Diffusive radial expansion effect on long-Rail spark dynamical impedances

By close examinations over the numerical simulations based on Rompe and Weisel (R&W) spark gap model [1], the calculated peaks and rise times of gap transient currents are significantly lower and slow than the empirical data extracted from recent experimental works for the preliminary designed prototype Direct Strike Lightning (DSL) Test Facility [2]. This implies the gap dynamical resistance Rs(t) implemented for employed Rail Gap Switch (RGS) in our SPARKGAP computational code is quite larger and decreasing slower than interpreted data from DSL experiments. These discrepancies are mainly originated from the RGS features of specific geometric structure and triggering schemes.