Design of a Nuclear Magnetic Resonance Fast Field Cycling Air Cored Magnet

A method for the design of a nuclear magnetic resonance fast field cycling air-cored magnet is presented in this paper. General analytic expressions relating the geometric parameters of the magnet with the flux density, the current density and the power losses were obtained. An optimization algorithm based on the thin circular loop coil model to determine the positions of the windings for a target flux density minimizing the power losses is described. The results obtained in this paper show that, in order to obtain a magnet with a reasonable practical size, the highest possible current density should be used. A prototype that can generate a magnetic flux density of 1.6 T was designed and built. This magnet is cooled using a coolant fluid circulating on longitudinal ducts. The magnet was tested in typical fast field cycling nuclear magnetic resonance experiments and presents a good performance.