Breakdown waves in argon and nitrogen

Extensive measurements are presented of initial electric breakdown wave speed in nitrogen and argon as a function of local electric field at the wavefront. The results are in basic agreement with the electron fluid dynamic theory of the phenomenon. The apparent gas density dependence over and above the E/p dependence predicted by theory, that has been found by other investigators, is confirmed and has been traced to observational limitations. The results indicate that photo-ionizing processes are not needed to explain the effects observed over most of the pressure range studied.