New technique to measure the mechanical quality factor of metals using spherical samples

We developed a new technique for measuring the mechanical quality factor of metals from room temperature down to 10 mK. Spherical resonators with a di ameter of 150 mm were suspended from the center with a copper rod. Since a sphere has a large number of resonant modes it is always possible to find s ome which are practically unaffected by the suspension and it can be assume d they are representative of the 'intrinsic' values. With this method we me asured a Q-factor of 120 million in A15056, the highest published value for a metal. (C) 2000 Elsevier Science B.V. All rights reserved.