Suspension losses in low-frequency mechanical pendulums

A series of tests on the geometry and the materials of the mechanical clamps of the suspensions for the test masses of a large interferometric gravity wave detector (VIRGO project) has been carried out with the purpose of improving the clamp design. A significant decrease of the losses due to the stick-and-slip mechanism on the clamp surfaces has been obtained by increasing and localizing the clamping pressure on the heads of the suspension wires or strips (monolithic suspensions). The total losses thus measured compare well with the internal friction losses in the wire (or strip) material.