IPAC2013 - List of Authors (Guo, L.)

Paper	Title	Page
MOPFI014	A Charge Lifetime Study of NEA GaAs Cathode by Ion Back-bombardment	312
	M. Kuriki KEK, Ibaraki, Japan L. Guo, H. Iijima, K. Miyoshi HU/AdSM, Higashi-Hiroshima, Japan
	Funding: Quantum beam project by the Ministry of Education, Culture, Sports, Science and Technology; The title is High Brightness Photon Beam by Laser-Compton Scattering. NEA GaAs cathode is one of the most important techniques for advanced future projects based on linac. Up to 90% polarized beam can be generated with high quantum efficiency, 0.1 – 10%. The extremely low emittance beam can be generated driven by optimized wavelength laser. Although these remarkable features, the less robustness has been the biggest issue on the real operation of this cathode. According to past experiments, there are three sources of the cathode degradation; gas absorption, thermal desorption, and ion-back bombardment. First two processes could be controlled by less vacuum pressure in order of 10^-10Pa and keeping the cathode temperature low. The ion back-bombardment is the last issue which should be solved for high brightness operation in such as ERL. We observed the cathode quantum efficiency evolution in various laser power density and bias voltage. We found that the cathode degradation was due to the ion back-bombardment quantitatively and the deactivation coefficient of NEA surface by one ion collision did not depend on the bias voltage. We report the experimental results and its analysis based on the ion back-bombardment hypothesis.

Paper

Title

Page

A Charge Lifetime Study of NEA GaAs Cathode by Ion Back-bombardment

312

M. Kuriki
KEK, Ibaraki, Japan
L. Guo, H. Iijima, K. Miyoshi
HU/AdSM, Higashi-Hiroshima, Japan

Funding: Quantum beam project by the Ministry of Education, Culture, Sports, Science and Technology; The title is High Brightness Photon Beam by Laser-Compton Scattering.
NEA GaAs cathode is one of the most important techniques for advanced future projects based on linac. Up to 90% polarized beam can be generated with high quantum efficiency, 0.1 – 10%. The extremely low emittance beam can be generated driven by optimized wavelength laser. Although these remarkable features, the less robustness has been the biggest issue on the real operation of this cathode. According to past experiments, there are three sources of the cathode degradation; gas absorption, thermal desorption, and ion-back bombardment. First two processes could be controlled by less vacuum pressure in order of 10^-10Pa and keeping the cathode temperature low. The ion back-bombardment is the last issue which should be solved for high brightness operation in such as ERL. We observed the cathode quantum efficiency evolution in various laser power density and bias voltage. We found that the cathode degradation was due to the ion back-bombardment quantitatively and the deactivation coefficient of NEA surface by one ion collision did not depend on the bias voltage. We report the experimental results and its analysis based on the ion back-bombardment hypothesis.