New feature of PHITS dedicated to calculate the atomic-size transport of radiation

Ogawa, Tatsuhiko   ; Hirata, Yuho   ; Matsuya, Yusuke  ; Kai, Takeshi   

Track-structure calculation, a method to simulate every secondary electron production reaction explicitly, has been extensively used as an important techniques in various fields such as radiation biology, material irradiation effect, and radiation detection. However, it requires the dielectric function of the target materials, which is not well known except for liquid water. Therefore we developed a model to perform track-structure calculation based on a systematic formula of secondary electron production cross section and that of stopping power. The model can therefore perform track-structure calculation regardless of the availability of dielectric function measurement data. Stopping range, and energy deposition radial distribution calculated by this model agreed well with the earlier experimental data and calculation by precedent codes. The lineal energy in tissue-equivalent gas calculated by this model agreed with measurement data taken from literature, showing distinct difference from that in liquid water. This model was implemented to PHITS Ver3.25, the general-purpose radiation transport simulation code of JAEA, being distributed to users as the first track-structure calculation model applicable to arbitrary materials available in general-purpose transport code.