Response of PS-TEPC filled with propane based tissue-equivalent gas to proton beam with energy of 230 MEV

We have been developing a position-sensitive tissue equivalent proportional chamber "PS-TEPC" as a dosimeter in spacecraft. We performed a beam experiment at HIMAC. Irradiating the PS-TEPC with proton beam with the energy of 230 MeV, it is recognized that the signal due to the incident proton has enough pulse height to be distinguished from that of noise. From the position information obtained by analyzing the same data, the track image which is consistent with the beam profile was obtained Additionally, the distribution of the track length shows a sharp peak corresponding to the distance limited by the size of μ-PIC. From the distribution of the collected charge, the energy resolution was estimated to be 25.9% (1σ). It is reported that collected charge in filling gas distorts due to the presence of impurities⁽¹¹⁾. The same effect might be occurred for our detector when the beam experiment performed. In this case, better energy resolution may be obtained if purity of the TE gas in our detector improves. Therefore, we plan to optimize our vacuum system and baking condition to improve the performance of our detector.