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 MgB₂ 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 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 MgB₂ can be tuned to virtually any value between 5 and 39 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.