NUMERICAL-SIMULATION OF A NEGATIVE-ION PLASMA EXPANSION INTO VACUUM

The expansion into vacuum of a one-dimensional, collisionless, negativ e ion plasma is investigated in the framework of the Vlasov-Poisson mo del. The basic equations are written in a ''new time space'' by use of a rescaling transformation and, subsequently, solved numerically thro ugh a fully Eulerian code. As in the case of a two species plasma, the time-asymptotic regime is found to be self-similar with the temperatu re decreasing as t(-2). The numerical results exhibit clearly the phys ically expected effects produced by the variation of parameters such a s initial temperatures, mass ratios and charge of the negative ions. ( C) 1997 American Institute of Physics.