A SEQUENTIAL PLASMA-FOCUS

Recent shadowgraph studies suggest that a target disc placed downstream of the anode of a plasma focus may become an auxiliary anode producing a second focusing event when the current sheet climbs over it after the first focus event. A model is set up, with each event assumed to comprise three phases: an axial phase, a radial phase, and a radial extension or expanded column phase. This model is seen to produce the current dip, voltage spike, and high radial speeds characteristic of a plasma focus. With two separated discs acting as auxiliary anodes downstream of the usual anode, there are now three focus events with nine phases in the computation. The equations are written in generalized form in terms of n, so that an equation, for example, applicable to the first axial phase (nA, n = 1), is also applicable to the second (nA, n = 2) and third axial phase (nA, n = 3) by putting n = 1, 2, 3 successively in the equation. The results of the model indicate that each anode produces sequentially the current dip, voltage spike, and high radial speeds characteristic of the plasma focus. These computations suggest the possibility and design of a sequential or cascading plasma focus.