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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Effect of detector dead time on the performance of optical direct-detection communication links

Avalanche photodiodes (APDs) operating in the Geiger mode can provide a significantly improved single-photon detection sensitivity over conventional photodiodes. However, the quenching circuit required to remove the excess charge carriers after each photon event can introduce an undesirable dead time into the detection process. The effect of this detector dead time on the performance of a binary pulse-position-modulated (PPM) channel is studied by analyzing the error probability. It is shown that, when background noise is negligible, the performance of the detector with dead time is similar to that of a quantum-limited receiver. For systems with increasing background intensities, the error rate of the receiver starts to degrade rapidly with increasing dead time. The power penalty due to detector dead time is also evaluated and shown to depend critically on badkground intensity as well as dead time. Given the expected background strength in an optical channel, therefore, a constraint must be placed on the bandwidth of the receiver to limit the amount of power penalty due to detector dead time.

Chen, C.-C.↗
NASA NTRS1988

Effect of Detector Dead Time on the Performance of Optical Direct-Detection Communication Links

Avalanche photodiodes (APDs) operating in the Geiger mode can provide a significantly improved single-photon detect ion sensitivity over conventional photodiodes. However, the quenching circuit required to remove the excess charge carriers after each photon event can introduce an undesirable dead time into the detection process. The effect of this detector dead time on the performance of a binary pulse-position-modulted (PPM) channel is studied by analyzing the error probability. It is shown that, when back- ground noise is negligible, the performance of the detector with dead time is similar to that o f a quantum-limited receiver. For systems with increasing background intensities, the error rate of the receiver starts to degrade rapidly with increasing dead time. The power penalty due to detector dead time is also evaluated and shown to depend critically on background intensity as well as dead time. Given the expected background strength in an optical channel, therefore, a constraint must be placed on the bandwidth of the receiver to limit the amount of power penalty due to detector dead time.

Chen, C.-C.↗
DOE OSTI2026

Performance Validation of Endcap Timing Layer Detector Modules for CMS Phase-2 Upgrade

The High-Luminosity Large Hadron Collider (HL-LHC) will operate up to 200 simultaneous collisions per bunch crossing, which is a significant jump from the current value of about 30 collisions per bunch crossing, producing significant pileup that challenges accurate event reconstruction. To address this, the Compact Muon Solenoid (CMS) experiment is implementing the Endcap Timing Layer (ETL), a precision timing detector designed to provide timing measurements with a resolution of approximately 50 ps per hit and 35 ps per reconstructed track. This project focuses on the characterization and validation of ETL detector modules using laboratory laser test data. ETL performance is evaluated by analyzing key quantities such as Bunch Crossing Identification (BCID), Time-of-Arrival (TOA), Time-over-Threshold (TOT), Noise Stability etc. The resulting analysis provides insight into the timing performance and operational stability of ETL modules, contributing to the quality assurance process req uired before their installation in the CMS experiment and ensure that the modules can meet the long-term reliability requirements of approximately 10 years of operation without replacement.

Chipara, Munashe [Fermilab]↗
DOE OSTI2021

Performance characterization of the Radionuclide Aerosol Sampler/Analyzer air sampler during a high-activity release event

The performance of the Radionuclide Aerosol Sampler/Analyzer (RASA) under high-activity conditions has been evaluated to maintain and protect the operations of International Monitoring System (IMS) radionuclide stations. Station measurements following the Fukushima Daichi accident of 11 March 2011 have been combined with laboratory measurements to understand how the quality of the measurements made using the RASA High-Purity Germanium (HPGe) gamma-spectrometer are impacted by increased sample activity and detector dead-time. Detector saturation has been identified to occur at a count rate of 175,000 counts s-1, at which level there are significant impacts to the sample live-time and detector resolution in addition to a system contamination risk. To safeguard against these effects, a dead-time limit of 16.6% is proposed that could be maintained by monitoring the activity collecting on the filter using a Cadmium Zinc Telluride (CZT) detector installed into the particulate collection area of the RASA. This limit would ensure that the IMS technical specifications for measurement time (> 20 h) and detector resolution (2.5 keV at 1332 keV) are met. The CZT would dynamically control the RASA air flow to limit the collection of particulate activity beneath the HPGe dead-time threshold and would also provide measurements useful for CTBT verification purposes and dose assessments.

Burnett, Jonathan L.↗
DOE OSTI2022

A Double Sided LGAD-Based Detector Providing Timing, Position, and Track Angle Information

We describe a detector concept which combines small pixels enabled by 3D sensor-electronics integration with gain produced by a Low Gain Avalanche Diode (LGAD) layer. The detector is double-sided, with electrons collected by the cathode, which provides timing information, and an anode with small pixels to provide position and angle information. The cathode can be coarse grained, providing timing with fewer fast amplifiers to limit power consumption. The anode layer benefits from the gain of the LGAD, with larger signals that also limit the power needed. Position can be reconstructed by measuring the pattern of total charge deposited on the anode. Angle and depth of charge deposit can be measured by the shapes of the anode pulses. We describe a possible assembly technology based on 3D integration.

3D Integration↗
DOE OSTI2022

Characterization of Low Gain Avalanche Detector Prototypes’ Response to Gamma Radiation

Motivated by the need for fast timing detectors to withstand up to 2 MGy of ionizing dose at the High Luminosity Large Hadron Collider, prototype low gain avalanche detectors (LGADs) have been fabricated in a single pad configuration, 2 × 2 arrays, and related p-i-n diodes, and exposed to Co-60 sources for study. Devices were fabricated with a range of dopant layer concentrations, and for the arrays, a variety of inter-pad distances and distances from the active area to the edge. Measurements of capacitance versus voltage and leakage current versus voltage have been made to compare pre- and post-irradiation characteristics in gain layer depletion voltage, full bulk depletion voltage, and breakdown voltage. Conclusions are drawn regarding the effects of the gammas on both surface and interface states and on their contribution to acceptor removal through non-ionizing energy loss from Compton electrons or photoelectrons. Comparison of the performances of members of the set of devices can be used to optimize gain layer parameters.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

PSEC5 Physical Verification

Ultra-Fast timing detectors, having a time resolution of 10pSec or less, are becoming increasingly important for many scientific disciplines, including High Energy Physics, Nuclear Physics, Medical Imaging and more. When developing ultra-fast detectors such as MCPs, LAPPDs, LGADs, SNSPDs, it is necessary to have access to a readout system that is low power, can support many channels and is cost effective. The PSEC5 chip was an application specific integrated circuit (ASIC) developed by the pioneering group of Prof. Henry Frisch at University of Chicago and micro electronic engineers at Fermi National Accelerator Laboratory. Three boards were designed, two to implement the readout system for an LAPPD and one to only characterize the PSEC1 chip. The main goal of the project shifted to setting up a testing environment to focus on the characterization of the chip. My student and I tested and characterized this ASIC using the third chip-on-board printed circuit board. Results show the successful fabrication and operation of some of the key building blocks and lead to the suggestions on modification for the second iteration of the chip.

Rico Aniles, H. D. [Unlisted]↗
DOE OSTI2022

Neutron time-of-flight detectors (nTOF) used at Sandia’s Z-Machine

Neutron time-of-flight (nTOF) detectors have been used on Sandia National Laboratories’ Z-Machine for inertial confinement fusion and magnetized liner fusion experiments to infer physics parameters including the apparent fuel-ion temperature, neutron yield, the magnetic-radius product (BR), and the liner rho-r. Single-paddle, dual-paddle, and co-axial scintillation nTOF detectors are used in axial lines-of-sight (LOS) and LOS that are 12° from the midplane. Detector fabrication, characterization, and calibration are discussed.

Chandler, G. A. (ORCID:0000000219640927)↗
DOE OSTI2023

Charged particle reconstruction in CLAS12 using Machine Learning

In this work, we present studies of track parameter reconstruction from raw information in CLAS12 detector's Drift Chambers, using Machine Learning (ML). We study the resolution of tracks reconstructed with different types of ML models/algorithms, including Multi-Layer Perceptron (MLP), Extremely Randomized Trees (ERT) and Gradient Boosting Trees (GBT) using simulated data. We find that the resulting ML model is capable of reconstructing track parameters (particle momentum, and polar and azimuthal angles) with accuracy similar to Hit Based (HB) tracking code, but $150$ times faster. Moreover, physics reactions can be identified using the particles reconstructed by the neural network in real-time (with a rate of about $34~kHz$) during experimental data collection. The developed model can be used in numerous applications, such as triggering specific physics reactions in real-time, detector performance monitoring, and real-time detector calibration.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Performance of a Front End prototype ASIC for picosecond precision time measurements with LGAD sensors

For the High-Luminosity phase of LHC, the ATLAS experiment is proposing the addition of a High Granularity Timing Detector (HGTD) in the forward region, to mitigate the effects of the increased pile-up. The chosen detection technology is Low Gain Avalanche Detector (LGAD) silicon sensors that can provide an excellent timing resolution below 50 ps. The front-end read-out ASIC must exploit the large signal derivative and small noise provided by the sensor, while keeping low power consumption. This paper presents the results on the first prototype of a front-end ASIC, named ALTIROC0, which contains the analog stages (preamplifier and discriminator) of the read-out chip. The ASIC was characterised both alone and as part of a module with a 2×2 LGAD array of 1.1×1.1 mm 2 pads bump-bonded to it. The various contributions of the electronics to the time resolution were investigated in test-bench measurements with a calibration setup. Both when the ASIC is alone or with a bump-bonded sensor, the jitter of the ASIC is better than 20 ps for an injected charge of 10 fC. The time walk effect, which arises from the different preamplifier response for various injected charges, can be corrected up to 10 ps using a Time Over Threshold measurement. The combined performance of the ASIC and the LGAD sensor, which was measured during a beam test campaign in October 2018 with pions of 120 GeV energy at the CERN SPS, is around 40 ps for all measured modules. All tested modules show good efficiency and time resolution uniformity.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Fabrication of Silicon Sensors Based on Low-Gain Avalanche Diodes

Low-Gain Avalanche Diodes are a recently-developed class of silicon sensors. Characterized by an internal moderate gain that enhances the signal amplitude and if built on thin silicon substrates of a few tens of microns, they feature fast signals and exhibit excellent timing performance. Thanks to their fast timing they are planned to be exploited in timing detectors in High-Energy Physics experiments, for example for the upgrades of the ATLAS and CMS detectors at the High Luminosity Large Hadron Collider (HL-LHC) at CERN. However, to achieve a spatially uniform multiplication a large pixel pitch is needed, preventing a fine spatial resolution. To overcome this limitation, the AC-coupled LGAD approach was introduced. In this type of device, metal electrodes are placed over an insulator at a fine pitch, and signals are capacitively induced on these electrodes. The fabrication technology is similar for the two LGAD families, although a fine tuning of a few process parameters needs to be carefully studied. Other R&D efforts towards detectors that can simultaneously provide good time and spatial resolution, based on the LGAD concept, are under way. These efforts aim also to mitigate the loss of performance at high irradiation fluences due to the acceptor removal within the gain layer. In this paper we describe the main points in the fabrication of LGADs and AC-LGADs in a clean-room. We also discuss novel efforts carried on related topics.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Integration of the FastIC front-end electronics into the Picosec MicroMegas detector

The Picosec MicroMegas collaboration aims to develop gaseous fast-timing detectors; experimentally, intrinsic time resolutions from around 50 ps to better than 20 ps are obtained, depending on the exact detector configuration. Parts of developments focus on exploring various options of fast-timing multi-channel front-end electronics, to meet the data processing demands of experimental applications. One option is the FastIC, which was developed for reading out positive and negative input polarity sensors with intrinsic amplification. In this paper, the first results from reading out the gaseous Picosec MicroMegas detector with the FastIC are presented. In laboratory studies, a basic description of the data processing chain was performed using a function generator. The results from test beam measurements are used to characterise the timing performance and the charge processing of the combination of FastIC and Picosec MicroMegas, as well as to demonstrate the possibility of a multi-channel detector readout. Although the timing-at-threshold level of the FastIC introduces a time walk of around 1.5 ns, time resolutions of around 50 ps have been achieved.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Time-resolved detectors for quantum ghost imaging

Quantum ghost imaging is a method that utilizes the correlated detection of two photons to generate an image. One photon is detected by an imaging sensor and the other by a single-element bucket detector. The selection of the imaging sensor and its capabilities relative to the bucket detector impact the quality of the ghost images. This work examines a SPAD array and a photocathode detector as imaging sensors for quantum ghost imaging. We discuss how to achieve optimal images using these two technologies. We also demonstrate that these devices are able to generate ghost images at 1Hz frame rates, expanding the technique to biologically relevant time scales.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Combined analysis of HPK 3.1 LGADs using a proton beam, beta source, and probe station towards establishing high volume quality control

The upgrades of the CMS and ATLAS experiments for the high luminosity phase of the Large Hadron Collider will employ precision timing detectors based on Low Gain Avalanche Detectors (LGADs). We present a suite of results combining measurements from the Fermilab Test Beam Facility, a beta source telescope, and a probe station, allowing full characterization of the HPK type 3.1 production of LGAD prototypes developed for these detectors. We demonstrate that the LGAD response to high energy test beam particles is accurately reproduced with a beta source. Finally, we further establish that probe station measurements of the gain implant accurately predict the particle response and operating parameters of each sensor, and conclude that the uniformity of the gain implant in this production is sufficient to produce full-sized sensors for the ATLAS and CMS timing detectors.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Expression of Interest in Contributions to the Electron-Ion Collider: Forward Silicon Vertex/Tracker Developments

The LANL EIC team would like to contribute to the EIC silicon vertex/tracking detector design, construction, commissioning and operation. Our primary focus is for a proposed forward silicon tracker with pseudorapidity coverage from 1 to 3.5 in the nucleon/nuclei beam going (forward) direction at IP-6 of the EIC. LANL LDRD is currently supporting this effort from FY20-FY22 with a funding of $5M. Meanwhile, we are open to collaborate on the other EIC detector sub-systems such as the central, backward silicon vertex/tracking detectors and/or a precision timing detector based on the LGAD technology.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Results for pixel and strip centimeter-scale AC-LGAD sensors with a 120 GeV proton beam

Here, we present the results of an extensive evaluation of strip and pixel AC-LGAD sensors tested with a 120 GeV proton beam, focusing on the influence of design parameters on the sensor temporal and spatial resolutions. Results show that reducing the thickness of pixel sensors significantly enhances their time resolution, with 20-μm-thick sensors achieving around 20 ps. Uniform performance is attainable with optimized n + sheet resistance, making these sensors ideal for future timing detectors. Conversely, 20-μm-thick strip sensors exhibit higher jitter than similar pixel sensors, negatively impacting time resolution, despite reduced Landau fluctuations with respect to the 50-μm-thick versions. Additionally, it is observed that a low resistivity in strip sensors limits signal size and time resolution, whereas higher resistivity improves performance. This study highlights the importance of tuning the n+ sheet resistance and suggests that further improvements should target specific applications like the Electron–Ion Collider or other future collider experiments. In addition, the detailed performance of four AC-LGADs sensor designs is reported as examples of possible candidates for specific detector applications. These advancements position AC-LGADs as promising candidates for future 4D tracking systems, pending the development of specialized readout electronics.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗