Speaker
Description
Vacuum breakdowns are common phenomena in nature and gain their important role in modern technologies. Although a lot of effort has been done to reveal the nature of the breakdown, the dispute over the roles and physical processes of anodes in the initial stage is not over. The objective of the paper is to experimentally investigate prerequisites for appearing anodic glow and its role in a vacuum breakdown. By employing a streak camera with high-time resolution up to several pico-seconds, we observed anodic glow during vacuum breakdowns accurately. Combined with analysis of I-V behaviors, it is found that different anode materials did not affect the delay times between the cathodic and anodic glow obviously as well as the breakdown voltages, and both the energy and charge deposited on anode surfaces are the necessary conditions for triggering anodic glow. Moreover, anodic glow is generated by the combined effect of evaporated atoms from the anode surface and the incident electrons from the cathode. Only the electron with low-energy can excite the atoms efficiently, so the effect of electron sheath, which can control and decelerate the incident electrons, is critical in the physical processes of the anodic glow. In addition, the low-energy electrons drift back to the cathode, changing the emission on it, leading to a final equilibrium of vacuum discharge. In the end, we reaffirm that a fully conductive channel after a vacuum breakdown triggered can be established without contributions from the anode.
