Superconductivity in MgB2 irradiated with energetic protons

•Bulk polycrystalline MgB2 irradiated with high energy protons.•High resolution electron microscopy of proton irradiated MgB2.•DC susceptibility shows a decrease of Meissner fraction.•The superconducting screening suggests a defect organization at high fluences•High field critical current density and pinning energy substantially increase.

A series of MgB2 samples were irradiated with protons of 11.3 and 13.2 MeV. Magnetization data shows an insignificant reduction of the critical temperatures but a continuous decrease of the Meissner fraction with increasing fluence or energy. All samples show a consistent improvement of the critical current density compared to the virgin sample and an increase of the pinning energy at high fields as resulted from relaxation data.