Modeling a Lossy Dieletric Polymer-based Thermoacoustic High Power Microwave Directed Energy Exposure Detection System

Abstract

Presented are design considerations for a potential detection and measurement technique that could provide operational awareness of high power microwave (HPM) directed energy weapon exposure for force health protection applications, leveraging thermoacoustic (TA) wave generation as the field interaction mechanism. The HPM electromagnetic frequency (EMF) regime, used in applications in both the counter-materiel and non-lethal counter-personnel design space, presents real-time personnel exposure warning challenges due to the potentially wide variation in time and frequency domain characteristics of the incident beam. As with other EM-thermal interactions, the thermoacoustic wave effect provides the potential to determine EM energy and power deposition without the need to measure ambient field intensity values or overload-sensitive EMF survey equipment. Following measurement of relevant EM, thermal, and elastic material property values, a carbon-filled polytetrafluoroethylene (CF-PTFE) lossy dielectric medium subject to pulsed HPM was computationally modeled using the commercial finite element method multi-physics simulation software package COMSOL. The simulation was used to explore the impacts of various material properties on TA signal output as a function of simulated incident field power density, EM frequency, and pulse length, thereby informing the selection of system components for the further development of a full TA-based HPM detection chain.

Characterization of a Thermoacoustic-based Pulsed High Power Microwave Detector Chain

“…A table top focused beam system (TT-FBS) (Thomas Keating Ltd, West Sussex, UK), leveraging curved reflectors and using thin nominally 6.5 mm thick sample plates, was used to obtain free-space 2-port scattering parameters across the 18-110 GHz frequency range, supplementing existing 2-18 GHz data (Frey et al 2022). As the various bands covered by the TT-FBS required different combinations of microwave horns, reflectors and sample mounts, scattering parameters below 67 GHz were obtained using nominally 305 mm  305 mm samples, while sample dimensions for data above 67 GHz were 152 mm  152 mm.…”