A Faceted Magnetron Concept Using Field Emission Cathodes

A magnetron concept using field emission cathodes has been modeled with the Air Force Research Laboratory particle-in-cell code ICEPIC and the 2D particle trajectory simulation Lorentz2E. In this approach, field emitters are used to provide a distributed cathode in place of a traditional thermionic cathode. The emitters are placed below the interaction space in a shielded structure. The cathode is comprised of facet plates with slits to protect the emitters. Simulation of an L-band rising sun magnetron shows that the faceted magnetron will oscillate using both five and ten facet cathodes. The startup times are very similar to that of a cylindrical cathode magnetron. The electron trajectories of the shielded slit structure have been modeled, and the results indicate that electrons can be injected through the slits and into the interaction space using lateral edge emitters and a pusher electrode design

Simulation of a Time-Varying Distributed Cathode in a Linear Format Crossed-Field Amplifier

The effects of a temporally modulated, distributed cathode in a linear format crossed-field amplifier (CFA) are simulated in VSim and analyzed. A linear format, 150 MHz, low power (100 W), moderate gain (7 dB), meander line CFA is used as the basis for the simulation model. This paper describes simulations with different time-varying distributed cathodes in which electron injection is modulated at the RF frequency both in and out of phase with the RF input. At low RF input power the modulated electron injection dominates the operation. Injecting in phase with the RF input shows gain increases from 23 dB at 150 mA to 32 dB at 1 A for low cathode modulation power (\u3c 0.1 W). The CFA efficiency increased from 2-4% to 20-24% using the electron modulation. The simulation shows distinct cylindrically shaped electron bunches as opposed to spokes because of the synchronous injection. These results suggest that for high power magnetrons electron modulation could improve gain

Effects of Electromagnetic Stimulation on Soil’s Hydraulic Conductivity

Our research involves the identification of the different effects that electromagnetic (EM) stimulation has on varying soil properties; properties such as hydraulic conductivity. This work could prove to be of importance in furthering our understanding of the effects of EM stimulation with regard to the hydraulic conductivity of soil. A positive correlation between EM stimulation and an increase in hydraulic conductivity could have broad applications for environmental contaminant mitigation in soils and for various geotechnical construction applications such as minimizing soil setup during pile driving operations. EM waves can be used to enhance soil and groundwater remediation in a way that no heat is generated, yet the desired mechanisms in soil are stimulated. Our approach in this project involved the construction of a customized permeameter that enabled us to measure the change in hydraulic conductivity given a tuned EM wave from an antenna. An EM wave with a fixed frequency and varying power output was sent through the permeameter while the hydraulic conductivity was measured in real time. Tests performed for the research project were successful in showing a correlation between hydraulic conductivity and EM stimulation

Electron Hop Funnel Measurements and Comparison with the Lorentz-2E Simulation

Electron hop funnels have been fabricated using a Low Temperature Co-Fired Ceramic (LTCC). Measurements of the hop funnel I-V curve and electron energy distribution have been made using gated field emitters as the electron source. The charged particle simulation Lorentz 2E has been used to model the hop funnel charging and to predict the I-V and energy characteristics. The results of this comparison indicate that the simulation can be used to design hop funnel structures for use in various applications

Hysteresis in Experimental I–V Curves of Electron Hop Funnels

Electron hop funnels provide a method to integrate field emission arrays into microwave vacuum electron devices, to protect the arrays, and to provide a method to study the secondary electron characteristics of dielectrics. A hop funnel is a dielectric material with an electrode, known as the hop electrode, placed around the narrow end (exit) of the funnel to control the current transmitted through the device. Current is transmitted through the funnel via electron-hopping transport. This work investigates a hysteresis observed in the current–voltage characteristic of the device. The experimental results showing the observed hysteresis will be presented. This work will demonstrate that charging on the bottom of the hop funnel is not the fundamental cause of the hysteresis