title: Direct measurement of thermal fluctuation of high-Q pendulum.
abstract: We have achieved a direct measurement of the thermal fluctuation of a pendulum in an off-resonant and wide frequency region using a laser interferometric gravitational-wave detector. These measurements have been well identified for over one decade by an agreement with a theoretical prediction, which is derived by a fluctuation-dissipation theorem. Thermal fluctuation was dominated by the contribution of resistances in coil-magnet actuator circuits. When we tuned these resistances, the noise spectrum also changed according to a theoretical prediction. The measured thermal noise level corresponds to a high quality factor on the order of 10(5) of the pendulum.
authors.affiliation: Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582, Japan. agatsuma@icrr.u-tokyo.ac.jp
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Agatsuma
authors.forename: Takashi
authors.initials: T
authors.lastname: Uchiyama
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Masatake
authors.initials: M
authors.lastname: Ohashi
authors.forename: Seiji
authors.initials: S
authors.lastname: Kawamura
authors.forename: Shinji
authors.initials: S
authors.lastname: Miyoki
authors.forename: Osamu
authors.initials: O
authors.lastname: Miyakawa
authors.forename: Souichi
authors.initials: S
authors.lastname: Telada
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Kuroda