A three-term Boltzmann equation analysis of electron swarms in gases for the time-of-flight condition

A Boltzmann equation method for calculating the electron swarm parameters parallel and perpendicular to the electric field by taking various orders of the moments in real space of the distribution function and by using the spherical harmonics multiterm expansion of the electron velocity distribution is proposed, and numerical examples in terms of a three-term expansion are presented for a ramp inelastic model gas and for argon. It is found that the present method can deduce accurately the swarm parameters at least for E/N values as considered here, i.e. from 1 to 24 Td for the ramp model gas and from 141 to 566 Td for argon.