In situ observation of the nanosecond two-dimensional surface charge evolution during the process of a surface discharge streamer

A surface streamer is a ubiquitous discharge in electric equipment and surface dielectric barrier discharge. It is expected to suppress this kind of surface discharge in the insulation system, but on the other hand, the surface streamer is also utilized for the generation of active ions and the control of a gas kinetic distribution. As a product of the surface streamer, surface charge influences and characterizes the streamer's behavior. This study observed the two-dimensional transient evolution of the surface charge and the tangential electric field in a single individual surface streamer at the nanosecond level. Using a reflective Pockels effect system and a framing camera system, the surface streamer propagation under a sub-microsecond pulse voltage was measured in real time and in situ. The inception, propagation, and deceleration of a surface streamer are observed. The measurement exhibits an electrodecharge equipotential region that equivalently extends the electrode boundary. Under an anode field with a weak tangential component, the interior of the surface streamer channel exhibits local deviations from the quasi-neutrality, and a reversed tangential electric field is observed. The lateral movement of the positive charge may be responsible for this reverse electric field. The diagnostic technique presented in this study can describe the surface charge transient behavior in pulsed surface discharges, which complements the streamer model.