On Approximating the EMP Response of Small Cavities

A straightforward (pedestrian) approximation scheme is applied to a transient electromagnetic field problem associated with a finite-length cylindrical cavity bounded by perfectly conducting walls. The cavity is filled with a homogeneous lossy dielectric material. Analytic expressions for the zeroth-and first-order terms of the perturbation solution for each of the relevant components of the electric and magnetic fields generated by an axially propagating current pulse are presented. Results obtained for various sample problems are examined and comparisons with the exact solutions are highlighted. The adequacy and limitations of such an approximation scheme are discussed, and the errors associated with ignoring the displacement and conduction currents are made evident.