Results of a traveling-wave tube life tesst program, including the description of a new technique for measuring cathode activity

The results of a life test on 29 twt’s all of the same type are reported. The life figures obtained range from 91 to over 19,000 hours with 9 of the tubes still operating. An explanation for this spread was found in the range of cathode temperatures required to give each tube the rated beam current unders pace change limited mission. The data obtained show a doubling of life for each reduction of 25° in cathode temperature. In all but one case, the failure was due to exhaustion of cathode material. The results indicate long life is achieved by high cathode activity level since this activity level determines how low an operating temperature can be used.