Experimental study of 50-kV/3.5-a hollow electron beam produced by ferroelectric cathode

An annular electron beam emitted from a flat ferroelectric cathode is demonstrated in this paper. The cathode with a pierced ring-shaped front electrode was operated in two different electron gun setups. In the first electron gun, the cathode was operated in low voltages and under different magnetic fields. The beam shape was photographed, and the beam radii were controlled by the magnetic field. In the second electron gun, with a high voltage of 50 kV, an annular beam was also obtained, with a current of ∼ 3.5 A. The configuration presented here may be the basis for an annular electron beam source for a gyrotron.