Update to the NLC injector system design

The Next Linear Collider (NLC) injector system is designed to produce low emittance 8 GeV electron and positron beams at 120 hertz for injection into the NLC main linacs. Each beam consists of a 265 ns train of bunches (190 bunches spaced by 1.4 ns or 95 bunches spaced by 2.8 ns); each bunch has a population of up to 1.6/spl times/10/sup 10/ particles for 2.8 ns (or 0.8/spl times/10/sup 10/ particles for 1.4 ns). Horizontal and vertical emittances are specified to be /spl gamma//spl epsi//sub x/=3/spl times/10/sup -6/ m-rad and /spl gamma//spl epsi//sub y/=2/spl times/10/sup -8/ m-rad; bunch length at injection is variable from 90-140 /spl mu/m. Electron polarization of greater than 80% is required. Electron and positron beams are generated in separate accelerator complexes each of which contains the source, damping ring systems, linacs, bunch length compressors, and collimation regions. Investigation into the feasibility of polarized positrons for the NLC has begun; operations at 180 Hz and the centralization of the injector complex have been studied. The need for affordable, low technical risk, reliable injector subsystems is a major consideration in the design effort. This paper presents an overview of the NLC injector systems with an emphasis on changes in the design since 1999 and discusses the planned R&D.