Stability of Space-Charged-Limited Electron Beam Diodes Including Applied- and Self-Magnetic Field Effects

The theoretical analysis of large-area diodes shows that the electron flow in the diode is subject to the transit-time instability (TTI). The TTI can modulate the electron beam energy at the anode and add a transverse beam temperature. Both of these effects can have negative consequences on many diode applications that require a high-quality mono-energetic electron beam. A distributed transmission line model of the diode is developed which allows techniques from microwave engineering to be applied to the unstable diode. The theory suggests that a resistively loaded, periodic structure of slots in the cathode can stabilize the TTI. The results from particle-in-cell (PIC) simulations of a large-area electron-beam diode in 2-D are presented that support this conclusion.