Performance of SRF Systems in Large Scale Applications

In the last ten years superconducting RF (sc) cavities have become a viable acceleration technique used at many facilities. Applications include electron accelerators like CEBAF, heavy ion accelerators like Atlas, and e(sup+)e(sup -) storage rings such as Tristan. The advantage of sc cavities is twofold: one, they can supply high gradients with a nominal RF source, and two, the state of the art in the design and production techniques has risen to a level that is acceptable. Systems such as Atlas and Tristan have proven that a reliable machine can be produced and have increased the confidence of the operability of SRF technology. As new and larger systems come on line, system performance becomes an issue. Because of the nature of SRF systems, rigid machine protection interlocks, vacuum requirements etc., different limitations that may have not occurred in normal conducting accelerators are being observed. Problems concerning gas discharges, tuning, gradient degradation and other phenomena have to be dealt with. This paper discusses operational performance of large scale SRF systems worldwide. Facilities discussed include high beta machines such as Tristan (KEK), LEP (CERN), HERA (DESY) and CEBAF and heavy ion linacs such as Atlas (Argonne). Key operational issues concerning interlocks, controls and system reliability are included. Particular emphasis is placed on CEBAF's operational experience because the author is closest to it and CEBAF will have 80% of installed SRF cavities by January 1994