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<專題討論>2019/3/5(二)13:10綜合大樓2樓48218教室演講 : Prof. Michiaki Inomoto(Graduate School of Frontier Sciences, The University of Tokyo, Japan)

張貼者:2019年2月26日 下午6:59Dabby Lu   [ Ann-Chen Jang 已於 2019年2月26日 下午6:59 更新 ]
講題:Torus Plasma Experiment for Exploring Application of Magnetic Reconnection Process on Fusion Plasma
摘要:Magnetically confined torus plasma is a potential candidate as a core plasma of a nuclear fusion reactor. Tokamak-type configuration has shown high performances on plasma confinement, stability, and controllability, and the world’s largest tokamak device ITER is under construction through international cooperation. However, tokamak’s low beta (= plasma pressure / magnetic pressure) limit requires expensive construction cost of fusion power plant. Since lowering the aspect ratio (= major radius / minor radius) of tokamak-type plasma will bring about improvement on the beta limit, “spherical tokamak (ST)”, which is a variety of tokamak configuration with aspect ratio lower than 2, attracts attention and is considered to be a potential cost-effective fusion core plasma. 

The ST concept has difficulty in initial plasma start-up because of its limited space near the geometrical axis. Thus, the center solenoid coil, which is employed in tokamak-type device to drive initial plasma current and to provide initial heating, must be removed or downsized in ST device. Center-solenoid-free start-up methods are investigated in many experimental devices, but the achieved plasma has not satisfied the plasma parameter such as plasma current, density and electron temperature required for a target plasma for additional heating.

Axial merging method is one of the candidates to provide center-solenoid-free start-up of high-beta ST plasma, in which two initially formed STs merge through magnetic reconnection in the presence of the guide (toroidal) magnetic field, which is perpendicular to the reconnection (poloidal) magnetic field. Magnetic reconnection between two STs is capable of heating the electrons in the vicinity of the reconnection point, however, its mechanism has not been identified in laboratory experiments yet. During ST merging start-up, electrons are effectively accelerated near the reconnection point where the reconnection electric field is approximately parallel to the magnetic field and will provide the local electron heating. Recent experimental results from soft X-ray observation in the UTST experiment show transient generation of energetic electrons accelerated along the field line during reconnection.  

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Ann-Chen Jang,
2019年2月26日 下午6:59
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