2011 Particle Accelerator Conference - List of Authors (Schaff, W.J.)

Paper	Title	Page
THP192	Effect of Surface Roughness on the Emittance from GaAs Photocathode	2480
	S.S. Karkare, I.V. Bazarov Cornell University, Ithaca, New York, USA L. Cultrera, A. Iyer, X. Liu, W.J. Schaff CLASSE, Ithaca, New York, USA
	Funding: This work is supported by NSF under Grant No. DMR- 0807731 and DOE under Grant No. DE-SC0003965. The surface roughness of GaAs photocathodes used in the injector prototype for the ERL at Cornell University was measured and compared to that of the atomically polished GaAs crystal surface using the atomic force microscopy (AFM) technique. The results show at least an order of magnitude rise in the GaAs surface roughness after subjecting it to heat cleaning, prior to activation. An analytical model for photoemission that takes into account the effect of surface roughness has been developed. This model predicts emittance values close to the experimental observations, explains the experimentally observed variation of emittance with incident light wavelength and reconciles the discrepancies in experimental data.

Paper

Title

Page

Effect of Surface Roughness on the Emittance from GaAs Photocathode

2480

S.S. Karkare, I.V. Bazarov
Cornell University, Ithaca, New York, USA
L. Cultrera, A. Iyer, X. Liu, W.J. Schaff
CLASSE, Ithaca, New York, USA

Funding: This work is supported by NSF under Grant No. DMR- 0807731 and DOE under Grant No. DE-SC0003965.
The surface roughness of GaAs photocathodes used in the injector prototype for the ERL at Cornell University was measured and compared to that of the atomically polished GaAs crystal surface using the atomic force microscopy (AFM) technique. The results show at least an order of magnitude rise in the GaAs surface roughness after subjecting it to heat cleaning, prior to activation. An analytical model for photoemission that takes into account the effect of surface roughness has been developed. This model predicts emittance values close to the experimental observations, explains the experimentally observed variation of emittance with incident light wavelength and reconciles the discrepancies in experimental data.