Characterization of a transmission positron/positronium converter for antihydrogen production

In this work a characterization study of forward emission from a thin, meso-structured silica Received 17 March 2017 positron/positronium (Ps) converter following implantation of positrons in light of possible antihydrogen production is presented. The target consisted of a similar to 1 mu m thick ultraporous silica film e-gun evaporated onto a 20 nm carbon foil. The Ps formation and emission was studied via Single Shot Positron Annihilation Lifetime Spectroscopy measurements after implantation of pulses with 3 4.10(7) positrons and 10 ns temporal width. The forward emission of implanted positrons and secondary electrons was investigated with a micro-channel plate phosphor screen assembly, connected either to a CCD camera for imaging of the impinging particles, or to a fast photomultiplier tube to extract information about their time of flight. The maximum Ps formation fraction was estimated to be similar to 10%. At least 10% of the positrons implanted with an energy of 3.3 keV are forward-emitted with a scattering angle smaller than 50 and maximum kinetic energy of 1.2 keV. At least 0.1-0.2 secondary electrons per implanted positron were also found to be forward-emitted with a kinetic energy of a few eV. The possible application of this kind of positron/positronium converter for antihydrogen production is discussed. (C) 2017 Elsevier B.V. All rights reserved.