MICRODOSIMETRIC INVESTIGATIONS IN A PROTON THERAPY BEAM WITH SEQUENTIALLY ETCHED CR-39 TRACE DETECTORS

The applicability of CR-39 nuclear track detectors to the field of mic rodosimetry was experimentally investigated through a series of tests with monoenergetic charged particle fields. A special etching techniqu e (intermittent etching and cleaning etch steps) was devised and emplo yed to determine LET values along individual tracks on irradiated dete ctor plates. The range of measurable LET values was inferred from the analysis of the etched track diameters created by monoenergetic proton s, 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.