Influence of liquid temperature on the characteristics of an atmospheric dc glow discharge using a liquid electrode with a miniature helium flow

摘要

An atmospheric dc glow discharge using a liquid cathode and an axial miniature helium flow was generated stably between a nozzle anode and an electrolyte cathode (NaCl solution) in ambient air. Under low-current operation, the typical structure of dc glow discharges, i.e. a negative glow, a Faraday dark space and positive column, was observed. With increasing discharge current, the visible negative glow became weak and was replaced by an intense yellow-light emission, which was considered to originate from sodium atoms vaporized from the electrolyte surface by local heating due to ion bombardment from the glow discharge. To examine the effect of the liquid electrode temperature on the discharge characteristics, we controlled the electrolyte cathode temperature using an injection-type cooler or heater. The intensity of the sodium emission decreased when the electrolyte cathode was cooled, while it increased when the electrolyte cathode was heated. When a pulse-modulated dc voltage was applied, the sodium emission appeared with a delay relative to the inception of discharge, while nitrogen molecular lines appeared in the emission spectra and reached their peak intensities immediately. The temperature of the liquid cathode is an important factor in controlling the plasma-liquid interaction from the discharge and in resolving the detailed mechanism of the electrolyte cathode discharge.