Neutron irradiation effect on superconductivity of Nb3Sn wire - 50 Hz data acquisition system -

Abstract

A research facility for neutron irradiation effect on superconducting materials has been installed at Oarai center in Tohoku University in 2012 as part of a post irradiation experiment. It consists of a 15.5 T superconducting magnet, a variable temperature insert and a data acquisition and control system. Since the sample holder is cooled by thermal conduction with G-M refrigeration, there is a small temperature difference between positive and negative electrodes and the sample temperature rises during the critical current test due to joule heating. To evaluate the temperature rise precisely, a new data acquisition system with a sampling rate of 50 Hz has been installed. By measuring the temperatures of both electrodes and the voltage at the center of the sample, the temperature of the sample was estimated and the measured critical current (IC) was converted to the current at 4.2 K with a critical surface equation. The comparison of IC at different conditions including neutron irradiated samples was implemented and the neutron irradiation effect on superconductivity of Nb3Sn wire is discussed based on the 4.2 K superconductivity. This paper will describe the outline of the new data acquisition system and some results of neutron irradiated Nb3Sn wires.

Keywords

• Neutron irradiation
• Nb3Sn
• Critical current
• Critical temperature
• Upper critical magnetic field