A series of experiments has been carried out on the flux trapping and shielding capabilities of a flat strip of Nbhyphen;Ti/Cu composite material. A circular piece of material from the strip was tested in a uniform field directed perpendicularly to the surface of the sample. Profiles of the normal component of the field along the sample diameter were measured. The criticalhyphen;state model was adapted for this geometry and proved capable of reproducing the measured field profiles. Model curves agreed well with experimental field profiles generated when the full sample was in the critical state, when only a portion of the sample was in the critical state, and when profiles were obtained after the direction of the rate change of the magnetic field was reversed. The adaption of the criticalhyphen;state model to disk geometry provides a possible method either to derive values of the critical current from measurements of field profiles above thin flat samples, or to predict the trapping and shielding behavior of such samples if the critical current is already known. This method of determining critical currents does not require that samples be formed into narrow strips or wires, as is required for direct measurements ofJc, or into tubes or cylinders, as is usually required for magnetizationhyphen;type measurements. Only a relatively small approximately circular piece of material is needed. The method relies on induced currents, so there is no need to pass large currents into the sample. The fieldhyphen;profile measurements are easily performed with expensive Hall probes and do not require detection of the resistive transition of the superconductor.
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