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Characterization of the CEBAF 100 kV DC GaAs photoelectron gun vacuum system

A vacuum system with pressure in the low ultra-high vacuum (UHV) range is essential for long photocathode lifetimes in DC high voltage GaAs photoguns. A discrepancy between predicted and measured base pressure in the CEBAF photoguns motivated this study of outgassing rates of three 304 stainless ste...

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Published in:Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Accelerators, spectrometers, detectors and associated equipment, 2007-05, Vol.574 (2), p.213-220
Main Authors: Stutzman, M.L., Adderley, P., Brittian, J., Clark, J., Grames, J., Hansknecht, J., Myneni, G.R., Poelker, M.
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container_title Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment
container_volume 574
creator Stutzman, M.L.
Adderley, P.
Brittian, J.
Clark, J.
Grames, J.
Hansknecht, J.
Myneni, G.R.
Poelker, M.
description A vacuum system with pressure in the low ultra-high vacuum (UHV) range is essential for long photocathode lifetimes in DC high voltage GaAs photoguns. A discrepancy between predicted and measured base pressure in the CEBAF photoguns motivated this study of outgassing rates of three 304 stainless steel chambers with different pretreatments and pump speed measurements of non-evaporable getter (NEG) pumps. Outgassing rates were measured using two independent techniques. Lower outgassing rates were achieved by electropolishing and vacuum firing the chamber. The second part of the paper describes NEG pump speed measurements as a function of pressure through the lower part of the UHV range. Measured NEG pump speed is high at pressures above 5×10 −11 Torr, but may decrease at lower pressures depending on the interpretation of the data. The final section investigates the pump speed of a locally produced NEG coating applied to the vacuum chamber walls. These studies represent the first detailed vacuum measurements of CEBAF photogun vacuum chambers.
doi_str_mv 10.1016/j.nima.2007.01.170
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identifier ISSN: 0168-9002
ispartof Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 2007-05, Vol.574 (2), p.213-220
issn 0168-9002
1872-9576
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source ScienceDirect Journals
subjects COATINGS
DEGASSING
Electron gun
ELECTROPOLISHING
GETTERS
MATERIALS SCIENCE
Non-evaporable getter (NEG)
Outgassing
PHOTOCATHODES
Photoinjector
Polarized electron source
Pump speed
STAINLESS STEELS
VACUUM SYSTEMS
VELOCITY
title Characterization of the CEBAF 100 kV DC GaAs photoelectron gun vacuum system
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