Abstract: A pulse sharpening circuit is disclosed for decreasing the current and voltage risetimes of pulse power devices. It is useful in many systems ranging from the particle beam fusion accelerator to field emission electron guns for intense microwave sources requiring an extremely quick high power turn-on for proper operation. A polyvinyl chloride dielectric flashover switch is used in combination with a velvet covered transmission line which has a metal ring near its end to produce switching when the initial radial electron flow is diverted to axial electron flow as the critical magnetic insulation current is exceeded. Nominal peak voltages of 500 Kv have been obtained with current and voltage risetimes of 0.5 nanoseconds.