Author: Floriana Fasolo
Publisher:
ISBN:
Category :
Languages : en
Pages : 185

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Author: Bader J. Almutairi
Publisher:
ISBN:
Category :
Languages : en
Pages : 187

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Book Description
"In part I, the pulse shape characteristics generated by a Geiger Muller (GM) detector and recorded by an oscilloscope manually, were investigated. The objective of part I was (1) to find a correlation between pulse shape and the operating voltage; and (2) to assess if pulse shape properties followed distinct patterns comparable to detector deadtime findings reported by a previous study. It was observed that (1) there is a strong correlation between pulse shape and operating voltage, and (2) pulse shape falls in three distinct regions similar to detector deadtime. Furthermore, parts II and III are companions and share the same experimental setup designed to simultaneously measure the GM detector's deadtime, and capture and record the generated pulses by an oscilloscope automatically. Four different pairs of radioactive sources (204Tl, 137Cs, 22Na, 54Mn) were used. For part II, it was observed that deadtime dependence on operating voltage followed a distinct pattern while using 204Tl, 137Cs, 22Na except for 54Mn.For part III, it was found that there is a strong correlation between deadtime behavior and several pulse shape properties. In addition to part I-III, part IV focused on the characterization of accident tolerant fuel cladding SiC for high burnup SMR core. First, reactor physics modeling for various accident tolerant fuel claddings was performed. It was found that SiC outperforms all other cladding candidates in terms of discharge burnup. Second, an experimental setup was designed to characterize weight loss and mechanical strength of SiC by examining the effects of neutron-irradiation in harsh environments. It was observed that (1) irradiated samples were more prone to material weight loss at higher temperatures, and (2) mechanical strength for control, non-irradiated, and irradiated samples were comparable"--Abstract, page iv.

Author: Mehdi Reisi Fard
Publisher:
ISBN:
Category : Detectors
Languages : en
Pages : 298

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Book Description
Abstract: In this dissertation, a fast neutron flux monitoring channel, which is based on the use of SiC semiconductor detectors is designed, modeled and experimentally evaluated as a power monitor for the Gas Turbine Modular Helium Reactors. A detailed mathematical model of the SiC diode detector and the electronic processing channel is developed using TRIM, MATLAB and PSpice simulation codes. The flux monitoring channel is tested at the OSU Research Reactor. The response of the SiC neutron-monitoring channel to neutrons is in close agreement to simulation results. Linearity of the channel response to thermal and fast neutron fluxes, pulse height spectrum of the channel, energy calibration of the channel and the detector degradation in a fast neutron flux are presented. Along with the model of the neutron monitoring channel, a Simulink model of the GT-MHR core has been developed to evaluate the power monitoring requirements for the GT-MHR that are most demanding for the SiC diode power monitoring system. The Simulink model is validated against a RELAP5 model of the GT-MHR. This dyanamic model is used to simulate reactor transients at the full power and at the start up, in order to identify the response time requirements of the GT-MHR. Based on the response time requirements that have been identified by the Simulink model and properties of the monitoring channel, several locations in the central reflector and the reactor cavity are identified to place the detector. The detector lifetime and dynamic range of the monitoring channel at the detector locations are calculated. The channel dynamic range in the GT-MHR central reflector covers four decades of the reactor power. However, the detector does not survive for a reactor refueling cycle in the central reflector. In the reactor cavity, the detector operates sufficiently long; however, the dynamic range of the channel is smaller than the dynamic range of the channel in the central reflector.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Book Description

Author: Manoj Kumar Parida
Publisher:
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 0

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Book Description

Author: Wolfgang J. Choyke
Publisher: Springer Science & Business Media
ISBN: 3642188702
Category : Technology & Engineering
Languages : en
Pages : 911

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Book Description
Since the 1997 publication of "Silicon Carbide - A Review of Fundamental Questions and Applications to Current Device Technology" edited by Choyke, et al., there has been impressive progress in both the fundamental and developmental aspects of the SiC field. So there is a growing need to update the scientific community on the important events in research and development since then. The editors have again gathered an outstanding team of the world's leading SiC researchers and design engineers to write on the most recent developments in SiC.

Author: Gerhard Lutz
Publisher: Springer
ISBN: 3540716793
Category : Technology & Engineering
Languages : en
Pages : 351

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Book Description
Starting from basic principles, this book describes the rapidly growing field of modern semiconductor detectors used for energy and position measurement radiation. The author, whose own contributions to these developments have been significant, explains the working principles of semiconductor radiation detectors in an intuitive way. Broad coverage is also given to electronic signal readout and to the subject of radiation damage.

Author: Brian W Cooper
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Book Description
Silicon carbide is a material of interest in many ventures as an intriguing semiconducting material for use as high voltage, high temperature, high power, or high frequency devices. Silicon carbide is physically extremely tough and durable and is also very chemically resistant. The work presented here details using silicon carbide (SiC) as the semiconducting substrate for a high-efficiency neutron detector. The work begins with the fabrication of planar SiC neutron detectors utilizing 10B as the neutron conversion material. The SiC substrate was patterned via photolithography techniques prior to the deposition of an etchant mask. The following materials were used as etchant mask materials; nickel, indium tin oxide, and aluminum. The SiC devices were plasma etched using SF6 based gas chemistries. The desired trench profile was 4 microns wide with desired depth between 10 and 20 microns. The formation of microfeatures within the trenches was observed during several etching trials as well as the trench profile narrowing to a point. After etching, titanium/gold contacts were fabricated using e-beam evaporation and various masking techniques. Next the devices were electrically tested for leakage current and capacitance. Typical leakage current was

Author: Sanchit Sharma
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Book Description
The work presented in this dissertation will serve as an essential tool for modern nuclear engineers to perform radiation transport with import of complex computer aided design (CAD) models efficiently. Performing radiation transport with complex CAD geometries and obtaining accurate detector response functions has been a major challenge. For micro-structured semiconductor detectors, results obtained from radiation transport alone are not enough to provide a clear picture of expected performance. Hence, the work presented in this dissertation is divided into two major research areas (RAs). RA 1 describes methods for sensor response modelling with hybrid Geant4 geometries consisting of both conventional C++ based models and complex CAD based models in a single simulation. This RA will address the methods developed for radiation transport models and benchmarking experimental detector responses. Additionally, this RA will further discuss how these models were later utilized for finalizing design parameters of a semiconductor radiation detection system (Timepix3 coupled with Dual-Sided Microstructured Semiconductor Neutron Detector). Multiple bugs were identified in Geant4 source code as a result of the work presented in RA 1. RA 2 of this dissertation will provide detailed analysis of the existing boundary conditions of the DS-MSND and MSND detectors. Finite Element Analysis based semiconductor physics modeling was performed to investigate various parameters of the Si-SiO2 interface. The radiation transport models were developed for simulating the Kansas State University Materials Interrogation (KSUMI) test facility that was set up to enable bulk-material irradiation experiments that replicate similar oil-well logging scenarios. These experiments were conducted with an aim to address the problem of replacement of conventional radioisotope sources commonly used in oil-well logging industries. An exploration tool similar to an oil-well logging tool was used to conduct experiments with water and sand as testing materials. The facility includes a 2500-gallon concrete test chamber to be filled with testing material with an aluminum pipe going horizontally through it, permitting placement of a neutron source and radiation sensors. A machine-based 14.1 MeV deuterium-tritium neutron source was used to irradiate the 2500-gallon testing material. Experiments were performed with tap water and sand as bulk testing materials. Irradiation was performed for one hour and results were obtained from a BF3/3He neutron sensor, a BF3 neutron sensor, and two NaI gamma sensors placed at different locations within the exploration tool. Geant4, a Monte-Carlo based toolkit, was deployed on a high-performance computing system to simulate the entire experiment in order to benchmark the experimental responses obtained from the photon and neutron sensors. The facility was modeled in detail with accurate dimensions and material compositions. Materials such as tap water, high-density polyethylene, and aluminum metal were modeled with thermal neutron scattering cross-sections. The reference physics list QGSP_BIC_HP along with G4NDL and S([alpha],[beta]) cross-sections were found to be appropriate for simulation of neutron interrogation experiments with neutron energies lower than 20 MeV. The experimental results obtained were successful in characterizing the bulk testing materials, and results obtained from Geant4 were found to be in good agreement with the experimental results in most cases. The source code developed for the above method was then utilized to design the physical parameters for an X-DS-MSND system. These detectors have the benefit of doubling neutron detection efficiency as compared to single-sided devices (X-MSND) by staggering 6LiF-filled trenches between the top and bottom surface of a silicon diode. This produces a more complex electric field distribution and depletion characteristics in the diode and creates an indirect path for signal carrier transport between device electrodes. Geant4 was extensively utilized for radiation transport and interaction modeling, and Allpix Squared was used for mobile charge carrier transport and total charge collection. The results of this simulation work provided an estimate of charge cluster shape and intensity for a pixel array configuration corresponding to Timepix3 read-out system. In addition, imaging performance for transmission radiography was demonstrated with a simple two-dimensional shape in a Gaussian beam of thermal neutrons. The simulated neutron detection efficiency was 57.6%. It was discovered that the Allpix Squared is not optimal for simulation of complex boundary conditions and charge carrier transport inside the DS-MSND. To understand the behavior of charge carriers in the presence of a complex electric field and boundary conditions, a simpler non-conformally doped MSND geometry was fabricated and analyzed. This sensor geometry produced a complex electric field distribution and depletion characteristics within the diode. The fixed oxide charge present at the trench walls and its effects on the depletion characteristics and electric field were analyzed. The capacitance-voltage and current-voltage curve characterizations were performed for these prototypes and compared with the COMSOL Multiphysics simulations. An 241Am alpha particle source was further utilized to perform spectral analysis. Geant4 was utilized for radiation transport, interaction modeling, and benchmarking the spectral data. The results of this simulation work provided a reasonable confidence in capability to obtain and benchmark electric fields and spectral data for complex micro-structured semiconductor radiation detectors. Further, COMSOL Multiphysics was used to account for time-dependent charge carrier motion and detector response for these boundary conditions. As a result of work presented in RA 1 and RA 2, important features in the MSND/DS-MSND geometry were discovered that could significantly impact the device's performance. These features were incorporated in the updated Monte-Carlo model of the DS-MSND sensor. Simulated response of the updated DS-MSND sensor as a replacement of BF3/3He was then analyzed for the oil-well logging irradiation environment using Geant4 simulations. The results obtained from these simulations establish DS-MSND as a strong contender for replacing BF3/3He sensors for oil well logging experiments.

Author: Diego Laramore
Publisher:
ISBN:
Category :
Languages : en
Pages :

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A semiconductor neutron imaging device is proposed (X-MSND) based on high efficiency, Micro-structured Semiconductor Neutron Detector (MSNDs) bump bonded onto a Timepix pixelated readout chip. The device serves as a combined neutron and photon imager with a 256x256 pixel array, using per-pixel time-over-threshold (ToT) energy deposition. The X-MSND design has produced thermal neutron detection efficiency of 14%, significantly greater than the theoretical maximum of less than 5% for planar devices. Simulated pixel clusters showed similar qualitative characteristics as planar neutron sensitive Timepix hybrid detectors. A workflow for simulating the semiconductor physics, ionization by radiation, and charge carrier transport for micro-structured sensors in general has been devised and described in this work. The simulation workflow began by steady state initial conditions of the X-MSND PIN diode sensor at full bias using COMSOL Multiphysics. This simulation step served the combined purpose of providing the necessary electric field solutions used in charge transport, and provided necessary design and operating parameters for device fabrication. Radiation transport code Geant4 was used to simulate the radiation detection characteristics of the sensor: thermal neutron detection efficiency, energy deposition per detection event, and the location of the ionized charge cloud per interaction are all calculated at this step. Dassault SolidWorks was used to generate Computer-Assisted Drafting (CAD) models of the full micro-structured device geometry, which was then converted and imported into a format that can be interpreted by Geant4 for the radiation transport. Geant4 can then interface directly with a modified version of Allpix^2 to perform charge carrier drift over the entire X-MSND geometry. Fabricated X-MSND devices were tested and evaluated at Kansas State University (KSU), and were found capable of producing high quality radiographs with both X-rays and neutrons. The fabrication of functioning X-MSND/Timepix assemblies was a collaborative effort among several research groups at KSU, domestic and international industrial partners, and international research groups. Fabrication of the X-MSND sensors was performed largely by Radiation Detection Technologies, Inc., with parametric design support from the Radiological System Integration Laboratory (RSIL) and Radiological Engineering Analysis Laboratory (REAL). The processes used in the production of X-MSND sensors are conventional micro-electro-mechanical system (MEMS) photolithography techniques; spin-on deposition and ultraviolet development of photoresist, metal lift-off, and wet etching of silicon are all used over the course of fabrication, and are described in detail. The Electronics Design Laboratory (EDL) of Kansas State University assisted in the design of custom printed circuit boards to which the X-MSND/Timepix assemblies are mounted. External to facilities located at KSU, various industrial manufacturing partners who specialize in Very Large Scale Integration (VLSI) and micro-fabrication assembly processes were also contracted to perform the specialized assembly processes required in assembling the full X-MSND/Timepix systems.