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laserKondoh, Takashi; Kawano, Yasunori; Hatae, Takaki; Sugie, Tatsuo; Hayashi, Toshimitsu; Kusama, Yoshinori
NIFS-PROC-68, p.126 - 129, 2007/09
High power and high repetition CO laser has been developed for collective Thomson scattering (CTS) diagnostic to establish a diagnostic method of confined 
-particles in burning plasmas. Pulse energy of 17 J at a repetition rate of 15 Hz has been achieved in a single-mode operation. This result gives a prospect for the CTS diagnostic on International Thermonuclear Experimental Reactor (ITER), which requires energy of 20 J with repetition rate of 40 Hz. The laser injection test into the vacuum vessel of the JT-60U tokamak has been carried out to check the electric noise and stray signals of the receiver system using the new CO laser without plasma. As a result, electrical noise has been decreased, however, stray signal due to multimode oscillation has been observed in about 30% of the pulses and a further improvement of the laser is needed.
Takenaga, Hidenobu; Oyama, Naoyuki; Asakura, Nobuyuki; Sakamoto, Yoshiteru; Sakata, Shinya
NIFS-PROC-68, p.62 - 65, 2007/09
A mm-wave interferometer has been developed for divertor density measurements in JT-60U. The measurements performed for several plasma phases indicated the feasibility of the system except for the ELMy H-mode phase. In the ELMy H-mode phase, the signal intensity was significantly reduced probably due to refraction. A sharp drop in the divertor plasma density was found during a transition to the ELM free H-mode phase concomitant with a sharp drop in D
emission intensity. Low frequency fluctuation of 
1.5 kHz was observed in the divertor plasma density during the quiescent H-mode phase. Feedback control of the divertor plasma density was successfully demonstrated using the mm-wave interferometer as a real-time monitor and the gas-puffing from the bottoms of the W-shaped divertor as an actuator.