Effect on heavy-ion irradiation of hydroxyl imides in alcohol solutions

Hydroxymaleimide (C₂H₂(CO)₂-NOH) was irradiated with He-ion (150 MeV/u), C-ion (290 MeV/u) and Ne-ion (400 MeV/u) in isopropyl alcohol, Linear Energy Transfer (LET) was 8-10 eV/nm for He-ion, 11.0, 13.2, 17.9 and 26.5 eV/nm for C-ion and 31 and 40 eV/nm for Ne-ion. The dose rate was 4.5 and 0.4 kGy/h. The G-values of degradation of hydroxymaleimide by heavier ion irradiation were smaller than those by lighter ion irradiation at the same LET value. The degradation efficiency became 1.5 times larger, when irradiation was carried out at 1/10 times smaller dose rate. Considering with the dose rate effect, the fitting curves of G-values obtained by irradiation of C-ion and Ne-ion at both Takasaki Ion Accelerators for Advanced Radiation Application (TIARA) and Heavy Ion Medical Accelerator in Chiba (HIMAC) Facilities were consistent with each other. Irradiated at lower LET value than 8 eV/nm, G-values increased little by little with decreasing LET value to the converged value. (author)