ANNULAR ELECTRON-BEAM GENERATION USING A FERROELECTRIC CATHODE

In this paper, we report on the emission of electrons from a ferroelec tric cathode in a coaxial gun geometry. The electrons are emitted from the inner conductor of the coaxial system and are accelerated radiall y. An axial magnetic field causes the formation of an azimuthal annula r electron flow. The electrostatic potential distribution then leads t o the ejection of the annular beam from the anode-cathode region into the drift space. A beam energy of up to 50 keV and an electron current of up to 250 A is typical in this proof of principle experiment. The Hull cutoff condition is found to considerably underestimate the magne tic field required to insulate the radial electron current flow in the diode, The results obtained are consistent with earlier data showing that the behavior of the ferroelectric is closely coupled to the chang ing state of the ferroelectric.