GB263110A - Improvements in or relating to gaseous conduction devices - Google Patents

Abstract

263,110. Raytheon Manufacturing Co., (Assignees of Smith, C. G.). Dec. 21, 1925, [Convention date]. Vacuum tubes; low-pressure metallic-vapour apparatus. -A gaseous conduction tube is provided with an inducing coil the field of which is restricted to the region of the cathode and away from the anode so that intense ionization is produced independently of the potential difference between the electrodes only in the region of the active surface of the cathode, gaseous conduction being produced at a low potential difference. In one arrangement, the cathode 2, Fig. 2, has the form of an incomplete hollow ring within which eddy currents in the gas are induced by the external high-frequency coil 11. current in the coil may have a frequency of 10<6> periods per second and its E.M.F. per turn preferably exceeds the ionization voltage of the gas or vapour, in which a current of several amperes may be induced. A tube 6 opening into the cathode dips into mercury 7 and may be heat-insulated at 8. It is surrounded by a collar 9 of magnetic material for heating it. The working pressure of the mercury vapour may be about 0.01 mm. The anode is a plate 10 in the plane of the gap in the annular cathode 2. A very low potential difference between the electrodes is suflicient, but mav need to be a little higher at starting. Such discharge devices, when used as rectifiers, can be connected in parallel without series reactances, or with small reactances only. In another construction, the cathode is an open cylindrical cup, its wall being close to the envelope and its base, in which is a central hole, being at a distance of about 1/16 inch from an anode disc. To avoid direct heating, tho cylindrical wall of the cup may be slit at intervals. A ring of magnetic material, heated by induced current to a temperature at which it emits electrons, is supported within the cup for starting purposes, aud connected thereto through an external current-limiting resistance. Argon, neon, helium, or the like is preferably contained in the device, which is surrounded by the highfrequency coil inducing eddy currents in the gas within the cathode. In a third construction, a hollow cathode has an opening in its top for the discharge to two rod anodes and communicates with a tube dipping in mercury. A heat shield surrounding the cathode has a corresponding discharge opening near the anodes and is slit so that eddy currents may be induced in the cathode and the gas inside, the high temperature of the cathode increasing the ionization of the gas. In a fourth construction, a closed conductor 33, Fig. 7, makes one turn 32 in the vicinity of an external high-frequency coil, and one or more turns near the anode 31, the gas being ionized either by eddy currents within the upper turns or by heat radiation therefrom. Radial shields 37 near the upper and a preferably insulating shield 38 near the lower turn, localize the eddy currents in the gas. Two anodes may be provided in all modifications. Specifications 246,036, 248,721, and 248,722 are referred to.