Random Walk Theory Applied to Electron Avalanche Formation

Use of microscopic detail in random walk theory describing the initial formations of a large number of avalanches show that concomitant electron transport coefficients quickly relax to equi­ librium values. This enables the use of random walks having step sizes and probabilities based only on local electric field strengths and densities. A self-consistent avalanche solution which accounts for collective long range Coulomb interactions as well as short range elastic and inelastic collisions between electrons and background atoms is demonstrated for helium. Avalanche growth retardation followed by an abrupt growth augmentation as time proceeds is shown to be associated with the formation of regions of charge density extrema near the avalanche axis and within the axial distance covered by the electron swarm.