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Charge and fluence lifetime measurements of a dc high voltage GaAs photogun at high average current [electronic resource].

Published
Washington, D.C. : United States. Dept. of Energy. Office of Science, 2011.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Physical Description
3,501 (12 pages) : digital, PDF file
Additional Creators
Thomas Jefferson National Accelerator Facility (U.S.), United States. Department of Energy. Office of Science, and United States. Department of Energy. Office of Scientific and Technical Information
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Summary
GaAs-based dc high voltage photoguns used at accelerators with extensive user programs must exhibit long photocathode operating lifetime. Achieving this goal represents a significant challenge for proposed high average current facilities that must operate at tens of milliamperes or more. This paper describes techniques to maintain good vacuum while delivering beam, and techniques that minimize the ill effects of ion bombardment, the dominant mechanism that reduces photocathode yield of a GaAs-based dc high voltage photogun. Experimental results presented here demonstrate enhanced lifetime at high beam currents by: (a) operating with the drive laser beam positioned away from the electrostatic center of the photocathode, (b) limiting the photocathode active area to eliminate photoemission from regions of the photocathode that do not support efficient beam delivery, (c) using a large drive laser beam to distribute ion damage over a larger area, and (d) by applying a relatively low bias voltage to the anode to repel ions created within the downstream beam line. A combination of these techniques provided the best total charge extracted lifetimes in excess of 1000 C at dc beam currents up to 9.5 mA, using green light illumination of bulk GaAs inside a 100 kV photogun.
Report Numbers
E 1.99:jlab-acc-11-1344
E 1.99: doe/or/23177-1548
doe/or/23177-1548
jlab-acc-11-1344
Subject(s)
Other Subject(s)
Note
Published through SciTech Connect.
04/01/2011.
"jlab-acc-11-1344"
" doe/or/23177-1548"
Phys.Rev.ST Accel.Beams 14 04 ISSN 1098-4402 FT
J. Grames, R. Suleiman, P.A. Adderley, J.
Funding Information
AC05-06OR23177
View MARC record | catkey: 14676680