V.V. Prasitsky, A.V Tai, N.I. Pchelintseva

This paper describes a comparative test of well-known helical and sintered electrodes. The designs of the sintered electrode discharge lamp - it contains the core of tungsten reinforced it sintered mass, which is a compressed and sintered mixture of tungsten powder and equity additions of emission-active substance. The complexity of creating sintered electrodes for high-pressure discharge lamps due to the fact that at the stage lights flare-ups, they should have the secondary-emission properties, and in native mode - thermoemission. At the first stage of combustion in a glow discharge should engage the entire active surface of the electrode, and the second, in an arc - a small area occupied by the cathode spot. When arcing power density flowing into the cathode spot reaches 3∙104 W/cm2. Therefore, a high heat conductivity, providing heat dissipation of the cathode spots to reduce the evaporation rate of the material. The result of these investigations was the fact that, as refractory material for the matrix who elected WShDK grade tungsten powder with a grain size of 1...3 m and the new emission-active substance based on barium. XRD analysis of samples of sintered electrodes fabricated with the selected tungsten powder showed no foreign phases and sufficiently high intensity peaks actively-emissive material of a given composition. The sintering temperature is selected from the conditions for ensuring the mechanical strength of the sintered electrode and its attachment to the core. The research carried out on samples of thermal conductivity of the electrode materials, in which the content of emission components were in the range of 10-30%. The choice of these values are based on the emission characteristics of the electrode materials used. The error in measuring the temperature of the sample within each experiment did not exceed 10%, and in a series of tests - 12%. The results showed that the thermal conductivity of the sintered electrode material is from 0,4 to 0,6 tungsten conductivity. From this it follows that in step a glow discharge electrode surface is heated rapidly and the organization of the cathode spot requires minimal time. In this case, the sintered electrode is stable and longer than the spiral.