On the similarity of electric breakdown waves propagating in shielded discharge tubes

Experimental and theoretical analyses of breakdown waves in helium-filled screened discharge tubes of different diameters, with geometrically similar cross sections, have been carried out. A model for the ionization wave propagation in these systems is presented. It incorporates charged particle transport using the local field approximation, resonance radiation transport using the Biberman-Holstein approach, and both direct and associative ionization. A similarity criterion is established to define the stationary wave velocity of wave propagation V: at a given value and polarity of the applied voltage pulse U, the wave velocity V is defined by multiplying the gas pressure p and the tube radius a (or the surrounding screen radius R). It is found that, for negative polarity waves, the appearance of a cathode flash on the initiating electrode shifts the dependence V(pR) to an area of higher values of pR.