Reduction of RF losses at 35 GHz in high purity copper resonant cavities by cooling to cryogenic temperature

Surface resistance Rs of microwave cavities made of high purity copper is measured at a frequency of 35 GHz and at three temperatures (293, 77 and 4.2 K). After convenient mechanical, chemical and annealing treatments, the experimental Rs value for a copper single crystal decreases by a factor of 4.5 when cooled down to 4.2 K, in excellent agreement with theory.