Long-life travelling-wave tubes use of "M" type cathode life prediction model

Extensive experimental testing of "M"-type cathodes has been performed, using Auger spectroscopy and diode testing of the electrode emission characteristics to determine optimum activation and operation temperatures. A theoretical model of cathode life is developed in terms of the work function and the cathode surface barium monolayer coverage. Comparison of theoretical and experimental values of the work function shows good agreement, and allows long-term cathode lifetime predictions. "M"-cathode behavior was followed in fifty flight model TWTs over a 2000 hour burn-in. This data and several thousand hours of lifetest data are compared to data for "S"-cathode TWTs.