A High Average Current DC GAAS Photocathode Gun for ERLS and FELS

Author

Hernandez-Garcia, C. ; Siggins, T. ; Benson, S. ; Bullard, D. ; Dylla, H.F. ; Jordan, K. ; Murray, C. ; Neil, G.R. ; Shinn, M. ; Walker, R.

Author_Institution

TJNAF, Newport News, VA 23606, U.S.A., Tel: 1-757-269-6862; fax: 1-757-269-5519; E-mail address: chgarcia@jlab.org

fYear

2005

fDate

16-20 May 2005

Firstpage

3117

Lastpage

3119

Abstract

The Jefferson Lab (JLab) 10 kW IR Upgrade FEL DC GaAs photocathode gun is presently the highest average current electron source operational in the U.S., delivering a record 9.1 mA CW, 350 kV electron beam with 122 pC/bunch at 75 MHz rep rate. Pulsed operation has also been demonstrated with 8 mA per pulse (110 pC/bunch) in 16 ms-long pulses at 2 Hz rep rate. Routinely the gun delivers 5 mA CW and pulse current at 135 pC/bunch for FEL operations. The Upgrade DC photocathode gun is a direct evolution of the DC photocathode gun used in the previous JLab 1 kW IR Demo FEL. Improvements in the vacuum conditions, incorporation of two UHV motion mechanisms (a retractable cathode and a photocathode shield door) and a new way to add cesium to the GaAs photocathode surface have extended its lifetime to over 500 Coulombs delivered between re-cesiations (quantum efficiency replenishment). With each photocathode activation quantum efficiencies above 6% are routinely achieved. The photocathode activation and performance will be described in detail.

Keywords

Anodes; Cathodes; Electron beams; Elementary particle vacuum; Gallium arsenide; Laser beams; Laser mode locking; Optical pulse generation; Optical pulses; Voltage;

fLanguage

English

Publisher

ieee

Conference_Titel

Particle Accelerator Conference, 2005. PAC 2005. Proceedings of the

Print_ISBN

0-7803-8859-3

Type

conf

DOI

10.1109/PAC.2005.1591383

Filename

1591383