Variations of the track etch rates along the alpha particle trajectories in two types of CR-39

The simulation of track formation processes in nuclear etched track detectors requires a quantitative formulation of registration criteria on the basis of the ratio of track etch to bulk etch rate. Whereas the bulk etch rate is measurable with sufficient accuracy by means of relatively simple techniques the track etch rate has been determined up to now indirectly by measuring the track diameters on the detector surface and assuming a constant etch rate along the particle trajectories. In deeper detector layers this assumption is, however, not valid because the energy loss strongly increases at the end of the particles range. The aim of the studies described was the direct experimental determination of the track etch rate as a function of the depth within the detector as well as the derivation of the relationship between the etch rate and the actual particle energy within the detector.