For pt.I see ibid., vol.10, no.7, p.1035 (1977). The electron swarm parameters for the steady-state Townsend, pulsed Townsend and time-of-flight experiments are calculated using a Boltzmann equation for argon at E/N values from 85 to 566 Td, when electron impact ionization is appreciable. The results suggest that the value of an electron swarm parameter depends on the type of the experiments involved, because of the presence of the ionization, in agreement with the Monte Carlo simulation work in the previous paper. The drift velocities and diffusion coefficients when ionization is present, are discussed.

Arrival-time spectra of the evolution of swarms in the hydrodynamic regime have been studied theoretically starting from the Boltzmann equation and its eigenvalue problem. In order to express the development of the number density of the one-dimensional pulse swarm, a new evolution equation with new transport parameters, which are obtained directly from the arrival-time spectra, is introduced. Relations between the longitudinal transport coefficients and the new parameters are also presented. By means of this theory, it is shown that the distribution functions for the different types of experiments (steady-state Townsend or pulsed Townsend) are distinguished from each other in non-conservative cases, and drift velocities defined by different principles have in general their own values even if the kind of gas and the value of E/N are the same.

The electron swarm behaviour in SF6 gas is studied for E/N values from 141 to 707 Td by a three-term Boltzmann equation method, in which the effect of generation and loss of electrons due to ionisation and attachment is considered properly. A consistent set of electron collision cross sections, which gives the swarm parameter values in agreement with previous measurements, is determined considering the latest cross section data. The calculation is performed mainly for the steady-state Townsend condition. The validity of the results obtained has been confirmed by a Monte Carlo simulation carried out parallel to the analysis. The present results are also compared with those of the usual two-term Boltzmann analysis. It is found that the two-term approximation is fully valid for deduction of the swarm parameters for E/N values as considered despite the fact that SF6 is a strongly electronegative gas.

The behaviour of electron avalanches in argon when appreciable electron impact ionization occurs, is studied by a Monte Carlo simulation. The values of electron swarm parameters are obtained for steady-state Townsend, pulsed Townsend and time-of-flight experiments, by applying sampling techniques appropriate to the respective experiments. The results suggest that the value of an electron swarm parameter, such as the ionization frequency or the electron drift velocity, depends on the type of experiments for which there is appreciable electron impact ionization. The properties of electron avalanches in an electron energy non-equilibrium region, for example the variation of the electron energy distribution with distance from the cathode, and the effect of anisotropic scattering of electrons on the swarm parameters very close to the anode, are also studied.

The electron swarm behaviour in SF6 gas is re-analysed over the E/N range 141-7000 Td by a six-term Boltzmann equation method and by a Monte Carlo simulation considering the latest cross section data, in particular, that of the elastic momentum transfer cross section. The Boltzmann equation analysis shows that the present set of cross sections gives the values of swarm parameters such as ionization and electron attachment coefficients, drift velocity, longitudinal and transverse diffusion coefficients in excellent agreement with the respective measurements for a wide range of E/N. The swarm parameters calculated by the six-term approximation analysis agree well with those by Monte Carlo calculation. Furthermore, the Monte Carlo simulation confirms the results of a previous computer simulation study for correspondence between experimental and theoretical electron drift velocities; that is, the drift velocity deduced from Schlumbohm's experiment (1965) assumes a value close to but slightly larger than Wm and the drift velocity deduced from Frommhold's experiment (1959) assumes a value represented by (Wr+Wm)/2, where Wm and Wr are the mean arrival time and the centre-of-mass electron drift velocities, respectively.