• D. Dowell, F. King, R.E. Kirby, J.F. Schmerge
  SLAC, Menlo Park, California

Funding: SLAC is operated by Stanford University for the Department of Energy under contract number DE-AC02-76SF00515.

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 ~200°C. If the qe is too low, the cathode is 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 non-uniform 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 copper samples, and the results showed a significant increase in qe after cleaning with a 1keV hydrogen ion beam. The H-ion beam cleans an area approximately 1cm in diameter and has 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 a H-ion cleaner on an s-band gun are presented.