Electron swarm parameters in helium and neon

Experimental values have been obtained for both the drift velocity and the ratio of longitudinal diffusion coefficient to mobility for electrons in helium (1.4<=E/N<=226 Td) and neon (1.4<=E/N<=339 Td). Comparison is made with a Monte Carlo computer simulation and a good fit is obtained with the present and previously measured data. The computer simulation results for ionisation coefficient and ratio of radial diffusion coefficient to mobility are compared with both experimental and other theoretical values over a wide range of E/N. A comparison between the mean swarm energy and the breakdown voltage shows that equilibrium conditions exist at the highest E/N (2260 Td for helium and 5600 Td for neon) for which the computations were carried out. A set of cross-sections which accurately simulate electron swarm behaviour in helium and neon are given. (author)