Defect cascades produced by neutron irradiation in YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}

Abstract

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n-Values of commercial YBCO tapes before and after irradiation by fast neutrons

“…MeV) and they produce spherical defects of amorphous material with a diameter of a few nm (so called collision cascades) [15,[17][18][19]. The point defects and clusters of point defects are created by neutrons with lower energies and they can act as effective pinning as well [34].…”

“…Measurements of n-values after introducing additional pinning centres require special attention. Irradiation by fast neutrons introduces randomly distributed spherical pinning centres with diameters of a few nm [15][16][17][18][19][20] into a superconductor. It is a proven method of introducing efficient pinning centres into HTS, resulting in critical currents enhancements.…”

Stress dependence of the critical currents in neutron irradiated (RE)BCO coated conductors

“…Fast neutrons (E > 0.1 MeV) generate collision cascades in cuprates by transferring sufficient energy to a primary knock-on atom, which initiates further collisions [15] [16]. These collisions lead to local melting of the lattice and the formation of spherical defects with a diameter of ≈ 6 nm [15]. The size of these normal conducting impurities matches the size of a flux line core (2ξ a,b ≈ 6 nm at 77 K) and is, therefore, optimal for flux pinning.…”

“…Fast neutrons (E > 0.1 MeV) generate collision cascades in cuprates by transferring sufficient energy to a primary knock-on atom, which initiates further collisions [15] [16]. These collisions lead to local melting of the lattice and the formation of spherical defects with a diameter of ≈ 6 nm [15].…”

“…Furthermore, these defects are uncorrelated and randomly distributed. Fast-neutroninduced cascades have been shown to be responsible for flux pinning and intra-grain critical current enhancement in (RE)BCO [17] [15].…”