Laserwire at the Accelerator Test Facility 2 with submicrometer resolution

A laserwire transverse electron beam size measurement system has been developed and operated at the Accelerator Test Facility 2 at the High Energy Accelerator Research Organization, Japan (KEK). Special electron beam optics were developed to create an approximately 1×100 μm (vertical×horizontal) electron beam at the laserwire location, which was profiled using 150 mJ, 71 ps laser pulses with a wavelength of 532 nm. The precise characterization of the laser propagation allows the non-Gaussian laserwire scan profiles caused by the laser divergence to be deconvolved. A minimum vertical electron beam size of 1.07±0.06(stat)±0.05(sys) μm was measured. A vertically focusing quadrupole just before the laserwire was varied while making laserwire measurements and the projected vertical emittance was measured to be 82.56±3.04 pm rad.