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The shielding of a DC magnetic field has been demonstrated to be complete at 4.2 K, at least up to 2 T, inside the 18 mm bore of a thick MgB 2 bulk cylinder, 70 mm tall. No hysteresis has been detected along the cycle of the field application and removal, and no flux jumps have been detected either. The MgB 2 cylinder was manufactured by the Reactive Mg Liquid Infiltration process, an 'in situ' technology able to give very dense MgB 2 manufacts. According to the previously measured J c (B, T ) characteristics of a MgB 2 bulk superconductor of the same origin and quality, a critical current density of about 30 kA cm −2 can be assumed at the fields of 2-3 T and at the temperature of 4.2 K of the reported shielding experiment. Accordingly, we estimate that the thickness of the MgB 2 cylinder filled by the shielding currents is about 5.75 mm, lower than the present cylinder thickness of 8.77 mm.

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