LLL 100-MeV electron linac: design considerations and performance of the beam-transport vacuum system

The vacuum system is described for the beam-transport lines used with the Lawrence Livermore Laboratory 100-MeV electron-positron linear accelerator. It is operated in the high (10-4 to 10-5 Pa) range using standard ion pumps with turbomolecular pumps for roughdown. The important factors considered during the initial design phases are reviewed; these factors contributed to the very reliable performance of the vacuum system since its startup five years ago. The cleaning and handling procedures used on the beam-transport lines, magnet vacuum chambers, and other vacuum components are discussed. (auth)