Al丝物理状态调控及对芯晕演化特性的影响

基于快直线脉冲变压器(FLTD)平台开展了数十kA电流下Al单丝芯晕演化特性研究，实验发现丝过早发生电压击穿会减少丝芯的能量沉积，而晕等离子体的迅速发展将约束丝芯的进一步膨胀，降低丝芯膨胀速度。通过调整负载两端的初始电压、丝长及增加闪络开关等手段，抑制了Al丝的过早击穿，增加了早期能量沉积，获得了不同的丝芯物理状态（部分气化或完全气化）。Al丝的气化提高了丝芯膨胀速度，最高达11~14 km/s，晕等离子体发展缓慢，延缓了边界处不稳定性的出现，降低了后期m=0的发展速度。FLTD负极性输出时，Al丝沿轴向的极性效应更加明显，靠近阴极处丝芯膨胀慢，边界处晕等离子体密度高，不稳定性的发展速度快。

Regulation of Physical State of Aluminum Wire and Effect on Evolution of Core-corona Structure

The core-corona evolution of single aluminum wire was studied based on fast linear transformer driver (FLTD) with dozens of kilo-ampere current. It is found that premature breakdown of the wire can reduce the deposited energy. The rapid development of the coronal plasma can restrain further expansion of the wire core and weaken the expansion rate. By adjusting the initial voltage across the load and wire length, and inserting the flashover switch at high voltage electrode, the premature breakdown was suppressed and different physical states of wire core (partially vaporized or completely vaporized) were obtained with substantial improvement of the deposited energy. The vaporization of aluminum atoms obviously increases the expansion rate of wire core (up to 11-14 km/s) and the coronal plasma develops slowly after the ionization of vaporized atoms at the boundary, which delays the occurrence of instability and decreases the development of m=0 instability at later stage. The polarity effect of aluminum wire core along the axis is more obvious with the negative output of FLTD. The expansion rate of wire core is slower near the cathode with a higher coronal plasma density at the boundary and the development of instability is faster.