Effect of Substrate Thickness on Exploding Films

Abstract

Abstract-The exploding wire phenomenon is well researched due to its vast and practical applications which include, but are not limited to, shock wave generation, pulsed power, Z pinch physics, plasma ignition, fuses, and fusing applications. However, the focus of this research is on a surrogate for exploding wires. In this research, metallized capacitor gradepolypropylene film was used as an alternative for the traditional wire of a uniform diameter. The films that were studied have a broad variety of thicknesses ranging from 7 micron to 5 mil, lengths ranging from 5.08 cm to 19.05 cm, and sheet resistances of 1 ohm/square and 7 ohms/square. These films were used to study the effect of film properties on the transient plasma generation mechanism when exposed to a rapid high voltage discharge. The effect of these properties can be seen in the current waveform, similar to that of a uniform diameter exploding wire. By precisely understanding how the film properties affect the transient plasma formation, one can fine tune these variables to control the resulting characteristic pulse wave shape to fit a desired application.

Geometrical effects of exploding film on plasma formation

“…The total duration refers to the time interval that includes the initiation of the initial current strike, the dwell time, the re-strike, and concludes when the plasma is quenched and the current returns to 0 A. A relationship has been established between film length and total duration where the total duration increased with an increase in film length [1]. There did not seem to be a discernable relationship to the film's geometry.…”

“…During this transition the pressure drops, the mean free path between collisions increases, and ionization by impact with attendant avalanche occurs [3]. Testing done at the Energy Systems Institute has shown a relationship between film length and re-strike current in a flat geometry [1]. This phase of testing shows a relationship between the film's geometry and re-strike current where the width and length of the film are held constant.…”

“…The Energy Systems Institute, at the University at Buffalo, has electrically characterized the plasma properties of many different MPPFs of differing lengths and widths in a flat geometry [1]. An application was proposed where it would be necessary to substitute a comparatively longer piece of MPPF for an exploding wire.…”