Test Results of the First Wax-Impregnated Nb-Ti Canted Cosine Theta Septum Magnet “SuShi”

In the framework of the future circular collider study, a new septum magnet concept (“SuShi”) has been developed, and a prototype was built at Wigner RCP, and tested at the FREIA facility of Uppsala University. The concept uses a canted cosine theta (CCT)-like superconducting magnet and a passive superconducting shield to create a zero-field and high-field region within its aperture. SuShi is the first CCT magnet with both of its winding layers simultaneously impregnated with wax. Details of the construction will be presented, with special emphasis on the wax impregnation procedure which deals with the
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15% contraction of wax upon solidification. The empty magnet (no shield in its aperture) was powered without training to 450 A with a peak field of 3.64 T, corresponding to 80% of the short sample limit of the conductor along the load line. No quench or other anomaly was observed during the entire testing period. A clear onset of quench-back was observed above about 200 A.