Mechanical quality factor of a sapphire fiber at cryogenic temperatures
  A mechanical quality factor of $1.1 \times 10^{7}$ was obtained for the 199 Hz bending vibrational mode in a monocrystalline sapphire fiber at 6 K. Consequently, we confirm that pendulum thermal noise of cryogenic mirrors used for gravitational wave detectors can be reduced by the sapphire fiber suspension. 
T. Uchiyama, T. Tomaru, D. Tatsumi, S. Miyoki, M. Ohashi, K. Kuroda,   T. Suzuki, A. Yamamoto, T. Shintomi