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Formation of Field Reversed Configuration Plasma with Toroidal Magnetic Field

用环形磁场形成场反构型等离子体

基本信息

批准号：
63580015
负责人：
TAKAHASHI Tsutomu
金额：
$ 1.22万
依托单位：
Nihon University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1988
资助国家：
日本
起止时间：
1988 至 1989
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-63580015/
关键词：
Field Reversed Configuration Toroidal Field Axial Alternating Current Amplification of Bias Flux Stabilization of Rotational Instability Fluctuating Magnetic Field Dipole Current Quadrupole Current 逆転磁場配位プラズマ動的安静化バイアス磁場の増幅多重極電流

项目摘要

The application of an axial current was proposed to form a field reversed configuration (FRC) plasma with a toroidal magnetic field. Effects of the axial current and threshold values of a successful FRC formation and confinement were investigated by NUCTE-3. Various frequencies (<=4.7x10^5rad/s) and amplitudes(<=6OkA) of axial currents were examined. In the formation phase, two effects were clarified ;(1) heating of the embedded plasma in the bias field (2) amplification of bias flux. In the confinement phase, the effect of stabilization of rotational instability were clarified. Though the kink instability was excited by a large axial current in both phases, it was confirmed that the instability can be avoided by using alternating current. Threshold value of the formation phase seemed to have relation with the poloidal flux limitation of a FRC formation and disturbances of preheating plasma and bias field. The stabilizing current value is almost the same as the theoretical value. But the frequency was not so high to suppress the kink mode.A FRC plasma is usually considered as an elongated compact toroid that contains no toroidal field. But an azumuthal fluctuating magnetic field was observed by magnetic probes located on the surface of the discharge tube. The Fourier analysis of the signals showed that the n=1 mode was kept at a small level throughout the discharge but the n=2 mode grew with onset of the rotational in- stability. Current distributions should be a dipole axial current for n=1 mode and a quadrupole axial current for n=2 mode, both of which are symmetrical to the axial mideplane of FRC plasma. The mechanism of the quadruple current generation was explained from the both effects of charge separation by centrifugal force and end shortening of the charge. The dipole current seemed to generate due to a plasma motion in the confining field.

提出了在环形磁场作用下，利用轴向电流形成场反转位形等离子体的方法。利用NUCTE-3研究了轴向电流和阈值对FRC成功形成和约束的影响。检测了轴向电流的各种频率（<= 4.7 × 10^5rad/s）和振幅（<= 60 kA）。在形成阶段，阐明了两种效应：（1）在偏置场中嵌入等离子体的加热（2）偏置通量的放大。在约束阶段，阐明了转动不稳定性的稳定化作用。虽然扭结不稳定性激发了一个大的轴向电流在两个阶段，它被证实，可以避免不稳定性，通过使用交流电。形成相的阈值似乎与FRC形成的极向通量限制以及预热等离子体和偏压场的扰动有关。稳定电流值与理论值基本一致。FRC等离子体通常被认为是一个不含环向场的细长紧凑环。但是，通过位于放电管表面的磁探针观察到了一个azumuthal波动磁场。信号的傅立叶分析表明，n=1模式在整个放电过程中保持在一个小的水平，但n=2模式随着旋转不稳定性的开始而增长。对于n=1模，电流分布应是偶极轴向电流，而对于n=2模，电流分布应是四极轴向电流，这两种电流都对称于FRC等离子体的轴向中面。从离心力分离电荷和电荷端部缩短两方面解释了四倍电流产生的机理。偶极电流似乎是由于等离子体在约束场中的运动而产生的。