AVS 49th International Symposium
    Vacuum Technology Tuesday Sessions
       Session VT-TuP

Paper VT-TuP10
XPS Studies of Al and Cu Samples Exposed to an Accelerator Environment

Tuesday, November 5, 2002, 5:30 pm, Room Exhibit Hall B2

Session: Poster Session
Presenter: R.A. Rosenberg, Argonne National Laboratory
Authors: R.A. Rosenberg, Argonne National Laboratory
M.W. McDowell, Argonne National Laboratory
Q. Ma, Argonne National Laboratory
Correspondent: Click to Email
Designers of present and future particle accelerators are becoming increasing concerned about the influence of the components surface chemistry on the accelerator performance. Bombardment of these surfaces by photons can cause desorption of gases and prod uction of primary and secondary electrons. In some cases interaction of these electrons with the particle beam and the chamber walls can lead to an amplification of the electron density which in turn can cause degradation of the beam. It is well known th a t exposure to an accelerator environment can cause "conditioning" of the chamber surfaces. In order to understand the manner in which the surface structure might influence the production of gases and electrons in the accelerator it is necessary to stud y s uch surfaces both before and after exposure to accelerator conditions. There have been numerous studies performed on representative materials prior to being inserted into an accelerator but very little done on materials that have "lived" in the accele r ato r for extended periods. In the present work we mounted Al and Cu coupons at different positions in a section of the Advanced Photon Source storage ring and removed them following exposures ranging from 6 to 18 months. XPS surface analysis was perfor me d be fore and after exposure. Changes were observed that depended on the location and whether the coupon was facing the chamber interior or chamber wall. These results will be presented and compared to data obtained from laboratory measurements meant to simulate the accelerator conditions. Work supported by U.S. Department of Energy, Office of Basic Energy Sciences under Contract No. W-31-109-ENG-38.