H+ SECONDARY IONS EMISSION STIMULATED BY IMPACT OF ENERGETIC IONS ON HEATED TARGET

The hydrogen secondary ion emission yield was measured for the impact of 2.0 MeV nitrogen ions on thin LiF targets using a time of flight ma ss spectrometer in a coincidence setup. The sample temperature was var ied from 20 degrees C up to 150 degrees C using a resistor facing the target holder and the incident ion charge varied between 1+ and 5+. Th e H+ relative yield measured was fitted to isothermal function allowin g the determination of the adsorption heat for the hydrogen and other contaminant molecules adsorbed on the LIF target surface. The secondar y H+ emission process was described assuming the contribution of two d ifferent mechanisms namely potential and kinetic mechanisms and the re sults were discussed laking into account existing models for this ion emission process. (C) 1997 Elsevier Science B.V.