Patent GB-1158864-A (GB)
Title: Thermionic Converters
Inventor: LAING ROBERT LOUIS
IPC: H01J45/00
Filed: 1966-08-08
Abstract: 1,158,864. Electron beam apparatus. R. L. LAING and C. D. FEEMSTER. 8 Aug., 1966, No. 35422/66. Heading H1D.  A beam-type thermionic converter includes an electron gun, comprising a thermionic cathode and an accelerator electrode for the electron beam, and a collector for the electrons having an internal conducting surface, and means for heating the cathode by the heat energy to be converted to electrical energy the means comprising the primary source of external energy applied to the converter, and a utilization circuit connected between the collector and cathode, the circuitry including no external source of energy not substentially less than that of the means for heating the cathode. The electrodes are housed in a gasfree enclosure which is maintained at a high vacuum. As shown in Fig. 1, cathode 22 is heated by burner 26 and electrons emitted as a beam 28 from emissive surface 13 are focused by control grid 14 and electromagnet 17, which surrounds the ceramic neck 11 housing the gun, and are accelerated through anode 15 into the interior of hollow, spherical collector 12, which comprises an inner conducting coating 20 on outer glass portion 19. An electrostatic electrode 16 modifies the field between the anode and the collector to prevent electrons returning to the anode, and once inside the collector, where the potential is uniform, the electrons flow to the collector then through load 38, where is developed the useful electrical output, and then back to the cathode. A modulating control voltage source 33 is connected between the cathode and control grid, and the anode has supplied a voltage 35 of about 10 kV. with respect to the cathode, which is earthed, and electrode 16 is held negative of the cathode by source 36. Two pre-accelerator electrodes may be placed between the control grid and the anode to uniformly distribute the potential between the anode and cathode, Fig. 2 (not shown). In a further modification, Fig. 3 (not shown), the electrodes are constructed to form a Pierce-type gun in which the cathode may be of the dispenser type having a flat or concave emissive surface (51) which is surrounded by a conical focusing electrode (53). The collector has a re-entrant frusto-conical flange (62) where it joins the neck (55) just above accelerating anode (56), and the electron beam may be focused either by a pair of U- shaped permanent magnets (63) or by electrostatic fields. In another embodiment, Fig. 4 (not shown), the electrodes are arranged in the form of a Hertz gun in which the cathode (76), electrostatic focusing electrode (77) and anode (90), with their respective insulation constitute a spherical surface with an aperture at the top which connects via a dielectric ring (93) with the aperture at the base of the spherical collector (92). Sweep coils (94, 95) adjacent ring (93) and connected to an A.C. source (96) may be used to aid in dispersing the electrons uniformly throughout the interior of the collector. The anode-cathode voltage may be 10-100 kV. and the cathode may be heated by a hot fluid in a pipe or directly by contact with a hot gas. Fig. 6 shows a further embodiment in which radioactive material 107 is used to heat cathode 105 and in which the electron beam expands after leaving the cathode and is focused to reconverge by a magnet 118 at the end of anode structure 113 before entering the cylindrical collector 123. In the lower portion of collector chamber 123, above annular anode flange 120, are disposed respectively a post-accelerator electrode 125 for further accelerating the electrons, a decelerating electrode 130 to reduce the positive field created by electrodes 113 and 125, and a pusher electrode 130 to repel electrons into the collector. An ion pump 141 disposed in a magnetic casing 143 may be connected to the chamber. The collector may have a series of projections spaced uniformly on its interior wall to act as pick-up probes. Although as shown the electrode potentials are supplied by batteries it is contemplated to derive these potentials from the energy generated by the converter through the load, which may be 180 volts on open circuit. The various features described specifically in connection with one embodiment may be employed in connection with other embodiments.