Title: Cryogenic RF Characterization of SC Materials at SLAC with Cu and Nb-Coated Cavities
Author: Paul Welander
Abstract: Paul B. Welander, Matt Franzi, Sami Tantawi SLAC National Accelerator Laboratory, Menlo Park, CA 94025
A second-generation, X-band cryostat has been developed for the characterization of superconducting materials at low temperatures and high powers. The system utilizes two interchangeable hemisperhical cavities that can accommodate 50 mm-diameter samples on the flat surface. Both operate in a TE013-like mode where the magnetic field is strongest on the sample surface, which accounts for about 1/3 of the total cavity loss. The first cavity is a medium-Q copper one, and is utilized for measuring the sample’s critical temperature and magnetic quenching field. The second is a high-Q niobium-coated cavity that is employed for measuring surface resistance in the low-temperature, low-power limit. We will discuss cryostat design, measurement limits, and testing of samples grown both at SLAC and elsewhere.