LOW RESONANT-FREQUENCY CANTILEVER SPRING VIBRATION ISOLATOR FOR GRAVITATIONAL-WAVE DETECTORS

An all metal multistage low frequency vibration isolator for a laser i nteferometer gravitational wave detector has been built and tested wit h a very sensitive accelerometer. Curved cantilever springs are used t o form a low frequency compact form of isolation element. Near center of mass suspension of the isolation stages reduces cross coupling betw een orthogonal directions. The isolator has a low-pass corner frequenc y of 6.5 Hz vertically and 1.8 Hz horizontally. The system shows low t emperature coefficients and absence of creep. Results demonstrate that steel curved springs near their elastic limit do not generate broadba nd acoustic noise at the 10(-15) m/square root Hz level.