GB1146713A - Thermionic generator - Google Patents

Abstract

1,146,713. Thermionic generator. UNITED STATES ATOMIC ENERGY COMMISSION. 31 May, 1966 [18 Aug., 1965], No. 24110/66. Heading H1D. A caesium-filled thermionic generator adapted to be operated without the use of liquid pools at a temperature above the condensing temperature of the caesium vapour includes a member which acts as a caesium vapour store by providing a large surface area for retaining at least ten times as many Cs atoms in the store as are present in the envelope space. As shown, the store is of the sponge type and comprises a sintered tungsten block 20 with a polished tungsten face 22 and may form at least part of the cathode 14, which is spaced from anode 16 by ring 18. The caesium stored in the pores above its condensation temperature may be liberated by heating the store to a still higher temperature, the temperature of the envelope remaining at the former temperature, e.g. 553‹ K., during tube operation. Because the binding energy of adsorbed Cs vapour is high (about 2 ev. at 550‹ K. compared with 0À75 ev. for a liquid pool type reservoir) large temperature fluctuations of the reservoir do not affect the vapour pressure which thus remains substantially unaltered. To fill the tube and store with Cs vapour, the envelope 12 and electrodes 16, 22 are raised to their operating temperatures and the tube via tubulation 24 is connected to an appendage containing a Cs pool. After equilibrium at the desired pressure, e.g. 1 torr, has been attained the tube is sealed. The store contains sufficient Cs to replenish lost Cs throughout the lifetime of the converter.