THE ATTAINMENT OF UHV IN SYNCHROTRON LIGHT-SOURCES - A REVIEW

In medium-to-high energy electron storage rings, designed to operate as synchrotron light sources, the stored beam lifetime is usually determined by electron scattering from residual gas molecules. For satisfactory operation, this implies that such machines must operate in the uhv region (approximately 10(-9) mbar). Attaining such vacuum levels presents a challenge to the vacuum designer since the synchrotron radiation desorbs high gas loads from the walls of the system, the available pumping speed is often severely limited by vessel conductance and, in any case there is seldom any room to accommodate large vacuum pumps. This paper will review the way in which vacuum system design for light sources has evolved over the past decade; how vacuum system performance can be predicted; and the techniques, including cleaning processes, which are utilised to ensure that adequate pressures are quickly reached and maintained.