Cable Loop Measurements

Abstract : Measurements were made of currents and voltages induced in two separate radial Minuteman cables and a wedge-shaped loop by the electromagnetic effects from a 1.6-kt boosted nuclear device (HOB = 10 feet). In addition, current was measured on a scaled-down simulation of a Minuteman cable loop with and without a proposed guard conductor. Of the two radial cables, one had a conductive outer sheath and the other an insulating sheath. Maximum passively measured peak current was approximately 3,600 amperes in the radial cable with the conductive sheath, and 2,500 amperes in the insulated small single-strand loop. Dynamic current records for the loops consistently showed a long-duration circulating current pulse of significant amplitude, rising to a peak in about 4 milliseconds and lasting about 100 milliseconds. Polarity of these records had a patterned inconsistency. Dynamic current results showed that the current in a guarded conductor and the guard had the same ratio as the cross section of the conductors. Peak core-tosheath voltage at the distant end of the radial cables was apparently limited only by the value of the protective arc gaps used, value of about 10 kv. (Author)