Studies On Discharge Characteristics Of Plasma Under High Voltage Nanosecond Pulse

The non-equilibrium plasma at atmospheric pressure being apply to material processing, sterilization, treatment of organic waste, due to excellent low temperature performances as well as good controllability, has been a hot reach topic in recent years. High-voltage nanosecond pulse gas discharge is one of the most accessible ways to produce plasma jet with uniform, stable, and high concentration of active particles. However, there are few reports concerning about this research in domestic. Therefore, further study on nanosecond pulsed plasma jet is needed to investigate its generation and discharge characteristics..A nanosecond pulse generator which produces an output 40kV with a rise time of 20ns, a full width at half maximum 50ns, and adjustable repetition-rate, was used in the experimental investigation. The experimental chamber, relevant measuring systems and shielded room have been developed and tested. In this study, three atmospheric nanosecond pulsed plasma jets are studied based on three different configurations. The first consists of an injection needle placed inside a hollow dielectric tube, while the second employs a ring electrode wrapped around a dielectric tube. The third is a hybrid of the first two configurations. The characteristics of the jets are diagnosed by optical and electrical methods, and the mechanism is studied. For these three plasma jets, the rotational temperatures are all 295K, while the vibration temperatures are 1900K,2000K, and 2100K, respectively. The results above demonstrate that plasmas generated by these three nanosecond pulsed plasma jets are of the state of nonequilibrium. Furthermore, the investigation suggest that the hybrid jet with both the needle and the ring electrode connecting to the high-voltage has a better performance, for which a uniform and stable discharge with low temperature and higher reactive species is achieved. It is conceivable that the cold atmospheric nanosecond pulsed plasma jets have a great potential of application in the area of material processing, plasma chemistry and plasma medicine, etc.It is very crucial to measure the electrical parameters between discharge gap under nanosecond pulse discharge. Intermittent noise, high-frequency oscillation noise and electromagnetic radiation be produced when applied nanosecond pulse voltage in the breakdown gap, and make a lot of interference to real signal. Therefore, this paper analyzed the sources of noise and implemented strict screening measures, measured to the applied voltage and discharge current. Using electrical diagnosis means presented the characteristics and physical mechanism of helium discharge plasma.