Measurement of the ionisation coefficients in binary and ternary mixtures of CO₂, N₂and He

The Townsend first ionisation coefficient alpha T and the secondary coefficients gamma T have been measured in binary and ternary mixtures of CO 2 , N 2 and He gases by the steady-state Townsend method for E/p 0 values from 54 to 215 V cm -1 Torr -1 . The results show that the alpha T /p 0 value in mixtures of CO 2 and N 2 increases monotonically with increasing N 2 partial pressure whereas in binary mixtures of He and N 2 , or of He and CO 2 there is a maximum value of alpha T /p 0 as the partial pressure of He is increased for E/p 0 >or=108 V cm -1 Torr -1 . The alpha T /p 0 values of ternary mixtures of these gases are shown on a trigonal prism plot. The value of gamma T is found to decrease rapidly with increase of the component having a small value of gamma T .