Effect of the axial magnetic field on a metallic gas-puff pinch implosion

The effect of an axial magnetic field B_z on an imploding metallic gas-puff Z-pinch was studied using 2D time-gated visible self-emission imaging. Experiments were performed on the IMRI-5 generator (450 kA, 450 ns). The ambient field B_z was varied from 0.15 to 1.35 T. It was found that the initial density profile of a metallic gas-puff Z-pinch can be approximated by a power law. Time-gated images showed that the magneto-Rayleigh-Taylor instabilities were suppressed during the run-in phase both without axial magnetic field and with axial magnetic field. Helical instability structures were detected during the stagnation phase for B_z < 1.1 T. For B_z = 1.35 T, the pinch plasma boundary was observed to be stable in both run-in and stagnation phases. When a magnetic field of 0.3 T was applied to the pinch, the soft x-ray energy was about twice that generated without axial magnetic field, mostly due to longer dwell time at stagnation.