Water radiolysis with heavy ions of energies up to 28 GeV; Investigation of track structure and intra-track reactions
28GeVまでの重粒子線による放射線水分解; トラック構造とトラック内反応の研究
山下 真一*; 勝村 庸介; Lin, M.; 室屋 裕佐*; 宮崎 豊明*; 村上 健*; Meesungnoen, J.*; Jay-Gerin, J.-P.*
Yamashita, Shinichi*; Katsumura, Yosuke; Lin, M.; Muroya, Yusa*; Miyazaki, Toyoaki*; Murakami, Takeshi*; Meesungnoen, J.*; Jay-Gerin, J.-P.*
Presently, heavy-ion therapy is already used for cancer treatment. However, the detailed mechanism for explaining the distinctive radiobiological properties of heavy ions is not clarified yet. In this work, the relevance of track structure to the distinctive irradiation effects is discussed by using yield measurements and simulations of intra-track reactions. In the first measurements, primary g-values of eaq, OH, and HO in pure water have been determined as track segment yields. In the second measurements, G-values of MV in methyl viologen (MV) aqueous solutions irradiated in the presence of various concentrations of formate have been obtained. In these measurements, temporal information during intra-track reactions can be extracted. In parallel, Monte Carlo simulations were also conducted to complement the lack of microscopic information. From these modeling calculations, it is found that the scavenging efficiency can fall down at scavenging capacity higher than 10 s because of the possible occurrence of "second-scavenging" reactions, and the relevance to radiobiological effects can be viewed as a result of clustered damage in DNA.