Measurement of lineal energy distributions for ion beams using a wall-less tissue equivalent proportional counter

Tsuda, Shuichi  ; Sato, Tatsuhiko   ; Ogawa, Tatsuhiko   

Energy deposition in and around ion beam is fundamental and important information when evaluating biological effect of ion beams based on dose contribution. Using a wall-less tissue-equivalent proportional counter, we measured the radial dependence of the lineal energy distribution, yf(y), of 30 MeV proton beam. The yf(y) distributions and the dose-mean of y for various kinds of energetic ion beams have been are measured and compared with calculations performed with the microdosimetric function of the Particle and Heavy Ion Transport code System (PHITS). To proceed the improvement of the PHITS code, the contribution of incident ions and the secondaries was investigated using narrow ion beam and the wall-less TEPC. Measured yf(y) and dose-mean of yf(y) for 30 MeV proton beam will be reported, as well as the calculated results using PHITS and the result of the dose contribution by the incident proton beam.