Measurement instrumentation for electrical transport experiments in extreme pulsed magnetic fields generated by flux compression

Abstract

We describe purpose-built instrumentation that has proved successful in making transport measurements of materials in ultrahigh magnetic fields generated by explosive-driven flux compression. The experimental arrangement minimizes severe problems of heating and pick-up associated with the microsecond pulsed field, for which dB/dt can be as large as 109 T/s. Electrical connection to multiple samples in the high field region is via long, lithographically-defined, nested coplanar transmission lines. Contactless measurements by capacitive coupling, as well as resistively coupled measurements, are made at frequencies of order 1 GHz so that pick-up from the microsecond pulse can be effectively filtered. We demonstrate our technique with data on semiconductor samples taken to 450 T using Russian MC-1 type flux compression generators combined with U.S. explosives at the Ancho Canyon firing point, Los Alamos National Laboratory. We discuss the obstacles encountered during these experiments, and outline improvements and refinements of our technique that should enable transport measurements to be made in the highest obtainable magnetic fields (∼1000 T) in samples at temperatures not exceeding a few kelvin. This technology may also be valuable for transport measurements in nondestructive pulsed fields of millisecond duration, now available in many laboratories worldwide.