Nb3Sn superconductors as they are applied in the ITER fusion programme, are equipped with diffusion barriers made of V, Ta, and V-Nb, all having superconducting properties. If an external ac magnetic field is applied, superconducting shielding currents are induced in the barrier which enclose a bundle of Nb3Sn filaments. As a consequence they are shielded and no ac loss will occur in the filaments. When the penetration field of the barrier material is exceeded, additionally the loss of the barrier and for higher fields also the loss of the Nb3Sn multifilamentary zone is generated. As long as the barrier is superconducting it will cause a substantial increase of ac loss. As a consequence the ac loss of the conductor in terms hysteresis loss per cycle and coupling time constants are strongly influenced. This aspect has to be considered carefully when properties of Nb3Sn conductors are determined at low magnetic fields.
|Number of pages||4|
|Issue number||Suppl. 1|
|Publication status||Published - 1994|
|Event||15th International Cryogenic Engineering Conference, ICEC 1994 - Genoa, Italy|
Duration: 7 Jun 1994 → 10 Jun 1994
Conference number: 15