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Results for “Neutron Detector”

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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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Neutron multiplicity ,easurements With 3 He alternative: Straw neutron detectors

Counting neutrons emitted by special nuclear material (SNM) and differentiating them from the background neutrons of various origins is the most effective passive means of detecting SNM. Unfortunately, neutron detection, counting, and partitioning in a maritime environment are complex due to the presence of high-multiplicity spallation neutrons (commonly known as “ship effect”) and to the complicated nature of the neutron scattering in that environment. In this study, a prototype neutron detector was built using 10 B as the converter in a special form factor called “straws” that would address the above problems by looking into the details of multiplicity distributions of neutrons originating from a fissioning source. This paper describes the straw neutron multiplicity counter (NMC) and assesses the performance with those of a commercially available fission meter. The prototype straw neutron detector provides a large-area, efficient, lightweight, more granular (than fission meter) neutron-responsive detection surface (to facilitate imaging) to enhance the ease of application of fission meters. Presented here are the results of preliminary investigations, modeling, and engineering considerations leading to the construction of this prototype. This design is capable of multiplicity and Feynman variance measurements. This prototype may lead to a near-term solution to the crisis that has arisen from the global scarcity of 3 He by offering a viable alternative to fission meters. This paper describes the work performed during a 2-year site-directed research and development (SDRD) project that incorporated straw detectors for neutron multiplicity counting. The NMC is a two-panel detector system. We used 10 B (in the form of enriched boron carbide: 10 B 4 C) for neutron detection instead of 3 He. In the first year, the project worked with a panel of straw neutron detectors, investigated its characteristics, and developed a data acquisition (DAQ) system to collect neutron multiplicity information from spontaneous fission sources using a single panel consisting of 60 straws equally distributed over three rows in high-density polyethylene moderator. In the following year, we developed the field-programmable gate array and associated DAQ software. Finally, this SDRD effort successfully produced a prototype NMC with ~33% detection efficiency compared to a commercial fission meter.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

The development of a 6 Li-based pixelated neutron detector for neutron reflectometry at the Spallation Neutron Source

We present a high-rate 6 Li-based pixelated neutron detector developed for neutron reflectometry instruments at the Spallation Neutron Source (SNS). The neutron detector has a pixelated design: each 6 Li scintillator element has its own photosensor and independent channel readout. This paper focuses on the general overview of the detector design and construction, the characterization of the pixelated detector, and the results of the first neutron reflectivity experiments conducted using the pixelated neutron detector at the SNS Liquid Reflectometer (BL-4B). The pixelated neutron detector demonstrated a global time-average count rate of ≥ 1.8 x 10 6 cps, at least 3 orders of magnitude higher than that of the existing neutron detector ( 3 He-based Multi-Wire Proportional Counter), and a local instantaneous count rate of ≥ 1.73 x 10 6 cps / cm 2 . The maximum counting rate of the detector has not yet been determined as the detector is capable of handling the maximum flux available at the beamline. Furthermore, the outcome of the neutron reflectivity experiments showed that the pixelated neutron detector is a promising candidate for next-generation neutron reflectometry instruments at the SNS.

6Li, silicon photomultiplier↗
DOE OSTI2019

Apparatus for use in a directional-neutron detector, directional-neutron detectors and methods of use thereof

An apparatus for used in a directional-neutron detector is disclosed. The apparatus comprises a structure having a plurality of parallel active channels separated by inactive regions. The plurality of active channels is filled with scintillating material. The scintillating material is configured to emit light in response to neutron scattering. The scintillating material may be neutron-gamma discriminating. The scintillating material may be sealed in the plurality of active channels. The seal is disposed on respective ends of the plurality of active channels. Directional-neutron detectors are also disclosed having the structure.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Used Fuel Storage Monitoring Using Helium-4 Scintillation Fast Neutron Detectors and Neutron Spectral Analysis

This project aimed to address the technology gap in the reliable methods to verify contents of sealed dry storage casks for spent nuclear fuel. Helium-4 gas scintillation neutron detectors was proposed to be developed into a neutron spectroscopy and imaging system for nuclear security and safeguards applications. 4 He gas is significantly more available than 3 He gas and it has unique advantages such as low gamma interaction probability and direct detection of fast neutrons. Due to the sheer amount of fissile materials in a single dry cask, there is a significant neutron fluence emitted whose energies range from thermal to uncollided high-energy neutrons suitable for the detection capability of the 4 He detectors. Our project demonstrated the first ever neutron spectroscopic capabilities using 4 He detectors, explored novel detector design and performed detector characterization. It further qualified the detectors for use in various applications including high-flux environments with significant gamma-fluence. Computer simulations were used to test various large cask measurement system designs and tests, beyond the compact prototype system and laboratory measurements exploring the feasibility of the neutron spectroscopic approach. Although some cask-characterization methods proved unfeasible, alternative characterization methods using the He-4 detectors were explored and generated promising results.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Ab initio response functions for Cherenkov-based neutron detectors

Neutron time-of-flight diagnostics at the NIF were of late outfitted with Cherenkov detectors. A fused silica radiator delivers sub-nanosecond response time and is optically coupled to a microchannel plate photomultiplier tube with gain from ~1 to 10 4 . Capitalizing on fast time response and gamma-ray sensitivity, these systems can provide better than 30 ps precision for measuring first moments of neutron distributions. Generation of ab initio instrument response functions (IRFs) is critical to meet the <1% uncertainty needed. A combination of Monte Carlo modeling, benchtop characterization, and in situ comparison is employed. Close agreement is shown between the modeled IRFs and in situ measurements using the NIF’s short-pulse advanced radiographic capability beams. First and second moments of neutron spectra calculated using ab initio IRFs agree well with established scintillator measurements. Next-step designs offer increased sensitivity and time-response.

47 OTHER INSTRUMENTATION↗
DOE OSTI2026

ICONS: Solid-State Composite Neutron Detector

Neutron detection is essential for identifying and monitoring nuclear materials and nuclear reactions. Most deployed neutron-detection systems rely on helium-3 ( 3 He) gas-filled tubes, which have been the standard technology for decades.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Godiva IV central cavity neutron environment characterization with threshold neutron detectors

Godiva IV is a cylindrical fast burst reactor comprised of approximately 65 kg of highly enriched uranium that is operated by Los Alamos National Laboratory and sited at the National Criticality Experiments Research Center at the Nevada National Security Site in Nevada in the United States. Godiva IV is typically operated at delayed critical and in the regime spanning from sub-prompt to super-prompt bursts. Godiva IV is used for sample irradiations, criticality safety demonstrations, dosimetry studies, and for studying super-prompt behavior. In preparation for both an upcoming experiment to reduce uncertainties in the prompt fission spectrum for 235U using threshold neutron detectors, and for future research using Godiva IV, it was desired to exercise the process of the selection of threshold neutron detectors/activation foils, radiation metrology, and the subsequent adjustment of the neutron spectrum. For this exercise, nine high purity threshold neutron detectors/activation foils were irradiated in a Godiva IV burst. The foils were then analyzed using a high-purity germanium detector in the NCERC counting laboratory to determine end of irradiation specific activities for available IRDFF-II reactions. This work summarizes the Godiva IV foil irradiation, radiation metrology results, and adjusted neutron spectrum. The results of this exercise ultimately characterized the neutron environment inside the sample irradiation cavity inside Godiva IV to a higher degree than previously performed, informed decisions for the upcoming larger scale experiment, and will inform future neutron spectrum characterizations at NCERC.

Whitman, Nicholas H.↗
DOE OSTI2021

Mutli-layered neutron detector

A neutron detector including a plurality of layers of converter material and a plurality of layers of detector material. Each layer of converter material can be immediately adjacent to at least one layer of detector material and each layer of detector material can be immediately adjacent to at least one layer of converter material. The neutron detector may further include a read out integrated circuit (ROIC) that is electrically coupled to the plurality of layers of detector material. A value output by the ROIC may be indicative of a neutron interacting with a layer of converter material from amongst the plurality of layers of converter material.

Rice, William Charles↗
DOE OSTI2019

Report on the Tin-II Thermal Neutron Detector

Thermal neutrons have recently become a concern in the semiconductor community where it has been reported that approximately 20% of the single-event upsets are due to thermal neutrons in some devices. The goal of this project is to measure the intensity of thermal neutrons in the High- Performance Computing (HPC) area. This is part of a larger effort to characterize the radiation environment in the HPC area which includes high-energy neutrons as well as thermal neutrons. To accomplish this goal, we designed and fabricated a neutron detector that is sensitive to thermal neutrons called Tin-II. The Tin-II detector consists of two identical 3He ionization chambers with one detector bare and one detector shielded with cadmium. Because the cadmium shielding effectively blocks the thermal neutrons, the difference in count rates between these two detectors reflect the number of thermal neutrons detected. This report summarizes the status of our efforts to develop this detector.

47 OTHER INSTRUMENTATION↗
DOE OSTI2016

Improved neutron-gamma discrimination for a {sup 6}Li-glass neutron detector using digital signal analysis methods

A {sup 6}Li-glass scintillator (GS20) based neutron Anger camera was developed for time-of-flight single-crystal diffraction instruments at Spallation Neutron Source. Traditional Pulse-Height Analysis (PHA) for Neutron-Gamma Discrimination (NGD) resulted in the neutron-gamma efficiency ratio (defined as NGD ratio) on the order of 10{sup 4}. The NGD ratios of Anger cameras need to be improved for broader applications including neutron reflectometers. For this purpose, six digital signal analysis methods of individual waveforms acquired from photomultiplier tubes were proposed using (i) charge integration, (ii) pulse-amplitude histograms, (iii) power spectrum analysis combined with the maximum pulse-amplitude, (iv) two event parameters (a{sub 1}, b{sub 0}) obtained from a Wiener filter, (v) an effective amplitude (m) obtained from an adaptive least-mean-square filter, and (vi) a cross-correlation coefficient between individual and reference waveforms. The NGD ratios are about 70 times those from the traditional PHA method. Our results indicate the NGD capabilities of neutron Anger cameras based on GS20 scintillators can be significantly improved with digital signal analysis methods.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Thermal Neutron Imaging Using A New Pad-Based Position Sensitive Neutron Detector

Thermal neutrons (with mean energy of 25 meV) have a scattering mean free path of about 20 m in air. Therefore it is feasible to find localized thermal neutron sources up to ~30 m standoff distance using thermal neutron imaging. Coded aperture thermal neutron imaging was developed in our laboratory in the nineties, using He-3 filled wire chambers. Recently a new generation of coded-aperture neutron imagers has been developed. In the new design the ionization chamber has anode and cathode planes, where the anode is composed of an array of individual pads. The charge is collected on each of the individual 5x5 mm2 anode pads, (48x48 in total, corresponding to 24x24 cm2 sensitive area) and read out by application specific integrated circuits (ASICs). The high sensitivity of the ASICs allows unity gain operation mode. The new design has several advantages for field deployable imaging applications, compared to the previous generation of wire-grid based neutron detectors. Among these are the rugged design, lighter weight and use of non-flammable stopping gas. For standoff localization of thermalized neutron sources a low resolution (11x11 pixel) coded aperture mask has been fabricated. Using the new larger area detector and the coarse resolution mask we performed several standoff experiments using moderated californium and plutonium sources at Idaho National Laboratory. In this paper we will report on the development and performance of the new pad-based neutron camera, and present long range coded-aperture images of various thermalized neutron sources.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Performance improvements of wavelength-shifting-fiber neutron detectors using high-resolution positioning algorithms

On the basis of FluoroBancroft linear-algebraic method [S.B. Andersson, Opt. Exp. 16, 18714 (2008)] three highly-resolved positioning methods were proposed for wavelength-shifting fiber (WLSF) neutron detectors. Using a Gaussian or exponential-decay light-response function (LRF), the non-linear relation of photon-number profiles vs. x-pixels was linearized and neutron positions were determined. The proposed algorithms give an average 0.03-0.08 pixel position error, much smaller than that (0.29 pixel) from a traditional maximum photon algorithm (MPA). The new algorithms result in better detector uniformity, less position misassignment (ghosting), better spatial resolution, and an equivalent or better instrument resolution in powder diffraction than the MPA. Moreover, these characters will facilitate broader applications of WLSF detectors at time-of-flight neutron powder diffraction beamlines, including single-crystal diffraction and texture analysis.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Probing the bandgap and effects of t-BN domains in h-BN neutron detectors

Thermal neutron detectors in a lateral scheme were fabricated from a 70μm thick freestanding B-10 enriched hexagonal BN (h- 10 BN). Two sets of channel peaks corresponding to the neutron capture by 10 B occurring in h- 10 BN comprising turbostratic domains (t- 10 BN) have been recognized in the nuclear reaction pulsed height spectrum, from which a bandgap of 5.5 eV was directly deduced for t- 10 BN. Improved device performance over the prior state-of-the-art implies that the transport properties in the lateral plane of t-BN domains are sufficiently good and their presence in h-BN is not a showstopper for the further advancement of h-BN detector technologies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Ion chamber based neutron detectors

A neutron detector with monolithically integrated readout circuitry, including: a bonded semiconductor die; an ion chamber formed in the bonded semiconductor die; a first electrode and a second electrode formed in the ion chamber; a neutron absorbing material filling the ion chamber; and the readout circuitry which is electrically coupled to the first and second electrodes. The bonded semiconductor die includes an etched semiconductor substrate bonded to an active semiconductor substrate. The readout circuitry is formed in a portion of the active semiconductor substrate. The ion chamber has a substantially planar first surface on which the first electrode is formed and a substantially planar second surface, parallel to the first surface, on which the second electrode is formed. The distance between the first electrode and the second electrode may be equal to or less than the 50% attenuation length for neutrons in the neutron absorbing material filling the ion chamber.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Direction sensitive neutron detector

A neutron detector includes a pressure vessel, an electrically conductive field cage assembly within the pressure vessel and an imaging subsystem. A pressurized gas mixture of CF 4 , 3 He and 4 He at respective partial pressures is used. The field cage establishes a relatively large drift region of low field strength, in which ionization electrons generated by neutron-He interactions are directed toward a substantially smaller amplification region of substantially higher field strength in which the ionization electrons undergo avalanche multiplication resulting in scintillation of the CF.sub.4 along scintillation tracks. The imaging system generates two-dimensional images of the scintillation patterns and employs track-finding to identify tracks and deduce the rate and direction of incident neutrons. One or more photo-multiplier tubes record the time-profile of the scintillation tracks permitting the determination of the third coordinate.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Response of alpha particles in hexagonal boron nitride neutron detectors

Here, thermal neutron detectors were fabricated from 10 B enriched h-BN epilayers of different thicknesses. The charge carrier generation and energy loss mechanisms as well as the range of alpha daughter particles generated by the nuclear reaction between thermal neutrons and 10 B atoms in hexagonal boron nitride (h-BN) thermal neutron detectors have been investigated via their responses to alpha particles from a 210 Po source. The ranges of alpha particles in h-BN were found to be anisotropic, which increase with the angle (θ) between the trajectory of the alpha particles and c-axis of the h-BN epilayer following (cos θ) -1 and are 4.6 and 5.6 μm, respectively, for the alpha particles with energies of 1.47 MeV and 1.78 MeV at θ = 0. However, the energy loss of an alpha particle inside h-BN is determined by the number of layers it passes through with a constant energy loss rate of 107 eV per layer due to the layered structure of h-BN. Roughly 5 electron-hole pairs are generated when an alpha particle passes through each layer. It was also shown that the durability of h-BN thermal neutron detectors is excellent based on the calculation of boron vacancies generated (or 10 B atoms consumed) by neutron absorption. Finally, the results obtained here provide useful insights into the mechanisms of energy loss and charge carrier generation inside h-BN detectors and possible approaches to further improve the overall performance of h-BN thermal neutron detectors, as well as the ultimate spatial resolution of future neutron imaging devices or cameras based on h-BN epilayers.

47 OTHER INSTRUMENTATION↗
DOE OSTI2019

Design and Benchmarking of a Proton Recoil Neutron Detector

A neutron spectroscopy detector was designed for analysis of neutrons produced by Lawrence Livermore National Laboratory's neutron imaging project. The detector was built and benchmarked at Lawrence Berkeley National Laboratory's Deuteron-Breakup Neutron Facility. Similar to a proton-recoil telescope, the setup detects protons elastically scattered from neutrons incident on a thin sheet of polyethylene. A silicon charged-particle detector several centimeters away detects the protons in a small angular range, such that the energies of the incident neutrons can be reconstructed from the energy of the detected proton and the scattering angle. A quick benchmarking experiment demonstrated that large backgrounds would be a significant challenge, and that additional measures must be taken to reduce these backgrounds. A Geant4 model of the detector was used to predict the sources of these backgrounds and how best to reduce them.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗