The spatial distribution of gas temperature in air plasma jet of dc glow microdischarge has been determined. The temperature field was measured by a thermocouple probe and compared to schlieren images. The jet can be separated in the radial direction into three characteristic regions with clearly pronounced boundaries. The central region represents a narrow hot zone corresponding to the visible plasma plume, in which the gas temperature varies from 50 to 200°C depending on the air flow rate and distance from the anode. This zone is surrounded by a warm “coat” of ~1-cm diameter and a temperature within 30–50°C. The outer region represented ambient air at room temperature. The zone of temperatures above 50°C did not extend to a distance above 3 cm from the output nozzle of the discharge cell.
Electrical characteristics of a glow discharge of atmospheric pressure with a constant current of up to 40 mA in atomic and molecular gas flows with a volume flow from 0.5 to 5 l/min were measured. It was found that in the flow of molecular gases the voltage drop on the discharge significantly depends not only on the rate of gas blowing, but also on the polarity of the supply voltage. With increasing of the blowing rate the discharge in oxygen and nitrogen becomes unstable, and the voltage on the discharge gap increases by several hundred volts. With a positive polarity of the supply voltage both effects are much more pronounced than with a negative one. In helium and argon flows with given blowing rates the polarity of the voltage on the electrodes does not affect on the discharge mode.
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