Vaccum system for 8GeV storage ring

The report describes major features of the accumulation ring designed for the large-scale synchrotron orbit radiation facilities which are being designed by the Joint Study Team for Synchrotron Orbit Radiation established under the Institute of Physical and Chemical Research and the Japan Atomic Energy Research Institute. The vacuum in the accumulation ring should be lnTorr or below in the electron-accumulated state to ensure a beam lifetime of about 20 hours. To achieve this vacuum, an Al alloy (A6063T6) extruded in an Ar+02 atmosphere is adopted as material for the vacuum chambers (straight chamber, bending chamber). Non-evaporation type getter (NEG) pumps and distributed ion pumps (DIP) are provided for the straight and bending chambers, respectively. Three types of pumps (centralized NEG pump, sputter ion pump, titanium sublimation pump) are provided for the crotch absorbers, which are to be directly irradiated with synchrotron radiations. The report briefly outlines the beam lifetime in the accumulation ring, some features of the vaccum chambers, thermal output and degassing rate associated with synchrotron radiation, and characteristics of the various pumps. (N.K.)