Radiation Effects in High Tc Superconductors for Space Applications

YBa2Cu3O7 is one of the new class of superconductors having a critical temperature (Tc) above 90 K. Devices using these materials would require minimal refrigeration to operate in space. It is important, therefore, to determine the effect of natural space radiation on these materials. Preliminary experiments have been performed to study displacement damage and ionization effects in 100¿m thick films of YBa2Cu3O7. Samples of these films were irradiated at room temperature with 1) 56 MeV electrons up to a total fluence of 1.6×1015 cm-2, 2) 6 MeV protons up to a total fluence of 5.0×1013 cm-2, and 3) 63 MeV protons up to a total fluence of 1.09×1014 cm-2. It is concluded from the electron irradiations that the major effect of ionization is to increase the normal resistivity of the material. Although Tc(onset) was not much affected by either the electron or the proton irradiations, Tc(completion) varied substantially with proton fluence and at the higher fluences there was evidence of a non-superconducting region even at 4 K. It appears from the shape of the resistivity-temperature curve that high energy proton irradiation induces a partially superconducting multi-phase mosaic. Comparing worst case space environments to the radiations described above, it is concluded that this high Tc material could be made to remain superconducting for extended space missions with only moderate shielding.