Design of electron guns and focusing structures for THz linear beam tubes

Results are reported for numerical modeling of concepts for non-circular beam formation for near-THz frequency TWT’s. Several methods for beam compression were examined, and one method appears promising for producing a 12 kV, 8 mA beam with a cross section 70 x 160 microns, while keeping the cathode loading to about 59 A/cm2. This would be suitable for a 650 GHz TWT. The beam loading is significantly lower than in similar frequency backward wave oscillators (BWO) and should result in much longer cathode lifetimes.