Verification of dose contribution due to short range secondary particles producee by high energy charged particles measured with CR-39

The secondary particles produced by the nuclear interactions of high energy photon, proton and heavy charged particles play significant roles for extra radiation exposure to not only patients during the medical treatment but also astronauts during space mission at lower-Earth orbit and beyond. For example, proton beams can deposit dose to surrounding healthy tissue through nuclear reactions with the production of secondary short range, high LET (linear energy transfer) target fragments. The LET of such particles extends from about 20 keV/μm up to several thousand keV/μm, meaning that their biological effectiveness is relatively high compared to primary protons. To fully understand the possible risks from the secondary target fragment component, including the induction of secondary cancers, the experimental verification of the dose contribution from the secondary target fragments. The results reported here will be applied to the evaluation of the secondary short range particle tracks produced by target fragmentation reaction in the radiation field used in proton cancer therapy