Ionisation of positive ions by electrons in the hollow-beam trap

The concentric-electron-beam device is operated in the steady-state mode as described previously by Hasted and Awad (see ibid., vol.5, p.1719 (1972)). Electron impact ionisation cross sections in the impact energy range 40-500 eV are reported for C+, C2+, O+ and O2+, the data conform to the empirical scaling formulae. Measurements on five previously measured cross sections have been repeated, and agreement is found. The hollow-electron-beam space-charge ion trap has been operated in a pulsed mode, and the rate at which the trap fills up with ions has been measured and analysed.