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High-speed hall probe measurements and field mapping system

A high-speed field-mapping system with 7 and 15 Hall probes, using 8 or 16-channel digital lock-in amplifier, was designed, constructed and is operational at frequencies up to 50Hz. The system is now able to simultaneously generate the Hall excitation current, to acquire the data simultaneously, to compute the lock-in product on 8 or 16 channels, and to store the results in adapted files.

The data for the measured dynamic field on the surface of the superconductor with applied transport current was then used in a specially developed inverse problem algorithm for finding the corresponding current distribution. The method is based on the application of Ampere¿s theorem to a superconductor in the Critical State Model. The reconstructed current distribution was compared to results from finite-element-method simulations in order to mutually validate the two methods. It was demonstrated that the current reconstruction method gives sufficiently accurate description of the current distribution in the superconductor.

The developed novel measurement system and reconstruction algorithm represent state-of-the-art characterization technique for describing dynamically the field and current distribution in high-Tc superconductors.

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Swiss Federal Institute of Technology – Lausanne (EPFL)
EPFL IN Ecublens
1015 Lausanne
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