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Jan 29, 2022, 8:59:51 AM
Jan 29, 2022, 10:59:51 PM
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Advancement on 4x4x1.5 cm3 CZT Detectors (#1260)
Z. He1, Y. Zhu1
1 University of Michigan, Nuclear Engineering and Radiological Science, Ann Arbor, Michigan, United States of America
Single-crystal three dimensional (3-D) position-sensitive CdZnTe (CZT) gamma-ray detectors have been commercially available up to about 2x2x1.5 cm3 in size. Larger 4x4x1.5 cm3 CZT detectors are being developed for higher detection efficiency and better gamma-ray imaging performance. This advancement has been carried out by the University of Michigan in collaboration with Redlen Technologies and Kromek, the two main CZT suppliers in the world. Improvements on energy resolution, bulk material uniformity, electrode fabrication and substrate attachment process have been observed. Energy resolution of close to 0.50% FWHM at 662 keV for single-pixel events from all of 22x22 pixel anodes have been obtained on multiple larger CZT detectors, showing the progress made by CZT manufacturers over the past years.
AcknowledgmentThis material is based upon work supported by the Defense Threat Reduction Agency under Contract # HDTRA1-18-C-0073. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of DTRA.
Keywords: CZT, 3-D position sensing, semiconductor, room-temperature, gamma ray spectrometers
First characterization of AC-LGAD sensors using a readout ASIC (#738)
G. D'Amen1, A. Tricoli1, G. Giacomini2, W. Chen2, E. Rossi2, L. Serin3, N. Seguin-Moreau4, C. De La Taille4, M. Moreans4
1 Brookhaven National Laboratory, Physics Department, Upton, New York, United States of America
The development of detectors that provide high resolution in four dimensions has attracted wide-spread interest in the scientific community for several applications in high-energy physics, nuclear physics, medical imaging, mass spectroscopy as well as quantum information. The Low-Gain Avalanche Diode (LGAD) silicon detector has already shown excellent timing performances, but since fine pixelization of LGADs is difficult to achieve, the AC-coupled LGAD (AC-LGAD) approach was introduced to provide high spatial resolution. In this type of device, the signal is capacitively induced on fine-pitched electrodes placed over an insulator and is shared among multiple electrodes. AC-LGADs are therefore considered as promising candidates for future detectors to provide 4-dimensional measurements with high resolution in both space and time dimensions. AC-LGAD sensors designed and fabricated at the Brookhaven National Laboratory (USA) have been coupled and read-out using a fast-time ASIC prototype, the ATLAS LGAD Timing Integrated Read-Out Chip (ALTIROC) that was developed by Omega/IJCLab (France) for the ATLAS timing detector at the HL-LHC. The response of two identical AC-LGAD strip sensors to beta particles and IR photons has been measured using the ALTIROC0 ASIC and a Trans-impedance amplifier custom electronic board and compared. Both readout setups have been used to study signal sharing, as well as spatial and time resolution of the AC-LGAD sensors.
AcknowledgmentThe authors wish to thank their colleagues at Brookhaven National Laboratory: Ron Angona, Wei Chen and Sean Robinson for sensor fabrication; Don Pinelli, Joe Pinz and Antonio Verderosa for board assembly and wire bonding. This material is based upon work supported by the U.S. Department of Energy under grant DE-SC0012704. This research used resources of the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704.
Keywords: silicon detectors, fast timing, tracking
Time Based Energy Discrimination for Analog SiPM Readout (#239)
N. Kratochwil1, 2, S. Gundacker3, I. Frank1, 4, M. Pizzichemi1, 5, E. Auffray1
1 CERN, Geneva 23, Genève, Switzerland
The development of solid state photodetectors likesilicon photomulipliers (SiPMs) has paved the way for a new generation of radiation detectors. By utilizing high frequency readout electronics it is possible to access information carried by the first few detected photons. This opens the door fora fully time based detector design without classical charge integration or time over threshold measurement of the full scintillation pulse. Analog SiPMs can be treated in a digital like approach by using two or more time thresholds.
In order to validate the feasibility of time based energy discrimination several types of time based estimators were experimentally evaluated with commercially available SiPMs and LYSO:Ce crystals upon 511 keV γ-excitation. By measuring the SiPM signal rise time within the first 150 ps, an error rate below 10 % for photopeak discrimination was achieved. A further thorough discussion and prospects on time based estimators is given, which allow to access information on energy, depth of interaction (DOI), promptphoton yield and time resolution.
AcknowledgmentThis work was performed in the framework of the Crystal Clear Collaboration. The authors thank Michele Baschiera for his help in preparing the PCBs for the SiPMs used in this study.
Keywords: Energy Resolution, Time-based-energy-discrimination, Signal processing, Analog Silicon Photomuliplier
High-resolution 3-D CZT drift strip detectors for prompt gamma ray and neutron detection in BNCT (#955)
L. Abbene1, F. Principato1, G. Gerardi1, A. Buttacavoli1, N. Auricchio2, E. Caroli2, S. Zanettini3, M. Bettelli4, A. Zappettini4
1 University of Palermo, Dipartimento di Fisica e Chimica E. Segrè, Palermo, Italy
Intense research activities have been carry out in the development of room temperature spectroscopic imagers for the detection of prompt gamma rays in boron neutron capture therapy (BNCT). BNCT is a highly selective tumour treatment based on the neutron capture reaction 10B(n,a)7Li. The key operation is represented by the detection of the prompt gamma rays (478 keV), produced by the7Li recoil nucleus, for a real-time monitoring of the spatial distribution of 10B during the treatment. In this work, we will present the potentialities of new high-resolution CZT drift strip detectors, recently fabricated at IMEM-CNR of Parma (Italy), for BNCT measurements. The detectors, exploiting the analysis of collected-induced charge pulses from anodes, cathodes and drift strips, show excellent energy resolution < 1% at 662 keV at room temperature. The results of gamma ray measurements at the thermal column (TC) of the T.R.I.G.A. Mark II research nuclear reactor of Pavia University (Pavia, Italy) will be presented.
Keywords: CZT drift strip detectors, BNCT
Hybrid Spectral and Image Deconvolution for High-Resolution CZT Imaging Spectrometers (#137)
C. G. Wahl1, D. Goodman1, W. Kaye1, S. Brown1, B. Kitchen1
1 H3D, Inc., Ann Arbor, Michigan, United States of America
Large-volume 3D-position-sensitive CdZnTe is used in many applications for spectroscopy and Compton imaging. In some of these applications, general users of the detectors are not experts. Therefore, the image and spectrum results must be automatically interpreted in near real time to give users actionable information. This work aims to automatically interpret the image and spectrum beyond isotope ID to include some estimates of source direction(s), shape(s), activity(ies) at a nominal distance, and shield material(s) and thickness(es), along with some idea of the confidence or uncertainty in these estimates. This is accomplished by first applying deconvolution methods to the simple-back-projection image and spectrum based on an empirical detector-system model. From this, estimates of source parameters and their uncertainty can be extracted. This work presents the algorithms and results of these algorithms in test cases of point, distributed, and shielded sources.
This material is based upon work supported by the Defense Threat Reduction Agency (DTRA) under Contract No. HDTRA118C0022.
Keywords: Gamma-ray detectors, semiconductor radiation detectors, CdZnTe, image deconvolution, isotope ID methods
Multi-modal 3D imaging using multiple hybrid Compton cameras (#196)
A. Omata1, M. Masubuchi1, J. Kataoka1, H. Kato2, A. Toyoshima3, T. Teramoto3, K. Ooe2, Y. Liu2, K. Matsunaga2, T. Kamiya2, T. Watabe2, E. Shimosegawa2, J. Hatazawa2
1 Waseda University, Graduate School of Advanced Science and Enginering, Tokyo, Japan
X-ray and gamma-ray imaging techniques are critical in nuclear medicine. However, it is generally challenging to realize simultaneous wide-band imaging because various interactions between photons and the detector material differ depending on the photon energy. Single-photon emission tomography (SPECT) and positron emission tomography (PET) play essential roles in radiological diagnoses, such as early detection of tumors and imaging a specific energy range of either X-rays or gamma rays. Photons from radionuclides have a wide energy range from a few keV to several MeV. This leads to a limited number of radioactive tracers that can be imaged using only current SPECT and PET scanners. Thus, we propose a hybrid Compton camera that realizes simultaneous Compton and pinhole imaging within a single detector system. Similar to conventional Compton cameras, the hybrid Compton camera consists of two layers of scintillator arrays, with the forward layer acting as a scatterer for high-energy photons (>200 keV) and an active pinhole for low-energy photons (<200 keV). In this study, we developed a new system that can simultaneously achieve 3D imaging using three modalities: Compton, pinhole, and PET, by synchronizing multiple hybrid Compton cameras. The experiments confirmed the performance of the hybrid Compton cameras as a multi-modal imager, and we succeeded in the simultaneous imaging of Cs-137 (Compton mode targeting 662 keV), Na-22 (PET mode targeting 511 keV), and Am-241 (pinhole mode targeting 60 keV) within the same field of view. Further, we verified that the 3D distribution of the At-211 tracer within a mouse can be imaged via the pinhole mode.
AcknowledgmentThis research was supported by JSPS KAKENHI Grant Number 20H00669. The At-211 was supplied through the Supply Platform of Short-lived Radioisotopes, supported by JSPS Grant-in-Aid for Scientific Research on Innovative Areas, Grant Number 16H06278.
Keywords: radiation imaging, multi-modality, nuclear medicine, radionuclide therapy
Detection of recoil electron tracks using an SOI pixel sensor for an advanced Compton camera (#1351)
M. Kagaya1, H. Katagiri2, A. Takeda3, K. Shimazoe4, T. G. Tsuru5, T. Tanaka6, M. Uenomachi7, L. Zhang4
1 National Institute of Technology, Sendai College/Japan, Department of General Engineering, Miyagi, Japan
Sub-MeV/MeV gamma-ray bands are essential energy regions for astronomical observations. For example, we can elucidate a mechanism of nucleosynthesis due to a supernova explosion by observing the types of line gamma rays and these amounts in these energy regions. To achieve high sensitivity for observing line gamma rays, a semiconductor detector is suitable because it can exclude continuum background gamma rays with good energy resolution. Also, an advanced Compton camera can achieve a large effective area for the sub-MeV/MeV observations because it does not require a shield or mask. Moreover, it can estimate an arrival direction of a gamma-ray event by event by detecting recoil electron tracks. We should use a small-pitch pixel sensor for detecting the complicated recoil directions of electrons. In this study, we focused on a silicon-on-insulator pixel sensor and developed a prototype Compton camera for the gamma-ray observations of less than a few MeV. We investigated the sensor’s detection capability by changing various conditions for running electrons, such as scattering angles, rotation angles, and depth directions. We succeeded in detecting electron tracks released from 511-keV gamma rays and estimating recoil directions on the detection plane using the reconstructed images of the electron tracks. We demonstrated that the sensor can detect gamma rays with scattering angles greater than 30−45 degrees, and identify the recoil direction when the rotation angle was changed. In this conference, we will report the results of the evaluation for detecting recoil electron tracks with an advanced Compton camera using the pixel sensor.
AcknowledgmentThis work was supported by JSPS KAKENHI Grant-in Aid for Young Scientists Number 17K14264 and 19K14743.
This work was partially carried out by the joint research program of the Institute for Cosmic Ray Research (ICRR), The University of Tokyo.
Keywords: Advanced Compton camera, Gamma ray, Silicon-on-insulator pixel sensor