Characterization of the NEPOMUC primary and remoderated positron beams at different energies

Abstract

We report on the characterization of the positron beam provided at the open beam port of the NEPOMUC facility at the Heinz Maier-Leibnitz Zentrum (MLZ) Garching. The absolute positron flux of the primary beam at 400eV and 1keV kinetic energy and of the remoderated beam at 5, 12 and 22eV were determined. Energy-dependent intensities in the range of (1–5)·108e+/s and (2–6)·107e+/s have been observed for the primary and remoderated beam, respectively. We attribute the significant losses for the primary beam, in comparison with the expected value, to the non-adiabatic positron guiding in the beam line. We also measured the longitudinal energy distribution of the remoderated beam, yielding an energy spread below 3.3eV. The mean transverse energy of the remoderated beam, determined from measurements in different final magnetic fields, was found to be below 1.3eV. These results are likely to apply to the NEPOMUC beam delivered to other user stations.