Title: An Approach to Chemical Free Surface Processing for High Gradient SRF Cavities
Author: Frederick Mako
Institution: FM Technologies
Abstract: Frederick Mako1, Ph.D., Bing Xiao1, Ph.D. and Larry Phillips2, Ph.D.
Chemical treatment such as buffered chemical polishing (BCP) or electro polishing (EP) followed by high pressure rinsing (HPR) of niobium (Nb) superconducting RF (SRF) cavities is expensive and complex multistep process. Furthermore, the cavity RF surfaces after the treatment still have numerous bubbles and pits that result from welding. These quench-producing weld defects together with the particulate contamination, result in significant scatter of the multi-cell Nb SRF cavities performance characteristics. This scatter is the major problem in the current manufacturing of the Nb SRF cavities. FM Technologies proposes a new approach to chemical-free processing for multi-cell Nb SRF cavities using an internal electron beam (IEB). Specifically, FMT proposes to develop a new electron gun system that will perform electron beam melting over the entire interior surface of Nb SRF cavities to produce a smooth surface, free from voids, bubbles, and other imperfections. This may allow manufacturing of the Nb SRF cavities with a reduction in the above chemical treatment procedures and increase the cavities high gradient performance. FM Technologies will design, build, test the new IEB system and process samples/cavities and Thomas Jefferson Laboratory will measure RF performance of processed samples/cavities. Preliminary electron beam melting results will be presented. 1FM Technologies, Inc., Chantilly, VA, USA, 2Thomas Jefferson Laboratory, Newport News, VA, USA