| Project/Area Number |
12480115
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
プラズマ理工学
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| Research Institution | The University of Tokyo |
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Principal Investigator |
ONO Yasushi High Temperature Plasma Center, Associate Professor, 高温プラズマ研究センター, 助教授 (30214191)
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| Co-Investigator(Kenkyū-buntansha) |
KATSURAI Makoto Graduate School of Frontier Sciences, Professor, 大学院・新領域創成科学研究科, 教授 (70011103)
ISHIDA Akio Niigata University, Graduate School of Sciences, Professor, 理学部, 教授 (30108013)
NAGAYAMA Yoshio National Institute for Fusion Science, Plasma Diagnostics Division, Associate Professor, プラズマ計測研究系, 助教授 (10126138)
ITAGAKI Tshifumi Graduate School of Engineering, Research Assistant, 大学院・工学系研究科, 助手 (60242012)
HAYASHIYA Hitoshi Graduate School of Frontier Sciences, Research Assistant, 大学院・新領域創成科学研究科, 助手 (80313013)
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| Project Period (FY) |
2000 – 2001
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| Keywords | Spherical Tokamak / Field-Reversed Configuration / Second Stability / Ballooning Instability / Plasma Merging / Magnetic Reconnection / Absolute Minimum B Configuration / Dimagnetism |
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| Research Abstract |
Novel CS(center solenoid)-less formations of ultra-high-beta Spherical Tokamaks (ST) have been developed in the TS-3 and TS-4 merging experiment using high power heating of magnetic reconnection. In Type-A merging, two STs were merged together to build up the plasma beta up to β_T【approximately equal】0.5. High power heating of reconnection transformed the low-beta merging STs into a high-beta ST within a short reconnection time. In Type-B merging, an oblate FRC was first formed by two merging spheromaks with .opposing toroidal field, and was transformed into an ultra-high-beta (β-_r【approximately equal】0.8) ST by applying external toroidal magnetic field. The ultra-high-beta STs by Type-B merging were found to have diamagnetic toroidal field and absolute minimum-B type configurations. We made (1) the BALLOO code stability analyzes of the produced STs for the first time and concluded formations of the first-stable / marginally ined ballooning-stable regime was almost consistent with measured high-n instabilities. The unstable STs by both merging formations suffered from high-n magnetic fluctuation and disrupted within a 10-30 Alfven time. Our experimental observation identified the ballooning stability window consistent with measured high-n instabilities. The stable regime became larger significantly by increasing the hollowness of current profile and broadness of pressure profile. This paper also addresses (2) normalized betas β_N of thus produced STs as large as 6-17 for comparison with the Troyon scaling and (3) a promising B^2 scaling of the reconnection heating. Those facts indicate that the axial merging is one of the most efficient startup methods for high-beta STs without powerful CS.
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