Time-Varying Inductance of the Plasma Sheet in the PF1000 Plasma-Focus Device

Abstract

The time-varying inductance Lp(t) of the system formed by the coaxial electrodes and the current sheet (CS) in plasma focus (PF) discharges was calculated for the first time by Mather and Bottoms [1] on a 13-kJ PF device in Los Alamos using measured values of V(t) , the voltage at the breach end of the electrodes, and dI/dt, the time derivative of the current circulating through the system. Recently, the same method was applied to assess Lp(t) in devices of lower energy [2]–[4]. This physical magnitude was also used for estimating other relevant parameters, like the voltage drop over the pinch column [5], [6]. The purpose of this paper is to extend this procedure to the high-energy device PF1000, operated by the International Center for Dense Magnetized Plasmas (ICDMP) from Warsaw, Poland, using measurements performed during an experimental campaign conducted in 2013. High-energy devices as PF1000, besides having much larger capacitor banks, also has larger electrodes, which leads to larger gun inductances and consequently higher voltage drops in the pinch. Hence, the goal of the present study is to validate the application of the mentioned technique in large PF devices and also to produce additional information, namely, the behavior of the voltage drop over the pinch plasma column.