Transportation properties of a high-current magnetically insulated transmission line and dynamics of the electrode plasm
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YNAMICS
Transportation Properties of a High-Current Magnetically Insulated Transmission Line and Dynamics of the Electrode Plasma S. S. Anan’eva, Yu. L. Bakshaeva, A. V. Bartova, P. I. Blinova, S. A. Dan’koa, A. I. Zhuzhunashvilia, E. D. Kazakova, Yu. G. Kalinina, A. S. Kingsepa, V. D. Koroleva, V. I. Mizhiritskiia, V. P. Smirnova, S. I. Tkachenkob, and A. S. Chernenkoa a Russian
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Research Centre Kurchatov Institute, pl. Kurchatova 1, Moscow, 123182 Russia Institute for High Energy Densities, Joint Institute for High Temperatures, Russian Academy of Sciences, Izhorskaya ul. 13/19, Moscow, 127412 Russia Received September 12, 2007; in final form, November 2, 2007
Abstract—Results are presented from experimental studies of a section of a magnetically insulated transmission line (MITL) with a current density of up to 500 MA/cm2 and linear current density of up to 7 MA/cm (the parameters close to those in a fast-Z-pinch-driven fusion reactor projected at Sandia Laboratories). The experiments were performed in the S-300 facility (3 MA, 0.15 Ω, 100 ns). At high linear current densities, the surface of the ohmically heated MITL electrode can explode and a plasma layer can form near the electrode surface. As a result, the MITL can lose its transmission properties due to the shunting of the vacuum gap by the plasma produced. In this series of experiments, the dynamics of the electrode plasma and the dependence of the transmission properties of the MITL on the material and cleanness of the electrode surface were studied. It is shown experimentally that, when the current with a linear density of up to 7 MA/cm begins to flow along a model MITL, the input and output currents differ by less than 10% over a time interval of up to 230 ns for nickel electrodes and up to 350 ns for a line with a gold central electrode. No effect of the oil film present on the electrode surface on the loss of the transmission properties of the line was observed. It is also shown that electron losses insignificantly contribute to the total current balance. The experimental results are compared with calculations of the electrode explosion and the subsequent expansion of the plasma layer. A conclusion is made that the lifetime of the model MITL satisfies the requirements imposed on the transmission lines intended for use in the projected thermonuclear reactor. PACS numbers: 52.59.Mv, 84.70.+p DOI: 10.1134/S1063780X08070064
1. INTRODUCTION This work is a continuation of our previous experimental studies [1] performed at the Russian Research Centre Kurchatov Institute. These experiments were initiated in the context of the conceptual project of a Z-pinch-driven fusion reactor proposed at Sandia Laboratories [2]. A key issue of the project is the use of replaceable magnetically insulated transmission lines (MITLs). MITLs are traditionally used to transport energy in different types of high-current high-power pulsed generators, and their properties have been thoroughly studied both experimentally and theoretically [3]. However, in [2], it is proposed to
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