PRESENT STATUS OF THE PHOTON FACTORY RF SYSTEM

An rf system for the 2.5-GeV Photon Factory (PF) storage ring at KEK was commissioned 1982, and it has been upgraded step by step. The present system comprises four 500-MHz damped accelerating cavities, four 200-kW klystrons with their power supplies, and an rf distribution network. Much effort has been made for achieving high reliability of the system. We describe the present status of the system together with the developments for the last two decades. BRIEF HISTORY The 2.5-GeV Photon Factory storage ring was commissioned in 1982 as one of the leading synchrotron light sources in the world. In the original rf system [1], four single-cell cavities were driven by two klystrons. The system was upgraded in 1988, so that the number of klystrons increased by two to four. This upgrade removed potential limitation on the beam currents due to rf power sources. In parallel with the above upgrade, an exhaustive study on the cavity-induced beam instabilities was carried out [1-5]. The resonance frequencies of HOMs in the cavity change with the temperature of the cavity. Therefore the coupled-bunch instabilities were expected to be correlated with the cavity cooling-water temperature. Then, a temperature stabilization and control system was incorporated in 1984. This was possibly the first experiment to control the coupled-bunch instabilities by cooling-water temperature [3]. Second, in order to damp some of the harmful higher-order-modes (HOMs) of the