On the precursor generated in plasma focus devices operated with molecular deuterium

A five-fluid, MHD one-dimensional and stationary model with a simplified treatment of the radiation has been developed to describe the precursor generated in plasma focus devices during the coaxial stage of the current sheath. Assuming D2 to be the filling gas, the relevant processes (within the conditions of the problem) which have been included are: molecular and atomic photoionization, dissociative recombination and dissociation by electronic impact. Taking into account that the main energy source for the precursor is radiation absorption, the model previously developed by Bilbao et al. 1986 has been adopted to provide the spectral energy flux emerging from the current sheath. The results obtained from the model indicate that precursors can be classified in terms of a nondimensional parameter xi , defined as the ratio of the radiant energy flux coming into the gas and the kinetic energy flux (as viewed in a frame of reference attached to the shock front) of the neutral gas impinging upon the shock. Although electronic thermal conduction across the shock front has been neglected, several estimations of its effects on the results are given.