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Title: In-situ plasma processing to increase the accelerating gradients of SRF cavities

Journal Article · · Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment

A new in-situ plasma processing technique is being developed at the Spallation Neutron Source (SNS) to improve the performance of the cavities in operation. The technique utilizes a low-density reactive oxygen plasma at room temperature to remove top surface hydrocarbons. The plasma processing technique increases the work function of the cavity surface and reduces the overall amount of vacuum and electron activity during cavity operation; in particular it increases the field emission onset, which enables cavity operation at higher accelerating gradients. Experimental evidence also suggests that the SEY of the Nb surface decreases after plasma processing which helps mitigating multipacting issues. This article discusses the main developments and results from the plasma processing R&D are presented and experimental results for in-situ plasma processing of dressed cavities in the SNS horizontal test apparatus.

Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
Sponsoring Organization:
USDOE Office of Science (SC)
Grant/Contract Number:
AC05-00OR22725
OSTI ID:
1234337
Alternate ID(s):
OSTI ID: 1251772
Journal Information:
Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 812; ISSN 0168-9002
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

References (26)

Evidence for surface‐state‐enhanced field emission in rf superconducting cavities journal February 1974
Thermal stabilities and optimal operating parameters for the Oak Ridge Spallation Neutron Source superconducting linear accelerator journal March 2007
Status of the SNS Superconducting Linac and Future Plan journal March 2008
Field emission from crystalline niobium journal February 2009
The origin of prebreakdown electron emission from vacuum-insulated high voltage electrodes journal January 1982
The work function of the elements and its periodicity journal November 1977
NbO as gate electrode for n -channel metal-oxide-semiconductor field-effect-transistors journal June 2004
Work Function Changes Induced by Charged Adsorbates: Origin of the Polarity Asymmetry journal March 2008
Effects of dislocation on electron work function of metal surface journal September 2002
Measurement of work function of transition metal nitride and carbide thin films
  • Gotoh, Yasuhito; Tsuji, Hiroshi; Ishikawa, Junzo
  • Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, Vol. 21, Issue 4 https://doi.org/10.1116/1.1591749
journal January 2003
Carbon on transition metal surfaces journal January 1991
Field electron emission enhancement of amorphous carbon through a niobium carbide buffer layer journal January 2009
Noise and the Kelvin method journal May 1991
Diffusional relaxation of H and D in V and Nb journal August 1970
Study of the chemical behavior of hydrofluoric, nitric and sulfuric acids mixtures applied to niobium polishing journal April 2004
The adsorption of CO on transition metal clusters: A case study of cluster surface chemistry journal June 2009
ITER glow discharge cleaning system journal October 2001
Glow discharge plasma treatment for surface cleaning and modification of metallic biomaterials journal April 1997
Glow discharge cleaning of vacuum switch tubes journal January 1991
Commissioning and operation of the horizontal test apparatus at SNS journal December 2015
Principles of Plasma Discharges and Materials Processing book January 2005
Optical emission spectroscopy characterization of oxygen plasma during degradation of Escherichia coli journal May 2007
Diffusion of carbon along grain boundaries in niobium journal November 2000
Status of cryogenic system for spallation neutron source's superconducting radiofrequency test facility at Oak Ridge National Lab
  • Xu, Ting; Casagrande, Fabio; Ganni, Venkatarao
  • ADVANCES IN CRYOGENIC ENGINEERING: Transactions of the Cryogenic Engineering Conference - CEC, Volume 57, AIP Conference Proceedings https://doi.org/10.1063/1.4707028
conference January 2012
Calculated influence of work function on SE escape probability and Secondary Electron Emission yield journal November 2010
The secondary-electron yield of air-exposed metal surfaces journal May 2003

Cited By (1)

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