Attenuation of Ultra-high-frequency Acoustic Waves in Quartz at Low Temperatures

Abstract

THE temperature-dependent part of the ultra-sonic attenuation in single crystal quartz at frequencies in the range 600–1,200 Mc/s has been investigated at low temperatures. Fig. 1 refers to measurements in natural quartz for longitudinal waves and Fig. 2 shows the attenuation of shear waves travelling in the AC-direction. Fig. 3 is a comparison of the attenuations of 1,100-Mc/s shear waves in natural and synthetic crystals. Both for shear and longitudinal waves the attenuation is found to be nearly proportional to frequency over the temperature-range investigated. Below about 20° K the attenuation of both shear and longitudinal waves in synthetic quartz is substantially greater than in natural quartz. It is also found (Fig. 1) that the attenuation of longitudinal waves in two natural quartz samples of different sizes are identical, to within the experimental error, indicating that the size-dependent thermal conductivity is not a significant parameter.