Advanced Dispenser Cathodes
Controlled porosity reservoir cathodes offer significantly improved performance over conventional impregnated cathodes. Optimized performance requires additional design to achieve reduced barium deposition on adjacent surfaces, increased lifetime, and high current density emission. This paper describes the achievable performance and the associated design requirements.
Cusp Guns for Helical-Waveguide Gyro-TWTs of a High-Gain High-Power W-Band Amplifier Cascade
The evaluation, design, and simulations of two different electron guns generating the beams for W-band second cyclotron harmonic gyro-TWTs forming a high-gain powerful amplifier cascade are presented. The optimum configurations of the systems creating nearly axis-encircling electron beams having velocity pitch-factor up to 1.5, voltage/current of 40 kV/0.5 A, and 100 kV/13 A with acceptable velocity spreads have been found and are presented.
The M-type cathode — No longer magic?
Recent progress in the understanding and quantification of the surface effects occurring in M-type and mixed metal matrix cathodes is described. A new mechanism for the mode of emission enhancement in these cathodes is proposed based on chemical rather than physical effects. A correlation has been established between the formation of osmium/tungsten alloy and reduced effective work function. Using this result an improved dispenser cathode has been constructed with a work function 0.2 eV lower than conventional B-type emitters.