トロイダルヘリアックの揺動に関する研究

概要

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The saturated state of density and space potential fluctuations has been studied in the electron cyclotron resonance heating (ECRH) plasma of the helical axis stellarator TU-Heliac using Langmuir probe techniques. These fluctuations are low-frequency and coherent. Mode structure are measured for two typical magnetic configurations having different rotational transform x. The result are: (i) a ratio of toroidal number n to poloidal number m is nearly equal to rotational transform x (x-n/m) ; (ii) k_<//> is very small as compared with k_⊥ (k_⊥/k_<//> = 40〜10000); (iii) a helicity of the fluctuations corresponds with the field line. Radial profile of fluctuation level and a relation between magnetic field strength and the frequency spectrum are measured experimentally. In particular the frequency spectrum are taken account of E X B plasma rotation. These experimental results are compared with four instability model (flute, ballooning, Kelvin-Helmholtz, and drift) . Consequently it is appeared that the collisional drift instability model is appropriate to explain the parameter dependence of the fluctuation in TU-Heliac. Cross field diffusion due to the fluctuation is roughly estimated and it is suggested that diffusion coeffilcient calculated from the fluctuation is more than half of the diffusion coefficient of ECRH plasma in TU-Heliac.
社団法人プラズマ・核融合学会の論文
1993-05-25