An undergraduate α-particle time-of-flight experiment for determining the mean excitation energy for electronic stopping power of Al, Cu, Ag, and Au

Abstract

A student experiment is presented in which α-particle time-of-flight measurements as well as direct α energy measurements are used to determine electronic stopping power parameters. For the time-of-flight measurements, α particles from a 244Cm source are allowed to pass through a 14.6-μm ΔE detector, then a foil, and finally come to rest in an E detector. The time-of-flight signals are obtained from the ΔE and E detectors. The measured energies and velocities are then used to determine Bloch’s constant in the Bethe stopping power theory for Al, Cu, Ag, and Au. These student results are then compared to the theory. In order to show the feasibility of this technique for other measurements, a 252Cf source is used to produce a fission fragment time-of-flight spectrum. The time resolution for the α group is 1.17 ns and that of the fission fragment light group is 1.68 ns.