24th International Workshop on Radiation Imaging Detectors

25 Jun 2023, 08:00 → 29 Jun 2023, 15:20 Europe/Oslo

Simula Auditorium (Ole-Johan Dahls Hus)

Angela Kok, Dirk Meier, Heidi Sandaker (University of Oslo (NO)), Ketil Roeed (University of Oslo (NO)), Marco Povoli (SINTEF MiNaLab)

The International Workshops on Radiation Imaging Detectors are held yearly and provide an international forum for discussing current research and developments in the area of position sensitive detectors for radiation imaging, including semiconductor detectors, gas and scintillator-based detectors.

Topics include processing and characterization of detector materials, hybridization and interconnect technologies, design of counting or integrating electronics, readout and data acquisition systems, and applications in various scientific and industrial fields. 

VENUE 

IWORID 2023 will take place at Oslo Science Park, in a district where Oslo Science Park, Department of Informatics at the University of Oslo and SINTEF MiNaLab are located. It is a meeting place for business and research, a workplace for knowledge-based businesses, and a start-up and scale-up arena for new entrepreneurial companies paving way for Norway’s future. All oral and poster presentations, and industrial exhibitions will take place in Ole Johan Dahls Hus at Oslo Science Park.

© UiO/Francesco Saggio

 

 

 

 

iworid_boat_masterlist-Christiania.pdf

iworid_boat_masterlist-Helena.pdf

Sunday, 25 June

16:00 → 20:30 Registration

17:30 → 20:30 Welcome Reception

Monday, 26 June

07:30 → 08:30 Registration

08:30 → 09:00 Opening

Convener: Angela Kok

iworid23_opening_AK.pdf

iworid23_opening_AK.pptx

social_evening_iworid.pdf

social_evening_iworid.pptx

09:00 → 10:30 Applications: 1

Convener: Ralf Hendrik Menk (Elettra Sincrotrone Trieste)

09:00 INVITED: Proton therapy centers in Norway

Proton therapy is a type of radiation therapy that causes less treatment-related toxicity than standard X- ray therapy and will be offered to Norwegian cancer patients during 2024. The proton therapy units in Oslo and Bergen will have a unique infrastructure for clinical and preclinical research and, when fully operational, will offer treatment to around 850 patients each year. It is a goal to include 75% of patients in clinical studies. This is to strengthen the evidence around proton therapy and further develop this treatment. The clinical studies will largely be carried out as multi-centre studies, and require national and international collaboration. A National proton and radiation therapy register is under development, and will be a central supplement to the clinical studies and also data mining for artificial intelligence. The preparation of the clinical studies will be interdisciplinary with the involvement of various professionals from clinics, basic research, universities and colleges. Preclinical research will include translational research with experimental combination therapy, mathematical modelling of proton transport and biological response, artificial intelligence, and technological innovations such as proton-FLASH.
With the coming proton therapy units in Oslo and Bergen, Norwegian researchers will be able to carry out high-quality clinical and interdisciplinary research that is expected to lead to better, evidence-based treatment. The talk will present some research opportunities at the two centers, with emphasis on translational research and technological developments.

Speaker: Eirik Malinen (Oslo University Hospital)

iWoRiD_Malinen.pdf

iWoRiD_Malinen.pptx

iWoRiD_Malinen wo video.pdf

iWoRiD_Malinen wo video.pptx

09:30 Lung cancer heavy ion therapy CMOS tracking device

In the past years, advanced techniques have been developed to treat lung cancer using particle therapy. This therapy aimed at delivering a more conformal dose to the tumor while minimizing damage to healthy tissues.
However, treating moving tumors with ion beams remains a significant challenge. In the case of lung cancer, the patient’s respiratory motion can cause inhomogeneities in the dose delivered and range shifts during both planning and treatment.
To address this issue, several range monitoring techniques have been investigated, including using secondary radiation produced during treatment (e.g., PET), but in this project, a new approach is proposed using a CMOS-based tracker system to detect the strong density gradients between the lung, tumor tissue, and bones, in order to provide a real-time monitoring of the beam position.
Preliminary experiments were conducted in 2022 but the final goal is to develop a conceptual version of this device, that could be used in clinical centers using carbon ion beam facilities with scanning pencil beam and gantry.
The proposed work involves conducting a full Monte Carlo simulation of a clinical case with GATE on real patient 4D-CT (breathing movement) with a pencil scanning beam treatment plan.
A complementary work to improve spatial accuracy of the reconstructed vertices include a deep learning algorithm for protons’ scattering and another one will be built for the clustering and tracking of secondary particles with CMOS trackers.

Speaker: Levana Gesson (IPHC, Strasbourg, France / GSI, Darmstadt, Germany)

Levana_GESSON.pdf

09:50 A two-layer Timepix3 stack for improved charged particle tracking and radiation field decomposition

Precise measurement of radiation levels and radiation field characteristics is a major concern in fundamental physics and life-science applications. In the present contribution, we describe a novel instrument which was in particular designed for application in harsh radiation environments, as found for example in ATLAS or, within the MOEDAL experiment, at a distance of ~1 m from the interaction point (IP8) at LHCb. The device consists of two Timepix3 [1] assemblies with 500 µm thick silicon sensors in a face-to-face geometry. These detectors are interleaved with a set of neutron converters: 6Li for thermal neutrons, polyethylene (PE) for fast neutrons above 1 MeV, and PE with an additional aluminium recoil proton filter for neutrons above ~4 MeV. The two-layer design combined with 3D track reconstruction capability in single layers, enabled by the nanosecond-scale time measurement of Timepix3, provides precise particle trajectory reconstruction [2]. Application of the coincidence and anticoincidence technique together with pattern recognition allows improved separation of charged and neutral particles, their discrimination against γ-rays and assessment of the overall directionality of the fast neutron field.
The instrument’s charged particle tracking and separation capabilities were studied at the Danish Center for Particle Therapy (DCPT), the proton synchrotron (PS), and super proton synchrotron (SPS) with protons (50-240 MeV), pions (1-10 GeV/c and 180 GeV/c), heavy fragments and lead (330 GeV/c). After developing temporal and spatial coincidence assignment methodology (see Figure 1), we determine the relative amount of coincident detections as a function of the impact angle, present the device’s impact angle resolving power (both in coincidence and anticoicidence channels) and illustrate its use as a stopping power spectrometer. The detector response to fast neutrons was determined at the Los Alamos Neutron Science Center (En up to 600 MeV), where measured tracks were assigned to their corresponding neutron energy by application of the time of flight technique [3]. We present the achieved neutron detection efficiency as a function of neutron kinetic energy and demonstrate how the ratio of events found below the different converters can be used to assess the hardness of the neutron spectrum, at least up to ~20 MeV neutron kinetic energy (Figure 2). To illustrate the applicability of the methodology in mixed fields, we will outline data analysis in the MoEDAL experiment, where we perform precise tracking of relativistic particles coming from IP8 and determine neutron fluxes, and at DCPT, where we determine the composition of the stray radiation around a PMMA phantom during irradiation with protons.

[1] T. Poikela et al 2015 JINST 10 C01057
[2] B. Bergmann et al. Eur. Phys. J. C 77, 421 (2017).
[3] B. Bergmann et al 2014 JINST 9 C05048

Speakers: Benedikt Ludwig Bergmann (Czech Technical University in Prague (CZ)), Dr Petr Smolyanskiy (IEAP CTU in Prague)

iWORID2023_Smolyanskiy_BB.pptx

10:10 Quantitative helium-beam radiograph of a head and neck model and comparison to X-ray CT projections

Introduction: Cancer treatment with ion-beams is a highly promising radiotherapeutic technique. Compared to the conventionally used photon irradiation, ion beams offer an advantage of concentrating the radiation dose to the tumor and sparing the surrounding healthy tissue. However, in order to use the full potential of ions, an accurate knowledge about the depth at which the ions stop in the tissue is crucial. With ion beam radiography the stopping position could potentially be verified on a daily basis before each irradiation. In this way, possible errors can be detected and thus uncertainties of the dose deposition in the patient minimized.
This contribution presents the potential of such method. A quantitative helium-beam radiograph (αRad) of an anthropomorphic head phantom is compared to the standard method.

Materials and Methods: Experiments were conducted at the Heidelberg Ion-beam therapy center (HIT) using helium-ion beams with energies of up to 197.01 MeV/u. A dedicated detection system was built in-house employing six Timepix detectors. The detectors, which utilize the Timepix chip developed at CERN, were purchased from ADVACAM s.r.o., Prague, Czech Republic. They have a sensitive silicon layer of 300µm, a pixel pitch of 55µm and can detect single ions with an efficiency of nearly 100%.
Two detectors each are used as front and rear trackers to measure the position and direction of ions entering and exiting the imaged object. With this information, the most likely path of each single ion can later be estimated using the Cubic Spline algorithm to improve the spatial resolution.
The remaining two detectors are used to measure the energy deposition of each single ion and to identify the corresponding information on the trackers via a coincidence window of 200ns. The energy deposition can then be connected to the water-equivalent-thickness (WET) of the object via recently established calibration curves.
In this way, a quantitative helium-beam radiograph of an anthropomorphic phantom (CIRS 731-HN) was acquired. To assess its accuracy concerning WET-prediction, it was compared to the potential gold standard of WET prediction, namely dual-energy X-ray CT (DECT). As this method is currently not yet used in many facilities, also the clinical standard, single-energy X-ray CT (SECT), was compared to the DECT. In this way, the performance of the presented imager can be put into perspective with the clinically used system.

Results: A 48x24 mm$^2$ region of the projection of a single-energy X-ray CT and a helium-beam radiograph were compared to the corresponding region of a dual-energy X-ray CT. The WET prediction of both helium-beam radiograph and SECT deviates from the one of DECT by (0.971 ± 0.016) % and (0.650 ± 0.011) %, respectively. The deviation was calculated in terms of mean absolute percentage difference.

Conclusion: The helium-beam radiograph of the anthropomorphic head phantom performs similarly well as the projection of the SECT, which is commonly used for ion range prediction in clinics. Therefore, we conclude that helium-beam radiography can compete with the SECT concerning WET accuracy. The presented new imaging modality based on very light and handy detectors is a promising tool to verify the range of ions in radiotherapy treatments on a daily basis, which could lead to less damage of healthy tissue during an ion radiotherapy treatment.

Speaker: Margareta Metzner (German Cancer Research Centre)

iWoRid.pptx

10:30 → 11:00 Coffee Break

11:00 → 12:30 Detector Systems: 1

Convener: Christer Froejd (Mittuniversitetet (SE))

11:00 INVITED: Detectors for the future European XFEL

The European XFEL is a state-of-the-art facility that produces brilliant X-ray flashes with unprecedented brilliance and pulse duration. It delivers up to 27,000 pulses per second in 10 trains per second, with each train containing up to 2700 pulses at a rate of up to 4.5 MHz. This has opened up new opportunities for scientific research in fields such as materials science, structural biology, and quantum technology. To fully exploit its potential, the facility employs advanced detectors based on cutting-edge technology. These detectors are designed to cope with the high repetition rate of the machine while providing low noise and high dynamic range.

Growing demand for intense and ultrafast light sources with a wide range of photon energies pushes and forms further advancements of the European XFEL. To cover this demand and stay up-front among leading free-electron laser facilities, European XFEL foresees offering beams with hard X-rays up to, or even greater than, 40 keV, keeping the MHz pulse rate with a possibly different pulse and train structure, to be defined in the near future. On the instrumentation side, the starting development program of the next generation of detectors will be devoted in the next few years to testing different technologies to identify the best solutions to encompass the needs emerging from the XFEL advancements. Building on the successes of the current state-of-the-art technology detectors in use at the facility, and incorporating the lessons learned from the first 5 years of operation, we aim at optimizing detector performance and operability while ensuring compatibility with existing systems and infrastructure.

The objective of achieving excellent data quality for users is a shared goal among detector developers, users, and instrument scientists. The success in this endeavor depends on the ability to combine diverse areas of expertise and perspectives to design and develop next-generation detectors that can deliver high-quality data while maintaining robustness and ease of operation. These requirements are underpinned by the need to reduce the enormous quantity of data produced at the source.

Speaker: Monica Turcato

20230626_IWORID_Turcato.pdf

11:30 A Photon counting soft X-ray detector capable of gated operation at extremely high input fluxes

Detection of soft X-ray photons with high spatial and temporal resolution often involves a process of electron multiplication as the charge produced by a single photon is not sufficient for an accurate event encoding. Microchannel plate (MCP) electron multipliers have been widely used in photon counting detectors where a photoelectron produced by the incoming X-ray photon is converted into a charge of 103-106 electrons. The position and time of incoming photon subsequently can be determined by various readouts with ~6 m and few tens of ps resolution, respectively. Originally such detectors were developed for low light sensing applications, where registration of one photon at a time was sufficient, e.g. astrophysical observations of weak soft X-ray and UV radiation. Recent developments of pixelated readout configurations substantially increased the count rate capabilities of MCP-based detectors and enabled detection of many simultaneous photons. Placement of Readout Specific Integrated Circuit devices, such as Timepix, directly behind the MCPs enabled operation at very high counting rates exceeding 108 ph/cm2/s [1]. These detectors were recently utilized in several synchrotron based studies [2], [3]. However, one fundamental limitation on the counting rate capabilities of such devices is imposed by the minimum recharge time, required to resupply the charge extracted from the MCP pore. The gain of a specific MCP pore drops temporarily until the positive charge at the exit side of the MCP pore is replenished. This limitation is often referred to as a charge saturation effect. The speed of recharging is limited by the strip current flowing through the MCP, which cannot be increased beyond a certain level due to the Joule heat generated within the MCP leading to a thermal runaway.
The high intensity of modern synchrotron sources provides unique experimental capabilities and at the same time impose extreme challenges to the instrumentation which should sustain operation at these high fluxes. Among such experiments are those where only a fraction of incoming photons conveys useful information, while the rest of photon pulses need to be ignored, e.g. in pump-probe experiments where the frequency of laser-based pumping is much lower than the frequency of the synchrotron source.
We have developed an MCP- based soft X-ray detector which can be gated with ~10 ns accuracy, preventing MCP saturation and enabling detector operation at high incoming fluxes which otherwise would be impossible.
In experiments where visible light is detected such gating can be performed on the photocathode itself, as in case of image intensifiers, where a semi-transparent photocathode is physically separated from the MCP and can be reverse-biased in a very short amount of time as virtually no current is flowing through it. It is much harder to perform gating for soft X-ray detection for which there are no efficient semi-transparent photocathodes and thus the entire MCP needs to be shut off in a very short time. A very large voltage drop (on the scale of a kilovolt) has to be implemented in order to turn off the MCP multiplication. Moreover, such a large dV/dt swing in the MCP bias voltage can couple to extremely sensitive readout electronics placed behind the MCP and thus permanently damage it.
We report here on the development and testing of a gated soft X-ray MCP detector with a Timepix readout. Our initial tests performed with a short-pulse UV LED demonstrated that gating time as short as ~10 ns FWHM can be achieved. We have also demonstrated with UV LED that the detector is completely insensitive to the incoming photons when it is gated off.
Subsequent experiment was conducted at the BESSY II Femtoslicing facility (beamline UE56/1-ZPM and DynaMaX end-station) at Helmholtz-Zentrum Berlin. Figure 1 shows the measured intensity distribution as a function of synchrotron cycle (800 ns period/1.25 MHz). The intensity was measured here by turning the detector on for only ~10 ns (FWHM) at a given time relative to the synchrotron trigger. The frequency of the detector High Voltage gaiting was ~6 kHz (each 125 s the detector was turned on for ~10 ns, synchronized with the source trigger pulse).
The results of our measurements indicate that the detector can indeed turn on and off within ~10 ns time. Another very important characteristic of our detector – there were no photons detected outside of the gated ON time period, indicating that the detector is completely turned off and the MCP does not extract any charge during off period. As a result, the detector can operate with extremely high (in terms of event counting detector) input fluxes without being “blinded”. This mode of operation is intended for the future experiments with MCP/Timepix3 detector where fast dynamics will be studied with very high timing resolution enabled by slicing at this beamline at BESSY II.
[1] A.S. Tremsin, J.V. Vallerga, "Unique capabilities and applications of Microchannel Plates detectors with Medipix/Timepix readout", Radiation Measurements 130 (2020) 106228.
[2] M.R. McCarter, A.I. U. Saleheen, A. Singh, R. Tumbleson, J.S. Woods, A.S. Tremsin, A. Scholl, L.E. De Long, J.T. Hastings, S.A. Morley, S. Roy, “Antiferromagnetic real-space configuration probed by dichroism in scattered x-ray beams with orbital angular momentum”, Physical Review B 107 (2023) L060407.
[3] J. Woods, X. Chen, R. V. Chopdekar, B. Farmer, C. Mazzoli, R. Koch, A. Tremsin, W. Hu, A. Scholl, S. Kevan, S. Wilkins, W.-K. Kwok, L. D. Long, S. Roy, J.T. Hastings, "Switchable X-ray Orbital Angular Momentum from an Artificial Spin Ice", Phys. Rev. Let. 126 (2021) 117201.
[4] K. Holldack, J. Bahrdt, A. Balzer, U. Bovensiepen, M. Brzhezinskaya, A. Erko, A. Eschenlohr, R. Follath, A. Firsov, W. Frentrup, L. Le Guyader, T. Kachel, P. Kuske, R. Mitzner, R. M¨uller, N. Pontius, T. Quast, I. Radu, J.-S. Schmidt, C. Schueßler-Langeheine, M. Sperling, C. Stamm, C. Trabant, and A. Foehlisch, “FemtoSpeX: a versatile optical pump–soft X-ray probe facility with 100 fs X-ray pulses of variable polarization”, J. Synchrotron Radiat. 21 (2014) 1090.

Speaker: Dr Anton Tremsin

iWoRID_2023_Tremsin.pdf

11:50 ALICE ITS3: a vertex detector based on truly cylindrical, wafer-scale Monolithic Active Pixel Sensors

ALICE is one of the four major experiments at CERN Large Hadron Collider (LHC), studying the physics of strongly interacting matter at the highest energy densities reached so far in the laboratory. For this purpose, the ALICE detector is optimised to study the collisions of nuclei at the ultra-relativistic energies provided by the LHC. The optimisation involves efficient and precise tracking at high multiplicities of the particles resulting from the collisions, down to very low transverse momentum ($p_{\text{T}}$ > 0.1 GeV/c).

The Inner Tracking System (ITS2) is the detector closest to the interaction point with the main goal to improve the precision of the reconstruction of the primary vertex as well as of decay vertices originating from heavy-flavour hadrons, and the performance in the detection of low-$p_{\text{T}}$ particles. It is based on state- of-the-art silicon monolithic active pixel sensor ALPIDE featuring chip size of 3 cm × 1.5 cm. The ALPIDE chips are arranged in seven, quasi-cylindrical, concentrical layers of which the innermost three feature a material budget of 0.36% X0.

The ALICE Collaboration is planning to upgrade the ITS2 by replacing its three innermost layers during the LHC Long Shutdown 3 (2026-2028) with a completely new detector, based on wafer-scale monolithic active pixel sensors. To produce wafer-scale sensors, small reticles are combined into large sensors during the CMOS manufacturing processes called stitching. These large sensors, fabricated on 300 mm wafers, will subsequently be thinned down to values below 50 μm, where they are flexible to be bent into truly cylindrical half-barrels. By exploiting the self-supporting property of this arched structure, the support mechanics can be almost completely removed, and by reducing the beampipe size, the first layer can be installed even closer to the interaction point. Therefore, the three innermost layers of the ITS3 will be at distances of 18, 24 and 30 mm from the interaction point with a target thickness of below 0.05% X0 per layer. The tracking resolution is projected to improve by a factor of about two at $p_{\text{T}}$ = 1 GeV/c with respect to the ITS2.

This contribution will review the ALICE ITS3 detector concept and the R&D path, focusing on the main results and milestones achieved in the first three years of the project. In particular, the following topics will be discussed: bending of the silicon layers, challenges relative to mechanics and air-cooling, assembly of detector mock-ups, technology qualification, design and testing of wafer scale monolithic active pixel sensors, and the detector integration.

Speaker: Miljenko Suljic (CERN)

2023-06-26_alice_its3_iworid_msuljic.pdf

12:10 Upgrade of Belle II Vertex Detector with CMOS Pixel Technology

The Belle II experiment at KEK in Japan is upgrading its vertex detector system to address the challenges posed by high background levels caused by the inceased luminosity of the SuperKEKB collider. A proposed vertex detector upgrade aims to install an all-layer monolithic pixel vertex detector based on fully depleted CMOS sensors in 2027. The new system will use the OBELIX MAPS chips to reduce the material budget and improve spatial resolution, and will consist of five layers using a single sensor type. This talk will focus on the design status of the OBELIX sensor and detection module developments based on the TJ-Monopix2, presenting laboratory and test beam results on pixel response, efficiency, and spatial resolution.

Speaker: Ms Marike Schwickardi (Uni Göttingen)

Schwickardi_IWORID2023.pdf

12:30 → 13:15 Lunch Break

13:15 → 14:45 Front-end Electronics and Readout: 1

Convener: Dirk Meier

13:15 INVITED: SWIR/NIR SPAD Image Sensors for LIDAR and Quantum Imaging Applications

In this talk, I will review the evolution of solid-state photon counting sensors from avalanche photodiodes (APDs) to silicon photomultipliers (SiPMs) to single-photon avalanche diodes (SPADs). The impact of these sensors on LiDAR has been remarkable, however, more innovations are to come with the continuous advance of integrated SPADs and the introduction of powerful computational imaging techniques directly coupled to SPADs/SiPMs. New technologies, such as 3D-stacking in combination with Ge and InP/InGaAs SPAD sensors, are accelerating the adoption of SWIR/NIR image sensors, while enabling new sensing functionalities. I will conclude the talk with a technological perspective on how all these technologies could come together in low-cost, computational-intensive image sensors, for affordable, yet powerful quantum imaging.

Speaker: Prof. Edoardo Charbon (EPFL)

EdoardoCharbon_iWorid23_compressed.pdf

EdoardoCharbon_iWorid23.pptx

SWIR/NIR SPAD Image Sensors for LIDAR and Quantum Imaging Applications

13:45 Development of Infrared Image Sensors

We present results from NIRCA – the near infrared readout controller ASIC for high-performance infrared image sensors, and we describe possible use with readout integrated circuits and microbolometer arrays. NIRCA features 16 analog inputs with programmable gain amplifiers, 16-bit/12MSPS analog-to-digital converters and high-speed serial outputs. We measured the performance in terms of linearity and noise, and we observe better than 1.5LSB integrated non-linearity (INL), less than 0.35LSB differential non-linearity (DNL) and 3LSB equivalent noise input (ENI). NIRCA is radiation hardened by design, making it suitable for use in both space and terrestrial applications at ambient temperatures ranging from -40°C to +85°C. At the workshop, we will present NIRCA features, performance, and describe a possible use with microbolometer arrays for thermal infrared imaging.

Speaker: Mr Torbjørn Østmoe (Integrated Detector Electronics AS)

IDEAS-NM2_and_TIR_IWORID2023.pptx

14:05 Spacepix-3: SoI MAPS Detector for Space Radiation Monitoring

Radiation in space is a potential risk to human health and electronic systems. Spacepix-3, the successor of Spacepix-2 [1], is a high voltage monolithic active pixel sensor (HV-MAPS) ASIC capable of measuring flux and distinguishing between types of radiation, protons, electrons, and ions. SpacePix3, improved version of the former SpacePix2, features a 64 × 64 pixel matrix with a pixel pitch of 60 µm and a total sensitive area of 3.84 × 3.84 mm$^2$. Analog signals from pixels are digitized by 32 10-bit column ADCs with a successive approximation register (SAR). The total power consumption is 43 mA from a 1.8 V power supply. Sensor diodes are biased at -150 V. Special Spacepix-3 functions are backside channel signal processing, SPI/LVDS readout modes, hit trigger output, debugging features, thermometer, radiation-hardened, multichip operation, and analog pixel output. Chip is implemented in 180 nm SoI technology.

Speaker: Dr Pavel Vancura (Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering)

vancura-iworid2023-spacepix3-16-9.pdf

14:25 High-rate, high-resolution single photon X-ray imaging: Medipix4, a large 4-side buttable pixel readout chip with high granularity and spectroscopic capabilities

Medipix4 is a hybrid pixel detector readout chip for single photon X-ray imaging, with 320 x 320 pixel array, each pixel being 75 µm x 75 µm in size. The chip operates in two modes: Fine Pitch Mode with a 75 µm sensor pixel pitch and two threshold bins per pixel, and Spectroscopic Mode with a 150 µm sensor pitch and up to eight energy threshold bins. The chip can be fully tiled in both x and y directions, allowing for seamless large area coverage. The chip has a size of 24.075 mm x 25.570 mm and covers 99.37 % active area when using TSV connections only. The readout architecture features energy analysis of the single photons, which includes charge sharing correction to bin the energy spread over adjacent incoming hits. This presentation will describe the chip architecture and show the first measurements.

Speaker: Viros Sriskaran (CERN)

Iworid2023_Medipix4_26_06_2023.pptx

14:45 → 16:15 Poster (incl. coffee): 1

Conveners: Ketil Roeed (University of Oslo (NO)), Dr Marco Povoli (SINTEF MiNaLab)

14:45 P1.1: RNDR-DEPFET detectors for single photon detection

The detection of single photons within the visible and near infrared spectrum became a key requirement for future space-based observations. Examples are the direct detection of exo-planets, multi object observation of high z-shift objects or high-cadence searches for short duration transients. One option to achieve photon number resolved measurements at non-cryogenic temperatures with a high quantum efficiency are silicon detectors with deep sub-electron noise. Such highly sensitive devices are especially prone to radiation damage, which presents a crucial parameter for space applications.

In this context, RNDR-DEPFET detectors offer complement properties to established technologies. The active pixel concept enables a high time resolution and good radiation hardness, while the fully depleted bulk of high purity silicon wafers ensure a high quantum efficiency and low dark count rate.

We will demonstrate the capability of a kilo-pixel RNDR-DEPFET sensor to detect signals as small as single electrons with a high time resolution, by continuously repeating a non-destructive readout. To evaluate the radiation hardness of this technology, we irradiated conventional DEPFET detectors – without repetitive readout – with 60 MeV protons. The results of this campaign provide information on the radiation hardness of DEPFETs in particular and of scientific silicon detectors with high-resistivity material in general.

Speaker: Wolfgang Treberspurg

14:46 P1.2: Prototype design of readout electronics for Transition Radiation Detector in High Energy cosmic-Radiation Detection

The High Energy cosmic-Radiation Detection facility (HERD) is a module being built with a planned launch in 2027. It will be installed on China’s Space Station as part of the Chinese Cosmic Lighthouse Program. An additional Transition Radiation Detector (TRD) will be placed on one of the lateral sides. It will calibrate Calorimeter (CALO) in the TeV energy range with cosmic rays. We have designed a readout electronics prototype system for TRD based on the SAMPA chip. The readout electronics board includes two SAMPA chips and has 64 channels. In addition, it has a DP78 interface to receive the negative charge pulse signal from the detector, and an optical interface communicates with the computer. The readout electronics uses a Xilinx Kintex7 XC7K70T-2FBG676I FPGA to analyze packets from SAMPA, and the valid events data is packed and transmitted to the computer by SiTCP. SAMPA internal registers are also configured within FPAG by the I2C bus. The event rate can be up to 10 kHz in the external trigger mode, and there is no dead time in the self-trigger mode. This system’s Integral Nonlinearity (INL) can reach 0.36%. Fe55 source testing results demonstrate that the readout system can perform well. The whole detect system’s resolution can reach 27%. Then we will go to CERN for a beam test in September 2023.

Speaker: Jieyu zhu (Institute of modern physics, Chinese Academy of Sciences)

14:47 P1.3: Firmware implementation of a displaced muon reconstruction algorithm for the Phase-2 Upgrade of the CMS muon system

This study presents the firmware implementation of an algorithm to reconstruct displaced muons for the Overlap Muon Track Finder (OMTF) of the Level-1 Trigger System (L1T) targeting the Compact Muon Solenoid (CMS) experiment upgrades for the High Luminosity Large Hadron Collider (HL-LHC). The firmware response is also compared to that of the software emulator.

The Upgrade L1T system of the CMS experiment, foreseen for the HL-LHC is fully described in a Technical Design Report (TDR) [1]. The foreseen system should greatly extend the throughput and capabilities of the current system despite the harsher environment. The L1T system has been designed to process 63 Tb/s input bandwidth with state-of-the-art commercial Field Programable Gate Arrays (FPGAs) and high-speed optical links reaching up to 28 Gb/s using generic-processing cards based on Advanced Telecommunications Computing Architecture (ATCA) technology.

The OMTF has been previously implemented both in VHDL [2] and HLS [3]. Neither of this versions includes a solution for displaced muons. The HLS version was developed as an assessment of the suitability of high-level synthesis for the design of complex hardware systems and and neither includes the latest design changes in the algorithm, nor is it optimized. This version is used as a starting point to add the displaced muon algorithm, include the latest design changes for the current run and also improve the design in terms of latency and area.

Displaced muons are an important signature of new physics beyond the standard model (BSM). There are models [4] that predict long lived muons that can be produced in the LHC collisions. These long-lived particles can decay inside the detector and produce displaced muons. For this task, the CMS trigger system should be updated to be able to trigger on these particular events.

Algorithm development in software and its subsequent implementation in hardware will allow to establish a comparison between both approaches efficiencies and help to trace the suitability of this hardware/software design method for the development of complex hardware systems in the field of particle detector physics.

Speaker: Pelayo Leguina Lopez (Universidad de Oviedo (ES))

14:48 P1.4: MPPC-based gamma camera with pinhole collimator to locate Cs-137 sources at high doses for the Fukushima nuclear power plant

The Fukushima Daiichi Nuclear Power Plant was severely damaged during the 2011 Great east Japan earthquake. Currently, investigations and various decontamination efforts are underway to de-commission the plants. However, it is difficult to perform decommissioning inside the reactor because the exact structure of the reactor is not yet known; the radiation level inside the reactor is extremely high, with a maximum of approximately 100 Sv/h. Under these circumstances, it is necessary to locate the radioactive sources to proceed with the work efficiently. Therefore, we developed a pinhole gamma camera consisting of a high-speed scintillator array (YGAG with a decay time of ~70 ns, Proterial Ltd.) and multi-pixel photon counters (MPPCs) that can detect individual gamma-ray photons to locate radioactive sources at high dose rates (~100 Sv/h). In this presentation, we report the system of the developed gamma camera and the measurement results of an extremely high dose of 137Cs (34 TBq) using the developed gamma camera. The gamma ray source position was determined with an angular size of ~4.5° at 2-m distance from the radiation source (~0.3 Sv/h). The direct gamma rays with a photoelectric peak at 662 keV and scattered gamma rays can be discriminated from the measured spectrum. We will also show that the imaging capability of the 137Cs depends on the detected gamma ray energies and the discussed details.

Speaker: Mr Takahiro Tomoda (Kanazawa University)

14:49 P1.5: The LHCb VELO Upgrade II: design and development of the readout electronics

The LHCb Upgrade-I detector is currently operating at the Large Hadron Collider at CERN and it isexpected to collect about 50 fb$^{−1}$ by the end of Run 4 (2032), when many sub-systems of the detector will reach their end of lifetime. In order to fully exploit the High-Luminosity LHC potential in flavour physics, the LHCb collaboration proposes a Phase-II Upgrade of the detector, to be installed during the LHC Long Shutdown 4 (2032-2034). This Upgrade will consist of a re-designed system with the capability of operating at an instantaneous luminosity of 2$\times10^{34}$ cm$^{−2}$s$^{−1}$, i.e. a factor 10 larger than that of the Phase-I Upgrade detector andwill allow the experiment to accumulate an integrated luminosity of about 300 fb$^{−1}$.

Operatingin the HL-LHC environment poses significant challenges to the design of the upgraded detector, and especially to its tracking system. In particular, the performance of the VErtex LOcator (VELO), which is the tracking detector surrounding the interaction region, is essential to the success of this Phase-II Upgrade. Data rates are especially critical for the LHCb full software trigger, and with the expected higher particle flux, the VELO Upgrade-II detector will have to tolerate a dramatically increased data rate: assuming the same hybrid pixel design and detector geometry, the front-end electronics (ASICs) of the VELO Upgrade-II will have to cope with rates as high as 8 Ghits/s, with the hottest pixels reaching up to 500 khits/s. With this input rate, the data output from the VELO will exceed 30 Tbit/s, with potentially a further increase if more information is added to the read-out.

The VELO collaboration is currently exploring new sensor technologies, and the benefits that would derive from adding a time stamp to the track reconstruction, such that interactions in the same bunch crossing can be more effectively disentangled. Achieving a hit resolution of 50 ps per pixel is considered possible within the timescale of the Phase-II Upgrade. With such resolution, each VELO track would have multiple time measurements from the traversed pixels, which will lead to a precise estimation of the production time of charged particles. Moreover, at the hit level, a precise timing information will also help reducing the number of possible combinations to be considered for the track reconstruction, thus improving its quality. The most recent advances in this field, and the potential candidates that can meet the VELO Upgrade II requirements, will be presented, with special focus on the PicoPix ASIC (an evolution of the Timepix4 design) and the TIMESPOT ASIC prototypes.

Speaker: Viros Sriskaran (CERN)

14:50 P1.6: The Influence of Parallax Effects in Thick Silicon Sensors in Coherent Diffraction Imaging

Structure determination is one of the most important application areas of 4th generation light sources, which in particular can fully exploit the coherent properties and pulsed nature of the X-ray radiation delivered by X-ray free-electron lasers (XFEL) as the European XFEL. The focus of scientific interest in this area is understanding the physical, biological, and chemical properties of samples on the nanometer scale. The properties of the X-rays provided by the FEL enable Coherent X-ray Diffraction Imaging (CXDI), an experimental technique where a sample is irradiated with coherent X-rays and a far-field diffraction pattern is registered with an imaging detector.

In this contribution, we discuss the influence of the parallax effect inherent in a detector with a 500 $\mu$m thick silicon sensor with a pixel size of 50 $\mu$m x 50 $\mu$m on the resolution of a CXDI experiment. To mathematically describe the imaging properties of the detector, we use the generalized concept of the Point Spread Function (PSF), considering its dependence on the photon energy and scattering angle.

The distorted and elongated shape of the PSF at scattering angles > 30° and photon energies > 12 keV significantly reduces the achievable signal-to-noise per pixel at high $q$. It can become a resolution-limiting factor in CXDI experiments. We further elaborate on the influence of the PSF on the signal-to-noise depending on energy, scattering pattern, and the position resolution of the detector.

Speaker: Dr Markus Kuster (European XFEL GmbH)

14:51 P1.7: Development and performance evaluation of high-speed gamma imaging system for Korea Customs Service

The Korea Customs Service presently employs radiation portal monitors (RPM) and hand-held survey meters to detect nuclear and radioactive materials in imported cargo at airports and harbors. However, these devices lack imaging capabilities and only provide count rates or dose rates, making it time-consuming to localize nuclear or radioactive materials. This study introduces a high-speed gamma imaging system developed for the Korea Customs Service, which quickly localizes and identifies radioactive materials in cargo using a hybrid gamma imaging technique that combines Compton imaging and coded aperture imaging. The system consists of eight rectangular (146 mm x 146 mm}) NaI(Tl) crystals, 72 square-type PMTs, a 72-channel high-speed FPGA-based DAQ, and a notebook computer. It offers exceptional performance in source localization, isotope identification, and dose rate estimation, while maintaining high mobility on a motorized cart that absorbs shocks and vibrations. The system's performance was assessed using Cs-137 check sources at various locations. In low dose rate scenarios (0.03 μSv/h above background dose rate), the system detected the source in approximately 0.3 milliseconds and localized its position within roughly 2 seconds. Even under lower dose rate conditions (9 μCi Cs-137 source at 5 m or 0.001 μSv/h incremental dose rate), the system imaged the location of the source within 5 minutes. Under these conditions, the system also estimated the ambient dose rate with an error of less than 25%. These experiments demonstrate the system's ability to quickly localize and identify nuclear and radioactive materials, and it is anticipated that this technology will effectively supplement existing radiation imaging devices at airports and harbors.

Speaker: Junyoung ­Lee (Hanyang University)

14:52 P1.8: A Timepix3 front-end simulator

Detector simulation is an important tool to understand and interpret experimental results. With the ground truth data included in the data set, a sufficiently realistic detector model is very valuable in the development and validation of track and particle reconstruction algorithms and can also be used to generate training data sets for neural network based data analysis. In order to correctly describe the behaviour of the full detector system, charge deposition, charge transport and the pixel front-end electronics need to be accurately modelled. This work focuses on the development of a front-end simulation code for the Timepix3 readout chip [1]. The front-end electronics channel is modelled using an integrator stage and parallel low-pass filtered feedback loops with individually configurable time constants. The system noise is implemented using independent bandwidth limited noise channels for pre-amplifier, feedback and threshold noise. The Timepix3 time of arrival (ToA) and time over threshold (ToT) measurement is computed using a discriminator model with independent rise and fall time constants and separate clock frequencies for the ToA and ToT time-stamping. An example of a simulated pre-amplifier output and the discriminator signal is shown in Figure 1. The measured dependence of the ToT on the pre-amplifier input charge using test-pulses of a Timepix3 assembly is correctly reproduced by this model for a wide range of discriminator threshold settings, shown in figure 2. Simulated data will be compared to measurements using radioactive sources. The model does however not cover all aspects of the Timepix3 front-end and its limitations will be discussed. The model is also available as a plug-in for Allpix2 [2].

Speaker: Lukas Tlustos (Czech Technical University in Prague (CZ))

14:53 P1.45: Spectroscopic effects of distributed-line phenomena in integrated feedback resistors for charge-sensitive pre-amplifiers

Charge-sensitive pre-amplifiers for semiconductor radiation detectors require a feedback discharge device to ensure proper functionality and avoid saturation. This can be a continuous-time device, like a simple resistor or trans-conductor, or an active structure that provides pulsed reset. Traditionally in the field of gamma spectroscopy such device is a discrete resistor of high value (1GΩ or more). This because the noise produced by this device is one of the key elements that concur in defining the total equivalent input noise of the pre-amplifier. For the same reason this device can be operated at liquid nitrogen temperature for noise minimization. The state-of-the-art spectroscopic filtering techniques require also this device to be exceptionally linear in order to produce exponential-shaped signals at the pre-amplifier output to ensure best energy resolution. Unfortunately such surface-mount devices are realized on ceramic substrates that are not radio-pure and this can be an issue if radio-purity is required, like in underground laboratories where rare-decay studies are carried out. Such devices are also bulky and may be an issue while pursuing maximum system integration in high-channel-number applications. Since active trans-conductors generally have a higher noise respect to passive resistors, integrated high-resistivity polysilicon resistors seem a viable solution to combine integration, low noise and radio-purity. In fact, silicon dies are naturally radio-pure due to their technological production process.
One factor that should not be underestimated is the capacitive coupling to bulk that characterize such integrated polysilicon resistors. Such capacitance turn integrated polysilicon resistors into distributed-line devices. The interaction of the resistor thermal noise with such distributed capacitance shapes the white power spectral density of noise that such resistor produces when connected as feedback device of charge-sensitive pre-amplifier. Interestingly, the net effect is the appearance of a current noise component with power spectral density proportional to the square root of frequency. When conventional spectroscopy shaping techniques are applied to the signals from charge-sensitive amplifiers equipped with such resistor, an equivalent noise charge component arises that is proportional to the square root of the shaping time (see Figure 1). Closed form calculations and experimental data are presented that explain the origins of this interesting phenomenon and the practical consequences in typical experimental contexts.

[1] Capra, S., IEEE Trans Nucl Sci, 67 (4) (2020), 722-731.
[2] Capra, S., Secci, G., Pullia, A., IEEE Trans Nucl Sci, 10.1109/TNS.2023.3259143, in press.

Speaker: Dr Stefano Capra

14:54 P1-9: Status of GE2/1 for the Phase-2 Upgrade of the CMS Muon System

The Large Hadron Collider (LHC) Phase-2 upgrade increases the instantaneous luminosity to 5 x 10^34 cm-2 s-1 and this very high luminosity will present a major challenge to the most forward regions of the CMS detector. To confront the high background rates, the CMS experiment plans to upgrade the forward muon system by installing three new detectors based on triple-GEM technology to maintain trigger capabilities. The GE2/1 station consists of 288 triple-GEM modules arranged in two layers of 18 chambers in both end-caps, covering the forward pseudorapidity range 1.6 < |eta| < 2.4 region to improve both muon triggering and reconstruction. It will be installed during YETS 2024 and 2025. We present the status of the GE2/1 project, including the progress of production and the performance based on the the results of QC tests performed on the assembled GE2/1 detectors.

Speaker: Seulgi Kim (University of Seoul, Department of Physics (KR))

14:55 P1.10: A 20 Gbps PAM4 Receiver ASIC in 55 nm for Detector Front-end Readout

High speed optical links with high bandwidth and large data capacity have been widely used in detector front-end readout. There are NRZ (Non Return to Zero) and PAM4 (4-level Pulse-Amplitude Modulation) signal modulation formats in optical link, the NRZ also known as PAM2 has been used for decades, but PAM4 is attracting more and more attention for its doubled bandwidth efficiency compared with NRZ with the increase of data rate. The optical receiver based NRZ and PAM4 modulation formats is a key component of the optical link for converting optical signals into electrical signals. Some receivers using NRZ format have been reported, such as GBTIA[1], a 5 Gbps optical receiver has been used in high-energy physics experimental detectors, and QTIA[2], a 2.5 or 10 Gbps 4 channel array optical receiver.
As a further study, this paper presents the design and simulation results of a 20 Gbps PAM4 receiver ASIC fabricated in 55 nm CMOS technology for detector front-end readout. The 20 Gbps PAM4 receiver ASIC mainly consists of an equalizer stage, voltage shifter, 3 hysteresis amplifiers, decoder and CDR (Clock and Data Recovery). A 20 Gbps PAM4 signal will be input to the equalizer stage with CTLE (Continuous Time Linear Equalizer) structure for high frequency signal attenuation caused by PCB transmission line and parasitic parameter from bonding wires and input pads. The voltage shifter provides a voltage shift by removing common mode voltage, then the central voltage of each eye of PAM4 will be removed to zero. The 3 PAM4 signals output by the voltage shifter will be further amplified by 3 hysteresis amplifiers respectively. Three MSDFFs (Master Slave DFFs) after the 3 hysteresis amplifiers will resample the three signals and the sampling clock will be provided by the 10 GHz clock recovered by CDR. The sampled signals will be sent to decoder for processing to obtain two NRZ signals (MSB and LSB). In order to improve the quality of the output NRZ signal, the decoded signal will be resampled by the clock signal recovered by CDR.
The 20 Gbps PAM4 Receiver ASIC has been designed in 55 nm CMOS technology with the chip area of 2.2 mm × 1.6 mm. The simulation results show that two logically NRZ (MSB and LSB) data can be obtain and the jitter of eye diagram of MSB and LSB are 1.67 ps and 1.73 ps, respectively. And the jitter of clock recovered by CDR is around 1.46 ps. The chip has been taped out and the tests are planned to be conducted in this June.

[1] Menouni M . The GBTIA, a 5 Gbit/s radiation-hard optical receiver for the SLHC upgrades[J]. Twepp Topical Workshop on Electronics for Particle Physics, 2009.
[2] Sun H , Huang X , Chao C P , et al. QTIA, a 2.5 or 10 Gbps 4-Channel Array Optical Receiver ASIC in a 65 nm CMOS Technology[J]. 2021.

Speakers: Qiangjun Chen, Prof. Di Guo (Central China Normal University)

14:56 P1.11: First Results of the Upgraded ALICE Inner Tracking System in LHC Run 3

Major upgrades of the ALICE experiment at CERN were completed during the LHC Long Shutdown 2 (2019-2021). The ALICE detector is currently taking data and has been doing so from the start of the third period of operation of the LHC (Run 3) on July 5th, 2022. One key part of these upgrades is the new Inner Tracking System (ITS2), a full silicon-pixel vertexing and tracking detector constructed entirely with CMOS monolithic active pixel sensors (ALPIDE). The ITS2 consists of three inner layers (50 μm thick sensors) and four outer layers (100 μm thick sensors) covering 10 m2 and containing 12.5 billion pixels with a pixel pitch of 27 μm x 29 μm. It offers a significant improvement in impact-parameter resolution and tracking efficiency, thanks to the increased granularity, the very low material budget (0.35% X0/layer in the inner barrel) as well as a smaller beam pipe radius.

The ITS2 was successfully installed in the ALICE experiment in May 2021, followed by a period of comprehensive on-site commissioning, before starting data taking in July 2022. In this talk, the detector construction and commissioning will be introduced briefly. The performance results from the first phase of proton-proton collisions recorded to date in LHC Run 3 will be discussed in detail, which include detector calibration, long-term evolution of the ALPIDE sensor threshold and noise, a first measurement of the detection efficiency and pointing resolution.

Speaker: Jian Liu (University of Liverpool (GB))

iWoRiD-2023.pdf

14:57 P1.12: Detector challenges of the strong-field QED experiment LUXE at the European XFEL

The LUXE experiment aims at studying high-field QED in electron-laser and photon-laser interactions, with the 16.5 GeV electron beam of the European XFEL and a laser beam with power of up to 350 TW. The experiment will measure the spectra of electrons, positrons and photons in expected ranges of $10^{-3}$ to $10^9$ per 1 Hz bunch crossing, depending on the laser power and focus. These measurements have to be performed in the presence of low-energy high radiation-background. To meet these challenges, for high-rate electron and photon fluxes, the experiment will use Cherenkov radiation detectors, scintillator screens, sapphire sensors, as well as lead-glass monitors for backscattering off the beam-dump. A four-layer silicon-pixel tracker and a compact electromagnetic tungsten calorimeter will be used to measure the positron spectra. The layout of the experiment and the expected performance under the harsh radiation conditions will be presented. The experiment has received stage 1 critical approval (CD1) from the DESY management and is in the process of preparing its technical design report (TDR). It is expected to start running in 2025/6.

Speaker: Matthew Wing (University College London)

14:58 P1.13: Improvement of metal artifact and noise characteristics in computed tomography incorporated with CdTe photon-counting detector and Tin filter

The use of a photon-counting detector (PCD) in computed tomography (CT) can reduce related artifacts such as beam-hardening and metal artifacts, improving the image quality and potential diagnostic value of CT images. However, PCD sets a threshold at a specific energy level to only collect photons with energies higher than the threshold. If the threshold value is high, the number of detected photons will decrease, thus increasing electronic noise. In this study, by changing X-ray energy spectrum using an additional filter, high-energy binned PCD image with reduced noise can be obtained by receiving selectively more high-energy photons. In addition, the proposed method can also reduce beam-hardening artifacts. In order to demonstrate the efficacy of the proposed method, we conducted a systematic simulation on a numerical dental arch phantom having metal inserts using a PCD toolkit (PcTK) available from Johns Hopkins University. In the simulation, several thicknesses of tin (Sn) filter in the range of 0.1-0.6 mm were added to aluminum (Al) filter of a thickness of 2.0 mm to find a thickness of tin filter appropriate for improving of metal artifact and noise characteristics in CT. Two tube conditions of 120 and 140 kVp were tested, simulations assume that the object receives the same number of photons and vary the threshold of PCD at 25, 55, 80, and 100 keV. Our results indicated that CT images of a dental arch phantom obtained at  tube voltages of 120 and 140 kVp and several thickness combinations of aluminum and tin filters using the PcTK toolkit. We noted that the metal artifact and noise characteristics were significantly improved for the conditions of 2.0 mmAl + 0.6 mmSn filter at 140 kVp. According to our preliminary results, a higher thickness of the tin filter reduced effectively electronic noise and metal artifacts, thus improving the image quality of CT images. More quantitative simulation results will be presented in the paper.

Speaker: Soohyun Lee

14:59 P1.14: Data Processing Engine for Mixed Radiation Field Characterization with Timepix Detectors

The hybrid semiconductor pixelated detectors of Timepix family provide online particle tracking. Each particle of various types and energies can be tagged with precise time stamp. This makes them suitable for large variety of applications: medical as radiotherapy or radiology, space on board of satellites and International Space Station and many industrial applications. The measured data is complex and several analyses were developed and exploited to derive needed information.
Presented data processing tool “Data Processing Engine” (DPE) comprehends most of these common processing techniques and several specialized ones to provide a user platform for accessible, fast and reliable data analysis for Timepix detectors.

Speaker: Lukas Marek (ADVACAM)

15:00 P1.15: Triple-energy virtual monochromatic imaging with a photon-counting detector for reducing metal artifacts in half-beam dental CT

Dental computed tomography (CT) has become an indispensable tool in dental practice for accurate diagnosis and precise treatment planning. However, metal artifacts induced by dental restorations or implants present considerable challenges in obtaining high-quality diagnostic images. Such artifacts can lead to misdiagnosis or suboptimal treatment planning. To address this issue, researchers have developed various techniques aimed at improving image quality and mitigating metal artifacts in dental and endodontic CT. One of these techniques is the triple-energy virtual monochromatic imaging (TEVM) method, which employs a photon-counting detector (PCD) to minimize noise and generate accurate virtual monochromatic images (VMIs). This technique synthesizes three images captured at distinct energy levels to produce a VMI with enhanced contrast and sharpness, particularly in regions affected by metal artifacts. In this study, we assessed the efficacy of the TEVM in mitigating metal artifacts in both half-beam dental CT and endodontic CT (Fig. 1). We conducted a comprehensive evaluation of the technique using dental phantoms containing various types and quantities of metal, comparing its performance to conventional metal artifact reduction approaches. Our findings demonstrated that the proposed TEVM was successful in reducing metal artifacts and enhancing image quality, compared to the conventional method. Utilizing TEVM in conjunction with PCD has the potential to significantly improve the quality and dependability of clinical imaging in patients with metallic restorations or implants. This can equip clinicians with more accurate and detailed information for diagnosis and treatment planning, ultimately leading to improved patient outcomes. Furthermore, the proposed technique can contribute to a reduction in radiation exposure for patients by minimizing the necessity for repeated scans to obtain accurate images (Figs. 2 and 3). In conclusion, TEVM combined with PCD represents a promising solution for mitigating metal artifacts in dental and endodontic CT, thus enhancing patient care and promoting optimal treatment outcomes.

Speaker: Minjae Lee (Yonsei University)

15:01 P1.16: The SparkPix-S ASIC for the sparsified readout of 1 MHz Frame-Rate X-ray Cameras at LCLS-II: pixel design and simulation results

Exploiting the “sparse” nature of the information in XPCS and XSVS experiments, we present the SparkPix-S, a 3-sides buttable Application Specific Integrated Circuit (ASIC) based on a sparsified readout strategy for large-format hybrid detectors. The SparkPix-S architecture, based on the successful ePix family, will be composed as follows: a front-end 2-D matrix of 384×352 square pixels with 50 μm pitch is arranged to match the dimensions of a PIN Si-sensor matrix; charge readout, signal shaping and amplitude discrimination is performed at pixel-level, by means of a low-power (<18 μW) analog processor, which, in case of an event, negotiates access to an analog bus placed every other column; on the chip periphery (balcony), the information on each bus is digitized by an array of successive approximation analog-to-digital converters (SAR-ADCs) running at 10 Msps; on the digital back-end the global logic will generate the output data stream using low-voltage differential signalling (LVDS).
A first prototype of the SparkPix-S, with a reduced matrix size of 96×96 pixels, is currently under production on a 130 nm CMOS technology. Simulated performance results show an equivalent noise charge <60 el. r.m.s. at 1 MHz repetition rate, with a maximum input energy of 60 keV and capability to discriminate charge signals with equivalent energy as low as 900 eV.

Speaker: Dr Filippo Mele (Politecnico di Milano and Istituto Nazionale di Fisica Nucleare)

15:02 P1.17: Analysis of discharge events in the CMS GE1/1 GEM detectors in presence of LHC beam

In July 2022, the experiments installed on the Large Hadron Collider accelerator ring started a new data taking phase, Run-3. Before this phase, an upgrade campaign took place during the so called Long Shutdown 2 phase (2018-2022). In particular, the muon system of the CMS experiment has been upgraded with the installation of a new gas detector station, GE1/1, based on Gas Electron Multiplier technology (GEM). The CMS experiment has scheduled the installation of two additional GEM stations: GE2/1 and ME0. The aim of the GEM stations is to maintain the performance of the muon system, reached during the last data taking phase (Run-2), with the increase of instantaneous luminosity expected at the LHC. The installed GE1/1 station covers the pseudorapidity region 1.55<|η|<2.18. GE1/1 participated in the CMS Run-3 data taking from July to November 2022 and, in this period, its detectors were exposed for the first time to the radiation produced during the collisions of the LHC beams, with a center of mass energy of 13.6 TeV. Since the first days of Run-3, where only a few bunches collided in CMS, the GE1/1 detectors started to experience a significant number of discharges, affecting their smooth operation during the data taking. In this talk, we present an analysis of discharges, which started by simply counting the number of discharges occurring per detector. An interesting phenomenon observed was that the discharge rate can vary a lot among the installed detectors; this is due to the fact that the occurrence of discharges is driven by the manufacturing of the GEM foils used in the detectors. Imperfections in their manufacturing can lead to large variation in the discharge rate. In addition, the rate can vary in time, due to the fact that discharges can produce damage at the site generating them, deactivating a particular hole or, in the worst case, producing a short circuit in the GEM foil, deactivating a part of the foil amplification region. We present the evolution of the discharge rate in time and its dependence on the HV working point and on the luminosity delivered by the LHC beams. We present actions taken to mitigate the discharge rate and to assure a smooth detector operation.

Speaker: Simone Calzaferri (Università degli studi di Pavia - INFN Pavia)

scalzafe_iWorid_2023_V1.pdf

15:04 P1.18: The BEAR chip prototype: Design and experimental results

This work presents the Boston Extended Amplitude Range (BEAR) ASIC that has been designed to work with ACSEPT (A Compact Solar Energetic Particle Telescope), a NASA funded solar energetic particle (SEP) telescope made up of a stack of 10 solid state detectors (SSD). Detailed characterization of ion species over wide energy ranges is required to understand the physics of generation, energization, and transport of SEPs. The BEAR ASIC is a single channel front-end, with 2 switchable capacitors sharing the charge deposited by SEPs at the input of the charge sensitive amplifier (CSA) thereby increasing the detectable energy range of SEP. The BEAR chip was designed to detect input energies of 0.5MeV to about 3GeV. The chip was fabricated using 130nm CMOS technology and, is currently being tested. We will present the design, simulation, and experimental results of the BEAR chip.

Speaker: Ashley Antony Gomez (Boston University)

15:05 P1.19: Use of the large area XSPA 500k detector for a time-resolved pump-probe-probe diffraction experiment at Synchrotron SOLEIL

The XSPA 500k detector is an X-ray single photon counting hybrid pixel detector based on UFXC32k readout chips, that has been developed by Rigaku Corporation. The detector offers several unique features such as a seamless array of uniform pixels of 76 × 76 µm², very high-count rate, very fast readout, and an ultra-short multi-gating operation. The double-gating operation has been verified experimentally in a time resolved pump-probeprobe diffraction experiment.
Recently the XSPA detector was tested at CRISTAL beamline to demonstrate its operability to conduct such experiments (Fig. 1). A Ti3O5 powder sample was excited with femtosecond laser pulses, and its structural response was monitored with two consecutive diffraction images (double-gating). The first one, taken shortly after the pump pulse, to study the excited sample, and a second one, taken at a longer pump–probe delay hen the sample is completely relaxed. The second image can be used to ormalize the photoinduced signal on a shot-to-shot basis, thus increasing quality of the acquired data.
During the conference the performance of the detector and experimental results will be discussed and presented.

Speaker: Dr Fabienne Orsini (Synchrotron SOLEIL)

iworid2023_poster_dawiec(final).pdf

15:07 P1.20: Optimizing and Characterizing the Timepix2 Hybrid Pixel Detector: Enhancing Performance and Precision for Scientific and Industrial Applications

The introduction of the new hybrid pixel detector Timepix2, as a successor to the well-known Timepix detector, has presented new opportunities for optimizing and characterizing this novel device. In this paper, we provide a detailed process for optimizing a Timepix2 detector and uncover its behavior, which enables better parameter setting for specific applications, resulting in enhanced device performance. Our newly developed calibration process, in conjunction with the optimization, has led to significant improvements in the detector's accuracy and performance, facilitating more precise data collection and analysis. These advancements pave the way for the broader utilization of Timepix2 in numerous applications, such as CubeSats and NDT.
Overall, our study provides valuable insights into the optimization and characterization of Timepix2, highlighting its potential as a powerful tool in various scientific and industrial fields.

Speaker: David Hladík (Advacam s r.o)

15:08 P1.21: In vivo verification by means of charged fragments detection in carbon ion therapy treatments at CNAO

In particle therapy the application of safety margins in treatment planning to account for possible morphological variations limits particle therapy intrinsic potential requiring the implementation of safety factors. The development of an in vivo verification system, still missing in clinical routine, is hence considered a crucial step forward in improving the clinical outcome, allowing to experimentally check the planned and delivered dose consistency and to re-schedule the treatment whenever needed. The Dose Profiler (DP) is a device designed and built to operate as an online verification system of 12C ion treatments, exploiting the secondary charged fragments escaping from the patient body. The DP capability of spotting morphological variations occurring during the treatment delivery has been investigated for pathologies of the neck-head district in the context of a clinical trial (ClinicalTrials.gov Identifier: NCT03662373) carried out at CNAO (Centro Nazionale di Adroterapia Oncologica, Pavia, Italy) from the INSIDE collaboration. The performance of a 3D imaging procedure capable of showing where the morphological change is located, will be presented and the results will be discussed in the context of CIRT online monitoring and planning.

Speaker: Gaia Franciosini (Dipartimento di scienze di base e applicate per l'ingegneria, Sapienza, University of Rome)

15:09 P1.22: Design and preliminary test results of the charge sensitive amplifier for Gain-less Charge Readout in High-pressure TPC

A new No neutrino Double-beta-decay Experiment (N𝜈DEx) at China Jinping Underground Laboratory (CJPL) of the deepest natural rock shield in the world is being developed to search for the 0𝜈𝛽𝛽 of $^{82}Se$ using a high-pressure gas time projection chamber (TPC) with $^{82}SeF_{6}$ as the working medium and read out directly by Topmetal sensor chip. The Topmetal sensor, named Topmetal-S, is composed of an exposure top-most hexagon metal with a diameter of 1 mm as a charge collection electrode, a Charge Sensitive Amplifier (CSA), an analog-to-digital converter and a digital readout network. The TPC detector of the N𝜈DEx experiment requires a meter-sized charge readout plane with ∼ $10^{5}$ Topmetal-S sensors on the plane without gas-electron avalanche. This scheme eliminates the conventional avalanche fluctuations but demands exceedingly low internal noise on the front-end amplifier to achieve sufficient energy resolution. This paper presents the design and preliminary test results of the low-noise CSA fabricated in a 130 nm CMOS process. The input linear dynamic range of the CSA is about 6.25 fC and the charge-conversion gain is about 223 mV/fC. The ENC is about 112 $e^{-}$ after a digital trapezoidal pulse shaper.

Speaker: Yichen Yang (Institute of modern physics, Chinese Academy of Sciences)

15:11 P1.23: Test beam studies of ALICE Forward Calorimeter prototypes

The ALICE experiment is currently conducting the third round of data-taking at the Large Hadron Collider, LHC Run 3, but is planning an additional detector upgrade for the next data-taking round, LHC Run 4. One of the proposed upgrades contains the extension of the forward physics capabilities of the experiment by including a new high-granularity forward calorimeter (FoCal). This calorimeter is designed to explore the poorly known forward kinematic regime of parton distributions in nuclei and nucleons at high energy [1].

The electromagnetic part of FoCal (FoCal-E) is a 20-layered sandwich sampling calorimeter consisting of 18 low-granularity silicon pad sensor layers and two high-granularity pixel sensor layers, while the hadronic calorimeter (FoCal-H) is a spaghetti calorimeter consisting of copper tubes filled with scintillating fibers.

The pixel layers are equipped with ALICE Pixel Detector (ALPIDE) chips that were developed for the upgrade of the Inner Tracking System (ITS) of the ALICE experiment. These sensors are based on monolithic active pixel sensors (MAPS) and CMOS imaging technology and have a granularity of 30 × 30 μm2 [2]. The combination of pad and pixel sensors achieves excellent energy and pointing resolution, which allows for discrimination between direct photons and photons from pi0 decay.

Different prototypes have been studied and tested in various particle beams at SPS in 2022. This talk will give an overview of the prototypes and show the most recent results from the beam tests conducted at CERN.

[1] ALICE Collaboration. A Forward Calorimeter (FoCal) in the ALICE experiment (2019)
[2] ALICE ITS ALPIDE development team. ALPIDE Operations Manual (2016)

Speaker: Emilie Solheim (University of Oslo (NO))

15:12 P1.24: High-speed Readout System of X-ray CMOS Image Sensor for the Time Domain Astronomy

We have developed an FPGA-based high-speed readout system for a CMOS image sensor to observe X-ray transients in future satellite missions such as HiZ-GUNDAM. The results of our previous research suggested that the CMOS image sensor has a low-energy X-ray detection capability (0.4–4 keV) and strong radiation tolerance, which satisfy the requirements of the HiZ-GUNDAM mission. However, CMOS sensors typically have small pixel sizes, resulting in large volumes of image data. The GSENSE400BSI we used has 2048 × 2048 pixels, producing 6-Mbyte per frame. These large volumes of the observed raw image data cannot be stored in the satellite bus system. Therefore, only X-ray events are extracted. Furthermore, the readout time of CMOS image sensors is approximately ten times faster than that of X-ray CCDs, thereby requiring faster event extraction. To address this problem, we developed an FPGA-based image signal processing system capable of high-speed X-ray event extraction on-board. The compact design of this system enables it to be mounted on a CubeSat mission, facilitating an early in-orbit operation demonstration. In this paper, we present the results of the performance evaluation tests of the proposed FPGA-based readout system using X-ray irradiation experiments. The results of on-board X-ray event extraction and off-line processing are consistent, validating the functionality of the proposed system.

Speaker: Naoki OGINO

15:13 P1.25: Experimental evaluation of signal-to-noise ratio in counting detectors under pile-up conditions

As a follow-up of the Signal-to-Noise Ratio study presented previously [1], this work discusses the experimental results obtained for the statistical analysis of photon counting detector measurements.
A SPHIRD v1.0 ASIC [2] bump-bonded to a 50µm pitch electron collection silicon sensor 400 µm thick was used as the device under test. The ASIC analogical circuit generates a pulse of tens of nanoseconds for each hit, and its digital circuit includes the implementation of both amplitude and time-based pile-up compensation methods, being therefore an ideal candidate for this study.
The detector was illuminated with a direct beam of 15 keV monochromatic X-ray photons from the ESRF beamline BM05. Aluminium filters with thicknesses varying from 60 µm to 4 mm were used to scan the photon flux reaching the detector in a controlled manner. 500 acquisitions were taken for each filter step, and the input flux was measured simultaneously by a transmission Silicon diode in front of the detector as a reference.
To avoid experimental artefacts coming from drifts of the synchrotron ring current and beam instabilities that could affect the measurement of the statistical response, the variance of the output counts was obtained from the ratio of each two consecutive measurements at each step. The SNR conserved at the end of the detection chain was then obtained by applying the numerical method presented in [1]. In addition to standard photon counting operation, two pile-up compensation methods implemented in SPHIRD were tested: adding a second voltage discriminator at 135% of the pulse height and summing the extra counts (a method hereon called “Voltage Discrimination 1”, or VDIS-1); and using an asynchronous clock pulse of 200MHz to measure the pulse length in time, later using this result to calculate the actual number of hits (method called “Fractional Photon Counting”, or FPHC) [2]. The latter was also evaluated for different threshold levels.
The results were evaluated for individual pixels. The standard photon counting results reproduce the simulated behaviour, presenting a SNR2 response that peaks around 10 Mcps/pixel, and then drops to almost zero. Meanwhile, both pile-up compensation methods have presented a comparable effect on improving not only the count rate but also the statistical response of the system, for the covered count-rate range of up to 35Mcps/pixel.
The obtained results were encouraging and validate the presented methodology to obtain the SNR, also elucidating the pile-up detrimental effect on the statistical quality of the data. Further improvements on the simulation tool to accurately reproduce the charge-sensitive amplifier response of SPHIRD v1.0 and allow the precise simulation of these and other pile-up compensation methods are under development.

Speaker: Debora Magalhaes Suarez

Poster_SNR_iWoRiD2023.pdf

15:14 P1.26: X-ray single photon detection with XPOL-III

XPOL-III is a newly developed CMOS ASIC simultaneously working for collecting charge and processing signals inside Gas Pixel Detector. Starting from the architecture of the XPOL ASIC and its successful operation in the IXPE space mission, we implemented specific design changes aiming at increasing the rate capability and the response uniformity.
XPOL-III includes more than 100k pixels at 50 um pitch in a total active area of 15 x 15 mm2. Each pixel acts as a charge-collecting anode and is connected to its own charge-sensitive amplifier, followed by a shaping circuit and a sample-and-hold system. The chip, like its predecessor, provides self-triggering capability, with automatic localization of the region of interest (ROI) to be readout for each single photon. A new programmable margin definition has been implemented to reduce readout time. Other improvements include the sensitivity of the trigger electronics and the maximum speed for the serial event readout.
In this work we will describe the design of this new ASIC and its first tests. In particular, in the context of the gas detector application, in which imaging the photo-electron track emitted by single X-ray absorption allows us to measure beam polarization together with timing, imaging and spectroscopy

Speaker: Carmelo Sgro'

15:15 P1.27: The ATLAS ITk Strip Detector for the Phase-II LHC Upgrade

ATLAS-ITK Strip Collaboration

(the speaker to be selected by the ITk Speakers Committee after the contribution acceptance)

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). At the ATLAS Phase-II Upgrade, the particle densities and radiation levels will exceed 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. The new detectors must be faster and they need to be more highly segmented. The sensors used also need to be far more resistant to radiation, and they require much greater power delivery to the front-end systems. At the same time, they cannot introduce excess material which could undermine tracking performance. For those reasons, the inner tracker of the ATLAS detector was redesigned and will be rebuilt completely.
The ATLAS Upgrade Inner Tracker (ITk) consists of several layers of silicon particle detectors. The innermost layers will be composed of silicon pixel sensors, and the outer layers will consist of silicon microstrip sensors. This contribution focuses on the strip region of the ITk. The central part of the strip tracker (barrel) will be composed of rectangular short (~ 2.5 cm) and long (~5 cm) strip sensors. The forward regions of the strip tracker (end-caps) consist of six disks per side, with trapezoidal shaped sensors of various lengths and strip pitches. After the completion of final design reviews in key areas, such as Sensors, Modules, Front-End electronics, and ASICs, a large scale prototyping program has been completed in all areas successfully. We present an overview of the Strip System and highlight the final design choices of sensors, module designs and ASICs. We will summarise results achieved during prototyping and the current status of pre-production and production on various detector components, with an emphasis on QA and QC procedures.

Speaker: Hannah Elizabeth Herde (Lund University (SE))

ForMobile-HERDE-ATLAS-ITk-Strips

HEH-iWoRiD-ATLAS-ITk-Strips.pdf

15:16 P1.28: The mass production of silicon sensors for the Phase-2 CMS Tracker

The high-luminosity upgrade of LHC (HL-LHC) will boost the design luminosity of the accelerator up to 5x10$^{34}$ cm$^{-2}$ s$^{-1}$ while the total integrated luminosity will reach 3000 or even 4000 fb$^{-1}$. The increased radiation levels as well as the higher data rates impose new challenges for the tracking system of CMS. The Tracker will undergo a full replacement in order to cope with the advanced environment of HL-LHC and preserve the excellent performance of the current one.

For the Outer Tracker in particular, the so-called Phase-2 upgrade requires about 200 m$^{2}$ or 28000 new silicon strip and pixel sensors. Ten years of R&D studies on different material, thickness and design options preceded the large-scale production period of the silicon sensors which began in 2020. This report will provide an overview of the new Outer Tracker silicon sensors, summarize the quality assurance plan and present results and conclusions after qualifying about 50% of the production using pre- and post-irradiation characterization of sensors and the production process.

Speaker: Konstantinos Damanakis (Austrian Academy of Sciences (AT))

15:17 P1.29: Assembly and characterization of the first TRISTAN detector modules

The nature of dark matter is one of the big open questions in physics. As a minimal extension to the standard model of particle physics, the so-called sterile neutrinos in the keV mass range pose a viable candidate for it. The signature of such a sterile neutrinos could be seen in a high precision spectroscopy measurement of the tritium beta decay. To perform this measurement the TRISTAN silicon drift detector (SDD) system with almost 1500 independent pixels is currently being developed as an upgrade for the KATRIN experiment. It will be capable of measuring electrons with a targeted energy resolution of 300 eV (FWHM) at 20 keV for count rates of up to 100 kcps per pixel.
In this presentation the current status of the project, as well as the first characterization measurements of the monolithic 166 pixel SDD modules will be shown.

Speaker: Daniel Siegmann (Technical University of Munich)

15:18 P1.30: Test measurements of ASIC dedicated for X-ray material discrimination by using on-chip time domain integration and CdTe detector.

Using time-domain integration (TDI) and a two-dimensional sensor for X-ray imaging of moving objects allows us to overcome the trade-off between SNR and position resolution. Applying on-chip instead off-chip TDI decreases several times required data throughput between an ASIC and the backend. This in turn allows us to significantly simplify the ASIC itself as well as the backend.
We would like to present the results of test measurements of ASIC dedicated for material discrimination X-raying (MDX) by using an on-chip TDI and CdTe detector.
The ASIC consists mainly of 192 x 64-pixel matrix. The pixel size is 100 µm x 100 µm, so the chip size is about 6.4 cm × 2 cm. The chip was manufactured in CMOS 130 nm technology with 8 metal layers. A single pixel analog front-end consists of a charge-sensitive amplifier, a shaper, and three discriminators followed by counters.
First, we will present the results of test measurements done with single energy radiation to evaluate gain and noise for different chip settings. Next results of moving objects imaging are done by using the industrial machine for X-ray for food inspection (continuous energy spectrum). They will be carried out to evaluate spatial resolution and material discrimination ability (Fig. 1) for different object types, movement speed, and temperature. The authors acknowledge funding from the National Science for Research and Development, Poland, contract No. MAZOWSZE/0099/19.

Speaker: Miroslaw Zoladz

15:19 P1.31: Design and characterization of multichannel front-end electronics for detectors at HIRFL and HIAF

Many kinds of detectors are highly desirable with a large number of experiments being performed at the heavy ion research facility in Lanzhou (HIRFL) and the high-intensity heavy-ion accelerator facility (HIAF)。A competent and cost-effective front-end electronics system is required for the signal processing of these detectors. In this paper, we present a multichannel front-end readout electronics (MFEE) design based on the AD8488 chip. The MFEE mainly consists of an AD8488 chip, an ADC chip, an FPGA, four DDR3 memories, and an SFP interface.The lab test results show that the MFEE is relatively less nonlinear, i.e., about 1.4%. The RMS of noise levels below 5.57 ADC value. The joint tests performed using plastic scintillator detectors（PSD） show that the MFEE has an excellent performance in measuring cosmic rays. We are currently designing a revision of MFEE to make it more compact and less noisy.

Speaker: Shucai Wan (Institute of Modern Physics, Chinese Academy of Sciences)

15:20 P1.32: System for Fast Readout and Tests of Pixel IC Operating in Single Photon Counting Mode using PCIe-based FPGA

Hybrid pixel detectors become popular in particle and photon detection techniques for many years [1]. A hybrid detector consists of two parts: a pixelated sensor (based on Si, Ge, GaAs, CZT, etc) and a readout Integrated Circuit (IC) usually containing a few tens of thousands of pixels and millions of transistors. Integrated circuits suffer from the inaccuracies of manufacturing processes and therefore they should be thoroughly tested before the bump-bonding process with the sensor.

The paper presents a highly efficient system for automated testing of IC of pixel architecture using PCI-based FPGA. Our solution is based on the Intel Arria 10 GX development kit and a Linux-powered PC connected via PCIe 8x Gen 3 interface. It has been built of well-thought-out modules connected through a set of precisely defined interconnects. This approach enabled development of an architecture that may be easily implemented in both PCIe-based systems and System-on-Chip devices such as Intel Agilex SoC. The overall architecture of the developed system is shown in Fig. 1. The presented architecture has been tested with both a manufactured integrated circuit and an FPGA RTL model [2].

During the tests with IC, we used a readout integrated circuit of pixel architecture, designed for CdTe pixel detectors used in X-ray imaging applications with moving objects. The IC core is a matrix of 192 x 64 square-shaped pixels of 100 µm pitch operating in single photon counting mode (see Fig. 2 and 3). Each pixel contains a fast analog front-end followed by 3 independently working discriminators and 3 ripple counters. Such pixel architecture allows photon processing one by one and selecting the X-ray photons according to their energy. During the data readout phase, the counter in each column forms a shift register. The data from the register is loaded, bit by bit, into the peripheral fast 192-bits registers and shifted out of the chip via 4 fast LVDS parallel lines. The peripheral area located at the bottom of the integrated circuit also contains a bandgap reference source, bias DACs, an I/O control logic, a slow control for settings the register configuration in each pixel, as well as LVDS drivers and receivers.

The test system based on FPGA allows a wide range of tests of different integrated circuits of pixel architecture (e.g. registers tests, counter tests, DAC tests, threshold scans with calibration pulses, DC offset correction, gain, and noise extraction, etc). The communication with IC can be performed with a controlled clock up to 0.8 GHz, which allows also testing the new generation of ICs equipped with SerDes interfaces operating in Gbps range. The authors acknowledge funding from the National Science for Research and Development, Poland, contract No. MAZOWSZE/0099/19.

[1] R. Ballabriga, et al., Photon Counting Detectors for X-Ray Imaging With Emphasis on CT, IEEE Trans. on Radiation and Plasma Medical Sciences, vol. 5, no. 4, pp. 422-440, July 2021.
[2] P. Skrzypiec and R. Szczygieł, Readout chip with RISC-V microprocessor for hybrid pixel detectors, Journal of Instrumentation, vol. 18, no. 1, p. C01030, Jan. 2023.

Speaker: Pawel Skrzypiec

15:21 P1.33: Development of a medium sized photon-counting UFXC-demonstrator at SOLEIL synchrotron

A medium sized hybrid photon-counting detector for hard X-ray diffraction experiments is under development at the SOLEIL synchrotron. This demonstrator is based on the small two-chips camera prototype described in [1] with the pixelated UFXC32k readout chip [2], which has proven its performance in several experiments at the beamlines of SOLEIL, e.g., time resolved pump-probe-probe measurements [3].
Thanks to a four times larger sensor size, the new demonstrator overcomes the main limitation of reduced sensitive area of the two-chip camera. Furthermore, the new firmware and data acquisition system enable an increased frame rate from 3.4 kHz up to 23 kHz with several acquisition modes while the mechanical design of the system stays very compact.
The demonstrator (illustrated on Figure 1-left) comprises one single pixelated Silicon sensor of 4 × 4 cm² (two thicknesses are available), bump-bonded to eight UFXC32k readout chips. The hybrid pixel module is wire bonded to a ceramic electronic board, which is mounted on a water-cooled support frame. The head of the detector is then connected to the control- and data acquisition board which streams out the data via four 10Gb UDP connections. The optimized firmware with several readout modes as well as a software library and integration into the TANGO environment are also part of the development.
This contribution presents the main characteristics of the demonstrator, the validation tests of the first hybrid pixel modules (e.g. gain behaviour, Figure 1-right) and current state of the demonstrator under development.

[1] A. Dawiec et al., AIP Conf. Proc. 2054, 060067, (2019)
[2] P. Grybos et al., IEEE Trans. Nucl. Sci. 63 1155, (2016)
[3] D. Bachiller-Perea et al., J. Synchrotron Rad. 27, (2020)

The UFXC32k detector was supported by the National Centre for Research and Development, Poland (PBS1/A3/12/2012).

Speaker: Marie Andrae (Synchrotron SOLEIL)

UFXC_8chip_demonstrator_poster_MAndrae_iWorid2023.pdf

15:23 P1.34: Ecological transition for the gas mixtures of the MRPC cosmic ray telescopes of the EEE project

The Extreme Energy Events (EEE) experiment consists of 61 muon telescopes based on Multigap Resistive Plate Chambers (MRPC), each telescope composed of 3 chambers filled with gas.
The EEE Collaboration is fully involved in the ecological transition of the gas mixture used in the detectors.
The use of the standard gas mixture (98% C$_2$H$_2$F$_4$ - 2% SF$_6$) was discontinued in favor of an alternative green mixture mainly based on C$_3$H$_2$F$_4$ with the addition of He or CO$_2$. The gas mixture currently being tested guarantee a significant reduction of Global Warming Potential (GWP) to reduce the emission of gases potentially contributing to the greenhouse effect.
Several EEE detectors are today completely fluxed with the new ecological mixture. This contribution will report recent results obtained with the alternative, eco-friendly, mixture, in terms of time and space resolution, detection efficiency, tracking capability and stability over long data taking periods.

Speaker: Dr Cristina Ripoli (Universita e INFN, Salerno (IT))

15:24 P1.35: Development and Characterization of an EUV/soft X-ray Single-Photon Sensitive sCMOS Camera

Ultrafast X-ray spectroscopy has recently been defined revolutionary in chemical dynamics [1], but despite the above-mentioned excellent progress, its full potential still needs to be uncovered. A significant challenge in X-ray spectroscopy is the ability to measure very small changes of the absorption near the K-edges of the atomic elements [2] under investigation with a very high signal to noise ratio. Schemes with high detection efficiency in the soft X-ray spectral range and high-speed readout for “pump-on” and “pump-off” measurements are a prerequisite for the success of these experiments with low photon-flux tabletop sources.
In this respect, greateyes GmbH is developing X-ray cameras adapted to time-resolved X-ray spectroscopy, including newly developed CMOS-based detectors. The project aims to optimize an existing CMOS camera platform towards an EUV/soft X-ray sensitive sCMOS camera suitable for high-repetition rate imaging or spectroscopy as well as single photon detection and its application for the investigation of molecules in solutions with the help of absorption spectroscopy in the soft X-ray range.
A detailed comparison of this new technology with existing CCD technologies and associated charge transfer processes is presented to understand the pros and cons of each technology depending on the energy range, photon flux, repetition rate and other parameters. A first prototype of a sensitive sCMOS camera which is based on back-illuminated CMOS sensor offered by Gpixel with a 4 Megapixels resolution [3] is constructed. Key points and challenges in the development of the detector are presented, such as e.g.:
• a flexible Region-of-Interest (ROI) function implemented on a Field-Programmable Gate Array (FPGA) to further reduce the image acquisition time for high repetition rate experiments,
• development of a high-density electrical (UHV) vacuum feedthrough using flexible Polyimide PCBs
• design of a multi-stage thermoelectric sensor cooling system to achieve temporarily and spatially homogeneous dark current levels
Currently, a second camera protype is being built and recent results from its characterization in first proof-of-principle experiments with X-Rays are to be presented, that are obtained with the help of the experimental infrastructure for ultra-fast X-Ray spectroscopy at the Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy (MBI). Lastly, an outlook on future applications of the new sCMOS X-ray detector is given, which is planned to be used in experiments for the investigation of the dynamics of ultra-fast charge transfer processes in donor-acceptor complexes in a solution (i.e., push-pull chromophores) [4] and experiments with transient absorption of soft X-rays in collaboration with MBI.

[1] P. Kraus, M. Zurch, S.K. Cushing, D. M. Neumark, S, R. Leone, “The ultrafast X-ray spectroscopic revolution in chemical dynamics”, Nat. Rev Chem. 2, 82–94 (2018).
[2] J. Stöhr, F. Sette, and Allen L. Johnson, “Near-Edge X-Ray-Absorption Fine-Structure Studies of Chemisorbed Hydrocarbons: Bond Lengths with a Ruler”, Phys. Rev. Lett. 53, 1684 (1984)
[3] https://www.gpixel.com/products/area-scan-en/gsense/gsense400bsi-11-%CE%BCm-4mp-rolling-shutter-image-sensor/
[4] C. Kleine, M. Ekimova, G. Goldsztejn, S. Raabe, C. Strüber, J. Ludwig, S. Yarlagadda, S. Eisebitt, M. J. J. Vrakking, T. Elsaesser, E. T. J. Nibbering*, and A. Rouzée, “Soft X-ray Ab-sorption Spectroscopy of Aqueous Solutions Using a Table-Top Femtosecond Soft X-ray Source” J. Phys. Chem. Lett., 10, 52–58 (2019)

Speaker: Nursulton Abdurakhimov

15:26 P1.36: Primary scintillation in Xe for electrons and alpha-particles

Gaseous xenon (GXe) is playing an increasingly significant role in important areas of neutrino physics such as double beta decay and double electron capture experiments, and is a potential alternative to MeV-region γ-ray imaging. The capability for simultaneous readout of both ionization and scintillation signals and for topology reconstruction of the ionizing particle tracks are important advantages of GXe. In addition, GXe allows for improved energy resolution when compared to liquid xenon (LXe). The precise knowledge of the xenon response to radiation interactions in both scintillation and ionization channels is of utmost importance for the exact understanding and modulation of xenon radiation detectors.

The primary scintillation yield, i.e. the mean energy required to produce a scintillation photon, wsc, of GXe is far less understood than the ionization yield due to the limited number of studies in the literature. While for 5.5-MeV α-particle interactions the wsc-value was measured to be in the 34-60 eV range, for electrons, measuring the primary scintillation produced by x- and γ-ray interactions, the wsc-value was measured to be in the 61 - 111 eV range.
The average energy expended per excited atom in GXe is expected to be similar for x-, γ-rays or electrons and almost equal to that obtained for α-particles. However, the results presented in the literature are inconsistent with that expectation and not fully understood, as can be only partially ascribed to the different gas density and/or drift field conditions. One may also pose the question of a dependence of wsc with photon energy.

We carried out a systematic study on the absolute primary scintillation yield in Xe under reduced electric fields in the 70–300 V/cm/bar range and near atmospheric pressure, 1.2 bar, using a Gas Proportional Scintillation Counter. Our results are supported by a robust geometrical efficiency simulation model. Neglecting the 3rd continuum emission, a mean wsc-value of 38.7 ± 0.6 (sta.) +7.7 −7.2 (sys.) eV was obtained for x/γ-rays in the 5.9–60 keV energy range and for α-particles in the 1.5–2.5 MeV range, and no significant dependence neither on radiation type nor on energy has been observed. If the Xe 3rd continuum emission is to be considered, the average energy to produce a 2nd and 3rd continuum photon can be calculated as w2nd = 43.5 ± 0.7 (sta.) +8.7 −8.1 (sys.) eV and w3rd = 483 ± 7 (sta.) +110 −105 (sys.) eV, respectively, while the energy to produce a 3rd or 2nd continuum photon is w2nd+3rd = 39.9 ± 0.6 (sta.) +8.0 −7.4 (sys.) eV, assuming a 3rd to 2nd continuum yield ratio of 0.09, as recently reported.
The absolute electroluminescence yield was also measured in our setup for a wide range of electric fields, showing a mean disagreement of 7% with the simulation data. If we consider the El-yield as reference, the mean wsc-value corrected for this difference is wsc = 41.6 ± 0.6 (sta.) +6.2 −6.4 (sys.). Our experimental wsc-values agree with both state-of-art simulations and literature data obtained for α-particles. The discrepancy between our results and the experimental values found in literature for x/γ-rays is discussed and attributed to undressed large systematic errors.

Speaker: Prof. Joaquim M, F, dos Santos (LIBPhys, Dept. of Physics, University of Coimbra, Portugal)

15:27 P1.37: Multichannel integrated circuit for time-based measurements in 28 nm CMOS

Recent advances in the design of readout integrated circuits (ROICs), together with improved time resolution in advanced CMOS nodes, open new possibilities for the construction and possible applications of hybrid pixel detectors. The increasing number of designs focusses on providing precise time and energy measurement capabilities for each detected photon. Time-of-Arrival (ToA) and Time-over-Threshold (ToT) measurement has been used in 3-D particle tracking and reconstruction experiments and is useful in various branches of applied science. We present the design and preliminary measurement results of the ROIC prototype designed in 28 nm CMOS technology, which consists of a matrix with 4 × 8 pixels with 50 μm pitch. Each pixel includes an analogue front-end, Vernier TDC, and digital part with configuration register and counters, and can operate in either SPC mode or in energy and time-of-arrival measurement mode using ToT and ToA methods, respectively. The analogue front-end has been optimised for the time measurement use case. It consists of an inverter-based front-end amplifier (FEA), capacitive feedback, and Zimmerman feedback. FEA is AC-coupled to the discriminator. The FEA gain is controlled by changing the feedback capacitance and current in the Zimmerman feedback. The effective discriminator offset is tuned either by changing the number of unit transistors that form its input, or by changing a current setting the threshold level on its non-inverting input. The discriminator output is routed to the logic that controls the ring oscillators. Their frequency is tuned locally using capacitance banks and DACs. The oscillator outputs are passed to the counters, which consist of 37 bits in total per pixel. Pixel has separate power domains for the analogue part, oscillators, and the digital part (the latter two having dedicated deep N-wells). Measurement results show that the proposed offset correction approach results in a 10-fold improvement, while the gain correction uniformity is improved 3.3 times. The oscillator frequency range for which counters operate properly reaches several gigahertz (5 GHz for the examplary pixel). Current work is focused on testing the full ToT/ToA measurement capability for each channel, and results are expected soon. The work was supported by the National Science Centre under contract no. UMO-2017/27/B/ST7/01217.

Speaker: Mr Lukasz Kadlubowski (AGH University of Science and Technology)

15:28 P1.38: Spreading of an active region of semi-insulating GaAs detectors after radiation degradation

Semi-insulating GaAs detectors represent an alternative to silicon detectors exhibiting a higher detection efficiency of gamma and X-rays due to higher material density and promising radiation hardness. Previous studies have shown their ability to withstand doses of a few MGy when degraded by MeV electrons with a main limiting factor which is the charge collection efficiency decreasing with overall dose [1]. On the other hand, we have observed the apparent improve of the detection efficiency after initial detector degradation by 5 MeV electrons up to doses of 200 kGy [2] when measuring both the gamma and also alpha particle spectra of 241-Am. This phenomenon was explained by assumed expansion of active detector volume. The projected range of used alpha particles was less than 20 µm in 230 µm thick GaAs substrate, irradiated from Schottky contact side. The detectors have the sandwich structure with 135 nm thick circular Ti/Pt/Au Schottky contact 1 mm in diameter on the top and full area Ni/AuGe/Au ohmic contact on the opposite side of substrate. The deepening of active volume of detector with increasing applied bias was proved previously. However, the short penetration depth of measured alpha particles indicates spreading of active detector volume also to the sides, behind the metallization edge. Fig. 1a shows the increase of detection efficiency with growing applied bias, which was more intensive before detector degradation.
In this paper we evaluate the alpha particle spectra of 241-Am measured by the same semi-insulating (SI) GaAs detectors described in [2] but degraded by 5 MeV electrons up to 2 MGy doses. The detection efficiency is evaluated through integrated counts in peak and shows the continuing increasing tendency up to doses of 600 kGy followed by deterioration in the range of doses from 1 to 2 MGy (Fig. 1b). The assumed spreading of the active area to the sides behind the Schottky metallization was experimentally confirmed by scanning the detector surface with a micro-focused X-ray beam. According to our results, the radiation degradation of SI GaAs detectors has influence on their electric field distribution, which might be important in the case of sensor structures for multipixel detectors.

[1] Sagatova et al.: Alpha-spectrometry by radiation-degraded semi-insulating GaAs detectors. In Materials Today: Proceedings, 2022, vol. 53, no. 293.
[2] Sagatova et al.: Radiation hardness study of semi-insulating GaAs detectors against 5 MeV electrons. In Journal of Instrumentation, 2018, vol. 13, no. C01006.

Acknowledgement: The authors acknowledge funding from the Slovak Research and Development Agency by grant No. APVV-18-0273 and the Scientific Grant Agency of the Ministry of Education of the Slovak Republic and the Slovak Academy of Sciences through grant No. VEGA 2/0084/20.

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

IWORID23poster_Sagatovafinal.pdf

15:29 P1.39: Design and optimization of a MPGD-based HCAL for a future experiment at Muon Collider

In the context of the European strategy for particle physics, a multi-Tev Muon Collider has been proposed as an interesting alternative to investigate the Standard Model with unprecedented precision after the full exploitation of the High-Luminosity LHC.
Some of the physics goals of the Muon Collider include precision measurements of the Higgs boson couplings (requiring excellent Z/H separation) and search for new physics at TeV scale. This demands accurate full event reconstruction, namely the identification and the four-momentum estimation of electrons, photons, muons, neutral and charged hadrons, as well as the clustering in jets. The most suited approach to accomplish this task is the Particle Flow (PF) algorithm, where the information of tracking, calorimeter and muon detectors are combined for particle identification and measurement of momenta/energies: the measurements of the charged particle momenta is performed in the tracking detectors, while the energy measurements for photons and neutral hadrons are obtained from the calorimeters. Therefore, the crucial step in PF, i.e. the correct assignment of the calorimeter hits to the reconstructed particles, requires a combination of an excellent tracking system with high granularity calorimeters.
At a Muon Collider, the PFA is complicated by the Beam Induced Background (BIB), that is due to the decays of the muons of the beam. It represents one of the major challenges for the experiment design and poses potential limitations on the detector performance and requirements on radiation hardness. The discrimination of signal showers from the BIB requires high granularity, superb energy resolution and precise timing. The calorimeter should thus provide 5D measurement (3D position, time and energy).
The hadron calorimeter (HCAL) that we propose in this contribution consists of a sampling of absorber and Micro Pattern Gas Detectors (MPGD) as active layer, for digital and semi-digital readout.
MPGDs represent the ideal technology, featuring high rate capability (up to 10 MHz/cm^2), flexible spatial and good time resolution (few ns), good response uniformity (30%); they use eco-friendly gas mixtures and have modest cost for large area instrumentation. Furthermore, gaseous detectors have the advantage of being radiation hard and allow for high granularity (1x1 cm^2 cell size).
Dedicated studies are needed to assess and optimize the performance, as well as the development of medium scale prototypes for performance measurements. In particular, the response of HCAL to the incoming particles is studied and presented in this contribution with Monte Carlo simulations performed using Geant4. The implementation of the HCAL geometry in Geant4 starts with a simplified model of Argon and Iron sampling with 1x1 m^2 transversal size with 1x1 cm2 segmentation, ~10 nuclear radiation lengths (𝝺) of longitudinal size. The response to pion beams is studied over an energy range of 1-100 GeV, comparing the performance of a digital and semi-digital readout, taking the energy resolution as a figure of merit. Besides, the same geometry has been implemented in the Muon Collider software to study the impact on the jet reconstruction in the context of the full apparatus and in presence of the BIB. Besides, a small size calorimeter cell is currently under preparation. It will be instrumented with the most advanced resistive MPGD technologies, resistive μ-RWELL and resistive Micromegas detectors, which demonstrate excellent performance for spatial resolution, operational stability (discharge quenching) and detector uniformity. The prototype will have 6-8 layers (~ 1 𝝺) of alternating 2 cm of absorber and MPGD detectors and will be tested in test beam with pions of energy ranging between 1 to 10 GeV. A preliminary test on the detectors alone will be performed with MIPs at CERN SPS in order to measure the efficiency, cluster size, hit multiplicity, spatial and time resolution. Some preliminary results obtained from the performance measurements on the detectors will be shown.

Speaker: Anna Stamerra (Universita e INFN, Bari (IT))

iworid2023_Stamerra.pdf

15:30 P1.40: The Nupix-S, a silicon pixel sensor for non-interceptive real-time beam monitoring.

As the leading research platform of heavy-ion science in China, the heavy-ion physics and heavy-ion applications at the Heavy Ion Research Facility in Lanzhou (HIRFL) drive the development of physics research, especially in the fields of nuclear physics and high-precision medical imaging. Therefore, the beam monitoring system is essential to ensure the quality of the beam delivery. Hence, we have designed a non-interceptive beam monitoring system named Hi'beam. The key component of the Hi'Beam system is the Nupix-S silicon pixel sensor. The heavy ions generate the charge by ionizing the gas while passing through the detector, and the charge is collected by the Nupix-S pixel sensor under the drive of the electric field. With this process, the Nupix-S can record the heavy ions' energy, position, and arrival time to reconstruct the beam track.
The total size of the Nupix-S is 4 mm × 5 mm, including a pixel matrix of 64 (row) × 120（column）with a pixel pitch of 37 μm and the periphery circuit. The charge is directly collected by the charge collection electrode, which is the exposed area of the topmost metal layer of each pixel. The size of the charge collection electrode is 23 μm, and it is implemented as a probe-PAD located at the center of each pixel.
The in-pixel circuit mainly consists of a low-noise Charge Sensitive Amplifier(CSA) and peak holding circuit (Peak Holding) to establish the signal for the energy reconstruction, and a discriminator with a Time-to-Amplitude Converter (TAC) for the Time of Arrival (TOA) measurement. The analog signal from each pixel is accessible through time-shared multiplexing over the entire pixel array. Furthermore, The charge conversion gain is about 98.6 μV/e− the output dynamic range is 1.48 V, the time accuracy is less than 50ns, and the Equivalent Noise Charge (ENC) is about 34 e−. This paper will present the design and performance of this Nupix-S pixel sensor.

Speaker: Yuan Tian (Institue of Modern Physics)

15:31 P1.41: Prototype Design of the Monolithic Active Pixel Sensor for Electron-ion collider in China

An Electron-ion collider in China (EicC) will be constructed as a future high-energy nuclear physics project. The vertex and tracking detectors are based on the Monolithic Active Pixel Sensor, which must simultaneously measure time, position, and energy. In addition, the MAPS is expected to be implemented with a commercial process, given the cost. Therefore, a MAPS called Nupix-R1 is developed in a 130 nm twin-well process for EicC, which consists of 128 x 128 pixels and can measure energy, time, and position. In addition, this MAPS can also record only hit position and reach a fast readout speed, according to the requirements of different detector layers. The Nupix-R1 is NMOS-only to avoid competition between N-wells containing PMOS and charge collection diodes.

Speaker: Ms Rui He (Institute of Modern Physics, Chinese Academy of Sciences)

15:32 P1.42: Design of Nupix-A2, a Monolithic Active Pixel sensor for heavy-ion physics

A MAPS named Nupix-A2 has been developed in a 130nm High Resistivity CMOS process for particle hit imaging applications. The Nupix-A2 can simultaneously measure particle hits’ energy, arrival time, and position. It consists of the pixel array with 128 x 128 pixel array, the digital-to-analog converter (DAC) array and a digital control (DC) module. To adapt to different imaging needs, the Nupix-A2 has two operation mode: full-readout mode and fast-readout mode. This paper will discuss the design and performance of the Nupix-A2.

Speaker: Ms Ju Huang (Institute of Modern Physics, Chinese Academy of Sciences)

15:33 P1.43: Timing performance and efficiency of irradiated 3D-trench silicon sensors

We present results of characterization measurements on irradiated 3D-trench silicon sensors, designed within the TimeSPOT project, and produced by FBK, Trento. The sensors were irradiated at different fluences at the Ljubljana reactor facility and then characterized both in the INFN Cagliari laboratory using a 90Sr source and under 180 GeV/c charged pions at the SPS (CERN, Geneve).
The sensors show nominal efficiency and high timing performance even after fluences of some 1-MeV neq/cm2, while requiring a modest overvoltage to recover the damage due to radiation exposure.
The paper illustrates the results on efficiency and timing across different measurement methods, fluences and experimental conditions. The systematic studies demonstrate that a time resolution around 10-ps can be obtained up to the maximum fluency, and that the radiation resistance limit of this technology is still to be reached.

Speaker: Michela Garau (Universita e INFN, Cagliari (IT))

15:34 P1.44: Test-beam timing characterisation of monolithic pixel sensors produced in modified CMOS imaging processes

Several advanced silicon pixel-detector technologies are under study within the strategic R&D programme on technologies for future experiments pursued by CERN's Experimental Physics department (EP R&D), reaching excellent spatial (1-4 µm) and sub-nanosecond temporal resolution.

FASTPIX is a monolithic pixel sensor demonstrator targeting sub-nanosecond timing precision and is designed in a modified 180 nm imaging process. It contains 32 mini-matrices with 68 hexagonal pixels each, with a pixel pitch ranging from 8.6 µm to 20 µm and differing in sensor design features. 4 pixels provide an analogue signal, while the other 64 pixels are connected to the digital readout.

The Digital Pixel Test Structure (DPTS) is a prototype monolithic pixel sensor fabricated in a 65 nm CMOS technology and aims to demonstrate the feasibility of using a 65 nm process in a monolithic sensor while testing custom digital cells and a new digital readout scheme. It is the most complex design on the first 65 nm test production run by EP R&D with a full sensor, analog front-end and digital readout. It consists of 32x32 square pixels with 15 µm pitch. The design and testing was part of a larger effort in EP R&D and the ALICE collaboration.

Both FASTPIX and DPTS utilise an asynchronous digital encoding of hit position, Time over Threshold, and Time of Arrival on one (DPTS) or three (FASTPIX) differential channels, which are read out using a fast oscilloscope or a custom time to digital converter on the FPGA of the readout system.

The characterisation of FASTPIX and DPTS devices was performed in the CLICdp Timepix3 telescope at CERN SPS, which was extended with a microchannel plate photomultiplier tube (MCP-PMT) as a precise timing reference with a resolution of better than 10 ps.

For FASTPIX, a time resolution between 100 ps and 200 ps after time-walk correction is obtained depending on the pixel pitch and sensor design parameters. The operating point of the DPTS was optimised to reach a sub-nanosecond time resolution after time-walk correction. This contribution introduces the monolithic FASTPIX and DPTS chips and presents the timing measurements and results.

Speaker: Eric Buschmann (CERN)

15:35 P1.46: N3G Experiment: Front-End Electronics and Mechanical Advances

In the framework of modern gamma spectroscopy, the high-flux and high-damage experiments highlight the need for a new generation of detectors, based on electrons-collecting electrodes. The N3G (Next Generation Germanium Gamma detectors) experiment is aimed at achieving this goal, by applying the PLM (Pulsed Laser Melting) doping-technique [1] to hyper-pure germanium (HPGe) crystals. N3G is also aimed at realizing an innovative detector containment system complete of contact structures and front-end electronics.

The electrodes of the detector are connected to the readout electronic chain through a flexible printed circuit board (PCB). It is realized on a Kapton substrate and enveloped around the detector itself. The crystal and its flexible connections are placed inside an aluminum canister set on vacuum. The canister is closed by a specifically designed flange, which is equipped with six feed-through connectors for the signals, a high-voltage rod and a vacuum inlet. The design of the entire canister has been thought to be compatible with the cryostats available at LNL. The functionality of the contact system has been tested with a gold-coated germanium crystal.

The Front-End Electronics (FEE) being developed for the experiment is based on an ASIC (Application-Specific Integrated Circuit) Charge Sensitive Preamplifier (CSP) realized in AMS C35B4C3 (350 nm) technology. It is characterized by 8MeV dynamic range, which can be extended up to 40MeV thanks to an innovative fast-reset system [2]. Below the saturation threshold, set by the power supply voltages, the pre-amplifier shows an excellent linear behavior and a 1.08 keV resolution, expressed as FWHM and referred to 1 MeV events. Above the saturation threshold, the energy information on the interactions that bring the pre-amplifier into saturation can be retrieved thanks to the fast-reset circuit: the time it takes to remove the charge excess from the input node of the CSP is proportional to the charge itself and, consequently, to the energy of the saturating interaction. For event of energies greater than 15MeV, a resolution, expressed as FWHM, better than 0.11% was measured. A second version of fast-reset circuit, characterized by zero power consumption, has been implemented on a second ASIC preamplifier. It extends the dynamic range of the device up to 190 MeV, with a linearity error lower than 0.2%.

[1] C. Carraro et al., Applied Surface Science. 509 (2020)
[2] S. Capra et al., IEEE Transactions on Nuclear Science. 69 (2022)

Speaker: Dr Stefano Capra

15:36 P1.47: Digitizing solutions for high-resolution nuclear spectroscopy

DAQ (Digital Acquisition) systems have progressively replaced the traditional analogue spectroscopic chains during the last two decades in the vast majority of nuclear physics experiments. The flexibility offered by the implementation of digital algorithms (both real-time implemented typically on FPGAs and offline implemented on computational clusters), as opposed to the fixed and limited functions of analogue modules, allowed for new experimental techniques that were simply unfeasible before. A good example of this evolution are the gamma-ray tracking techniques performed with the digital acquisition of the signals from segmented HPGe (High-Purity Germanium) detector arrays [1]. Another example is the implementation of digital pulse-shape analysis algorithms for ion discrimination using silicon detectors [2]. In both these two cases the signal digitization is performed with dedicated flash-ADC-based digitizer boards.

The first actor in this scene is the digitalization infrastructure, that can be reduced to the ADC chip and the front-end analogue signal conditioning circuit. The DAQ performance is strictly dependent on the ADC sampling frequency and bit depth. Such chips, however, are never designed specifically for nuclear spectroscopy, being others the main market applications (Network Analyzers, Military applications, Telecommunications, Microwave Receivers, Software-Defined Radios, just to name a few). In the same way, the typical AC-coupled (often transformer-based) front-end signal conditioning circuits suggested in datasheets and application notes are not suited to the spectroscopy techniques with semiconductor radiation detectors.
Signal conditioning circuits that are suitable for nuclear spectroscopy are discussed together with preliminary results obtained with the ADC32J4X family from Texas Instruments as a substitution for the now-obsolete ADC1413D. Thermal figures show the dramatic effects of the difference in power consumption between the two different ADC chips mentioned above.

[1] Reiter P., γ-ray tracking with AGATA: A new perspective for spectroscopy at radioactive ion beam facilities (2020) Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms, 463, pp. 221 - 226.
[2] Cieplicka-Oryńczak N. et al., Towards the lowest-energy limit for light ions identification with silicon pixel-type detectors, (2018) European Physical Journal A, 54 (12), art. no. 209.

Speaker: Dr Stefano Capra

15:38 P1.48: A prototype Radiation Energy Measuring Integrated Circuit with an asynchronous current-pulse reset block providing analog-to-digital conversion in 28 nm CMOS

In this work, we present a prototype Radiation Energy Measuring Integrated Circuit (REMIC). This chip has been fabricated in 28 nm CMOS node, works in single photon counting mode and consists of 100 pixels of size 50 µm × 50 µm (Fig. 1). Each pixel is equipped with a cascoded-inverter-based charge sensitive amplifier (CSA) with Krummenacher feedback [1], and three reset circuits: switch-based [2], click-clack [3] and current-pulse reset [4].

The working principle of the latter is to discharge the CSA feedback capacitor after a pulse by injecting small current pulses, each of which is counted by the pixel logic. Importantly, the number of pulses required do return the CSA output to baseline is proportional to the amplitude of the CSA output pulse and hence to the particle energy. The amount of the injected current can be regulated by a digital-to-analog converter (DAC), allowing a trade-off between speed of operation and resolution of energy measurement (Fig. 2).

Having 12-bit pixel counters responsible for current-pulses counting, REMIC enables fast and precise colorful imaging. Simulated static power consumption per pixel is 7 µW, whereas dynamic power consumption depends on current-pulse reset configuration and may be about 60 µW or less. The chip is currently under measurements, and in the contribution, we will present the most recent results, possibilities and conclusions.

[1] F. Krummenacher, Nucl. Instrum. Meth. A 305 (1991) 527
[2] H.-S. Kim et al., IEEE J. Solid-State Circuits 48 (2013) 541
[3] R. Kłeczek et al., ESSCIRC 2019—IEEE 45th Eur. Solid State Circuits Conf. (ESSCIRC), 85
[4] P. Kaczmarczyk and P. Kmon, 2023 JINST 18 C03010

The authors acknowledge funding from the Ministry of Education and Science of Poland for the research project under the ‘Diamond Grant’ program (0071/DIA/2018/47).

Speaker: Piotr Kmon (AGH University of Science and Technology)

15:39 P1.49: TEMPUS – A Timepix4 readout system for photon science experiments

A readout system for the Timepix4 pixel ASIC, TEMPUS, is being developed for photon science experiments such as time-resolved X-ray scattering. In timestamping mode, this system will offer nanosecond timing when detecting X-rays with a silicon sensor, and will have an event rate capability around 1 Mhit/mm2/s. When working in frame mode, higher frame rates than currently-available photon-counting detectors will be achievable (40kfps). To make effective use of Timepix4, high-data-rate board designs and firmware have been developed. So far, a single-chip system with a silicon sensor has been built and images have been obtained. In the longer term, multi-chip modules are under development, in order to build multi-megapixel systems with minimal gaps between sensors.

Speaker: David Pennicard

15:40 P1.50: Experimental analysis of small pixel effect in SI GaAs detectors via alpha particles

Semi-insulating (SI) GaAs detectors represent a perspective alternative of commercially available silicon detectors, exhibiting high radiation hardness and better efficiency for gamma and X-ray registration due to higher density. The SI GaAs detectors found already application also as sensors for Timepix based detectors [1]. Here the miniaturization of Schottky contact to dimensions fitting the Timepix ASIC readout with 55 um pitch was utilized. However, the area of detector contact affects its detection parameters, e.g. the charge collection efficiency (CCE). In [2], the Monte Carlo simulations have revealed so called small pixel effect in highly pixelated X-ray imaging detectors fabricated from SI GaAs. The 300 um thick detector with 40 and 150 um pitch pixelated Schottky contacts on one side and a large area ohmic contact on the opposite surface of substrate were compared to larger detectors. The simulations show that the CCE changes with the depth of GaAs substrate depending on the Schottky contact size. The small pixel detector CCE increases steeply from Schottky pixel electrode and then mildly decreases to ohmic one. On the other hand, the larger area detector shows mild increase of CCE from Schottky pixel electrode up to the ohmic one. Finally, the CCE of small pixel detectors near Schottky electrode is higher than of large ones and on the opposite, near the ohmic electrode the larger detectors exhibit higher CCE.
We have prepared the SI GaAs detectors from 350 um double-side polished Vertical Gradient Freeze (VGF) substrate produced by Wafer Technology Ltd. The Schottky contacts of a circular shape with various diameters from 100 up to 1000 um from Ti/Pt/Au (15/35/50 nm) multilayer and a whole area Ni/AuGe/Au (30/50/60 nm) ohmic electrodes were evaporated at Institute of Electrical Engineering of Slovak Academy of Sciences in Bratislava. At first, we measured current-voltage characteristics of prepared Schottky barrier detector structures. We revealed the dependence between the break down voltage and the Schottky area contact. With decreasing the contact area, the breakdown voltage increases.
Following, the small pixel effect was studied experimentally by alpha spectrometry, where 241Am source with 84.8% yield of 5486 keV alpha particles was used. These alpha particles have the longitudinal projected range in GaAs of 20 um after penetrating the used metallization of electrodes, according to SRIM [3] simulation. Measuring the alpha spectra irradiating detector from two different sides reveals the CCE in region near Schottky vs. ohmic electrode. Measured alpha spectra when irradiating the Schottky electrode show increasing CCE with decreasing the Schottky contact area. On the other hand, the alpha spectra measured during ohmic electrode side irradiation proved the improvement of the CCE with increasing Schottky electrode area. This is in accordance with simulated small pixel effect theory of CCE variation with SI GaAs detector depth [2]. The utilization of SI GaAs based sensor in Timepix type detector with 55 um pixel pitch and its irradiation from common ohmic electrode will have positive effect on detector CCE when comparing with single large area SI GaAs detector typically tested by exposition from Schottky contact side.

[1] B. Zatko, et al., JINST 13 (2018), C01034
[2] P.J. Sellin, NIM-A 434 (1999), 75-81
[3] J. F. Ziegler et al., NIM-B 268 (2010), 1818-1823

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)

15:41 P1.51: Design and TCAD simulation of modified 3D-trench electrode sensors

Future experiments at high-luminosity hadron colliders will involve unprecedent levels of pile up, calling for ultrafast detectors in order to add time information to distinguish between particle tracks. The unique geometry of 3D sensors enables to achieve very good timing performance, with the additional benefit of high radiation hardness. Remarkable results in terms of timing resolution have been reported for 3D sensors with columnar electrodes (~30 ps) [1] and even better with trenched electrodes (~10 ps) [2], because of a more uniform distribution of the electric field and weighting field. However, 3D-trench technology is more complex, and has still to be optimized in terms of both fabrication process and pixel layout. To this purpose, as an alternative to the existing design which features continuous (p+) ohmic trenches, we propose a new variant with dashed p+ trenches. This modification is aimed at reducing the lithographical defects that were observed in mm’s long ohmic trenches, thus improving the fabrication yield. The performance of the two designs has been compared by TCAD simulations. The gaps between the p+ trenches can be made small (~10 μm) and placed offset with respect to the readout (n+) trenches, so that the impact on the uniformity of the electric and weighting field is minimum, and good timing performance is preserved. This is confirmed from the analysis of 2d maps of the instantaneous current, i, induced at the electrodes according to Ramo’s theorem: i = qEw·vd, where q is the elementary charge, Ew is the weighting field and vd is the carrier drift velocity, as obtained from TCAD simulations. As an example, Figure 1 shows the Ramo’s maps for electrons for the existing and modified designs, that are indeed very similar. The considered designs have been implemented in a fabrication batch currently under way at FBK in the framework of the AIDA-Innova Project. A comprehensive TCAD study, including post irradiation performance based on advanced radiation damage models, will be presented at the Conference.

Speaker: Jixing Ye

15:42 P1.52: Per pixel calibration of the MÖNCH0.3 hybrid pixel detector

Charge sharing can be used to improve the spatial resolution of hybrid pixel detectors [1] with small pixels through interpolation. However, it also complicates the calibration process due to the distortion of the measured spectrum.

In this paper we present lab based per pixel calibration method for MÖNCH0.3 [2], a charge integrating hybrid pixel detector with 25 x 25 μm2 pixels, bump bonded to a 320 μm thick silicon sensor. MÖNCH0.3 features 8 static gains selected depending on the required dynamic range. For short exposure times in the highest gain setting the noise is ~35 e- RMS.

We used X-ray fluorescence above 15 keV since the shallow absorption in combination with charge sharing means that the peak is not visible for lower energies. The data was processed online, including pedestal subtraction and histogramming, using an application written in Python and C++ that reduces the otherwise prohibitive data volumes resulting from the low photopeak efficiency with up to a factor of 105. Finally, the measurement results were compared to simulations to validate the method.

[1] S. Cartier et. al. JSR. (2016). 23, 1462-1473
[2] M. Ramilli et al., JINST 12 (2017) C01071
[3] A. Bergamaschi et. al. JINST 10 (2015) C01033

One of the authors (V. Hinger) has received funding from MSCA PSI-FELLOW-III-3i (EU Grant Agreement No. 884104).

Speaker: Erik Fröjdh (Paul Scherrer Institut)

15:43 P1.53: The Trans-Iron Galactic Element Recorder for the International Space Station (TIGERISS)

Selected as a NASA Astrophysics Pioneers mission, TIGERISS is designed to measure the nuclear composition of cosmic rays above 350 MeV/nucleon from 5B through 82Pb with individual element resolution. TIGERISS will obtain high-statistics measurements of the Ultra-Heavy Galactic Cosmic Rays (UHGCRs; Z > 27), including the first ever single-element resolution measurements of elements above 56Ba. TIGERISS’s ability to precisely measure a wide, continuous span of elements produced in s-process and r-process neutron capture nucleosynthesis, provides unique data needed to determine the relative contributions of supernovae (SN) and Neutron Star Merger (NSM) events to r-process nucleosynthesis. The high exposure provided by TIGERISS space-based measurements provide the needed high statistics to test models for cosmic-ray origins and acceleration after processing by the Galaxy. TIGERISS uses the heritage of the TIGER and SuperTIGER long-duration balloon instruments, including Cherenkov detectors using aerogel and acrylic radiators but with SiPM read out, while incorporating silicon strip detectors (SSDs) for both the cosmic ray charge and trajectory measurements. The current concept study phase will provide guidance for the optimal ISS external attachment accommodation for TIGERISS, including the JAXA JEM-EF and the ESA Columbus Laboratory. In this presentation, the TIGERISS science goals, instrument design concepts, and mission profile will be discussed with a focus on the performance of the Cherenkov- and SSD-based instruments.

Speaker: Dr John Krizmanic (NASA/GSFC)

15:44 P1.54: Imaging Performance of Wide-Field X-ray Transient Localization Experiment onboard Microsatellite KOYOH

Since direct gravitational wave and neutrino detections has achieved [1], a new field of research called multi-messenger astronomy has emerged, which combines multiple signals beyond electromagnetic waves to investigate astrophysical phenomena more deeply. KOYOH is a microsatellite project that monitors and observe X-ray transients associated with gravitational waves, developed by Kanazawa University. It rapidly alerts other telescopes to the trigger time and direction of the detected X-ray sources. Accurate measurement of the precise direction of gravitational wave sources promotes the identification of their host galaxies and follow-up observations in other wavelengths. This satellite has two mission instruments: a wide-field X-ray imaging detector, and a wide-field gamma-ray detector. The X-ray imaging detector system is referred to as Transient Localization Experiment (T-LEX) [2]. T-LEX is designated to have a field-of-view of 1 steradian, an energy range of 2 – 20 keV, and localization accuracy of 15 arcminutes. The unique feature of this project is the ability to perform wide-field imaging with sensitivity to X-rays below 10 keV. It consists of silicon strip detectors (SSDs) with analog/digital Application Specific Integrated Circuits (ASICs) [3] for low energy X-ray signal readout and two sets of one-dimensional random-aperture coded mask imaging system made of 50-μm-thick tungsten plate. The mask and SSD is positioned at a distance of 68.6 mm, and the pitch of the aperture elements of the mask and the electrodes of the SSD is 0.3 mm. To demonstrate the imaging performance, we performed experiments in which X-ray beams were irradiated onto the flight model of the detector (as shown Figure 1) from various angles. We calculate the cross correlation between the mask's aperture pattern and the detector image, which results in the appearance of a peak at the shifted position corresponding to the arrival direction as shown in Figure 2. In this experiment, we varied the incident angle from -20 degrees to +20 degrees at 5-degree intervals and investigated the peak position of the reconstructed image. As expected from geometric considerations, a response that depends on the tangent with respect to the incident angle was confirmed. The discrepancy between the angle response predicted by a geometric model using the design parameters and the experimental results was found to be up to a maximum of 16 arcminutes. On the other hand, by leaving the design parameters free and fitting them to best replicate the experimental angular response, we obtained parameters that satisfy the 15-arcminute requirement at the all incident angles. We intend to carefully determine the optimal values of geometric parameters in the angular response model, including onboard calibration after satellite launch. In this presentation, we report the result of the imaging performance experiment.

Speaker: Tatsuya Sawano (College of Science and Engineering, School of Mathematics and Physics, Kanazawa University)

15:45 P1.55: The Phase-2 Upgrade of the CMS Inner Tracker

The LHC machine is planning an upgrade program, the High Luminosity scenario (HL-LHC), which will smoothly bring the luminosity to about 5-7.5$\times$10$^{34}$ Hz cm$^{-2}$, to possibly reach an integrated luminosity of 3000-4000 fb$^{-1}$ over about a decade.

In order to fully exploit the delivered luminosity and to cope with the demanding operating conditions, the whole silicon tracking system of the CMS experiment will have to be replaced and substantially upgraded before the HL-LHC start, expected in 2029. Both the CMS inner tracker (IT) and the outer tracker (OT) detectors will be replaced, and the new detector will feature increased radiation hardness, higher granularity and capability to handle larger data rates.

This talk will describe the most relevant achievements obtained in the last years in view of the construction of the upgraded IT pixel tracker. Design choices are discussed, along with some highlights on the technological approaches chosen and the latest results on the system testing of the prototypes.

Speaker: Ernesto Migliore (Universita e INFN Torino (IT))

15:46 P1:56: Experiment of EMPIX prototype detector for MeV ultra-fast electron diffraction and microscopy

EMPIX[1] is a high dynamic range diamond pixel detector for MeV ultra-fast electron diffraction and microscopy. The prototype readout ASIC integrates 32×8 pixels electronics with each pixel consisting of a dual range charge integrator, a correlated double sampler and a 12-bit Wilkinson type ADC. The strong penetration of MeV electrons brings possibilities for electron microscopy of thick samples, but also challenges both the sensor and the readout circuit. By adaptive gain adjustment design, the ASIC is skilled at signal processing and readout for applications of high brightness pulsed particle sources. From our previous simulation studies, we chose diamond as the sensor for MeV electron microscopy.

Through re-distribution layer (RDL) fabrication at wafers, 20 prototype readout chips are packaged together to a module that can be bump bonded to 32×128 pixel detectors of 150 m pitch (not all pixels are used). A detector prototype, that is, four of the RDL chip modules bump bonded to a diamond sensor with full matrix of 128×128 was tested. Fig.1 shows the 4 modules that are wire bonded to the evaluation board.

The data of the chips is read through a high-speed data acquisition system with a maximum bandwidth of 80 Gbps, and then transferred to computer via 2 lane optical fibers (Fig.1). Corresponding electron microscope camera systems have also been designed, including vacuum, refrigeration, and other items. The detector and chip are placed in the vacuum for direct electron detection, and the temperature is set to about -20 ℃. The data acquisition system is outside the vacuum, and the two are connected through a vacuum feedthrough and flexible circuit board. The entire system is also equipped with a water cooling device to remove heat from the vacuum.

The performance of the detector was evaluated and some imaging experiments were conducted. We evaluated and calibrated the noise, linearity, and energy resolution characteristics of the detector in the air. After that, using the camera system, ultra-fast electron diffraction (UED) experiment was performed on a 2.6 MeV high-energy pulsed electron source in Accelerator Laboratory of Tsinghua University.

Speaker: Tong Wei (Tsinghua University)

15:47 P1.57: Regression-based detector gain optimization method to improve position estimation performance of high-speed gamma imaging system

To combat illicit trafficking at airports and harbours, the presence of nuclear and radioactive material in imported goods must be carefully inspected. For fast and precise inspection, we are developing a high-speed gamma imaging system, which rapidly localizes and specifies nuclear and radioactive material in a wide outdoor environment, as shown in Figure 1. This system offers a number of advanced features, including (1) high imaging sensitivity achieved by utilizing two quad-type detectors, each of which includes four large-area NaI(Tl) crystals (146 x 146 mm²) coupled with 36 photomultiplier tubes (PMTs), and (2) a broad energy range of imaging by utilizing a hybrid gamma imaging technique that combines Compton imaging and coded aperture imaging. In both imaging techniques, high-precision position estimation for gamma-ray interaction in the crystal is required to obtain high resolution image and, in the present study, the estimation of gamma-ray interaction location is done via the maximum likelihood position estimation (MLPE) method [1], which compares ratio of the nine PMT signals to pre-measured data, making PMT gain maintenance critically important. The outdoor operation of the system, however, can cause variation in system temperature, which will affect the uniformity of PMT gains as the gain of PMTs is highly dependent on temperature [2]. To address this issue, we have proposed a regression-based gain optimization method to maintain the uniformity of PMT gains and have evaluated its performance through several experiments. This method involves four main steps: first, acquiring training data (i.e., PMT signals) using sources of known energies; second, calculating the gain optimization matrix, which compensates for inter-channel deviation, by applying linear regression on training data and true interaction energy; third, repeating the calculation of the matrix to acquire optimal gain by refining the training data (i.e., applying the gain optimization matrix to the training data and updating the matrix until the ratio of the newly and previously acquired matrix is under 3%); and finally, applying the gain optimization matrix to the new measured PMT signals by matrix multiplication to optimize the performance of position estimation. To evaluate the performance of the proposed method, experiments were conducted under two conditions; when all the original PMT gains were maintained, and when the gains of five PMTs were randomly changed within the range of 0.75-1.6 times. For both conditions, the position estimation performance was evaluated at 20 mm intervals using a 137Cs pencil-beam source to compare the position estimation performance without and with the method. As a measure of the accuracy in position estimation and spatial resolution, the mean displacement (MD), which is calculated by the estimation error of each event, was evaluated for 49 positions in each experiment condition. The estimated interaction position of the 49 positions with and without gain optimization when PMT gains were maintained and changed are shown in Figure 1. When the PMT gains were maintained, the developed method marginally reduced the MD, i.e., from 4.5±0.7 mm (average ± standard deviation) to 4.3±0.5 mm. On the other hand, when the PMT gains were changed, the MD was significantly reduced, i.e., from 12.7±7.1 mm to 4.6±0.6 mm; that is, the original MD was successfully recovered. These results indicates that the developed gain optimization method maintains the position estimation performance of the gamma imaging system even when the PMT gains are changed by temperature during outdoor operation. Future works will include using background radiations on the developed method.

[1] L. R. Furenlid, et al., Penetrating Radiation Systems and Applications VIII (2007), 6707, 67070N.
[2] M. Moszyński, et al., Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 568(2) (2006), 739–751

Speaker: Goeun ­Lee (Department of nuclear engineering, Hanyang university, Seoul, Republic of Korea)

15:48 P1.58: Temperature and vacuum related effects on X-rays hybrid sensor calibration

The PIMEGA Series of high-resolution, Medipix-based pixel hybrid semiconductor detectors are extensively used at Sirius X-ray source of LNLS research facility, for imaging and data acquisition from X-rays driven experiments on material science. This contribution summarizes the results of the analysis performed on a dataset of images acquired at different sensor temperatures, under vacuum conditions,

with the aim to understand time-dependent effects which are observed during detector operation such as photon-counting efficiency variation and appearance of evolving spots. Qualitative and quantitative figures are provided, followed with the evaluation pertinent hypotheses which could explain such effects, as well specific procedures for calibration taking it into account.

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

Speaker: Dr Antonio Augusto Alves Junior (LNLS - CNPEM)

15:49 P1.59: Setups for eliminating static charge of the ATLAS18 strip sensors

Construction of the new all-silicon Inner Tracker (ITk), developed by the ATLAS collaboration to be able to track charged particles produced at the High-Luminosity LHC, started in 2020 and is expected to continue till 2028. The ITk detector will include 22,000 highly segmented and radiation hard silicon strip sensors (ATLAS18). Mechanical and electrical characteristics of produced sensors are measured upon delivery for acceptance at several institutes participating in a complex testing program (the Quality Control (QC)). During the QC production testing of the ATLAS18 strip sensors, an increased number of sensors that failed the electrical tests was observed. Moreover, a high surface electrostatic charge reaching a level of several hundreds of volts was measured on a large number of sensors and on the plastic sheets. Accumulated data indicates a clear correlation between observed electrical failures and the sensor charge up. To mitigate the above described issues, the QC testing sites significantly modified the sensor handling procedures and introduce sensor recovery techniques based on irradiation of the sensor surface with UV light or application of intensive flows of ionizing gas. In this presentation, we will describe the setups implemented by various QC testing sites to treat silicon strip sensors affected by static charge, and evaluate the effectiveness of these setups in terms of improvement of the sensor performance.

Speaker: Pavla Federicova (Czech Academy of Sciences (CZ))

15:50 P1.60: Hybrid Pixel Array Detector for Time-resolved and Imaging Applications with 56,000 fps Sustainable Frame Rate

It has been more than ten years since HPAD (Hybrid Pixel Array Detectors) had been widely utilized as X-ray diffraction and imaging detectors. Thanks to its single photon counting capability, HPAD shows images without background noise and wide dynamic range. Due to limitations of the fabrication process, most HPADs are made with monolithic sensor and tiled readout ICs. In conventional HPAD, there were so-called “inter-chip pixels” on the edges of readout ICs. These inter-chip pixels have 1.5 times or wider width and/or height than non-inter-chip pixels. This means, we are losing position information of a hit of photons on those pixels.
We have successfully dealt with this inter-chip pixel problem by use of re-distribution layer on the Silicon sensor. So, in our new detector, non-uniformity in a single sensor module is eliminated.
This new detector is designed based on UFXC32k IC [1] designed by AGH University of Science and Technology and named XSPA-500k [2]. XSPA-500k detector consists of 16 UHXC chips tiled and 1024 x 512 76 um sq. pixels per module. No inter-chip pixels in between ROICs which terribly suffer the image quality.
XSPA-500k is aiming not only for X-ray imaging but also for time-resolved X-ray measurements. Dealing with “inter-chip pixels” is our main feature for imaging, and for time-resolved measurements we understand that frame rate is as important as the size of the pixels and the area of the detector. Thanks to UFXC32k IC’s high count-rate and fast operation capability, combined with our high data throughput backend circuits, XSPA-500k is capable of up to 56,000 fps with full-frame readout and 100,000 fps with 100 lines ROI in the center of the modules with continuous exposure (zero-deadtime mode operation with 2-bit counter/pixel.) If the non-continuous exposure (burst-mode operation [3]) is allowed, it can achieve over 970,000 fps with approximately 2 % duty ratio.

REFERENCES
[1] P. Grybos et al., “32k Channel Readout IC for Single Photon Counting Pixel Detectors with 75 μm Pitch, Dead Time of 85 ns, 9 e−rms Offset Spread and 2% rms Gain Spread,” IEEE Trans. Nucl. Sci., vol. 63, no. 2, pp. 1155-1161, Apr. 2016.
DOI: 10.1109/TNS.2016.2523260
[Online] Available: https://ieeexplore.ieee.org/document/7454876.
[2] Y. Nakaye, et al., “Characterization and performance evaluation of the XSPA-500k detector using synchrotron radiation,” J. Synchrotron Rad. vol. 28, pp. 439-447, Mar. 2021.
DOI: 10.1107/S1600577520016665
[Online] Available: https://scripts.iucr.org/cgi-bin/paper?S1600577520016665
[3] Q. Zhang et al., “Sub-microsecond-resolved multi-speckle X-ray photon correlation spectroscopy with a pixel array detector,” J. Synchrotron Rad., vol. 25, pp. 1408-1416, Jun. 2018.
DOI: 10.1107/S1600577518009074
[Online] Available: http://scripts.iucr.org/cgi-bin/paper?S1600577518009074

Speaker: Yasukazu Nakaye (Rigaku Americas Corporation)

2023_06_iWoRiD_Nakaye.pdf

15:51 P1.61: X-ray and Gamma-Ray Photon Spectroscopy with Continuous Sampling Readout

We present results from a new x-ray and gamma-ray spectrometer with continuous sampling of detector
signals. The system was designed for Compton scatter collimation with up to 4 detector crystals of
cadmium zinc telluride (CZT of 20mm x 20mm x 10mm). Here, we report on the capability to sample
positive and negative polarity charges from detector electrodes at programmable sampling frequency.
This feature is important for the use with other room-temperature semiconductor detectors like
germanium, TlBr3, and CsPbBr3 (CPB). Using Cs-137 gamma-rays and a CZT with 121 pixelated anodes at
room-temperature, we measure energy resolution of 4keV FWHM, i.e., 0.60% FWHM at 661.7keV for 121
pixels (100%). The system allows one to measure positive and negative charge polarity in the range
from -700fC to +700fC. With CZT, we find that 50-MHz sampling speed is well suited, and we demonstrate
sampling at 25MHz, 12.5MHz, and 6.25MHz which would suit “slower” detector materials, like TlBr3 and
CPB. The sampling readout of signals from anodes and cathodes allows one to measure the exact location
of Compton-scatter interactions in the detector crystal which enables Compton scatter collimation.
Possible applications are high-resolution energy spectroscopy and imaging of radiation from a distance.

Speaker: Sofia Godoe (Integrated Detector Electronics AS)

iworid poster a0.jpg

15:52 P1.62: Estimation of airborne background spectrum using deep denoising autoencoder

Airborne gamma-ray survey is widely used to quickly identify the composition of territorial radioelement and the extent of soil contamination due to artificial radioactive isotope over a wide area. Unlike radiation detection on ground, background correction is essential in airborne radiation measurements due to the significant impact of radon in the atmosphere and cosmic-ray.
This study reports on deep denoising autoencoder to extract the features of the spectrum and reconstruct a denoised spectrum for estimation of the airborne background spectrum. Investigations revealed that the proposed method estimated the background spectrum even when there is a change in radon distribution in the atmosphere where a large error of estimation occurs. In addition, the proposed method shows robust estimation of the background spectrum even when the soil was contaminated by unexpected radioactive materials. In particular, in the case of Cs137, the Region of Interest (ROI) overlaps with 609 keV, the main energy of radon and U238, making it difficult to estimate background spectrum with conventional methods. Furthermore, the proposed method is suitable for airborne gamma-ray survey with limited operating time, as it can estimate background spectrum with a low count.
Therefore, the proposed method enables more accurate analysis of radioactive materials on ground by estimating and removing unnecessary airborne background spectrum.

Speaker: Mr Sangho Lee (Korea Advanced Institute of Science and Technology)

15:53 P1.63: SpacePix Radiation Monitor: Data from the First Year of Operation in Orbit

Czech technological satellite VZLUSAT-2 was launched to Sun-synchronous orbit in January 2022 onboard with Space Dosimetry System Demonstrator (2SD). The 2SD system contains SpacePix Radiation Monitor (SXRM) and Soft X-ray Monitor (SXM) subdetectors based on monolithic pixel detector technology.
SXRM is a multi-layer pixel detector with SpacePix2[1] ASICs designed to determine the type of a particle, its energy and trajectory. The sandwich structure of SXRM with five layers of SpacePix ASICs interleaved with copper absorbers, allows sampling of the Bragg curve and particle energy estimation. The SXRM is capable of identifying protons, electrons and heavy ions and is used for radiation monitoring. The SXM detector is based on XChip-03 ASIC [2].
SpacePix2 is a radiation tolerant monolithic active pixel detector with a 64×64 pixel matrix fabricated in 180 nm SoI process. The dimensions of the pixels are 60×60 μm, and the sensitive area is 3.84×3.84 mm. The dynamic range of the SpacePix2 is 2 ke- to 60ke- in the pixel front-end and 300 ke- to 30 Me- in the sensor backside layer. The analog signal from pixels generated by an impinging particle is processed by charge sensitive amplifier and digitalized by 10-bit SAR ADCs. Readout digital part offers 400 MHz LVDS or 50 MHz SPI interface. The total current consumption is 43 mA.
The poster presents measured data from the first year of operation in Sun-synchronous orbit, demonstrating the capabilities of the detector.

Speaker: Pavel Stanek (Czech Technical University in Prague (CZ))

15:54 P1.64: Calibration procedures and data correction of ePix100 detectors at the European XFEL

The European XFEL is a research facility that delivers extremely bright and short coherent X-ray pulses of tunable energy at MHz repetition rate, providing unprecedented capabilities to conduct scientific research in multiple domains by internal and external users.

Among the suite of detectors deployed in the European XFEL, there are several ePix100 units belonging to the family of ePix detectors developed at SLAC [1], charge integrating hybrid pixel detectors capable of single photon resolution for energies above 2 keV. Additionally, they are small, easily maneuverable, vacuum compatible, have small pixels (50 µm) and show low noise. By virtue of these features, they are regularly used at two of the X-ray instruments of the European XFEL in imaging, spectroscopy and scattering experiments at low frequency rates (10 Hz).

The European XFEL commits to providing users with completely corrected detector data, to reduce their need to focus on the specifications and functioning intricacies of the detector used, and instead concentrate on the analysis of experimental data. For that purpose, calibration procedures are periodically carried out to generate calibration constants that allow converting the raw detector output into physically meaningful information through the deployment of several data correction steps.

In this work, an overview of the ePix100 calibration procedures and correction algorithms will be presented, with emphasis on particularly relevant processes for this detector, such as common mode noise suppression and reconstruction of photon events with shared charge across neighbouring pixels. Additionally, an assessment of how effectively the latter can be used to achieve sub-pixel resolution through interpolation algorithms shall be discussed.

[1] A Dragone et al., J. Phys.: Conf. Ser. 493 (2014) 012012

Speaker: Nuno Duarte (European XFEL)

15:55 P1.65: Comparison of photon-beam scans on 3D-positioning CZT with a defect-enabled numerical simulation

Comparison of photon-beam scans on 3D-positioning CZT with a defect-enabled numerical simulation

Alexandre Delcourt1*, Guillaume Montémont1, Anthony Schaal1

1. CEA Leti, 17 Avenue des Martyrs, 38000 Grenoble, France
2. Corresponding author, alexandre.delcourt@cea.fr

Imagers capable of 3D positioning are useful for localizing photon-emitting sources as they enable Compton imaging, parallax correction and also spectral correction of collection inhomogeneities. In the case of pixelated-anode CZT detectors, one can take profit of signals induced on a group adjacent electrodes to compute sub-pixel position of the photon interaction inside the detector. This is combined with a depth estimation to obtain the 3D position of the interaction [1]. However, it is known that CZT detectors contain structural defects, which alter the measurement as they influence the physical properties of the detector, such as the electric field or internal conductivity [2]. These defects can be studied by various characterization methods but their effect on the inducted signal is not easy to estimate and understand; also, we wish to use simulations to improve knowledge of their effects.

To study the impact of these defects we developed 3D realistic simulations enabling to implement different types of geometrical defects (point, plane, sphere), each modifying differently the physics of the detector (Figure 1.). Using these simulations, we can observe the behavior of the detector on the collection of charges on the electrodes [3].

Therefore, we can also perform XY scans of the simulated detector to obtain interactions maps and compare it with the experimental results. The objective of this study is to replicate the observed measurements with the simulations to approach the intern structure of the real CZT detector (Figure 2.).

The strengths of our simulation approach are a fast computation and its versatility. In this way, we can get to an approximation of the physical behavior of the detector. Finally, this study might help us to have a better understanding of the defects structure in a CZT crystal, and the simulation may be a tool to improve the performances of these detectors correcting the induced signals impacted by the defects.

[1] G. Montémont, S. Lux, O. Monnet, S. Stanchina and L. Verger, Studying spatial resolution of CZT detectors using sub-pixel positioning for SPECT, IEEE Trans. Nucl. Sci. 61 (2014) 2559.
[2] A.E. Bolotnikov, S. Babalola, G.S. Camarda, Y. Cui, R. Gul, S.U. Egarievwe et al., Correlations
Between Crystal Defects and Performance of CdZnTe Detectors, IEEE Trans. Nucl. Sci. 58 (2011) 1972.
[3] A. Delcourt, G. Montémont, GPU-accelerated CZT detector simulation with charge buil-up effects, 2023 JINST 18 P02005

Speaker: Mr Alexandre Delcourt (CEA Leti)

Poster Iworid A_Delcourt.pdf

15:56 P1.66: Track Lab: an extensible software package for fast acquisition (not only) of pixel detector data, online analysis and automation

Due to ongoing innovation in physics instrumentation, modern semiconductor detectors like Timepix3 [1] and Timepix4 [2] impose increasingly large demands on bandwidth and computational capabilities of data acquisition (DAQ) software. This motivates optimizations that achieve parity with intractable input data rates by various means: for instance, by offloading expensive calculations from software to dedicated hardware accelerators, by rejecting undesirable events using fast low-fidelity online analysis or machine learning models, or by implementing divide-and-conquer algorithms that scale well horizontally over many CPU cores.

This contribution presents Track Lab, a multi-platform DAQ software for physics detectors designed with versatility and high-performance applications in mind. Since its initial application with Timepix3 and the Katherine readout [3], Track Lab has been generalized to work with a diverse set of research instruments. The latest version is compatible with 3 Timepix3 readouts and 2 photomultiplier readouts, with ongoing plans to bring support for Timepix2 [4] and Timepix4 [5] devices later in 2023. In addition to detector equipment, Track Lab can orchestrate X-ray tubes, robotic arms and motorized stages to automate repetitive tasks like scans or calibrations.

One of Track Lab’s fundamental features is its capability to perform online analysis by composing complex data pipelines from simple building blocks, such as filters, transformations or aggregations. Inspired by large-scale systems like MapReduce and Hadoop [6], Track Lab allows for an arbitrary number of processing elements to be visually linked together in the user interface to form a tree-like graph topology (shown in Figure 1), which is usually terminated in persistent storage or real-time 1D or 2D plots that conveniently generate immediate feedback for the user (shown in Figure 2). For extensibility, the logic of these elements is implemented in plug-in modules that are included with the software. While the latest program version ships 14 such modules, their programming interface is publicly documented, so as to allow custom plug-ins to be developed easily.

Track Lab utilizes many conventional strategies to resolve a commonly encountered trade-off between high performance and extensibility. Firstly, thanks to multi-threaded implementation of all data processing elements, stages of data processing can operate simultaneously in parallel, enabling them to fully utilize advantages of many-core CPU architectures. Secondly, data flow is handled by ZeroMQ [7], an industry-standard message-passing middleware, which significantly reduces the memory footprint of the program by transparently multiplexing data between a single sender and multiple receivers in branching points of the data pipeline. Broad adoption of ZeroMQ also permits nearly effortless interoperability with data sources and sinks provided by external programs, as well as a possible extension point for data transmission over the network. Finally, the capacity for high data throughput is achieved by utilizing asynchronous memory-mapped file access, and wide-bandwidth system buses.

While Track Lab’s development is continuously ongoing, its stable versions have been thus far successfully deployed in calibration measurements, Mini.PAN [8] test beam campaigns at PS and SPS, medical research and nuclear safety applications [9], cosmic ray monitoring, and at the ATLAS-TPX3 [10] and MoEDAL-TPX3 [11] detector networks at LHC. Thanks to such a wide range of applications, its compatibility has been verified for all three major operating systems: Linux, Windows and macOS. The binaries of the software as well as its programming interface can be freely used by the public, and its sources are available to Medipix3 collaboration members upon request.

[1] T Poikela et al., JINST 9 (2014), C05013
[2] X Llopart et al., JINST 17 (2022), C01044
[3] P Burian et al., JINST 12 (2017), C11001
[4] WS Wong et al., J. Rad. Meas. 131 (2020), 106230
[5] X Llopart et al., JINST 17 (2022), C01044
[6] J Dean et al., Commun. ACM 51 (2008), 107-113
[7] ZeroMQ, https://zeromq.org/
[8] G Ambrosi et al., IEEE NSS/MIC (2019), 1-8
[9] B Biskup et al., EPJ Web Conf. 253 (2021), 07010
[10] B Bergmann et al., NIM A 978 (2020), 164401
[11] P Mánek et al., JINST 17 (2022), C01062

The authors acknowledge funding from the Czech Science Foundation (GACR) under grant number 23-04869M. We thank Lukáš Meduna for valuable contributions to Track Lab in initial stages of development, as well as extensive on-premises testing.

Speaker: Mr Petr Manek (Czech Technical University)

15:58 P1.67: UniCorn – a universal readout system for ColorPix-2 ASIC

Silicon photon counting pixel detectors suffer from low absorption efficiency in the gamma spectrum. Therefore, a high-Z material such as CdTe/CZT is frequently used as the sensing material as its absorption efficiency is much higher than silicon sensors. However, these sensors suffer from the charge-sharing effect and secondary fluorescent photons with long mean free paths, which deprive the incident photons of energy. To compensate for these effects, we have developed the ColorPix-2 test ASIC with built-in charge sharing and hit allocation algorithm that compensate for these effects. The pixel matrix of the ColorPix-2 is 32 x 32 pixels. The ASIC consists of several blocks, such as an internal bandgap reference from which the reference currents for tuning DACs are derived, setting the operating point of the analog front-end electronics. A 3.2 Gbps serial readout system with CML logic to read data from the pixel matrix.
A new readout system called UniCorn has been developed to acquire data from the detector. The readout system consists of a computer running a UniCorn application connected to an Artix-7 FPGA via USB 3.0. The FPGA is responsible for ASIC configuration and data readout. The system is capable of working at readout speeds of 3.2 Gbps. First results of the ASIC testing will be presented.

Speaker: Jakub Jirsa (Czech Technical University in Prague (CZ))

15:59 P1.68: A low-noise read-out electronics for high energy resolution X-ray strip detectors

Semiconductor strip sensors are widely applied for X-ray imaging applications such as spectroscopy. X-ray imaging devices are required to provide good position resolution and spectroscopic features, which implies very tight noise level requirements too [1]–[3]. This work presents a design and simulations of the front-end electronics designed to work with 1D silicon strip sensors with a 75 μm pitch and 1 cm length, exhibiting around 1.5 pF capacitance. The detector is DC-coupled to a read-out ASIC built of 16 read-out channels. The detector read-out system is expected to operate with an X-ray energy range from 4 to 10 keV.

The charge processing chain comprises a CSA, a shaping amplifier with a selectable peaking time value, a discriminator, and some supporting circuits. It provides various modes of operation: a continuous read-out with a pole-zero canceling circuit and a mode with digitally-assisted pulsed reset of the charge-sensitive amplifier (CSA) as well as the active baseline restorer. The presented front-end is designed in the CMOS 180 nm process and occupies an area equal to 1525 x 1525 μm. Each channel dissipates the power of around 6 mW and the total noise is below 20 e- rms. In the fast operation mode with a digital reset, the front-end can process the incoming hits at a rate of 50 kps/ch. The analysis of the designed ASIC including reliability and PVT test results will be presented.

[1] P. O’Connor and G. De Geronimo, “Prospects for charge sensitive amplifiers in scaled CMOS,” Nucl. Instruments Methods Phys. Res. Sect. A Accel. Spectrometers, Detect. Assoc. Equip., vol. 480, no. 2–3, pp. 713–725, 2002, doi: 10.1016/S0168-9002(01)01212-8.
[2] M. Campbell et al., “Towards a new generation of pixel detector readout chips,” J. Instrum., vol. 11, no. 01, p. C01007, 2016, [Online]. Available: http://stacks.iop.org/1748-0221/11/i=01/a=C01007.
[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.

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

Speaker: Weronika Zubrzycka

16:00 P1.69: Probability distribution maps of deposited energy with sub-pixel resolution for Timepix3 detectors

The data driven mode of Timepix3 allows for energy bins, which can be adaptively re-binned during material reconstruction with spectroscopic X-ray imaging. This work aims to generate probability maps for the initial interaction position and energy for detected clusters with Timepix3 detectors. The correction maps are calculated for various cluster shapes, energies and subpixel center of mass position. Using these probability maps to correct measured X-ray datasets should lead to higher energy and spatial resolution spectroscopic X-ray imaging. The simulations using the simulation tool of Allpix2 are compared with experimental data.

Speaker: Pinelopi Christodoulou (Czech Technical University in Prague (CZ))

IWORID POSTER_CHRISTODOULOU.pdf

16:01 P1.70: R&D of Fast Timing Multi Anode MCP-PMT for Radiation Imaging

The time performance of photodetector is a critical parameter for the development of Radiation Imaging Detectors based on time of flight (TOF) technique, for example TOF positron emission tomography (TOF-PET). In 2020, the proposal of roadmap toward the 10 ps TOF-PET challenge [1] places higher requirement on the time performance of the photodetector. Microchannel Plate Photomultiplier (MCP-PMT) is a popular candidate photodetector of TOF-PET for its high gain, good detection efficiency, single photon detect ability, magnetic field resistance, ultimately its good time resolution and spatial resolution. This manuscript introduces the R&D of fast timing MCP-PMT with 8*8 anodes with a rise time (RT) less than 300 ps and Transit time spread (TTS) less than 40 ps under single photon mode. In addition to the performance evaluation of the MCP-PMT itself, the performance of this kind of MCP-PMT coupled with crystal array also be calibrated under proton and neutron beam respectively, including the energy resolution and uniformity, the time resolution and uniformity. The experiment is in progress, and the relevant results are being analysed step by step, and the full results will be presented in a formal report or article.

Speaker: Sen Qian

16:02 P1.71: A 12x16-Gbps/ch VCSEL array driving ASIC in 130-nm SiGe BiCMOS for heavy-ion physics experiments

The Heavy Ion Research Facility at Lanzhou (HIRFL) and the High-Intensity heavy-ion Accelerator Facility (HIAF) are the leading heavy-ion physics centers. Since the scale of experiments at HIRFL and HIAF are significantly increased, the High-speed and the high-density data transmission links have become urgent requirements for the heavy-ion physics experiments. VCSEL-based array optical transmission system with advantages of high data throughput, compact size and low power consumption is an effective solution for transmission links in these heavy-ion physics experiments. As a key component for optical transmission links, a 12-channel, anode-driving, 16G-per-channel VCSEL array driver ASIC has been designed for VCSEL-based array optical transmitters.
The VCSEL driving ASIC is fabricated in a 130-nm SiGe BiCMOS technology and its block diagram is shown in the Figure 1. The chip consists of an I2C module and 12 independent channels. The power supply for the whole chip is 3.3 V and we use a Low Dropout regulator (LDO) to generate 1.2 V power supply for I2C module. In each channel [1], it consists of an equalier, a limiting amplifier, and an output driver. The equalizer is used to compensate high frequency attenuation of the input signal at PCB traces. And we employ a signal detector to monitor the input data stream. The signal detector will generates an system interrupt when the received data amplitude is very low. In the limiting amplifier design, the function of polarity inversion is equipped. Polarity inversion allows the user to implement the equivalent of a board level crossover without additional via impedance discontinuities that degrade the high frequency integrity of the signal path. In the output driver stage design, the output driver translates the differential signals into switching single-end current to drive the VCSEL array. We use a programmable pre-emphasis to enhance the bandwidth of the output driver and a VCSEL supervisor to monitor the voltage at VCSEL anode. The modulation current and bias current for VCSEL is adjustable via I2C module. The power consumption of the channel is 48mW when it operates at 16-Gbps data rate. The die area of the whole chip is 3.6x2 mm2. The design have been verified in simulation and submitted for prototype fabrication. We will test the chips in this June.

Speaker: wei zhou (China Electronics Technology Group Corporation 58th Research Institute)

16:03 P1.72: 50.3ps time resolution and an 11-channel time measuring chip for Topmetal detectors

Pixel detectors are widely used in the inner tracking detectors of high-energy physics experiments due to their superior position resolution. With the development of detector systems, pixel detectors and associated readout electronics are required to conduct high-precision time measurements along with positions.
This paper aims to elaborate on a new front-end ASIC design to expand Topmetal pixel detectors for time measurement. The front-end circuit for each pixel mainly consists of two reverse delay chains and 11 edge acquisition circuits. The inverter is used as the base unit of the delay chain to effectively increase the transmission bandwidth, and the acquisition circuit uses two reverse clocks to generate 22 sets of time-stamped signals. The position and time information of the hit pixels is obtained by the time difference between the two ends of the delay chain. The function of time measurement based on time interpolation is achieved by TDC, which includes Time-to-Amplitude Converter (TAC), analog gate, weight count module, and Wilkinson Analog-to-Digital Converter (ADC). Coarse time measurement is implemented based on an 8-bit counter with a working frequency of 500 MHz, and fine time measurement is achieved by the combination of TAC and ADC. The TAC converts the time difference values into voltages which are stored in a capacitor. Multiple voltage signals are sampled sequentially via an analog selector. The ADC consists of a ramp generator, a comparator, and a 10-bit Gray code counter. The corresponding time difference values are obtained via the coarse and fine counters.
The design prototype was taped out with the GSMCR130 nm technology. Test results show that this circuit can handle up to 11 consecutive cases, with the minimum time interval of adjacent cases being 500 ps, the bin size up to 2 ps, and Differential Non-Linearity (DNL) is between -0.8 to +1.4 LSB. The time measurement accuracy is better than 50.24 ps RMS, and the PVT robustness of the input delay chain circuit is validated, showing the stable performance of the design.

Speaker: Ni Fang

16:04 P1.73: 3-Dimensional photoelectron track reconstruction and the future X-ray polarimeter

The field of X-ray imaging polarimetry has expanded significantly since the development of the first photoelectron-based X-ray polarimeter. This sophisticated system measures the polarization of X-ray photons by reconstructing the initial direction of the photoelectron track created by an interaction of an incident photon with a gas mixture. The current photoelectron-based X-ray polarimeter, the Gas Pixel Detectors (GPD) on board the Imaging X-ray Polarimetry Explorer (IXPE), has shown efficient performance as the first imaging X-ray polarimeter mission since its successful launch on December 9, 2021. Despite the remarkable achievements of IXPE, the window of X-ray polarimetry is still restricted by the brightness of the source and the long exposure time required for faint objects. To expand our perspective and reach deeper into the universe with X-ray polarimetry, it is essential to improve sensitivity. One effective approach to improve the modulation factor, which expresses the amplitude of polarization properties from measurements, is to refine the photoelectron track reconstruction process. Currently, polarization properties are extracted from a two- dimensional projected track image using standard moment analysis. Thus, a three-dimensional understanding of the track geometry will enhance the sensitivity of polarimetry measurement. The future X-ray polarimeter will employ a three-dimensional track reconstruction as exploiting the timing information as a z-axis, which can be achieved with the TIMEPIX3, a hybrid readout chip with a high time resolution. This advancement will provide new opportunities to expand our views of the polarized X-ray sky with shorter exposure times and a broader energy range. Therefore, in this talk, we will present our reconstruction algorithms and prospective improvements in X-ray polarimetry.

Speaker: Dawoon Edwin Kim (INAF Istituto di Astrofisica e Planetologia Spaziali)

16:05 P1.74: Ultra-Fast Energy Resolved Imager for ’Pseudo’ Laue diffraction experiments at synchrotron facilities

‘Pseudo’ Laue diffraction experiments [1], with multi pink beam, is being considered as an option for the upgrade of SOLEIL [2] for fast time resolved crystallographic applications in the energy range from 5 to 30 keV. A factor of over 1000 in acquisition speed, compared to current performances, may be expected and the capability of simultaneous measurements of photon fluxes at different energies is a mandatory requirement for the detector. Such a detector would address thematic as serial synchrotron crystallography, in situ macromolecular crystallography, in vivo crystallography and high-pressure/temperature crystallography (quasi-crystal). Pump-probe time resolved technique is also considered.

For this purpose, a feasibility phase has been launched within a SOLEIL-AGH collaboration for the design of a new photon counting ASIC prototype (named UFERI), with some architecture parts inspired from previous work [3]. A very high counting rate for the ASIC has been an essential requirement to be compatible with the photon flux expected on the future detector surface, and three discriminators and counters have been implemented in each pixel of 75 µm pitch. The UFERI ASIC prototypes have been tested successfully and the very first hybrid pixel modules are now under tests with X-rays in laboratory. Preliminary results will be presented at time of the conference.

[1] Z. Ren et al, J. Synchrotron Radiation (1999)., vol 6, 891-917.
[2] Conceptual Design Report for SOLEIL upgrade (2021) https://www.synchrotron-soleil.fr/
[3] R. Kleczek et al, IEEE Journal of Solid-State Circuits (2018) PP. 1-12. 10.1109/JSSC.2018.2851234.

Speaker: Fabienne Orsini (Université Paris-Saclay (FR))

Poster_IWORID23_FORSINI_June2023_v2.pdf

16:06 P1.75: Dark-field Radiography for Detection of Infectious Lung Diseases: COVID-19

Dark-field chest radiography allows for assessment of lung alveolar structure by exploiting wave optical properties of x-rays. Here we present first results on the qualitative and quantitative characteristics of dark-field chest radiography in participants with COVID-19 pneumonia. Dark-field radiography shows high accuracy for the detection of COVID-19 and significantly improves diagnostic performance compared to conventional radiography.
In addition, we discuss how spectral information, e.g. from photon-counting detectors, could further improve these clinical darkfield results in the future.

Speaker: Prof. Daniela Pfeiffer (Technical University of Munich)

16:07 P1.76: Spectral Dual-Energy and Photon Counting Detector Computed Tomography: Applications for Medical Imaging in Stroke Patients

Dual Energy Computed Tomography (DECT) and Photon-Counting CT (PCCT) provide information about the examined tissue at two/multiple energy levels and therefore offer the possibility to calculate (virtual) monoenergetic images at different energy levels, virtual non-contrast images (VNC), material specific images such as iodine maps and images indicating the atomic number of the scanned materials (z-effective maps). We have investigated the effect of spectral images from DECT and photon counting detectors for neurological applications. Spectral image information improves visualization of ischemic areas in stroke patients, and material-specific images calculated from photon-counting detectors allow differentiation between hemorrhage and contrast within the brain.
In conclusion, DECT and PCCT have the potential to significantly improve the diagnostic decision-making process in stroke patients, especially for advanced characterization of thrombotic material, precise definition of ischemic brain tissue, and material-specific detection of hemorrhage.

Speaker: Prof. Daniela Pfeiffer (Technical University of Munich)

16:08 P1.77: First simulations of Open-IMAGING PET

This work presents the first simulations performed in the context of Open-IMAGING project (ERC-2022-POC1 Grant agreement ID: 101069298) which consists in the development of two PET detector paddle modules.
In this project, one detector module will be composed by a 4x4 array of Broadcom SiPM 4x4mm2 each, coupled to an 8x8 scintillator array of 2x2x12mm3 LYSO crystals, separated with ESR and having the top and bottom surfaces polished to increase the light collection. Four of these modules will conform a so-called supermodule. The final paddle will be formed by 4x4 supermodules with a total detector area of 256x256mm2.
The results of the simulations show that at 300 mm distance between paddles, 180ps TOF resolution is suitable for organ exploration as brain or cardiac applications.

Speaker: Laura Moliner

16:09 P1.78: Development and validation of the KAERI-NDP system

Neutron depth profiling (NDP) is an analytical technique used to determine the amount and distribution of light elements in materials. This method is beneficial for the study of thin films and surface layers. A sample is exposed to a thermal neutron beam in a vacuum chamber, and the emitted charged particles lose energy while passing through the material. The energy lost depends on the particle's path length, determined by the stopping power. Lithium, beryllium, boron, and sodium are commonly used in NDP because their neutron cross-sections are much larger than those observed in other particle-producing reactions. NDP is a straightforward technique that can be used to quantify the depth profiles of certain isotopes in various materials, including semiconductors, thin films, and lithium batteries.

The Korea Atomic Energy Research Institute (KAERI) is now developing the KAERI-NDP system, an upgraded version of the conventional NDP system using cold neutrons generated from the HANARO (High-flux Advanced Neutron Application ReactOr) research reactor. To analyze trace elements using the KAERI-NDP system, improvements were made by focusing on several points. First, a focusing lens was used to reduce the background signal caused by radioactive materials by minimizing neutron irradiation to the material around the sample and to increase the neutron flux in the sample. Also, the focal distance between the sample and the focusing lens was optimized. Second, shielding was designed inside and outside the vacuum chamber to block unwanted gamma rays that could interfere with the measurement. The shielding was carefully calibrated to provide the best possible signal-to-noise ratio, ensuring the system could detect even small changes in the neutron flux. Lastly, a neutron beam monitoring system was built using a thin boron film to improve the accuracy of the analysis. Since the neutron flux changes according to the output of the research reactor, correcting it through neutron beam monitoring is crucial. The KAERI-NDP system was tested and validated using the SRM-2137. Overall, the KAERI-NDP system represents a significant step forward in the field of NDP analysis. Its design and implementation might promise to contribute significantly to a wide range of scientific applications, including materials science, semiconductor manufacturing, and battery research.

Speaker: Jinhwan Kim (Korea Atomic Energy Research Institute)

16:15 → 22:00 Fjord Cruise - Ferries leave at 17:00 from Rådhusbrygge 3, Aker Brygge, closest metro stop 'Nationaltheatret'

Please take the metro down to National Theatre and follow a short walk to Aker Brygge Marina

Tuesday, 27 June

08:30 → 10:20 Applications: 2

Convener: Renata Longo (UNIVERSITY OF TRIESTE & INFN)

08:30 INVITED: Recent development of solid state microdosimetry and its applications in particle therapy and space

Particle therapy has many advantages over conventional photon therapy, particularly for treating deep-seated solid tumours due to its greater conformal energy deposition achieved in the form of the Bragg peak (BP). Successful treatment with protons and heavy ions depends largely on knowledge of the relative biological effectiveness (RBE) of the radiation produced by primary and secondary charged particles. The RBE prediction based on microdosimetric approach using the tissue equivalent proportional counter (TEPC) measurements in 12C therapy has been reported, however large size of commercial TEPC is averaging RBE which dramatically changes close to and in a distal part of the BP that may have clinical impact. Moreover, the TEPC requires high voltage and gas supply that are not always practical for a quality assurance (QA) purpose in a routine clinical setup.

Based on many years of experience in development of silicon-on-insulator (SOI) microdosimeter, the Centre for Medical Radiation Physics, University of Wollongong, has successfully developed a microdosimetric probe which is based on a SOI microdosimeter with 3D micron sized sensitive volumes (SVs) mimicking dimensions of cells, known as the “Bridge” and “Mushroom” microdosimeters, to address the shortcomings of the TEPC [1, 2]. Several designs of high definition 3D SVs fabricated at SINTEF, Norway using 3D MEMS technology were implemented. 3D SVs were fabricated in different sizes and configurations with diameters between 18 and 30µm, thicknesses of 2-50 µm and at a pitch of 50 µm in linear array of single or multiple volumes or matrixes of 20×20 and 50×50 volumes. SVs were segmented into sub-arrays to reduce capacitance and avoid pile up in high dose rate pencil beam scanning applications. Detailed electrical and charge collection charaterisation of these devices will be presented at the conference. The silicon microdosimeters were used to evaluate the RBE of various ions [3] and were successfully utilised for validation of treatment planning system (TPS) in multiple ion therapy at Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan [4]. In multiple ion therapy, the dose and linear energy transfer (LET) distributions can be optimized simultaneously resulting in an improved RBE-weighted dose distribution. By measuring the response of the microdosimeter in a He, C, O and Ne ion spread out BP (SOBP), and applying a dose-weighted summation of the acquired spectra, the combined ion dose mean lineal energy (yD) and cell surviving fraction in MIA PaCa-2 pancreas cells is found for combinations of He+O and C+Ne ions along the SOBP. The survival fraction results are then compared against the in-house TPS showing very good agreement (Fig. 2). These results demonstrate that the 3D SOI microdosimeter is a suitable candidate for the QA system in multiple ion radiotherapy.

Beside application in particle therapy, the SOI microdosimeter is also useful for radiation protection in space. The first study on a comparison of the SOI microdosimeter and the TimePix [5] developed at CERN and currently deployed on the International Space Station (ISS) was performed. Both detectors were placed behind the aluminum plates of various thicknesses to evaluate the radiation field exposed to the astronauts behind shielding. 290 MeV/u 12C, 400 MeV/u 20Ne, 800 MeV/u 28Si and 650 MeV/u 40Ar ions were used in this study. The lineal energy spectra obtained with the SOI microdosimeter and the dE/dX spectra derived with TimePix and converted to tissue are compared and agreed reasonably well. The average quality factor Q of the radiation field obtained with the 2 detectors has shown good agreement for Ar and Ne ions ranging from 1.54% to 11% while some discrepancies between the two detectors of around 15 % were observed for no Al or thin Al wall in case of C, Fe and Si ions. Some discrepancies observed can be related to the fact that the TimePix is measuring dE/dX that is higher than the y due to escaping high energy delta electrons from SV in SOI microdosimeter that is typical for high energy ions like in this experiment. SOI microdosimeter and TimePix can provide the Hp(10) and Q values as well as LET instantly through microdosimetry approach and via data processing of tracks, respectively.

Speaker: Linh T. Tran (Centre for Medical Radiation Physics (CMRP), University of Wollongong, Wollongong, Australia)

LinhTran_Iworid presentation_Oslo_Final_1.pptx

09:00 WIDMApp (Wearable Individual Dose Monitoring Apparatus): an innovative approach for individual dose monitoring in Targeted Radionuclide Therapy

In Targeted Radionuclide Therapy (TRT), radio tracers having specificity for the tumor to treat are administered to the patient in order to selectively damage diseased cells via the decay radiation of the isotope. However, given their systemic administration, these molecules not only concentrate on the tumor, but also diffuse to healthy tissues which thus receive an unavoidable dose of radiation.
A high level of personalization in TRT could bring advantages in terms of treatment effectiveness and toxicity reduction. Individual organ-level dosimetry is crucial to describe the radiopharmaceutical biodistribution expressed by the patient, to estimate absorbed doses to normal organs and target tissue(s).

A new approach for individual radioagent biokinetics determination is proposed with the Wearable Individual Dose Monitoring Apparatus (WIDMApp).
WIDMApp has been conceived as a multi-channel radiation detector associated with data processing system for in vivo patient measurement and collection of radiopharmaceutical biokinetic data (i.e., time-activity data) [1]. This system could provide an effective tool to characterize more accurately the radiopharmaceutical biokinetics in TRT patients, reducing the need of resources of nuclear medicine departments, such as technologist and scanner time, to perform individualized biokinetics studies.
A diagram of the WIDMApp paradigm is presented in Figure 1. The multi-channel detector system is composed by sensors that will be stably positioned within compartment of a wearable garment. Each sensor is placed to maximize its sensitivity to an organ of interest, even though it will generally detect radiations emanating from positions throughout the body as shown in Figure 1. The sensors can be used individually or grouped in any number to cover, as a unique subsystem, a wider area. Data are acquired at a fixed or variable sampling frequency during the entire MRT treatment and even continuously over 24 hours per day.

An experimental proof-of-principle of WIDMApp was realized using a NEMA phantom. A first prototype of the WIDMApp detecting element was developed based on a plastic scintillating crystal and silicon photomultiplier technology. It was used to detect the gamma radiation emitted from radionuclides with different decay time: 18F, 99mTc and 64Cu. Solution of these radionuclides with 54, 53 and 28 MBq respectively were injected in three spheres of the NEMA phantom to mimic organs with different time-activity trend - i.e. different radioagent biokinetics. The WIDMApp sensor was placed in three positions on the phantom surface, and used to measure the time evolution of the counts due to the gamma emitted by the three radionuclides. Data was collected over four days with a frequency of 24 minutes at each measurement point. The decay times of the three sources were estimated by fitting the data and were compared with the proper radionuclide decay constants.
The results obtained from this firse feasibility studies and from a Monte Carlo simulation of the system justify the development of an actual prototype system to characterize this technique under realistic clinical conditions.
In this contribution an overview of WIDMApp, as well as the first experimental feasibility study, are presented. Particular attention will be paid to the description of the brand-new multi-channel detector system design, the front-end electronics and its characterization.

Speaker: Riccardo Mirabelli

WIDMApp_iWorid23.pptx

09:20 Measuring spill microstructure of medical synchrotron on primary and secondary ion radiation fields using Timepix3 detectors

Radiation therapy with ions has been used for cancer treatments showing high dose conformity while sparing surrounding organs at risk and healthy tissue. For such treatments, synchrotrons are used to produce pencil-like ion beams, which are magnetically deflected laterally and modulated in range to cover the entire cancer volume [1]. As the beam extraction is in terms of spills at a fixed beam energy, spill quality is of high importance [2]. Moreover, this is also highly important in the field of ultrahigh dose-rate radiotherapy well-known as FLASH. However, there is a lack of detectors giving information about the spill structure either for radiobiology studies with ions or treatment radiation fields [3]. This contribution aims at the measurement of the spill microstructure of a medical synchrotron in ion radiation fields.

In this contribution, Timepix3 detectors with a silicon sensitive area of 2 cm2 and 300 µm thickness were used, exploiting their nanosecond time resolution. Irradiations were carried out at the Heidelberg Ion Beam Therapy Center in Germany. Three ion types (protons, helium and carbon ions) were used as primary ion radiation field (see fig. 1a). Measurements of the spill microstructure were also performed behind a patient-like head model in order to not interfere the primary radiation field. To generate a secondary ion radiation field, a carbon-ion treatment field was designed to irradiate the head model, producing secondary charged fragments which were detected by the Timepix3 detectors (see fig. 1b).

For the primary radiation field, individual spills of each ion type and energy were analyzed by applying the fast Fourier transformation to calculate the acceleration frequency (see fig. 2a). From it, the periods of the spill microstructure were obtained (see fig. 2b). These results are in agreement to those obtained by Magalhaes Martins et al, [4]. For the secondary radiation field, each spill of the treatment plan was analyzed (see fig. 2c). The corresponding frequency and period of each spill were then obtained. From the obtained periods, beam energies were measured and compared to the nominal ones (see fig. 2d).

We have shown the capabilities of Timepix3 detectors for measuring the spill microstructure and also the primary beam energy even in clinic-like treatment situations. This procedure is of great interest to be used in radiobiology research and as complementary spill quality assurance during cancer treatment irradiations.

Speaker: Dr Renato Félix-Bautista (German Cancer Research Center (DKFZ))

iworid2023_talk_renato.pptx

09:40 2.5D Imaging: obtaining additional depth information from helium-beam radiographs for applications in ion beam radiotherapy using silicon pixel detectors

Introduction: Ion beam radiotherapy (IBR) can provide a depth dose distribution with a low dose in the entrance channel and a high dose in the tumor region due to the characteristic peak in the depth-dose curve of ions, called Bragg Peak. This results in a high dose concentration in the tumor and sparing of surrounding organs allowing a more accurate treatment compared to conventional X-ray therapy. IBR is often used for tumors surrounded by critical healthy structures or deeply seated tumor regions. Due to the steep gradients of the dose distribution in the patient, IBR is sensitive to potential uncertainties like anatomical changes of the patient geometry or conversion errors of the CT dataset into stopping power, which is the relevant quantity for IBR treatment planning.
Using the same kind of radiation for imaging and treatment, ion-beam radiography (iRad) provides the potential of frequent treatment-plan verifications by direct and accurate measurements of the integrated stopping power (called water-equivalent thickness (WET)) at low imaging doses. This contrasts with X-ray imaging modalities, which have larger uncertainties due to the error-prone conversion of CT units to stopping power.
A daily monitoring based on iRad could help to detect and quantify inter-fractional changes resulting in a shift of the Bragg Peak which could otherwise lead to damage in healthy tissue and a reduced tumor control. Hence, iRad could be a valuable tool to complement conventional X-ray imaging.
Inter-fractional changes occurring within the beam path have a big impact on the dose profile, while changes behind the target are of minor importance. Therefore, not only the detectability of an anatomical change but also its location within the patients’ geometry is of high interest. In this contribution, the possibility of using 2D helium-beam radiography to access a third-dimension information is introduced (referred here in the following as 2.5D imaging/radiography).

Material and Methods: An in-house developed detection system was used to perform the experiments at the Heidelberg Ion-beam therapy center using helium ions at low helium ion fluences and fluence rates. The system consists of thin, pixelated silicon detectors (TimePix). They are capable of detecting single ions. Two tracking units measure the position and direction of single ions in front and back of the imaged object. The energy deposition of the ions leaving the imaged object is measured in a third unit – the energy deposition unit. This results in a need of 6 detectors.
To test the feasibility of 2.5D imaging with ions, a homogenous 161mm-thick PMMA block with an air slab of 1mm thickness at different depths was imaged first. The air slab position was estimated with a accuracy of 10 ± 16 mm. To get closer to a clinical situation, a PMMA cylinder with a diameter of 160mm was imaged with air cavities which have diameters of 10 mm. They were positioned in various depths within the phantom.
With the direction and position information of the impinging ions on the front and rear-tracking units, the most-likely path for every single ion is evaluated every 1mm along the depth of the object using the cubic spline algorithm. The energy deposition of each single ion is measured in a single sensitive layer in the energy deposition unit behind the imaged object. Using a calibration curve the energy deposition is translated to WET of the object. In that way, images are reconstructed at planes with 1mm spacing using the most-likely position of each ion and their connected WET.

Results: In the conducted experiment two measurements were performed: one with a completely homogeneous cylindrical phantom and one with an air cavity inserted. In this way, an inter-fractional change should be mimicked. The 2D iRads of the phantom with the air cavity evaluated at different depths already indicate qualitatively its position based on their sharpness. Then, the iRads with the air cavity were each compared to the homogeneous phantom in order to reconstruct the depth of the change in geometry. As a first investigated image quantity, the increase of the SSD indicates already the location of the insert. The average accuracy of this second experiment was determined to be approximately 18 ± 12 mm.

Conclusion: In conclusion, it could be shown that helium-beam radiography based on a detection system using silicon pixel detectors has the potential to not only produce a 2D image to verify the estimated WET values and detect anatomical changes, but also can give an estimation of their position in depth.

Speaker: Annika Schlechter (German Cancer Research Centre DKFZ)

iWoRiD_2023_Schlechter_Annika.pptx

10:00 10ps Time-of-Flight PET scanner: From Hope to Practice

The future generation of radiation detectors is more and more demanding on timing performance for a wide range of applications, in particular for time-of-flight (TOF) techniques in PET cameras.
There is in particular a consensus for gathering Europe's multi-disciplinary academic and industrial excellence around the ambitious challenge to develop a 10 ps TOF PET scanner (TOFPET). The goal is to reduce the radiation dose (currently 5-25 mSv for whole body PET/CT), scan time (currently > 10 minutes), and costs per patient (currently > 1000 € per scan), all by an order of magnitude. To achieve this very ambitious goal it is essential to significantly improve the performance of each component of the detection chain: light production, light transport, photodetection, readout electronics.
The possibility to reach 10 ps time-of-flight resolution at small energies, as required in PET scanners, although extremely challenging, is not limited by physical barriers.
This talk will show how progress in nanotechnologies open new perspectives for the development of meta-scintillators, a new class of multifunctional multi-intelligent scintillators.
Indeed, a number of disruptive technologies, such as multifunctional heterostructures, combining the high stopping power of well know scintillators with the ultrafast photon emission resulting from the 1D, 2D, or 3D quantum confinement of the excitons in nanocrystals, photonic crystals, photonic fibers, as well as new concepts of 3D digital SiPM structures, open the way to new radiation detector concepts with unprecedented performance.
A first generation of metascintillators will be presented (Fig. 1), allowing an improvement by a factor of 2 in time-of-flight resolution (and therefore in PET equivalent sensitivity) as compared to the state-of-the art, and perspectives for an ultimate gain of 20 (time-of-flight resolution of 10 ps) will be discussed.
Fig.1: First generation of metascintillators showing: right, 2 LYSO/EJ232 metapixels 3x3x25mm, middle: two 4 x 4 matrices of metapixels, left: 2 8 x 8 matrices of metapixels.

Speaker: Paul Rene Michel Lecoq (CERN)

PL-IWORLD23-The 10ps challenge.pdf

PL-IWORLD23-The 10ps challenge.pptx

10:20 → 10:50 Coffee Break

10:50 → 12:40 Detector Systems: 2

Convener: Roelof de Vries

10:50 INVITED: X-ray Detectors for LCLS-II with real-time information extraction: the SparkPix family

We will present an overview the development of a series of detectors in the SparkPix family, designed to match the increased repetition rate of LCLS-II. Each detector is customized to meet the specific requirements of different experiments, and dedicated information extraction engines are integrated into each SparkPix ASIC to enable frame rates up to 1 MHz. The article discusses the overall approach behind the SparkPix family and presents updates on the ongoing progress of four different detectors: SparkPix-ED, SparkPix-T, SparkPix-S and SparkPix-RT.

SparkPix-ED [1] is designed for X-ray scattering experiments and captures rare events by recording high-resolution images at closely spaced times and streaming low-resolution images to an EDGE computing system for trigger generation.
SparkPix-S is a novel ASIC for X-ray Photon Correlation Spectroscopy (XPCS) and Speckle Visibility Spectroscopy (XSVS) experiments. It offers fine spatial resolution and can operate at 1 MHz, with on-line information extraction implemented through a sparsified readout. A detailed description of the electronics will be presented in a dedicated presentation by Filippo Mele.

SparkPix-T is a front-end ASIC with spatial and time resolution capabilities, specifically designed for massive multi-particle coincidence experiments at the TMO instrument at LCLS-II. It has 100 µm x 100 µm pixels arranged in a 176 x 192 matrix, capable of measuring charged particle time-of-arrival (TOA) with 100 ps resolution and 6.5 µs range. Signal energy is indirectly assessed through 8-bit time-over-threshold (TOT) measurements.

Lastly, SLAC and Argonne National Laboratory (ANL) are collaborating to develop SparkPix-RT, an ASIC designed for continuous real-time (RT) readout with a high bandwidth detector rate. This ASIC implements a novel digital compression algorithm in the periphery of the ASIC to extract information in real-time [2].

[1] L. Rota et al., “SparkPix-ED: a readout ASIC with 1 MHz frame-rate for rare event experiments at LCLS-II”, IWORID 2021
[2] M. Hammer, S. Strempfer, A. Miceli (ANL) - https://arxiv.org/abs/2208.00069

Speaker: Lorenzo Rota

Lorenzo_Rota_IWORID_SparkPix.pdf

Lorenzo_Rota_IWORID_SparkPix.pptx

11:20 Characterization results of the first small pixel high rate (SPHIRD) photon counting hybrid pixel detector prototypes

This work presents experimental performance results of a first set of p-type Si and CdTe SPHIRD (Small Pixel High Rate photon counting Detector) prototypes [1]. The SPHIRD project targets a new generation of photon counting hybrid pixel detectors for synchrotron radiation applications with small pixels and operating between 10 and 30 keV. The current prototypes are based on an MPW test readout ASIC in CMOS 40nm technology that features an active area of 64×32 pixels with a 50 µm pitch. The readout ASIC is designed to explore techniques that boost the count rate capabilities of the detector and methods to manage, or in some cases exploit, the effects of charge sharing that are unavoidable in this type of device with small pixels.
The management of high photon rates relies on the implementation of a fast charge-sensitive amplifier in the pixel together with time-based and amplitude-based pile-up compensation techniques. These techniques, which consist of the use of additional discriminators or time-over-threshold methods, have been compared experimentally. The results obtained show and quantify their effectiveness in increasing the count rate handled by the detector.
The readout chip also includes dedicated circuitry for the relocation of photon hits, something necessary to reduce the photon losses that are observed in photon counting detectors due to charge sharing when the discrimination threshold is set to 50% of the photon energy. The pixel relocation circuitry, based on an interpixel arbitration logic, allows the detector to operate with a threshold of 25% or less of the incident photon energy. The X-ray measurements, both with uniform illumination and with pencil beams, demonstrate how this relocation approach successfully recovers those undesired counting losses.
The relocation circuitry in the SPHIRD ASIC is not limited to full pixel relocation. It also implements resources to reassign X-ray hits within regions smaller than the physical pixel. This sub-pixel relocation capability is intended to increase the effective spatial resolution of the detectors and has also been experimentally evaluated with a pencil beam and with full field images.

Speaker: Debora Magalhaes Suarez

SPHIRD_detector_iWoRiD2023.pdf

11:40 Design and characterisation of a treatment monitoring system for carbon-ion radiotherapy based on 28 Timepix3 detectors

Compared with conventional X-ray radiation therapy, carbon-ion beam radiotherapy reduces the dose to the healthy tissue around a tumor thanks to the escalating dose at the Bragg peak. We developed a tracking system for secondary radiation from carbon-ion beams based on seven modules of four Timepix3 detectors (“quad module”). The tracking system measures the secondary radiation of different treatment fractions delivered on consecutive days, and thus detects undesired treatment variations. In this contribution, the design and characterisation of the tracking system will be presented. The characterisation focused on the detection, localisation and identification of internal density changes in human head models. A clinical study focusing on monitoring the treatment of tumors of the head and neck region has been started.

Speaker: Dr Laurent Kelleter (German Cancer Research Centre DKFZ)

12:00 Flexible X-Ray Imaging Detectors Using Scintillating Fibers

Some medical and industrial X-ray imaging applications need to reconstruct an image on a flexible surface, so they use photographic film rather than electronic detectors. Current flat-panel X-ray imaging detectors are difficult to adapt to these applications. We will present the FleX-RAY project, which aims to create an electronic X-ray detector with the flexibility of photographic film, suitable for a variety of applications.

FleX-RAY uses a sheet of flexible scintillating fibers to detect X-rays and guide the scintillation light to arrays of silicon photomultipliers. The detector also self-reports its curved shape using optical waveguides with Bragg gratings in a flexible glass substrate, which act as curvature sensors. Multiple reconstruction algorithms have been developed, suitable for different X-ray energies.

In this contribution, we present the advances in scintillating fibers, self-shape-reporting sensors, and image reconstruction algorithms made by the FleX-RAY collaboration. We will also present simulations of the expected detector performance and results of the initial tests on the FleX-RAY prototype.

This project has received funding from the European Union's Horizon 2020 Research and Innovation Program under grant agreement No. 899634.

Speaker: Scott Wilbur (University of Sheffield (GB))

flex_ray.pdf

12:20 Single photon counting pixel detector below 1 keV using LGAD sensors

Soft X-rays (in the range of 200-2000 eV) are of great interest for imaging applications for a large variety of sectors. These include: imaging of organic samples, e.g., in the “water window” (between C and O, K-edges: 277 eV to 525 eV), anomalous scattering experiments around many K-edges of light elements, and L-edges of 3d transition metals (relevant to magnetic and superconducting materials). Many of the techniques performed at synchrotrons in the tender and hard X-ray regimes are currently hindered in the soft X-ray range by the lack of fast, large area, high dynamic-range detectors, sensitive to photons <2 keV [1].
To extend the application of the state-of-the art hybrid X-ray detectors to a lower energy range, PSI and FBK are developing silicon sensors based on Low Gain Avalanche Diodes (LGADs). These LGAD sensors are optimized for soft X-ray detection: they include a charge multiplication layer with a gain of ~10 in order to amplify the signal and improve the signal-to-noise ratio, combined with a thin entrance window in order to increase the quantum efficiency at lower photon energies [2]. This contribution will present tests performed in the soft X-ray regime using the developed pixelated LGAD sensors with a pixel pitch of 75 μm, bump-bonded to the EIGER single photon counting read-out chip [3]. LGAD sensors with different multiplication layer designs and a large detection area of 4×4 cm2 have been characterized at the SIM beamline at SLS (PSI, Switzerland) between 200 eV and 900 eV. Additionally, as a proof-of-principle, ptychographic scans in the soft X-ray energy range have been performed. The high dynamic range, large area, fast frame rate, and low noise of the detector outdo the results previously obtained with hybrid charge-integrating detectors (such as Mönch), and allow to achieve a high resolution, mainly limited by the size of the detector [4]. Characterization results of the sensor performances will be presented, as well as preliminary ptychographic reconstructions obtained with 500-700 eV photons.

[1] A. Hitchcock, J. Electron Spectrosc. Relat. Phenom. 200 (2015): 49-63.
[2] J. Zhang, et al., JINST 17.11 (2022).
[3] R. Dinapoli et al., NIM A 650.1 (2011): 79-83.
[4] M. Holler, et al., Nature Electronics 2.10 (2019): 464-470.

Speaker: Filippo Baruffaldi (Paul Scherrer Insitut (Switzerland))

Baruffaldi_Singlephotoncountingpixeldetectorbelow1keVusingLGADsensors_iWoRiD_2023.pptx

12:40 → 13:30 Lunch Break

13:30 → 15:20 Sensors: 1

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

13:30 INVITED: Resistive read-out and built-in amplification: two key innovations to achieve 4D tracking with silicon sensors

In the past few years, two design innovations have radically changed the performance of silicon detectors and turned silicon sensors into high-resolution timing detectors, fit to meet the very demanding requirement of future 4D trackers. In this presentation, I will review the performance improvements that these two design innovations, low-gain (LGAD) and resistive read-out (RSD) [1], have brought to silicon sensors. Due to the LGAD mechanism, large signals lead to improved temporal precision, while charge sharing, due to the RSD design, has removed the need for very small pixels to achieve excellent spatial precision. LGAD- and RSD- based silicon sensors are now adopted, or considered, in several future experiments and are the basis for almost every next 4D-trackers. In the final part of the presentation, I will show how the introduction of multiple sampling front-end electronics and reconstruction methods based on machine learning can further improve the performances of future 4D
trackers.

Speaker: Nicolo Cartiglia (INFN Torino (IT))

IWORID_Cartiglia.pdf

IWORID_Cartiglia.pptx

14:00 Sub-pixel spatial resolution of single soft x-ray photons using the JUNGFRAU hybrid pixel detector with iLGAD sensors

Soft x-ray photon science at free-electron laser (FEL) and synchrotron radiation (SR) facilities plays a vital role in many research fields. With light sources advancing and upgrades such as SLS 2.0 (PSI, Switzerland) and LCLS-II (Stanford University, USA) on the horizon, detector systems that meet the requirements of high-performance x-ray science at next generation sources are becoming a necessity. Experimental techniques such as resonant inelastic x-ray scattering (RIXS) require high-frame-rate, large-area detectors that can resolve single photon hits at energies around the oxygen K-edge (525 eV) with a spatial resolution of, ideally, 1-2 µm.

Current systems that can fulfill resolution requirements (CCDs and CMOS monolithic sensors) struggle to meet the high frame rate and large area requirements. Hybrid pixel detectors (HPDs) such as JUNGFRAU, on the other hand, provide frame rate and size but, until recently, were limited to experiments with tender and hard x-rays due to their electronic noise (i.e., 34 electrons r.m.s. in high gain for JUNGFRAU). Recent advances have combined charge-integrating (JUNGFRAU and MÖNCH) and single-photon-counting (EIGER and MYTHEN) readout chips with inverse low-gain avalanche diode (iLGAD) sensors with a thin entrance window. This approach successfully increased the signal of low-energy photons above the noise threshold while achieving quantum efficiencies > 80% in the soft x-ray regime.

HPDs can utilize charge sharing between neighboring pixels to interpolate the photon position down to a fraction of the pixel pitch. We recently designed JUNGFRAU-iLGAD prototypes featuring rectangular pixels ("strixels"). To match the ASIC array of square pixels, the strixels measure a fraction of the original 75 µm pitch in the vertical direction (25 µm, 18.75 µm, and 15 µm) and a multiple in the horizontal direction. This sensor design is aimed at experimental techniques such as RIXS, which only require high spatial resolution in one dimension.

We report on the spatial resolution capabilities of these iLGAD strixel prototypes as evaluated in recent experiments. The modules were raster-scanned with a micron-sized x-ray beam at the SLS POLLUX beamline. We compare the photon detection efficiency and interpolation performance at x-ray energies between 400 eV and 1 keV and discuss the prospects of spatially resolving soft x-ray photons in the sub-10 µm range. Based on these recent results, we will give an outlook on the promising prospects of JUNGFRAU for high-throughput, low-energy x-ray applications such as RIXS at FELs and SR facilities.

Speaker: Dr Viktoria Hinger (Paul Scherrer Institut)

IWORID_JFRIXS_VH.pptx

14:20 Characterization, Simulation and Test Beam Data Analysis of Stitched Passive CMOS Strip Sensors

In the passive CMOS Strips Project, strip sensors were designed and produced at LFoundry in 150 nm technology, with an additional backside processing from IZM Berlin. Up to five individual reticules were connected by stitching at the foundry in order to obtain the typical strip lengths required for the LHC Phase-II upgrade of ATLAS or CMS trackers. After dicing, sensors were tested in a probe station and characterised with a Sr90-source as well as laser-based edge- and top-TCT systems. Sensors were also simulated using Sentaurus TCAD. At last, detector modules were constructed from several sensors and thoroughly studied in a test beam campaign at DESY. All of these measurements were performed before and after irradiation. This presentation will provide an overview of simulation results, summarize the laboratory measurements and in particular present the test beam results for irradiated and unirradiated passive CMOS strip sensors. We will demonstrate that large area sensors with sufficient radiation hardness can be obtained by stitching in this CMOS process, and present our plans for the next CMOS submission in the framework of this project.

Speaker: Iveta Zatocilova (Albert Ludwigs Universitaet Freiburg (DE))

iworid2023_iveta-cmos_strips.pdf

14:40 On sensitivity of detectors based on hydrogenated amorphous silicon (a-Si:H) for measuring radiation beams

The HASPIDE project aims to investigate the use of a-Si:H as a material for detecting different types of ionizing radiation in applications like radiation flux measurement, dosimetry, and measurement of ionizing radiation in the spatial environment. The demand for radiation-resistant detectors capable of high dynamic range and precise measurement of fluxes is increasing and a-Si:H thanks to its characteristic of being very resistant to radiation damage, it’s an excellent candidate.The project involves building detectors with different configurations and using different contact techniques. Preliminary results, shows good uniformity and low noise levels, and a linear correlation between dose rate and signal. Sensitivity, an important parameter for low radiation conditions, was extracted for photons and all the devices grants a sufficient sensitivity for radiation flow measurement ( > tens of pA) coupled with a low noise, it was also found that there’s a dependence of the sensitivity on the geometric configuration of the detector. The next step is to test the sensitivity of the detectors to different types of ionizing radiation.

Speaker: Francesca Peverini (INFN Sez. di Perugia, Perugia University)

Francesca_Peverini_iworid2023.pdf

15:00 The CIGS semiconductor detector for particle physics

The Cu(In,Ga)Se2 (CIGS) semiconductor, initially developed for solar cells, is expected to have high radiation tolerance with a recovery of radiation damage with the compensation of the defects by ions and would shed new light on the use for particle detector and camera under the high radiation environment.
In this talk, results of Xe ion irradiation will be presented.

Speaker: Manabu Togawa (High Energy Accelerator Research Organization (JP))

IWORID_20230627_mtogawa.pdf

15:20 → 15:50 Coffee Break

15:50 → 17:20 Applications: 3

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

15:50 INVITED: Monolithic Active Pixel Sensors for High-Energy Physics Applications

The CMOS Monolithic Active Pixel Sensors (MAPS) technology combines sensitive volume and front-end readout logic in the same piece of silicon. Invented in the ‘90s as an imaging device, only in the last decade MAPS achieved the radiation tolerance, power consumption and integration time which are required to equip tracking detectors for high-energy physics experiments.

The first example of MAPS-based vertex detector in a collider experiment is the STAR Heavy Flavor Tracker (HFT) [1]. It consisted of 0.16 m2 of MIMOSA series sensors (developed by the IPHC PICSEL group) arranged on two layers. The sensor implemented a rolling-shutter readout architecture and was thinned down to 50 μm to minimize the material budget. The HFT operated from 2014 to 2016 at RHIC proving the CMOS MAPS technology as suitable for high-energy physics experiments.

Following this successful experience, the CMOS MAPS technology was chosen to upgrade the Inner Tracking System (now ITS2 [2]) of the ALICE Experiment at LHC. The ALPIDE chip, based on 180 nm TowerJazz CMOS Imaging Process, was specifically developed to equip the seven ITS2 layers, covering about 10 m2 of active area. The manufacturing process of the chip, implemented on wafers with a high-resistivity epitaxial layer, provides deep p-wells, allowing for the use of full CMOS circuits in the active area. The readout architecture is hit driven, with minimal power consumption and
integration time. After a multi-year construction process which involved more than 10 institutes, the ITS2 is now fully integrated in the ALICE Experiment and included in the data-taking campaign since 2022, while other Experiments, like sPHENIX at RHIC and MPD at NICA, have adopted replicas of this detector sections for their trackers.

In the continuous effort to improve the performance of the CMOS MAPS and extend their range of applications, an aggressive R&D program has started to develop wafer-size sensors based on a stitched design, with the possibility of thinning them down to 30-40 μm to produce flexible active detectors. A first example of such a novel sensor concept is being pursued for a further upgrade of the ALICE ITS, called ITS3 [3], which is now exploring the 65 nm TPSCo CMOS Imaging Process to build a truly cylindrical ultra-thin vertex detector to be installed in 2026. The same sensor is of interest for the tracking system of the future ePIC Experiment at EIC and will represent a proof of principle for the tracking system of the ALICE 3 Experiment, which has been proposed to replace ALICE after 2034.

This contribution will outline the evolution of the CMOS MAPS technology through the experience and the lessons learned from the implementation of these MAPS-based particle detectors for high- energy physics, also providing an outlook on the plans for future applications.

[1] G. Contin, et al., NIM A 907 (2018), 60-80,
[2] F. Reidt, ALICE Collaboration, NIM A 1032 (2022), 166632
[3] G. Aglieri Rinella, ALICE Collaboration, NIM A 1049 (2023), 168018

Speaker: Giacomo Contin (Universita e INFN Trieste (IT))

MAPS_for_HEP_Contin_iWoRiD_20230626.pdf

16:20 Radiation Measurements with the Timepix based HERA Instrument on Artemis I and Biosentinel

The Artemis I mission of November 22 marks the start of the NASA Artemis program to resume lunar exploration. It launched the Orion spacecraft into cis-lunar space on November 16th 2022 for 25 days before returning to Earth December 11th. During this mission the radiation levels and particle fluxes inside the crew cabin of the (unmanned) Orion spacecraft were measure by the NASA “HERA” instrument, which uses three Timepix hybrid pixel detectors in distinct for crew monitoring and protection. In addition, a fourth Timepix based instrument, the “LETS” on the Biosentinel cubesat was also launched on Artemis I and is now in heliocentric orbit. This instrument has been continuously (at the time of writing) monitoring the deep space environment since November 2022 and is slated to run until at least December 2023.

During this flight a number of distinct and interesting radiation environment have been measured by the Timepix based instruments, including the inner (proton rich) and outer (electron rich) Van Allen belts, the quiescent free space galactic cosmic rays and in the case of Biosentinel several small energetic solar particle events.

This contribution will briefly outline the motivations for space radiation measurement, the Artemis I mission, the design of the instruments and showcase a selection of interesting results from HERA and Biosentinel. Finally it will discuss planned measurements on the future Artemis missions and the lunar surface.

Speaker: Dr Stuart George (Space Radiation Analysis Group, NASA Johnson Space Center)

16:40 COSINUS- A cryogenic NaI dark matter detector using the novel “remoTES” design.

Over the past twenty-five years, the DAMA/LIBRA experiment has observed an annual modulation signal that is consistent with a dark matter explanation. Unfortunately, in a standard halo scenario, this observation is contradicted by the null-results of numerous experiments utilizing different target materials. In order to perform a true, model-independent investigation of the DAMA/LIBRA result, a study with the same target material is required. The COSINUS (Cryogenic Observatory for SIgnatures seen in Next-generation Underground Searches) experiment, located at the Gran Sasso underground laboratory, will use NaI crystals operated as cryogenic scintillating calorimeters to cross-check the DAMA/LIBRA result. These detectors will be cooled to milli-Kelvin temperatures and provide a measurement of both the phonon and scintillation light signals via transition edge sensors (TES). This is the first cryogenic measurement of NaI detectors for a dark matter search and the dual channel capability will allow particle discrimination between electron and nuclear recoils on an event-by-event basis. However, attaching a TES directly to the surface of NaI is difficult due to the soft and hydroscopic nature of the crystal. This issue was overcome with the novel “remoTES” (Figure 1) design where the TES is attached to an external wafer crystal and connected to the crystal through a gold bond wire. In this talk we will detail the recent results and implications of the new “remoTES” detector system and present the current status of the experiment.

Speaker: Matthew Jake Stukel (Gran Sasso Science Institute)

COSINUS_A_cryogenic_NaI_dark_matter_detector_using_the_novel_“remoTES”_design..pdf

17:00 Test beam results of a fluorescence-based monitor for ultra-high dose rates

The great interest around the experimental evidence of the FLASH effect has led to an intense research activity on the development of monitoring techniques for charged beams at ultra-high dose rates. FLASH poses an unprecedented challenge since the performances of conventional detectors are usually compromised by non-linear effects due to the very high flux of particles.

The FlashDC (Flash Detector beam Counter) exploits the air fluorescence to monitor in real time the beam fluence and spatial distribution with high accuracy and minimal impact on treatment delivery. According to literature data this mechanism could provide a linear response for any charged beam and in a wide range of dose rates and energies.

Several prototypes have been developed for proof-of-principle studies. The latest results, obtained irradiating the monitor with an electron FLASH beam delivered by the ElectronFlash LINAC at CPFR (Pisa, Italy), provided strong indication that fluorescence is linearly correlated with the relevant parameters under study, in particular with the dose delivered within each micro-pulse.

In this contribution the detailed study on the expected performances will be presented together with the characterization of the readout system and preliminary test beam measurements taken at CPFR.

Speaker: Antonio Trigilio

2023-06-27 FlashDC IWORID.pdf

Wednesday, 28 June

08:30 → 10:20 Applications: 4

Convener: Seppo Nenonen

08:30 INVITED: Direct electron detectors in electron cryo-microscopy

In the last decade electron cryo-microscopy (cryoEM) has risen from relative obscurity to being one the most important techniques in structural biology. The rise of cryoEM has been made possible by the introduction of large area direct electron imaging detectors. The higher detective quantum efficiency, (DQE) possible with these is key but also important is ability to take many more images with a large field of view and to acquire these images as a series of frames with which corrections for sample motion and radiation damage dose weighting can be made.

Electron microscopes used for cryoEM are typically operated between 100 and 300 keV and as phase contrast imaging is used, electrons arrive at the detector with essentially their initial energy. The small amount of energy that is lost in passing through the sample due to inelastic scattering events rapidly destroys radiation sensitive biological samples. This limits the number of electrons that can be used to form a useful image and is the reason why the highest possible DQE is required.

Detectors for cryoEM must themselves be radiation hard and to be useful they need to be both fast and have a large field of view. Bigger and faster detectors are always desirable but even with current detectors of ~16 Mpixels that can take an image every few seconds it is possible to generate over 1 PB of data per year from a single cyroEM system.

The stochastic scattering and associated variable energy deposition of incident electrons in a sensor layer is the limiting factor in degrading the DQE of cryoEM detectors. I will discuss how this overcome and the different strategies that are needed for 100 keV and 300 keV electrons.

Speaker: Greg McMullan (MRC-LMB)

iworid_2023_mcmullan.pdf

09:00 Enhancing spatial resolution in MÖNCH detectors for electron microscopy via deep learning

Hybrid Pixel Detectors (HPDs) have been widely adopted for diffraction-based modalities in electron microscopy thanks to their high frame rates (> 1 kHz) and large dynamic range. However, they are less suitable for imaging applications because of their poor spatial resolution due to relatively large pixels (≥ 25 μm) and to the multiple scattering of high-energy electrons (> 100 keV) in the thick sensor layer. To fully realize the potential benefits of fast, radiation hard HPDs for all modalities of electron microscopy, we are developing deep learning methods to reconstruct the impact points of incident electrons for the 25 μm MÖNCH pixel detector.
We have developed several deep learning models to localize the electron impact point based on both simulations and measured data. Sub-pixel resolution has been achieved for 200 keV electrons. We will show details of the deep learning model training, evaluation results including images of some standard samples, and the data processing pipeline for the MÖNCH detector for its use in electron microscopy.

Speaker: Xiangyu Xie (Paul Scherrer Institut)

Enhancing spatial resolution in MÖNCH detectors for EM via deep learning.pptx

09:20 Development of the grade selection of X-ray events using machine learning for a CubeSat application

X-ray observation covering a wide field of view with a high sensitivity is essential in searching for an electromagnetic counterpart of gravitational wave events. A combination of Lobster-eye optics (LEO) and a large-area CMOS sensor is an ideal instrument to achieve this goal. Furthermore, thanks to the light weight of LEO, it can be installed on a small platform such as a CubeSat.
SEAGULL is a future 3U CubeSat mission for searching the electromagnetic counterpart of gravitational waves in the soft X-ray band (0.4 ~ 4 keV) [1]. As the X-ray detector in the SEAGULL, a back-illuminated CMOS image sensor, GSENSE4040BSI, with 4096×4096 pixels fabricated by Gpixel Inc is a good candidate. We conducted an experiment for the spectroscopic performance, and the X-ray lines of Mn-Kα (5.9 keV) and Mn-Kβ (6.4 keV) were clearly detected.
However, the real-time identification of X-ray events is challenging with restricted resources. Therefore, we use one of the machine learning models for a convolutional neural network (CNN) to extract X-ray events in the image taken from a CMOS sensor. Moreover, we use a Sony microcontroller board, Spresense, that provides ultra-low power consumption and supports machine learning libraries for the process. This paper introduces our machine learning-based X-ray event selection process that is targeted for use on a CubeSat.

Speaker: Hsien-Chieh Shen (Aoyama Gakuin University)

iworid2023_HS.pdf

09:40 Speckle-based imaging (SBI) applications with spectral photon counting detectors at the newly established OPTIMATO (OPtimal IMAging and TOmography) lab

Speckle-based imaging (SBI) is an advanced X-ray technique that enables measuring phase and dark-field signals in addition to conventionally accessible absorption signals [1]. SBI uses random modulators such as sandpapers that, placed at a proper propagation distance from the detector, produce a reference speckle pattern. The technique requires the acquisition of two images; the first with the speckle pattern alone (reference image) and the second after introducing the sample in the beam (sample image). If compared to the reference image, the speckle pattern in the sample image is modulated in terms of reduction of intensity (transmission signal), lateral displacement (refraction), and blurring (dark-field signal). SBI reconstruction algorithms operate by comparing the reference and sample images to retrieve the three signals (transmission, refraction, dark-field). Among the existing algorithms for SBI, the Unified Modulated Pattern Analysis (UMPA) algorithm provides a fast solution for SBI image reconstruction [2].
Though an ideal setup for SBI requires a coherent source, such as a synchrotron beamline, SBI can easily be adapted to laboratory facilities with (quasi-coherent) micro-focus X-ray sources. The main advantage of SBI over other techniques, such as grating-based imaging and edge illumination, is the possibility to use cheap modulators such as silicon carbide sandpapers, although at the cost of reduced visibility of the reference pattern. To obtain optimal results in SBI, it is crucial to ensure the visibility of speckles. This is typically achieved through low-energy photons (<20/30 keV), which maximize the contrast of the speckles, and high statistics so that the variations of speckles intensities dominate over the Poissonian noise. These conditions are not always reproducible with compact X-ray sources. In this context, direct-detection CdTe X-ray photon counting detectors (XPCD) provide an attractive solution for SBI, featuring multiple advantages compared to widespread indirect charge-integrating flat-panel detectors. First, direct conversion with thick (>0.5mm) CdTe sensors allow for both high detection efficiency (up to 100 keV) and optimal spatial resolution. Second, the photon counting architecture counts each photon regardless of its energy. This leads to better speckle visibility in SBI compared to an ideal charge-integrating detector that, integrating the charge from all photons, weighs high-energy photons more than low-energy ones. Finally, by implementing one or more energy thresholds, XPCDs enable spectral capabilities, thus allowing a deeper characterization of the energy-dependent absorption, dark-field, and phase signals.
This work will present a newly established X-ray setup at the OPTIMATO lab hosted at the Elettra synchrotron (Italy), and discuss the main advantages of XPCDs in SBI applications. The lab, implemented in the framework of the S-BaXIT (Scattering-Based X-ray Imaging and Tomography) project, is equipped with a micro focal, high-brilliance liquid-metal-jet X-ray source (MetalJet D2+, Excillum, Sweden), featuring maximum acceleration voltage160 kV, power of 250 W, and adjustable focal spot sizes (>15 μm). The source can emit photons on two opposite sides, allowing the implementation of two semi-independent imaging branches. The experimental setup is assembled in a 7×2.5 m lead-shielded hutch. The first branch uses two coupled optical tables (2×0.8 m each), resulting in a maximum source-detector distance (SDD) of 4 m (‘long branch’); the other uses a single table, allowing a maximum SDD of 2 m (‘short branch’). The long branch, dedicated to SBI applications and micro-CT with a maximum achievable resolution of 15 μm, is equipped with two detectors. The first is the LAMBDA 350k (X-Spectrum, Germany), an XPCD made by 3×2 Medipix3 chips bump-bonded with a single 1 mm thick CdTe sensor. This detector has an active area of 28×42 mm2 (512×768 px) with 55 μm pixel pitch. The second detector is a charge-integrating flat-panel detector (Varex imaging’s 1512 CMOS camera) with a 200 μm thick micro columnar CsI scintillator, featuring an effective area of 145×115 mm with a pixel pitch of 74.8 μm. On the long branch, samples can be mounted on a Meca500 robotic arm (Mecademic Robotics, Canada) with 5 μm repeatability. With 6 degrees of freedom (3 of translation, 3 of rotation), the robotic arm serves both for translations and tomographic acquisitions. The short branch, under development, will be devoted to imaging at resolutions of up to 1 μm. On both branches, modulators can be mounted onto a motorized translation stage (Newport 2×MFA-CC).
Images were acquired under identical conditions with both detectors available in the long branch to assess the potentials of XPCDs compared to flat-panels for SBI applications. The sample was a test object consisting of a row of three cuvettes (one filled with water), an aluminum rod, and a toothpick. The source-detector and source-sample distances were set to 300 cm and 150 cm. The source was operated at 60 kV and 4 mA with no additional filtration. Reference and sample images were collected at 20 different diffuser positions. The total exposure time for each image was 30 s for both detectors. As a first result, the visibility (usually defined as (Imax-Imin)/(Imax+Imin), with I the intensities in the speckle images) obtained with the XPCD is four times higher than the one obtained with the flat panel. Figure 1 shows how the XPCD outperforms the flat panel in terms of image resolution and contrast, especially for the dark-field and the differential-phase images, where optimal detected visibility is crucial for the convergence of SBI algorithms. The potential of the spectral weighting approach via multi-threshold acquisitions with XPCDs will be discussed.

Speaker: Vittorio Di Trapani (University of Trieste, Department of Physics)

Speckle-based imaging (SBI) applications with spectral photon counting detectors at the newly established OPTIMATO (OPTimal IMAging and TOmography) lab.pdf

Speckle-based imaging (SBI) applications with spectral photon counting detectors at the newly established OPTIMATO (OPTimal IMAging and TOmography) lab.pptx

10:00 Real-time Autoradiography on Environmental Samples with a Parallel Ionization Multiplier Gaseous Detector

Autoradiography, an imaging technique providing high resolution two-dimensional images of radioactive emissions, serves as a critical tool in the detection and monitoring of radioactivity from various samples (e.g., radiopharmaceutical, geological, environmental, etc.). For example, during the Fukushima Daiichi Nuclear Power Plant accident, phosphor screen autoradiography was employed to locate and isolate radioactive particles from air filters and regional soil [1,2]. However, this current technique is laborious, prone to error (trial and error must be used for optimal measurements), and does not provide spectrometry data. As an improvement from phosphor screen autoradiography, we propose the use of a micro-pattern gas detector (MPGD) incorporating a parallel ionization multiplier [3] to perform real-time autoradiography in environmental samples.

Real-time autoradiography with a MPGD can provide an advancement in monitoring and detection of radioactivity in complex environmental samples. With its high sensitivity (0.0005 cpm/mm$^{2}$) and activity detection range (over 5 order of magnitudes), a MPGD is advantageous in differentiating hotspots from a sample with heterogeneously distributed radioactivity. In addition, a MPGD can provide potential identification of different alpha- and beta-emitting radionuclides via spectrometry. However, this technique requires ground-truthing to ensure sensible and reliable analysis of environmental samples. In this contribution, we explore the application of a MPGD in real-time autoradiography of environmental samples in terms of the spatial resolution, sample preparation, minimum detectable activity, spectrometric capabilities, and artefact contributions. Utilizing the results from Monte Carlo simulation with a GEANT4 toolkit and experimental data from the detector (when measuring radioactive Cs-134, Cs-137, and low enriched uranium), we demonstrate that real-time autoradiography using a MPGD can reliably provide results with good reproducibility.

[1] K Adachi et al., Sci. Rep. 3 (2013), 2554
[2] R Ikehara et al., Environ. Sci. Technol. 52 (2018), 6390–6398
[3] J Donnard et al., Nucl. Instrum. Methods Phys. Res., Sect. A 610 (2009), 158–160

Speaker: Joyce W. L. Ang (University of Helsinki)

2023-June-28_iWoRiD_JA.pptx

10:20 → 10:50 Coffee Break

10:50 → 12:40 Sensors: 2

Convener: Angela Kok

10:50 INVITED: Monolith - picosecond time stamping capabilities in fully monolithic highly granular silicon pixel detectors

The Horizon 2020 MONOLITH ERC Advanced project aims at producing a monolithic silicon pixel ASIC with 50μm pixel pitch and picosecond-level time stamping. The two main ingredients of the project are fast and low-noise SiGe BiCMOS electronics and a novel sensor concept, the Picosecond Avalanche Detector (PicoAD). The PicoAD uses a patented [1] multi-PN junction to engineer the electric field and produce a continuous gain layer deep in the sensor depleted volume. The result is an ultra-fast current signal with low intrinsic jitter in a full fill factor and highly granular monolithic detector.

A proof-of-concept PicoAD monolithic prototype was produced in the SG13G2 130nm process of IHP. It contains a matrix of hexagonal pixels with 100 μm pitch. Laboratory measurements with a 55Fe X-ray
source showed that the sensor displays avalanche gain up to a maximum electron gain of 23, although a study of the avalanche characteristics, corroborated by TCAD simulations, indicates that space-charge effects due to the large primary charge produced by the conversion of X-rays from the 55Fe source limits the effective gain [2].

The proof-of-concept ASIC was tested [3] with a beam of 180 GeV pions at the CERN SPS. At a sensor bias voltage of 125 V, the detector provides full efficiency and average time resolution of 30, 25 and 17 ps in the overall pixel area for a power consumption of 0.4, 0.9 and 2.7 W/cm2, respectively. In this first prototype the time resolution depends significantly on the distance from the center of the pixel, varying at the highest power consumption measured between 13 ps at the center of the pixel and 25 ps in the inter-pixel region.

A second monolithic prototype with improved electronics, for the moment produced on a 350Ωcm substrate without internal gain layer, provides full efficiency and 20 ps time resolution. As shown in Figure 1, this second prototype shows less dependency of the time resolution on the position within the pixel [4]. Special PicoAD wafers, including different junction depths and several gain-layer implants, have been produced. Monolithic matrices containing the new and improved electronics using these wafers are in production.

[1] G. Iacobucci, L. Paolozzi and P. Valerio, Multi-junction pico-avalanche detector, 19/11/2018, EU patent EP3654376A1 and US patent US2021280734A1.
[2] L. Paolozzi et al., Journal of Instrumentation 17 (2022) P10032.
[3] G. Iacobucci et al., Journal of Instrumentation 17 (2022) P10040.
[4] S. Zambito et al., Journal of Instrumentation 18 (2023) P103047.

This research is supported by the H2020 MONOLITH project, ERC Advanced Grant ID: 884447. The authors acknowledge the support of EUROPRACTICE in providing design tools and MPW fabrication services.

Speaker: Giuseppe Iacobucci (Universite de Geneve (CH))

230628_iWoRiD_Oslo_iacobucci-no animations.pdf

11:20 Characterization of SiC Timepix3 Detector and Spectral-Tracking Response to Protons and Mono-Energetic Fast Neutrons

The semiconductor pixel detectors of the Timepix family provide position-, time- and directional-sensitive spectrometry for high-resolution wide-range spectral tracking of single particles [1]. These properties are valuable also for inspection and as testing probe of properties and homogeneity of radiation response and charge collection of the semiconductor sensor. The hybrid architecture of the Timepix family of detectors enables the use of different semiconductor sensors most commonly silicon or also high-density materials such as CdTe and GaAs. Newly radiation hard materials are being investigated, such as SiC [2], which offer large displacement energy, large band gap, and can operate at elevated temperatures up to several hundreds of degrees Celsius. As a result, this sensor material is more suitable for radiation harsh environments compared to traditionally available Si sensors. In this work we use two newly developed SiC sensors operated at 200V bias with depleted depth of 65 µm out of 80 µm thick epitaxial layer [2] which are bump-bonded to the Timepix3 ASIC chip. The detector is operated and readout in the compact radiation camera MiniPIX Timepix3 [3]. We performed measurements with proton beams at 13, 20 and 31 MeV at the U-120M cyclotron at NPI CAS Rez near Prague and at 100 and 226 MeV at the Proton Therapy Center Prague. In addition, the response of the SiC Timepix3 detector to fast neutrons was also studied. Measurements were carried out with mono-energetic fast neutrons at selected energies in the range 400 keV to 16 MeV at the Van de Graaff accelerator at the IEAP CTU Prague. The detection of protons and neutrons of selected energies by the SiC Timepix3 MiniPIX detector is shown in Fig. 1. High-resolution pattern recognition analysis and spectral tracking of single particles serve as a probe for inspection and detailed understanding of the SiC sensor signal and charge collection response, homogeneity. The goal is to use the device as a particle tracker for composition and spectral characterization [4] of different radiation fields. Distributions of deposited energy, linear-energy transfer spectra (LET) and selected cluster-track parameters are shown in Fig. 2 for data from selected experiments. Results will be presented including energy resolution, neutron detection efficiency and comparison with other sensors (Si, CdTe, GaAs).

[1] C Granja et al., NIM-A 908 (2018), 60-71
[2] B. Zatko et al., JINST 17 (2022) C12005
[3] C. Granja, et al., JINST 17 (2022) C03019
[4] A. Novak et al., JINST 18 (2023) C01022

Work in Advacam was performed in frame of Contract No. 40001250020/18/NL/GLC/hh from the European Space Agency. Work at STUBA was supported by the Slovak Research and Development Agency grant APVV-18-0273.

Speaker: Andrej Novák (Slovak University of Technology in Bratislava)

IWORID_2023_Novak_SiC.pdf

IWORID_2023_Novak_SiC.pptx

11:40 Chromium compensated gallium arsenide sensors evaluation using Timepix1, Timepix3, Medipix3 and Timepix2 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 [1]. These advantages result in a fast charge collection, good absorption efficiency up to 50 keV and a better uniformity compared to Cd(Zn)Te. Applications for the GaAs are foreseen in medical, mammography, small animal imaging, electron microscopy, synchrotrons, XFELs and non-destructive testing of composite materials.

High-quality GaAs wafers grown with vertical gradient freeze (VGF) and liquid encapsulated Czochralski (LEC) methods are widely available on market, which makes attractive the adaptation of silicon processing technology for the large-scale production of GaAs detectors. The problem of intensive
carrier trapping in commercial semi-insulating GaAs has been solved by the application of GaAs material compensated by post-growth doping with chromium [2].

In frame of Eurostar GoNDT project [3], Advacam has developed radiation detectors by chromium compensation of commercially available 3” n-type 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 500 um thick GaAs using sensor designs compatible with Timepix/Medipix family readout ASICs. Individual diced sensors were flip chip bonded to Timepix1 [4], Timepix2 [5], Timepix3 [6] and Medipix3 [7] ASICs using conventional SnPb or InSn low temperature solder bumps. Assemblies were evaluated to study the optimal sensor design and bias voltage; uniformity; sensor stability; energy resolution; Modulation Transfer Function (MTF) and high X-ray flux operation.

Presentation summarises the GaAs performance results received from the contributing authors. It presents analytical comparisons to the other commercially available GaAs sensor material in terms of uniformity and spectral resolution. The Advacam’s GaAs presents better uniformity and similar or better energy resolution.

The presentation includes the first high photon flux open beam results up to 160 Mcnt/s/mm2, where small part of the sensor shows recoverable polarisation effect.

Finally, the presentation covers the future development work and gives an outlook to the GaAs radiation detector applications.

Speaker: Dr Juha Kalliopuska (Advacam Oy)

GaAs Kalliopuska Iworid 28062023-pdf.pdf

12:00 Development of TlBr hybrid pixel detector combined with Tl electrode sensor and photon counting ASIC

The hybrid pixel detectors are powerful technologies for the radiation imaging. Sensors and ASICs can be improved for performance in the individual processes. In particular, photon counting ASICs are revolutionizing various applications. We developed a cadmium telluride (CdTe) pixel detector (WERPAD: Wide Energy Range Pixel Array Detector). Dual energy and energy dispersive X-ray diffractions could be achieved at the synchrotron radiation facility of SPring-8. In this scientific work, we have been studying thallium bromide (TlBr) pixel detectors combined with the WERPAD ASIC for further performance improvement.
TlBr is a promising compound semiconductor material for high energy X-ray and gamma ray detections. It has higher photon stopping power than CdTe because of the atomic numbers (Tl: 81 and Br: 35) and the high density (7.56 g/cm3). Owing to its wide band-gap energy of 2.68 eV, TlBr crystals exhibit a high resistivity of 10^10 – 10^11 Ω cm. We have investigated Tl/TlBr/Tl configuration. The Tl electrodes realized an excellent energy resolution (< 2% @ 662 keV) and stable operation at room temperature (25 degrees Celsius) in overcoming the polarization problem.
The WERPAD ASIC has a preamplifier, a shaper, 3-level window-type comparators, a 24-bits counter in the pixel size of 200 μm and 95 × 100 pixels in the full size chip. We have investigated a prototype sensor by using a high resistivity TlBr single crystal of 5 × 5 mm2 in the electrode sides and 2 mm in thickness. The sensor was bump-bonded with the test purpose WERPAD ASIC (20 × 100 pixels). 137Cs gamma-ray images have been stably measured at room temperature, successfully. In this workshop we will describe the detail performances of this prototype detector and future prospects for synchrotron radiation and medical applications.

Speaker: Dr Hidenori Toyokawa (Japan Synchrotron Radiation Research Institute)

iworid2023_toyokawa.pdf

iworid2023_toyokawa.pptx

12:20 INDet: Lessons Learnt from Boron-coated 3-D Silicon Detector Production

Due to their lack of charge, low-energy neutrons are not detectable in typical semiconductors often applied to radiation detection, and instead detectors use expensive or dangerous gases (e.g., 3He, BF3) in bulky, immobile devices. Using a neutron-sensitive material however, silicon can be used to indirectly observe neutrons via detection of decay products. The INDet (Improved efficiency for Neutron DETection) project used deep reactive ion etching to produce a 3-D surface on silicon which was subsequently coated with boron carbide via chemical vapour deposition (CVD). By making use of the $^{10}$B(n, $^{11}$B*) capture reaction, the spontaneous fission of the excited 11B nucleus into two charged decay products (α and $^{7}$Li) can be used as a signature for a neutron event by detecting either product in the silicon.

3-D neutron detectors have been created previously, but performance has been limited due to lack of optimisation in the microstructures, thick inactive layers at the silicon-converter interface, and non-conformal deposition of the neutron converter. INDet aimed to overcome these issues using atomic layer deposition of an aluminium oxide passivation layer, a new CVD process, and shape optimisation. Various geometries, with different structure shape, size, depth and pitch, were produced and tested, with these dimensions optimised using the NCrystal library with the Geant4 framework.

Several challenges have been uncovered during the production phase of the INDet project. In particular, the CVD process takes place at a high temperature of over 400 ̊C in a relatively dirty environment, affecting the properties of the silicon and charge collection. Simulations have attempted to reproduce the observed spectra from PSI, Switzerland, which lack clear peaks from heavy particles.

Initial tests at PSI led to some changes in production, with several sensors created using sputtered B$_{4}$C deposition. These were tested in-beam at BNC, Hungary, and show promising early results seen in figure 1. Multiple angle measurements have been taken at this facility, and the effect of incident angle on neutron detection will be shown.

This presentation will discuss the neutron detection efficiency and results from characterisation. This will focus on the outcome of tests at neutron facilities, lessons learnt from the manufacture process, and prospects for future development with these devices, within the context of existing work done using coated silicon sensors for neutron detection. These outcomes will be contrasted with the expected performance, presented at the 23$^{rd}$ International Workshop on Radiation Imaging Detectors.

Speaker: Dr George O'Neill

iWoRiD23_1033.pdf

iWoRiD23_1033.pptx

12:40 → 13:30 Lunch Break

13:30 → 15:00 Front-end Electronics and Readout: 2

Convener: Jiaguo Zhang (Paul Scherrer Institut)

13:30 INVITED: Challenging the limits of detection technology to overcome society’s most important challenges

DECTRIS Ltd. was founded as a spin-off of Paul Scherrer Institut in 2006. At this time synchrotron and laboratory X-ray science were severely detector limited. The noise-free, high frame and count-rate performance of Hybrid Photon Counting (HPC) detectors not only overcame these limitations but has transformed X-ray science. In combination with an ever-increasing source brightness, improved optics, accurate and fast goniometry as well as novel software operating on fast computers, it enabled innovative applications such as in-situ and operando studies of real-life functional and materials and devices [1]. In 2016, inspired by the resolution revolution in single particle cryo-electron microscopy, largely driven by a new generation of MAPS detector [2], DECTRIS started the development of dedicated Hybrid Counting detectors for electrons.

The presentation will give an overview of development of the company from a spin-off to a successful SME (small & medium sized enterprise). The current detector family EIGER2 and its applications in high energy, high-resolution protein crystallography as well as operando studies will be discussed. The advantage of the use of fast, noise-free, high dynamic range detectors in electron microscopy will be illustrated with experimental results in EELS [3, 4], 3D electron diffraction [5] and cryo-electron microscopy [6]. Scanning transmission electron microscopy (STEM) is widely used for imaging, diffraction, and spectroscopy of materials down to atomic resolution. The ARINA detector is based on a new ASIC [7] custom developed to exploit the potential of 4D scanning transmission electron microscopy (4D STEM) in material and life sciences. First, promising experimental results demonstrate the advantages of recording the full scattering pattern at acquisition speeds and doses similar to conventional STEM imaging [8]. The presentation will conclude with an outlook on future detector.

[1] A Vamvakeros et al., NATURE COMMUNICATIONS | (2018) 9:4751
[2] W. Kühlbrandt, Science 343, (2014) 1443.
[3] B. Plotkin-Swing et al., Ultramicroscopy 217, (2020), 113067
[4] A.R. Ruiz Caridad et al., Micron 170, (2022), 103331
[5] P.B. Klar et al., bioRxiv preprint https://doi.org/10.1101/2022.09.15.507960
[6] Ch. Russo et al., in preparation, (2023)
[7] P. Zambon et al., Nuclear Inst. and Methods in Physics Research, A 1048 (2023) 167888
[8] D.G. Stroppa et al., Microscopy Today, Volume 31, Issue 2, 1, (2023) 10

Speaker: Clemens Schulze-Briese (D)

2023IWoRID_DECTRIS_CleS.pdf

2023IWoRID_DECTRIS_CleS.pptx

14:00 ePixUHR-35kHz: a read-out ASIC for tender X-ray imaging at LCLS-II with 35 kHz frame-rate

The ePixUHR-35kHz is a novel Application Specific Integrated Circuit (ASIC) developed at the SLAC National Accelerator Laboratory to meet the demanding requirements of the Linac Coherent Light Source II (LCLS-II) X-ray laser facility. The ASIC consists of an array of pixels with a pitch of 100 µm, organized into clusters of 72 pixels each. Each cluster includes a Successive Approximation Register (SAR) Analog-to-Digital Converter (ADC) operating at 8 MSPS, with digital logic to synchronize the analog and digital sections. By distributing 448 ADCs throughout the pixel array and pipelining the integration and conversion processes, the ePixUHR-35kHz achieves high frame-rates. The pixel front-end incorporates an automatic gain-switching charge integrating amplifier in each pixel, extending the dynamic range up to 104/photons/pixels/frame.

In the first prototype of the ASIC, the full-frame readout speed is constrained to 35 kHz due to the limited bandwidth of Low-Voltage Differential Signaling (total data throughput is 16 Gb/s). However, the pixel front-end and the ADCs have been designed to achieve up to a frame-rate of 100 kHz, which is the goal of the next development phase. A Region-of-Interest (ROI) logic enables characterization of such blocks at the maximum frame-rate.

ePixUHR-35kHz has been designed on a 130 nm CMOS technology and the first full-reticle size prototype with a matrix size of 192×168 pixels has been fabricated. In this presentation, we will discuss the design of the various blocks and the overall ASIC architecture. Testing of the ASIC has started in April and preliminary characterization results will be discussed. ePixUHR-35kHz represents a first significant milestone towards the development of the next generation of full-frame readout X-ray detectors for
LCLS-II.

Speaker: Lorenzo Rota

Lorenzo_Rota_ePixUHR.pdf

Lorenzo_Rota_ePixUHR.pptx

14:20 Balancing gain and dynamic range in a 25 μm pitch hybrid pixel detector

MÖNCH is a hybrid pixel detector featuring 25 μm pixel pitch and analogue readout for X-ray imaging at synchrotron radiation (SR) facilities. Sub-pixel spatial resolution has been demonstrated using charge sharing and interpolation algorithms [1]. The current prototype version, MÖNCH0.4, features 19 different pixel architectures to assess the design choices and components for an optimised architecture to be used at SR facilities, and to explore the potential use of dynamic gain switching in fine pitch pixels for applications at X-ray free electron lasers (XFELs).

Previous characterisation results of the pixel architectures without dynamic gain switching have shown noise levels as low as 21.7 e$^{-}$ r.m.s. [2], which have now been pushed to sub-20 e$^{-}$ r.m.s at room temperature using standard 300 μm-thick silicon sensors. Achieving low noise values however requires high conversion gain and necessitates design choices such as the simplification of the pixel architecture (e.g. by limiting the available choice of in-pixel gains). These compromises ultimately restrain the available dynamic range and prevent the use of MÖNCH with LGADs [3] or high-Z sensors because of the large signals (internal amplification and high photon energies, respectively) and of large leakage currents.

In this presentation, we will introduce the MÖNCH project followed by a description of the current prototype along with characterisation results of the pixel architectures without dynamic gain switching for synchrotron applications with an emphasis on noise and dynamic range. These experimental results will be used to fine-tune the design of MÖNCH0.5 to validate the final pixel design. This small prototype should also include additional features from the continuous developments of the PSD detector group towards a full-scale 2 × 3 cm$^{2}$ MÖNCH1.0.

[1] A. Bergamaschi et al., Synchrotron Radiation News 31:6 (2018), 11‐15
[2] J. Heymes et al., Poster presented at: 23 rd iWoRiD. 27 June 2022; Riva del Garda (IT)
[3] J. Zhang et al., JINST 17 C11011 (2022)

Speaker: Dr Julian Heymes (Paul Scherrer Institut)

Julian_Heymes-iWoRiD2023-Balancing_gain_and_dynamic_range_in_a_25_um_pitch_hybrid_pixel_detector.pptx

14:40 An Analog Neural Network ASIC for Image Reconstruction Embedded in Detectors

Two key emerging trends in sensors and detectors are: (1) the application of machine learning (ML) to data processing and (2) the migration of processing from the back-end towards the front-end. Embedded processing allows to reduce the amount of data transmitted (both in terms of data rate and interconnection lines), with evident advantages also in the field of high-count-rate, densely pixelated radiation detectors, especially for imaging applications, such as emission tomography (PET and SPECT, especially with large fields of view) for both diagnostics and monitoring of particle therapy [1].
Within this context, we present an analog ASIC, implementing in charge domain neural networks (NN) with the multilayer perception architecture. Differently from traditional digital implementations of ML based on embedded devices such as microcontrollers, dedicated accelerators or FPGA, this analog CMOS ASIC is realized in the same microelectronic technology of the analog front-end of radiation detectors and, thus, a full monolithic integration of these blocks is envisioned (Fig. 1). We consider, in particular, the problem of estimating the planar scintillation coordinates (x,y) of a gamma ray in a crystal read by bottom tiles of SiPM. However, any other type of signal processing leveraging NNs, such as the estimation of energy and timing of detected events [2] or the correction of charge sharing, for instance in CZT detectors [3], could be addressed by this ASIC.
As shown in Fig. 2, each neuron consists of a charge integrator summing the charge provided by the previous layer of neurons. The weight is obtained with a programmable capacitance (made of a bank of N switched capacitors) multiplied by the neuron voltage. As activation function, the integrator implements a ReLU. We have selected a NN with 64 input nodes, two inner layers of 20 neurons each and two output neurons for inference of x and y. The 64 input voltages represent the outputs of the front-end: the peak energy sampled for the individual currents of the SiPMs in the Anger camera by a multichannel ASIC such as GAMMA [4]. The ASIC implementing this architecture is under design and its circuit details (and full ASIC Cadence simulations) will be presented at the conference. We expect the first ASIC prototype (fabricated in 0.35 μm node) to fit in an area below 10 mm2 and solve the NN in 4.6 μs (with a clock period of 100 ns) with a power dissipation of 14 mW (1.8 TOPS/W).
At the same time, the NN has been trained on both simulated and experimental data for monolithic gamma-ray detectors based on arrays of 64 SiPMs for both PET and SPECT. Here we report the reconstruction performance of this NN on an experimental dataset collected with a state-of-the-art monolithic PET detector made of a 32 mm  32 mm  22 mm LYSO:Ce scintillator read by 64 SiPMs [5]. The comparison of the proposed NN (both for an ideal and quantized case with N = 5 bits) with respect to a k-nearest neighbour (kNN [5]) is shown in Fig. 3: the spatial resolution, measured with different metrics, is similar, with a potentially relevant advantage in terms of computational effort.

Speaker: Marco Carminati

Carminati Analog NN ASIC IWORID 2023.pdf

15:00 → 15:30 Coffee Break

15:30 → 16:40 Detector Systems: 3

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

15:30 INVITED: Instrumentation for FLASH Radiotherapy

Text BoxFLASH radiotherapy (RT) is attracting a significant interest since the first investigations carried out in 2014 [1]. Several preclinical studies worldwide have demonstrated that ultra-high dose rate (UHDR) beams produce an improvement of normal tissue sparing, compared to conventional dose-rate RT, while maintaining same tumor control probability (FLASH effect). However, to fully understand the mechanisms behind the effect and to support the future clinical translation of FLASH radiotherapy, novel beam monitoring and dosimetry technologies must be developed, and new approaches studied [2]. Currently used detectors for reference dosimetry for conventional radiotherapy, such as ionization chambers, saturate at these extreme regimes, therefore the optimization of already established technologies as well as the investigation of new instrumentation for dosimetry are required [3]. Alternative approaches, such as calorimetry or the use of solid state detectors are currently being studied and their usage at UHDRs is under assessment. The challenges characterizing dosimetry for FLASH radiotherapy vary considerably depending on the accelerator type and technique used to produce the relevant UHDR radiation environment. Different beam pulse structures can be used for the acceleration of the radiation beams, depending on the specific accelerator, and the related dose and dose-rate per pulse can affect the detector response. A reliable measurement also of the instantaneous dose rate, beyond an accurate measurement of the dose, are relevant at these extreme regimes. The main challenges coming from the peculiar beam parameters characterizing UHDR beams for FLASH RT will be discussed. A status of the current technology will be provided, including recent developments for established detectors and novel approaches currently under investigation with a view to predict future directions in terms of dosimetric approaches and practical procedures for the clinical translation of FLASH RT.
[1] V. Favaudon et al., Science Translational Medicine, 6(245), 245ra93 (2014).
[2] F. Romano et al., Medical Physics, 49:4912-4932. (2022), doi: https://doi.org/10.1002/mp.15649
[3] M. McManus M., SCIENTIFIC REPORTS, vol. 10, ISSN: 2045-2322 (2020).

Speaker: Francesco Romano

iWoRiD2023 - Francesco Romano.pdf

16:00 Photon Induced Scintillation Amplifier - The PISA Concept

Research at the frontier of particle physics often requires the search for phenomena of extremely low probability of occurrence, known as "rare events". One such search is for the hypothetical particles that may compose the mysterious dark matter (DM) of the Universe, such as Weakly Interacting Massive Particles (WIMPs) or axions. These low-energy events with faint probability of occurrence are buried under high levels of background events from environmental radiation, posing significant challenges for detection.

Currently, there are ongoing efforts worldwide to directly detect DM in terrestrial particle detectors using dual-phase gas/liquid xenon or argon. Xenon has emerged as a promising detection medium due to its high liquid density and moderate price, making it scalable for next-generation multi-ton experiments. However, the current generation of noble liquid DM detectors is limited by the radioactivity from the detector materials, particularly the photomultiplier tubes (PMTs) used for photon detection, which contribute to the background at approximately 80% level. PMTs also have limitations such as less than full active photocathode area and high cost per unit of area.

To address these challenges, we propose a simple concept as a new photosensor, called the Photon Induced Scintillation Amplifier (PISA) for photoelectron signal amplification in Gas Photomultipliers (GPMs). In PISA, the secondary scintillation produced in the charge avalanches that occur inside the holes of solely one micropattern electron multiplier is read out by silicon photomultipliers (SiPMs), instead of using a multi-element stack of micropattern electron multipliers.

We have shown that a large number of photons are produced in micropattern electron multipliers, enabling the use of a single microstructure. One electron may produce about 10^5 and 10^4 photons in the charge avalanches in xenon and argon, respectively. A Micro-Hole and Strip Plate (MHSP), etched on Kapton for radiopurity, can be used instead of the traditional GEM/THGEM, as it presents higher photon output. The large photon output in the final charge avalanche ensures single-photon sensitivity.

The PISA concept has several advantages, including improved radiopurity, as the materials used for the MHSP can be obtained with reduced radioactivity levels. It also allows for the deployment of remote "hot" electronics, as the high gains achieved in the SiPMs enable signal transmission over large distances without significant degradation. Moreover, the PISA is cost-effective compared to vacuum PMTs and allows for area coverage above 80%, maximizing photon detection efficiency.
PISA is also an alternative to read out the gas scintillation of Xe and Ar directly with SiPMs, because the area coverage can be less than 10% compared to the over 80% coverage when only SiMs are used, implying a much less number of SiPMs needed when the PISA is used.

In this presentation, we will provide detailed information on the PISA concept and present experimental results obtained with a first prototype equipped with a GEM or a MHSP, including the total number of scintillation photons produced in the charge avalanches and the number of photons per avalanche electron. The PISA concept represents a breakthrough in photon detection technology for low background Dark Matter detectors, with potential implications for the field of particle physics and our understanding of the nature of the Dark Universe.

Speaker: Dr Cristina M. Bernardes Monteiro (LIBPhys, Department of Physics, University of Coimbra, Portugal)

16:20 Progress with CdTe and high-flux CdZnTe XIDER detector prototypes

This work provides an update on the XIDER project, a study aimed at developing a 2D X-ray charge integrating hybrid pixel detector designed to operate with high-Z semiconductor sensors by implementing the incremental digital integration readout. The XIDER front-end chips are designed in 65 nm CMOS technology with a pixel pitch of 100 µm. Each pixel includes a charge integrator and a digitiser capable of sub-microsecond analog-to-digital conversion, as well as logic and built-in digital memory.
The XIDER front-end deals with very high photon fluxes of up to 10^9 photons per second and pixel, operating with either continuous or pulsed X-ray beams with a rate of up to 5.6 MHz, the ESRF pulse repetition frequency in 16-bunch filling mode. The performance of XIDER prototypes has been evaluated with pulsed LED illumination in the laboratory and with both continuous and pulsed X-ray synchrotron beams at ESRF beamlines under different operating conditions.

Speaker: Pablo Fajardo

2023.06.28_XIDER_iWoRiD-2023.pdf

16:40 → 18:10 Poster (incl. coffee)

Conveners: Ketil Roeed (University of Oslo (NO)), Dr Marco Povoli (SINTEF MiNaLab)

16:40 P2.1: GEANT4 simulation study of low-Z material identification using muon tomography

Traditional X-ray scanning systems for cargo use ionising radiation which can be harmful to operators and the environment and requires shielding. Fully passive muon tomography is a promising alternative or a complementary approach to X-ray scanners. Muon tomography is a non-invasive technique that uses naturally occurring cosmic-ray muons and their scattering in various materials to create images of cargo in trucks or containers without applying ionising radiation. Muons are high-energy particles that are produced when primary cosmic rays collide with the Earth's atmosphere. These muons can penetrate through thick materials, such as concrete or metal, and are therefore useful for detecting hidden objects, including contraband. Muon tomography is expected to be used for detection of a wide range of materials, including metals, plastics, and organic materials like drugs or cigarettes, as well as weapons and explosives. In this work we have used the GEANT4 toolkit to simulate the performance of muon tomography in identifying the contraband cigarettes hidden inside the legal low-Z materials in a truck trailer. We have used the Point of Closest Approach (PoCA) reconstruction algorithm to reconstruct the three-dimensional image of a loaded truck. As an example we have considered cigarettes hidden among wood pellets, plasterboards and wood planks. In all investigated scenarios cigarettes were detected and localised. We have applied CRY and MUSIBO muon generators to sample cosmic-ray muons at the surface of the Earth. The CRY software package generates muons on a horizontal plane while MUSIBO, based on a well-known Gaisser’s parameterisation of the muon spectrum and angular distribution, modified to account for muon decay and Earth surface curvature, generates muons on the surfaces of a box (rectangular parallelepiped) which is more appropriate for simulation of inclined muons. This simulation study using GEANT4 and relatively simple but reliable PoCA reconstruction algorithm demonstrates the potential of muon tomography for detecting hidden materials in cargo. We conclude that muon tomography is capable of producing detailed images of various objects and can become a powerful tool for detecting contraband cigarettes and other goods in a non-invasive and harmless way.

Speaker: Anzori Georgadze (Institute of Physics, University of Tartu)

IWORID2023_GEORGADZE.pdf

16:41 P2.2: Imaging and spectrometric performance of SiC Timepix3 radiation camera

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 of 3-5E6 V/cm, carriers saturation velocity of 2×E7 cm/s and excellent physical and chemical stability. A large band gap energy is advantageous for low leakage current and high radiation tolerance.
We developed first prototype of Timepix3 camera based on 4H-SiC sensor depicted in Fig. 1. [1]. First results show high quality X-ray imaging performance. The active volume of the SiC sensor consists of an 80 um thick epitaxial layer that is grown on a 350 um SiC substrate and depleted to 65 um under 200 V applied. The used bias is 200 V. The SiC Timepix3 radiation camera has great potential in tracking of heavy ions and neutrons as SiC radiation hard material. In this work we concentrated on spectrometric performance of SiC Timepix3 radiation camera using X-rays and gamma-photons. We compared the results with standardly used Silicon Timpex3 camera of 300 um thick sensor. We evaluated several X-ray fluorescence peaks generated by X-ray tube irradiation of different high purity materials and also various radioisotopes (241-Am, 133-Ba, 57-Co). Following we evaluated X-ray imaging performance where we used various types testing object. Also obtained images and data images we compared with Silicon camera to consider of SiC Timepix3 radiation camera quality and stability.

[1] Zaťko B., Šagátová A., Gál N., Novák A., Osvald J., Boháček P. Polansky Š., Jakůbek J., Kováčová E.: From a single silicon carbide detector to pixelated structure for radiation imaging camera. In Journal of Instrumentation, 2022, vol. 17, no. C12005.

Acknowledgement: The authors acknowledge funding from the Slovak Research and Development Agency by grants Nos. APVV-18-0273 and the Scientific Grant Agency of the Ministry of Education of the Slovak Republic and the Slovak Academy of Sciences through grant No. VEGA 2/0084/20.

Speaker: Bohumir Zatko

Poster-Zatko_ElU SAV_Iworid2023.pdf

16:42 P2.3: Advapix TPX3 detector with Realsense L515 Lidar Camera for Localization and Characterization of Hotspots.

In nuclear decommissioning projects, localising and characterizing hotspots is critical to prevent risks to workers and the environment, especially in the presence of high dose rates. Manual radiological measurements are commonly used for hotspot identification, but they can be time-consuming, inefficient, and pose potential risks to operators. Compared to using classical measurement devices, a Compton camera is able to extract directional information about the hotspot, eliminating the need for repeated measurements.

In this research, a promising method for localizing and characterizing hotspots is proposed. An Advapix TPX3 detector with a 3D reconstruction algorithm was utilized, which can serve as a single-layer Compton camera. This method is similar to the one described in [1]. A Realsense L515 lidar camera was added to this Compton camera in a measuring setup to visualize the radioactive sources and measure the distance from detector to source. Tests were performed in laboratory conditions, and radiological data were projected onto the point cloud of the 3D camera to visualize the sources' locations in the environment. This combination allows for better visualization and interpretation of the hotspots.

Measurements were made using a 137Cs source, and a direct back projection algorithm was used to retrieve the source's direction. After correcting for the physical distance between the two detectors, the measurement of the Compton camera was superimposed with the point cloud to visualize the hotspot. The Advapix TPX3 detector with Realsense L515 Lidar Camera accurately located and visualized hotspots in 3D, and using the lidar camera to retrieve distance information improved the accuracy of activity estimation.

This method has several advantages over conventional hotspot identification methods, including reducing the cost and complexity of Compton cameras by eliminating the need for a second detector, and improving visualization with the lidar camera. Using this method, a measurement device could be set up in a single location and perform a 360-degree measurement of the room, limiting the need for human intervention during the measurement and therefore reducing risk. This research demonstrates the potential of this method for improving efficiency and safety in nuclear decommissioning projects.

Speaker: Mattias Simons (Hasselt University)

poster_mattias.pdf

16:43 P2.4: RIPTIDE, a proton-recoil track imaging detector for fast neutrons

RIPTIDE is a new detector concept aiming to track fast neutrons. It is based on neutron-proton elastic collisions inside a plastic scintillator, where the neutron momentum can be measured by imaging the scintillation light [1-3]. More in detail, by stereoscopically imaging the recoil-proton tracks, the proposed apparatus provides neutron spectrometry capability, and enable the online analysis of the specific energy loss along the track (see Fig. 1). In principle, the spatial and topological event reconstruction enables particle discrimination, which is a crucial property for neutron detectors.
In this contribution, we report the advances on the RIPTIDE detector concept. In particular, we have developped a Geant4 optical simulation to demonstrate the possibility of reconstructing with sufficient precision the tracks and the vertices of neutron interactions inside a plastic scintillator. To realistically model the optics of the scintillation detector, monoenergetic protons were generated inside a 6x6x6 cm3 cubic BC408 scintillator, and the ensuing optical photons were recorded on a scoring plane corresponding to the surfaces of the cube. The photons were then trasported throug an optical system to a 2x2 cm2 photo sensitive area with 1 Megapixel. The first panel of Fig. 1 show an example of one of the 6 projections of a track on a pixellated photosensor.
Moreover, we have developed 2 different analysis procedures to reconstruct 3D tracks: one based on least square fitting and one on Principal Component Analisys. The main results of this study will be presented with a particular focus on the role of the optic system and the attainable spatial/energy resolution.
[1] A. Musumarra et al 2021 JINST 16 C12013
[2] C. Massimi et al 2022 JINST 17 C09026
[3] P. Console Camprini et al 2023 JINST 18 C01054

Speakers: Agatino Musumarra (INFN-Sezione di Catania (IT)), Patrizio Console Camprini (ENEA (IT))

16:44 P2.5: Thickness-dependent characteristics of silicon-based Medipix3RX detectors at Sirius beamlines

X-Ray imaging techniques at synchrotron facilities often rely on 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 along a pixelated array of discrete 55 x 55 µm counting units. Recently, our group published an initial set of characterization experiments on the PIMEGA detectors, which were developed and employed at the Brazilian Synchrotron Facility [1]. Our previous work focused on the physical responses of 300 µm thick silicon sensors integrated into Medipix3RX ASICs. In this report, we compare the physical responses of 300 and 675 µm thick silicon-based detectors. Among the experiments gathered within this contribution, we have performed the slanted edge technique for measuring the Modulation Transfer Function (MTF) [2,3]. This measurement was employed for assessing the thickness dependence of the detector’s spatial resolution, and its results are depicted in Figure 1. This experiment was conducted under 5.9 keV incident energy (E0), for equivalent energy threshold values of 0.5 and 0.7 E0. Our work demonstrates that, even though thicker sensors present higher absorption efficiencies, their MTF values are lower 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, which lead to more pronounced charge-sharing effects on thicker sensors. Our results suggest a compromise between sensor absorption efficiency and spatial resolution. Future characterization experiments will also be employed to fully describe the thickness dependence of the detector's physical outputs.

Speaker: Raul Back Campanelli

16:45 P2.6: Detection of gastrointestinal foreign bodies in pets using single grid-based dark-field X-ray imaging

Gastrointestinal (GI) foreign bodies occur when pets consume items that are nondigestible and will not readily pass through their stomach or intestines. Traditional radiography has been widely used to detect GI foreign bodies in pets. However, particularly, detecting low-density GI foreign bodies such as wood, plastic, clothing, and sticks is often difficult in conventional absorption-based radiography. In this study, to overcome this difficulty, we propose a novel imaging method, the so-called single grid-based dark-field X-ray imaging (SG-DFXI), for more clearly detecting low-density foreign bodies in pets. SG-DFXI is a single-exposure, non-interferometric imaging method for retrieval of absorption and dark-field images using a conventional X-ray grid. To demonstrate the efficacy of the proposed method, an experiment was conducted with a mouse phantom containing a piece of wooden chopstick. The preliminary results of an absorption and a dark-field images of a mouse phantom that contained a piece of wooden chopstick. According to our preliminary results, the proposed approach significantly improved the ability to detect low-density foreign bodies in pets.

Speaker: Mr Jonghyeok Lee (Yonsei university)

16:46 P2.7: Development and Evaluation of Relative QA Dosimeter for Electron Beam Based on CsPbBr3

Medical linear accelerators are used to treat patients by irradiating X-rays and electron beams. Electron beams deliver most of their energy to the skin surface due to their short range. Radiation therapy uses these characteristics to treat superficial tumors such as skin cancer, breast cancer, and head and neck cancer. Since accurate dose delivery is required for such electron beam treatment, quality classification (QA) of electron beam must be performed regularly.
However, in clinical electron beam QA, it is recommended to cross-calibrate the Plane-parallel ionization chamber using the absorbed dose to water correction factor of the cylindrical ionization chambers to improve the accuracy in high-energy electron beam measurement. This complicates the measurement.
Therefore, in this study, a relative QA dosimeter for electron beams that can measure low and high energy electron beams without cross-calibration was developed by using CsPbBr3 material with excellent high-energy radiation detection efficiency. In addition, the detection performance was evaluated by analyzing the electrical response characteristics.
The CsPbBr3 dosimeter was manufactured as a unit cell type polycrystalline dosimeter. Electrical response characteristics were measured at energies of 6, 9 and 12 MeV, and reproducibility, linearity, and PDD were analyzed and evaluated by irradiating the dosimeter with a radiation dose of 100 MU at 500 MU/min.
In the reproducibility evaluation, the relative standard deviation (RSD) at 6, 9 and 12 MeV was analyzed to be 1.06%, 1.39% and 1.49%, respectively. In the linearity evaluation result, the coefficient of determination according to the linear regression analysis was analyzed to be 0.9997, 0.9997 and 0.9993 at 6, 9 and 12 MeV, respectively. The PDD evaluation was shown to show the correct Dmax point. As a result of the evaluation, the manufactured CsPbBr3 dosimeter was evaluated to have suitable performance for application as a dosimeter in various energy bands of 6 MeV, 9 MeV and 12 MeV.
As a future study, if a large-area flat-panel dosimeter is manufactured by analyzing the dependence characteristics according to the dosimeter area and field size, QA of electron beam treatment will be possible with a more simplified procedure. This is a basic study of the development of the electron beam QA dosimeter, indicating the potential use.

Speaker: Mr Seung-woo Yang (Department of Radiation Oncology, Collage of Medicine, Inje University, Republic of Korea)

16:47 P2.8: Effect of the shift-variant focal spot blur on the image quality in radiography

Since Roentgen's discovery of X-rays, anode angulation technique has been widely used in medical X-ray tubes to reduce the focal spot size and transmit sufficient X-rays through the anode. Unfortunately, this technique inevitably produces the so-called shift-variant image blur that causes the focal spot to have a different shape, depending on the position of the detector plane [1, 2]. This effect becomes more pronounced as the distance from the center of the detector plane (or the source magnification) increases. However, it is neglected in traditional radiography because isolating and analyzing this effect from other effects, such as scattered X-rays produced through the object and detector-induced blur, are often difficult. The purpose of this study is to characterize the effect of the shift-variant focal spot blur on the image quality as a function of detector position with various X-ray imaging parameters in radiography, including magnification, focal spot size, and so on. Figure 1 shows the schematics of (a) an X-ray imaging geometry and (b) the formation of X-ray image of an ideal point object, depending on the direction of the finite focal spot of the X-ray tube. We used a simple model of the focal spot that decomposes it into three independent components. According to this model, shift-invariant image blur can be caused by the x and y-components (FSx and FSy) perpendicular to the beam direction; shift-variant image blur by the z-component (FSz) parallel to the central beam direction. To validate the efficacy of the proposed method, we conducted a Monte Carlo simulation and an experiment using an X-ray imaging system that consisted of an X-ray tube with a focal spot size of 3 mm and a CMOS detector with a pixel size of 0.14 mm and an active area of 460 × 460 mm2. Figure 2 shows the geometry of an X-ray imaging system used in the Monte Carlo simulation and the X-ray imaging system used in the experiment. Figure 3 shows the MTF curves measured at the center (i.e., beam angle = 0) and periphery (beam angle = 10) of the detector for three different object magnifications of M = 1.00, 1.27, and 2.00. Our preliminary results showed that nonnegligible shift-variant image blur occurred especially when an X-ray tube with a large focal spot and a detector with a large area are used in radiography. More quantitative simulation and experimental results will be presented in the paper.

Speaker: Hunwoo Lee (Yonsei University)

16:48 P2.9: Deep learning-based soft-tissue decomposition in chest radiography using fast fuzzy C-means clustering with computed tomography dataset

Chest radiography is the most routinely used X-ray imaging technique for screening and diagnosing lung and chest diseases, such as lung cancer and pneumonia. However, the clinical interpretation of the hidden and obscured anatomy in chest X-ray images remains challenging because of the bony structures overlapping the lung area. Thus, multi-perspective imaging with a high radiation dose is often required. In this study, to address this problem, we propose a deep learning-based soft-tissue decomposition method using fast fuzzy C-means (FCM) clustering with computed tomography (CT) dataset (Fig. 1). In this method, FCM clustering is used to decompose a CT dataset into bone and soft-tissue components, which are synthesized into digitally reconstructed radiographs (DRRs) to obtain large amounts of X-ray decomposition datasets as ground truths for training. In the training stage, chest DRRs and soft-tissue DRRs are used as input and label data, respectively, for training the network. During testing, a chest X-ray image is fed to the trained network to output the corresponding soft-tissue image component. To verify the efficacy of the proposed method, we conducted a feasibility study on clinical chest CT data from the AAPM Lung CT Challenge. Figure 2 shows the decomposed bone and soft-tissue components of the original CT image using the fast FCM and their synthesized DRRs. Figure 3 shows two cases of soft-tissue decomposition obtained using the proposed method and the measurements of the structural similarity index metric (SSIM). Consequently, the findings of our feasibility study indicate that the proposed method can offer a promising outcome for this purpose. More quantitative results will be presented in the paper.

Speaker: Mr DUHEE JEON (Yonsei university)

16:49 P2.10: Feasibility of Using 3D CZT Drift Strip Detectors for Small Compton Camera Space Missions

The electromagnetic emission from astronomical sources in the MeV-energy band (0.1 to 100 MeV) is exceedingly difficult to detect – both due to low flux, and the fact that photons may penetrate significant thicknesses of material without interacting. However, in an astrophysical context, photons in this energy band carry specific and valuable information about gamma-ray lines that originate from radioactive nuclei created in supernova explosions, or ejected from colliding neutron stars. Gamma-rays from matter-antimatter annihilation, and accreting black holes are further examples of sources exciting the interest in this energy band. New state-of-the-art sensor technology is a key factor to improve sensitivity of observations in this energy range.

The detector group at DTU Space started a development program, focusing on improving the spectral performance of CdZnTe (CZT) detectors, a special readout technique, the so-called Drift Strip Method (DSM) was developed. The DSM method leads to a considerable improvement of the achievable energy resolution even for CZT crystals of limited quality, despite suffering inefficient charge collection [1], [2], [3]. Contrary to the common pixelated electrode geometry (where the typical number of readout channels required increase with cubic power with the sensitive detector volume), the 3D CZT drift strip detector minimizes the number of readout channels. Recent prototypes of size 2cm x 2cm x 0.5 cm perform with sub-millimeter position resolution (<0.5mm @662 keV) in 3D and energy resolution (<1% @662 keV) [4], [5], [6]. The latest development is a set of new 3D CZT drift strip detector module of size 4cm x 4cm x 0.5cm (Figure 1).

It has previously been demonstrated that a single 3D CZT drift strip detector crystal can be operated as a Compton Camera [7]. The next step of the development program is to fly several 3D CZT drift strip detectors on a small payload (e.g. CubeSat) operating as a Compton Camera. This is to increase technology readiness level of the detector. We will present the initial design and simulations of a Compton Camera concept utilizing the detector using the simulation software “The Medium-Energy Gamma-ray Astronomy library” (MEGAlib) [8]. We will present in-orbit simulations of effective area, sensitivity, and minimal detectable polarization, utilizing the simulations to optimize design choices and improve sensitivity of the Compton Camera, and to give first light insight on the 3D CZT drift strip detector performance on a small satellite MeV space mission.

Speaker: Ms Selina Ringsborg Howalt Owe (Technical University of Denmark)

POSTER_Feasibility%20of%20Using%203D%20CZT%20Drift%20Strip%20Detectors.pdf.pdf

16:50 P2.11: A Study on the Feasibility of High-Energy X-ray CT for Inspection of AM Products

In the industrial sector, commonly used non-destructive testing techniques include ultrasonic testing (UT), radiographic testing (RT), penetration testing (PT), magnetic testing (MT), and other methods. These techniques have undergone significant development, particularly in real-time testing, low cost, high efficiency, and high precision, with the concomitant development and release of novel industrial products. Moreover, these techniques are being integrated with artificial intelligence to enhance product reliability.
Several research studies have attempted to apply computed tomography (CT) technology, commonly employed in the medical industry, to the industrial sector by incorporating it into the RT testing method. This enables easy detection of internal product defects, although its application is limited by system size and cost.
The increasing adoption of additive manufacturing (AM), which employs 3D printing technology, in the manufacturing industry has further emphasized the need for non-destructive testing. AM products necessitate precision analysis through 3D cross-sectional images of material layers, and non-destructive testing using CT methods within RT is becoming an increasingly valuable testing technique. Therefore, this study applied CT non-destructive testing to in-house AM products to ensure their reliability and confirmed the applicability of CT testing to AM products by varying testing parameters.

Speaker: hunhee kim (Doosan Enerbility)

16:51 P2.12: The R&D of The Glass Scintillator for Nuclear Detection

Scintillation materials can convert high-energy rays into visible light. Generally, solid scintillator can be divided into crystal scintillator, plastic scintillator, glass scintillator and ceramic scintillator. Compared with crystal scintillator, the glass scintillator has many advantages, such as a simple preparation process, low cost and continuously adjustable components. Therefore, glass scintillator has long been conceived for application in the nuclear detection such as hadron calorimeters, the HCAL of CEPC. In 2021, the researchers in the Institute of High Energy Physics (IHEP) have set up the Large Area Glass Scintillator Collaboration (GS group) to study the new glass scintillator with high density and high light yield. Currently, a series of high density and high yield scintillation glasses have been successfully developed. The maximum density of the glass can exceed 6.9 g/cm3. And the maximum light yield can reach up 3400 ph/MeV. Moreover, Ce3+-doped borosilicate glass can balance the targets of high density and high light yield. In addition, the glasses can achieve neutron/gamma dual detection due to presence of Li, B and Gd element.

Speaker: Sen Qian

16:52 P2.13: All-electrical control of micromechanical bolometers for THz detection

Radiations in the terahertz and infrared spectrum have proven useful in practical applications such as security screening, medical imaging, and wireless communication [1,2,3]. Many of these applications would greatly benefit from practical and compact detectors capable of working at room temperature, capturing tens of images per second and providing a low-medium number of pixels (typically around 104 - 105 pixels). In order to fulfill all these requirements in the frequency range of 0.3-10 THz, where classic electronic devices are highly inefficient, we make use of Si3N4 micro-bolometers which shift their mechanical resonance frequency as they heat-up by absorbing terahertz radiation.
In previous works, the vibration of these devices was induced by a piezo membrane, while the resonance frequencies were determined through optical interferometry [4]. However, in our latest sensors (as shown in Figure 1), we have implemented a novel approach that greatly simplifies the excitation and measurement of the sensor's resonance frequency. Specifically, two golden stripes are integrated into the device, and under appropriate conditions, current injected through one of these stripes can vibrate the sensor, inducing a modulated current on the other strip for electrical readout, whose frequency is a function of the absorbed radiation.
In the presented work, we describe the setup used to perform a fully electrical readout of these sensors (Figure 2), which not only simplifies the measurement process but also provides a significant improvement in measurement speed and accuracy. We thoroughly discuss the first measurements obtained using this setup and compare them with both the interferometry results and our previous simulations, where we have modelled a sensor with a lumped parameter passband filter [5]. Our results demonstrate the efficacy of this approach for real-time terahertz imaging and other applications where fast and accurate measurements are critical.

Speakers: Mr Leonardo Gregorat (DIA, University of Trieste, 34127 Trieste, Italy), Mr Marco Cautero (DIA, University of Trieste, 34127 Trieste, Italy)

16:53 P2.14: Timepix3 multi-layer detector setup for the measurement of anomalies in angular correlation of electrons and positrons internally produced in excited 8Be and 4He

This contribution describes a new Timepix3 [1] multi-layer detector setup that is part of a spectrometer for the measurement of anomalies in angular correlation of electrons and positrons internally produced in excited 8Be and 4He [2].
Six detector layers are arranged hexagonally in the new design. There are some unique requirements that had to be addressed, including the capacity to operate in a vacuum, the accurate time synchronization of all detectors, and the small material budget behind detectors (due to the mitigation of influence on other detectors).
The whole measurement chain consists of chipboard modules (fingers), the main board, and the readout system. Chipboard modules carry a Timepix3 chip with a silicon 500µm sensor and local power supplies providing excellent voltage stability. The Timepix3 assembly is glued to an aluminum block only by means of the inactive part of the ASIC chip (periphery part + pads extender) due to the demand for minimization of the material budget behind the sensor. Aside from that, specially thinned Timepix3 ASICs with a thickness of 200 µm (instead of the typical 720 µm) are used.
Data from all six modules is concentrated on the main board, which ensures the main power voltage supply, fanout of control signals, and interconnectivity with the readout system via vacuum feed-through.
The modified Katherine readout for Timepix3 Generation 2 is used as a readout system [3]. This device's capabilities have previously been demonstrated in a number of projects, and it is based on a 1 G Ethernet and USB 3.0 interface.
Each chipboard module may give up to 20 Mhit/s. The maximum hit/data rate for the entire system is 120 Mhit/s, which corresponds with a raw data rate of about 6 Gbps (the PCI Express interface is considered for these maximal rates in future). The clock shift of each Timepix3 detector is measured to guarantee the accurate, consistent timing of the entire system.
In contribution, a demonstration of the whole setup, including sensor characterization and timing performance, will be shown.

[1] T. Poikela et al., 2014 JINST 9 C05013.
[2] Cortez, A. F. V., et al. "A spectrometer for the measurement of anomalies in the angular correlation of electron and positron internally produced in excited 8Be and 4He." Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 1047 (2023): 167858.
[3] P. Burian et al., 2017 JINST 12 C11001.
The authors acknowledge funding from project 21-21801S of Czech Science Foundation.

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

16:54 P2.15: The impact of individual cosmic rays on a DEPFET spectroscopic X-ray imager for space telescopes

For the Wide Field Imager of the Athena X-ray space telescope, a DEpleted P-channel Field Effect Transistor (DEPFET) sensor was chosen. In a dedicated development phase, the DEPFET has been optimised for the mission objectives. ESA’s Athena mission has been designed to investigate the hot and energetic universe, represented by the large-scale structures of galaxy clusters and the densest objects of the universe, black holes. Athena comprises two scientific instruments—provided by the European X-ray astrophysics community. A cryogenic integral field unit, the X-IFU, provides an excellent energy resolution of a few eV over the entire energy range of 200 eV to 15 keV. Wide field imaging capabilities are added by the WFI instrument with its large detector array consisting of four 512 × 512 pixel sensors with pixels of 130 µm edge length. The chosen DEPFET active pixel sensor enables significantly higher readout speeds compared to previous missions that had similar detectors using pnCCDs while conserving the Fano-limited spectral performance. The sensor bases on a fully depleted silicon bulk. It enables a high quantum efficiency for X-ray photons even at an energy of 10 keV and above. A field effect transistor is the first amplification and readout node. Below its transistor channel, a potential minimum for electrons is implemented. Electrons generated by an incident photon are collected there and influence the conductivity of the transistor channel proportional to their number. This is why it is called Internal Gate. The change in the transistor current is a measure for the energy of the incident photon. The measurement is non-destructive. Afterwards, the collected charge can be removed via clear contacts at both sides of the DEPFET gate.

While the detection of photons in the energy range of 200 eV to 15 keV is the purpose of the sensor, the harsh environment of space creates additional challenges for radiation detectors to be operated there. High energetic particles not only degrade the sensor performance over time. Individual particles create effects that need to be considered. Large amounts of charge carriers may switch on a DEPFET pixel unintendedly. Due to the limited resources on a space observatory, a rolling shutter readout has been chosen for the Wide Field Imager. In this row-wise readout, a switched on pixel may affect an entire sensor column. To investigate the immediate influence of high energetic particles, we irradiated the sensor with different sources. With an infrared LED, the capacity and the temporal behaviour of an Athena WFI DEPFET pixel
was examined. To get a more realistic representation, alpha particles from an americium source and protons measured in the non-clinical research program of MedAustron were investigated. The results of these measurement programs will be presented in this work.

Speaker: Dr Johannes Müller-Seidlitz (Max Planck Institute for Extraterrestrial Physics)

16:55 P2.16: Development of Red/Infra-red Emitting Scintillators for an Alpha Dust Monitor

We have development alpha dust monitor with a red or infrared emitting scintillators, and the scintillation properties were investigated for Ce:Y₃(Mg_x Al_5-2x Si_x)O₁₂ (x=0.0, 0.5, 2.0) crystals were grown by the micro-pulling-down method.Ce-doped Y₃(Mg₂ Al Si₂)O₁₂ had an emission wavelength of 620 nm, and the red-shift of emission bands was observed for Mg and Si-admixed samples due to changing lattice constants compared to the Mg and Si free sample.

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

16:56 P2.17: Enhanced Readout System for Timepix3 Detectors in Large-Scale Scientific Facilities

The Timepix3 ASIC readout chip [1] has already proven great results and benefits for a lot of projects [2, 3, 4]. It was used as a radiation monitor in the ATLAS Experiment (CERN) [5, 6], its good performance in various low-power modes [7] was also demonstrated. However, the utilization of a higher number (well synchronized) of Timepix3 detectors in environments with large research infrastructures (typically accelerators) is still challenging. We developed a novel readout system dedicated to applications where high data rates, long distances, and harsh radiation fields are expected.

The presented system deals with all aspects of the modern measurement chain (see Figure 1) – from hardened chipboard to fast data transfer to computer. The system consists of several fundamental elements: Chipboards, Data Concentrator, Back-End unit and computer/server.

Dual-stack (a pair of Timepix3 detectors) chipboard carries a pair of Timepix3 detectors. It ensures very stable power supplies for readout ASICs by means of radiation hardened voltage regulators. The housing was designed with high emphasis on good heat dissipation, which is important for the thermal stability of sensors.

Data concentrator unit (DC; front-end) controls up to three chipboards (6 pieces of Timepix3 detectors) via a metallic (cable) connection. The unit accumulates pixel data and translates it into two common data streams that are sent to Back-End unit by means of two 10 Gbps fiber connections. Apart from this data accumulation/translation functionality, the data concentrator also implements three independent power supplies for chipboards and high-voltage bias sources with a range of 25 V – 500 V in both polarities; leakage current measurement is included as well.

In the final stage, data are received by the Back-End unit (BE). This device implements the main functionality (DC implements only data transfers) of the readout system. It produces configuration streams for detectors, controls internal DACs, sets bias, etc. Fundamental data processing is implemented directly in the FPGA. Back-End unit is controlled via a 1G Ethernet interface. However, due to high data rates, the PCI Express Gen3 4x interface is used as the main data channel into the computer or server (although the user can also use Ethernet for data acquisition).

The system's designed architecture makes it possible to use it in a radiation field. The chipboard consists only of the Timepix3 ASIC and power supplies; no radiation-sensitive components are used. The Data Concentrator uses more complex and sensitive components, making it more susceptible to upsets caused by radiation. However, Data Concentrator can be placed up to 20 meters away from chipboards, which can decrease the expected dose and reduce the probability of failure. Flash-based FPGA devices also increase hardness. The most sensitive element of the system - Back-End unit – should be placed in a safe area because it is based on commercial components. However, due to fiber connectivity, the distance between Data Concentrator and Back-End is almost unlimited (hundreds of meters are considered in real applications).

The system is designed to be able to process a high data rate. Each of the chipboards can produce up to 2x40 Mhit/s, which corresponds to a pure data rate of over 12 Gbps between the Data Concentrator and Back-End unit. This is why a pair of 10 Gbps fibers is used. Final data transfer to the computer is implemented as a PCI Express Gen3 4x interface featuring a rate up to 3.5 GB/s. The chain can also offer precise and uniform timing over the whole system by means of clock shift measurements in individual nodes.

[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.
[7] P. Burian et al., 2019 JINST 14 C01001.

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

16:57 P2.18: Investigation of fast neutron interactions in semiconductor sensors with Timepix3

Neutron radiation effects on semiconductor detectors have long been investigated, as it offers a more complete understanding of the amount of damage to which such sensors can be subjected while operating them under extreme experimental conditions. The competition between ionizing (IEL) and non-ionizing energy losses (NIEL) was described theoretically through partition functions, which are in a fair degree of agreement with silicon sensor experimental observations and prompt the need for extending the studies to other materials which are used for radiation detection, like gallium arsenide(GaAs) and cadmium telluride(CdTe).The pixelation of Timepix3 detectors together with the energy deposition measurement and pattern discrimination algorithms which are exploited for separating the different neutron interactions (elastic and inelastic). In order to measure the competition of IEL and NIEL in different semiconductors with unprecedented accuracy, an experiment was performed at the Weapon Neutron Research facility in the Los Alamos Neutron Science Centre, where several Timepix3 sensors were placed in a neutron radiation field of an energy spectrum ranging from hundreds of keV to hundreds of MeV. The presentation aims to deliver a comprehensive look at the analysis process leading to new results on the competition between IELs and NIELs of recoil nuclei in several semiconductor lattices following fast neutron interactions with Timepix3 sensors.

Speaker: Radu-Emanuel Mihai (Institute of Experimental and Applied Physics, Czech Technical University in Prague)

16:58 P2.19: Angular correlation measurement and magnetic field response of 169Yb for double photon coincidence imaging

Nuclear medicine imaging is an important non-invasive technique in medical care for obtaining information inside the body by detecting radiation emitted from within the body to the outside and visualizing its distribution. In this study, we developed a new nuclear medicine imaging technique that combines magnetic field and RI imaging by utilizing the characteristic that the emission angle of gamma rays changes due to the influence of external fields such as magnetic and electric fields in the intermediate state of cascade nuclear decay and measuring angle correlation. We also conducted exploration and quantification of medical RI tracers that are more susceptible to perturbations by external fields.

Speaker: Mr Boyu Feng (The University of Tokyo)

16:59 P2.20: Characterization of a Megapixel JUNGFRAU Detector with Novel GaAs:Cr Sensor for Photon Science Applications

As more synchotrons and X-ray free electron lasers move towards using high (> 20 keV) energy X-rays, there is an increased need for efficient, large area, high-speed X-ray detectors for use at these facilities. High-Z sensors, such as GaAs:Cr, are preferable to Si in detectors of high-energy photons, due to their increased stopping power and therefore improved efficiency at higher energies. However, high-Z sensor materials often feature defects that introduce distortions into the images recorded. These defects also have an adverse impact on the material's charge-transport properties and enable unwanted behaviour such as afterglow effects and polarization.

We will present the characterization of a one-megapixel detector based on the JUNGFRAU1.0 ASIC with a sensor made from a new type of GaAs:Cr. The charge-integrating nature of JUNGFRAU makes it ideal for studying the behaviour and properties of new sensor materials. Results will include measurements of the new material’s charge-carrier properties and propensity to display afterglow effects, as well as the device's I-V and I-t characteristics, gain and energy resolution. We will compare the performance of the new material with that of GaAs:Cr sensors from other sources, also bonded to JUNGFRAU, to quantify the degree of improvement offered by the new material.

Speaker: Kirsty Paton (Paul Scherrer Institut)

17:01 P2.21: Fast Neutron Imaging with a p-Terphenyl Pixel Scintillation Array

p-terphenyl crystals were grown by the self-seeding vertical Bridgman technique, and its scintillation properties were investigated for fast neutron scintillator applied in high temperature condition around 400K. light outputs were approximately 9,000 photons/(5.5-MeV alpha) and 19,000 photons/MeV for alpha-ray and gamma-ray excitation, respectively. we embedded a p-terphenyl pixel scintillation array and succeeded in imaging irradiated with fast neutrons with a multi-anode photomultiplier tube.

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

17:02 P2.22: Alpha-ray Imaging with Alkali Copper Halide Scintillator

Radiation monitor is an important technique for the decommissioning of the Fukushima Daiichi Nuclear Power Plant (FDNPP) with safety, and the internal exposure of workers who inhale alpha-emitting dust, such as plutonium dioxide particles, in nuclear facilities is a crucial matter for human protection from radiation. Detailed information on the radiation dose distribution and alpha-emitting dust inside the nuclear reactor is necessary to operate the decommissioning of FDNPP. Thus, we have developed an alpha-ray imaging detector with high positional resolution consisting of a scintillation sheet, optical microscope and Complementary Metal Oxide Semiconductor (CMOS) camera (ORCA-Flash4.0 V3, Hamamatsu).
To obtain the high-resolution imaging, high-light output scintillator is required, and Cs3Cu2I5 (CCI) was selected as the scintillator for the alpha detector in this time owing to a high light output of 41,500 photon/MeV. Moreover, this material has been applied to high-resolution X-ray imaging techniques. In this paper, we show the feasibility study on the application of the CCI scintillator for alpha-ray imaging.

Speaker: Mr Yusuke Urano (Graduate School of Engineering, Tohoku University)

17:03 P2.23: SpacePix3 - response characterization and total ionising dose testing for space applications

This work presents SpacePix3, an improved version of the SpacePix2 ASIC [1]. It is a novel MAPS sensor developed for soft advanced space dosimetry fabricated in a 180 nm PDSoI CMOS process. The sensitive area is a matrix of 64×64 pixels with a 60 μm pitch. The detection diode is integrated in a handle wafer, with the depletion depth of approximately 35 μm at -150 V bias. The signal is digitised by 32 column ADCs with 10 bit resolution. The effective dynamic range of the pixel front-end amplifier is 5 to 65 ke−, with the possibility of backside pulse digitization of signal 0.25 to 30 Me−. The first measurement results using nuclide sources and accelerator ion beams are presented.
This ASIC is suitable for the proposed Czech lunar mission, where it will be exposed to ionising radiation ranging from electrons and protons in the van Allen belts to the heavy ions in the galactic cosmic rays. Therefore, its survivability and response to the TID irradiation was tested according to the relevant standards such as ESCC Basic Specification No. 22900
up to a total dose of 5 kGy in semilogarithmic steps. Results of power consumption and detection response to 238Pu X-ray photons were evaluated before and after irradiation.

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

17:04 P2.24: Preliminary results from the Submarine Gamma Imager

We present preliminary results of a novel submarine gamma imager (SUGI) based on pixelated CdZnTe detector modules. The instrument, mounted on a remotely operated vehicle (ROV), has been tested in a series of field deployments performed at the hydrothermal fields of the island of Milos, Greece. The analysis of the collected data demonstrate the capabilities of the instrument being developed, while comparison with a reference gamma detector confirms the validity of the results.

Speaker: Dr Valsamis Ntouskos (National Technical University of Athens)

Ntouskos_sugi_poster.pdf

17:05 P2.25: On the possibility of Spectral Imaging for Cell Location and Cell Tracking

With an incidence of 1 - 4 per 100,000 habitants in the western world, glioblastoma is the most common primary malignant brain tumour [1]. Significant advances have been made in our understanding of the pathophysiology of glioblastoma over the past decade, however, glioblastoma remains an incurable disease with a median survival time after diagnosis of approximately 15 months [2]. Moreover, therapies that have had better results in other types of cancer were ineffective in glioblastoma. In order to combat this disease new therapeutic modalities are needed to develop truly effective treatments. One approach is based on the use of genetically modified cells, in particular human mesenchymal stem cells (hMSC). It could be shown that hMSCs have the ability to selectively migrate to glioblastoma tumours in animal models, suggesting their potential for engineered cell glioblastoma therapy [3,4]. hMSCs can be isolated from different tissues, including bone marrow and adipose tissue, the latter being a very accessible and abundant source. Therefor each potential patient can be their own donator of hMSCs. It was demonstrated [3] that GNP loaded hMSCs injected into the carotid artery of nude mice migrated towards and integrated into U87 glioma tumours present in mice. Moreover, hMSCs can be permanently labelled with gold nano particles (GNP) as described in [5] constituting thus a selective marker, which subsequently can be detected utilizing X-rays imaging modalities. Here we report on the explorative implementation of spectral X-ray computer tomography (CT) in combination with GNPs as a permanent cell marker for hMSCs for investigating micrometric tumour cell distribution in rodents. Preliminary experiments have been carried out at the PEPI lab [6] utilizing a CdTe hybrid pixel detector [7] with a pixel size of 62 µm x 62 µm. We were able to obtain post mortem high-resolution 3D spectral images (figure1) of mice bearing U87 glioma tumours, which prior scarification had been injected with GNP loaded hMSCs. In this contribution we will present first encouraging results of this promising imaging technique, which could significantly improve the understanding of complex processes of disease progression and the effects of therapies in preclinical trials.

Speaker: Prof. Ralf Hendrik Menk (Elettra Sincrotrone Trieste)

17:06 P2.26: Helical sample-stepping for faster speckle-based multi-modal tomography with the Unified Modulated Pattern Analysis (UMPA) model

Speckle-based imaging (SBI) is a multi-modal X-ray technique that gives access to attenuation, phase-contrast, and dark-field signals. The signal retrieval with the Unified Modulated Pattern Analysis (UMPA) algorithm is based on the modulation of a reference speckle pattern generated from a sandpaper when a sample is inserted in the beam. By stepping the diffuser or the sample transversely to the beam direction, it is possible get a better convergence of the model. Here, we show how a continuous helical acquisition can extend the detector's field-of-view and speed up the acquisition while maintaining a multi-frame approach for the signal retrieval of a test object.

Speaker: Sara Savatović (Department of Physics, University of Trieste, Via Valerio 2, 34127 Trieste, Italy; Elettra-Sincrotrone Trieste, Strada Statale 14 – km 163.5, 34149 Basovizza, Italy)

Savatovic-poster-200.pdf

17:07 P2.27: A simulation study of instant-retrigger technology for pulse pileup correction in clinical photon-counting tomography

Photon-counting technology matured enough to be implemented in clinical computed tomography (CT) scanners with the potential to revolutionize clinical practice due to low imaging noise, uniform spectral weighting, and inherent spectral separation. Photon fluxes in clinical CT can reach up to $10^{8}$ counts mm$^{-2}$s$^{-1}$, imposing significant technical challenges on the counting speed of photon-counting detectors [1]. Pulse pileup is the effect in which two or more photons impinging the same detector pixel are processed as a single event, leading to counting loss and spectral distortion of the signal. In clinical CT, the conditions for pulse pileup to occur are usually met at high tube currents and can be observed inside the lungs or at the edges of the patient’s body. Spectral distortions also have a significant impact on quantitative imaging tasks such as iodine quantification and virtual monochromatic imaging. An effect occurring independently of photon flux is charge sharing due to fluorescence effects and the spreading of a charge cloud, causing multiple counts at lower energies and blurring of the image. Pulse pileup and charge sharing contradict each other to some extent because i) larger pixel sizes reduce charge sharing between pixels while increasing the probability for pulse pileup and ii) faster ASIC helps distinguish single photons in high-flux conditions while reasonably slower detectors allow for integration of split charges created due to the charge sharing. Thus, hardware-based methods are often implemented to correct for one or both effects depending on the detector design and intended application.
In this work, we investigated the potential of instant-retrigger technology developed by DECTRIS Ltd. to improve non-paralyzable detectors in high-flux conditions [2]. Instant retrigger technology re-evaluates the pulse signal after a predetermined deadtime interval after each count and potentially retriggers the counting circuit in case of pulse pileup. The respective deadtime interval is adjustable and accounts for the width of a single photon pulse. The instant-retrigger analytical model was developed and implemented inside the DukeSim CT simulator to generate realistic CT simulations of the XCAT chest [3] phantom containing iodine contrast. DukeSim contains primary ray-tracing and Monte Carlo scattering models, realistic models of CT geometries, and a model of a photon-counting detector including charge sharing model and paralyzable and non-paralyzable detector configurations [4]. For this work, we used a 1.6 mm thick CdTe sensor bulk and 0.5x0.5 mm detector pixel size. The instant-retrigger analytical model [5] was applied after charge sharing and compared against the other two models for the task of material decomposition. Material decomposition is described as:
$\mu(E) = \mu_{1}(E)\,x_{1} + \mu_{2}(E)\,x_{2}$
where $\mu_{1}(E)$ and $\mu_{2}(E)$ are known linear attenuation coefficients of basis materials (e.g., soft tissue and bone), $x_{1}$ and $x_{2}$ are energy-independent coefficients (in 2D called basis images/maps), and $\mu(E)$ is the measured value for each voxel. The basis images, which represent the equivalent concentrations of basis materials for each voxel, encode the quantitative information about the voxel composition. Figure 1 shows how the retriggering mechanism improves spectral information in high flux conditions in comparison with slightly slower non-paralyzable and paralyzable detectors. Figure 2 shows decomposed soft tissue and bone maps of the virtual XCAT phantom obtained using the simulation without modeling the pulse pileup effect. Figure 3 shows how the accuracy of material decomposition depends on the retrigger time.
Faster retriggering time improves spectral response and maintains accurate material decomposition in spectral CT. Although retriggering times of 15 ns are achievable with current detectors, more accurate analytical models accounting for variable pulse lengths generated by polychromatic sources might be needed to determine optimal values.
[1] M Danielsson et al Phys Med Biol. (2021), 66(3):03TR01.
[2] T Loeliger et al IEEE NSS/MIC (2012), p. 610–5.
[3] WP Segars et al 4D Med Phys. (2010), 37(9):4902–15.
[4] E Abadi et al IEEE Trans Med Imaging. (2019), 38(6):1457–65.
[5] P Zambon et al, Dectris Ltd., Manuscript in preparation (2023)

Speaker: Stevan Vrbaski

17:08 P2.28: Distinguishing Neutron and Gamma Pulses of EJ-200 Scintillation Detector using Artificial Intelligence

In the field of security and defense, the detection of special nuclear materials and other radioactive materials requires the use of neutron and gamma-ray detection systems. Silicon photomultipliers have been employed in these detectors due to their advantages of being lightweight, compact, and low power consuming. Accurate identification of neutron and gamma-ray pulses from these detectors plays a crucial role in the reliability of radiation measurements. To improve the discrimination of pulse shapes, various pulse shape discrimination techniques have been studied, developed, and applied. In this research, a minimal neural network artificial intelligence (AI) configuration was designed to correspond to the identification characteristics of neutron and gamma-ray pulses obtained from an EJ-200 scintillation detector. The principle of minimum error was applied in the design, so that despite the minimal configuration, the accuracy of the identification results was not compromised. Experiments showed that with this design, AI achieved higher accuracy in identification compared to the pulse shape integration method. Monte Carlo simulations were validated by laboratory measurements and field tests were performed using real gamma-ray and neutron sources. Detection and localization within one meter were achieved using a maximum likelihood estimation algorithm for ¹³⁷Cs sources (4 MBq), as well as the detection of ²⁴¹Am–Beryllium (1.45 GBq) source placed inside the shipping container. For the measured pulses from a ⁶⁰Co source, the AI-based MNRNT accurately identified 97.90% of the pulses in the energy range of 50-2000 keVee (keV electron equivalent), and achieved 96.80% accuracy for pulses in the low energy range of 50-150 keVee. These results demonstrate that artificial intelligence methods can be applied to improve the identification and analysis of radiation events even with small-scale radiation detectors.
Keywords: Pulse shape discrimination, AI, neutron detection, scintillation detector.

Speaker: Dr Sy Minh Tuan HOANG (Thu Dau Mot University)

17:09 P2.29: Radiation Portal monitor performances at low energies

Dedicated to the control of radiation on industrial, research and civil sites, the portal monitors produced by Bertin Technologies, automatically detects radioactive source carried by trucks, cars, and trains. An
alarm classification can discriminate natural and artificial radiation.
The research and development division is working on the detection at low energy, where the performances of the detector needs to be improved. Energy-weighted algorithm is applied at low energy to reduce
the false alarm and detect the 226Ra radioelement. Preliminary experimental analysis and simulation on Geant4 are presented and discussed.

Speaker: Mrs Celia LEY (Bertin Technologies, Nuclear detection R&D)

17:10 P2.30: Exploring coded aperture imaging with the MiniPIX EDU for high-resolution radiation belt electron pitch angle observations

This work explores coded aperture imaging methods using the MiniPIX system for high-resolution angular observations of energetic electrons (100s of keV to several MeV) in Earth’s radiation belts. Observing energetic electron pitch angle is critical to understanding energetic particle dynamics, and in particular, particle precipitation into the upper atmosphere.

We present a simulation study in Geant4 of the instrument design space, including coded aperture pattern, aperture thickness, and instrument geometry. Performance characteristics evaluated include angular resolution and field-of-view. We present the results of a proof-of-concept experiment using Advacam’s MiniPIX EDU and a photochemical-etched Tungsten coded aperture mask to validate our simulation work.

We find that coded aperture imaging can achieve an angular resolution better than 1° across a narrow field-of-view (<10°), or resolution better than 10° across a larger field-of-view (>25°) but with losses in sensitivity and resolution across the field-of-view due to aperture collimation. Previous radiation belt electron observations typically provide no better than 10° resolution. We find that the MiniPIX EDU is a suitable high-resolution low-noise platform to validate our simulation work wherein we image sealed gamma emitters. We further explore the viability of the Timepix for high-resolution pitch angle observations of radiation belt electrons. The authors acknowledge funding from the National Aeronautics and Space Administration (NASA) (Award #80NSSC21K1394).

Speaker: Riley Reid (University of Colorado Boulder)

17:11 P2.31: Chromatic detector-based spectral µCT of iodine-perfused osteochondral samples

Micro-computed tomography (µCT) is the gold standard for non-destructive 3D imaging of samples on the centimeter scale. Despite offering micrometric spatial resolution, conventional µCT provides limited detail visibility when applied to biological samples due to the small attenuation differences that exist among soft tissues. To overcome this limitation, highly absorbing contrast media are introduced in the sample, selectively filling structures or bonding to compounds of interest, enhancing their visibility. This technique is referred to as contrast-enhanced µCT (CEµCT) [1]. On the other hand, CEµCT does not allow for any material-specific discrimination or quantification, as the presence of the contrast is recognized purely on a morphological and/or grey-scale basis. This implies, for instance, that a contrast-medium-filled region might not be distinguishable from a contiguous highly absorbing detail (e.g., bone).
In this context, the availability of small-pixel spectral detectors equipped with multiple energy thresholds has enabled the development of spectral µCT (SµCT) systems. By using this type of detector, two (or more) images corresponding to tunable X-ray energy intervals are collected in a single shot. Owing to the different energy dependence of X-ray attenuation of different materials, these energetically binned images can be given as input to a spectral-decomposition algorithm to yield quantitative 3D density maps of selected decomposition materials. If the contrast medium has a convenient K-edge energy, images can be binned above and below the K-edge, enhancing the discrimination capabilities through material decomposition. This overcomes the intrinsic non-specificity of CEµCT and allows for the quantitative evaluation of contrast media concentration and the generation of virtual-non-contrast images.

In this contribution we present SµCT results obtained on osteochondral bovine samples perfused with a cationic iodine-based contrast medium (CA4+), having a selective affinity with negatively charged glycosaminoglycans (GAGs) in cartilage due to electrostatic attraction [2]. Images are acquired with a novel multimodal X-ray imaging system [3], integrating a CdTe spectral detector (Pixirad-PixieIII) with a pixel size of 62 × 62 µm2 over a matrix of 512 × 402 pixels (32 × 25 mm2) [4]. Pixirad features 2 energy thresholds and a charge-sharing compensation mode. The latter is of great importance as the energy crosstalk between bins induced by charge sharing negatively impacts material decomposition. Accurate spectral imaging is made possible by thorough energy response characterization and subsequent modeling, whereby the content of each energy bin can be estimated and used to compute the material-decomposition matrix (Fig. 1) [5]. Acquisitions are performed at a tube voltage of 50 kV, current of 200 µA, geometrical magnification of 1.85, and sample-to-detector distance of 65 cm.

Imaging results shown in Fig. 2 demonstrate a well-defined separation between the iodine-perfused cartilage and the underlying trabecular bone structure without requiring any manual segmentation. In addition, they allow quantifying the contrast medium concentration, reflecting the GAGs gradient naturally found across the cartilage, which can be considered as an indicator of the health state of the tissue. Compared to acquisitions CEµCT performed a commercial scanner based on a conventional integration detector (SkyScan 1072, SkyScan, Aartselaar, Belgium) and similar X-ray tube parameters and exposure, SµCT images demonstrate quantitative material discrimination capabilities and comparable spatial resolution.
[1] S de Bournonville et al., Contrast Media & Molecular Imaging 2019 (2019), 8617406
[2] NS Joshi et al., J. Am. Chem. Soc. 131 (2009), 13234–13235
[3] L Brombal et al., Scientific Reports 13.1 (2023), 4206
[4] R Bellazzini et al., JINST 10.01 (2015), C01032.
[5] V Di Trapani et al., Optics Express 30.24 (2022), 42995-43011.

The authors acknowledge funding from INFN-CSN5, call 22260/2020, project PEPI)

Speaker: Renata Longo (UNIVERSITY OF TRIESTE & INFN)

17:12 P2.32: X-ray computed tomography of the periodically moving object

X-ray computed tomography is now a common method of non-destructive testing of a wide range of static objects. In recent years, time-dependent tomography has been on the rise, for which it is necessary to record a series of tomographic data covering the event of interest. For slower events, conventional laboratory CT scanners can be used, while when events are faster, a very intense X-ray source is usually required. For high resolution requirements, the need for an intense X-ray source leads to the use of a synchrotron. This is because it is clear that in the case of an insufficiently intense X-ray source, the statistics in a single X-ray image are too low and a high quality tomographic reconstruction cannot be achieved. An exception is tomographic tracking of periodic events. As will be shown, for these, a good quality reconstruction can be achieved even in the case of a relatively low-intensity X-ray source. A crucial condition is the precise synchronization of all components of the system. While sufficient statistics in a single projection is achieved by integrating very short images acquired at an identical position of the moving object. In all cases, it is necessary to have an imaging detector with a sufficiently high frame rate, accurate synchronization via a common trigger signal and the possibility of very short exposure times.

Tomography of a periodically moving sample with a frequency of 4 Hz and an amplitude of 2.5 mm was performed using a Dexela 1512NDT detector. The resulting tomographic reconstruction has almost the same quality as in the case of tomography of a static object. The Dexela detector with 2x2 binning has a minimum exposure time of 25 ms, using external HW triggering. As an alternative, a 2x5 MPX3 detector with a sensor thickness of 500 mm was tested, which has excellent temporal resolution and thus allows tomography at higher frequencies.

Speaker: Daniel Vavrik

X-ray computed tomography of the periodically moving object.ppsx

17:13 P2.33: DEVELOPMENT OF A SMALL- SIZE SCINTILLATOR-BASED NEUTRON GAMMA RAY SPECTROMETER FOR TERRESTRIAL AND SPACE APPLICATIONS

We present the development of a neutron and gamma ray spectrometer for possible use in terrestrial and planetary science. The spectrometer module is called the Cosmogenic Neutron Detector (CosmoNeD) and is based on a monolithic scintillator with a silicon photomultiplier (SiPM) array and an integrated readout electronics. The prototype is under development and evaluation for small neutron spectrometers for terrestrial and space applications and will detect neutrons with energies of 0.025 eV – 1 MeV with energy resolution of 4% at 662 keV (Cs) with the capability of distinguishing gamma-rays in the same range. It has the objective to measure the abundance of hydrogen bearing compounds and some rock-forming elements in the soil for moisture measurements and planetary geology studies. The preliminary results regarding its performance with various gamma-ray sources are presented here.

Speaker: Deniz Ölçek (CENSSS, IDEAS)

17:14 P2.34: Particle Tracking and Monitoring of High-Intensity Proton Beams with Scattering Foil and Pixel Detector Timepix3

Monitoring and characterization of accelerator particle beams is necessary for operation of the facilities and their use in a broad range of applications from basic research (nuclear and high-energy physics) to applied research such as particle radiotherapy. Particle beams are typically produced in high beam intensities (> nAmp) which can be directly monitored by current-integrating devices and gas-based detectors. Conventional beam monitors provide namely the total beam current intensity and time profile with limited information on beam composition, beam size and directionality (beam divergence). When the beam intensity can be significantly decreased, detailed and more complete information can be provided by placing a high-resolution imaging detector directly on the beam path. Detailed information on the beam can be thus directly measured with hybrid semiconductor pixel detectors of the Timepix family [1]. For high-intensity beams however, positioning the detector on the beam path is no longer feasible. For this purpose, we make use of a scattering foil and detect the scattered beam particles behind the target and away from the beam axis – see Fig. 1b. A high-density thin foil (Ta, < 1 mm thick) is chosen for optimal yield of Rutherford scattering. We use a Timepix3 detector operated in compact electronics MiniPIX Timepix3 (Fig. 1a) [2] for directional- and energy-sensitive tracking of the scattered particles (Fig. 1c) [3]. Experiments were performed with proton beams of intensity in the nAmp range at the light ion cyclotron U 120M of the NPI Prague (33 MeV) and at a cyclotron Proteus 235 at the PTC Prague (100 and 226 MeV). We tested various beam settings in terms of beam energy, intensity, beam size, distance, and geometry. Tilting the detector-sensor plane to the direction of the particles increases the spectral-tracking resolution. Pattern recognition analysis of the pixelated tracks of single particles enables to reconstruct the trajectory of the scattered particles in wide (2π) field-of-view (FoV) without the need for collimators and with particle-type resolving power and high discrimination of background [4]. At the detector position Timepix3 registers the spatial and also the directional distribution of scattered protons (Fig. 2). The angular resolution for heavy charged particles and protons is around 10º along the elevation direction and around 2º along the sensor plane (azimuth angle) [3]. The particle beam can be imaged along the beam axis at the foil position by back-projection reconstruction (will be presented). Results provide multiple-parametric information on the primary beam in terms of particle flux, beam size (limited resolution), time dependence and spectral distribution. We extrapolate the detector results and derive information on the primary beam intensity by dedicated Monte-Carlo simulations using MCNP6.2 [5].

Speaker: Dušan Poklop

17:15 P2.35: Preclinical PET scanner with timing and 3D positioning capabilities based on semi-monolithic crystals

Semi-monolithic crystals have the potential of combining the timing capabilities of pixelated crystals and the 3D positioning of monolithic crystals. These crystals are monolithic blocks segmented in one direction, in pieces named slabs. If these slabs are optically isolated, the scintillation light spreads among a reduced number of photodetectors, increasing the number of optical photons that reach each photodetector, which improves the timing capabilities. In the monolithic direction, the Light Distribution can be characterized and, thus, the Depth of Interaction information can be retrieved, while preserving the sensitivity and good spatial resolution of monolithic detectors. We present here a prototype of a small-animal PET based on 28 semi-monolithic detector modules arranged in two rings of 106 mm inner diameter and covering an axial length of 52 mm.

Speaker: Jose M. Benlloch

17:17 P2.36: Detection of Secondary Neutrons in Proton and Gamma Radiotherapy Fields with the Pixel Detector Timepix3

Mixed-radiation fields such as space radiation in LEO orbit, atmospheric cosmic rays, high-energy accelerator and particle radiotherapy environments can produce or contain neutrons as secondary radiation. The neutron energy spectrum can cover a wide range from keV level up to hundreds of MeV (referred as fast neutrons) in addition to a thermalized meV component. Their presence can contribute to the deposited dose and also distort the overall monitoring and dedicated measurement of other radiations (charged particles, gamma rays). At the same time, the detection and measurement of neutrons in such fields can be challenging due to the indirect detection mechanisms, low detection efficiency and limited discrimination from background and unwanted radiations (e.g., protons, electrons and gamma rays).

For the detection of neutrons in broad energy range, we use the semiconductor pixel detector Timepix3 [1] operated and readout in compact radiation camera MiniPIX Timepix3 [2] – Fig. 1a. The pixel detector with a 500 µm thick silicon sensor was equipped with a neutron converter mask of thermal (6Li, few µm thick) and fast (plastic of three thickness: 50, 100, 150 µm) segments [3] – Fig. 1b. The detector was tested and calibrated at fast neutron fields [3] and newly with thermal neutrons at CMI Prague. In this work we measure the neutron component in mixed-radiation fields produced in water-equivalent (WE) PMMA phantoms by energetic protons (100 and 190 MeV at radiotherapy cyclotrons at CCB Krakow and PTC Prague) and gamma rays (from 9 and 18 MeV electrons from a radiotherapy LINAC). The detector was placed in the forward direction behind the phantoms of size greater than the beam range – Fig. 1c.

The neutron induced signals in the pixel detector [4] are determined by the given chip-sensor-converter architecture configuration and exhibit a wide variability in terms of spectral-tracking morphology and detection efficiency [3]. The single-particle pixelated tracks are analyzed and classified according to particle-type classes [5] which can be used as neutron-sensitive detection channels [3] which are also partly spatially correlated to the neutron mask regions [3]. We apply this methodology and a calibration response function to detect and resolve the broad neutron component in the mixed-radiation fields studied. The response of the detector to one beam-phantom-detector configuration is shown in Fig. 2. The plots correspond to the mixed-radiation field decomposition in terms of components (three selected track-type classes are shown). The derived neutron detection efficiency is overall below 1% [3]. Data analysis and the results for various beam– phantom – detector configurations will be presented.

Speaker: Carlos Granja (ADVACAM)

17:18 P2.37: Experimental and simulation study of near-field coded-mask imaging for proton therapy monitoring

I will present the results of testing the coded-mask imaging technique for monitoring the range of proton beams during proton therapy. The objective was to investigate the performance of experimental imaging setups, each consisting of a structured tungsten collimator in the form of a Modified Uniformly Redundant Array (MURA) mask and a LYSO:Ce scintillation detector of fine granularity with 1.36 mm pitch. The focus was on 22Na and 137Cs point-like source reconstruction.
The setups featured masks of different patterns and different detectors enabled the reconstruction of either only longitudinal or together with lateral coordinates of the hit position. Consequently, one of the tested setups allowed 1D image reconstruction and the other 2D. Additionally, Monte Carlo simulations of a larger 1D-imaging setup of the same type as one of the prototypes were conducted to assess the feasibility of reconstructing a realistic source distribution. A series of measurements with 22Na and 137Cs sources were performed to test the setups performance of near-field gamma imaging. The images of point-like sources reconstructed from the two small-scale prototypes data using the MLEM algorithm provided experimental proof of principle for the near-field coded-mask imaging modality in both the 1D and 2D modes.
The simulation of the full-scale 1D setup with realistic source distribution yielded a mean distal falloff retrieval precision of 0.72 mm, demonstrating that the proposed full-scale setup is competitive with the knife-edge-shaped and multiparallel slit cameras investigated by other groups. The results of this study indicate that coded-mask imaging is a viable option for proton therapy monitoring, with relatively fast image reconstruction times of several seconds on a desktop PC using CPU.
I would like to give an oral presentation.

The authors acknowledge funding from the Polish National Science Centre (grants 2017/26/E/ST2/00618 and 2019/33/N/ST2/02780). The exchange of staff and students between Poland and Germany was possible thanks to the support of the Polish National Agency for Academic Exchange (NAWA) as well as the German Academic Exchange Service (DAAD) (project-ID 57562042). Sensor tile and electronics were developed within the European Union’s Horizon 2020 research and innovation programme under grant agreement No 667211.

Speaker: Vitalii Urbanevych (Master)

17:19 P2.38: Development of near-infrared-sensitive single photon avalanche diode prototypes for a quantum ghost imaging system

Detection of photons in the near-infrared (NIR) range is utilized to implement several quantum imaging and key distribution techniques for remote sensing [1-3]. Our research group is working on a quantum ghost imaging system (QGIS) project that aims to obtain images of distant objects using entangled photons in the NIR region. The photon source exhibiting quantum correlation is composed of a 1554 nm signal photon and an 809 nm idler photon which are generated through spontaneous parametric down-conversion by injecting a 532 nm pump beam into a periodically poled lithium niobite (PPLN) crystal. We have confirmed that the point source is feasible [4] and are now developing a line source to reduce the imaging acquisition time. To detect the 1D idler photons, we are also working on a NIR-sensitive single photon avalanche diode (SPAD) 1D array. In the first stage of the SPAD array development, single SPAD prototypes of different sizes were designed at the Korea Advanced Institute of Science and Technology (KAIST) and fabricated in a 180 nm CMOS technology at the Advanced Micro Foundry (AMF). This study presents the results of the characterization of NIR-sensitive SPADs that operate with a passive quenching mechanism. The key parameters required in QGIS, such as the dark count rate (DCR) and photon detection efficiency (PDE), were evaluated. As a result, the PDE (@ 810 nm) for a SPAD with an area of 60 x 60 um2 ranged from 5% to 25%, and the DCR was at the level of 2 to 75 kHz. Although the results from this prototype are promising, there are still areas that need to be solved to enhance its performance in the future.

Speaker: Gyohyeok Song

17:20 P2.39: Enhancing Design, Calibration, and Characterization of Detectors at the European XFEL with the Pulsed X-ray Test System (PulXar)

Fourth-generation light sources, like free-electron lasers (FELs) and synchrotrons, have greatly advanced X-ray research in many fields. However, high-performance detector technology is needed to fully utilize these facilities. The PulXar system addresses these challenges by offering a range of tunable features for studying detector performance. It provides uniform X-ray illumination and has shown excellent performance in tests. This work presents the design and results of testing various detectors using the PulXar system.

Speaker: David Lomidze (European XFEL)

17:21 P2.40: Spectral response of the iLGAD sensors to soft X-rays

Single photon detection of fluorescent X-rays down to 452 eV with a signal-to-noise ratio greater than 20 has been demonstrated using 25 um pitch iLGAD sensors, bump-bonded to a charge-integrating readout chip Moench. These iLGAD sensors combined with a thin entrance window developed in collaboration with FBK are optimized for soft X-ray detection by having an excellent quantum efficiency in the corresponding energy range. Additional measurements using monochromatic X-ray photons from 390 eV to 900 eV have been performed recently at the SIM beamline of the Swiss Light Source. The spectral response features double peaks at each photon energy, corresponding to the signals generated by electron- and hole-initiated charge multiplication. It has been found that the ratio of the signals height depends on the design of the gain layer of the iLGAD sensor and the counts under the peaks change with photon energy. To understand this behavior, a customized simulation program has been developed: it takes into account the impact ionization process, carrier drift and diffusion, charge collection by the readout electrodes as well as the electronic and shot noise. The simulation results have been compared to the measurements, which show good agreement to a large extent. The measurement and simulation results will be discussed.

Speaker: Jiaguo Zhang (Paul Scherrer Institut)

17:22 P2.41: Performance testing of gas-tight portable RPC for muography application

Muography is a technique used for scanning by analysis of muon interaction with a target object. Our aim is to develop a portable gas sealed RPC detector prototypes for muography application and to test it for long-term operation to ensure gas stability. For this purpose, various experiments have been conducted such as the I-V curve (which gives information about the working voltage), efficiency with respect to the trigger from plastic scintillators and time response.

Speaker: Mr Vishal Kumar (UCL - CP3)

17:23 P2.42: Field Test for Performance Evaluation of a New Spent-Fuel Verification System in Heavy Water Reactor

There are four CANDU-type reactors under IAEA safeguards at the Wolsung site in South Korea; One of them (Wolsung unit 1) was permanently shut down on the 24th of December, 2019. A new spent-fuel verification system(IOVES) in our previous studies was developed to deal with problems of the existing instrument(OFPS), which has been used to re-verify spent-fuels of the CANDU-type reactors. A field test at Wolsung unit 4 in Korea is carried out to evaluate the performance of the newly developed spent-fuel verification system. This paper aims to discuss the results of the field test in terms of sensitivity, ability to distinguish signals from above and below spent-fuel assemblies, effects of radiation scintillation materials, and the validity of using a reference optical fiber to remove background radiations.
Using the existing and new verification systems, as shown in figure 1, we have measured 19 layered spent-fuel bundles in the spent-fuel storage pool of the Wolsung unit 4. The scan speeds of the existing and new ones are 2 mm/sec and 50 mm/sec, respectively. To evaluate the performance of the new instrument according to the scintillator type, the new instrument examined the multi-layered spent-fuels using three different scintillators (p-terphenyl, BC400, and GS30). The signal generated in the optical fiber itself by the interaction of background radiations and the optical fiber has been obtained using a reference optical fiber to which a radiation scintillator is not bonded.
Although the scan speed of the new instrument was more than 20 times faster than that of the existing one, as shown in figure 2, the former’s sensitivity and ability to distinguish the above and below spent-fuel bundles was far superior to the latter. Experimental results also showed that the p-terphenyl organic scintillator performed the best of the three scintillators. Signals that were not visible in results obtained by the Li glass scintillator (GS30) were observed in the signal obtained by the p-terphenyl and BC400 scintillators. The excellent performance of the new verification instrument appears to be mainly due to the high light output and low decay time of the p-terphenyl. It was also confirmed that in the present instrument, the ability to distinguish between the above and below spent-fuel assemblies was improved to some degree by extracting the background radiation signal from the total signal which was produced by both the optical fiber and the scintillation material. On the other hand, for the new instrument, there is little difference in the ability to distinguish the spent-fuel bundle layers. The effects of removing the background radiation would depend on the relative signal amplitude of the scintillation material and the optical fiber. The newly developed verification system is expected to reduce the time and effort required for IAEA safeguards inspection activities and to lower the nuclear operator’s burden.

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

17:24 P2.43: Application and image characterization of the deconvolution algorithm in an indirect X-ray imaging detector with scintillators

In recent years, X-ray imaging detectors in combination with scintillator screens have been widely used in digital x-ray imaging applications. These indirect X-ray imaging detectors are incorporated in the combination of a TFT or CMOS back plane array with different scintillation screens such as typical CsI and GOS materials. Some detectors can be applied with different scintillators in order to optimize the sensitivity and spatial resolution for a dedicated application. The intensity and scattering of visible light generated in the scintillator layer of indirect conversion detector is primarily determined by the X-ray absorption efficiency and light conversion efficiency of the used material.
In this work, we have employed efficient Gd2O2S:Tb(GOS) scintillator film with high atomic number and different thickness for X-ray imaging detectors. A large-area image detector consists of CMOS array with a 204mm x 200mm active area with 2048x2000 pixel array and 100um pixel pitch. A mount of light generated by incident x-ray energy is rapidly scattered before it is sensed on photodiode arrays. Thick GOS screens, which are better at absorbing high-energy x-rays, show strong light blurring and can't be used for high-resolution imaging tasks. In order to solve this severe problem, different deblurring algorithms such as a simple deconvolution using the estimated PSF (point spread function) and special blind deconvolution were applied in indirect X-ray imaging detector and its imaging characterization and the effect in performance was also investigated.
The relative sensivity to X-ray dose, signal to noise ratio (SNR), and spatial resolution in terms of the modulation transfer function (MTF) of different scintillator screens were measured to analyzed the imaging performance. The experiment imaging characerization in accordance with dfferent debluring technique were compared and analyzed. The initial results demonstrated its ability to achieve a high-spatial resolution imaging under low X-ray exposure condition.

Speakers: Dr Bo Kyung Cha (KERI), Mr Hynwoo Lee (Yonsei University)

17:25 P2.44: Relative dosimeter study of therapeutic radiation beam energy based on photochromic switching film and semiconductor oxide composite for evaluating the feasibility of radiation detection capability

Current commercially available therapeutic radiation beam energy detection sensors have excellent signal detection efficiency, but have characteristics in which stability is deteriorated due to the occurrence of micro-cracks in the detection sensor according to the change in incident beam energy. In addition, noise generated by the drift of remaining electron-hole pairs for which signal collection has not been performed degrades the reproducibility and precision of the sensor, resulting in a problem in overall signal detection efficiency. In particular, as a major problem in commercial sensors, the energy dependence of the photon beam, directional dependence, thermal effect, and damage to the device due to incident radiation are being discussed as limitations of the silicon diode. This reduces the signal detection efficiency when used for a long period of time, making it impossible to detect signals stably. Therefore, this study aimed to develop a photochromic switching film and a sensor based on a photoconductor-metal oxide composite structure that can exhibit excellent signal detection efficiency in therapeutic radiation QA verification and excellent sensor precision and reproducibility. For measurements, 6 MV and 15 MV energies from LINAC systems (CLINACiX-S, Varian Inc., USA) were used. Electrometers (6517A, Keithley, USA) and oscilloscope (WaveSurfer 510, Teledyne LeCroy, USA) were connected to the manufactured dosimeter to obtain electrical signals from radiation. The sample-to-sample distance is set to 100 cm. The waveform and signal when irradiated with radiation were obtained using an oscilloscope. The obtained signal was calculated from the accumulated amount of charge using ACQ software (Biopac, Acq Knowledge 4.2, Canada).
As a result of plotting the transmission voltage (T-V) curve using a photodiode, the saturation voltage and threshold voltage according to the voltage are estimated to be about 2.54 V for 10% transmittance of the bias voltage and 10.25 V for 90% transmittance bias voltage. It became. Therefore, if the charge carriers generated in the photoconductor-metal-oxide composite set the sensor driving voltage within the dynamic range, the signal detection efficiency can be increased by increasing the linearity of transmission. The reproducibility results according to radiation irradiation. RSD measured values at 6 MV and 15 MV energies were 1.32c% and 1.24%, respectively. As a result of the reproducibility evaluation, evaluation criteria of 1.5% were satisfied at 6 MV and 15 MV energies. This indicates that the signal stability is suitable for use as a radiotherapy QA dosimeter. The linearity results according to dose changes. The R2 values according to linear regression analysis at 6MV and 15MV energies are 0.998. Hence, the evaluation criteria are satisfied, and the output signal is proportional to the dose change. This indicates that it is suitable for use as a radiation therapy QA dosimeter. These results suggest that the film-type perovskite dosimeter is suitable for a radiotherapy QA dosimeter.
[1] D. A. Low, M. M. Jean, F. D. James, D. Lei and O. Mark, Dosimetry tools and techniques for IMRT, Medical Physics 38 (2011) 1313.
[2] Z. Li, Radiation damage effects in Si materials and detectors and rad-hard Si detectors for SLHC,JINST 4 (2009) P03011.

Speakers: YEJI HEO (Department of Nuclear Applied Engineering), Dr Seung Woo Yang (Department of Radiation Oncology, Busan Paik Hospital, Inje University)

17:26 P2.45: SiPM characterization for the SBC dark matter search

In the continuing search for dark matter, new and more complex technologies have been developed with increasing accuracy and background requirements. The Scintillating Bubble Chamber (SBC) detector combines two proven technologies: bubble chambers and liquid argon scintillator experiments. In order to reach the ultimate projected goal, a Seitz threshold of 100eV is required and therefore the scintillation system needs to be well understood.
This system consists of a liquid argon (LAr) scintillator doped with on the order of 100ppm of Xe, with the light collection accomplished using 32 Hamamatsu VUV4 silicon photomultipliers (SiPMs). One of the requirements of the scintillation detection system is the ability to veto single photoelectron (pe) signals. Distinguishing scintillation pe pulses from dark noise and correlated avalanches requires a well understood model of the pe gain, dark noise rate, $\mu$, and the number of correlated avalanches, $N_{CA}$, as a function of temperature and over-voltage. This talk will discuss the efforts of the SiPM characterization chamber consisting of a temperature-variable RF shield inside a vacuum chamber with $10\text{mK}$ temperature stability from 233K to 293K. A preliminary overview on the analysis to extract the pe gain, breakdown voltage, $\mu$ and $N_{CA}$ in a 5us window will also be discussed.

Speaker: Hector Hawley Herrera

Hector Hawley Herrera Poster.pdf

17:27 P2.46: Neutron Radiation induced Effects in 4H-SiC PiN Diodes

Silicon Carbide (SiC) is a wide-bandgap semiconductor that has recently become a topic of intensified interest in the HEP instrumentation community due to the availability of high-quality wafers from the power electronics industry. SiC features multiple advantageous material properties over silicon. It is insensitive to visible light, hypothesized to be more radiation hard, and has much lower leakage currents, even after irradiation. Especially for future high-luminosity experiments, the radiation hardness is an essential parameter. One of the most important metrics associated with radiation hardness is the charge collection efficiency (CCE), which typically decreases with irradiation due to the formation of traps and defects. A thorough understanding of these traps and defects is crucial for estimating the performance of a detector over its lifetime and can open to the door to techniques such as defect engineering.
We present the current status of characterization and simulations for 50 μm thick 4H SiC PiN diodes together with radiation hardness studies. The characterization work includes determination of material parameters of 4H-SiC (ionization energy and Fano factor) and comparisons to TCAD and Monte-Carlo simulations. Recently, significantly increased signals (with respect to unirradiated samples) were reported for neutron-irradiated SiC diodes in forward bias using UV-TPA-TCT, hinting at charge multiplication [1]. We re-investigate neutron irradiated 4H-SiC PiN diodes (fluences between 5·10¹⁴ and 1·10¹⁶ cm⁻² 1 MeV neutron equivalent neq) which have been previously characterized using UV-TCT [2] and alpha spectroscopic measurements [3]. The CCE and transient waveforms were measured in forward and reverse bias using alpha and UV-TCT measurements. Furthermore, I-V and C-V measurements for forward as well as reverse bias voltages of up to 3kV were performed to serve as additional input in understanding observed radiation damage.
For samples irradiated to 5·10¹⁴ and 1·10¹⁵ neq cm⁻², the CCE in the forward direction grows exponentially, surpassing 100% and coinciding with an increase in the leakage current. At the highest irradiation fluence, no exponential behavior was observed. However, the CCE in the forward direction was found to be larger than for reverse bias. For this fluence, the leakage current remained below 1 nA.

Speaker: Andreas Gsponer (Austrian Academy of Sciences (AT))

poster.pdf

17:28 P2.47: Patient positioning based on a helium-beam radiograph (αRad)

Introduction: In particle radiotherapy it is even more important to precisely align the patient with the treatment beams than in the conventional photon radiotherapy. Currently two orthogonal X-ray projections are used in clinics for patient positioning. We developed a unique method to perform such alignment of the patient with the beam based on radiography with helium ion beams (αRad). The advantage of such method is a capability of simultaneous verification of stopping power of the tissue, which is crucial in ion beam radiotherapy. Spatial resolutions of approximately 0.5 lp/mm (MTF10%) were demonstrated. With the method presented here, inter- and intrafractional variations, including movements, could be detected and corrected for prior to each treatment. In this contribution, the feasibility of patient positioning using αRad was assessed for an anthropomorphic head phantom.

Materials and Methods: First, we identified a region of interest (ROI) in a head phantom that shows high sensitivity to movements. We performed it on projections of an X-ray CT after small rotations and translations by comparing it to the unaltered CT projection. High sensitivity was typically observed in regions at bone-soft tissue interfaces.
Subsequently, these regions (approx. 3 cm by 3 cm) were imaged by helium ion radiography at the Heidelberg Ion-beam therapy center. The previously developed ion beam imaging system was used. The system consists of six parallel thin silicon pixel detectors using the detector technology Timepix. The sensitive area is 256 pixels by 256 pixels (14 mm x 14 mm) and each detector is capable of detecting single ions with either information on time of arrival or energy deposition. The detectors are placed parallel in pairs. The tracking unit in front and behind the imaged object are used to trace the most-likely path of single ions in the imaged object. The additional unit to measure the energy deposition of the single ions is positioned at the rare of the imager. Helium beams with initial beam energies between 166.8 MeV/u and 186.7 MeV/u were used at fluences and fluence rates far below the clinically used ranges. Calibration curves were developed to translate the energy deposition to water-equivalent thickness of the traversed material of the imaged object.
To investigate the feasibility and accuracy of patient positioning based on αRad, two αRads of the previously identified regions of interest (ROIs) were acquired. The aim was to mimic a possible small rotation of the patient’s head at exactly 1˚ with respect to a reference measurement. The phantom was rotated along its coronal axis by 1˚ with a high-precision rotation table. An in-house 2D-to-3D image registration algorithm, a tool for aligning a 2D image to a 3D image volume, was used to line up the two radiographs to the original X-ray CT image.

Results: The performance of method was evaluated for three sets of two radiographs by comparing the suggested changes in translation and rotation to the ground truth rotation of 1˚. The rotations along the coronal, axial and sagittal axes were accurate to -0.07˚, 0.17˚, 0.12˚, and precise to 0.15˚, 0.31˚, 0.10˚, respectively. For translations, an accuracy of 0.02 mm for x-axis, 0.06 mm for y-axis, and a precision of 0.03 mm for both axes were calculated.

Conclusion: This study of accuracy and precision of patient positioning using αRads demonstrates the feasibility of the usage of helium-beam radiography for patient positioning in future clinical application.

Speaker: Daria Zhevachevska (Deutsches Krebsforschungszentrum)

17:29 P2.48: Characterization of interpad "no-gain" region in the novel, trenched LGADs, from the TI-LGAD RD50 batch production using a fs-laser based TCT-SPA and TPA -TCT at the ELI Beamlines, ELI ERIC

In this report we present the results from the two extensive campaigns at the ELI Beamlines, ELI ERIC, on the TI-LGAD prototypes from the TI-LGAD RD50 run production. The focus has been given to the study of the inter-pad region and to the inter-pad distance (IPD) measurements. The TI-LGAD prototypes with the one trench are compared to those with the two tranches. Also, untypical UFSD Type 10 Prototype, with 2p-stops and guard bias ring in between p-stops (produced as a reference prototype in the same batch and from the same wafer as trenched LGADs), is compared to the trenched LGADs with two trenches. The two experimental techniques, the fs-laser based TCT-SPA and the TPA-TCT are compared. In particular, the potential of fs-laser based SPA in resolving the structures of the inter-pad region will be emphasized. We will also discuss the the inter-pad region response to very high intensity injections.

Speaker: Prof. Gordana Lastovicka-Medin (University of Montenegro)

17:30 P2.49: First measurements and results of monolithic active pixel test structures produced in a 65 nm CMOS process

The ALICE Inner Tracking System (ITS) [1] at CERN will undergo an upgrade during the LHC long shutdown 3, in which the three innermost tracking layers will be replaced. This upgrade, named the Inner Tracking System 3 (ITS3) [2], employs stitched wafer-scale Monolithic Active Pixel Sensors 280 mm in length fabricated in a 65 nm CMOS technology thinned to < 50 μm and bent to form truly cylindrical half-barrels. The feasibility of this technology for the ITS3 was explored with the first test production run (MLR1) in 2021, whose goal was to evaluate the charged particle detection efficiency and performance under non-ionising and ionising radiation up to the expected levels for ALICE ITS3 of 1×10$^{13}$ 1 MeV n$_{eq}$ cm$^{−2}$ (NIEL) and 10 kGy (TID). Three sensor flavours were produced to investigate this technology: Analog Pixel Test Structure (APTS), Circuit Exploratoire 65 (CE65) and Digital Pixel Test Structure (DPTS) each measuring 1.5 mm × 1.5 mm in size.

The APTS incorporates a 6×6 pixel matrix with direct analogue readout on the central 4×4 pixels. Two versions of the output buffer were implemented: a source-follower (APTS-SF) and a fast operational amplifier (APTS-OA). In addition, the sensor was produced in four different pixel pitches ranging from 10 μm to 25 μm. The CE65 is a “large” area chip with an analogue rolling shutter readout. The pixel matrix either consists of 64×32 or 48×32 pixels implemented in two pixel pitch sizes: 15 μm and 25 μm. The DPTS features a 32×32 pixel matrix with a pitch of 15 μm and a digital front-end with asynchronous readout. All the pixels are read out simultaneously via a differential digital output that time encodes the pixel position and Time-over-Threshold (ToT).

The performance of the MLR1 chips was evaluated through extensive characterisation in the laboratory and with in-beam measurement. The measurements show that the MLR1 was a success due to the large number of operational prototypes that allow the parameter space of the technology to be mapped out. Furthermore, the MLR1 exhibits excellent performance in terms of detection efficiency (> 99%) and spatial resolution (3-4 μm) from the in-beam measurements for all three sensor flavours. The radiation hardness is demonstrated by the sensors maintaining a detection efficiency of 99% for APTS-SF and DPTS chips irradiated with a dose of 1×10$^{15}$ 1 MeV n$_{eq}$ cm$^{−2}$ and operated at +15 °C and +20 °C, respectively. The detection efficiency and the fake-hit rate for DPTS sensors irradiated to different levels are shown in Fig. 1. In addition, a time resolution of < 100 ps for the APTS-OA and < 10 ns for the DPTS has also been measured.

This contribution will cover an overview of the MLR1 submission, a description of the different sensor flavours and present the results of the performance measurements in the laboratory and with particle beams at various settings and irradiation levels for all three sensor flavours.

[1] ALICE Collaboration, doi:10.48550/arxiv.2302.01238
[2] ALICE Collaboration, doi:10.17181/CERN-LHCC-2019-018
[3] G. Aglieri Rinella et al., doi: 10.48550/arXiv.2212.08621

Speaker: Matthew Daniel Buckland (Universita e INFN Trieste (IT))

17:31 P2.50: Enhancing accuracy of effective atomic number mapping with deep learning-based conversion: A promising alternative to dual-energy CT

Effective atomic number (Zeff) is a critical parameter in radiation therapy and nondestructive testing applications. Although dual-energy computed tomography (DECT) is widely utilized for the determination of Zeff, it is associated with several limitations, including increased patient exposure and substantial equipment costs. To overcome these challenges, we propose a novel approach that employs a deep learning model (RegGAN) to achieve accurate Zeff calculation. This method involves the conversion of low-energy CT to high-energy CT, followed by Zeff map generation. In this study, we conducted an in-depth comparative analysis between the RegGAN-based conversion technique and traditional DECT methodologies, evaluating their respective accuracy and noise reduction capabilities. Our experimental results showed that the proposed RegGAN-based conversion method outperformed DECT in terms of Zeff mapping accuracy (approximate 10% improvement). Furthermore, the RegGAN model showed superior performance to alternative deep learning models, such as U-Net, GAN, and Cycle-GAN. Of particular note, the proposed method effectively mitigated noise in high-energy image, leading to enhanced Zeff accuracy. Our findings suggest that the deep learning-based conversion technique presents a promising alternative to DECT, providing a more precise and cost-effective solution for Zeff mapping in radiation therapy and nondestructive testing applications.

Speaker: Minjae Lee (Yonsei University)

17:32 P2.51: Eliminating grid artifacts of crisscrossed antiscatter grids in CBCT for improving its image performance

Cone-beam computed tomography (CBCT) is an efficient X-ray imaging modality that can reconstruct a wide area with single scan, compared to multi-detector CT. However, in CBCT, more scatters produced through the object reach detector surface, resulting in the reduction of image contrast. Recently, to address this problem, JPI healthcare Co. in Korea developed a prototype two-dimensional antiscatter grid, the so-called crisscrossed antiscatter grid, by adopting micro-controlled sawing process and carbon interspace material to improve its scatter removal ability. However, the most critical obstacle remaining for the successful use of crisscrossed grids in CBCT is the observation of grid artifacts (e.g., ring artifacts on CBCT images), which can result in a misdiagnosis by physicians [1]. In a previous study [2], we developed an effective software-based grid artifact reduction (GAR) algorithm for eliminating the related artifacts in two-dimensional (2D) radiography. In this study, to demonstrate the feasibility of the GAR algorithm to CBCT system with a crisscrossed grid, we modified the GAR algorithm for CBCT and conducted an experiment using a table-top setup. Figure 1 shows the schematic of a crisscrossed grid and an experimental setup used in this study. The setup primarily comprised a conventional X-ray tube (100 kVp and 4 mA), a focused crisscrossed grid (strip density of 43.8 lines/inch), and an a-Si/CsI flat-panel detector (145 μm pixel size).
Figure 2 shows the projection images of MK pro-CT II and ACR phantoms before and after applying the modified GAR algorithm. Figure 3 shows the resulting CBCT images of the phantoms using the standard filtered backprojection algorithm before and after applying the GAR algorithm. Figure 4 shows the measurements of contrast-to-noise ratio (CNR) and HU error of the two phantoms. Here the CNR and HU error of reference images without grid are also shown for comparison. According to our preliminary results, the image quality of the CBCT images were effectively improved by using the crisscrossed grid and the modified GAR algorithm. More quantitative experimental and simulation results will be presented in the paper.

Speaker: Mr DUHEE JEON (Yonsei university)

17:33 P2.52: Advances in the TCAD modelling of non-irradiated and irradiated Low-Gain Avalanche Diode sensors

The recently developed Low-Gain Avalanche Diode (LGAD) technology has gained growing interest within the high-energy physics (HEP) community, thanks to its capability of internal signal amplification that improves the particle detection [1]. Since the next generation of HEP experiments will require tracking detectors able to efficiently operate in environments where expected fluences will exceed 1E17 neq/cm2 [2], it is of the utmost importance the design of radiation-resistant particle detectors. To this purpose, Technology Computer-Aided Design (TCAD) simulations are a relevant part of the current detector R&D, not only to support the sensor design and optimization, but also the radiation damage understanding and modelling. In this contribution, the recent advances in the TCAD modelling of non-irradiated and irradiated LGAD sensors are presented, whose validation relies on the agreement between the simulated and experimental data - in terms of current-voltage (I-V), capacitance-voltage (C-V), and gain-voltage (G-V) characteristics, coming from devices manufactured by different foundries (e.g. HPK, FBK), and accounting for different irradiation levels and temperatures.

Speaker: Tommaso Croci (INFN, Perugia (IT))

poster_Croci_92_iWoRiD_2023_v1.pdf

17:34 P2.53: Scintillators and image characterization of a flat-panel X-ray detector for single-exposure dual energy imaging

In recent years, digital X-ray imaging detectors with indirect detection technology have been widely used in many medical imaging applications such as radiography, fluoroscopy and cone-beam CT. These indirect X-ray imaging detectors are based on the combination of a thin film transistor (TFT) array with several scintillating screens such as typical CsI, GOS materials. Currently, dual-energy (DE) imaging task using a dual-layer X-ray detection type allows the soft and hard structures (e.g. soft and bone tissues) in the object to be selectively visualized,
In this work, we have designed and employed dual-layer based a-Si array backplanes with top layer and bottom layer for X-ray imaging tasks. A prototype large area image detector consists of TFT array with a 43cm x 43cm active area with 3072x3072 pixel array and 140um pixel pitch. Different scintillation combination such as columnar CsI:Tl and Gd2O2S:Tb(GOS) with various thickness and spectral middle filters were used to investigate the imaging characterization. The specific scintillators in dual-layer configuration were selected and implemented for good image quality at low X-ray dose condition.
For imaging characterization of the dual-layer X-ray imaging detector, different scintillating screens were directly coupled on the prototype photodiode array panel. The preliminary important X-ray characterization such as the detector sensitivity to X-ray exposure dose, signal-to-noise-ratio (SNR) and modulation transfer function (MTF) and phantom imaging were measured under practical imaging systems with 60-120kVp tube voltage and adjustable tube current. The experimental results with a dual-layer based flat panel detector using combination of different scintillators and intermediate filter demonstrated its ability to perform accurate dual-energy imaging with single –exposure.

Speakers: Dr Bo Kyung Cha (KERI), Prof. Chang-Woo Seo (Yonsei University), Mr Minjae Lee (Yonsei University)

17:35 P2.54: Enhancing X-ray Detection Sensitivity through Hybrid Active Layers of PCDTBT and CdSe Core/CdTe Crown 2D Nanoplatelets

Due to their unique properties, nanocrystals (NCs) have attracted significant attention in various research fields. The NCs are classified into 0D quantum dots (QDs), 1D nanowires (NWs), and 2D nanoplatelets (NPLs) depending on their structures. Especially, 2D NPLs have the advantage of restricting quantum confinement effects only in the z-axis, unlike other NCs. Furthermore, NPLs composed of core and shell can adjust their properties by changing their structure. In this study, type-II cadmium telluride (CdTe) crowns were combined with cadmium selenide (CdSe) cores to improve the optical and electrical properties. Using 2D CdSe/CdTe core/crown NPLs, an improved indirect X-ray detector with an inorganic/organic hybrid active layer was developed. Figure 1a, shows the hybrid active layer was composed of Poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT), and CdSe core/CdTe crown NPLs. Figure 1b shows the corresponding energy levels of the proposed detector and the process of charge collection. To perform experiments on the blending ratio, PCDTBT:CdSe core/CdTe crown solutions were prepared in four different ratios of 1:2, 1:1, 2:1, and 3:1. Figure 2a, shows J-V characteristics of the proposed detectors, and Figure 2b, shows the trend of X-ray radiation parameters (CCD − DCD, sensitivity). The detector was optimized when the blending ratio of PCDTBT and NPLs was 2:1, and the highest JSC was 0.190 mA/cm2. Furthermore, radiation parameters showed a similar trend as JSC, and sensitivity was 0.173 mA/Gy∙cm2, which was 77.8% higher than that of the PCDTBT:CdSe core detector [1]. Our results suggest that the use of Type-II CdTe crowns represents a promising approach for enhancing the properties of semiconductor materials and have important applications in a wide range of fields, including electronics, optoelectronics.

Speaker: JAIWON SON (Convergence Semiconductor Research Center, Dankook University, Yongin-Si, 16890, Gyeonggi-Do, Republic of Korea)

17:38 P2.55: Development of prototype backscatter X-ray security scanner for luggage inspection

Backscatter X-ray imaging techniques are sensitive to organic materials (i.e., low-Z elements) due to a larger Compton scattering cross-section than that of other photon interactions. Therefore, it has the potential to be used as a security screening system to detect organic compounds, such as drugs and explosives. Additionally, it is possible to make a compact device because the X-ray generator and detector are positioned on the same side of the object. Because of these favorable characteristics, backscatter X-ray detection systems have been widely used for detecting illegal items concealed in luggage, screening vehicles, and containers, including detecting landmines in military border areas.
In the present study, a prototype of a backscatter X-ray security scanner for luggage screening was developed, and its performance was evaluated at various tube voltages. This system consists of an X-ray generator, a disk-shaped rotating collimator (i.e., chopper wheel), monolithic large-area detectors with associated signal processing electronics, and a conveyor. By rotating the disk-shaped collimator with slits, a vertically-swept pencil beam is formed, and then the conveyor is moved horizontally to perform an overall scan of the object. To obtain backscatter X-ray images, we utilized phantoms fabricated in accordance with the international standard (ANSI N42.46) as well as actual contrabands provided by the Korea Atomic Energy Research Institute. Using the prototype system, the isolation contrast, which represents the thinnest discernible thickness of an object when the background material differs from the object to be imaged, was determined to be about 1 mm. As shown in Figure 1, the contraband items (i.e., methamphetamine and cannabis) randomly hidden inside the luggage were clearly visible at tube voltages ranging from 80 to 160 kVp. It is expected that the backscatter X-ray security scanner can provide improved detection efficiency for thin objects and/or organic materials.

Speaker: Geunyoung An (Jeonbuk National University)

17:39 P2.56: Automatic inline defects inspection of lithium-ion battery cells using parallel-triple detection filtering (PTDF) algorithm

As a demand for lithium-ion battery (LIB) cells in industry continues to grow, more accurate inspection techniques are required for ensuring quality assurance (QA) during production. Detecting defects accurately, such as metallic foreign matters and crack, is important for inline QA testing, where both fast-processing speed and high accuracy are essential. Particularly, in the post-packaging step, X-rays are usually used for the inspection of LIB cells. Although several detection algorithms have been applied for the inline QA testing, those methods are often difficult to satisfy the requirements of the inline QA testing, mainly because of the computational cost and accuracy. In this study, to overcome this challenge, we proposed an effective method, the so-called parallel-triple detection filtering (PTDF) algorithm. Figure 1 shows the simplified flowchart representing the proposed PTDF algorithm that consists of two processes of the defects detection through the triple filtering consecutively and image fusion. By combining the filtered images with different sensitivity and specificity, the proposed algorithm can improve the detection accuracy of the defects in the LIB cells, saving the processing time. To demonstrate the feasibility of the proposed method, we performed an experiment using a table-top setup that consisted of an X-ray tube (70 kV_P and 1.4 mAs) and a CMOS flat-panel detector (49.5 μm pixel resolution). Figure 2 shows the experimental setup, battery cell used in the experiment and its radiograph, and the defects detection maps obtained using the Ostu, adaptive thresholding, k-means, and proposed methods. According to our preliminary results, the proposed algorithm effectively detected the abnormal structures in LIB cells and outperformed the existing algorithms in terms of accuracy and time. More quantitative experimental results will be presented in the paper.

Speaker: Mr Woosung Kim (Yonsei university)

17:40 P2.57: Effective noise reduction using a modified image pyramid incorporated with guided filtering for animal X-ray imaging

Radiography is one of the most commonly used diagnostic tools in veterinary practice and, particularly, denoising is one of the important image processing tasks. Robust noise removal will improve the image quality of diagnosis. There are many state-of-the-art noise reduction methods that have been studied in the image processing literature. Nevertheless, no algorithm that can robustly remove image noise has been universally accepted because the resulting image performance of a denoising algorithm can vary substantially, depending on the imaged subject, X-ray imaging system, and operating conditions. In this study, to overcome this challenge, we proposed an effective denoising method based on a modified image pyramid incorporated with guided filtering for the practice of companion animals. Compared to traditional pyramid-based approaches that use a Gaussian filter and two-stage pyramid, our approach uses a guided filter and three-stage pyramid to robustly separate noise component from the image, keeping image details . Figure 1 shows the schematics of the traditional and proposed pyramids. To demonstrate the feasibility of the proposed denoising algorithm, we performed the noise reduction of a dog’s radiograph, which was taken at an animal hospital, using the proposed algorithm, and evaluated the image quality in terms of the structural similarity and peak signal-to-noise ratio. Figure 2 shows the resulting images of a dog using several denoising algorithms: noisy image and denoised images using wavelet, traditional pyramid, proposed pyramid with Gaussian filtering, and proposed pyramid with guided filtering, followed by BayesShrink-based hard thresholding, respectively. According to our preliminary results, the proposed algorithm achieved the highest image performance among the other denoising algorithms, indicating its efficacy for reducing noise in animal radiography. More quantitative evaluation of the image performance will be presented in the paper.

Speaker: Mr Woosung Kim (Yonsei university)

17:41 P2.58: Study of bulk damage of high dose gamma irradiated p-type silicon diodes with different resistivities

The irradiation study of silicon diodes was carried out in order to evaluate the effects of gamma-irradiation on p-type silicon. Three types of n-in-p diodes from different manufacturers were studied. The diodes had comparable active area and thickness but different initial resistivities and oxygen concentration. Thanks to that we were able to determine how different initial parameters influence radiation-induced changes in measured electrical characteristics. The diodes were irradiated by a Cobalt-60 gamma source to total ionizing doses ranging from 0.50 up to 8.28 MGy, and annealed for 80 minutes at 60°C. The main goal of the study was to characterize the evolution of the full depletion voltage with total ionizing dose, by measuring capacitance-voltage characteristics, and the gamma-radiation induced displacement damage by measuring current-voltage characteristics.

Speaker: Iveta Zatocilova (Albert Ludwigs Universitaet Freiburg (DE))

17:43 P2.59: Simulation of Energy-Dispersive X-ray Spectroscopy Systems

Energy Dispersive X-ray Spectroscopy (EDS) is a common technique in electron microscopy to identify the chemical composition of samples. The standard method for analyzing the measurement data is semi-empirical, where the necessary correction factors have been determined decades ago using detectors much less sensitive than current ones.
This work shows that the Geant4[1] and AllPix2[2] open-source simulation tools can be used to accurately model the full EDS system. This is a first step towards a complete first-principles determination of the elemental composition from measured data, precluding the need for independently determined correction factors.
The simulations are compared to Scanning Electron Microscopy (SEM) measurements for validation and differences between simulation and measurements are highlighted.

Speaker: Thijs Withaar (Sioux Technologies)

poster_v1.1.pdf

17:44 P2.60: Time-efficient scanning schemes for x-ray μ-CT with a 2D structured beam

Introduction. Structuring the x-ray beam into a 2D beamlet array, as shown in Fig. 1, enables three-modal x-ray micro-computed tomography (μ-CT). The beamlets are created by placing an amplitude modulator (mask) with round apertures upstream of the sample [1,2]. Images with the following contrasts can be obtained: attenuation, refraction, and ultra small-angle scattering. Images with contrast based on the refraction channel, are integrated to yield phase-based images. This source of contrast provides 3D information of a sample’s internal structure which is complementary to attenuation, revealing details which are weakly attenuating and classically have a diminished contrast-to-noise ratio (CNR). Image contrast generated using the ultra small-angle scattering channel enables the visualisation of sample inhomogeneities below the imaging system’s resolution. The 2D beam structuring provides refraction sensitivity in two orthogonal directions, which reduces inherent image artefacts associated with phase integration. Beam tracking image acquisition [3] allows for the aforementioned three contrast channels to be retrieved from a single frame, with a hardware requirement of a high-resolution detector.

However, a single frame also contains heavily under-sampled data, since the parts of the sample covered by the mask septa cannot contribute to the image. To acquire fully sampled datasets, a “dithering” scheme needs to be applied. Here, the sample is imaged at each dithering step, and an up-sampled image is then obtained by combining the frames. Due to the 2D beam structuring, the sample must be scanned horizontally (along x) and vertically (along y), with a step size equal to, at most, the aperture size, and the full 2D scan must be repeated at each rotation angle. This results in an isotropic spatial resolution driven by the aperture size [4]. While providing adequate sampling, dithering results in long scan times as it cannot be implemented as a fly scan (characterised by a continuous rotation of the sample), but necessitates a step-and-shoot scan, which can be considered time-inefficient as it suffers from non-negligible scan time overheads. On the other hand, without dithering, i.e., if the sample is simply rotated and a single frame is acquired at each angle (a so-called “rotation-only” scheme), the spatial resolution is limited by the mask period [4], and aliasing artefacts may occur.

In our talk, we will report on two different fly scan compatible scanning schemes for x-ray μ-CT with a 2D structured beam (2D beam tracking method), developed to facilitate time-efficient three-modal scans. In addition, the detector requirements for such a method will be discussed.

1.Cycloidal-spiral scanning.
Here, the sample is continuously translated along two-dimensions (both vertically and horizontally), simultaneously with being continuously rotated. As for a rotation-only scan, a single frame is acquired per angular step. However, the “roto-translation” of the sample leads to a much more balanced distribution of the acquired datapoints, providing complementary information; missing data may be adequately restored via a dedicated data-recovery scheme. We have implemented the cycloidal-spiral sampling scheme at the Diamond Light Source (UK) with an sCMOS camera. We investigated the effect of the roto-translation trajectory of the sample and of different data-recovery schemes on the resulting image quality. The results suggest that an optimised cycloidal-spiral data acquisition and analysis scheme enables high-quality μ-CT images to be reconstructed with a spatial resolution which is isotropic and better than that achieved with rotation-only scans (Fig. 2), while also being fully fly scan compatible and therefore time-efficient. Acquired flyscans will be shown in the talk.

2. Isotropic resolution through unidirectional dithering.
We have adapted our mask design to remove the need for vertical dithering by minimising the vertical aperture separation, while still keeping the beamlets separated to allow for their effective tracking. This is achieved by using a mask that has 1) a horizontal aperture separation longer than the vertical and 2) apertures distributed in a staggered (slanted) manner (offset adjacent rows); the mask design fulfilling the above requirements will the described in the talk. This method offers the potential to fully illuminate a sample with a 2D beamlet array while only applying unidirectional dithering to achieve isotropic sampling in both directions. We implemented this scanning scheme with a laboratory microfocus x-ray source and a CMOS-based flat panel detector. The results of this first proof-of-concept study (Fig. 3) suggest that this simplified sampling scheme is indeed effective. While our initial results were obtained through a step-and-shoot scan, the approach is compatible with cycloidal CT, which is a fly scan compatible (and therefore time-efficient) scanning scheme by which the sample is continuously translated horizontally while simultaneously being continuously rotated [5].

Conclusion. We present two methods that provide a step toward the volumetric investigation of dynamic processes through CT fly scans, while enlarging the range of applications of three-modal tomography.

[1] C. Navarrete-León et al. arXiv:2212.07963 (2022). [2] G. Lioliou et al. Sci. Rep. 12, 21336 (2022).
[3] F.A. Vittoria et al. Sci. Rep. 5, 16318 (2015). [4] P.C. Diemoz et al. Opt. Express 22, 15514 (2014).
[5] C.K. Hagen et al. Phys. Rev. Appl. 14, 014069 (2020).

Speaker: Dr G. Lioliou (University College London)

17:45 P2.61: Feasibility Study of One-Dimensional Imaging with an Optical Fiber for Radiation Dose-Rate Monitoring System in the Decommissioning Process

For the decommissioning of Fukushima Daiichi Nuclear Plants, a real-time dose-rate monitor under the high dose-rate situation is required to remove the debris remaining inside the plants. We have proposed a dose-rate monitor consisting of a scintillator, optical fiber, and CCD spectrometer. Since an over 100-m long optical fiber is used, some noises (“fiber noise”) such as scintillation photons generating from the fiber itself and Cherenkov photons with a dominant emission band of below 550 nm must be separated from the signal from the scintillator. Therefore, longer emission wavelength (over 650 nm) and high light output are required for the scintillator.
　We focused on a Cr-doped Gd3Ga5O12 (Cr:GGG) scintillator as such applications. In addition, we focused on noise region in emission spectra that has some information originating from fiber noise. This noise is expected to show the dose rate information through the fiber. Thus, we report the radiation dose-rate monitoring system and the analysis of the noise data that we describe as “one-dimensional dose-rate distribution”.
Cr:GGG single crystal was grown with micro-pulling method and its optical properties were evaluated.
　One-dimensional dose-rate distribution was also evaluated with the fiber noise. Using this noise information, we can evaluate the integrated dose through the fiber. Moreover, emission spectra of the fiber noise are expected to be changed due to the absorption in the fiber, and the shapes of the spectra are expected to have position information for source of fiber noise. To evaluate the one-dimensional dose-rate distribution, demonstration of the monitoring system coupled with 20 m-long optical fiber and CCD spectrometer was operated. Optical fiber was placed around the 60Co source (approximately 60 TBq), and emission spectra of the fiber was acquired at each irradiated fiber length under high dose rate conditions (approx. 10-700 Gy/h).
　We grew Cr:GGG single crystal with Its emission wavelength was approx. 730 nm. As results of the demonstration, the noise intensities were well fitted with power function as a function of the product of fiber length and dose rate (integrated dose), and the fiber noise information can be used as dose rate information as one-dimensional imaging. In this paper, we discussed the evaluation of the relation of the intensity ratio of Cr:GGG and optical fiber noise and irradiated length of the fiber.

Speaker: Daisuke Matsukura (Tohoku University)

17:46 P2.62: Ex/in-vivo imaging of small animals using MPPC-based photon-counting CT

Photon counting computed tomography (PC-CT) is a new type of CT that is being studied worldwide. The radiation dose produced by PC-CT can be reduced up to 1/100 of that produced by the currently available CT scanners. In addition, obtaining information from multiple energy bands makes it easier to acquire images without artifacts and leads to accurate material decomposition. In this study, we use a detector system composed of a 64-channel multi-pixel photon counter (MPPC) coupled with a scintillator, which renders the proposed system to be simple and cost effective. We used the PC-CT in three experiments performed on mice and rats. The first experiment involves the in-vivo imaging of iodine-injected mice. The results showed that iodine accumulated in the kidneys and the bladder. Furthermore, we also captured time-shift images of the mice and successfully observed iodine being faded out of the kidneys. The second experiment involves the imaging of gold nanoparticle (AuNP)-injected mice. In this experiment, mice were sacrificed before imaging. AuNPs were successfully imaged in the kidneys. In addition, we performed high-resolution imaging and 3D reconstruction. The final experiment involved ex-vivo imaging of rat livers injected with a Gd-based contrast agent. Liver imaging revealed a difference in contrast between the non-injected liver and the Gd -injected liver. In addition, we estimated the concentration of the contrast agent, and the results indicated that the liver could not absorb more than 2.5 mg/mL of Gd-based contrast agent. We conclude that these findings have the potential to advance the clinical application of PC-CT. In the future, we aim to visualize the mechanism of drug delivery system in the human body and expand the detector area.

Speaker: Mayu Sagisaka

17:47 P2.63: A novel reconstruction method of angle-limited backprojection (ALBP) for low-dose dental panoramic imaging using a long-rectangular detector

Dental panoramic imaging is a standard X-ray technique in dentistry that produces a single image of the facial structures, including both maxillary and mandibular arches and their supporting structures. A typical panoramic system consists of a slit-collimated X-ray tube, a linear-array type detector, and predetermined sequences for the panoramic scan motion and signal readout from the detector to focus a specific dental arch. Panoramic image is commonly reconstructed using the shift-and-add (SAA) algorithm [1], where it is gradually built up by adding panoramic projections in a way that stacks the focusing sections of the panoramic projections consecutively. In this study, we propose a new panoramic reconstruction method, the so-called angle-limited backprojection (ALBP) algorithm, for low-dose panoramic imaging [2]. Figure 1 shows the schematics of panoramic reconstruction methods of the SAA and proposed ALBP algorithms. In the ALBP algorithm, rays to be backprojected onto a given spherical voxel, which is established along the dental arch, are selected from the measured panoramic projection data and then backprojected, as in computed tomography reconstruction. To validate the efficacy of the proposed algorithm, we conducted a series of simulations and successfully reconstructed panoramic images using both the SAA and ALBP algorithms. Figure 2 shows the simplified data processing for the proposed ALBP algorithm and the 3D numerical dental arch phantom used in the simulation. Figure 3 shows the resulting panoramic images of the phantom reconstructed using the SAA and ALBP algorithms: (a) with all and (b) with half projection data. The preliminary simulation results showed that the image quality of the panoramic image obtained using the ALBP was better than that of the image obtained using the SAA. In addition, the panoramic image reconstructed using the ALBP with half projection data gave much better image quality than that using the SAA with the same projection data, indicating the potential of low-dose panoramic imaging. More quantitative simulation and experimental results will be presented in the paper.

Speaker: Hyesun Yang

17:48 P2.64: Design and simulation studies of the micro-pattern gaseous beam monitor of the CSR external-target experiment

A micro-pattern gaseous detector with pixel readout is being developed for the beam monitoring for the CSR external-target experiment (CEE) at HIRFL. Demanded by the physics program of the CEE experiment, it not only monitors the lateral beam density distribution, but also measures the lateral position of each beam particle with a spatial resolution better than 50 $\mu$m and with a rate up to $10^6$ pps. The beam monitor mainly consists of two field cages inside a gas vessel with electrical fields orthogonal to each other, and four custom-designed charge sensing and readout chips on the anode of each field cage. The gas electron multiplier (GEM) is adopted for some beams with less ionizing power. The simulation of the drift electric field, gas properties, signal induction and spatial resolution of the detector has been carried out to optimize the geometrical set-up, to evaluate the expected performance, and to calculate the requirements on the chip characteristics. In particular, as the beam intensity increases, the ion back flow (IBF) from electron avalanches inside the GEM and the ions produced by the beam particles leads to sizable electric field distortion in the drift region, which worsens the spatial resolution of the detector. In this poster, the design and simulation studies of the beam monitor, especially the modelling and the correction of the space charge effect, are presented

Speaker: Zhen Wang

17:49 P2.65: Charge reset shaping multiplexing for SiPMs using deep learning architecture

This study proposes a new signal multiplexing method for molecular imaging systems used in nuclear medicine, which can reduce the number of readout channels by utilizing charge reset amplifiers and a deep learning model. The results show that the proposed method can reduce 16 readout channels to one without distorting the original signal, using charge reset preamplifier and deep learning architecture. The proposed method is tested using a 4x4 Ce:GAGG scintillator array and a 4x4 SiPM array with a 137Cs radiation source. The average energy resolution was 11.87%, and the crystal positioning map also indicates that distinct SiPM array pixel identification is possible without the need for a charge division method. The proposed method could help reduce the cost and complexity of NM systems while maintaining or improving their performance. Future work will focus on expanding the technique to accurately identify a greater number of crystals while also increasing the ratio of crystals to SiPMs.

Speaker: Semin ‍Kim (Department of Bioengineering, Korea University, Seoul, South Korea)

17:50 P2.66: First application of sparse-view image reconstruction with total-variation minimization for SiPM-based photon-counting CT

Photon-counting computed tomography (PC-CT) is a type of next-generation X-ray CT system for medical applications. It enables quantitative evaluation, such as concentration estimation, which is not possible with conventional CT systems. This is because the number and energy information of the individual incident X-rays can be obtained by reading them out in pulse form. By utilizing this property to estimate the concentration of contrast agents injected into the body, it is expected to expand the possibilities of novel diagnostics, such as drug delivery systems. Therefore, we established the SiPM-based PC-CT system combined with the YGAG scintillators [1, 2, 3] and evaluated its performance in several cases [4, 5]. However, to estimate the concentration of contrast agents flowing inside small animals more accurately, the temporal resolution of CT imaging needs to be improved [5]. In such a situation, the sparse-view CT technique, which involves reconstructing CT images from the smaller number of projections than that of conventional way [6], is an attractive method that enables CT imaging with shorter duration without degrading image quality. In this presentation, we report the initial results of an image quality evaluation of sparse-view CT images obtained with our established SiPM-based PC-CT system. We used static phantoms equivalent to an iodine contrast agent as the subject (Fig. 1). The six energy thresholds were set to 11, 33, 55, 65, 75, and 90 keV; and the tube voltage and tube current were set to 120 kV and 0.1 mA, respectively. We then obtained the projection data and applied the image reconstruction method based on total variation minimization to the sparsely view-sample sinogram data with the number of projections reduced to 1/5 of the original (Fig. 2). As part of the results, from the sparsely sampled data, we successfully reconstructed the CT images equivalent to ones from the sinogram data of the original. Furthermore, we obtained the correct CT values in the region of 5 mg/mL of iodine within the standard deviation. In addition, the standard deviation with sparse-view CT is 34.0% smaller than the conventional one in the 11–33 keV energy band (Fig. 3). This means that the total imaging time could be reduced to 1/5 while improving image quality by 34.0%, i.e.; the X-ray dose could also be reduced to 1/5. Finally, we also performed sparse-view CT imaging on mice injected intravenously with iodine contrast agents. We briefly report the results of the quantitative evaluation.

Speaker: Daichi Sato (Kanazawa University)

17:51 P2.67: Stationary CT baggage scanner with a dual-layer detector and pi-angle sparsity for enhancing the detection of threats

Two-dimensional (2D) X-ray inspection systems have been widely used for homeland and aviation security, but they still have limitations in recognizing 3D shape of the hidden threats. Hence, there has been increasing demand for computed tomography (CT) scanner for carry-on baggage screening. In a previous study [1], we designed a new stationary CT baggage scanner with compressed-sensing (CS) algorithm and -angle spacity, comprising several dozen pairs of X-ray source and linear array-type detector placed within a scan angle of 180 degrees at an equiangular distance. Our previous results showed that the proposed CT configuration significantly reduced the streak artifacts appearing in the standard filtered-backprojection (FBP) reconstruction, thereby considerably improving the image quality. In this study, as a continuation of our X-ray imaging R&D, we replaced the linear array-type detector in a previous design with a dual-layer detector (X-Card 1.5-64DE, Detection Technology Co.) and applied a typical material decomposition algorithm to separate soft and dense materials for enhancing the detection of threats. Dual-energy CT is a theoretically well-established X-ray technique used to differentiate and classify material composition in CT using projection images acquired at two different X-ray energy spectra [2]. In addition to material-specific images, the dual-energy projection data can be used to synthesize virtual monochromatic CT images as the potential to reduce beam-hardening artifacts that are usually observed in traditional polychromatic CT images. Before the practical implementation of the proposed dual-energy CT baggage scanner, we conducted a series of simulations to validate its efficacy. Figure 1 shows (a) the schematic of a stationary dual-energy CT scanner with pi-angle sparsity and a dual-energy detector and (b) X-ray energy spectra used in the simulation for material decomposition. Figure 2 shows the schematic of the proposed dual-energy CT algorithm to separate soft and dense materials. Figure 3 shows the preliminary simulation results of a stationary dual-energy CT scanner with pi-angle sparsity and material decomposition. More systematic and quantitative simulation and experimental results will be presented in the paper.

Speaker: Jiyong Shim (Yonsei university)

17:52 P2.68: Improvement of phoswich detector-based β+/γ-ray discrimination algorithm with deep learning

Positron probes are widely used to accurately localize malignant tumors by directly detecting positrons emitted by positron-emitting radiopharmaceuticals that accumulate in malignant tumors. However, the conventional method of direct positron detection cannot distinguish some γ-rays, resulting in misidentification of γ-rays as positrons and increasing the error rate of positron detection. In this study, an Autoencoder-based positron detection algorithm is proposed to improve the accuracy of positron detection by analyzing the energy distribution in each scintillator of the multilayer scintillator detector for discriminating between true and false positrons. The Autoencoder was trained to separate the combined signals generated by the multilayer scintillator detector into two signals from each scintillator. An energy window was then applied to the energy distribution obtained using the trained Autoencoder to distinguish true positrons from false positrons. The proposed method was evaluated and compared with the conventional method in terms of performance, sensitivity and error rate for positron detection. The results showed that the proposed method can increase the sensitivity of positron detection while maintaining a low error rate compared to the conventional method. Specifically, the proposed method had a higher sensitivity than the conventional method when both methods had the same error rate. In addition, the proposed method had a lower error rate than the conventional method when both methods had the same sensitivity.

Speaker: Dr Chanho ‍Kim (Korea Atomic Energy Research Institute (KAERI), Daejeon, South Koreauth Korea)

17:53 P2.69: Signal and noise analysis of a metal oxide transistor-based flat-panel detector

Recently, a metal-oxide thin-film transistor (TFT)-based flat-panel x-ray detector has been paid attention to its fast readout time and low-noise characteristic. We analyze empirically the signal and noise characteristics of an indium gallium zinc oxide (IGZO) TFT-based detector in comparison with those of the conventional hydrogenated amorphous silicon (a-Si:H) TFT-based detectors. We compare the large-area transfer functions of the detectors as a function of air kerma at their entrance surface. We perform the mean-variance analysis to address the systems’ gain and electronic noise. The signal and noise performances are evaluated by measuring the modulation-transfer function (MTF), noise-power spectrum (NPS), and detective quantum efficiency (DQE). The low-dose imaging capability of detectors is assessed by investigating the large-area or zero-frequency DQE, including a DQE reduction factor which is introduced in this study, as a function of air kerma. Throughout this study, we evaluate the value of the IGZO detector in terms of dose efficiency, in particular, compared to the conventional a-Si:H detectors.

Speaker: Seokwon Oh (School of Mechanical Engineering, Pusan National University)

17:54 P2.70: Analysis of absorption signal and noise in thin phosphor detectors for high-energy transmission radiography

For the application to megavoltage (MV) or mega-electron volt (MeV) imaging, we investigate theoretically and empirically the signal and noise characteristics of thin gadolinium oxysulfide phosphor detectors. For several phosphor detector designs, we perform the Monte Carlo (MC) simulations for various MV x-ray spectra from linear accelerators and gamma-rays (ranging from hundreds of keV to a few MeV) from radioisotopes. Applying the moment analysis to the MC pulse-height measurements, we estimate the energy-absorption signal, its induced noise, and the detective quantum efficiency (DQE). In the analysis, we also take into account the effect of electron-buildup metal layers for possible signal enhancement, which are placed on the top of phosphor detectors, and investigate the role of secondary radiations on the DQE. We construct phosphor-coupled CMOS detectors and report their detection performance for image quality indicators under MV and MeV irradiation environments. This study will be helpful for the development of bendable detectors.

Speakers: Ho Kyung Kim (School of Mechanical Engineering, Pusan National University), Seungjun Yoo (School of Mechanical Engineering, Pusan National University)

17:55 P2.71: Detective quantum efficiency of double-layered detectors for dual-energy x-ray imaging

A sandwich-like, double-layered detector can perform dual-energy imaging (DEI) at a single shot of x-ray exposure without object-motion artifacts. The energy separation between the measurements from two (front and rear) detector layers can be further adjusted by inserting an x-ray beam-attenuating material between them. However, the design of the interdetector filter highly impacts the dose efficiency by changing the number of x-ray photons reaching the rear detector layer in the sandwich detector. We develop a cascaded-systems model to assess the signal and noise propagation in the sandwich DE detector and estimate the DE detective quantum efficiency (DQE) in terms of filter designs. We validate the developed DE-DQE model by comparing it to the measurements. The developed model will be helpful for better design and operation of sandwich detectors.

Speaker: Hubeom Shin (School of Mechanical Engineering, Pusan National University)

17:56 P2.72: Eye Lens Dosimetry with Dosepix

The eye lens is one of the most radiation sensitive organs of the human body [1]. Therefore, the maximally allowed organ equivalent dose to the eye lens per year for occupationally exposed personnel has been reduced from 150 mSv/a to 20 mSv/a within a 5-year average with the dose not exceeding 50 mSv in any year [2]. Active eye lens dosimeters are of need in interventional radiology and cardiology marking the fields of largest dose exposure to the lens of the eye [3]. No active eye lens dosimeter certified in accordance with IEC standards is available on the market at the time of this abstract (March 23). In this work, first measurements of an active personal eye lens dosimeter prototype in photon reference fields are presented.
The dosimeter prototype (Figure 1) is based on the hybrid photon-counting energy-resolving pixelated detector Dosepix [4] which has been developed by a collaboration of Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) and the European Organisation for Nuclear Research (CERN). A 300 µm thick silicon sensor layer is attached to Dosepix ASIC. Deposited energies are sorted into a histogram of 16 energy bins by the individual pixel electronics. The eye lens dose is estimated via a weighted sum of the entries of those histograms where the weighting factors are determined from simulation results and measurements at reference conditions. The quantities of interest are the operational dose quantity for eye lens dose $H_\text{p}(3)$ [5] and the response which is given by the measured dose divided by the actually applied dose.
No significant influence of the photon pulse duration on the response of the dosimeter is found for pulse durations ≥1 ms (Figure 2). The response also stays within the official limits, stated in IEC/EN 61526:2020, for irradiations of RQR-5 and RQR-8 (acc. IEC/TS 61267:2005) with dose rates up to 1 Sv/h (Figure 3). Continuous irradiations with mean photon energies from 12 keV to 248 keV and irradiation angles from -75º to +75º show no deviation of the response, normalized to the response of the radiation quality N-60 at 0º angle of incidence (acc. ISO 4037-1:2021), of more than ±20% from 1.0 fulfilling the official limit stated in IEC/EN 61526:2020 (Figure 4). Reproducibility of dose estimation within the limits according to IEC/EN 61526:2020 is shown by applying selected radiation qualities at least four times at two identical eye lens dosimeter prototypes (Figure 5). The influence on the measured dose value of beta radiation from a $^{85}$Kr-source (acc. to ISO 6980-1 and ISO 6980-3) is shown to be less than 0.1% of the irradiated personal surface dose $H_\text{p}(0.07)$.

The results show the ability of the presented active eye lens dosimeter prototype to estimate the eye lens dose in real time in continuous and pulsed photon fields. This enables active radiation protection of occupationally exposed staff in interventional medicine.

[1] G Chodick et al., Am J Epidemiol. 2008 Sep 15;168(6):620-31
[2] FA Stewert et al, Annals of the ICRP 41, no. 1–2, February 2012: 1–322.
[3] GK Korir et al, Radiation Protection Dosimetry (2012), Vol. 152, No. 4, pp. 339– 344
[4] W Wong et al, Radiation Measurements, vol. 46, no. 12, pp. 1619–1623, 2011
[5] WG Alberts et al, PTB-Dos-23, 3. Edition, 1995

Speaker: Mr Florian Beißer (Erlangen Centre for Astroparticle Physics)

17:57 P2.73: Position-sensitive semiconductor detectors for nuclear fuel imaging

The Passive Gamma Emission Tomography (PGET) device was approved by the IAEA for spent nuclear fuel safeguards inspections at the end of 2017. It is based on a collimator, consisting of a linear array of narrow slits with a pitch of 4 mm, with a relatively small CZT (cadmium-zinc-telluride) gamma ray detector behind each slit. Larger detectors would have a higher probability for detecting the full energy of gamma rays, increasing the effective sensitivity and image quality (in terms of statistics and contrast-to-noise ratio). However, a larger detector would cover more than one collimator slit, requiring position sensitivity to determine through which slit a gamma ray travelled in order to maintain image spatial resolution. We are studying the use of state-of-the-art 3D position-sensitive CZT and germanium gamma ray detectors. In addition to utilizing the position sensitivity along the direction of the collimator, which gives transaxial position information, we are investigating to what extent Compton imaging can provide information on the origin of a gamma ray along the axis of a spent fuel assembly. This opens the prospect of creating 3D images with the PGET device in a single axial position, adding axial information to the current 2D transaxial images. The technology being developed is also useful for other than safeguards applications, such as the non-invasive post-irradiation examination of nuclear fuel to characterise its important properties.

A Monte Carlo simulation framework has been developed using the Geant4 toolkit and measurements using point-like and rod-shaped Cs-137 sources, the latter mimicking spent nuclear fuel, have been performed. The status and prospects of the project will be reported.

Speaker: Prof. Peter Dendooven (Helsinki Institute of Physics, University of Helsinki)

17:58 P2.74: Experimental validation of Monte Carlo simulation model for X-ray security scanner

Transmission X-ray security scanners are used to detect the smuggling of contraband articles, including weapons, narcotics, and explosives for homeland security. Current X-ray scanners use fixed tube voltages (i.e., 160 kVp); hence, it has a limitation in detecting thinly coated and/or low-density objects. To overcome this limitation, we are designing an X-ray scanner applying a variable tube voltage depending on the physical/chemical properties of the object being inspected. To this end, the Monte Carlo simulations with Geant4 and MCNP6 were performed to optimize the design of the X-ray scanner with variable tube voltages.
In the present study, we experimentally validated the reliability of the Monte Carlo simulation model for the X-ray scanner. The X-ray images obtained by the experiment were compared with the simulated images. The experimental setup is shown in Figure 1. The source-to-object distance (SOD) and the source-to-detector distance (SDD) was 70 cm and 120 cm, respectively, as applied to a typical security scanner. The tube voltage and the current were 80 kVp and 10 mA, respectively. The object was scanned at a speed of 0.2 m/s on a conveyor system to obtain the images. Simulated images were obtained using the X-ray source term produced from a monoenergetic electron beam bombarded onto the target (i.e., 80 kVp). 4-D simulations were performed for a moving object. The profiles of the simulated and experimental images were compared to validate the simulation model. It was found that the difference in pixel count between experiment and simulation was less than 5%. Thus, we concluded that our simulation model for the X-ray scanner can be considered reliable.

Speaker: Junsung Park (Jeonbuk National University)

17:59 P2.75: Introduction of CRYTUR’s GAGG+ single crystal scintillator for imaging applications

Crytur is a leading Czech producer of scintillation materials. Their latest product, GAGG+, is a single crystal scintillator of exceptional optical and technological quality. The GAGG+ scintillator is commercially available from Crytur and can be customized to fit specific imaging applications. A screen can be manufactured in a thickness as low as 5 microns, ensuring sub-micrometer spatial resolution in imaging applications. The developed scintillator offers the best combination of low afterglow, fast decay time, high light yield, and resolution.

We present a thorough characterization of the optical, scintillation, and luminescence properties of the GAGG+ scintillator, as well as Crytur's production capabilities.

Speaker: Ondrej Zapadlik

18:00 P2.76: A comparative study for pile-up correction based on deep neural networks

The pile-up phenomenon can cause distortion in the recorded data and make it difficult to accurately measure the properties of individual radiation events. This issue can lead to an underestimation of the quantitative analysis, especially in radioisotope identification through gamma-ray spectroscopy. Recently, deep learning-based studies for pile-up correction have been conducted. Those studies established datasets including bi-exponential shapes through experimental or mathematical modeling and proposed deep neural networks that were robust to noise, which resolved spectrum distortion. In this study, we perform a comparative study using three kinds of deep neural networks to select the best model for restoring piled-up pulses. We will optimize deep neural networks and choose the best pile-up correction model based on the restoration results of the spectrum distortion. We expect that this study serves as useful data to select and utilize the best deep neural network for the correction of pile-up caused in high radiation environments.

Speaker: Mr Wonku Kim (Korea Advanced Institute of Science and Technology)

18:10 → 21:30 Gala Dinner (transport leaves at 18:20)

Thursday, 29 June

08:30 → 10:20 Applications: 5

Convener: Nicolo Cartiglia (INFN Torino (IT))

08:30 INVITED: X-ray Dark-Field Imaging: From Basic Principles to First Clinical Applications

The basic principles of X-ray image formation in radiography have remained essentially unchanged since Röntgen discovered X-rays over a hundred years ago. The conventional approach relies on X-ray attenuation as the sole source of contrast and uses only ray or geometric optics to describe and interpret image formation. This approach ignores another potentially more useful source of contrast, namely phase information. Phase-contrast (and Dark-Field) imaging techniques, which can be understood using wave optics rather than ray optics, offer opportunities to improve or complement standard attenuation contrast by incorporating phase information.

This talk will review the basic physics, milestones and state of the art of grating-based X-ray phase-contrast and dark-field imaging in general, focusing in particular on our recent efforts to evaluate X-ray dark-field contrast for clinical applications in radiography and computed tomography.

We will discuss in more detail the results of the first clinical evaluations, for which we built a novel dark-field chest X-ray system for patients that can also take a conventional chest X-ray at the same time. With this system, the first of its kind in the world, we are currently conducting several patient studies, among others on chronic obstructive pulmonary disease (COPD), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and lung cancer.
These findings are also important from a societal perspective, as diseases of the respiratory system are a major cause of chronic disease and mortality worldwide. While modern medical imaging techniques now provide detailed diagnostic information, there is still a lack of a low-dose, rapid and cost-effective option for early detection and/or follow-up.
As an outlook, we then discuss the further development of a first human prototype for dark-field computed tomography, where the use of novel spectral hybrid pixel photon counting detectors is of particular interest. These offer several technical advantages that can be expected to significantly improve the image quality, especially for dark-field imaging.

Speaker: Franz Pfeiffer

20230629_FranzPfeiffer_iWorid.pdf

20230629_FranzPfeiffer_iWorid.pptx

09:00 High-speed x-ray CT for industrial inspection through high-brightness x-ray sources and photon counting detectors

Here we demonstrate high-speed CT down to 200 ms for battery inspection suitable for in-line use in factories. The combination of high-brightness MetalJet x-ray sources combined with high frame rate photon counting detectors enables 3D inspection that can keep up with production lines. CT inspection is a promising approach to improve quality assurance in the fast-growing battery industry, allowing to robustly assess anode/cathode overhang while also enabling particle detection.

Speaker: Till Dreier (Excillum AB, Lund University)

iworid_till_dreier_2023_pdf.pdf

iworid_till_dreier_2023.pptx

09:20 ThyroPIX – Mobile Compton camera based on Timepix3 technology for monitoring of thyroid gland cancer treatment

Thyroid tumors are relatively rare, but their incidence is steadily increasing in recent times. The goal of preclinical and clinical studies is therefore to find a way to detect and successfully treat this type of cancer early. The main problem is that the current imaging methods don't provide sufficient spatial resolution to reveal the remnants after the chirurgical removal of the gland. Due to their presence the disease relapses. ThyroPIX is a new-generation multimodal device for imaging the thyroid gland and thyroid cancer treatment monitoring. The ThyroPIX device is equipped with a fully spectral single-photon counting detector of a new generation based on Timepix3 technology which exploits the ability to measure the position, energy, and time of every detected particle. Thanks to this information related to very precise time detection of every incoming gamma photon is possible to determine the position of the interaction of primary and Compton scattered photons in sensitive layers of detector materials. Together with the energy information direction of a primary photon is then calculated and based on the backward reconstruction the source is localized in space.This new imaging method concept called the Compton camera brings possibilities of emission imaging for various types of radioisotopes of a broad range of energies. This approach leads to the development of a unique system without using any other usually necessary equipment (e.g. heavy collimators). Besides the absence of collimators, the main benefits of the novel system include better spatial resolution, low weight, and significantly higher sensitivity. Thanks to the implementation of the detector on a mobile collaborative robotic arm and the execution of either a planar or tomographic image, it will be possible to perform a quick, basic examination of the patient in any part of the hospital. This contribution presents the imaging system and shows the measured data and its results in the framework of preclinical tests on phantoms.

[1] TURECEK, D., J. JAKUBEK, E. TROJANOVA a L. SEFC. Compton camera based on Timepix3 technology. Journal of Instrumentation [online]. 2018, 13(11)
[2] TURECEK, D., J. JAKUBEK, E. TROJANOVA a L. SEFC. Single layer Compton camera based on Timepix3 technology. Journal of Instrumentation [online]. 2020, 15(01)

Acknowledgment
This project was implemented with financial support from the state budget through the Technology Agency of the Czech Republic in project FW01010471.

Speaker: Eliška Trojanova

ThyroPIX IWORID.pptx

09:40 First Results from the 4D-PET Scanner for the Brain Examination

We present the first experimental results of the 4D-PET scanner, a novel system for neurological studies. The 4D-PET detector geometry consists of a cylinder with 20 super-modules.
The attached abstract summarizes the results obtained both at super-module level (experimental validation) and system level (simulated data using the measured performance to model its response).
These results demonstrate that the new 4D-PET brain scanner configuration allows for simultaneous determination of the 3D-impact position of the gamma-ray and also of its arrival time. The improvement in the specification that this new design offers should make possible to visualize small critical structures of the brain (sustantia nigra, Raphe nuclei, …), opening unprecedented opportunities for clinically relevant discoveries in neurophysiology and neuropsychiatry. We are currently working on the assembly of the full scanner, results will be available at the conference time.

Speaker: Prof. Jose Maria Benlloch (Institute for Instrumentation in Molecular Imaging, I3M)

IWORID2023.pdf

IWORID2023.pptx

10:00 Feasibility studies of a novel ultra-low dose stationary tomographic molecular breast imaging system utilising 3D position of interaction CZT detectors

Mammography is widely used as a screening procedure for breast cancer. However, its cancer detection sensitivity is limited in patients with dense breast tissue [1]. Molecular breast imaging (MBI) using a pair of planar detector arrays has been shown to have high sensitivity even in dense breast tissue [2]. Nonetheless, long imaging time and radiation dose, that is higher than mammography, impede the widespread adoption of MBI in clinical practice. Several tomographic MBI systems have been proposed in the past [3-4], including systems with rotating head or multi-pinhole (MPH) collimation. A prototype of a novel ultra-low-dose MBI system offering tomographic imaging with stationary detectors is currently under development by Kromek. It is based on the use of dual opposing CZT detector arrays and densely packed MPH collimators leading to significant multiplexing (MX) in the acquired projections. Proprietary de-multiplexing image reconstruction algorithms were developed to reduce the adverse effects of the multiplexing artefacts using the high-resolution 3D position capabilities of CZT detectors. The goal is to achieve at least the same sensitivity for lesion detection as planar MBI, but with the effective patient dose similar to mammography. This new concept for the MBI camera and first imaging results from a proof-of-principle prototype were presented in 2021 [5-7]. The performance of the prototype was evaluated further and the results, along with further development of the image reconstruction algorithms, provided a basis for designing and building an upgraded feasibility prototype. The new prototype is currently under evaluation including spectral and phantom measurements.
The new feasibility prototype was built with an upgraded version of the previously used D-Matrix gamma imager technology. It is comprised of a 2x2 detector array of 5 mm thick CZT detectors with Depth-of-Interaction (DOI) capability and an MPH collimator with 49 pinholes. The spectral performance of the new prototype was characterised using collimated Am-241 and Co-57 sources (see Fig.1), with uncorrected FWHM of 3.94% and 2.82% respectively. The DOI is calculated using the anode over cathode ratio. The DOI resolution (FWHM) was measured with a 0.5 mm pencil beam collimator. It slightly varies between 0.93 and 1.02 mm depending on the depth.
The detector performance is also studied with a detector simulations model based on COMSOL Multiphysics and GEANT4. The model is a further development of the work presented at iWORID 2017 [8]. The simulations have been improved with the addition of Coulomb repulsion and a pulse shaping model based on the analytical representation of a pulse shaping circuit outlined in [9] and charge pulses produced by the COMSOL model. The goal of the detector simulation model is to provide realistic detector data as an input for the image reconstruction development and optimisation.
The imaging performance of the new prototype was characterised using a number of “activity-painted” [5] phantoms. The new image reconstruction and de-noising algorithms were optimised to maximise the contrast-to-noise ratio (CNR) and reduce the fluctuations of the correlated background noise associated with MPH image reconstruction. The collimator parameters studied were the pinhole size, opening angle, and separation distance. Non-local noise filtering and a relaxation scheme were applied to the results. The optimal system, achieving the CNR of ~15, was obtained with collimator hole size of 1.75 mm, opening angle of 90 and inter-aperture spacing of 10 mm. An example of the reconstructed 3D image comprised of a 6 mm “lesion” on a uniform background obtained with Tc-99m is shown in Fig.2.
The latest experimental and simulation results indicate that we can achieve the goal of the dose reduction to the mammography level and a strong reduction in the measurement time from current 40 min / 4 views to ~20-25 min. Those achievements remove the main regulatory roadblocks defined by American College of Radiology [10] which have prevented the acceptance of MBI as a screening modality for detecting breast cancer. In addition, the combination of the dose and time reduction makes our Ultra-Low-Dose Tomographic MBI technology more competitive with other modalities that are currently being evaluated for screening patients with dense breast tissue.

[1] Rhodes DJ et al. AJR, 204 (2015), 241-51.
[2] Hruska CB. AJR, 208 (2017), 275-83.
[3] van Roosmalen J et al. Phys Med Biol, 61 (2016), 5508-28.
[4] Brzymialkiewicz CN et al. IEEE Trans Med Imag, 24(7) (2005), 868-77.
[5] A. Cherlin et al. Proc. Virtual IEEE NSS RTSD MIC (2021).
[6] B. Hutton et al. Proc. Virtual IEEE NSS MIC (2021).
[7] K. Erlandsson et al. Proc. Virtual IEEE NSS MIC (2021).
[8] A. Cherlin, iWORID (2017).
[9] A. Makeev et al. Proc. of SPIE, Vol. 9412, 94124V-1.
[10] Debra L. Monticciolo et al. J Am Coll Radiol 15 (2018), 408-414.

The authors acknowledge funding from the Innovate UK grant (104296) and NIHR University College London Hospitals Biomedical Research Centre.

Speaker: Dr Alexander Cherlin (Kromek plc)

IWORID 2023 A Cherlin final.pdf

10:20 → 10:50 Coffee Break

10:50 → 12:40 Detector Systems: 4

Convener: heinz graafsma (DESY)

10:50 INVITED: Position-sensitive detectors and their readout as an enabling technology for high-energy astrophysics

The progress in high-energy astrophysics is driven by two engines: deepening and development of the science objectives, and the progress in the measurement techniques, supported by the available detectors. The detectors in astrophysical instruments carry out 3 basic kinds of measurements: timing, spectral, and position. However, in most cases, these must all be accomplished within one detector.
First, I will introduce the basic principles of the instruments used in the modern ground-based and space/ balloon-borne astrophysical missions. Next, I will make a quick tour through the development history of position-sensitive detectors, and ultimately I will focus in detail on the modern semiconductor detectors (silicon, germanium, and CZT), gaseous and liquid detectors, and scintillator detectors. Special attention will be given to the development and role of the detector readout: silicon photomultipliers, application-specific integrated circuits, and field-programmable gate arrays.

Speaker: Alexander Moiseev

Moiseev_talk.pdf

11:20 Monolithic HV-CMOS sensors for a beam monitoring system of therapeutic ion beams

Today, cancer treatment with ion beam is well established and studied. This method allows to deposit the maximum dose to the tumor and minimize the damage of healthy tissue, due to the Bragg peak of the ion energy deposition near the end of the particle range. During the treatment it is possible to provide volumetric dose delivery by changing the particle energy (penetration depth) and adjusting the beam position via magnetic system. For the beam monitoring system, the precise measurement of the beam position, shape and fluence in real time becomes crucial to provide effective and safe dose delivery to the tumor. Additionally, the system should work for beam intensities up to $10^{10}$ s$^{−1}$ for protons, be tolerant to 1 MeV neutron equivalent fluences up to $10^{15}$ cm$^{-2}$ per year and magnetic fields (for MRI-guided proton therapy).

The studies presented in this talk are focused on the application of the HitPix sensor family with counting electronics and frame-based readout for such a beam monitoring system. The HitPix sensors are monolithic pixelated silicon sensors based on HV-CMOS technology and have been developed at the ASIC and Detector Lab (ADL, KIT). Recent measurements with ion beams and a multi-sensor readout as well as future developments are discussed.

Speaker: Bogdan Topko (KIT - Karlsruhe Institute of Technology (DE))

iWoRiD_Topko_Monolithic_HV_CMOS_sensors_for_a_beam_monitoring_system.pptx

11:40 A new nuclear imaging detection technology for total body, flexible and fast SPECT diagnoses.

The International Agency for Research on Cancer estimated a 25% risk of tumor incidence in the European population (2018), destined to increase in the coming years. Prevention and early diagnosis remain the fundamental tools, and nuclear imaging plays a pivotal role for noninvasive diagnosis.
One of the most used diagnostic technology is the Single Photon Emission Computed Tomography (SPECT).
While the conventional SPECT detector heads are generally built using collimators coupled to monolithic inorganic crystals, in this contribution we investigate a gamma detector concept that relies on a tungsten metal frame (hive), that serves both as a collimator and as a container for the scintillator segments. The active material has been chosen to be organic scintillators enriched with high-Z elements to profit from the extremely fast scintillation process and a still remarkable photoelectric effect probability.

Thanks to the very short scintillation time of the active material and to the pixellated readout, an incredibly high count-rate capability will be achievable.
The readout system is a custom design tuned for fast scintillation events with an independent channel for each scintillator segment allowing the simultaneous measurement of the gamma arrival time and energy.
This device has the potential of opening the way to a new family of gamma imaging detectors based on organic scintillators combined with 3D printed collimators, allowing for a significant cost reduction while
achieving a beyond state-of-the-art count-rate capability and field of view.
Images from conventional SPECT from patients of Policlinico Umberto I Hospital have been exploited as starting point for a Montecarlo based reconstruction study with the aim of optimizing the detector geometry and of evaluate the achievable performances.
In this contribution, the expected performances of a total body system will be presented together with the results obtained with the first prototypes.

Speaker: Michela Marafini

reSPECT.pdf

12:00 Particle tracking with Miniaturized Timepix3 detectors as Compton gamma camera and applications in space

In nuclear and high-energy physics research and in radiation related applications the measurement of the deposited energy and direction of charged particles may be needed with high discrimination against background and unwanted radiation. This task can be challenging in particular in mixed-radiation fields containing light charged particles (e.g., electrons, muons) and heavy charged particles (protons, ions) in wide range of energies and direction. Conventional instrumentation, such as particle telescopes assembled from single-pad diode detectors, exhibit limitations such as narrow field-of-view (FoV) which require shielding and collimators, limited detection threshold, limited discrimination, complexity, large size and cost. We aim at addressing these issues with a compact integrated device assembled from two detectors Timepix3 stacked in particle telescope architecture MiniPIX-Timepix3 [1]. We make use of the quantum imaging sensitivity, per-pixel spectrometry and tracking response of the semiconductor pixel detector Timepix3 [2] to recognize particle-type events on both pixel detectors operated and readout in sync. This architecture enables to sample the energy loss of single particles in two detectors with different sensors (different material and/or different sensor thickness). The interaction points are registered on each pixel detector with sub-pixel level (55 µm) spatial resolution [3]. Thus, charged particles crossing the telescope can be tracked with high angular resolution (sub degree level) in wide field of view (FoV) – 60% of the full 2π for a 10 mm spacing gap [1]. In order to further increase the spectral sensitivity and FoV as well as enhance the tracking response and event-type discrimination [4], valuable e.g., for detection and characterization of atmospheric cosmic rays, we constructed a MiniPIX-Timepix3 telescope with different sensors (Si 500 µm top tracker, CdTe 2000 µm bottom tracker) assembled in closer geometry (4 mm spacing gap) – see Fig. 1. To evaluate the tracking response and resolving power of event discrimination we performed particle beam experiments with 8 – 33 MeV protons and 16 – 22 MeV electrons at the U-120M cyclotron and microtron accelerators, respectively at the NPI Rez near Prague. We are measuring also atmospheric cosmic rays for which the Si+CdTe configuration provides enhanced muon discrimination against background and unwanted radiations (electrons, gamma rays). Fig. 2 shows the response by the telescope bottom tracker (TPX3 CdTe 2000 µm) to 33 MeV protons resolved in two spectral-tracking groups [4] – shown in Fig. 1a and Fig. 1b – components in the same measured data. Correlated patter recognition analysis of the single particle tracks (Fig. 2c) provides resolving power of particle-type events [4]. Correlated maps of ΔE/Δx values in both tracker sensors are derived for selected events with higher discrimination together with directional flux maps of charged particles in high angular resolution (<1°).

Speaker: Jan Jakubek (ADVACAM)

12:20 A four-dimensional timing RPC neutron detector concept

A detection technology for thermal neutrons combining hybrid double gap timing resistive plates chambers lined with a 10B enriched solid neutron converter (10B-RPCs) is being developed at LIP-Coimbra [1]. Our previous studies performed on neutron beamlines at ILL (Institut Laue-Langevin) and FRMII (Research Neutron Source Heinz Maier-Leibnitz) have already demonstrated the feasibility of 10B-RPC based neutron detectors, capable of a detection efficiency to thermal neutrons above 50% and a spatial resolution in 2D better than 250 µm FWHM [2]. In this work we present a concept of a detector with four-dimensional readout capability (XYZ and time), called nRPC-4D, based on the 10B-RPCs. Application for this type of detector is foreseen in ToF (time-of-flight) neutron diffraction/ reflectometry, energy- and time-resolved neutron imaging, as well as in other applications requiring simultaneous readout of neutron event position and time.
The basic design of a nRPC-4D detector consists of several timing 10B-RPCs, stacked on top of each other. Such a multilayer configuration is required to surpass low detection efficiency of a single layer of the 10B4C neutron converter, oriented normally to the neutron incidence direction [1]. The optimal number of 10B-RPC detection units depends on the range of neutron wavelengths and the specific requirements of a particular application. From a simulation-based optimization of a nRPC-4D detector with ten 10B-RPCs units we compute a detection efficiency of ~ 60% for a neutron pencil beam (4.7 Å) with normal incidence at the center of the detector [3]. The timing 10B-RPCs are designed to act as standalone and versatile detection units, making a nRPC-4D detector straightforward to build and maintain, and adapt to different applications with specific sets of requirements. A 10B-RPC unit has a double gap configuration and is formed by two resistive anode plates made from 0.3 mm thick float glass, and a 0.3 mm thick aluminium cathode plate between them, all parallel to each other and separated by PEEK spacers defining two 0.28 mm wide gas gaps (see Figure 1). The glass plates are lined on the face opposite to the gas gap with a thin layer of resistive ink used to apply uniform potential across the entire anode active area. The aluminum plates, with an area of 190×190 mm2, are coated on both sides with a 0.4 to 2.3 μm thick layer of B4C (10B enrichment level > 97%). The 10B4C coatings were made in the ESS Detector Coatings Workshop. To read both X and Y event coordinates, a thin polyamide (25 μm thick) flexible printed circuit board (FPCB), with one array of parallel signal pick-up strips (1 mm pitch, 0.3 mm wide) on each side and orthogonal to each other, is placed at the top and bottom of the 10B-RPC unit (see Figure 1). To reduce the number of electronic channels, the X strips of each FPCB with the same index are interconnected, and read by the same electronic channel. The same applies to Y strips. The Z coordinate of a neutron event (position of the neutron capture along the stack), and the neutron ToF are defined using the cathode signal of the triggered 10B-RPC unit. Due to the fast (sub-ns) timing properties of RPCs [4] and the short flight time (~ 1 ns) of thermal neutrons through a 10B4C layer before capture, an nRPC-4D detector should be able to determine the ToF up to sub-microsecond precision.
Here we present the configuration of an nRPC-4D detector and describe its working principles. We also report results of the preliminary tests of the timing 10B-RPC units, performed on the BOA neutron beamline at Paul Scherrer Institut. The experimental results demonstrate the capability of the 10B-RPC units to determine the XYZ position of the neutron events and the ToF. They also show that the correlation between the amplitudes of the signals from the X and Y strips allow to identify the gas gap of the 10B-RPC where an event has occurred (see Figure 2, Left and Center). In Figure 2 (Right) the neutron wavelength spectrum at BOA beamline computed from the ToF values is shown. The results validated the design of the 10B-RPC units for a detector prototype that is currently being built, and prove that the nRPC-4D detector concept is suitable for Time-of-Flight neutron diffraction/reflectometry and energy- and time-resolved neutron imaging.

[1] L.M.S. Margato and A. Morozov 2018 JINST 13 P08007, DOI: 10.1088/1748-0221/13/08/P08007
[2] L.M.S. Margato et al 2020 JINST 15 P06007, DOI: 10.1088/1748-0221/15/06/P06007
[3] L.M.S. Margato, et al., Nucl. Instr. Methods A, 2023, https://doi.org/10.1016/j.nima.2023.168267
[4] A Blanco et al 2012 JINST 7 P11012, DOI: 10.1088/1748-0221/7/11/P11012

This work was supported by Portuguese national funds OE and FCT-Portugal (grant EXPL/FIS-NUC/0538/2021).

Speaker: Luís Margato (Laboratory of Instrumentation and Experimental Particles Physics, Dep. of Physics, University of Coimbra)

225_Luis_Margato_IWORID_2023.pdf

12:40 → 13:00 Closing

Conveners: Angela Kok, Dirk Meier

12:40 Closing

Speakers: Angela Kok, Dirk Meier

iworid23_closing_AK.pptx

12:55 iWoRiD 2024 Lisbon

Speaker: Dr Cristina Bernardes Monteiro (University of Coimbra)

13:00 → 13:50 Lunch Break

13:50 → 15:20 Visit to SINTEF cleanroom (for those interested, limited spaces)