Magnetohydrodynamics of Metallic Foil Electrical Explosion and Magnetically Driven Quasi-Isentropic Compression

Abstract

The electrical explosion of conductors, such as metallic foils and wires, refers to rapid changes of physical states when the large pulsed current (tens or hundreds of kA or more, the current density j106 A/cm2) flows through the conductors in very short time(sub microsecond or several microseconds), which may produce and radiate shock waves, electrical magnetic waves, heat and so on. There are many applications using some characteristics of the electrical explosion of conductors. The Techniques of metallic foil electrical explosion had been developed since 1961, which was first put forward by Keller, Penning[1] and Guenther et al[2]. However, it develops continually until now because of its wide uses in material science, such as preparation of nanometer materials and plating of materials[3,4], shock wave physics[5-7] , high energy density physics[8] and so on. Especially the techniques of metallic foil electrically exploding driving highvelocity flyers, are widely used to research the dynamics of materials, hypervelocity impact phenomena and initiation of explosives in weapon safety and reliability. Therefore, in this chapter we focus on the physical process of metallic foil explosion and the techniques of metallic foil electrically exploding driving highvelocity flyers. Here the explosion of metallic foils are caused by the large current flowing through in sub microsecond or 1~2 microsecond or less. During the whole physical process, not only does the temperature rising, melting, vaporizing and plasma forming caused by instantaneously large current, but also the electrical magnetic force exists and acts on. Because the whole process is confined by rigid face and barrel, and the time is very short of microsecond or sub microsecond or less, and the phynomena is similar to the explosion of explosives, we call the process electrical explosion of metallic foils. This process is a typically hydrodynamic phenomena. It is also a magnetohydrodynamic process because of the exist and action of the magnetic force caused by large current and self-induction magnetic field. Magnetically driven quasi-isentropic compression is an relatively new topic, which was developed in 1972[9]. At that time the technique of magnetically driven quasi-isentropic compression was used to produce high pressure and compress the cylindrical sample materials. Until 2000, the planar loading technique of magnetically driven quasi-isentropic