GB1379140A - Offswitching of metal arc switching device by internal current diversion to an auxiliary electrode - Google Patents

Abstract

1379140 Metal vapour discharge apparatus; cold cathode tubes HUGHES AIRCRAFT CO 5 Sept 1972 [7 Sept 1971] 41123/72 Heading H1D A metal arc device comprises panel shaped auxiliary electrodes 56 positioned parallel to the plasma jet flow direction and which on application of a negative potential, extract ions from the plasma to cause secondary electron emission from the auxiliary cathodes at least equal to the cathode-anode current and so stopping conduction therebetween. The cathode may be Cs, Li, Ga or Hg, the latter preferably with Mo main electrodes. Solid metal cathode devices may include rod shaped anode and cathode. Anode 16 has coolant on heating passage 16, the envelope is at least partly insulative and includes condenser 50, cathode 22, pool retaining walls 30, heater 40, heat exchanger 44, and optional temperature sensors, and the liquid metal may be either fed or provided by intermediate vaporization and recondensation. The metal need not be fed as a liquid, and feed line 46 may include restriction 48. For vapour feed, a capillary passage restriction is preferred. Condensed metal in trough 52 is recirculated by lin 54. Arc initiators may be aux. electrode, s/c, laser or plasma gun type. Fig. 2 (not shown) includes pool keeping walls (120), cooling or heating coils (122), heater coils (124) preventing metal condensation and arc transfer, and cooling coils (126). Voltage graded screens concentric to screen (132) may be included, also heat insulator (140), corona shields (144), (150). The device may be sealed off or continuously pumped. Electrical and other operational features are disclosed. Ion bombardment of the auxiliary electrodes on initiation of the off switching may form an arc spot, which may be inhibited by reduced area auxiliary cathodes for example. Applications are exemplified.