Dipole Mode Detuning in the NLC Injector Linacs

Abstract

The injector linacs of the JLC/NLC comprise the e+ booster, the e- drive linac, the e+ booster, and the two prelinacs. These four systems together transport the two types of beams from the 80 MeV point at the end of their respective bunchers up to the storage rings, and then from the storage rings to the 10 GeV point at the beginning of the bunch compressors. Nominally, the e+ booster structure will be L-band and the others S-band. In transport through these linacs it is important that the emittances and particle losses stay within specified tolerances. In particular, the effects of the dipole wakefield-especially the long-range dipole wakefield-need to be carefully considered. We present designs of the injector linac structures that employ simple mode detuning, without damping, and that allow us to satisfy our tolerance requirements, for both the nominal (2.8 ns) and alternate (1.4 ns) bunch spacing options.