Soft X-ray Generation and Its Role in Breakdown of Air Gap at Elevated Pressures

Fast runaway electrons, which appear during the electric breakdown in an air-filled discharge gap under the action of a short-front voltage pulse, generate 525-eV photons from the K-shell of oxygen. This soft X-ray emission effectively generates new electrons in the region of enhanced field. The proposed mechanism may explain the fast streamer propagation and the formation of a diffuse discharge at atmospheric pressure.