Commissioning of the UCLA Neptune x-band deflecting cavity and applications to current profile measurement of ramped electron bunches

A 9-cell standing-wave deflecting cavity has recently been constructed and installed at the UCLA Neptune Laboratory for use as a temporal diagnostic for the 13 MeV, 300 to 700 pC electron bunches generated by the Neptune photoinjector beamline. The cavity is a center-fed Glid- Cop structure operating in at TM₁10-like deflecting mode at 9.59616 GHz with a pi phase advance per cell. At the maximum deflecting voltage of 530 kV, the theoretical resolution limit of the device is 50 fs, although with current beam parameters and a RMS spot size of 460 mum the effective resolution is approximately 400 fs. We discuss the operation and testing of the cavity as well as its intended application of measuring the temporal current profile of ramped electron bunches generated using the Neptune dogleg compressor, and we present the first measurements of the electron beam current profile obtained using the deflecting cavity.