Obtaining Microscopic Images Under a High 20-T Pulse Magnetic Field Using an Optimized Coil

Abstract

We optimized the coil of a pulsed electromagnet to be able to obtain dynamically microscopic images of crystals in a pulsed magnetic field of a maximum intensity of 20 T and pulsewidth of 3 ms. The pulsed field induces an eddy current that influences the nearby apparatus and objective lens made up of a conducting non-magnetic material. Developing a much shorter length of coil was required, because the working distance of the objective lens was incapable of preventing eddy currents. We calculated the maximum field and pulsed width; as a result, a coil wound with wire of 1-mm diameter in ten layers gives an ideal shape of the magnetic field when using a 10-mF capacitor bank with charge voltage of 700 V. Wound to the prescribed coil parameter values, the coil performed as expected. We demonstrate its performance with microscopic images taken using the optimized coil of the dynamic orientational behavior of diamagnetic monosodium urate crystals suspended in aqueous solution. The lying down of the acicular crystals through magnetic orientation just after application of the pulse field was observed dynamically.