Apparatus and Technique for Measuring Low RF Resistivity of Tube Coatings at Cryogenic Temperatures

In-situ technique for coating of stainless steel vacuum tubes with Cu, to mitigate the problems of electron clouds and wall resistivity in accelerators trying to increase luminosity, was developed. Before coating the RHIC vacuum system with copper, it is imperative to test Cu coating conductivity at cryogenic temperatures to ensure coating effectiveness in lowering resistivity. Folded quarter wave resonator structures are to be built inside a cryogenic system to measure RF resistivity of copper coated RHIC tubing. Samples prepared with different magnetron deposition modes are to be measured by the apparatus. Cu coating is to be optimized by iterative processes. Design an apparatus that would facilitate experimental determination and optimization of the RHIC copper coating that would result in minimal RF resistivity of the RHIC vacuum chambers at cryogenic temperatures. Design is based on making the resonator structure out of a superconducting material (niobium or copper plated lead) such that the copper coating is the most lossy material. Commercial Applications and Other Benefits: Device for measuring electrical resistivity of materials at low temperatures can impact couplers & amp; other components that transmit power between cryogenic & amp; higher temperatures. In-situ coating of existing accelerator vacuum tubes with Cu is cost effective for mitigating problems in accelerators trying to increase luminosity. The ability to in-situ coat tubes & amp; pipes can enhance the capability of existing high purity material processing operations.