Experimental study of magnetization AC loss in MgB2 wires and cables with non-magnetic sheath

• The dependence of MgB2 AC magnetization losses on temperature.
• External AC field was ranged from 0.7 mT to 70 mT.
• The influence of wire construction on magnetization AC losses in MgB2 was studied.
• Loss of two MgB2 cables was compared to loss of wires.
• Effect of decoupling vs critical current degradation in twisted wires was discuss.

The influence of MgB2 wires design on the magnetization AC loss was studied. AC loss in external AC magnetic field perpendicular to the wire axis was measured in the temperature range from 18 K up to 40 K and at the frequencies of 72 Hz and 144 Hz, respectively. For this purpose the experimental apparatus combining magnetization measurement system and non-magnetic vacuum vessel with two-stage crycooler for sample cooling has been used.To clarify the influence of wire architecture on the AC loss in non-magnetic GlidCop sheathed MgB2 composites experiments on a single-core, 30-filament un-twisted and also twisted samples were performed. MgB2 cables containing 7 mono-core strands and 30 filament strands were also measured. While in the cable containing single core strands the hysteresis loss was dominant, in the un-twisted wire and the cable with un-twisted filaments the coupling loss prevailed. The effect of decoupling was observed in all twisted filamentary wires. The obtained results show that in 7 strands cable the AC loss of strands is crucial to the overall AC loss of a cable.