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a-Si:H TFT-silicon hybrid low-energy x-ray detector
Direct conversion crystalline silicon X-ray imagers are used for low-energy X-ray photon (4-20 keV) detection in scientific research applications such as protein crystallography. In this paper, we demonstrate a novel pixel architecture that integrates a crystalline silicon X-ray detector with a thin-film transistor amorphous silicon pixel readout circuit. We describe a simplified two-mask process to fabricate a complete imaging array and present preliminary results that show the fabricated pixel to be sensitive to 5.89-keV photons from a low activity Fe-55 gamma source. Furthermore, this paper presented can expedite the development of high spatial resolution, low cost, direct conversion imagers for X-ray diffraction and crystallography applications.
Front-End ASIC for Liquid Argon TPC
We present a front-end application-specific integrated circuit (ASIC) for a wire based time-projection-chamber (TPC) operating in liquid Argon (LAr). The LAr TPC will be used for long baseline neutrino oscillation experiments. The ASIC must provide a low-noise readout of the signals induced on the TPC wires, digitization of those signals at 2 MSamples/s, compression, buffering and multiplexing. A resolution of better than 1000 rms electrons at 200 pF input capacitance for an input range of 300 fC is required, along with low power and operation in LAr (at 87 K). We include the characterization of a commercial technology for operation in the cryogenic environment and the first experimental results on the analog front end. The results demonstrate that complementary metal-oxide semiconductor transistors have lower noise and much improved dc characteristics at LAr temperature. Finally, we introduce the concept of '1/f equivalent' to model the low-frequency component of the noise spectral density, for use in the input metal-oxide semiconductor field-effect transistor optimization.
Characterization of CLYC Detectors for a Next-Generation Unattended Sensor
We are developing a next-generation unattended sensor for detecting anomalous radiation sources. The system uses a scintillator material with dual sensitivity to gamma rays and neutrons, Cs 2 LiYCl 6 :Ce (CLYC), to reduce the size and complexity of the design. CLYC also offers a best-case energy resolution under 4% full width at half maximum at 662 keV, and allows for particle discrimination by pulse amplitude as well as pulse shape. The unattended sensor features sixteen one-inch CLYC detectors, each read out by a photomultiplier tube and custom readout electronics. A field-programmable gate array implements a suite of efficient processing algorithms for anomaly detection and isotope identification, and transmits alarm information to a base station via a wireless link. The system is designed to operate on battery power for several weeks. In this paper, we report the energy resolution, linearity, detection efficiency, and temperature stability of the first CLYC detectors acquired for the project. Rather than characterizing the scintillator material under ideal conditions, we evaluate the detectors with the components selected for the unattended sensor, acknowledging the tradeoffs imposed by small size, limited power budget, and uncontrolled environmental conditions.
Strip Detectors Processed on High-Resistivity 6-Inch Diameter Magnetic Czochralski Silicon (MCz-Si) Substrates
Tracking detectors for future high-luminosity particle physics experiments have to be simultaneously radiation hard and cost efficient. This paper describes processing and characterization of p^+ /n^-/n^+ (n-type silicon bulk) detectors made of high-resistivity Magnetic Czochralski silicon (MCz-Si) substrates with 6-inch wafer diameter. The processing was carried out on a line used for large-scale production of sensors using standard fabrication methods, such as implanting polysilicon resistors to bias individual sensor strips. Special care was taken to avoid the creation of Thermal Donors (TD) during processing. The sensors have a full depletion voltage of 120-150 V which are uniform over the investigated sensors. All of the leakage current densities were below 55 nA/cm^2 at 200 V bias voltage. A strip sensor with 768 channels was attached to readout electronics and tested in particle beam with a data acquisition (DAQ) similar to the system used by the CMS experiment at the CERN LHC. The test beam results show a signal-to-noise ratio greater than 40 for the test beam sensor. The results demonstrate that MCz-Si detectors can reliably be manufactured in the industrial scale semiconductor process.
Reliable and redundant FPGA based read-out design in the ATLAS TileCal Demonstrator
The Tile Calorimeter at ATLAS [1] is a hadron calorimeter based on steel plates and scintillating tiles read out by PMTs. The current read-out system uses standard ADCs and custom ASICs to digitize and temporarily store the data on the detector. However, only a subset of the data is actually read out to the counting room. The on-detector electronics will be replaced around 2023. To achieve the required reliability the upgraded system will be highly redundant. Here the ASICs will be replaced with Kintex-7 FPGAs from Xilinx. This, in addition to the use of multiple 10 Gbps optical read-out links, will allow a full read-out of all detector data. Due to the higher radiation levels expected when the beam luminosity is increased, opportunities for repairs will be less frequent. The circuitry and firmware must therefore be designed for sufficiently high reliability using redundancy and radiation tolerant components. Within a year, a hybrid demonstrator including the new readout system will be installed in one slice of the ATLAS Tile Calorimeter. This will allow the proposed upgrade to be thoroughly evaluated well before the planned 2023 deployment in all slices, especially with regard to long term reliability. Different firmware strategies alongside with their integration in the demonstrator are presented in the context of high reliability protection against hardware malfunction and radiation induced errors.
Unattended Sensor System With CLYC Detectors
We have developed a next-generation unattended sensor for detecting anomalous radiation sources. The system combines several technologies to reduce size and weight, increase battery lifetime, and improve decision-making capabilities. Sixteen Cs2LiYCl6:Ce (CLYC) scintillators allow for gamma-ray spectroscopy and neutron detection in the same volume. Low-power electronics for readout, high voltage bias, and digital processing reduce the total operating power to 1.3 W. Computationally efficient analysis algorithms perform spectral anomaly detection and isotope identification. When an alarm occurs, the system transmits alarm information over a cellular modem. In this paper, we describe the overall design of the unattended sensor, present characterization results, and compare the performance to stock NaI:Tl and 3He detectors.
Characterization of the Photon Counting CHASE Jr., Chip Built in a 40-nm CMOS Process With a Charge Sharing Correction Algorithm Using a Collimated X-Ray Beam
Not Available
Quality Assurance on Undoped CsI Crystals for the Mu2e Experiment
The Mu2e experiment is constructing a calorimeter consisting of 1,348 undoped CsI crystals in two disks. Each crystal has a dimension of 34 x 34 x 200 mm 3 , and is readout by a large area silicon PMT array. A series of technical specifications was defined according to physics requirements. Preproduction CsI crystals were procured from three firms: Amcrys, Saint-Gobain and Shanghai Institute of Ceramics. We report the quality assurance on crystal's scintillation properties and their radiation hardness against ionization dose and neutrons. With a fast decay time of 30 ns and a light output of more than 100 p.e./MeV measured with a bi-alkali PMT, undoped CsI crystals provide a cost-effective solution for the Mu2e experiment.
Design and Evaluation of the LAr Trigger Digitizer Board in the ATLAS Phase-I Upgrade
The Phase-I upgrade of the trigger readout electronics for the ATLAS Liquid Argon (LAr) calorimeters will be installed during the second long shutdown of the Large Hadron Collider (LHC) in 2019-2020 which will enable enhanced instantaneous luminosities during LHC Run 3 from 2021 through 2023. In this trigger upgrade, so-called supercells are introduced to provide higher granularity, higher resolution and longitudinal shower shape information from the LAr calorimeters to the Level-1 trigger processors. A new LAr Trigger Digitizer Board (LTDB) will process and digitize up to 320 channels of supercell signals, and transmit them via 40 fiber optical links to the back end where the data are further processed and transmitted to the trigger processors. Five pairs of bidirectional GBT links are used for slow control and monitoring between LTDB and the Front-End LInk eXchange (FELIX) in the ATLAS Trigger and Data Acquisition (TDAQ) system. Here, the LTDB also outputs 64 summed analog legacy signals to the current Tower Builder Board via a new baseplane. A test system for the production of 124 LTDBs has been developed, supporting configuration and calibration of all ASICs
Characterization of a Small-Scale Prototype Detector With Wide Dynamic Range for Time-Resolved High-Energy X-Ray Applications
We present characterization measurements of a fast-framing, wide-dynamic-range x-ray area detector intended for high-energy applications (≥20 keV photons). The MM-PAD-2.1 combines an integrating pixel front-end with a charge-removal mechanism to extend the maximum measurable signal to > 107 20-keV ph/pixel/frame. The charge-removal mechanism is dead-time-less (i.e., incoming signal continues to be integrated by the front-end while charge removal is taking place) up to an incoming photon rate of > 109 20-keV ph/pix/s. A 16×16 pixel prototype was fabricated and characterized using both laboratory and synchrotron x-ray sources, allowing for measurements from single-photon to high-flux conditions. High-flux measurements show linear performance up to ~1010 ph/s in a spot spanning approximately 2×1.5 pixels (FWHM). The onset of temporary radiation damage in the detector was observed during these measurements, manifesting as failure of the digital readout from the detector. These effects were seen to reverse after annealing at 30° C for several hours.
Development of a Portable Pixelated Fast-Neutron Imaging Panel
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The VMM3a ASIC
The VMM3a is a custom low-noise Application Specific Integrated Circuit. It is intended to be used in the front end readout electronics of both the Micromegas and sTGC detectors of the ATLAS New Small Wheels upgrade project at CERN. It is fabricated in the 130 nm GlobalFoundries 8RF-DM process. Here, the 64 channels with highly configurable parameters, although designed for a specific project, can meet the processing needs of signals from various detector types in several other applications. In this note, the VMM3a, which is the production version of the VMM family, will be presented along with the features incorporated and its performance.
Testing of a Line Driver With Configurable Pre-Emphasis on Lossy Transmission Lines
Rare-event physics experiments such as the Deep Underground Neutrino Experiment (DUNE) or the next Enriched Xenon Observatory (nEXO) experiment search for rare, low-energy events, detected by sensitive detectors immersed in a cryogenic noble liquid (e.g., liquid argon or xenon). Readout electronics used within such detectors must consume minimal power while operating reliably in cryogenic environments. Furthermore, in the case of nEXO, maximizing the radiopurity of the environment is vital to minimize background noise, thus placing strict limits on the volume of dielectric materials, leading to high-loss data cables spanning distances up to 12 m. Such cables cause high attenuation and intersymbol interference (ISI), resulting in a high bit-error rate (BER). These issues were addressed by developing an integrated line driver with configurable pre-emphasis in a 65-nm CMOS process. The pre-emphasis parameters can be programmed to minimize BER for specific cables and data rates under power constraints. Here, the driver was tested at both room and cryogenic temperatures. In both cases, the output BER was found to be strongly correlated with the pre-emphasis settings. Furthermore, analysis and simulation showed that adapting the pre-emphasis settings based on the incoming bit sequence can further improve performance with minimal changes to the current solution.
The DUNE-DAQ Application Framework
The deep underground neutrino experiment (DUNE) is a next-generation neutrino experiment that will probe the properties of these elusive particles with unparalleled precision. It will also act as an observatory for neutrino bursts caused by nearby supernovae, in the event that one occurs, while the experiment is in operation. Given these goals, the DUNE trigger and DAQ system must be able to maintain extremely high uptime and provide a path for full readout of the detectors for very long times (up to 100 s). To achieve these ends, we have designed the DUNE DAQ system around a flexible “application framework,” which provides a modular interface for specific tasks while handling the interconnections between them. The application framework collects modules into applications, which can then be interacted with as units by the control, configuration, and monitoring systems. One of the key features of the framework is its communication abstraction layer, which allows for modules to interact with both internal queues and external network connections with a single transport-agnostic interface. We will report on the architecture and features of the framework.
A Ce-Doped LiI Scintillator Film-Based High Rate, High Spatial Resolution Neutron Anger Camera for Neutron Scattering Facilities
The 2-D position sensitive neutron detectors featuring a significantly improved count rate capacity and a sub-mm spatial resolution are in high demand by neutron scattering facilities, especially the next generation high-flux spallation neutron sources (SNSs). They are anticipated to play a crucial role in fully utilizing the unprecedentedly high neutron brightness offered by these sources. In this work, a high rate and high spatial resolution neutron Anger camera has been successfully developed based on a Ce-doped microcolumnar LiI scintillator film and the PETsys TOFPET2 ASIC readout electronics. The performance evaluation was conducted in a standard laboratory environment as well as the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL) with regard to light yield, γ-ray sensitivity, neutron detection efficiency, count rate capability, spatial resolution, and position linearity. The LiI:Ce scintillator was found to have a higher light yield and a lower γ-ray sensitivity than GS20 (i.e., 11729 versus 6000 photons/n and 1.67 × 10 −5 versus on the order of 10 −4 ). The neutron detection efficiency was measured to be 63% at 4.2 Å. This camera demonstrated an exceptional count rate capability, up to at least 481 kHz without rate loss. The spatial resolution was as good as 0.47 mm. Here, the position linearity was also enhanced.
Data-Driven Optimization of Pixelated CdZnTe Spectrometers for Uranium Enrichment Assay
Here, in recent work [Vavrek et al. (2025)], we developed the performance optimization framework spectre-ml for gamma spectrometers with variable performance across many readout channels. The framework uses non-negative matrix factorization (NMF) and clustering to learn groups of similarly-performing channels and sweep through various learned channel combinations to optimize the performance tradeoff of including worse-performing channels for better total efficiency. In this work, we integrate the pyGEM uranium enrichment assay code with our spectre-ml framework, and show that the U-235 enrichment relative uncertainty can be directly used as an optimization target. We find that this optimization reduces relative uncertainties after a 30 -minute measurement by an average of 20%, as tested on six different H3D M400 CdZnTe spectrometers, which can significantly improve uranium non-destructive assay measurement times in nuclear safeguards contexts. Additionally, this work demonstrates that the spect re-ml optimization framework can accommodate arbitrary end-user spectroscopic analysis code and performance metrics, enabling future optimizations for complex Pu spectra.
Data-Driven Performance Optimization of Gamma Spectrometers With Many Channels
In gamma spectrometers with variable spectroscopic performance across many channels (e.g., many pixels or voxels), a tradeoff exists between including data from successively worse-performing readout channels and increasing efficiency. Brute-force calculation of the optimal set of included channels is exponentially infeasible as the number of channels grows, and approximate methods are required. In this work, we present a data-driven framework for attempting to find near-optimal sets of included detector channels. The framework leverages non-negative matrix factorization (NMF) to learn the behavior of gamma spectra across the detector and clusters similarly-performing detector channels together. Performance comparisons are then made between spectra with channel clusters removed, which is more feasible than brute force. The framework is general and can be applied to arbitrary, user-defined performance metrics depending on the application. We apply this framework to optimizing gamma spectra measured by H3D M400 CdZnTe (CZT) spectrometers, which exhibit variable performance across their crystal volumes. In particular, we show several examples optimizing various performance metrics for uranium and plutonium gamma spectra in non-destructive assay (NDA) for nuclear safeguards, and explore trends in performance versus parameters such as clustering algorithm type. We also compare the NMF + clustering pipeline to several non-machine-learning (ML) algorithms, including several greedy algorithms. Although, we find that the NMF + clustering pipeline tends to find the best-performing set of detector voxels, significantly improving over the unoptimized spectra, but that a greedy accumulation of spectra segmented by detector depth can, in some cases, give similar performance improvements in much less computation time.