Positron annihilation spectroscopy on a beam of positrons the LEPTA facilityE.V. Ahmanova, M.K. Eseev, A.G. Kobets, I.N. Meshkov, O.S. Orlov, A.A. Sidorin, K. Siemek and P. HorodekEPJ Web Conf., 132 (2017) 03014DOI: https://doi.org/10.1051/epjconf/201713203014