Publication Date

5-2012

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Electrical Engineering

Department

Electrical and Computer Engineering

Supervisory Committee Chair

Jim Browning, Ph.D.

Abstract

To integrate field emitter arrays (FEAs) into microwave vacuum electron devices, the use of insulating funnels, called electron hop funnels, is proposed. Electrons are emitted into the wide end of the funnel, and utilizing secondary electron emission to sustain current, the electrons "hop" up the funnel walls. Eventually the electrons exit the funnel as a denser and more uniform electron beam. To pull the electrons up the funnel, an electrode, called the hop electrode, is placed around the exit of the funnel to generate an electric field between the funnel exit and the electron source. The current transmitted through the device depends directly on the hop voltage, and experimental work has found that there is hysteresis in the transmitted current vs. the hop voltage (I-V characteristic). The shape of the I-V curve changes when the voltage is ramped up or down. To characterize and explain the hysteresis, a model of the hop funnel was simulated in the particle trajectory code LORENTZ 2E. The results of the simulations show that hysteresis is a fundamental characteristic of hop funnels. Experimental data does not directly match the simulation results but confirms the general trend found in the simulations.

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