Experimental verification of the technique for calculating a plasma opening switch and its matching to the load
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MA DYNAMICS
Experimental Verification of the Technique for Calculating a Plasma Opening Switch and Its Matching to the Load G. I. Dolgachev, D. D. Maslennikov, and A. A. Shvedov Russian Research Centre Kurchatov Institute, pl. Kurchatova 1, Moscow, 123182 Russia Received May 26, 2008
Abstract—A technique for calculating a plasma opening switch in an external magnetic field and its matching to a load the impedance of which increases with time was verified experimentally. The experiments were per formed in the RS20 facility both in the absence of a load and with various inductive loads. The amplitude of the voltage pulse at the input of the plasma opening switch was 0.36–0.84 MV, the current amplitude was 280–320 kA, and the pulse duration was ~2 µs, whereas the corresponding parameters of the output pulse were 0.8–3.2 MV, 0–240 kA, and ~100 ns. PACS numbers: 52.59.Mv, 52.75.Kq, 84.70.+p DOI: 10.1134/S1063780X09030040
1. INTRODUCTION Plasma opening switches (POSs) in a magnetic field produced by an external source were proposed at the Kurchatov Institute in 1986. Such POSs have a number of advantages as compared to those without an external magnetic field. Insulation of the POS gap by an external magnetic field allows one to reach the maximum possible output voltage, most efficiently (down to zero) break the current, and use a compact plasma bridge that expands slowly towards the load. It is proposed to use such a POS as an output power sharpener in a superpower generator (80 MA, 10 MV) that is intended for inertial confinement fusion exper iments and is currently being developed under the Baikal project [1]. The possibility of applying this POS scheme to sharpen the power of an explosive magnetic generator was considered in [2]. In the upgraded UIN10 highpower pulsed Xray generator, electri cally exploding wires will be replaced with a POS in an external magnetic field [3]. The great interest in apply ing POSs in highpower pulsed generators necessitates the development of a reliable technique for calculating POSs and their matching to nonlinear loads. Such a technique was developed based on vast amount of experimental data [4, 5] in [6], In [7], it was proposed to use an intermediate inductance (inductive load) to match the POS to a liner load the impedance of which is initially low and increases with time. In the present study, the POS parameters are calcu lated and measured experimentally, the POS matching scheme is considered, and the parameters of the input pulse are calculated. The calculated results are com pared with the experimental data. The experiments were performed in the RS20 facility [8].
2. CALCULATION OF A POS IN A LONGITUDINAL MAGNETIC FIELD FOR THE RS20 FACILITY The voltage UPOS developed at an erosion POS is determined by the energy density wi spent on ion acceleration (i.e., on plasma erosion) [9]: 4/7
UPOS ∝ w i
4/7
∝ W0 ,
(1)
where W0 is the energy stored in the capacitor bank of the Marx generator (MG). Since wi ∝ qU0, where q is the density of the charge transferred thorou
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