An accelerated life test method for highly reliable on-board TWT´s with a coated impregnated cathode

Author

Mita, Nagahisa

Author_Institution

Satellite Commun. Syst. Lab., NTT Radio Commun. Syst. Labs., Kanagawa, Japan

Volume

41

Issue

7

fYear

1994

fDate

7/1/1994 12:00:00 AM

Firstpage

1297

Lastpage

1300

Abstract

An accelerated life-test method is established for on-board TWT´s with an M-type cathode. This method is shown to be effective to predict the TWTs reliability. The M-type cathode has two life-limiting factors: impregnant reduction and surface coating degradation. The theoretical calculations of these factors under the accelerating conditions are confirmed by the life-test results. The highest acceleration is obtained at the cathode temperature of 1100 °C_B with the cathode current density of 0.6 A/cm². In this case the acceleration factor is derived to be 31. The lifetime distribution of TWT´s at the optimum cathode temperature is predicted using the derived acceleration factors. The Weibull distribution of BTTs (beam test tubes) fits a line with a slope of 3.2. From this result, TWT´s with an M-type cathodes at optimum cathode temperature show wear-out failure and their cumulative failure rate is under 0.5% during a useful life of 100 000 h

Keywords

electron tube testing; life testing; oxide coated cathodes; reliability; travelling-wave-tubes; 100000 hour; 1100 C; M-type cathode; TWT reliability prediction; Weibull distribution; accelerated life test method; accelerating conditions; coated impregnated cathode; cumulative failure rate; highly reliable on-board TWT; impregnant reduction; life-limiting factors; surface coating degradation; wear-out failure; Acceleration; Cathodes; Coatings; Current density; Degradation; Kelvin; Life estimation; Life testing; Space exploration; Temperature;

fLanguage

English

Journal_Title

Electron Devices, IEEE Transactions on

Publisher

ieee

ISSN

0018-9383

Type

jour

DOI

10.1109/16.293361

Filename

293361