Modeling and Design of a Silicon-Based High-Pressure 3HE Replacement Neutron Detector
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3He has stood as a major isotope used for neutron detection for many years. Due to national concerns of a possible 3He shortage, significant effort has been put forth, in the form of 3He alternative research, to push the community to develop more cost effective and higher intrinsic efficiency devices. The major focus of this thesis is on how a Si-based micro-structured neutron detector (MSND) assembly, of size and shape comparable to that of a commercially available high-pressure 3He-based neutron detector, can yield higher neutron detection efficiencies than its 3He-based counterpart. With careful consideration of MSND assembly geometry, along with clever utilization of neutron moderating high-density polyethylene (HDPE), a high-pressure 3He replacement (HP-HeRep) device, consisting of eighty tightly packed 1-cm2 MSND’s, has been designed and will be compared with a high-performance 8.3 absolute atmosphere 3He-based neutron detector. The MSND, designed and developed by the S.M.A.R.T. Lab at Kansas State University, is a high purity Si-based, highly anisotropic pin structure diode (i.e., 350-μm by 20-μm trenches in a 525-μm thick substrate). Given the novelty and complexity of the MSND, little is known in regard to its electric field character and resultant charge sweep-out properties. As a first step toward the development of a thorough understanding of these properties, this thesis also focuses on the equivalent circuit analysis and comparison of the MSND with a planar-type neutron detector, via impedance spectroscopy.
Table of Contents
Introduction -- First and second-generation neutron detector designs -- High-pressure 3He replacement -- Impedance spectroscopy -- Future work