Radioactivity of $\hbox {Nb}_{3}\hbox {Sn/Cu}$ Wires After Proton Irradiation

Superconducting magnets based on Nb₃Sn technology are being developed for the LHC high luminosity upgrade. In this context, irradiation induced changes of the superconducting properties of state-of-the-art Ti and Ta doped Nb₃ Sn wires are presently studied. During irradiation tests with protons of 65 MeV at the cyclotron of Université Catholique de Louvain (UCL), 1.4 GeV at the CERN ISOLDE facility, and 24 GeV at the CERN IRRAD1 facility, the superconductor samples become radioactive and their handling must follow the legal specifications for radioactive materials. We have estimated the activation and the resulting ambient dose equivalent rate up to a fluence of 10¹⁷ p/cm² with the Monte-Carlo Code FLUKA. The estimates were verified with experimental activation spectra. Samples for magnetization measurements with a mass of approximately 20 mg have to be considered as radioactive, but they do not have the potential to harm the operators handling them at radiation levels below 1 μSv/h. Larger samples (longer wires and sample holder materials like Cu and TiAl₆V₄) show correspondingly higher ambient dose equivalent rates and activation levels and they must be handled by radiation workers in designated areas, taking into account the standard precautions for work with radioactive materials. The use of radiation shielding during handling is recommended.