Expected radiation environment and damage for YBCO tapes in compact fusion reactors

We investigate the neutron damage expected in high-temperature superconducting tapes that will be employed in compact fusion reactors. Monte Carlo simulations yield the expected neutron spectrum and fluence at the magnet position, from which the primary knock-on atom energy distributions can be computed for each atomic species comprising the superconductor. This information is then employed to characterize the displacement cascades, in terms of size and morphology, through molecular dynamics simulations. The expected radiation environment is then compared with the neutron spectrum and fluences achievable at the facilities currently available for experimental investigation in order to highlight similarities and differences that could be relevant to the understanding of the radiation hardness of these materials in real fusion conditions. We find that the different neutron spectra result in different damage regimes, the irradiation temperature influences the number of generated defects, and the interaction of the neutrons with the superconductor results in a local increase in temperature. These observations suggest that further experimental investigations are needed in different regimes and that some neutron shielding will be necessary in compact fusion reactors.

Automated summary

We investigated the expected neutron damage in high-temperature superconducting tapes used in compact fusion reactors. Monte Carlo simulations were performed to obtain the neutron spectrum and fluence at the magnet position, which were then used to calculate the energy distributions of primary knock-on atoms for each atomic species in the superconductor. Molecular dynamics simulations were used to characterize the displacement cascades in terms of size and morphology. The expected radiation environment was compared with the neutron spectrum and fluences achievable in current experimental facilities to identify similarities and differences that are relevant to the understanding of radiation hardness of these materials in real fusion conditions. Our findings show that different neutron spectra result in different damage regimes, irradiation temperature influences the number of defects generated, and neutron-superconductor interaction leads to local temperature increase. These observations suggest the need for further experimental investigations in different conditions and the necessity of neutron shielding in compact fusion reactors.