Product yields of water radiolysis with high-energy heavy-ion beams relevant to spatial and temporal track structures

Radiolysis of neutral water with high-energy heavy ions has been investigated since the FY 2002. It has been purposed to clarify track structure and its dynamics based on product yields, which are macroscopically measurable. Until the end of the FY 2008, following 4 things has been accomplished: (A) measurement of primary yields of main products (e^-_aq, ·OH, H₂O₂), which are defined as yields approximately at 100 ns after irradiation, (B) investigation of temporal behavior of water radicals during ns-μs, (C) development of a sensitive method to determine ·OH yield and its application to heavy-ion irradiations, and (D) investigation of ·OH yields near the Bragg peak. In the FY 2009, experimental data obtained in activity, (D) were carefully discussed based on fragmentation simulation with HIBRAC and PHITS. In addition, two new challenges, (E) utilization of ESR and (F) development of online analysis apparatus of gaseous products, have been started. (author)