Effects of Neutron Irradiation on Carbon Doped MgB2 Wire Segments

TL;DR

This study investigates how neutron irradiation and subsequent annealing affect the superconducting properties of carbon-doped MgB2 wires, revealing independent effects of doping and damage on superconductivity recovery.

Contribution

It provides detailed analysis of the effects of neutron damage and annealing on superconductivity and lattice parameters in carbon-doped MgB2, highlighting their independent influences.

Findings

Superconductivity is suppressed by neutron irradiation and restored by annealing.

The upper critical field scales with T_c during recovery.

Carbon doping and neutron damage independently affect superconducting properties.

Abstract

We have studied the evolution of superconducting and normal state properties of neutron irradiated Mg(B$_{.962}$C$_{.038}$)$_2$ wire segments as a function of post exposure annealing time and temperature. The initial fluence fully suppressed superconductivity and resulted in an anisotropic expansion of the unit cell. Superconductivity was restored by post-exposure annealing. The upper critical field, H$_{c2}$(T=0), approximately scales with T$_c$ starting with an undamaged T$_c$ near 37 K and H$_{c2}$(T=0) near 32 T. Up to an annealing temperature of 400 $^ o$C the recovery of T$_c$ tends to coincide with a decrease in the normal state resistivity and a systematic recovery of the lattice parameters. Above 400 $^ o$C a decrease in order along the c- direction coincides with an increase in resistivity, but no apparent change in the evolution of T$_c$ and H$_{c2}$. To first order, it appears that carbon doping and neutron damaging effect the superconducting properties of MgB$_2$ independently.