Geometrical effect on the measurement of stopping powers: Angle-dependent energy loss of 7-MeV protons in Be, Al, Cu, Ag, and Ta

Abstract
The geometrical effect on the measurement of stopping powers for 7-MeV protons, which was a hitherto-not-noticed effect until our previous experiment, has been studied more systematically with 7-MeV protons by changing the target thickness for Be, Al, Cu, Ag, and Ta. An improved experimental arrangement has been used to prevent the edge-scattered protons from affecting the energy-loss measurement. For all targets, the observed energy losses have been confirmed to increase with increasing emergence angle. It has also been found that this effect has a strong dependence on the thickness of the target. The dependence of this effect on the target atomic number cannot be judged properly from the present experiment. Angular distributions of protons due to multiple scattering agree fairly well with the predictions of Molière's theory. The comparison between our geometrical effect and the angular dependence of the energy loss observed for low-energy heavy ions has been discussed.