Simulant development for liquid explosive materials using millimeter wavelength characterization and ensemble averaging

This work describes the characterization of liquid explosive materials and the development of a simulant material. A Keysight coaxial probe was used to characterize the complex permittivity of the liquid explosive of interest and the simulant material formulations as a function of frequency. Data was collected over the frequency range of 500 MHz to 50 GHz. The frequency range overlaps several existing millimeter wavelength imaging systems. Complex permittivity data was processed using a Fresnel reflection/transmission model which produces an effective reflection coefficient for a sample of material as a function of frequency. The model accounts for sample thicknesses and backing materials such as skin and air. An ensemble average across the bandwidth of the millimeter wave system of interest is then applied to model the response of the material to the imaging system of interest. Complex permittivity data will be presented along with model results showing excellent agreement between the explosive material and its paired simulant material for MMW imaging systems of interest.