A new apparatus for mechanical Q-factor measurements between 5 and 300 K

Abstract

Today’s laser interferometric gravitational wave detectors are sensitivity limited by thermal noise of the optical components within the detection band of about 0.1–1 kHz. Cooling down these parts to cryogenic temperatures is a promising technique to increase the sensitivity of the gravitational wave detectors by at least one to two orders of magnitudes. Cooling substantially increases the material Q-factor contributing to reduced thermal noise. This article describes a new cryogenic apparatus which allows the measurement of the mechanical Q-factor – as a measure of internal losses – in a temperature range from 5 K up to 300 K. The requirements for cryogenic Q-factor measurements and their realization are shown. The measuring technique as well as the key parameters are discussed. Exemplary, measurements on crystalline quartz and silicon (1 0 0) are given to characterize the setup.