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Fusion Science and Technology
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A more open future for nuclear research
A growing number of institutional, national, and funder mandates are requiring researchers to make their published work immediately publicly accessible, through either open repositories or open access (OA) publications. In addition, both private and public funders are developing policies, such as those from the Office of Science and Technology Policy and the European Commission, that ask researchers to make publicly available at the time of publication as much of their underlying data and other materials as possible. These, combined with movement in the scientific community toward embracing open science principles (seen, for example, in the dramatic rise of preprint servers like arXiv), demonstrate a need for a different kind of publishing outlet.
Masami Fujiwara, Nobuyoshi Ohyabu, Keisuke Matsuoka, Shoichi Okamura, Osamu Motojima, Tokuhiro Obiki, Fumimichi Sano, Katsumi Kondo, Masahiro Wakatani, Tohru Mizuuchi, Kiyoshi Hanatani, Yuji Nakamura, Kazunobu Nagasaki, Hiroyuki Okada, Sakae Besshou, Masahiko Nakasuga
Fusion Science and Technology | Volume 42 | Number 1 | July 2002 | Pages 32-49
Technical Paper | doi.org/10.13182/FST02-A211
Articles are hosted by Taylor and Francis Online.
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 ~14 MW. The LHD achieved the maximum stored energy Wp dia of > 1 MJ, the maximum value of the volume averaged beta <dia*gt; of >3.0% at B of 0.5 T, high confinement time E of 0.3 s at Te(0) of 1.1 keV and <ne> of 6.5 × 1019 m-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 <ne> of ~4 to 5 × 1019 m-3, Te(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 Wp ~ 0.7 kJ and <> ~ 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.
