaging, with applications in security screening and advanced non-destructive testing. In X-ray fluorescence (XRF) spectroscopy, HEXITEC’s high spectral resolution facilitates element-specific imaging, allowing for precise compositional mapping in mining, recycling, and materials science. Within nuclear medicine, the technology supports advanced gamma imaging and radionuclide detection, contributing to improved diagnostic imaging and personalised treatment planning in theragnostics.
HEXITEC MHz further expands the scope of applications, enabling real-time imaging in dynamic environments and high-count-rate scenarios, such as in synchrotrons and industrial process monitoring. The HEXITEC and HEXITEC MHz ASIC platforms present transformative opportunities for industries seeking enhanced imaging capabilities, particularly where spectral information, spatial resolution, and high frame rates are critical. Their continued development is poised to impact a wide range of sectors, accelerating innovation in imaging-intensive processes and applications.

Speaker: Dr Diana D Caprotti (Science and Technology Facilities Council (STFC), UK Research and Innovation (UKRI))

DianaDCaprotti_An overview of HEXITEC and HEXITEC MHz and its applications.pdf

DianaDCaprotti_An overview of HEXITEC and HEXITEC MHz and its applications.pptx

89 C100: A 4-Megapixel, 2000 FPS Wafer Scale Direct Electron Detection Sensor for 100keV Electron Cyro-Microscopy

In the past decade, Electron Cryo-Microscopy (cryoEM) has developed into a popular technique for biological molecular structure determination, driven largely by the rapid development of increasingly capable direct electron detectors. Traditionally, cryoEM has been performed on 300 keV transmission electron microscopes, which are costly to acquire and operate, and consequently out of reach for many potential users. In recent years, there has been interest in conducting cryoEM in 100 keV transmission electron microscopes, which are as much as an order of magnitude less expensive to procure and operate. Additionally, studies have indicated that cryoEM at 100 keV may permit the extraction of significantly more structural information from a sample, as by reducing the electron energy, the sample radiation damage is reduced.
This interest has been hampered by the absence of sensors suitable for operation at 100 keV, with most optimised for operation at 300 keV. The nature of cryoEM presents the challenging requirement for such a sensor to simultaneously possess a large sensitive area (>10cm diagonal), high frame rate operation for discrete electron counting operation and high detector quantum efficiency.
At the Science and Technology Facilities Council we have extensive experience developing direct electron detectors for electron microscopy and have been developing a collection of reusable ‘building blocks’, notably including a sigma-delta ADC and 4.3 Gbit/s serialiser, for the development of image sensors in the Tower Semiconductor’s, 2D stitching capable, 180nm CMOS image sensor process. The capability to deliver a single device, filling an 8” wafer, is ideal to fulfil the large detector area requirements of 100 keV cryoEM.
We present the outcome of that development: ‘C100’, a wafer scale, 4-megapixel, direct electron detection sensor, capable of operating at frame rates in excess of 2500 FPS. The >120cm2 active area of the sensor consists of a 2048-by-2048 array of 54-micrometre pitch radiation hardened 3T pixels. These pixels are then read out and digitised through 16576 sigma-delta 13-bit ADCs operating at up to 640k samples-per-second (design rate of 1M samples-per-second, but is limited here by readout rate). The converted data is shifted out of the ADCs into 34 4.3 Gbit/s serialisers, implementing the AMD Aurora 64b/66b protocol, handling a total system bandwidth in excess of 140 Gbit/s. Off-chip these serialisers are connected to Samtec FireFlyTM transceivers for optical transmission to the data acquisition system.
While optimised and appropriately radiation hardened for direct electron detection, C100’s pixels are also suitable for the detection of light and charged particles.
Here we intend to present the high-level design and architecture of C100, along with the challenges we overcame during development and the results of device characterisation. Additionally, we plan to outline our next steps at 180nm, furthering the development of our reusable ‘building blocks’, and our plans to take this forward for our 65nm development program.

Speaker: Daniel Brown

c100_iworid_2025.docx

C100_IWORID_v1.pptx

90 Second-Generation Percival Sensor and System for upgraded soft X-ray imaging at FELs and Synchrotrons

PERCIVAL, "pixellated energy-resolving CMOS imager versatile and large," is a 2-megapixel soft X-ray imager developed for use at FELs and modern-day synchrotrons by a collaboration of light sources (DESY, Elettra, Diamond, Pohang Accelerator Lab, and Soleil) together with Rutherford Appleton Laboratories. To meet the science needs at these facilities, a combination of capabilities is necessary: a large, uninterrupted imaging area with small pixels, high dynamic range, high frame rate, and soft X-ray suitable entrance window to the sensor. PERCIVAL's stitched sensor offers over 4cm x 4cm uninterrupted imaging area (1408x1484 pixels of 27x27 um2). Three gains combine to deliver Percival's dynamic range: in the highest gain, noise levels below 13e- are achieved - suitable for single-photon discrimination down to ~250eV. In the lowest gain, up to 3.6Me- can be digitized per pixel per image. The imager is designed for 300Hz frame rate, operates essentially in a rolling-shutter mode, and can be run correspondingly faster in ROI mode utilizing a reduced number of its rows. BSI processing with thin entrance window makes the sensor suitable for soft X-ray use.

The first generation of the sensor had some shortcomings - in particular, severe crosstalk in the sensor hampered parallel operation of ADC, streamout, and pixel switches. Circumventing these issues by separating the sensitive ADC operation in time from the aggressors resulted in significantly reduced maximum frame rate - and some non-linearities remained. Moreover, inadequate grounding of the pixel matrix resulted in current bias variation over the matrix ... and ultimately in significantly different baselines at center and edges of the detector. This limited the useable dynamic range in particularly in higher gains ... and rendered pixels at the edges of the sensor useable only in higher-noise, lower-amplification modes. The first-generation readout FPGA card and firmware added restrictions on data streamout speed, limiting the overall sensor operation to below 100Hz frame rate.

Today, we are commissioning a 2nd-generation sensor and readout:
The 2nd-generation "respin" sensor's design was modified to eliminate the crippling crosstalk to the ADC, and grounding of the pixel matrix was improved to enable use of the full sensor area also in highest gain modes. In parallel, completely new DAQ hard- and firmware now have the capability to handle data streams at the originally envisioned rates.
To date, we have verified elimination of the crippling crosstalk and established our capability to use the full sensor - i.e. validated the chip design improvements. We are in the process of bringing the system to the original design speed of 300Hz frame rate - as this entails operating both the digital streamout and the ADCs at almost twice the previously-used clock speeds, debugging and commissioning fully will take some time. We will report on the state of the system, and the performances demonstrated with the upgraded sensor and system.

Speaker: Cornelia Wunderer (DESY)

2025_07_08_iWoRID_Percival_Wunderer_v2--slides1-20--upload.pdf

91 The prototype DynamiX camera system, a high-frame rate, high-dynamic range hard X-ray integrating detector for 4th generation synchrotrons

The advent of fourth-generation synchrotrons, such as the Diamond II upgrade, offers unprecedented flux increases of 10–100×, reaching up to $10^{12}$ photons/s/mm² over a wide energy range (20–100 keV). Fully leveraging these photon fluxes and high X-ray energies necessitates readout chips with exceptional frame rates and dynamic ranges, alongside the use of high-Z sensor materials. To address these requirements, STFC has developed DynamiX, a novel test structure using a two-stage charge cancellation circuit fabricated on a 65 nm CMOS process. This design achieves a dynamic range spanning 0.2 ph/pix/frame to $3 \times 10^{11}$ ph/s/mm² at 30 keV. The ASIC features a 16 × 16-pixel array on a 110 μm pitch, which is hybridized to a 2-mm-thick Redlen high-flux cadmium zinc telluride (HF-CdZnTe) sensor. Operating at 533,000 fps, the device outputs data via a 14 Gbps serializer, with frames assembled and stored using a custom DAQ system. Performance evaluations were conducted at the Diamond Light Source B16 beamline using a monochromatic X-ray beam with varied beam sizes and energies. Results include measurements with sub-pixel beam for single-photon detection, and an X-ray tube was used for linearity studies up to $2 \times 10^{10}$ ph/s/mm² (30 keV equivalent). These results feed directly into the design of the scaled-up 192x144-pixel version of the ASIC.

Speaker: Simon Knowles (on behalf of the XIDyn Collaboration)

DynamiX-iWorid25-Knowles.pptx

15:30 Coffee Break

Detector Systems: Session 7

Christer Fröjdh

Convener: Valeria Rosso

92 Optimization of a 3D Micro-Structured Neutron Imaging Sensor Through Combined Simulation Approaches

Neutron imaging offers additional information compared to X-ray imaging because of the different types of interaction of the two different types of radiation. This technique is particularly valuable in fields such as nuclear engineering and non-destructive industrial diagnostics.

Based on 3D sensor technology, an innovative thermal neutron detection and imaging device has been developed within the INFN HYDE2 project. This device has a 3D microstructure design. It is based on the standard planar n-on-p pixel structure, but the backside is processed with Deep Reactive Ion Etching (DRIE) to create deep ($\sim$25 µm) and narrow cavities, which are later filled with $^6$LiF or $^{10}$B converter. The sensor consists of a 256$\times$256 pixel array, with a size of 55$\times$55 $\mu$m$^2$, making it compatible with the Timepix readout electronics.

A key objective of this study is to optimize the geometry of the cavities, specifically their radius and distance, to maximize the neutron detection efficiency. Achieving this requires careful evaluation of neutron capture, detection of the resulting charged particles, and collection of the generated charges. Taking all these aspects into account is not a trivial task.

To address these challenges, the study is structured into multiple steps. First, GEANT4 simulations are used to generate an energy deposition map of charged particles resulting from neutron capture. In this step, the neutron capture probability and the trajectory of the resulting charged particle are taken into account. Next, TCAD Sentaurus static simulations are used to extrapolate the electrical properties of the silicon device, like weighting potential and electric field. This step is essential as a starting point for studying the charge motion inside the device.
With TCAD, it is also possible to perform transient simulations to estimate the charge collection efficiency (CCE), but evaluating multiple geometries using this method is computationally demanding.

To overcome this limitation, the Allpix2 simulation framework is used, integrating the results from GEANT4 and TCAD. The Weighting Potential, Electric Field, and Doping Profile extracted from TCAD are imported into Allpix2. Charge injection is simulated using the DepositionPointCharge module, following the energy distribution obtained from GEANT4. Furthermore, a modified version of the TransientPropagation module is implemented to account for the specific geometry of the HYDE2 device and accurately model charge transport. The total CCE is computed for different geometries and validated against transient TCAD simulations for selected configurations, ensuring the precision of the Allpix2 results.

Finally, all the partial simulation results are merged to find the optimal geometry to maximize the neutron collection efficiency.

Speaker: Matteo Polo (University of Trento and TIFPA)

Abstract_iworid_2025_polo_matteo_unitn.pdf

presentazione_IWORID2025_mp.pdf

presentazione_IWORID2025_mp.pptx

93 The SABRE South Experiment at the Stawell Underground Physics Laboratory

SABRE is an international collaboration that will operate similar particle de-
tectors in the Northern (SABRE North) and Southern Hemispheres (SABRE
South). This innovative approach distinguishes possible dark matter signals
from seasonal backgrounds, a pioneering strategy only possible with a southern
hemisphere experiment. SABRE South is located at the Stawell Underground
Physics Laboratory (SUPL), in regional Victoria, Australia.
SUPL is a newly built facility located 1024 m underground (∼2900 m water
equivalent) within the Stawell Gold Mine and its construction has been com-
pleted in 2023.
SABRE South employs ultra-high purity NaI(Tl) crystals immersed in a Linear
Alkyl Benzene (LAB) based liquid scintillator veto, enveloped by passive steel
and polyethylene shielding alongside a plastic scintillator muon veto. Signifi-
cant progress has been made in the procurement, testing, and preparation of
equipment for installation of SABRE South. The SABRE South muon detector
and the data acquisition systems are actively collecting data at SUPL and the
SABRE South’s commissioning is planned to be completed by the end of 2025.
This presentation will provide an update on the overall progress of the SABRE
South construction, its anticipated performance, and its potential physics reach.

Speaker: Zuzana Slavkovská (The Australian National University)

IWORID_2025_Zuzana_Slavkovska.pdf

94 CYGNUS: Directional recoil detection for dark matter, particle physics and nuclear applications

The Australian National University (ANU) has been conducting studies in directional detector technology, with the aim of building a large detector called CYGNUS. Eventually, such a detector is likely to be located in Australia's new underground physics laboratory at Stawell in regional Victoria.

The ANU group leads the experimental efforts of the Australian CYGNUS-Oz consortium through the prototype detectors. The most recent prototype called CYGNUS-n is based on gaseous Time Projection Chamber (TPC) technology. TPCs have an advantage in areas such as directional dark matter searches, as they allow for event-by-event reconstruction of three-dimensional particle tracks with excellent particle discrimination and a high degree of spatial and energy resolution. Recent studies suggest that a large-scale gaseous TPC would be sensitive enough to study solar neutrino fluxes and may offer other novel physics or industrial applications.

This contribution presents the status and results of studies with CYGNUS-n with the future direction of the dark matter research and other applications like particle and nuclear physics. It focuses on R&D and development of optimal TPCs with specific research focus. This includes studies of gas impurities effect on TPC gain and negative ion drifts and the detachment of the electrons from the gain stage.

Speaker: Prof. Gregory Lane (Australian National University)

CYGNUS-Oz-iWoRiD2025-v3a.pdf

95 Development of Accurate Dosimetry SiPM-based Detectors for FLASH RT

Radiotherapy (RT) using X-rays is the main treatment strategy employed to treat human tumors with ~50% of all cancer patients receiving RT. The major drawback of RT treatment is that in order to deliver a lethal dose to cancerous cells, short- and long-term adverse side-effects are evident due to the irradiation of the surrounding normal healthy tissues that can severely impact the health and quality of life of the cancer patient.
One way to circumvent the irradiation of the surrounding tissue is through Proton Beam Therapy (PBT) where instead of photons, protons are used to deliver the radiation with higher precision, thanks to their favorable ratio of Relative dose to Depth (Bragg Peak).
Another way is through FLASH radiotherapy and particle therapy. Both are performed with the delivery of ultra-high dose rate radiation (UHDR), specifically a dose rate higher than 40 Gy/sec. The advantage of FLASH compared to conventional therapy (CONV) is based on the “FLASH effect”: improved normal tissue sparing while still maintaining tumor control. Accurate dosimetry and real-time beam monitoring are critical for its clinical translation, but current detectors suffer from saturation effects in the signal production and signal read-out when dealing with fast and intense beams.
We report on our development and preliminary tests of a novel dosimeter for Ultra high-dose rate particle therapy, based on advanced Silicon Photomultiplier (SiPM) detectors coupled with scintillating fibers (SciFi). The SciFi detector aims towards an improved time and space resolution, with respect to the present commercial readout system. It will be suitable for both CONV and UHDR irradiations.
We will describe the present status of the devices and facilities used for FLASH RT. We will show the preliminary design of the detector that is expected to be tested using a proton UHDR beam with the beam's energy ranging from 70 MeV (CONV) to 228 MeV (FLASH RT). The ultimate goal is a detector suited both for FLASH PBT and for Conventional RT, with good sensitivity, as well as spatial and energy resolution.

Speaker: Georgios Mystridis (University of Foggia, Fondazione Bruno Kessler)

IWORID 2025 SiPM based detectors for FLASH.pdf

96 Development of Real-Time FPGA computing for Hyperspectral Imaging with CITIUS

X-ray hyperspectral detectors using charge-integrating pixels detect individual photons at frame rates generally higher than one kilo frames per second (kfps). Owing to the slower analog processing, they enable spectroscopic analysis with sharper energy resolution, typically better than 1 keV FWHM.
CITIUS is a recently introduced large-area, direct-detection X-ray detector, of which the development was led by RIKEN SPring-8 Center (Japan). It integrates a 650 µm-thick silicon sensor with a CMOS readout chip comprising a matrix of (728×384) integrating-type pixels with 72.6 µm pitch. In the spectro-imaging operating mode, CITIUS operates as a hyperspectral detector at 26.1 kfps to detect isolated photons in each acquired frame. Under optimal conditions, CITIUS achieves an energy resolution of 380 eV FWHM (full width half maximum of photo peak) at 8.0 keV for events where the charge released is confined to a single pixel. Additionally, an improved energy resolution of 220 eV FWHM at 5.9 keV has been demonstrated at the cost of a reduced frame rate of 2.2 kfps, using an eight-frame sampling mode. Note that these results were obtained at room temperature. The combination of high frame rate, large detector area, room temperature operation, and good energy resolution makes CITIUS a promising candidate for spectral Computed Tomography (CT), as demonstrated using a laboratory liquid metal-jet X-ray source [1].
A major limitation of hyperspectral detectors using charge-integrating devices is the need to acquire a large number of frames, each containing sparsely distributed photons, to reconstruct spectral information with specialized post-processing procedures. This approach requires high data volumes, large storage capacities, and time-consuming post-processing. To address these limitations, we propose an innovative real-time FPGA-based spectral reconstruction algorithm, implemented for the CITIUS detector in the spectro-imaging mode. This solution ensures real-time data reduction and visualization, significantly enhancing the suitability of CITIUS for spectral CT applications by eliminating extensive post-processing, reducing storage requirements, and shortening acquisition times due to minimized data transfer.
For the CITIUS detector, deducing photon energy requires computation over a 3×3 pixel matrix per event, posing a significant challenge given the data throughput of 7.296 Gpixels/s per module (29.19 GB/s). To enable low-latency and reliable processing, we implemented the spectro-imaging algorithm in Verilog HDL on three custom-developed FPGA cards, which we call Data Framing Boards (DFBs) [2]. Each DFB hosts three Arria10 FPGAs (Intel Corporation, USA): two are dedicated to the calibration of pixel data streams output from CITIUS, and one to the spectro-imaging mode. Preliminary results obtained at 26.1 kfps show strong agreement between the spectra reconstructed by the FPGA and those computed offline by a CPU (Figure 1).
In this presentation, we provide an overview of the implemented algorithm and report on the experimentally validated performance of the real-time spectro-imaging pipeline.

[Figure1.jpg]
Figure 1: Energy spectra measured by X-ray photon event from a Fe55 and a Cd109 radioactive sources. The number of measured frames is 261,000 frames for FPGA and 30,000 frames for CPU. CITIUS detector was operated in the spectro-imaging mode at 26.1 kfps. The sensor temperature was +30 degree Celsius.

References
[1] V. Di Trapani, et.al., presented at iWoRiD 2024
[2] H. Nishino et.al., Nucl. Instrum. Methods Phys. Res. Sect. A, Vol. 1057, p. 168710, (2023)

Speaker: Mr Kyosuke Ozaki (1)

abstract_citius.pdf

Figure1.jpg

iWoRiD2025_presentation_KO.pdf

Social events: Committee Dinner

Wednesday 9 July

Medical Applications: Session 8

Convener: Renata Longo (UNIVERSITY OF TRIESTE & INFN)

97 Timepix detectors for development of novel imaging techniques for ion beam radiotherapy

Ion radiotherapy is used to treat tumors located close to critical structures such as the brainstem, spinal cord, or optic nerves. In these cases, it is crucial to deliver an adequate dose to the tumour to halt its progression, while minimizing exposure to adjacent healthy tissues. Even minor variations in dose distribution—on the order of several millime-ters—can have significant clinical consequences. These variations may arise from anatomical changes occurring dur-ing the course of treatment, which typically spans several weeks. Factors such as tumor shrinkage, tissue swelling, filling or draining of natural cavities, can alter the range of the ion beam within the body. Such changes can lead to overdosage of healthy tissues or underdosage of the tumour itself. Our research group is currently developing two methods to address this challenge:

1) Helium ion beam imaging is intended to be performed when the patient is ready for the treatment on the couch. We have developed a dedicated imager prototype using six Timepix1 detectors [1]. Two pairs of detectors serving as front and rear tracker are followed by an energy deposition unit providing the image contrast [2]. This unique concept replaces the bulky calorimeters used in other designs. The information about eventual changes of the internal patient geometry has the power of deciding whether the treatment has to be adjusted before the patient is irradiated.

2) In vivo monitoring of carbon ion beam treatments by tracking secondary ions relies on detecting nuclear fragments created in the patient during the irradiation. The core idea is to measure the distribution of secondary around the patient on two treatment days and to compare these distributions. If significant differences are detected, the treatment to be delivered on the next day can be adjusted accordingly. Since changes in the secondary ion emission profiles are very subtle, a major challenge lies in accuratelly detecting and interpreting these signal in terms of their spatial location and intensity. After more than a decade of experimental research, a clinically viable device based on Timepix3 detectors [3] has been developed and delivered by the Advacam s.r.o. Prague, Czech Republic [4]. The corresponding clinical trial called InViMo has been in progress since late 2023.

Both techniques were implemented at the Heidelberg Ion Beam Therapy Center in Germany. The presentation will demonstrate the performance of precision imaging by helium ion beams, together with the recent clinical results from the InViMo trial.

[1] X. Llopart, R. Ballabriga, M. Campbell, L. Tlustos and W. Wong 2007: Timepix, a 65k programmable pixel readout chip for arrival time, energy and/or photon counting measurements NIM A 581, 485 (2007)
[2] M. Metzner, D. Zhevachevska, A. Schlechter, F. Kehrein, J. Schlecker, C. Murillo, S. Brons, O. Jäkel, M. Martišíková and T. Gehrke: Energy painting: helium-beam radiography with thin detectors and multiple beam energies, Physics in Medicine and Biology 69, 055002 (2024)
[3] T. Poikela et al.: Timepix3: a 65K channel hybrid pixel readout chip with simultaneous ToA/ToT and sparse readout, JINST 9, C05013 (2014)
[4] L. Kelleter, L. Marek, G. Echner, P. Ochoa Parra, M. Winter, S. Harrabi, J. Jakubek, O. Jäkel, J. Debus, M. Martisikova: An in-vivo treatment monitoring system for ion-beam radiotherapy based on 28 Timepix3 detectors. Nature Scientific Reports 14, 15452 (2024)

Speaker: Maria Martisikova (German Cancer Research Center)

Martisikova_IWORID_2025.8.7.pptx

98 Recent developments of helium-beam radiography (αRAD) aiming at image guidance in ion-beam therapy

Ion-beam therapy can offer advantages over the standard radiotherapy with photons, especially for cancer treatments where organs at risk are in close proximity to the tumor to be treated. These advantages mainly result from the characteristic of delivering highly focused doses to the tumor. However, this potential can sometimes not be fully used in clinics, since the focused dose distribution is connected to a higher sensitivity to uncertainties. Uncertainties can, e.g., arise from anatomical changes—such as cavity fillings, weight loss or tumor regression—that might go unnoticed during the course of the therapy.
In this context, we consider ion-beam radiography a very promising transmission imaging modality, since it could detect and quantify these potential anatomical changes on a daily basis. The verification of therapy could be performed directly before each treatment fraction in the treatment room at low imaging doses of ~100 µGy per radiograph.
We have been investigating this imaging modality since 2015 using our unique and compact detection system [1] of six thin (~400 µm) silicon pixel Timepix detectors [2] for helium-beam radiography (αRAD). It contains a pair of trackers for measuring each helium-ion path in front and behind the imaged object.

An obstacle that remained until recently was that a 2D ion radiograph¬—a projection along the beam direction¬—could not provide the information whether an anatomical change was in the treatment beam path (i.e. of high relevance for the outcome of the therapy) or behind the tumor (irrelevant for the treatment accuracy).
In this contribution we report on our development of an experimental method that is capable of providing depth information of anatomical changes from 2D helium-beam radiographs. This method is referred to as 2.5D imaging in the following.

2.5D imaging, which was recently also suggested in a Monte Carlo study [4], is investigated in experiments where simple geometrical objects and complex anthropomorphic phantoms were imaged before and after inserting a geometrical change that mimics an internal anatomical change. By reconstructing helium-beam radiographs at many different depths inside the object and deploying suitable metrics for spatial resolution assessment, the depth at which the change appears the sharpest was identified. The difference between this measured and the actual depth at which internal changes were introduced was defined as the accuracy of the method. It was determined to be smaller than 11 mm in both studied phantom types. Such a depth accuracy is sufficient for evaluating whether a detected anatomical change is of relevance for the subsequent treatment (i.e. in the treatment beam path).

Moreover, in a second recent study the accuracy of radiological thickness was assessed by comparing the measured helium-beam radiographs to projections of dual-energy CTs that were acquired with a commercially available CT scanner using clinical protocols. Dual-energy CTs are currently considered as gold standard for measuring radiological thickness of complex human-like objects. The agreement between the two imaging modalities in terms of radiological thickness was better than 0.65 % (mean absolute percentage deviation) while the imaging dose of the helium-beam radiograph and the dual-energy CT was estimated to be 290 µGy and 23.8 mGy, respectively [3]. Figure 1 shows a comparison of the images obtained by αRAD and dual energy CT.

Overall, these promising results encourage next steps towards a clinical application in the future that are presented as outlook.

References:
1. Amato, C., M. Martisikova, and T. Gehrke, A technique for spatial resolution improvement in helium-beam radiography. Medical Physics, 2020. 47(5): p. 2212-2221.
2. Llopart, X., et al., Timepix, a 65k programmable pixel readout chip for arrival time, energy and/or photon counting measurements. Nucl. Instrum. Methods Phys. Res., 2007. 581: p. 485-485.
3. Metzner, M., et al., Accuracy of a helium-beam radiography system based on thin pixel detectors for an anthropomorphic head phantom. Medical Physics, 2025. n/a(n/a).
4. Volz, L., et al., Focus stacking single-event particle radiography for high spatial resolution images and 3D feature localization. Physics in Medicine & Biology, 2024. 69(2): p. 024001.

Speaker: Tim Gehrke (Heidelberg University Hospital, Radiation Oncology, Heidelberg, Germany)

Figure1_iWoRiD_2025_193.jpg

WET_veri_2d5radiography_TG_shorter.pptx

99 Carbon-ion radiotherapy monitoring by tracking of charged nuclear fragments: recent clinical results

Carbon-ion radiotherapy provides superior precision in targeting tumors, while significantly reducing the exposure of surrounding healthy tissue to radiation dose as compared to conventional X-ray radiotherapy. However, the same underlying principle increases the sensitivity of the dose distribution to variations of patient positioning and anatomical changes such as nasal cavity filling or tumor shrinkage. Such changes can result in overdosage of healthy tissue as well as underdosage in the tumor, thereby potentially compromising the treatment outcome.

To mitigate these risks, we are developing a novel, non-invasive in-vivo monitoring technique that uses charged nuclear fragments resulting from nuclear interactions of the carbon ions with the patient’s tissue. These fragments, which are a by-product of the treatment irradiation, are tracked by a self-developed detection system incorporating 28 Timepix3 silicon pixel detectors. By reconstructing and analyzing the spatial distributions of the fragments’ origins, we aim to identify anatomical changes of the patient between treatment sessions. This method is currently tested in the InViMo (In-Vivo Monitoring) clinical trial at the Heidelberg Ion Beam Therapy Center (HIT), focusing on patients with tumors in the skull base region. To facilitate detailed investigations of observed signals, patient specific Monte Carlo simulations of the monitoring method have been implemented.

This contribution demonstrates the clinical potential of the monitoring method on the example of the most recent patient cases from the InViMo clinical trial. Signals in fragment distributions are presented, which can be explained by anatomical changes visible in CT scans taken over the treatment course. These changes result in clinically relevant deviations of the delivered from the planned dose distribution, which can make a treatment-plan adaptation necessary. The signals observed in the measurement data are confirmed by Monte Carlo simulations, which are based on the patients’ CTs. These results represent a significant step toward optimizing carbon-ion radiotherapy by incorporating in-vivo monitoring, which could decrease dose deposition uncertainties and therefore permit dose escalation.

Speaker: Rebekka Kirchgässner (Department of Medical Physics in Radiation Oncology , German Cancer Research Centre DKFZ, Heidelberg, Germany)

2025Iworid.pptx

100 Carbon-ion radiotherapy monitoring with secondary ions: exploiting multi-angle projections for 3D reconstruction of inter-fractional changes

Introduction

Carbon-ion radiotherapy (CIRT) enables highly precise dose delivery through its highly localized dose deposition and enhanced biological effectiveness. However, current treatment guidelines generally do not include daily control imaging throughout the course of a multi-day therapy. As a result, anatomical changes that may occur between fractions cannot be considered due to the lack of reliable evidence for their presence. This introduces uncertainty regarding the anatomical state at the time of treatment and, consequently, reduces confidence in the accuracy of dose delivery. Our research focuses on in vivo monitoring during treatment by detecting secondary charged particles emitted during irradiation using our group’s custom detection system based on TimePix3 detectors. The goal is to reliably detect, localize, and 3D reconstruct inter-fractional anatomical changes, thereby reducing reliance on conventional imaging modalities such as computed tomography (CT), which involves additional radiation exposure for the patient.

Materials and Methods

To extract 3D localization information of potential anatomical changes, the presented method combines data from multiple projection angles into a unified 3D reconstruction. The low signal-to-noise ratio when comparing measurements from different treatment fractions presents a significant challenge to achieving the robustness required for clinical applicability. To address these challenges and ensure robustness in the presence of natural variations, our method combines information from projections in the spatial domain with insights gained through frequency domain analysis, specifically localized joint frequency band variations. In doing so, the method builds on our own detection and localization techniques while incorporating established principles of multi-perspective analysis in medical imaging, adapted to the characteristics of secondary particle data to enable robust and clinically meaningful detection of anatomical variations. These frequency-based features reflect local particle density changes between measurements, which serve as indicators of inter-fractional anatomical variation. Validation of the reconstruction approach was conducted through irradiation experiments at the Heidelberg Ion Beam Therapy Center (HIT). The experiments utilized homogeneous Polymethyl Methacrylate (PMMA) head phantoms containing coin-sized air cavities at varying depths, providing a controlled environment for detailed qualitative and quantitative assessment of the method.

Results

The modularity and flexibility of the proposed framework for localization and detection of changes within the patient were demonstrated by extending it with a multi-perspective analysis step. This extension aggregates multiple point cloud projections to enhance the detection and localization of inter-fractional anatomical changes in three dimensions. The 3D spatial change information obtained through this approach enables more accurate assessment of both the location and extent of anatomical variations. The accuracy of the 3D reconstruction was validated by comparing the estimated change locations with ground truth renderings of the experimental setups, demonstrating a high degree of spatial congruence and a mean centroid loss of <5mm over the test sets.

Conclusion

The results demonstrate that the information carried by secondary ions can be effectively harnessed for in vivo monitoring and has not yet been fully utilized in current clinical practice. When mapped to planning CT images, the resulting 3D reconstructions provide valuable spatial cues. These can support clinical decision-making by offering insights into anatomical changes occurring over the course of a treatment delivered in fractions across multiple consecutive days.

The authors acknowledge funding by Helmholtz Information & Data Science School for Health (HIDSS4Health).

Speaker: Mr Patrice Schlegel (Department of Medical Physics in Radiation Oncology , German Cancer Research Centre DKFZ, Heidelberg, Germany)

10:30 Coffee Break

Medical Applications: Session 9

Convener: Joaquim Marques Ferreira Dos Santos (Universidade de Coimbra (PT))

101 SiC Minipix Timepix3 Detectors for Radiation Research in Particle Therapy

Silicon carbide (SiC) detectors have become essential in advancing dosimetry for high-energy and high-dose rate radiotherapy. Achieving accurate dose tracking under high-dose-rate requires dosimeters that can withstand challenging environments and provide reliable measurements. Conventional silicon detectors, although sensitive, often experience degradation under such conditions due to radiation damage and thermal and dose-rate dependencies, affecting their long-term accuracy and stability. In contrast, SiC detectors demonstrate resilience under radiation, minimal leakage current, and thermal stability due to their wide bandgap, high radiation hardness, and low sensitivity to environmental fluctuations. The Timepix3 with SiC sensors [1,2] is a high-resolution radiation detection camera capable of real-time beam monitoring and particle tracking. SiC-based detectors are a strong candidate for precise, stable measurements in complex radiation environments, thus supporting the reliable dose delivery essential for modern radiotherapy applications. This study aims to characterize radiation fields in terms of beam structure, particle tracking, and flux using a novel SiC pixelated detector. Moreover, this work provides methodologies for measuring radiation quality in both primary and mixed radiation fields of various beams including protons, carbon ions, electrons and other particles.
The detector is built with an active 65 μm-thick SiC sensor, bump-bonded to a Timepix3 ASIC chip. This combination functions as a pixelated radiation-sensitive volume, enabling spatially resolved measurements and detailed particle tracking. The detector operates under a bias voltage of +200 V and supports per-pixel energy calibration, enabling the measurement of individual particle interactions within its pixel matrix. Each pixel measures 55 × 55 μm, allowing for high-resolution tracking of particle paths and energy deposition. The full field-of-view (4π) and advanced per-pixel electronics facilitate the detection of various radiation types, including protons, carbon ions, electrons and even fast neutrons. The SiC Timepix3 can be used for neutron detection in wide-energy range with higher selectivity as compared with silicon sensor.
The detector’s compact build and ease of integration with data processing systems make it well-suited for real-time dosimetry and radiation imaging, supporting precise tracking and dose distribution measurements.
An experiment was carried out at MedAustron. It is a medical facility for proton and carbon ion therapy, where high-energy particle beams are used for both treatment and research purposes. The experimental setup at MedAustron allows for precise control over beam parameters, with protons accelerated to energies between 62 and 250 MeV and carbon ions up to 402 MeV/u. The facility supports high particle fluxes, reaching up to 109 particles/cm²/s in clinical mode. A reduced current mode is also available for proton beams, yielding approximately 105 particles/cm²/s for detailed measurements without excessive particle overlap.
In these experiments, the Minipix Timepix3 SiC detector was placed above the beam isocenter, where single-energy pencil beams were directed at the detector to capture particle interactions. This setup enabled the collection of high-quality data with minimal background interference, allowing the evaluation of the detector’s response for both proton and carbon ion beams.

The Minipix Timepix3 SiC detector was used to provide single particle tracking of carbon and proton beams. In Figure 2 shows particle visualization and energy spectrum of 120 MeV carbon beam. The results demonstrate the potential of the Minipix Timepix3 SiC as a new detector sensor material for quality assurance and beam characterization in various accelerators.

References
[1] Novak, A., Granja, C., Sagatova, A., Jakubek, J., Zatko, B., Vondracek, V., Andrlik, M., Zach, V., Polansky, S., Rathi, A., & Oancea, C. (2023). Silicon Carbide Timepix3 detector for quantum-imaging detection and spectral tracking of charged particles in wide range of energy and field-of-view. Journal of Instrumentation, 18(11), C11004. https://doi.org/10.1088/1748-0221/18/11/C11004

[2] Granja, C., Barber, C., Barna, S., Chancellor, J., Chvatil, D., Grevillot, L., Inzalaco, D., Jakubek, J., Kohout, Z., Magrin, G., Marek, L., Mihai, R., Oancea, C., Olsansky, V., Olsen, T., Poklop, D., Pospisil, S., Resch, A., Sagatova, A., … Zatko, B. (2024). Detection resolving power of SiC Timepix3 detector to electrons, neutrons, ions and protons. Journal of Instrumentation, 19(11), C11007. https://doi.org/10.1088/1748-0221/19/11/C11007

Speaker: Cristina Oancea

ABSTRACT IWORID.docx

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IWORID_Bratislava_Oancea_Final.pdf

IWORID_Bratislava_Oancea_Final.pptx

102 Imaging and tracking of clinical proton beam delivery with miniaturized stack telescope Timepix3: Feasibility study of Quality Assurance for Medical Proton Therapy

In current particle radiotherapy practice, it is necessary to evaluate and monitor the beam delivery for the purposes of quality assurance [1]. The current approach at PTC utilizes a scintillator detector (IBA Lynx PT) for determining the accuracy of beam delivery. This detector, while being heavy and large, requires individual dedicated measurements. Additionally, it has a restricted surface area of 30x30 cm, while the nozzle’s maximum field size is 30x40 cm. An alternative that could measure the maximum field size, be permanently measuring and mounted on the nozzle would represent a significant improvement. We make use of a concept exploiting scattered beam particles detected with a compact stack telescope of Timepix3 detectors. This alternative could potentially be also used for higher than conventional dose rates (ultra-high dose rate or FLASH dose rate). In this study, we evaluate the feasibility of this approach.
Protons in the delivered beam scatter along the beam path, particularly at the accelerator nozzle window and, to a lesser extent, in the air along the beam path. We measure in detail these scattered protons at a position beyond the isocenter and away from the beam axis (see Figure 1). For testing and evaluation purposes, a scattering foil (100 μm thick plastic) is placed along the beam axis between the accelerator vacuum nozzle and the isocenter. We use a miniaturized stack pixel telescope MiniPIX-Timepix3 which directionally maps energetic charged particles in a wide (60%) field of view with enhanced discrimination and high angular resolution [2].
This non-invasive approach [3, 4] is applied to track and visualize the beam from a position outside the field, several meters away. Protons reaching the pixel telescope are registered with fast timing (< 100 ns) and resolved with enhanced discrimination thanks to high-resolution spectral-sensitive particle tracking. The trajectories of individual protons are determined as 3D directional vectors with subpixel resolution (≈ μm) and high angular resolution (sub-degree) [2]. The vertex map, indicating the origin of the registered protons, can be obtained as a backplane projected image at specific positions along the beam, as shown in Figure 2. The back-projection plane corresponds to the scattering foil position at 194 cm from the detector (Figure 1). The image visualizes the beam along its path in a wide field of view.
The data shown corresponds to 7 minutes of measured time, collected with a therapeutic beam of clinical intensity. Various beam-target-detector geometries and delivered dose plans were investigated. The results and projected scattering planes produced can be used to examine treatment plans and potentially also for studies of beam quality. Information can be extracted on the intensity and positioning of the beam with this non-invasive approach.
The ultimate goal is to correlate these measurements with a dosimetric quantity, or a substitute closely correlated with it. Although this approach still requires further rigorous measurements and testing under clinical conditions, the results suggest that our objective is achievable.

Speaker: Samuel Kurucz (Proton Therapy Center)

iworid2025.pdf

103 Spatial resolution characteristics of a clinical Photon-Counting Computed Tomography scanner

Introduction
Computed Tomography (CT) is an integral part of contemporary medicine. Conventional CT scanners are equipped with Energy Integrating Detectors (EID), which are based on indirect conversion of the incoming photons into electric signal for the image generation. EID-based CT shows limitations regarding tissue contrast and spatial resolution. A turning point of the actual CT technology is reached by Photon-Counting CT (PCCT), which embodies Photon-Counting detectors (PCDs) in substitution of EIDs. PCDs are characterized by a semiconductor layer, usually cadmium telluride (CdTe) or cadmium zinc telluride (CZT), where x-ray photons are absorbed, generating electron-hole pairs that are collected by pixelated anodes. The resulting signal is proportional to the absorbed photon energy and a reading logic based on a calibrated threshold permits to distinguish and count detected photons. The final pixel value reflect the number of detected photons and the use of multiple thresholds permits also to recover information related to the energy of such photons. By means of dedicated software, this allows the generation of virtual monocromatic images, at all the energies of the incident X-ray spectrum.
State-of-the-art clinical applications of PCCT regard cardiovascular exams, thoracic and lung imaging, and neuroimaging [1].
In this work, we characterized the first clinical PCCT in terms of spatial resolution performances. The scanner is the Naeotom Alpha® (Siemens Healthineers equipped with CdTe PCDs

Materials and methods
Image quality was assessed by investigating spatial resolution properties of the PCCT scanner. We measured the high-contrast pre-sampled Modulation Transfer Function (MTF) that quantifies the system response to an impulsive input in the transformed Fourier domain, bearing information regarding the signal transfer across the spatial domain [2]. We acquired a tungsten wire (purity of 99.95%) with a diameter of 12.5 μm. The wire was located both at the isocenter of the CT gantry and at lateral positions (4 cm horizontally and 5 cm vertically) in the axial plane (Fig. 1). Images were acquired using Inner Ear clinical protocol, at 140 kV and 80 mAs (these parameters were chosen based on routine clinical practice). Images were acquired with helical scans with pitch of 0.85.To obtain the pre-sampled MTF, the wire was positioned slightly angled in the coronal plane (approximatively 2-3°). Acquisitions were made both at conventional (144x0.4mm) and at ultra-high resolution (120x0.2mm) mode, resulting in different reconstructed slice thicknesses. 0.4 mm - slice images are 640x640 matrix with a pixel size of 0.3125 mm, while 0.2 mm - slice images are 1024x1024 matrix with pixel size of 0.1953 mm. We reconstructed the final images using multiple kernels, chosen among those available for standard and high-resolution inner ear exams (Hr72, Hr80, Hr98, and Hv89). In detail, Hr72, Hr80, and Hr98 are kernels used for head exams, while Hv89 is used for vascular protocols. Increasing the kernel index means improving spatial resolution but also increasing image noise [3].

Results
Spatial resolution depends on the reconstruction kernel and the position of the test object within the gantry in the axial plane. Spatial resolution is quantified by means of the spatial frequencies f50% and f10%, corresponding to 50% and 10% values of MTF maxima. Figg. 2,3,4 show MTF curves for the three positions of the tungsten wire. Results for f50% and f10% are also collected in Tab. 1.
Standard reconstruction kernels with higher index (Hr80 and Hr98) show higher MTF parameters, as expected. MTF curves and parameters calculated for the displacement in x and y direction differ from those found at isocenter. This could be attributed to the x-y length of the focal spot of the system as well as to the reduced sampling for peripheral portion of the FOV.

Conclusions
This work aimed to provide a characterization of the spatial resolution of a PCCT scanner used in clinical practice. First results show that iterative reconstruction kernels impact axial-plane resolution, imparting non-isotropic 3D resolution characteristics.
In addition, MTF curves vary across the radial (x-y) directions in the axial plane. Further investigation will involve an improved experimental setup and more acquisition of the tungsten wire at added locations in the scanner gantry, also to characterize longitudinal and azimuthal spatial resolution of the CT system.

References

[1] M. Tortora, L. Gemini, I. D’Iglio, L. Ugga, G. Spadarella, and R. Cuocolo, ‘Spectral Photon-Counting Computed Tomography: A Review on Technical Principles and Clinical Applications’, J. Imaging, vol. 8, no. 4, p. 112, Apr. 2022, doi: 10.3390/jimaging8040112.

[2] H. Fujita et al., "A simple method for determining the modulation transfer function in digital radiography," IEEE Trans. Med. Imaging, vol. 11, no. 1, pp. 34-39, 1992, doi: 10.1109/42.126908.
[3] H. Onishi et al., "Photon-counting CT: technical features and clinical impact on abdominal imaging," Abdom. Radiol., vol. 49, no. 12, pp. 4383-4399, 2024, doi: 10.1007/s00261-024-04414-5.

Speaker: Francesca Saveria Maddaloni (Università degli Studi di Milano, Dip. di Fisica 'Aldo Pontremoli, Milan (Italy))

abstract_figures_IWORID_2025.pdf

IWORID_PRESENTATION_Maddaloni.pdf

104 Innovative Light Detection System for Rapid 3D Radiation Dose Monitoring

Innovative Light Detection System for Rapid 3D Radiation Dose Monitoring

B. Mindur on behalf of Dose3D Future, AGH University of Krakow, Poland

Introduction

According to the World Health Organization (WHO), cancer remains one of the leading causes of death worldwide. Radiotherapy is often the primary or sole therapeutic approach used in treatment. Ensuring that each patient receives fast, efficient, and safe treatment is essential. To address this need, our team has developed a scalable detection system that utilizes 3D-printed plastic scintillators as active elements for evaluating the therapeutic dose distribution in spatially reconfigurable detectors (phantoms). Such a phantom could be used to cross-check and validate the simulation results during the preparation of photon radiotherapy treatment plans. The system’s reconfigurability allows for adaptation of the phantom’s geometry. Thanks to 3D printing, individual scintillation voxels can be connected in nearly any configuration, enabling a customized measurement setup tailored to specific requirements. The phantom is designed to replicate the affected tissue area and its surroundings, ensuring precise dosimetric assessment. Each scintillator is connected to the readout electronics via an optical fiber, allowing the generated photons to be transmitted outside the phantom’s active region. The system’s hardware has been designed with modularity and scalability, making it suitable for both small- and large-scale detection systems across various applications.

Key Features of the System

From a hardware perspective, the system's modularity is evident in its fundamental building blocks, referred to as slices. A single slice comprises a set of printed circuit boards (PCBs) and components connected, capable of reading out visible light from 64 channels. Each slice consists of a baseboard (BB), a front-end board (FEB) with a Maroc-3A application-specific integrated circuit (ASIC), a high-voltage power supply board (HVB), a calibration board (CALB), and a multichannel photomultiplier tube (PMT). Additionally, a timing board (TIMEB) ensures system-wide time synchronization.
The BB serves as the central hub for data communication and signal interconnection between the FEB, the programming and debugging interface, a Gigabit Ethernet interface for PC communication, and power distribution. It also hosts the Mars-3A mini module, which is equipped with an AMD Artix 7 field-programmable gate array (FPGA). The compact FEB has been designed to interface the ASIC and the PMT assembly with the FPGA module, HV power supply board, and the CALB. The Maroc-3A ASIC processes and measures signals from the multichannel PMT, providing event detection and charge measurement capabilities. For this project, the Hamamatsu H7546B 64-channel PMT was selected due to its sensitivity to visible light, with peak sensitivity around 420 nm, closely matching the scintillator’s emission spectrum.

Due to space constraints on the FEB, the HVB was designed as a separate PCB, providing isolation between the high-voltage unit and the rest of the system. This modular design also enables the independent replacement of faulty components, significantly reducing maintenance and repair costs. The CALB is responsible for providing precise calibration signals to the Maroc-3A ASIC and includes monitoring headers and pins for extended diagnostics. All boards—BB, FEB, HVB, and CALB—are stacked together to form a single slice, also providing mechanical support for the 3D-printed PMT handler components and the PMT itself.
The TIMEB ensures synchronization across the system by generating a reference clock and reset signals for all slices. A 19-inch crate serves as a key component of the data acquisition (DAQ) infrastructure, designed to house up to eight slices along with the TIMEB in a well-organized manner. The DAQ system can be easily expanded by adding more slices to additional crates, thereby increasing the number of available readout channels.

Results

Key hardware parameters of the system, such as trigger threshold linearity, analog signal amplification gain and offset, and timing characteristics, have been measured, providing detailed insights into critical system performance. These evaluations include electronic tests using a pulse generator as well as laser light pulses to simulate realistic operational conditions. Laser pulse testing enables a detailed characterization of the PMT’s optical properties, including spectral response and optical crosstalk, both of which play a significant role in test-beam measurements. A dedicated analysis confirms that the PMT’s individual channel response remains highly uniform across the photocathode surface, with only minor fluctuations of approximately 5%. Tests using plastic scintillators have also been conducted. Amplitude spectra obtained from these tests confirm that the system is capable of detecting single-photoelectron signals generated by weak scintillation light.

With a fully functional detection system and a set of dedicated phantoms, a series of carefully planned test measurements have been performed. Test-beam sessions have been conducted at the Maria Sklodowska-Curie National Research Institute of Oncology in Kraków. The treatment center is equipped with a Varian TrueBeam flat-field X-ray generator, which was used in all test-beam campaigns to validate the system’s performance under realistic irradiation conditions using an actual therapeutic photon beam. Preliminary results of reconstructed dose values compared to the treatment calibration dose profiles are very promising.

Conference Presentation

At the conference, we will present the complete prototype system, including dedicated hardware, firmware, and software, as well as a set of configurable phantoms made from tissue-equivalent, 3D-printed plastic scintillator cubes. Key design features, such as system modularity, scalability, and potential applications, will be highlighted. Additionally, we will demonstrate the flexibility of the phantom, which can be customized into nearly any arbitrary 3D arrangement, and share results from test-beam campaigns conducted using a clinical linear accelerator at a cancer treatment facility. Preliminary results of actual dose reconstruction compared to the treatment calibration dose profiles will also be presented, along with details of measurement procedures. Our presentation will focus on recent results that have not been previously shared.

References

[1] B. Mindur, et al., System for radiation dose distribution monitoring in radiotherapy treatment planning, Nuclear Instruments and Methods in Physics A 1069 (2024) 169834.
[2] https://dose3d-future.fis.agh.edu.pl/

Speaker: Bartosz Mindur (AGH University of Krakow (PL))

2025-07-09_12-00_Mindur_Bartosz_Dose3DFuture.pdf

2025-07_IWORID_summary_BM.pdf

105 Validation of a µCT system simulation with a small-pixel photon-counting spectral detector

Photon-counting spectral detectors (PCD) have significantly advanced CT imaging by reducing image noise, enhancing contrast and spatial resolution, and enabling spectral imaging [1]. These benefits have extended to µCT imaging, where small-pixel (<100 µm) PCDs have allowed material-specific quantitative imaging at high spatial resolution [2]. Similarly, phase-contrast x-ray imaging (XPCI) has proven to be an important technique in laboratory µCT setups for the visualization of low-contrast structures [3]. These experimental advances create a demand for a new simulation tool that incorporates and accurately models the photon-counting detector spectral response and phase effects.
We present PEPIsim (https://baltig.infn.it/coathup/PEPIsim), a new and freely available simulation software written in Matlab. PEPIsim simulates the µCT imaging system available at the INFN’s PEPI Lab [4], producing quantitatively accurate µCT images through the use of a validated detector model [5]. Propagation-based phase-contrast x-ray imaging (PBI) effects have also been included, expanding its utility to low Z materials such as soft tissues. This allows for a complete optimization of the phase-contrast, spectral x-ray µCT acquisitions performed at the PEPI Lab.
PEPIsim simulates the complete µCT imaging pipeline, from x-ray spectrum generation and detector response to projection image creation and the final CT reconstruction. A GUI allows users to configure a variety of experimentally relevant parameters involved in the simulation process including the imaging setup geometry, the x-ray tube settings, the detector characteristics, the object definition, and the reconstruction parameters, enabling highly customizable simulations.
PEPIsim has been experimentally validated using the photon-counting spectral µCT setup at the PEPI Lab, featuring a microfocus x-ray tube with a tungsten anode (source size: 5–30 µm) and a Pixirad-PixieIII detector [6] (650 µm thick CdTe sensor, 62 µm pixel size, 512×402 matrix, two thresholds per pixel, charge-sharing correction). Validation experiments were performed using a PMMA phantom (8 mm diameter) containing four material inserts (PE, PTFE, PVC, PEEK) each with a 2 mm diameter. Simulated and experimentally acquired images were compared across three key acquisition parameters: tube voltage (45 – 100 kVp), source-to-detector distance (40 – 133 cm), and magnification (1.35 – 3.74 x).
Quantitative evaluation included attenuation coefficient accuracy, signal-to-noise ratio (SNR) in attenuation images, SNR in phase images, and the PBI-induced edge enhancement fringe visibility. Results demonstrated excellent agreement between simulated and experimental data, with attenuation values showing an average relative error below 2% and phase-contrast fringe visibility reproducing experimental measurements within 6% accuracy across the five tube voltage settings that were tested. The attenuation SNR and phase SNR had relative errors of 6.4% and 3.7% respectively across the five tube voltage settings. An example of a CT reconstruction of the PMMA phantom along with the PEPIsim simulated CT reconstruction of the same phantom are included in Figure 1. The phase-retrieved images of each of the attenuation images are also included.
The imaging system spectral response, including the combination of PCD response and the filtered x-ray tube spectrum was also validated by means of a detector threshold scan. The photon counts in both an experimental flatfield image and a simulated flatfield image were counted over a range of detector threshold settings, ranging from 10 keV up to the x-ray tube kVp in steps of 2 keV. This was repeated for seven different tube voltage settings ranging from 40 kVp to 100 kVp in steps of 10 kVp. Figure 2 shows the results of the detector threshold scan. There is good correspondence between the simulated and experimental images at all tested tube voltage settings. There was an average normalized root mean square error of 0.6% between simulated and experimental threshold scans averaged across all tested detector thresholds.
A key application of PEPIsim the optimization of acquisition parameters for diverse µCT samples. Its flexibility supports the development of tailored imaging protocols based on sample material and geometry, paving the way for improved experimental design and image quality. Furthermore, while PEPIsim has been developed to simulate the current imaging setup at the PEPI Lab, its modularity allows for different detectors to be incorporated as well, provided that their spectral response is known.

References
[1] Flohr, T., et al. "Photon-counting CT review." Physica Medica 79 (2020): 126-136.
[2] Di Trapani, V., Brombal, L., and Brun, F. "Multi-material spectral photon-counting micro-CT with minimum residual decomposition and self-supervised deep denoising." Optics Express 30.24 (2022): 42995-43011.
[3] Kiarash, T., et al. "3D virtual histopathology by phase-contrast X-ray micro-CT for follicular thyroid neoplasms." IEEE Transactions on Medical Imaging (2024).
[4] Brombal, L., et al. "Pepi lab: a flexible compact multi-modal setup for x-ray phase-contrast and spectral imaging." Scientific Reports 13.1 (2023): 4206.
[5] Brombal, L., et al. "A Geant4 tool for edge-illumination X-ray phase-contrast imaging." Journal of Instrumentation 17.01 (2022): C01043.
[6] Bellazzini, R., et al. "PIXIE III: a very large area photon-counting CMOS pixel ASIC for sharp X-ray spectral imaging." Journal of Instrumentation 10.01 (2015): C01032.

Speaker: Andrew Coathup (INFN Trieste, University of Trieste)

Coathup_iworid2025_ppt_GOOD.pdf

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12:40 Lunch break Lunch 13.00

Applications: Session 9

Convener: Bernd Schmitt

106 Composition and Spectral Characterization of Space Radiation in LEO Orbit onboard JoeySat Satellite with MiniPix-Timepix3

Knowledge and measurements of the space radiation field in outer space are valuable for science and applied research (space weather, earth-solar physics) as well as satellite industry engineering and spacecraft operations. Radiation effects on spacecraft components and electronics [1] are becoming increasingly sensitive to the varying characteristics and large gradients of the harsh space radiation field in space. Measurements of the complex and highly dynamic mixed-radiation field in space require particle-type discrimination and wide-dynamic range response of radiation field intensity, particle energy distributions, directionality, spatial (satellite orbit location) and time. For this purpose, the semiconductor pixel detector Timepix3 has been deployed in LEO orbit onboard OneWeb JoeySat (launched May 2023, 600-1200 km polar orbit). Timepix3 provides detailed wide-range data on the complex space radiation field in the satellite environment. Payload implementation with miniaturized COTS electronics [2] of low mass and reduced power consumption provides deployment advantages and reduced cost. The MiniPix-TPX3 Space (Fig. 1 - see summary material attached) is operated and readout to the satellite SOCAN bus interface by a customized control and readout computer. Intended for operation in high intensity radiation environment, the detector is behind a 5 mm thick aluminum shield the intense plasma and EV field and suppress the low-energy radiations (electrons below ≈ 1 MeV, protons below ≈ 30 MeV, low-energy X rays below ≈ 10 keV). The radiation field is measured continuously and registered at selected intervals (ranging from ms up to 25 sec) overall nearly every minute. The total raw data rate is up to 24 MB/day which is downlinked to ground to be processed offline.
The registered radiation is processed and analyzed along the satellite orbit with particle-type resolving power [3-5]. Total and partial particle fluxes (Fig. 2 - - see summary material attached) and dose rates are accurately produced in wide range of radiation field intensity. Detailed time-stamped data (Fig. 2a,b) are produced for further physics analysis. In the data shown, the large spikes observed on the first hours correspond to the satellite crossings of the polar horns. Distinct variations are observed according to particle type with specific correlation to orbit and time. The proton component is closely correlated to the storm onset period. Other components – electrons, low-energy gamma rays and X rays (not shown) – exhibit partly overlapping and also distinct orbit-time dependance. Corresponding results are produced for particle dose rates (total, partial), deposited energy distributions, linear-energy-transfer (LET) spectra and directional fluxes. The derived data products are evaluated also along the satellite orbit. Fig. 2c,d shows results of particle flux (all particles) over several day periods prior and after a geomagnetic storm. The evaluated quantity (particle flux, all particles) spans many, nearly 6, orders of magnitude. Systematic and extensive results including post-processing physics evaluation will be presented over the satellite varying orbit (600 km, 1200 km, transfer intervals) and periods of solar-geomagnetic activity.
Acknowledgments
The JoeySat satellite has been developed under the Sunrise Partnership Project between ESA and telecommunications operator OneWeb, with support from the UK Space Agency. The Timepix3-MPX payload was procured and deployed by OneWeb contract.
References
[1] V. U. J. Nwankwo, N. N. Jibiri, and M. T. Kio, The Impact of Space Radiation Environment on Satellites Operation in Near-Earth Space, Satellites Missions and Technologies for Geosciences. book (2020)
[2] C. Granja, J. Jakubek, et. al., MiniPIX Timepix3 — a miniaturized radiation camera with onboard data processing for online characterization of wide-intensity mixed-radiation fields, JINST 17 (2022) C03019
[3] C. Granja, J. Jakubek, et al., Resolving power of pixel detector Timepix for wide-range electron, proton and ion detection, Nuclear Instr. Methods A 908 (2018) 60-71
[4] C. Granja, A. Owens, S. Pospisil, et al., The SATRAM Timepix spacecraft payload in open space on board the Proba-V satellite for wide range radiation monitoring in LEO orbit, Planetary and Space Science 125 (2016) 114-129.
[5] Gohl S., Bergmann B., Granja C., et al., Measurement of particle directions in low eath orbit with Timepix, JINST 11 (2016) C11023

Speaker: Carlos Granja (ADVACAM)

iworid2025_ABS_OneWeb_TPX3_CG.pdf

107 Demonstration of radiation source localization in a narrow space using multiple robots equipped with Compton cameras

In the decommissioning of the Fukushima Daiichi Nuclear Power Station (FDNPS), understanding the distribution of radiation sources and identifying radioactive hotspots—areas with localized high concentrations of radiation sources—is crucial for developing a detailed decontamination plan and minimizing worker exposure. To address this, we are developing a system and method for remotely locating radiation sources while reducing worker exposure by integrating a Compton camera, a type of gamma-ray imager, with a robot.
　In environments with multiple corridors and rooms, such as the buildings of FDNPS, surveying the entire area with multiple robotic systems is more efficient than using a single robot. Based on this consideration, we are conducting demonstration tests using multiple robots equipped with Compton cameras to locate radiation sources in narrow corridors.
　One challenge of using gamma-ray imagers, including Compton cameras, is that the visualized radiation source image lacks depth information. For example, if a radiation source appears projected on a wall, it is difficult to determine whether the source is in front of or behind the wall. A potential solution to this issue is to take measurements from multiple viewpoints, including different angles around walls, to determine the three-dimensional (3D) location of the radiation source. In fact, previous studies have reported methods for using Compton cameras from multiple viewpoints to achieve 3D localization of radiation sources [1].
　However, in many cases, measuring the target area from multiple viewpoints is not feasible within the buildings of FDNPS due to the presence of narrow corridors and other obstacles. Consequently, it may be necessary to determine whether a radiation source is in front of or behind a wall using measurements taken from only one direction with a Compton camera. To address this issue, Sato, one of the authors, has previously succeeded in determining the position of a radiation source—specifically, the distance between the Compton camera and the source—using measurements from a single direction [2].
　Building on this work, we conducted a demonstration test using two robots equipped with Compton cameras to visualize and locate radiation sources in narrow corridors. We intentionally created a scenario in which a single robotic system would incorrectly determine the exact location of the radiation source. To mitigate this, a second robotic system was deployed to accurately locate the source using measurements taken from only one direction.
　At the international workshop IWORID 2025, we will present the results of several demonstration tests, including the one described above.

[1] Sato, Y., Terasaka, Y., Ozawa, S. et al. Development of compact Compton camera for 3D image reconstruction of radioactive contamination, JINST 12, C11007 (2017).
[2] Sato, Y., Identification of depth location of a radiation source by measurement from only one direction using a Compton camera, Appl. Radiat. Isot. 195, 110739 (2023).

Speaker: Dr Yuki Sato (Japan Atomic Energy Agency)

108 Characterization of a LINAC-based Inverse Compton Scattering Source using a color X-ray camera

Recently, a novel design for an X-ray source based on Inverse Compton Scattering (ICS) has produced first light. Based on a linear X-band accelerator, the interaction of the electron bunch with an energy up to 25 MeV and the infrared laser pulse produced pulses of X-rays with a relatively small spectral bandwidth. The linear design is particularly useful to tune the X-ray energy, enabling methods such as K-edge imaging.
Due to the fundamental mechanism behind ICS, the spectrum of the X-ray beam exhibits a specific spatial dependency. Indeed, the spectrum is concentric, with the highest energy along the optical axis and decreasing energy further away from this axis. To investigate this behavior and characterize this novel source, the color X-ray camera or SLcam [1] has been used, directly imaging the spatial dependency of the spectrum. Figure 1 presents an illustrative RGB image, with the red channel representing 13-14 keV, green 14-15 keV and blue 15-16 keV.

In this work, we present the results of several experiments characterizing the X-ray beam as a function of a set of parameters and detail the data analysis required to visualize the results.

Speaker: Matthieu Boone

20250708 - MNB - iWoRID SmartLight.pdf

20250708 - MNB - iWoRID SmartLight.pptx

smartlight spatio-spectral.png

109 The Compact Electron Proton Spectrometer - Space Weather Nowcasting with a CdTe Timepix2 Based Instrument

Space weather poses significant hazards for space travelers beyond low Earth orbit, particularly during large solar energetic particle events (SEPs), which can result in acute radiation exposures, especially during lightly shielded activities such as extravehicular activities (EVAs).

There has been great progress in recent years in the development of ‘nowcasting’ models that provide early warning of space weather events after they have started at the sun and predictions of peak fluxes based primarily on measurements of energetic electrons for early warning and energetic protons for flux and dose prediction. However current instrumentation to support this is large and primarily based on satellites. As exploration expands beyond initial lunar missions and existing instrumentation situated along the Sun-Earth line, it becomes increasingly important for crew to carry these detection and forecasting capabilities with them. Thus there is a need for a highly reliable compact instrument aimed at the measurement of electron and proton fluxes in the energy ranges relevant to solar energetic particle events.

Following an initial selection process, we chose the Timepix2 ASIC coupled with a 1 mm CdTe sensor. This decision builds upon our heritage with Timepix-based instrumentation developed for numerous human and scientific spaceflight missions, including the International Space Station, Artemis I–III, Polaris Dawn, Fram2, Biosentinel, LEIA, Astrobotic Peregrine, and Beresheet II.

We discuss the rationale behind selecting Timepix2, emphasizing its capability to provide track-like data at exceptionally high particle fluxes characteristic of Carrington-class storms. The pixelated ASIC offers exceptional electron-proton separation capability, and the high stopping power of the CdTe sensor further enhances both particle discrimination and electron spectroscopy. All these capabilities have been demonstrated through beamline testing, which is detailed herein.

Subsequently the system with significant funding from the NASA Development of Lunar Instrumentation Program and the Mars Campaign Office Radworks program has been developed into a compact high reliability prototype. We also discuss some of the unique challenges in incorporating this technology into a very high reliability system especially with regards to very limited radiation tolerant processing and data rate capability.

Finally we discuss future developments of this system including possible spaceflight demonstrations and future applications of this technology.

Speaker: Stuart Patrick George (NASA Johnson Space Center)

IWORID_2025.pdf

110 Invitation for the IWORID2026

Speaker: Matthieu Boone

galadinner.pdf

galadinner.pptx

iWoRID 2026 invitation - updated.pdf

15:40 Coffee Break

Poster: Session 2

Convener: Andrea Sagatova (Slovak University of Technology in Bratislava)

111 X-ray Spectrum Estimation Using a Combined Deterministic-Stochastic Approach in Dual-Material Phantoms

X-ray spectrum estimation is essential for dose calculation, image quality optimization, and material decomposition in diagnostic radiology. This study implements and evaluates an X-ray spectrum estimation method based on the Birch-Marshall model with three advanced scatter correction techniques. Using a dual-material step wedge phantom composed of acrylic (0-60 mm) and aluminum (0-6 mm), we generated realistic projection images with a tungsten-target X-ray tube across clinical diagnostic energy ranges (40-140 kVp) and a CsI detector model, incorporating Monte Carlo-simulated scatter and quantum noise. We then estimated the spectrum using the Birch-Marshall model combined with different scatter correction methods: Scatter Kernel Superposition Method (SKSM), Statistical Photon Transport Simulation (SPTS), and a proposed Combined Deterministic-Stochastic Approach (CDSA). Performance was evaluated using mean squared error (MSE), normalized root mean squared error (NRMSE), half-value layer (HVL), and mean energy metrics. The CDSA method demonstrated superior performance with 96.34% MSE improvement compared to uncorrected data, followed by SPTS (93.87%) and SKSM (68.25%). Mean energy estimations with CDSA and SPTS (both 40.8 keV) closely matched the reference spectrum (41.2 keV), while SKSM and uncorrected estimates produced identical values of 38.6 keV. Characteristic radiation peaks at tungsten K-shell energies (59.32 keV) were accurately reproduced by CDSA and SPTS methods. These results demonstrate that appropriate scatter correction is crucial for accurate X-ray spectrum estimation, with the proposed CDSA method providing optimal balance between computational efficiency and estimation accuracy.

Speaker: Prof. Hyemi Kim (Department of Radiological Science, Jeonju University)

MJ_iWoiRid2025_abstract.docx

112 Investigating heavy ion radiation damage in Timepix3 detectors for applications in ion-beam therapy

Due to their ability to track single particles and measure energy deposition,Timepix detectors are successfully used for various research projects in particle therapy. Examples include the helium-beam radiography project or the estimation of LET spectra for ion radiation fields at the German Cancer Research Center (DKFZ) and the Heidelberg Ion-Beam Therapy Center (HIT) in Heidelberg, Germany. Some of these projects are advancing towards clinical applications. Using Timepix detectors in clinics requires a stable and reliable performance over a long time. After multiple exposures to ion radiation, an unexpected pattern of cluster shapes was observed in Timepix3 data at DKFZ.In this context, potential radiation damage due to ions was investigated. Since different kinds of ions were used for the experiments especially the comparison between protons and oxygen ions was of interest.

To investigate the radiation damage in clinical ion beams, two Timepix3 detectors were irradiated in a stepwise manner, one with oxygen ions and one with protons at HIT in Germany. After each step, a control measurement with helium ions at moderate fluence rates of 10^4 to 10^5 ions per second per active area was taken. Due to a saturation effect in Timepix3 at high LET events, these measurements were done with a partially depleted sensor. To test the radiation damage in the sensor, cluster size and the cluster energy from the control measurement with helium ions were investigated after each step of the high-intensity irradiation with protons and oxygen ions.

Two counteracting effects make it challenging to derive accurate and precise quantitative statements about the sensor’s response. Hadronic radiation is known to produce defects in the crystalline structure of the sensor, which can lead to charge trapping reducing the collected charge. On the other hand, radiation damage can lead to an extension of the depletion depth in the sensor. However, for the time being, it is our understanding that none of the original unexpected patterns seem to be related to radiation damage. Nevertheless, radiation damage could alter the detector’s response. Therefore, when using a Timepix3 detector in future experiments with ion beams care has to been taken to these effects.

Speaker: Maike Saphorster (CERN / German Cancer Research Center DKFZ)

113 Enhancing X-ray Absorption Spectroscopy with Time-Resolved Pixel Detectors

X-ray absorption spectroscopy (XAS) is a powerful technique for probing the local atomic structure of specific elements, providing crucial insights into oxidation states and atomic coordination environments [1]. Typically performed at a synchrotron light source, XAS involves scanning the incident X-ray energy across an element’s absorption edge while recording the transmitted intensity, traditionally using a set of ionization chambers [2]. This conventional approach assumes a uniform sample composition within the X-ray beam path; however, variations in thickness, structural defects, or material inhomogeneities can distort the spectra, leading to inaccurate structural parameters. During in-situ and operando studies, such as catalytic reactions or battery cycling, these spectral distortions significantly affect data quality. Ionization chambers provide only an averaged absorption measurement across the entire sample providing an average information of the samples and masking localized effects. In contrast, 2D pixel detectors [3-5] enable spatially resolved absorption measurements, allowing the detection of sample heterogeneities that would otherwise go unnoticed. When combined with high frame rates, this capability becomes particularly valuable for tracking dynamic material changes under experimental conditions.
In this study, we evaluate the performance of a Timepix 3 hybrid pixel detector for Extended X-ray absorption fine structure (EXAFS) measurements using model and real samples at the XAFS beamline at Elettra Sincrotrone Trieste. Our findings demonstrate the advantages of localized detection in improving data quality and reliability, reinforcing the potential of pixel detectors as a transformative tool for complex material investigations.
References
[1] J.J. Rehr, A.L. Ankudinov, Progress in the theory and interpretation of XANES, Coordination Chemistry Reviews, Volume 249, Issues 1–2, (2005), Pages 131-140, ISSN 0010-8545
[2] O. Müller J. Stötzel, D. Lützenkirchen-Hecht and R. Frahm, Gridded Ionization Chambers for Time Resolved X-Ray Absorption Spectroscopy, Journal of Physics: Conference Series 425 (2013) 092010, doi:10.1088/1742-6596/425/9/092010
[3] D. Lützenkirchen-Hecht, J.-C. Gasse, R. Bögel, R. Wagner and R. Frahm, XAFS data acquisition with 2D-detectors: Transmission mode XAFS and grazing incidence EXAFS spectroscopy, (2016) J. Phys.: Conf. Ser. 712 012147, DOI 10.1088/1742-6596/712/1/012147
[4] Mingyuan Ge and Wah-Keat Lee, PyXAS – an open-source package for 2D X-ray near-edge spectroscopy analysis, J. Synchrotron Rad. (2020). 27, 567–575, SSN 1600-5775
[5] Valerie Briois et al.,Hyperspectral full-field quick-EXAFS imaging at the ROCK beamline for monitoring micrometre-sized heterogeneity of functional materials under process conditions, J. Synchrotron Rad. (2024). 31, 1084–1104, ISSN 1600-57750

Speaker: Ralf Hendrik Menk (Elettra Sincrotrone Trieste and INFN Trieste, Itay, Department of Computer and Electrical Engineering, Midsweden University, Sundsvall, Sweden)

114 Studies of ultrafast dynamics in substrate-free nanoparticles at ELI using Timepix3 optical camera

We present a novel application of the Timepix3 optical camera (Tpx3Cam) for investigating ultrafast dynamics in substrate-free nanoparticles at the Extreme Light Infrastructure European Research Infrastructure Consortium (ELI ERIC). The camera, integrated into an ion imaging system based on a micro-channel plate (MCP) and a fast P47 scintillator, enables individual time-stamping of incoming ions with nanosecond timing precision and high spatial resolution.
The detector successfully captured laser-induced ion events originating from free nanoparticles disintegrated by intense laser pulses. Owing to the broad size distribution of the nanoparticles (10–500 nm) and the variation in laser intensities within the interaction volume, the detected events range in occupancy from near-zero to extremely high—approaching the readout limits of the detector.
By combining time-of-flight and velocity map imaging (VMI) techniques, detailed post-processing and analysis were performed, allowing for the reconstruction of the three-dimensional ion momentum distributions. The results presented here focus on the performance of Tpx3Cam under high-occupancy conditions, which are of particular relevance to this study. These conditions approach the limitations imposed by the camera’s readout capabilities and challenge the effectiveness of standard post-processing algorithms.
We investigated these limitations and associated trade-offs, and we present improved methods and algorithms designed to extract the most informative features from the data.

Speaker: Dmitrij Ševaev (FNSPE CTU)

SevaevDmitrij_IWORID_poster.pdf

115 Optimizing biplanar X-ray angles for deep learning-based CT reconstruction for accurate patient positioning in image-guided radiotherapy

Radiation therapy demands high precision in patient positioning due to its tumor-conformal dose distribution characteristics. Image-guided radiotherapy (IGRT) is employed to verify and ensure accurate patient positioning prior to treatment, thereby reducing uncertainties in the exact location of the planning target volume (PTV). Digital X-ray imaging, a common modality in IGRT, typically utilizes two orthogonal projections to visualize the patient's position from different perspectives (Figure 1). However, while X-rays provide two-dimensional images, the PTV is defined using three-dimensional (3D) images obtained from computed tomography (CT) scans. To align these, image registration is performed by comparing digitally reconstructed radiographs (DRRs) with acquired X-ray images. This DRR-based registration, however, suffers from a limited capture range, reducing robustness in clinical settings. Recent advances in deep learning have shown promising results in reconstructing 3D CT volumes from just two X-ray projections. Biplanar X-rays obtained from different angles provide complementary anatomical information, which is essential for accurate volumetric and stereoscopic reconstruction. Figure 2 illustrates the deep learning architecture used in this study—X2CT-GAN—which employs two parallel encoder-decoder networks to process posterior-anterior (PA) and lateral (LAT) X-rays, with a fusion network integrating features from both views. In this study, we analyze the impact of varying biplanar X-ray angle combinations on the accuracy of 3D CT reconstruction. We evaluate nine different angle pairs (θ = 10°–90°) to identify the optimal configuration. Preliminary reconstruction results are shown in Figure 3. Quantitative evaluation using the structural similarity index measure (SSIM) and peak signal-to-noise ratio (PSNR) shows that the best performance is achieved at θ = 70°, with SSIM of approximately 0.59 and PSNR of 26.7 dB. Additionally, organ segmentation is performed to qualitatively assess the anatomical accuracy and boundary clarity of the reconstructed CT volumes. Comprehensive experimental results and analysis will be presented in the full paper.

Speaker: Prof. Changwoo Seo

Abstract IWORID 2025.pdf

116 Enhancement of Radiation Detectors for Verification of CANDU-Type Spent Fuel

The Optical Fiber Radiation Probe System (OFPS), which utilizes an optical fiber-based scintillation detector, has been employed by inspectors from the International Atomic Energy Agency (IAEA) and South Korea to verify spent fuel bundles from CANDU-type heavy water reactors. To address challenges identified in previous studies, the OFPS is currently undergoing enhancements to improve its performance. As part of these upgrades, two new optical fiber-based scintillation detectors have been designed and manufactured. A field test was conducted at the Wolseong Nuclear Power Plant, a CANDU-type facility in South Korea, to evaluate and compare the performance of the existing detector with the newly developed detectors. The primary objectives of this study were to assess the detection sensitivity and dynamic range of the optical fiber-based scintillation detectors. Four different radiation detectors?one existing OFPS detector and three newly developed detectors for the Improved Optical Fiber-based VErification System (IOVES)?were evaluated during the field tests. These detectors varied in terms of optical fiber diameter, radiation scintillator material, and scintillator size. The tests were performed at the spent fuel storage pool of Wolseong Unit 3. Experimental results indicated that the IOVES detector featuring a 0.6 mm optical fiber diameter and a 2.5 mm x 2.5 mm x 10 mm p-Terphenyl organic scintillator exhibited the highest performance among all tested detectors. Unlike the other three detectors, this detector clearly differentiated spent fuel bundle layers with both long and short cooling periods, and notably avoided signal saturation even with shorter cooling periods. These findings demonstrate that the newly developed scintillation detector has superior sensitivity and a significantly enhanced dynamic range. Consequently, this optical fiber-based radiation detector is expected to improve the efficiency and effectiveness of inspection activities by the IAEA and national authorities because it can reliably measure spent fuel bundles regardless of their cooling periods.

Speaker: Dr Sung-Woo KWAK (Korea Institute of Nuclear Non-proliferation and Control)

2025 iWoRID abstract.docx

117 XRF mapping with polycapillary optics for assessing sulfonate distribution in impregnated CTMP fibers

Uniform sulfonation using Na₂SO₃ is critical in chemithermomechanical pulp (CTMP) production for ensuring efficient processing and high product quality. However, achieving even distribution of sulfonate groups (–SO₃⁻) across wood fibers is challenging due to variability in wood chip size. To investigate sulfur(S) at the microscale, we developed a cost-effective X-ray fluorescence (XRF) imaging system utilizing polycapillary focusing optics. This setup enables high-resolution elemental mapping, achieving a spot size of ~15 µm and spatial resolution of 15–20 µm, as confirmed with a chromium test pattern. A 3D-printed sealed chamber enables helium flushing, significantly enhancing the detection of low atomic number elements, particularly sodium (Na). XRF imaging of CTMP sheets reveals the distribution contours of S along individual wood fibers. This method offers a practical tool for evaluating and optimizing sulfonation uniformity during fiber impregnation in industrial CTMP processes.

Speaker: Farangis Foroughi

IWORID abstract 2025.pdf

118 Optimizing AGIPD with Calibration: How Do We Keep a Billion Parameters Under Control?

The Adaptive Gain Integrating Pixel Detector (AGIPD) [1] is a hybrid pixel detector developed to cope with high dynamic range and megahertz repetition rates of the European XFEL. Its adaptive gain mechanism enables simultaneous detection of single-photon events and high-intensity X-ray signals. AGIPD’s adaptive gain combined with its ability to handle the unique time structure of European XFEL’s pulses makes it indispensable for time-resolved X-ray diffraction, spectroscopy, and imaging studies [2]. 

To ensure reliable and accurate experimental results, the detector’s raw signal must be precisely calibrated (i.e. converted into meaningful physical units) while accounting for variations in detector pixel-to-pixel response and characteristic. The accuracy of the final experimental data depends directly on the precision of the calibration constants used to correct the detector response; higher-quality calibration leads to improved detector performance and enhanced scientific output.

While the calibration methodologies have been developed and validated on single-ASIC systems [3], extending these approaches to the full 1MPixel AGIPD detector (AGIPD1M) introduces additional challenges. Beyond the detector’s scale, system-level electronic effects must be accounted for, necessitating adaptations and novel approaches to certain calibration methods for full-detector implementation. Characterising AGIPD1M’s behaviour requires deriving coefficients from three distinct datasets: dark data, dynamic range scans, and low-intensity fluorescence measurements. The process entails calibrating every memory cell in each pixel across three gain stages, resulting in over $10^9$ calibration parameters. Furthermore, calibration is an ongoing process as calibration constants must be periodically updated to compensate for detector aging, radiation damage, and evolving operational scenarios. The required datasets are acquired at different intervals, ranging from a few hours for dark data to $6-12$ months for dynamic range scans and fluorescence measurements, making calibration a continuous challenge. 

To streamline this complex detector calibration and characterisation procedure, a suite of highly automated calibration and characterisation routines has been developed as part of the European XFEL offline calibration framework [4]. Given the vast number of calibration parameters, automated validation methods are essential to ensure the reliability of the calibration process. In this work, we present the implementation of these routines, describe the algorithms used for processing calibration data, and demonstrate their impact on optimising the performance of AGIPD detectors at the European XFEL.

[1] Allahgholi, A., et al. (2019). J. Synchrotron Rad. 26, 74-82.
[2] Sztuk-Dambietz, J., et al. (2024). Front. Phys. 11, 1329378.
[3] Mezza, D., et al. (2022). Nucl. Instrum. and Methods Phys. Res. A 1024, 166078
[4] Schmidt, P., et al. (2024). Front. Phys. 11, 1321524.

Speaker: Vratko D. Rovensky (European XFEL)

Poster_iworid2025_final.pdf

119 Timewalk correcting Timepix4 data for imaging resolution and particle identification

The Timepix4 provides time of arrival (ToA) and time over threshold (ToT) information on detected events, which is used to improve its imaging capabilities. We present an evaluation of the correction of the ‘timewalk’ effect of a Timepix4.2 pixel detector ASIC, bump-bonded to a 300 um planar silicon sensor, performing time-of-flight-based particle identification, spatial resolution measurements for TEM, and lab-based laser and test-pulse measurements. We show a comparison between the three different methods – using test-pulse data, photon data, and charged-particle data, and discuss the scope of the application of each.
A timewalk correction is applied in two separate campaigns involving the Timepix4:
Charged-particle data was obtained at the PSI PiM1 beam line using coincidence with a MALTA-based beam telescope. The positron beam was used to study the fractional radiation length of ATLAS, CMS, and Mu3e detector modules. The time of flight of scattered particles was measured by the Timepix4 with respect to a beam clock, thus separating in time the positron component of the beam from muon and pion contamination. After applying a timewalk correction based on test-pulses and the charged beam data, the FWHM of the positron peak decreases from ~ 4 ns to ~ 3 ns. Further, performing ToT-charge calibration decreases the peak width down to ~ 2ns, limited by the trigger system of the telescope.
Measurements of the Timepix4 imaging resolution were performed with a TEM at the Rosalind Franklin Institute. The Modulation Transfer Function (MTF) of the detector was evaluated for 100 keV and 200 keV electrons. After applying a timewalk correction based on photon data taken with an IR laser, and calibrating the ToT values per-pixel, offline geometric and temporal hit clustering is performed. The MTF at Nyquist frequency is improved by factors of ~ 2 and ~ 3 for low- and high-energy electrons respectively.

Speaker: Nina Dimova

Poster_iWoRiD25_Dimova.pdf

120 Machine Learning for Correcting Simulation Outputs in Alpha Particle Measurements with Hybrid Semiconductor Detectors

Accurate modeling of alpha particle interactions in hybrid semiconductor detectors remains challenging, as standard simulation tools like Geant4 and Allpix Squared (CERN) often fail to simulate specific sensor and detector electronics responses. This results in discrepancies between simulated and experimental data, particularly in reproducing key features such as the "halo" effect surrounding particle tracks.
To mitigate these differences, we employ a machine learning approach to refine simulation outputs, making them more consistent with experimental measurements. Using alpha particle data in the 1–5 MeV energy range recorded with a Timepix 3 ASIC chip and a 500 μm silicon sensor, our model learns to correct structural and intensity variations without requiring explicitly paired training data.
Our results demonstrate that machine learning methods effectively enhance the realism of simulated data, improving their agreement with experimental observations. This approach provides a scalable method for generating synthetic experimental datasets, aiding in detector characterization and improving the accuracy of future simulations.

Speaker: Kamilla Sabirzyanova (Advacam, Prague, Czeck Republic)

Abstarct Sabirzyanova.pdf

121 Nanoscale Structured Illumination Microscopy with Extreme-Ultraviolet Ultrafast Transient Gratings

Visualizing nanostructures within macroscopic materials is fundamental to understanding their physical and chemical properties. Over the past decades, super-resolution techniques have revolutionized visible-light microscopy [1-3]. Among these, structured illumination microscopy (SIM) [4-6] provides a straightforward implementation to access a full range of spatial information limited by the Abbe limit.
Achieving nanometer-scale spatial resolution together with high temporal resolution extends the investigation to ultrafast material dynamics. Free-electron laser (FEL) sources are well-suited for this purpose, delivering fully coherent, ultrashort pulses at nanometer wavelengths.
To implement SIM with FEL pulses [7], we employed the extreme-ultraviolet (EUV) transient grating (TG) technique, which generates a sinusoidal intensity modulation by crossing two ultrafast and fully coherent FEL beams [7,8].
This structured illumination setup, combined with a fluorescent system, allows us to reconstruct sample details beyond the diffraction limit by exploiting Moiré fringes created by the interference between the sample’s spatial frequencies and the structured beam. The modulation periodicity can be tuned down to a few nanometers [9] by adjusting the FEL wavelength or crossing angle.
Using this approach, we have improved the performance of previous studies, achieving nanometer-scale spatial resolution by exploiting the tunability of FERMI FEL. Since this method employs ultrafast pulses, it enables time-resolved studies, allowing not only the visualization of nanometric details but also the potential investigation of their dynamics.
The system’s ability to detect fluorescence across a broad spectral range makes it applicable to nanostructures, disordered molecular systems, and phase transitions in mesoscopic materials. It could also be used for imaging biological specimens, quantum materials, and nanoscale defects in optoelectronic devices, providing a powerful tool for high-resolution imaging in different research areas.
Future developments include adapting the setup for the hard X-ray regime by replacing the visible objective with an X-ray zone plate for X-ray fluorescence detection. The X-ray optics are being fabricated.
Performing SIM using pulsed X-ray sources will open new opportunities for studying dynamic processes, such as phase transitions and catalytic reactions. The next step involves implementing X-ray structured beams with sub-10 nm periodicity, combined with X-ray fluorescence imaging. This would remove the need for optically fluorescent samples while enabling high-resolution elemental and chemical mapping. Additionally, the short lifetime of X-ray fluorescence eliminates the need for optical up/down-conversion techniques to achieve ultrafast temporal resolution.

[1] Hell, S. W., et al., Opt. Lett. 19(11), 780–782 (1994).
[2] Lelek, M., et al., Nat. Rev. Methods Primers 1(1), 39 (2021).
[3] Reinhardt, S. C. M., et al., Nature 617(7962), 711–716 (2023).
[4] Heintzmann, R., et al., Proc. SPIE 3568, 185–196 (1999).
[5] Gustafsson, M. G. L., et al., J. Microsc. 198(2), 82–87 (2000).
[6] Gustafsson, M. G. L., et al., Biophys. J. 94(12), 4957–4970 (2008).
[7] Mincigrucci, R., et al., Opt. Express 32(17), 30813–30823 (2024).
[8] Mincigrucci, R., et al., Nucl. Instrum. Methods Phys. Res. A 907, 132–148 (2018).
[9] Bencivenga, F., et al., Sci. Adv. 5(7), eaaw5805 (2019).

Speaker: GINEVRA LAUTIZI (Università di Trieste, Dipartimento di Fisica)

122 Compact and autonomous radiation tracking unit for use in aviation

Space weather refers to the changing conditions in space, primarily caused by solar activity, ultimately affecting human activities on Earth and in space. The solar emissions interact with Earth's magnetic field and atmosphere, leading to disruptions in technology and communication systems. Severe solar storms can cause errors in digital electronics and disrupt high-frequency radio signals, GPS navigation, the electrical power grid, and satellite operations. Monitoring and forecasting space weather is important to limit the negative effects of solar emissions. Currently, space weather predictions rely on monitoring solar activity, modeling its effects on Earth's environment, and using ground-level cosmic radiation monitors.

This contribution will introduce a compact autonomous unit utilizing Timepix3-based radiation detectors, developed by Advacam s.r.o. for monitoring radiation dose and particle flux. These position-sensitive detectors record information about individual particles, including Linear Energy Transfer (LET), direction, particle type, and more. Such detailed information about the radiation environment is crucial for monitoring and eventually forecasting space weather.

For these purposes, an automatic and compact radiation monitoring device featuring a MiniPIX TPX3 particle detector and a minicomputer was developed for use on board airplanes. This device is so small that it fits into a pilot's pocket.

A set of several of these devices will be used in parallel. Part of them will automatically collect data in aircraft during flight, and the other part will be used as a reference to measure radiation at the ground level. Comparison of the recorded data will contribute to a better understanding of the local radiation environment and its correlation with existing space weather forecasts.

Speaker: Karolína Melovská (Advacam)

123 Restoring low resolution response in phosphor-coupled X-ray detectors via diffusion deblurring network

Phosphor-coupled or indirect-conversion X ray detectors are widely used in both industrial non destructive testing (NDT) and medical imaging. However, there is an inherent tradeoff between spatial resolution and conversion efficiency: detectors with a thin phosphor offer higher spatial resolution but suffer from lower X ray conversion efficiency, leading to higher quantum noise, whereas those with a thick phosphor achieve better conversion efficiency at the expense of reduced spatial resolution. In industrial imaging applications, where factors such heat loading on the X ray source and inspection throughput are critical, the use of a thicker phosphor is desirable, even though it leads to degraded spatial resolution.
To address this limitation, we propose a deep learning-based image processing approach. The aim is not merely to convert low-resolution (LR) images to high-resolution (HR) ones, but to enhance the detector’s response function itself. We have incorporated the diffusion model [1,2] into the network architecture and trained it to improve the detector's response function by restoring HR details in images acquired from a thick-phosphor detector. The HR ground truth images for printed-circuit board (PCB) samples were obtained using a detector with a thin phosphor. To simulate the response of a thick phosphor detector, we generated blurred HR (BHR) images by convolving each HR image with a point spread function derived from the ratio of the modulation-transfer functions measured for both thin and thick phosphor detectors. A series of intermediate degraded images, $I_j$, required for training the diffusion model, was generated by blending the HR and BHR images:$I_j = (1 - w_j) \, I_{\mathrm{HR}} + w_j I_{\mathrm{BHR}}$, where the blending weight $w_j$ at the jth stage increases linearly over a predefined number of stages, thereby emulating the gradual degradation from HR to LR. These $I_j$ images were then used as inputs to a modified U‑Net deblurring network [3], trained to recover HR details from progressively degraded inputs. Fig. 1 shows the preliminary results of the diffusion deblurring network, which effectively restores HR images. Fig. 1(a) shows the input, output, and target images. Fig. 1(b) presents the structural similarity index measure (SSIM) maps for the corresponding target images. The average SSIM values for the BHR images and the network outputs were 0.75 and 0.96, respectively.
The proposed network enables the restoration of high‑resolution images obtained from thick-phosphor detectors under low-dose X‑ray conditions. This capability has the potential to significantly enhance inspection capacity, improving sensitivity in defect detection for PCB inspections and other industrial NDT applications.

Reference
[1] A. Bansal, et al., Cold diffusion: Inverting arbitrary image transforms without noise. NeurIPS, Vol. 36, pp. 41259-41282, 2023.
[2] J. Ho, J. Ajay, and P. Abbeel. Denoising diffusion probabilistic models, NeurIPS, Vol. 33, pp. 6840-6851, 2020.
[3] J. Kim, S. Oh, and H. K. Kim, Fourier analysis of multi-scale neural networks implemented for high-resolution X-ray radiography, NDT & E international, Vol. 139, pp. 102923, 2023.

Acknowledgement
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. RS-2024-00340520). S. Oh was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (No. RS-2024-00408137)

Speaker: Seokwon Oh (Computational X-ray Imaging Laboratory, School of Mechanical Engineering, Pusan National University)

124 Optimizing robot-CT trajectories for data completeness

Computed tomography (CT) generates 3D volumetric images by numerically processing projection views obtained from various angles, and is widely used both in medical and industrial fields. However, industrial CT faces challenges, such as limited field of view for large objects and severe photon starvation or metal artifacts. These artifacts can be reduced or eliminated by avoiding highly attenuating regions during scanning. However, this approach is rarely implemented in cone-beam CT (CBCT) with a conventional circular gantry. To address these limitations, recent studies have proposed robotic CT [1], in which the X-ray source and detector are mounted on a 6-degree-of-freedom robotic arms, enabling projection acquisition along arbitrary trajectories. However, robot CT with poorly designed scanning paths can reduce data completeness and degrade the quality of reconstructed images. Data completeness is essential for the exact reconstruction. The Tuy-Smith condition [2,3] states that any plane passing through the object must intersect the scanning trajectory at least at once.
In this study, we propose an algorithm based on the Tuy measure to optimize the scanning trajectory of a robotic CT system. The goal is to maximize data completeness within a specific volume of interest (VOI) while achieving high-quality images with a minimal number of projections. Additionally, the algorithm evaluates the quality of each projection to filter out those that may cause metal artifacts within the VOI.
To simulate a two-robot-arm system, we developed a laboratory-scale robot-CT system that uses a single robotic arm to manipulate the motion of the object to be scanned, as shown in Fig. 1(a). As an example, a postmortem mouse was used, with 5-mm-diameter metal balls attached around it to induce metal artifacts. The projections were acquired over a rotation range of $\theta$ from 0° to 360° with a 2° interval. For each $\theta$, tilted angles $\phi$ of 0°, 30°, and 45° were considered, resulting in a total of 540 possible projections. Image reconstruction was performed using the FDK algorithm. Fig. 1(b) shows the reconstruction results using the trajectory determined by the proposed algorithm. In each sub-panel, the number of projections used for reconstruction is displayed in the top-right corner, and the corresponding trajectory ($\phi$ or arbitrary) is shown in the bottom-right corner. The results demonstrate a significant reduction in metal artifacts with the optimized trajectory. Although some data loss is inevitable compared to the conventional circular trajectory (180 projections at $\theta=$ 0°), the optimized trajectory with only 46 projections was able to reconstruct most of the internal structures of the mouse. A detailed description of the proposed algorithm, including systematic examples for finding optimal trajectories for various sample objects, will be provided.

Reference
[1] W. Holub, F. Brunner, and T. Schön, RoboCT application for in-situ inspection of join technologies of large scale objects, International Symposium on Digital Industrial Radiology and Computed Tomography, 2019.
[2] H. K. Tuy, An inversion formula for cone-beam reconstruction, SIAM Journal on Applied Mathematics, Vol. 43, No. 3, pp. 546-552, 1983.
[3] B. D. Smith, Image reconstruction from cone-beam projections: Necessary and sufficient conditions and reconstruction methods, IEEE Transactions on Medical Imaging, Vol. MI-4, No. 1, pp. 14-25, 1985.

Acknowledgement
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (RS-2024-00340520).

Speaker: Seungjun Yoo (Computational X-ray Imaging Laboratory, School of Mechanical Engineering, Pusan National University)

125 Characterization of a LYSO Crystal and SiPM Array-Based Detector for Radiation Source Localization

Radiation source localization is a critical technology in fields such as emergency response and nuclear decommissioning, where identifying the position of radioactive materials is essential for safety and operational efficiency. In such scenarios, compact and deployable systems are particularly important to enable rapid and flexible detection in constrained or hazardous environments. While several systems have been developed in the past, most rely on bulky photomultiplier tube (PMT)-based detectors, limiting their field applicability. Furthermore, many of these studies focus only on the localization of one or two radioactive sources under controlled conditions. This highlights the need for compact, high-accuracy detection technologies capable of more versatile and scalable source localization..
The detection system consists of an 8×8 cerium-doped lutetium yttrium oxyorthosilicate (LYSO) crystal array directly coupled to an 8×8 silicon photomultiplier (SiPM) array, forming a compact 64-channel detector. Using this setup, 64 distinct spectra can be acquired through a multi-channel analyzer. Since the LYSO crystal serves both as a scintillation material and a radiation attenuator, each channel produces a unique spectral response influenced by the interaction between radiation and the scintillator. These spectral variations are affected by factors such as the scintillator properties, radioisotope types, and their spatial positions.
In this study, a performance evaluation was conducted to develop a position-sensing system based on an LYSO crystal array and a SiPM array. The system was composed of an 8×8 array of 3×3×20 mm³ LYSO crystals coupled one-to-one with a 64-channel SiPM array (S14161-3050AS-08, Hamamatsu). Output signals were digitized using a DT5202 module (CAEN) and transmitted to a computer via Janus DAQ software (CAEN). To evaluate the system's capability, a 137Cs point source was measured at azimuthal and polar angles ranging from 0° to 180° and 0° to 90°, respectively, in 10° intervals. The acquired spectra from each channel were calibrated using a spectrum stabilization method, and the photopeak areas were extracted to form 8×8 feature maps. Centroid analysis of these feature maps was performed to estimate the source positions. The results demonstrated that the proposed detection system could accurately identify the location of the radiation source using relatively simple computational techniques.

Speaker: Prof. Gyuseong Cho (Korea Advanced Institute of Science and Technology)

iworid2025_WONKU_KIM_KAIST.pdf

126 Upper-limit resolving power of semiconductor X-ray detector materials: A cascaded-systems model of interaction-specific MTFs

The modulation transfer function (MTF) is a critical metric for quantitatively assessing the contrast-transfer capability of X-ray imaging devices, particularly in terms of their ability to resolve fine details. Photon-counting detectors (PCDs), which use semiconductor sensor materials, typically exhibit superior MTF performance compared to scintillator-coupled detectors [1]. This is primarily because the diffusion of charge carriers in semiconductors is much smaller than that of light in scintillators. To mitigate the effects of lateral light diffusion, structured designs of scintillators have developed.

The upper limit of spatial resolution in X-ray detectors is determined by the spatial distribution of absorbed energy resulting from X-ray interactions. In a recent study [2], we demonstrated that when the MTF induced by X-ray interactions is combined with a charge-sharing compensation scheme in PCD operation, the overall MTF of the detector can be significantly reduced, as illustrated in Fig. 1(a). Thus, it is essential to understand the contribution of each type of interaction to the upper-limit MTF in a given detector material to improve PCD imaging performance. While numerous studies have explored detector materials in terms of detection efficiency, research into the spatial-resolution effects caused by X-ray interactions remains relatively limited.

In this study, we present a cascaded-systems model to describe the MTF induced by X-ray interactions, as depicted in Fig. 1(b). This model categorizes interactions such as the photoelectric effect, Rayleigh scattering, and Compton scattering, and takes into account energy absorption at both local and remote sites, as well as energy escape. It enables a modular and traceable analysis of how various photon events contribute to signal spreading or resolution loss [3]. We implement the model using the Monte Carlo technique, and we analyze the impact of each interaction mechanism on the total MTF by tracking energy-absorption events through each interaction history. For this purpose, we utilize the pTrac output from MCNP (Version 5, RSICC, Oak Ridge, TN), which provides photon energy and spatial coordinates at each interaction site.

Fig. 1(c) presents the interaction-specific transfer functions in the Fourier domain for a CdTe detector. Each curve corresponds to a specific X-ray interaction pathway, including the photoelectric interaction ($T_{\text{PKL}},\ T_{\text{PK}},\ T_{\text{PL}}$), scattering event ($T_{\text{CL}},\ T_{\text{CPKL}},\ T_{\text{CPK}},\ T_{\text{CPL}}$), and multiple scattering ($T_{\text{MC}}$). This detailed decomposition facilitates an in-depth analysis of how each type of interaction affects spatial resolution. The proposed model offers a systematic approach for isolating and quantifying the individual contributions of various X-ray interactions to the overall MTF. We apply this model to investigate the upper-limit MTF for different detector materials, such as CsI, Si, CdTe, GaAs, HgI₂, and PbO.

Reference
[1] J. Lee, S. Yoo, S. Oh, S. Park, C. H. Lim, J-W. Park, J. Tanguay, and H. K. Kim, “Analysis of the detective quantum efficiency of a dual-energy photon-counting X-ray detector”, NDT & E International. In publication.
[2] H. K. Kim, “Development of Energy-Integrating Detectors for Large-Area X-Ray Imaging”, in Radiation Detection Systems, K. Iniewski and J. S. Iwanczyk eds. CRC Press, pp. 163-224, 2021.
[3] S. Yun, J. Tanguay, H. K. Kim, and I. A. Cunningham, “Cascaded-systems analyses and the detective quantum efficiency of single-Z x-ray detectors including photoelectric, coherent and incoherent interactions”, Medical physics, Vol. 40, No. 04, pp. 041916, 2013.

Acknowledgement
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (RS-2024-00340520). J. Lee was supported by the 'Human Resources Program in Energy Technology' of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), which was funded by the Ministry of Trade, Industry & Energy (MOTIE, Korea) (No. RS-2024-00398425).

Speaker: Junho Lee (Computational X-ray Imaging Laboratory, School of Mechanical Engineering, Pusan National University)

127 A high energy-resolution pixelated ASIC chip designed for electron and X-ray microscopy

The development of advanced Application-Specific Integrated Circuits (ASICs) for Scanning Transmission Electron Microscopy and X-ray Micro-CT has emerged as a crucial driver for achieving high-precision material characterization. In particular, acquiring 2D distribution of the electrons or X-ray photons along with measuring their energy is desired for imaging the chemical elements at microscale, however cannot be achieved with pixelated detectors currently available. This work presents a monolithic pixel sensor test chip designed for electron microscopy applications, fabricated using 180 nm CMOS technology with a pixel size of 85 μm × 85 μm. Each pixel incorporates a low-noise amplifier, a feedback circuit, and a high-speed analog-to-digital converter (ADC) to ensure optimal performance. The ASIC achieves an energy resolution of 205.2 eV, measured using a Fe-K X-ray at 5.9 keV, and a time resolution of approximately 1.2 ns, enabling precise measurements in key applications such as electron energy loss spectroscopy (EELS), time-resolved imaging and diffraction. This publication introduces several innovative design features of the ASIC, along with its characterization and measurement results, demonstrating its potential to advance the field of electron and X-ray microscopy.

Speakers: Hui Zhang (Institute of High Energy Physics), Zijun Xu

128 Imaging detectors at MAX IV

The MAX IV Synchrotron facility in Lund, Sweden, relies on a diverse array of over 30 specialized X-ray detectors and cameras that are essential for the operation of its experimental beamlines.

We will provide an overview of the detection technologies employed at the MAX IV Synchrotron, covering both the operational aspects and the supporting systems that enable their effective use.

We use a range of detector technologies depending on the required spatial and temporal resolution, as well as the beamline energy range. We employ both photon counting and charge integration, to meet the diverse experimental requirements.

While the facility procures the majority of its detectors from commercial partners, it also collaborates with other research laboratories to obtain some of the most cutting-edge detection solutions. In both cases, we take care and effort to thoroughly understand and properly calibrate the detectors acquired.

We will also present the streaming based software infrastructure we have developed to store the data produced by these detectors. Finally we show the map-reducelive data processing pipeline that enables fast feedback on experimental results by running the most common analysis tasks on the fly.

Speaker: Michele Cascella

129 Deep Learning-Based Isotope Identification for Radiological Crime Scene Investigations Using Convolutional Neural Networks

Introduction

Accurate identification of radioactive isotopes is a critical task in nuclear security, environmental monitoring, and emergency response. Traditional gamma spectroscopy analysis relies on peak fitting, template matching, or expert-driven methods, which can struggle in low-resolution, low-statistics, and high-background environments. These challenges are particularly relevant when using portable NaI(Tl) detectors, which, despite their widespread field use, suffer from poor energy resolution compared to high-purity germanium (HPGe) detectors.

Advancements in deep learning offer a new approach to spectral analysis, leveraging convolutional neural networks (CNNs) to automatically extract spectral features and classify isotopes with high accuracy. CNNs, particularly in one-dimensional (1D) architectures, are well-suited for handling gamma-ray spectra directly, eliminating the need for extensive preprocessing.

This work presents a 1D convolutional neural network (1D-CNN) trained for isotope identification using simulated gamma spectra from a low-resolution 3″ NaI detector. The model is trained to classify 32 isotopes under realistic source strengths and background conditions, achieving a global classification accuracy of 0.94. Additionally, ongoing work is extending this approach to Cadmium Zinc Telluride (CZT) small-form-factor detectors, which offer higher resolution but present new challenges due to their small active volume and statistical noise.

Methodology

Data Generation and Simulation

To train and evaluate the proposed 1D-CNN, a dataset of simulated gamma-ray spectra is generated using Monte Carlo (Geant4) methods. The spectra are designed to reflect real-world measurement conditions by incorporating detector response, energy resolution, and background radiation levels.
The key parameters defining the dataset include:

• Event count per spectrum: Ranges from 5,000 to 100,000, simulating measurements from weak sources, short acquisition times, and varying detection distances.
• Signal-to-(signal+background) ratio (S/S+B): Randomized between 0.1
  and 1.0, reflecting conditions from strong, isolated sources to
  highly obscured signals.
• 32 individual isotopes: The dataset covers a broad spectrum of radionuclides relevant to nuclear security, medical, and industrial applications. Each spectrum is histogrammed into 1,024 energy bins covering an energy range of 0–3 MeV, which includes common gamma-ray emissions from these isotopes.

CNN Architecture

The 1D-CNN is designed to process raw energy spectra as one-dimensional signals, capturing the essential spectral features for classification. The model consists of:
- Input layer: Takes a 1,024-bin gamma spectrum as input.
- Convolutional layers: Multiple 1D convolutional layers with ReLU activation to extract spectral features.
- Softmax output layer: Produces a probability distribution over 32 isotope categories.

Training and Optimization

The model is trained using the Adam optimizer and a categorical cross-entropy loss function. The dataset is split into 60% training, 20% validation, and 20% testing, ensuring comprehensive evaluation.

Performance Metrics

Model performance is assessed using:
- Global classification accuracy (fraction of correctly classified spectra).
- Confusion matrix analysis to identify isotope misclassification patterns.
- Precision, recall, and F1-score for assessing model robustness across varying signal strengths and noise levels.

Results and Discussion

The 1D-CNN achieves a global classification accuracy of 0.94, demonstrating strong performance across a broad range of measurement conditions. The confusion matrix reveals that most misclassifications occur between isotopes with similar gamma emissions.

Ongoing work is extending this approach to small-form-factor CZT detectors, which provide superior energy resolution compared to NaI but introduce new challenges:
- Small active volume leads to lower event counts, requiring adaptation of the CNN to handle noisier, lower-statistics data.
- More precise peak structure in CZT spectra allows for finer isotope discrimination but necessitates retraining with high-resolution data.

Conclusion

This study demonstrates that 1D convolutional neural networks (1D-CNNs) can accurately classify gamma-ray spectra from a low-resolution NaI detector, achieving 94% accuracy even under challenging measurement conditions. The model’s robustness to low counts and background variations makes it well-suited for real-time isotope identification in nuclear security and field applications. By enhancing isotope identification capabilities in low-resolution NaI and high-resolution CZT detectors, this approach helps bridge the gap between laboratory methods and real-world radiological security challenges. The development of portable, AI-driven radiation detection systems has the potential to improve border security, emergency response, and illicit trafficking prevention.

Speaker: Dr Konstantinos Karafasoulis (Hellenic Army Academy)

IWORID_2025.pdf

130 Dependence of Fast Neutron Imaging on Scintillators

Fast neutron imaging has emerged as a powerful tool for non-destructive testing, particularly in environments where traditional X-ray and thermal neutron imaging methods are limited. In this study, we investigate the feasibility of fast neutron imaging using a compact D-D neutron generator and the KSTAR tokamak as neutron sources. Various scintillators for fast neutrons were employed to evaluate their impact on image quality and detection efficiency. By comparing imaging performance across different scintillators, we analyzed their spatial resolution, signal-to-noise ratio, and neutron detection efficiency. The results demonstrate that scintillator selection significantly influences image clarity and detection sensitivity, providing crucial insights for optimizing fast neutron imaging systems for industrial and scientific applications. This study highlights the potential of fast neutron imaging in advanced diagnostics, with implications for fusion research, material analysis, and non-destructive evaluation.

Speaker: Youngseok Lee (Korea Institute of Fusion Energy)

iworid 2025_KFE_Youngseok Lee_20250423_fin.pdf

131 Development of a Compact Electronics System for a Drone-Mounted Gamma Radiation Detector Aiming at Aerial Mapping and Surveillance

This project presents a specialized gamma radiation detector electronics system optimized for aerial mapping, surveillance, and radiation safety applications. The drone-mounted design effectively addresses radiation safety requirements across challenging terrains and sensitive locations. We discuss the main features of the detector electronics, starting from powering the detector up to data output to the onboard computer (OBC).
The detector integrates four high-resolution scintillation crystals read by photomultiplier tubes (PMTs) and surrounded by a plastic scintillator veto system employing silicon photomultipliers (SiPMs). The custom electronics architecture emphasizes compactness, miniaturization, and low power consumption. It features analog front-end processing, digitally-controlled high-voltage bias modules, high-speed digitization (50 MHz, 16-bit ADC), and advanced FPGA-based digital signal processing, including trapezoidal finite impulse response (FIR) filtering, precise peak detection, and robust coincidence/anticoincidence trigger logic. Processed data are stored in onboard histogram memories, providing detailed gamma-ray spectra with adjustable resolution and dynamic range, complemented by integrated temperature and pressure sensors for environmental corrections. An STM32 microcontroller interfaces these subsystems with a Raspberry Pi acting as the onboard computer, facilitating data acquisition, storage, analysis, and real-time control using a 4G/LTE cellular modem kit, which also provides GPS tagging capabilities.

Keywords: Gamma-ray detection, Radiation mapping, Drone-mounted detector, FPGA signal processing.

Speaker: Joaquim Marques Ferreira dos Santos (University of Coimbra)

132 Simulation and Tests of Multithreshold Charge Sharing Compensation Algorithm Implemented in SPC Readout Integrated Circuits Operating in Si and CdTe Pixel Detectors

This paper presents the tests of the charge-sharing compensation algorithm implemented in the single photon counting readout integrated circuit for Si and CdTe pixel detectors. The multi-threshold pattern recognition algorithm with four energy thresholds was tested in 96 × 192 pixel matrix with 100 µm pixel pitch. With the readout pixel noise of only 124 el. rms and the threshold spread below 1 mV for all discriminators, the algorithm operates uniformly on the entire pixel matrix. The multi-threshold algorithm enables not only to measure radiation energy but also to increase the hit allocation accuracy. The algorithm performance was tested both with Si and CdTe detectors in the energy range from 6-150 keV. The hybrid detector module consisting of a sensor, readout IC, and back-end electronics was used for the food inspection on the fast-moving belt. The charge-sharing compensation algorithm, together with the time domain integration method implemented in the integrated circuit significantly improves the quality of images collected during tests.
(This work is supported by the National Science Centre, Poland, project no. 2023/51/B/ST7/01782. )

Speaker: Dr Miroslaw Zoladz (AGH University of Krakow)

Zoladz_IWORID_2025_RK.docx

133 SPECTRUM 1k – Single Pixel Counting Readout Chip with In-Pixel Energy Histogramming

A new single photon-counting IC prototype called SPECTRUM1k with pixel matrix 40 × 24 and pixel pitch 75 µm is developed by the Microelectronics Group of the AGH University of Krakow as a solution for X-ray color imaging. The chip, produced in CMOS 40 nm technology, is made up of 960 individually configured pixels, each composed of an amplifier, an analog-to-digital converter, and 64 × 12-bit memory cells that allow one to perform in-pixel energy histogramming. Thanks to the proposed architecture working with the 200 MHz chip clock and 1 Gcps/mm2 multi energy photon intensities up-to about 23 ms exposition time is feasible (365 µs exposition time whenever monoenergetic photons are used only). In-pixel offset (Ϭ = 3.5%) and gain (Ϭ = 5.8%) spread, the amplifier performance (ENC = 95 e- rms) and the ADC resolution (ENOB = 5.4 b) allow to convert the incoming photons’ energy with FWHM = 3.7 ke @134.2 keV upon 45 µW (high-speed mode) or 12 µW (low-speed mode) per pixel power consumption.

Speaker: Piotr Kmon (AGH UST Krakow)

SPECTRUM1k_AGH_2025.pdf

134 Development of an Innovative Real-Time Dosimetry Monitoring System for Heavy Ion Radiotherapy

Cancer is the second leading cause of mortality globally. As a critical technological approach in oncology treatment, radiation therapy is evolving from conventional radiotherapy to ultra-high dose rate radiotherapy (FLASH-RT). With the significant escalation in radiotherapy dose rates, real-time dosimetry monitoring faces the dual challenges of enhancing both response time and measurement precision. This work successfully developed a real-time dosimetry monitoring system for radiotherapy, designed to accommodate a broad range of dose rates. The system consists of a dual-gated integrator architecture front-end circuit and a high-speed data acquisition circuit, providing accurate detection of bipolar current pulse signals spanning from -190 µA to +200 µA, the minimum current measurement range is from -1 pA to 1 pA. Two significant technological advancements were accomplished: first, the elimination of signal processing dead time resulted in a reduction of the single-event readout time to 5 µs; second, the nonlinear error from -190 µA up to the maximum current is within 0.67%, with a linear correlation coefficient R² of 0.99992. The experiments were conducted using an ionization chamber detector at the Heavy Ion Research Facility in Lanzhou (HIRFL-TR4). This system, combined with a dose detector, achieves real-time dose measurement within the dose rate range of 65 Gy/min to 120 Gy/min. It demonstrates excellent real-time monitoring performance in the high-dose rate range of radiation therapy and shows potential for further application in dose monitoring for electron and proton beam radiotherapy.

Speaker: Dr Lingling Liu

Development of an Innovative Real-Time Dosimetry Monitoring System for Heavy Ion Radiotherapy.pdf

135 Front-End Circuit Optimization of CMOS Pixel Detectors for High-Performance X-ray Polarization Measurements

The Topmetal series CMOS pixel detectors employ metal electrodes for direct charge collection and have been widely adopted in gas pixel detectors (GPDs) for X-ray polarization measurements. The performance of these detectors, particularly in terms of dynamic range, event rate capability, and energy measurement accuracy, is critical to achieving high detection efficiency. This work presents a detailed analysis of the pixel front-end circuit architecture of Topmetal detectors and introduces a series of optimizations to enhance their performance. To validate the proposed improvements, a prototype pixel front-end ASIC was designed and fabricated using the GSMC 130 nm CMOS process. Each pixel primarily consists of a low‑noise charge sensitive amplifier (CSA), a peak-hold circuit, a comparator, and a two-stage buffer. Results demonstrate that the optimized pixel achieves an equivalent noise charge (ENC) of $22.48 e^- + 0.51 e^-/fF$, a charge-voltage conversion gain of $66.95 \mu V/e^-$, and a dynamic range of $25k e^-$ with a non-linearity of 2.93%. Compared to previous Topmetal generations, the optimized pixel exhibits an extended dynamic range, improved linearity, enhanced energy measurement accuracy, and increased event rate capability (supporting up to 10 kcps), demonstrating its potential for large-scale integration in next-generation high-performance pixel detectors for X-ray polarization measurements.

Speaker: Zhuo Zhou

136 Development and Validation of a Readout Electronics System for Bragg Peak Range Detection

This study addresses the clinical demand for real-time localization of Bragg peaks in heavy-ion radiotherapy, overcoming the technical limitations of conventional readout electronics such as dead time and slow response. A multi-channel electronic readout system based on application-specific integrated circuits (ASICs) was developed. By integrating the high-precision digitalization chip ADAS1134 with FPGA dynamic configuration, gigabit Ethernet real-time transmission, and adaptive host computer algorithms, a comprehensive signal processing architecture encompassing signal conditioning, analog-to-digital conversion, and data analysis was established. The system employs anti-aliasing filtering and noise-shaping technologies to achieve synchronous acquisition of weak currents (50–700 nA) across 128 channels, with a nonlinearity error below 0.8% at a sampling rate of 200 kSPS per channel. Beam tests conducted with a Bragg peak detector demonstrated that the system successfully captured characteristic Bragg peak signals at carbon-ion radiotherapy terminals with energies of 260 MeV/u and 400 MeV/u. The system achieved a range positioning accuracy of 0.35 mm and a response time of 3.5 μs, representing a two-order-of-magnitude improvement over traditional current integration methods. This advancement provides a cost-effective technical solution for particle therapy range verification and demonstrates significant clinical application value.

Speakers: Mr Qianshun She (Institute of Modern Physics, Chinese Academy of Sciences), Ms Yuhan Dou (Institute of Modern Physics, Chinese Academy of Sciences)

137 A high throughput, radiation-hardened encoder/ decoder ASIC for the tracking system in HIAF

The High-Intensity Heavy-Ion Accelerator Facility (HIAF) is a next-generation heavy-ion accelerator currently under construction in China. A compact, large-acceptance spectrometer equipped with silicon pixel detectors will be constructed at HIAF to detect final-state particles at high event rates. The pixel-based tracking system, a key component of the spectrometer, is designed to precisely determine the spatial coordinates of collision points and secondary vertices from particle decays within the beam pipe. It must accurately track charged particles generated at collision rates of up to 100 MHz, while handling a data throughput exceeding 350 Gbps in a high-radiation environment. Serializer/Deserializer (SerDes) technology is widely used in such high-speed data links due to its ability to mitigate multi-channel skew. However, as transmission rates increase, DC imbalance and Single-Event Upsets (SEUs) can significantly elevate the bit error rate (BER). Encoding and decoding techniques provide a cost-effective solution to mitigate these errors. This study presents a radiation-hardened encoder/decoder ASIC, implemented in a 55 nm CMOS process, achieving a throughput of up to 20 Gbps. The chip employs an 84b/88b encoding scheme instead of the conventional 8b/10b encoding, enhancing efficiency while maintaining DC balance. Additionally, forward error correction (FEC) based on Reed-Solomon (RS) coding is integrated to detect and correct errors by appending redundancy bits, significantly reducing the BER. An optimized pipeline structure further enhances the throughput, meeting the stringent demands of large-scale data readout. To mitigate SEU-induced errors, triple modular redundancy (TMR) is implemented at critical nodes. Post-layout simulations demonstrate that, under a 1.2V supply, the encoder and decoder consume as little as 0.813 pJ/bit and 1.899 pJ/bit, respectively. The chip achieves a maximum error correction capability of 13.3% with 70% encoding efficiency and a 20 Gbps data rate, ensuring that the readout SerDes of the tracking system operates with high speed and low BER. Further test results will be presented in the poster.

Speaker: Chaojie Zou (Institute of Modern Physics, Chinese Academy of Sciences)

A high throughput, radiation-hardened encoder decoder ASIC for the tracking system in HIAF.docx

138 Digital implementation of the Inverse Error Function for subpixel resolution algorithms in hybrid pixel detectors.

Hybrid pixel detectors are segmented devices used for X-ray detection that consist of a sensor attached to the readout electronics. Detectors working in single-photon counting mode process each incoming photon individually, have essentially infinite dynamic range and by applying energy discrimination they provide noiseless imaging [1].

To improve the resolution of the detector and allow operation with high-intensity photon fluxes, the pixel size is reduced. However, with decreasing pixel size, a charge sharing effect is more severe. This leads to false event registration or omitting the event, and thus, degradation of the energy and position resolution of the detector. Algorithms aiming at reducing the influence of charge sharing are already implemented on-chip [1]. However, the spatial resolution of the detector can be increased beyond the physical pixel size if charge proportions collected by neighboring pixels are analyzed [2], [3]. An alternative digital algorithm using approximation of the inverse error function can be implemented on-chip.

This work focuses on the core of the new digital algorithm, namely, the implementation of the Inverse Error Function (erf-1) in a 40nm CMOS technology. The design is modeled using SystemVerilog hardware description language (HDL) and verified through targeted and random simulations. A fixed-point arithmetic approach is employed to approximate the function. The impact of architectural trade-offs on power, precision, and area are evaluated. The design is optimized for the digital in-pixel algorithm allowing photon registration with subpixel resolution in photon counting detectors. However, the methodology of the approximation of the erf-1 function can be used for future research in efficient hardware computation of other complex mathematical functions.

[1] R. Ballabriga et al., “Photon Counting Detectors for X-Ray Imaging with Emphasis on CT,” IEEE Trans Radiat Plasma Med Sci, vol. 5, no. 4, pp. 422–440, Jul. 2021, doi: 10.1109/TRPMS.2020.3002949.
[2] P. Grybos, R. Kleczek, P. Kmon, P. Otfinowski, and P. Fajardo, “Small pixel high-spatial resolution photon-counting prototype IC for synchrotron applications,” Journal of Instrumentation, vol. 18, no. 1, Jan. 2023, doi: 10.1088/1748-0221/18/01/C01052.
[3] A. Krzyzanowska and P. Otfinowski, "Digital subpixel algorithm for small pixel photon counting devices," Opto-Electronics Review, ISSN 1896-3757. — 2025 — vol. 33 no. 1 art no. e152768, s. 1–6.

Speaker: Mr Tomasz Litwinek (AGH University of Krakow)

iworid2025_abstract_Krzyzanowska_Otfinowski_Litwinek.pdf

139 A High-Precision Time Measurement Circuit for Pixel Detectors Using a Two-Stage Timing Scheme

Pixel detectors are widely used in high-energy physics experiments for their superior position resolution. In applications such as X-ray polarization detection and particle 3D trajectory imaging, precise time measurement is essential for event reconstruction and improving detection accuracy. These demands impose stringent requirements on the time measurement circuit, necessitating high precision, low power consumption, and compact integration in pixel detector chips.

This paper presents a two-stage time measurement architecture that combines coarse timing and fine timing to improve time measurement accuracy. Coarse timing provides a global clock reference through a 10 MHz counter, while fine timing employs a time-to-amplitude converter (TAC) to overcome the limitations of counter accuracy and achieve higher time resolution. The pixel array in the design consists of 128 $\times$ 128 pixels, with each pixel unit measuring 50 $\mu$m $\times$ 50 $\mu$m, integrating a low-noise charge-sensitive amplifier (CSA), a comparator, and a TAC. Through this architecture, the proposed solution achieves picosecond-level time resolution, effectively enhancing the time measurement accuracy of particle collision events.

Experimental results indicate that the CSA achieves a charge conversion gain of 82.5 $\mu$V/e$^{-}$, an input dynamic range of 0 to 16.7 ke$^{-}$, and a non-linearity error below 4.5%, with an equivalent noise charge (ENC) of approximately 35 e$^{-}$, ensuring excellent low-noise performance. Furthermore, the time measurement path achieves a time resolution of approximately 76.7 ps with an effective range of 100 ns, validating its capability for high-precision timing applications. This work provides a viable solution for applying the Topmetal chip to low-energy X-ray polarization time measurement, as well as other high-precision timing applications.

Speaker: Ni Fang

140 Strip Sensor Readout Circuit for X-ray Spectroscopy: Design and Performance Evaluation

X-ray imaging systems designed for X-ray spectroscopy, based on semiconductor strip sensors, have recently been a key research area. A major objective is to enhance spectroscopic and spatial resolution [1–3]. In spectroscopic applications, short-strip silicon detectors are widely employed due to their low capacitance and leakage current. Using a strip pitch below 100 μm enables high spatial resolution, which is crucial for energy-dispersive X-ray detection [3]. The Charge Sensitive Amplifier (CSA) has been optimized for a detector capacitance of approximately 1.5 pF, with a shaping amplifier default peaking time of about 1 μs, controlled via switchable settings.
To minimize noise, both internal sources (related to front-end electronics) and external disturbances in the radiation imaging system were analyzed [4]. Maintaining a noise level below 50 electrons rms is a key design goal, alongside low power consumption (below 10 mW per channel) and a compact layout. To accelerate processing of incoming events (more than 100 kps/ch), a continuous-time resistive CSA feedback combined with a digital feedback reset is utilized. These approaches align with previous advancements in low-noise charge-sensitive preamplifiers used in high-resolution X-ray spectrometry.
The prototype integrated circuit was designed and fabricated in 180 nm CMOS technology, incorporating eight charge-processing channels, biasing circuits, reset and baseline restoration logic, and a calibration system. This work presents the design, characterization, and measurement results of the strip sensor readout circuit, contributing to the ongoing development of high-performance silicon-based X-ray detectors.

1. P. O’Connor and G. De Geronimo, “Prospects for charge sensitive amplifiers in scaled CMOS,” Nucl. Instrum. Methods Phys. Res. Sect. A Accel. Spectrom. Detect. Assoc. Equip., vol. 480, no. 2–3, pp. 713–725, 2002, doi: 10.1016/S0168-9002(01)01212-8.
2. R. Ballabriga et al., “Photon counting detectors for X-ray imaging with emphasis on CT,” IEEE Trans. Radiat. Plasma Med. Sci., vol. 5, no. 4, pp. 422–440, 2021.
3. P. Wiącek et al., “Position sensitive and energy dispersive X-ray detector based on silicon strip detector technology,” J. Instrum., vol. 10, no. 4, pp. P04002–P04002, 2015, doi: 10.1088/1748-0221/10/04/P04002.
4. W. Zubrzycka and K. Kasiński, “Noise considerations for the STS/MUCH readout ASIC,” GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, 2018.

The authors acknowledge funding from the National Science Centre (Research Project 2020/37/N/ST7/01546).

Speaker: Ms Weronika Zubrzycka-Singh (AGH University of Krakow)

Abstract WZ.pdf

141 Design and Implementation of Irradiation Test Circuit for Low grade HERD-TRD Components

The High Energy Cosmic Radiation Detection (HERD) facility is scheduled for deployment on the China Space Station in 2027. A key load subsystem of the HERD, the Transition Radiation Detector (TRD), requires high-precision energy calibration and astronomical observations in the TeV energy range. However, the reliability of low-grade commercial off-the-shelf (COTS) chips used in the TRD under space radiation environments has not been adequately validated. These chips may be susceptible to risks of single-event latch-up (SEL) and single-event upset (SEU). To address this concern, this study proposes designing an anti-radiation test system with a modular architecture consisting of a master control board and some devices under test (DUTs). This system facilitates irradiation experiments on critical TRD chips, including high-voltage modules, ASIC chips, TVS diodes, precision operational amplifiers, and temperature-pressure sensor chips. The separation of the master control board and DUT ensures signal isolation and minimizes interference, enabling rapid testing of various chip types. China's major SEE test platforms are the single event effect experiment terminal at the Heavy Ion Research Facility in Lanzhou (HIRFL) and Space Environment Simulation and Research Infrastructure (SESRI). It utilizes a centimeter-level uniformly distributed beam for chip irradiation. Real-time monitoring of electrical parameters (such as output current and voltage drift) and functional states of the chips under irradiation allows for assessing SEL trigger thresholds and SEU occurrence rates. The separated architecture effectively isolates radiation interference between the master control system and the DUT, preserving the integrity of test data. This study provides an experimental validation method for assessing the radiation resistance of low-grade COTS chips in the TRD subsystem. It offers a framework for the reliability assessment of COTS chips in space detectors more broadly. Future work will incorporate long-term irradiation data to develop chip failure prediction models, ensuring the stability of HERD during its decade-long in-orbit operation. The electronics test system has been manufactured and is undergoing comprehensive electrical performance testing in preparation for anti-radiation testing. The test results will be reported at the forthcoming conference.

Speaker: Xiangwei Peng (Guangxi University)

Design and Implementation of Irradiation Test Circuit for Low.pdf

142 Design and Implementation of a screening platform for SAMPA ASIC in front-end electronics of HERD-TRD

The High Energy Cosmic Radiation Detection (HERD) facility is one of several planned space astronomy payloads to be deployed onboard the upcoming China Space Station (CSS). HERD is expected to begin operation around 2027 and continue for approximately ten years. Among its key subsystems, the Transition Radiation Detector (TRD) is designed to calibrate the TeV energy spectrum of the Calorimeter (CALO) and assist in X-ray observations. The TRD will be mounted on one side of HERD and primarily consists of detection units, front-end electronics (FEE), back-end electronics (BEE), and a one-dimensional turntable. The FEE architecture employs a combination of SAMPA application specific integrated circuit (ASIC) chips and a field-programmable gate array (FPGA). Developed by CERN, the SAMPA ASIC demonstrates strong radiation tolerance, making it suitable for use in high-radiation environments. However, as it is an industrial-grade chip, its ability to meet aerospace-grade requirements—particularly in terms of long-term stability and low-noise performance under space conditions—remains uncertain. To address this challenge, a dedicated SAMPA chip screening system has been developed. This system comprises a SAMPA chip screening board and corresponding host computer software. The screening board integrates two SAMPA test sockets, a Xilinx Kintex-7 XC7K325TFFG900 FPGA, level shifters, quad serial peripheral interface (QSPI) flash memory, two oscillators, gigabit ethernet, and various other serial peripheral interfaces. The FPGA receives serial scientific data from the SAMPA chips via scalable low voltage signaling (SLVS) and performs data parsing, checksum verification, and data packaging. The processed data is transmitted to the host computer over gigabit ethernet for acquisition. The host software enables comprehensive control of the system by issuing configuration commands and managing data flow. In addition to command transmission and data reception, the software supports both real-time and online data analysis. It facilitates the evaluation of key performance indicators such as noise, linearity, and gain. The SAMPA screening system has been fully designed and implemented, and is currently undergoing a comprehensive electrical performance evaluation. The results of these tests will be reported at the conference.

Speaker: Xin Sun (Institute of Modern Physics, Chinese Academy of Sciences)

Design and Implementation of a screening platform for SAMPA ASIC in front-end electronics of HERD-TRD.pdf

143 Measurement of Dual-Component Attenuation Length in Square BCF-92 Wavelength-Shifting Fibers

Wavelength Shifting (WLS) fibres shift UV/blue light to green, granting efficient scintillation conversion in the process. These fibres enhance detection accuracy in particle physics experiments due to reduced interference susceptibility, improving overall signal quality.
The attenuation length of WLS fibres, defined as the distance over which the signal is reduced by a factor of 1/e, is a critical parameter for light collection and signal uniformity in scintillation detectors.
We are studying optical properties of WLS fibres, with a particular focus on the attenuation length, using a square double-clad BCF-92 fibre from Saint-Gobain. The decrease in light intensity along the WLS fibre is measured using a pulsed light source, and the resulting attenuation curve is fitted to two exponential functions to determine both the short and the long attenuation parameters.
To evaluate the reliability of the measurements, several parameter tests were performed regarding the fibre and external factors. No significant variation was observed across these conditions, indicating a high degree of consistency in the results.
In this presentation, experimental setup, conditions and the obtained results will be assessed and discussed.

Speaker: Dr C. M. B. Monteiro (LIBPhys-UC, LA-REAL, Department of Physics, University of Coimbra, PORTUGAL)

avatar.svg

144 Evaluation of CZT Detector Performance in Alpha and Gamma Spectrometry

This work presents the results of performance studies conducted on 1.5 mm thick cadmium zinc telluride (CZT) detector structures with differing electrode configurations. The aim was to gain a better understanding of the correlation between the physical processes and the electrical and spectroscopic properties of the studied devices. We performed current-voltage (IV) and capacitance-voltage (CV) measurements, as well as gamma and alpha spectroscopies for multiple CZT samples. To increase the signal-to-noise ratio and get an estimation of the absorbed energy of the radiation sources, we designed the detector enclosure with a built-in collimator 1 mm in diameter.

This suite of measurements yields parameters required to assess the depletion behavior, bulk resistivity, charge collection efficiency, and energy resolution for characteristic peaks of different energies. We observed a correlation between spatial variations in charge induction and non-uniformities of the electric field through the detector response to Am-241, Ba-133, and Cs-137 isotopes emitting gamma and x-ray radiation. Varying the potential difference between the electrodes and irradiating the sample with alpha emissions provides insight into mobility-lifetime characteristics, as well as charge transport and trapping mechanisms within the bulk. The role of defect density across the semiconductor bulk of the measured structures is being investigated in an adjacent study and is yet to be formulated.

The inter-peak distance differences relative to peak centroids and energy resolution of the peaks were used as metrics of performance for alpha spectroscopy. Physical properties of electrical contact interfaces and the external signal path toward the amplifying electronics have a defining influence on signal formation.

To summarize, the results highlight the impact of undesired effects on energy resolution and the performance of CZT-based structures for gamma and alpha detection. This is relevant to the global goal of developing room-temperature, well-performing, high-Z semiconductor devices.

Speaker: Nikita Kramarenko (Helsinki Institute of Physics (FI))

145 Radiation detection with Polycrystalline CVD Diamond Film: Effects of Film Thickness and Irradiation on Detector Performance

Diamond is a highly attractive material due to its excellent chemical and physical properties, making it suitable for various applications, including heavy particle detection, neutron detection, and radiotherapy dosimeters. Atomic and mass numbers 6 and 12 are considered to be almost tissue-equivalent, providing an important advantage over alternative materials such as silicon. Although single-crystal diamonds are extremely expensive, polycrystalline chemical vapor deposited (pCVD) diamond films offer a cost-effective alternative [1]. Data reported in the literature indicate that pCVD diamond exhibits similar behavior to single-crystal diamond.
In this study, we fabricated and tested charged particle detectors based on pCVD diamond films operated at zero bias. The pCVD diamond films were grown on a conductive silicon (100) substrate. Polycrystalline diamond films with varying thicknesses from 0.5 um to 10 um were prepared by microwave plasma-enhanced CVD. We investigated two types of polycrystalline diamond films, distinguished by the grain size: nanocrystalline and microcrystalline. The samples had a total area of about 1 cm2. On the back side (Si substrate), a full-area Ti/Au (5/50 nm) contact was evaporated using ultra-high vacuum deposition equipment. Circular contacts with a diameter of 1 mm to 3 mm were prepared on the diamond layer using the same metallization.
The current-voltage characteristics of the pCVD diamond detector were measured at RT using a custom-built picoampermeter/voltage source. The measurements were performed from -100 V to 100 V, with typical currents in the range of tens of picoamperes. The prepared pCVD diamond samples operate at zero bias and the current-voltage measurements conformed good ohmic contacts. The detector structures were subsequently placed in a vacuum chamber and connected to the spectrometric chain for alpha particle detection. A 241-Am radiosotope was used to generate monoenergetic alpha particles with an energy of 5489 keV. Samples with a contact diameter of 1 mm exhibited the best performance, achieving a relative energy resolution of 15%. Further investigation involved degradation of pCVD diamond with microcrystalline grains using 3.5 MeV protons at various fluences up to 1E15 p/cm2. Subsequent testing with alpha particles revealed a significant impact on the detected alpha particle spectrum. At a fluence of 1E13 p/cm2, the detected peak is shifted to the lower channels, corresponding to 20% of its original value. At the maximum proton fluences, the pCVD diamond detectors were unable to distinguish alpha particles from noise.

References:
[1] M. Bruzzi et al.: Diamond & Related Materials 20 (2011) 84.

Acknowledgement: This work was partially supported by grants of the Slovak Research and Development Agency No. APVV-22-0382, SK-CZ-RD-21-0116, the Ministry of Education, Youth and Sports of the Czech Republic No. LU-ASK22147 and the Scientific Grant Agency of the Ministry of Education of the Slovak Republic and the Slovak Academy of Sciences No. 2/0063/24.

Speaker: Dr Bohumir Zatko (Institute of Electrical Engineering, Slovak Academy of Sciences)

Abstrakt_Zatko_figure.pdf

146 Study of the charge carrier properties of a pixelated 4H-SiC with Timepix3

Recent advantages in the detector production have facilitated the manufacture of pixelated 4H-SiC detectors, which can be an alternative to silicon ones especially in the harsh radiation environment, or in the environment with high temperatures, where such sensors profit from their higher band gap. Moreover, thanks to an elastic scattering cross-section of carbon for fast neutrons the SiC sensors have higher neutrons detection efficiency than Si sensors.

In the present contribution, we characterize pixelated 4H-SiC sensors of ~80 µm sensitive thickness flip-chip bonded to the Timepix3 ASIC. Comprehensive testing was performed including measurement of IV curves, depletion voltage scans, determination of the achievable energy resolution for gammas and MIPs, as well as a study of the response to monoenergetic fast neutrons, and mixed relativistic ions. By performing measurements at grazing angle, the latter measurement allows to study the dependence of the holes drift velocity on the electric field when irradiating at grazing angle utilizing the 1.5 ns time-stamp measurement precision of Timepix3 [1]. The holes mobility was measured to be μh = (35.2±3.5) cm2/V/s, consistent with literature.

References
[1] P. Smolyanskiy et al 2021 JINST 16 C12023

Acknowledgements
B.B. and P.S. acknowledge funding from the Czech Science Foundation (GACR) under Grant No. GM23-04869M.

Speaker: Dr Petr Smolyanskiy (Czech Technical University in Prague (CZ))

iworid2025_SiC_figures.pdf

147 Metal-oxide-semiconductor structures based on Ni/Y2O3/4H-SiC for alpha particle spectroscopy

Silicon carbide belongs to the wide band gap semiconductor materials, and it is very perspective in the detection of various types of radiation. Another advantage is the commercial availability of high-quality crystalline material required for the preparation of radiation detectors. The 4H-SiC has the band gap energy of 3.23 eV at room temperature, breakdown voltage about 2×10$^6$ Vcm$^{-1}$, carriers saturation velocity of 2×10$^7$ cms$^-$$^1$ and excellent physical and chemical stability. A large band gap energy is advantageous for low leakage current and high radiation tolerance. Despite all the above advantages, fabricated Schottky barrier detectors have certain drawbacks. One of them is the large dispersion of reverse current values, and usually only a small percentage of structures have low currents in the order of pA. For this reason, we have focused on the preparation of SiC MOS (Metal Oxide Semiconductor) structures where the oxide interlayer can be beneficial to achieve lower leakage current and higher breakdown voltage [1, 2].

We have fabricated Ni/Y$_2$O$_3$/4H-SiC structures on 100 $\mu$m thick 4H-SiC epitaxial layers. The Y$_2$O$_3$ layers with three different thicknesses (5, 20 and 30 nm) were deposited by pulsed laser deposition. The wide bandgap (5.6 eV) of Y$_2$O$_3$ and high dielectric constant (14-18) is advantageous for the junction leakage current and increasing breakdown voltage. The quality and thickness of deposited oxide layer was tested with X-ray diffractometry. The circular Ni contacts with different diameters (1 and 2 mm) were deposited on the oxide layers. First, we measured the current-voltage characteristics in both directions and the structures show excellent rectification properties. The forward current analysis shows an increase in the Schottky barrier height from the value about 1.08 eV up to 1.24 eV with oxide thickness, while the reverse current decreases to an average value of about 30 pA/cm$^2$ at -400 V. Radiation detection properties were tested using a triple alpha particle source $^{238}$Pu, $^{239}$Pu, $^{244}$Cm up to a reverse bias of 400 V. The best obtained energy resolution of 17.4 keV FWHM (Full Width at Half Maximum) for 5.8 MeV alpha particles was measured using the detector with a 20 nm oxide layer. This corresponds to a relative value about 0.3%. Despite the best electrical properties of the MOS structures with the thickest oxide layer, the energy resolution was slightly worse with a value of about 25.0 keV (0.43 %). This is because the oxide layer represents the dead layer for alpha particles and increasing its thickness degrades the energy resolution of the detector. However, for other types of radiation such as X-rays or neutrons, the oxide layer thickness shouldn’t be a serious problem.

References: [1] OmerFaruk Karadavut, Ritwik Nag, Josh W. Kleppinger, Gene Yang, Dongkyu Lee, Sandeep K. Chaudhuri, and Krishna C. Mandal “Investigation of Ni/Y2O3/n-4H-SiC metal-oxide-semiconductor structure for high-resolution radiation detection”, Proc. SPIE 12241, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XXIV, 1224107 [2] Sandeep K. Chaudhuri; OmerFaruk Karadavut; Joshua W. Kleppinger; Ritwik Nag; Gene Yang; Dongkyu Lee, Krishna C. Mandal “Enhanced Hole Transport in Ni/Y2O3/n-4H-SiC MOS for Self-Biased Radiation Detection”, IEEE Electron Device Letters 43(9) pp.1416-1419

Acknowledgement: This work was partially supported by grants of the Slovak Research and Development Agency Nos. APVV-22-0382, SK-CZ-RD-21-0116, Ministry of Education, Youth and Sports of the Czech Republic No. LU-ASK22147 and of the Scientific Grant Agency of the Ministry of Education of the Slovak Republic and the Slovak Academy of Sciences No. 2/0063/24

Speaker: Marcel Talacko (Institute of Electrical Engineering, Slovak Academy of Sciences)

iworid2025_abstract_Talacko_1.docx

148 JUNGFRAU Prototypes with iLGAD Sensors for Soft X-ray RIXS

The recent development of inverse Low Gain Avalanche Diode (iLGAD) sensors with optimized thin entrance windows has made hybrid pixel detectors available for applications with soft X-rays. One promising use case is Resonant Inelastic X-ray Scattering (RIXS), which requires high statistics and multidimensional scans while being inherently photon-starved. The multi-kHz image rates and large area coverage of hybrid pixel detectors would substantially improve RIXS efficiency and throughput compared to existing detectors.
We have developed multiple detector prototypes combining iLGAD sensors fabricated by Fondazione Bruno Kessler with different versions of the charge-integrating JUNGFRAU readout ASIC. These include various single-chip (2 × 2 cm$^2$) and four-chip (4 × 4 cm$^2$) systems, featuring rectangular pixels (with 225 × 25 µm$^2$, 300 × 18.75 µm$^2$, or 375 × 15 µm$^2$ pixel dimensions) that fit to the native JUNGFRAU pixel matrix (75 × 75 µm$^2$). This design enables one-dimensional position interpolation via charge sharing, crucial for enhancing spatial resolution and, consequently, RIXS energy resolution.
The prototypes have undergone extensive characterization in the lab and at the Pollux beamline of the Swiss Light Source, with larger systems tested at RIXS spectrometers at SwissFEL and European XFEL. This contribution summarizes the results collected to date, discussing noise performance, device uniformity, pixel yield, stability, and interpolation effectiveness, comparing rectangular-pixel and regular square-pixel designs. Additionally, we will introduce prototypes with a modified version of the JUNGFRAU ASIC, aimed at further reducing electronic noise and thereby extending single photon resolution to lower X-ray energies.

Speaker: Dr Viktoria Hinger (Paul Scherrer Institut)

iworid2025_HingerV_abstract.pdf

JF_RIXS1_new2.pdf

149 X-ray performance evaluation between Timepix based CdTe detector and scintillator film based CMOS flat panel imager

X-ray detections have wide applications in medical imaging, security inspection and scientific research. At present, the realized way of X-rays detector can be typically divided into two types, direct and indirect conversion method. Direct radiation detection based on semiconductors like CdZnTe, a-Se and metal halide perovskites, have experienced rapid development and the demonstration of multiple application including X-ray imaging. Direct detector with a wide linear response range, fast pulse rise time, high-energy resolution, and spatial resolution can be obtained. The indirect detector refers to the conversion of X-rays into visible light through scintillators which can be further captured by an array photodiode (PD). At present, indirect X-ray detectors are widely used in ordinary flat panel X-ray detectors.
In this work, Both detection methods have been used to characterize and evaluate the imaging capabilities of two different imaging systems: a CMOS flat panel with Gadox and CsI:Tl scintillation films and a hybrid semiconductor pixelated detector(Timepix). A micro-focus X-ray source with a tungsten target was used for the measurements. A CMOS flat panel detector is consisted of photodiode array surface with 512(width) x 1,024(height) pixels and 48μm pixel pitch. 24.6x49.2mm2 photodiode array area is connected to camera module and the measured 12-bit image data are transferred to image acquisition software. Timepix3 is a single-photon counting type based readout ASIC chip. This hybrid pixel device (256x256 square pixels, 55mm pitch) developed at CERN consists of a semiconductor sensor layer (2mm CdTe in our sensor) bump-bonded to the readout ASIC. The imaging capability is evaluated in terms of several important characteristics: spatial resolution, relative X-ray sensitivity, signal to noise ratio (SNR) and contrast to noise ratio (CNR). The corresponding X-ray transmission imaging measurements with object phantoms were done under identical conditions in order to assure comparability.

Speaker: 보경 차

iworid 2025 timepix CdTe detector.docx

150 Test of COFFEE2, the first 55nm High Voltage CMOS sensor prototype

To meet the increasingly demanding requirements of future tracking detectors for the LHCb Upgrade II and the future Circular Electron-Positron collider, advanced detector technologies with enhanced hit density processing capabilities and superior radiation tolerance are essential. To study the sensor performance and electronic response in the next generation process of HV-CMOS, a sensor chip, COFFEE2, is designed and tested. This poster will present the test results of COFFEE2, which is the first 55nm HV-CMOS sensor prototype in high energy physics. Charge injection and red laser are used to test the in-pixel circuit functionality and their uniformity in pixel array. Radioactive sources are used to study the sensor performance in comparison with TCAD simulation.

Speaker: Cheng Zeng (Chinese Academy of Sciences (CN))

iWoRiD_poster_v2.pdf

151 3D Doping Concentration Imaging of Silicon Sensors Using Backside Pulsing

Mapping the distribution of dopants in three dimensions provides a deeper understanding of the characteristics of silicon sensors, such as depletion voltage, electric field distribution, and charge collection properties. A uniform distribution across a large sensor area and depth is essential for high manufacturing yield and device reliability. However, conventional measurement techniques face significant limitations when applied to high-resistivity silicon sensors commonly used in high-energy physics and photon science. Methods such as secondary ion mass spectrometry provide high-resolution measurements but are insensitive to doping concentrations below 1×10^12 cm^(-3), while capacitance-voltage profiling and spreading resistance profiling offer only coarse granularity. There is a need for a reliable, high-granularity method capable of characterizing doping concentration in 3D.
To address this, we have developed a novel 3D doping concentration imaging method for silicon sensors, leveraging the backside pulsing technique [1]. The tested sensors, with 75 μm and 25 μm pixel pitches, were bump-bonded to the charge-integrating readout chips JUNGFRAU [2] and MÖNCH [3], respectively. Careful calibrations were first performed using X-ray fluorescence and the backside pulsing method, with the sensors biased above full depletion. The 3D doping concentrations were then extracted for individual pixels by applying backside pulsing at different bias voltages and numerically solving the 1D Poisson’s equation for electrostatics.
We will present 3D doping concentration distributions from sensors with up to 4×8 cm^2 with 75 μm pixels and up to 1×1 cm^2 sensors with 25 μm pixels. Furthermore, we will discuss the observed inhomogeneity in integrated doping concentration, both laterally across the sensor plane and vertically through the sensor depth. Finally, the potential impact of observed doping non-uniformity on the detector’s operation and performance will be outlined.

[1] D. Mezza, et al 2016 JINST 11 C11019
[2] A. Mozzanica, et al 2018 Synchrotron Radiation News 31(6) 16-20
[3] M. Ramilli, et al 2017 JINST 12 C01071

Speaker: Dr Xiangyu Xie (Paul Scherrer Institut)

2025_iWoRiD_3D Doping Concentration Imaging of Silicon Sensors Using Backside Pulsing.pdf

152 High-Z Sensors and AGIPD: First results

The Adaptive Gain Integrating Pixel Detector (AGIPD) is a hybrid pixel, large area detector tailored to the unique beam structure of the European XFEL [1]. The development is a collaborative effort of Deutsches Elektronen-Synchrotron (DESY), the University of Hamburg, the University of Bonn and the Paul Scherrer Institute (PSI) in Switzerland, and has been in operation with silicon sensors since 2017. It is currently the main detector system of 2 scientific instruments (SPB/SFX and MID) and a very valuable tool for the High Energy Density (HED) scientific instrument.

The HED instrument aims at applications in the photon energy range of 20 to 30 keV, where silicon sensors become inadequate due to their low quantum efficiency. To address this limitation, we proposed to develop an AGIPD detector with high atomic number (high-Z) sensor materials. Compound semiconductors such as chromium-doped gallium arsenide (GaAs:Cr), cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) were considered, and an electron-collecting version of AGIPD ASICs (ecAGIPD) was designed to leverage from the higher mobility and longer lifetime of electrons with respect to holes in such materials.

While these sensor materials have been extensively characterized by the synchrotron community, their use at XFELs has, to date, been extremely limited. While initial measurements made at LCLS using CdZnTe and GaAs:Cr LPD sensors demonstrated encouraging performance [2], these measurements were limited to pulse repetition rates of 120Hz. Their performance at the high instantaneous flux and MHz repetition rates delivered by the EU.XFEL is yet to be stablished and is the focus of this work.

Prototypes consisting of either 4 single chips or 2x2 quads where flip-chipped and mounted onto AGIPD front-end modules. After initial characterization, the 4 best-performing modules, comprising GaAs:Cr and CdZnTe of different generations and hybridization methods, were mounted side by side on a detector head. The system was tested at HED during beamtimes in November 2024 and February 2025, focusing on the characterization of the system performance and comparison of the sensor materials. A Sparta silicon module produced by X-Spectrum with AGIPD 1.1 technology was used as a reference. In the first beamtime the prototypes were exposed to powder diffraction rings at 18 and 24 keV photons, while the second used homogeneous scattering of 8 keV photons to explore higher intensity conditions.

The ecAGIPD ASICs presented a lower gain compared to AGIPD 1.1 ASICs, even after correcting by the electron-hole pair creation energy of each sensor material. The signal formation in the CdZnTe sensors was delayed by 15 to 25ns with respect to Si and GaAs:Cr, which is consistent with an enhanced small-pixel effect on such materials: while all sensors have an identical pixel pitch of 200um, CdZnTe sensors are 2mm thick, in contrast with 500um thick Si and GaAs:Cr sensors. The preliminary results indicate good linearity and residual after-pulse signal contributing less than 1% of the pulse intensity on all investigated sensor materials, up to an estimated flux of 3.5e+04 8 keV photons/mm2/pulse of 200ns.

[1] Allahgholi, A. et al. (2019). J. Synchrotron Rad. 26, 74-82.
[2] Veale, M.C. et al. (2019). J. Phys. D: Appl. Phys. 52, 085106.

Speaker: Debora Magalhaes Suarez (DESY)

153 Gamma-ray imaging using a single segmented HPGe detector and a lightweight Pulse Shape Analysis (PSA) machine learning method

Gamma-ray imaging based on Compton scattering typically requires a two-component system, consisting of a scatterer and an absorber. The present work explores an alternative approach using a single, segmented high-purity germanium (HPGe) detector from the Advanced GAmma Tracking Array (AGATA) [1] collaboration for reconstructing the position of a radioactive source. A key advantage of using a single HPGe detector is its superior detection efficiency, compared to a scatterer-absorber device, as it can simultaneously capture and process gamma rays from nearly the full solid angle. The detector’s segmentation, 36 segments and a central core contact, allows pulse shape analysis (PSA) [2,3] techniques to enhance position resolution of the gamma rays interactions. Additionally, the excellent energy resolution of HPGe intrinsically reduces uncertainty in the half-opening angle of the Compton cone, enhancing the reconstructed image resolution.
The present study introduces a lightweight PSA machine learning model based on a 3D basis of waveforms, of more than 46000 points equally spaced by 2 mm along X, Y and Z axes in the HPGe crystal volume, constructed using the IPHC scanning table with the Pulse Shape Comparison Scan (PSCS) [4] method. By replacing the computationally intensive 𝜒2 comparison between recorded waveforms and a 3D database, this model improves processing speed, making it well-suited for real-time applications. These advancements highlight the potential of a single segmented HPGe detector for timeefficient and precise gamma-ray imaging.
Keywords Gamma-ray imaging, 4𝜋-detection, lightweight PSA, single-volume device
[1] S. Akkoyun et al., “AGATA—advanced GAmma tracking array,” Nucl. Instrum. Methods Phys. Res. A, vol. 668, pp.
26–58, Mar. 2012, doi: 10.1016/j.nima.2011.11.081.
[2] B. Bruyneel, B. Birkenbach, and P. Reiter, “Pulse shape analysis and position determination in segmented HPGe detectors: The AGATA detector library,” The European Physical Journal A, vol. 52, no. 3, Mar. 2016, doi: 10.1140/ epja/i2016-16070-9.
[3] R. Venturelli and D. Bazzacco, “Adaptive Grid Search as Pulse Shape Analysis Algorithm for γ-Tracking and Results.” [Online]. Available: https://www1.lnl.infn.it/~annrep/read_ar/2004/contrib_2004/pdfs/FAA122.pdf
[4] B. De Canditiis and G. Duchêne, “Simulations using the pulse shape comparison scanning technique on an AGATA segmented HPGe gamma-ray detector,” The European Physical Journal A, vol. 56, no. 10, Oct. 2020, doi: 10.1140/epja/s10050-020-00287-6.

Speaker: Antoine Corbel (CNRS or Unistra (Strasbourg university))

abstract_Antoine_CORBELtalk.pdf

154 Development and evaluation of linear array type ring detector for patient dose delivery monitoring system in high dose-rate brachytherapy

High dose-rate brachytherapy (HDR-BT) is a treatment technique in which a radioisotope (RI) is directly inserted into the human body. This allows for minimizing the dose to surrounding critical organs while concentrating the radiation dose on the tumor tissue, resulting in high therapeutic efficacy. Treatment planning for HDR-BT is performed based on anatomical images including the clinical applicator, and the prescribed dose is delivered to the clinical target volume. The dose distribution is determined by adjusting the dwell positions and dwell times of the source within the applicator, necessitating verification of dose accuracy under specific dwell conditions. In external beam radiotherapy, patient-specific quality assurance (PSQA) is routinely performed prior to treatment to verify the patient dose, typically using a flat panel detector mounted on the treatment machine. Similarly, research has been conducted to implement a PSQA system for HDR-BT using flat panel detectors. However, such systems are subject to limitations due to the dependency on irradiation distance and angle of the RI. Therefore, a new approach is required that allows for consistent control of source distance and angle while accommodating the curved geometry of clinical applicators.
In this study, a ring detector with a fixed radius was developed to evaluate the feasibility of measuring dose distributions under specific RI dwell conditions. Monte Carlo (MC) simulation results using GATE v9.1 were also compared to validate the experimental results. A flexible material based on polydimethylsiloxane (PDMS) polymer was fabricated to allow bending to the irradiation radius of the Iridium-192 (Ir-192) source. Polycrystalline mercury (II) iodide, a material with high radiation conversion efficiency, was used as the sensing material, and mixed with PDMS to create a flexible detector. A flexible printed circuit board (fPCB) with 25 pixel electrodes was configured as a linear array, with each electrode measuring 2 cm × 0.1 cm and spaced at 0.3 cm intervals. The ring detector was constructed by fixing the fPCB into a semicircular shape, resulting in a radius of 3.85 cm.
The repeatability of the detector was evaluated using the median value of the 25 pixels (57.0 nC), with a relative standard deviation of 0.87% over 10 repeated measurements. The linearity of dose with respect to dwell time showed a coefficient of determination of 0.9997. Dose measurements were conducted at positions spaced 0.5 cm apart from the pixel center point up to a distance of 2.5 cm. The experimental results were compared with MC simulations. The dose distribution decreased linearly as the Ir-192 source moved further from the detector. The slope of the linear function was 0.0051 for the measurement and 0.0137 for the simulation, indicating a difference of 0.0086 and a more gradual decrease in the measured data. Ir-192 follows the inverse square law, resulting in a power function for dose fall-off with distance.
This study fixed the detector radius at 3.85 cm based on the detector size, resulting in a source-to-surface distance (SSD) of over 1 cm. In the future, by configuring an SSD of less than 1 cm to monitor the rapid intensity changes near the source, a PSQA system capable of verifying the calculated dose of HDR-BT applicators could be established.

Speaker: Dr Moo-Jae Han (Seoul National University Bundang Hospital)

155 Metal artifact reduction in computed tomography using single-energy material decomposition-driven virtual monochromatic imaging

Metal artifacts—arising from the interaction between the high-density metals and the X-ray beams— pose a significant challenge to computed tomography (CT) by degrading image quality and hindering accurate diagnosis and treatment planning. Although numerous metal artifact reduction (MAR) techniques have been proposed, none have achieved universal adoption due to their varying effectiveness, which depends heavily on the scanned object and CT system characteristics. In this study, we present a novel MAR method that utilizes single-energy material decomposition (SEMD)-driven virtual monochromatic imaging (VMI). As illustrated in Figure 1, the proposed method comprises three main stages: 1) SEMD, which separates soft and dense material components from a single-energy CT scan by analyzing attenuation length in the reconstructed CT image, 2) VMI generation, in which virtual monochromatic projections are synthesized using selectively decomposed SEMD data to enhance contrast and suppress artifacts, and 3) MAR processing, where conventional interpolation-based MAR is applied to the synthesized projections, followed by CT image reconstruction via filtered backprojection. To evaluate the efficacy of the proposed approach, we conducted simulations using a three-dimensional numerical cylindrical phantom containing various human biomaterials (Figure 2). The resulting image quality was quantitatively assessed. Figure 3 presents representative outcomes, including the reference slice image, the original metal-corrupted image, the VMI output, the MAR-corrected image, and the final image after combining VMI and MAR. Preliminary results indicate that the proposed method can significantly reduce metal artifacts in CT images. Comprehensive quantitative results and discussions will be presented in the full paper.

Speaker: Mr Juyong Shin (Department of Radiation Convergence Engineering, Yonsei University, Wonju, Republic of Korea)

[2025iWoRiD]JYShin.pdf

156 Towards a Compact Readout Device for Timepix4

Timepix4 [1] is the latest readout chip in the Timepix family of detectors, developed at CERN within the Medipix collaboration. Compared to its predecessor, it offers higher resolution (512 × 448 pixels with a 55 µm pitch) and significantly improved Time-of-Arrival (ToA) performance, with time binning down to 195 ps. Timepix4 is also capable of handling extremely high hit rates — up to 2.5 Ghits/s per chip — transmitted via sixteen serial output lines, each supporting data rates of up to 10 Gbps.

Currently, the primary readout system used with Timepix4 is SPIDR4, developed by Nikhef [2]. While this system excels in high-speed performance for test beams and large-scale experiments, it lacks a user-friendly interface and is not ideally suited for compact laboratory setups or educational environments.

In this contribution, the authors present and discuss the architecture of a proposed compact acquisition system for Timepix4, designed specifically for laboratory measurements, demonstrations, and educational use. The system will support a single Timepix4 chip and is expected to provide a reduced bias voltage range, suitable primarily for silicon sensors. A USB interface is being considered to ensure simple connectivity with laptops or tablets.

The authors also explore strategies to avoid the use of expensive FPGA platforms with high-speed transceivers, while still enabling basic operation of Timepix4. The contribution includes an overview of the system’s planned features and describes the current status of its development.

References:
[1] Llopart, Xavier, et al. "Timepix4, a large area pixel detector readout chip which can be tiled on 4 sides providing sub-200 ps timestamp binning." Journal of Instrumentation 17.01 (2022): C01044.
[2] Online. https://indico.nikhef.nl/event/2243/contributions/5102/attachments/2401/2807/SPIDR4-MF-GP-apr2020.pdf

Speaker: Dr Pavel Broulim (University of West Bohemia (CZ))

157 Performance Evaluation of Ultra-Thin Low Gain Avalanche Diodes (LGADs) for Fast Timing and 4D Tracking

Low-Gain Avalanche Diodes (LGADs) are advanced silicon sensors developed for the fast and precise detection of minimum ionizing particles (MIPs), offering promising performance for certain applications in high-energy physics experiments. Fabricated on thin silicon wafers—typically ranging from 20 to 50 microns in thickness—with internal gain that results in a high signal-to-noise ratio (SNR), they enable exceptional timing resolution. These characteristics make LGADs particularly attractive for 4D tracking applications in future collider environments, such as the High-Luminosity Large Hadron Collider (HL-LHC) and the planned Electron-Ion Collider (EIC), where fine spatial and temporal resolution is critical for disentangling high pile-up events, studying complex collision dynamics and particle identification.
LGADs produced by Brookhaven National Laboratory (BNL) have been studied in detail in this work, focusing on devices fabricated on 20 μm and 30 μm thick substrates. Comprehensive electrical characterization confirms stable gain layers and low leakage currents, while charge collection studies using the Transient Current Technique (TCT) demonstrate uniform signal response across the sensor surface. Time-resolution measurements performed with fast laser systems reveal timing performance on the order of tens of picoseconds (ps). Future radiation damage studies using high-fluence proton beams are planned to evaluate the long-term performance and address known limitations in radiation hardness.

Speaker: Fasih Zareef (AGH University of Krakow (PL))

IWORID_2025_FZareef.pdf

158 SpacePix Chip Development from VZLUSAT-2 Flight to SpacePix3 Laboratory Characterization

We report on the evolution of the SpacePix chip series designed for compact, high-resolution space radiation detection. The SpacePix2-based system was deployed onboard the VZLUSAT-2 nanosatellite and successfully operated in low Earth orbit, collecting in-situ data on the radiation environment over several months. The detector demonstrated stable operation, directional sensitivity, and the ability to discriminate between ionizing particle species, confirming the potential of pixelated semiconductor sensors for real-time space dosimetry.
Leveraging the flight experience, we have developed and characterized the next-generation SpacePix3 chip. This iteration introduces significant enhancements, including improved signal-to-noise ratio, refined energy calibration, and integrated timing capabilities, while maintaining a low power profile and minimal volume critical for nanosatellite missions.
At IWORID 2025, we present a comprehensive overview of the laboratory performance of the SpacePix3 detector system. Characterization includes pixel response uniformity, energy resolution, and validation against simulations and flight data from SpacePix2. These results demonstrate SpacePix3 as a promising platform for future spaceborne radiation imaging systems, enabling both dosimetric monitoring and particle identification in compact form factors suitable for long-duration and multi-directional exposure scenarios.

Speaker: Radek Novotny (Czech Technical University in Prague (CZ))

RadekNovotny-IWORID2025.pdf

159 Characterizing cross-talk in linear SPAD array and harnessing it for system calibration

In this work, we present a detailed study of cross-talk in a linear single-photon avalanche
diode (SPAD) array using the LinoSPAD2 detector, which features 512 time-resolved
channels with a timing precision of 40 ps r.m.s. By characterizing and leveraging cross
talk effects, we were able to calibrate the intrinsic delays in the system readout, reducing
the uncertainty in the position of coincidence peaks from ±10 ns down to ±50 ps. While
such detectors are increasingly used in diverse fields – from quantum communications to
time-resolved imaging and quantum-assisted astronomy – their performance can be
critically affected by inter-channel cross-talk, especially in photon correlation
measurements such as the Hanbury Brown and Twiss (HBT) effect. Cross-talk can mimic
genuine correlation signatures, posing a fundamental challenge in experiments relying on
spatial or temporal intensity correlations.
We compare two versions of the LinoSPAD2 sensor: one equipped with microlenses to
enhance photon collection efficiency, and one without. Our measurements reveal a clear
difference in cross-talk behavior between the two. Specifically, we observe that the
addition of microlenses, while beneficial for photon detection efficiency, also leads to a
measurable increase in cross-talk probability between neighboring channels. We analyze
the spatial decay of cross-talk and discuss its implications for experiments sensitive to
second-order correlations. These findings offer valuable insight into the trade-offs
involved in SPAD array design and optimization for low-noise, high-resolution single
photon detection.
[1] Kulkov, Sergei, et al. "Inter-pixel cross-talk as background to two-photon interference
effects in SPAD arrays." Journal of Instrumentation 19.12 (2024): P12015.
[2] Kulkov, Sergei, et al. "Characterizing and exploiting cross-talk effect in SPAD arrays
for two-photon interference." arXiv preprint arXiv:2504.01185 (2025).

Speaker: Lou-Ann PESTANA DE SOUSA

Iworid_2025_abstractPESTANA_DE_SOUSA.pdf

Poster Iworid_2025_LouAnnPESTANADESOUSA.PNG

160 Title： The Layer 0 upgrade of the AMS-02 experiment on the ISS

Abstract:

AMS-02 is a multipurpose particle physics detector installed on the International Space Station. The objective includes search of dark matter, the primordial anti-matter, and the origin and propagation of cosmic rays. L0 (Layer 0) is a double-layer plane of silicon strip detector to be installed on AMS-02, which increases the acceptance of cosmic rays by 300% and significantly improves the ability of identifying heavy ions.

We will introduce the construction process and quality control (QC) of the building process. In order to keep stable performance in the extreme environment of space, mechanical accuracy and strength, detector leakage current, and noise levels must be tightly controlled during the construction process and finally tested and verified. Visual inspection, OGP metrology, and Electrical-Test will be done during construction. All the relevant results will be presented.

Speaker: Qinze Li (Chinese Academy of Sciences (CN))

IWORID poster_Qinze.pdf

IWORID poster_Qinze.pptx

161 aare – A Flexible Data Analysis Library for Hybrid Pixel Detectors

The data rates of hybrid pixel detectors are rapidly increasing, with next-generation systems moving from 10 Gbit/s to 100 Gbit/s readout. For Matterhorn, a new single-photon counting detector under development at PSI, a 16-megapixel configuration would generate data rates of up to 3.2 Tbit/s (or 400 GB/s). These high data rates are not only a challenge for beamline operation but also make laboratory testing more difficult, emphasizing the need for efficient data handling tools. Aare is a library designed to help scientists analyze terabyte-scale datasets from hybrid pixel detectors. It features for example cluster finding, interpolation and detector calibration. The core is implemented in C++ for performance, but we also offer low-overhead Python bindings for ease of use. The code is multi-threaded capitalizing on the parallelizable nature of pixel and frame processing. Development plans include support for heterogeneous hardware architectures (GPU/FPGA) to further enhance performance.

Speaker: Erik Fröjdh (Paul Scherrer Institut)

162 A comparative response study of a Medipix3 Silicon Sensor Detector using X-rays and Electrons

The Medipix3 hybrid pixel detector has found use globally, with applications such as colour x-ray CT scanners and electron microscopy detectors. These detectors are typically characterised using x-rays, either at a synchrotron facility, or using x-ray flouresence. While this is a convenient and well understood characterisation method, as the application range of these detectors broadens it is important to understand their response to other particles. This work presents results of characterisation done using both x-rays and electrons at an energy range of 5-30keV. The x-ray characterisation was performed using x-ray flouresence. A novel technique is presented to perform characterisation with electrons -the electron mirror. A broad range of detector modes were investigated, including various gain modes and pre-amplifier settings. Additionally, the Medipix3 chip contains a unique feature called charge summing mode (CSM). In charge summing mode, incident hits in neighbouring pixels can be recorded and the sum of all charge assigned to the pixel with the greatest proportion at the pre-amplifier level. The effect of charge summing mode on the detector response is investigated for both x-rays and electrons.

Speaker: Rory Mcfeely (University of Glasgow)

163 Design of electronics readout system based on zero compression and threshold comparison algorithm

This paper presents Cosmic X-ray Polarization Detection-Topmetal-M2 (CXPD-M2), a CubeSat electronic system based on the Topmetal-M2 pixel chip, specifically designed for X-ray polarization detection in the 2–10 keV energy range. The CXPD-M2 system comprises both hardware and firmware. The hardware, developed under stringent power and space constraints, adopts a three layer electronic board architecture consisting of a chip bonding board, a front-end signal processing board, and a back-end control board. The firmware not only provides essential communication, device control, and data transmission functionalities but also integrates zero-suppression and threshold comparison algorithms within a rolling shutter readout mode for large area pixel arrays, effectively reducing noise while preserving valid particle signals. Experimental validation using alpha-particle and neutron-source demonstrated that, with a 400 $\times$ 512 pixel Topmetal-M2 operating at a 20M readout rate, the system achieves a 99$\%$ reduction in redundant data, confirming its feasibility. This compact and efficient CubeSat based solution for X-ray polarimetry establishes a promising platform for future spaceborne detection applications and offers opportunities for further advancements in pixel chip algorithm integration and optimization.

Speaker: Dong chunlai

164 Design and Evaluation of CZT-based Micro-activity Calibration System for TAT Application using Monte Carlo Simulation

A novel dose calibrator based on CZT detector has been designed to accurately measure low-level activities that conventional dose calibrators cannot reliably measure. In order to ensure that the dose delivered to the patient is what is intended in radiopharmaceutical therapies, dose calibrator is a priory. Errors in exact activity measurement would otherwise result in overdose or underdose which are both undesirable effects. Especially for targeted alpha therapy (TAT), low-activity alpha emitters as low as μCi to nCi is typically used. However, conventional dose calibrator, or high pressurized gas-filled ionization chamber has limited sensitivity and lack of energy discrimination which makes it not suitable for measuring micro-activity. Therefore, we designed a CZT based micro-activity calibration system (20mm x 20mm x 10mm) in a box shaped well configuration to achieve nearly 4π solid angle coverage using GATE simulation.
The performance of the designed CZT-based micro-activity calibrator was evaluated by comparing it with NaI-based well counter or gamma counter (HIDEX Automatic Gamma Counter) which serves as an alternative to conventional dose calibrator. An alpha-emitting 225Ac point source was simulated using Monte-Carlo based GATE simulation sequentially lowering its activity from 1 μCi to 0.01 nCi while measuring for the same duration each. As the activity decreased, the CZT-based micro-activity calibrator showed lower error rate compared to the NaI-based gamma counter. Future work will involve constructing the system based on this simulation and conducting real-world experiments.

Speaker: Seoyun Jang (Korea Advanced Institute of Science and Technology)

165 Modelling of Silicon Drift Detectors using a full-stack Energy Dispersive X-Ray Spectroscopy Simulation

Energy Dispersive X-Ray Spectroscopy (EDS) is a well-established chemical element analysis method with applications in material characterization, device testing, biosciences, forensics, food science and many more. In EDS, characteristic X-rays are generated by hitting a sample with an electron beam. These X-rays are then captured by a Silicon Drift Detector (SDD), where the photon energy is converted to a signal by creating and transporting electron-hole pairs.

In these SDDs, various parasitic effects, such as recombination and electrons captured in the front layer of the detector, cause Incomplete Charge Collection (ICC). Other effects, such as electron repulsion in the created electron clouds, cause signal rise-times, a key quantity in signal processing. To correct for incorrect signal measurements caused by these effects, a full understanding of the physical processes inside the SDD is required.

We have developed a full EDS simulation pipeline, from electron beam to signal creation, to allow accurate modelling of these physical processes. Monte Carlo simulations are performed using CERN’s software package Allpix Squared [1] to simulate the electron-hole transport inside the SDD. To model the physical processes causing the ICC, we perform Scikit-FEM simulations to calculate the electric field, with an extra focus on the first micron of the front contact of the SDD: the P+ layer. Using these methods, we achieved results that show the ICC and rise-time effects. These results were validated by comparing them to analytical expressions [2] and experimental results [3] found in literature.

This validation of our EDS simulation pipeline opens the possibility to answer complex design questions and gain system understanding by running simulations, where this would normally require expensive experiments.

References
[1] Spannagel et al., Allpix2: A modular simulation framework for Silicon Detectors 2018, https://doi.org/10.1016/j.nima.2018.06.020
[2] Scholze & Procop, Modelling the response function of energy dispersive x‐ray spectrometers with Silicon Detectors 2009, https://doi.org/10.1002/xrs.1165
[3] Prigozhin et al., Characterization of the silicon drift detector for NICER instrument 2012, https://doi.org/10.1117/12.926667

Speaker: Jurgen Snijders (Sioux Technologies)

avatar.svg

166 Testing setup of IntPixel hybrid X-ray detector with on-chip and in-pixel artificial neural network

ABSTRACT

We present a testing setup for a hybrid pixel array (HPAD) radiation detector with an on-chip and in-pixel Artificial Neural Network (ANN). The setup takes advantage of the IC design, which supports testing of it’s individual blocks, and allows for full characterization of the IC as well as facilitates training of per-pixel ANN.

The setup is dedicated to testing of an “IntPixel” detector [1], [2]. The IntPixel integrated circuit (IC) was designed at AGH University of Krakow as a matrix of 8 x 8 square-shaped pixels, each 200 µm pitch. In every pixel, there is a charge-sensitive amplifier followed by a shaper, an analog-to-digital converter, and ANN.

The presented system design emphasize focusing on device-under-test rather than embedded system design itself. It consists of NI sbRIO 9609, an embedded and commercially available controller incorporated with an FPGA and microcontroller. It is connected to the power and bias distribution board, that also hosts a small daugherboard with the IntPixel ASIC. Along with basic IO operations, presented system provides fast data analysis and high data throughout. The testing IC is packaged and uses a socket allowing for quick exchange of individual units. We present details of our platform allowing for full characterization of all the IC’s components including charge amplifier, ADC, discriminator and an ANN.

The research leading to these results has received funding from the Norway Grants 2014–2021 via the National Centre for Research and Development (research project NOR/SGS/Intelligent_XRay_Det/0196/2020-00).

REFERENCES

[1] A. Koziol et al., “Semiconductor sensor readout integrated circuit with in-pixel artificial neural network for pulse amplitude measurement", IEEE Nuclear Science Symposium, Vancouver, Canada, 2023

[2] A. Koziol et al., “Artificial neural network on-chip and in-pixel implementation towards pulse amplitude measurement,” J. Instrum., vol. 18, no. 2, 2023, doi: 10.1088/1748-0221/18/02/C02048.

Speaker: Mateusz Jurczak (AGH)

abstract_ts.pdf

167 Description of ME0 GEM Detectors for the Phase-2 Upgrade of the CMS experiment at the LHC

The CMS experiment at CERN is foreseen to receive a substantial upgrade during Long Shutdown-3 (LS3) to handle the large number of pileup events in the High-Luminosity LHC. The objective is to increase the integrated luminosity by a factor of 10 beyond the LHC design value (~10^34 cm⁻² s⁻¹). The CMS just commissioned the Gaseous Electron Multiplier (GEM) detector, namely GE1/1, at the endcap during LS2. GEM detectors represent a new addition to the muon system in CMS, in order to complement the existing systems in the endcap, part of CMS most affected by large radiation doses and high event rates.The CMS GEM detectors are made of three layers, each of which is a 50 μm thick copper-clad polyimide foil. The GEM chambers will provide additional redundancy and measurement points, allowing a better muon track identification and also wider coverage in the very forward region. For Phase-2 Upgrade, CMS has outlined plans for further endcap upgrades, such as GE2/1 and ME0, as part of the LS3 upgrade. For ME0 detectors, the part of the detector assembly is expected to take place at different production sites including Panjab University, India. Besides ME0 assembly, also all QCs will be performed before sending them to CERN for installation. This contribution will describe assembly, quality control checks and corresponding results of the triple GEM detector for the ME0 system.

Speaker: Bhawana Chauhan (Panjab University (IN))

iWoRID_2025.pptx_print.pdf

168 Simulation of MPGD based Hadron Calorimeter HCal for future Muon Collider

This contribution presents a detailed GEANT4 based simulation study of the
MPGD-HCAL prototype. The simulation implements the geometry of the prototype that
is going to be tested under pions beam in November 2025 at PS facility at CERN. The
prototype consists of 12 layers of alternating stainless steel absorber and the MPGD.
The first 8 layers have an area of 20x20 cm² and this setup has already been tested in
the previous test beam campaigns, showing good performances also in terms of
data-to-simulation agreement. The setup, both in the simulation and in the experimental
prototype, is currently extended to include 4 additional layers with an area of 50x50 cm².
This study , carried out with pion beams with energies ranging from 1 to 10 GeV , targets
the optimization of the prototype layout in terms of shower containment and energy
resolution and to support the future analysis of the experimental data.

Speaker: Mr Muhammad Ali (Universita e INFN, Bari (IT))

ABSTRACT_MUHAMMAD_ALI.pdf

169 Performance and long-term ageing studies on Eco-Friendly Resistive Plate Chamber detectors

Resistive Plate Chambers detectors are extensively used in several domains of Physics. In High Energy Physics, they are typically operated in avalanche mode with a high-performance gas mixture based on Tetrafluoroethane (C2H2F4), a fluorinated high Global Warming Potential greenhouse gas.
The RPC EcoGas@GIF++ Collaboration has pursued an intensive R&D activity to search for new gas mixtures with low environmental impact, fulfilling the performance expected for the LHC operations and for future and different applications.
In this talk, results obtained with new eco-friendly gas mixtures based on Tetrafluoropropene and carbon dioxide even under high-irradiation conditions will be presented. Long term ageing tests carried out at the CERN Gamma Irradiation Facility will be discussed together with their possible limits and future perspectives.

Speaker: Michael Tytgat (Vrije Universiteit Brussel (BE))

170 Progress in experimental setup and reconstruction algorithms in RIPTIDE

Tracking imaging systems have evolved from manual analysis to advanced photodetectors, such as SiPM arrays and CMOS cameras, enabling the conversion of scintillation light into digital data for precise physical measurements. This study presents RIPTIDE, a recoil-proton track imaging system for fast neutron detection. The system employs a plastic scintillator where fast neutrons scatter elastically with protons, producing scintillation light. The generated signal is then captured by an optimized optical setup comprising a lens system, a Microchannel Plate (MCP), and a high-frame-rate CMOS sensor. Monte Carlo simulations have been conducted to explore the detector's performance and to generate image datasets for testing reconstruction algorithms. These algorithms aim to infer neutron tracks by analyzing the direction and range of recoil protons. Additionally, a deep neural network is implemented to correct optical aberrations introduced by the lens system, enhancing the accuracy of proton range measurements. The experimental setup is currently under construction, and initial acquisitions have been performed to validate the Monte Carlo simulations. Results obtained in the laboratory using laser beams, radioactive sources, and cosmic muons will be presented.

Speaker: Samuele Lanzi (Universita e INFN, Bologna (IT))

lanzi_iworid.pdf

171 MDA Assessment of Liquid Radioactive Waste for On-Site Application using CeBr3, LaBr3(Ce), and NaI(Tl) Scintillators

On-site gamma spectroscopy enables real-time decision-making by measuring radionuclide concentrations without sample extraction, reducing environmental and human-induced errors. While NaI(Tl) scintillators are widely used for field applications, they suffer from poor energy resolution compared to High-Purity Germanium (HPGe) detectors, making isotope identification challenging. To overcome these limitations, LaBr₃(Ce) and CeBr₃ scintillators have been introduced. LaBr₃(Ce) offers superior energy resolution but has a higher intrinsic background due to naturally occurring radioisotopes, whereas CeBr₃ provides slightly lower resolution but reduced intrinsic background. This study evaluates the MDA of NaI(Tl), LaBr₃(Ce), and CeBr₃ to determine their suitability for in situ measurements of liquid radioactive waste.
MDA comparisons were conducted using 1-inch diameter NaI(Tl), LaBr₃(Ce), and CeBr₃ scintillators under identical conditions. Liquid waste samples containing 137Cs and 60Co were collected from KAERI’s research reactor operations. Three samples with varying concentrations were analyzed using a 3600-second measurement time in Marinelli beakers. The gamma-ray spectra were processed with Genie 2000 software, employing the Currie MDA method. Background measurements were taken for 600 seconds, and MDAs were calculated for energy levels of 661.7 keV, 1173 keV, and 1332 keV.
Across all samples and energy levels, LaBr₃(Ce) exhibited the lowest MDA, followed by CeBr₃, while NaI(Tl) consistently had the highest MDA, indicating lower detection sensitivity. Despite LaBr₃(Ce)’s higher intrinsic background, its superior energy resolution resulted in the best performance. CeBr₃ provided stable detection performance with lower intrinsic background, making it a viable alternative. In contrast, NaI(Tl)’s poor energy resolution hindered its ability to detect low-activity radionuclides effectively.
The study confirms that LaBr₃(Ce) is the most suitable scintillator for on-site liquid radioactive waste assessment due to its superior energy resolution and lowest MDA. CeBr₃ also demonstrated reliable performance with a lower intrinsic background. NaI(Tl), despite being widely used, showed the highest MDA, making it less effective for low-activity measurements. These findings highlight the importance of selecting appropriate scintillator materials to optimize field-based radiation monitoring.

Speaker: JAEHYUN PARK

172 BabyMOSS stitched sensors: results of characterisation tests for ALICE ITS3 upgrade

During the Long Shutdown 3 (LS3, scheduled 2026-2030), the innermost 3 layers (Inner Barrel, or IB) of the present ALICE ITS2 will be replaced with 6 large-area, flexible, stitched CMOS 65 nm sensors, in the framework of the ITS3 upgrade project. For the first time in a High Energy Physics experiment, such large-scale sensors will be bent into a truly half-cylindrical shape, requiring little mechanical support. This will also help lowering the material budget: a reduction down to an average of 0.09% X0 per layer is expected, benefitting ITS tracking and vertexing capabilities especially at low momenta.
In the wafer yield and stitching assessment stage for ITS3 R&D, test devices from the Engineering Run 1 (ER1) submission were developed, including the MOnolithic Stiched Sensors (MOSS) and smaller variants of them (babyMOSS). In particular, babyMOSS is a single Repeated Sensor Unit (RSU) of a MOSS device: the chip is ~14×30 mm2 in size, and consists of 8 digitally read out pixel matrices (regions) arranged in 2 rows, i.e. half-units (HUs).
BabyMOSS chip characterisation tests have been performed in laboratory and test beam environments. Laboratory tests include systematic functional scans to study the behaviour of front-end electronics over a range of different settings, whereas test beam measurements, under high-energy charged particle beams, were used to investigate the detection efficiency and spatial resolution.
In this contribution, we will present the babyMOSS chip characterisation campaign, with a focus on recent test beam results. So far, babyMOSS test beam results have been consistent with full MOSS, and confirmed that babyMOSS devices meet the ITS3 requirements: a detection efficiency > 99%, fake hit rate < 10-6 hits pixel-1event-1, and a spatial resolution < 6 μm.

Speaker: Alessandro Sturniolo (University of Messina - INFN Catania)

Sturniolo_Abstract_IWoRID2025_v2.pdf

Sturniolo_babyMOSS_TB-Sep24_IWORID2025_rev4.pdf

173 Design Optimization of Neutron Scatter Imager for Carbon Beam Range Verification

Carbon-ion radiotherapy (CIRT) is capable of delivering a precise dose distribution using the Bragg peak. However, the generation of secondary neutrons and the uncertainty of the beam range can potentially affect the efficacy of the treatment and could also result in damage to surrounding organs at risk (OAR). In order to ensure patient safety, it is essential to accurately characterize secondary neutrons and implement real-time dose verification. Carbon ion beams have been observed to produce significantly higher secondary neutron emissions relative to prompt gamma rays compared to proton beams. The use of neutron measurement techniques in CIRT can improve detection efficiency due to the high neutron production rate and contribute to higher accuracy. In this study, the design of a neutron scatter imager for carbon beam range verification was optimized using Geant4-based Monte Carlo simulations. A carbon beam with an energy range of 56–430 MeV/u and a water phantom with dimensions of 10×10×40 cm³ were employed in Geant4 simulations (Fig.1). The neutron scatter imager, which consists of two pixelated plastic scintillator detectors (EJ-276), was optimized for three key parameters: detector thickness (0.5–5 cm), inter-detector distance (5–20 cm), and pixel size (1–10 mm). Furthermore, the effectiveness of lead (Pb) shield in reducing the gamma-ray effect was evaluated. To achieve effective image reconstruction in fast neutron scatter imaging, it is necessary that single scattering occurs in each detector. Accordingly, the optimal thickness of the detector was determined to be 1 cm by considering the probability of single scattering and multiple scattering. An inter-detector distance of 10 cm was selected based on considerations of resolution and efficiency, facilitating suitability for real-time imaging. A pixel size of 3 mm was determined to be optimal imaging resolution, and a 5 cm Pb-shield was found to reduce gamma-ray transmission to below 20% while maintaining neutron detection efficiency. In the present study, a neutron scatter imager for CIRT beam range verification was optimized using Geant4 simulations. The identified parameters (detector thickness, inter-detector distance, pixel size, and Pb-shield thickness) enable precise neutron imaging, thereby enhancing the accuracy of the treatment and patient safety.

Speaker: HAYOUNG SIM (Jeonbuk National University)

Fig.1.Simulation model of a neutron scatter imaging system for carbon beam range verification.png

174 Empirical Testing of Gamma Emission Tomography to Inspect Partial-defects within Spent Nuclear Fuel of Pressurized Water Reactor

Nuclear power plant generates electricity by nuclear fission reactions, from which Spent Nuclear Fuel (SNF) and radioactive waste are inevitably generated. Since SNF includes 235U, 239Pu, and fission products, the effective management and supervision techniques are necessary for non-proliferation of nuclear materials. The IAEA has conducted Safeguards activities using varying non-destructive analysis techniques for early detection of the misuse of nuclear material. Among the IAEA’s techniques, Gamma Emission Tomography (GET) is one of the most reliable techniques for detecting partial-defects within the SNF. In our previous study, we fabricated the prototype of scintillation crystal-based GET instrument named Yonsei Single-photon Emission Computed Tomography (YSECT), and its performance was evaluated in air using the fresh nuclear fuel. The current study aims to experimentally evaluate the performance of YSECT with the mock-up of SNF and pool (test water tank).
The YSECT instrument consisted of 4 detection modules, and each detection module was composed of the tungsten collimator, 46-channel GAGG scintillation crystals, and silicon multiplier. Data acquisition module (from PETsys Electronics Co. Ltd.), Peltier device-based heat reduction module, and rotating stage were also employed. Moreover, a slip ring was applied to implement the spiral rotation without kink and damage of the cable. The mock-up of SNF was determined as 137Cs P04 capsule from Eckert & Ziegler Co. Ltd. taking into account of the actual SNF in terms of geometry and major gamma-ray energy. Also, the test water tank was fabricated in agreement with the geometry of the prototype YSECT. The prototype YSECT rotated a total of 360° in 5° intervals, and the sinograms were obtained in air and water to assess the degree of attenuation & scatter under different conditions. The quality of each tomographic image was analyzed through spatial resolution and Signal-to-Noise Ratio (SNR).
The spatial resolution of projection images acquired in air and water was analyzed as 10.8 and 14.12 mm, respectively. The SNR of each projection image was calculated to be 8.31 and 5.21, respectively, since the noise level of the projection image obtained underwater increased by a factor of 1.65 due to scattering, as well as the gamma-ray was not sufficiently detected due to attenuation compared to the air condition. To reconstruct the sinogram into the tomographic image, the filtered back-projection with Ram-Lak filter was employed using the MATLAB program. Despite image quality degradation due to high-attenuation and -scatter condition, the SNR of tomographic image acquired underwater was analyzed to be 5.18. In agreement with the rose model, in that the SNR was greater than 5, the source distribution on the tomographic image obtained with the prototype YSECT can be distinguished to the human eye. These results indicated that the developed YSECT can be effectively applied to Safeguards activities to detect partial-defects within SNF.
In the current study, the performance of prototype YSECT was experimentally evaluated with the mock-up of SNF and pool. Based on the results, we believe that the developed instrument can meet the objectives of the IAEA Safeguards activities to prevent proliferation of nuclear material. For further study, a 3-dimensional reconstruction algorithm will be developed to rapidly obtain the full tomographic image of 400 cm long PWR-type SNF.

Speaker: Naufal Wafa Nabila Aliyas (일반대학원 방사선융합공학과) Bella

iWoRiD 2025_abstract_Hyung-Joo.docx

175 Design of a Time-over-Threshold Bilinear Front-End for Photon Science Applications with High Dynamic Range in 28 nm CMOS

In the context of the so-called PRIN 2022, funded by the Italian Ministero dell’Università e della Ricerca, the project Front-end channels in a 28 nm CMOS process for Pixel detectors in future High Energy physics colliders and advanced X-ray imaging instrumentation (PiHEX) has, as one of its objectives, the development of ASIC prototypes for modern photon science applications, which require front-end electronics capable of processing signals with a wide dynamic range, while maintaining low noise levels.
In this paper, a new front-end channel designed in a commercial 28 nm CMOS technology based on a bilinear, dynamic gain architecture is presented. The front-end is designed to operate with energies in the range from 1 to 10000 photons at ∼ 9 keV and a maximum frame period of 250 ns.
Each channel consists of a preamplifier with an automatic mode switching
system: a high-gain mode for weak signals (from 1 to 100 photons) and a low-gain mode for strong signals (from 100 to 10000 photons). Cascaded with the preamplifier is a comparator whose output is fed to the Time-over-Threshold counting system employing a ring oscillator and an 8-bit counter. The Time-over-Threshold behavior is adapted according to the selected gain mode. This ensures that the counter does not overflow and that the counted time over the threshold value remains within the 250 ns time frame in both the operating modes. The pixel has a size of 110 μm × 55 μm.
Simulations show that in the high gain mode, the Signal to Noise Ratio
(SNR) is about 10. The low-gain configuration features an SNR of about 20. Post-layout simulations confirm a linear relationship between input photons and Time-over-Threshold in both low gain and high gain modes, supported by a ring oscillator at ∼ 1 GHz, which demonstrates good stability even in the presence of process and power supply variations. Additionally, post-layout simulations show that, for 1 to 100 photons, the input-output characteristic has a non-linearity index of 3.3%. For 100 to 10000 photons, the non-linearity index drops to 2.3%.
These simulation results validate the bilinear Time-over-Threshold approach implemented as an effective solution to extend the dynamic range and optimize the noise performance of front-ends conceived for synchrotrons and advanced imaging systems. The first prototype will be submitted in Q2 2025 and will integrate two versions of the same channel, one that exposes the output of the preamplifier, whose signal is driven by buffers connected to the chip PADs, and one that allows the study of the entire channel.

Speaker: Andrea Galliani (Università degli Studi di Bergamo)

Abstract_iWorid_2025_v3.pdf

176 Backside Pulse Processing for Energetic Particle Detection with Timepix2

Timepix is a hybrid pixel detector used to measure mixed radiation fields. Several Timepix-based instruments are currently used on the International Space Station, as part of the Artemis program on the Orion Spacecraft, the Gateway lunar space station, and the Lunar Human Landing System, and on various scientific missions such as Polaris Dawn. New space-based instruments are being developed with Timepix2. Timepix2 allows measurements of particles in energy mode—Time over Threshold (ToT) mode—with ToT signal length being proportional to energy. However, energy measurements in Timepix2 have a limitation due to a pixel saturation effect that occurs beyond the upper end of the Timepix2 dynamic range (>3.4 MeV).

We present a parallel signal processing route for signals from high energy depositions that avoids saturation in measurement. When energy is deposited in the Timepix2 sensor, the resulting pulse is processed in the ASIC. This pulse also appears on the bias of the detector, allowing for a potential additional measurement of the same energy deposition. We developed the capability to measure this pulse on the bias, the backside pulse, and route this simultaneous measurement data back into the data stream. We constructed a circuit that takes pulses off the bias and converts them to a ToT signal. Timepix2 has a set of digital pixels that can receive external information, which we implement to receive the ToT signal and send the backside pulse data to be processed in the Timepix2 chip. To our knowledge, we are the first to test and use this digital pixel capability. We present beamline tests of the backside pulse processing and digital pixel system and discuss system linearity with energy, applicable energy ranges, and applications of this system to space dosimetry and radiation measurement.

Speaker: Stuart Patrick George (NASA Johnson Space Center)

Social events: Conference Dinner

Thursday 10 July

Front-end Electronics: Session 11

Convener: Roelof de Vries

177 TEMPUS, an event-driven X-ray detector

TEMPUS is a novel two-dimensional, event-driven X-ray detector developed to meet the growing demand for high temporal resolution in time-resolved synchrotron and FEL experiments. Based on the Timepix4 ASIC, TEMPUS enables continuous acquisition of individual photon events with nanosecond timestamping, offering a significant advancement over traditional frame-based systems. TEMPUS now serves as a core platform in DESY’s fast photon science program and has demonstrated clear potential for broader adoption across next-generation light sources.

In this talk, I will present results from our proof-of-concept experiments at the ESRF, Eu.XFEL and PETRA III where TEMPUS achieved effective time resolutions down to 10 nanosecond (and improving) when working at a Nuclear Resonance Scattering (NRS) beamline . I will also discuss how this approach allows for cross-pixel correlation, enabling high-dynamic-range X-ray Photon Correlation Spectroscopy (XPCS) over more than nine orders of magnitude in timescale.

Finally I will discuss what are the next steps in our development and the challenges ahead.

Speaker: Dr Jonathan Correa

jcorrea_iWoRiD_2025_2.pdf

jcorrea_iWoRiD_2025.ppt

Screencast from 2025-07-09 08-55-10.webm

178 Characterization of Medipix4, a high granularity four side buttable pixel readout chip for high resolution X-ray spectroscopy

The Medipix4 ASIC is the latest hybrid pixel detector in the Medipix family, developed using commercial 130nm CMOS technology for high-rate spectroscopic X-ray imaging. Like Timepix4, the Medipix4 chip features a four-side buttable design, enabling seamless large-area tiling via Through-Silicon Vias (TSV). Alternatively, the chip can be interfaced via top and bottom peripheral wirebonding, achieving a two-side buttable configuration. The chip consists of a 320 × 320 pixel matrix with a 75 $\mu$m pitch in Fine Pitch Mode (FPM), or a 160 × 160 pixel matrix with a 150 $\mu$m pitch in Spectroscopic Mode (SM). The SM is specifically optimized for high-Z sensor materials.

In Fine Pitch Mode, the chip supports two effective thresholds, whereas in Spectroscopic Mode, it supports up to eight thresholds. The chip can operate in Single Pixel Mode (SPM) or Charge Summing Mode (CSM), the latter of which corrects for charge-sharing effects among neighboring pixels. Each 75 $\mu$m pixel is equipped with two 12-bit counters, which can be used in continuous read/write mode (CRW) or configured for 1-bit, 2-bit, 12-bit, or 24-bit counter operation in sequential read/write mode (SRW). Additionally, threshold window discrimination and a pileup filter are available for enhanced performance. The Medipix4 chip operates in a highly configurable frame-based readout mode. It can be read out using up to 16 high-speed links, each capable of 640 Mbps, achieving 8.3k frames per second (fps) in 12-bit counter mode.

In this presentation, we will provide an overview of the Medipix4 architecture and its operating principles, alongside initial characterization results, including energy resolution estimation and rate sustainability.

Speaker: Riccardo Bolzonella (CERN)

Bolzonella_abstract_iWoRiD_Medipix.pdf

Bolzonella_iWoRiD_2025_presentation.pdf

179 Katherine Readout for Timepix4: A Novel Acquisition Ecosystem for Timepix4-Based Detectors

The Timepix4 [1] readout chip introduces significant improvements over its predecessor, Timepix3 [2], in multiple aspects. One of the key advantages is the 3.5× larger active area, which allows for the coverage of a wider surface. Another major improvement is support for Through-Silicon Vias (TSV) technology. This feature enables the construction of large-area detectors with minimal dead zones — a crucial factor in many imaging applications. Despite the increased size, Timepix4 retains the same 55 µm pixel pitch as Timepix3, resulting in a resolution of 512×448 pixels. A significant enhancement is also found in time resolution, with 195 ps time binning for Time-of-Arrival (ToA) data. This enables novel applications such as Compton-scattering-based detectors or advanced Time-of-Flight measurements. Timepix4 also offers significantly higher data throughput compared to Timepix3. It features 16 data output lines, each capable of 10 Gbps, resulting in a theoretical maximum data rate of 3.58×10⁶ hits/mm²/s, or approximately 2.5 Ghits/s per chip.

To support our research and meet the needs of the Medipix community, a novel acquisition system — the Katherine readout for Timepix4 — has been developed as the successor to the widely used Katherine acquisition systems for Timepix2 and Timepix3 [3, 4]. It is primarily targeted at laboratory measurements and test beam experiments, and may also serve as a platform for more demanding experiments in the future, including x-ray imaging systems using large-area detectors.

The presented device is capable of operating up to four Timepix4 detectors (with future support for the Timepix4 Quad chipboard). It supports up to 8 serial data lines from Timepix4, each operating at speeds up to 10 Gbps (although 2.5 Gbps is commonly used due to chip limitations). The device performs low-level data processing directly in hardware, converting raw data into fixed-point representations of energy (ToT) and timestamps (ToA). This eliminates the need for data decoding in the control software. In addition, configuration data handling is simplified — each pixel can be addressed directly via its position. For data transfer to a host computer, two interfaces are provided. The first is Gigabit Ethernet, which offers convenient remote access but is limited in throughput (approximately 10 Mhits/s). The second is PCI Express Gen3 x4, which enables significantly higher data rates — up to 350 Mhits/s. As with previous Katherine devices, several GPIOs are available for integration into complex experimental setups. These include support for external triggers, feeding external signals into Timepix4 digital pixels, and time-stamping of external events (via an FPGA-based TDC or a dedicated hardware TDC with 50 ps binning). A high-voltage bias source is also integrated, supporting a range from -1 kV to +1 kV with leakage current monitoring.

However, the Katherine acquisition system is more than just a data readout device. It also supports the broader use of the Timepix4 chip. Our contribution presents dedicated chipboards and a modular approach in which Timepix4 assemblies are mounted on small PCBs that can be plugged into baseboards. This enables reusability of detectors and facilitates rapid setup of customized experiments without the need for new wirebonding. The ecosystem also includes user-friendly control software.
This contribution presents the capabilities of the developed ecosystem and demonstrates them using measured data from radioactive sources, x-ray imaging, and test beam experiments.

References:
[1] Llopart, Xavier, et al. "Timepix4, a large area pixel detector readout chip which can be tiled on 4 sides providing sub-200 ps timestamp binning." Journal of Instrumentation 17.01 (2022): C01044.
[2] T. Poikela et al., 2014 JINST 9 C05013.
[3] Burian, P., et al. "Katherine: ethernet embedded readout interface for Timepix3." Journal of Instrumentation 12.11 (2017): C11001.
[4] Burian, Petr, et al. "Ethernet embedded readout interface for Timepix2—Katherine readout for Timepix2." Journal of Instrumentation 15.01 (2020): C01037.

Speaker: Dr Petr Burian (Czech Technical University in Prague (CZ))

burian_iworid_10_7_2025.pdf

burian_iworid_10_7_2025.pptx

180 28nm front end ASIC and 12” LGADs for 3D integration

The 3DIntSenS Collaboration—a joint effort between SLAC, Fermilab, and LLNL—is developing enabling technologies for next-generation radiation imaging detectors that combine ultra-fine spatial resolution (~10 μm) with precision timing (<20 ps), while maintaining low power <1W/cm2 and high data throughput. The approach leverages 3D integration between advanced CMOS readout ASICs and finely pixelated LGAD sensors to achieve the performance and scalability required for large-area, high-rate applications.
High-granularity, precision-timing detectors are essential for scientific advances in HEP, NP, BES, and FES, but widespread adoption is limited by the cost and complexity of 3D integration. To close this gap, the collaboration is developing LGAD sensors compatible with 12-inch commercial CMOS processes, enabling cost-effective integration with high-performance ASICs under development.
We present the design and results from a 28 nm CMOS ASIC prototype, including a low-jitter front end, and in-pixel TDC demonstrating sub-10 ps timing resolution. We also report on the co-design and characterization of reticle-scale LGAD sensors with 50 μm and 100 μm pixels, and introduce the next 10k-pixel ASIC designed for full 3D integration. These advances represent a critical step toward scalable, high-resolution radiation imaging systems for future scientific instrumentation.
Summary:
Highly granular precision timing detectors are essential for advancing scientific discovery across High Energy Physics (HEP), Nuclear Physics (NP), Basic Energy Sciences (BES), and Fusion Energy Sciences (FES). Their critical importance has been emphasized in multiple strategic planning efforts, including the DOE Basic Research Needs (BRN) Report, the European Strategy for Particle Physics, and Snowmass. A key enabling technology for these detectors is 3D integration of finely segmented sensors with advanced CMOS readout ASICs. However, current 3D integration approaches remain cost-prohibitive for large-scale scientific applications.
Addressing this challenge is the focus of the 3D Integrated Sensing Solutions (3DIntSenS) collaboration between SLAC, Fermilab, and LLNL, supported by the DOE Accelerated Innovation in Emerging Technologies program. In partnership with a leading commercial semiconductor foundry, the collaboration is developing LGAD sensors compatible with 12-inch CMOS wafer processes, optimized for cost-effective 3D integration with high-performance readout ASICs. A co-design approach ensures simultaneous optimization of both sensor and ASIC technologies.
The first prototype ASIC features a linear array of 50 μm and 100 μm pixels, matched to LGAD cell variants. Each pixel integrates a low-jitter front-end, fast comparator, and a high-resolution in-pixel Time-to-Digital Converter (TDC). The system targets timing resolution below 20 ps with power consumption under 1 W/cm². Initial testing confirms sub-10 ps jitter for the in-pixel TDC.
The TDC employs a 2D Vernier ring oscillator architecture with an embedded sliding-scale technique, enabling simultaneous measurement of Time-of-Arrival (TOA) and Time-over-Threshold (TOT) with resolutions of 6.25 ps (8-bit) and 50 ps (5-bit), respectively. Power consumption scales with occupancy, averaging 18.4 μW at 10% and 2.9 μW at 1% occupancy per TDC.
The prototype has been characterized using on-chip charge injection and will be wire-bonded to LGAD sensors, including designs from the reticle-scale 12-inch wafers. Finally, we will present the design of the second-generation 10k-pixel ASIC in final design stages and scheduled for fabrication by the end of the year, to be bump bonded testing and system validation, and eventually for 3D integration.

Speaker: Davide Braga (FERMILAB)

IWORID2025_3DIntSenS.pdf

IWORID2025_3DIntSenS.pptx

10:30 Coffee Break

Front-end Electronics and Imaging Theory

Convener: Matthieu Boone

181 Enhancing the Performance of High-Z Sensors for Photon Science Applications

The increased flux of coherent high-energy (> 20 keV) photons at fourth generation light sources enables many new experimental possibilities. At such energies, the absorption efficiency of Si (Z = 14) sensors is < 50 %. As the photoelectric absorption cross-section increases with the average atomic number (Z) of a sensor, materials such as GaAs:Cr (Z$_{\textrm{Av}}$ = 32) and CdZnTe (Z$_{\textrm{Av}}$ = 50) offer a solution, making it possible to exploit the advantages of hybrid pixel detectors (e.g. kHz framerates, large areas, low noise and high count-rates/large dynamic range) at higher photon energies.
However, the attenuation lengths of As and Ga K$_{\textrm{α}}$ fluorescence photons in GaAs:Cr (15.6/40.6 µm) as well as those of Te and Cd K$_{\textrm{α}}$ photons in CdZnTe (60.1/119.7 µm) are much greater than that of Si K$_{\textrm{α}}$ photons in Si itself (11.9 µm). This leads to the problem of auto-fluorescence in high-Z sensors, whereby a photon characteristic of one of the elements in the sensor deposits their energy some distance from the primary interaction site, causing a deterioration in spatial and energy resolution [1].
To develop ways of correcting for auto-fluorescence, we have measured the imaging performance (as quantified by the modulation transfer function) and spectral response of GaAs:Cr and CdZnTe sensors, supplied by DECTRIS and Redlen respectively, bonded to the JUNGFRAU 75 µm pitch charge-integrating ASIC [2]. This has been done at specific energies above and below the K-series fluorescence energies of the elements present in each sensor using monochromatic energies at the SYRMEP beamline of Elettra (Trieste, Italy).
We will present the results of these measurements and of complementary simulations, which enable elucidation of the extent to which auto-fluorescence causes a deterioration in the energy and spatial resolution of the tested devices. Furthermore, we will outline our planned work developing neural networks using these experimental and simulated datasets to identify fluorescence events in the sensor and their corresponding parent interaction. This is with the aim of reconstructing the primary event, thereby improving the spatial and energy resolution of GaAs:Cr and CdZnTe sensors.

[1] S. Chiriotti et al., JInst, 17, 2022
[2] A. Mozzanica et al., JInst, 11, 2016

K.A. Paton gratefully acknowledges funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 884104 (PSI-FELLOW-III-3i).

Speaker: Kirsty Paton (Paul Scherrer Institut)

KPaton_iWoRiD_2025.pdf

182 First Characterization of the DECTRIS JUNGFRAU hybrid charge-integrating ASIC for High-Flux Time-Resolved X-ray Applications

We present the first characterization results of a single-chip prototype of the DECTRIS JUNGFRAU detector, a hybrid charge-integrating readout ASIC based on the original concept developed at the Paul Scherrer Institut (PSI) [1]. The prototype features 75 µm pitch pixels in a 256×256 array, for an active area of 2×2 cm², bump-bonded to a 450 µm p-on-n Si sensor. Designed specifically for high-intensity and time-resolved X-ray experiments at synchrotrons, the ASIC delivers high dynamic range, noise levels compatible with medium energy X-ray detection, and fast frame rates. These properties are critical for quantitative measurements in high-flux environments typical of e.g., serial crystallography, coherent diffraction imaging (CDI), and Bragg CDI [2,3]. Based on charge integration, JUNGFRAU can provide accurate measurements under high instantaneous photon fluxes and enable the precise recording of intense diffraction peaks independently from the beam time structure, thus overcoming the limitations imposed by the finite count-rate of traditional counting detectors [4].
The chip features a continuous frame rate of up to 2 kHz, with integration times from 1 to 480 µs, and a dynamic range up to 12,000 photons per pixel at 12 keV. Each pixel includes a three-level gain-switching mechanism that dynamically adjusts the gain frame-by-frame, based on the incoming flux. This capability ensures precise detection across a wide range of intensities, from low-flux regions with single-photon accuracy, to high-intensity diffraction spots, without saturation.
In this contribution, we present the characterization results of early single-chip prototypes, such as noise performances, single-photon sensitivity, linearity, dynamic range, temperature dependence, and the calibration concept of the chip. These preliminary results from laboratory and synchrotron measurements at BESSY and DESY validate its potential for experiments requiring accurate intensity recording under high instantaneous flux, establishing the DECTRIS JUNGFRAU ASIC as a robust building block for next-generation X-ray detectors at 4th generation synchrotron facilities.
[1] Mozzanica, A., et al., Synchrotron Radiation News, 31(6), 2018.
[2] Orlans, J., et al., Commun. Chem., 8(1), 2025.
[3] Leonarski, F., et al., IUCrJ, 10(6), 2023.
[4] Fröjdh et al., Front. Phys. 12 (2024): 1304896

Speaker: Filippo Baruffaldi (Dectris AG)

iWORID_2025.pptx

183 High frame rate Skipper CCD-in-CMOS imaging array

We present advancements in image sensor technology combining Skipper Charge Coupled Devices (Skipper-CCDs) with CMOS imaging techniques to achieve exceptional low-noise and high-speed readout capabilities. The Skipper-in-CMOS image sensor merges the non-destructive readout advantage of Skipper-CCDs with the high conversion gain of a pinned photodiode and integrated in-pixel signal processing within a CMOS process. A 15 × 15 μm² pixel cell in a 200 × 200 array was fabricated using Tower Semiconductor’s commercial 180 nm CMOS Image Sensor process. Measurements demonstrate significant readout noise reduction reaching sub-electron noise levels of 0.15e⁻ for pixel test structures with off-chip readout and deep-sub electron level of 0.075e- with the on-chip integrated read-out chain, thus validating single photon counting capability when exposed to illumination.
Complementing this, the Skipper CCD-in-CMOS Parallel Read-Out Circuit V2 (SPROCKET2) is designed in a 65 nm CMOS process to facilitate high frame rate readout, integrating with pixelated Skipper CCD-in-CMOS sensors. Each SPROCKET2 readout pixel, covering a 60 × 60 μm² area, interfaces with an array of 16 active image sensor pixels. Utilizing correlated double sampling and analog-domain accumulation of ten successive samples, SPROCKET2 achieves low noise, high-speed digitization at 66.7 ksps, with measured Differential Non-Linearity (DNL) and Integral Non-Linearity (INL) of approximately 0.44 LSB and 0.58 LSB, respectively.
Currently, a large-area array consisting of 20,000 SPROCKET2 ADC pixels, designed to multiplex at a 1:16 ratio to 320,000 sensor pixels is being fabricated. By employing a 10.24 Gbps optical data link, the design supports a frame rate of 4 kfps over extensive sensing areas, minimizing deadtime. In simulation, the pixel demonstrates an input-referred resolution of 10 μV in its highest gain mode and consumes 50 μW with a constant current draw to reduce power-rail crosstalk.
Additionally, we showcase the development of pixel detector ASIC readout integration using silicon photonics at both room temperature and cryogenic temperatures (~100 K), addressing future detector challenges through tight integration of sensing, computing, and communication functions. This development involves co-design and optimization of pixel electronics with integrated silicon photonic micro-ring modulators (MRMs), facilitating high-speed optical modulation (10.24 Gb/s per channel) directly at the pixel level.

Speaker: Farah Fahim (Fermi National Accelerator Lab. (US))

Farah.jpg

IWoRID2025.pdf

IWoRID2025.pptx

184 Comparison between simulated neutron interactions and captured images for fast neutron imaging

Neutron imaging with digital imaging detectors has recently been introduced and is driving the development of modern neutron imaging instruments. In most cases, scintillator screens are used in conjunction with complementary metal oxide semiconductor (CMOS) cameras, with the ability to read out images digitally. The scintillator in combination with a CMOS astro camera is superior in terms of dynamic range, signal-to-noise ratio and thus provides improved image quality. The detector system has a strong influence on the achievable image quality. Several detector components need to be optimized, such as the optical lens system and the scintillator screen, both of which are the focus of ongoing improvements. However, even with technically optimized neutron imaging setups, there is almost always a trade-off between exposure time and spatial resolution. These factors can be optimized and will vary depending on the experiment and instrumentation setup. This paper focuses on the experimental verification of simulations performed for simple objects and the response of the scintillator crystal to the incident neutron flux. The GEANT4 code is used to model neutron-proton interactions, with the output in the form of a radiographic image. Simulated and experimental images are compared and the performance of both systems is verified. The purpose of this paper is to quantify the difference between the simulated and captured images and to identify areas for improvement of the developed neutron radiography system. The results are the first step for future optimization of neutron radiography experiments using the plastic scintillator detector and fast neutron sources.

Speaker: Filip Revai

IWORID_abstract_Revai.docx

Revai_IWORID.pptx

185 IWORID 2025 closing

The 26th Workshop on Radiation Imaging Detectors, the IWORID 2025, will be closed.

Speakers: Andrea Sagatova (Slovak University of Technology in Bratislava), Christer Froejd (Mittuniversitetet (SE))

PresentationBratislavaIWORIDclosing.pdf

PresentationBratislavaIWORIDclosing.pptx

12:40 Lunch break Lunch 13.00

Social events: Guided tour around Bratislava