Monte Carlo analysis of the oxygen knock-on effects induced by synchrotron x-ray radiation in the Bi2Sr2CaCu2

Abstract

We investigate the microscopic mechanism responsible for the change of macroscopic electrical properties of the Bi2Sr2CaCu2O8+δ high-temperature superconductor induced by intense synchrotron hard X-ray beams. The possible effects of secondary electrons on the oxygen content via the knockon interaction are studied by Monte Carlo simulations. The change in the oxygen content expected from the knock-on model is computed convoluting the fluence of photogenerated electrons in the material with the Seitz-Koehler cross section. This approach has been adopted to analyze several experimental irradiation sessions with increasing X-ray fluences. A close comparison between the expected variations in oxygen content and the experimental results allows determining the irradiation regime in which the knock-on mechanism can satisfactorily explain the observed changes. Finally, we estimate the threshold displacement energy of loosely-bound oxygen atoms in this material Td =0.15 −0.01 +0.025 eV.

Materials characterization by synchrotron x-ray microprobes and nanoprobes

“…14 are performed with three different approaches depending on the energy and time values of the process. The x-ray inelastic scattering, photon absorption, XRF, and Auger relaxation processes and collisional ionization are usually simulated via a MC approach where, starting from a high number of primary x rays (typically 10 6 ), and using the known energy-dependent atomic photoabsorption and scattering cross sections (Henke, Gullikson, and Davis, 1993), the paths of primary and secondary photons and electrons are simulated in a probabilistic manner (London et al, 2001;Moukhametzianov et al, 2008;Dettmar et al, 2015;Torsello et al, 2018). MC simulations produce a quantitative space and time-dependent description of the distribution of the particles (photons, electrons, and ions) and ultimately a distribution of dose.…”

Scaling laws for ion irradiation effects in iron-based superconductors

“…In addition to the estimate of dpa produced by ions, also the dpa resulting from electron irradiation can be computed and their effects can be compared. In the case of 2.5 MeV electron irradiation, the overall dpa can simply be computed by multiplying the electron fluence by the displacement cross section for each atom, and summing atomic dpa contributions weighted on their stoichiometric coefficients 47 . The displacement cross section is composed of the cross section for primary knock-on atoms (derived by McKinley and Feshbach 48 ) and that for the (very small) cascade that each primary atom could produce.…”

Creation of pure non-crystalline diamond nanostructures via room-temperature ion irradiation and subsequent thermal annealing

“…In this context, the employment of other types of radiation (e.g. x-ray nano-beams) could be successfully employed to engineer structural damage with high spatial resolution, as already successfully demonstrated in other types of substrates [24][25][26].…”