Cascaded thermionic energy converter tube

Claim 1

A THERMIONIC ENERGY CONVERTER TUBE COMPRISING: (A) A HOLLOW CYLINDRICAL HEAT TUBE FORMING THE INNER WALL OF AN ANNULAR ENVELOPE; (B) AT LEAST TWO AXIALLY-SPACED HOLLOW CYLINDRICAL THERMIONIC EMITTERS SURROUNDING SAID HEAT TUBE; (C) MEANS MOUNTING SAID EMITTERS ON SAID HEAT TUBE IN HEAT CONDUCTING RELATION THEREWITH AND IN ELECTRICAL INSULATING RELATION WITH EACH OTHER; (D) AT LEAST TWO AXIALLY-SPACED HOLLOW CYLINDRICAL COLLECTORS EACH SURROUNDING ONE OF SAID EMITTERS IN SPACED RELATION THEREWITH TO FORM A DIODE UNIT; (E) ENVELOPE MEANS SURROUNDING SAID EMITTERS AND AT LEAST THE INNER SURFACES OF SAID COLLECTORS AND SEALED TO THE ENDS OF SAID HEAT TUBE TO COMPLETE SAID ANNULAR ENVELOPE; (F) MEANS WITHIN SAID ENVELOPE ELECTRICALLY CONNECTING EACH COLLECTOR EXCEPT THE LAST ONE TO THE EMITTER OF THE NEXT DIODE UNIT; SAID (G) MEANS FOR PRECISELY SPACING AND INSULATING ONE OF SAID EMITTERS FROM THE SURROUNDING COLLECTOR, COMPRISING: (1) A PAIR OF COMPLEMENTAL CIRCUMFERENTIAL GROOVES OF SUBSTANTIALLY SEMICIRCULAR CROSS-SECTION FORMED IN THE ADJACENT SURFACES OF SAID EMITTER AND COLLECTOR; (2) A PAIR OF LONGITUDINAL GROOVES OF THE SAME CROSS-SECTION AND DEPTH AS SAID CIRCUMFERENTIAL GROOVES FORMED IN THE ADJACENT SURFACES OF SAID EMITTER AND COLLECTOR, EXTENDING FROM SAID CIRCUMFERENTIAL GROOVES TO ONE END OF SAID ELCTRODES; AND (3) A PLURALITY OF SPHERICAL BALLS OF REFRACTORY INSULATING MATERIAL DISTRIBUTED AROUND AND SNUGLY FITTING IN SAID CIRCUMFERENTIAL GROOVES.