Ionization coefficients and sparking voltages in argon and argon-ethane mixtures

• Published in: Journal of physics. D, Applied physics Applied physics, 1968-02, Vol.1 (2), p.179-188
• Main Author: Heylen, A E D
• Format: Article
• Language: English
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/1/2/307

Townsend primary and secondary ionization coefficients have been experimentally determined in pure argon and in argon mixed with up to 3% of ethane gas for a total pressure in the range 0·5-700 torr, corresponding to 3less, similar E/p 0less, similar2000 v cm −1 torr −1 at 0°C. Ionization enhancement takes place and it is shown analytically that the major contribution to this is due to the Penning process. At an optimum concentration of about 0·66% of ethane in argon the primary coefficient is increased to forty times its value for pure argon. The presence of common impurities increases the coefficient by up to five times, whilst a similar concentration of electron-attaching gases lowers the coefficient by a factor of 10. Because of the quenching nature of ethane it is shown possible to reduce the secondary ionization coefficient of argon by as much as 10 7 times; with the addition of less than 0·03% of ethane it is possible to increase the secondary coefficient at low E/p 0 by a factor of 10 above that for pure argon. At the optimum concentration the sparking voltage is a factor of 2·2 below that for pure argon, whilst the presence of 0·000 03% of ethane still lowers the sparking voltage of pure argon, by a factor of 1·3. All the sparking voltages lie well below that for pure argon.