The study of photodesorption process for cryosorbed CO2

The performance of the vacuum system of the superconducting super colliders will depend critically on desorption of gas by the synchrotron radiation from relativistic protons and the re-adsorption of that gas back onto the cold surface. Here are presented the results of experiments to study the desorption of cryosorbed CO2 molecules from a stainless steel surface at LN2 temperatures. In contrast to our earlier experiments [1] which were performed in a “closed” geometry setup, new experiments have been carried out in “open” geometry. At ∼284 eV critical photon energy the photodesorption yield of cryosorbed CO2 has an increasing dependence with surface coverage up to about 0.5 molecules/photon at ∼1019 molecules/cm2. It is shown that in photon induced desorption of CO2, the desorption process is dominated by cracking of CO2 to CO and O.