Development of MgB2 Strands for High Field Magnet Applications

1. Development of MgB2 Strands for High Field Magnet Applications Laboratories for Applied Superconductivity and Magnetism (LASM) MSE/OSU Global Research and Development, Inc Hyper Tech Research, Inc ++ Prepared for the LTSW/2006, NHMFL, Tallahassee, FL November 7-9, 2006

2. Materials Science Laboratories for Applied Superconductivity and Magnetism (LASM) MSE/OSU Global Research and Development, Inc Hyper Tech Research, Inc ++ Research & Development Manufacturing & Commercialization

3. ISEM, University of Wollongong S. X. Dou, S. Soltanian Y. Zhao, E. Getin Z. Chen, O.Shcherbakova J. Horvat, W.K.Yeoh LASM / Ohio State Mike Sumption Ted Collings Mohit Bhatia Scot Bohnenstiehl Hyper Tech Mike Tomsic Matt Rindfleisch Jinji Yue Kevin McFadden Xuan Peng David Doll Florida State U. S. A. Shaheen MIT Yuki Iwasa Juan Bascuñán IEMM, Inc. Yusuf Hascicek Brookhaven National Lab Arup Ghosh Lance Cooley CAPS (NHMFL) Tom Baldwin Hyper Tech Research, Inc ++ Manufacturing & Commercialization

4. Outline of the Survey Basic Materials Science Formation of MgB2 from its elements Charge-carrier scattering and Bc2 Bc2-defind regimes of applicability Thin-film results pointing towards improved Bc2 in bulks/wires Selection of dopants to improve scattering and hence Bc2 Manufacturing and Commercialization Multifilamentary strand design and processing Transport properties of long-piece-length strands Long length manufacturing capability Survey of coil-winding for demonstration and commercialization Directions for Future Research and Development Development of fine-filament- and high-filament-count strands Introduction of all-Cu stabilization Chemical modifications and dopants to improve high-field-Jc Introduction of nano-particle pinning centers to improve HF-Jc Thin film results pointing towards high-field-Jc improvement -- reductions in porosity, increases in connectivity HTR Dept of Materials Science and Engineering GLOBAL

5. HTR Department of Materials Science and Engineering Materials Science Formation of the compound, MgB2 Critical Fields Doping Characterization

6. Formation: DSC traces for Mg + B(amorphous) and pure Mg Mg exotherm MgB2

7. Mg melting Mg+2B MgB2 Mg(OH)2 MgO+H2O (weak endo) Mg+H2O MgO+H2 (strong exo)

8. Formation: DSC traces for MgH2 + B(amorphous) MgH2 Mg + H2 exotherm Mg + 2B MgB2

9. Structure & Upper Critical Field -- charge-carrier scattering, and the influence of dopants The presence of Mg in the compound MgB2 stabilizes the B sub-lattice in the form a honeycomb-like stack of hexagonal networks. • The B honeycomb dominates the electronic structure which can be thought of as deriving from: • -bonding orbitals within the B planes and • -bonding orbitals both within and out of the plane. • The in-plane  orbitals give rise to a 2-D  band • The in-plane and out-of-plane  orbitals form the 3-D  band.

10. The Upper Critical Field, Hc2, and its Enhancement through Impurity Scattering In the case of dirty MgB2 films the fact that D << D (i.e  scattering is much stronger than  scattering) leads to the approximations: Thus increases in Hc2nearTcwould expect to follow decreasesinD. As for Hc20, again for D << D, it has been shown that: Thus increases in Hc20 would follow decreases inD These relationships in principle allow Hc2 to be manipulated by introducing dopants into the MgB2 lattice – for example:

11. Some dopants and their expected effects on the Hc2s • O and C when substituting for B provide strong  scattering leading to enhancement in Hc2nearTc • disorder on the Mg sublattice can increase the  scattering hence to enhanced Hc20 • macroscopic particles that contribute to lattice distortion enhance  and  scattering ----- after Gurevich and Larbalestier

12. Encouraging Thin-Film Results The prospect of high field applications of MgB2 has been stimulated by the discovery of very high upper critical fields in dirty MgB2 films --- as evidenced, for example, by the following results: 49 T at 0 K, parallel orientation, in “in-situ-doped MgB2 films -- A. Gurevich et al. 51 T at 4.2 K , parallel orientation, in doped MgB2 films -- V. Braccini et al. 52 T at 4.2 K, parallel orientation, in C-doped -- C. Ferdeghini et al.

13. “new magnet domain” Spectacular performance of MgB2 in Hc2/T space ---- after Gurevich et al. --- a concept to be exploited in the further development of MgB2

14. Development of High Bc2 in Practical MgB2 Materials by a study of Bulk Pellets Bulk samples with compositions (MgB2)0.9(SiC)0.1, (MgB2)0.9C0.1, (MgB2)0.925(XB2)0.075 where (X= Zr, Nb and Ti) plus an MgB2 control sample were prepared by in-situ reaction of mixtures of 99.9 % pure Mg (-325 mesh), amorphous B powders (typically sub-μm) plus the powdered dopants

15. Birr Bc2 Bc2and BirrMeasurement: Metal-Diboride-Doped Bulk Samples Birr Bc2 Max Bc2 for the ZrB2 addition

16. Bc2and Birr Measurement: Doped Bulk Samples

17. Lack of correlation between Hc20,// and the measured residual resistivity, r,40K – which raises the “connectivity” issue, see later Collected data due to V. Braccini et al., Phys. Rev. B 71, 012504 (2005)

18. HTR Department of Materials Science and Engineering Manufacturing and Commercialization Strand Development and Properties Production Capacity Application

19. HTR Department of Materials Science and Engineering Manufacturing & Commercialization ISEM, University of Wollongong S. X. Dou, S. Soltanian Y. Zhao, E. Getin Z. Chen, O.Shcherbakova J. Horvat, W.K.Yeoh LASM / Ohio State Mike Sumption Ted Collings Mohit Bhatia Scot Bohnenstiehl Hyper Tech Mike Tomsic Matt Rindfleisch Jinji Yue Kevin McFadden Xuan Peng David Doll Florida State U. S. A. Shaheen MIT Yuki Iwasa Juan Bascuñán IEMM, Inc. Yusuf Hascicek CAPS (NHMFL) Tom Baldwin Brookhaven National Lab Arup Ghosh Lance Cooley

20. Cu MgB2 Nb HTR Department of Materials Science and Engineering Strand architectures Cu-30Ni

21. HTR Department of Materials Science and Engineering Development of high filament counts 36 filaments plus Cu, Nb CTFF in Cu ---- restacked in CuNi 54 filaments plus Cu, Nb CTFF in Cu ---- restacked in CuNi 18 filaments plus Cu, Nb CTFF in Cu ---- restacked in CuNi 7 filaments, Fe CTFF in Cu ---- restacked in CuNi

22. HTR Department of Materials Science and Engineering Typical Multifilamentary Strand Barrel (1m) Results 105 A/cm2 5 T 1 meter long samples

23. HTR Department of Materials Science and Engineering Further Multifilamentary Strand Barrel Results With SiC

24. Barrel measurements of km-Class Strands HTR Department of Materials Science and Engineering All 19 filament, monel-clad Strand lengths vary from 900-1800 m • At 4.2 K and 4 T: Jc s range from 0.64-1.7 x 105 A cm-2 • At 4.2 K and 8 T: Jc s range from 0.42-1.3 x 104 A cm-2

25. HTR Department of Materials Science and Engineering Long length manufacturing Milestones: 1 km monofilament, 3Q 2004 1 km multifilament, 3Q 2005 produced over twelve 1-1.5 km lengths of 19-fil. 0.8 mm wire Developing 3-5 km lengths during current year (2006) Present Manufacturing Capacity Up to 250 km / year capacity in 2006 Target Capacity 500-800 km/ year in 2007 3000-5000 km /year in 2008

26. HTR Department of Materials Science and Engineering Piece lengths more than 1 km The two upper spools are insulated

27. HTR Department of Materials Science and Engineering Products for commercialization and demonstration

28. HTR Department of Materials Science and Engineering Solenoid winding and development

29. HTR Department of Materials Science and Engineering Flat Solenoid Development

30. HTR Department of Materials Science and Engineering Racetrack coil testing at LASM

31. Developmental Coil for a Closed MRI HTR Department of Materials Science and Engineering 80 cm bore Cu coil segment former, designed for 1 km insulated 0.8 mm wire. Hyper Tech will supply strand to MIT for fabricating 10 – 14 coil segments. MIT will assemble and test segments as a full-size magnet. 450 m 0.98 mm insulated 19-filament wire before heat treatment

32. HTR Department of Materials Science and Engineering • Development and Commercialization Summary • Numerous racetrack coils and small solenoids have been wound and tested • A model 4 T solenoid wound with 1 km of 0.96 mm MgB2 strand has been conservatively designed • Two 3-4 T (4 K) solenoids have been wound and tested • A model gyrotron coil has been wound and tested. • An MRI coil has been wound and is under test • A model undulator coil set has been the subject of a design study • A rotor coil, one pole of a NASA/USAF 2 MW generator (~600 m wire) is under construction

33. HTR Dept of Materials Science and Engineering Directions for Further Research and Development Increase fill factor Reduce filament diameter Increase filament count Provide stabilization Increase Jc especially at high fields -- increase flux pinning -- reduce porosity, increase connectivity progress under way Progress under way GLOBAL

34. HTR Dept of Materials Science and Engineering High filament counts are starting to be achieved in standard strands With SiC 54 filaments plus Cu, Nb CTFF in Cu ---- restacked in CuNi GLOBAL

35. HTR Dept of Materials Science and Engineering The replacement of Mg with brittle MgH2 in the starting mixture is a route towards finer filaments and hence high filament counts MgH2-based strands GLOBAL

36. HTR Dept of Materials Science and Engineering Progress towards all-Cu stabilization ODS-Cu (Glidcop) Stabilized Strand GLOBAL

37. Jc(T) for monel-clad and ODS-Cu-stabilized MF strands HTR Dept of Materials Science and Engineering 19 filament samples, heat treated at 700°C, 20 min • 4.2 K, 4 T, Jc (105 A/cm2) • ODS Cu : 0.27-0.96 • Monel : 0.70-1.5 Similar results for 40 min HT GLOBAL

38. HTR Dept of Materials Science and Engineering Introduction of all-Cu stabilization a.Cu strand fabricated by using sacrificial monel and Nb (monel etched off; Nb peeled off) GLOBAL

39. HTR Dept of Materials Science and Engineering Jc(B) comparison for monel-clad (M), glidcop-clad (G) and Cu-stabilized (Cu) 19-filament strands GLOBAL

40. HTR Dept of Materials Science and Engineering Improvements in high-field Jc in response to the additions of extra Mg Mg1.15B2 GLOBAL

41. HTR Dept of Materials Science and Engineering Scaling curve for “Mg-enriched” monocore MgB2 Mg1.15B2 Irreversibility Fields T, K BKirr ,T Birr, T 10 12.9 15 15 11.3 14 17.5 10.2 12 20 9.22 10 22.5 8.45 8.0 25 6.43 - 27.5 4.74 - 30 2.72 - Pinning Parameters NbCu+M (700-40) A 7.285 p 0.9795 q 2.281 GLOBAL

42. HTR Dept of Materials Science and Engineering nano-SiC addition Improvements in high-field Jc in response to the additions of nano-SiC GLOBAL

43. HTR Dept of Materials Science and Engineering The Mg-added and nano-SiC-doped strands GLOBAL

44. HTR Dept of Materials Science and Engineering High-field Jcs of Mg-added and nano-SiC-doped strands n-SiC Mg GLOBAL

45. HTR Dept of Materials Science and Engineering Further advances in wire-Jc should be possible based on thin-film results GLOBAL

46. p gb gb A a HTR Dept of Materials Science and Engineering Porosity and Connectivity p% = 100/F GLOBAL

47. p gb gb A a HTR Dept of Materials Science and Engineering Basis for Resistive Estimations of Porosity/Connectivity Measured resistance/unit length GLOBAL

48. Lack of correlation between Hc20,// and the measured residual resistivity, r,40K Collected data due to V. Braccini et al., Phys. Rev. B 71, 012504 (2005)

49. HTR Dept of Materials Science and Engineering Resistivities of four MgB2 bulk samples GLOBAL

50. HTR Dept of Materials Science and Engineering * Measured – after Eltsev ** Obtained by fitting Eltsev’s resistivity data to the B-G function. GLOBAL