Fabrication and rf surface resistance of superconducting lead cavity by a press forming technique

Abstract

AbstractThis paper describes fabrication and characteristics of 10‐GHz‐band TM010‐mode superconducting cavities with electroplated lead films on the walls of press‐formed copper shells. The cavity is made up of two symmetrical pieces of copper, and rf current flows parallel to their joint planes. Homogeneous lead films are obtained on copper substrate by using a lead anode with a hemispheric projection. In order to make the rf joints in the cavity, either (a) lead wires were inserted between the copper subtrates with lead films, or (b) indium wires are used between copper substrates on which lead is electroplated. Temperature dependence of Q‐factors of the lead cavities was measured at low temperatures for input power less than 3 mW in an environment where terrestrial magnetism was compensated to be within 20 mG. Q‐factors on the order of 109 were obtained for cavities prepared by the method (b). They also showed residual rf surface resistances as low as 2 × 10‐8ω, which is less than that of TE‐mode lead cavities reported so far for the same frequency range.