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Formation and Stability of Oblate Field-Reversed Configuration Plasmas

扁圆场反构型等离子体的形成及其稳定性

基本信息

批准号：
12680495
负责人：
TAKAHASHI Tsutomu
金额：
$ 2.3万
依托单位：
Nihon University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

项目摘要

An oblate field-reversed configuration (FRC) is formed by a control of a mirror ratio and a magnetic field index of the confinement field of a negative biased theta-pinch (FRTP). An elongation of FRC plasmas decreases less than about 2.5 by the increase of the mirror ratio (1.8) and the field index (0.3). The field index is possible to contribute to the adjustment of a radial implosion strength and an axial contraction.An n=1 mode motion of FRC plasmas is investigated by using a mirror and a cusp configuration of the bias field of the FRTP. The n=1 motion reaches 20-40% of the plasma radius in the former bias configuration, although it is a low level in the latter configuration. It is experimentally confirmed that the violent n=1 motion can be controlled by a multipole field. A critical strength needed to push back the plasma to the equilibrium position is theoretically derived by using a simple model including a conductor effect of the wall and is compared with the experimental results. Both values agree within the experimental reproducibility. The critical field strength of which is required to be about 15% of the confinement field. It is found that the n=2 rotational instability can also be stabilized by the same order.Several diagnostics for the n=1 motion, a plasma shape and an internal plasma structure are a newly developed. Optical diagnostics is developed for the n=1 motion. A plasma shape diagnostic by a diamagnetic measurement is improved. It is found that the plasma shape can be determined by solving a Grad-Shafranov equation iteratively. The boundary condition is the measured magnetic flux and magnetic field strength. The initial value is the plasma shape of the diamagnetic method. A plasma cross-sectional view can be observed by a CCD camera with fast-gated image intensifier

通过控制镜面比和负偏置缩紧（FRTP）约束场的磁场指数，形成了扁圆场反转构型（FRC）。随着反射比（1.8）和场指数（0.3）的增加，FRC等离子体的伸长率下降小于2.5。现场指数可能有助于调节径向内爆强度和轴向收缩。利用反射镜和FRTP偏置场的尖峰结构研究了FRC等离子体的n=1模运动。在前一种偏置配置中，n=1运动达到等离子体半径的20-40%，而在后一种配置中则是一个较低的水平。实验证实了多极场可以控制剧烈的n=1运动。利用一个包含壁面导体效应的简单模型，从理论上推导出了将等离子体推回到平衡位置所需的临界强度，并与实验结果进行了比较。这两个值在实验重现性上是一致的。其临界场强要求约为约束场的15%。结果表明，n=2的旋转不稳定性也可以被同一阶稳定。对n=1运动、等离子体形状和等离子体内部结构的几种诊断是最近发展起来的。对n=1运动进行了光学诊断。改进了用抗磁测量法诊断等离子体形状的方法。发现等离子体的形状可以通过迭代求解Grad-Shafranov方程来确定。边界条件为实测磁通量和磁场强度。初始值为抗磁法的等离子体形状。用带快速门控图像增强器的CCD相机可以观察到等离子体的横切面