Interpretation of photo-desorption data in a diffusion model and application to candidate SSC beam tube surfaces.

摘要

In this paper, a diffusion model is developed as a phenomenological description of the photodesorption process. Expressions are derived for the dependence of the photodesorption coefficients on certain semi-phenomenological parameters. Photodesorption data for possible Superconducting Super Collider (SSC) beam tube surfaces are fitted to the derived form, and values for the parameters are extracted from the fits. In an application to the vacuum problem for the SSC, the time required to desorb a monolayer is derived as a function of the model parameters. The range of parameter space required for long monolayer desorption times (up to 4000 hrs) is established, and this is compared with the values of the parameters obtained from the fits to photodesorption data discussed above. The sensitivity of the results to various model assumptions is also explored.