Development from dielectric barrier discharge to atmospheric pressure plasma jet in helium: Experiment and fluid modeling

The development of atmospheric pressure helium plasma jet from dielectric barrier discharge (DBD) under different ground electrodes and applied voltages is investigated by experiment and numerical simulation. The distribution of helium metastable atoms, electron density, electron temperature, surface charges, electric potential, and space charges during the development of the plasma jet are calculated. It is shown that the plasma jet can only form when the ground-electrode width is small enough so that the electric field outer side of the ground electrode is larger than a critical value. The length, the current peak, and the propagating velocity of the plasma jet decrease at increasing ground-electrode width, while the critical voltage for plasma jet forming outside the ground electrode and the current peak of the DBD increase. The time-resolved images of emission around 337.1 nm and 706.5 nm show that electrons of high energy exist in front of the discharge towards the cathode and of the outside plasma jet, while those of low energy exist in the whole discharge area. The formation and propagation of the plasma jet can be controlled by the operating conditions of the DBD.