MEASUREMENT OF THE EFFECTIVE IONIZATION COEFFICIENT AND THE STATIC BREAKDOWN VOLTAGE IN SF6 AND NITROGEN MIXTURES

The effective ionisation coefficient alpha /p20 is measured for E/p20 from 70 to 160 V cm-1 Torr-1, and the static breakdown voltage Vs between parallel plates for p 20d from 8 to 130 Torr cm, for SF6 and nitrogen mixtures. It is found that the alpha /p20 of the mixtures may be approximated by a linear function of the partial pressure of SF6 at fixed E/p 20 and that Paschen's law holds for the p20d may be estimated with good accuracy from the Vs of the respective pure gases using an experimental formula of Takuma et al. (1972) which has been used for much larger p20d.