Radial dependence of lineal energy distribution of 290-MeV/u carbon and 500-MeV/u iron ion beams using a wall-less tissue-equivalent proportional counter

Tsuda, Shuichi  ; Sato, Tatsuhiko   ; Watanabe, Ritsuko; Takada, Masashi*

Radial dependence of lineal energy distribution, yf(y), have been experimentally evaluated for a 0.72 micrometer site in tissue using 290 MeV/u carbon and 500 MeV/u iron ion beams using a wall-less tissue equivalent proportional counter. The yf(y) distributions and dose-mean of y, are compared with the calculation by a track structure simulation code TRACION and a microdosimetric function of the PHITS code. The values of the measured agree with those of the calculation within 20% but differences in the shape of yf(y) were found in the case of the iron ion irradiation. The result indicates that further improvement of the calculation model for yf(y) distribution in PHITS is needed in terms of the analytical function that reproduce energy deposition by delta rays, in the case that primary ions have LET more than a few hundred keV/micrometer.