Dissipation of mechanical energy in fused silica fibers

For thermal noise considerations of LIGO suspensions, the sources of dissipation in the suspending fibers must be analyzed. To determine the dissipation induced by the surface of fused silica fibers, we measured the quality factor of fibers having various diameters. We measured a maximum quality factor of 21 million and extrapolated to obtain an intrinsic quality factor for fused silica of 30 million. Dissipation in the surface dominated at diameters less than about 1 mm. We developed a method for characterizing surface-induced dissipation that is independent of sample geometry or mode shape.