Neutral fractions in proton beams passing through solids

The neutral fractions of back-scattered protons from thick C and Au targets and those of transmitted particles through C, Si and Au foils were measured in the energy range between 100 and 310 keV, and the medium dependence of the neutral fractions was studied. The charge state distributions were measured by the back-scattering method as well as the transmission method. The proton beam from a Cookcroft-Walton accelerator was used as projectile. The back-scattered particles or the transmitted particles were detected with Si (Li) detectors. The neutral fractions of the back-scattered and the transmitted particles with the Au, Si and C targets are shown in a figure. There is no difference between the results of the two different methods. In case of the C target, the neutral fractions which were obtained from gas phase cross section were in good agreement with the experimental results. The emergence angle dependence of the neutral fraction was also measured, and the effects of surface contamination are discussed qualitatively. (Kato, T.)