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A time-of-flight technique has been developed to measure accurately the longitudinal diffusion coefficient (DL) and the drift velocity (v) for electron swarms drifting and diffusing through uniform electric fields at high E/N.A pulse of electrons is released at the cathode, and a `box-carÂ¿ detector system is used to record the anode current distribution. The drift velocity is obtained from the mean delay time, and the longitudinal-diffusion coefficient is obtained from the standard deviation of the distribution. Results have been given for both hydrogen and nitrogen gas for the range 3 Â¿ E/N Â¿ 43 Td (1 Td = 10Â¿21 Vm2). The values for the drift velocity are in good agreement with theory, whereas the values for DL have revealed inadequacies in the present theoretical values for nitrogen.
Electrical Engineers, Proceedings of the Institution of (Volume:122 , Issue: 3 )
Date of Publication: March 1975