Torsional oscillator for internal friction data at 100 kHz

We describe a method for measuring the internal friction of solids at low temperatures. Our design uses a composite oscillator vibrating in torsion at 100 kHz. The oscillator makes good thermal contact to the cryostat while maintaining a low background loss of Q−1≂2×10−6 at 2 K. The usefulness of the design is demonstrated by data for BaF2 and a-SiO2 from 2 to 300 K.