EFFECT OF A THIRD ELECTRODE ON A LOW-VOLTAGE ARC.

The discharge in a low-pressure cesium-barium mixture with an indirectly heated cathode and a third electrode is discussed. Comparison of the I-V characteristics for two- and three-electrode gaps under identical conditions in the same apparatus indicates an additional voltage drop with a third electrode. The nature of the descending part of the characteristic for the two-electrode arrangement and the current cutoff in the three-electrode arrangement are discussed. A negative potential applied to the third electrode not only increases the anode breakdown voltage to 150-200 V, but can also quench the discharge. Analysis of the quenching characteristics for the three-electrode arrangement with various diameters of the apertures in the control electrode indicates that various quenching mechanisms operate, depending on the gas pressure and the discharge current.