Speaker
Description
We report preliminary data from a prototype Electro-Optic Sampling Beam Position Monitor (EOS-BPM) at the FACET-II Facility at SLAC National Accelerator Laboratory. In EOS-BPM, a birefringence is induced in two electro-optic crystals on either side of the electron beam's trajectory as it passes by. Laser pulses traveling through each crystal pick up a spacially encoded polarization which is detected. The signal from each crystal provides a single-shot, non- destructive diagnostic of the relative time of arrival of the beam and, in two bunch operation, the longitudinal separation between the drive and witness bunches. By comparing the relative strengths of the signals on each crystal, the instrument can measure the transverse $x$ position of a bunch. We discuss how the installed prototype is currently being employed at FACET-II for plasma acceleration experiments and two bunch commissioning. We present preliminary results of the beam position monitor functionality of the prototype. Finally, we discuss work on an improved prototype capable of measuring bunch position in both transverse dimensions and with increased transverse resolution.
