An Experimental Investigation of Electromagnetic Penetration through Apertures in a Conducting Cylinder

During the past decade fixed-site EMP (electromagnetic pulse) simulators have been designed to provide a relatively high quality replication of anticipated EMP environments. Concurrently, efforts have also been directed toward development of a transportable EMP test technique which will allow EMP hardness checks of military systems in the field. 1,2 Because of the importance of aperture penetration in the transfer of electromagnetic radiation from the outside to the interior of many of the systems of practical interest, a portion of this development effort has been devoted to an examination of electromagnetic responses of a wire located within a conducting cylinder containing deliberate apertures. Similar empirical studies have been conducted by several investigators for configurations with a single aperture. 3'4 In this paper we will discuss exterior and interior responses obtained with a test cylinder subject to illumination by the EMP simulator for aircraft (EMPSAC) located at the Naval Air Test Center, Patuxent River, Maryland. Excitation of the inner wire through one or two apertures will be examined for configurations in which the orientation of apertures with respect to the ground and the terminations at the ends of the interior wire were varied. After discussion of the experiment and presentation of test data, comparisons between numerical estimates of surface and interior responses and measured data are provided.