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Title: Characterization of the CEBAF 100 kV DC GaAs Photoelectron Gun Vacuum System

Abstract

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.

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Thomas Jefferson National Accelerator Facility, Newport News, VA
Sponsoring Org.:
USDOE - Office of Energy Research (ER)
OSTI Identifier:
902157
Report Number(s):
JLAB-ACO-06-614; DOE/ER/40150-4258
Journal ID: ISSN 0168-9002; NIMAER; TRN: US200717%%149
DOE Contract Number:
AC05-84ER40150
Resource Type:
Journal Article
Resource Relation:
Journal Name: Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment; Journal Volume: 574; Journal Issue: 2
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; COATINGS; DEGASSING; ELECTROPOLISHING; GETTERS; PHOTOCATHODES; STAINLESS STEELS; VACUUM SYSTEMS; VELOCITY

Citation Formats

Stutzman, M L, Adderley, P, Brittian, J, Clark, J, Grames, J, Hansknecht, J, Myneni, G R, and Poelker, M. Characterization of the CEBAF 100 kV DC GaAs Photoelectron Gun Vacuum System. United States: N. p., 2007. Web. doi:10.1016/j.nima.2007.01.170.
Stutzman, M L, Adderley, P, Brittian, J, Clark, J, Grames, J, Hansknecht, J, Myneni, G R, & Poelker, M. Characterization of the CEBAF 100 kV DC GaAs Photoelectron Gun Vacuum System. United States. doi:10.1016/j.nima.2007.01.170.
Stutzman, M L, Adderley, P, Brittian, J, Clark, J, Grames, J, Hansknecht, J, Myneni, G R, and Poelker, M. Tue . "Characterization of the CEBAF 100 kV DC GaAs Photoelectron Gun Vacuum System". United States. doi:10.1016/j.nima.2007.01.170. https://www.osti.gov/servlets/purl/902157.
@article{osti_902157,
title = {Characterization of the CEBAF 100 kV DC GaAs Photoelectron Gun Vacuum System},
author = {Stutzman, M L and Adderley, P and Brittian, J and Clark, J and Grames, J and Hansknecht, J and Myneni, G R and Poelker, M},
abstractNote = {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 = {10.1016/j.nima.2007.01.170},
journal = {Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment},
number = 2,
volume = 574,
place = {United States},
year = {Tue May 01 00:00:00 EDT 2007},
month = {Tue May 01 00:00:00 EDT 2007}
}