Determination of atom displacement distribution in YBCO superconductors induced by gamma radiation

Abstract

The calculation results of the atom displacement distribution induced by gamma radiation in the superconducting material YBa2Cu3O7–x are presented. Firstly, a direct calculation procedure for the atom displacement distribution inside a given material is introduced, starting from the application of the energy flux distribution values of secondary electrons, formerly calculated using the Monte Carlo method based code system MCNP‐4C. Finally, calculation results of the atom displacement distribution, regarding the occupied oxygen crystalline sites, are presented for different incident gamma radiation energies, where an atom displacement threshold energy value of 20 eV was assigned to O(1–3) sites, while a value of 3.45 eV was used for the copper–oxygen chain sites at the basal plane. According to the present calculations, a predominating atom displacement rate at copper‐oxygen chain sites was obtained. On the other hand, nearly linear correlations among atom displacements and energy deposition profiles were also found. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Studies on the Gamma Radiation Responses of High Tc Superconductors

“…However, Piñera et al had shown by means of Monte Carlo Methods assisted gamma quanta transport calculations in YBCO matrix, that Φ(E i , z) does not follow such a "model" dependence on regard of both, E i and z as it is shown in Fig. 2 (Piñera et al, 2007a). …”

“…4 shows that each atomic specie contributes to atom displacement processes only over a given critical electron kinetic energy E c . A critical evaluation among MCSAD predictions with those previously obtained by Piñera et al and Fukuya-Kimura is in course (Piñera et al, 2007a(Piñera et al, , 2007b(Piñera et al, , 2008a(Piñera et al, , 2008bFukuya & Kimura, 2003). …”

“…Therefore, this complex electron kinetic energy distribution behaviors seen before do not agreed with the starting assumptions taken in by Belevtsev et al for the direct calculation of dpa rate in YBCO (Belevtsev et al, 2000), clearly supporting the introduction of a more realistic treatment for secondary electron transport as done in Monte Carlo based codes here applied. This is the aim of the Monte Carlo assisted Classical Method (MCCM) introduced by I. Piñera et al (Piñera et al, 2007a(Piñera et al, , 2007b(Piñera et al, , 2008a(Piñera et al, , 2008b …”

“…From the atom displacement main requirement, it follows that secondary electrons will induce atom displacements processes through the elastic atomic scattering for E i ≥ E C (Corbett, 1966;Piñera et al, 2007a) (Bourdillon & Tan, 1995). The removed atom as a result of an electron elastic atomic scattering is known as Primary Knock-on Atom (PKA).…”

“…These findings agreed well with those previously reported X-ray Diffraction ones. X-Ray Diffraction and Mössbauer Spectroscopy studies on 60 Co -quanta irradiated YBCO samples lead to the conclusion, that gamma radiation induced oxygen displacements in both, Cu(2)-O 2 planes and Cu(1)-O chains (Piñera et al, 2007a), as well as secondary electrons are eventually trapped in unoccupied O(4) and O(5) sites in crystal unit cell basis plane, provoking a strengthening of the orthorhombic structural phase, specially at relative low exposition dose E 0 ≈120 kGy.…”