Beam Test of a Novel CNT Cathode-Based Electron Gun Assembled in a TWT

A magnetic-focused X-band traveling wave tube (TWT) based on carbon nanotube (CNT) cathode is presented. The CNT TWT has a simple structure of the electron gun, consisting of a CNT emitter electrode and a ring-shaped anode, with no metallic mesh extracting electrode, nor electrostatic focusing electrode. The field emission electrons are extracted directly by the ring-shaped anode, while the electron beam focusing is realized by an extra magnetic field. Apart from the CNT electron gun, the TWT mainly has a high-frequency interaction circuit and a collector. All these components are totally immersed in a uniform axial magnetic field, and thus, electrons are confined by the Lorentz force during their traveling process from the cathode surface toward the collector. The fabricated CNT TWT was tested in a superconducting system providing a uniform axial magnetic field. The dc mode testing showed about 86% of the emission electrons can reach collector, which is better than a common gate-controlled CNT electron gun.