Development of MgB2-based, bulk supermagnets

International audience; A series of disk-shaped, bulk MgB2 superconductors (sample diameter up to 40 mm, reaction temperatures ranging between 750 °C and 950 °C) was prepared in order to improve the performance for superconducting supermagnets. These samples were characterized by magnetic and electric measurements in fields up to 7 T and at various temperatures 10 K < T < 35 K. The irreversibility lines, the current densities, the resistance and the achievable trapped fields were determined. To analyze the data, a scaling of the flux pinning forces, Fp = jc × B, was performed. The different scaling behavior of the samples prepared at low and high reaction temperatures is discussed considering the achieved microstructures.