Electron swarm parameters in ramp electric fields

The behavior of electron swarms in gases in time-varying ramp electric fields is investigated using a Monte Carlo simulation. In particular, we consider the case of swarms in chlorine gas. Swarm parameters as a function of instantaneous E/N(E is the electric field and N is the gas number density) for different dE/dt are determined. At higher dE/dt, all the parameters as a function of E/N are shifted to larger E/N when compared to the steady-state case. The drift velocity curve develops a peak which shifts to higher E/N and increases in magnitude as dE/dt is increased. Next, we pay attention to the definition of the swarm parameters, where the parameters derived from kinetic theory and by analogy to experiment are compared. For the high dE/dt cases, differences in the swarm parameters at the same E/N values are caused by the inertia of the electrons and their transient beam-like high drift velocity, while discrepancies due to the difference between the definitions in the kinetic theory and in the analogy to experiment appear significantly. (C) 1996 American Institute of Physics.