1 Applied Superconductivity Research - University of Cambridge Click to edit Master title style Click to edit Master text styles –Second level Third level –Fourth level »Fifth level B.A.Glowacki Transport AC losses of a helix - Cable configuration Transport AC losses of a helix: a) potential taps position and potential wires arrangement on the outer surface of the central turn, b) Measured transport ac losses. t wcorr represent the t w voltage signal corrected by the c voltage to provide truly transversal voltage losses. (Majoros 1999c, 1999d)

2 Applied Superconductivity Research - University of Cambridge Click to edit Master title style Click to edit Master text styles –Second level Third level –Fourth level »Fifth level B.A.Glowacki Double helix configuration

3 Applied Superconductivity Research - University of Cambridge Click to edit Master title style Click to edit Master text styles –Second level Third level –Fourth level »Fifth level B.A.Glowacki Cable -Conclusions The distribution of AC currents dominated by the mutual inductances, For two layer of equal pitch, the current divides very narly equly between the two helical layers For higher number of layers of equal pitch the current flows preferentially in the outermost layers For practical pitch angle of 30 degrees the hysteretic losses at low current applied are about 13% lower for two layers Gap between the tapes would increase losses by the factor roughly equal to the width/ tape thickness Tapes should be arranged edge to edge so radial magnetic fields are negligible, local fields have only longitudinal and asimutal components Tapes can carry supercurrents only parallel to their length. These currents screen magnetic field component perpendicular to tapes.

4 Applied Superconductivity Research - University of Cambridge Click to edit Master title style Click to edit Master text styles –Second level Third level –Fourth level »Fifth level B.A.Glowacki MgB 2

5 Applied Superconductivity Research - University of Cambridge Click to edit Master title style Click to edit Master text styles –Second level Third level –Fourth level »Fifth level B.A.Glowacki

6 Applied Superconductivity Research - University of Cambridge Click to edit Master title style Click to edit Master text styles –Second level Third level –Fourth level »Fifth level B.A.Glowacki H.L. Suo, C. Beneduce, X.D. Su and R. Flükiger J c eng ?? MgB 2 /YSZ/Hastelloy 0.4 m/1 m/300 m J c eng = 10 3 Acm J c MgB2 = 10 5 Acm J c eng ˜ 10 4 Acm J c MgB2 > 10 5 Acm K. Komori, K. Kawagishi, Y. Takano, S. Arisawa, H. Kumakura, M. Fukutomi, K. Togano MgB 2 conductors

7 Applied Superconductivity Research - University of Cambridge Click to edit Master title style Click to edit Master text styles –Second level Third level –Fourth level »Fifth level B.A.Glowacki IRRADIARION Pinning force - MgB 2 conductors

8 Applied Superconductivity Research - University of Cambridge Click to edit Master title style Click to edit Master text styles –Second level Third level –Fourth level »Fifth level B.A.Glowacki Current vs Field Superconducting/magnetic structures Twisting may be a problem with hard Fe matrix. Twisting of Cu/MgB 2 with the internal reinforcement can be viable solution. Monocore: MgB 2 OD=0.871mm, magnetic later thick. 19 filaments: MgB2 OD=0.2mm, magnetic double layerm shielding 10 m thick 10 m separation around each filament as well as around whole composite ( r =10 or r Fe).

9 Applied Superconductivity Research - University of Cambridge Click to edit Master title style Click to edit Master text styles –Second level Third level –Fourth level »Fifth level B.A.Glowacki Cryomagnetic stability

10 Applied Superconductivity Research - University of Cambridge Click to edit Master title style Click to edit Master text styles –Second level Third level –Fourth level »Fifth level B.A.Glowacki Critical Current distribution - Multifilament Magnetic coating : critical current improvement Magnetic stability a) Spatial distribution of the critical current density in a 19 filament MgB 2 wire cross section in self field, (no magnetic screens) I c =442A b) Spatial distribution of the critical current density in a 19 filament MgB 2 wire cross section in self field, for non-linear Fe rmax =9000, I c =628A.

11 Applied Superconductivity Research - University of Cambridge Click to edit Master title style Click to edit Master text styles –Second level Third level –Fourth level »Fifth level B.A.Glowacki MgB 2 Cu in-situ wires stability ( coils) J c = Acm -2

12 Applied Superconductivity Research - University of Cambridge Click to edit Master title style Click to edit Master text styles –Second level Third level –Fourth level »Fifth level B.A.Glowacki Cryogenic stability defected MgB 2 -Fe-Cu Fe/MgB 2 wire with defect - applied electric field 1 Vcm -1 and 13 Vcm -1 MgB 2 wire 0.6mm in diameter, Fe layer 0.2mm thick Temperature MgB 2 Fe Cu E=13 Vcm -1 Current