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M. Shah, "Radiation Detection Using Integrated Circuits," Ph.D. Dissertation, Nuclear Engineering, Texas A&M University, College Station, TX (2016).


The research objective of this dissertation is to evaluate the capability of 'radiation' integrated circuits (RICs) to serve as a new type of radiation detection medium. Designed at Texas A&M University, the RIC contains both radiation-sensitive areas (RSAs) and radiation-hardened areas (RHAs). RSAs are designed so that their electrical properties change when exposed to charged-particle. RHAs monitor such changes in RSAs to detect the presence of radiation. Novel detector designs utilizing the same RICs were assessed and optimized, using both analytical and simulation methods, to register the major types of radiation: alpha particles, beta particles, gamma rays, and neutrons. The detector system materials and components were varied to characterize different configurations and recommend optimized RIC detector designs to perform beta-test.

The proposed revolutionary RIC-alpha/beta probe design has two regions: one to detect alpha particles and another to detect betas along with their Eβmax. In order to perform the Eβmax discrimination, the maximum penetration depth property of betas in attenuator was utilized. In MCNPX, plate glass, Pyrex® glass, Lucite® and natural rubber were studied as attenuator materials. For the proof of concept, materials in the wedged form were analyzed. The natural rubber in the form of a wedged attenuator was observed to show superior Eβmax discrimination compared to other defined attenuators. The Eβmax resolution capability of 50-keV is possible using natural rubber attenuator.

The proposed RIC-neutron detector design uses enriched boron (96% 10B) as a neutron-reactive coating to generate secondary charged particles. In MCNPX, other neutron-reactive materials (natural boron, B4C, and LiF) were also studied. The interaction of alpha was observed predominantly to facilitate the signal generation in RSAs to detect neutrons. With the optimal thickness of 3-μm enriched boron, the signal to noise ratio of thermal neutrons was estimated better by a three orders of magnitude.

The proposed RIC-gamma ray detection system uses a sodium iodide crystal, photocathodes, and RICs. Photocathodes are placed on all crystal surfaces to collect optical photons and generate photoelectrons. These photoelectrons interact to generate an electrical signal in RSAs and thereby, the RIC detects gamma rays. The collection ratio was found to be a function of the crystal size, gamma-ray energy, and the source position. However, this ratio was found to increase for all the defined scenarios. The concentration of photoelectrons as a function of the RSA radius size was assessed to optimize the RSA size.

Associated Project(s):

  • Radiation Detection Using Integrated Circuits

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