US 4,277,721 AGranted

Multistage depressed collector for dual mode operation

AssigneeThe United States of America as represented by the Administrator of the National Aeronautics and Space Administration

InventorHenry G. Kosmahl

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Abstract

The object of the invention is to provide a depressed collector which captures the spent electrons of a microwave transmitting tube at high efficiency in both high and low power modes of operation. The collector comprises entrance and end electrodes (14 and 18, respectively), electrode (18) having a spike extending toward entrance electrode (14). Intermediate electrodes (15, 16 and 17) and the entrance electrode (14) each have a central aperture and, together, these electrodes capture most high power mode spent electrons. The apertures of the electrodes (14-17) increase in size in a downstream direction. To capture low power mode spent electrons a low power mode electrode (19) is positioned between the last intermediate electrode (17) and the end electrode (18). This electrode (19) has a central aperture preferably smaller but no larger than that of electrode (17). An auxiliary low power mode electrode 20 may be disposed between electrodes 19 and 18 and has a central aperture larger than that of the low power mode electrode (20). All of the electrodes 14-20 are at voltages provided by a voltage divider 21 connected between a potential as at a negative terminal (21) and a common ground return 23.

Claims22

Dependent claims

In a microwave traveling wave transmitting tube (TWT) of the type having an electron emitting cathode, a depressed collector and having high power and low power modes of operation, said TWT serving as a source providing a beam of spent electrons whose trajectories diverge from the beam axis in a downstream direction from said source;

a collector for said electrons, said collector comprising:
a first beam entrance electrode, said first electrode having a central aperture and being bowed toward said source of spent electrons;
a conical end electrode downstream from said first electrode having a spike extending from its apex toward said source of electrons, said spike lying on said beam axis;
at least one intermediate electrode positioned between said first electrode and said conical end electrode and having a central aperture, said aperture being of greater diameter than the aperture of said first electrode, said intermediate electrode being bowed toward said source of spent electrons;
at least one low power mode electrode positioned between said intermediate electrode and said conical end electrode and having an aperture no larger than that of said intermediate electrode, and being axially positioned such that no more than about one-quarter of said spike extends through said aperture whereby most of said spent electrons pass between said spike and the edge of said aperture in said low power electrode when said tube is operated in said low power mode.

2 more elements

Dependencies are inferred from the claim text.