Optical observation of the instability in microsecond gas-puff z-pinch plasmas

The occurrence of fluid instabilities in gas-puff z-pinch plasmas have been investigated using laser diagnostic systems. An interferometer system was employed to investigate the temporal evolution of the structure in the plasma column during the pinch. The z-pinch plasma was driven by a fast bank, which provided a current of 160 kA at 1.5 µs (T/4). Initially the plasma was formed in a conical shape due to the initial gas distribution. The plasma layer moved toward the z-axis and its shape gradually changed into columnar. The plasma layer splits into two layers on the way to implosion. The inner layer, which was indicated to be shock front, propagated toward the z-axis faster than the outer layer. The outer layer seemed quite smooth while the implosion by the inner layer took place at the z-axis. After the blast from the implosion expanded and came across the outer layer, the disturbance occurred at the outer layer. It is concluded that the plasma instability is significantly influenced by the shockwave rather than the initial gas formation in the case of a microsecond implosion.