Water radiolysis near the Bragg peak of therapeutic heavy ions, 2; Contribution of fragmentations to OH-radical yield

Maeyama, Takuya*; Yamashita, Shinichi; Baldacchino, G.*; Taguchi, Mitsumasa; Kudo, Hisaaki*; Murakami, Takeshi*; Katsumura, Yosuke

Yield of hydroxyl radical (OH), which is assumed to be most responsible species in indirect action, has been measured near the Bragg peak of therapeutic heavy ions. Such a highly energetic heavy ions go through fragmentation reactions, leading to production of lighter ions. Contribution of fragmentation to dose and so on increases near the Bragg peak. In this study, fragmentation reactions are simulated with PHITS code, which is developped by a group of JAEA. In the trial, the same irradiation system as used in actual experiment was taken into account, and each fragmentation ion was estimated quantitatively. In addition, measured OH yield was reproduced by using established knowledge.