High quality factor measured in fused silica

We have measured the mechanical dissipation in a sample of fused silica drawn into a rod. The sample was hung from a multiple-bob suspension, which isolated it from rubbing against its support, from recoil in the support structure, and from seismic noise. The quality factor, Q, was measured for several modes with a high value of $\text{57.1±0.1}$ million found for the mode number 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 handling, 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.