title: Novel pulsed particle accelerator for energy dependent positron re-emission experiments.
abstract: We report on a novel device for particle acceleration based on elevation of the potential energy of beam pulses. This so-called energy elevator is particularly beneficial if both the particle source and the sample have to be near ground potential due to experimental constraints. We applied this new technique to enable depth dependent measurements of re-emitted positrons using the surface spectrometer at the NEPOMUC positron beam facility. First, a two-stage bunching system is used to generate positron pulses with a repetition rate of 5 MHz and a duration of 1.663(5) ns before their energy is raised to several keV. The whole system was shown to work with an exceptional efficiency of 88%. We demonstrated the usability of our setup by investigating the positron re-emission spectra of Ni and Pd as function of positron implantation energy. For Ni the positron work function could be determined to be ΦNi (+)=-1.4(2)eV. In addition, as predicted by theory, our experimental findings imply a positive positron work function for Pd.
authors.affiliation: Physik-Department E21 and FRM-II, Technische Universität München, Lichtenbergstraße 1, D-85748 München, Germany.
authors.forename: Niklas
authors.initials: N
authors.lastname: Grill
authors.affiliation: Physik-Department E21 and FRM-II, Technische Universität München, Lichtenbergstraße 1, D-85748 München, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Piochacz
authors.affiliation: Physik-Department E21 and FRM-II, Technische Universität München, Lichtenbergstraße 1, D-85748 München, Germany.
authors.forename: Samantha
authors.initials: S
authors.lastname: Zimnik
authors.affiliation: Physik-Department E21 and FRM-II, Technische Universität München, Lichtenbergstraße 1, D-85748 München, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Hugenschmidt