Simulations for initiation of vacuum insulator flashover

The vacuum/dielectric interface of insulators is often the weakest part in high voltage and pulsed power systems. Surface flashover can occur for electric field values much lower than that of bulk breakdown through the material. Although much empirical data and many theories can be found in the literature, there are no models that can be used to optimally design insulators and reliably predict when flashover will occur. In this presentation we will discuss the results of a FDTD-PIC code that is being used to model physics phenomena common to many flashover theories. In order to simulate the initiation of vacuum insulator flashover, VORPAL is being used on the Linux clusters at LLNL. In we presented the results for implementing physics modules that included the effects of field distortion due to the dielectric, Fowler-Nordheim field emission, low energy secondary emission, insulator charging, and magnetic fields. We have extended our previous work to include a thin gas layer near the surface of the insulator. Electrons may cause ionization depending on their energies and the collision cross section of the gas. The inclusion of these physics effects leads to a more complete model and better understanding of vacuum insulator flashover.