Proton energy straggling measurements in aluminum, titanium, silver and tungsten foils

Abstract

Measurements of the transmitted energy straggling are made using a silicon surface barrier detector for 2 to 7 MeV protons incident on thin foil targets of Al, Ti, Ag and W. The straggling widths are studied as a function of target thickness, proton energy and target species. The combination of several incident energies with many target thicknesses provides data for the investigation of energy straggling in the region where Tschalär's theory is applicable. The theoretical estimates are found to agree with the measured values for higher energy beams, but are about 10% lower than the data for lower incident energies. A simple empirical expression for the straggling is given which agrees with the experimental data for energy losses up to 60%.