Acoustic quality factor of molybdenum and tungsten at low temperatures

摘要

The amplitudehyphen;independent acoustical mechanical quality factorsQof 99.95percnt; pure polycrystalline molybdenum and tungsten have been measured as a function of temperature and heat treatment from 50 mK to 300 K. Data were obtained from 1 kHz torsional modes of resonators designed to minimize extraneous loss effects. Thermal annealing at temperatures above the recrystallization temperatures yielded strongly enhancedQ. MaximumQvalues of 4.38times;107in Mo and 1.23times;107in W were observed in annealed material at the lowest measurement temperatures. Internal friction peaks and backgrounds are discussed. The temperature dependence of the resonator frequency is reported. Mo and W are compared with Alhyphen;5056 as suitable materials for fabrication of cryogenic resonanthyphen;bar gravityhyphen;wave antennas.