Control of the Translation Velocity and Position on a Field Reversed Configuration

在场反转位形平移实验中，为了控制反射的回弹系数，使等离子体在短时间内不反弹，可以通过被动和主动两种方法控制平移速度和等离子体位置。平移等离子体产生的外加磁场在金属衬里上产生脉冲感应电流。脉冲磁场作用于FRC等离子体。诱导力取决于金属调谐器的电阻、等离子体半径与衬里半径之比。用0.005ms皮肤时间的金属衬里稳定3 mg的氦等离子体，平移速度为10 km/S，在平移区安装脉冲磁场线圈。脉冲电流从电源提供给脉冲线圈，使等离子体运动同步。通过控制当前值和当前…更多的形式，等离子体被反射和稳定下来。在40kA的脉冲电流和0.01ms的上升时间下，40 Km/S的FRC等离子体被反射并依波形稳定下来。这些实验结果与基于系统能量守恒和刚体的简单计算机模拟的结果一致。从禁闭场场梯度的角度重新考虑了对n=1模运动的控制。负场梯度会抑制运动。研究表明，具有较高分离线伸长率的等离子体更有利于减小波幅。N=1模的运动是由于等离子体周围的限制场有一个小的负梯度。为了产生高度拉长的等离子体，在装置中安装了辅助导体。观察到的n=1模运动的幅度被控制在没有任何辅助导体的一半左右，这从磁结构上得到了很好的解释。研制了60通道可见光诊断系统和多路单圈排除测量系统。通过磁学测量和光学测量相结合的方法，阐明了磁场和等离子体结构与开场线区的关系，如等离子体的β值、边缘层深度以及n=1模运动时的非对称压力分布。通过将测量的磁通量与Grad-Shafrov方程进行比较，确定了场反转组态(FRC)等离子体的分界线形状和内部结构。这一分析还提出了边缘层等离子体的宽度w^*r_i(w是离子回旋半径r_i的个数)，分界线上的β值(B_S)，以及零场附近磁岛的形成。为了用磁法证实这些发现，测量了FRC的辐射功率密度。结果表明，w和b_S的值与辐射测量结果吻合较好。然而，磁岛的位置与辐射强度等值线图上出现的位置不一致。对于压力恒定面的非同心性，还讨论了辐射的不对称分布。当纤维混凝土中心移动0.1-0.2r_S(r_S为分界线半径)时，测量的轮廓可以解释，而分界线表面不发生任何移动。较少

The translation velocity and the plasma position in translation experiments of a field reversed configuration are controlled by passive and active methods in order to control a rebound co-efficient of the reflection and to reset the plasma in short period without bouncingIn the passive method, a resistive metal liner is installed in the region. A pulsed inductive current is induced on the metal liner by the excluded magnetic field due to the translation plasma. The pulsed magnetic field is applied on the FRC plasma. The induced force is dependent on the resistance of the metal Tuner, ratio of the plasma radius to the liner radius. Deuterium plasma of 3mg with the translation velocity of 10km/s is settled down by a metal liner of 0.005ms skin time.In active method, the pulsed magnetic field coil, installed in the translation region. The pulsed current is supplied to the pulse coil from the power supply, synchronizing the plasma motion. By the control of the current value and the current … More form, the plasma is reflected and settled down. By the pulsed current of 40kA and the rising time of 0.01ms, the FRC plasma with 40km/s is reflected and settled down in dependent of the wave form. These experimental results agree with that of a simple computer simulation, which is based on energy conservation of system and with a rigid body.The control of n=1 mode motion is reconsidered from the point view of the field gradient of the confinement field. A negative field gradient suppresses the motion. The investigation suggests that the plasma having high separatrix elongation is preferable for reducing the amplitude of. the n=1 mode motion because of a small negative gradient of the confinement field around the plasma. In order to produce highly elongated plasmas, auxiliary conductors are installed into a device. The observed amplitudes of the n=1 mode motion are controlled to about a half level of those without any auxiliary conductors, which is explained well from the magnetic structure.Several plasma diagnostic for the internal structure have been improved. 60 channel visible optical diagnostic system and multi one turn excluded measurement system are developed. By the combining of the magnetic measurement and the optical measurement, magnetic field and plasma structure with the open field line region, for example, plasma beta value and the depth of edge layer and the asymmetrical pressure profile with the n=1 mode motion are clarified. Separatrix shapes and internal structures of field-reversed configuration (FRC) plasmas are determined by comparing the measured magnetic fluxes with the Grad-Shafranov equation. This analysis also suggests a width of an edge-layer plasma w^*r_i (w is the number of ion gyro-radius r_i), a beta value at the separatrix (b_s), and the formation of magnetic islands near the field null. In order to confirm these findings by the magnetic method, a radiation power density of the FRC is measured. It is found that the w and b_s, values agree well with those obtained by the radiation measurement. However, the positions of the magnetic islands do not coincide with those appearing in an intensity contour map of the radiation. Asymmetrical profiles of the radiation are also discussed with respect to the nonconcentricity of the pressure constant surface. The measured profiles can be explained when the center of the FRC is shifted by 0.1-0.2r_s (r_s is a separatrix radius) without any shift of the separatrix surface. Less