Microwave induced thermoelastic process in dielectrics-theory and experiments

Theoretical and experimental studies on microwave pulse induced pressure waves are reported. A thermodynamical formulation of microwave interaction with dielectrics is summarized. It is shown that acoustic waves may be generated by pulsed microwaves even in the absence of inhomogeneity of microwave absorption, owing to discontinuities of thermodynamical variables and microwave exposure conditions across the dielectric interface. The formulation is applied to a spherical system and some numerical results are presented. Experimental results include measurement of pressure waves in a cylinder filled with an aqueous solution of electrolytes exposed to pulsed microwaves and estimation of the coupling efficiency between the liquid dielectric and the adjacent air. Pressure scaling with energy per pulse is also demonstrated.