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A research activity involving the detailed consideration of novel high-voltage transformers for pulsed-power applications has recently begun at Loughborough University. Although the main goal is the demonstration of a compact and lightweight unit employing magnetic insulation under vacuum conditions, the initial stage of the work is directed toward the development of a conventional air-cored transformer as a main component in a compact power supply for high power microwave sources. In cooperation with the Swedish Defence Research Agency (FOI), the power supply has been tested with a microwave source of the vircator type. The power generator for the system uses a 70-kJ/25-kV capacitor bank and an exploding wire array to generate a 150-kV voltage pulse in the primary circuit of a transformer. A pressurized SF6 spark gap in the secondary circuit sharpens the high-voltage output so that pulses approaching 500 kV and with a rise time well below 100 ns are generated on a 20-Ω high-power resistor, with the peak power in excess of 10 GW. Experimental results are presented from final testing of the system, where a reflex triode vircator replaces the 20-Ω resistor. Measurements of the microwave emission using free-field sensors are presented, and comments are made with the microwave emission from the same vircator when powered by a Marx generator at FOI. [ABSTRACT FROM AUTHOR]

A simple method is described for calculating the shielding performance of a two-dimensional (2-D) thin finite-width shield made of imperfect material in the presence of the magnetic field from line source conductors. First, solutions to two canonical problems with closed-form simple analytic formulas are presented; shielding by reflection from and absorption in thin planar shields of infinite extent and shielding by perfect conductor shields of finite width. Then the method for calculation of magnetic-field shielding by perfect conductor finite-width shields is extended using the simple interpolation method, to thick shields made of imperfect material. Finally, the hybrid solution is developed by adding the two results in quadrature. The result is a simple theory for shielding by finite-width shields made of any real shielding material of arbitrary thickness. Its accuracy has been validated by comparison to finite-element method solutions and existing measurements. [ABSTRACT FROM AUTHOR]

Simple approximate methods are developed and described for calculating the extremely low-frequency magnetic-shielding effectiveness for single- and double-layer infinite planar shields. In addition, exact expressions are given and "nearly exact" expressions are derived. Each expression has been compared to the exact expression in order to determine the range of parameters over which it is valid. Each of the approximate expression can be calculated rapidly and has a simple physical interpretation that leads to physical insight into the shielding process. [ABSTRACT FROM AUTHOR]