Date of Award:

12-2022

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Physics

Committee Chair(s)

JR Dennison

Committee

JR Dennison

Committee

Jan Sojka

Committee

David Peak

Committee

Lee Pearson

Committee

Reyhan Baktur

Abstract

Radiation Induced Conductivity (RIC) is the change in conductivity of a material due to bombardment from incident high energy radiation. RIC has consistently been found to follow a standard power law relation, πœŽπ‘…πΌπΆ(𝑇)=π‘˜π‘…πΌπΆ(𝑇)π·βˆ†(𝑇), between conductivity, πœŽπ‘…πΌπΆ and adsorbed dose rate, 𝐷. π‘˜π‘…πΌπΆ(𝑇) and βˆ†(𝑇) are material dependent parameters. Previous RIC models were developed in the 𝑇→0 limit. Now expanded models are developed in the low temperature limit (within a few π‘˜π΅π‘‡ of the effective Fermi level) by approximating the Fermi-Dirac equation within a few π‘˜π΅π‘‡ of the effective Fermi level. Derivations are based on seven density of states (DOS) models for highly disordered insulating materials: three monotonically decreasing models within the bandgap (exponential, power law, and linear) and two symmetric peaked models within the bandgap (Gaussian and delta function), plus a limiting case with a uniform DOS for each type.

In addition, temperature dependent RIC data is compiled from literature for five polymeric materials used commonly in spacecraft: KaptonTM (polyimide or PI), polyethylenes (PE, low density polyethylene or LDPE, high density polyethylene or HDPE), TeflonTM (polytetrafluoroethylene or PTFE), MylarTM (polyethylene terephthalate or PET), and fluorinated ethylene propylene (FEP). Comparisons are made between compiled data from the literature and Utah State University RIC data, along with pertinent discussion of the results with a focus on the relevance of structural phase transition temperatures on measured RIC values. The second part of this work addresses the serious dearth of pertinent RIC data available needed to make critical design decisions for spacecraft, namely for the current NASA Europa Clipper and Lander missions.

Included in

Physics Commons

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