Influence of the gas composition on the electron transport coefficients inhelium-based gas mixtures

For several helium-isobutane and helium-methane gas mixtures the drift velo city and the longitudinal and transversal diffusion coefficients have been measured with a time of flight method using single-drift electrons. The inf luence of the hydrocarbon, water and nitrogen content in the gas mixture on the transport coefficients was studied in detail for concentrations typica l for the operation of drift chambers. (C) 1999 Elsevier Science B.V. All r ights reserved.