Vacuum performance of the ultraviolet and x-ray rings at the National Synchrotron Light Source

Abstract

The gas density and its composition expressed in partial pressures of various gases determine the lifetime of circulating current through bremsstrahlung and Coulomb scattering losses. The above quantities depend primarily on the gas desorption due to synchrotron radiation and on the installed pumping speed. During operation of the storage rings, the pressure decreases as the walls of the vacuum system are cleaned by synchrotron radiation. Since long lifetime is essential for good operation of all storage rings, accurate information on pressure around the ring should be available. Calibrated Bayard–Alpert gauges and residual gas analyzers have been installed in both rings. From their readings, average pressure and gas composition are evaluated and the beam lifetime calculated. In this paper we will present (a) National Synchrotron Light Source pressure measuring system, (b) time-dependent pressure and lifetime behavior, and (c) comparison of calculated lifetimes with measured lifetimes.