High β experiment and confinement regimes in a compact helical system

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. KawamotoS. Kubo, T. Kuroda, O. Motojima, T. Ozaki, V. D. Pustovitov, A. Sagara, C. Takahashi, K. Toi, T. Watari, I. Yamada

Research output: Contribution to journalArticle

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Abstract

A volume-averaged equilibrium β value 〈βeq〉 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 β 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: Bt = 0.61 T; beam power through the port, 1.1 MW (coinjection) and 0.8 MW (counterinjection); line-averaged electron density ne = 6.5 × 1013cm-3. Amplitudes of magnetic fluctuations integrated over the frequency range from 3 kHz to 100 kHz become saturated at 〈βeq〉 higher than 1%. Dominant coherent modes are m n = 2 1 and 1 1 when 〈βeq〉 is lower and higher respectively than 1%. Dependence of the energy confinement time τE on ne (up to 8 × 1013 cm-3) and Bt (from 0.6 to 1.8T) is also studied in this high β experiment. When the density increases τE degrades compared with the LHD scaling; the density dependence exhibits Bohm-like behaviour. On the contrary, τE scales as Bt≈0.75, which is rather close to the LHD scaling (gyro-Bohm-like behaviour).

Original languageEnglish
Pages (from-to)135-140
Number of pages6
JournalFusion Engineering and Design
Volume26
Issue number1-4
DOIs
Publication statusPublished - Jan 1 1995
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Civil and Structural Engineering
  • Nuclear Energy and Engineering
  • Materials Science(all)
  • Mechanical Engineering

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  • Cite this

    Matsuoka, K., Okamura, S., Nishimura, K., Tsumori, K., Akiyama, R., Yamada, H., Sakakibara, S., Lazaros, A., Xu, J., Ida, K., Tanaka, K., Morisaki, T., Morita, S., Arimoto, H., Ejiri, A., Fujiwara, M., Idei, H., Iguchi, H., Kaneko, O., ... Yamada, I. (1995). High β experiment and confinement regimes in a compact helical system. Fusion Engineering and Design, 26(1-4), 135-140. https://doi.org/10.1016/0920-3796(94)00178-A