Accession Number : ADA310387

Title :   Design, Fabrication, and Performance of Brazed, Graphite Electrode, Multistage Depressed Collectors with 500-W, Continuous Wave, 4.8- to 9.6-GHz Traveling-Wave Tubes.

Descriptive Note : Technical paper,

Corporate Author : NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CEN TER

Personal Author(s) : Ramins, Peter ; Ebihara, Ben

PDF Url : ADA310387

Report Date : MAR 1989

Pagination or Media Count : 19

Abstract : A small, isotropic graphite electrode, multistage depressed collector (MDC) was designed, fabricated, and evaluated in conjunction with a 500-W, continuous wave (CW), 4.8- to 9.6-GHz traveling wave tube (TWT). 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 brazing technique, which used copper braze filler metal, is compatible with both vacuum and the more commonly available hydrogen atmosphere brazing furnaces. The TWT and graphite electrode MDC bakeout, processing, and outgassing characteristics were evaluated and found to be comparable to TWT's equipped with copper electrode MDC's. The TWT and MDC performance was optimized for broadband CW operation at saturation. The average radiofrequency (RF), overall, and MDC efficiencies were 14.9, 46.4, and 83.6 percent, respectively, across the octave operating band. A 1500-hr CW test, conducted without the use of an appendage ion pump, showed no gas buildup and excellent stability of the electrode surfaces.

Descriptors :   *TRAVELING WAVE TUBES, *ACCUMULATORS, CONTINUOUS WAVES, GRAPHITE, COPPER, ISOTROPISM, BROADBAND, SECONDARY EMISSION, BRAZING, OUTGASSING, ION PUMPS.

Subject Categories : Electrical and Electronic Equipment

Distribution Statement : APPROVED FOR PUBLIC RELEASE