Beam diagnostic challenges for facet-ii ∗

FACET-II, the Facility for Advanced Accelerator Experimental Tests II, is a new accelerator R&D test facility to be constructed at SLAC. It will provide high-energy, highdensity electron and positron beams to advance the development of beam driven plasma wakefield acceleration and support a broad range of experiments. The FACET-II beams are expected to have 10 GeV energy, contain 2 nC of charge, have a transverse normalized emittance of 7 microns, be compressed to about 1 micron long and focused to about 6 micron wide at the interaction point. The nominal peak current is 20 kA and is expected to fluctuate up to 200 kA. Most experiments desire complete knowledge of the incoming beam parameters on a pulse-to-pulse basis. However, the extreme beam densities and strong fields of the beam current will destroy any diagnostics intercepting the beam in a single shot and impose unique challenges for beam diagnostics. Moreover, non-intercepting diagnostics are desirable to provide feedback for machine setup and characterization. We need to look beyond conventional diagnostics to seek new solutions for measurements of the high charge, small beam size, short bunch length, and low emittance.