Measurements of Lateral Diffusion Coefficients and First Townsend Coefficients for Electrons in Helium by an Electron-Density Sampling Method

Abstract

Direct experimental measurements of electron diffusion coefficients $D$ in helium have been carried out at 300°K in the range of $0<~\frac{E}{N}<2.7\mathrm{}\times {10}^{-16\mathrm{}}$ V ${\mathrm{cm}}^2$ ($0<~\frac{E}{P_0}<10\mathrm{}$ V ${\mathrm{cm}}^{-1\mathrm{}}$ ${\mathrm{Torr}}^{-1\mathrm{}}$) by an improved electron-density sampling method. Absolute errors less than ± 0.5% are claimed in the range $0<~\frac{E}{N}<9\mathrm{}\times {10}^{-17\mathrm{}}$ V ${\mathrm{cm}}^2$ and less than 1.5% in the range $9\times {10}^{-17\mathrm{}}<\frac{E}{N}<2.7\mathrm{}\times {10}^{-16\mathrm{}}$ V ${\mathrm{cm}}^2$.