Application of SBS phase conjugate mirror to fusion plasma diagnostics

SBS位相共役鏡の核融合プラズマ計測への応用

波多江 仰紀; 北村 繁; 佐久間 猛; 濱野 隆; 東條 寛; 吉田 英次*; 藤田 尚徳*; 中塚 正大*; 成原 一途*; 山田 一博*; 舟場 久芳*; 安原 亮*

Hatae, Takaki; Kitamura, Shigeru; Sakuma, Takeshi; Hamano, Takashi; Tojo, Hiroshi; Yoshida, Hidetsugu*; Fujita, Hisanori*; Nakatsuka, Masahiro*; Narihara, Kazumichi*; Yamada, Ichihiro*; Funaba, Hisamichi*; Yasuhara, Ryo*

Two applications using the SBS phase conjugate mirror (SBS-PCM) have been developed to increase the intensity of scattered light for Thomson scattering diagnostics. For the first application, we have developed a new optical design to provide a double-pass scattering method with the SBS-PCM. The SBS-PCM reflects a laser beam passing through the plasma, then the reflected beam passes the plasma again via the same path by means of the phase conjugation. In JT-60U, the double-pass Thomson scattering method using the SBS-PCM has been demonstrated an increase of the scattered light by a factor of 1.6, compared with the single-pass scattering method. A multi-pass Thomson scattering method in which the laser beam can be confined between a pair of SBS-PCMs is also proposed. It is estimated that the multi-pass scattering method generates the scattered light more than five times compared to the single-pass scattering method. We prepare the multi-pass Thomson scattering system for the proof-of-principle tests in Large Helical Device (LHD). For the second application, a high average-power YAG laser system has been developed using the SBS-PCM. The SBS-PCM effectively compensated thermal degradation at two amplifier lines, and the average power was increased by 8 times from 45 W (1.5 J, 30Hz) to 373 W (7.46 J, 50Hz).