To replace a hard tube design, a solid-state kicker pulser for the Dual-Axis Radiographic Hydrodynamic Test facility (DARHT-2) has been designed and tested. This kicker modulator uses multiple solid-state modules stacked in an inductive-adder configuration where the energy is switched into each section of the adder by a parallel array of MOSFETs. The modulator features very fast rise and fall times, pulse width agility and a high pulse-repetition rate in burst mode. The modulator can drive a 50 /spl Omega/ load with voltages up to 20 kV and can be easily configured for either positive or negative polarity. The presentation includes test and operational data.

Events associated with the rapid commutation of the current in a diffuse vacuum arc are explored experimentally and analytically in the short interval during which the current is brought to zero and the recovery voltage is established across the residual plasma. A brief pause of the order of 100 ns is observed between the passage of current through zero and the point where the recovery voltage starts to rise. Current zero is interpreted as the instant when the ion and electron currents are equal. During the subsequent pause the electrons are brought to rest and only then does a positive ion sheath develop, allowing voltage to build up across it. The charge remaining in the gap at current zero is observed to depend on the initial steady-state current and the rate at which the current is ramped to zero. Qualitative agreement is obtained by analysis, but the decay of the charge residue appears to be more rapid than the analysis predicts.