Doctoral Dissertations

Date of Award

5-2022

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Materials Science and Engineering

Major Professor

Philip D. Rack

Committee Members

Philip D. Rack, Dustin A. Gilbert, Sarah M. Cousineau, Nicholas J. Evans, Nickolay V. Lavrik

Abstract

The Spallation Neutron Source (SNS) is currently preparing for a Proton Power Upgrade project that will increase the operating power of the beamline. Due to this increase in power, a major concern is whether the current stripper foils will be able to withstand the higher power beam. Here, we analyze the current nanocrystalline diamond as well as microcrystalline diamond stripper foils in order to assess their ability to withstand the higher power beamline. In this work we assess the samples’ room temperature thermal conductivity, as well as other material constants, develop a method for in situ analysis of stripper foil failure, and compare the micro and nanocrystalline diamond samples for their viability in the SNS beamline. In the first chapter the mechanical properties of the samples are assessed. Bilayer cantilever are manufactured and photothermally excited to obtain excitation and relaxation curves due to induced deformation. The relaxation curves are fit to COMSOL simulations and the room temperature thermal conductivity is determined. The second chapter outlines the foil test stand electron beam mimic. This consists of testing the nanocrystalline diamond sample by irradiating spots with a 30 keV electron beam. Correlations are found between foil failure and measurements taken in the foil test stand. Lastly, the third chapter overviews the comparison between the micro and nanocrystalline diamond samples in the foil test stand. Both samples are irradiated using the same beam parameters and assessed to determine relative thermal robustness of the samples.

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