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Developments in the kinetic theories of ion and electron swarms in the 1960s and 70s

The two decades between 1960 to 1980 saw quite a fantastic development in diverse areas in physics, and so also in the quantitative theoretical treatment and deeper understanding of the behaviour of isolated electrons and ions in gases—that is ‘charged particle swarm physics’. The evolution in swarm theory was strongly correlated with the contemporary advances in computer technology and the emergence of new and accurate experimental methods for finding charged particle transport parameters, as drift velocities, diffusion coefficients and reaction rates, and also with developments in neighbouring fields as plasma physics and the physics of electronic and molecular collisions. In 1960, low energy electron behaviour could already be calculated with reasonable accuracy in the so-called two-term approximation, while ion behaviour could only be treated at weak electric fields. By 1980, reasonably complete theories had been developed for perhaps most cases in interest—which is reflected in a number of reviews, books and journal articles published in the early 1980s. We will present a journey through the developments in this period and the basic theories behind the Boltzmann equation and Maxwell’s transfer equations. We will also indicate how the interaction between different studies of the same basic processes have led to the elimination of shortcomings and a better understanding.