Improving the reliability of space-use traveling wave tubes and confirming the improvement

This study establishes the design method for the high reliability for the space-use traveling wave tube (TWT) and presents the verification experiment of the high-reliability performance for the case of TWT to be installed on CS-3, as an example. Based on the relation between the cathode current density and the lifetime, which is derived from the degradation theory of the coated impregnated cathode, the convergence ratio of the electron gun and the cathode current density are optimized. A method is presented which realizes the long-life and highly reliable TWT, by the high-reliability design and the screening based on theory. To verify the high-reliability design, the wear-out failure distribution is estimated by the accelerated temperature test; and the failure rate due to the random failure is estimated from the actual in-orbit data. As a result of analysis of this mixed Weibull distribution, it is shown that the failure rate of 1000 fit, which is set as the design goal, can be achieved for 7 years of planned working period. It is shown also that by employing the high-reliability design, the failure rate of 1000 fit or less can be achieved even if the working period of 10 years is defined.