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Research Interests:
Perforated semiconductor neutron detectors are compact, high-efficiency, diode detectors that operate at low power. Microstructured neutron detector fabrication methods have been improved over previous manufacturing methods. The neutron... more
Perforated semiconductor neutron detectors are compact, high-efficiency, diode detectors that operate at low power. Microstructured neutron detector fabrication methods have been improved over previous manufacturing methods. The neutron detectors are easily fabricated from high purity n-type Si, in which patterned trenches are etched into the Si substrate, wherein shallow p-type junctions are diffused. The trenches are then backfilled with 6LiF powder, making the devices sensitive to reaction products from the 6Li(n,t)3He reaction. Pulse height spectra show improved signal-to-noise ratio, higher neutron counting efficiency, and excellent gamma-ray discrimination over previous microstructured neutron detector designs. Thermal neutron detection measurements from a 0.0253 eV diffracted neutron beam, yielded 20.4% intrinsic detection efficiency for devices with 245 micron deep trenches and 21% intrinsic detection efficiency for two back-to-back devices each having 113 micron deep trenches.
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Research Interests:
Semiconductor diode detectors coated with neutron reactive materials are generally fashioned as planar diodes coated with 10B, 6LiF, or Gd. Planar detectors coated with 10B or 6LiF are limited to less than 5% intrinsic thermal neutron... more
Semiconductor diode detectors coated with neutron reactive materials are generally fashioned as planar diodes coated with 10B, 6LiF, or Gd. Planar detectors coated with 10B or 6LiF are limited to less than 5% intrinsic thermal neutron detection efficiency. Detectors coated with Gd can achieve higher efficiencies, but the low-energy signatures are problematic in the presence of background radiations. Microstructured semiconductor neutron detectors (MSND) can now achieve a tenfold increase in neutron detection efficiency over the planar diode designs. These semiconductor neutron detectors are fashioned with a matrix of microstructured patterns etched deeply into the semiconductor substrate and, subsequently, backfilled with neutron reactive materials. Intrinsic thermal-neutron detection efficiencies exceeding 35% have been achieved with devices no thicker than 1 mm while operating on less than 5 volts, now allowing for instrumentation to be realized with similar performance as 3He gas...
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Research Interests:
Non-streaming high-efficiency perforated semiconductor neutron detectors, method of making same and measuring wands and detector modules utilizing same are disclosed. The detectors have improved mechanical structure, flattened angular... more
Non-streaming high-efficiency perforated semiconductor neutron detectors, method of making same and measuring wands and detector modules utilizing same are disclosed. The detectors have improved mechanical structure, flattened angular detector responses, and reduced leakage current. A plurality of such detectors can be assembled into imaging arrays, and can be used for neutron radiography, remote neutron sensing, cold neutron imaging, SNM monitoring, and various other applications.
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The present work employs MSND technology as a He-3 gas-tube direct-replacement technology. The MSND-based Helium Replacement (HeRep) is a single instrument utilizing thirty 4-cm2 active area MSNDs to directly replace 3He-based... more
The present work employs MSND technology as a He-3 gas-tube direct-replacement technology. The MSND-based Helium Replacement (HeRep) is a single instrument utilizing thirty 4-cm2 active area MSNDs to directly replace 3He-based proportional neutron counters. The HeRep Mk II prototype yielded 102.71+-0.84% of the neutron detection efficiency of a 4-atm Reuter Stokes 3He gas-filled detector with the same active dimensions and test setup from a Cf-252 source. The HeRep Mk II met the efficiency of the 3He detector while using MSNDs that had 20% intrinsic-efficiency for thermal-neutrons.
Charge collection efficiency (CCE) mapping was performed by simulating a 5.0 x 5.0 x 10.0 mm3 Frisch-collared BiI3 gamma-ray detector with an applied bias of 4800V and comparing the results to those previously published for a 4.7 x 4.7 x... more
Charge collection efficiency (CCE) mapping was performed by simulating a 5.0 x 5.0 x 10.0 mm3 Frisch-collared BiI3 gamma-ray detector with an applied bias of 4800V and comparing the results to those previously published for a 4.7 x 4.7 x 9.5 mm3 Frisch-collared CdZnTe device with an applied bias of 1200V. The BiI3 mobility-lifetime products used for CCE mapping were μeτe = 9.5 x 10-6 cm2 V-1 and μhτh = 1.0 x 10-7 cm2 V-1 for electrons and holes, respectively. The simulations were performed using the modified form of the Hecht equation and the necessary weighting-potential and weighting-field distributions were simulated using the commercially available software package COULOMB. After comparing the simulation results to CdZnTe, the applied bias and mobility-lifetime products were adjusted separately until the Frisch-collared BiI3 device resembled the CCE of the CdZnTe Frisch-collared device. Using the previously stated mobility-lifetime products, an applied bias of 2.1 MV is necessar...
A method, system and a radiation detector system for use therein are provided for determining the depth distribution of radiation-emitting material distributed in a source medium, such as a contaminated field, without the need to take... more
A method, system and a radiation detector system for use therein are provided for determining the depth distribution of radiation-emitting material distributed in a source medium, such as a contaminated field, without the need to take samples, such as extensive soil samples, to determine the depth distribution. The system includes a portable detector assembly with an x-ray or gamma-ray detector
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Position-dependent free charge carrier losses during transport can prevent efficient charge carrier extraction from semiconductor detectors and severely reduce energy resolution. Hole trapping losses in CdZnTe radiation detectors are far... more
Position-dependent free charge carrier losses during transport can prevent efficient charge carrier extraction from semiconductor detectors and severely reduce energy resolution. Hole trapping losses in CdZnTe radiation detectors are far worse than electron trapping losses and resolution degradation in CdZnTe detectors results primarily from severe hole trapping during transport. Coplanar radiation detectors improve energy resolution by sensing the induced charge
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ABSTRACT Silicon diodes with large aspect ratio perforated microstructures backfilled with 6LiF show a dramatic increase in neutron detection efficiency beyond that of conventional thin-film coated planar devices. Described in this work... more
ABSTRACT Silicon diodes with large aspect ratio perforated microstructures backfilled with 6LiF show a dramatic increase in neutron detection efficiency beyond that of conventional thin-film coated planar devices. Described in this work are advancements in the technology with increased microstructure depths and detector stacking methods that work to increase thermal-neutron detection efficiency. Models for ion energy deposition and intrinsic thermal-neutron detection efficiency for the straight trench design are described and results presented. A dual stacked device was fabricated by coupling two detectors back-to-back, along with counting electronics, into a single detector. Experimentally verified results and modeled predictions are compared. The stacked device delivered 37% intrinsic thermal-neutron detection efficiency, lower than the predicted value of 47%. It was determined that this lower observed efficiency is due to detector misalignment in the stacked structure and ballistic deficit from slow charge collection from the deep trench structures. The intrinsic thermal-neutron detection efficiency depends strongly upon the geometry, size, and depth of the perforated microstructures. This work is part of on-going research to develop solid-state semiconductor neutron detectors with high detection efficiencies.
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ABSTRACT A micro-pocket fission detector (MPFD) array is being deployed in the Kansas State University TRIGA Mark-II nuclear reactor in order to produce a real-time 3-dimensional neutron flux map. A total of 75 MPFD3-Ts make up the array... more
ABSTRACT A micro-pocket fission detector (MPFD) array is being deployed in the Kansas State University TRIGA Mark-II nuclear reactor in order to produce a real-time 3-dimensional neutron flux map. A total of 75 MPFD3-Ts make up the array where each MPFD3-T consists of an uncoated detector for background subtraction, a 93% enriched 235U coated detector for thermal neutron sensitivity, a natural uranium coated detector for mixed energy neutron sensitivity, and a thermocouple for thermal monitoring. The array is located in fixed in-core positions between fuel elements and is capable of being read out in pulse, MSV, and current modes allowing for operation from shutdown to full power. In addition, using off-the-shelf electronic components, the system is able to track reactor pulses with power changes spanning 7 orders of magnitude in less than 100 milliseconds.
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... In this simulation the chevron angle was taken to be 90 ◦ , so the detector manifests a ... The MonteCarlo simulations show that the angular depen-dence of perforated detectors in the ... Y. Yang, H. Gersch, and R. Klann, De-sign... more
... In this simulation the chevron angle was taken to be 90 ◦ , so the detector manifests a ... The MonteCarlo simulations show that the angular depen-dence of perforated detectors in the ... Y. Yang, H. Gersch, and R. Klann, De-sign considerations for thin film coated semiconductor ...
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Abstract Microstructured semiconductor neutron detectors have superior efficiency performance over thin-film coated planar semiconductor detectors. The microstructured detectors have patterns deeply etched into the semiconductor... more
Abstract Microstructured semiconductor neutron detectors have superior efficiency performance over thin-film coated planar semiconductor detectors. The microstructured detectors have patterns deeply etched into the semiconductor substrates subsequently ...
ABSTRACT
Semi-insulating undoped bulk LEC GaAs was investigated as a possible detector material for room temperature operated charged particle and gamma ray spectrometers. GaAs Schottky based diode detectors were fabricated with thicknesses of 45... more
Semi-insulating undoped bulk LEC GaAs was investigated as a possible detector material for room temperature operated charged particle and gamma ray spectrometers. GaAs Schottky based diode detectors were fabricated with thicknesses of 45 microns, 100 microns, 250 microns, and 750 microns. Pulse height analysis utilizing an alpha particle source disclosed non-constant electric field distributions that decreased rapidly from the Schottky
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ABSTRACT The common methods of analyzing gamma-ray spectra obtained from detectors capable of energy discrimination are discussed. Gamma-ray spectra generally are in the form of detector response versus discrete channel number. The... more
ABSTRACT The common methods of analyzing gamma-ray spectra obtained from detectors capable of energy discrimination are discussed. Gamma-ray spectra generally are in the form of detector response versus discrete channel number. The methods considered for gamma-ray spectroscopy are somewhat general and can be applied to other types of spectroscopy. The general objective of spectroscopy is to obtain, at a minimum, the qualitative identification of the source (e.g., source energies or nuclides present). However, most spectroscopy applications seek quantitative information also, as expressed by, e.g., the source strength or the nuclide concentration. Various different methods for qualitative and quantitative analysis are summarized, and an illustrative example is provided. A review of detectors used for gamma-ray spectroscopy is included.
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Micro-pocket fission detectors (MPFD) have been fabricated and tested as in-core flux monitors in the 250kW TRIGA nuclear reactor at Kansas State University. The prototype devices have been coated with a natural uranyl-nitrate to provide... more
Micro-pocket fission detectors (MPFD) have been fabricated and tested as in-core flux monitors in the 250kW TRIGA nuclear reactor at Kansas State University. The prototype devices have been coated with a natural uranyl-nitrate to provide a neutron reactive ...
The effects of crystal geometry and aspect ratio on a CdZnTe Frisch collar device were investigated. A 19.08x19.34x4.95mm3 device fabricated from CdZnTe grown by Redlen Technologies was used as the starting material. The crystal was... more
The effects of crystal geometry and aspect ratio on a CdZnTe Frisch collar device were investigated. A 19.08x19.34x4.95mm3 device fabricated from CdZnTe grown by Redlen Technologies was used as the starting material. The crystal was re-fabricated many times to achieve several aspect ratios while the device length was held constant at 4.75+/-0.15mm. The following aspect ratios were successfully fabricated from
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... [4] QM Jahan and WL Dunn (2006), “Modeling of highly efficient portable neutron dosimeters,” American Nuclear Society Student Conference, 30 March – 1 April, 2006, Rensselaer Polytechnic Institute, Troy, NY. [5] WL Dunn, QM Jahan, DS... more
... [4] QM Jahan and WL Dunn (2006), “Modeling of highly efficient portable neutron dosimeters,” American Nuclear Society Student Conference, 30 March – 1 April, 2006, Rensselaer Polytechnic Institute, Troy, NY. [5] WL Dunn, QM Jahan, DS McGregor, WJ McNeil, EL Patterson ...
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Research Interests:
Research Interests:
... AbstractA first generation 120 micron pitch pixel array system for neutron detection using the PATARA amplifier chip was assembled and tested. ... Pulses from the PATARA were observed at 0.5 V in height and 500 ns wide from neutron... more
... AbstractA first generation 120 micron pitch pixel array system for neutron detection using the PATARA amplifier chip was assembled and tested. ... Pulses from the PATARA were observed at 0.5 V in height and 500 ns wide from neutron interactions. ...
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Research Interests:
ABSTRACT Silicon diodes with large aspect ratio microstructures backfilled with 6LiF show a dramatic increase in neutron detection efficiency beyond that of conventional thin-film coated planar devices. Described in this work are... more
ABSTRACT Silicon diodes with large aspect ratio microstructures backfilled with 6LiF show a dramatic increase in neutron detection efficiency beyond that of conventional thin-film coated planar devices. Described in this work are advancements in the technology with increased microstructure depths and detector stacking methods that work to increase thermal-neutron detection efficiency. An individual 4-cm2 MSND was fabricated. A stacked 4-cm2 MSND was fabricated by coupling two detectors back-to-back, along with counting electronics, into a single detector. The individual MSND delivered 16% intrinsic thermal-neutron detection efficiency and the stacked MSND delivered 32% intrinsic thermal-neutron detection efficiency. The intrinsic thermal-neutron detection efficiency depends strongly upon the geometry, size, and depth of the silicon microstructures. This work is part of on-going research to develop solid-state semiconductor neutron detectors with high neutron detection efficiencies.
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Abstract A prototype neutron detector array has been developed for the Spallation Neutron Source (SNS). The High Efficiency Neutron Detector Array (HENDA) will be the highest spatial resolution neutron detecting linear array available... more
Abstract A prototype neutron detector array has been developed for the Spallation Neutron Source (SNS). The High Efficiency Neutron Detector Array (HENDA) will be the highest spatial resolution neutron detecting linear array available anywhere. The front-end ...
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Research Interests:
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Research Interests:
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High resistivity bulk grown GaAs has been used to produce thermal neutron imaging devices for use in neutron radiography and characterizing burnup in spent fuel. The basic scheme utilizes a portable Sb/Be source for monoenergetic (24 keV)... more
High resistivity bulk grown GaAs has been used to produce thermal neutron imaging devices for use in neutron radiography and characterizing burnup in spent fuel. The basic scheme utilizes a portable Sb/Be source for monoenergetic (24 keV) neutron radiation source coupled to an Fe filter with a radiation hard B-coated pixellated GaAs detector array as the primary neutron detector. The