M type cathode life tests for space TWTs

BVERI evaluated the M cathodes lifetime in 40 diodes and 18 electron guns (including 2 TWTs) in DC mode under the conditions of temperature acceleration and current density acceleration. The total accumulate time of 40 diodes and 18 electron guns (including 2 TWTs) were more than 681000 hours and 275000 hours separately. Based on the tiny change of cathode surface work function, the authors present the primary life model of the M cathode, which shows that the life of 6112M cathode operating at 999 °C_b are 331936 hours (37.9 years) at the current density of 1.0A/cm² and 254374 hours (29.0 years) at the current density of 2A/cm².