Nuclear Electromagnetic Pulse (NEMP) Hardened Cables.

Energy from a Nuclear Electromagnetic Pulse NEMP couples into a system via the interconnecting cables. Calculations of the current induced on the sheath of a horizontal cable above a ground plane are discussed. These currents on the exterior of the sheath then excite the interior of the cable via the surface transfer impedance Z sub T. The objective of reducing NEMP coupling into cables is met by reducing the transfer impedance of the cable sheath. A standard test procedure is used to measure Z sub T. Typical military and commercial braided cable shields are measured first. Then, to more systematically approach the problem of reducing Z sub T, a set of twelve preliminary prototype cable shields are constructed. The effects of braid angle, braid material, distance separating braid layers and interbraid materials specifically insulators, aluminized Mylar foils, carbon loaded polyethylene and a ferromagnetic foil on Z sub T are investigated.