Vibration and rotation temperature distributions optimization of microwave plasma jets in atmospheric pressure

In this paper, the discharge characteristics and reactive species of atmospheric pressure pulse-modulated microwave plasma jets are diagnosed using emission spectrum diagnosis. According to the emission spectrum measured by the experiment, the spatial resolved rotational temperature, vibrational temperature, and electron density are calculated under different discharge parameters. The experimental results show that pulse-modulated microwave plasma jets can produce abundant active species and that the microwave power and duty cycle can effectively regulate the characteristics of microwave discharge. The vibrational temperature is the highest at the tip of the needle, while the rotational temperature is more evenly distributed in the radial direction. Under conditions of high power and a high-duty cycle, active species can be generated, and the rotational temperature can be significantly increased. In contrast, the vibrational temperature remains low at a high-duty cycle.