REVIEW OF SSC AND LHC BEAM SCREEN VACUUM EXPERIMENTS

As part of Fermilab’s recent Very Large Hadron Collider (VLHC) feasibility study, a water-cooled photon stop was proposed as a possibility to intercept the intense synchrotron radiation in the high field stage VLHC with minimal plug-power. The photon stop, if feasible, promises not only significant savings in cooling power compared to a solution in which the synchrotron radiation is extracted from a beam screen at cryogenic temperatures, but also virtually removes the synchrotron radiation limitation to beam energy and luminosity in a future VLHC. A first series of tests is being prepared at the Argonne Advanced Photon Source (APS) synchrotron light source. These tests should verify thermal models and yield information about photo- induced gas and electron desorption as well as X-ray fluorescence from the photon stop exposed to synchrotron radiation. The following presents the results of a literature study on photo-desorption experiments conducted in the context of the Large Hadron Collider (LHC) and the ill- fated Superconducting Super Collider (SSC) vacuum R&D. The photo-desorption coefficients measured in the these tests are an important input parameter to the model that is used to simulate the first photon-stop vacuum test. The photon stop vacuum model is an important tool for the design of the vacuum measurement