Progress of the injector linac upgrade for the BEPC II Project

BEPC II - an upgrade project of Beijing Electron Positron Collider ( BEPC) is a factory type of e(+) e(-) collider. It requires its injector linac to have a higher beam energy ( 1.89 GeV) for on-energy injection and a higher beam current (40 mA e(+) beam) for a higher injection rate ( 50 mA/min). The low beam emittance ( 1.6 pi mm (.) mrad for e(+) beam, and 0.2pi mm (.) mrad for 300 mA e(-) beam) and the low beam energy spread ( +/- 0. 5%) are also required to meet the storage ring acceptance. Thus the original BEPC injector linac must be upgraded to have a new electron gun with its complete tuning system, a new positron source with a flux concentrator, a new RF power system with its phasing, loops and a new beam tuning system with orbit correction and optics tuning devices. These new components have been designed, fabricated, tested and will be installed in,their final positions in this spring and summer, which are described in this paper.