Measurement Of The Third-Order Transport Coefficient In N-2 And Its Effect On The Longitudinal Diffusion Coefficient Measured From The Arrival-Time Spectra Of An Electron Swarm

Arrival-time spectra (ATS) of an electron swarm in N-2 from 50 Td to 700 Td (1 Td = 10(-17) Vcm(2)) were measured by double-shutter drift tube, and then the first Townsend ionization coefficient, mean-arrival-time drift velocity, longitudinal diffusion coefficient, and longitudinal third-order transport coefficient were obtained from the measured ATS. This is the first successful measurement of the third-order transport coefficient in a gas. Furthermore, we went back to an expression of the longitudinal diffusion coefficient in terms of the alpha parameter, which is the electron transport coefficient derived from ATS, and then demonstrated that the third-order and higher-order electron transport coefficients, which are traditionally ignored in the electron swarm experiment, should be considered to obtain the longitudinal diffusion coefficient properly at moderate and high reduced electric fields.