100MeV/u 12Cビーム入射荷電粒子生成反応の研究

Even though carbon-ions provide highly conformal dose distributions thanks to the Bragg peak and the high straightness of the track, they will induce undesired dose outside the primary beam field. The undesired dose arises from secondary particles produced through beam interactions with the patient's body. Despite intensive studies, lateral dose distributions are not understood well, because there are no energy-angle double-differential cross sections (DDXs) of heavy-charged particle productions at large angles. The purpose of this study was to measure DDXs of carbon-ion nuclear reactions to improve accuracy of secondary dose estimation in carbon-ion radiotherapy. The measurement was performed at the Heavy Ion Medical Accelerator in Chiba (HIMAC), National Institute for Radiological Sciences, Japan. The carbon-ions were accelerated to 100 MeV/u and bombarded the target (C, Al, and Co). Emitted charged particles were detected by counter-telescopes installed at the PH2. Light particles (p, d, t. 3He and α) were detected with two dE-E telescopes comprising two silicon-surface-barrier detectors (SSDs), a GSO(Ce) crystal and four PWO crystals. Particles heavier than α were detected with two dE-E telescopes consisting of two SSDs and a CsI(Tl) crystal. Thanks to their high energy resolutions, isotope separation was achieved for many of detected particles. This report describes experimental results obtained during 2018-2019 at HIMAC.