The operation of the electron-positron storage ring LEP at an energy of 100
GeV leads to the deposition of a high-power flux on the vacuum chamber wal
ls. The high critical energy of the photons emitted as synchrotron light (7
40 keV), places the photon-stimulated desorption in this machine in a compl
etely new energy range compared to the existing electron storage rings. At
this high photon energy, the energy dissipation of the photons in aluminium
is done predominantly via the Compton process. This absorption mechanism l
eads to a larger enhancement of the gas desorption with the photon energy c
ompared to the photoelectric effect. Measurements made at 100 GeV to study
the variation of the pressure increase, of the gas composition and of the c
leaning rates as a function of the beam dose and energy are presented and d
iscussed in the context of the absorption of high-energy photons in alumini
um. (C) 2001 Elsevier Science Ltd. All rights reserved.