Pulsed flashover developing across alumina ceramic in vacuum

The flashover phenomena in vacuum have been an interesting issue among many researchers in the fields of both electrical and electronic systems for more than half a century. However, the phenomena are so complicated and up to now the related mechanisms are still not understood clearly. In this paper the ICCD camera was used to grasp the dynamic flashover images on the surface of alumina ceramic in vacuum under pulsed voltage excitation. These images show the developing process of the flashover phenomena. The results indicated that the flashover develops rapidly in less than 50 ns and the electrode edge shows the highest light intensity. The sample with sputtered metal film electrode has also been employed to obtain the flashover photos with ICCD camera, and these photos were compared with those samples without sputtered electrode. And these two groups of photos show a different optical distribution, possibly due to their different local electric field distribution near the electrode edge.