Crossed-Field Device Physics in Perturbed Systems

The project consists of theoretical, simulation, and experimental studies of electron stability and interactions in simple crossed-field systems and in magnetrons. Simulation results in planar crossed-field configurations demonstrate electron stability thresholds in current density and magnetic field tilt that agree with 1D theory and have been compared to experimental results. These experiments agree well with theory and simulation and utilized gated field emitters arrays as the electron sources. The experimental efforts have begun advancing as new gated field emitter arrays have been fabricated and are being tested. Eight devices have demonstrated > 40 mA of current at 60 V pulsed and were used in the experiments. Magnetron simulations in 2D and 3D (industrial magnetron) have been analyzed using two newly developed electron population techniques: intensity plots and breadth ratio. These new techniques show that prior to oscillation there is a dip in the azimuthal velocity distribution indicating highly cycloidal electrons near the cathode. To study the startup physics, electrons were injected in a counter rotation direction to purposely create highly cycloidal electrons. These simulations show much faster startup of the magnetron indicating that the dip in the azimuthal breadth ratio may show an electron population condition leading to startup. In other simulations, a cylindrical smooth anode geometry was used to study the transition to Brillouin flow by turning electron injection off and watching the azimuthal breadth ratio change versus time as it should go to infinity for purely laminar flow.