Charging of dust grains in a nuclear-induced plasma at high pressures

The process of dust-grain charging in plasmas produced by radioactive decay products or spontaneous fission fragments in air and xenon at high pressur es is studied numerically in the hydrodynamic approximation. It is shown th at, at sufficiently high rates of gas ionization, the dust grains in air ar t: charged by electrons rather than ions, so that the grain charge in air i s comparable to that in electropositive gases. The results of numerical cal culations based on a complete model agree well with the experimental data. The time evolution of the grain charge is investigated, and the characteris tic time scales on which the grains acquire an electric charge are establis hed. The validity of approximate theories of dust-grain charging in electro positive and electronegative gases at high pressures is examined. (C) 2001 MAIK "Nauka/Interperiodica".