UCL Discovery
UCL home » Library Services » Electronic resources » UCL Discovery

Positronium formation at surfaces and studies towards the production of low energy antihydrogen

Cassidy, David Barry; (1999) Positronium formation at surfaces and studies towards the production of low energy antihydrogen. Doctoral thesis (Ph.D), UCL (University College London). Green open access

[thumbnail of Positronium_formation_at_surfa.pdf]
Preview
Text
Positronium_formation_at_surfa.pdf

Download (5MB) | Preview

Abstract

A magnetically guided slow positron beam has been used to measure positronium formation fractions via spectroscopy of annihilation radiation. Positrons with energies in the range 0-3 keV were implanted into tungsten, copper, magnesium oxide powder and silica aerogel targets at room temperature and at cryogenic temperatures (~30 K). This was done with and without nitrogen gas condensed on the surface of these materials. The resulting gamma rays were detected by a CsI detector and an associated PC-based spectroscopy system. In most cases studied the measured energy dependence of the positronium fractions was consistent with previous similar work, however, anomalous behaviour was found in some of the data when gas was condensed on metal surfaces. Using the same positron beam initial measurements of positronium energy distributions have been made. This was accomplished using a HPGe detector to measure the Doppler shift of the energy' of the positronium annihilation radiation. This novel technique has not yet been refined and estimates of its potential are reported. A Monte Carlo simulation of the reaction to form antihydrogen by positronium impact upon antiprotons has been undertaken. Total and differential cross sections have been utilised as input to the simulation which models the conditions foreseen in planned antihydrogen formation experiments using antiprotons and positrons held in Penning traps. Thus, predictions of antihydrogen production rates, angular distributions and the variation of the mean antihydrogen temperature as a function of the incident positronium energy have been made.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Positronium formation at surfaces and studies towards the production of low energy antihydrogen
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Pure sciences; Antihydrogen
URI: https://discovery.ucl.ac.uk/id/eprint/10122830
Downloads since deposit
56Downloads
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item