Theory of electron current filamentation instability and ion density filamentation in the early development of a DPF discharge

Two‐dimensional simulations of the initial stages of plasma formation in a dense plasma focus show the formation, in a few tens of nanoseconds, of a dense layer of plasma (ne∼1018 cm−3,Te∼3 eV) in a thin layer surrounding the insulator‐covered central anode of the focus device, and carrying axially‐directed current at rather high current density.Earlier work on the filamentation of dense cathode plasma in high‐power diodes [1] seems to indicate that the anode plasma current layer in a dense plasma focus (DPF) device could be subject to the same instability, creating a growth of axially‐directed filaments in the current density. The growth rate for resistive‐thermal‐driven filamentation, e.g. at 30 torr and ∼3 eV electron temperature, exceeds the that due to non‐thermal current (J×B) driving, and is determined by electron dynamics [1], so its evolution is quicker than the response‐time of the ions.Nonetheless, with such a growing current‐density perturbation as a seed and its increasing rippling of the azi...