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Title: Large-Volume Resonant Microwave Discharge for Plasma Cleaning of a CEBAF 5-Cell SRF Cavity

Large-Volume Resonant Microwave Discharge for Plasma Cleaning of a CEBAF 5-Cell SRF Cavity We report the preliminary results on plasma generation in a 5-cell CEBAF superconducting radio-frequency (SRF) cavity for the application of cavity interior surface cleaning. CEBAF currently has {approx}300 of these five cell cavities installed in the Jefferson Lab accelerator which are mostly limited by cavity surface contamination. The development of an in-situ cavity surface cleaning method utilizing a resonant microwave discharge could lead to significant CEBAF accelerator performance improvement. This microwave discharge is currently being used for the development of a set of plasma cleaning procedures targeted to the removal of various organic, metal and metal oxide impurities. These contaminants are responsible for the increase of surface resistance and the reduction of RF performance in installed cavities. The CEBAF five cell cavity volume is {approx} 0.5 m2, which places the discharge in the category of large-volume plasmas. CEBAF cavity has a cylindrical symmetry, but its elliptical shape and transversal power coupling makes it an unusual plasma application, which requires special consideration of microwave breakdown. Our preliminary study includes microwave breakdown and optical spectroscopy, which was used to define the operating pressure range and the rate of removal of organic impurities.
Authors:
Publication Date:
OSTI Identifier:OSTI ID: 1047529
Report Number(s):JLAB-ACP-12-1556; DOE/OR/23177-2145; WEPPR094
TRN: US1203950
DOE Contract Number:AC05-06OR23177
Resource Type:Conference
Resource Relation:Conference: IPAC 2012, 20-25 May 2012, New Orleans, Louisiana
Research Org:Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:USDOE Office of Science (SC)
Country of Publication:United States
Language:English
Subject: 43 PARTICLE ACCELERATORS; ACCELERATORS; BREAKDOWN; CAVITIES; CEBAF ACCELERATOR; CLEANING; HIGH-FREQUENCY DISCHARGES; IMPURITIES; OXIDES; PERFORMANCE; PLASMA; PRESSURE RANGE; REMOVAL; SHAPE; SPECTROSCOPY; SURFACE CLEANING; SURFACE CONTAMINATION; SYMMETRY