Space Qualification of M- and MMC-type Cathodes at High Current Density

The need for higher current densities in combination with a long lifetime in recent TWT development, in particular in Q-band, drives a permanent improvement of cathode technology, models and operating conditions at Thales. Building on the very positive on-orbit experience with the M-type cathode up to 2.5 A/cm2 we show in this presentation that this cathode can safely operate at 4 A/cm2 for a space mission with a lifetime exceeding 15 years provided that its operating temperature is adequately adjusted. In parallel Thales is pursuing the development of an improved MM-type cathode doped with chromium (so-called MMC-type) targetting a qualification at 5A/cm2. We update on the latest results.