GB706722A - Improvements relating to gas filled electric discharge devices - Google Patents

Abstract

706,722. Thermionic-cathode tubes. RADIO CORPORATION OF AMERICA. Sept. 18, 1951 [Sept. 20, 1950], No. 21898/51. Class 39(1) A gas-filled discharge device, Fig. 5, with cathode 42, control electrode 43 and anode 44, has also means for establishing an auxiliary ionizing current, said auxiliary means comprising cathodes 56, 57 and anodes 62, 63. The auxiliary electrodes are energized at greater than ionizing potential, the main electrodes at less, and may operate at as little as one or two volts. Increased efficiency is obtained by surrounding cathodes 56, 57 with focusing electrodes 58, 59 at the same potential, and having slots 60, 61 therein. The auxiliary electrodes may be duplicated on each side of the grid 43, as shown in Fig. 5, so that the plasma may be maintained by separate auxiliary discharges on both sides of the grid, independently of diffusion therethrough, thus improving the frequency response. In a simpler arrangement, Fig. 4 (not shown), only one set of auxiliary electrodes is provided, the focusing electrode now having two slots, opening respectively into the grid-cathode and grid-anode regions. In Fig. 5 the auxiliary cathodes may be connected together, and also the auxiliary anodes, the latter being at the potential of the main cathode 42. In a still further simplified form, Fig. 3 (not shown), the same electrode acts as both main and auxiliary anode. In the arrangement of Fig. 1, auxiliary cathode 25, with slotted focusing electrode 23, is as before. The anode is a U-shaped member 17, and the control grid a number of parallel wires 20 across two U-shaped supports; the spacing between adjacent grid wires is large compared to the mean free path of the electrons and ions in the gas, which is helium at about 750 microns pressure. The auxiliary ionizing potential is applied between cathode 25 and main cathode 13. In the mixer tube shown in Fig. 8, the anode 95 is rectangular, and the two control grids are coplanar and interleaved: wires 96 forming one grid are supported from an upper U-shaped collar, and alternate wires 98 forming the other grid from a similar lower collar. Fig. 10 (not shown) is a set of characteristic curves given by the form of device of Fig. 1, showing how the grid retains continuous control of the discharge from zero to upwards of 200 milliamps.