Abstract
The progress in the understanding of the physics and the concurrent parameter extension in the large helical device since the last IAEA-FEC, in 2012 (Kaneko O et al 2013 Nucl. Fusion 53 095024), is reviewed. Plasma with high ion and electron temperatures (Ti(0) ∼ Te(0) ∼ 6 keV) with simultaneous ion and electron internal transport barriers is obtained by controlling recycling and heating deposition. A sign flip of the nondiffusive term of impurity/momentum transport (residual stress and convection flow) is observed, which is associated with the formation of a transport barrier. The impact of the topology of three-dimensional magnetic fields (stochastic magnetic fields and magnetic islands) on heat momentum, particle/impurity transport and magnetohydrodynamic stability is also discussed. In the steady state operation, a 48 min discharge with a line-averaged electron density of 1 × 1019 m−3 and with high electron and ion temperatures (Ti(0) ∼ Te(0) ∼ 2 keV), resulting in 3.36 GJ of input energy, is achieved.
Highlights
Simultaneous achievement of high electron (Te ) and ion temperature (Ti ) is one of the most important issues in nuclear fusion research
This study demonstrated that profile control is a key to combining the ion internal transport barrier (ITB) and the electron ITB
The location at which the spatial derivative in the Er structure (∇Er ) has a local maximum value move outwards from the vacuum last closed flux surface location as the volume-averaged plasma beta increases. This fact suggests that the magnetic topology, whether the magnetic field lines are open or closed can be distinguished by the radial structure of Er and the measurement of Er would be a useful tool to identify the topology near the plasma periphery when the resonant magnetic perturbation (RMP) is applied in tokamak plasmas
Summary
Overview of transport and MHD stability study : focusing on the impact of magnetic field topology in the Large Helical Device. The Graduate University for Advanced Studies, 322-6 Oroshi, Toki, Gifu 509-5292, Japan. Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-kouen, Kasuga, Fukuoka 816-8580, Japan. Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba-ken 277-8561, Japan. Radioscience Research Laboratory, Faculty of Science, Shizuoka University, 836 Oya, Suruga-ku, Shizuoka 422-8529, Japan. Plasma Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan. Graduate School of Engineering, Osaka University, 1-1 Yamadaoka, Suita, Osaka 565-0871, Japan. High ion and electron temperature plasma (Ti (0) ∼ Te (0) ∼ 6 keV) with simultaneous ion and electron internal transport barrier (ITB) is obtained by controlling recycling and heating deposition.
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