Analysis of Injected Electron Beam Propagation in a Planar Crossed-Field Gap

Ranajoy Bhattacharya,Adam M Darr,Allen L Garner,Jim Browning

doi:10.3390/app11062540

Ranajoy Bhattacharya, Adam M Darr + Show 2 more

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https://doi.org/10.3390/app11062540

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Abstract

This paper examines basic crossed-field device physics in a planar configuration, specifically electron beam perturbation and instability as a function of variation in magnetic field, and angle between magnetic and electric field. We perform a three-dimensional (3-D) simulation of electron perturbation in a planar crossed-field system using the full 3-D particle trajectory solver in CST Particle Studio (CST-PS). The structure has a length, height, width and anode-sole gap of 15 cm, 2 cm, 10 cm, and 2 cm, respectively. The anode to sole voltage is fixed at 3 kV, and the magnetic field and injected current varied from 0.01 T to 0.05 T and 1.5 mA to 1 A, respectively. The simulations show that applying a magnetic field of 0.05 T makes the beam stable for a critical current density of 94 mA/cm2 for an anode-sole gap of 20 mm. Above this current density, the beam was unstable, as predicted. Introducing a 1° tilt in the magnetic field destabilizes the beam at a current density of 23 mA/cm2, which is lower than the critical current density for no tilt, as predicted by our theory. The simulation results also agree well with prior one-dimensional (1-D) theory and simulations that predict stable bands of current density for a 5° tilt where the beam is stable at low current density (<13.3 mA/cm2), unstable above this threshold, and then stable again at higher current density, (>33 mA/cm2).

Highlights

High power microwave crossed-field tubes such as magnetron oscillators [1] and crossed field amplifiers (CFA) [2] are used in many applications, including radars, communication systems, and material processing
This paper primarily focuses on validating the 1-D space charge limited theory for a crossed-field device [5,11] by performing a 3-D simulation of a simple, planar crossed-field injected beam geometry, which will be validated experimentally
The instability instability study thethe parameters listed in TaThe study entails entailsperforming performingsimulations simulationsfor for parameters listed in ble

Summary

Introduction

High power microwave crossed-field tubes such as magnetron oscillators [1] and crossed field amplifiers (CFA) [2] are used in many applications, including radars, communication systems, and material processing. Improvements of these devices in terms of power density, phase-locking or control, and faster startup times are of particular interest. Showed the feasibility of controlling the phase of a magnetron by modulating the electron injection Simulating these approaches requires validated electron transport models and an understanding of the stability of crossed-field electron transport under high current density and magnetic field tilt. Additional assumptions, such as zero electric field on the cathode surface, are sometimes introduced [4,5,6]

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