Formation and Stability of Oblate Field-Reversed Configuration Plasmas

通过控制负偏置theta箍缩(FRTP)的限制场的镜比和磁场指数，形成了扁平场反转位形(FRC)。随着镜面比(1.8)和场折射率(0.3)的增大，FRC等离子体的伸长率减小不到2.5。场折射率可能有助于径向内爆强度和轴向收缩的调节。利用FRTP偏置场的反射镜和尖点结构，研究了FRC等离子体的n=1模运动。在前一种偏置构型中，n=1运动达到等离子体半径的20-40%，而在后一种构型中，n=1的运动水平较低。实验证实，n=1的剧烈运动可以由多极场控制。利用考虑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。这两个值都在实验重现性范围内。其临界场强要求约为禁闭电场的15%。结果表明，n=2转动不稳定性也可以以相同的级数稳定。对n=1运动、等离子体形状和内部等离子体结构的几种诊断方法是一种新的发展。发展了n=1运动的光学诊断。改进了通过抗磁测量来诊断等离子体形状的方法。结果表明，可以通过迭代求解Grad-Shafrov方程来确定等离子体的形状。边界条件是测量的磁通量和磁场强度。初始值是抗磁法的等离子体形状。用带快选通像增强器的ccd相机可以观测到等离子体的横截面。

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