Abstract
Measurements of the low temperature specific heatC p (0.04K≦T≦2.4K) and thermal conductivityk (0.5K≦T≦20K) of high purity vitreous silica (Suprasil W) in the as-received and electron-irradiated states are reported. In the temperature range where the localized excitations inherent in glasses dominateC p (T≲0.5K) no change is observed upon electron irradiation of up to 1019e− (total dose). An anomalyδC around 1.8K is observed inC p which is reduced by 40% upon irradiation. However, ask is not affected by electron irradiation, localized excitations as origin forδC can be ruled out. The density of paramagnetic centers in the most heavily irradiated sample is 5⋅1017cm−3 as obtained from the ESR signal. It has been suggested that these centers have diamagnetic “precursors” in the unirradiated glass. Our measurements indicate that those defects are not associated with the localized excitations.
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