| AVS 59th Annual International Symposium and Exhibition | |
| Vacuum Technology | Monday Sessions |
| Session VT-MoM |
| Session: | Vacuum Gauging and Metrology |
| Presenter: | M.L. Stutzman, Thomas Jefferson National Accelerator Facility |
| Authors: | M.L. Stutzman, Thomas Jefferson National Accelerator Facility P.A. Adderley, Thomas Jefferson National Accelerator Facility M.A. Mamun, Old Dominion University M. Poelker, Thomas Jefferson National Accelerator Facility |
| Correspondent: | Click to Email |
The spin-polarized electron beam used at Jefferson Lab’s nuclear physics accelerator is generated through photoemission from a strained-superlattice GaAs/GaAsP photocathode. The operational lifetime of the photogun depends strongly on the pressure in the system since residual gasses are ionized by the electron beam and accelerated into the photocathode causing damage. To date, photoguns at Jefferson Lab have relied on NEG and ion pumps. Incremental vacuum improvements have been made through a combination of better bake protocol, chamber heat treatment, NEG pump geometry and activation protocol, improved ion pump technology and the addition of a load-lock to enable photocathode replacement without venting the photogun. This work describes pressure measurements inside a gun-style vacuum chamber with a commercial bakeable cryopump in addition to the NEG and ion pumps. Much of the talk will focus on an assessment of our ability to measure the pressure in the system using three commercial UHV/XHV vacuum gauges.