Measurements of trapped-flux density for bulk high-temperature superconductors

Large grain bulk superconductors with large critical current density can trap large fields and thus have potential for various engineering applications. For the design of the devices utilizing the bulk superconductors, one needs to know the maximum trapped-flux density. There are several parameters to affect the trapped-field values. The trapped-fields decay with time due to flux flow and flux creep, and therefore, some waiting time is necessary to determine the value, which can be used for the design of industrial machines. For comparative study, one needs to apply large enough fields to ensure the saturation of field-trapping capability. Furthermore, one needs to specify the sample geometry and the correct gap distance between the sample and the magnetic sensor. (C) 2001 Elsevier Science B.V. All rights reserved.