Ionization coefficients and sparking voltages in krypton and in krypton—olefin gas mixtures†

Townsend primary and secondary ionization coofficiont3 and the sparking voltage have boon obtained in pure krypton and in 0003% to 3% mixtures of ethylene and of propylene in krypton for a total pressure in the range 0.5 to 700 torr and for a uniform field gap up to 1 cm. In krypton-ethylene mixtures, in which the Penning condition is not satisfied, only moderate ionization enhancement takes place, mostly due to direct ionization whilst in krypton—propylene mixtures the established Penning effect takes place, as expected, because of the fulfilment of the Penning condition. The addition of the olefin gases to krypton lowers the secondary ionization coefficient by up to a factor of 106 times and greatly reduces the sparking voltages by up to a factor of five times below that for pure krypton and by more than a factor of ten times below that of either olefin. The data for pure krypton are in reasonable agreement with those quoted in the literature.