In-Situ Cleaning of Metal Cathodes Using a Hydrogen Ion Beam

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Improving and maintaining the quantum efficiency (QE) of a metal photocathode in an s-band RF gun requires a process for cleaning the surface. In this type of gun, the cathode is typically installed and the system is vacuum baked to {approx}200 degrees C. If the QE is too low, the cathode is usually cleaned with the UV-drive laser. While laser cleaning does increase the cathode QE, it requires fluences close to the damage threshold and rastering the small diameter beam, both of which can produce nonuniform electron emission and potentially damage the cathode. This paper investigates the efficacy of a ... continued below

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4 pages

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Dowell, D.H.; King, F.K.; Kirby, R.E.; Schmerge, J.F. & /SLAC September 1, 2005.

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Description

Improving and maintaining the quantum efficiency (QE) of a metal photocathode in an s-band RF gun requires a process for cleaning the surface. In this type of gun, the cathode is typically installed and the system is vacuum baked to {approx}200 degrees C. If the QE is too low, the cathode is usually cleaned with the UV-drive laser. While laser cleaning does increase the cathode QE, it requires fluences close to the damage threshold and rastering the small diameter beam, both of which can produce nonuniform electron emission and potentially damage the cathode. This paper investigates the efficacy of a low energy hydrogen ion beam to produce high-QE metal cathodes. Measurements of the QE vs. wavelength, surface contaminants using x-ray photoelectron spectroscopy and surface roughness were performed on a copper sample, and the results showed a significant increase in QE after cleaning with a 1keV hydrogen ion beam. The H-ion beam cleaned an area approximately 1cm in diameter and had no effect on the surface roughness while significantly increasing the QE. These results and a comparison with theory as well as a scheme for installing an H-ion cleaner on an s-band gun are presented.

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4 pages

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  • Contributed to 27th International Free Electron Laser Conference (FEL 2005), Stanford, California, 21-26 Aug 2005

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  • Report No.: SLAC-PUB-11455
  • Grant Number: AC02-76SF00515
  • Office of Scientific & Technical Information Report Number: 878437
  • Archival Resource Key: ark:/67531/metadc878638

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Office of Scientific & Technical Information Technical Reports

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  • September 1, 2005

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  • Sept. 21, 2016, 2:29 a.m.

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  • Nov. 29, 2016, 2:41 p.m.

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Dowell, D.H.; King, F.K.; Kirby, R.E.; Schmerge, J.F. & /SLAC. In-Situ Cleaning of Metal Cathodes Using a Hydrogen Ion Beam, article, September 1, 2005; [Menlo Park, California]. (digital.library.unt.edu/ark:/67531/metadc878638/: accessed November 14, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.