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All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

White Rabbit Time Synchronization for Radiation Detector Readout Electronics

As radiation detector arrays in nuclear physics applications become larger and physically more separated, the time synchronization and trigger distribution between many channels of detector readout electronics become more challenging. Clocks and triggers are traditionally distributed through dedicated cabling, but newer methods such as the IEEE 1588 Precision Time Protocol and White Rabbit allow clock synchronization through the exchange of timing messages over Ethernet. Consequently, we report here the use of White Rabbit in a new detector readout module, the Pixie-Net XL. Herein, the White Rabbit core, data capture from multiple digitizing channels, and subsequent pulse processing for pulse height and constant fraction timing are implemented in a Kintex 7 FPGA. The detector data records include White Rabbit time stamps and are transmitted to storage through the White Rabbit core's gigabit Ethernet data path or a slower diagnostic/control link using an embedded Zynq processor. The performance is characterized by time-of-flight style measurements and by time correlation of high energy background events from cosmic showers in detectors separated by longer distances. Software for the Zynq processor can implement "software triggering", for example to limit recording of data to events where a minimum number of channels from multiple modules detect radiation at the same time.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2012

High-speed, multi-channel detector readout electronics for fast radiation detectors

In this project, we are developing a high speed digital spectrometer that a) captures detector waveforms at rates up to 500 MSPS b) has upgraded event data acquisition with additional data buffers for zero dead time operation c) moves energy calculations to the FPGA to increase spectrometer throughput in fast scintillator applications d) uses a streamlined architecture and high speed data interface for even faster readout to the host PC These features are in addition to the standard functions in our existing spectrometers such as digitization, programmable trigger and energy filters, pileup inspection, data acquisition with energy and time stamps, MCA histograms, and run statistics. In Phase I, we upgraded one of our existing spectrometer designs to demonstrate the key principle of fast waveform capture using a 500 MSPS, 12 bit ADC and a Xilinx Virtex-4 FPGA. This upgraded spectrometer, named P500, performed well in initial tests of energy resolution, pulse shape analysis, and timing measurements, thus achieving item (a) above. In Phase II, we are revising the P500 to build a commercial prototype with the improvements listed in items (b)-(d). As described in the previous report, two devices were built to pursue this goal, named the Pixie-500 and the Pixie-500 Express. The Pixie-500 has only minor improvements from the Phase I prototype and is intended as an early commercial product (its production and part of its development were funded outside the SBIR). It also allows testing of the ADC performance in real applications.The Pixie-500 Express (or Pixie-500e) includes all of the improvements (b)-(d). At the end of Phase II of the project, we have tested and debugged the hardware, firmware and software of the Pixie-500 Express prototype boards delivered 12/3/2010. This proved substantially more complex than anticipated. At the time of writing, all hardware bugs have been fixed, the PCI Express interface is working, the SDRAM has been successfully tested and the SHARC DSP has been booted with preliminary code. All new ICs and circuitry on the prototype are working properly, however some of the planned firmware and software functions have not yet been completely implemented and debugged. Overall, due to the unanticipated complexity of the PCI Express interface, some aspects of the project could not be completed with the time and funds available in Phase II. These aspects will be completed in self-funded Phase III.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS2016

Assessment of the Influence of the RaD-X Balloon Payload on the Onboard Radiation Detectors

The NASA Radiation Dosimetry Experiment (RaD-X) stratospheric balloon flight mission, launched on 25 September 2015, provided dosimetric measurements above the Pfotzer maximum. The goal of taking these measurements is to improve aviation radiation models by providing a characterization of cosmic ray primaries, which are the source of radiation exposure at aviation altitudes. The RaD-X science payload consists of four instruments. The main science instrument is a tissue-equivalent proportional counter (TEPC). The other instruments consisted of three solid state silicon dosimeters: Liulin, Teledyne total ionizing dose (TID) and RaySure detectors. The instruments were housed in an aluminum structure protected by a foam cover. The structure partially shielded the detectors from cosmic rays but also created secondary particles, modifying the ambient radiation environment observed by the instruments. Therefore, it is necessary to account for the influence of the payload structure on the measured doses. In this paper, we present the results of modeling the effect of the balloon payload on the radiation detector measurements using a Geant-4 (GEometry ANd Tracking) application. Payload structure correction factors derived for the TEPC, Liulin, and TID instruments are provided as a function of altitude. Overall, the payload corrections are no more than a 7% effect on the radiation environment measurements.

Gronoff, Guilluame↗
DOE OSTI2021

Colorimetric radiation detector

A low cost, rapid, flexible radiation detector uses inorganic metal halide precursors and dyes that respond to self-quenching hybrid scintillation. Remote, high-contrast, laser sensing can be used to determine when exposure of the detector to radiation occurs (even temporally).

Boyle, Timothy J.↗
DOE OSTI2023

Colorimetric radiation detector

A low cost, rapid, flexible radiation detector uses inorganic metal halide precursors and dyes that respond to self-quenching hybrid scintillation. Remote, high-contrast, laser sensing can be used to determine when exposure of the detector to radiation occurs (even temporally).

Garzon, Fernando Henry↗
DOE OSTI2016

Monolithic active pixel radiation detector with shielding techniques

A monolithic active pixel radiation detector including a method of fabricating thereof. The disclosed radiation detector can include a substrate comprising a silicon layer upon which electronics are configured. A plurality of channels can be formed on the silicon layer, wherein the plurality of channels are connected to sources of signals located in a bulk part of the substrate, and wherein the signals flow through electrically conducting vias established in an isolation oxide on the substrate. One or more nested wells can be configured from the substrate, wherein the nested wells assist in collecting charge carriers released in interaction with radiation and wherein the nested wells further separate the electronics from the sensing portion of the detector substrate. The detector can also be configured according to a thick SOA method of fabrication.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Monolithic active pixel radiation detector with shielding techniques

A monolithic active pixel radiation detector including a method of fabricating thereof. The disclosed radiation detector can include a substrate comprising a silicon layer upon which electronics are configured. A plurality of channels can be formed on the silicon layer, wherein the plurality of channels are connected to sources of signals located in a bulk part of the substrate, and wherein the signals flow through electrically conducting vias established in an isolation oxide on the substrate. One or more nested wells can be configured from the substrate, wherein the nested wells assist in collecting charge carriers released in interaction with radiation and wherein the nested wells further separate the electronics from the sensing portion of the detector substrate. The detector can also be configured according to a thick SOA method of fabrication.

47 OTHER INSTRUMENTATION↗
NASA NTRS1975

Design of a transition radiation detector for cosmic rays

Transition radiation detectors consisting of sandwiches of plastic foam radiators and multiwire proportional chambers can be used to identify cosmic ray particles with energies gamma ? E/mc-squared is greater than 10 to the 3rd and to measure their energy in the region gamma is roughly equal to 10 to the 3rd

Hartmann, G.↗
NASA NTRS1981

A new transition radiation detector for cosmic ray nuclei

Test measurements on materials for transition radiation detectors at a low Lorentz factor are reported. The materials will be based on board Spacelab-2 for determining the composition and energy spectra of nuclear cosmic rays in the 1 TeV/nucleon range. The transition radiation detectors consist of a sandwich of radiator-photon detector combinations. The radiators emit X-rays and are composed of polyolefin fibers used with Xe filled multiwired proportional chamber (MWPC) detectors capable of detecting particle Lorentz factors of several hundred. The sizing of the detectors is outlined, noting the requirement of a thickness which provides a maximum ratio of transition radiation to total signal in the chambers. The fiber radiator-MWPC responses were tested at Fermilab and in an electron cyclotron. An increase in transition radiation detection was found as a square power law of Z, and the use of six radiator-MWPC on board the Spacelab-2 is outlined.

Lheureux, J.↗
DOE OSTI2019

A new Transition Radiation detector based on GEM technology

Transition Radiation Detectors (TRD) have the potential feature of separating particles by their gamma factor. Classical TRDs are based on Multi-Wire Proportional Chambers (MWPC) or straw tubes, using a Xenon based gas mixture to efficiently absorb transition radiation photons. These detectors operate well in experiments with relatively low particle multiplicity. The performance of MWPC-TRD in experiments with luminosity of order 10 34 cm 2 s –1 and above, is significantly deteriorated due to the high particle multiplicity and channel occupancy. Replacing MWPC or straw tubes with a high granularity Micro Pattern Gas Detectors (MPGD) like Gas Electron Multipliers (GEMs), could improve the performance of the TRD. In addition, GEM technology allows one to combine a tracker with TRD identification (GEM-TRD/T). This report presents a new TRD development based on GEM technology for the future Electron Ion Collider (EIC). The first beam test was performed at Jefferson Lab (Hall-D) using 3–6 GeV electrons. A GEM-TRD/T module has been exposed to electrons with and without a fiber radiator. First results of test beam measurements and comparison with Geant4 Monte Carlo are introduced here.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

High Performance Pd/4H-SiC Epitaxial Schottky Barrier Radiation Detectors for Harsh Environment Applications

Although many refractory metals have been investigated as the choice of contact metal in 4H-SiC devices, palladium (Pd) as a Schottky barrier contact for 4H-SiC radiation detectors for harsh environment applications has not been investigated adequately. Pd is a refractory metal with high material weight-to-thickness ratio and a work function as high as nickel, one of the conventional metal contacts for high performing 4H-SiC Schottky barrier detectors (SBDs). In this article, Pd/4H-SiC epitaxial SBDs have been demonstrated for the first time as a superior self-biased (0 V applied bias) radiation detector when compared to benchmark Ni/4H-SiC SBDs. The Pd/4H-SiC SBD radiation detectors showed a very high energy resolution of 1.9% and 0.49% under self- and optimized bias, respectively, for 5486 keV alpha particles. The SBDs demonstrated a built-in voltage (V bi ) of 2.03 V and a hole diffusion length (L d ) of 30.8 µm. Such high V bi and L d led to an excellent charge collection efficiency of 76% in the self-biased mode. Capacitance mode deep level transient spectroscopy (DLTS) results revealed that the “lifetime-killer” Z 1/2 trap centers were present in the 4H-SiC epilayer. Another deep level trap was located at 1.09 eV below the conduction band minimum and resembles the EH5 trap with a concentration of 1.98 × 10 11 cm –3 and capture cross-section 1.7 × 10 –17 cm –2 ; however, the detector performance was found to be limited by charge trapping in the Z 1/2 center. The results presented in this article revealed the unexplored potential of a wide bandgap semiconductor, SiC, as high-efficiency self-biased radiation detectors. Such high performance self-biased radiation detectors are poised to address the longstanding problem of designing self-powered sensor devices for harsh environment applications e.g., advanced nuclear reactors and deep space missions.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Geant4-based multiphysics simulation toolkit for analysis of radiation detector performance

Often only a single physical process or component is investigated in the simulation of radiation detector systems. The results are then considered to be representative of what is expected in the correlating physical experiment. Although singular assessments may serve as a good estimate, the overall performance of a radiation detector system depends on several physical processes and the performance of all components within the system. Our Geant4-based multiphysics simulation toolkit couples radiation transport with optical photon processes, providing simulations of radiation detector systems components from the scintillator through the photocathode of the photodetector. Work to incorporate the back-end detector components, including the complete photodetector and subsequent electronics (e.g., amplifiers, digitizers), is underway. Geant4 is used to model the radiation transport and optical photon processes that occur in the front-end detector system components when exposed to a chosen source. These components include the scintillator, detector housing, optical coupling to the photodetector, and photocathode of the photodetector. Characteristics of several detector systems that have been studied include time response; pulse height spectra; number of photoelectrons per MeV; detector efficiency versus incident quanta energy; and effects on detector response due to change in geometries, materials, and reflectivity. Comparison of these characteristics by means of this toolkit enables the selection of the optimal individual components; thus, it is possible to specify the radiation detector system best suited to meet the requirements of any physical experiment.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

The Urban Deployment Model: A Toolset for the Simulation and Performance Characterization of Radiation Detector Deployments in Urban Environments

Static and mobile radiation detectors can be deployed in urban environments for a range of nuclear security applications, including radiological source search-and-tracking scenarios. Modeling detector performance for such applications is challenging, as it does not depend solely on the detector capabilities themselves. Many factors must be taken into consideration, including specific source and background signatures, the topology and constraints of the deployment environment, the presence of nuisance sources, and whether detectors are mobile or static. When considering the simultaneous deployment of multiple, heterogeneous detectors, assessment of the system-wide performance requires the simulation of the individual detectors, and a system-level analysis of the detection performance. In radiological source search-and-tracking scenarios, performance is mostly dominated by the probability of encounter, which depends on the specifics of a given deployment, e.g., static vs. mobile detectors or a combination of both modalities, the number of detectors deployed, the dynamic vs. static setting of false alarm rates, and individual vs. networked operation. The Urban Deployment Model (UDM) toolset was specifically developed to cover the gap in the available generic frameworks for the simulation of radiation detector deployments at city scales. UDM provides a unified and modular framework to support the simulation and performance characterization of heterogeneous detector deployments in urban environments. This paper presents the key components along the UDM workflow.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2019

Gating grid driver for gas radiation detectors

A gating grid driver for use with radiation detectors, such as time projection chambers and other similar devices that require a gating grid that operates in a bipolar mode with different electrostatic potentials on alternating wires. To open such gating grids, the driver shorts the alternate wires to a common voltage Va. Later, this driver closes the grid by restoring the voltage differences in the adjacent wires. By connecting the driver circuit to the gating grid via low impedance transmission lines, the driver circuit opens the gating grid in 0.35 μs, minimizing the lost drift length associated with this opening time. The circuit consists of 2 pairs of N- and P-MOSFET switches and includes two adjustable capacitors and resistors that can be used to adjust the opening time, and shift the balance of positive and negative charge for individual radiation detector.

Tangwancharoen, Suwat↗
DOE OSTI2012

Large dynamic range radiation detector and methods thereof

According to one embodiment, a radiation detector comprises a scintillator and a photodiode optically coupled to the scintillator. The radiation detector also includes a bias voltage source electrically coupled to the photodiode, a first detector operatively electrically coupled to the photodiode for generating a signal indicative of a level of a charge at an output of the photodiode, and a second detector operatively electrically coupled to the bias voltage source for generating a signal indicative of an amount of current flowing through the photodiode.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Ultra-thin plasma radiation detector

A position-sensitive ionizing-radiation counting detector includes a radiation detector gas chamber having at least one ultra-thin chamber window and an ultra-thin first substrate contained within the gas chamber. The detector further includes a second substrate generally parallel to and coupled to the first substrate and defining a gas gap between the first substrate and the second substrate. The detector further includes a discharge gas between the substrates and contained within the gas chamber, where the discharge gas is free to circulate within the gas chamber and between the first and second substrates at a given gas pressure. The detector further includes a first electrode coupled to one of the substrates and a second electrode electrically coupled to the first electrode. The detector further includes a first discharge event detector coupled to at least one of the electrodes for detecting a gas discharge counting event in the electrode.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS2008

Integrator Circuitry for Single Channel Radiation Detector

Input circuitry is provided for a high voltage operated radiation detector to receive pulses from the detector having a rise time in the range of from about one nanosecond to about ten nanoseconds. An integrator circuit, which utilizes current feedback, receives the incoming charge from the radiation detector and creates voltage by integrating across a small capacitor. The integrator utilizes an amplifier which closely follows the voltage across the capacitor to produce an integrator output pulse with a peak value which may be used to determine the energy which produced the pulse. The pulse width of the output is stretched to approximately 50 to 300 nanoseconds for use by subsequent circuits which may then use amplifiers with lower slew rates.

Holland, Samuel D.↗