Title :
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
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;
Conference_Titel :
Particle Accelerator Conference, 1997. Proceedings of the 1997
Conference_Location :
Vancouver, BC
Print_ISBN :
0-7803-4376-X
DOI :
10.1109/PAC.1997.752767
