Performance of magnesium cathode in the S-band RF gun

Author

Srinivasan-Rao, T. ; Ben-Zvi, I. ; Smedley, J. ; Wang, X.J. ; Woodle, M. ; Palmer, D.T. ; Miller, R.H.

Author_Institution

Brookhaven Nat. Lab., Upton, NY, USA

Volume

3

fYear

1997

fDate

12-16 May 1997

Firstpage

2790

Abstract

In this paper, we present the preliminary results of the performance of the magnesium cathode in a high frequency RF gun. The quantum efficiency of Mg showed a dramatic improvement upon laser cleaning, increasing from 10^-5 to 4×10^-4 after two hours of cleaning, and to 2×10^-3 after systematic cleaning. The cleaning procedure for this increase is described in detail. Charge measured as a function of the laser injection phase relative to the RF phase indicates that the temporal variation of the field on the cathode both due to the RF and the shielding effect of the emitted electrons play a critical role in the emission and extraction of electrons. A model that includes this variation is numerically fitted to the measured charge and the results are presented. The unexpected outcome of the fit was the low field enhancement factor (0.1) predicted by the model for the photoemission. The physical origin of this is still under investigation

Keywords

accelerator RF systems; cathodes; electron guns; electron sources; magnesium; particle beam extraction; shielding; 2 h; Mg; Mg cathode performance; S-band RF gun; electron gun; electron sources; extraction; high frequency RF gun; laser cleaning; laser injection; low field enhancement factor; quantum efficiency; shielding effect; temporal variation; Cathodes; Charge measurement; Cleaning; Current measurement; Electron emission; Laser modes; Magnesium; Phase measurement; Predictive models; Radio frequency;

fLanguage

English

Publisher

ieee

Conference_Titel

Particle Accelerator Conference, 1997. Proceedings of the 1997

Conference_Location

Vancouver, BC

Print_ISBN

0-7803-4376-X

Type

conf

DOI

10.1109/PAC.1997.752767

Filename

752767