Experimental conditions for generation of space-charge limitation in atmospheric pressure non-thermal-equilibrium argon plasma

Abstract

The dependence of the charge of an atmospheric-pressure non-thermal-equilibrium argon plasma incident on a copper object under floating conditions was investigated. The plasma generation and propagation charges, which are the time integral of the current, were estimated from the power-line current and the current passing through a quartz tube from which the plasma was emitted, which was measured using a current monitor. The plasma generation and propagation charges increased with the surface area of the copper object. The phenomenon of space-charge limitation was confirmed from the dependence of the plasma charge on the surface area of the copper object. The drift velocity of the plasma charge was estimated based on the relationship between the difference in measurement times considering the positions of the current monitors. The charge flux was estimated from the plasma charge and its drift velocity. The charge flux was linearly proportional to the product of the square of the applied voltage and the surface area of the copper object. Consequently, from Gauss's law, it was clarified that space-charge limitation occurs when the sum of the charge flux and the product of the square of the applied voltage and the surface area of the copper object is excessive for the product of the constants of permittivity and electron mobility.