Calculations of the effects of incomplete preionization in high voltage theta pinches

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Abstract
The hybrid model presented previously has been extended to include the effects of incomplete pre‐ionization by the addition of a multistep ionization process. The difference between a fully pre‐ionized and a weakly pre‐ionized implosion is illustrated, and the predictions of the model are compared with data from high voltage ϑ‐pinch experiments by illustrating the degree to which the computed density and magnetic field profiles agree with experiment. Due to incomplete pre‐ionization, all the plasma at a point is not accelerated simultaneously by the sheath, so that the radial density profiles are broader and the peak densities are lower than in the corresponding fully pre‐ionized implosion. A differential rotation of the imploding plasma column is shown to affect the implosion dynamics and radial density distribution. It is demonstrated that the withdrawal of flux from the tube during a staged theta pinch experiment may result in plasma hitting the wall and traumatizing it.