Water-dielectric-breakdown relation for the design of large-area multimegavolt pulsed-power systems

We have developed an empirical electrical-breakdown relation that can be used to design large-area water-insulated pulsed-power systems. Such systems often form an integral part of multiterawatt pulsed-power accelerators, and may be incorporated in future petawatt-class machines. We find that complete dielectric failure is likely to occur in water between a significantly field-enhanced anode and a less-enhanced cathode when E_pτ_eff^0.330±0.026=0.135±0.009. In this expression E_p≡V_p/d is the peak value in time of the spatially averaged electric field between the anode and cathode (in MV/cm), V_p is the peak voltage across the electrodes, d is the distance between the anode and cathode, and τ_eff is the temporal width (in μs) of the voltage pulse at 63% of peak. This relation is based on 25 measurements for which 1≤V_p≤4.10   MV, 1.25≤d≤22   cm, and 0.011≤τ_eff≤0.6   μs. The normalized standard deviation of the differences between these measurements and the associated predictions of the relation is 12%.