Development of collective Thomson scattering for alpha-particle diagnostic in burning plasmas

Kondoh, Takashi; Hayashi, Toshimitsu; Kawano, Yasunori; Kusama, Yoshinori; Sugie, Tatsuo

A diagnostic of fusion-generated alpha-particles is important to understand burning plasma physics, however, an effective measurement method has not yet been established. A collective Thomson scattering (CTS) diagnostic CO laser is being developed to establish a diagnostic method of confined alpha-particles. To realize the CTS diagnostic, a high-repetition Transversely Excited Atmospheric (TEA) CO has been developed. In order to obtain single-mode output, which is needed for the CTS diagnostic, seed laser is injected to the cavity with an unstable resonator. Using this technique, output energy of 17J with the frequency of 15 Hz has been achieved with single-mode output. These results gives a prospect for the CTS diagnostic on International Thermonuclear Experimental Reactor (ITER), which requires energy of 20 J with the repetition rate of 40 Hz. Proof-of-principle test is being performed with the improved laser system on the JT-60U tokamak.