Studies on the Gamma Radiation Responses of High Tc Superconductors

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The Future applications of new solid state materials, electronic devices and detectors in radiation environments like Fission and Fusion new generation of Nuclear Reactors, as well as astronomical researches, require a well established understanding about the radiation response of all these items. In addition to foregoing applications the Gamma Radiation (┛R) combined effects of energy dependent displacement per atom (dpa) rates and high penetration strength might be attractive for getting a deeper understanding. In particular for high temperature superconductors (HTS) these are interesting for get a better comprehension about their superconducting mechanisms. Quite controversial results have been reported in ┛R damage studies on HTS, especially on regard to the YBa2Cu3O7-x (YBCO) superconducting behavior. On this way, the papers dedicated to study gamma irradiation effects on the HTS properties are characterized for a lack of coincidence in criteria and results. Some authors have observed an improvement of the superconducting properties with dose increment (Boiko et at., 1988; Leyva et al., 1992), some others report exactly the opposite (Vasek et al., 1989; Elkholy et al., 1996), and other studies have not found any dependence (Bohandy et al., 1987; Cooksey et al., 1994). These contradictions have not been completely explained yet; some authors even attribute these behaviors to a “sample effect” (Polyak et al., 1990). However, Belevtsev et al. (Belevtsev et al., 2000) has determined the relationship between the superconducting order parameter ┦2 and the density of oxygen vacancy rate lower bound, expressed in displacement per atom, in order to achieve significant modification of the superconducting behavior. On this ground, by means of the Oen-Holmes-Cahn atom displacement calculation algorithm (Oen & Holmes, 1959; Cahn, 1959), they calculated the incoming gamma quanta total flux inducing a dpa rate of about 0.02. That makes the YBa2Cu3O7−├ superconducting material mean intervacancies distance close to its superconducting coherence length or order parameter ┦2, in which case the superconducting properties will be modified. Consequently, a systematic behavior of HTS material properties upon ┛R must be expected to be observed, where superconducting intrinsic properties (crystal and electronic structures, critical superconducting temperature), as well extrinsic ones (critical