量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum and Radiological Science and Technology.
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In addition to energy loss by ionization process, protons of energy >∼50 MeV, such as those used in proton radiotherapy, can undergo nuclear interactions with nuclei of Z > 1, resulting in the production of short range (<20 μm), high-LET (linear energy transfer) target fragment particles. One of the few methods to detect these short-range particles is by means of CR-39 plastic nuclear track detector (PNTD) analyzed with an atomic force microscope (AFM). However, due to the LET-dependent angular sensitivity of CR-39 PNTD, multiple detectors exposed at a range of incident angles to the primary proton beam, must be analyzed in order to accurately determine the LET spectrum, absorbed dose and dose equivalent. The LET spectrum of 160 MeV proton-induced secondary particles was experimentally measured with CR-39 PNTDs, which were exposed at six different incident angles to take into account the intrinsic sensitivity of the critical angle for track registration. The irradiated detectors were chemically processed to remove a 1 μm thick volume of CR-39 PNTD. The measured LET range of short range tracks was from 15 keV/μm up to 1.5 MeV/μm. The absorbed dose contribution (Ds/Dp) from secondary particles to primary proton dose was ∼1%, while the dose equivalent contribution (Hs/Dp) was found to be ∼20%. Analysis of CR-39 PNTD by AFM yielded ∼60% higher value for absorbed dose compared to standard optical microscopy analysis.
雑誌名
Nuclear Instruments and Methods in Physics Research B
On the use of CR-39 PNTD with AFM analysis in measuring proton-induced target fragmentation particles
