Electro-Optic Sampling Beam Positioning Monitor for relativistic electron beams

Non-destructive diagnostics able to resolve transverse offsets and longitudinal separation of ultra-relativistic, two-bunch electron beams are necessary for a variety of applications including the ion channel laser (ICL), a variety of plasma wakefield (PWFA) experiments, as well as other accelerator applications. We present an electro-optic sampling beam positioning monitor (EOS-BPM) design utilizing an ultra-fast laser pulse passing through an axicon lens to create a donut which images a multi-crystal structure placed around the axis of propagation of the electron beam. This EOS-BPM design has been installed at the SLAC National Accelerator Laboratory FACET-II facility. This system is capable of order 5 fs temporal resolution and order 10 µm transverse position resolution and replaces the previously installed prototype design which was capable of order 10 fs and 100 µm transverse position resolution. Experimental results of the EOS-BPM in addition to the simulated response of this design to the ultra-relativistic, two-bunch electron beam used for PWFA experiments at FACET-II will be presented.