In recent years the technology of thin film preparation and the fabrication of gold surface barrier detectors and their associated electronics have become highly developed. This has enabled improved energy loss measurements to be made more conveniently for a large range of absorbers and charged particles. The basic interaction processes of heavy charged particles with matter have been investigated by analysing the energy spectra of charged particles before and after passing through absorbers. Results concerning the variation in energy loss, stopping power and energy straggling are given for alpha particles and fission fragments in various absorbers. Experimental studies of energy straggling have been carried out for Am-241 alpha particles using surface barrier detectors to observe the energy dispersion following transmission through solid absorbers. Energy straggling of the emitted alpha particles increased with increasing absorber thickness in accordance with theory, until the energy spectra of the helium ions entered the capture and loss region, when the trend is reversed and straggling began to decrease with increasing absorber thickness. An explanation of the phenomenon is given by reference to the stopping power of alpha particles as a function of their energy. Similarly measurements have been made of the energy straggling of Cf-252 fission fragments through air and solid films using a heavy ion surface barrier detector. Analysis of the energy spectra of the heavy and light fragments show a decreasing energy straggling with increasing absorber thickness. Again this and other spectra parameters are explained by reference to stopping power data for fission fragments
