Diagnosis of discharge plasma's temperature by lifbase using atmospheric pressure pulsed discharge in air

Abstract

The temperature is very important for the application of the discharge plasma such as in the spray coating, surface modification and health care especially. Most diagnosis means of the discharge plasma's temperature, for an example, Langmuir probe, interfere in the discharge process. That is not expected. Optical emission spectroscopy (OES) diagnosis collecting optical signal by optical fibre detector and analyzing by special software overcomes above drawback to some extent. Recently, OES is widely used to diagnose the discharge plasma, especially, the active species such as the OH radicals and so on. The OH radical's rotational temperature could be thought as the discharge plasma's temperature at atmospheric pressure1. So the OH radical's rotational temperature in the negative pulsed air discharge at atmospheric pressure with nozzle-cylinder electrode is simulated by the software LIFBASE basing on the OH radical's OES. The effects of the flow rate of the air, the humidity of the air, and the position in the discharge area on the OH radical's rotational temperature is researched. That the OH radical's rotational temperature in the experiments is about several hundred Celsius degree demonstrates low-temperature plasma is produced in the discharge processes. The OH radical's rotational temperature is shown decreasing trend when the flow rate or the humidity of the air is increased. Possible reason is the residence time of high-energy electrons is shortened with the bigger flow rate of the air passed the discharge area or more negative charges are attached to the H2O molecules with the higher humidity of the air in the reactor. That the energy decreases causes the discharge plasma's rotational temperature decreases. The change trend of OH radical's rotational temperature isn't shown obviously trend affected by the different position of the diagnosis. The point of the discharge nozzle is taken as the centre of the OES diagnosis with the 0∼1.5 cm space range from left to right or from up to down.