Effects of neutron irradiation on superconducting critical temperatures of in situ processed MgB₂superconductors

Abstract

Effects of neutron irradiation on the superconducting properties of the undoped MgB 2 and the carbon(C)-doped MgB 2 bulk superconductors, prepared by an in situ reaction process using Mg and B powder, were investigated. The prepared MgB 2 samples were neutron-irradiated at the neutron fluence of 10 16 -10 18 n/cm 2 in a Hanaro nuclear reactor of KAERI involving both fast and thermal neutron. The magnetic moment-temperature (M-T) and magnetization-magnetic field (M-H) curves before/after irradiation were obtained using magnetic property measurement system (MPMS). The superconducting critical temperature (T c ) and transition width were estimated from the M-T curves and critical current density (J c ) was estimated from the M-H curves using a Bean's critical model. The T c s of the undoped MgB 2 and C-doped MgB 2 before irradiation were 36.9-37.0 K and 36.6-36.8 K, respectively. The T c s decreased to 33.2 K and 31.6 K, respectively after irradiation at neutron fluence of 7.16×10 17 n/cm 2 , and decreased to 22.6 K and 24.0 K, respectively, at 3.13×10 18 n/cm 2 . The J c cross-over was observed at the high magnetic field of 5.2 T for the undoped MgB 2 irradiated at 7.16×10 17 n/cm 2 . The T c and J c variation after the neutron irradiation at various neutron fluences were explained in terms of the defect formation in the superconducting matrix by neutron irradiation.

Neutron Irradiation of Electronic Materials at HANARO

“…Therefore, neutron technology can be applied effectively toward the development of new materials. Recently, several efforts have been made at HANARO to evaluate the effect of neutron irradiation on the physical properties of various functional materials [5]- [8].…”

“…Although several impressive effects of neutron irradiation on the properties of electronic materials were reported at HANARO [5]- [8], it was difficult to interpret clearly their behaviors due to the broad energy spectrum of the neutron as shown in Figure 3. The undesirable effects due to thermal and fast neutrons should be reduced to separate each neutron's effect on the properties of the sample.…”