The dynamics of plasma and ejection characteristics of spheromaks produced by a magnetized coaxial plasma gun are studied. By placing three magnetic probes at various axial positions, the distribution of current paths in the gun is found to vary in two distinct discharge modes. During the first half-period of a discharge, the plasma moves forward in the form of a current sheet, while the diffuse distribution of current paths in the second half-period indicates a deflagration mode. The evolution images and photodiode signals of the plasma show that only a single spheromak is ejected during the entire discharge. This is because the diffuse current paths reduce the J × B Lorentz force on the leading-edge plasma, which cannot be ejected from the gun. In addition, the existence of kinks in the plasma flow in two discharge modes proves that the instability is driven by E r × B z drift, which causes rotation of the central column. Spheromak velocities increase linearly with discharge current amplitude but are inversely proportional to the gas puff mass. In ejected spheromaks, both toroidal and poloidal magnetic fields are axisymmetric, with field strength increasing with discharge current. During magnetic reconnection events, the toroidal electric field V z × B r drives toroidal current that generates an additional poloidal field that amplifies the starting magnetic field in the spheromak plasma. This study clarifies the relationship between the formation of a single spheromak and the current distribution, and also provides a new way to optimize the spheromak's injection performance.

中文翻译：

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磁化同轴等离子枪中无侧限球体及其电流路径研究

研究了由磁化同轴等离子枪产生的球体的等离子体动力学和喷射特性。通过在不同的轴向位置放置三个磁探针，发现枪中电流路径的分布在两种不同的放电模式下发生变化。在放电的前半周期，等离子体以电流片的形式向前移动，而在后半周期电流路径的扩散分布表明了爆燃模式。等离子体的演化图像和光电二极管信号表明，在整个放电过程中，只有一个球体被喷射出来。这是因为扩散电流路径降低了前沿等离子体上的 J × B 洛伦兹力，无法从枪中喷射出来。此外，两种放电模式下等离子体流中扭结的存在证明不稳定是由 E r × B z 漂移驱动的，这导致中心柱的旋转。Spheromak 速度随放电电流幅度线性增加，但与气体喷射质量成反比。在喷射球体中，环形和极向磁场都是轴对称的，场强随着放电电流而增加。在磁重联事件期间，环形电场 V z × B r 驱动环形电流，产生额外的极向场，放大球体等离子体中的起始磁场。该研究阐明了单个球体形成与电流分布之间的关系，也为优化球体注入性能提供了一种新方法。