A Study of Ionization Coefficients and Electrical Breakdown in Hydrogen
Proceedings of the Royal Society A
Experim ental m easurements o f the Townsend ionization coefficient a for hydrogen have been made from a study of pre-breakdown currents in uniform electric fields over a range o f the parameter Ejp from 15 to 40 V /cm m m H g. The results indicate th at earlier measure m ents m ay be in error below Ejp = 25 V tom m m H g, and show good agreement w ith the theoretical calculations o f Em eleus, Lunt Meek ( 1936) which are based on a Maxwellian distribution of electron energies. Furthermore, m
... s. Furthermore, m easurements made at different gas pres sures for the same value o f the parameter EIp show th at a/p is a function o f Ejp. The growth o f pre-breakdown currents has been measured to w ithin a small percentage o f the sparking distance and is found to be well represented by the Townsend equation e <xd i = i0 ---------------, showing the existence o f a secondary ionization m echanism denoted by y. The results are discussed in the light o f existing theories o f electrical breakdown, and it is concluded that the Townsend m echanism is sufficient to explain the initiation o f breakdown in hydrogen up to a pd value of at least 2800 cm mm Hg. I n t b o d u c t i o n The mechanism of the electrical breakdown of a gas at high pressures is par ticularly complex, and until recently neither of the two more widely accepted theories of breakdown, namely, the theory of Townsend (1915) and the streamer 22 Vol. 235. A.