Observation of EMH effects in a tri-plate POS

Summary form only given. Experiments on the Hawk generator using a tri-plate plasma opening switch (POS) and an 8-channel interferometer have shown that for the same initial plasma distribution the POS behaves differently depending on whether the center plate of the triplate is pulsed at positive high voltage (positive polarity) or negative high voltage (negative polarity). In positive polarity, the conduction time is 50% longer compared with negative polarity operation. Gap formation always occurs near the negative electrode and the evolution of the plasma distribution associated with the J/spl times/B forces acting on the plasma during the POS conduction phase is markedly polarity dependent. These observations cannot be explained by MHD only. Fluid simulations carried out with a Hall/MHD code, which accounts for electron magnetohydrodynamics (EMH), suggest that the difference in the POS plasma density evolution during conduction is associated with EMH effects. Local field penetration predicted by EMH can evolve into macroscopic current flow paths and associated J/spl times/B plasma distortion that are very different depending on the direction of the electron current relative to the density gradient.