Systematic study of the superconducting and normal-state properties of neutron-irradiated MgB2

We have performed a systematic study of the evolution of the superconducting and normal state properties of neutron-irradiated ${\mathrm{MgB}}_{2}$ wire segments as a function of fluence and post exposure annealing temperature and time. All fluences used suppressed the transition temperature, ${T}_{c}$, below $5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and expanded the unit cell. For each annealing temperature ${T}_{c}$ recovers with annealing time and the upper critical field, ${H}_{c2}(T=0)$, approximately scales with ${T}_{c}$. By judicious choice of fluence, annealing temperature, and time, the ${T}_{c}$ of damaged ${\mathrm{MgB}}_{2}$ can be tuned to virtually any value between 5 and $39\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. For higher annealing temperatures and longer annealing times, the recovery of ${T}_{c}$ tends to coincide with a decrease in the normal state resistivity and a systematic recovery of the lattice parameters.