Eddy current damping of high Q pendulums in gravitational wave detection experiments

The test masses of a large interferometric gravity wave detector (VIRGO project) will be controlled by actuators consisting of magnets attached to the masses and solenoids attached to an auxilliary and potentially electrically conductive reference mass. A brief analytic model of the damping produced by the eddy currents induced by the magnets' motion relative to the reference mass is presented. The results of a series of experimental tests to verify this model are also given. They demonstrate that a conducting reference mass should not degrade the Q of the pendulum sufficiently to affect the sensitivity of the VIRGO detector. © 1998 American Institute of Physics.