Characterization of an Electron Spectrometer for Laser Wakefield Experiments

Two integrated neodymium dipole magnets, one with a 25-mm gap and a 60-mm gap, were characterized for use in the new electron spectrometer built for laser wakefield acceleration experiments in the UDP Chamber using the MTW-OPAL laser at the University of Rochester Laboratory for Laser Energetics. Magnetic field maps were generated by scanning a Gauss probe in planes parallel to the magnetic field at varied distances within the magnet gap and surrounding fringe fields. Maximum magnetic fields of 6.7kG (25-mm gap) and 4.2kG (60-mm gap) were recorded. Results show high spatial uniformity and closely match manufacturers' measurements, with maximum percent differences of 4.3% and 2.4%, for the 25-mm gap and 60-mm gap, respectively. Theoretical predictions of the magnet from SIMION were validated with deviations of 4.9% and 2.9%, for the 25-mm gap and 60-mm gap, respectively.