MEASUREMENT INSTRUMENTATION FOR ELECTRICAL-TRANSPORT EXPERIMENTS IN EXTREME PULSED MAGNETIC-FIELDS GENERATED BY FLUX COMPRESSION

We describe purpose-built instrumentation that has proved successful i n making transport measurements of materials in ultrahigh magnetic fie lds generated by explosive-driven flux compression. The experimental a rrangement minimizes severe problems of heating and pick-up associated with the microsecond pulsed field: for which dB/dt can be as large as 10(9) T/s. Electrical connection to multiple samples in the high fiel d region is via long, lithographically-defined, nested coplanar transm ission 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 f iltered. We demonstrate our technique with data on semiconductor sampl es taken to 450 T using Russian MC-1 type flux compression generators combined with U.S. explosives at the Ancho Canyon firing point, Los Al amos National Laboratory. We discuss the obstacles encountered during these experiments, and outline improvements and refinements of our tec hnique that should enable transport measurements to be made in the hig hest obtainable magnetic fields (similar to 1000 T) in samples at temp eratures not exceeding a few kelvin. This technology may also be valua ble for transport measurements in nondestructive pulsed fields of mill isecond duration, now available in many laboratories worldwide. (C) 19 97 American Institute of Physics.