An Improved magnetron injection gun using advanced high current density cathodes for a W-band TE01 Gyro-TWT

Improving the electron beam power and quality is essential to increasing the power and performance of the gyro-TWT. We have designed, and tested, a new magnetron injection gun (MIG) with nominal alpha=1.5 and calculated axial velocity spread (via EGUN) of 3.9% (neglecting cathode surface roughness, emission non-uniformity, and other defects). The gun is designed to nominally operate at 100 kV with ~8 Amp beam current at a cathode current density of 30 A/cm² and uses Scandate impregnated cathodes. Beam analyzer tests show that the gun performs with excellent beam quality and that the design is flexible with respect to maintaining the beam quality with variable operating parameters such as voltage, current, and compression. This is a low compression (only 12) thin beam design. The surface quality of advanced high current density cathodes can be inferred from the beam quality measurements. Advanced gyro-TWT design using the improved MIG is discussed.