Dynamics of mass transport and magnetic fields in low wire number arrays

Abstract

Summary form only given. Dynamics of mass transport were investigated in the implosion of low number wire arrays by multiframe laser probing diagnostics. It was observed that imploding plasma "bubbles" realize a mass transport in wire arrays. In the Zebra generator, bubbles were observed in all experiments with Al, Cu, Ti, and W loads. Multiframe laser diagnostics delivered fine details of implosion and material movement. Development of plasma bubbles from breaks in the wire core, movement to the axis, and collision with the precursor were investigated in Al and Cu 4-8-wire arrays. Interferometry shows that the leading edge of the bubbles brings material from wires to the axis. An implosion velocity of >3middot10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> cm/s was measured for the bubble leading edges. Four-frame shadowgraphy showed that material accelerated only in the beginning of the implosion because of current switch back to the gap in the wire. Faraday rotation indicates magnetic fields in wire gaps. The electron plasma density in the gap is ~10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">19</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> . Diagnostics shows current in jets extending from the bubbles to the precursor. Current switches to the precursor at the beginning of the X-ray pulse. The shape of the leading edge of a bubble during collision with the precursor could indicate a shock. The results are compared with experiments and models developed on the MAGPIE generator at Imperial College. Here the higher wire number and/or longer rise times can act to shield the precursor from current and may alter the current profile during the implosion