Operational experiences at existing accelerator facilities

Over the past several years the author has been conducting a study consisting of literature searches and visits to selected existing accelerator facilities to gather information with the ultimate objective of assembling a database of reliability information for typical accelerator components such as ion sources, focusing magnets, magnet power supplies, RF windows, circulators, high voltage components, etc. The resulting database will be used in support of the design effort for planned high power proton accelerator projects. This presentation describes the major findings and the current status of this ongoing effort. Generally, most surveyed facilities collect information on beam downtimes and their causes (insofar as these are actually understood). The survey shows that existing facilities consistently operate with availability between 80-90% of scheduled time. However, it should also be noted that the surveyed facilities are normally scheduled to operate only 30-75% of the year. Also, short but frequent interruptions are found to be a typical characteristic of all the large accelerator installations. Detailed time series of accelerator failure events for several operating cycles have been obtained from two facilities: LANSCE and TJNAF. Such time series data permit statistical estimation of the parameters of the underlying random process which can then be used to generate facility specific reliability predictions and to derive failure and repair rates for some of the system's components. Examples of such analyses are presented.