Sparking Potential and Electrode Material

A consideration of the character of the normal spark breakdown in air with external ionization and involving time lags of greater than ${10}^{-4\mathrm{}}$ seconds indicates that with the assumption of space charges the original Townsend theory of sparking can be maintained and that the spark mechanism as is experimentally found will be independent of electrode material. It is shown that the results of Duffendack, Wolfe and Randolph in which they find a dependence of sparking potential on the work function of the electrodes is due to their special experimental arrangement and in no sense contradicts the Townsend theory as asserted by them. It is shown that short time (less than ${10}^{-5\mathrm{}}$ seconds) surge impulse breakdown in gaps of small area with insufficient ionization necessitates a new breakdown mechanism involving probable impact ionization at the cathode by positive ions to replace the deficient ionization. On the basis of this point of view further much needed investigations are indicated.