Magnetically insulated transmission line oscillator

Date

2022-08

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Abstract

A multi-year project at Texas Tech University focused on developing a low-impedance magnetically insulated transmission line oscillator (MILO) as a high-power microwave (HPM) source. The MILO is driven by a pulse forming line (PFL) charged by a compact Marx bank capable of producing a high voltage pulse of over 500 kV with a 50 ns duration with less than a 20 ns rise time. The MILO design aimed to meet design criteria set out by the project's sponsor, the Office of Naval Research (ONR). These requirements set out that the MILO must achieve an output microwave pulse with a minimum of 1 GW peak power, a center frequency within the S-Band frequency range, and a target efficiency of at least 10%. The MILO contains a bellows system for setting the beam dump position relative to the cathode. It changes the amount these components overlap, altering the insulation current and testing its effect on the peak output power of the outputted signal.

This document will detail the process of design, simulation, implementation, and testing of such a device detailing the entire process and covering key concepts of its operation. The design followed a set of base design equations that define the critical dimensions of the MILO's slow-wave structure (SWS), cathode, and beam dump required to achieve magnetic insulation and produce the desired output frequency. This initial design was simulated within CST Studio Suite, a commercially available three-dimensional computer simulation software suite, with the Particle-in-Cell (PIC) simulation. An additional thermal simulation was performed to ensure the stability of the MILO during operation using the COMSOL simulation suite. The simulation results were used to optimize the design to maximize the outputted microwave signal's peak power while remaining within the target frequency range. The MILO was then constructed and attached to a test bed, including a compact Marx generator as the pulsed power supply. The MILO was run through a series of tests determining its peak output power and center frequency at various inputs and with varied cathode overlap depths. The results of which are presented and discussed.


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Keywords

HPM, MILO, High Power MIcrowave, Pulsed Power, Magnetically Insulated Transmission Line Oscillator

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