Desorption measurements of copper and copper alloys for PEP-II

• Published in: Vacuum 1993-05, Vol.44 (5), p.489-491
• Main Authors: Foerster, CL, Halama, H, Korn, G, Calderon, M, Barletta, W
• Format: Article
• Language: English
• ISSN: 0042-207X; 1879-2715
• DOI: 10.1016/0042-207X(93)90079-P

PEP-II will be a meson factory circulating asymmetric beams of 9 GeV and 3.1 GeV having maximum currents of 3.0 A. Copper beam chambers and absorbers will intercept resulting synchrotron radiation and it is critical that the dynamic gas load from photo stimulated desorption (PSD) and thermal outgassing is below 2 × 10 −6 molecules per photon. An experiment was set up to measure PSD from 1 m long bar samples and a chamber sample, fabricated from selected copper and copper alloys, then exposed to white light with a critical energy of 500 eV, on beamline U10B at the VUV ring of the National Synchrotron Light Source (NSLS). Based on U10B results a prototype chamber was built and will be exposed to white light with higher critical energies up to 5 keV, on beamline X-28A at the X-ray ring of the NSLS. This paper presents the measurements of H 2, CO, CO 2 and CH 4 desorption yields as function of accumulated photon flux, angle of incidence, sample material, and surface condition. The results are compared with that of previous work on similar materials and with that of others for copper.