AVS 65th International Symposium & Exhibition
    Vacuum Technology Division Monday Sessions
       Session VT-MoM

Paper VT-MoM11
Pressure Measurements from Combining Non-evaporable Getter Pumps and a Novel Extreme High Vacuum Cryopump

Monday, October 22, 2018, 11:40 am, Room 203B

Session: Vacuum Measurement
Presenter: Marcy Stutzman, Thomas Jefferson National Accelerator Facility
Authors: M.L. Stutzman, Thomas Jefferson National Accelerator Facility
A. Segovia Miranda, Universidad Aut´onoma de Zacatecas
P.A. Adderley, Thomas Jefferson National Accelerator Facility
M. Poelker, Thomas Jefferson National Accelerator Facility
Correspondent: Click to Email
The Jefferson Lab polarized electron source requires vacuum approaching extreme high vacuum for long operational lifetime for the GaAs photocathodes. Currently the system is pumped with a combination of non-evaporable getter (NEG) pumps, ion pumps, and a NEG coating on the chamber walls. Exploring further improvement of the vacuum for the system, we have assembled a system using an array of NEG modules and a novel cryopump with Boron Nitride Nanotubes (BNNT) instead of the traditional charcoal. The BNNT has been mechanically attached to the cryosorption surfaces of a commerical cryopump, and the system fully baked to remove water with no adhesive present in the system. We report here on the pump speed of the BNNT cryopump, and characterize the base pressure achieved in the combined NEG/cryopump system using both an extractor gauge and a Watanabe 3BG XHV ionization gauge which has reached at least the x-ray limit of the extractor gauge.