- s - ’ SLAC Modulate ; Operation and Reliability in the SLC Era * SLAC - PUB - 5863

A bsnact A discussion of the operation and reliability of the 244 modulators in the SLAC linac with an emphasis on the past three years of operation. The linac modulators-were desi ned and built in the 60's, upgraded f for the SLAC Linear Collider (S C) in the mid 8Os, and despite their age are still reliable accelerator components. The 60s modulator qpcrated at 65 MW peak and 83 kW average power. The upgrade resulted in 150 MW peak output at an average power of 87 kW, a modest increase since the repetition rate was dropped from 360 to 120 Hz [I]. In the present accelerator configuration, the Linac operates as a source of electrons and positrons to a &gle uass collider. The classic c&ider is a storage ring filled with oppositely charged, counter-rotating particles which are allowed to collide until an accelerator fault occurs and the stored beams are aborted. A reasonable storage ring can store and collide particles for as long as eight hours with a 10 or 20 minute filling time. A single pass collider,. " on the other hand, can only produce e-and e+ collisions at whatever rate the source operates. To be effective the SLC must operate at 120 IG with a very high degree of reliability and on a continuous basis. Fortunately, the linac has a modest excess of modulator/klystron-systems which allows some measure of redundancy and hence some freedom from the constraint that all 244 modulator/klystrons operate simultaneously. Nonetheless, high importance is placed on modulator MTJ3F a$ MTTR or, in the parlance of reliability experts and-accelerator physicists, availability. This is especially true of the modulators associated with the fundamental requirements of a collider such as injecfion;wmpression and positron production. The past three years of high power opzration will provide a reference for modulator design and reliability. The presentation of material related to modulator characteristics, system operation, problem frequency, repair times, idjtistment interventions (e.g., thyratron ranging), .component lifetimes (e.g., thyratrons), and improvements for present problems is based on detailed analysis of the 1991 SLC run.