Research Activities for the Plasma Confinement of Helical Configurations (Large Helical Device, Compact Helical System, and Heliotron J) in Japan

Journal Article · Mon Jul 15 04:00:00 EDT 2002 · Fusion Science and Technology

OSTI ID:20845835

Fujiwara, Masami ^[1]; Ohyabu, Nobuyoshi ^[1]; Matsuoka, Keisuke ^[1]; Okamura, Shoichi ^[1]; Motojima, Osamu ^[1]; Obiki, Tokuhiro ^[2]; Sano, Fumimichi ^[2]; Kondo, Katsumi ^[2]; Wakatani, Masahiro ^[2]; Mizuuchi, Tohru ^[2]; Hanatani, Kiyoshi ^[2]; Nakamura, Yuji ^[2]; Nagasaki, Kazunobu ^[2]; Okada, Hiroyuki ^[2]; Besshou, Sakae ^[2]; Nakasuga, Masahiko ^[2]

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1. National Institute for Fusion Science (Japan)
2. Kyoto University (Japan)

Experimental results are summarized for major helical devices in Japan: Large Helical Device (LHD), Compact Helical System (CHS), and Heliotron J. The LHD and CHS have planar magnetic axes, while Heliotron J has a nonplanar magnetic axis.The LHD, the largest superconducting device in the world, has the following machine parameters: major radius R of 3.9 m, average minor radius a of 0.6 m, magnetic field on axis B of 3 T, multipolarity l of 2, toroidal period number m of 10, and auxiliary heating power P of {approx}14 MW. The LHD achieved the maximum stored energy W{sub pdia} of > 1 MJ, the maximum value of the volume averaged beta <{beta}{sub dia}*gt; of >3.0% at B of 0.5 T, high confinement time {tau}{sub E} of 0.3 s at T{sub e}(0) of 1.1 keV and <n{sub e}> of 6.5 x 10{sup 19} m{sup -3}, and long pulse operations up to 120 s at high temperature.The CHS has the following machine parameters: R = 1 m, a = 0.2 m, l = 2, and m = 8. The parameters of neutral beam heated plasmas are in the range with <n{sub e}> of {approx}4 to 5 x 10{sup 19} m{sup -3}, T{sub e}(0) of 500 to 700 eV, and energy confinement time of several milliseconds. Progress has been made in studies of bifurcation phenomena of electric potential, neoclassical internal transport barriers, and plasma flows in the toroidal and poloidal directions.The most important achievement from recent CHS and LHD experiments is to realize the internal transport barriers on the basis of potential bifurcation.Heliotron J, which was converted from the Heliotron E (H-E) device, employs a helical magnetic axis by the use of l = 1 continuous helical coil and auxiliary coils such as poloidal and toroidal coils. The machine parameters are as follows: R = 1.2 m, a = 0.1 to 0.2 m, and B = 1 to 1.5 T. Initial results show the maximum stored energy W{sub p} {approx} 0.7 kJ and <{beta}> {approx} 0.2%.The range of plasma parameters has been greatly expanded by the LHD, CHS, H-E, and Heliotron J experiments. The confinement data in helical devices are scaled empirically as ISS-95 (International Stellarator Scaling), and plasma performance is comparable with that in tokamaks.

• OSTI ID: 20845835
• Journal Information: Fusion Science and Technology, Journal Name: Fusion Science and Technology Journal Issue: 1 Vol. 42; ISSN 1536-1055
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
AUXILIARY HEATING
BIFURCATION
CHS TORSATRON
CONFINEMENT TIME
ELECTRIC POTENTIAL
EV RANGE
HELICAL CONFIGURATION
HELIOTRON
JAPAN
KEV RANGE
LHD DEVICE
MAGNETIC FIELDS
NEOCLASSICAL TRANSPORT THEORY
PLASMA
PLASMA CONFINEMENT
STORED ENERGY
SUPERCONDUCTING DEVICES
TOKAMAK DEVICES