Relevance of the irreversible degradation of superconducting Nb3Sn wires and cables caused by transverse stress at room temperature within the FCC study at CERN

Within this thesis, the irreversible degradation of superconducting Nb₃Sn wires and cables caused by transverse stress at room temperature was analysed in the frame of the FCC study at CERN.

First, stress was exerted on Rutherford cables at room temperature and their performance was measured with the FRESCA cable test station at low temperature to obtain results under conditions mimicking the real situation during magnet assembly.

Subsequently, tests with single Nb₃Sn wires were performed to analyse the cause of degradation. To deliver measurement data metallographic techniques were elaborated and refined as well as a cryostat for transport current measurements close the critical temperature was build and tested to additionally imitate a cryogenic refrigerator system (cryocooler). The study was supplementary extended by magnetisation measurements using a SQUID magnetometer as well as FEM analysis of wires and cables based on X-ray tomography.

The gained results were compared with other scientific investigations and one of the commonly-used scaling laws. Moreover, the implementation of the transport current measurements for wires under the defined requirements using a cryocooler was assessed.