Electron beam Propagation Analysis of a Simple, Planar Crossed-Field Structure

Abstract

Electron beam stability in the crossed-field gap in terms of magnetic (B) field, magnetic field tilt 1 , and applied voltage 2 have not been studied thoroughly except for a few 1-D theoretical works 1,2 . In this research, we will analyze electron beam propagation and perturbation experimentally, and then the results will be compared with prior theoretical, and simulation works. The planar geometry contains an anode (150 mm long, and 100 wide), sole electrode, gated field emission cathode, and collector. The anode-sole gap was fixed at 20 mm . A B-field of up to 250 Gauss was applied perpendicularly by two Helmholtz coils. A -3 kV DC voltage was applied to the sole, and the anode was biased at 0 V. An in-house developed driver circuit for current emission and data acquisition, was used. The injected beam source is comprised of five gated field emitter arrays (GFEAs) 3 . These GFEAs were arranged to provide uniform electron emission. Each GFEA is capable of producing a field emission current of ≈ 4 mA for a total beam current of ≈ 20 mA, for a gate pulse of 50V. The experimental results show a nominal match with the theory and simulation 4 in terms of magnetic field of 0 T to 0.02 T and magnetic field tilt of 1° to 5°. Experiments are ongoing to further elucidate this behavior.