Research and Development for an X-Band Linear Collider

At SLAC and KEK research is advancing toward a design for an electron-positron linear collider based on X-Band (11.4 GHz) rf accelerator technology. The nominal acceleration gradient in its main linacs will be about four times that in the Stanford Linear Collider (SLC). The design targets a 1.0 TeV center-of-mass energy but envisions initial operation at 0.5 TeV and allows for expansion to 1.5 TeV. A 1034 cm-2s-1 luminosity level will be achieved by colliding multiple bunches per pulse with bunch emittances about two orders of magnitude smaller than those in the SLC. The key components needed to realize such a collider are under development at SLAC and KEK. In this paper we review recent progress in the development of the linac rf system and discuss future R&D.