23rd International Workshop on Radiation Imaging Detectors

26 Jun 2022, 16:30 → 30 Jun 2022, 14:00 Europe/Rome

Room Garda (Riva del Garda, Italy)

Gian Franco Dalla Betta (Universita degli Studi di Trento and INFN (IT))

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.

More information on the venue, accomodation, etc. can be found here. 

If you have any questions or comments, please do not hesitate to contact us at iworid2022@unitn.it.

Kind regards,

Gian-Franco Dalla Betta, LOC
Roberto Iuppa, LOC
Lucio Pancheri, LOC
Alberto Quaranta, LOC
Coralie Neubüser, LOC 
Nicola Massari, LOC
Giovanni Paternoster, LOC

At present there are no significant problems and restrictions with Covid.  Comprehensive and up to date information on the Covid situation and rules to enter Italy and take part in events can be found on the governmental website at this link.

Plaase note that face masks are not mandatory in Italy in this period (except for public transport and hospitals), but their use in crowded situations, like the conference,  is strongly recommended. 

BOOK_OF_ABSTRACTS.pdf

Group_Photo1.jpg

Group_Photo2.jpg

IWORID2022_Poster_30x70_web.pdf

SOCIAL DINNER INFORMATION.pdf

Sunday, 26 June

Registration

Participants can check-in and the badge and the kit

Welcome reception

Monday, 27 June

Registration

Participants can check-in and the badge and the kit

Opening

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

1 Introduction

Speaker: Gian Franco Dalla Betta (Universita degli Studi di Trento and INFN (IT))

Opening_Talk_GFDB.pdf

Opening_Talk_GFDB.pptx

Detector Systems

Convener: Prof. Christer Fröjdh (Mid Sweden University)

2 INVITED: Advances in Thermal Neutron Detection: Retrospective of the Past Decade and Current Trends in Future Developments in the Context of Construction of the European Spallation Source

The European Spallation Source (ESS), currently under construction in Lund, Sweden has the goal to become the world’s leading neutron source for the study of materials. Fifteen neutron instruments are currently being built as part of the construction project, which started in 2013 with the completion of the Technical Design Report (TDR).
These instruments present numerous challenges for detector technology in the absence of the free availability of Helium-3, which is the default choice for detectors for instruments built until today and due to the extreme rates and challenge in requirements expected across the ESS instrument suite, which are a significant factor more than at current sources. Additionally, this poses a challenge for the electronics due to a much higher channel count on the detectors.
This contribution presents the neutron detector baseline for the instruments currently under construction. The data acquisition strategy is outlined. A retrospective of the past decade of advances in neutron detector development is given. This effort has involved a wide collaboration of ESS in-house, in-kind arrangements with partner institutes and grant- based funding to realise.
Lastly some personal perspectives are given on current and likely trends for future neutron detector developments as well as promising avenues of exploration.

Speakers: Richard Hall-Wilton (E), Richard Hall-Wilton (ESS - European Spallation Source (SE))

220627_IWORID2022_RJHW.pdf

3 RIPTIDE: a proton-recoil track imaging detector for fast neutrons

Fast neutron detection is often based on the neutron-proton elastic scattering reaction: the ionization caused by recoil protons in a hydrogenous material constitutes the basic information for the design and development of a class of neutron detectors. Although experimental techniques have continuously improved, proton-recoil track imaging remains still at the frontier of n-detection systems, due to the high photon sensitivity required. More in detail, several state-of-the-art approaches for neutron tracking by using n-p single and double scattering – referred to as Recoil Proton Track Imaging (RPTI) – can be found in the literature. So far, they have showed limits in terms of detection efficiency, complexity, cost, and implementation. In order to address some of these deficiencies, we have proposed RIPTIDE a novel recoil-proton track imaging detector in which the light output produced by a fast scintillator is used to perform a complete reconstruction in space and time of the interaction events. The proposed idea is viable thanks to the dramatic advances in low noise and single photon counting achieved in the last decade by new scientific CMOS cameras as well as pixel sensors, like Timepix or MIMOSIS.
In this contribution, we report the advances on the RIPTIDE concept: Geant4 Monte Carlo simulations, light collection tests as well as state-of-the-art approach to image readout, processing and fast analysis.

Speaker: Mauro Villa (Universita e INFN, Bologna (IT))

RIPTIDE_ IWORID2022_Villa2.pdf

4 J- PET detection modules based on plastic scintillators for performing studies with positron and positronium beams at the Anti-Matter Laboratory

The J- PET detector, which consists of inexpensive plastic scintillators, has demonstrated its potential in the studies of fundamental symmetries [1,2] and in applications to medical physics [3,4]. In recent years, a prototype with 192 plastic scintillators arranged in 3 layers has been optimized to register the multiple annihilation photons emitted in the decays of positronium atoms (Ps) [5]. This allows performing precision tests of the discrete symmetries (C, P, T) in the decays of ortho-positronium atoms (o-Ps: triplet state of Ps) by measuring the expectation value of the odd symmetry operators consisting of the momentum vector of photons and the spin of o-Ps [2,6]. Moreover, the geometric acceptance of J- PET allows the measurement of the polarization direction of the photon based on Compton scatterings and thus, for the first time, the study of a new set of operators including the polarization of photons. Since it can measure the lifetime of o-Ps atoms, it also enables positronium imaging, which has direct applications in the medical field [3,7].
Recently, a new prototype was put into operation based on a modular design consisting of 24 individual units [8]. Each module consists of 13 plastic scintillators and can be used as a stand-alone, compact and portable detection unit. Data acquisition is performed in triggerless mode and is based on real-time data processing using the Field Programmable Gate Array (FPGA), which can process 48 data streams, each at a rate of 5Gbps [9].
At the University of Trento, a facility for the production of a bunched positron beam and positronium into vacuum has been commissioned at the Anti-Matter Laboratory (AML). With the know-how to produce transmission targets [10] (which convert positrons into positronium atoms in the forward direction) and to manipulate positronium atoms into a metastable state with increased lifetime [11], the production of Ps beam is envisaged. It is planned to move the portable modules of the J- PET detector to the AML facility to perform studies with positrons and metastable positronium atoms in defined quantum states.

The presentation will cover the main features of the J- PET detector, the modular prototype, and preliminary plans to perform studies with positron and positronium beams.

References:
[1] P. Moskal et al., Nature Communications 12 ((2021) 5658
[2] P. Moskal et al., Acta. Phys. Polo. B 47, 509 (2016)
[3] P. Moskal et al., Science Advances 7 (2021) eabh4394
[4] P. Moskal et al., Pet Clinics 15 (2020) 439
[5] K. Dulski et al., Nucl. Instrum. And Meth. A 1008 (2021) 175015
[6] A. Gajos et al., Nucl. Instrum. And Meth. A 819 (2016) 54-59s
[7] P. Moskal et al., Eur. Phys. J. C 78 (2018) 970
[8] P. Moskal et al., Phys. Med. Biol. 66 (2021) 175015
[9] G. Korcyl et al., IEEE Trans. On Medical Imaging 37 (2018) 2526
[10] S. Mariazzi et al., Phys. Rev. B 105 (11) 5422
[11] C. Amsler et al., Phys. Rev. A 99 (2019) 033405

The authors gratefully acknowledge support from the Foundation for Polish Science through programmes TEAM POIR.04.04.00-00-4204/17; the National Science Centre of Poland through grant nos. 2019/35/B/ST2/03562; the Ministry of Education and Science through grant no. SPUB/SP/490528/2021 and Jagiellonian University through project no. CRP/0641.221.2020. The authors also gratefully acknowledge the support of Q@TN, the joint laboratory of the University of Trento, FBK- Fondazione Bruno Kessler, INFN- National Institute of Nuclear Physics, and CNR- National Research Council, the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement No.754496 – FELLINI and Canaletto project for the Executive Programme for Scientific and Technological Cooperation between Italian Republic and the Republic of Poland 2019-2021.

Speaker: Dr Sushil SHARMA (Jagiellonian University, Poland)

SharmaIWORIDl_Final2.pdf

5 Diagnostics at pulsed radiation sources using a hyperspectral, high framerate HEXITEC camera system

Hyperspectral X-ray systems such as those based on the HEXITEC[1] ASIC typically employ high readout framerates in order to capture single photon events. Each of these frames is also fully digitized using ADCs, rather than comparators and counters, which provides a full wideband deposited energy measurement for each pixel in each frame. The HEXITEC specifically has 80 × 80 pixels at 250 µm pitch, read out at over 9 kHz, an operational energy range of 4 keV to 200 keV, and with an energy resolution better than 1 keV FWHM at 60 keV.

Because of this combined availability of sub-millisecond time resolution, good spectral resolving performance over a wide energy range without fixed thresholds, and spatial information at 250 µm resolution, it is an ideal camera system to investigate the temporal, spatial and spectral profile of pulsed radiation sources.

In this work the authors present the capabilities, limitations, and required developments when using a HEXITEC sensor at pulsed neutron sources. On the hardware side only minimal changes are required compared to normal operation, with good synchronization between camera and beamline master clock defining the temporal performance and jitter. In terms of software, the developments on top of the SpeXIDAQ[2] framework are presented which enable efficient and precise processing and storage of the 4D datasets (XY-position, energy, time).

The full raw output of a HEXITEC ASIC running at 9 kHz requires around 1 Gbit/s of processing and storage bandwidth, which can be challenging to manage over longer measurements. By carefully matching the processing strategy to the specific observables required for further analysis, the demand placed on storage and ease of this subsequent analysis is improved significantly.

[1] Veale, Matt .C. “HEXITEC: A High-Energy X-ray Spectroscopic Imaging Detector for Synchrotron Applications.” Synchrotron Radiat. News 2018, 31, 28–32.
[2] Van Assche, Frederic, et al. “The Spectral X-ray Imaging Data Acquisition (SpeXIDAQ) Framework” Sensors 21(2) (2021): 563

The authors acknowledge funding from the Research Foundation Flanders (FWO) under grant number G0A0417N and the Industrial Research Fund (IOF) under grant F2020/IOF-StarTT/135, and the STFC Centre for Instrumentation 2020-2021.

Speaker: Mr Frederic Van Assche (Radiation Physics, Dept. of Physics and Astronomy, Ghent University, Ghent, BE)

iWoRiD 2022 - Frederic Van Assche - final.pdf

10:30 Coffee break

Applications: 1

Convener: Ralf Hendrik Menk (Elettra Sincrotrone Trieste)

6 INVITED: Imaging and time-stamping single optical photons with nanosecond resolution for quantum applications

I will discuss fast optical cameras based on the back-illuminated silicon sensor and Timepix3 data driven readout. The intensified version of the camera is single photon sensitive and since recently has been used for a variety of quantum imaging and other applications. I will talk about recent results and new ideas, focusing on topics of quantum-assisted astronomical interferometers. I will also discuss possible future directions for the fast imaging technology in the optical.

Speaker: Dr Andrei Nomerotski (BNL)

NomerotskiIWORID20220626.pdf

NomerotskiIWORID20220626.pdf

NomerotskiIWORID20220626.pptx

7 Event driven Timepix3 hybrid pixel detector for cryo-EM at 200 keV

The development of direct pixelated detectors has played a key role in the resolution revolution in which structures of macromolecular complexes are obtained at near-atomic resolution by cryo-EM [1]. Monolithic active pixel sensor (MAPS) detectors are currently widely applied for cryo-EM, however, they have their best performance at 300 keV and have relatively low readout speed. The Timepix3, a hybrid pixel detector (HPD), can operate at very broad energy range (2 - 400 keV) and has an extremely high time resolution (event-driven 1.56 ns).
Previously, we have shown that the incident position of the electron can be predicted at sub-pixel accuracy using convolutional neural networks (CNN), thereby boosting the modulation transfer funcion (MTF) of experimental knife-edge data both at 200 keV and 300 keV [2]. Here we present the Timepix3 fully integrated in a cryo-EM Single Particle Analysis workflow. We determined its detective quantum efficiency (DQE), an important factor for cryo-EM which is affected by both MTF and noise power spectrum (NPS). Our hard- and soft-ware integration allows for full control of all the factors important for the performance of a detector for a certain application. We studied the effect of deterministic blur to DQE and the final protein single particle analysis (SPA) reconstructions resolution. We could compare results obtained with our workflow with those obtained data collected from the same protein on the same microscope, using a commercial available camera.
Our results show that our implementation of the Timepix3 for SPA applications can rival the data obtained with commercial MAPS detector. We discuss the versatility of our detector setup, which allows for a huge range of fluence settings, it could be used to study radiation-damage onset, it could be used both in imaging and diffraction mode, does not require dose-protection, and could be used at the widest possible energy range. Furthermore, we discuss its successor, the Timepix4, which we hope to use for liquid-cell applications as well as cryo-ptychography on biological samples.

[1] W. Kuhlbrandt, Biochemistry. Science 343, 1443–1444 (2014).
[2] J. P. van Schayck et al., Ultramicroscopy. 218, 113091 (2020).

We thank Ye Gao and Eve Timlin for providing protein samples. We are grateful to the M4I Microscopy CORE Lab team of FHML Maastricht University for their support and collaboration. We thank Amsterdam Scientific Instruments team members for their support in building and operating the detectors. This research is funded by the Netherlands Organisation for Scientific Research (NWO) in the framework of the Fund New Chemical Innovations, project MOL3DEM, number 731.014.248; European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement No 766970 Q-SORT; this project is co-funded by the PPP Allowance made available by Health~Holland, Top Sector Life Sciences & Health, to stimulate public-private partnerships; Alzheimer DE-19082CB, as well as by the Link program from the Province of Limburg, the Netherlands.

Speaker: Mr Yue Zhang (Maastricht University)

IWORiD 2022-YZ.pdf

IWORiD 2022-YZ.pptx

8 The FlashDC project: development of a beam monitor for FLASH radiotherapy

The possibility to implement the beneficial outcomes of FLASH effect in clinical practice lately has been object of extensive research activity. From the experimental point of view a significant challenge is related to the monitoring at FLASH intensities of therapeutic beams, since conventional monitors are affected by saturation effects and discharges due to the extremely high instantaneous dose. The FlashDC (Flash Detector beam Counter) exploits the air fluorescence to provide an accurate beam quality control, performing real time verification of the beam position and intensity with minimal impact on the treatment delivery. According to data in literature a linear response in a wide range of dose rate and beam energy could be achieved. A prototype ($2\times2\times60$ cm$^3$) filled with air, readout by two photomultipliers, has been used for proof of principle studies and test beam campaigns. The fluorescence signal with respect to beam position and intensity has been studied irradiating the monitor with electron FLASH beams provided by the ElectronFlash LINAC by SIT (Aprilia, Italy). The detector position has been moved with respect to the beam axis and the dose rate per pulse has been varied in the range $2.5-5\times10^6$ Gy/s. The obtained results, indicating that fluorescence is correlated with the relevant parameters under study, will be presented, as well as the FLUKA MC simulation developed in order to optimize the final detector layout.

Speaker: Antonio Trigilio (Università degli studi di Roma “La Sapienza”, Dipartimento di Fisica, Roma, Italia, and INFN Istituto Nazionale di Fisica Nucleare, Sezione di Roma, Roma, Italia)

FlashDC.pdf

9 Measurement of the Energy Loss during proton therapy: a new treatment verification technique

To overcome particle therapy limitations, several treatment verification techniques based on the detection of secondaries have been developed, but a clinical device to be included in the patient routine is yet to be available. Recently, we developed a reconstruction model to estimate the time-depth distribution of the prompt photon emission with a multiple Prompt-Gamma Timing (PGT) detector setup with which to assess the primary particle range. PGT relies on time-of-flight measurements, i.e. the difference between the detection time of the prompt photon and the delivery time of the primary proton. This time difference depends on the prompt photon production points, which are, in turn, related to the slowing down of primary particles inside the target. Therefore, information about the primary particle motion can be obtained. We present here, for the first time, an analytical approach to estimate one of the main critical parameters for treatment optimization: the stopping power of proton beams. Simulation results show an agreement within 2.8% between the reconstructed stopping power and the expected values from NIST, proving the potentiality of the technique.

Speaker: Veronica Ferrero

IWORID22.pdf

10 Timepix3-based mini-tracker of charged nuclear fragments to detect anatomical changes in radiotherapy with carbon ions

Cancer treatments have been performed with X-rays and ions (e.g., protons and carbon ions) over the years. The high dose conformity that allows better sparing of healthy tissue is a demonstrated advantage of carbon ions over x-rays [1]. This dose conformity can be impacted by to anatomical changes between treatment fractions, which can lead to an increase of the dose to healthy tissue and to a dose reduction in the tumor. Therefore, it is of great interest to monitor those anatomical changes to ensure such dose conformity. When carbon ions interact with human tissue, charged fragments are generated in nuclear interactions, which, if energetically enough, can escape the patient and provide valuable information about the ion beam during the treatment delivery [2-3]. This contribution presents a monitoring method to detect anatomical changes between treatment fractions based on charged nuclear fragment tracking.
To evaluate the performance of this treatment monitoring method, a treatment plan was delivered to a head-sized PMMA model with a typical clinical dose of 3 Gy (RBE) at the Heidelberg Ion Beam Therapy Center in Germany. Charged nuclear fragments were detected with a mini-tracker of 2 cm2 sensitive area, based on the silicon pixel Timepix3 (ADVACAM s.r.o. in Prague) detector technology developed at CERN [4]. To mimic anatomical changes inside the head model, a disk-shaped air cavity of 2 cm diameter and 0.2 cm thickness was inserted at different transverse positions (see fig.1). Moreover, three measurements for each cavity were performed: a first measurements as reference, a second measurement as fraction with no anatomical change, and a third measurement with the inserted cavity. During the data analysis, the tumor area was divided into 9 sub-regions in order to group the irradiated carbon-ion pencil beam spots (see fig.1).
By comparing the charged nuclear fragment emission profiles of the three measurements (see fig.2a), significant changes were found in the sub-regions where the air cavity was located. The detectability of the air cavity, taken as the significance of a measurement above 3𝜎, was then calculated (see fig.2b). It was found that the air cavity located closer to the mini-tracker reached a detectability of 4.8𝜎. When the cavity was located in the center position, a significance of 3.9𝜎 was obtained. A value slightly below 3𝜎 was found when the cavity was located on the far side of the mini-tracker due to the lower number of tracked fragments. Other more sophisticated data analysis strategies are being further investigated.
This contribution has quantitatively demonstrated the ability of a non-invasive monitoring method for the detection of small anatomical changes in realistic treatment deliveries, as well as its limitations. The obtained results are found to be of high clinical relevance. Therefore, this method is promising to be further investigated in clinical trials.
[1] Jäkel, Br. J. Radiol. 93 (2020) 20190428
[2] Félix-Bautista et al., Med. Phys. 48 (2021) 4411–4424
[3] Ghesquière‐Diérickx et al., Med. Phys. 49 (2022) 1776–1792
[4] Poikela et al., J. Instrum. 9 (2014) C05013–C05013

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

RFB_talk_iworid2022.pdf

12:50 Lunch break

Front End

Convener: Bernd Schmitt (Paul Scherrer Institut)

11 INVITED: Design challenges of hybrid pixel detectors for spectral imaging

Hybrid pixel detectors with spectral imaging capability have multiple energy bins in each pixel capable of creating ‘colour’ images of an incoming polychromatic X-ray beam. The energy information, which is extracted for each incoming photon, can be used for image contrast enhancement, improved material identification or reduction of beam hardening artifacts in Computed Tomography. One important field of application is medical radiology where clearer images with higher contrast can be produced with reduced dose to patients. Such applications typically require high-Z semiconductor detectors which have high detection efficiency in the range of 10’s of keV but which exhibit non-ideal behaviour in terms of charge deposition and collection. Highly integrated CMOS pulse processing with interpixel communication can mitigate many of the sensor non-idealities. In this talk we will review the advantages and challenges of the pulse processing hybrid pixel detector technology for spectral imaging applications with a focus on the new Medipix4 ASIC.

Speaker: Xavi Llopart Cudie (CERN)

Xavi_Iworid2022_Final.pdf

12 Development of Timepix4 readout for experiments at synchrotrons and FELs

Timepix4 is a versatile readout chip with 55 µm pixels, developed by CERN on behalf of the Medipix4 collaboration. Detector group at Deutsches Elektronen-Synchrotron (DESY) develops readout systems for the Timepix4 chip that can be used for experiments at modern synchrotrons and free-electron lasers (FELs). Timepix4 has two operating modes. Detectors with this chip operated in photon counting mode are able to replace detectors carrying the Medipix3 readout chip like LAMBDA in their existing applications. Applications like small-angle/wide-angle X-ray scattering (SAXS/WAXS), as well as powder diffraction can benefit from a 10 times higher count rate capability of Timepix4. When operated in the event-by event mode, Timepix4 can replace its predecessor Timepix3. Techniques for X-ray scattering experiments using correlation analysis will benefit the most of the ns time resolution. For instance, it will enable time-resolved experiments with single-bunch time resolution at the PETRA IV Storage Ring Facility. Timestamping is also useful in pump-probe experiments carried out at synchrotrons and FELs.
The development of Timepix4 readout boards is ongoing at DESY. A carrier board for a single chip has been designed, produced and tested. The layout of the board and the position of the chip at the edge of it allows for 2-chip tiled systems. For this first iteration, a commercially available readout board hosting a powerful Zynq UltraScale+ System on Chip has been chosen. Data is transferred to a control PC over Firefly optical links. This device is able to deal with the high readout bandwidth of the chip. Chip testing, as well as firmware and software developments are currently in progress.
The next step is development of multi-chip modules. New custom readout boards carrying 3 chips are currently under design. In the long term, multi-megapixel systems composed of multi-chip modules will be developed.

Speaker: Alexandr Ignatenko

Ignatenko_iWoRiD_Timepix4.pdf

13 First tracks and initial timing results with Timepix4 Detectors

A single arm beam telescope based on the recently developed Timepix4 ASIC was built in order to perform first tests of synchronous multiple-detector readout and track reconstruction. The Timepix4 is a hybrid pixel detector readout ASIC designed to record time-of-arrival (TOA) and time-over-threshold (TOT) simultaneously in each pixel. It has a 448x512 pixel matrix with square pixels at a 55 μm pitch. The TOA is digitised with a 195 ps TDC bin size and the TOT is proportional to the charge collected by the silicon sensor. The telescope is composed of four planes with n-on-p silicon sensors. Two of these planes are instrumented with 300 𝜇𝑚 thick sensors tilted with respect to the beam, to provide high quality spatial measurements, while the remaining two have 100 𝜇𝑚 thick sensors to achieve a better time response. Each detector assembly (sensor + Timepix4 ASIC) is cooled by a 3D printed titanium block directly attached to the test PCB, through which a cooling fluid is circulated. The cooling block has a circular cut-out to minimise the amount of material traversed by incident particles. The Timepix4 ASICs are read out by the FPGA based SPIDR4 systems, capable of 10 Gbit ethernet readout. In addition to the Timepix4-based detectors, scintillators were placed in the beam acceptance (2 upstream and 1 downstream of the telescope) in order to give a reference timing measurement. The signals from the scintillators are treated with a constant fraction discriminator for optimal temporal resolution. The discriminated signal is digitised by TDCs in the Timepix4 ASIC with the same resolution as the pixels. First tracks were reconstructed using information from all four planes, which allows the assessment of temporal resolution using high energy particles. In this presentation, the initial results of the timing and spatial resolution of this telescope and plans for the complete telescope will be shown.

Speaker: Martin Van Beuzekom (Nikhef National institute for subatomic physics (NL))

FirstTracksTimepix4_v1.pdf

FirstTracksTimepix4_v1.pptx

14 The new monolithic ASIC of the preshower detector for di-photon measurements in the FASER experiment at CERN

The FASER experiment at the LHC is designed to look for new, long-lived fundamental particles. To extend its discovery potential, a W-Si preshower detector is currently under construction, with the objective of enabling the discrimination of photon pairs with O(TeV) energies and separation down to 200 µm. The detector will be based on a new monolithic silicon pixel sensor in 130nm SiGe BiCMOS technology, featuring a matrix of N-on-P hexagonal pixels of 65 µm sides. The ASIC will integrate SiGe HBT-based fast front-end electronics with O(100) ps time resolution, and will feature an extended dynamic range for the charge measurement. Analog memories inside the pixel area will provide the capability of storing charge information for thousands of pixels per event, allowing for a frame-based event readout with minimum dead area. After a short description of the preshower detector and its expected performance, the design of the monolithic ASIC and the test results on the ASIC prototypes will be presented.

Speaker: Sergio Gonzalez Sevilla (Universite de Geneve (CH))

20220627_faser_preshower_sgs_16x9.pdf

15 A flexible, customizable and open-source software for the Timepix4 ASIC configuration and read-out

We present a new C++ software for the configuration and read-out of Timepix4, a
large 4-side buttable ASIC developed by the Medipix Collaboration for high-rate
radiation imaging with improved energy and time resolution.
The software is organized in a structure of classes that allows to configure and
manage both the Timepix4 ASIC and the Control Board for data-handling and
interface with the server, using both the slow and fast read-out modes, up to a
maximum bandwidth of 160 Gbps. Moreover, storage, the post-acquisition analysis
and every other custom class can be easily added without modifying the basic
organization of the software. Thanks to the use of virtual classes, this software
structure can be totally customized depending on the data acquisition system.
A complete and ready-to-use software can be obtained by editing just some functions,
in order to manage different types of Control Boards, regardless of the type of
hardware and of the communication protocol.
In addition to the software architecture, the results of acquisitions made using this
software and a 300 µm silicon sensor bump-bonded to the Timepix4 ASIC will be
presented.

Speaker: Viola Cavallini (Universita e INFN, Ferrara (IT))

Readout-software for TImepix4-based detectors.pdf

15:50 Coffee break

Poster: 1

Conveners: Coralie Neubuser (Universita degli Studi di Trento and INFN (IT)), Giovanni Paternoster (Fondazione Bruno KEssler)

16 Specifications and Pre-production Experience of n$^{+}$-in-p Large-format Strip Sensors fabricated in 6-inch Silicon Wafers, ATLAS18, for Inner Tracker of ATLAS Detector for High-Luminosity Large Hadron Collider

The full volume of the inner tracker of the ATLAS experiment will be replaced with new all-Silicon detectors for HL-LHC. The strip detectors, in the radial extent of 40 to 100 cm, are made of four layers of cylindrical-structures in the barrel and six layers of disk-structures in the endcap section with 2 layers of strip sensors for stereo-viewing in each layer-structure. The corresponding area of strip sensors, at 165 m$^{2}$, will be covered with 10976 barrel and 6912 endcap sensors. A new approach is adopted to use p-type material to be more radiation-tolerant, making the readout in n-strips, so-called n$^{+}$-in-p sensors, to cope with the fluence and ionizing dose of 9.7$\times$10$^{14}$ (1.6$\times$10$^{15}$) 1-MeV neutron-equivalent (n$_{eq}$)/cm$^{2}$ and 44 (66) Mrad at the maximum in the barrel (endcap in the parenthesis) section, for its lifetime including a safety factor of 1.5. In the barrel sensors, the geometry is square, 9.8$\times$9.8 cm$^{2}$, to have the largest area of sensor possible from a 6-inch wafer. The strips are laid out in parallel with a strip pitch of 75.5 $\mu$m and 4 or 2 rows of strip segments in two types of sensors, "short strips (SS)" for the inner 2 layers and "long strips (LS)" for the outer 2, respectively. In the endcap, we have designed roughly trapezoidal sensors with built-in stereo angle, curved edges along the circumference, and in 6 different shapes in each radial extent, R0 to R5. The strips are in fan geometry, with a mean pitch of approximately 75 $\mu$m and 4 or 2 rows of strip segments. The readout is AC-coupled and the strips are biased via Polysilicon resistors for all sensors. The sensors of this specification are labelled as "ATLAS18xx" where xx stands for SS, LS, Rx (x=0 to 5). With the specifications of mechanical features and electrical performance, CAD files for processing were laid out by succeeding from a sequence of successful designs of ATLAS12 and ATLAS17LS of the barrel sensors, and ATLAS12EC/R0 of the R0 endcap sensors, together with a number of optimizations. In the open space of the wafer outside the main sensor, called "halfmoons", we laid test structures, miniature sensors, monitor diodes, etc. for monitoring the processing and wafer characteristics. "Pre-Production" amount of 1041 wafers were fabricated and delivered with the tests carried out by vendor. The quality of the sensors was reviewed through the data as provided by the vendor. These sensors were used for establishing and exercising acceptance procedures, and subsequently to be used for pre-production of strip modules and layer structures.

Speaker: Marcela Mikestikova (Czech Academy of Sciences (CZ))

17 Establishing the Quality Assurance Programme for the Strip Sensor Production of the ATLAS Tracker Upgrade Including Irradiation with Neutrons, Photons and Protons to HL-LHC Fluences

The successful pre-production delivery of strip sensors for the new Inner Tracker (ITk) for the upgraded ATLAS detector at the High Luminosity LHC CERN has completed and based on their performance full production has commenced. The overall delivery period is anticipated to last 4 years to complete the approximately 22000 sensors required for the ITk. For Quality Assurance (QA), a number of test structures designed by the collaboration, along with a large area diode and miniature version of the main sensor, are produced in every wafer by the foundry (HPK). As well as Quality Control (QC) checks on every main sensor, samples of the QA pieces from each delivery batch are tested both before and after irradiation with results after exposure to neutrons, gammas or protons to doses corresponding to those anticipated after operation at the HL-LHC to roughly 1.5 times the ultimate integrated luminosity of 4000fb-1.
Since the QC testing cannot reliably catch all the possible variations in production parameters that may influence deterioration during operation at the HL-LHC, the QA procedures are essential for guaranteeing long-term survival and are beyond the scope of what any manufacturer can reasonably check themselves. It is therefore vital that these procedures are as robust as possible and seen by the manufacturer to be fully reliable as they have the potential to lead to rejection of batches otherwise satisfying all the agreed QC tests. As a result ATLAS, with input from independent experts, has developed detailed sensor QA plans, looking at the planned sampling rate; the proposed acceptance criterion; the measurement and irradiation procedures; along with the required standards of precision, consistency and reproducibility, among the participating irradiation facilities and QA institutes.
This presentation outlines these procedures and the studies carried out to establish that the seven ITk QA Strip Sensor irradiation and test sites meet all the requirements to support this very extensive programme throughout the strip sensor production phase for the ITk project.

Speaker: Ioannis Kopsalis (University of Birmingham (GB))

poster_iWoRiD2022_ATLAS_ITk_IKopsalis.pdf

18 Image characterization and optimization of high-resolution scintillators on digital X-ray imaging detector

In recent years, digital X-ray imaging detectors with indirect detection technology have been widely used in dental digital radiography such as intra-oral, panorama and dental CT. These indirect X-ray imaging detectors are based on the combination of a complementary metal-oxide semiconductor (CMOS) array with various high-resolution scintillating screens such as CsI, GOS materials. Currently, a CMOS panel-based indirect X-ray imaging detector with low radiation dose and excellent spatial resolution has been widely utilized for digital intra-oral radiography.
In this work, different high-resolution scintillation screens such as FOS (fiber optic scintillator) with needle structured CsI:Tl and Gd2O2S:Tb(GOS) materials with different mass density were used to investigate and optimize the imaging characterization. The used different FOS screens are a highly X-ray absorption material that minimizes and removes the direct X-ray induced noise. The used scintillator’s configuration parameters were tested and optimized for superior image quality at low X-ray exposure condition.
For image characterization and optimization of the X-ray image device, different scintillating screen were directly combined on the bare high-resolution CMOS photodiode array. The imaging performance such as the light response to X-ray exposure dose, signal-to-noise-ratio (SNR), modulation transfer function (MTF) and low-contrast detail resolution was measured under practical dental system condition with 60-70kVp tube voltage and 2-5mA tube current. The high spatial resolution with 16.6lp/mm could be implemented through the experimental results with a CMOS imaging detector using a CsI scintillator.

Speaker: Dr Bo Kyung Cha (KERI)

19 Radiation detectors and their applications in medical imaging

The evolution of radiation in medicine is one of the major breakthroughs recorded in medical sciences. Advanced techniques in the diagnostic and therapeutic radiation are the reasons for successes in researches, industries and in nuclear medicine. Medical radiation is considered as a field that focuses on human health and the application of advanced radiation techniques to solve health complications. Therefore, there are more emphasis on using novel and advanced approaches to solve medical issues. Moreover, there is now the need to study and understand the major radiation detectors used in disease detection, diagnosis and treatment. In this study, radiation detectors were identified based on their individual impacts in the medical imaging systems. The study focuses on the various advanced radiation detection devices such as X-ray systems, positron emission tomography, single-photon emission computed tomography, and presents a brief survey of the type of radiation detectors including gas-filled detectors, solid-state detectors, and scintillation detectors for medical imaging systems.

Speaker: Ilker Ozsahin (Near East University, Nicosia/TRNC, Turkey)

20 Digital signal processing for position-sensitive gamma ray detectors

Room temperature semiconductor sensors (CdZnTe, TlBr) have been proven to be exceptionally performing in gamma-ray spectrometer for many applications [1,2,3]. In particular, the 3D position-sensitive Virtual Frisch-Grid (VFG) detector configuration is advantageous for integrating CZT crystals into large area arrays, where the signals captured by the anode, cathode and four pads electrodes, enable the 3D reconstruction of interaction points and measurements of the energies deposited in the event. The conventional ASIC architecture implementation of a suitable readout electronic for such applications consists of a low noise charge sensitive amplifier (CSA) and a pulse-shaping stage followed by a peak and time of peak detector [4]. Another approach is to couple a multi-channel front-end ASIC, where each channel is composed of a low noise CSA and shaper stage, to ADCs, forming a waveform “digitizer” and convert the captured signals into a time series of digital values. Then, an optimized Finite Impulsive Response (FIR) digital filter is applied to extract the information about energy and time of the particle interaction event. This solution adds the flexibility to adapt the signal processing parameters and tailor the optimal filter on a specific digitized set of waveforms without being constrained by the implemented ASIC electronic. Moreover, further corrections can be applied to the processed data to mitigate detector defects and non-uniformities improving the energy resolution response [5].
In this work, we present the development of a waveform digitizer composed of the front-end ASIC [6] and the readout electronic (ADCs and FPGA). Also, we describe the optimization of the FIR filter applied to characterize the energy resolution of gamma-ray detectors, demonstrating the energy resolution of ~1% (FWHM) at 662 keV.
[1] K.S. Shah et al, IEEE Trans. Nucl. Sci., vol. 36, no. 1, pp. 19 –202, 1989.
[2] K. Hitomi et al, Nucl. Instr. and Meth. A 458, no. 1, pp. 365–369, 2001.
[3] A. Owens and A. Peacock, Nucl. Instrum. Methods, vol. A531, pp. 18–37, 2004.
[4] E. Vernon et al, IEEE Trans. Nucl. Sci., vol. 57, no. 3, pp. 1536-1542, 2010.
[5] A.E. Bolotnikov et al, Nucl. Instr. and Meth. A 954, 161036, 2020.
[6] G. Pinaroli et al, 2022 JINST 17 C02011
This abstract has been authored by employees of Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U.S. Department of Energy.

Speaker: Giovanni Pinaroli

21 Resistive read-out in silicon detectors

This contribution will cover the novel field of silicon detectors with resistive read-out. Resistive read-out is a well-known technique, extensively used, for example, in gas detectors. Its application to silicon sensors requires the development of new sensor designs, where a resistive cathode shares the signal among several read-out pads. Measurements performed on first prototypes have demonstrated that the charge sharing mechanism allows achieving excellent spatial and temporal resolutions with large pixels.
This design opens the possibility of reducing the number of read-out channels by about a factor of 100 with respect to standard sensors, decreasing significantly the power consumption.

Speaker: Marco Ferrero (Universita e INFN Torino (IT))

22 Tomographic Image Reconstruction Techniques for Accurate Spent Fuel Assembly Verification

To realize the non-proliferation and security of nuclear material, the international atomic energy agency (IAEA) considers a tomographic image acquisition technique of spent fuel assemblies as a promising technique to accurately verify rod-by-rod spent fuel conditions stored in a water pool. Our previous research developed and experimentally validated a highly sensitive single-photon emission tomographic (SPECT) system to quickly evaluate the radioactivity distribution of test fuel rods in the Korea Institute of Nuclear Nonproliferation and Control (KINAC) (Figure 1). In order to quickly verify the fuel assembly, it is important to develop a high-quality image reconstruction algorithm that enables image acquisition within a short time. The purpose of this study is to evaluate advanced tomographic image reconstruction techniques to accurately identify patterns of missing fuel rods.
Rotational projection image data sets were obtained for 15 patterns of test fuel rods for a total of 900 seconds using the SPECT system installed at KINAC. The projection images were acquired every 5 degrees while four 64-channel detectors rotated 90 degrees. The acquired images were reconstructed in the following methods: filtered back-projection (FBP), simultaneous iterative reconstruction technique (SIRT), order-subset simultaneous algebraic reconstruction technique (OS-SART), and maximum likelihood expectation maximization (MLEM). Among the reconstruction algorithms used in this study, the image quality of the MLEM showed the best performance. This algorithm preserved the image intensity and edge, and global homogeneity was significantly better with the reduced generative noise than that of other algorithms. Therefore, to accurately verify the patterns of fuel rods, we improved the signal-to-noise ratio of the tomographic image with the advanced image reconstruction technique (Figure 2). We expect that even for the low-quality measured data with the short-time scan of the SPECT system, this advanced technique will show better discriminability of the patterns of fuel rods in the assembly.

Speaker: Dr Hyemi Kim (Wonju Severance Christian Hospital, Yonsei University Wonju College of Medicine)

23 Water mapping neutron spectrometer HardPix for EL3 Polar Explorer

A current renaissance of lunar exploration enables to search for lunar water deposits directly on the surface of the Moon with robotic rovers like those onboard the planned EL3 Polar Explorer. IEAP CTU is participating on ESA study to trade-off possible mobile instruments and develop preliminary payload design for neutron spectrometer serving as the water ice detector. We developed a miniature Timepix3-based detector HardPix capable of mapping the water deposits using non-invasive detection of neutrons created underground by cosmic rays and thermalized by hydrogen. This device consists of a HardPix neutron spectrometer to measure flux of neutrons moderated by water, a HardPix cosmic radiation detector to monitor the natural source of neutrons and an optional miniature gamma-ray spectrometer to provide a basic elemental composition of the lunar subsurface. Two HardPix units will also be part of ERSA for Lunar Gateway to monitor the radiation environment in deep space.

Speaker: Robert Filgas (Czech Technical University in Prague)

24 A Scattered X-ray Correction Method and its Verification by Energy-resolved CT

In X-ray transmission measurements, scattered X-rays distort X-ray images. Medical doctors will overcome such distortion with their experience in reading images of an X-ray film and a flat panel detector. Computed tomography (CT), however, gives images after processing digital data given by transmission measurements, and sometimes results in wrong images. Hardware and software have been developed for removing the scattered X-rays. A grid is a hardware which absorbs the scattered X-rays, however, it also reduces primary X-rays which are necessary for imaging and brings higher dose exposure to a subject for having a proper image. Simulation calculation [1] and deep learning [2] are software for rejecting the scattered X-rays, but they require long calculation time and huge amount of data.

In this paper, we propose a method for the scattered X-ray correction with a simple experiment and deterministic calculation. The scatter correction methods are described in three stages: scatter correction with (1) a scatter-correction (SC) cylinder phantom which dimensions are the same with a subject under inspection (SUI), (2) SC cylinder phantoms smaller and larger than the SUI, (3) SC cylinder phantoms smaller and larger than the SUI with a deformed shape which is similar to a human body. The SUI is made of acrylic with six kinds of resin rods, which effective atomic numbers are similar to the ones of inner organs.

With CT data without and with SC, energy-resolved analysis was performed to have linear attenuation coefficients of resins. The linear attenuation coefficients without SC showed smaller values than the ones of the National Institute of Standard and Technology (NIST), however, the ones with SC agree with the ones of the NIST excellently as shown in Figure 1 [3].

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[1] T.-H. Tsai, I. Kanno, J. Nucl. Sci. Technol., 54, 205-212 (2016).
[2] S. Xie, C. Yang, Z. Zhang, et al. IEEE Access. 6, 78031-78037 (2018).
[3] M. J. Berger, J. H. Hubbel, S. M. Seltzer, et al. http://nist.gov/pml/xcom-photon-cross-sections-database.

Speaker: Prof. Ikuo Kanno (Kyoto University)

25 Design Optimization of X-ray Security Scanner Based on Dual-energy Transmission Imaging with Variable Tube Voltages

At domestic ports and airports, an X-ray security scanner based on dual-energy transmission imaging has been operated to prevent the importation of contraband articles including weapons, narcotics, and explosives. Korea Customs Service (KCS) also conducts X-ray screening for all baggage and express shipments. Security scanners operated by KCS use a fixed tube voltage (i.e., 160 kVp); hence, it has limitation to detect the thinly-coated organic contraband articles. In this study, Monte Carlo simulation codes (MCNP6 and GATE) were used to optimize the performance of a dual-energy X-ray security scanner with variable tube voltages. Monte Carlo simulation could be the best option for optimizing and estimating performance under various conditions. The X-ray generator, dual-array detector, and integrated system were optimized in terms of various parameters (Figure 1).

To estimate the performance of the optimized system, dual-energy material classification variables (i.e., R-value) for various materials were derived and pseudo-coloring images classifying between organic and inorganic materials were obtained [1]. Through the security screening with variable tube voltages, it was possible to detect organic contraband articles that are relatively hard to be confirmed by the conventional X-ray security screening. The optimized tube voltage for obtaining the best security image of organic, inorganic, and metal material was determined to be 100, 120, and 160 kVp, respectively.

For quantitative performance estimation, an ASTM F792 test kit, which is applied to the performance evaluation of the X-ray security scanner was modeled [2]. Two evaluation parameters of simple penetration and wire display performance were estimated using the test kit. The results showed that the simple penetration of 30 mm at 160 kVp and wire display above 42 AWG (Φ 0.064 mm) at 80 kVp was achievable with the optimized design (Figure 2).

The wire display performance of commercial security scanners was up to 38 AWG (Φ 0.102 mm), and simple penetration performance was over 30 mm (Table 1). Because simple penetration depends on the tube voltage, it was estimated to have similar performance with that of commercial products. In the case of wire display, the performance was estimated to be improved by more than 30% compared to commercial products thanks to the optimized design and tube voltage.

The results of this study can be used for the development of a dual-energy X-ray security scanner with variable tube voltages customized for different types of material to be inspected. It is expected that the newly designed system will contribute to the improvement of the detection rate for organic contraband articles.

Speaker: Junsung Park (Jeonbuk National University)

26 Development of deep learning-based C-arm CT/SPECT imaging system for online adaptive brachytherapy

Adaptive radiation therapy (ART) enables an accurate targeting of tumors by accounting for ongoing changes in the patient’s anatomy and/or physiology during the course of treatment. Currently, the ART technique is quickly evolving owing to the development of diverse deep learning methods and their application to medical imaging techniques. Even though the high dose rate brachytherapy technique has been significantly improved, its current state of the art has various limitations in online ART due to the absence of an efficient imaging system and a proper beam delivery verification process. In this study, therefore, we developed a deep learning-based image quality improving technique applicable to a C-arm CT/SPECT imaging procedure for online adaptive brachytherapy. Image dataset of 35 noncontrast pelvis CT studies (~5000 image series) was acquired from The Cancer Imaging Archive data repository and the limited-angle Cone-beam CT (CBCT) images were generated by mathematically calculating sinograms for voxel phantoms based on these CT images with MatlabTM. With a cycle-consistent generative adversarial network (Cycle-GAN), low-quality CBCT images obtained by a 110° limited-angle rotating C-arm fluoroscopic system were transformed to high-quality diagnostic CT images. The performances of these networks were evaluated by comparing them with CBCT images reconstructed by an iterative reconstruction method and ground truth images. The synthetic CT images were successfully transformed from the low-quality CBCT images considerably reducing the streaking artifacts and preserving anatomical structures. Because of the use of the correlation coefficient loss and shape consistency information to directly enforce the structural similarity between the CBCT and the synthesized image, the Cycle-GAN showed the highest performance when evaluating image qualities with the parameters such as structural similarity, root mean square error, and spatial resolution. In this study, we confirmed the availability of online high-quality CT imaging with the limited-angle rotating C-arm fluoroscopic system by applying the deep learning technique, which enables the image-guided brachytherapy and online adaptive treatment planning.

Speaker: Minjae Lee (Yonsei University)

27 Preliminary Study on Neutron Activation Analysis for Various Substances Using Room-temperature CZT Detector

Since the neutron activation analysis (NAA) technique is capable of non-destructive material analysis, it can be used in various areas including the detection of drugs and explosives that require the analysis of hazardous substances not specified in shape. In this study, we carried out various NAA experiments for several substances and obtain energy spectra of the gamma-ray emitted from the substances using a room-temperature CdZnTe (CZT) detector and neutron source including 252Cf and D-T generator. First, we figured out the characteristics of the prompt gamma-ray emitted from the hazardous substances by using MCNP6 toolkit. In the simulation, we modeled a neutron target substance with a cylindrical structure of 5 cm (R) × 10 cm (H), and the target substance was assumed to be composed of a single element (H, C, O, Si, and P). For the detector, we modeled 4 CZT detector modules composed of 4 CZT crystals with a dimension of 2.2 × 2.2 × 1.0 cm3. For the source, neutron with energy spectrum equivalent to 252Cf was modeled. Then, we carried out several NAA experiments for general substances including water, wood, glass, polyethylene, and PVC. In the experiment, the substance to be measured was placed in the center of 4 detector modules, and a 252Cf source (90 uCi) was attached to the substance. In addition, we carried out NAA experiments for 5 explosives using D-T generator of 2.5 × 109 n/s with the irradiation time of 20 minutes. The used explosives were provided by R.O.K Army Engineer School. The results show that the existence of element including H, C, O, Si, and P can be identified roughly by the analysis of the prompt gamma-ray energy spectra. In addition, the existence of N and O in the explosives was identified experimentally, and it was confirmed that the explosives can be identified and analyzed by NAA technique.

Speaker: Jae Hyeon Kim (Korea Atomic Energy Research Institute)

28 Ion imaging and material determination using a beam telescope

Ion-beam therapy has become a well-established method to treat deep-seated malignant tumors. Typically, the treatment planning is based on an x-ray computed tomography (CT) scan, which is performed prior to irradiation. However, in the planning process, the Hounsfield units (HU) that are obtained from the x-ray CT scan have to be converted to relative stopping powers (RSPs), which describe the energy loss of an ion beam within the investigated tissue. To avoid this conversion and the accompanying uncertainties in the dose distribution, the idea of ion imaging, which directly returns RSP values, was developed.

A typical ion CT system consists of an upstream and a downstream tracker (to measure each ion’s position and direction) and a range or energy measurement device (range telescope or calorimeter). A small ion CT demonstrator system was developed by HEPHY and TU Wien and tested at MedAustron, an ion therapy center in Wiener Neustadt, Austria. The system consists of four double-sided silicon strip (DSSD) detectors with an active area of 2.56 x 5.12cm^2 and a range telescope composed of plastic scintillator slabs. Besides conventional ion CT, recent measurements with the demonstrator included scattering radiographies and attenuation radiographies with high statistics (O(10^6-10^7) protons per image).

For a full ion CT scan, the setup has to be rotated around the patient or object to be imaged (phantom) and measurements are taken at several angles. In order to obtain a 3D map containing the RSPs, a reconstruction algorithm, which takes the non-straight ion paths into account, is essential. Recent developments within the CT reconstruction toolbox TIGRE for ion CT image reconstruction will be presented. Furthermore, hardware and software investigations for a future upgrade of the ion CT demonstrator will be discussed. On the hardware side, this includes the newest research results for an ion CT system based on 4D-tracking detectors and a residual energy measurement based on time-of-flight. Such a system was studied using Monte Carlo simulations and was shown to yield RSP errors < 0.6 %.

Speaker: Philipp Gaggl (Austrian Academy of Sciences (AT))

Ion imaging and material determination using a beam telescope.pdf

29 Improvement of β+/γ discrimination algorithm based on deep-learning

In this study, we proposed a deep-learning based algorithm for discriminating positron/gamma-ray in a phoswich detector (two-layer scintillator). However, both Compton scattered gamma rays and positrons can deposit energy in both layers. Therefore, conventional pulse shape discrimination (PSD) algorithms incorrectly identified Compton scattered gamma-ray as positron. Compton scattered gamma-ray and positron may be discriminated should one acquired energy distribution of each scintillator because the distribution of energy deposited in each scintillator differs depending on the type of radiation. Therefore, we introduced an Autoencoder, an unsupervised deep learning architecture, to separate the coincidence signal into their original signals of each scintillator. The distribution of energy deposited on both scintillators was then obtained using the separated signal. False positrons can be rejected based on this energy distribution, which led to improvement of positron detection accuracy. The positron/gamma-ray discrimination algorithm using the autoencoder increased the sensitivity (true positive) by 14.4% and decreased the error rate (false positive) by 43.4% compared to conventional PSD algorithms.

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

30 Design Optimization of Backscatter X-ray Security Scanner Based on Pencil Beam Scanning

Security screening is conducted at national borders and high-security facilities to block the importation of illegal goods. Currently, Korea Customs Service conducts a transmission X-ray security screening using fixed energy. However, with the current system, the detection efficiency of drugs or explosives composed of organic substances is rather low. The backscatter X-ray detection system is sensitive to materials with low atomic numbers [1]; therefore, it can play a complementary and essential role in security screening.

For the backscatter X-ray image, there are several collimation methods that can be applied to the detector or the source for determining an image pixel. In the case of the detector collimation method, because the detector should be highly segmented to obtain accurate position information, it is relatively noisy due to its low efficiency [2]. In contrast, the source collimation method has a high intensity per pixel with the pencil beam scanning technique. This pencil-beam-based backscatter X-ray detection system consists of an X-ray generator, a rotating collimator, and large area detectors.

In this study, the design of a backscatter X-ray security scanner was optimized and, then, its performance was estimated for various conditions using the Monte Carlo simulation technique (Figure 1). For the X-ray generator, we optimized the tube voltage and the geometry of the chopper wheel collimator. The detector parameters of its area, thickness, and distance between the detectors were also optimized in terms of the detection efficiency. Finally, the performance of the optimized system was estimated for various object conditions (i.e., material compositions and thicknesses).

It is expected that this study will contribute to developing backscatter X-ray security scanners and thereby enhancing national security.

Speaker: Mr Geunyoung An (Jeonbuk National University)

31 A time-of-flight based neutron background reduction for imaging of proton-induced secondary-electron-bremsstrahlung x-rays: A Monte Carlo study

Therapeutic proton beams generate secondary-electron-bremsstrahlung (SEB) x-rays along the beam passing through the patient body. Yamaguchi et al. have successfully imaged beam trajectories in water during proton beam irradiation by measuring the SEB x-rays using a low-energy dedicated x-ray camera. Unfortunately, the measured x-ray images contain neutron background as well as the SEB x-rays signal. To reduce the neutron background in the measured x-rays images, we proposed to apply a time-of-flight (TOF) method to the SEB x-rays imaging. The purpose of this study is to investigate the optimal time window for SEB x-rays imaging without the neutron background from the difference in time spectra between photons and neutrons. In the presentation, we will show the simulated results of SEB x-rays images without the neutron background by applying the TOF method with the optimal time window.

Speaker: Dr Takuya Yabe (Takasaki Advanced Radiation Research Institute, National Institutes for Quantum Science and Technology / Postdoctoral Research Fellow of the Japan Society for the Promotion of Science)

32 Particle beam imaging by measuring secondary electron bremsstrahlung using a CdTe imager

Particle beam therapy is recognized as an excellent method for cancer treatment. On the other hand, due to their high dose localization, deviation of the irradiated area from the planned has a significant adverse effect on surrounding normal tissues. Non-invasive visualization of the therapeutic beam is required to optimize the treatment effect. The objective of this study is to establish a real-time beam imaging technique for measuring secondary electron bremsstrahlung by use of a CdTe imager. In the presentation, we will report on the analysis of beam image and on the accuracy of the estimated range variation derived from the analysis.

Speaker: Michiko Tsuda (Faculty of Science and Technology, Gunma University / Takasaki Advanced Radiation Research Institute, National Institutes for Quantum Science and Technology)

33 Simulation study on carbon-ion beam imaging by measuring secondary electron bremsstrahlung using an imaging plate

Beam-imaging methods in particle therapies are expected to eliminate deviations of the irradiation areas and to improve treatment results. Recently, we proposed a beam-imaging method by measuring secondary electron bremsstrahlung using imaging plates (IP) and confirmed that high-resolution therapeutic carbon-ion beam images could be acquired using an imaging device combining an IP and pinhole-type tungsten collimator. The purpose of this study is to evaluate the effect of a lead radiation shield on the range-estimation accuracy. Monte Carlo simulations were performed using PHITS. A carbon-ion beam was injected to a acrylic target. A tungsten collimator having a pinhole was placed at the distance of 31.2 cm from the beam. A lead radiation shield was placed on the tungsten collimator. To evaluate the effect of the lead radiation shield, simulations were repeated with changing the thickness of the radiation shield. We found that the noise component in the acquired image decreased and the accuracy improved with increasing the thickness of the radiation shield.

Speaker: Dr Mitsutaka Yamaguchi (National Institutes for Quantum Science and Technology)

34 Flexible Data Acquisition Software for Imaging of Radiation Dose Spatial Distribution for Radiotherapy Treatment Planning

It is well known that cancer is one of the deadliest diseases worldwide, accounting for nearly ten million deaths in 2020 [1]. There are various treatment methods proposed and one of the most frequently used is radiation therapy. This method requires precise knowledge of radiation dose distribution to limit damage to the surrounding healthy tissues. To address this complex problem, we present the state-of-the-art reconfigurable Dose-3D detector concept based on the active voxels approach to improve radiotherapy treatment planning. Three of its key components are radiation imaging scintillation detectors controlled by the data acquisition system (DAQ) and the high-level data analysis software.

The DAQ consists of hardware, firmware and low-level software (Figure 1.). A single hardware unit, called a slice (with multianode photomultiplier, Application Specific Integrated Circuit (ASIC) and an FPGA), gives access to 64 detection channels of the read-out ASIC while the low-level software (Server Application) handles operation with any number of slices simultaneously. The modular architecture of this software follows concepts of the recently published DAQ [2] with further modifications. Communication with each slice is handled using 1 Gbit/s UDP/IP protocol. The software maps registers and data sources from each slice independently and broadcasts such data to any consumer application giving high-level access to the underlying hardware. This way there might be any number of consumer applications in the network monitoring in real-time specific aspects of the hardware operation.

The main advantage of the proposed DAQ design is its scalability and portability to other FPGA-based DAQ systems. It might be a solid foundation for future designs which would only require a redefinition of registers binding and data sources while the protocol of data management by the Server Application will remain virtually the same. The development of consumer applications is also simpler and less labour demanding since they are separate processes possibly running on a different machine than the one running the Server Application. All in all, we believe that the proposed DAQ design will greatly contribute to deepening the understanding of radiation dose distribution in the human body.

Speaker: Mr Paweł Jurgielewicz (AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Krakow, Poland)

35 Visualization of Sulfur Impregnation on Single Fibre Level for Chemical Thermo Mechanical Pulp

In pulp & paper industry, even small improvements in efficiency can generate significant decrease in energy consumption and also reduction in the environmental impact. One key parameter during Chemical Thermo Mechanical Pulp (CTMP) impregnation is even distribution of sodium sulphite (Na2SO3) [1]. This study aims at deciding the necessary XRF image quality for a laboratory setup capable of process relevant homogeneity measurements of sulfur distribution in wood fibres. Hence, the necessary spatial and spectral resolution to be able to visualize sulfur impregnation into single wood fibers needs to be retrieved. The first part of the study is synchrotron measurements of different elemental distributions. Measurements on single fibre level has been performed at the synchrotron facility APS, Advanced Photon Source, at the Argonne National Laboratory in the USA. Several different CTMP samples manufactured at different operating conditions were used, and elemental mapping images were retrieved by using a synchrotron beam with one micrometre scanning step. One example of sulfur distribution is shown in Figure 1.

The impregnation of sulfur and other elements into the wood fibres for varying production parameter settings are also investigated in the synchrotron images. From the pulp process perspective, significant uneven distribution of sulfur between fibres are revealed in the images of CTMP samples. Another detail worth noting is that, on individual fibre level, the sulfur impregnation is concentrated mainly in the fibre shell.

Studies of XRF imaging to improve paper productions processes exists. One example is calcium measurements for improving the coating of paperboard [2]. However, measurement of individual paper fibers is a greater challenge due to their small size of about 20 µm. Since the objective is direct sulfur distribution measurements on site at paper mills, XRF imaging must be achievable on site. To achieve this, a scanning imaging setup for energy dispersive X-ray fluorescence (ED-XRF) is the goal. Figure 2 shows how degenerating the spatial resolution blurs information about sulfur distribution inside the fibers, and eventually also the visualization of single fibers are lost. A system consisting an X-ray tube equipped with polycapillary focusing optics must hence be capable of about 10 µm resolution. Apart from spatial resolution, the spectral resolution also needs consideration. The use of an X-ray tube instead of a synchrotron will increase the spectral background and the sulfur signal might be lost. In this work, a setup using a sealed titan box and helium atmosphere to improve spectral performance is considered [1].

For the further development of the methodology, the spatial resolution that still contains the necessary homogeneity information is extracted. The background and achieved spectral resolution is characterized.

[1] Rahman, H. Aspects of optimizing pulp fibre properties for tissue and packaging materials, PhD Thesis, Mid Sweden University (2021).
[2] Norlin, B. Reza, S. Fröjdh, C. Nordin, T. Precision scan imaging for paperboard quality inspection utilizing X-ray fluorescence. Journal of Instrumentation. 2018, Volume: 13, Article number C01021.

The authors acknowledge funding from Vinnova (Renewable packaging materials - Impregnation depth measurements for pulping industry using synchrotron) and discussions with Henrik Edlund at BillerudKorsnäs and Fredrik Lundström at Valmet. The synchrotron measurements are performed in collaboration with Barry Lai at Argonne National Laboratory.

Speakers: Barry Lai (Argonne National Laboratory), Börje Norlin

36 Silicon-Carbide detectors operating at increased temperatures

The 4H-SiC is a wide band gap semiconductor, the detector structures made of which are capable of operation at higher temperatures. In this article, we present an experimental result of 4H-SiC detectors operating at temperatures up to 500 °C. The polytype 4H-SiC has the band gap energy of 3.23 eV at room temperature. Moreover, this material has excellent physical and chemical stability and also breakdown voltage (3-5×10⁶ Vcm^-1) and high carrier saturation velocity (2×10⁷ cms^-1). In our previous works we studied electrical and spectrometric performance of fabricated SiC detectors showing a very promising properties for working in radiation harsh environments [1, 2].
In this contribution we are concentrating on electric properties and spectrometric performance of the detectors operating at very high temperatures up to 500 °C. The precise temperature stabilization was achieved by a low-noise custom microcontroller-controlled system with a PID loop using ceramic heaters in the customized vacuum chamber. At first the current-voltage characteristics were measured. The leakage current at 300 V was 1 pA and 10 nA at RT and 500 °C, respectively. The detectors also show a very little temperature dependence of the energy resolution of α-particle peak generated by ²³⁸Pu radioisotope. Fig. 1 demonstrates the comparison of α-particle spectra measured at 25 and 500 °C, respectively. The calculated energy resolution in FWHM (Full Width at Half Maximum) increases from 34 keV at RT up to 36 keV at 500 °C. In summary we can state that the 4H-SiC detector is a good candidate for high resolution α-particles spectroscopy in a wide range of increased temperatures.

Speaker: Norbert Gál (Institute of Electrical Engineering, Slovak Academy of Sciences)

37 New Insight into Gain Suppression and Single Event Burnout Effects in LGAD

Gain Suppression has been observed [1-5] and dramatic reduction in gain in LGAD is observed after ion beam has been injected, Fig 1. Also, the degradation of gain in LGAD is the highest at normal incidence. Significant reductions in the degradation rates are observed at beam tilting angles. This observation could be examined from different perspectives than it was given until now (charge space effects and screening of the electric field dependence on charge density). Here we examine the effect by studying the differences in the prompt thermal effects within the LGAD structure at different tilting angles.

The dissipated power density that governs the heating depends on the product of the electric field and the current density. Hence, at higher angles, the reduced collected charge density will result in reduced power densities, which can be assumed to cause the reduction in the
surface leakage current-induced degradation (noticed in the SEB effect).

Moreover, the lower energy dissipation at higher angles can be explained by the misalignment of the ion-induced charge eh pair - plasma-like/filament and the potential gradient within the depletion region, as reported by some authors. This reduces the current density within the LGAD structure, which leads to a reduced density of overall energy dissipation. An insight into the significance of degradation of leakage surface current by thermal runaway facilitating fatalities in SEB and the looping effect between bulk and surface leakage current in facilitating the thermal runaway effect is studied for the first time. For this purpose, a dedicated experiment to investigate responses of the peripheral units used for the optimization of LGAD is conducted. Both, experimental results, and concussions from modelling on observed behavior will be presented. Plasma formation mechanism coupled to thermal runaway is explored in SEB results as well, also through more advanced microscopic inspections of fatality SEB features, Fig 1(bottom image) [6], some of them not yet publicly presented. Also, for the first time we present results dedicated for gain suppression search during different SEB phases.

Speaker: Gordana Lastovicka Medin (University of Montenegro (ME))

38 The ATLAS ITk Strip Detector System for the Phase-II LHC Upgrade

The ATLAS ITk Strip Detector System for the Phase-II LHC Upgrade

The High Luminosity Large Hadron Collider (HL-LHC) is expected to provide an integrated luminosity of 4000 fb-1, that will allow to perform precise measurements in the Higgs sector and improve searches of new physics at the TeV scale.
The HL-LHC higher particle fluences and will requested radiation hardness, the increased average proton-proton pile-up interactions, require a significant scaling of the existing Inner Detector. ATLAS is currently preparing for the HL-LHC upgrade, and an all-silicon Inner Tracker (ITk) that will replace the current Inner Detector, with a pixel detector surrounded by a strip detector. The strip system consists of 4 barrel layers and 6 EC disks. After 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 on various detector components, with an emphasis on QA and QC procedures and the preparation for the production phase distributed over many institutes, which is foreseen to start in a few months.

Speaker: Christian Scharf (Humboldt University of Berlin (DE))

iWoRiD_2022_poster_ITk_strip_upgrade_cscharf.pdf

39 Tolerance of MIMOSIS-1 to ionizing radiation

The MIMOSIS CPS will equip the Micro Vertex Detector of the Compressed Baryonic Matter experiment at FAIR. It is to combine a 5µs/5µm space and time resolution with a peak rate capability of 80 MHz/cm² and a tolerance to > 5 MRad and 1e14 neq/cm². A first full size prototype, MIMOSIS-1 has been produced by IPHC Strasbourg, Goethe University Frankfurt and GSI.
The in-beam performance of non-irradiated and X-ray irradiated sensors is reported.

Speaker: Mr Hasan DARWISH (GSI Helmholtz Center for Heavy Ion Research)

iWorid_poster_2022.pdf

40 X-rays DSLR

Image quality evaluation and optimization of different scintillators-coupled DSLR X-ray imaging detector

Speaker: Lee Hunwoo

41 Results Obtained with FBK Pixel Sensor Prototypes for the HL-LHC Tracker Upgrade of the CMS Experiment

The High Luminosity Phase of CERN Large Hadron Collider (HL-LHC) will require an extensive upgrade of CMS tracker system, requiring, for the Inner Tracking system, high radiation tolerant silicon pixel sensors capable of withstanding fluences up to 1.9E16 neq/cm2 (1MeV equivalent neutrons). Thin planar and 3D pixel sensors have been recently chosen by CMS to be installed in the upgraded pixel tracker. Thanks to their peculiar structure, the 3D pixel sensors have some advantage with respect to planar ones, and are presently more suitable candidates for the innermost layer of the tracker. In this presentation results obtained with FBK planar and 3D sensors interconnected with prototype read-out chip RD53A will be shown. First single chip modules are being assembled in April 2022 with the new RD53C final chip prototype, also known as CMS Read Out Chip (or CROC); if available in time for this conference the first laboratory tests will be also presented. Both RD53A and CROC type sensors have 25x100 μm2 pitch and 150 μm thickness, and they were manufactured by FBK foundry in Trento, in collaboration with INFN. The sensors interconnected with RD53A chip were also irradiated over a wide range of fluences and then tested in different test beam facility in order to validate them up to the fluences foreseen for HL-LHC. The analysis of collected data shows very high hit detection efficiencies and good spatial resolutions as measured after irradiation. All the results in this presentation are obtained on

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

Iworid_2022_gbardelli.pdf

42 GaAs radiation-degraded detectors: gamma spectrometry at lowered temperatures

Semi-insulating (SI) GaAs is a wide band gap (1.42 eV) semiconductor material suitable for preparation of detectors of ionizing radiation operating at room temperature. The radiation hardness, which affects detector lifetime, has been studied utilizing degradation by various types of radiation. It was shown that GaAs detectors are radiation hard against a few MGy of high-energy (MeV) electrons. The main reason of detector functionality degradation was the reduction of charge collection efficiency (CCE) together with reverse current increase, raising the total noise of detector. Both factors lead to drop of the signal to noise ratio (S/N) down to close to 1 disabling detector functionality. Thus, the measuring ability of degraded detector depends on how large signal the registered radiation creates [1, 2] and less ionizing particles, like keV gamma rays, might not be detectable with degraded detector.
In this paper we improve the ability of SI GaAs detectors degraded by 5-8 MeV electrons to measure the gamma spectra of 30 – 80 keV photons by reducing the noise level in spectra by cooling the detector. It might have interesting outcomes for SI GaAs detector limits in space applications.
First, the current-voltage characteristics were measured during detector degradation (Fig. 1). An increase of reverse current in typical detector operating region of 150 – 300 V reverse bias can be observed with increasing dose, which was accompanied with vanishing of the current saturation. After 1000 kGy the current almost linearly increases with reverse bias and the detector exhibits ohmic-like behavior. The reverse current increases from 7 to 85 nA at 200 V reverse bias after degradation by 1500 kGy dose and the signal from gamma spectra disappears in the noise [2]. Cooling the detector from room temperature down to 0, -20 and -40C led to gradual decrease of detector reverse current (Fig. 2). The reverse current of the same degraded detector was reduced to 38 pA after detector cooling to -40C at 200 V reverse bias, which improved its spectrometric ability. Moreover, the cooling of detector increases its breakdown voltage, which enables using the higher operating voltage, leading to higher CCE and better detector spectrometric abilities. The cooling effect on gamma spectrometry of various types of SI GaAs detectors degraded by high energy electrons will be compared.
[1] Šagátová, A. Zaťko, B., et al., AIP Conference Proceedings 2411 (2021), 080013.
[2] Šagátová, A., et al., Materials Today: Proceedings 53 (2022) 293–298.
The authors acknowledge funding from the Slovak Research and Development Agency with grants Nos. APVV-18-0273 and APVV-18-0243 and from 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)

Sagatova_Iworid_poster8.pdf

43 Large area hybrid detectors based on Medipix3RX: commissioning and characterization at Sirius beamlines

Pixel detectors with low noise, fast speed, and small pixel size are necessary for many X-ray imaging and many diffraction experiments at synchrotron facilities. For X-ray imaging, photon-counting hybrid technologies have significant advantages. The PIMEGA detector line, which employs Medipix3RX chips, delivers 55 x 55 mm² pixel size, with high frame rates, and noise-free detection, satisfying most application challenges.

Several commissioning experiments have been carried out using these detectors at the Sirius beamlines, such as Carnaúba (Coherent X-ray Nanoprobe Beamline) and Cateretê (Coherent and Time-Resolved Experiments). The Cateretê beamline was the first to employ one fully mounted module of PIMEGA 540D, whereas the Carnaúba beamline received a PIMEGA 135D. Here, we present some results from detector characterization and application experiments, highlighting its distinctive properties.

Speaker: Raul Back Campanelli (LNLS Brazilian Synchrotron Light Laboratory)

44 Technological, computational and methodological aspects of High Dynamic Range Imaging

Synchrotron and Free Electron Laser sources have enabled powerful imaging techniques with high impact research applications. Techniques like Computed Tomography (CT), X-ray Ptychography, and Coherent Diffraction Imaging (CDI) have a strong computational component due to their reconstruction algorithms [1] but also have high requirements from their detectors and electronics [2]. Those detector requirements regard energy sensitivity, QE, speed, resolution and dynamic range. This work reviews various characteristics of detectors applied on specific imaging techniques but focuses on that of dynamic range. In particular, it highlights the importance of high dynamic range on modern techniques like Ptychography and CDI (Figure 1). It presents technological issues related to detectors and electronics, computational aspects of HDR during reconstruction and processing, and finally outlines recent methodological research aiming at extending dynamic range [3].

Simulated data and actual acquisitions during beamtime experiments in an X-ray spectromicroscopy beamline (TwinMic @ Elettra Sincrotrone Trieste [4]) are presented.

Speaker: Dr Guzzi Francesco (Elettra Sincrotrone Trieste)

45 The LumiTracker: a hybrid pixel detector for luminosity measurements

The LumiTracker is a newly proposed detector upstream of the LHCb interaction point. It consists of a compact telescope design, composed of six consecutive planes, each one based on hybrid silicon pixel detectors. The main goal is to provide a real-time luminosity estimate by reconstructing tracks. Two construction phases are already envisioned: an initial demonstrator using 200 μm n-on-p sensors read out by VeloPix ASICs to be installed in the end of the year shutdown of 2023/2024; Followed by a state-of-the-art detector equipped with thinner sensors (100 μm or below are considered) bonded to Timepix4 chips.
Detailed simulation studies were performed to optimise the detector layout. Our results show that a 1% precision is achievable over an integration time of 5 seconds, considering an average number of 7.6 proton interactions per bunch crossing. In particular, the LumiTracker is designed to perform measurements of the longitudinal profile of the luminous region with an expected resolution of order of 1 mm per track. With the improved track time resolution of better than 200 ps, the LumiTracker would be the first detector at LHCb to exploit precise timing information for track reconstruction and thus an important stepping-stone for future upgrades of the experiment. In addition, the LumiTracker would be able to identify spurious collisions caused by satellite bunches.
In this talk, the feasibility studies together with the LumiTracker projected performance and the detector planning and specifications within the global LHCb detector framework are presented.

Speaker: David Rolf (Technische Universitaet Dortmund (DE))

46 Multi-modal Approach to Ionizing Radiation Source Localization by an Unmanned Aerial Vehicle

Unmanned aerial vehicles (UAV, drones), equipped with compact radiation detectors, are becoming an essential tool in environment monitoring. Most of the commercially available platforms enable simple pre-planned trajectories to be followed without the need for a dedicated pilot. However, systematic mapping of large areas requires a lot of time, making it an inefficient strategy for localization of radiation sources concentrated in compact hotspots. We propose an efficient radiation source localization method, which employs a single UAV equipped with a miniaturized Compton-effect camera based on the Timepix3 sensor [1]. By processing the measurements directly onboard a UAV, the position of the radiation source can be estimated on-the-fly [2]. Since Compton scattering only constitutes a small fraction of the observed ionizing events (less than 1%), we propose a data fusion method, which combines the Compton measurements with an integrating dosimetry approach. Over the course of the mission, the flight trajectory is continuously updated to maximize the information gained by the Compton camera.

Speaker: Mr Petr Štibinger (Czech Technical University (CZ))

47 THCOBRA Detector Operating in Mixtures of Kr/Xe

THCOBRA Detector Operating in Mixtures of Kr/Xe

L. F. N. D. Carramate*, R. Nunes, A. L. M. Silva, C. D. Azevedo, P. M. S. Carvalho, F. Leite, J. F. C. A. Veloso

I3N, Physics Dept, University of Aveiro, 3810-193 – Aveiro, Portugal
* Corresponding author, laracarramate@ua.pt

THCOBRA based detectors have been studied during the past years aiming to improve the performance for X-ray imaging applications. Efforts have been made to improve portability, spatial resolution, gain and detection efficiency by implementing a purification system and characterizing the detector operation with different gas mediums, such as NeCH4 (95/5) and pure Kr. When operating in a gas flow mode using NeCH4 (95/5), a charge gain of 104, an energy resolution of about 22% (FWHM for 8 keV), and a spatial resolution close to1.2 mm (for about 4 keV) were achieved [1]. Some of these properties were improved operating the detector in sealed mode with pure Kr: an energy resolution of 23% (FWHM for 5.9 keV) and a spatial resolution of 650 um (for 16.5 keV) were determined [2].
Recently, to improve spatial resolution and detection efficiency [3, 4], the detector’s performance was assessed operating in mixtures of Kr and Xe, namely 98/2, 95/5 and 90/10, with the best results achieving an energy resolution of 20% (FWHM for 5.9 keV) for the 98/2 mixture and a spatial resolution of ~350 um (for energies between ~16 and ~22 keV) for the 90/10 mixture. The detector stability also increased, since the applied voltage to the detector decreased considerably to achieve similar gains, even when adding small portions of Xe.
These results, that show an improvement of detector performance comparing with the previously obtained, will be presented. Complementary results regarding charge gain and count rate evaluation for the three Kr/Xe mixtures will also be shown and compared with data from previous detector configurations.

[1] L. F. N. D. Carramate, A. L. M. Silva, C. D. R. Azevedo, D. S. Covita and J. F. C. A. Veloso, THCOBRA X-ray imaging detector operating in Ne/CH 4, J. Instrum. 10, (2015) P01003.
[2] L. F. N. D. Carramate, A. L. M. Silva, C. D. R. Azevedo, I. Fortes, S. G. Monteiro, S. Sousa, F. M. Ribeiro, S. De Francesco, D. S. Covita, et al., THCOBRA X-ray imaging detector operating in pure Kr, J. Instrum. 12, (2017) T05003.
[3] M. J. Berger, J. H. Hubbell, S. M. Seltzer, J. Chang, J. S. Coursey, R. Sukumar, D. S. Zucker and K. Olsen, XCOM: Photon Cross Sections Database, (2011)http://www.nist.gov/pml/data/xcom/index.cfm.
[4] C. D. R. Azevedo, S. Biagi, R. Veenhof, P. M. Correia, A. L. M. Silva, L. F. N. D. Carramate and J. F. C. A. Veloso, Position resolution limits in pure noble gaseous detectors for X-ray energies from 1 to 60 keV, Phys. Lett. B 741, (2015) 272.

Acknowledgements: The costs resulting from the FCT (Fundação para a Ciência e a Tecnologia, I.P–Portuguese Foundation for Science and Technology) hiring L.F.N.D. Carramate were funded by national funds (OE) in the scope of the framework contract CEECIND/01369/2017. This work was partially supported by project PTDC/FIS-AQM/32536/2017 through FEDER and FCT (Lisbon).

Speaker: Lara Filipa Das Neves Dias Carramate (University of Aveiro (PT))

48 Applications of soft X-ray Synchrotron camera based on Back Side Illuminated CMOS sensor

In recent years, an effort has been done by major sensor compagnies to increase the performances of 2D CMOS sensors. Principally, the development of thin Back Side Illuminated CMOS sensors (CMOS-BSI) has achieved a high detection efficiency in visible and relatively good in UV, a high frame rate and a good signal to noise ratio. One example of this development is the performant and cost efficient GSENSE400BSI sensor, from GPIXEL (https://www.gpixel.com). This sensor has been integrated at SOLEIL synchrotron in a vacuum compatible camera and its good characteristics have been demonstrated [1] in soft X-ray domain. This sensor is based on 2048 by 2048 pixels matrix of 11 µm pitch. Two gains per pixel allow achieving a dynamic up to 92 dB with a low readout noise (< 2 e- rms) and a relatively large charge capacity (80 ke-). The acquisition speed can reach 48 Hz, however, it has limited in this version of the camera at 24 Hz.

Currently, three detectors are in operation at beamlines at the SOLEIL synchrotron. The main contribution of this work is to recall the measured characteristics of the sensor in the soft X-ray range (30 eV to 2000 eV) and to present the first user applications in different domains: (i) a soft X-Ray Ptychography [2] above the Carbon K-edge (at 280-300 eV) at HERMES beamline (ii) diffraction and spectroscopy applications in the tender X-ray domain with camera installed on FORTE (multipurpose high-vacuum diffractometer) experimental station at SIRIUS beamline and (iii) X-ray Fourier Transform Holography (FTH) experiments on COMET II instrument at SEXTANT beamline [3] and also (iv) time resolved X-ray scattering [4] performed with XUV FEL beam at FERMI.

[1] Desjardins, K. et al. Journal of Synchrotron Radiation, 27(6), pp.1577-1589 (2020)
[2] Mille, N. et al., Communications Materials, 3(1), 1-8 (2022)
[3] Popescu et al., SRI 2022 proceeding (submitted). (2022)
[4] Léveillé C.. et al. J. Synchrotron Rad. (2022). 29, 103-110

Speaker: Mr Kewin Desjardins (Synchrotron SOLEIL)

49 The LIME gaseous TPC prototype for the CYGNO experiment

The CYGNO experiment aims at the development of a large gaseous TPC with GEM-based
amplification and an optical readout for the directional detection of rare events such as Dark Matter and solar neutrino interactions. The 3D reconstruction of electronic and nuclear recoils is made possible by the combined use of high-granularity sCMOS cameras and PMTs. This technique provides an accurate measurement of the energy with a O(keV) threshold and good sensitivity to the directionality of the events.
In order to demonstrate the scalability of this design, many prototypes were built and tested, the largest of which is the 50 L active volume LIME, with 4 PMTs and a single sCMOS imaging a 33×33 cm2 area. The detector is operated at atmospheric pressure with a He:CF4 mixture in 60/40 proportion. LIME was installed underground at LNGS in February 2022, and it will be soon commissioned.
We will show the results on the performance of LIME, which was tested overground at LNF with different radioactive X-ray sources. The detector’s stability, particle identification capability, energy response and energy resolution were studied. A comparison between actual data and Monte Carlo simulations is also ongoing for the characterization of the detector’s response. The radioactive instrinsic and environmental background expected at LNGS was simulated, and it will be shown together with the perspectives on the upcoming data taking, including the spectral measurement of the neutron flux underground. LIME will serve as a demonstrator of this technique, which finds applications not only in Dark Matter direct detection, but also in the study of the Migdal effect, and in X-ray polarimetry.

Speaker: Flaminia Di Giambattista

50 Simulations using NCrystal & Geant4 for innovative solid-state neutron detectors

Due to their lack of charge, low-energy neutrons are not detectable in typical semi-conductors often applied to radiation detection, and instead detectors use expensive or dangerous gases (e.g., 3He, BF3) in bulky, immobile devices. An INDet (Improved Neutron DETection) detector aims to fix these issues using pulse plasma etching (described in more detail in [1]) to generate a 3-D silicon diode consisting of a series of sub-structures each with an enriched boron carbide (B¬xC) coating. By making use of the 10B(n, 11B*) capture reaction, the spontaneous fission of the excited 11B nucleus into two charged decay products (α and 7Li) can be used as a signature for a neutron event by detecting either product in the silicon.

Using 3-D sensors allows for an increase in the thickness of the deposited BxC layer, and thus an increase in conversion efficiency. However, the optimal coverage of boron does not necessarily correspond to the best detection geometry, nor what is manufacturable reliably.

A simple mathematical treatment can determine the expected number of converted events for regular geometries, but Monte Carlo methods are required in order to determine the performance of the entire detector; to this end, a series of simulations were created using the NCrystal library [2], developed by the detector group at the European Spallation Source, which allows for more accurate simulation of sub-keV neutrons within Geant4. These simulations have been compared to existing work and geometries, such as pyramids on top of a planar surface [3], and improved via comparison to ‘real-world’ scenarios.

Simulations of trenches have shown a detection efficiency of over 30% when using a converter thickness of 1 µm. Other geometries consisting of a series of holes, squares, and pyramids have also been generated with lower efficiency, but allowing for better comparison with experimental datasets.

This presentation will discuss the capabilities and advantages of NCrystal, the setup and technique used to simulate many small sub-structures atop the main diode, and the comparison with existing physical devices

Speaker: George O'Neill

Illustrated Abstract

Poster

51 Degradation of signal-to-noise ratio in counting detectors due to pile-up effects

This work discusses how to properly evaluate the signal-to-noise ratio (SNR) of measurements taken with counting detectors, and how it is impacted detrimentally by the non-linearity of the detector response associated to pulse pile-up effects. This study is relevant for detection systems operating at high count rate regimes, where pile-up may be not negligible. Those cases can be managed in actual experiments by implementing pile-up compensation methods in the detector readout chain, by applying correction algorithms to the measured data or by a combination of both. What has been less discussed, to our knowledge, is the impact of those techniques on the final SNR of the resulting data and the detective quantum efficiency (DQE) of the detection process.
While it is well-known that a counting system follows Poisson statistics at low count rates and that the SNR becomes sub-Poissonian as pulse piling up starts being noticeable, a much less obvious result presented in this study is that the SNR of the measurements can actually drop with input flux at a relatively moderate level of pulse pile-up. This result could be perceived as counterintuitive, as it implies that from a certain value of input flux and for a given counting interval, more counts in the detector corresponds a lower signal-to-noise ratio.

The methodology adopted in this study is presented from a conceptual point of view, and justified and validated by both analytical and computer simulation methods. An in-house developed Monte Carlo code was adapted to reproduce the behavior of several theoretical pile-up models discussed in the literature [1]. This approach has also been applied to full X-ray 2D detection photon counting systems, by including in the simulation all the primary physical effects as well as the readout process of the detectors under consideration. This type of study can also be applied to compare the effectiveness different types of pile-up compensation or pulse recovery schemes by investigating their impact on the resulting data statistics.

[1] D. Yu and J. Fessler, Phys. Med. Biol. 45 (2000), 2043–2056

Speaker: Debora Magalhaes Suarez

Poster-Print.pdf

52 Design and optimization of the read-out electronics for high energy resolution X-ray strip detectors

Semiconductor strip sensors applied as solid-state radiation or particle detectors can be used in radiation detection and measurement for various applications in particle physics experiments, X-ray imaging (e.g. medical), or material science. The X-ray imaging devices with spectroscopic and position resolution features are a very important research topic at many research institutes and companies worldwide [1-3]. Short strip silicon detectors are good candidates for X-ray spectroscopy, because of their relatively small capacitance and leakage current. If additionally, strip pitch is below 100 µm, then the high spatial resolution is also possible.
In this paper, the analysis and design of the read-out electronics for short silicon strip detectors with Charge Sensitive Amplifier and shaper are presented. The CSA is optimized for the detector capacitance of around 1.5 pF, and the shaper peaking time is about 1 µs (controlled by the sets of switches). We take into account the sources of noise in a radiation imaging system (current parallel noise, voltage series noise, and 1/f or flicker series noise) both internal (related to the front-end electronics itself) but also external, stemming from a sensor, interconnect, or printed circuit board parasitic components [4]. We target the noise level below 30 el. rms, considering low power consumption (a few mW) and limited channel area. To increase the speed of analog front-end electronics we take into account both continuous-time resistive CSA feedback and the application of digitally assisted analog techniques such as a digital feedback reset.

[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] R. Ballabriga, et al.,” Photon counting detectors for X-ray imaging with emphasis on CT,” IEEE Trans. Radiation and Plasma Medical Science, vol. 5, no. 4, p. 422–440, 2021.
[3] P. Wiącek et al., “Position sensitive and energy dispersive x-ray detector based on silicon strip detector technology,” J. Instrum., vol. 10, no. 4, pp. P04002--P04002, 2015, doi: 10.1088/1748-0221/10/04/P04002.
[4] W. Zubrzycka and K. Kasiński, “Noise considerations for the STS/MUCH readout ASIC,” GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, 2018. doi: 10.15120/GSI-2018-00485.

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

Speaker: Weronika Zubrzycka

53 Characterisation of the noise performance of the HEXITEC-MHz ASIC

STFC has begun work on a new generation of detector technology, capable of operating at MHz frame rates. The HEXITEC-MHz ASIC, developed for the HEXITEC-MHz detector system, is the first of these technologies and allows spectroscopic X-ray imaging up to frame rates of 1 MHz. At this frame rate it is possible to record per-pixel X-ray spectra for X-ray fluxes of >10$^{6}$ photons mm$^{-2}$s$^{-1}$, a 100× improvement over the original HEXITEC ASIC [1].

The ASIC is optimised for the detection of electron signals from materials including CdTe, CdZnTe, GaAs, and p-type Si and comprises an array of 80 × 80 pixels on a pitch of 250 μm. This array is divided into 8-pixel regions (2 × 4 pixels) called Super-Pixels. Each individual pixel is capable of measuring single X-ray photons with energies up to 200 keV and is readout, following in-pixel 12-bit digitisation via a time-to-digital converter with timing shared on a per Super-Pixel level. Digitised data is output over 20 serial outputs which operate at 4.1 GHz using the Aurora protocol. These specifications will allow the ASIC to be utilised across a broad range of applications, including energy-dispersive X-ray diffraction (EDXRD) [2], X-ray computed tomography [3], solar physics [4], and in studies of the chemical dynamics of the charge-discharge cycle of batteries [5] and alloy impurities [6].

In this paper, preliminary results relating to the characterisation of the HEXITEC-MHz ASIC and hybrid detectors will be presented. Test pulse measurements of bare ASICs, in which a voltage pulse is used to inject charge into individual preamplifiers, were carried out and equivalent Full Width at Half Maximum (FWHM) of ~750 eV in CdZnTe were measured at ~100 keV. These results will be presented alongside studies into the variation in performance across each device and the spectroscopic performance of hybrid detectors.

[1]M.C. Veale et al., HEXITEC: A high-energy X-ray spectroscopy imaging detector for synchrotron applications, Synchrotron Radiat. News 31 (2018) 28.

[2]D. O’Flynn et al., Pixelated diffraction signatures for explosive detection, Proc. SPIE 8357 (2012) 83570X.

[3]C. Egan et al., 3D elemental mapping of materials and structures by laboratory scale spectroscopic X-ray tomography, J. Phys. Conf. Ser. 849 (2017) 012013.

[4]D. Ryan et al., Modelling and measuring charge sharing in hard X-ray imagers using HEXITEC CdTe detectors, Proc. SPIE 10397 (2017) 1039702.

[5]T. Connolley et al., An operando spatially resolved study of alkaline battery discharge using a novel hyperspectral detector and X-ray tomography, J. Appl. Cryst. 53 (2020) 1434.

[6]S. Feng et al., Nucleation bursts of primary intermetallic crystals in a liquid Al alloy studied using in situ synchrotron X-ray radiography, Acta Mater. 221 (2021) 117389.

Speaker: Ben Cline

54 Quantum efficiency measurements of FBK sensors with optimized entrance window for soft X-Rays

Single photon detection of X-rays in the energy range from 250 eV to 1 keV for hybrid detectors is difficult due to two main reasons, namely the low quantum efficiency (QE) and the low signal-to-noise ratio (SNR). Combining LGADs technology, which will increase the SNR, with an optimized entrance window (EW) technology for soft X-rays will allow hybrid detectors to become a useful tool also for soft X-ray detection.

In the present work, the QE of single pad silicon p-i-n diodes with nine different EW variations is studied. The sensors were characterized at the Surface Interfaces Microscopy (SIM) beamline of the Swiss Light Source (SLS) using soft X-rays ranging from 200 eV to 1250 eV. From the investigation, a QE of 62.5% at 250 eV is obtained with one of the variations.

In addition, the QE of inverse LGADs (iLGAD) with a thin entrance window were also investigated. The first measurements show QE values, which are similar to the optimized QE technology for p-on-n sensors without multiplication, thus demonstrating the feasibility of implementing optimized QE technology into LGAD technology. Further studies on the iLGADs optimized for soft X-rays, in particular their gain variation as a function of the photon absorption depth, will be presented as well.

Speaker: Maria del Mar Carulla Areste

55 Ion-Backflow Measurements of a Single Gas Electron Multiplier Foil

For gaseous detectors in high energy physics experiments the Ion-Backflow (IBF) into the drift space is often an unwanted feature, especially for large Time Projection Chambers (TPC) that are used for example in the ALICE experiment at LHC or the STAR experiment at RHIC. Both use Gas Electron Multiplier (GEM) technology for their readout chambers. The IBF can be minimized using a stack of GEM foils with an optimized field setup to suppress the majority of ions from drifting back into the drift space. In case the IBF is small of around 1% and less, the distortion of the drifting electrons from primary ionization points can be corrected to maintain accurate tracking with high efficiency. However, the correction mechanism works best by assuming a homogeneous IBF over the drift space.

We present a systematic study of the IBF in a single foil GEM detector by using custom made GEM foils produced by single mask technique by TECHTRA SP. Z O.O., Poland. The GEM foils with a size of 10 x 10 cm2 are divided in four segments with different hole dimensions. The diameters vary from less than 40 μm to more than 70 μm. Differing from previous studies, the foil design allows us to compare the effects of the different hole dimensions simultaneously without the need of modifying the measurement setup.

We defined the hole dimensions from high resolution optical scans [1]. The scans were used to map the hole distributions. We have shown earlier that the relative gain of a GEM foil depends on the geometry of the holes [2,3]. Non-uniformity in the hole properties will lead to non-uniform gain behavior. This will lead to variation in IBF, which is the subject of this study.

We measured the effective gain and the IBF in a standard gas enclosure with a 2D strip readout plane. The strips were combined to 4 sectors, readout in current mode by a set of picoammeters. The isotope $^{55}$Fe was used as an X-ray source and we used two different gas mixtures, Ar-CO$_2$ (70-30) and Ne-CO$_2$- N$_2$ (90-10-5). The irradiation was done separately for each foil segment. This allows us to compare the different hole geometries. Finally, we compared the results with simulations we made with Garfield++ toolkit.

We show that the IBF depends on the individual hole sizes and shapes of the GEM foil. Maintaining the drift field and the effective gain of a GEM foil we found that a lower IBF is possible by choosing the right hole diameter and shape. The results can help to choose for example an optimal GEM foil for the first amplification instance in a TPC readout chamber that is most responsible for letting the ions pass into the drift space.

[1] M. Kalliokoski et al., Nucl. Instrum. Meth. A 664 (2012) no.1, 223.
[2] T. Hildén et al., Nucl. Instrum. Meth. A 770 (2015) 113.
[3] E. Brücken et al., Nucl. Instrum. Meth. A 1002 (2021), 165271.

Speakers: Jens Erik Brucken (Helsinki Institute of Physics (FI)), Matti Kalliokoski (Helsinki Institute of Physics (FI))

56 Characterization of a Timepix3 quad for space application in the penetrating particle analyzer (PAN)

A Timepix3 [1] quad module (262,144 pixels, pixel pitch 55 µm) was developed for application in the penetrating particle analyser (PAN), i.e. a magnetic spectrometer for the measurement of galactic cosmic ray fluxes, their kinetic energies and to study the antimatter content in deep space [2]. The pixel detector therein provides accurate measurement of particle position and the energy left in the thin silicon sensor (dE/dX). Their low material budget is essential to reduce the impact of multiple low angle scattering on particle energy determination. However, the use of Timepix3 devices in space comes with challenges for carrier board, readout electronics and firmware design. For example, operation in vacuum requires proper cooling schemes; printed carrier boards and mechanics should be light weight while providing enough strength to survive vibration and shock; limited resources on the spacecraft impose strict limits on power consumption; and low downlink rates require data pre-processing capabilities. These issues are addressed in the present contribution.

A redesign of the Katherine [3] readout was used to study the Timepix3 tracking module’s response to a 120 GeV/c hadron beam at the Super-Proton-Synchrotron (SPS) at CERN and to protons of 100-230 MeV at the Danish Center for Proton Therapy (DCPT). “Low” power operation was achieved by changing the internal DAC settings of Timepix3 and reducing the matrix clock (see [4]). We present a comprehensive study of the impact of the changes on the particle tracking performance, as well as the energy and time resolutions. The power consumption of 6 W with standard settings was reduced to 4 W by changing the Timepix3 DACs. While these changes did not affect the energy measurement resolution, the time stamping precision was reduced from 1.7 ns to 12.4 ns (Figure 1). Further reduction of the power consumption was achieved by reducing the matrix clock. Using a matrix clock of 5 MHz, we achieved a power consumption of 1.6 W. Moreover, the energy device performance (energy resolution) was studied in vacuum conditions and at different energies in a thermal chamber.

[1] T. Poikela et al., JINST 9 (2014) C05013.
[2] X. Wu et al., Advances in Space Research, 63 (2019), Issue 8, pp 2672-2682.
[3] P. Burian et al., JINST 12 (2017) C11001.
[4] P. Burian et al., JINST 14 (2019) C01001

This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 862044. The work was carried out in the Medipix collaboration. This work has been done using the INSPIRE Research Infrastructures and is part of a project that has received funding from the European Union’s Horizon2020 research and innovation programme under grant agreement No 730983.

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

57 The compact Timepix2 based radiation detector for radiation tracking and imaging in space and industry

The new miniaturized particle tracking and imaging detector MiniPIX TPX2 has been developed as a new member of a very versatile MiniPIX family. It uses the Timepix2 CMOS ASIC developed by CERN based Medipix2 collaboration. The Timepix2 read-out chip can be combined with various types of pixelized semiconductor sensors with matrix of 256 x 256 square pixels with pitch of 55 µm.
The previous versions of MiniPIX detector with Timepix and Timepix3 chips are widely used in various applications: space radiation monitors (eight pieces running on board of ISS), electron microscopy, X-ray diffraction, X-ray radiography, science and education of physics (many secondary schools), gamma and Compton cameras etc. The compactness of these devices as well as its performance and versatility play a key role for their broad applicability.
The new device with Timepix2 chip has these main features: configuration with positive and negative semiconductor sensors (Si, CdTe, CZT, GaAs), single energy threshold, four multipurpose digital counters per pixel, many modes of operation including particle counting, per-pixel energy and time measurement, continuous read/write of frames. The MiniPIX TPX2 detector is connected to the controlling computer via micro USB2.0 connector enabling transfer speeds of about 100 frames per second. The whole device is vacuum compatible and eligible for space applications (same construction as MiniPIX TPX3).
In this contribution the evaluation of the detector properties will be presented. The energy resolution of about 1.4 keV (at 60 keV), minimal threshold of 2.5 keV and excellent imaging stability are the highlights (all of them routinely and relatedly reached with 300 µm thick Si sensors of either polarity). Especially the outstanding device stability allows for reaching the exceptional signal-to-noise-ratio of 2000 or even more. The examples of detector performance in several practical applications will be shown as well.

Speaker: Jan Jakubek

58 Spacepix-2: SoI MAPS Detector for Space Radiation Monitoring

Radiation in space is a potential risk to human health and electronic systems. Spacepix-2, the successor of Spacepix-1 [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. Spacepix-2 features 64 × 64 pixels matrix with a pixel pitch of 60 μm and a total sensitive area of 3.84 × 3.84 mm2. Analog signals from pixels are digitized by 32 10-bit column ADCs with 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-2 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: Pavel Vancura

59 Small pixel ultra-fast photon-counting prototype IC for synchrotron applications

Single-photon counting Hybrid Pixel Detectors (HPD) become increasingly popular in various 2-D X-ray imaging techniques and scientific experiments, mainly in solid-state physics, material science and medicine. Current research and development of HPDs are following several different directions [1] and one of them is the possibility of operation with high intensity of X-ray beam [2]. This paper presents the design and preliminary measurements results of a prototype SPHIRD chip designed in the CMOS 40 nm process. The chip is dedicated for ultra-high count rate and high spatial resolution operation at ESRF-EBS synchrotron. The core of the prototype IC is the matrix of 64x32 pixels of 50 µm pitch. Each pixel contains a Charge Sensitive Amplifier (CSA) with a fast discharge block and detector leakage current compensation circuit. The CSA is connected to set of discriminators with offset trimming possibility. The priority of the design is ultra-fast signal processing in the analog front-end electronics up to 30 Mcps/pixel. Therefore, the pulse time width at the CSA output is only 22 ns, keeping at the same time the equivalent noise charge at the level of 120 el. rms with a power consumption equal to 32 µW/pixel. Additionally, the set of discriminators equipped with extra blocks allows compensation for the effect of pulse pile-up in the voltage or time domain. The chip is optimized for the operation with a monochromatic X-ray beam with an energy up to 30 keV. Furthermore, because of the charge sharing effects, several algorithms of interpixel communication are implemented in the chip to increase detector resolution below pixel pitch.
[1] R. Ballabriga, et al.,” Photon counting detectors for X-ray imaging with emphasis on CT,” IEEE Trans. Radiation and Plasma Medical Science, vol. 5, no. 4, p. 422–440, 2021.
[2] R. Kleczek, et. al. “Single photon counting pixel readout chip operating up to 1.2 Gcps/mm2 for digital X-ray imaging systems” IEEE J. Solid-State Circuits, vol.53, no. 9, pp. 2651–2662, 2018.

Speaker: Pawel Grybos (AGH University of Science and Technology)

60 Hardware acceleration and machine learning for detector data processing at synchrotrons and FELs

The rapid development of very intense X-ray sources and faster detectors make it possible to perform entirely new experiments, such as studying very fast processes in biology and materials science. However, this also leads to increasing volumes of data that need to be stored and processed; for example, a 4 megapixel detector taking images at 100,000 frames per second will produce around 800 Gigabytes/s data. To provide fast feedback to experimenters and to reduce demands on storage, it is necessary to develop a data processing pipeline to convert raw data to meaningful images on the fly and perform appropriate data reduction.

Firstly, we are working on speeding up data processing with hardware acceleration. Vendors now offer FPGA accelerator cards for data centre PCs with built-in 100 Gigabit Ethernet links and high bandwidth memory, which could be used to directly receive and buffer detector data before processing it. Additionally, vendors provide software tools for programming these FPGAs with more conventional programming languages (e.g. C++ with OpenCL) rather than hardware description languages. The data processing will consist of image correction (which is relatively fixed for a given detector) and then a first phase of relatively generic data reduction. This data reduction includes, for example, implementation of standard lossless data compression methods.

Secondly, we are working on new methods for data reduction, particularly using machine learning. For example, in FEL experiments such as serial crystallography or serial particle imaging, a large fraction of images are bad, due to the beam missing the sample, and rejecting these images before saving them to disk would greatly reduce the data volume [1]. Machine learning techniques allow this distinction to be learned from simulated data or previous experiments, rather than explicitly programmed, which could allow data rejection during an experiment without expert intervention. To do this task, we have tested a range of “conventional” machine learning methods, based on feature detection algorithms from computer vision, as well as deep learning methods. These methods show good success rates on existing datasets, and work is continuing on ensuring these methods can be generalized to new, unfamiliar datasets.

[1] M Wiedorn et al. Nature communications 9-1 (2018), 1-11

We acknowledge “Helmholtz IVF project InternLabs-0011 (HIREX)” and “Helmholtz Innovationspool project Data-X” for funding.

Speaker: David Pennicard

61 Optimising the design of small pitch Hybrid Pixel Detectors with MÖNCH04

MÖNCH (Micropixel with enhanced pOsition rEsolution usiNg CHarge integration) is a 25 µm pixel pitch charge integrating hybrid pixel detector with analogue readout designed at the Paul Scherrer Institut to explore the limits of the technology for high-resolution imaging at synchrotrons and XFELs (X-ray Free Electron Lasers) [1]. The latest prototype, MÖNCH04, features an array of 400 x 400 pixels separated in 19 variants for either soft X-ray synchrotron or XFEL applications. Most of the variants also include very high configurability to optimise the readout scheme and to isolate sections of the pixel. Testing independent elements will permit the selection of the optimal components and designs to fit in the small pitch for a large-scale MÖNCH detector.

The characterisation of the pixel variants optimised for the lowest noise and highest responsivity have demonstrated an improvement in noise performance, down to 21.5 electrons rms. The improvements are especially visible with the spectral response (Figure 1) when comparing the reference design to the super high gain variant (SHG).

In this paper, we will first introduce the MÖNCH detector and its applications as well as the benefits of using small pixels. We will then give an overview of the different pixel designs incorporated in MÖNCH04 with an emphasis on the available testing capabilities implemented. The characterisation results of full pixel variants and specific design elements will finally be presented to support the design of the next generation MÖNCH detector.

[1] A Bergamaschi et al., (2018) The MÖNCH Detector for Soft X-ray, High-Resolution, and Energy Resolved Applications, Synchrotron Radiation News, 31:6, 11-15.

Speaker: Dr Julian Heymes (Paul Scherrer Institut)

JulianHeymes_iworid2022.pdf

62 Gamma-Ultrasound Signal Separation Using Autoencoder

Recently, research on Gamma-Ultrasound(γ-US) probe has been conducted. The Gamma-Ultrasound(γ-US) probe is a dual modality probe that can obtain anatomical structure and molecular information. In this system, the ultrasonic and the gamma signals can be obtained in one readout channel by summing the both signals.
In the previous studies, The combined signal was separated by using FIR filter. In order to use the FIR filter, a frequency difference is required between ultrasonic and gamma-ray signals. For this reason, there is a problem in that the frequency band of the ultrasonic signal and the gamma-ray signal is limited.
Here, we propose a new separation method to solve this problem by using deep learning autoencoder model. The proposed method can discriminate gamma and ultrasonic signals regardless of frequency bands. In this study, the signal separation performance in the FIR and Autoencoder models was compared by changing the gamma signal length.
As a result of the study, As the width of the gamma signal narrowed, the peak voltage of the gamma signal decreased dramatically.(47.44%) On the other hands, the Autoencoder method showed similar performance to the original signal regardless of the signal length, and only a 0.17% decrease occurred. These results show that the proposed method has better performance regardless of frequency. Through this Autoencoder method, it is expected that the Gamma-Ultrasound probe can be applied to various fields.

Speaker: Kyung-Seok ‍Choi (KoreaUniversity)

63 First demonstration of on-chip interpolation using a single photon counting microstrip detector

Despite being used in many X-ray applications, hybrid single photon counting detectors are limited in spatial resolution due to the diffusion of the charge produced by single photons between neighbouring electronic channels, also called charge sharing.
In this work, we demonstrate that interpolation can be used to increase the number of virtual channels and improve the effective spatial resolution in a single photon counting microstrip detector.
With respect to reducing the physical strip pitch, this comes with the additional advantage of overcoming the technological challenge of increasing the number and density of interconnects between the sensor and the readout electronics.
We describe a digital communication scheme between neighboring channels, implemented for the first time in the MYTHEN III microstrip detector, which exploits charge sharing to obtain a spatial resolution better than the strip pitch. The interpolation is achieved directly on-chip at the time that the photons are absorbed reducing the data throughput and the computational effort and allowing a higher photon flux compared to interpolation using analogue detectors.
Here, we show the first results obtained with this interpolation mechanism, characterizing the spatial resolution in terms of Modulation Transfer Function (MTF) when varying several parameters (photon energy and flux, chip thresholds and settings, sensor voltage, thickness and strip pitch).

Speaker: Anna Bergamaschi (Paul Scherrer Institut)

64 Charge sharing measurements for digital algorithms achieving subpixel resolution in hybrid pixel detectors.

Hybrid pixel detectors are segmented devices used for X-ray detection, consisting of a sensor attached to readout electronics. Detectors working in single-photon counting mode process each incoming photon individually, have essentially infinite dynamic range and by applying energy discrimination they provide noiseless imaging [1].
To improve the resolution of the detector and allow operation with high-intensity photon fluxes, the pixel size is reduced. However, with decreasing pixel size, a charge sharing effect is more significant. This leads to false events registration or omitting the event and degradation of the energy resolution of the detector. The algorithms aiming at reducing the influence of charge sharing are already implemented on-chip [1]. However, the spatial resolution of the detector can be increased beyond the physical pixel size if charge proportions collected by neighboring pixels are analyzed. Today's technology allows the implementation of an ADC in each readout channel [2], which makes the implementation of a digital algorithm achieving subpixel resolution possible.
The simulations show that charge cloud size referred to pixel size and noise are the key parameters that determine the subpixel algorithm accuracy and final detector resolution [3]. Therefore, two chips attached to the sensors of different materials and different thicknesses were tested to observe and quantify the charge sharing effect. Devices under test were the LNPIX IC, consisting 128 x 256 pixels of 75 um pitch, attached to 320 µm Si detector, and MPIX IC, consisting 96 × 192 pixels of 100 μm pitch, attached to 0.75 mm and 1.5 mm CdTe detector [4]. The spectral response was measured for each device and the Edge Spread Function (ESF) was calculated.

[1] R. Ballabriga et al., “Photon Counting Detectors for X-Ray Imaging with Emphasis on CT,” IEEE Transactions on Radiation and Plasma Medical Sciences, vol. 5, no. 4, pp. 422–440, Jul. 2021, doi: 10.1109/TRPMS.2020.3002949.
[2] P. Kmon et al., “Spectrum1k — integrated circuit for medical imaging designed in CMOS 40 nm,” Journal of Instrumentation, vol. 17, no. 03, p. C03023, Mar. 2022, doi: 10.1088/1748-0221/17/03/C03023.
[3] A. Krzyżanowska and R. Szczygieł, “Simulation study on improving the spatial resolution of photon-counting hybrid pixel X-ray detectors,” Opto-Electronics Review, vol. 29, no. 4, pp. 187–191, 2021, doi: 10.24425/OPELRE.2021.139756.
[4] P. Grybos et al., “Hybrid Detector with Interpixel Communication for Color X-ray Imaging,” 2021 28th IEEE International Conference on Electronics, Circuits, and Systems, ICECS 2021 - Proceedings, 2021, doi: 10.1109/ICECS53924.2021.9665489.

Speaker: Aleksandra Krzyżanowska

65 Analysis and Characterization of CdTe Material Surface Defects

We use atomic layer deposition (ALD) to create a layer of aluminium oxide (Al$_2$O$_3$) on single, semi-insulating CdTe crystals. The ALD process, particularly the choice of the oxygen precursor, can affect the charge and interface properties of the Al$_2$O$_3$ layer.
To study the impact of the ALD layer we used scanning laser Transient Current Technique. This provides us with data of the signal rise time and charge collection homogeneity across the detector. We investigate the impact of the ALD alumina-CdTe interface and negative fixed charge trapping using both passivated and non-passivated CdTe crystals. By comparing with the information, we obtain e.g. from optical or SEM images, or from IRM scans, we can separate the surface defects.
In this contribution we will discuss the ALD methods we use to passivate our CdTe detectors and show the results of the TCT measurements compared to SEM and IRM scans.

Speaker: Mihaela Bezak (Rudjer Boskovic Institute (HR))

main.pdf

66 Charge sharing in sub-millimetre CdZnTe linear array detectors grown by the vertical Bridgman technique

In the framework of the Avatar X project, we developed sub-millimetre CdZnTe linear arrays for high-flux spectroscopic X-ray imaging up to 150 keV. As widely demonstrated, CdZnTe (CZT) is one of the key materials for the development of room temperature X-ray and gamma ray detectors and great efforts have been made on both the device and the crystal growth technologies. In this work, we will present the results of spectroscopic and charge sharing investigations on new boron oxide encapsulated vertical Bridgman (B-VB) grown CZT detectors with linear pixel anodes, recently developed at IMEM-CNR Parma, Italy [1,2]. CZT linear arrays with pixel pitches of 250 µm and inter-pixel gap of 25 µm were developed. The X-ray response of the detectors was measured taking into account the mitigation of the effects of incomplete charge collection, pile-up, charge sharing and high flux radiation induced polarization phenomena. Preliminary tests showed good room temperature energy resolution FWHM of 4 % (2.4 keV) at 59.5 keV at high bias voltage operation (7000 V/cm).

[1] L. Abbene et al., J. Synchrotron Rad. 27 (2020), 319-328.
[2] L. Abbene et al., Nucl. Instr. and Meth. A 835 (2016) 1-12.

The authors acknowledge funding from the Italian Ministry for University and Research (MUR), under AVATAR X project No. POC01_00111 and from the European Union (EU) under the project - FESR o FSE, PON Ricerca e Innovazione 2014-2020 - DM 1062/2021.

Speaker: Dr Antonino Buttacavoli (University of Palermo)

67 TCAD optimization of LGAD sensors for extremely high fluence applications

The next generation of high-energy physics experiments will require tracking detectors able to efficiently operate in extreme radiation environments, where expected fluences will exceed 1E17 n/cm^2. This new operating scenario imposes many efforts for the design of effective and radiation-resistant particle detectors. Low-Gain Avalanche Diode (LGAD) represents a remarkable advance because the radiation damage effects can be mitigated by exploiting its charge multiplication mechanism after heavy irradiation [1]. To obtain the desired gain (~ 10 – 20) on the sensors output signal, a careful implementation of the “multiplication” region is needed (i.e. the high-field junction implant). Moreover, a proper design of the peripheral region (namely, the bias guard-ring structure) is crucial to prevent premature breakdown and large leakage currents at very high fluences, when the bias voltage applied creates an electric field higher than 15 V/µm. In this contribution, the design of LGAD sensors for extreme fluence applications is discussed, addressing the critical technological aspects such as the choice of active substrate thickness, the gain layer design and the optimization of the sensor periphery. The impact of several design strategies is evaluated with the aid of Technology-CAD (TCAD) simulations based on a recently proposed model for the numerical simulation of radiation damage effects on LGAD devices [2].

[1] G. Pellegrini et al., 2014 J. NIMA 12 765
[2] T. Croci et al., 2022 JINST 17 C01022

Speaker: Tommaso Croci

poster_Croci_88_iWoRiD_2022_vFinal.pdf

68 Monte-Carlo simulation of charge sharing in 2 mm thick pixelated CdTe sensor

Pixel detectors allow for the measurement of position and energy of the incident particles. Readout chips of hybrid pixel detectors can be bump-bonded to pixelated sensors made of different materials. The R&D has made fine pitch pixelated CdTe/ CdZnTe sensors commercially available in the last decades. These sensors are used in medical imaging applications due to their high absorption efficiency in the X-ray spectrum [1]. The decreasing pixel pitch size causes the charge to spread across multiple pixels, due to the charge sharing effect and fluorescent photons [2]. These two effects cause signal induction in multiple pixels, thus distorting the measured spectra. Chargesharing compensation and hit allocation algorithms are needed to compensate for these effects. An investigation of charge spread across pixels is needed to develop such algorithms.

This work presents a Monte-Carlo simulation of a 2 mm thick 70 µm pixelated CdTe sensor upon the absorption of X-ray photons from a monochromatic X-ray beam. Based on the simulation outcome, we estimated the dependence of active pixels on photon energy, i.e., cluster size and total charge distribution between neighbouring pixels. The detailed results will be presented.

[1] M F Walsh et al., Journal of Instrumentation. 6 (2011), 1748-0221
[2] D. Pennicard et al., Journal of Instrumentation. 6 (2011), 1748-0221

The work was supported from European Regional Development Fund-Project "Center of Advanced Applied Science" No. CZ.02.1.01/0.0/0.0/16-019/0000778 and by the Grant Agency of the Czech Technical University in Prague, grant No. SGS20/175/OHK3/3T/13.

Speaker: Jakub Jirsa (Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering)

69 From single silicon carbide detector to pixelated structure for radiation imaging camera

Silicon carbide belongs to wide band gap semiconductor materials. The 4H-SiC polytype is very perspective for radiation detector fabrication. Nowadays, the high-quality material of 4H-SiC is commercially available. The 4H-SiC has the band gap energy of 3.23 eV at room temperature, breakdown voltage of 3-5×10E6 Vcm-1, carriers saturation velocity of 2×10E7 cms-1 and excellent physical and chemical stability. A large band gap energy is advantageous for low leakage current and high radiation tolerance. In our previous works we studied electrical and also spectrometric performance of fabricated SiC detectors [1, 2]. We observed high energy resolution for X-rays and also for alpha-particle detection.
Today we are concentrated on preparation of pixelated structures based on 4H-SiC high-quality epitaxial layer. As a base material we used two wafers with different thickness of epitaxial layer 80 and 100 um. We prepared Ni pixelated Schottky contact on the one side and full area Ti/Pt/Au ohmic contact on the other side. The pixel pitch is 55 um and the structures are optimized for Timepix/Timepix3 readout chips. Motivation of this work is that detectors based 4H-SiC reach high energy resolution comparable to Si detectors, Schottky barrier structures have low current density (<100 pA/cm2), are stable up to 500 °C with reasonable leakage current, have higher radiation hardness in comparison to Si for more than two orders of magnitude according to our measurements, high reaction rate due to high electric field at operated bias. The drawback of SiC semiconductor material is low detection efficiency for X- and gamma-rays but comparable to Si detectors and its price. The main utilization of SiC detectors is perspective mainly in heavy ion detection and operation in harsh radiation environment and also at elevated temperatures.

[1] Zaťko, B., Hrubčín, L., Šagátová, et al., Applied Surface Sci 536 (2021) 147801.
[2[ Osvald, J., Hrubčín, L., Zaťko, B., Mater. Sci. Semicond. Process. 140 (2022) 106413.

The authors acknowledge funding from the Slovak Research and Development Agency by grants Nos. APVV-18-0273 and APVV-18-0243 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: Dr Bohumir Zatko (Institute of Electrical Engineering, Slovak Academy of Sciences)

Poster-Zatko_ElU SAV_Iworid2022.pdf

70 Performance Evaluation of the Stitched Passive CMOS Strip Sensors before and after irradiation

Future particle physics experiments are motivated by the increase in luminosity and thus the need for intelligent tracking detectors providing fast track and momentum information to select events of interest. The next-generation tracking detectors are mostly all silicon-based detectors, thus they will cover large areas and therefore be the main cost driver. The currently used silicon sensors are available only from very few manufacturers, thus finding a cost-effective solution to maximize the output is important.
Commercial CMOS technology for silicon strip sensors is a prime candidate, which allows the use of large and high-resistive wafers and also provides the advantage of widely established industrial production processes.

The passive CMOS silicon strip sensors presented in this contribution is processed by a European foundry, in a 150 nm CMOS technology. The sensor has three different strip designs to study in two different lengths 4.1 cm and 2.1 cm. They are formed by stitching individual reticles and a maximum of five reticles are stitched into one 4.1 cm long sensor.

The key investigation is to evaluate the impact of stitching and the overall sensor performance with novel tools. The sensors are irradiated with proton and neutron beams to study the effects of radiation damage. This study presents the electrical measurements and test beam results of the sensors before and after irradiation

Speaker: Surabhi Sharma (Deutsches Elektronen-Synchrotron (DE))

71 CsPbBr3 Nanowire Scintillator for High-resolution X-ray tomography

Metal halide perovskite (MHP) nanomaterials show large potential as scintillators for X-ray imaging. They have a high light yield and micrometer spatial resolution. Compared to 2d imaging, tomography requires excellent stability of the scintillator, since many projections with identical flat field images are necessary to reconstruct artefact-free 3d volumes. To provide this stability is challenging for MHPs, which often suffer from fast degradation under X-ray irradiation and ambient conditions.
Here, we show that CsPbBr3 nanowires grown in an anodized aluminum oxide membrane (CsPbBr3 NW/AAO) [1] have sufficient stability to acquire an X-ray micro tomogram with a commercial Cu lab source. During the measurement the scintillator brightness changed less than 5% of its peak value, which enabled a successful 3d reconstruction. Furthermore, over 2 weeks of continuous X-ray exposure the scintillator showed less than 14% brightness fluctuations and a stable resolution of (180 ± 20) lp/mm, despite changes in the ambient humidity from 7.4 %RH to 34.2 %RH.
This demonstrates that our CsPbBr3 NW/AAO scintillators are a promising material for new high resolution X-ray imaging detectors.

Speaker: Hanna Dierks (Lund University)

72 Alpha-Particle Imaging Device with Super-Resolution Technique

In this study, we propose an alpha-particle imaging device in conjunction with a super-resolution technique. A high-resolution image is recovered using the four images obtained by moving the device along the x- and y-directions. The results show that, using the device with a pre-defined pixel resolution, the proposed technique produces the images of alpha-particles with an improved resolution of approximately 16%. We conclude that the proposed technique has potential in the development of radiopharmaceuticals for targeted alpha therapy.

Speaker: Dr JONG-GUK KIM (Korea Institute of Radiological and Medical Sciences)

73 Optimization of energy threshold for fluorescence rejection in K-edge subtraction in synchrotron-based imaging with a spectral CdTe detector

K-edge Subtraction (KES) X-ray imaging is used to single out and quantify the presence of a contrast agent embedded in a biological matrix, and its most well-known application is in the field of cardiovascular imaging [1]. KES exploits the sudden increase of the linear attenuation coefficient of the contrast material corresponding to its k-shell electrons binding energies that, for commonly used contrast agents (e.g., iodine, barium, gadolinium), is in the range from 30 to 50 keV.
By acquiring two images at different energies, respectively above and below the k-edge, and performing logarithmic subtraction, it is then possible to highlight the presence of the sole contrast medium avoiding anatomic noise. This, in traditional systems, is typically accomplished by using two different energy spectra (dual-energy) or a layered detector (dual-layer). In this context, the advent of photon-counting detectors (SPCDs) with pixel-by-pixel energy discriminating capabilities is revolutionizing the field of KES imaging. Specifically, the possibility of acquiring in a single shot two (or more) images over different energy bins brings to a great simplification of the imaging system, where only one spectrum and one detector are required, and allows to target, in principle, any contrast medium without changing the hardware. On the other hand, the spectral response of SPCDs featuring high-Z sensors (e.g., CdTe) is significantly affected by the presence of fluorescence and escape photons generated within the sensor. These effects, along with threshold calibration and energy resolution, must be modeled and accounted for when performing KES imaging, to maximize image quality and/or reduce radiation dose.
In this framework, we report for the first time on a KES imaging study performed at the Gadolinium k-edge (50.2 keV) by using a spectral detector and an ad-hoc spectrally shaped (pink) synchrotron radiation (SR) beam at the Elettra synchrotron facility (Trieste, Italy). The used detector is Pixirad-PixieIII, featuring a 650 um thick CdTe sensor, 512 X 402 pixels with 62 um pitch, two tunable energy thresholds per pixel that can be both operated in the charge-sharing recovery (NPISUM) mode, leading to an energy resolution comprised between 3 and 4.5 keV [2]. The high intensity of SR allows to optimally shape the X-ray spectrum that can be centered at the k-edge energy and made sufficiently narrow to maximize KES signal while retaining a sufficient flux. Specifically, a low energy threshold optimization has been performed experimentally and cross-validated with a dedicated Geant4 simulation including a detailed description of the detector’s energy response [3]. Results on Gd-filled phantoms show that a careful threshold enables for effective rejection of fluorescence, therefore, reducing the contamination between the two energy bins, this leading to a maximization of the gadolinium KES signal.

[1] W Thomlinson, et al., Physica Medica 49 (2018): 58-76
[2] V Di Trapani, et al, Nucl. Instrum. Methods Phys. Res. A 955 (2020): 163220.
[3] L Brombal, et al., JINST 17.01 (2022): C01043.

Speaker: Prof. PASQUALE DELOGU (University of Siena, Department of Physical Sciences, Earth and Environment, Siena, Italy and INFN Division of Pisa, Pisa, Italy)

74 Fast-Settling high input dynamic range Automatic Gain Control Front-end circuit for particle detect

The calorimeter is the most important device in the field of particle detection. In recent years, the research of SiPM as the sensor of the calorimeter has attracted a lot of attention. There are two ways of traditional SiPM readout circuit, one is multi-channel readout, setting readout paths with different gains, the disadvantage is that the power consumption is high and the layout area is large. The other is to adjust the gain off-chip, which is inconvenient for practical application and slow in response. In this paper, a variable gain amplification chain is designed using GMSC 0.13um CMOS process to cover signal measurement with a large dynamic range. The post-simulation result shows that the gain dynamic range is -6.6dB ~19.73dB, covering 60dB the input dynamic range, from 160fC to 160pC. The -3dB bandwidth is about 20MHz, and the gain adjustment time is less than 5ns. And the linearity of the circuit is good. This method can cover a large input dynamic range and save power consumption by using only one analog-to-digital conversion and single measurement.

Speaker: Mr Yunqi Deng (Central China Normal University)

75 A new design of stationary dual-energy CT baggage scanner with pi-angle sparsity using compressed-sensing reconstruction

For homeland and aviation security applications, two-dimensional (2D) x-ray inspection systems have been widely used, but they have limitations in recognizing 3D shape of the hidden objects. Hence, there has been increasing demand for x-ray computed tomography (CT) scanner for carry-on baggage screening. In a previous study [1], SSTLabs developed a prototype stationary CT baggage scanner with 2pi-angle sparsity where 9 pairs of x-ray sources and dual-energy detectors (linear-typed) in the opposite direction were distributed at the same angular interval. Each pair of x-ray source and detector is arranged along the z-direction so that different projection view data can be collected while the carry-on baggage moves continuously on the conveyor belt. This type of CT scanner is suitable for routine carry-on baggage inspection. However, owing to the limited number of projection views, a conventional CT reconstruction algorithm such as filtered backprojection (FBP) produces severe streak artifacts. In this study, we propose a new design of stationary dual-energy CT baggage scanner with pi-angle sparsity using compressed-sensing (CS) reconstruction for improving the image quality. The CS is a state-of-the-art mathematical theory for solving the inverse problems, which exploits the sparsity of the image with substantially high accuracy [2]. Figure 1 shows the proposed design of a stationary dual-energy CT baggage scanner with pi-angle sparsity of 15 projection views and preliminary simulation results of a numerical baggage phantom (300×300×100) obtained using the FBP and CS reconstruction algorithms. More systematic and quantitative simulation and experimental results will be presented in the paper.

Speaker: Mr Jiyong Shim (Yonsei University)

76 A 2.56 Gbps or 10 Gbps 1:16 Deserializer for High-Energy Physics Experiments

Abstract—Deserializer is used to convert the high-speed serial data into a low-speed parallel data in the downlink direction of data transmission system in high-energy physics experiments. The 2.5Gbps rate can fully meet the downlink data transmission requirements of the current experimental equipment. But as the experimental equipment is upgraded, the amount of data will be greatly increased. In order to meet the demand of current data volume and adapt to upgrade of the equipment in the future, this paper presents the design and simulation results of a 1:16 deserializer ASIC which can be compatible with data rate of 2.56 Gbps and 10 Gbps.
The 2.56 Gbps or 10 Gbps 1:16 deserializer ASIC mainly consists of an equalizer, 1:4 DEMUX module, 4:16 DEMUX module, clock divider by 4, LVDS drivers and an automatic frequency comparator. The 1:4 DEMUX module and 4:16 DEMUX module are implemented by one and four 1:4 DEMUX units, respectively. According to different data rates, there are two different 1:4 DEMUX units (High-speed 1:4 DEMUX unit and Low-speed 1:4 DEMUX unit) with the same overall structure have been designed. The two 1:4 DEMUX units are composed of 7 DFFs, which are sampled by four quadrature phase clocks (CLK0, CLK90, CLK180, CLK270) generated by a clock divider by 4. According to different clock frequency, there also two clock divider by 4 (High-frequency clock divider by 4 and Low-frequency clock divider by 4) have been designed. In order to improve the bandwidth, the high-speed 1:4 DEMUX unit and the high-frequency clock divider by 4 adopt the latches with an optimized compressed CML structure. And the low-speed 1:4 DEMUX unit and the low-frequency clock divider by 4 adopt CMOS latches to save power consumption.
At 10 Gbps data rate, the input data will be compensated first by equalizer for high frequency signal attenuation caused by PCB transmission line and parasitic parameter from bonding wires and input pads. The equalized data will be divided into 4 parallel 2.5 Gbps/Ch data by the first 1:4 DEMUX module with CML structure. The second 4:16 DEMUX module following the first 1:4 DEMUX module divides 4 parallel 2.5 Gbps/Ch data into 16 parallel 625 Mbps/Ch data. The sampling clocks of the first 1:4 DEMUX module and the second 4:16 DEMUX module are provided by a first high-frequency clock divider by 4 and a second low-frequency clock divider by 4, respectively.
At 2.56 Gbps data rate, the input differential data is converted into single firstly, and then send into a third 1:4 DEMUX module with CMOS structure to obtain 4 parallel 640 Mbps/Ch data. The second 4:16 DEMUX module following the third 1:4 DEMUX module divides 4 parallel 640 Mbps/Ch data into 16 parallel 160 Mbps/Ch data. The sampling clocks of the third 1:4 DEMUX module and the second 4:16 DEMUX module are provided by third low-frequency clock divider by 4 and second low-frequency clock divider by 4, respectively.
The second 4:16 DEMUX module at the data rate of 10 Gbps and 2.56 Gbps share the same module, and the second low-frequency clock divider by 4 at the clock frequency of 10 GHz and 2.56 GHz share the same module, too.
In order to cope with the incorrect sampling position caused by phase offset at different process corners, the clock divider by 4 adopts the structure of four cascaded latches to obtain 8 phase clock signals. And a phase selector following the clock divider by 4 selects the clock signal with appropriate phase according to the offset under the different process corners. And a duty cycle correction and clock aligner is added to the low-frequency clock divider by 4 to improve the quality of the sampling clocks. An automatic frequency comparator is designed into the ASIC to switch the operating rate automatically according to the input clock frequency.
The 2.56 Gbps or 10 Gbps 1:16 deserializer ASIC has been designed in 55 nm CMOS process with core area of 1120 μm × 600 μm. The simulation results show that the logic of output data at 2.56 Gbps and 10 Gbps are correct in different process corners. And the clean and open output eye diagrams can be obtained at the input data rate of 2.56 Gbps and 10 Gbps, respectively. The power consumption is 217 mW with 1.2 V power supply. The chip has been taped out and the tests are planned to be conducted in this June.
This work is supported by General Program of National Natural Science Foundation of China (Grant No.11875145)

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

77 Neutron Imaging Detectors using Ultra-Thin Converter Layers

We present a novel methodology for application to neutron imaging detectors equipped with boron layers. State of the art boron coated neutron detectors are equipped with 10B films deposited on substrate plates with combined thickness larger than the range of the fission fragments emitted upon a neutron capture reaction. Since these fission fragments are emitted back-to-back, one of them (at least) is always lost into the converter foil with the 10B material. Our novel methodology uses an ultra-thin converter foil, which allows for both fission fragments to reach its surface and be detected in coincidence by two gaseous detector, placed on the sides of the converter foil. By combining the information extracted from tracks produced in the gas by the two fission fragments, it is possible to achieve superior position reconstruction, for shorter exposures, and to provide intrinsic gamma-ray suppression. Through GEANT4 simulations, we verified that the spatial resolution obtained by centre of gravity charge readout methods can be significantly improved: our results show that, by using 0.5 µm thick B4C layers deposited on a 0.9 µm Mylar substrate, the spatial resolution can be improved by a factor of 8, compared to conventional detectors with thick 10B detection layers.
We will present the novel methodology and, along with the requirements and advances in the production of ultra-thin converter foils, share the results obtained so far and the prospects for future neutron imaging applications.

Speaker: Cristina Bernardes Monteiro (University of Coimbra)

78 Evaluation of new scintillator crystals with multi-criteria decision-making methods for brain PET

In the last decades, brain positron emission tomography (PET) imaging has become highly demanding for better diagnosis and staging in brain cancer and other brain disorders. The performance of a PET system is majorly described by its overall image quality where it depends on many factors including the selection of the radiation detection medium. Previously, we simulated novel transparent optical scintillator crystals for brain PET system [1]. The purpose of this research is to evaluate and compare them using multi-criteria decision-making (MCDM) methods, namely fuzzy Preference Ranking Organization Method for Enrichment Evaluations (PROMETHEE) and fuzzy Visekriterijumska Optimizacija I Kompromisno Resenje (VIKOR).
The crystals used in this study are Strontium hafnate (SHO), Gadolinium aluminium gallium garget (GAGG), Gadolinium yttrium gallium aluminum garget (GYGAG), Gadolinium lutetium gallium aluminum garget (GLuGAG), and lastly Lutetium Oxyorthosilicate (LSO) for comparison. The density, effective atomic number, energy resolution, light output, and decay time were selected as important criteria. Importance weights of each criteria are then assigned by considering the high resolution and high sensitivity detectors.

With both MCDM methods, the results showed that SHO is outranked the other scintillator materials followed by LSO and GLuGAG. GYGAG, and GAGG are found as the least favorable crystals, in agreement with the previous simulation studies [1]. This study can be extended by including more scintillators as they become available in the future.
[1] I. Ozsahin et al., JINST 15 (2020), C05024.

Speaker: Dr Ilker Ozsahin (Near East University (TRNC))

79 Xray-CMOS: a wide field of view X-ray polarimeter

We are going to present the prospects of the Xray-CMOS project (recently funded as Progetto di Ricerca di Rilevante Interesse Nazionale PRIN 2020), for the development of a TPC for wide field of view X-ray polarimetry, in which no requirement is imposed to the orientation of the incoming X-ray with respect to the drift field. This could open a new window of observation on the Universe through the study of rapid transient phenomena, like gamma ray bursts, soft gamma repeaters and transient black holes, among the many.
The Xray-CMOS project will capitalize on the innovative optical 3D readout approach for TPCs recently developed by the CYGNO/INITIUM collaboration in the context of directional Dark Matter searches [1]. This is based on the use of a scientific CMOS (sCMOS) camera and a PMT to readout the secondary scintillation light produced in the TPC amplification stage (typically, by a GEMs stack). Thanks to the proper optics, current sCMOS can image a 100 x 100 mm2 area with 45 x 45 um2 effective pixel size, improving of about a factor 50 with respect to the area of the detectors installed on IXPE while keeping the same granularity [2]. The time profile of the scintillation light measured by the PMT provide the track pattern along the drift direction (dZ), complementing the X-Y projection provided by the sCMOS for 3D track reconstruction, allowing for off-axis sources polarization measurement without significant systematic effects. The use of low diffusion gas mixtures can allow to extend the drift region to about 10 cm without significant degradation of the performances. We will present the experimental results achieved within the CYGNO/INITIUM project and discuss the expected performances of a Xray-CMOS detector based on such principles for X-ray polarimetry.

[1] F. D. Amaro et al, Instruments 6 (2022) 1, 6 
[2] L Baldini et al., Astropart.Phys. 133 (2021) 102628

Speaker: Elisabetta Baracchini

80 The design and implementation of an ANN architecture for in-pixel signal processing

Modern hybrid pixel X-Ray detectors produce more and more data, exceeding tens of GB/s, and so the communication with the detector becomes an important issue. One way to manage the issue of increased amount of data being produce by the detector, is the information extraction on the sensor level, before sending them to the control system. The information can be extracted with certain, fixed functionality as long as we do know precisely how the signal behaves, which is very difficult to predict due to imperfection of the technology etc., However, it is often possible to utilize an artificial neural network (ANN), which can be trained towards desired functionality.
With this work we present a design of a hardware processor suitable for implementation of the ANN having different architectures, like e.g. Multi-Level Perceptron (MLP). Designed using CMOS 28 nm, the area of the automatically synthetized block is lower than 150 um x150 um. With such as small size it is possible to fit the ANN inside a single pixel of an X-ray detector.
We present the design of the scalable processor, capable of providing an ANN functionality as well as we demonstrate an in-house developed tools, allowing automatic conversion of an ANN model designed with the TensorFlow library from Google, into a HDL code. The hardware code is written in SystemVerilog, and the synthesized module can perform calculations of a neural network with very high speed exceeding 400MHz. Our software-tool supports the conversion of an arbitrary multilayer perceptron neural network into a state machine module that can perform calculations. It is also dynamically reconfigurable so that the ANN operating in the hardware can be changed after deployment to an ASIC.
The project aims the in-pixel implementation towards x-ray photon energy estimation with the accuracy exceeding the accuracy of an ADC converter used to digitize the pulse generated by the photon.

Speaker: Anna Kozioł (AGH University of Science and Technology in Cracow)

Cocktail Dinner Party (with live music)

Tuesday, 28 June

Sensors: 1

Convener: heinz graafsma (DESY)

81 INVITED: Timepix detectors in Space: From radiation monitoring in low earth orbit to astroparticle physics

Hybrid pixel detectors (HPD) of Timepix [1,2] technology have become increasingly interesting for space applications. While up to date, common space radiation monitors rely on silicon diodes, achieving particle (mainly electron and proton) separation by pulse-height analysis, detector stacking, shielding or electron removal by a magnetic field, the key advantage of HPDs is that, in addition to the energy deposition measurement, particle signatures in the sensor are seen as tracks with a rich set of features. These track characteristics can be exploited for identification of particle type, energy, and its trajectory. Determining these pieces of information on a single layer bypasses the need for sensor stacking or complex shielding geometries, so that HPD based space radiation devices provide science-class data with a large field of view at an order of magnitude lower weight and approximately half of the power consumption compared with commonly used space radiation monitors.
The first Timepix (256 x 256 pixels, 55 μm pitch) used in open space is SATRAM (Space Application of Timepix Radiation Monitor), attached to the Proba-V satellite launched to low earth orbit (LEO, 820 km, sun-synchronous) in 2013. Up to now, 9 years after its launch, it provides data for mapping out the fluxes of electrons and protons trapped in the Van-Allen radiation belts [3]. Noiseless detection of individual particles allows to detect even rare signatures of highly ionizing events.

In the present contribution, I will discuss different data analysis methodology, relying on track feature analysis, novel machine learning approaches (e.g. [5]) and using statistical interpolation.
Based on the success of SATRAM, advanced and miniaturized space radiation monitors based on Timepix3 [2] and Timepix2 [4] technology have been developed for the European Space Agency (ESA). These will be flown on the GOMX-5 mission (launch in 2023) and used within the European Space Radiation Array. Large area Timepix3 detectors (512 x 512 pixels, 55 μm pitch) were developed for the demonstrator of the penetrating particle analyzer [5] (mini.PAN), a compact magnetic spectrometer (MS) to precisely measure the cosmic ray flux, composition, spectral characteristics and directions. Mini.PAN employs position-sensitive (pixel and strip) detectors and (fast) scintillators to infer the particle type and velocity of GeV particles (and antiparticles) passing through the instrument’s magnetic field by measuring their bending angles, charge deposition and time-of-flight.

I will describe the mini.PAN development status, challenges imposed by the space environment, and outline how a MS purely relying on Timepix4 would reduce the PAN mass budget.

References:
[1] X. Llopart et al., NIM A 581 (2007), pp. 485-494.
[2] T. Poikela et al., JINST 9 (2014) C05013.
[3] St. Gohl et al., Advances in Space Research 63 (2019), Issue 1, pp. 1646-1660.
[4] W. Wong et al., Rad. Meas. 131 (2021), 106230.
[5] M. Ruffenach et al., in IEEE TNS 68 (2021), Issue 8, 1746-1753.
[6] X. Wu et al., Advances in Space Research, 63 (2019), Issue 8, pp 2672-2682.

Speakers: Benedikt Bergmann, Benedikt Ludwig Bergmann (Czech Technical University in Prague (CZ))

Bergmann_IWORID2022_short.pptx

82 Imaging X-Ray Photons and Electrons with the Spectroscopic 166-Pixel SDD Monolithic TRISTAN Detector

We present a spectroscopic detection module with position sensitivity based on the largest monolithic array of Silicon Drift Detectors (SDD) ever reported. It consists of 166 pixels of 3 mm diameter with integrated JFET. This module has been developed within the TRISTAN project, aiming at investigating the existence of the sterile neutrino in the keV mass range by beta spectroscopy [1]. The TRISTAN detector will be installed in the KATRIN focal plane to profit of the Tritium generation facility. The investigation of the whole spectrum of electrons (up to 30 keV) leads to very high count rates, spread across 3486 pixels (each one counting at 100 kcps) and grouped into 21 modules, each one featuring a monolithic array of 166 SDDs. SDD proved to be excellent detectors also for electron spectroscopy [2]. The compact size of the module (4 cm) and the need for four-side buttability, poses demanding challenges in terms of signal integrity and module design.
After achieving preliminary results with a smaller detector, already commissioned in the monitor spectrometer of KATRIN (47 pixels [3]), we present here the design and characterization of the final detection module with 166 channels (Fig. 1). Analog processing of events and data acquisition is performed by means of the FPGA-based Athena platform, featuring 4 Kerberos modules [4], each one acquiring 48 channels. The average energy resolution of all pixel simultaneously acquired (Fig. 2) is below 250 eVFWHM (at 5.9 keVm with 6 µs shaping time and 0°C cooling). Despite satisfying the experiment requirements, detector improvements are ongoing.

Speaker: Mr Daniel Siegmann (MPP and TUM)

2022_06_28_IWorID_TRISTAN.pdf

83 The DSSC soft X-ray Detectors with Mega-frame Readout Capability for the European XFEL

The DSSC camera [1] was developed for photon science applications in the energy range 0.25-6 keV at the European XFEL in Germany. The first 1-Megapixel DSSC camera is available and is successfully used for scientific experiments at the “Spectroscopy and Coherent Scattering” and the “Small Quantum System” instruments. The detector is currently the fastest existing 2D camera for soft X-rays.
The camera is based on Si-sensors and is composed of 1024×1024 pixels. 256 ASICs provide full parallel readout, comprising analog filtering, digitization and data storage. In order to cope with the demanding X-ray pulse time structure of the European XFEL, the DSSC provides a peak frame rate of 4.5MHz. The first megapixel camera is equipped with Miniaturized Silicon Drift Detector (MiniSDD) pixels. The intrinsic response of the pixels and the linear readout limit the dynamic range but allow one to achieve noise values of ~60 electrons r.m.s. at 4.5MHz frame rate.
The challenge of providing high-dynamic range (~10⁴ photons/pixel/pulse) and single photon detection simultaneously requires a non-linear system, which will be obtained with the DEPFET active pixels foreseen for the advanced version of the camera. This technology provides lower noise and a non-linear response at the sensor level. The readout ASICs and the camera-head electronics are compatible with both type of sensors. We will present the architecture of the whole detector system with its key features, focusing on the sensors and the integrated electronics. We will summarize the main experimental results obtained with the MiniSDD-based camera and give a short overview of the performed user experiments. We will present for the first time the experimental results with complete sub-modules of the DEPFET camera which is in the final stages of assembly. Measurements obtained with full size sensors and the complete readout electronics have shown an unprecedented mean noise of ~10 el. rms with 1.1 MHz frame rate and ~20 el. rms with 2.25 MHz frame rate. The obtained dynamic range is more than one order of magnitude higher with respect to the MiniSDD camera.

[1] M. Porro et al., IEEE TNS , vol. 68, no. 6, pp. 1334-1350, June 2021, doi: 10.1109/TNS.2021.3076602
[2] S. Aschauer, et al. Journal of Instrumentation, Volume 12, November 2017

Speaker: Matteo Porro (European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld, Germany Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, 30172 Venezia, Italy.)

DSSC_IWORID_2022_Final_Porro.pdf

DSSC_IWORID_2022_Final_Porro.pptx

84 Qualification and Modeling of the Non-Linear Response of the First Large-Area DEPFET Pixel Sensors with Internal Signal Compression

A novel design of the Depleted P-Channel Field Effect Transistor (DEPFET) with non-linear response is at the heart of the 1 Mpixel DSSC camera (DEPFET Sensor with Signal Compression) currently being developed for ultra-fast imaging of soft X-rays at the European XFEL. The simultaneous requirement of single-photon detection down to 0.5 keV and dynamic range up to 104 photons/pixel/pulse is here solved by introducing a non-linear compression of the DEPFET transistor response while the readout electronics is kept linear [1, 2]. The first full-size sensors produced by PNSensor GmbH have been mounted to give birth to the first ladder (128x512 pixel), one of the 16 independent units forming the DSSC camera.

Now the calibration of a 1 Mpixel DEPFET sensor with signal compression is the key to reach the desired performances but also the major challenge, due to the need to accurately qualify the full response of each pixel in different conditions [3]. The aim of this work is to discuss the general calibration strategy and to present the experimental results of the first calibration campaigns on the DSSC ladder.

X-ray spectra were acquired using a pulsed X-ray source (PulXar) in order to assess gain and noise performances in the linear region of the DEPFET response. PulXar can in fact provide trains of X-ray pulses with duration as short as 25 ns at high burst rate (up to 4.5 MHz) which effectively mimics the time structure of the beam at XFEL.

To qualify the full non-linear response of each pixel, from the linear region to the high intensity end, we conducted a dedicated test at the SQS beam line where we can produce intense shots of monochromatic photons (soft X-rays) with a smooth spatial distribution to allow irradiation of a whole quadrant of the camera. The XFEL beam hits an Aluminum target and the DEPFET ladder is at 90-degree to collect fluorescence photons (Al Ka 1.48 keV).
The XFEL beam intensity is accurately monitored and the linear relationship between the production of fluorescence and the beam intensity has been previously qualified with a silicon drift detector.
The presentation will focus on the evaluation of the DEPFET ladder performance with low energy photons and on the measurement technique, modelling and parametrization of the non-linear response in different gain conditions. The achieved results confirm the possibility to reach noise levels below 20 electrons rms and an input range of deposited energy of several MeV/pixel/pulse.

[1] M. Porro et al., IEEE TNS , vol. 68, no. 6, pp. 1334-1350, June 2021
[2] S. Aschauer, et al. Journal of Instrumentation, Volume 12, November 2017
[3] A. Castoldi, et al., 2020 IEEE NSS/MIC Conf. Records

Speaker: Andrea Castoldi (Politecnico di Milano, INFN sez. Milano)

talk_IWORID2022_Castoldi.pdf

talk_IWORID2022_Castoldi.pptx

85 3D integration approaches for Silicon Photomultipliers: from backside-illuminated to Through Silicon Via interconnections

Silicon Photomultipliers (SiPMs) are Geiger-mode photodetectors largely used in scientific experiments of high energy physics as well as in medical imaging. Recently, SiPMs are also being considered the detectors of choice for autonomous driving based on light detection and ranging (LiDAR) systems [1].
In the last few years, Fondazione Bruno Kessler (FBK) has been working on the development of new 3D integration approaches for SiPMs, by using backside-illuminated (BSI) devices and Through Silicon Via (TSV) interconnections, to improve both performances and functionalities. To increase the photon detection efficiency (PDE) of the device and at the same time enable a direct 3D integration with the read-out electronics, FBK is developing two different technological approaches for near-infrared (NIR) and near and vacuum ultra-violet (NUV/VUV) light detection, respectively.
A BSI-SiPM design offers three principal advantages compared to the Frontside-illuminated (FSI) scheme: i) an enhancement of the fill factor (FF) of the single-photon avalanche diode (SPAD) to almost 100% because all the reflective and absorbing components (metal, quenching resistor) remain on the front side; ii) a possible light-trapping for NIR photons because the photons are reflected back and forth in the thin silicon layer and iii) high-segmentation access to SiPM output directly from the front-side (see Figure 1 a).
The same BSI approach used for NIR detection is not suitable for NUV/VUV light detection, since i) the carrier glass and the adhesive material used for wafer bonding are not transparent to wavelengths lower than 380 nm and ii) most NUV/VUV photons interact with the first tens of nanometers of the silicon. Therefore, our approach for FSI SiPM exploits the so-called “bulk-TSV” Via-Last. This TSV technology uses a portion of the silicon substrate as a conductive material, instead of metals, taking the advantage that most of the SiPM substrate is highly doped, except a few microns of an epitaxial layer. The silicon volume acting as a conductive interconnection is insulated by the rest of the bulk wafer using deep trenches filled with a dielectric material.
Experimental
The process flow of BSI SiPM for NIR starts with the fabrication of SiPM based on the conventional FBK SiPM-HD technology [2,3]. When the front-end is completed, the wafer is temporary bonded to a handling wafer. The device wafer is then thinned down to about 10 μm, i.e. a few μm larger than the nominal epi-layer thickness and the entrance window is fabricated on the backside. To make available the frontside contacts for the subsequent integration and, at the same time, provide mechanical stability to the structure, a glass support wafer (transparent to NIR photons) is permanently bonded to the backside and the handle wafer is debonded. The final device can work in both BSI and FSI configurations as shown in Figure 1 a).
On the other hand, the process flow of the NUV/VUV SiPM with TSV interconnections starts with the conventional FSI SiPM (with an optimized antireflective coating and passivation specific for NUV/VUV photons) [4]. Then, the wafer is temporary bonded to a glass carrier and thinned down to 150 μm. Subsequently, fully pass-through trenches are realized from the backside and filled with a dielectric material. Finally, the device wafer is debonded from the carrier glass, obtaining a SiPM with the contacts on the back and illuminated from the front. In this scenario, the 3D integration density is limited by the TSV dimensions (about 100 μm).
Results
FBK has been able to successfully fabricate and characterize the first batch of BSI-SiPM for NIR photon detection. The electrical characterization showed about 90% yield on the ultra-thinned wafers with a similar breakdown voltage and dark current compared to non-thinned wafers, proving that the thinning process itself does not degrade the electrical and noise performance. Using a hollow PCB, the PDE at 900 nm was measured on both configurations for the same chip and also compared with a SiPM device with a metal reflector on the front side, covering most of the active area. As shown in Figure 2, the last-mentioned device shows the highest PDE for every overvoltage mainly due to an effective light trapping mechanism.
Regarding the process fabrication of SiPM for NUV/VUV, results are promising: the first tests have shown proper electrical isolation of the TSV, as shown in the SEM image of Figure 1 b). Furthermore, the Front-end-of-line (FEOL) of the first prototypes has been successfully fabricated (as shown in Figure 3).
Conclusions
The first demonstrator of BSI SiPM for NIR photon detection has been developed at FBK. Compared to the FSI technology, the BSI sensors with metal reflectors show a clear increase in PDE at 900 nm. Ongoing work on the development of SiPMs for the detection of NUV/VUV photons is addressed by taking advantage of silicon bulk-TSV interconnections. We expect that the preliminary electrical and functional results will be available in the following months to be presented at the conference.
Bibliography
[1] R. Agishev et al., (2013).
[2] A. Gola et al., Sensors (Switzerland) 19 (2019).
[3] C. Piemonte et al., IEEE Trans. Electron Devices 63 (2016) 111-1116.
[4] M. Capasso et al., Nucl. Instruments Methods Phys., Detect. Assoc. Equip. 982 (2020) 1-4.

Speaker: Laura Parellada Monreal (Fondazione Bruno Kessler)

IWORID2022-LParellada.pdf

10:20 Coffee break

Detector Systems: 2

Convener: Roelof de Vries (Malvern-PANalytical)

86 Design study and spectroscopic performance of SOI pixel detector with a pinned depleted diode structure for X-ray astronomy

We have been developing silicon-on-insulator pixel detectors with a pinned depleted diode structure, named ``XRPIX'', for X-ray astronomy. XRPIX, using a reverse-biased p-type substrate, has a pinned, undepleted p-well at the back-gate surface under the buried oxide layer and a depleted n-well underneath the p-well. The latter has two important roles: one is to prevent leakage current from the p-well to the substrate (punch-through) creating a potential barrier, and the other is to improve charge collection efficiency creating lateral electric field toward the n$+$ charge sensing node. Optimization of the dopant concentration of the n-well is the key ingredient to finalize XRPIX because higher dopant concentration could result in a higher potential barrier but make it harder to deplete the n-well, and vice versa. Based on TCAD simulations, we fabricated five candidate chips having different n-well dopant concentrations and configurations. We successfully found out the best candidate chip, which showed a satisfactory X-ray spectroscopic performance and suppressed a large leakage current. Too high or too low dopant concentration chips showed a degraded X-ray spectroscopic performance or a large leakage current as expected from the TCAD simulations. We also evaluated the dependency of X-ray spectroscopic performance on the n-well dopant concentration and configuration. In this presentation, we will report the above design study and spectroscopic performance of XRPIX.

Speaker: Mr Masataka Yukumoto (University of Miyazaki)

iworid_yukumoto_slide.pptx

87 Results from Single Event Effect Tests with MIMOSIS-1

The MIMOSIS CPS will equip the Micro Vertex Detector of the Compressed Baryonic Matter experiment at FAIR. It is to combine a 5µs/5µm space and time resolution with a peak rate capability of 80 MHz/cm² and a tolerance to > 5 MRad and 1e14 neq/cm². Moreover, it is to tolerate ~ 1 kHz relativistic Au-ions from the beam halo. A first full size prototype, MIMOSIS-1, has been produced by IPHC Strasbourg, Goethe University Frankfurt and GSI.
The cross-section for single event latch-ups and bit flips in the state machines of the sensors was measures by exposing it to a direct, intense heavy ion beam. The experimental findings are reported.

Speaker: Joshua Benedict Arnoldi-Meadows (Goethe University Frankfurt (DE))

IWORID_Arnoldi-Meadows_SEE_tests.pdf

IWORID_Arnoldi-Meadows_SEE_tests.pptx

88 The PERCIVAL 2-Megapixel soft X-ray CMOS Imager – Status and Prospects

The PERCIVAL soft X-ray 2-Megapixel CMOS imager has been developed by a collaboration of light sources and RAL to meet experimental needs at todays Synchrotron and FEL soft X-ray sources. Systems have been in operation at two collaboration facilities, and are currently under commissioning at two more.
First user experiments at FLASH and Petra III’s soft X-ray beamline P04 have demonstrated the system’s potential, with new parameter space and experiments becoming accessible primarily thanks to Percival’s high dynamic range (single-photon discrimination at 250eV to full well of 3.6Me-) and comparatively high frame rate (83 Hz achieved with current DAQ firmware, 300Hz aim) over a large area.
The first-generation sensor has some shortcomings, primarily due to crosstalk – these are currently being addressed in a redesign of the Silicon layout. In parallel, we are upgrading DAQ hard- and firmware and head mechanics, and addressing sensor nonlinearities in improved calibration.
We will report on the status of the project, give an overview of user experiments performed, and describe the sensor and system upgrades in progress.

Speaker: Cornelia Wunderer (DESY)

2022_06_28_iWoRID_Percival_Wunderer_v2_upload.pdf

89 Development of Low Noise Pixels and Readout Architectures for Scientific Applications in a 180nm CMOS Image Sensor Process

Development of Low Noise Pixels and Readout Architectures for Scientific Applications in a 180nm CMOS Image Sensor Process

I Sedgwick S Benhammadi, B Marsh, N Guerrini

Progress in the performance of CMOS Image Sensors (CIS) in recent years has been extremely rapid, especially in the area of low noise, where values below 1e- have been reported [1] [2] and are even commercially available [3], allowing new science and improved performance in many fields.

However, there are also areas of scientific imaging (electron microscopy, X-ray imaging, proton therapy, FEL and synchrotron detectors) where low noise is required alongside other performance parameters such as radiation hardness, high dynamic range, or high frame rate. Achieving this performance means further developing low noise pixels and circuits to include additional features. This requires not just improved pixel performance, but also advanced readout circuitry.

With these goals in mind, we present PRECISE, a test structure in a 180nm CMOS Image Sensor process, which contains several flavours of 3T and 4T pixels targeting different application areas. Some are optimised for low noise, others implement radiation hardened architectures, and some show high dynamic range performance. The chip also implements a capacitive Programmable Gain Amplifier (PGA), a Sigma-Delta ADC and implements on-chip CDS. These features are crucial for the integration of the low noise pixels in real systems. The goal of the chip is to demonstrate the performance of the various “building blocks” needed for a larger scientific detector. Suitable blocks can then be combined with the desired pixel type for best performance.

With this device, we have so far demonstrated noise as low as 2e- at room temperature with a 1us ADC conversion time (for 12 bits). We will present these results alongside results from the pixels which exhibit other functionalities, and discuss the performance of the ADC and PGA blocks. To complete the necessary set of “building blocks”, the chip implements a separate 5 Gbps serialiser, whose performance will also be briefly discussed.

[1] A. Boukhayma, A. Peizerat and C. Enz, "A Sub-0.5 Electron Read Noise VGA Image Sensor in a Standard CMOS Process", IEEE Journal of Solid-State Circuits, vol. 51, no. 9, pp. 2180-2191, 2016. Available: 10.1109/jssc.2016.2579643.

[2] J. Ma and E. Fossum, "Quanta Image Sensor Jot With Sub 0.3e- r.m.s. Read Noise and Photon Counting Capability", IEEE Electron Device Letters, vol. 36, no. 9, pp. 926-928, 2015. Available: 10.1109/led.2015.2456067.

[3] Hamamatsu.com, 2022. [Online]. Available: https://www.hamamatsu.com/eu/en/product/cameras/qcmos-cameras.html. [Accessed: 30- Mar- 2022].

Speaker: Nicola Carlo Guerrini

IWORID_PRECISE_v5.pdf

IWORID_PRECISE_v5.pptx

90 Development of CoRDIA: An Imaging Detector for next-generation Synchrotron Rings and Free Electron Lasers

Currently the landscape of Synchrotron Radiation sources is experiencing a major change by planned or ongoing machine upgrades: Most storage rings reach the diffraction limit, causing an expected increase in brilliance by about two orders of magnitude. Most FEL sources increase repetition rates to around 100kHz. This also holds true for the European XFEL, where a change from the train mode (with 27kHz average rate) to CW operation at around 100kHz could be imaginable.

To fully exploit the increased performance of these sources, also imaging detectors need to be upgraded – from today’s imagers at storage rings and low rate FELs, capable of a few-kHz continuous frame rate, to ≥100kHz. The ASICS of most imaging detectors for the European XFEL (like AGIPD or LPD) can cope with image recording at up to 4.5MHz, but lack the readout bandwidth required for continuous rates faster than ≈10kHz. Furthermore the pixel size of these detectors is severely compromised by their in-pixel memory, not needed for continuous operation. However, the new requirements of diffraction limited storage rings and upgraded FELs overlap enough to be catered by a common detector system:

CoRDIA, the Continuous Readout Digitising Imager Array, developed by a collaboration between DESY and Bonn University.
Design goals are continuous operation at ≥100kframe/s, single-photon sensitivity at 12keV or less, a dynamic range up to $10^4$ photons at the same energy, and a pixel pitch of 100µm. Complete detector systems will be composed as an array of hybrid assemblies, consisting of several readout ASICs bump-bonded to a sensor. This ASIC will be compatible with different sensor materials and types:

• p-doped Silicon for the central (≈10keV) energy range,
• high-Z materials for higher energies, and
• LGAD sensors (with built-in amplification) for soft X-rays.

To achieve an (almost) dead time free operation, the ASIC implements a pipelined signal processing chain: While one image is digitised, the next one is integrated by the preamplifier, and the preceding one is read out.
This readout is based on the principle of the GWT-CC solution developed by Nikhef for Timepix4.
Basic circuit blocks have been manufactured on 2 MPW chips in TSMC 65nm technology and are currently being tested:

• An adaptive-gain charge integrating preamplifier, building on the experience of the AGIPD detector
• A sampling stage with charge injection compensation
• A Correlated Double Sampling (CDS) stage capable of operation in
  different topologies.

Four variants of an SAR ADC developed by Bonn University

After verification and characterisation of these building blocks, we will follow a gradual approach with a first generation ASIC focusing on the ‘time domain’ i.e. reaching the specifications for pixel pitch and readout speed, while a $\rm 2^{nd}$ generation chip will focus on ‘analogue specs’ optimising noise and extending the dynamic range to the final goal. This way unforeseen effects like crosstalk and substrate coupling as well as ‘scale effects’ will be known and can be countered on the $\rm 2^{nd}$ generation chip.
We will present the CoRDIA ASIC’s architecture along with test strategies and results from the MPW prototypes.

Speaker: Ulrich Trunk

2022-06-27_Cordia iWORID UT.pdf

2022-06-27_Cordia iWORID UT.pptx

91 Development of the Control Plane and Data Path for a 1MHz Continuous Frame Rate Spectroscopic X-ray Imaging Detector System

The latest iteration of the HEXITEC ASIC, HEXITEC$_{MHz}$ has utilised on-chip digitisation to accelerate frame rates by two orders of magnitude over its analog-readout based predecessor, now with 1 MHz continuous readout [1]. This advancement places significant demand on the capabilities of the accompanying readout hardware; an 80x80 pixel array with 12-bit resolution results in a continuous throughput of over 76 Gbps that must be transferred, processed and stored.

This talk will outline the architecture used to cover the control and data planes. The former—a Xilinx Zynq SoC based embedded Linux board—forms an experimental first application of a new control architecture dubbed LOKI, which aims to provide a flexible solution for hosting the Odin Control framework that can be adapted to future detectors [2].

The latter plane will trace the path of pixel data from packetisation and egress from the ASIC via 20 serialisers (outputting Aurora-encoded scrambled streams at 4.1 Gbps over differential CML) through de-scrambling, reordering, reduction, processing and presentation.

An update on the latest development progress and testing of these external components will also be presented.

[1] M.C. Veale et al., HEXITEC: A high-energy X-ray spectroscopy imaging detector for synchrotron applications, Synchrotron Radiat. News 31 (2018) 28
[2] https://accelconf.web.cern.ch/icalepcs2017/papers/tupha212.pdf

Speaker: Joseph Nobes (Science and Technology Facilities Council)

Control-Data-HEXITEC-MHz-Spectroscopic-XRay_Nobes2022.pptx

12:50 Lunch break

Applications: 2

Convener: Matthieu Boone

92 INVITED: Spectral and phase-contrast imaging: from crystal-based synchrotron setups to detector-based compact systems

Spectral and phase-contrast imaging techniques have been widely exploited at synchrotron radiation facilities. Their implementation requires in many cases the use of crystals either to prepare or to analyze the X-ray beam. For instance, energy dispersive spectral systems make use of multiple or bent crystal monochromators to spatially resolve different energy components at the detector position. Similarly, low-dose clinical applications require monochromators to select the X-ray energy that maximizes image quality for a specific diagnostic task. On the other hand, analyzer-based phase-contrast imaging employs an analyzer crystal to decode absorption, phase, and small-angle-scattering information encoded by the sample. In this context, spectral photon-counting detectors are key in the transition from synchrotrons to compact laboratory setups. The availability of photon-counting devices equipped with multiple thresholds and effective charge-sharing compensation circuitry allowed the implementation of quantitative spectral imaging at the micrometer scale and high energy to be performed in a compact laboratory environment. At the same time, their use combined with phase-contrast techniques with relaxed coherence requirements, such as edge-illumination, has boosted laboratory systems towards simpler experimental arrangements and combined spectral phase-contrast applications.
In this talk, an overview of some spectral and phase-contrast imaging techniques, applications, and related challenges is presented. A more in-depth discussion is dedicated to the development of a new compact experimental setup based on the edge-illumination technique and a spectral detector enabling spectral and phase-contrast imaging.

Speakers: Luca Brombal, Luca Brombal

Presentation_iworid_mod.pdf

Presentation_iworid_mod.pptx

Presentation_iworid.pptx

93 High-resolution Large-area Medipix3 Camera for X-ray Spectral Imaging of fast-moving Objects

A new generation of a modular high-resolution spectral imaging camera has been developed from synchronized array of pixel detectors Medipix3 within the European Union Horizon 2020 project X-mine. The aim of the project was to increase the potential of European mineral resources without generating adverse environmental impact by supporting more efficient ore extraction in existing mining operations, making the mining of smaller deposits economically feasible. The presented Medipix3 based camera can be operated in Time-Delayed-Integration mode allowing for continuous imaging of fast-moving objects such as rocks carried on conveyor belt. The modular architecture of the camera enables to build imagers with essentially unlimited size and no spacing gaps between the camera segments. The camera was assembled in single chip-row architecture of several Medipix3 chips for total width size: 7 cm (1×5), 14 cm (1×10), 21 cm (1×15) and 42 cm (1×30). The aim is to analyse the composition and recognize the content of valuable minerals during the mining extraction process. The pixel-level spatial resolution of 55 μm makes possible to image and analyse the internal structure of the rock particles and directly detect intrusions of minerals and metals like copper, zinc, lead or even gold [1]. A theoretical maximum scanning speed of the camera is about 5 m/s. A series of measurements were performed with a speed of 3.5 m/s in laboratory conditions. This level corresponds to imaging and analysing a total area of 1.5 m2 per second. Results of these experiments will be presented. The hybrid chip-sensor architecture enables the possibility of usage different sensor materials like CdTe, Si or GaAs of varying thickness for customized configuration of a large variety of implementations. Applications include continuous moving X-ray inspection and dynamic X-ray robotic scanning in medical imaging, food inspection, automotive industry and more. The USB3 communication interface ensures high speed data transfer preserving universality of connection.

Speaker: Stepan Polansky

2022.06.28_STEPAN_POLANSKY.pptx

94 Ultra-fast line camera based on TI-LGAD for beam diagnostics and photon science

New generation of synchrotron and plasma accelerators will produce coherent radiation with extremely high brightness. Photon beams from these machines will greatly extend the present research capabilities and will reveal new opportunities in imaging, spectroscopy, structural and dynamic studies, and other applications. Development of beam diagnostic instrumentation with high precision becomes essential for these purposes.
The energy spread of the electron bunch is an important parameter for the studies of the microbunching dynamics. At Karlsruhe Research Accelerator (KARA) a visible light diagnostics port (VLD) is utilized to measure the incoherent synchrotron radiation emitted at a 5° port front end at a dipole magnet. To accommodate several measurement modalities, this radiation is split in several spectral ranges, for example, to the range between 400 nm to 500 nm. At present, measurements are limited by performance of the detector. The major limitations are the frame rate of the camera as well as the low dynamic range [1]. In order to improve the performance, a line array camera with Trench Isolated Low Gain Avalanche Diodes (TI-LGAD) is in development. TI-LGADs are a new generation of segmented LGAD type sensors with fast timing, internal gain, high spatial resolution and good signal-to-noise performance [2]. The line array camera, named KALYPSO (KArlsruhe Linear arraY detector for MHz-rePetition rate SpectrOscopy), has been designed and produced. Several versions of TI-LGADs have been characterized and successfully mounted in the ultra-fast line camera KALYPSO, which is capable of frame rates up to 12 MHz [1]. In this contribution, the performance of the sensor as well as first results from the beam time measurements at KARA will be presented.

Speaker: Ekaterina Trifonova (KIT - Karlsruhe Institute of Technology)

Trifonova_iWORID_3.pdf

95 3D localization of radioactive sources by triangulation method using a single gamma camera

Localization of radioactive sources is a major concern in the nuclear industry whether in decommissioning phases of nuclear facilities, nuclear waste management applications, radiation protection or Homeland Security. Therefore, gamma imaging emerges as a measurement solution that allows localizing and identifying radioactive sources in near and far field, which reduces the dose received by operators and hence respecting the ALARA principle.
Gamma cameras based on hybrid pixel detectors such as Timepix3 [1] technology, enables the localization of radioactive hot spots by superimposing a gamma image on a visible image. The last generation of gamma camera developed at the CEA List is Nanopix, a very compact gamma camera that allows remote localization, visualization and gamma spectrometry measurement of radioactive hot spots. With a weight lower than 400 g and a size of 8×5×5 cm3, Nanopix is currently the smallest coded aperture camera in the world.
However, this generation of gamma imager has two main limitations considering its deployment in complex radiological environments. Indeed, the localization of hot spots requires maintaining a stationary measurement position. In addition, the two-dimensional reconstructed image provides information about the direction of the source, but does not allow a direct estimate of the distance to the source. The work presented here aims to overcome these limitations to have a system able to estimate the three-dimensional localization of a hot spot.
The imaging technics used in our applications are based either on the principle of spatial encoding by coded aperture, or on the principle of Compton scattering kinematics. As part of the work, these two techniques have been adapted through algorithms to provide a spatial localization of hot spots in three-dimensions. The developed method requires moving the gamma camera as sort to know every single position according to every gamma image reconstructed.
The results obtained by Monte Carlo simulations, and then by experimental measurements, show the capacity Nanopix to locate in three-dimensions radioactive sources emitting gamma rays from 59.5 keV (241Am) to 1.33 MeV (60Co) at distances from 60 cm to 500 cm with uncertainties below 10 %. The results obtained with Nanopix and the techniques developed in this work pave the way for 3D radiological mapping of crowded and unknown areas.

Speaker: Kamel Benmahi (CEA)

iWORID2022.pdf

iWORID2022.pptx

96 Correlated X-ray photons for incoherent diffraction imaging

Established methods for high-resolution X-ray structure determination are based on far-field coherent diffractive imaging (CDI). However, in the interaction of light with matter incoherent processes occur, that are sometimes predominant over the coherent ones. They are considered detrimental in the CDI approach. The approach called incoherent diffractive imaging (IDI) opens up fundamentally new strategies for X-ray structure determination. It considers photon correlations of higher order rather than the photon distribution itself. Here, we show how IDI will be explored in a promising regime provided by nuclear resonances of Mössbauer nuclei. X-ray emission from excited states, i.e. incoherent nuclear resonant fluorescent radiation, will be employed. The experiment for incoherent nuclear resonant fluorescent radiation puts stringent requirements on the utilized pixelated detectors in terms of time and energy resolution. Detectors with sufficiently small pixel size of about 50 µm and nanosecond time resolution are currently not available commercially. The detector based on Timepix4 readout chip being developed by the detector group at Deutsches-Elektronen Synchrotron (DESY) matches the required specifications.

Speaker: Dr Alexandr Ignatenko (Friedrich-Schller-University Jena)

Ignatenko_iWoRiD_correlated_photons.pdf

15:50 Coffee break

Sensors: 2

Convener: Seppo Nenonen

97 INVITED: High-flux CdZnTe detectors: Spectral Computed Tomography and Beyond

Recent advances in THM growth and contact engineering of high-flux CdZnTe sensors have enabled dramatically improved hole mobility-lifetime product resolving historical problems with detector polarization. To illustrate superior performance of high-flux CZT we will show some experimental studies in Spectral Computed Tomography (SCT), High-Intensity X-Ray Imaging and Theranostics.

Computed Tomography (CT) is a state-of-the-art X-ray imaging modality that uses either dual tube, kVpp switching, or dual scintillator detectors. Further improvements in tissue discrimination, spatial resolution and development of new clinical applications, as K-edge contrast imaging, are expected as a result of currently deployed Spectral CT scanners that utilize 4-8 energy bins and operate under 650+ Mcps/mm2 count rates. To illustrate this technology potential, we have performed spectral CT acquisition of a small phantom with three contrast agents with a 330-µm pixel pitch detector. Spectral CT images were reconstructed for all six energy bins matched to the K-edges of the contrast agents as well as for integrated signal mimicking a photon-integrating CT. The K-edge contrast-only images were in excellent agreement with true contrast agent locations and provided a complimentary information to the integrated CT image.
Outside of medical applications, there is also a growing need for CdZnTe-based detectors amongst the high-energy physics community. Over the next decade, the development of diffraction limited storage ring (DLSR) synchrotrons and continuous wave (CW) free electrons lasers will see an increase in average source brightness and a move towards higher X-ray energies (>10 keV). At these energies and fluxes the poor radiation hardness and stopping power of traditional silicon-based detector systems is driving a move to CdZnTe detectors. Recent testing of CZT detectors at the Linac Coherent Light Source (LCLS) FEL have demonstrated the capability of this material to carry out X-ray imaging at extreme fluencies of 8 GeV mm-2 per 40 fs wide X-ray pulse. We anticipate future use of high-flux CZT detectors in other photon sciences experiments.
The author acknowledges numerous colleagues from Redlen Technologies that have developed high-flux CdZnTe technology and several research collaborators internationally that I had a privilege to work with over last several years.

Speaker: kris iniewski

2022 Iniewski iWORID v4.pdf

98 Manufacturing of pixel detectors for radiation imaging by chromium compensation of gallium arsenide wafers

Gallium arsenide has noticeable advantages over silicon for radiation detector manufacturing. There is particularly a higher electron mobility (8000 vs 1400 cm2/(V·s)), bigger average atomic number (31.5 vs 14) and wider bandgap (1.43 vs 1.12 eV). These advantages result in a better charge collection, higher radiation absorption efficiency, superior radiation hardness and lower noise.

In frame of EU H2020 X-MINE project Advacam has studied the possibilities to produce radiation detectors by chromium compensation of commercially available 3” n-type GaAs wafers. Wafers were annealed in a quartz reactor; processed by polishing and CMP; and then patterned, metallised, and diced. We have demonstrated a wafer-level processing using sensor designs compatible with Timepix/Medipix family readout ASICs.

It was concluded that radiation sensors of chromium compensated GaAs demonstrate X-ray imaging quality that is comparable to the level of commercially available CdTe semiconductor sensors.

Speaker: Dr Juha Kalliopuska (Advacam Oy)

IWORID_2022_GaAs_Kalliopuska 28.06.2022.pdf

99 Gain, noise, and collection efficiency of GaAs SAM-APDs with staircase structure by means of synchrotron radiation

In hard-X-ray applications that require high detection efficiency and short response times, III/V compound semiconductors offer some advantages over the Si-based technologies traditionally used in solid-state photodetectors. Amongst them, GaAs is one of the most valuable materials thanks to its outstanding properties. At the same time, implementing charge-multiplication mechanisms within the sensor may become of critical importance in cases where the photogenerated signal needs an intrinsic amplification to be acquired with adequate precision by the front-end electronics. To fulfill these needs, a number of GaAs-based avalanche photodiodes (APDs) were grown by molecular beam epitaxy; through bandgap engineering, it was possible to realise devices with separate absorption and multiplication regions, the latter of which featuring a so-called staircase structure to reduce the multiplication noise. This work reports on the experimental characterisation of gain, noise and charge collection efficiency of three series of GaAs APDs featuring absorption regions of different thicknesses. Several measurements were carried out on such devices both with lasers and synchrotron light sources. The results, supported by simulations based on state-of-the-art modelling, show the capability of these devices to operate in non-punch-through regime with promising performances in terms of collection efficiency, gain and associated noise.

Speaker: Mr Matija Colja (DIA, University of Trieste, 34127 Trieste Italy)

2022_06_28_iworid5.pdf

2022_06_28_iworid5.pdf

2022_06_28_iworid5.pptx

100 3D silicon detectors for neutron imaging applications.

Neutron detection has historically been achieved using $^3$He or BF$_3$ gas detectors. The scarcity of $^3$He, and the toxicity of BF$_3$, have driven detector research into finding new solutions for efficient neutron detection. For applications in neutron imaging with thermal neutrons, planar silicon detectors coated with neutron converting materials ($^{10}$B and $^6$Li) have shown promising results in terms of space and time resolution [1]. The limitations in neutron detection efficiency of planar detectors come from non-optimised converter thickness (self-absorption of the conversion products in the film) and geometrical effects resulting in loss of conversion products [2]. The use of micro-machining promises to eliminate many of these issues, by creating high-aspect ratio micro-structures housing the converter material which should increase both the neutron conversion probability and the chances of detecting the conversion products [3]. Many research groups have investigated 3D neutron detectors by means of single- and double-sided trenches, pillars, and single-sided matrixes of micro-structures in different configurations [4]. Although not all these approaches are compatible with imaging applications, experimental neutron detection efficiency over 40% were reported using the 'stacked' method and the 'pillar' method [4].

Several aspects are cited in the literature as limiting factors of current 3D neutron detectors: (i) non-optimized micro-structure geometry (diameter/width, depth, and pitch), (ii) inactive layers at the silicon/converter interface, and (iii) difficult conformal deposition of the neutron converters.
Our project, "INDET – Improved efficiency for Neutron DETectors", aims at addressing several of these limitations.
The sensors were designed and fabricated at SINTEF MiNaLab, using a N-on-P planar process with a shallow entrance window and p-spray isolation. The wafer layout includes diodes, strip detectors and pixel detectors compatible with the Medipix/TimePix readout chips. The micro-structures housing the neutron converter are etched by means of Deep Reactive Ion Etching - DRIE.
The 3D microstructures are not doped to reduce the extension of the dead layers that could negatively affect the detection of the conversion products. Passivation of the structures is achieved by Atomic Layer Deposition (ALD) of Al$_2$O$_3$, an excellent passivation material with high content of negative trapped charge (>2x10$^{12}$ cm-2) and low interface defects [5]. The ALD process parameters (deposition temperature, thickness, post process anneal etc.) were studied in detail at the University of Oslo by means of QSSPC lifetime measurements and C-V measurements on MOS capacitors with Al$_2$O$_3$ dielectrics before and after irradiation. Optimal passivation was achieved in the presence of native oxide and for Al$_2$O$_3$ thicknesses in the range of 30-90nm, deposited at temperatures spanning wide range (150-300$^\circ$C) [6]. Successful passivation was maintained after 1MRad $\gamma$ and $\beta$ irradiations, with only minimal variation in trapped charge and interface defects density.
The neutron converter of choice is $^{10}$B$_4$C, deposited at Linköping university with a newly developed CVD process that will ensure extremely conformal deposition into the high aspect ratio 3D structures [7]. The deposition process was tested on dedicated structures fabricated at SINTEF with excellent results in conformality and step-coverage and will soon be implemented on the sensor wafers.
The final 3D micro-structures implemented on the sensors were designed with the aid of Geant4 simulations using the NCrystal library [8]. Simulations were carried out at the University of Bergen. Different combinations of structure shape, size, depth, and pitch were investigated to study their effect on neutron conversion probability and detection efficiency. The peak simulated efficiency was found to be 31.8% for trenches of width $2\mu m$, filled with converter, with a pitch of $4\mu m$ and etched to a depth of $100\mu m$. The impact of the neutron converter thickness was also studied, and the optimal converter thickness was found to be in the order of $1\mu m$. Many of the investigated structures are being fabricated on wafer to verify the simulation results.
In this presentation, we will report on the details of the design aspects, microstructure geometry and their fabrication/passivation, neutron converter depositions and electrical measurements. The expected neutron detection efficiency will be discussed. In-depth characterisation of the sensors in neutron beams will be carried out at different facilities. The first results are expected before the end of 2022.

[1] J. Jakubek, et al., Nucl. Instr. Meth. Phys. Res. Sec. A, 560 (1), 2006, 143-147.
[2] D. S. McGregor, et al., Nucl. Instr. Meth. Phys. Res. Sec. A, 500, (1-3), 2003, 272-308.
[3] S. L. Bellinger, et al., IEEE TNS, vol. 59, no. 1, pp. 167-173, Feb. 2012.
[4] R. Mendicino, et al., Nucl. Instr. Meth. Phys. Res. Sec. A, 878, 2018, 129-140.
[5] M. Christophersen, et al., Nucl. Instr. Meth. Phys. Res. Sec. A, 699, (2013), 14-17.
[6] M. N. Getz, et al., Journal of Applied Physics, 129, 205701 (2021).
[7] L. Souqui, Chem. Mater. 2019, 31, 5408−5412.
[8] X.-X. Cai, et al., Comp. Phys. Comm. 246 (2020) 106851.

The authors acknowledge funding from the Norwegian Research Council (Research Project no. 289437 – NANO2021 program).

Speaker: Dr Marco Povoli (SINTEF MiNaLab)

IWORID2022_Povoli.pdf

101 Graphene-Enabled Silicon-Integrated Photodiode for DUV Imaging

We present a novel scalable graphene-silicon hybrid photodiode that enables deep UV imaging. We have a created a photodiode with a reduced dead layer entrance window. Existing photodiodes are limited in sensitivity for low wavelengths due to the low penetration depth of photons of < 400 nm. Typical photodiodes have a junction implant which causes the low penetrating photons to be recombined in this dead layer. Here, we have utilized the near transparent nature of single layer graphene to create a junction with a minimum dead layer. To have a full active bulk volume we have combined a single junction ring (n++ bias ring) with single layer graphene. The graphene acts as a large field plate which overhangs the junction ring, on top of a thin dielectric, and covers the entire active area, 5x5 mm2. When a reverse bias is applied the detector depletes as one would expect the region underneath a field plate to deplete. Transient Current Technique (TCT) measurements have been performed to study the charge uniformity of the device and it has been shown that the charge collected is 100% across the entire area of the detector, however the collection time increases as you move further away from the junction ring this is due to the path length of the electrons along the surface of the device as shown in figure 2. Additional characterizations have been performed to evaluate the sensitivity of the device as a function of wavelength in comparison to a device with an ultra-shallow junction implant. The results show that the graphene-enhanced device shows far greater performance in the 200-400 nm wavelength range. It has been shown that this technology can be used to create a hybrid pixel detector for DUV imaging as shown in figure 3

Speaker: Neil Moffat (Consejo Superior de Investigaciones Cientificas (CSIC) (ES))

Moffat_iWorid.pdf

Moffat_iWorid.pptx

Wednesday, 29 June

Detector Systems: 3

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

102 INVITED: Reading 4D pixels at 20 ps in CMOS 28-nm technology

Inner trackers in high-energy experiments of the next generation must cope with unprecedented high rates and track densities. This poses the need for precise timing information at the pixel level (below 50 ps per hit), high readout frequency (several hundreds of kHz per pixel) and radiation hardness (more than 1 Grad on electronics and more than 1016 1-MeV equivalent neutrons per cm2 on sensors).
While on the sensor side it appears already that such requirements can be met (refer for example to the recent developments on 3D-trench silicon sensors [1, 2, 3]), the challenge is still widely open on the electronics side, where strong area and power density constraints are present. Furthermore, adding precise timing information at the pixel level generates a major amount of information, which imposes extremely high data bandwidth, in the range of hundreds of Giga bit per second per single ASIC. Such value is approximately one order of magnitude more than the present state-of-the-art developments in the field.
28-nm CMOS technology appears having the whole set of characteristics to satisfy the experimental requirements referred above. A first complete 28-nm CMOS ASIC to elaborate technical solutions about the challenging issues of such complex future detectors has been recently developed and tested.
The ASIC, named Timespot1, features a 32x32 channels hybrid-pixel matrix and integrates one analogue front-end, one discriminator and one high-resolution time-to-digital converter per pixel. The system aims to achieve a timing resolution of 30 ps or better at a maximum event rate of 3-MHz per channel with a Data-Driven interface. Power consumption can be programmed to range between 1.2W/cm2 and 2.6 W/cm2.
The present paper intends to deal with the different technological aspects in the challenge for 4D pixels. It will report and discuss on recent studies describing a full set of experimental requirements for 4D tracking. It will also illustrate the experience and the results gained in the design and tests of the Timespot1 ASIC. Other ongoing and possible developments will also be addressed.

Speaker: Adriano Lai (Universita e INFN, Cagliari (IT))

iworid2022_20ps4D_ALai.pdf

103 A Silicon Vertex Detector with Timing for the Upgrade II of LHCb

LHCb has recently submitted a physics case for an Upgrade II detector to begin operation in 2031. The upcoming upgrade is designed to run at instantaneous luminosities of $1.5\times10^{34}cm^{−2}s^{−1}$, to accumulate a sample of more than 300 fb$^{−1}$. The LHCb physics programme relies on an efficient and precise vertex detector (VELO). Compared to Upgrade I, the data output rates, radiation levels and occupancies will be O(10) higher To cope with the pile-up increase, new techniques to assign b hadrons to their origin primary vertex, and to perform the real time pattern recognition, are needed. To solve these problems a new 4D hybrid pixel detector with enhanced rate and timing capabilities in the ASIC and sensor will be developed. This presentation will discuss the most promising technologies to be used in the future upgrade for the HL-LHC, with emphasis on the timing precision as a tool for vertexing in the next generation detectors. The most recent results from beam tests motivated by time measurements will be presented together with the R\& D scenarios for the future upgrade. Improvements in the mechanical design of the Upgrade II VELO will also be needed to allow for periodic module replacement. The design will be further optimised to minimise the material before the first measured point on a track and to achieve a fully integrated module design with thinned sensors and ASICs combined with a lightweight cooling solution.

Speaker: Jakob Haimberger (Technische Universitaet Wien (AT))

A Silicon Vertex Detector with Timing for the.pdf

104 ATLAS ITk Pixel Detector Overview

In the high-luminosity era of the Large Hadron Collider, the instantaneous luminosity is expected to reach unprecedented values, resulting in up to 200 proton-proton interactions in a typical bunch crossing. To cope with the resulting increase in occupancy, bandwidth and radiation damage, the ATLAS Inner Detector will be replaced by an all-silicon system, the Inner Tracker (ITk). The innermost part of the ITk will consist of a pixel detector, with an active area of about 14m2. To deal with the changing requirements in terms of radiation hardness, power dissipation and production yield, several silicon sensor technologies will be employed in the five barrel and endcap layers. Prototype modules assembled with RD53A readout chips are being built to evaluate their production rate, thermal and electrical performance before and after irradiation. In addition, the new powering scheme – serial – will be employed in the ITk pixel detector, which will help to reduce the material budget of the detector as well as power dissipation. Multiple system-level tests are done with serial powering of pixel modules. This contribution presents the latest development of prototype modules, serial powering tests, and procedures of integration of modules and electrical services.

Speaker: Andreas Lokken Heggelund (University of Oslo (NO))

Iworid_ITk_overview_v4.pdf

105 The CMS Pixel Detector for the High Luminosity LHC

The LHC machine will be upgraded to increase its peak luminosity ( $5-7.5x10^{34} cm^{-2}s^{-1}$) and to possibly reach an integrated luminosity of $3000-4000\;$fb$^{-1}$, with an average number of pileup events of 140-200. The CMS experiment is called for an upgrade to keep up with the new challenges such as unprecedented radiation environment, bringing to high resilience needs, and increased number of events per bunch crossing, requiring higher detector granularity. Thus a completely new Inner Tracker will be installed: design choices for the Inner Tracker Phase-2 upgrade, highlighting R&D activities and technological approaches, will be presented.

Speaker: Antonio Cassese (INFN, Firenze (IT))

Cassese_CMS_Tracker_Upgrade.pdf

106 First results of the newly installed, MAPS based, ALICE Inner Tracking System

During the second long shutdown of the LHC, the ALICE Inner Tracking System (ITS) has been replaced with a full-pixel detector entirely built with CMOS monolithic active pixel sensors (ITS2). 

The ITS2 consists of three inner layers with 50 um thick sensors and four outer layers with 100 um thick sensors. The entire tracker covers 10 m^2 and includes approximately 12.5 billion pixels with a single pixel size of 27 um x 29 um. 

Its increased granularity, the very low material budget (0.35% X0 for each of the three innermost layers) as well as the small radius of the innermost layer combined with a thin beam pipe, will result in a significant improvement of impact-parameter resolution and tracking efficiency at low pT with respect to the previous tracker. 
The assembly of the full detector and services, completed in December 2019, was followed by a comprehensive on-surface commissioning campaign. The detector has been installed in the experiment in the first half of 2021. After further in-situ commissioning, both standalone and integrated with the entire ALICE experiment, the detector has seen first collisions during LHC pilot beam tests. 

In this talk, results from the ITS2 commissioning with and without beam will be presented. This includes results from full detector calibration measurements, like threshold and noise performance, and from cosmic tracks and collisions, which will give a first measurement of the detector efficiency and spatial resolution.

Speaker: Prof. Stefania Maria Beole (Universita e INFN Torino (IT))

Beole_finale.pdf

10:20 Coffee break

Applications: 3

Convener: renata longo (University of Trieste & INFN)

107 INVITED: Photon-counting CT with edge-on silicon

Photon counting detectors can enable increased spatial resolution and improved contrast and/or lower radiation dose. In particular, lower concentrations of iodine can potentially be detected and quantified, which is important in angiography or perfusion imaging. Moreover, beam hardening artefacts will disappear with material base decomposition in the projection domain. Electronic noise can be eliminated by using a minimum energy threshold that exceeds the electronic noise level, which helps with imaging of large patients and enables reduced radiation dose compared to what is possible today. So called “deep silicon” has emerged as an alternative to high Z cadmium-based compounds such as CdTe and CZT. The maturity and availability of silicon is an attractive advantage and with an edge-on geometry a high detection efficiency can be achieved. Compton interaction in the silicon can be detected as photon counts and the scattered photons is absorbed in W-foils interleaved between the silicon sensors. Moreover, the silicon sensors can be divided in depth to decrease the input x-ray flux and together with high charge carrier mobility in silicon for both electrons and holes this results in a robust x-ray sensor with low pile-up even for the high x-ray flux encountered in CT.

Speakers: Mats Danielsson, Mats Danielsson (KTH)

raddiationdetectors20220629_pub.pdf

108 Integration mode proton imaging with pixelated large-area CMOS sensor

A novel irradiation platform for pre-clinical proton therapy studies foresees proton imaging for positioning and accurate treatment planning [1]. While proton imaging at synchrocyclotron-based proton therapy centers is challenging in single particle tracking mode due to high instantaneous particle fluxes, it is feasible in integration mode. Large-area CMOS sensors allow the determination of a small-animal sized object’s water-equivalent thickness (WET) by variation of the incoming proton beam energy (here called probing energy). Previous work has shown the feasibility of such proton imaging for preclinical studies. We present results from proton radiography experiments at two proton therapy centers with a CMOS detector.

Image contrast is achieved by recording the proton energy deposition in the detector pixels for several probing energies and applying a signal decomposition method to retrieve the WET. Proton imaging of a micro-CT calibration phantom was performed by placing the 12×14 cm² CMOS sensor Lassena (Nordson, Ohio, USA) with 50μm pixel pitch behind it to acquire up to 2000 frames with 60ms integration time in each frame. Experiments were performed at the Danish Centre for Particle Therapy (DCPT, Aarhus, Denmark) and the Centre Antoine-Lacassagne (CAL, Nice, France) with automated energy switching to generate the probing energies suitable for small-animal sized objects.
To assess WET accuracy, a micro-CT calibration phantom (SmART scientific solutions, Maastricht, The Netherlands) with 10 inserts of tissue-mimicking materials was imaged. The phantom-to-detector distance was varied to be 0 cm, 1 cm, 2 cm and 3 cm at DCPT and 0 cm for the proof of feasibility at CAL in order to determine the influence of the air gap on the measurement quality. Calibration measurements were done with PMMA plates of 5 mm, 10 mm and 20 mm for the experiments at DCPT and 10 mm at CAL, all of which the WET was measured with the peakfinder (PTW, Freiburg, Germany). FLUKA Monte Carlo simulations were used to complement the lookup-table that will be used to determine the WET for each pixel with a linear signal decomposition [2].

Proton radiographs obtained with the beam from the isochronous synchrotron at DCPT reached an average relative WET error of 1% for 0 cm phantom-detector distance and 1.5% for 1 cm and a spatial resolution of 0.2 mm and 0.4 mm, respectively. For larger phantom-detector distances, proton scattering considerably impacts the spatial resolution so that WET determination gives 10% and 25% relative WET error.
Imaging time for one radiograph was 45s and dose below 2 cGy.
At the synchrocyclotron facility, results prove feasibility of integration mode proton radiography at high particle flux and give 0.2 mm spatial resolution without air gap. Detailed data analysis is ongoing and final results will be presented.

This study demonstrates that proton radiographs with promising WET accuracy and spatial resolution are achievable at isochronous cyclotron and synchrocyclotron with the compact setup including the new Lassena detector.

[1] Parodi, K. et al., Acta Oncologica. 58(10) (2019), 1470–1475
[2] Meyer et al., PMB. 62(2017), 1096-1112

This project is supported by European Research Council (SIRMIO, Grant 725539), BayFrance (Grant FK312019) and the European Union’s H2020 Research and Innovation Programme INSPIRE (Grant 730983). The authors would like to thank Michael Allum, Tim Edwards, Jonathan Jacobs-Headspith and David Reynolds from Nordson for their support with the Lassena detector.

Speaker: Ms Katrin Schnürle (Ludwig-Maximilians-Universität München, München, Germany)

20220323_Schnuerle_IWORID_V0_comp.pptx

109 In-vivo patient treatment verification with in-beam PET at the National Center for Oncological Hadron-therapy: inter-fractional data analysis using the gamma evaluation method

Background and purpose: In-beam Positron Emission Tomography (PET) is one of the modalities that can be used for in-vivo non-invasive treatment monitoring in proton therapy. The INSIDE system, installed at the National Center of Oncological Hadron therapy (CNAO), has acquired in-beam PET data during several patient proton therapy treatments. Despite the fact that PET treatment monitoring has been applied in several treatment centers, there is still no straightforward method to translate the acquired images into easy to interpret information for clinical personnel. The purpose of this work is to apply the gamma evaluation method, mostly used to compare dose distributions, to in-beam PET images to identify regions where morphological changes occur in patients.

Methods: For our study we first simulated a series of PET data of a patient, that gradually changed during the treatment course, using the FLUKA Monte Carlo code. We studied how the PET signal changed and performed the 3d-gamma evaluation method to compare the PET images with a reference image without changes. Then we applied the 3d-gamma evaluation method to real PET data, acquired with the INSIDE system during the treatment of eight patients. The results of the gamma analysis were compared to the CT scan.

Results and conclusions: For the simulated patient, we found that it was clearly possible to locate the anatomical changes with the gamma evaluation method (Figure 1). Regarding the real data, despite the image artefacts typically present in in-beam PET images and the limited statistics, we found that it was possible to identify variations in patients.

In this presentation we show the most recent results of the gamma analysis applied to in-beam PET data analysis of simulated data, and a selection of new results obtained for real patient in-beam PET imaging data will be presented.

Speaker: Aafke Christine Kraan (Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, Pisa, Italy)

20220629_iWoridINSIDE_final_compressed.pdf

110 TimePix detector for mixed radiation field characterization in particle therapy

Proton and ion beams are commonly used worldwide for radiation therapy, offering advantageous dose distribution and increased relative biological effectiveness (RBE) compared to photons. While the RBE is assumed to vary with linear energy transfer (LET) of particles, currently only the constant RBE is taken into account in treatment planning due to a lack of tools for its experimental validation. Here, we present an approach for experimental characterization of proton LET using pixel semiconductor TimePix detectors aiming at advancing RBE modeling in proton therapy.
Extensive measurements (>300) were performed in a gantry treatment room of Krakow proton therapy facility with pencil beams of various energies. A compact TimePix MiniPIX detector was protected by a waterproof cover and placed inside a water phantom (Figure 1. a, b). The unique TimePix capability of individual particle tracking and energy deposition measurement allowed distinguishing protons from other particles using a convolutional neural network and computing their LET. Corresponding GATE/Geant4 Monte Carlo simulations were performed for comparison with experimental data.
The deep-learning particle identification model was trained using the homogeneous data sets and then used for proton identification with an accuracy over 90%. Figure. 1. c shows the LET spectrum of protons for a 150 MeV proton pencil beam, at the depth of Bragg peak in water, and 45 mm away from the beam axis. The measured dose-averaged LET of protons is 5.8 keV/μm, while for simulation results it is 5.3 keV/μm. What is also important, a wide range of proton LET values in mixed radiation fields causes different complexity of DNA damage. In general, we obtained a good agreement comparing measured and simulated LET spectra and dose-averaged LET of protons.
Any LET-based variable RBE model, to be applied in the clinical routine of treatment planning, requires accurate simulation and measurement methods for validation and quality assurance. Presented results demonstrate the ability of commercially available TimePix detectors, enhanced by artificial intelligence, for wide-range event-by-event characterization of mixed radiation field and LET measurements in proton radiation therapy. Our simple and accessible methodology can be applied in any proton radiation therapy facility.

Speaker: Ms Paulina Stasica (Institute of Nuclear Physics Polish Academy of Sciences, Krakow, Poland)

Stasica-IWORID2022.pdf

111 A proton Computed Tomography scanner for biological phantoms imaging

To study the 'proton Computed Tomography' (pCT) technique the INFN-Prima collaboration has built and successfully tested a 20x5cm2 field of view system based on a silicon microstrip tracker and a YAG:Ce scintillating calorimeter. This apparatus has demonstrated the feasibility of the pCT for objects with size suitable for pre-clinical studies [1]. Recently a possible clinical application of the proton tomography apparatus (INFN XpCalib project), has been proposed to explore the possibility of a new method for x-ray computed tomography (CT) calibration using pCT data. This methodology aims at a more accurate conversion of CT Hounsfield Units into proton stopping power ratio relative to water (SPR) to be used in proton-therapy treatment planning to eventually reduce the uncertainties in proton range evaluation [2]. In this respect the use of biological phantom, is of particular importance due to the fact that plastic tissue substitutes, that are presently used in clinical practice, are not always accurate in mimicking biological samples. To accomplish this goal a set of formalin stabilized phantoms has been prepared and tested under a 200 MeV proton beam at the experimental area of the Trento proton therapy center. An example of tomographic image of a bovine stabilized phantom is shown in Figure 1.
In this contribution a detailed description of the apparatus, together with the data analysis procedure, will be presented with a particular focus on the calorimeter energy calibration. This last aspect is of paramount importance in the accuracy of the SPR measurements and consequently on the precision of the proton treatment plans. Moreover, the XpCalib project will be introduced and the tomographic images of biological phantoms will be shown.

[1] C. Civinini et al., ‘Relative stopping power measurements and prosthesis artifacts reduction in proton CT’ Phys. Med. Biol. 65 (2020) 225012;
[2] P. Farace et al., ‘Technical Note: CT calibration for proton treatment planning by cross-calibration with proton CT’ Med. Phys. 48 (3), (2021), 1349-1355;

The authors acknowledge funding from the INFN-CSN5.

Speaker: Monica Scaringella (INFN Florence)

Scaringella_IWORID_2022.pdf

12:40 Lunch break

Sensors: 3

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

112 INVITED: Optimization of planar silicon sensors and LGADs for soft X-ray detection

Soft X-ray applications at synchrotrons and FELs are limited by the performance of the currently available detectors using silicon sensors. The main issues are their low quantum efficiency (QE) due to the photon absorption in the entrance window of the sensor, and their difficulties in achieving single photon resolution, since the small amount of charge generated by the low energy X-rays is often comparable to the electronic noise charge. At present, the hybrid X-ray detectors are the technology widely used for hard X-ray experiments thanks to their high frame rate, fast readout, large dynamic range, large sensitive area, stability and robustness. Further development of the hybrid X-ray detectors with equivalent performance in the soft X-ray energy range would be beneficial for several diffraction, spectro-microscopy and imaging experiments which have to be performed at low energies due to the low interaction of the sample with the radiation or to the presence of characteristic edges interesting for research.

In collaboration with the sensor manufacturer FBK, we are developing and optimizing the LGAD sensor technology as well as the thin entrance window technology targeting soft X-rays. The thin entrance window technology enables the improvement of QE for the soft X-rays and the LGAD technology increases the signal amplitude and signal-to-noise (SNR) ratio and thus it makes single photon resolution possible in this energy regime.

In this talk, the challenges and progress of the development will be introduced. The optimization strategies will be discussed. In addition, first results on the QE and single photon detection of soft X-rays will be reported.

Speakers: J Zhang (Paul Scherrer Institut), Jiaguo Zhang (Paul Scherrer Institut)

iWoRID2022_SoftXrays_LGADs_JZhang_V1.1_upload.pdf

113 MONOLITH - picosecond time stamping capabilities in fully monolithic highly granular silicon pixel detectors

The MONOLITH ERC Advanced project aims at producing a monolithic silicon pixel ASIC with picosecond-level time stamping by using fast SiGe BiCMOS electronics and a novel sensor concept, the Picosecond Avalanche Detector (PicoAD).
The PicoAD uses a multi-PN junction to engineer the electric field and produce a continuous gain layer deep in the sensor volume. The result is an ultra-fast current signal with low intrinsic jitter in a full fill factor highly granular monolithic detector.
A proof-of-concept ASIC prototype confirms that the PicoAD principle works according to simulations. Testbeam measurements show that the prototype is fully efficient and achieves time resolutions down to 18ps.

Speaker: Stefano Zambito (CERN)

Zambito_Monolith_iWoRiD2022.pdf

114 Exploration of the TPSCo 65 nm CMOS imaging process for building wafer-scale, thin and flexible detection layers for the ALICE Inner Tracking System upgrade (ITS3)

The ALICE experiment is planning next upgrade of the Inner Tracking System (ITS3) during the LHC Long Shutdown 3 (LS3) in 2025 – 2028. The main aim of this upgrade is to reduce material budget of the three innermost layers from 0.3% X$_0$ to 0.05% X$_0$ per layer. Such a significant improvement is within the reach if segmented layers of the current detector would be replaced with truly cylindrical layers made of wafer-scale, thin and flexible stitched CMOS pixel sensors.

The 65 nm CMOS imaging process by Tower Partners Semiconductor Company (TPSCo) provides stitching of 300 mm wafers allowing to produce CMOS pixel sensors as large as ~27×9 cm2. After thinning to 50 µm or below each sensor can be bent to a radius as low as 18 mm to form a half of the cylindrical detection layer. Therefore, six stitched sensors are sufficient to construct three new innermost layers made essentially of only thin silicon.

In order to start the exploration of the TPSCo 65 nm CMOS process the first test production run (MLR1) was submitted in 2021. Among multiple test structures and prototype circuits included in MLR1 the following three sensor types were specifically designed to evaluate the charged particle detection performance of the technology. Analogue Pixel Test Structure (APTS) chips are the simplest ones: they feature 4×4 pixel matrix with fast analogue readout of each pixel individually. CE65 chips have larger matrix of 64×32 pixels with rolling shutter analogue readout. Finally, Digital Pixel Test Structure (DPTS) chips have 32×32 pixel matrix with one channel digital readout.

The present contribution will cover the results of performance measurements of APTS, CE65 and DPTS chips obtained in the laboratory and with particle beams in 2021 and 2022. Finally, the outlook for the next submissions towards the final sensor will be given.

Speaker: Serhiy Senyukov (Centre National de la Recherche Scientifique (FR))

Exploration of the TPSCo 65 nm CMOS imaging process - Senyukov - IWORID22.pdf

115 ARCADIA MAPS process qualification through the electrical characterization of passive pixel arrays

In the last two decades several collaborations have been involved with the development of novel Monolithic Active Pixel Sensors (MAPS) technologies [1-2]. The ARCADIA project aims at the design of fully depleted MAPS for HEP, medical, space and X-ray detection applications, that can be produced with a commercial 110nm CMOS production process. Passive pixel arrays have been included in the test structures of the first two engineering runs of the project to evaluate the feasibility and the characteristics of pixels with different pixel pitch and layout. Electrical measurements, namely IV and CV curves, have been used to evaluate the main characteristics of the produced devices in terms of dark current, depletion voltage, punch through current and pixel capacitance, which were rated against the results of TCAD simulations. In particular, we took the dips in the pixels and pwell currents as a reference for the extraction of the full depletion and punch-through voltages, that represent the limits of the operating voltage range. We extracted groups of four samples from specific positions within each wafer and we characterized them from the electrical point of view to obtain information on the variability in the operating voltage range and in the pixel capacitance, reflecting variations in the production process. At the workshop, we will present the results of the characterization of samples extracted from wafers produced in both engineering runs with an active, fully depleted thickness of 48, 100 and 200 μm. The sensors functionality has been confirmed for all the wafers, and the observed intra-wafer and inter-wafer non-uniformities are in line with the expected variability of process parameters. CV curves confirm that, once the full depletion is reached, the main contribution to the pixel capacitance is due to the sensor perimeter, and thus devices with different thicknesses show similar capacitance.

[1] Mager M. ALPIDE, the Monolithic Active Pixel Sensor for the ALICE ITS upgrade. NIM-A 824 (2016) 434–438.
[2] Pernegger H., et al. First tests of a novel radiation hard CMOS sensor process for Depleted Monolithic Active Pixel Sensors. JINST 12 (2017) P06008.

The authors acknowledge funding from the Istituto Nazionale di Fisica Nucleare, CSN5 (ARCADIA project).

Speaker: Thomas Corradino

Corradino_IWORID_2022_ARCADIA.pdf

Corradino_IWORID_2022_ARCADIA.pptx

116 First characterization results of ARCADIA FD-MAPS after x-ray irradiation

The ARCADIA collaboration is developing fully-depleted (FD) Monolithic Active Pixel Sensors (MAPS) in a 110nm CMOS process in collaboration with LFoundry. The sensor design incorporates an n+ collection node within a highly doped n-type epi-layer on top of a n-type substrate and p+ backside. Thus, the pn-junction sits on the backside and through an applied backside bias, the full substrate gets depleted. The targeted applications of this technology range from future high energy experiments to space applications, and medical and industrial scanners. Together, these applications set the minimum requirements on the detector; data collection at hit rates of (10-100) MHz/cm2, full signal processing within (1-10)us, maximum power consumption (5-20) mW/cm2 and radiation tolerances of up to 50krad or 1x10^11 1MeV neutron equivalence fluence. In order to proof the performance of the technology, a demonstrator chip of 512x512 pixels with 25um pitch was designed and fabricated in a first engineering run in 2021, together with additional test structures of pixel and strip arrays with different pitches and sensor geometries. The production run has successfully produced functioning passive and active pixel matrices. In this contribution we will give an overview of the status of the project and present the main results, before concentrating on the first measurements of passive pixel matrices irradiated using an x-ray tube with a Tungsten anode, up to a dose of 10Mrad (SiO2). The measurements are complemented by TCAD simulations using three different parametrisations of the new Perugia model. The positive oxide charges and traps at the Si-SiO2 interface, introduced by ionizing radiation, have been shown to affect the depletion region around the collection electrode, increasing the pixel capacitance. By varying the gap size between collection node and pwells, the geometry can be optimized to keep the capacitance also low after irradiation. The measured and simulated CV curves, normalised per pixel and corrected for parasitic contributions of metal connections and probe pad, of the ARCADIA pixels with 50m pitch are shown in Figure 1. The capacitances range for different layouts from 10 to 28fF per pixel, after a dose of 1Mrad and an applied Vptop voltage of -0.8V. The simulation results, shown as bands, reproduce the measured data within the errors at Vptop=-0.8V. This agreement validates the choice of geometries based on previous simulation studies and confirms the accuracy and reliability of the TCAD simulation models as a design tool for the next application-specific MAPS in ARCADIA process.

Speaker: Coralie Neubuser (Universita degli Studi di Trento and INFN (IT))

20220629_iWorid_surfDamage.pdf

15:50 Coffee break

Poster: 2

Conveners: Lucio Pancheri (University of Trento and TIFPA-INFN), Nicola Massari (Fondazione Bruno Kessler)

117 ATLAS-ITk strip sensor quality control procedures and testing site qualification

The high luminosity upgrade of the Large Hadron Collider, scheduled to become operational in 2029, requires the replacement of the ATLAS Inner Detector with a new all-silicon Inner Tracker (ITk). Radiation hard n+-in-p micro-strip silicon sensors were developed by the ATLAS ITk strip collaboration and are produced by Hamamatsu Photonics K.K. Production of the total amount of 22 000 ITk strip sensors has started in 2020 and will continue until 2025. The ATLAS ITk strip sensor collaboration has the responsibility to monitor the quality of the fabricated devices by performing detailed measurements of individual sensor characteristics and by comparing the obtained results with the on-site tests done by the manufacturer. Dedicated Quality Control (QC) procedures were developed to check whether the delivered large-format sensors adhere to the ATLAS specifications.

Although most of the ATLAS institutes have extensive experience with sensor studies and measurements, the institutes performing the QC testing of the pre-production and production ATLAS ITk strip sensors (QC sites) had to initially be qualified for multiple high-throughput tests by successfully completing a two-step Site Qualification Process. In the first step, the QC sites had to show that the necessary infrastructure for all required test operations was in place. In the second step, the capability of properly performing all QC test procedures on prototype sensors had to be demonstrated. To cross-check the results obtained by individual QC sites, reference samples with identified defects were exchanged among the participating sites and their results were compared. Excellent agreement was achieved among the participating QC sites that matched well the data provided by the manufacturer. Finally, the QC sites had to demonstrate safe handling procedures of the delivered sensors as well as the ability to correctly process the data, including uploading into the ITk Production Database.

The qualification process lasted less than a year, in spite of COVID slow-down. All seven QC sites went successfully through this process and were fully qualified in June 2021. Moreover, most of the QC tests achieved sensor testing throughputs that were already at the level required during the sensor production deliveries, which started in August 2021.

Speaker: Marcela Mikestikova (Czech Academy of Sciences (CZ))

118 A Study on Changes in Detection Sensitivity of Indirect X-ray Detector by Adjusting 2D Nanoplatelet Aspect Ratio

In this study, we evaluated an indirect X-ray detector having an organic active layer blended with two-dimensional (2D) cadmium selenide (CdSe) nanoplatelets (NPLs). Figure 1 shows the active layer was composed of poly[N-90-heptadecanyl-,7-carbazole-alt-5,5-(40,70-di-2-thienyl-20,10,30-benzothiadiazo-le)] (PCDTBT), phenyl-C71-butyric acid methyl ester (PC71BM), and CdSe NPLs. The PCDTBT and PC71BM formed an organic bulk-heterojunction. Nanocrystals (NCs) refer to small crystals having a range of nanometer sizes of at least one dimension. In particular, the 2D NPLs used in our experiment have the advantage of reducing the Auger recombination loss and enhancing charge carrier extraction by applying the quantum confinement effect in one direction [1]. Moreover, the CdSe NPLs can easily adjust the aspect ratio by changing the blending ratio of precursors and changing the aspect ratio can affect the optical and electrical characteristics. The PCDTBT:PC71BM solution was prepared in ratio of 1:4, and CdSe NPLs with different aspect ratios (6:1, 1:1 and 3:1 as shown in Figure 2(b)) were added. Figure 2 (a) shows the trend of X-ray detector parameters, such as Jsc, CCD – DCD and sensitivity, according to 2D NPLs blending effect. In the case of aspect ratio = 1:1 NPLs, the sensitivity showed 2.34 mA/Gy∙cm2, which was increased by 15.3% compared to the pristine PCDTBT:PC71BM detector. The 2D NPLs added to the organic active layer enhanced the sensitivity by promoting carrier generation and transport.

Speaker: Mr Kwanyong Lee (Department of Electronic and Electrical Engineering, Dankook University, Yongin 16890, Republic of Korea)

119 Design abd Development of Gd2O2STb phosphor compound coupled Lead iodide photo dosimeter for gamma-ray detecting

In general, superior spatial resolution is expected from the direct detection type, in which Ion-chamber-type detectors and Si diodes based on the radiation–ionization phenomenon are used for high-energy dose detection. However, because the ion chamber has a high work function, the speed for collecting electrons and holes is slow, and thus, the dose-detection characteristic deteriorates. In addition, because of the low electron–ion-pair detection rates in ionization chambers, signal detection may decrease in response to the temporal changes during the continuous detection of high-energy radiation, resulting in a possible decrease in the reproducibility and sensitivity to signals. In this paper, the thin coplanar lead iodide(PbI_2)films as a photosensitive converter requiring only a few tens of volts of bias, associated with a thick columnar coating of phosphor layer, were simulated and designed. PbI_2, which was used in this study, is a very important material with technological applicability as a room-temperature radiation detector. It is a wide-band-gap semiconductor (Eg > 2.0 eV) with a high environmental stability efficiency[1]. In this structure, gamma rays are converted into visible light on a thick Gd_2O_2S:Tb phosphor layer which is then converted to electric charges in a thin PbI_2 layer. The electron-hole pairs can also be generated from gamma-ray interaction in the PbI2 photoconductor, which can improve the generation efficiency of electric charges. To optimize the thickness of the phosphor coupled PbI_2 multilayer structure in range of iridium-192 gamma ray energy, the gamma-ray absorption was estimated using the MCNPX code. In addition, the photoluminescence and electrical measurements of phosphor coupled PbI_2 dosimeter were evaluated. From the experimental results, the 180 μm Gd_2O_2S:Tb coupled 10 μm - PbI2 dosimeter proposed in this work exhibited a low dark current and excellent gamma-ray sensitivity, and in particular, excellent linearity to x-ray exposure dose. The measured dark currents were below 100 pA/cm2 at an electric field of 1 V/μm for PbI_2. The preliminary sensitivity measurements give a signal in the range of about 12.6 and 4.2 nC/cm^2 for 250μm Gd_2O_2S:Tb / PbI_2 and 250 μm PbI_2 at the exposure conditions respectively. The results of this research suggest that the new coplanar gamma -ray dosimeter with a hybrid-type structure can resolve the following problems: high sensitivity from the conventional dosimeter, and low conversion efficiency from the indirect conversion method.

This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education(NRF-2020R1I1A1A01074908)

[1] R. Ahuja et al., Electronic and optical properties of lead iodide, J. Appl. Phys. 92(12) (2012) 7219-7224.

Speakers: YEJI HEO (Department of Radiation Oncology, Busan Paik Hospital), Mr Seung Woo Yang (Department of Radiation Oncology, Busan Paik Hospital, Inje University)

Design and Development of Gd2O2STb phosphor compound coupled Lead iodide photo dosimeter for gamma-ray detecting.pdf

120 Long-drift position-sensitive virtual Frisch-grid CdZnTe detectors for gamma ray imaging and spectroscopy

Long-drift position-sensitive virtual Frisch-grid CdZnTe detectors for gamma ray imaging and spectroscopy

A. Bolotnikov1,*, G. Carini1, A. Dellapenna1, J. Fried1, G. Deptuch1, J. Haupt1, S. Herrmann1,
A. Moiseev2, G. Pinarolia1 M. Sasaki2, L. Smith2, E. Yates2

1. Brookhaven National Laboratory, Upton, NY 11793, USA
2. CRESST/NASA/GSFC and University of Maryland, College Park, MD 20771, USA
3. Corresponding author, bolotnik@bnl.gov

Arrays of 3D position-sensitive virtual Frisch-grid (VFG) CdZnTe (CZT) detectors are very attractive for spectroscopy and imaging of gamma-rays in many fields including space and nuclear security applications [1]. The long electron lifetime in today’s CZT crystals allows for making practical CZT drift detectors with a drift length up to 30-40 mm. Here, we report on the results from testing of position-sensitive bar-shaped detectors with length up to 32 mm and cross-sections up to 10x10 mm2 and the arrays prototype that have been considered for the two future gamma-ray telescopes, AMEGO and GECCO [2]. The VFG arrays allow for the flexibility to scale-up the dimensions of the detectors for the desired instrument dimensions and efficiency, while the position information along with precise energy measurement make them usable as Compton telescope. Also, position resolution allows for correcting the detectors’ response non-uniformity caused by crystal defects and devices geometry, thereby reducing the instrument cost, and making them more feasible for emerging applications in gamma-ray astronomy, nonproliferation, portal screening and nuclear safeguards, where large detector arrays are often required.
We report on the results from testing 6x6x20 mm3 and 8x8x32 fabricated from recently available large volume CZT crystals developed by Redlen Technologies, Inc. The cross-section areas and thicknesses are much greater than those previously used in conventional VFG detectors. The VFG detector design was found to provide economical fabrication and the flexibility to extend the dimensions of the crystals for producing more efficient detection, while correcting the detector response non-uniformity, thereby offering an approach to overcome one of the principal technological barriers limiting the application of CZT detectors. The readout system allowed us to capture the signals from individual cathodes, anodes and pads. To calculate the normalized X and Y coordinates, we used the center of gravity method. For the Z coordinate we used the C/A ratio. As we described it previously [3], this approximation is sufficient to for correcting the response non-uniformity. The measured XYZ values constitute a configuration space, which correlates to the spatial variations in the measured anode signals. Fig. 1 shows 8x8x32 mm3 position sensitive virtual Frisch-grid detector and 4x4 array prototypes.

[1] A. E. Bolotnikov, G. S. Camarda, E. Chen, S. Cheng, Y. Cui, R Gul, R. Gallagher, V. Dedic, G. De Geronimo, L. Ocampo Giraldo, J. Fried, A. Hossain, J. M. MacKenzie, P. Sellin, S. Taherion, E. Vernon, G. Yang, U. El-hanany and R. B. James, “CdZnTe Position-Sensitive Drift Detectors with Thicknesses Up to 5 cm”, Appl. Phys. Lett. 108, p. 093504 (2016).
[2] A. A. Moiseev et al., A new mission concept: Galactic Explorer with a Coded Aperture Mask Compton Telescope (GECCO), 2021 International Cosmic Ray Conference (Berlin, 2021), PoS (ICRC2021) 648.
[3] L. Ocampo Giraldo, A. E. Bolotnikov, G.S. Camarda, S. Cheng, G. De Geronimo, A. McGilloway, J. Fried, D. Hodges, A. Hossain, K. Ünlü, M. Petryk, V. Vidal, E. Vernon, G. Yang, R. B. James, "Arrays of Position-Sensitive Virtual Frisch-Grid CdZnTe Detectors: Results From a 4x4 Array Prototype," in IEEE Transactions on Nuclear Science, vol. 64, no. 10, pp. 2698-2705, Oct. 2017.

The authors acknowledge support from the U. S. Department of Energy, Office of Defense Nuclear Nonproliferation Research & Development (DNN R&D), and BNL’s Technology Maturation Award. The manuscript has been authored by Brookhaven Science Associates, LLC under Contract No. DE-SC0012704 with the U. S. Department of Energy. The efforts of A. Moiseev and M. Sasaki are supported by NASA awards 80GSFC21M0002 and 80NSSC20K057. The efforts of E. Yates and L. Smith are supported by NASA award 80NSSC20K057

Speaker: Giovanni Pinaroli (Brookhaven National Laboratory)

121 Radiation spectrometer HardPix for Lunar Gateway

IEAP CTU developed miniaturized Timepix-based radiation environment monitors onboard ISS and numerous satellite missions. For example, SATRAM onboard ESA Proba-V satellite is characterizing radiation environment in LEO for 9 years. The new generation of our radiation monitors HardPix is equipped with the newest Timepix3 and Timepix2 pixelated chips developed within the CERN Medipix collaboration and with onboard processing which substantially reduces the data transfer from the detector. HardPix is capable of identifying the particle species and measuring their energetic spectra together with the total ionizing dose in orbit, providing vital data about the radiation environment and risks for both humans and the equipment. Two HardPix units will be part of the ERSA onboard Lunar Gateway orbital station, a European suite of experiments monitoring radiation environment in deep space. HardPix spectrometers will provide information for forecasting radiation events and understanding how to build better spacecraft and protection for astronauts on and around the Moon, as well as other deep space environments such as on the way to Mars.

Speaker: Robert Filgas (Czech Technical University in Prague)

122 Characterization Analysis of Benign or Malignant Microcalcifications Using Dual-Energy Imaging

The purpose of this study is to distinguish and characterize breast microcalcification types (benign and malignant) non-invasively using a mass ratio based on the dual-energy method. In this study, a photon-counting spectral mammography system was simulated and dual-energy images were acquired using two energy bins. Two types of microcalcification were embedded in the breast phantom. Calcium oxalate (CO, CaC2O4) and calcium hydroxyapatite (HA, Ca5(PO4)3(OH)) were used for benign and malignant microcalcifications, respectively. As a quantitative characteristic evaluation for two types of microcalcification related to etiology, an analytical model was implemented for the determination of the Calcium/Phosphorus mass ratio (mCa/mP) based on the dual-energy method. In the chemical composition of each microcalcification, the calcium hydroxyapatite has a phosphate substance, and calcium oxalate has an oxalate substance. Because unknown microcalcification types should be characterized by attenuation intensity measurements, the calculation of mCa/mP uses linear attenuation coefficients of PO4 for all calcification types. The thicknesses of the CO corresponding to HA were calculated to preserve equal photon beam attenuation (Figure 1, Table 1). Figure 2 (a) shows the variation in the mass ratio of each microcalcification and indicates a higher mass ratio value in malignant microcalcification compared to benign. In these results, because the benign microcalcification used thicker, the difference in mass ratio calculated at the same thickness will be greater. Figure 2 (b) shows the comparison of the mass ratio of HA and CO according to breast thickness. Although the breast thickness increased to 3, 4, and 5 cm, the difference in mass ratio showed a similar tendency. We demonstrated that it is possible to quantitatively distinguish the two types of microcalcification using a mass ratio based on the dual-energy method. Therefore, we propose a mineral characterization method as a quantitative analysis criterion for non-invasively differentiating between malignant and benign.

Speaker: Dr Hyemi Kim (Wonju Severance Christian Hospital, Yonsei University Wonju College of Medicine)

123 Configuration and X-ray image characterization of a dual-layer based flat panel detector

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 different scintillating screens such as typical CsI, GOS materials. Currently, a large area TFT-based X-ray flat panel detector with low dose and high spatial resolution has been widely utilized for dual energy imaging tasks such as material decomposition.
In this work, we have designed and developed a dual-layer integrated a-Si array panel with high-resolution top layer and high-sensitive bottom layer for medical imaging tasks. A prototype image detector consists of TFT array with a 43cm x 43cm active area with 3072x3072 pixel array and 140um pixel pitch. Different high efficient scintillation model such as columnar CsI:Tl and powder type Gd2O2S:Tb(GOS) with various thickness and spectral middle filter were used to investigate the imaging characterization. The used scintillator’s configuration parameters were selected and tested for excellent image quality at low X-ray dose condition.
For evaluation and optimization of the dual-layer X-ray detector structure, different scintillating screen materials were directly coupled on the prototype panel photodiode array. The initial imaging performance such as the detector sensitivity to X-ray exposure dose, signal-to-noise-ratio (SNR) and modulation transfer function (MTF) was measured under practical general imaging systems with 60-120kVp voltage and adjustable tube current. The experimental results with a dual-layer based flat panel detector using different scintillators demonstrated its ability to perform accurate dual-energy radiography and fluoroscopy with single –exposure.

Speaker: Bo Kyung Cha (KERI)

124 ThyroPIX – Mobile Compton camera based on Timepix3 technology for imaging in the field of preclinical and clinical praxis

The preclinical studies and clinical tests are an indispensable part of the research of new drugs and methods for cancer treatment. The emission imaging techniques such as SPECT (Single Photon Emission Computed Tomography and PET (Positron Emission Tomography) belong among these methods, allowing observation of physiological and pathological processes. Each of these techniques require different radioisotope, use of different scintillator cameras and they are based on a totally different principle of detection. SPECT and PET modalities must be used separately for these reasons.

Imaging using a fully spectral single-photon counting detector of new generation based on Timepix3 technology exploits the ability to measure position, energy and time of every detected particle. Thanks to time information related to charge drift speed it is possible to determine the depth of interaction of the primary photon and the scattered photon in one layer of sensitive material. The direction of a primary photon is then calculated and based on the backward reconstruction the source is localized in space. This new concept brings possibilities of emission imaging using a single layer Compton camera for various types of radioisotopes of broad range of energies. This approach leads to the development of an unique multimodality 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 low weight and significantly higher sensitivity.
ThyroPIX is a new generation multimodal device for imaging the thyroid gland and small organs by nuclear medicine methods. The main advantages of the ThyroPIX device are the ability to detect high photon fluxes and display with high spatial resolution. 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.

The presented results were measured using ADVAPIX Timepix3 detectors with CdTe sensor material of thickness 2 mm. This contribution shows the first pilot test using a single layer Compton camera for imaging of the thyroid gland during radiotherapy by 131I in clinical practice as well.

Speaker: Eliska Trojanova

125 3D reconstruction of the positron annihilation position using J-PET modules coupled to an intense positron beam

A dense positronium beam is currently under development at the Anti-Matter Laboratory (AML) of the Department of Physics of the University of Trento. Positronium (Ps) is the bound state of an electron and its antiparticle, the positron (e$^+$). Despite the short lifetime (singlet state, para-, has a lifetime of 125ps, the triplet state, ortho-, of 142ns), Ps atoms are the easiest lab-produced matter-antimatter bound systems. In order to produce the Ps beam, we start with a ${}^{22}$Na radioactive source, which emits positrons in a wide range of energies [1]. Part of these positrons is moderated to a few eV of energy by a solid noble gas film on top of the source [1]. The moderated charged particles are then magnetically velocity selected and transported. Up to now we obtained a continuous beam with up to 50000 positrons per second per millicurie. To produce dense clouds of Ps, the continuous positron beam will be bunched with a buffer-gas Penning trap [2]. The 104 e$^+$ bunches will be accelerated to keV of energy and implanted into silicon target engineered with nanochannels cover in silica, from which the positronium atoms are emitted in vacuum [3]. The positronium so obtained has a short lifetime, for this reason our laboratory already tested a two-photon transition which excite Ps in a metastable state with lifetime of 1.1 µs [4].
Thanks to the longer lifetime, metastable Ps has been suggested as a candidate for inertial sensing measurements on this exotic matter-antimatter system [5]. A proposed measurement scheme requires that metastable Ps bunches cross through a deflectometer composed by a series of grids. The passage of Ps through the deflectometer create a fringe pattern whose vertical displacement is indicative of the external force exerted on the bunch. In order to measure this displacement, it is necessary a 3D reconstruction of the annihilations on the grids [5]. In view of this objective, the Jagiellonian- Positron Emission Tomography (J-PET) [6-7] modular detector has been considered. Each J- PET module is composed by 13 inexpensive plastic scintillator strips [7], permitting a spatial reconstruction of the annihilation points.

In this work, we will present the preliminary results from the test of the J- PET modules on the AML continuous positron beam. The e$^+$ have annihilated on a plane and only two modules have been used to reconstruct their annihilation position. In this configuration, a spatial resolution of a couple of millimetres has been demonstrated. This result shows the applicability of J-PET modules for the construction of a detector for Ps inertial sensing measurements.

[1] A. P. Mills Jr. et al., Appl. Phys. Lett. 49, 1121 (1986)
[2] R. G. Greaves et al., NIM B 192 (2002)
[3] S. Mariazzi et al., Phys. Rev B 105, 115422 (2022)
[4] C. Amsler et al., Phys. Rev. A 99, 033405 (2019)
[5] S. Mariazzi et al., Eur. Phys. J. D 74, 79 (2020)
[6] P. Moskal et al., Science Advances 7 (2021) eabh4394
[7] P. Moskal et al., Nature Communications 12 (2021) 5658
[8] P. Moskal et al., Phys. Med. Biol. 66 (2021) 175015

The authors gratefully acknowledge the support of Q@TN, the joint laboratory of the University of Trento, FBK- Fondazione Bruno Kessler, INFN- National Institute of Nuclear Physics, and CNR- National Research Council; the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement No.754496 – FELLINI; Canaletto project for the Executive Programme for Scientific and Technological Cooperation between Italian Republic and the Republic of Poland 2019-2021. The authors also gratefully acknowledge support from the Foundation for Polish Science through programmes TEAMPOIR.04.04.00-00-4204/17; the National Science Centre of Poland through grant nos. 2019/35/B/ST2/03562; the Ministry of Education and Science through grant no. SPUB/SP/490528/2021; Jagiellonian University through project no. CRP/0641.221.2020.

Speaker: Luca Povolo

Poster_iWoRiD_Garda_5.pdf

126 Assembly and tests of the first TRISTAN detector modules

Sterile neutrinos are a natural extension of the Standard Model of particle physics. If their mass is in the keV range, they are a viable dark matter candidate. One way to search for sterile neutrinos in a laboratory-based experiment is via tritium beta decay. A sterile neutrino with a mass up to 18.6 keV would manifest itself in the decay spectrum as a kink-like distortion. The objective of the TRISTAN project is to extend the KATRIN experiment with a novel multi-pixel silicon drift detector and readout system to search for a keV-scale sterile neutrino signal. To reach a high sensitivity to the sterile neutrino mixing angle the strong activity of the KATRIN tritium source is required. The resulting high electron rate is one of the greatest challenges for the keV sterile neutrino search with KATRIN. It will be approached by distributing the rate among 3500 pixels, resulting in count rates of 100 kcps per pixel. To resolve the kink-like signature of the keV sterile neutrino signal the detector needs to maintain an energy resolution of 300 eV (FWHM) at 20 keV and a low energy threshold. The new detector system is segmented into 21 identical modules, each hosting 166 independent pixels. Each individual pixel is read out independently from each other.
This presentation will give an overview on the current status of the project and show first characterization measurement results obtained with a 166 pixel module.

This project has received funding from the European Research Council (ERC) under the European Union Horizon 2020 research and innovation program (grant agreement no. 852845).

Speakers: Carlo Fiorini (Politecnico di Milano - INFN Milano), Daniel Siegmann (Max Planck Institut for Physics), Frank Edzards (MPP & TUM), Korbinian Urban (TUM), Marco Carminati, Matteo Gugiatti (Politecnico di Milano & INFN), Peter Lechner (MPG HLL), Pietro King (Politecnico di Milano), Susanne Mertens

2022_06_12_IWorID_Poster.pdf

127 Angular sensitivity of 2D phase-sensitive Beam-Tracking X-ray Micro Computed Tomography systems

X-ray phase contrast imaging is a well-established technique for the non-destructive visualization of low-density samples with applications ranging from biomedical to material sciences [1]. Although originally restricted to synchrotron radiation, extensive efforts have been made to adapt interferometric and non-interferometric methods to non-coherent laboratory X-ray sources [2,3], even for CT [4, 5]. This has enabled multi-contrast tomographic reconstructions of the internal structure of an object.
Most of the developed methods are based on phase or attenuation modulators with 1D sensitivity to refraction. Single 2D structures in the form of phase gratings [6], random phase-modulators [7] and absorption masks [8] have become relevant due to their capability for attenuation, differential phase-contrast, and omni-directional scattering retrieval with a single-shot. Among this, the use of single absorption masks, also referred to as Hartmann wave front sensors [9, 10], has shown potential for the translation towards more compact systems, due to its relaxed coherence requirements and achromaticity.
We have implemented a lab-based X-ray Phase Contrast Micro-CT system with a single two-dimensional absorption mask, which allows for complementary phase and attenuation volumetric representations of a sample. The x-ray source is Hamamatsu micro-focus and the amplitude modulator is obtained from readily available Tungsten foil and with laser-ablation.
The system’s working principle is to collimate the beam into a series of periodic beamlets which are resolved by the detector pixels and analyzed independently (see Figure 1). The refraction is retrieved by estimating the sample-induced displacement with a subpixel cross-correlation algorithm, which gives access to two orthogonal phase gradients, allowing a robust and artifact-free phase integration. When used in single shot, the resolution is limited by the mask pitch. However, the system’s resolution is ultimately limited by the mask aperture when using sample or mask dithering.
Due to its beam tracking mechanism, micro-focus X-ray sources or small-pitch detector technologies are often required. Photon-counters exhibit low-electronic noise and high-detection efficiency which leads to considerably lower spill-out of the signal in neighboring pixels compared to indirect conversion detectors, allowing to retrieve smaller refraction angles. However, despite significant progress in the past few years, low count-rate and small field of view are still obstacles to translate these technologies towards clinical systems. In this work, we study the angular sensitivity of the Hartmann wavefront sensor implementation with different radiation imaging detectors: a Pixirad-2/PIXIE-III photon-counter with a 650 μm CdTe sensor and 62 μm pitch, a Medipix 3RX photon-counter with a 500 μm Si sensor and 55 μm pitch, and a Hamamatsu Flat Panel detector with indirect conversion from a CsI scintillator and a CMOS sensor. The sensitivity is studied as a function of the system’s parameters through modeling and experimental measurements. The relative advantages of each detector technology will be discussed and tomographic reconstructions of samples from engineering and biomedical application fields (as shown in Figure 2 for a piglet-derived oesophagus) will be presented.

Speaker: Marco Endrizzi (University College London)

128 Spectral-tracking characterization of mixed-radiation fields with the miniaturized radiation camera MiniPIX Timepix2

The semiconductor pixel detector Timepix2 [1] has been newly implemented in highly integrated readout electronics as a compact and portable detector [2] for radiation imaging and particle tracking. The device has plug-and-play connectivity for flexible measurements of a wide range of radiation fields and applications [2]. Power, control and readout require a single USB 2.0 cable providing online response with the integrated software tool PIXET. The detector is operated and readout in frame mode with data rate up to e.g., 31 fps (ToT 14 bit + ToA 14 bit) and 61 fps (ToT 14 bit). The resulting miniaturized radiation camera (Fig. 1) equipped with the Timepix2 ASIC chip provides extended spectral per-pixel response suitable for measurements of highly interacting (i.e., large energy loss) particles. For such particles Timepix2 makes use of the adaptive gain mode [1] to maintain proportionality in spectrometry measurements such as energy loss, deposited energy distributions and linear-energy-transfer (LET) spectra of ions, fission fragments and low-energy protons and light ions e.g., approaching the Bragg peak.
We evaluate the spectral-tracking response of MiniPIX TPX2 equipped with a 300 µm thick silicon sensor. The detector was energy calibrated per-pixel with discrete X ray and low-energy gamma rays [2]. Tests and spectrometry (energy loss) measurements are performed with well-defined radiation sources in terms of particle type (alpha particles – see Fig. 2, gamma rays, protons), energy (monoenergetic at selected energies, and broad spectrum) and direction (accelerator beam, secondary products from light target experiments). We analyse and describe the Timepix2 response and resolving power for particle-event type discrimination of radiation field components folded in terms of particle type, energy loss and direction [3]. Data products are produced in wide spectral range such as particle fluxes and dose rates (Fig. 3) also characterized in terms of particle-type classes. The results shown indicate the contributions of the main components of the radiation field used (a radionuclide source 241Am) in terms of low-LET particles (X rays, gamma rays, blue data points), high-LET heavy charged particles of low energy and perpendicular direction (PP) (alpha particles, red data points), and doublets of alpha particles resolved by pattern recognition and spectral-tracking analysis of the micro-scale tracks.
Data from well-defined radiation fields such as in-beam measurements of low-intensity accelerator beams are used to construct the detector response matrix for particle-type event discrimination [3]. We apply this technique to provide wide-spectral range LET spectra and composition characterization of unknown and mixed-radiation fields in proton radiotherapy environments using high energy (70 – 225 MeV) protons incident on water-equivalent/PMMA targets.

[1] W Wong et al., Rad. Meas. 131 (2020) 106230
[2] J Jakubek, et al., this Workshop
[3] C. Granja et al., NIM-A 908 (2018) 60-71

Work by C.G. and L.M. performed in frame of 40001250020/18/NL/GLC/hh Contract from the European Space Agency. A.G., P.S. and A.R. acknowledge funding from the National Center for Research and Development (NCBiR), Grant No. LIDER/43/0222/L-12/20/NCBR/2021. Measurements at the IFJ PAN CCB cyclotron are carried out in frame of H-2020 INSPIRE program.

Speaker: Dr Carlos Granja

129 Improvement of double photon emission Compton imaging using polarization correlation in cascade photons.

Double Photon Emission Computed Tomography (DPECT) is an imaging method using radionuclides that emit two cascade photons. It can be applied to ring Compton camera system. Two Compton cones are generated per DPECT coincidence event and the intersection can be taken as system matrix component. It was reported that DPECT in Compton imaging reduces background and improves spatial resolution in Compton camera application.[1] In addition to previous DPECT study using Compton camera, this study utilizes additional properties of cascade photons.[2,3]
Angular correlation is about the angle between the first and the second photons in cascade. 111In was used in this study and 245 keV is the second photon and its polarization shows correlation. Figure 1(a) shows the description of cascade photons. Figure 1(b) shows differential Compton scattering cross section of 245 keV on azimuthal scattering angle in case of 90° angular correlation angle and different polar scattering angles. The information on azimuthal angle dependence has potential to further improve the quality of the image.
Geant4 simulation was conducted to using 111In point source. List-mode Maximum Likelihood Expectation Maximization (MLEM) was used to reconstruct images from double coincidence events. System matrix with polarization information was calculated event by event from theoretical angular and polarization correlation and energy deposition in each detector. The difference between corrected and uncorrected images is shown in Figure 1(c) and (d). Additional details will be reported.

[1] M. Uenomachi, Y. Mizumachi, et. al. Nucl. Instruments Methods Phys. Res. Sect. A Accel. Spectrometers, Detect. Assoc. Equip. 954, 161682 (2020).
[2] D. R. Hamilton, Phys. Rev. 58, 122 (1940).
[3] D. R. Hamilton, Phys. Rev. 74, 782 (1948).

Speaker: Donghwan Kim (The University of Tokyo)

130 Timepix3 based coded aperture camera for X-ray fluorescence surface mapping

X-ray fluorescence surface mapping is a technique that enables non-invasive material identification of selected area on investigated specimen with just single exposure. The sample is excited at once with the primary cone-beam X ray source and fluorescent X-rays emitted from the surface are recorded through coded-aperture with position- and energy-sensitive detector. This approach eliminates the time needed for sample scanning with point-based mapping methods. The coded-apertures, similarly like the polycapillary x-ray optics, provide viable alternative to low efficiency pinhole collimator. This imaging technique originates from astrophysics but lately it has found its use in medical physics, natural and environmental sciences. We would like to extend the usage to the field of cultural heritage by this contribution.

We have used a custom build Timepix3 imaging camera dedicated for the X-ray fluorescence and scattering imaging. The detector is shielded by 4 mm thick tungsten carbide cover to avoid undesirable scattering signal from primary X-ray beam and the detector backplate contains water cooling system for detector temperature stabilization. The coded-aperture collimator is mounted in the modular objective that defines camera field of view. The hybrid pixel detector Timepix3 records full spectroscopic information about each photon in so called data driven mode enabling material identification based on their X-ray fluorescence energy.

The reference measurements were done with 50 and 100 µm large double-cone pinholes. The coded-aperture utilizes no-two-holes-touching (NTHT) pattern based on rank 17 modified uniformly redundant array (MURA). All collimators were laser drilled in tungsten plates. The pattern designs were evaluated by raytracing-based simulation and several reconstruction approaches based on pattern rotation, different deconvolution methods and iterative maximum-likelihood expectation-maximization (MLEM) were tested. Presented results cover both phantom objects measurements and cultural heritage samples.

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

131 Prototype of a module of a Compton camera for online beam range monitoring in proton therapy

The main advantage of proton therapy over conventional radiotherapy is the scheme of dose deposition: unlike X-rays, protons are fully stopped in patient’s tissues with a distinct maximum at the end of their range: the Bragg peak. Such a distribution allows for a precise coverage of a tumor volume while sparing the nearby healthy tissues. However, accurate control of the proton beam range is still considered a challenge. The SiFi-CC (SiPM and scintillation Fiber based Compton Camera) project aims to develop a method of in vivo proton range monitoring with the use of a Compton camera. Such a detector exploits the Compton effect and can register prompt gamma rays produced when protons interact with the nuclei of the tissues. We propose a design which is a trade-off between the camera performance and its cost, dependent on the number of channels. In our approach, both detector modules (scatterer and absorber) will consist of multiple layers of scintillation fibers with dual readout via silicone photomultipliers. The scintillation material and fiber coating were chosen based on an extensive study of the fiber properties [1]. Our simulation studies have shown that such a solution is feasible and appropriate for online range monitoring in proton therapy [2].
I am going to present the idea and overview of the SiFi-CC project and elaborate on the single module prototype of a Compton camera that is already assembled and examined. I will present the results of the prototype performance tests: a comparison of different types of optical coupling, crosstalk effect, position- and energy resolution, along with conclusions for the construction of a full two-module Compton camera detector.

[1] K. Rusiecka et al., JINST 16 (2021) P11006
[2] J. Kasper et al., Phys. Med. 76 (2020) 317

The authors acknowledge funding from the National Science Centre (Sonata Bis 7 2018/26/E/ST2/00618 and Preludium 2019/33/N/ST2/02780) and the Jagiellonian University (MNS2021 U1U/P05/NO/03.29).

Speaker: Magdalena Kołodziej (Jagiellonian University)

132 Modular Data Acquisition System of a Reconfigurable Detector for Measuring the Spatial Distribution of Therapeutic Radiation Dose

Radiation dose reconstruction is crucial for the success and safety of radiation therapy in cancer patients. In this paper, a modular data acquisition system (DAQ) for a novel reconfigurable Dose-3D detector intended for a full spatial therapeutic dose reconstruction to improve radiotherapy treatment planning by providing a breakthrough detector with active voxels is presented. The reconfigurability of the active volume of the detector implies that the DAQ hardware and firmware need to be as flexible as possible.
The data acquisition hardware is divided into single slices, each comprising a 64-channel multianode photomultiplier tube (PMT) assembly, a front-end readout ASIC and an FPGA (see Figure 1). The system is designed in such a way that the number of slices can be easily adjusted to accommodate different detector geometries without sacrificing performance.
The modular FPGA firmware is based on an open-source platform to share a UDP/IP over an Ethernet link between many functional modules [1]. Intermediate modules were created to interface between the UDP layer of the platform and control registers and data streams. These, in turn, control independent units orchestrating the communication with the ASIC (see Figure 2). The communication between the FPGA and a DAQ PC is realised using a custom software package based on one of our previous designs [2].
Both the hardware and the firmware have reached the maturity level needed for the operation of the fully reconfigurable detector. The system has undergone an extensive set of calibration tests with promising results.

[1] A. Forencich. Extensible FPGA Control Platform
[2] P. Jurgielewicz et al., Modular data acquisition system for recording activity and electrical stimulation of brain tissue using dedicated electronics. Sensors, 21(13), 2021

The POIR.04.04.00-00-15E5/18 project is carried out within the “TEAM-NET” programme of the Foundation for Polish Science co-financed by the European Union under the European Regional Development Fund.

Paweł Jurgielewicz has been partially supported by the EU Project POWR.03.02.00-00-I004/16.

Speaker: Maciej Paweł Kopeć (AGH University of Science and Technology, Mickiewicza 30, 30-059 Krakow, Poland)

133 Empirical design criteria for improving image quality in grid-based phase-contrast x-ray imaging system

Grid-based phase-contrast x-ray imaging technique (gPCXI) is capable of acquiring the absorption, refraction and scattering information of an object in a single exposure using the Fourier processing [1]. One of the important issues is that the use of anti-scatter grid causes the aliasing artifacts in the image domain. Previously the size of the x-ray source with magnification was only considered to eliminate the artifacts but it induced excessive magnification of the object, limiting the field of view and simultaneously reducing the image resolution [2, 3].
In this study, we derived the empirical design criteria that include the whole blurring effects of the imaging system. The purpose of this study was to design a system configuration that produces high-resolution images without aliasing artifacts using the criteria and to demonstrate the validity of the criteria through experiments.
We employed a CMOS imaging detector coupled to structured CsI:Tl scintillating screens with pixel pitch of 49.5um and a microfocus x-ray tube with 35um, which limits the possible position of the object and the grid frequency. Figure 1 shows (a) schematic illustration of gPCXI and (b) the table-top setup we established for the experiment. To demonstrate the validity of the criteria, the imaging system was configured by adjusting the source-to-object distance (SOD) of 10, 14, 18, and 22 cm and the source-to-grid distance (SGD) of 35, 45, 55, and 65 cm with a fixed grid frequency of 200 lines per inch.
As shown in Fig. 2 (top row), artifacts were seen in the images acquired at SOD of 18 and 22 cm that unsatisfied the criterion, and the degree of the artifact increased as the object magnification decreased. As shown in Fig. 2 (bottom row), artifacts were seen in the images acquired at SGD of 35 and 45 cm that unsatisfied the criterion, and the degree of artifacts increased as the grid magnification increased. Importantly the decrease in resolution due to artifacts was more significant than the decrease in resolution due to the increase in magnification.
We demonstrated that an artifact-free image with larger field of view and higher resolution can be achieved with the empirical design criteria that includes not only the source size but also the detector characteristics. It is expected that these criteria are useful to optimize the system configuration with various type of detectors.

Speaker: Hunwoo Lee (Yonsei University)

134 Unified Modulation Pattern Analysis algorithm (UMPA) for 1D sensitive X-Ray Phase Contrast Imaging techniques

X-ray phase-contrast imaging (XPCI) techniques give access to phase and small-angle-scattering signals, which are inaccessible to conventional absorption X-ray imaging. Among XPCI techniques, differential phase techniques are based on the measurement of the refraction induced by the sample, which is proportional to the gradient of the phase shift (differential-phase image). By integrating the differential-phase image it is then possible to obtain the 2D map of phase signals (integrated phase image) which, being orders of magnitude greater than the absorption signals, allow increasing the contrast between weakly absorbing features of a sample.

Among XPCI techniques, edge illumination (EI) and grating interferometry (GI) make use of one or more absorbing masks featuring periodically repeated apertures [1]. A different approach to the use of masks is provided by speckle-based imaging (SBI). This latter technique uses a partially coherent X-ray beam and randomly distributed scatterers, such as silicon carbide grit in sandpapers, to create a reference speckle pattern at the detector position [2]. In the usual setups for EI, GI and SBI, both the refraction and the small-angle scattering are extracted by comparing the images of the wavefront markers (masks or speckles) before and after the introduction of a sample in the field of view.

Several algorithms have been proposed to extract the phase information from datasets acquired with EI, GI or SBI setups. However, many of them are application specific, computationally expensive and time consuming [3, 4, 5]. The Unified Modulation Pattern Analysis (UMPA) uses a template-matching approach where a least-squares minimization of a model including transmission, refraction and dark-field signal is carried out for each pixel in the images within a user-defined neighbourhood [6]. A new version of UMPA, written in C++ and Cython, and parallelized with OpenMP, has been recently implemented with the main advantage of being about 120x faster than the previous version implemented in Python. This new implementation of UMPA will be released along with an upcoming publication.

Though the SBI technique has an intrinsic 2D sensitivity to refraction angles, the sensitivity of EI or GI depends on the structure of the mask, which can be 1D (e.g., a bar pattern with fixed period) or 2D (e.g., a grid with fixed period both along the vertical and horizontal axes). The original version of UMPA was designed for datasets that contain refraction along both horizontal and vertical axes. Here, we present a modified version of UMPA to extend its applicability to datasets with sensitivity only along one axis, as is the case with 1D masks. To demonstrate the 1D version of UMPA, we imaged a plant specimen with a beam-tracking setup for EI using a single mask featuring a bar pattern with apertures of 19 μm and 116 μm period. Data were collected at the SYRMEP beamline of Elettra synchrotron (Trieste, Italy) with a polychromatic filtered white beam with an effective photon energy of 21 keV. Images were acquired with a qCMOS camera (ORCA Quest, Hamamatsu) coupled with a 45 μm thick GGG:Eu scintillator and a high numerical aperture optic, whereby the effective pixel size was adjusted to 4.5 μm. Results show that the proposed algorithm is effective in reconstructing the experimental dataset with sensitivity only along the horizontal axis (Figure 1). Furthermore, because of the reduced parameter space, this 1D-UMPA implementation provides a speed-up factor of 2 compared to the original 2D implementation, an especially convenient feature for tomographic datasets.

The UMPA algorithm provides a fast general solution for XPCI techniques making use of masks or speckles in beam-tracking mode, i.e. where the intensity patterns are directly resolved by the detection system. The extension of the original algorithm to the 1D case expands the range of applications to EI and GI setups making use of 1D periodic masks.

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

135 Multi Module >50 kfps Detector System for Time Resolved Experiments

We have successfully developed multi module version of the XSPA detector series. XSPA detector is one of the fastest solution for time resolved X-ray and electron experiments. it has maximum of 56 kfps sustainable framerate and 970 kfps burst mode framerate. XSPA module is designed based on UFXC readout chip designed at AGH University [1].
Conventional multi module detectors have lower framerate due to the limitation of the band width. We also have the same option to reduce the cables and controlling PC for the ease of use. But we know there are some experiments which requires large area and speed at the same time. So we have decided to design the multi module version to maintain the framerate and proved it works with 56 kfps without any drawback.
Some test results of the prototype multi module detectors will be presented.

[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.

Speaker: Dr Yasukazu Nakaye (Rigaku Corporation)

2022_06_iWoRiD_Poster.pdf

136 Commissioning of the upgraded RICH system at the LHCb experiment

The Ring-Imaging Cherenkov (RICH) system is an essential element of the LHCb experiment: it consists of an upstream detector (RICH1), located close to the interaction point, and a downstream detector (RICH2), placed after the tracking system, and has the task of identifying charged hadrons over the momentum range 2-100 GeV/c.

Currently the LHCb experiment is completing an upgrade phase to allow data collection at a five-fold increase in instantaneous luminosity up to 2*10^(33) cm(-2)s^(-1) and read out data at a rate of 40 MHz. The challenges of the higher luminosity are: a significant increase of the detector occupancy and a larger radiation dose. In order to match the new experimental requirements, both RICH detectors have been upgraded with a redesigned opto-electronic chain and new photon detectors. In addition RICH1 has a modified layout with new mechanics and spherical mirrors in order to reduce the maximum occupancy. A summary on the upgrade programme and the current status of the commissioning operations will be presented.

Speaker: Shinichi Okamura (Universita e INFN, Ferrara (IT))

poster_okamura_iworid2022.pdf

137 Design and performance of the FOOT calorimeter with particle-ID capabilities

Fragmentation cross sections in beam-tissue nuclear interactions are crucial for clinical treatment-planning systems in hadron therapy. The FOOT experiment will fill the gap in differential cross- section measurements for the production of secondary fragments in such interactions with beam energies up to 400 MeV/u. Extending this range up to 800 MeV/u it will also be indispensable for studies on radioprotection in space to optimise shielding of future spacecrafts.
The calorimeter of the FOOT experiment is designed to provide linear response over the wide dynamic range from tens of MeV to about 10 GeV with an energy resolution below 2% for the identification of heavy fragments in a
reverse-kinematics configuration. The detector will be composed of 320 BGO crystals coupled to SiPM photosensors and read out by the WaveDAQ data- acquisition system, allowing pulse-shape analysis for particle-type estimation.
This contribution presents an overview of the
FOOT calorimeter design and detailed
performance results obtained in a series of
experimental measurements with proton and
carbon beams at CNAO (Pavia, Italy). Furthermore, an algorithm for compensation of thermal variations on the detector response is described, which eliminates the need for a dedicated temperature-stabilisation system. Finally, the effect of the ion penetration depth has been carefully studied using both experimental data and Monte Carlo simulations, taking into account the optical propagation of scintillation photons. The developed correction of this effect is presented, which is an essential component of the future particle-identification algorithm in the FOOT experiment.

Speaker: Nazar Bartosik (Universita e INFN Torino (IT))

poster_bartosik_v1.pdf

138 Study of Performance Parameters for a SiPM-Based Digital Positron Annihilation Lifetime Spectrometer

Positron annihilation spectroscopy (PAS) is an outstanding technique to study defects in material science such as polymer, semiconductor and irradiated material. Positron annihilation lifetime spectroscopy (PALS) which measures the lifetime of positrons specialized in analyzing defects of materials among various PAS technique. [1]. DRS4 evaluation board are widely used for PALS system and Silicon Photomultiplier (SiPM) has many advantages compared with PMT. Our goal is development cheap SiPM-DRS4 based PALS and investigate the performance of system according to various parameters.
3.07 x 3.07 mm2 size of two SiPMs which mounted on evaluation board are used for PAL spectrometer (MicroFJ-SMA -30035, SensL, Ireland). They have fast signal output which improve coincidence timing resolution (CTR) of detector. The DRS4 evaluation board (PSI, Switzerland) has high bandwidth (700MHz) and high sampling rate (5.12Gs/S). LYSO scintillators (Epic crystal, China) is coupled with optical grease (EJ-550, Eljen Technology) to SiPM in sizes of 3 x 3 x 20 mm3, 3 x 3 x 15 mm3 and 3 x 3 x 10 mm3.
CRT measurement was performed using two radiation sources (22Na , 60Co) that emit a pair of 511 keV and 1173, 1332 gamma rays simultaneously. Each of sources were used to optimize the CTR of start and stop signal detector. Off-line digital constant fraction discrimination (dCFD), one of the time pick off method which eliminate time walk occurred from pulse height difference, was used to determine the arrival time of gamma ray [2]. To recover the discrete signal from DRS4 board, we conduct various interpolation methods (Linear, Spline, Polynomial, Gaussian) to find the best algorithm for our system. We found the best fraction value for each detector and the optimal applied voltage to SiPM from 30V to 33V with 0.5V steps. In addition, we investigate the trade-off relationship between energy window and CTR.
After optimizing the parameters, we measure PAL spectrum and analyse it by PALSFit program and investigate the material analyse ability.

Speaker: Mr Hyunwoong Choi (Korea Advanced Institute of Science and Technology)

139 Investigating the Effect of Depth of Interaction on Coincidence Timing Resolution

Coincidence timing measurement has a wide range of applications in the detection of high energy physics, material science, and medical device. A scintillator detector is commonly used for the aforementioned applications due to its favorable physical properties including high energy resolution and brilliant timing resolution.

Unlike positron emission tomography (PET), which measures annihilation quanta having identical energy, measurement of particle momentum (in a large ion collider experiment) or positron annihilation lifetime spectroscopy (PALS) treat quanta having non-identical energy. This research aims to study the effect of the coincidence timing resolution due to the above discrepancy. Since the energy of the radiation to be measured could represent a different distribution of depth of interaction within the scintillator and it could affect the resolution as a factor of uncertainty To this end, we utilized ‘order statistics’-based photon statistics for the purpose of reflecting the scintillator properties, and particle tracking in the Monte Carlo simulation to only designate the distribution of photoelectric interaction.

As a result of this study, we found significant differences in coincidence timing resolution depending on radiation energy. In addition, the correlation and degree of contribution to the timing uncertainty between photon statistics and depth of interaction regarding incident radiation energy were studied.

Speaker: Mr KILYOUNG KO (KAIST)

140 An analytical model for Fluorescent and Scattering X-ray Beam Monitor designing

An analytical model for Fluorescent and Scattering X-ray Beam Monitor designing

Elio Sacchetti1,, Kewin Desjardins1
1SOLEIL Synchrotron, Detectors Group, l’Orme des Merisiers, France
elio.sacchetti@synchrotron-soleil.fr

At modern light-sources facilities, a majority of synchrotron beamlines are equipped with Xray Beam Intensity/Position Monitors (XBPM). Among those monitors, a relatively simple device is aiming at measuring the fluorescent and scattered X-ray signal emitted by a foil with a point detector [1], a combination of point detectors [2][3] or a 2D detector [4].
In order to improve design of this kind of detectors, an easy-to-use analytical algorithm has been developed to estimate the X-ray Beam Inducted Current (XBIC) for different detector parameters, such as the type of geometry, type of foil, type of sensor, etc. This algorithm allows computing the quantity of signal from X-ray fluorescence, elastic scattering (Thompson effect) and inelastic scattering (Compton effect). Several different parameters of the X-ray incident beam are taken in account in the simulation: the incident photon flux, energy, dimensions and polarization. Furthermore, in contrast to the complex and time-consuming method using a toolkit dedicated to the interaction of particles through matter, this estimation is performed in few seconds with a user-friendly interface. The estimation is obviously less precise than Geant4 simulation toolkit, less parameters and interactions are considered.
To validate results of the simulation, a series of measurements have been performed on the METROLOGIE beamline at SOLEIL Synchrotron. In this experiment, several foils such as titanium, aluminum or Kapton© have been used, with different configurations of the beam (energy, size, flux) and detector geometry (position and angle of foil and photodiode). The Figure 1 illustrates a comparison between the measurement and the simulation. The obtained experimental result is in accordance with the simulation. The relative error of the estimated current is less than 20 % for a fluorescent foil, and less than 50% in case of the scattering element.

References
[1] Alkire, R. W. & Rotella, F. J. (1997). J Appl Crystallogr. 30, 327–332.
[2] Alkire, R. W et al.. (2000). J Synchrotron Rad. 7, 61–68.
[3] Goulon, J et al.. (2005). J Synchrotron Rad. 12, 57–69.
[4] Van Silfhout, R. et al., (2011). Opt. Lett. 36, 570.

Speaker: Elio Sacchetti (Synchrotron SOLEIL)

141 Calibration and first operation of the JUNGFRAU detector in 16-memory cells mode at European XFEL

The JUNGFRAU detector is a now established hybrid pixel detector developed at Paul Scherrer Institute (PSI), featuring 75 µm pixel pitch with a charge integrating dynamic gain switching architecture [1] designed for FEL applications [2]. Optionally, the dynamic gain switching mechanism can be bypassed, and the detector can operate with a fixed feedback capacitor in the pre-amplifier.
Originally designed to cope with the SwissFEL 10 Hz pulse rate, it is however endowed with an array of 16 analog memory cells per pixel, which makes it possible to store more than one image per pulse train at a ‘burst’ repetition rate greater than 100 kfps.
The possibility to tap into the so-called ‘burst’ operation mode, would allow the scientific instruments to exploit more efficiently the European XFEL (EuXFEL) pulse train structure.
Clear beneficiaries of the 16-memory cell operation would be the serial femtosecond protein crystallography experiments, which, with an increased throughput, can make better and more efficient use of the sample. Many pump-and-probe experiments would also benefit greatly from the possibility of correlating on a pulse-by-pulse basis measurements performed with JUNGFRAU with ones performed with other pulse-resolving detectors available at the facility, like the LPD and the AGIPD.
However, due to the uniqueness of the bunch structure within the train at EuXFEL, the 16-memory cell operation mode has never been fully tested before and characterized in conditions comparable to the ones available at our facility.
Therefore, we will present the current status of the implementation of the 16-memory cell operation mode at the European XFEL and the issues we have encountered, focusing on the detector characterization, and the consequent path towards the establishment of a validated calibration procedure. First preliminary results from a standard sample crystallography measurement will also be presented.

[1] Mozzanica A. et al., Synchrotron Radiation News 31, 16 (2018)
[2] Redford S. et al, JINST 13, C11006 (2018)

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

iWoRiD_2022_Ramilli.pdf

142 Novel technique for large GEM-foils production the “Random Segmentation”; Simpler production method with higher GEM detector performances

Production of large-size Gaseous Electron Multiplier (GEM) [1] foils, relay on the multiple sectorization of the electrode for the High Voltage distribution; typically, with sector size of about 100 cm2.
The GEM sectorization allow for reduction of the capacitance between the two side of the foil, quenching consequently the energy released in the discharge events, moreover even in the extreme case of destructive high voltage breakdown causing a permanent short sectorization make only a small fraction (one sector) to fail.
Sectorization is realized stripping the conductive layer (typically copper) deposit on the base material, polyimide, between two sectors patterned with the GEM holes, reverting in an insulation region. The insulating region never overlap the gem hole to avoid irregularities on the HV distributions which could make the GEM foils unstable. The stripping process relies on lithography and chemical etching process which, on large GEM foils, require nontrivial alignment process. The insulating strips usually not less than 200 um wide, which directly affect the detector performance with efficiency drops in the corresponding areas.
Resuming an old GEM manufacturing idea [2,3,4], we investigated a new design of GEM-foil sectorization with a random alignment between the hole pattern and the sector gap. Such alternative design is a promising solution also in terms of manufacturing of large area foils, as this technique does not require a precise alignment of the sector gap with the hole pattern.

The authors will describe the recent R&D phases currently ongoing on triple-GEM detector prototypes, mounting a double-sided random segmented GEM-foils based on the single-mask photolithography technique. Detectors with different sizes have been designed and assembled to prove the stability and performance of random sectorization compared with those obtained with the traditional blank insulating gaps. Results from beam tests, proving the higher detector performance with respect to the traditional sectorization method are also presented.

[1] F. Sauli, GEM: a new concept for electron amplification in gas detectors, Nucl. Instrum. Meth. A 386 (1997) 531.
[2] C. Altunbaset al, NIMA 490(2002)177
[3] M. Zigler, PhD Thesis, Development of a triple GEM detector for the LHCb Experiment, CERN-THESIS-2004-006
[4] F. Brunbaueret al, NIMA 875 (2017) 16

The authors acknowledge the CMS-GEM collaboration for the support in test beam preparation and realization.

Speaker: Michele Bianco (CERN)

MBianco_Poster_for_iWorid2022_V2.pdf

143 A New Multiplexing Method for SiPM Using a Deep Learning Architecture

Many studies have been conducted to reduce the number of SiPM readout channels in the nuclear medicine systems. We recently proposed a shaping resistive network using artificial neural network, which can reduce the output channels to one channel. This method generates output signals with different decay time and combines them into a single output. The single output is separated back into their original signals using deep learning. However, it has difficulty in signal separation since decay time difference alone cannot clearly represent the features of each channel. To solve the problem, we proposed a new multiplexing method for SiPM using a deep learning architecture. The method can be divided into two parts: 1) the pre-processing circuit that produces distinct features for each channel and 2) the deep-learning architecture that separates the summed signal into their original signals. The signal separation performance of the method was evaluated by comparing it with shaping resistive network. Using a singles pixel detector (GAGG-SiPM), the proposed method showed a mean absolute percentage error of 0.61% in photopeak voltage before and after deep learning. Energy resolution improved by 0.94 percent points (%p) compared to original signal. On the other hand, the shaping resistive network has a mean absolute percentage error of 1.02%, twice as large as the proposed method. And energy resolution was poorer by 1.07%p than before. In addition, this method can sufficiently discriminate signals even with a short signal length difference compared to shaping resistive network. These results show that the proposed method has better signal separation performance than the previous method. During the presentation, we will apply the method to a SiPM array to verify multiplexing performance.

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

144 SpacePix Radiation Monitor: SoI MAPS Detector for Space Radiation Monitoring

Space radiation presents a risk to both unmanned spacecraft systems and human exploration of the Solar System. Thanks to advances in semiconductor technologies, it is possible to design and manufacture low-power pixel detector ASICs with backside pulse digitization, which allows a large dynamic range. The SpacePix2 is a radiation detection ASIC designed for radiation sensing in an aerospace environment. It is a monolithic pixelated detector with a matrix of 64x64 pixels with 60 μm pitch developed in a 180 nm PDSoI technology. It is suitable for electron, proton and heavy ion energy deposition measurement.
The SXRM is a compact lightweight multi-layer particle telescope detector, where detection layers of SpacePix2 ASICs are interleaved with a copper ionization energy absorber. It allows sampling of dE/dx losses in multiple layers, and by using pattern recognition techniques (clustering, topologies), it enables particle identification, its energy estimation and reconstruction of incoming particle trajectory.

Designed for charged particle energy and species determination, reconstruction algorithms allow the determination of particle track parameters.

The SXRM was launched on Janurary 13, 2022 on the Czech technological nanosatellite VZLUSAT-2 as a part of the 2SD radiation monitoring instrument. First data are expected in spring 2022.

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

145 Detection of MeV electrons using a charge integrating hybrid pixel detector

Electrons are emerging as a strong complement to X-rays for diffraction based studies. In this paper we investigate the performance of a JUNGFRAU [1] detector with 320 um thick silicon sensor at a pulsed electron source [2]. Originally developed for X-ray detection at free electron lasers, JUNGFRAU features a dynamic range of 120 MeV/pixel (implemented with in-pixel gain switching) which translated to about 1200 incident electrons per pixel and
frame in the MeV region.

We preset basic characteristics such as energy deposited per incident particle (Figure 1), resulting cluster size and spatial resolution along with dynamic (intensity) range scans. Measurements were performed at 4, 10 and 20 MeV/c. We compare the measurements with GEANT4 [3] based simulations and extrapolate the results to different sensor thicknesses using these simulations.

[1] A. Mozzanica et al., Characterization results of the JUNGFRAU full scale readout ASIC JINST 11 (2016)
[2] D. Angal-Kalinin et al, Design, specifications, and first beam measurements of the compact linear accelerator for research and applications front end, Phys. Rev. Accel. Beams 23, (2020)
[3] S. Agostinelli et al, Geant4—a simulation toolkit NIMA 506 (2003)

Speaker: Erik Fröjdh (Paul Scherrer Institut)

146 Safeguards Implement Equipment for Spent Nuclear Fuel of CANDU

This paper describes the development of safeguards implement equipment for spent nuclear fuel of heavy water reactor stored in a wet interim storage facility. OFPS (Fig. 1 (Left)) is one of the safeguards equipment for the nuclear nonproliferation. It has been using in PIV, Physical Inventory Verification, of the PHWR spent nuclear fuel in wet interim storage.

It compensated for imperfections in the OFPS improved performance and user convenience. Specifically, the lithium glass scintillator currently used in OFPS was changed to a plastic scintillator with the high economic efficiency and light yield, and the probe design for radiation measurement was also changed to facilitate replacement of the scintillator. In addition, the manual cable loading method, which was an obstacle to the safeguards implementation, was redesigned to be automatically loaded on a drum-shaped structure using a motor. All analog systems such as radiation signal processing and cable loading systems that used to run the entire equipment were replaced digitally so that every operations could be made with display panels.

Newly developed safeguards equipment was able to achieve two purposes, performance improvement and user convenience enhancement. The replacement of scintillators and probes improved performance by about 10 times, and the new equipment design reduced the number and weight of parts to less than about half.

The developed equipment is verifying its performance so that it can be used as IAEA's advanced safeguards equipment, and it is expected to play a major role in the safeguards implement for spent nuclear fuel through the registration of IAEA inspection equipment.

KEYWORDS: Safeguards, Spent nuclear fuel, PHWR, Plastic scintillator, Physical Inventory Verification

Speaker: Yewon Kim (KINAC(Korea Institute of Nuclear Nonproliferation and Control))

147 The CirPAD, a novel circular 1.4M pixel detectors for X-ray diffraction measurements at Synchrotron SOLEIL

The CirPAD (Circular Pixel Detector Array) is a unique hybrid pixel detector with a circular shape that has been developed by the DiffAbs beamline, the Detectors and Design and Engineering teams at Synchrotron SOLEIL, in collaboration with the Cegitek company [1]. The unique geometry combined with a very good characteristics of the XPAD3.2 readout chip results in a very versatile detector that covers a large panel of different experiments, such as materials science and physical chemistry scientific applications or time-resolved pump-probe X-ray diffraction measurements.
The complete detector is assembled from a 20 high speed XPAD modules [2] for a total of 1.4 Mpixels (see Figure 1). Each module is tilted with an angle of 6.7° which in total covers a 135° diffraction angular range, with a radius of 645 mm and a 0.01150 angular resolution. The detector has been installed on a dedicated motorized crane that surrounds the 6-circle diffractometer (see Figure 2), allowing operation in a large angular range in horizontal and vertical axes. One of the main advantages of the detector is its high-speed readout, short (gated) acquisition time and a large area that allows to reduce the acquisition times significantly.
In this work we present the main characteristics of the detector and several examples of results obtained at the DiffAbs beamline.

[1] K. Desjardins et al., J. Synchrotron Rad. (2022). 29, 180–193
[2] P. Pangaud et al., Nucl. Instrum. Methods Phys. Res A (2007). 571, 321-324

Speaker: Dr Arkadiusz Dawiec (Synchrotron SOLEIL)

148 A machine learning approach in the estimation of a radioactive source position using a coded aperture device

In this work we compare the traditional correlation process of a Coded Aperture device to estimate the spatial coordinates of γ-emitters with a different approach: We have developed machine learning algorithms based on Gradient Boosted Decision Trees (BDTG) and Deep Neural Networks (DNN). The algorithms have been trained using 18000 shadowgrams created with simulation. A custom fast simulation tool was used to produce shadowgrams due to sources placed randomly at 18000 different positions within the FOV and up to a distance of 4.5m from the detector plane. The performance of the algorithms has been evaluated with the aid of a different independent sample of shadowgrams.

Speaker: Dr Ioannis Kaissas (Greek Atomic Energy Commission)

149 A dE/dx-E position sensitive charged particle spectrometer

Hybrid pixel detectors- Timepix are very promising detectors considering their advantages getting simultaneously information about the position, energy, and time of arrival of a particle hitting the detector. These types of multi-parameter detectors can be effectively used to study and/or reinvestigate some fission processes such as the rare fission modes (ternary, quaternary, quinary), which are planned. In studying nuclear reactions, it is necessary to consider the following features: the energy resolution of the detecting system, angular distribution information, coincident timing, discrimination of different particles, background problem etc. Silicon solid-state detectors are commonly used for measuring the specific ionization (dE/dx), in instruments designed for identifying energetic nuclei using the dE/dx versus total energy technique. Using Timepix detector as E detector in this method gives the possibility to get simultaneous measurement of energy, coordinate, interaction time and the type of charged particles. This work is devoted to application of multi-parameter detectors- Timepix in dE/dx-E particle identification measurements. In constructing tailor-made dE/dx-E spectrometers, our requirement is the measurement of angular distributions, energy spectra, coincident time, yield of rare fission mode products. In order to test the spectrometers, a spontaneous fission source 252Cf was used as a light particle source, since LCPs (mainly alpha particles) are formed along with the heavy fragments in ternary fission. The tailor-made dE/dx-E spectrometers consist of transmission type ΔE detectors and the Timepix detector. The particles (1H, 2H, 3H, 4He, 7Li, and 8Be et.c) have been identified by the method dE/dx-E, since the dE/dx-E value is unique to the type of particle. The specific energy loss (dE/dx) is measured using the transmission type ΔE detector (16 or 150 um thicknesses) ordered from the company Micron Semiconductors, while the residual energy (E) is measured by a Timepix detector with thicknesses of 300 and 600 um.

Speaker: Ondrej Urban (Faculty of Electrical Engineering, University of West Bohemia in Pilsen)

150 Concept of a mobile gamma spectrometer based on the SIPM

The development of nuclear technologies, the production and active use of radioisotopes, and the production of other radioactive materials are increasing every year. Therefore, the importance of ensuring the safety of highly active isotopes, as well as providing the necessary instruments for measuring and identifying radioactive materials, must be taken into account. Modern equipment such as HPGE is costly and requires specialized staff skills as well as special operating conditions such as low temperatures and high voltages. It is proposed to explore the possibilities of using SIPM with a deep pixel structure in nuclear gamma spectrometry, which will make it possible to increase the efficiency of scintillation detectors. The paper presents the results of a study of the newest silicon photomultipliers MAPD-3NM II and a 16-element matrix based on them, which was the detector part of the proposed LaBr3 scintillation spectrometer. The study was carried out using radioisotopes of Uranium and Plutonium of various enrichment. The data obtained were compared with data from a laboratory HPGE spectrometer.

Speaker: Michael Holik (IEAP CTU in Prague, FEE UWB in Pilsen)

151 Spectroscopic Imaging of Hard X-rays for Material Science Applications

The HEXITEC and HEXITEC_MHz detector systems have been developed for spectroscopic X-ray imaging for photon science applications. Both systems consist of 80 × 80 pixels on a 250 $\mu$m pitch and utilise high-Z sensor materials for detection of X-rays in the energy range 2 – 200 keV. The original HEXITEC system was capable of operating at a maximum frame rate of 9 kHz allowing per-pixel spectroscopy with an energy resolution of 800 eV to be captured at photon fluxes of up to 10⁴ photons s^-1 mm^-2 [1]. The 1 MHz continuous frame rate of the HEXITEC_MHz means that the same spectroscopic imaging can be carried out at photon fluxes of the order 10⁷ photons s^-1 mm^-2.

In this paper an update will be given on the current status of the HEXITEC technology and examples of how this has been applied for materials science applications. These examples will include the imaging and characterisation of in-operando lithium-ion batteries conducted at the I12 – JEEP beamline at the Diamond Light Source. In this experiment a monochromatic beam of 115 keV X-rays was used to illuminate a 0.25 mm thick slice through the width of a battery coin cell. The Compton scattered X-rays at 90 degrees to the battery were projected through a 0.2 mm pinhole to form an image on a 2 mm thick Redlen HF-CdZnTe HEXITEC detector. Images of the Compton signal were formed by integrating the counts around 93 keV with an integration time of 15 to 60 minutes. The strength of the Compton signal recorded at the detector was proportional to the ion density in the coin cell which evolves over the charging and discharge cycle. The battery cell was moved vertically through the beam to image slices through the cathode region of the battery cell. Using this technique, it was possible to image changes in the energy density of the battery during the charging and discharging cycle [2].

[1] M. C. Veale, et al., HEXITEC: A High Energy X-ray Spectroscopic Imaging Detector for Synchrotron Applications, Synchrotron Radiation News, 31, (6), 28-32, 2018. DOI:10.1080/08940886.2018.1528431

[2] K. Suzuki, et al., In operando quantitation of Li concentration for a commercial Li-ion rechargeable battery using high-energy X-ray Compton scattering, J. Synchrotron Rad., 24, 1006-1011, 2017. DOI:10.1107/S1600577517010098

Speaker: Matthew Veale

152 Hybrid Pixel Smart Detector with Integrated RISC-V Microprocessor

Hybrid single-photon counting pixel detectors have recently been widely used for X-ray and ionizing particle detection in medicine, high-energy physics, and material science. Many different chips have been developed for the readout of semiconductor pixel sensor [1,2]. Usually, developed ASICs have very limited digital logic and do not provide substantial data processing.

In this article, we present a Hybrid Pixel Smart Detector (HPSD) that integrates a matrix of readout channels with a RISC-V-based microprocessor SoC. The designed device has been developed for manufacturing in a CMOS 45nm process with an area of 1.92 mm x 1.92 mm. A layout of the designed integrated circuit is shown in Fig. 1.

Integration of a pixel matrix with the RISC-V-based central processing unit (CPU) significantly improves detector functionality. It enables the device to work independently without external assistive device usage and execute many algorithms, e.g. on-chip calibration, threshold scanning, and data filtering. Communication between the CPU and the pixel matrix is carried out through a dedicated Pixel Matrix Controller (PMC). This specialized peripheral consists of a coprocessor responsible for precise matrix control, data conversions between formats used by matrix and CPU, and control and status registers connected to the core address space and enables fast and independent detector calibration [3]. Another exemplary application of such a solution is intelligent real-time filtering of regions of interest.

The described device is currently at the final stage of the design process, and the integrated circuit will be sent to production at the end of April 2022. The architecture of HPSD is released as an open source project, and its RTL source code, together with developed software were published on GitHub [4].

[1] M. Garcia-Sciveres and N. Wermes, A review of advances in pixel detectors for experiments with high rate and radiation, Reports Prog. Phys., vol. 81, no. 6, p. 066101, Jun. 2018.
[2] R. Ballabriga et al., Review of hybrid pixel detector readout ASICs for spectroscopic X-ray imaging, J. Instrum., vol. 11, no. 1, p. P01007, Jan. 2016.
[3] P. Skrzypiec and R. Szczygieł, Development of On-Chip Calibration for Hybrid Pixel Detectors, 2021 24th International Symposium on Design and Diagnostics of Electronic Circuits & Systems (DDECS), April 2021.
[4] P. Skrzypiec and R. Szczygieł, pixel_riscv_soc, https://github.com/agh-riscv/pixel_riscv_soc, 2022.

Speakers: Pawel Skrzypiec, Robert Szczygiel

153 Development of a Prompt Gamma-ray Neutron Activation Analysis System for the detection of explosive materials

Unlike x-ray imaging which can display images according to the degree of absorption of x-rays by the objects, neutron activation analysis can be used for the detection of explosives because it can be used for determining the presence of unknown elements in the objects. Also, since neutrons are able to penetrate through some heavy metals and they significantly interact with some light and organic materials, it can be used for the baggage scanner in airport. In neutron activation analysis, neutrons can convert stable atomic nuclei into radioactive nuclei and make it emit gamma-rays according to the elemental composition. Therefore, to design a neutron activation analysis system for the detection of explosive materials, we determined a neutron source, neutron collimator, a transport system, a gamma-ray detector, a sealed shielding box made of lead and high hydrogen content shielding around the detectors.
As a neutron source, the deuterium-tritium(D-T) neutron generator was determined that emits 2.5e+09 n/s with 14.1 MeV. Also, neutron collimator made of high hydrogen content shielding with 2 centi-meters of slit was designed to expose fan beam shaped neutrons to the luggage. Also, a transport system was designed to adjust the inspection speed. In addition, as a gamma-ray detector, CdZnTe semiconductor type detector were determined after the consideration into its energy resolution and high atomic number. To mitigate the unintended neutron activation, we designed a sealed shielding box made of 10 centi-meter thickness of lead and 10 centi-meter thickness of polyethylene shielding around the detectors. As a result, we acquired the gamma-ray spectroscopy induced by fast neutrons and calculated the atomic ratios of carbon to oxygen and nitrogen to oxygen to detect the explosive materials.

Speakers: Kyungmin Oh, Jae Hyeon Kim (Korea Atomic Energy Research Institute)

154 Characterisation of heavily irradiated dielectrics for AC-coupled pixel detectors

An increase in the radiation levels during high-luminosity operation of the LHC and future colliders calls for the development of silicon based pixel detectors used for particle tracking and vertex reconstruction. Capacitively coupled (AC-coupled) detectors are anticipated to be in operation in future collider experiments as they provide an enhanced isolation between pixel areas due to radiation-induced leakage currents. The motivation of this study is the development of next generation capacitively coupled (AC-coupled) pixel sensors with coupling insulators having a good dielectric strength and radiation hardness simultaneously. The AC-coupling insulator thin films were aluminum oxide and hafnium oxide grown by Atomic Layer Deposition (ALD) method.

Our work focuses on a comparison study based on the dielectric material used in MOS, MOSFET and AC-pixel sensors processed on high resistivity p-type Magnetic Czochralski silicon (MCz-Si) substrates. These prototypes were irradiated with 10 MeV protons upto a fluence of 5e15 protons/cm² as well as with Co-60 source upto 1 MGy. Capacitance-voltage measurements of MOS and MOSFET test structures indicate negative oxide charge accumulation induced by irradiation. These studies are coherent to numerical simulations. Furthermore, electrical characterization using current-voltage and edge-TCT methods indicate very good dielectric strength performance in both materials as well as show the impact of the dielectric-silicon interfaces on the functionality of the sensors, even after irradiation. The negative oxide charge during the irradiation is an essential pre-requisite of radiation hardness resiliency of n⁺/p⁻/p⁺ (n on p) particle detectors widely intended to be used in future high-luminosity experiments.

Speaker: Shudhashil Bharthuar (Helsinki Institute of Physics (FI))

iWoRiD_2022_Final_Bharthuar.pdf

155 Performance of triple-GEM detectors for the Phase-2 CMS upgrade and a high-resolution GEM telescope measured in a test beam

In view of the LHC Phase-2, the CMS experiment is being upgraded with three stations of triple-GEM detectors (GE1/1, GE2/1 and ME0) to maintain the excellent trigger pT resolution of its muon spectrometer in the high-luminosity LHC environment and extending its coverage to the very-forward pseudorapidity region 2.4<|η|<2.8. The challenges faced for adapting the triple-GEM technology to a large-area detector have required the introduction of innovations such as discharge protection, an optimized GEM foil segmentation, and the development of complex front-end electronics. The Phase-2 CMS GEM detectors have been tested for the first time under beam irradiation in their final design with their complete front-end electronics and data acquisition software in Fall 2021 and Spring 2022 at the CERN North Area, with the goals of demonstrating the operation of their full readout chain, measuring their efficiency and space resolution under intense beam irradiation, and verifying the operating principle of a new foil sectorization. We describe the setup of the test beam, made of a GE2/1 detector and a second-generation ME0 detector and completed by a high-space resolution beam telescope made of four 10x10 cm2 triple-GEMs. We discuss the preparation of the full DAQ chain, made by the VFAT3 front-end ASIC, an OptoHybrid front-end FPGA and a custom back-end made of a commercial FPGA (CVP-13), all operated with the final CMS GEM acquisition software. We report on the performance of both the large-area detectors and the tracker, measured with muons and pions.

Speaker: Yechan Kang (University of Seoul, Department of Physics (KR))

156 Electrical characterisation and gain measurement of 50um thick pads LGAD

This work reports the electrical characterisation and gains measurement of a 50um thick Low Gain Avalanche Detector (LGAD) fabricated at Micron Semiconductor Ltd. Devices with a square pixel of 0.22 x 0.22mm2, 0.5 x 0.5mm2, and 1.0 x 1.0mm2 from wafers with three gains region doping values were studied. The electrical properties of the devices were studied by means of I-V and C-V measurements. Device gain was evaluated using the Transient Current Technique (TCT) with a 1064 nm infrared laser at temperatures between 20 ° to -30 ° C. The I-V profiles in Figure 1(A) show the breakdown voltages were between 150V to 200V. Figure 1(B) indicates the total capacitance at full depletion for the 0.22 x 0.22mm2, 0.5 x 0.5mm2, and 1.0 x 1.0mm2 square pixel devices were approximately 0.3pF, 0.9pF and 2.8pF respectively. The full-depletion voltage (Vfd) calculated from the 1/C2 plots was between 26 to 33 volts. Figure 2(A) shows the 2D and 3D plots of the TCT response for the 0.5 x 0.5mm2 device at 150V bias voltage, corresponding to a gain of 5. The non-uniform nature of the response is understood, and it was due to the structure of the device. Figure 2(B) shows an increasing gain from 3 to 6 measured for a 1-MIP equivalent IR laser input for bias voltages from 120V to 200V.

Speaker: Mr Lojius Lombigit

iworid22_poster.pdf

157 Low-energy X-ray detection with JUNGFRAU

The hybrid silicon pixel detector JUNGFRAU has found widespread use at free-electron laser (FEL) and synchrotron facilities worldwide. Its charge-integrating architecture combines three dynamically switching gains per pixel and allows single photon resolution down to 1.5 keV while, simultaneously, providing a dynamic range of $10^4 $photons at 12 keV. Although JUNGFRAU initially targeted applications with hard X-rays between 2 keV and 16 keV, its low noise, high spatial resolution, fast readout, and high dynamic range make the detector an attractive choice for photon science at lower energies.

The first JUNGFRAU system aiming at low-energy X-ray detection was installed at the Maloja end station of the Swiss free-electron laser (SwissFEL) in 2021. It combines an improved version of the JUNGFRAU readout ASIC and sensors with thin entrance windows. The new ASIC (labelled JUNGFRAU 1.1) reduces the noise of the detector to 34 electrons rms in high gain, and the sensors with thin entrance windows increase the quantum efficiency for low-energy photons. With these improvements, the system can detect single photons down to 800 eV.

In this contribution, we discuss the capabilities of JUNGFRAU for low-energy X-ray detection based on the system at Maloja. We present recent measurement results and provide an outlook on ongoing improvements to the sensor design aiming to enable single photon resolution down to 250 eV.

Speakers: Dr Viktoria Hinger (Paul Scherrer Institut), Bernd Schmitt (Paul Scherrer Institut)

Poster_JUNGFRAU_IWORID2022.pdf

158 Development of novel single-die hybridisation processes for small-pitch pixel detectors

Hybrid pixel detectors require a reliable and cost-effective interconnect technology adapted to the pitch and die sizes of the respective applications. During the ASIC and sensor R&D phase, moreover for small-scale applications, such interconnect technologies need to be suitable for the assembly of single dies, typically available from Multi-Project-Wafer submissions. Within the CERN EP R&D programme and the AIDAinnova collaboration, innovative hybridisation concepts targeting vertex-detector applications at future colliders are under development. Recent results of two novel interconnect methods for pixel pitches of 25 μm and 55 μm are presented in this contribution – an industrial fine-pitch SnAg solder bump-bonding process adapted to single-die processing, as well as a newly developed in-house single-die interconnection process based on Anisotropic Conductive Film (ACF).

The fine-pitch bump-bonding process is qualified with hybrid assemblies from a recent bonding campaign at IZM. Individual CLICpix2 ASICs with 25 μm pixel pitch were bump-bonded to active-edge silicon sensors with thicknesses ranging from 50 μm to 130 μm. The device characterisation was conducted in the laboratory as well as during a beam test campaign at CERN SPS beam-line, demonstrating an interconnect yield of above 99.9%.

On the other hand, the ACF interconnect technology replaces the solder bumps by conductive micro-particles embedded in an epoxy film. The electro-mechanical connection between the sensor and ASIC is achieved via thermocompression of the ACF using a flip-chip device bonder. The required pixel pad topology is achieved with an in-house Electroless Nickel Gold (ENIG) plating process. This newly developed ACF hybridisation process is first qualified with Timepix3 ASICs and sensors with 55 μm pixel pitch. The technology can be also used for ASIC-PCB/FPC integration, replacing wire bonding or large-pitch solder bumping techniques. This contribution introduces the ACF and ENIG processes and presents first test results on Timepix3 hybrid assemblies.

Speaker: Peter Svihra (CERN)

iworid_2022_poster_svihra.pdf

159 Characterization of 3.2 Gbps readout in 65 nm CMOS technology

The current trends in particle detector design are increasing pixel resolution and readout rates. Therefore, new requirements for the readout systems and their bandwidths have arisen. Fast differential serial communication is mainly used for its robustness against external interference and better electromagnetic compatibility than the legacy serial-parallel communication. However, its implementation provides extra challenges [1-2].

Transmitters described in this work use channel encoding that adds bit redundancy to assure the neutral DC balance of the transmission line. The encoding 8b/10b also provides enough state transitions for the receiver clock recovery circuit to lock onto and provides word error correction. Encoded data then passes into a chain of registers that serialize the data with the phase-locked loop synthesized clock of 1.6 GHz, as shown in Figure 1. The transmitter drivers use current-mode logic with 1-tap preemphasis to ensure proper adaptation to the transmission channel. Current approaches and design of gigabit transmitter implemented in 65 nm CMOS technology will be presented in this work. It will describe the functionality of its internal blocks and data flow. Its functionality, jitter and channel performance will be characterized.

[1] C. Chen et al., “Characterization of a gigabit transceiver for the ATLAS inner tracker pixel detector readout upgrade,” Journal of Instrumentation, vol. 15, no. 3, pp. T03005–T03005, Mar. 2020, doi: 10.1088/1748-0221/15/03/t03005.
[2] E. A. Lee and D. G. Messerschmitt, Digital communication. Springer Science & Business Media, 2012.

The work was supported from European Regional Development Fund-Project "Center of Advanced Applied Science" No. CZ.02.1.01/0.0/0.0/16-019/0000778 and by the Grant Agency of the Czech Technical University in Prague, grant No. SGS20/175/OHK3/3T/13.

Speaker: Marek Jansky (Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering)

160 Backside channel for extended range of Spacepix-2 SoI MAPS detector

Monolithic pixel detectors allow integration of sensing diode together with the pixel front-end electronics to fit in tens of micrometers pixel pitch. The high granularity of such detectors makes it difficult to measure the total energy deposition by high energy particles [1]. Especially heavy ion interactions are not detectable due to the saturation of charge sensing amplifier of individual pixels. A backside channel measurement is a novel technique that can measure energy deposition in the whole sensor, thus extending the detector range.

The backside channel collects total deposited amount of charge across the sensor and thus determines the amount of signal charge originating from heavy ion interactions. The backside channel consists of a front-end amplifier and a peak detector optimized for long hold time to operate at longer shutter times. Output of the backside channel is converted on chip by a 10-bit ADC. For calibration and debugging purposes, charge injection through injection capacitance into backside can be utilized in the same way as charge injection into pixels, as shown in Figure 1.

The PDH output is buffered and connected to analog pin for testing purposes. Charge sensitive amplifier is implemented as a folded cascode [2] with PMOS input transistor and a high compliance current cascode for improved voltage swing. The feedback capacitor has a value of 3pF allowing us to measure the total charge deposited on the detector up to 40 Me– with 10-bit resolution. Sensor diodes are biased with voltage of –150 V. In the backside configuration, bias voltage is AC coupled, to ensure the proper function. The backside channel is fabricated in 180 nm SoI process. The design and results of the backside channel will be presented in this work.

Speaker: Josef Gecnuk (CTU in Prague)

161 Automated, adaptive, fast reset circuit for wide-energy range detector front-end

In this paper, we present a precise and fast reset circuit that restores the charge sensitive amplifier (CSA) output baseline voltage from a pulse level. The circuit is self-clocking, and its operation speed can be adjusted with the delay line configuration. This method is especially promising for wide-energy range CMOS detectors, as it adapts the discharge speed to the pulse amplitude. Additionally, the proposed method strongly mitigates the parasitics influence on its operation.

Working with high-intensity wide-energy radiation, fast discharging of the feedback capacitor after pulse processing is especially important whenever high count-rate performance is expected. A common solution is to use Krummenacher feedback with a high polarisation current [1]. However, since this approach discharges the capacitor right after the event, precise ADC-based energy measurement is extremely difficult or even impossible.

The possible solution is to apply Krummenacher feedback with a larger time constant, but equipped with additional circuitry responsible for baseline restoration whenever the amplitude measurement is done. The simplest approach consists in shorting both capacitor plates using a switch [2]. Such a solution may result in either high overshoot or temporary oscillations, disenabling pulses amplitude measurement or even their detection.

An interesting method is the so-called click-clack circuit, which works with two parallel capacitors and is based on switching the plates' connections to antiparallel to perform discharging [3]. Importantly, in this method, all capacitances must be precisely matched, and sharp discharging with no overshoot can be obtained only for a narrow range of pulse amplitudes.

We propose a self-clocking and automated reset circuit based on additional and simple circuitry to perform feedback for restoring the CSA baseline (Fig. 1.). This is realized by current sources that inject current pulses into the CSA input node, compensating the capacitor charge. Each step is followed by a comparison of the CSA output voltage and the reference voltage level, and a decision is made if further discharge is needed. The discharge process is divided into two phases – coarse and fine. During the latter, only I1 feeds current to the capacitor, making it quite slow, but reducing the overshoot. The coarse phase checks the MSB of the ADC conversion result. If it is set, all sources I1-I3 work, if not, only I1-I2. The transition from coarse to fine phase is controlled by the inverter-based comparator that monitors the CSA output.

The proposed solution allows for working with both high count-rate and wide-energy pulses, keeping the Krummenacher feedback equivalent resistance very high, thus enabling fast and precise photon energy measurement. Due to the adaptation of the discharge speed to the pulse amplitude, a fast reset without significant overshoot can be achieved for a wide energy range (Fig. 2.). The solution is implemented in 28 nm CMOS technology and will be manufactured soon.

[1] F. Krummenacher, Nucl. Instrum. Methods A vol. 305 (1991), 527-532
[1] H.-S. Kim et al., IEEE J. Solid-State Circuits vol. 48 no. 2 (2013), 541-558
[3] R. Kleczek et al., IEEE 45th Eur. Solid State Circuits Conf. (ESSCIRC) (2019), 85-88

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 Kaczmarczyk (AGH University of Science and Technology)

Automated_adaptive_fast_reset_circuit_for_wide_energy_range_detector_front_end.pdf

162 SMAUG_ND_1 - an integrated circuit that implements the prototype method of indirect voltage measurements by measuring the noise distribution curve.

We present the design of the integrated circuit named SMAUG_ND_1 which implements the prototype of the method of indirect voltage measurement by measuring the noise distribution curve [1]. The IC is designed in a CMOS 28nm process. The die size is 1x1mm2 and contains a 7x7 matrix with 68 µm pixel pitch. The chip allows testing of the prototype method in coincidence with the CDS algorithm.

[1] G. Węgrzyn, R. Szczygieł, Przegląd Elektrotechniczny, 10/2021, 161-163

We acknowledge funding from the Polish Ministry of Science and Education (MEiN) (Research Project 0138/DIA/2020/49).

Speaker: Grzegorz Jan Wegrzyn (AGH-UST)

163 Performance of the isolated components of a hybrid spectrometer

The construction of a cylindrical hybrid spectrometer for the measurement of angular correlations in electron-positron emissions from nuclear internal pair creations is on going at the Van de Graaff accelerator of the Institute of Experimental and Applied Physics of Czech Technical University in Prague. Each module of the spectrometer consists of three different detection layers, formed by a Timepix3 detector [1] in the innermost layer, followed by a Multiwire Proportional Counter (MWPC) in the middle layer and a Time Projection Chamber (TPC) [2] in the outermost. While the needed angular resolution will be provided by the Timepix3 along with the MWPC, the energy resolution will be given by the TPC, under a magnetic field provided by permanent magnets. A good particle identification will be needed for an effective background suppression.
For this project, the performance of all three types of detectors in suitable geometrical configurations is under study. In this work, results with the Timepix3 detectors and with a TPC prototype will be reported. To address the target position determination and the angular correlation measurement capability, a triangle of synchronised Timepix3 detectors mounted on a vacuum chamber, surrounding a fluorine target bombarded with protons at e- e+ creation resonant energies was used as a model for the future inner layer of the spectrometer. We will show the main results obtained so far and a discussion on some geometrical aspects. Regarding the TPC, the current status of the integration of the SAMPA chip [3] in CERN's scalable readout system, carried out in the High Energy Physics and Instrumentation Center of the University of São Paulo, will be reported and the results of the reconstruction of the first cosmic tracks with a prototype mounted in Prague will be presented.

Speakers: Benedikt Bergmann, Benedikt Ludwig Bergmann (Czech Technical University in Prague (CZ))

164 Optoelectronic properties of High-Flux CdZnTe with optimized electrodes

With the rise of 4th Generation Synchrotron Light Sources such as the Extremely Brilliant Source (EBS) of the ESRF[1], the need for direct X-ray detection under high photon flux with moderate to high energies (30-100keV range) has increased. One of the candidate materials for this application is Cadmium Zinc Telluride (CdZnTe or CZT). In particular, the novel CZT material developed by Redlen for high-flux applications (HF-CZT) seems promising as it limits the polarizing phenomena observed in standard CZT under high photon flux[2], [3]. However, when it comes to electrical contacts, it appears that the standard gold electroless blocking contacts lead to much higher leakage current in HF-CZT than in the standard CZT [4]. The IMEM-CNR laboratory (Parma) has been developing novel contacts more suited to the HF-CZT.
In this work, the optoelectronic and transport properties of Redlen HF-CZT single crystals are studied. The single crystals were processed in IMEM-CNR where electroless gold and sputtered platinum electrodes were deposited. They have then been characterized both in IMEM-CNR and at the ESRF.
From this common work, we report low leakage current under dark conditions (8pA/mm2 at 5.103V/cm), good stability under moderate irradiation (107 to 1010 photons.mm-2.s-1), good linearity with incident flux and reduced transient phenomena (stabilization time, afterglow and polarization effects) as compared to standard CdTe material. The transport properties of the HF-CZT will also be discussed.

Speaker: Dr Oriane Baussens (ESRF)

Optoelectronic_properties_of_high-flux_CdZnTe_with_optimized_electrodes.pdf

165 Timepix3 Compton camera and its evaluation for selected application fields

The Compton camera allows reconstructing the direction of gamma photons coming from a radiation source based on the Compton scattering occurring within the detector. The incoming gamma photon interacts with the sensor material producing a recoiled electron. The scattered photon is then detected by photoelectric absorption. For the reconstruction of the incident photons' trajectory, the energy and time of interaction of both Compton products - the recoiled electron and the scattered photon - is needed. This contribution presents the Compton camera using miniaturized semiconductor pixel detector based on Timepix3, which represents a new generation of chips developed by the Medipix3 collaboration.
The traditional approach assumes a double-layer detector, when the recoiled electron is detected in the first layer (usually thin, low-Z sensor), while the scattered photon is absorbed in the second layer (usually thick, high-Z sensor) [1]. However, it was verified that it is possible to implement the Compton camera principle in a single detection layer [2] where both of these events are recorded by the single Timepix3 chip. The third coordinate is determined by measuring the drift time for both events with an accuracy of 30 µm. Thus, it has been shown that the single Timepix3 detector can serve as a fully functional Compton camera. This solution offers many advantages over the two-layer variant: compactness, lower weight and consumption and higher detection efficiency.
Various configurations of the Compton camera were tested within several research projects. Four application fields are considered: autonomous searching and localization of radiation sources using drone(s) [3], static monitoring of the radiation situation, handheld mobile Compton camera for rescue operations and medical imaging for diagnostics and therapy. It was demonstrated experimentally that the 2 mm CdTe sensor has a good performance for the single-layer Compton camera. In addition, the new CdTe sensors with thicknesses of 3 mm and 5 mm were studied. The thicker sensors would significantly increase the detection efficiency of gamma rays. A brief overview of the application fields and the current results will be presented.

Speaker: Daniela Doubravova

166 Experimental determination of charge carrier transport models for improving simulation of the HR GaAs:Cr detectors response

The response study of Timepix3 [1] (256 x 256 pixels, pixel pitch 55 µm) with 300 μm and 500 μm thick HR GaAs:Cr [2] sensors was continued with particle beams at the Danish Centre for Particle Therapy in Aarhus, Denmark and at Super-Proton Synchrotron at CERN. The detectors were irradiated at different angles with protons and pions of energies ~200 MeV and 120 GeV/c, respectively.

By performing measurements at grazing angle (as e.g. done in [3]), we extracted the charge carrier transport properties, i.e., the charge collection efficiencies and the charge carrier drift times as a function of the interaction depth, and measured the dependency of the electron and, for the first time, the hole drift velocity on the electric field. The latter one was found to be well described by a linear function. Moreover, we studied the dependence of the charge cloud size on the interaction depth (see Figure 1). Here, a good agreement was found with the Ruch model. All measurements were done for different detector assemblies to estimate systematic differences between them and to generalize the results.

The experimental findings were implemented into the Allpix2 simulation framework [4] and validated by comparison of measurement and simulation for various X- and γ-ray sources in the energy range from 5.9-122 keV (see Figure 2). Several approaches for charge carrier propagation were applied and the areas of their applicability were discussed.

Speaker: Dr Petr Smolyanskiy (IEAP CTU in Prague)

167 Study of MIPs effects on a MAPS for Electron Ion Collider in China

The Electron-ion collider in China (EicC) is a future high-energy nuclear physics project. It will be constructed based on an upgraded heavy-ion accelerator, High-Intensity heavy-ion Accelerator Facility (HIAF), which is currently under construction, together with a new electron ring. Due to its high spatial resolution, low material budget, and fast readout speed, the Monolithic Active Pixel Sensor (MAPS) has been chosen for the vertex detectors of the EicC. Charge deposited by the Minimum Ionizing Particles (MIPs) that pass through the MAPS is collected by the charge sensing node, formed by an n-well/p-substrate junction. Hence, the CMOS process is vital for developing MAPS.
The Nupix-A2, a MAPS with a pixel pitch of ~30µm, is designed for the EicC. The cost and detecting efficiency are the key concerns for CMOS process selection. Two 130nm CMOS processes have been proposed as candidates for this Nupix-A2. The first one is a commercial standard twin-well low resistivity (<50Ω·cm-3) process, and the other one is a quadruple-well high resistivity (>1kΩ·cm-3) process. A 3-dimensional TCAD model has been established to evaluate these two processes' feasibility for Nupix-A2. This paper will discuss the simulation and analysis of the effects of the MIPs on the Nupix-A2, which includes the study of the thickness of the depletion layer, charge collection efficiency, and charge collection time with different bias voltages and MIPs hitting locations.

Speakers: Prof. Chengxin Zhao (Institute of Modern Physics, CAS), Mr Liuqing Jing (Heilongjiang University)

168 Spectral tracking of protons by the Timepix3 detector with GaAs, CdTe and Si sensors

Position and directional-sensitive spectrometry of energetic charged particles can be performed with high resolution and wide dynamic range with the hybrid semiconductor pixel detectors Timepix/Timepix3 [1]. The choice of semiconductor sensor material, thickness and properties such as the reverse bias voltage greatly determined the sensitivity and resolving power for spectrometry and particle tracking (see Fig. 1). We investigated and evaluated the spectral-tracking resolving power such including deposited energy and linear-energy-transfer (LET) spectra (see Fig. 2 and Fig. 3) with the Timepix3 detector with different semiconductor sensors using well-defined radiation sources in terms of radiation type (protons, also alpha particles, X rays), energy and incident direction to the detector sensor. Measurements of particle incident direction in wide range were performed with collimated mono-energetic proton beams of various energies in the range 8 – 31 MeV at the U120-M cyclotron at the NPI CAS Rez near Prague. All detectors were per-pixel calibrated. The results will include correction for the per-pixel high-energy distortion [2]. This work enables to examine and perform detailed study of charge sharing and charge collection efficiency in semiconductor sensors. The results serve to optimize the detector chip-sensor assembly configuration for measurements especially with high-LET particles in ion radiotherapy and outer space. Work underway includes evaluation of newly refined GaAs sensors [3] as well as enhanced rad hard semiconductor sensors SiC.

[1] C Granja et al., NIM-A 908 (2018), 60-71
[2] M. Sommer, et al., NIM-A 1022 (2022) 165957
[3] B Zatko et al., JINST 15 (2020) C04004

Work in Advacam was performed in frame of Contract No. 40001250020/18/NL/GLC/hh from the European Space Agency. Measurements at the Prague Cyclotron were carried out in frame of the CANAM infrastructure of the NPI CAS Rez supported by Grant Project No. LM2011019 of the Ministry of Education, Youth and Sports of the Czech Republic. Work at SUT was supported by the Slovak Research and Development Agency grant APVV-18-0273.

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

Novak_iworid2022_poster.pdf

169 Silicon Detectors Beyond LHC – RD50 Status Report

Within the RD50 Collaboration, a large and dedicated R&D program has been underway for more than two decades across experimental boundaries to develop silicon sensors with high radiation tolerance for Phase-II LHC trackers. Based on the success of this R&D, these trackers are now entering their construction phase. RD50 is continuing its mission to study silicon sensors for particle tracking, shifting the focus to applications beyond the LHC. The next generation of collision experiments, such as the FCC, requires unprecedented radiation hardness in the range of a few 10$^{17}N_{eq}$ as well as time resolutions of the order of 10ps. Another key challenge is to move the sensor technology away from traditional planar passive float-zone sensors, which form large parts of the current trackers to sensor technologies such as CMOS where front-end electronics can be integrated, and where a wide availability in industry promises cost advantages.

Key areas of recent RD50 research include technologies such as Low Gain Avalanche Diodes (LGADs), where a dedicated multiplication layer to create a high field region is built into the sensor, resulting in time resolutions of a few tens of ps. LGADs will be employed by both ATLAS and CMS for their Phase-II LHC Upgrade. The radiation hardness of LGADs can be increased by using Carbon-implanted sensors which can be processed on 8-inch wafers. We also study 3D sensors as extremely radiation-hard sensors for the innermost layers of Phase-II LHC trackers. Fig. 1 shows SEM images from a pre-production 3D sensor made for the ATLAS pixel upgrade at CNM Barcelona. In addition, we investigate dedicated 3D sensors as a radiation-tolerant alternative to LGADs for fast timing applications. In another R&D-line we seek for a deeper understanding of the connection between macroscopic sensor properties such as radiation-induced increase of leakage current, doping concentration and trapping, and the microscopic properties at the defect level. A new measurement tool available within RD50 are the Two-Photon-Absorption (TPA) TCT systems, which allow position-resolved measurements down to a few um.

We will summarise the current state-of-art in silicon detector development in terms of radiation hardness and fast timing, and give an outlook on silicon sensors options for e.g. the FCC.

Speaker: Fasih Zareef (AGH University of Science and Technology (PL))

170 Indium Bump Deposition Techniques on Wafers and Individual Die Chips for Flip-Chip Bonding of Hybrid X-ray Detectors

Andreas Schneider*, Navid Ghorbanian, Jack Osborne, Simon P. Cross, John D. Lipp, Marcus J. French

UKRI - Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Campus, Didcot OX11 0QX, United Kingdom
* Corresponding author, andreas.schneider@stfc.ac.uk

Flip-chip bonding is a common method for joining ASICs to pixelated sensors in order to build hybrid X-ray detectors. STFC-RAL is using two methods for the interconnects between ASIC and sensor pixels. These are either indium bumps which are deposited on ASIC and sensor prior to bonding or alternatively electrically conductive adhesive dots are printed on the sensor pixel array and flip-chip bonded to gold studs attached to each pixel of the ASIC.
Conventionally the indium deposition is carried out on wafer-scale using a photolithographic lift-off process [1]. Sensor and ASIC with indium bumps are singulated from wafers afterwards.
However, some sensor material (e.g. CdZnTe) which is required for high-energy and high-flux X-ray detectors at XFEL or other scientific experiments is only available as individual die instead of wafers. The stencil printing of conductive epoxy dots onto those sensor dies together with gold ball studding of ASICs is a suitable method for those dies [2]. However, due to the size of printed epoxy dots this method has a limited pixel pitch and is currently only used down to 250µm-pitch. A novel method for indium deposition was developed for such dies. A shadow mask with small apertures is optically aligned to the pixel array and mechanically clamped to the sensor die. After indium evaporation onto this assembly and after removal of the mask, indium bumps as small as 50µm with a height of ~5µm are deposit onto the pixel array of the sensor. The same is done for a matching ASIC. Fig. 1 compares these two methods and indicates that indium bumps created by this method are approx. half the size of the epoxy dots and comparable with gold studs.
This novel indium deposition method will be compared with the conventional wafer-scale indium lift-off method and the epoxy/gold stud flip-chip bonding in terms of interconnect quality, bond yield, and suitability for hybrid X-ray detectors.

[1] C. Broennimann et al., Nuc. Inst. & Meth. In Phys. Res. A 565 (2006), 303-308
[2] A. Schneider et al., JINST 10 (2015), C02010
[3] W. Decker et al. Society of Vacuum Coaters 59th Ann. Tech. Conf. (2016) 95-100

The authors acknowledge funding from STFC’s Centre of Instrumentation for funding this research.

Speaker: Navid Ghorbanian

171 Quality Control (QC) of FBK 3D Si Sensors from the ATLAS ITk Preproduction

The High Luminosity upgrade of LHC (HL-LHC) is envisioned to reach an ultimate luminosity of 7.5×10^34 cm-2s-1 (integrated luminosity up to 4000 fb-1) and an average 200 pp collision per bunch crossing [1]. Such a challenging environment in terms of high particle rate, hit occupancy, and associated radiation damage has pushed the design of a new generation of small-pitch, and thin 3D Si pixel sensors [2].
FBK has recently produced a pre-production batch of 3D sensors with 50×50 µm2 pixel geometry compatible with the full-size ITKPix1v1.1 (RD53B) readout chip. Temporary metal shorting all pixels’ junction electrodes allowed to probe and electrically qualify the production yield at wafer level at FBK. Two wafers holding the temporary metal were diced at IZM, Germany. Later, a systematic QC test campaign has been carried out at the University of Trento.
As an example, Fig.1 shows the electrical behaviour of RD53B sensors from two different wafers. After dicing, the I-V of sensors (normalized to 20 ºC) shows a very good agreement with FBK data. C-V plot (Fig.1(b)) confirms the expected inter-electrode lateral depletion just in a few volts (~2V). 48 hr. long stability test (Fig.1(c)) near room temperature for a recommended operating bias, -30V, presents a stable leakage (fluctuation well below 10%). This study also comprises the additional parametric analysis, i.e., oxide charge density, oxide thickness, inter-pixel resistance, inter-pixel capacitance, etc., with the aid of Process Control Monitor (PCM) structures.

[1] C. Gemme et al., The ATLAS Tracker Detector for HL-LHC, JPS Conf. Proc., 010007 (2021).
[2] G.-F. Dalla Betta et al., Development of a new generation of 3D pixel sensors for HL-LHC, DOI: 10.1016/j.nima.2015.08.032

Speaker: Dr D M S Sultan (Universita degli Studi di Trento and INFN (IT))

Poster_DmsSultan_IWoRiD2022.pdf

172 Performance of neutron-irradiated 4H-Silicon Carbide pad diodes subjected to Alpha Particles, UV Laser Pulses, and proton beams

The material properties of Silicon-Carbide (SiC) make it a promising candidate for application as a particle detector at high beam rates. In comparison to Silicon (Si), the increase in charge carrier saturation velocity and breakdown voltage allows for high intrinsic time resolution while mitigating pile-ups. A larger bandgap and higher atomic displacement threshold energy suppresses dark current and potentially improve radiation hardness, respectively. In addition to the lower susceptibility to temperature variations, it allows the operation of irradiated devices at room temperature and daylight illumination. On the contrary, current TCAD and Monte-Carlo simulation tools are challenged regarding SiC due to its low carrier density, anisotropic effects, and insufficient knowledge of material parameters. Furthermore, limitations of the epitaxial growth process restrict the active layer thickness of SiC samples to a maximum of 100-150 μm, limiting the number of charge carriers generated by traversing particles, especially when approaching minimum ionizing particles (MIP) energies.
We present selected experiments carried out on 50 μm thick SiC p-in-n pad sensors. In-lab measurements providing high signal amplitudes and stable conditions, such as an Alpha-source and a UV-TCT-Laser setup, deliver insight into intrinsic material properties, while detector performance under high rate particle accelerator conditions was studied at the medical ion beam facility MedAustron, exploiting proton beams at a wide range of particle energies up to several hundred MeV. Samples exposed to neutron fluences of up to 1016 neq cm-2 were included in all experiments to extend our studies regarding the potential radiation hardness of SiC. Setup simulations based on GEANT4 were used for output comparison to ensure proper data evaluation.

Studies using UV-TCT and protons from particle beams to determine the charge collection efficiency of the irradiated samples will be shown. For all fluence levels, measured dark current at room temperature remains in the nA-range. To overcome the decrease in signal-to-noise-ratio (SNR) in the MIP region, efforts are taken to implement SiC into an LGAD design for prototype production. To take full advantage of the fast charge collection of potential SiC-LGADs, we are developing advanced single-channel readout electronics to be used in beam tests and to study the material properties further. Moreover, progress towards the development of a multi-channel ASIC, capable to switch between single particle detection and charge integration over larger time periods, for using SiC as high-rate beam intensity and position monitor will be shown.

Speaker: Philipp Gaggl (Austrian Academy of Sciences (AT))

Performance of neutron-irradiated 4H-Silicon Carbide pad diodes subjected to Alpha Particles, UV Laser Pulses, and proton beams.pdf

173 Cold Temperature Characterization of Ring Triplets based on RD53a readout chip

After ten years of massive success, the Large Hadron Collider (LHC) at CERN is going for an upgrade to the next phase, The High Luminosity Large Hadron Collider (HL-LHC) which is planned to start its operation in 2029. This is expected to have a fine boost to its performance, with an instantaneous luminosity of 5.0×1034 cm-2s -1 (ultimate value 7.5×1034 cm-2s -1) with 200 average interactions per bunch crossing which will increase the fluences up to more than 1016 neq/cm2, resulting in high radiation damage in ATLAS detector [1]. To withstand this situation, it was proposed to make the innermost layer with 3D silicon sensors, which will have a radiation tolerance of more than 1×1016 neq/cm2 with a TID of 9.9 MGy [2]. From the Final Design Review of November 2019, it was decided that the whole innermost layer (L0) will be made with 3D sensors. The Endcap part (ring part) will be made with 50 × 50 1E sensors, which will be jointly produced by FBK and SINTEF. To house these sensors, Ring Triplets will be made at the INFN Genova, and Milan, Italy. To achieve this future goal, six ring triplets have been already made in Genova with planar sensors and RD53a readout chip. Among them, three triplets have been tested in cold temperature setup for the first time at the University of Trento, cooling them down to -350C to check the possibility of starting up at such a cold temperature (Fig. 1(a)). At the conference, we will report on triplet cold test procedure in detail, with results from first three triplets, including IV characteristics at -250C. The chips were trimmed and tuned at cold temperature with suitable bias voltage on the sensors, to evaluate performance appropriately. A threshold scan (Fig. 1(b)), and ToT scan were done to check the response of chips towards tuning at cold temperature. An analog-injection crosstalk based disconnected-bump scan was done to check bump bonding quality (Fig. 1 (c)), an X-ray scan was done to check hits per pixel, as well as backup discbump scan results (Fig. 1(d)). All the results fulfill the ATLAS ITk requirements for the QA/QC process.

Speaker: Md Arif Abdulla Samy (Universita degli Studi di Trento and INFN (IT))

174 SiPM readout chip design for Heavy-ion Physics

Duo to the small size, high gain, high time resolution, low operating voltage, and insensitivity to magnetic fields of the SiPM, the research of SiPM as the sensor of the calorimeter has attracted a lot of attention. This work has designed 8-channel readout chips SICC0 and SICC1, which can simultaneously record the hit time and the energy information of particles. Each channel uses the traditional readout structure, including two readout path, one path uses a counter-type TDC to record the arrival time and the other path uses front-end and ADC to save the energy information, three different gear selections are used for the energy detect to cover a large dynamic input range. The test results show the performance of the SICC0 is as expected. The linearity input range is from 10uA to 3mA, and the time resolution is less than 1LSB (25ns) which can be up to 5ns, the dynamic range is 25ns-6.375us. To improve the time resolution, a new two-step TDC is designed on chip SICC1. The post simulation results shows that the time resolution of the new TDC is 140ps, the dynamic range is 640ns, and the RMS is about 3ps. SICC1 chip is still under testing now.

Speaker: Mr Binqiang Xiong (Central China Normal University)

175 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 109 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 with GaAs sensors 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. Beam tests for the Cherenkov detector and the electromagnetic calorimeter were performed at DESY recently and results will be presented. The experiment received a stage 0 critical approvement (CD0) from the DESY management and is in the process of preparing its technical design report (TDR). It is expected to start running in 2024/5.

Speaker: Arka Santra

176 A 20 Gbps PAM4 Receiver ASIC in 55 nm for Detector Front-end Readout

Abstract—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 core area of 1 mm × 0.8 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.

This work is supported by General Program of National Natural Science Foundation of China (Grant No.11875145)

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

177 Fast neutron measurement for homeland security using PSD of neutrons and X-rays generated by LINAC

To classify dangerous materials for homeland security, the structure of baggage can be identified through X-ray images, which are non-destructive testing (NDT). When an X-ray image and a neutron image are used together, various materials can be distinguished by the difference in the reaction mechanism of X-rays and neutrons in the material. It is intended to measure neutrons and X-rays through an integrated generator that simultaneously produces neutrons and X-rays using a high-energy linear electron accelerator. If the energy of the X-ray is greater than 8 MeV, a photonuclear interaction occurs in the tungsten target and generates neutrons. Organic, liquid, and plastic scintillators are generally used to obtain fast neutron images. These detectors have a high scattering cross-section for fast neutrons because it is composed of hydrogen and carbon, such as a low atomic number. Nevertheless, since the organic scintillator is also affected by the Compton scattering of X-rays, radiation signals generated in the scintillator should be distinguished. The method used in this case is the pulse shape discrimination (PSD) method. However, it is difficult to measure neutrons because the pile-up signals are produced in an environment where the X-ray flux generated from the electron accelerator is high. X-ray flux was reduced by lead shielding, and neutrons were measured through pile-up rejection to distinguish neutrons from X-rays. After the pile-up rejection process for the neutron region, the number of neutrons decreased from 15,477 to 8,983, and 6,494 counts were the pile-up signals.

Speaker: Gyohyeok Song (Korea Advanced Institute of Science and Technology)

178 Characterization of Micro Pore Optics for Full-field X-ray Fluorescence Imaging

Elemental mapping images can be achieved through step scanning imaging, static pinhole optics imaging or static imaging by micro pore optics (MPO). The MPO square micro pores act as waveguides for the X-ray photons, with the maximum angle for total refection of photons depending on the photon energy [1]. X-ray optics can be manufactured with different micro-channel geometries like square (MPO [2]), hexagonal or circular channels. Each optic geometry creates different imaging artefacts. Square micro pores generate a high intensity central spot due to two reflections via orthogonal channel walls inside a single channel - which is the desirable part for image formation - and two perpendicular lines forming a cross due to just a single reflection on a channel wall, as seen in Figure 1.

We have studied usage of an MPO in a full-field XRF imaging system. It consists of a commercially available MPO provided by Photonis and a Timepix3 readout chip with a 55 µm pixel pitch silicon detector. The flat MPO has a thickness of 1.2 mm, 20 µm square channel width and 25 µm channel pitch. The channel walls are coated with a ~25 nm iridium layer to achieve a flat surface and hence improve the optical properties.Imaging of fluorescence from small metal particles reveals the expected distinct cross patterns, as shown in Figure 1. Transmission through MPO channels and variation of critical reflection angle are characterised by measurements of metal fragments with different fluorescence energies. The experimental setup will be discussed in detail. To further characterise channel transmission and energy dependence of total reflection of the square MPO, it is mounted aligned with a 10 µm circular lead glass polycapillary array [3, 4].

This paper is a continuation of the previous work by the authors, where an X-ray optic with circular channels was compared with a pinhole optic [3]. Our purpose is to identify elemental imaging applications and spatial resolution limitations for an XRF instrument using these novel square pore MPOs.

[1] Gailhanou, M., Sarrazin, P. and Blake, D., 2018. Modeling of x-ray fluorescence full field imaging using planar square pore micro-channel plate optics. Applied optics, 57(23), pp.6795-6807.
[2] Sarrazin, P., Blake, D.F., Gailhanou, M., Walter, P., Schyns, E., Marchis, F., Thompson, K. and Bristow, T., 2017, September. Full field x-ray fluorescence imaging using micro pore optics for planetary surface exploration. In International Conference on Space Optics—ICSO 2016 (Vol. 10562, p. 105622G). International Society for Optics and Photonics.
[3] An, S., Krapohl, D., Norlin, B. and Thungström, G., 2020. Full-field X-ray fluorescence imaging with a straight polycapillary X-ray collimator. Journal of Instrumentation, 15(12), p.P12033.
[4] Yonehara, T., Yamaguchi, M. and Tsuji, K., 2010. X-ray fluorescence imaging with polycapillary X-ray optics. Spectrochimica Acta Part B: Atomic Spectroscopy, 65(6), pp.441-444.

The authors acknowledge funding from the Swedish Knowledge Foundation (ImSpec - Multiple energy band imaging spectroscopy for material and object classification). The measurements were performed using detectors, software and readout system developed within the MEDIPIX collaboration, hosted by CERN.

Speaker: Börje Norlin

179 ANN on-chip and in-pixel implementation towards pulse amplitude measurement

We present the design and simulation results of an intelligent pixel consisting of an analogue front-end, Analog-to-Digital Converter (ADC) and an Artificial Neural Network (ANN) for in-pixel data pre-processing. The source of signals is a silicon X-ray sensor connected to the front-end optimized for 4 keV - 12 keV. The low-noise operation in the order of 60 el. rms. allows for precise signal representation before digitizing with 6-bit and 5 MHz – 10 MHz sampling rate ADC. 6-bit samples are buffered and further processed by an ANN, which main goal is to give the precise estimation of the pulse amplitude with the resolution exceeding 6 bits. With the presented approach we overcome the traditional photon energy measurement, where analogue blocks are used for keeping the pulse amplitude information and then digitizing it with more precise ADC. The state-of-the-art solutions that offer the highest accuracy are Medipix3RX [1] with up to 8 energy discrimination levels, Timepix3 [2] with the implementation of time-over-threshold (ToT) functionality and Flora [3] with successive approximation ADC.

In this work, we present novel approach with on-chip implementation of an ANN together with simulation results explaining the idea, providing the information about achievable accuracy, and an optimization procedure. The design is being prepared utilizing deep sub-micron technology of CMOS 28 nm, which allows for dense logic synthetizing and therefore gives an opportunity for ANN placing as close to the signal as possible.

[1] E. N. Gimenez, R. Ballabriga, G. Blaj, M. Campbell, I. Dolbnya, E. Frodjh, I. Horswell, X. Llopart, J. Marchal, et al., Medipix3RX: Characterizing the Medipix3 Redesign with Synchrotron Radiation, IEEE Trans. Nucl. Sci. 62, (2015) 1413.
[2] T. Poikela, J. Plosila, T. Westerlund, M. Campbell, M. De Gaspari, X. Llopart, V. Gromov, R. Kluit, M. Van Beuzekom, et al., Timepix3: A 65K channel hybrid pixel readout chip with simultaneous ToA/ToT and sparse readout, J. Instrum. 9, (2014).
[3] G. A. Carini, G. W. Deptuch, F. Fahim, Ł. A. Kadłubowski, P. Klabbers, S. Lauxtermann, P. O. Petterson and T. Zimmerman, Hybridized MAPS with an in-pixel A-to-D conversion readout ASIC, Nucl. Instruments Methods Phys. Res. Sect. A Accel. Spectrometers, Detect. Assoc. Equip. 935, Elsevier Ltd, (2019) 232.

The authors acknowledge funding from the Norway Grants through National Centre for Research and Development in Poland (Research Project NOR/SGS/Intelligent_XRay_Det/0196/2020-00).

Speaker: Anna Kozioł (AGH University of Science and Technology in Cracow)

180 A 2.56 Gbps or 10 Gbps Clock Data Recovery ASIC for Detector Front-end Readout

The bi-directional serial optical data transceiver system is employed between the front-end and the back-end in the detector readout electronics. The low jitter clock data recovery (CDR) ASIC is one of the key components in the high-speed serial down link direction. It receives a pair of high-speed serial input data, recovers the clock signal from the data and resamples the input data at the same time. Some similar ASICs used in particle physics experiments have been reported, such as the GBTx [1] (2.56 Gbps CDR in down link) and LpGBT [2] [3] (2.56 Gbps CDR in down link). The proposed CDR ASIC has been fabricated in a 55 nm CMOS technology for detector front-end readout, which is selectable to operate at 2.56 Gbps or 10 Gbps data rate.
The CDR ASIC consists of an input equalizer stage, a bang-bang phase detector (BBPD), a charge pump circuit (CP), a low-pass filter (LPF), two selectable LC voltage-controlled oscillator (LC-VCO) circuits and a SPI module. The input equalizer stage adopts a 5-step continuous-time linear equalizer (CTLE) structure [4] to compensate the high frequency loss from the system level including PCB traces, bonding wires and pads. The CTLE boosts maximum up to 9.8 dB at 7 GHz while providing a DC gain of 4.7 dB. The BBPD is used to detect the phase difference between the input data jump edge and sampling clock. To obtain low leakage current and reduce dynamic mismatch, two feedback operational amplifiers are employed in the charge pump circuit. To accommodate the two different data rates (2.56 Gbps or 10 Gbps), the two LC-VCOs which is configured by the SPI module are employed in the CDR. The LC-VCO1 and LC-VCO2 circuits can operate at 2.56 GHz and 10 GHz, respectively. They adopt the two-step capacitor tuning structure and the capacitor array unit to obtain a reasonable frequency range and an optimized Q factor performance.

The low jitter CDR ASIC was presented with a 2.56 Gbps or 10 Gbps data rate in a 55 nm CMOS technology for detector front-end readout and the ASIC features a size of 1.5 mm  1.5 mm. Widely-open resampling data eye has been observed at 2.56 Gbps or 10 Gbps data rate. The simulation results show that the jitters of 2.56 Gbps or 10 Gbps resampling data eye are 1.4 ps and 2.8 ps, respectively. At 2.56 GHz, the recovered clock achieves a phase noise of -112 dBc/Hz at 1 MHz offset and a jitter of 1.2 ps. At 10GHz, the recovered clock achieves a phase noise of -106 dBc/Hz at 1 MHz offset and a jitter of 1.5 ps. The chip has been taped out and the tests are planned to be conducted in this April. The test and total ionizing dose (TID) test will be performed. The test results will be reported in the meeting.

[1] Paulo Moreira et al., The Radiation Hard GBTX Link Interface Chip. https://indico.cern.ch/event/267408/attachments/477815/661090/eseSeminar26november.pdf
[2] Paulo Moreira et al., lpGBT – a User’s Perspective. https://indico.cern.ch/event/697988/contributions/3075493/attachments/1720215/2776778/lpGBTtutorialTwepp20180921.pdf
[3] Stefan Biereigel et al., A Low Noise Fault Tolerant Radiation Hardened 2.56 Gbps Clock-Data Recovery Circuit With High Speed Feed Forward Correction in 65 nm CMOS. IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS–I 2019.
[4] S. Gondi et al., A 10 Gb/s CMOS Adaptive Equalizer for Backplane Applications, IEEE ISSCC 2005 (2005) 328-329.

This work is supported by General Program of National Natural Science Foundation of China (Grant No. 11875145).

Speakers: Cong Zhao, Di Guo (Central China Normal University)

181 Design and preliminary performance of scintillators-based unmanned aerial vehicle for low-cost remote radiation detection

Unmanned aerial vehicles (UAVs) provide an efficient method of remotely sensing environments that humans cannot approach with conventional aircraft due to serious hazard or access limit. The use of UAVs has been suggested as suitable solution in numerous disciplines, including wildfire thermal imaging, radiological survey and radiation activity monitoring since the Fukushima nuclear accident. Many researches have adopted different types of UAVs and radiation detection sensors and have proposed various radiation monitoring systems and data management systems in a site.
In this work, we propose a novel method of using a commercially available drone for aerial radiation detection, which consists of a high-resolution image camera for environmental observation. We have designed and developed the low-cost and remote radiation monitoring system with different types of scintillating screens for radiation detection tasks. A latest compact drone (model: mavic 2 pro) with 322(L) x242(W) x84(H) mm dimension consists of CMOS image array for vision imaging acquisition. Different commercial scintillation screens such as CsI:Tl and powder Gd2O2S:Tb materials were applied to measure the X-ray exposure dose and gamma ray activity. The various design parameters such as scintillator types and radiation types were selected and investigated for preliminary possibility under practical X-ray and gamma-ray condition.
For evaluation and optimization of the X-ray image device characterization, different configuration parameters are investigated. The characteristics of the CMOS image sensors with and without scintillator in a drone, such as dose response linearity, dose rate dependence, and minimum detectable activity were evaluated. This result has demonstrated that the unmanned aerial vehicle with a camera and scintillator can be used as a low sensitivity dose rate meter.

Figure. 1. Design concept of a scintillator-based unmanned aerial vehicle (left) and a histogram distribution of an X-ray image (right).

Speaker: Mrs Jiyong Sim

Trip to Arco

Social Dinner

Thursday, 30 June

Applications: 4

Convener: Valeria Rosso (University of Pisa, Pisa, Italy)

182 INVITED: Semiconductor Drift Detectors: history, present and future

At 40 years from its invention, this presentation would like to remember the history of the Semiconductor Drift Detector (SDD) since its conception by E. Gatti and P. Rehak, the technological efforts and studies done in Brookhaven, Milan and Munich to develop the first prototypes, the many different device topologies conceived, the theoretical studies and the many applications in which SDDs have given a fundamental contribution.

The presentation will highlight also the research activities regarding the development of low noise front-end electronics aimed to exploit the high potentiality of SDDs , from the discrete and integrated
JFETs to the more advanced CMOS ASICs implementations. The engineers and scientists who contributed from all over the world to this fascinating scientific and technological journey will be mentioned.

Although nowadays, the maturity of SDDs technology is very high and successful commercial spectrometers are made available by many companies, research and development activities are still open and are continuously stimulated by the challenges lead by many scientific applications as in Synchrotron radiation facilities for fundamental and applied Science or in Astrophysics with complex and very large format imaging X and Gamma ray spectrometers for space missions. Starting from the currently running research on SDDs, a perspective view of the still open possibilities and challenges for future developments and applications will be presented.

Speaker: Prof. Giuseppe Bertuccio (Politecnico di Milano)

Bertuccio_IWORID_2022_Semiconductor_Drift_Detectors_Published.pdf

183 Beam Test Studies with the latest Silicon Sensor Module Prototypes for the CMS Phase-2 Outer Tracker

The Large Hadron Collider (LHC) at CERN will be upgraded to the High-Luminosity LHC (HL-LHC) until 2029. In order to fully exploit the physics potential of the high luminosity era the experiments must undergo major upgrades. In the context of the upgrade of the Compact Muon Solenoid (CMS) Experiment the silicon tracker will be fully replaced. The outer part of the new tracker (Outer Tracker) will be equipped with about 13.000 double-layer silicon sensor modules with two different flavours: PS modules consisting of a macro-pixel and a strip sensor and 2S modules made of two strip sensors. These modules can discriminate between trajectories of charged particles with low and high transverse momentum. The different curvature of the trajectories in the CMS magnetic field lead to different hit signatures in the two sensor layers. By reading out both sensors with the same set of chips, matching hits in the seed and correlation layer (stubs) are identified. This stub information is generated at the bunch crossing frequency of 40 MHz and serves as a direct input for the first stage of the CMS trigger.

In order to measure the hit and stub detection efficiency beam tests have been performed for detailed studies. This talk gives an overview of beam test measurement results that have been gathered during two beam tests at the DESY test beam facility with the latest 2S prototype modules. In order to compare the module performance at the beginning and end of the CMS runtime, modules with un/irradiated sensors and front-end hybrids have been built and intensively tested. The talk gives a direct comparison of the unirradiated and irradiated module performance in terms of hit efficiency, stub efficiency at different rotation angles (simulating particles with different transverse momenta) and resolution.

Speaker: Florian Wittig (KIT - Karlsruhe Institute of Technology (DE))

iWoRid.pdf

184 Test of ITk 3D sensor pre-production modules with ITkPixv1.1 chip

ITk detector, the new ATLAS tracking system at High Luminosity LHC, will be equipped with 3D pixel sensor modules in the innermost layer (L0). The pixel cell dimensions will be either 25x100 µm2 (barrel) or 50x50 µm2 (endcap), with one read-out electrode at the centre of a pixel and four bias electrodes at the corners. Sensors from pre-production wafers (50x50 µm2) produced by FBK have been bump bonded to ITkPixv1.1 chip at IZM. Bare modules have been assembled in Genoa on Single Chip Cards and characterized in laboratory and at test beam.

Speaker: Alessandro Lapertosa (INFN e Universita Genova (IT))

iWoRiD_FBK_3D_30Jun22.pdf

185 Experimental Characterization of a Fast X-Ray Spectroscopic Imager Module for Real-Time Contaminants Detection

We present the experimental characterization of a fast spectroscopic imager for real-time room-temperature detection of low-density contaminants in food production lines. The presented imager is part of XSpectra®, an innovative inspection technology which combines a fast X-ray detection hardware and neural network processing techniques to improve the current limits in detection systems for food quality, material recycling, pharma safety and security applications [1,2].The detection unit consists of a 1-D array organized in four detection modules: each module is composed of a 32-pixel CdTe crystal, which have demonstrated promising results in the field of fast spectroscopy [3], coupled to four 8-channel read-out ASICs. The analog pre-amplified signals are sampled by an off-chip A/D converter and processed numerically by an FPGAs in the back-end electronics board. Due to the real-time requirements of the target application, the incoming events must be processed in the deep sub-microsecond range. A new version of the front-end ASIC has been recently designed to improve energy resolution and the dynamic characteristics of the system at short shaping times (<100 ns), allowing a consistent stability of spectroscopic performance in presence of high incoming photon fluxes.

The complete detection unit (128 channels in total) has been characterized to assess both low-rate spectroscopic performance and the ability to withstand high incoming photon fluxes. An average line width of 3.6 keV FHWM has been recorded on the 59.5 keV peak of a 241Am calibration source at a peaking time of 60 ns, with the low-energy threshold lying at 6 keV. Spectral resolution has been measured on all tested channels, with a deviation of ±10% with respect to the average value. The spectroscopic imager can cover an energy range of 200 keV, while keeping non-linearity error below ±1%.

A tungsten target X-ray tube, with a voltage working point of 30 kV, has been used to assess the imager performance in a realistic operational environment using contaminated food samples, showing a stable operation of the system up to an input count-rate of 2.1 Mcps.

[1] B. Garavelli et al., IEEE NSS/MIC, (2019), 1-3
[2] B. Garavelli et al., IEEE BioCAS, (2017), 1-4
[3] M. Sammartini et al., IEEE TNS, 68 (2021), 1, 70-75

Speaker: Jacopo Quercia (Politecnico di Milano)

IWORID_2022_Quercia.pdf

186 Performance studies of Low Gain Avalanche Detectors (LGAD) coupled to the Timepix3 ASIC

In this work the properties of 200 μm thick highly pixelated LGAD sensors bonded to a Timepix3 readout ASIC were characterised for the first time. Recent advances in the control of the LGAD fabrication process by Micron Semiconductor Ltd has allowed the manufacture of highly segmented devices where each pixel has an internal gain. Devices with 55 μm pixel with 5 μm Junction Termination Element (JTE), 110 μm pixel with 10 μm JTE and 110 μm pixel with 20 μm JTE where bump bonded to a Timepix3 readout ASIC and characterised with a micro-focus monochromatic 15 keV X-ray beam.
Figure 1 shows the response profile from the 110 μm pixel device from the X-ray beam as the pixel array was moved relative to the beam for the pixel of interest (PoI), and its neighboring pixels (left-hand side and right-hand side pixels). The quantity plotted is the integrated time-over-threshold (ToT) for the pixel from an illumination of 5 seconds per illumination position. This corresponds to the total collected charge at the pixel electrode. The PoI boundaries can be seen between motor positions -17.55 and 17.44 mm. A region of gain in the middle of each pixel can clearly be observed. The gain of factor approximately three can be extracted directly from the pixel profile. Figure 2 shows a 2D map obtained by a raster scan of the pixel array recording the integrated ToT from the PoI. The regions of gain and no gain are clearly visualized. Results obtained suggest a good degree of understanding of the fabrication processes involved but demonstrated the limitations of the standard LGAD process with a JTE for small pixel. This work will report on the characterisation of fabricated devices and suggest mechanisms for mitigating the effects of limited gain regions for small sized pixel.

Speaker: Dr Dima Maneuski (University of Glasgow (GB))

220630-maneuski-iworid_2022.pdf

220630-maneuski-iworid_2022.pptx

10:35 Coffee break

Sensors: 4

Conveners: Gian Franco Dalla Betta (Universita degli Studi di Trento and INFN (IT)), Gian-Franco Dalla Betta (INFN and University of Trento)

187 Innovative means of operation of optical readout Time Projection Chamber

We are going to present the R&D developed within the CYGNO/INITIUM projects towards innovative means of operation of optical readout Time Projection Chamber (TPC) for lower energy threshold and improved tracking performances. CYGNO goal is to develop an high precision TPC with an He:CF4 gas mixture at atmospheric pressure readout by scientific CMOS cameras and PMT, in order to achieve 3D tracking with head tail capability and particle identification down to O(keV) energy for directional search of Dark Matter and solar neutrino spectroscopy [1]. The ERC Consolidator project INITIUM aims at realising Negative Ion Drift operation at atmospheric pressure within CYGNO optical readout approach.
We are going to illustrate the possibility of enhancing the light yield (hence effectively lowering the energy threshold) up to a factor 10 without degrading the tracking performances in He:CF4 gas mixtures by means of luminescence of non-ionising electrons drifted beyond the amplification stages [2]. We are going furthermore to discuss TPC Negative Ion Drift operation at atmospheric pressure with He:CF4:SF6 optically readout by both CMOS camera and PMT. Negative Ion Drift operation is a peculiar modification of the TPC principle by which, thanks to the addition of an highly electronegative dopant to the gas mixture, anions act as image carriers rather than electron, reducing down to the thermal limit the diffusion during drift [3]. This characteristics allows for the use of longer drift distances, combined with improved tracking.
Each of these features can significantly boost the performances of any experimental approach that requires high precision imaging TPCs, such as, among the others, X-ray polarimetry, neutron spectroscopy, neutrinoless double beta decay searches, Migdal effect measurements and tracking in high energy physics.

Speaker: Elisabetta Baracchini

Baracchini_iWorid_EL_NID_June_2022_nonid.pdf

188 Edge-TCT evaluation of High Voltage-CMOS test structures with unprecedented breakdown voltage for high radiation tolerance

High Voltage-CMOS (HV-CMOS) sensors can offer a thin, cost effective, and radiation tolerant solution to future experiments using current manufacturing capabilities. At present HV-CMOS sensors are not capable of reaching the time resolution, pixel size, and radiation tolerances specified for the next generation of high luminosity colliders, such as the Future Circular Collider (FCC), or further upgrades to the Large Hadron Collider (LHC). Further research and development is needed for a step change improvement in the performance of HV-CMOS sensors. The monolithic nature of HV-CMOS sensors allows front-end electronics to be embedded in the collecting electrode, isolated from the bulk which gets biased to high voltage. There is no need for bump-bonding like that of hybrid pixels. As the embedded electronics are isolated from the substrate higher biases, compared to conventional CMOS designs, can be achieved giving faster collection times, through drift rather than diffusion, and better radiation tolerance.

UKRI-MPW0 is a proof-of-concept monolithic, backside biased, HV-CMOS chip aiming to improve radiation tolerance. The chip implements a dedicated sensor cross-section, which achieves a breakdown voltage of more than 600 V before irradiation. The sensing junction made between the deep n-well (DNWELL) and the p-substrate uses backside biasing only; an absence of any topside p-wells in direct contact with the substrate further improves the breakdown voltages. UKRI-MPW0 uses a high substrate resistivity of 1.9 kΩ∙cm and is in the 150 nm technology of the LFoundry HV-CMOS process.

This contribution presents the first edge-TCT measurements of the test structures, included on the edge of the UKRI-MPW0 pixel chip, irradiated with neutrons to high fluences.

The authors acknowledge funding from UK Research and Innovation (UKRI) (Research Project MR/S016449/1).

Speaker: Benjamin Wade (University of Liverpool (GB))

iWoRiD2022-1.pdf

189 Timing performance of radiation hard MALTA monolithic Pixel sensors

The MALTA family of DMAPS produced in Tower 180 nm CMOS technology target radiation hard applications for the HL-LHC and beyond. Several process modifications and front-end improvements have resulted in radiation hardness up to 2e15 n/cm² and time resolution below 2 ns, with uniform charge collection efficiency across the Pixel of size 36.4 x 36.4 um² with a 3 µm² electrode size. The MALTA2 demonstrator produced in 2021 on high-resistivity epitaxial silicon and on Czochralski substrates implements a new cascoded front-end that reduces the RTS noise and has a higher gain. This contribution will show results from MALTA2 on timing resolution at the nanosecond level from the CERN SPS test-beam campaign of 2021.

Speaker: Giuliano Gustavino (CERN)

2022.06.16.GGustavinoIWORID2022.pdf

190 Investigation of the Time Resolution in 3D silicon sensors

Collider experiments as the upcoming Phase II-LHC or the future circular collider (FCC) will increase the demands of the detectors used for tracking. In the FCC hadron collider , sensors will not only face fluences up to to $1×10^{17}~ n_\mathrm{eq}/\mathrm{cm}^2$, but also high pile-up scenarios. Therefore, sensors will be required that not only have a good spatial resolution and a very high radiation hardness, but also an excellent time resolution of 5ps.
Currently, Low Gain Avalanche Diodes (LGADs) are the prime candidates when it comes to timing, achieving a resolution of below 30ps. However, their radiation hardness is not sufficient for future colliders. As an alternative, 3D sensors are an interesting research area due to their superior radiation hardness. In 3D sensors, the drift distances are short, the depletion voltage is very low and the electric field can be very high, thus the signals are fast and short.

In this study, the time resolution of different 3D sensors was investigated with signals generated by MIP-like electrons, as well as by measurements using a laser with an infrared wavelength. We will show that 3D pixel sensors can achieve time resolutions competitive with LGADs. Additionally, Transient Current Technique (TCT) Timing measurements allow to study the position dependence of the time resolution, which is interesting for 3D sensors due to their more complex electric field structure. These measurements prove the direct correlation between the time resolution and the electric field distribution. Furthermore, the performance of the sensors will be demonstrated before and after irradiation with reactor neutrons.

Speaker: Dennis Sperlich (Albert Ludwigs Universitaet Freiburg (DE))

Iworid_Timing.pdf

191 10ps timing with 3D trench silicon pixel sensors

Future collider experiments operating at very high instantaneous luminosity will greatly benefit in using detectors with excellent time resolution to facilitate event reconstruction. In the case of the LHCb Upgrade2 at CERN, when the experiment will operate at 1.5x10^34/cm/s, 2000 tracks from 40 proton-proton interactions will cross the vertex detector at each bunch crossing. To properly reconstruct primary vertices and b-hadron decay vertices, it is required to develop sensors and electronics capable of a hit time stamping with 50ps accuracy. Within such developments, several technologies are under study and one of the most promising today is the 3D trench silicon pixel, developed by the INFN TimeSPOT collaboration. These 55µmx55µm pixels are built on a 150µm-thick silicon and consist of a 40µm-long planar junction located between two continuous bias junctions, providing charge-carriers drift paths of about 20µm and total charge collection time close to 300ps. Two batches of sensors were produced by FBK in 2019 and 2021. The most recent beam test was performed at SPS/H8 in November 2021. Various test structures were readout by means of low-noise custom electronics boards featuring a two-stage transimpedance amplifier, and the output signals were acquired with an 8GHz 20GS/s oscilloscope. The arrival time of each particle was measured with an accuracy of about 7ps using two 5.5mm-thick quartz window MCP-PMTs. Two 3D trench silicon pixel test structures and the two MCP-PMTs were aligned on the beam line and acquired in coincidence. Signal waveforms were analyzed offline with software algorithms and pixel signal amplitudes, particle time of arrival and efficiencies were measured. Data analysis indicates efficiencies close to 100% for particles impinging at more than 10 degrees with respect to normal incidence, and time resolutions close to 10ps. 3D trench-type silicon pixels appear to be a promising technology for future vertex detectors operating at very high instantaneous luminosity

Speakers: Adriano Lai (Universita e INFN, Cagliari (IT)), Andrea Lampis (Universita e INFN, Cagliari (IT))

Andrea_Lampis_iworid2022.pdf

Closing

Conveners: Gian Franco Dalla Betta (Universita degli Studi di Trento and INFN (IT)), Gian-Franco Dalla Betta (INFN and University of Trento)

192 Next IWORID

Speaker: Dr Marco Povoli (SINTEF MiNaLab)

iWoRriD_2023_Oslo.pdf

193 Announcing HiZPAD Workshop

Speaker: Matthew Veale

HiZPAD_Teaser_Oct22.pdf

HiZPAD_Teaser_Oct22.pptx

194 Farewell

Speaker: Prof. Gian Franco Dalla Betta (Universita degli Studi di Trento and INFN (IT))

Closing_Talk_GFDB.pptx

13:00 Lunch break