NEMP fields inside a metallic container with an aperture in one wall

The finite-difference time-domain (FDTD) method was used to study the nuclear electromagnetic pulse (NEMP) waves coupling into one metallic container through a small aperture in one face of the container. The incident electric fields of NEMP waves were expressed by double exponential forms with two different decay constants. The time-domain behavior of the electric field inside the metallic container excited by the waves was obtained by the FDTD method. The electric field distributions on various layers for the area of the aperture of 10/spl times/10 cm/sup 2/ were also calculated. It was found that the shielding effectiveness is greatly improved by a factor of 255 by reducing the area of the aperture from 10/spl times/10 to 1/spl times/1 cm/sup 2/. The aperture filled with dielectric materials was also studied for shielding effectiveness. The coupled electric field inside the metallic container was round to be a nonlinear function of the relative dielectric constant of insulators filled in the aperture.>