Effect of Low-Temperature Deuteron Irradiation on Some Type-II Superconductors

Abstract

To study the effects of low-temperature irradiation on some type-II superconductors, the critical current density ${j}_{c}$, transition temperature ${T}_{c}$, upper critical field ${H}_{c2}$, and normal-state resistivity ${\ensuremath{\rho}}_{n}$ were measured after irradiation with 15-MeV deuterons. The ${10}^{17}$-deuteron / ${\mathrm{cm}}^{2}$ irradiations produced about 0.3% atomic displacements. The ribbon samples consisted of Nb-61% Ti, Nb-25% Zr, ${\mathrm{Nb}}_{3}$Sn, Nb, and Pb. These samples were held at about 30\ifmmode^\circ\else\textdegree\fi{}K during irradiation and 5\ifmmode^\circ\else\textdegree\fi{}K between irradiation and measurement. The cryostat contained a 50-kOe superconducting magnet for in situ measurements. All effects were studied after irradiation and after annealing at 77 and 300\ifmmode^\circ\else\textdegree\fi{}K. The resistivities were generally increased and the transition temperatures decreased by irradiation. Changes in ${H}_{c2}$ (generally reductions) are correlated with changes in ${T}_{c}$, ${\ensuremath{\rho}}_{n}$, and the Ginzburg-Landau parameter $\ensuremath{\kappa}$. Reductions of \ensuremath{\sim}20% in ${j}_{c}$ of cold-worked NbTi and NbZr were observed, whereas the only ${j}_{c}$ effect in strain-free NbZr was the production of a peak effect near ${H}_{c2}$. Large, thermally stable ${j}_{c}$ changes were found in vapor-deposited ${\mathrm{Nb}}_{3}$Sn; an increase in low-${j}_{c}$ material and a decrease in high-${j}_{c}$ material. The induced effects in the alloys and pure metals were reduced by 75% or more upon warming the samples to room temperature. For ${\mathrm{Nb}}_{3}$Sn, less than 25% of the induced effects were recovered by annealing at 300\ifmmode^\circ\else\textdegree\fi{}K.