The performance of REBCO coated conductor during in situ cryogenic irradiation with fusion-spectrum neutrons

Understanding the tolerance of REBa2Cu3O 7−x (REBCO) high-temperature superconductors to neutron damage is essential for compact fusion reactor design. Here we report the first in situ measurements of the superconducting performance of REBCO coated conductor (CC) during neutron irradiation. The CC was exposed to 14 MeV neutrons at fluxes up to 7.3 × 107 n cm−2 s−1 while carrying current at 40 K. In situ voltage measurements revealed no instantaneous disruption of superconductivity, but the critical current ( Ic) decreased linearly with fluence at 0.03 A per 1012 n cm−2. Careful analysis excluded thermal effects as the origin of this degradation. Consistent with a point-defect damage mechanism, superconducting performance was recovered fully following room temperature annealing. This observed onset of Ic reduction occurred several orders of magnitude below the critical neutron fluences anticipated by previous ex situ studies, indicating that service lifetimes of REBCO-based magnets may be substantially shorter than current projections.