High β experiment and confinement regimes in a compact helical system

✍ Scribed by K. Matsuoka; S. Okamura; K. Nishimura; K. Tsumori; R. Akiyama; H. Yamada; S. Sakakibara; A. Lazaros; J. Xu; K. Ida; K. Tanaka; T. Morisaki; S. Morita; H. Arimoto; A. Ejiri; M. Fujiwara; H. Idei; H. Iguchi; O. Kaneko; T. Kawamoto; S. Kubo; T. Kuroda; O. Motojima; T. Ozaki; V.D. Pustovitov; A. Sagara; C. Takahashi; K. Toi; T. Watari; I. Yamada

• Book ID: 103932808
• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 470 KB
• Volume: 26
• Category: Article
• ISSN: 0920-3796
• DOI: 10.1016/0920-3796(94)00178-a

✦ Synopsis

A volume-averaged equilibrium # value of 2.14% is achieved in a compact helical system using two neutral beam lines with balanced injection and intense wall conditioning with Ti gettering. This value is the highest # value realized so far in helical systems. Reheat mode, where the stored energy increases after turn-off of a strong gas puff, is employed in the experiment. Discharge conditions are as follows: B t = 0.61 T; beam power through the port, 1.1 MW (coinjection) and 0.8 MW (counterinjection); line-averaged electron density/']e = 6.5 x 1013 cm -3. Amplitudes of magnetic fluctuations integrated over the frequency range from 3 kHz to 100 kHz become saturated at (/3¢q) higher than 1%. Dominant coherent modes are m/n = 2/1 and 1/1 when (#eq) is lower and higher respectively than 1%. Dependence of the energy confinement time r E on/']e (up to 8 X l013 cm -3) and B t (from 0.6 to 1.ST) is also studied in this high # experiment. When the density increases rE degrades compared with the LHD scaling; the density dependence exhibits Bohm-like behaviour. On the contrary, rE scales as Bt °-75, which is rather close to the LHD scaling (gyro-Bohm-like behaviour).