AC Loss Measurement in Nb₃Sn Coil for a New Fast Switching-field MR Concept Magnet

The ability to perform magnetic resonance (MR) imaging or spectroscopy at significantly different magnetic field strengths during scanning holds great potential for expanding the range of contrast parameter options and obtaining high "superthermal" spin polarization for increased signal-to-noise ratio (SNR) or measuring certain spins at what would otherwise be impractically high RF frequencies. Enabling measurements at multiple field strengths heretofore has required either rapidly altering the strength of a resistive magnet with pulsed currents or shuttling the specimen between two field regions. We propose a novel approach to switching-field MR that we expect to be practical for live animal and ultimately human imaging. In this paper we propose the design of a liquid-helium-free fast switching-field MR magnet that can change the field very quickly in time (≤ 1 s) between significantly different field strengths. For this magnet, two types of Nb₃Sn wire are selected, and AC loss is measured by electrical method, and characteristics are analyzed.