Effect of targets on plasma focus dynamics

Shadowgraphs were taken of a 3-kJ plasma focus in the presence of a flat disc target placed downstream of the anode and a 1-mm wire target inserted along the axis at the anode. It was found that: (i) the flat disc target does not affect the dynamics of the focus proper when it is placed downstream at a distance greater than the anode radius; (ii) the current sheet moves over the disc and forms a pinch beyond it as though the disc had become a new anode; and (iii) the plasma focuses strongly onto a 1-mm wire on-axis. These observations may be used to design beam-target experiments in a plasma focus machine. They indicate the possibility of focus-fiber experiments, and also raise the possibility of and indicate the guidelines for designing a sequential focus device