MgB 2 wire performance Giovanni Grasso May 20 th , 2008

1. MgB2 wire performance Giovanni Grasso May 20th, 2008

2. Coworkers • BASIC R&DCNR-INFM: A. Malagoli, V. Braccini, C. Bernini, C. Fanciulli, M. Tropeano, M. Vignolo, C. Ferdeghini, M. Putti • CONDUCTOR DEVELOPMENTColumbus Superconductors: S. Brisigotti, A. Tumino, D. Pietranera, E. Demencik, S. Berta, R. Penco • POWDERS DEVELOPMENTFerrania Technologies: S. Magnanelli, A. Gunnella • MAGNET DEVELOPMENTASG Superconductors: R. Marabotto, M. Modica, D. Damiani, D. Nardelli

3. Preamble • MgB2: this new material represents the natural evolution for applied superconductivity of today and tomorrow • Superconductivity in MgB2 was publicly announced in January 2001 by Japanese scientists • From then on MgB2 represents the known binary material showing superconductivity at the highest temperatures to date • As virtually all superconductors used in large-scale industrial applications are binary materials (NbTi, Nb3Sn), it appeared immediately evident that MgB2 might have represented a new option • So far researchers worldwide produced literally hundreds of scientific manuscripts focused on this surprising discovery • Helium (liquid) is a natural resource available in limited quantities and it represents a bottleneck to industrial developments using superconductivity : MgB2 is a convenient solution to that

4. Important parameters for industrial applications

5. World market MgB2 is an HTS with properties and price more near to an LTS The questions are: how much of the current and future LTS and HTS market MgB2 will grab? and how big will the new market generated by MgB2 be?

6. At 4.2 K Unless Nb-Ti: Max @4.2 K for whole LHC NbTi 100,000 strand production (CERN-T. Boutboul) Otherwise Stated Nb-Ti: Max @1.9 K for whole LHC NbTi strand production (CERN, Boutboul) Nb-Ti: Nb-47wt%Ti, 1.8 K, Lee, Naus and Larbalestier UW-ASC'96 YBCO µ-bridge Nb-37Ti-22Ta, 2.05 K, 50 hr, Lazarev et al. H||c (Kharkov), CCSW '94. 10,000 Nb3Sn: Non-Cu Jc Internal Sn OI-ST RRP 1.3 mm, ASC'02/ICMC'03 YBCO Nb3Sn: Bronze route int. stab. -VAC-HP, µ-bridge non-(Cu+Ta) Jc, Thoener et al., Erice '96. H||ab 75 K Nb3Sn: 1.8 K Non-Cu Jc Internal Sn OI-ST RRP 1.3 mm, ASC'02/ICMC'03 2212 Nb3Al: JAERI strand for ITER TF coil 1,000 round wire 2223 2223 Nb3Al: RQHT+2 At.% Cu, 0.4m/s (Iijima et al Nb Al:   Critical Current Density, A/mm²   tape B|_ 2002) 3 tape B|| RQHT Bi-2212: non-Ag Jc, 427 fil. round wire, Ag/SC=3 (Hasegawa ASC-2000/MT17-2001) NbTi +HT Bi 2223: Rolled 85 Fil. Tape (AmSC) B||, UW'6/96 100 MgB 2 Nb Al: ITER Bi 2223: Rolled 85 Fil. Tape (AmSC) B|_, film 3 UW'6/96 Nb Sn 3 MgB YBCO: /Ni/YSZ ~1 µm thick microbridge, 2 1.8 K H||c 4 K, Foltyn et al. (LANL) '96 Nb Sn tape Nb Sn 1.8 K 3 2 K 3 YBCO: /Ni/YSZ ~1 µm thick microbridge, ITER Nb-Ti Internal Sn H||ab 75 K, Foltyn et al. (LANL) '96 Nb-Ti-Ta 10 MgB2: 4.2 K "high oxygen" film 2, Eom et al. (UW) Nature 31 May '02 0 5 10 15 20 25 30 MgB2: Tape - Columbus (Grasso) MEM'06 Applied Field, T Critical currents of technical superconductors at 4.2 K Superconductors choice is ‘in principle’ quite wide,but jc is not the only important parameter for selection

7. Drivingforcesfor MgB2 Performance B,T Low cost • Low cost and wide availabilityof the rawmaterials, particularly in Europe • Excellentchemical and mechanicalcompatibilitywithvariouselements (Ni, Fe, Ti, Nb, Ta, Cr, althoughnotwith Cu) • Potentialforverygood performance at high fields ( thinfilms show Hc2 > 60 T ! ) • Low anisotropy and potentialforpersistent mode operation (high n-value, low currentdecay at medium magneticfields) MgB2 superconductor Little investmentfor end-usersto test it on theirproducts SC joints, AC losses, n-factor, etc. Handling

8. About our today’s structure 2 professors 3 senior researchers 4 Postdocs 2 PhD students 7 engineers 7 workers 2 consultants Indirect activities to ASG R&D Powderproduction The new plant is ready and operational for a wire production scalable up to 3’000 Km/year Wire unit length up to 5 Km single pieces Total plant area 3’400 m2 – 50% only used today Columbus Superconductors activities involve about 30 people 3 employees

9. Fabrication of MgB2 wires by the ex-situ P.I.T. method used 325 mesh 99% purity + MgB2 B Mg amorphous 95-97% purity reaction at 900°C in Ar mixing reaction at 900-1000°C in Ar wire drawing to 2 mm cold rolling tube filling 1.3 g/cm3

10. Fabrication of MgB2 wires by the ex-situ P.I.T. method advantages • Straightforward multifilament processing • Significant homogeneity over long lengths • Allows careful control of the MgB2 particle size and purity disadvantages • Need of hard sheath materials and strong cold working • Jc is very sensitive to the processing route • More tricky to add doping and nanoparticles effectively Reliable method for exploring long lengths manufacturing

11. MgB2 Fe Ni Cu Microstructure Composite wire: 99.5% pure Nickel matrix 14 MgB2 filaments OFHC 10100 Copper core 99.5% pure Iron barrier Dimension 3.6 mm x 0.65 mm ( w x t ) Standard batch length: > 1700 m Transverse cross section area: • MgB2 0.21 mm2 (total area) • Cu 0.35 mm2 • Fe 0.19 mm2 • Ni 1.54 mm2

12. Constant improvement of conductors from production: Ic at 20K of 1.7 Km tapes 1.2T 20K Ic at 20K, 1 T always >> 90 A n-factor at 20K, 1 Tesla >> 30 Minimum bending diameter: 65 mm Maximum tensile strain: 150 MPa 1.4T 1.6T A total of 50 lengths of 1.7 Km each have been successfully produced and tested until Nov. 2006 They have been used for two Open MRI systems

13. Optimisation of the wires fabrication by varying sheaths, geometry of the conductor,… Wire B 37 filam Cu stab Cu Ni Monel Wire C 19 filam no Cu up to 61 Going from flat tape to round-square wires cleans up conductor anisotropy, and the field dependence of Ic improves accordingly

14. P.I.T. e-situ method + MgB2 B Mg Commercial MgB2 High energy ball milling wire drawing to 2 mm cold rolling tube filling reaction at 900-1000°C in Ar Possible routes: Commercial precursors Doped boron B Mg MgB2 MgB2(doped) B(doped) Mg dopant B + + + Home made boron MgB2 B Mg B2O3 +

15. Progress in the Ic of the flat tape conductor in multi Km-length With Monel sheath minimum bending radius 30 mm 3.6 x 0,65 mm 2.3 mm2

16. MgB2 grains are covered by 5 nm of MgO layer within 2 hours of exposition of powders to air ( this layer has a thickness ~ξ ) Working in Oxygen-cleaner conditions is mandatory!

17. Critical current improvement followed by inert-atmosphere handling Ic is improved by a factor larger than 2 at virtually all fields just by inert atmosphere powder handling during the entire process

18. MgB2 powder synthesis temperature Jc vS T @ 5K-4,5T SQUID Wires T=5K

19. Effect of synthesis temperature Not controlled atmosphere Glove box Decreasing synthesis temperature Decreasing synthesis temperature Point Defect Pinning Grain Boundaries Pinning 5K 5K

20. The effect of high energy ball milling is evident To increase the milling time (up to a certain value) – the tightness of the jars needs to be improved on longer times

21. Milling B=4.5T T=5K new Giara da 500ml in SS BPR=8.4

22. Milling B=4 T T=5 K

23. Milled with different BPR 50g MgB2

24. Carbon additions can be also introduced during ball milling. Because it does not enter MgB2 in a very uniform way by such a process, it is benificial if it is added to a very low levels.

25. Doping with ex-situ is underway Doping with nanosized SiC is effective provided that it is added to the Boron powders prior to MgB2 synthesis Further improvement is expected while SiC is added to optimized milling process

26. Control of powder production process is crucial to achieve optimal particle size Commercial MgB2 MgB2 from commercial Boron 1000 nm 450 nm MgB2 from own Boron

27. SQUID measurements T = 20 K

28. Whatisnecessaryto do tomeetcurrentwiredemands? Some applications do not need better powders than today’s production (dedicated low-field MRI, FCL, CERN), only more engineered conductors are preferrable – strong activity is ongoing to reach targets over long lengths Fully non-magnetic, high resistive matrix, twisted, for low-AC loss applications

29. Whatisnecessaryto do tomeetcurrentwiredemands? Most of the applications do need better powders than today’s production in very large quantities, as well as more engineered conductors are preferrable – the last point has been already addressed – wires are twisted with no degradation, and electrically insulated with different techniques as braiding, wrapping, etc. All wires produced in Km-class length with no degradation

30. Materials cost estimate • Boron • Magnesium • Other metals and alloys constituents of the wire In a wire we have: 60% Ni 15% Cu 15% MgB2 10% Fe Materials cost target for large production volumes: below 1 €/m

31. MgB2 wire technologies • The production of long length of MgB2 wires has been demonstrated in the past years, with supply to ASG and other customers of about 150 Km of conductor • In 2008 the wire production will be of about 200-300 Km, although our production capability, considering some additional limited investment, can be raised to >1’000 Km/year in 3-6 months time in the present production plant • Survey of different technologies to produce wires (in-situ, ex-situ), and different ways to produce and improve B and MgB2 powders is always active • Most of today’s effort is concentrated on reliability demonstration and on scaling-up technologies as much as possible in-house in order to produce enhanced MgB2 in relevant quantities (> 10 Kg/day) using cost-effective technologies