Development of A Self Biased High Efficiency Solid-State Neutron Detector for MPACT Applications

Development of A Self Biased High Efficiency Solid-State Neutron Detector for MPACT Applications
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Release: 2013
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Neutron detection is an important aspect of materials protection, accounting, and control for transmutation (MPACT). Currently He-3 filled thermal neutron detectors are utilized in many applications; these detectors require high-voltage bias for operation, which complicates the system when multiple detectors are used. In addition, due to recent increase in homeland security activity and the nuclear renaissance, there is a shortage of He-3, and these detectors become more expensive. Instead, cheap solid-state detectors that can be mass produced like any other computer chips will be developed. The new detector does not require a bias for operation, has low gamma sensitivity, and a fast response. The detection system is based on a honeycomb-like silicon device, which is filled with B-10 as the neutron converter; while a silicon p-n diode (i.e., solar cell type device) formed on the thin silicon wall of the honeycomb structure detects the energetic charged particles emitted from the B-10 conversion layer. Such a detector has ~40% calculated thermal neutron detection efficiency with an overall detector thickness of about 200?m. Stacking of these devices allows over 90% thermal neutron detection efficiency. The goal of the proposed research is to develop a high-efficiency, low-noise, self-powered solid-state neutron detector system based on the promising results of the existing research program. A prototype of this solid-state neutron detector system with sufficient detector size (up to 8-inch diam., but still portable and inexpensive) and integrated with interface electronics (e.g., preamplifier) will be designed, fabricated, and tested as a coincidence counter for MPACT applications. All fabrications proposed are based on silicon-compatible processing; thus, an extremely cheap detector system could be massively produced like any other silicon chips. Such detectors will revolutionize current neutron detection systems by providing a solid-state alternative to traditional gas-based neutron detectors.

Modeling and Analysis of a Portable, Solid-state Neutron Detection System for Spectroscopic Applications

Modeling and Analysis of a Portable, Solid-state Neutron Detection System for Spectroscopic Applications
Author: Thomas Michael Oakes
Publisher:
Total Pages: 184
Release: 2012
Genre: Electronic Dissertations
ISBN:
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This paper discusses a new neutron detection system that allows local volumetric identification of fast neutron thermalization in the context of forming a solid state Bonner-like neutron spectrometer. The resulting departure and subsequent improvement from the classical Bonner spectrometer is that the entire moderating volume is sampled locally for thermal neutrons. Such volumetric resolution is possible through the layering of weakly perturbing and pixilated high thermal efficiency solid state neutron detectors into a cylindrically symmetric neutron moderator. The overall system exhibits >10% total detection efficiency over the neutron energy range from thermal to 20 MeV and the data can be acquired simultaneously from all detector elements in a single measurement. These measurements can be used to infer information on incident neutron energy spectra and direction, which provides capabilities not available in current systems. The end result is a highly efficient, man-portable device with significantly improved methods for determination of pervading neutron energy spectra and the corresponding dose equivalent.

Improvements in Thin Film Solid State Neutron Detectors for Cost Effective Applications

Improvements in Thin Film Solid State Neutron Detectors for Cost Effective Applications
Author: Lindsey Michelle Smith
Publisher:
Total Pages: 340
Release: 2016
Genre: Cadmium telluride
ISBN:
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Solid state thermal neutron detectors offer a cost effective alternative to 3He based neutron detectors. Solid state neutron detectors consist of a neutron conversion layer and a charged particle sensing diode layer. The conversion layer converts neutrons into charged particles which are sensed in the charged particle sensing region. In this work, thin film CdTe is optimized to be a gamma-ray insensitive charged particle sensor with high charge collection efficiency. A cost effective conversion film made from a 10B4C/polymer composite is fabricated that can be deposited by the simple spin coating method. An experimental setup for neutron detection is demonstrated for the first time at UTD. Using detector design strategies such as a hydrogen dense backing layer, intrinsic thermal neutron efficiencies of up to 16% are reported while maintaining a gamma discrimination that is greater than 10−6.

Dual-side Etched Microstructured Semiconductor Neutron Detectors

Dual-side Etched Microstructured Semiconductor Neutron Detectors
Author: Ryan G. Fronk
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Total Pages:
Release: 2017
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Interest in high-efficiency replacements for thin-film-coated thermal neutron detectors led to the development of single-sided microstructured semiconductor neutron detectors (MSNDs). MSNDs are designed with micro-sized trench structures that are etched into a vertically-oriented pvn-junction diode, and backfilled with a neutron converting material, such as 6LiF. Neutrons absorbed by the converting material produce a pair of charged-particle reaction products that can be measured by the diode substrate. MSNDs have higher neutron-absorption and reaction-product counting efficiencies than their thin-film-coated counterparts, resulting in up to a 10x increase in intrinsic thermal neutron detection efficiency. The detection efficiency for a single-sided MSND is reduced by neutron streaming paths between the conversion-material filled regions that consequently allow neutrons to pass undetected through the detector. Previously, the highest reported intrinsic thermal neutron detection efficiency for a single MSND was approximately 30%. Methods for double-stacking and aligning MSNDs to reduce neutron streaming produced devices with an intrinsic thermal neutron detection efficiency of 42%. Presented here is a new type of MSND that features a complementary second set of trenches that are etched into the back-side of the detector substrate. These dual-sided microstructured semiconductor neutron detectors (DS-MSNDs) have the ability to absorb and detect neutrons that stream through the front-side, effectively doubling the detection efficiency of a single-sided device. DS-MSND sensors are theoretically capable of achieving greater than 80% intrinsic thermal neutron detection efficiency for a 1-mm thick device. Prototype DS-MSNDs with diffused pvp-junction operated at 0-V applied bias have achieved 53.54±0.61%, exceeding that of the single-sided MSNDs and double-stacked MSNDs to represent a new record for detection efficiency for such solid-state devices.

Advanced Microstructured Semiconductor Neutron Detectors

Advanced Microstructured Semiconductor Neutron Detectors
Author: Steven Lawrence Bellinger
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Total Pages:
Release: 2011
Genre:
ISBN:
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The microstructured semiconductor neutron detector (MSND) was investigated and previous designs were improved and optimized. In the present work, fabrication techniques have been refined and improved to produce three-dimensional microstructured semiconductor neutron detectors with reduced leakage current, reduced capacitance, highly anisotropic deep etched trenches, and increased signal-to-noise ratios. As a result of these improvements, new MSND detection systems function with better gamma-ray discrimination and are easier to fabricate than previous designs. In addition to the microstructured diode fabrication improvement, a superior batch processing backfill-method for 6LiF neutron reactive material, resulting in a nearly-solid backfill, was developed. This method incorporates a LiF nano-sizing process and a centrifugal batch process for backfilling the nanoparticle LiF material. To better transition the MSND detector to commercialization, the fabrication process was studied and enhanced to better facilitate low cost and batch process MSND production. The research and development of the MSND technology described in this work includes fabrication of variant microstructured diode designs, which have been simulated through MSND physics models to predict performance and neutron detection efficiency, and testing the operational performance of these designs in regards to neutron detection efficiency, gamma-ray rejection, and silicon fabrication methodology. The highest thermal-neutron detection efficiency reported to date for a solid-state semiconductor detector is presented in this work. MSNDs show excellent neutron to gamma-ray (n/[gamma]) rejection ratios, which are on the order of 106, without significant loss in thermal-neutron detection efficiency. Individually, the MSND is intrinsically highly sensitive to thermal neutrons, but not extrinsically sensitive because of their small size. To improve upon this, individual MSNDs were tiled together into a 6x6-element array on a single silicon chip. Individual elements of the array were tested for thermal-neutron detection efficiency and for the n/[gamma] reject ratio. Overall, because of the inadequacies and costs of other neutron detection systems, the MSND is the premier technology for many neutron detection applications.

Roadmap for High Efficiency Solid-State Neutron Detectors

Roadmap for High Efficiency Solid-State Neutron Detectors
Author: T. Wang
Publisher:
Total Pages: 11
Release: 2005
Genre:
ISBN:
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Solid-state thermal neutron detectors are generally fabricated in a planar configuration by coating a layer of neutron-to-alpha converter material onto a semiconductor. The as-created alpha particles in the material are expected to impinge the semiconductor and create electron-hole pairs which provide the electrical signal. These devices are limited in efficiency to a range near (2-5%)/cm{sup 2} due to the conflicting thickness requirements of the converter layer. In this case, the layer is required to be thick enough to capture the incoming neutron flux while at the same time adequately thin to allow the alpha particles to reach the semiconductor. A three dimensional matrix structure has great potential to satisfy these two requirements in one device. Such structures can be realized by using PIN diode pillar elements to extend in the third dimension with the converter material filling the rest of the matrix. Our strategy to fabricate this structure is based on both ''top-down'' and ''bottom-up'' approaches. The ''top down'' approach employs high-density plasma etching techniques, while the ''bottom up'' approach draws on the growth of nanowires by chemical vapor deposition. From our simulations for structures with pillar diameters from 2 {micro}m down to 100 nm, the detector efficiency is expected to increase with a decrease in pillar size. Moreover, in the optimized configuration, the detector efficiency could be higher than 75%/cm{sup 2}. Finally, the road map for the relationship between detector diameter and efficiency will be outlined.

Development of High Efficiency Neutron Detectors

Development of High Efficiency Neutron Detectors
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Total Pages: 10
Release: 1993
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We have designed a novel neutron detector system using conventional 3He detector tubes and composites of polyethylene, and graphite. At this time the design consists entirely of MCNP simulations of different detector configurations and materials. These detectors are applicable to low-level passive and active neutron assay systems such as the passive add-a-source and the 252Cf shuffler. Monte Carlo simulations of these neutron detector designs achieved efficiencies of over 35% for assay chambers that can accommodate 55-gal. drums. Only slight increases in the number of detector tubes and helium pressure are required. The detectors also have reduced die-away times. Potential applications are coincident and multiplicity neutron counting for waste disposal and safeguards. We will present the general design philosophy, underlying physics, calculation mechanics, and results.

The Development of a Novel Diamond-based Neutron Detector and Quantum Color Center Fabrication Framework

The Development of a Novel Diamond-based Neutron Detector and Quantum Color Center Fabrication Framework
Author: Henry Matthew Thurston
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Total Pages: 0
Release: 2023
Genre: Electronic dissertations
ISBN:
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This work investigates the use of single crystal diamond in sensing technologies. First, homoepitaxial chemical vapor deposition (CVD) grown semiconducting diamond is used to build an ultra-fast neutron detector. Diamond based neutron detectors are extant technology, but typically limited to neutron energies of less than 14 MeV. This work introduces the Positionally Opposed Schottky Semi-Metal (POSSM) solid state neutron detector. The POSSM device employs two boron-doped P-type semiconducting diamonds in conjunction with a lanthanide foil to create a pair of Schottky junction diodes with a shared cathode. Under reverse bias the diamond-Schottky diodes have undetectable reverse bias leakage current, resulting in a detector with excellent signal-to-noise properties. Preamplifier circuitry has been designed to exploit the favorable properties of the Schottky architecture. Field testing of the device at the Los Alamos Neutron Science Center (LANSCE) yielded successful ultra-fast neutron detection with excellent charge conversion efficiency. Several drawbacks were identified in the performance of the POSSM detector, mainly involving durability of the diodes and speed of the preamplifier. An improved design was developed and is presented in this work, though the improved design has not been built.Secondly, this work presents a novel framework for the simulation of quantum color center formation in diamond. Diamond color centers have been shown to have unique quantum spin properties making them of interest to quantum computing and field sensing. A mesoscale reaction-diffusion framework is developed and a computational solver is built. The Color Center ANnealing And Reaction-Diffusion (CCANARD) program solves the nonlinear reaction-diffusion system by linearization using the Gateaux Derivative and the Crank-Nicolson method. CCANARD is benchmarked for computational efficiency and accuracy. The results are presented and analyzed. An experiment is proposed to further test and develop CCANARD.

Development of Wide Bandgap Solid-state Neutron Detectors

Development of Wide Bandgap Solid-state Neutron Detectors
Author: Andrew Geier Melton
Publisher:
Total Pages:
Release: 2011
Genre: Gallium nitride
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In this work novel solid-state neutron detectors based on Gallium Nitride (GaN) have been produced and characterized. GaN is a radiation hard semiconductor which is commonly used in commercial optoelectronic devices. The important design consideration for producing GaN-based neutron detectors have been examined, and device simulations performed. Scintillators and p-i-n diode-type neutron detectors have been grown by metalorganic chemical vapor deposition (MOCVD) and characterized. GaN was found to be intrinsically neutron sensitive through the Nitrogen-14 (n, p) reaction. Neutron conversion layers which produce secondary ionizing radiation were also produced and evaluated. GaN scintillator response was found to scale highly linearly with nuclear reactor power, indicating that GaN-based detectors are suitable for use in the nuclear power industry. This work is the first demonstration of using GaN for neutron detection. This is a novel application for a mature semiconductor material. The results presented here provide a proof-of-concept for solid-state GaN-based neutron detectors which offer many potential advantages over the current state-of-the-art, including lower cost, lower power operation, and mechanical robustness. At present Helium-3 proportional counters are the preferred technology for neutron detection, however this isotope is extremely rare, and there is a global shortage. Meanwhile demand for neutron detectors from the nuclear power, particle physics, and homeland security sectors requires development of novel neutron detectors which are which are functional, cost-effective, and deployable.