Experimental investigation of high-voltage glow discharge efficiency as a source of beams of run-away electrons

To determine the energetic efficiency of the formation of the run-away electron beam in a highvoltage glow discharge, we measure the temperature of the electron beam generator. According to the measurements, the energetic efficiency (the part of the input discharge power carried away by the beam) was $50$–$70\%$ at the generator supply voltage of $4.4$ kV and it increased up to $\sim85\%$ at $\sim8$ kV. The measurements are performed for the discharge in helium with copper, steel, molybdenum, and lanthanum hexaboride cathodes.