AVS 47th International Symposium
    Vacuum Technology Wednesday Sessions
       Session VT-WeM

Paper VT-WeM3
Measurements of Photon Stimulated Desorption from Thick and Thin Oxide of KEKB Collider Copper Beam Chambers and a Stainless Steel Beam Chamber@footnote 1@

Wednesday, October 4, 2000, 9:00 am, Room 201

Session: Sorption Processes and Leak Detection
Presenter: C.L. Foerster, Brookhaven National Laboratory
Authors: C.L. Foerster, Brookhaven National Laboratory
C. Lanni, Brookhaven National Laboratory
K. Kanazawa, KEK, Japan
Correspondent: Click to Email
Photon Stimulated Desorption(PSD) from KEKB factory copper chambers was measured at the National Synchrotron Light Source(NSLS), located at the Brookhaven Laboratory. The KEKB is an asymmetrical collider recently constructed in Ibaraki, Japan. The collider utilizes two UHV ring chambers, one for a 3.5 GeV positron beam and the other for a 8 GeV electron beam, for B-meson studies. Two each, one meter long, 94mm inner diameter, chemically deoxidized copper beam chambers with conflat end flanges, were provided by KEKB to the NSLS, for measurment of PSD. PSD and specular reflection were measured on NSLS VUV ring beamline U9a. It has been reported that a high temperature air bake on large stainless steel vacuum systems reduces the need for a vacuum bake. To determine the effect of surface oxide, following the initial PSD measurment, the chambers were chemically cleaned and then oxidized in air for a week at 250 °C. PSD was remeasured after the air bake. A similar process and measurment was performed on a stainless steel beam chamber, with the exception of oxidation at 450°C. After the chambers were installed on beamline U9a, they were exposed to a minimum of 10@super23@ photons direct from the source having a critical energy of 595 eV, striking at an incident angle of 100 mrad. The major PSD yields for hydrogen, carbon nonoxide, carbon dioxide, methane, and water vapor are reported as a funtion of accumulated photon flux, incident surface oxide, and chamber preparation. The results are compared with other PSD measurments on NSLS beamlines and those of other laboratory publications for copper and stainless steel. @FootnoteText@ @footnote 1@Work performed under the auspices of the U.S. Department of Energy, under contract DE-AC02-98CH10886.