Gated Field Emitter Arrays for Planar Crossed-Field Device Experiment

High power magnetrons and crossed-field amplifiers (CFA) are advantageous in terms of power density and efficiency. However, electron beam stability in the crossed-field gap in terms of magnetic field tilt 1 , current density, and AC modulation of the applied voltage 2 have not been studied thoroughly except for prior 1-D theoretical work 1 , 2 . In this work, we will compare simulation results of a simple 3-D crossed field model to the experimental results obtained with a planar crossed-field geometry consisting of an anode (150 mm long), sole electrode, injected beam gated field emission cathode, and collector. The sole to anode gap is varied from 5 to 20 mm. A perpendicular magnetic field of up to 250 Gauss is supplied by Helmholtz coils. A -3 kV DC voltage is applied to the sole and the anode is biased at 0 V. An in-house developed drive electronics, including a driver circuit for current emission and data acquisition, is currently being developed. The injected beam source is comprised of eight individual gated field emitter arrays (GFEA). These GFEAs are 7.5 mm long, 2.5 mm wide, 0.7 mm thick and consist of eighteen array elements each with 100×100 silicon tips, formed in a mesh structure to provide uniformity of emission. Highly resistive ballasting structures in the emitters provide current stability. Such GFEAs are capable of producing a current density of > 100 A/cm 2 as previously reported 3 . Here, we have characterized similar GFEAs, which generate > 50 mA each at 50 V pulsed after UV exposure, potentially providing > 400 mA for the experiment. The initial results of this experiment will be presented and compared with our simulation.