Abstract: A hollow-cathode gas-discharge tube comprises an anode and a cathode contained within a suitable envelope and isolated from one another, the cathode being provided with a cylindrical cavity having a diameter d, which is open on the side of the anode. The anode represents a hollow body of revolution arranged coaxially with the cathode cavity and composed of a hollow cylindrical portion mating a hollow variable-section portion. One portion of the anode represents a hollow cylindrical structure having a cavity diameter D, its bottom being provided with a central opening and disposed level with or below the end surface of the cathode. The other portion of the anode contains a cavity whose diameter evenly increases in the direction of emission from the cavity diameter D of the cylindrical portion of the anode, a height 1 of the cylindrical portion of the anode, its cavity diameter D, and the diameter d of the cylindrical cavity of the cathode being related to one another as follows:3d.ltoreq.1.ltoreq.6d2.ltoreq.