Study On The Characteristics Of Discharge With Wire Electrodes Under Repetitive Nanosecond Pulses

Atmospheric non-equilibrium plasma is a plasma form which can exist at room temperature and atmospheric pressure. The density of active particles in atmospheric non-equilibrium plasma is relatively high. Moreover, this kind of plasma does not need high temperature, vacuum or other complicate conditions. Due to these advantages, atmospheric non-equilibrium plasma has broad application potential. However, it is hard for plasma to remain non-equilibrium state in atmospheric air. To obtain stable non-equilibrium plasma in atmospheric air, so me special technical proposals are needed.With the development of pulsed power technology, the performance of repetitive pulse generator is getting better. The application of high performance pulse generator is wider and deeper. Recent studies have showed that using repetitive nanosecond pulse is more effective to form atmospheric non-equilibrium plasma than traditional AC power. In addition, suitable electrode type is very important to the formation of non-equilibrium plasma. The special researching point in this paper is to choose thin copper wires as the electrodes. The electric filed formed by long wire electrodes is highly uniform. The application of wire electrodes is helpful to obtain larger scale of non-equilibrium plasma.Firstly, this paper proposed the needed electric field conditions based on the formation mechanism of atmospheric non-equilibrium plasma. The electric filed distribution of wire electrodes is analyzed and the feasibility of this discharge mode is verified. Furthermore, a repetitive nanosecond pulse generator developed by ourselves is applied as the power source. A pair of naked copper wires with 0.4 mm diameter is applied as the electrodes. And stable non-equilibrium plasma is obtained with the electrode length ranges from 15.0 cm to 110.0 cm in experiments.Secondly, the circuit model of discharge with wire electrodes is analyzed. And the discharge experiments are carried out under different electrode distances and electrode lengths. The waveforms of discharge current and applied vo ltage are measured. The varying trends of displacement current and conduction current are analyzed by comparing the waveforms of discharge current. The study on the characteristics of discharge current demonstrates that the increase of conduction current density is an important factor to cause the formation of spark channels.Finally, the images of discharge with wire electrodes are taken for digital image analysis. The discharge images are processed by gray-scale transformation technology. By combining three-dimensional gray-scale distribution curves with gray-scale statistics, the spatial uniformity of the plasmas generated by discharge with wire electrodes is analyzed. The study indicates that using gray-scale transformation technology can not only analyze the spatial uniformity, but also help to distinguish the discharge mode.