DOUBLE AND SINGLE IONIZATION OF HELIUM BY HIGH-VELOCITY FULLY STRIPPED IONS

The ratio, R, of the double ionization cross section to that of single ionization for helium by fully stripped carbon, oxygen, silicon and s ulphur ions in the energy range of 2.8 to 6.3 MeV amu(-1) have been me asured. The data obtained using carbon and oxygen projectiles show tha t in this energy range R is in better agreement with the fit given by Knudsen et al than the recent measurements using N7+ projectiles in th e energy range 10-30 MeV amu(-1) and Kr36+ projectiles with energies 0 .5 and 1 GeV amu(-1).