Plasma density profile measurement of discharged capillary for laser electron acceleration

Kameshima, Takashi; Kotaki, Hideyuki; Kando, Masaki; Daito, Izuru; Kawase, Keigo; Fukuda, Yuji; Chen, L. M.; Faenov, A. Y.; Pikuz, T. A.*; Homma, Takayuki; Kondo, Shuji; Kimura, Toyoaki; Tajima, Toshiki; Bulanov, S. V.; Sugiyama, Kiyohiro*; Nakajima, Kazuhisa; Kurokawa, Shinichi*; Kumita, Tetsuro*

In recent years, It is noted to use of discharge capillary for laser plasma electron acceleration in order to solve the limit owing to laser focal distance. As the higher plasma density is, the lower the refraction index is, laser propagetes into and interacts plasma, keeping its focal size because discharge plasma behaves like optical fiber. This tequnique would make acceleration space much longer, compared to conventional method with several mm length. This time, we measured plasma density profile inside capillary in order to research optimum distribution of the refraction index, which is very important for R&D of capillary. Here, we will talk about the experimental result.