Design of a Compact Inductor Matched to a Homopolar Generator

A liquid nitrogen pool-cooled, coaxial energy storage inductor is being designed and built to provide a load for a prototype compact homopolar generator HPG. This is part of a continuing effort to produce a compact field-portable electromagnetic accelerator power supply. Initial design parameters are that the coil store 3.1 MJ, representing a 50 percent transfer efficiency of energy stored in the HPG, with a transfer current of 1.0 MA. Coaxial conductor configurations are being investigated to eliminate high external magnetic fields, which have undesirable effects on nearby components. Also, coaxial inductors having a solid central conductor can withstand compressive magnetic loading at the inner radius of the material. This increases the achievable energy density, which is a function of the square of the magnetic flux density. The inductor will be made of aluminum and will be nested with the HPG in a low-resistance, compact configuration. Design and fabrication of the inductor are discussed.