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At least 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Monte Carlo simulation of a quantum noise limited Čerenkov detector based on air-spaced light guiding taper for megavoltage x-ray imaging

Purpose: Electronic Portal Imaging Devices (EPIDs) have been widely used in radiation therapy and are still needed on linear accelerators (Linacs) equipped with kilovoltage cone beam CT (kV-CBCT) or MRI systems. Our aim is to develop a new high quantum efficiency (QE) Čerenkov Portal Imaging Device (CPID) that is quantum noise limited at dose levels corresponding to a single Linac pulse. Methods: Recently a new concept of CPID for MV x-ray imaging in radiation therapy was introduced. It relies on Čerenkov effect for x-ray detection. The proposed design consisted of a matrix of optical fibers aligned with the incident x-rays and coupled to an active matrix flat panel imager (AMFPI) for image readout. A weakness of such design is that too few Čerenkov light photons reach the AMFPI for each incident x-ray and an AMFPI with an avalanche gain is required in order to overcome the readout noise for portal imaging application. In this work the authors propose to replace the optical fibers in the CPID with light guides without a cladding layer that are suspended in air. The air between the light guides takes on the role of the cladding layer found in a regular optical fiber. Since air has a significantly lower refractive index (∼1 versus 1.38 in a typical cladding layer), a much superior light collection efficiency is achieved. Results: A Monte Carlo simulation of the new design has been conducted to investigate its feasibility. Detector quantities such as quantum efficiency (QE), spatial resolution (MTF), and frequency dependent detective quantum efficiency (DQE) have been evaluated. The detector signal and the quantum noise have been compared to the readout noise. Conclusions: Our studies show that the modified new CPID has a QE and DQE more than an order of magnitude greater than that of current clinical systems and yet a spatial resolution similar to that of current low-QE flat-panel based EPIDs. Furthermore it was demonstrated that the new CPID does not require an avalanche gain in the AMFPI and is quantum noise limited at dose levels corresponding to a single Linac pulse.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

MO-G-17A-01: Innovative High-Performance PET Imaging System for Preclinical Imaging and Translational Researches

Purpose: To develop a practical and compact preclinical PET with innovative technologies for substantially improved imaging performance required for the advanced imaging applications. Methods: Several key components of detector, readout electronics and data acquisition have been developed and evaluated for achieving leapfrogged imaging performance over a prototype animal PET we had developed. The new detector module consists of an 8×8 array of 1.5×1.5×30 mm{sup 3} LYSO scintillators with each end coupled to a latest 4×4 array of 3×3 mm{sup 2} Silicon Photomultipliers (with ∼0.2 mm insensitive gap between pixels) through a 2.0 mm thick transparent light spreader. Scintillator surface and reflector/coupling were designed and fabricated to reserve air-gap to achieve higher depth-of-interaction (DOI) resolution and other detector performance. Front-end readout electronics with upgraded 16-ch ASIC was newly developed and tested, so as the compact and high density FPGA based data acquisition and transfer system targeting 10M/s coincidence counting rate with low power consumption. The new detector module performance of energy, timing and DOI resolutions with the data acquisition system were evaluated. Initial Na-22 point source image was acquired with 2 rotating detectors to assess the system imaging capability. Results: No insensitive gaps at the detector edge and thus it is capable for tiling to a large-scale detector panel. All 64 crystals inside the detector were clearly separated from a flood-source image. Measured energy, timing, and DOI resolutions are around 17%, 2.7 ns and 1.96 mm (mean value). Point source image is acquired successfully without detector/electronics calibration and data correction. Conclusion: Newly developed advanced detector and readout electronics will be enable achieving targeted scalable and compact PET system in stationary configuration with >15% sensitivity, ∼1.3 mm uniform imaging resolution, and fast acquisition counting rate capability for substantially improved imaging and quantification performance for small animal imaging and image-guided radiotherapy applications. This work was supported by a research award RP120326 from Cancer Prevention and Research Institute of Texas.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Optical delay encoding for fast timing and detector signal multiplexing in PET

Purpose: The large number of detector channels in modern positron emission tomography (PET) scanners poses a challenge in terms of readout electronics complexity. Multiplexing schemes are typically implemented to reduce the number of physical readout channels, but often result in performance degradation. Novel methods of multiplexing in PET must be developed to avoid this data degradation. The preservation of fast timing information is especially important for time-of-flight PET. Methods: A new multiplexing scheme based on encoding detector interaction events with a series of extremely fast overlapping optical pulses with precise delays is demonstrated in this work. Encoding events in this way potentially allows many detector channels to be simultaneously encoded onto a single optical fiber that is then read out by a single digitizer. A two channel silicon photomultiplier-based prototype utilizing this optical delay encoding technique along with dual threshold time-over-threshold is demonstrated. Results: The optical encoding and multiplexing prototype achieves a coincidence time resolution of 160 ps full width at half maximum (FWHM) and an energy resolution of 13.1% FWHM at 511 keV with 3 × 3 × 5 mm{sup 3} LYSO crystals. All interaction information for both detectors, including timing, energy, and channel identification, is encoded onto a single optical fiber with little degradation. Conclusions: Optical delay encoding and multiplexing technology could lead to time-of-flight PET scanners with fewer readout channels and simplified data acquisition systems.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

WE-G-204-05: Relative Object Detectability Evaluation of a New High Resolution A-Se Direct Detection System Compared to Indirect Micro-Angiographic Fluoroscopic (MAF) Detectors

Purpose: To evaluate the task specific imaging performance of a new 25µm pixel pitch, 1000µm thick amorphous selenium direct detection system with CMOS readout for typical angiographic exposure parameters using the relative object detectability (ROD) metric. Methods: The ROD metric uses a simulated object function weighted at each spatial frequency by the detectors’ detective quantum efficiency (DQE), which is an intrinsic performance metric. For this study, the simulated objects were aluminum spheres of varying diameter (0.05–0.6mm). The weighted object function is then integrated over the full range of detectable frequencies inherent to each detector, and a ratio is taken of the resulting value for two detectors. The DQE for the 25µm detector was obtained from a simulation of a proposed a-Se detector using an exposure of 200µR for a 50keV x-ray beam. This a-Se detector was compared to two microangiographic fluoroscope (MAF) detectors [the MAF-CCD with pixel size of 35µm and Nyquist frequency of 14.2 cycles/mm and the MAF-CMOS with pixel size of 75µm and Nyquist frequency of 6.6 cycles/mm] and a standard flat-panel detector (FPD with pixel size of 194µm and Nyquist frequency of 2.5cycles/mm). Results: ROD calculations indicated vastly superior performance by the a-Se detector in imaging small aluminum spheres. For the 50µm diameter sphere, the ROD values for the a-Se detector compared to the MAF-CCD, the MAF-CMOS, and the FPD were 7.3, 9.3 and 58, respectively. Detector performance in the low frequency regime was dictated by each detector’s DQE(0) value. Conclusion: The a-Se with CMOS readout is unique and appears to have distinctive advantages of incomparable high resolution, low noise, no readout lag, and expandable design. The a-Se direct detection system will be a powerful imaging tool in angiography, with potential break-through applications in diagnosis and treatment of neuro-vascular disease. Supported by NIH Grant: 2R01EB002873 and an equipment grant from Toshiba Medical Systems Corporation.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

SU-F-I-16: Short Breast MRI with High-Resolution T2-Weighted and Dynamic Contrast Enhanced T1-Weighted Images

Purpose: To develop and demonstrate a short breast (sb) MRI protocol that acquires both T2-weighted and dynamic contrast-enhanced T1-weighted images in approximately ten minutes. Methods: The sb-MRI protocol consists of two novel pulse sequences. The first is a flexible fast spin-echo triple-echo Dixon (FTED) sequence for high-resolution fat-suppressed T2-weighted imaging, and the second is a 3D fast dual-echo spoiled gradient sequence (FLEX) for volumetric fat-suppressed T1-weighted imaging before and post contrast agent injection. The flexible FTED sequence replaces each single readout during every echo-spacing period of FSE with three fast-switching bipolar readouts to produce three raw images in a single acquisition. These three raw images are then post-processed using a Dixon algorithm to generate separate water-only and fat-only images. The FLEX sequence acquires two echoes using dual-echo readout after each RF excitation and the corresponding images are post-processed using a similar Dixon algorithm to yield water-only and fat-only images. The sb-MRI protocol was implemented on a 3T MRI scanner and used for patients who had undergone concurrent clinical MRI for breast cancer screening. Results: With the same scan parameters (eg, spatial coverage, field of view, spatial and temporal resolution) as the clinical protocol, the total scan-time of the sb-MRI protocol (including the localizer, bilateral T2-weighted, and dynamic contrast-enhanced T1-weighted images) was 11 minutes. In comparison, the clinical breast MRI protocol took 43 minutes. Uniform fat suppression and high image quality were consistently achieved by sb-MRI. Conclusion: We demonstrated a sb-MRI protocol comprising both T2-weighted and dynamic contrast-enhanced T1-weighted images can be performed in approximately ten minutes. The spatial and temporal resolution of the images easily satisfies the current breast MRI accreditation guidelines by the American College of Radiology. The protocol has the potential of making breast MRI more widely accessible to and more tolerable by the patients. JMA is the inventor of United States patents that are owned by the University of Texas Board of Regents and currently licensed to GE Healthcare and Siemens Gmbh.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

SU-F-J-163: In Vivo Quantification of Sequence Parameter Effect On Geometric Distortion Caused by Implanted Titanium Brachytherapy Applicator

Purpose: The use of MR to plan and evaluate brachytherapy treatment for cervical cancer is increasing given the availability of MR conditional or safe applicators and MRI’s proven superiority to CT for characterizing soft tissue lesions. The titanium applicators, however, cause geometric distortions or imaging artifacts, which reduce the utility of MRI for dosimetry. We sought to quantify the observed volume of the same applicator on a previously optimized T2 sequence in comparison to the conventional T2 sequence and CT obtained for brachytherapy planning. Methods: Prior work with testing in phantoms showed that increases in readout bandwidth yielded reductions in artifact area and distortion measurements even with voxel increases. Following IRB approval, nine patients with titanium tandem & ovoid applicator (Varian Medical Systems) in place were scanned with a standard periprocedural protocol which included sagittal T2 fast spin echo (FSE) acquisition (res 0.98×0.78×4.0 mm{sup 3}; BW 200Hz). An additional T2-weighted FSE sequence (res 0.98×0.98×3–4 mm{sup 3}; BW500Hz) with increased readout bandwidth, readout voxel size, and echo train length was added to the protocol. Volume measurements of the applicator (from tip to cervical stop) were hand-segmented in Velocity AI 3.1 (Velocity Medical Solutions) for the two T2 FSE sequences and a planning CT obtained shortly after MRI. Differences were analyzed using a paired t-test. Results: Average apparent volumes of the applicator on standard T2 sequence, decreased bandwidth T2 sequence and CT were 5.922±1.283 cm{sup 3}, 4.544±1.524 cm3, and 2.304±0.509 cm{sup 3} respectively. Conclusion: Apparent volumes of a brachytherapy applicator can be compared in vivo. The modified sequence results in decreased apparent size of the cervical applicator. Both MR sequence volumes were larger than the planning CT, which was expected. Future work will focus on the diagnostic quality of the new sequence and quantifying any geometric shifts after CT to MRI registration based on anatomical landmarks.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

TH-CD-201-05: Characterization of a Novel Light-Collimating Tank Optical-CT System for 3D Dosimetry

Purpose: Comprehensive 3D dosimetry is highly desirable for advanced clinical QA, but costly optical readout techniques have hindered widespread implementation. Here, we present the first results from a cost-effective Integrated-lens Dry-tank Optical Scanner (IDOS), designed for convenient 3D dosimetry readout of radiochromic plastic dosimeters (e.g. PRESAGE). Methods: The scanner incorporates a novel transparent light-collimating tank, which collimates a point light source into parallel-ray CT geometry. The tank was designed using an in-house Monte-Carlo optical ray-tracing simulation, and was cast in polyurethane using a 3D printed mould. IDOS spatial accuracy was evaluated by imaging a set of custom optical phantoms, with comparison to x-ray CT images. IDOS dose measurement performance was assessed by imaging PRESAGE dosimeters irradiated with simple known dose distributions (e.g., 4 field box 6MV treatment with Varian Linac). Direct comparisons were made to images from our gold standard DLOS scanner and calculated dose distributions from a commissioned Eclipse planning system. Results: All optical CT images were reconstructed at 1mm isotropic resolution. Comparison of IDOS and x-ray CT images of the geometric phantom demonstrated excellent IDOS geometric accuracy (sub-mm) throughout the dosimeter. IDOS measured 3D dose distribution agreed well with prediction from Eclipse, with 95% gamma pass rate at 3%/3mm. Cross-scanner dose measurement gamma analysis shows >90% of pixels passing at 3%/3mm. Conclusion: The first prototype of the IDOS system has demonstrated promising performance, with accurate dosimeter readout and negligible spatial distortion. The use of optical simulations and 3D printing to create a light collimating-tank has dramatically increased convenience and reduced costs by removing the need for expensive lenses and large volumes of refractive matching fluids.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Event Localization in Bulk Scintillator Crystals Using Coded Apertures

The localization of radiation interactions in bulk scintillators is generally limited by the size of the light distribution at the readout surface of the crystal/light-pipe system. By finding the centroid of the light spot, which is typically of order centimeters across, practical single-event localization is limited to ~2 mm/cm of crystal thickness. Similar resolution can also be achieved for the depth of interaction by measuring the size of the light spot. Through the use of near-field coded-aperture techniques applied to the scintillation light, light transport simulations show that for 3-cm-thick crystals, more than a five-fold improvement (millimeter spatial resolution) can be achieved both laterally and in event depth. At the core of the technique is the requirement to resolve the shadow from an optical mask placed in the scintillation light path between the crystal and the readout. In this paper, experimental results are presented that demonstrate the overall concept using a 1D shadow mask, a thin-scintillator crystal and a light pipe of varying thickness to emulate a 2.2-cm-thick crystal. Spatial resolutions of ~ 1 mm in both depth and transverse to the readout face are obtained over most of the crystal depth.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

High Energy Micron Scale Pixel Hybrid Detector

The objective of this technology development project has been to fabricate and characterize a new X-ray area image sensor innovation designed for high efficiency detection and imaging of hard X-rays (>20 KeV) with micron scale pixel resolution. A key technology component consists of a monolithic hybrid X-ray detector built by layering an amorphous Selenium X-ray photoconductor film directly deposited on a small pitch (7.8μm) CMOS active pixel readout array. A specific goal of this work is to provide a new detector tool to researchers working with synchrotron light sources, to extend the depth of exploration into nanoscale structures, and do so cost effectively. Early generation X-ray imaging detector tools fail to provide adequate resolving power and efficiency at high energies and our innovation provides a solution. A majority of proposed phase I tasks were completed. Those tasks included, in collaboration with KA Imaging, successful fabrication of specified a-Se layers on a 1Mpixel CMOS readout array to create the direct hybrid X-ray imaging array, packaging of the imaging array, assembly of electronics into a shielded detector box, loading user interface software for camera control and image capture, and performing initial (no X-ray) detector evaluation at Farrier Microengineering facilities. After initial tests, extensive testing using the X-ray beam line 1-BM source at Argonne National Laboratory Advanced Photon Source(ANL-APS) was performed. Imaging performance studies were conducted at multiple X-ray beam energies. Studies included X-ray response vs. X-ray energy, vs. applied detector field strength (HV), response linearity vs. integration time, MTF vs. beam energy, image lag measurements, and micron scale resolution pattern target imaging. This high energy micron scale X-ray detection technology is a first of a kind to be evaluated at the ANL-APS and is supported by Dr. Antonino Miceli, head of the detector physics group. Accomplishments include the first successful demonstration of a 1Mpix amorphous Selenium on CMOS readout direct hybrid X-ray imaging detector at a DOE sponsored National Laboratory. Modeled performance predictions were confirmed, proving micron scale resolution as well as an order of magnitude increase in conversion efficiency over conventional scintillator detector performance. A discovery of evidence of propagation-based phase contrast edge enhancement was unplanned and will be exploited in future experiments. This phase 1 technology demonstration verifies the efficacy of proposed high energy micron scale pixel X-ray hybrid a-Se imaging array products. The new detector products will cost effectively replace early generation detector technologies that currently fail to address increasing demand for tools to study nano structures and physical processes at high X-ray energies above 20keV. For example, current systems for transmission X-ray microscopy have low efficiency and available large pixel (~55µm) direct detectors do not offer sufficient resolution for Bragg fringe imaging at high energies. This detector innovation will solve these inadequacies. The new detector technology will compete in a $50M scientific X-ray detector market, growing at 6%, and will benefit Microtomography(µCT), X-ray diffractometry (XRD), Coherent Diffraction Imaging (CDI) applications. One application specified by Dr. Miceli at ANL is the 3D reconstruction of compact crystals at high energies requires small pixel high efficiency X-ray detectors. Farrier Microengineering, working with colleagues at KA Imaging and the University of Waterloo, successfully achieved the critical objectives of the Phase I proposal. We have proven the technical feasibility of this innovation by building and successfully testing a 1Mpixel a-Se/CMOS hybrid direct X-ray imaging array. Our commercialization roadmap of detector products will be implemented during a phase II project. We will demonstrate a migration of the technology to larger detector array sizes, improved temporal performance with detector layer engineering, and improved environmental and operational stability. Manufacturability and cost effectiveness are key objectives and product designs will leverage current state of the art CMOS wafer fabrication quality and volume manufacturing economics.

36 MATERIALS SCIENCE↗
DOE OSTI2018

SPT-3G: A Multichroic Receiver for the South Pole Telescope

A new receiver for the South Pole Telescope, SPT-3G, was deployed in early 2017 to map the cosmic microwave background at 95, 150, and 220 GHz with similar to 16,000 detectors, 10 times more than its predecessor SPTpol. The increase in detector count is made possible by lenslet-coupled trichroic polarization-sensitive pixels fabricated at Argonne National Laboratory, new 68x frequency-domain multiplexing readout electronics, and a higher-throughput optical design. The enhanced sensitivity of SPT-3G will enable a wide range of results including constraints on primordial B-mode polarization, measurements of gravitational lensing of the CMB, and a galaxy cluster survey. Here we present an overview of the instrument and its science objectives, highlighting its measured performance and plans for the upcoming 2018 observing season.

CMB↗
DOE OSTI2020

Performance of Al-Mn Transition-Edge Sensor Bolometers in SPT-3G

SPT-3G is a polarization-sensitive receiver, installed on the South Pole Telescope, that measures the anisotropy of the cosmic microwave background (CMB) from degree to arcminute scales. The receiver consists of ten 150-mm-diameter detector wafers, containing a total of similar to 16,000transition-edge sensor (TES) bolometers observing at 95, 150, and 220 GHz. During the 2018-2019 austral summer, one of these detector wafers was replaced by a new wafer fabricated with Al-Mn TESs instead of the Ti/Au design originally deployed for SPT-3G. We present the results of in-laboratory characterization and on-sky performance of this Al-Mn wafer, including electrical and thermal properties, optical efficiency measurements, and noise-equivalent temperature. In addition, we discuss and account for several calibration-related systematic errors that affect measurements made using frequency-domain multiplexing readout electronics.

Al-Mn↗
DOE OSTI2019

Microwave Multiplexing on the Keck Array

In this paper, we describe an on-sky demonstration of a microwave-multiplexing readout system in one of the receivers of the Keck Array, a polarimetry experiment observing the cosmic microwave background at the South Pole. During the austral summer of 2018–2019, we replaced the time-division multiplexing readout system with microwave-multiplexing components including superconducting microwave resonators coupled to radio frequency superconducting quantum interference devices at the sub-Kelvin focal plane, coaxial-cable plumbing and amplification between room temperature and the cold stages, and a SLAC Microresonator Radio Frequency system for the warm electronics. In the range 5–6 GHz, a single coaxial cable reads out 528 channels. The readout system is coupled to transition-edge sensors, which are in turn coupled to 150-GHz slot-dipole phased-array antennas. Observations began in April 2019, and we report here on an initial characterization of the system performance.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Commercially Fabricated Antenna-Coupled Transition Edge Sensor Bolometer Detectors for Next-Generation Cosmic Microwave Background Polarimetry Experiment

We report on the development of commercially fabricated multi-chronic antenna-coupled transition edge sensor (TES) bolometer arrays for cosmic microwave background (CMB) polarimetry experiments. The orders of magnitude increase in detector count for next-generation CMB experiments require a new approach in detector wafer production to increase fabrication throughput. Here, we describe collaborative efforts with a commercial superconductor electronics fabrication facility (SeeQC, Inc.) to fabricate antenna-coupled TES bolometer detectors. We have successfully fabricated an operational dual-polarization, dichroic sinuous antenna-coupled TES detector array on a 150-mm-diameter wafer. The fabricated detector arrays have average yield of 95% and excellent uniformity across the wafer. Both RF characteristics and TES bolometer properties are suitable for CMB observations. We successfully fabricated different types of TES bolometers optimized for frequency multiplexing readout, time-domain multiplexing readout, and microwave SQUID multiplexing readout. We also demonstrated high production throughput. We discuss the motivation, design considerations, fabrication processes, test results, and how industrial detector fabrication could be a path to fabricate hundreds of detector wafers for future CMB polarimetry experiments.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Bandwidth and Aliasing in the Microwave SQUID Multiplexer

The microwave SQUID multiplexer (μmux) has enabled higher bandwidth or higher channel counts across a wide range of experiments in particle physics, astronomy, and spectroscopy. The large multiplexing factor coupled with recent commercial availability of microwave components and warm electronics readout systems make it an attractive candidate for systems requiring large cryogenic detector counts. Since the multiplexer is considered for both bolometric and calorimetric applications across several orders of magnitude of signal frequencies, understanding the bandwidth of the device and its interaction with readout electronics is key to appropriately designing and engineering systems. Here we discuss several important factors contributing to the bandwidth properties of μmux systems, including the intrinsic device bandwidth, interactions with warm electronics readout systems, and aliasing. Further, we present simulations and measurements of μmux devices coupled with SLAC Microresonator RF (SMuRF) tone-tracking electronics and discuss several implications for future experimental design.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Scalable Detector Design for a High-Resolution Fast-Neutron Radiography Panel

Development of a scalable flat-panel neutron radiography device is needed to meet the nondestructive testing needs of a growing industrial market. Flood field images from a Cs-137 gamma source and a Cf-252 fission neutron source were generated using a detector composed of a 3-mm-thick sheet of EJ-200, and 3-mm-thick sheet of acrylic light spreader, an 8 $\times$ 8 array of SensL MICROFJ-60035-TSV SiPMs, and an IDEAS ROSSPAD readout module. The readout module can be tiled together with similar systems to create a panel of any size, and is only limited by the number of available Ethernet ports in a switching system. A collimated gamma line image demonstrated a 90% spatial resolution of approximately 0.47 line pairs per centimeter and a 10% spatial resolution of approximately 2.32 line pairs per centimeter. A neutron edge image demonstrated a 90% spatial resolution of approximately 0.70 line pairs per centimeter and a 10% spatial resolution of approximately 3.35 line pairs per centimeter. Both of these images show the ability to generate radiographs with sub-SiPM spatial resolution. Using these readout modules, a large-scale radiographic panel can be developed by tiling ROSSPAD modules together.

36 MATERIALS SCIENCE↗
DOE OSTI2018

A linear array of position-sensitive virtual Frisch-grid CdZnTe for low-energy gamma rays

Large-area arrays of position-sensitive virtual Frisch-grid CdZnTe (CZT) detectors with enhanced energy resolution and high efficiency have been proposed for spectroscopy and imaging of gamma-ray sources. We present the design and test results of a linear array of such detectors optimized for use in handheld instruments. There are several application areas for such detectors including uranium enrichment measurements, storage monitoring, dosimetry and other nuclear safeguards related tasks. The array configuration provides a large area with minimum number of readout channels, which potentially allows the developers to avoid using ASIC-based readout electronics by substituting it with hybrid preamplifiers followed by digitizers. The array prototype consists of 6 5 x 7 x 25 mm 3 CZT detectors side-oriented with respect to the source to achieve the maximum area. Each detector is furnished with 5 mm-wide charge-sensing pads placed near the anode. As an option, the pads can be grouped together to reduce the number of readout channels. The same can be done with the cathodes. The pads signals are converted into X–Y coordinates and combined with the cathode signals (for the Z coordinates) to give 3D positional information of each interaction point. This information is used to correct the response non-uniformity caused by material inhomogeneity, which allows the developers to use standard grade (unselected) CZT crystals, while retaining high spectroscopic performance.

3D position-sensitive virtual Frisch-grid detector↗
DOE OSTI2019

LAB4D: A low power, multi-GSa/s, transient digitizer with sampling timebase trimming capabilities

The LAB4D is a new application-specific integrated circuit (ASIC) of the Large Analog Bandwidth Recorder and Digitizer with Ordered Readout (LABRADOR) family, for use in direct wideband radio frequency digitization such as is used in ultrahigh energy neutrino and cosmic ray astrophysics. The LAB4D is a single channel switched-capacitor array (SCA) 12-bit sampler with integrated analog-to-digital converters (ADC), developed in the TSMC 0.25um process. The LAB4D, operating at 3.2GSa/s, contains 4096 total samples arranged in 32 windows, for a total record length of 1280ns. The 3dB bandwidth is approximately 1.3GHz, with a directly-coupled 50ohm input. This represents a factor of 16 increase in the sample depth and an increase in analog bandwidth and sampling depth in comparison to the previous generation LAB3 digitizer. Individually addressable windows allow for sampling and digitization to occur simultaneously, leading to nearly deadtime-free readout for kHz readout rates. All biases and current references are generated via internal digital-to-analog converters (DACs), resulting in a stand-alone digitizer with no additional support circuitry. In addition, the LAB4D contains sample cell timebase trimming capabilities, reducing the intrinsic sample-to-sample time variance to less than 5ps; an improvement of about 80%. This allows the LAB4D to be used in precision timing applications with minimal post-hoc calibration.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

The Majorana low-noise low-background front-end electronics

The Majorana Demonstrator will search for the neutrinoless double beta decay (ββ(0ν)) of the isotope ⁷⁶Ge with a mixed array of enriched and natural germanium detectors. In view of the next generation of tonne-scale germanium-based ββ(0ν)-decay searches, a major goal of the Majorana Demonstrator is to demonstrate a path forward to achieving a background rate at or below 1 cnt/(ROI-t-y) in the 4 keV region of interest (ROI) around the 2039-keV Q-value of the ⁷⁶Ge ββ(0ν)-decay. Such a requirement on the background level significantly constrains the design of the readout electronics, which is further driven by noise and energy resolution performances. We present here the low-noise low-background front-end electronics developed for the low-capacitance p-type point contact (P-PC) germanium detectors of the Majorana Demonstrator. This resistive-feedback front-end, specifically designed to have low mass, is fabricated on a radioassayed fused-silica substrate where the feedback resistor consists of a sputtered thin film of high purity amorphous germanium and the feedback capacitor is based on the capacitance between gold conductive traces.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗