Study of the Time Dependence of the Plasma Formation Intensity at the Current Implosion of Cylindrical Wire and Fiber Arrays from Different Substances

A characteristic feature of the implosion of multiwire arrays on powerful high-current electrophysical facilities (ZR, Angara-5-1, Julong-1 (PTS), MAGPIE, etc.) is the process of extended wire ablation. It is based on the fact that the substance of the wires is not converted into plasma instantly, but is supplied into the discharge relatively slowly at the rate $$\dot {m}(t)$$ in about 70–80% of the rise time of the facility current. It is believed that the plasma is formed on the surface of the cores of the exploded wires due to the energy coming from the hot plasma corona surrounding the core of the wire in the form of the heat flux and emission. In this paper, we propose a new approach to determining the quantity $$\dot {m}(t)$$ as the main quantitative characteristic of the process of the extended wire ablation in wire (or fiber) arrays. A method is presented, using which it is possible to determine experimentally the time dependence of the quantity $$\dot {m}(t)$$ both at the initial stage of the plasma formation and at its final stage, when $$\dot {m}(t)$$ → 0. In fact, by measuring the current Ip with a magnetic probe located inside the wire array near the surface of the wires, it is possible to find the current flowing in the plasma formation region Is as the difference between the total current through the liner and the current Ip. The time dependence Is(t) thus defined is nonmonotonic, and the quantity $$\dot {m}(t)\sim I_{s}^{2}\left( t \right)$$ correspondingly decreases at the final stage of the implosion of the wire array. The intensity of the plasma formation of arrays made form wires and fibers of different substances (Al, Cu, Mo, W, Bi, and kapron) was determined in experiments at the Angara-5-1 facility, the decay rate of this quantity at the stage of the plasma formation termination and its effect on the pulse and emission parameters were analyzed. The obtained results are compared with the data of the numerical MHD simulation.