Vacuum system of SPring-8 storage ring

The construction of SPring-8 is in progress in Harima Science Park City in Hyogo Prefecture toward the completion in 1997. For the vacuum system of the storage ring, in order to attain the beam current of 100 mA and the beam life of about 20 h, the superhigh vacuum below 133 nPa is required at the time of electron beam operation. The feature of this vacuum system is to irradiate most of the synchrotron radiation from deflection electromagnets on crotches and absorbers without directly irradiating the vacuum chamber, and to carry out concentrated exhaust of the gas arising by light release reaction locally. As to the vacuum system, the recently changed points are mainly reported. The arrangement of the vacuum chamber of basic single cell is explained. The exhaust system is roughly divided into main exhaust system and rough drawing system. The vacuum measuring system, the control system comprising centralized control board and field control board, and heating degasing treatment are described. The problems of thermal stress fatigue and the local boiling phenomena of cooling water must be overcome. (K.I.)