Energy spectroscopy of positrons re-emitted from polycrystalline tungsten

Energy spectra of positrons re-emitted from the surface of polycrystalline tungsten foil have been measured as a function of incident positron energy E in the range 100 eV-3 keV. The measurements were made using an electrostatic positron-beam apparatus incorporating a hemispherical energy analyser. At high E values the re-emitted spectra tend to a characteristic shape, dominated by a work-function peak at 2.7 eV with a low-energy shoulder …