Measurement of the stochastic radial dose distribution for a 30-MeV proton beam using a wall-less tissue-equivalent proportional counter

Tsuda, Shuichi; Sato, Tatsuhiko; Ogawa, Tatsuhiko

Radiation Protection Dosimetry, 168(2), p.190 - 196, 2016/02

https://doi.org/10.1093/rpd/ncv285

Deposit energy distribution in microscopic site in a living cell is important information for understanding of biological effects of energetic heavy ion beams. In this work, a wall-less tissue equivalent proportional counter has been used for the measurement of lineal energy (y) distributions and dose-mean of y (yD) at radial direction of 30 MeV H at TIARA, for the verification of the microdosimetric function of PHITS. The measured yf(y) summed in radial direction agree with the corresponding data from the microdosimetric calculations using the PHITS code fairly well. The yD of 30 MeV proton beam presents the smallest value at r = 0.0 and gradually increase with radial distance, while the values of heavy ions such as iron showed rapid decrease with radial distance. This experimental result demonstrates that the stochastic deposit energy distribution of high-energy protons in microscopic region is rather constant both in the core and in the penumbra region of the track structure.