Ferroelectric Cathode Electron Emission Dependence on Magnetic Field

Many experiments on microwave and millimeter wave tubes, which are based on ferroelectric (FE) cathodes include a magnetic field in the emission region. For such electron devices, an optimal magnetic field leads to overall performance enhancement. In this paper, the dependence of the electron emission from an FE cathode on the magnetic field is experimentally examined and presented. The electron current emitted from an annular FE electron gun, suitable for gyrotron tubes, was measured with different magnetic fields. It was found that adding magnetic field extends the emitted current until a maximal working point is reached. Magnetic field above this point reduces the emission. A ~20 % enhancement in the emitted current relative to the emission in the absence of a magnetic field is obtained. Another observation relates to the gap closure and breakdown effects. The influence of the magnetic field on these effects is also reported. A suitable working point for an electron tube is chosen according to these observations.