Acoustic and Thermal Properties of Stycast 1266 below 100 mK

No Heading We report on the acoustic and thermal behavior of a Stycast 1266 - quartz composite torsional oscillator below 100 mK. The epoxy exhibits heat release manifested by a strong time dependence of the sound velocity below 10 mK. Also, the Stycast sample is sensitive to both ? and µ radiation, displaying transients superposed on the resonant response of the composite oscillator, as well as heating when exposed to a 22Na source. The long thermal relaxation time of the tunneling states together with the high thermal resistance limits the lowest achievable temperature in this insulating amorphous material.