Isotropic graphite multistage depressed collectors-a progress report

Author

Ramins, Peter ; Ebihara, Ben T.

Author_Institution

NASA Lewis Res. Center, Cleveland, OH, USA

Volume

36

Issue

4

fYear

1989

fDate

4/1/1989 12:00:00 AM

Firstpage

817

Lastpage

824

Abstract

A small, isotropic graphite electrode multistage depressed collector (MDC) was designed, fabricated, and evaluated in conjunction with a 500-W, CW (continuous wave), 4.8-to-9.6-GHz TWT (traveling wave tube). The carbon electrode surfaces were used to improve the TWT overall efficiency by minimizing the secondary electron emission losses in the MDC. The design and fabrication of the brazed graphite MDC assembly are described. The TWT and graphite electrode MDC bakeout and processing (outgassing) characteristics were evaluated and found to be comparable to those for TWTs equipped with copper electrode MDCs. The TWT and MDC performance was optimized for broadband CW operation at saturation. The average RF, overall, and MDC efficiencies were 14.9, 46.4, and 83.6%, respectively, across the octave operating band. A 1500-h CW test showed no gas buildup and excellent stability of the electrode surfaces

Keywords

electrodes; electron tube manufacture; graphite; travelling-wave-tubes; 14.9 percent; 4.8 to 9.6 GHz; 46.4 percent; 500 W; 83.6 percent; C; SHF; TWT; bakeout characteristics; brazed graphite assembly; broadband CW operation; continuous wave; electrode surface stability; fabrication; isotropic graphite electrode; loss minimisation; microwave tubes; multistage depressed collectors; octave operating band; outgassing characteristics; saturation; secondary electron emission losses; traveling wave tube; Carbon dioxide; Circuits; Copper; Electrodes; Electron emission; Filler metals; Furnaces; Hydrogen; Radio frequency; Vacuum technology;

fLanguage

English

Journal_Title

Electron Devices, IEEE Transactions on

Publisher

ieee

ISSN

0018-9383

Type

jour

DOI

10.1109/16.22492

Filename

22492