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Title:The effect of neutron irradiation on the density of low-energy excitations in vitreous silica
Author(s):Smith, Terry Lee
Doctoral Committee Chair(s):Anderson, A.C.
Department / Program:Physics
Subject(s):Neutron irradiation
Low-energy excitations
Vitreous silica
Thermal conductivity
Specific heat
Dielectric constant
Ultrasound velocity
Abstract:Systematic low-temperature measurements of the thermal conductivity, specific heat, dielectric constant, and temperature-dependent ultrasound velocity have been made on a single piece of vitreous silica. These measurements were repeated after fast neutron irradiation of the material. It was found that the irradiation produced changes of the same relative magnitude in the low-temperature excess specific heat C , the thermal conductivity K, ex and the anomalous temperature dependence of the ultrasound velocity Deltav/v. A corresponding change in the temperature dependent dielectric constant was not observed. It is therefore likely that K and Deltav/v are determined by the same localized excitations responsible for C , but the temperature dependence of the dielectric constant may have a different, though possibly related, origin. Furthermore, a consistent account for the measured C , K, ex and Deltav/v of unirradiated silica is given by the tunneling-state model with a single, energy-dependent density of states. Changes in these three properties due to irradiation can be explained by altering only the density of tunneling states incorporated in the model.
Issue Date:1979
Genre:Dissertation / Thesis
Rights Information:Copyright 1979 Terry Lee Smith
Date Available in IDEALS:2011-06-29
Identifier in Online Catalog:397342

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