High quality factor measured in fused silica

We have measured the mechanical dissipation in a sample of fused silica dra wn into a rod. The sample was hung from a multiple-bob suspension, which is olated it from rubbing against its support, from recoil in the support stru cture, and from seismic noise. The quality factor, Q, was measured for seve ral modes with a high value of 57.1 +/-0.1 million found for the mode numbe r 2 at 726 Hz. This result is about a factor of 2 higher than previous room temperature measurements. The measured Q was strongly dependent on handlin g, with a pristine flame-polished surface yielding a Q three to four times higher than a surface which had been knocked several times against a copper tube. (C) 2001 American Institute of Physics.