Gravitational Wave Group

Mechanical Quality Factor Enhancement of
Cryogenic Sapphire test Mass

Motivation

Thermal noise will limit the part of the sensitivity of the laser interferometric gravitational wave detectors. To suppress the thermal noise which is proportional to square root of T/Q, where T is temperature and Q is the mechanical factor of a test mass and a suspension wire, cooling and Q enhancement are promising approaches. Fortunately, sapphire has the multiplier effect because the cooler sapphire test mass has higher Q factor! In this experiment, we investigated the Q factor enhancement of several internal modes of one cooled sapphire test mass.

Experimental setup


Result

We could obtain the Q factor of 2.5*10^8 at 4 [K] for the longitudinal mode, which was 40 times as much as that at room temperature.