Microdosimetric Investigations in a Proton Therapy Beam with Sequentially Etched CR-39 Track Detectors

The applicability of CR-39 nuclear track detectors to the field of microdosimetry was experimentally investigated through a series of tests with monoenergetic charged particle fields. A special etching technique (intermittent etching and cleaning etch steps) was devised and employed to determine LET values along individual tracks on irradiated detector plates. The range of measurable LET values was inferred from the analysis of the etched track diameters created by monoenergetic protons, alpha particles and fission fragments. Based on these calibrations, measurements of track densities and LET distributions were performed at different depths in a CR-39 stack irradiated with 62 MeV protons.