Observations on the formation of spark discharge and its influence by an external magnetic field

Abstract

Described are a series of experiments executed to characterize the physical and chemical nature of spark discharge in argon at atmospheric pressure. Results are reported concerning the expansion properties of the spark and the distribution and longevity of cathode material in and around the spark channel following cessation of the discharge current. The nature of a previously reported symmetrical post-discharge torus is studied at high spark repetition rates. The interaction of residual vapor on following sparks is investigated. Basic features of the spark process are generalized with a set of Schlieren photographs that show bulk motion of the spark plasma. Time-resolved and space-resolved emission and absorption experiments on magnesium electrodes suggest a charged nature to the post-discharge environment. The bulk plasma character is probed further with external magnetic fields to determine the existence of charged species within the post-discharge torus, and the effects of magnetic forces on its formation.