Plasma Cleaning of LCLS-II-HE verification cryomodule cavities

Abstract

Plasma cleaning is a technique that can be applied in superconducting radio-frequency (SRF) cavities in situ in cryomodules in order to decrease their level of field emission. We developed the technique for the Linac Coherent Light Source II (LCLS-II) cavities and we present in this paper the full development and application of plasma processing to the LCLS-II High Energy (HE) verification cryomodule (vCM). We validated our plasma processing procedure on the vCM, fully processing four out of eight cavities of this CM, demonstrating that cavities performance were preserved in terms of both accelerating field and quality factor. Applying plasma processing to this clean, record breaking cryomodule also showed that no contaminants were introduced in the string, maintaining the vCM field emission-free up to the maximum field reached by each cavity. We also found that plasma processing eliminates multipacting (MP) induced quenches that are typically observed frequently within the MP band field range. This suggests that plasma processing could be employed in situ in CMs to mitigate both field emission and multipacting, significantly decreasing the testing time of cryomodules, the linac commissioning time and cost and increasing the accelerator reliability.

arXiv comment11 pages, 10 figures

References in corpus (5)

• The Superconducting TESLA Cavities
• Nitrogen and argon doping of niobium for superconducting radio frequency cavities: a pathway to highly efficient accelerating structures
• Field emission mitigation studies in LCLS-II cavities via in situ plasma processing
• Low RF power plasma ignition and detection for in-situ cleaning of 1.3 GHz 9-cell cavities
• LCLS-II-HE verification cryomodule high gradient performance and quench behavior

Cited by in corpus (1)

• Report on first plasma processing trial for a FRIB quarter-wave resonator cryomodule