Slow energy deposition in an exploding wire and plasma evolution for longer times than the electrical discharge time

Abstract

Plasmas are created by means of explosive systems in laboratories to explore plasma densities and temperatures not attainable in a controlled manner with other systems. Usually, when such systems are modelled, a key characteristic is the delivery of all the explosion energy in a time much shorter than the after explosion dynamic time. Therefore, systems where the whole energy delivery has a characteristic time of the order of the dynamical motion of resultant elements had received less attention in the scientific literature. In order to study this kind of systems, using an exploding wire experiment, first measurements of the late dynamics of its final plasma products had been made with iron, platinum and tungsten wires of a fixed length of ≈7 cm. Wires were surrounded by air and maximum current was on the order of kiloamperes, with a period of 5 μs. One framing camera with arbitrary waiting time between the 16 frames and a minimum of 5 nanoseconds acquisition time for imaging the wire expansion directly has been used to observe the shock wave radial expansion dynamics. Using the images acquired at later times from the frame camera, plasma evolution at a time much larger than time of the energy deposition at the wire are here presented for the first time.