ELECTRON AND ION CURRENTS RELEVANT TO ACCURATE CURRENT INTEGRATION IN MEV ION BACKSCATTERING SPECTROMETRY

The magnitude and characteristics of the currents which flow in the target and the chamber of MeV ion backscattering spectrometer are examined. Measured energy distributions and the magnitude of high-energy secondary electron currents are reported. An empirical universal curve is shown to fit the energy distribution of secondary electrons for several combinations of ion energy, targets and ion species. The magnitude of tertiary electron currents which arise at the vacuum vessel walls is determined for various experimental situations and is shown to be non-negligible is many cases. An experimental arrangement is described which permits charge integration to 1% accuracy without restricting access to the target as a Faraday cage does. © 1979.