Fast breakdown process and characteristics diagnosis of nanosecond pin–pin discharge

Abstract

In this paper, the characteristics of nanosecond spark discharge with a pin-pin electrode configuration have been systematically studied. Both streak camera with high temporal resolution and ICCD camera are employed together to investigate the breakdown and evolution process of the discharge. And the formation of initial breakdown and mode transition from streamer to spark in the electrode gap are clearly observed in the time scale of several nanoseconds with the temporal resolution of 100 ps. In addition, the time-resolved spectra technology is also used to analyze the generation and quenching mechanisms of reactive species, the electron density and electron temperature. The results show that there is a 1.25 ns initial discharge breakdown and that a bright cathode spot exist before the transformation from streamer to spark channel. After a faster cathode filament and a slower anode filament propagate and merge at the electrode gap, the spark discharge phase begins. The generation processes of different reactive species depend on discharge phase to a great extent. The N2 * is first generated during the streamer phase while the O*, N*, and N+ are mainly generated under the spark phase in which the electron temperature calculated by Boltzmann plots is 2.74 eV, and the electron density determined from the stark broadening of O lines is on the order of 1016 cm-3.

Ultra-high temporal resolution images of a homogeneous electric field short air gap negative streamer at overvoltage and atmospheric pressure

“…2) The streak camera can achieve time continuous imaging and is also used by researchers to photograph streamers in extremely homogeneous fields. [20][21][22][23][24][25][26] However, the streak camera has only onedimensional spatial resolution. 27,28) The morphology of the streamer cannot be recorded by a streak camera.…”