Impact of coatings on the quality factor of a quartz crystal resonator at liquid helium temperature

Effects of coatings on the quality factor of quartz crystal resonators operating at liquid helium temperature are analyzed. A first set of tests demonstrates the effects of gold and chromium electrodes at low temperature. The second set of tests involves a multilayer tantala/silica coating used to reach an extreme reflectance on mirrors such those used in optical cavities or Michelson interferometers. Mechanical losses are measured and discussed from the theoretical model the most frequently used.