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Electro-Mechanical characterization of HTS and LTS conductors at the NHMFL

Electro-Mechanical characterization of HTS and LTS conductors at the NHMFL. Presented by H.W. Weijers 1 Input also provided by Jun Lu 1 , Ulf Trociewitz 2 , Bob Walsh 1 , Denis Markiewicz 1 Presented at KERI, Changwon July 15 th 2009 1 Magnet Science & Technology, NHMFL

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Electro-Mechanical characterization of HTS and LTS conductors at the NHMFL

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  1. Electro-Mechanical characterization of HTS and LTS conductors at the NHMFL Presented by H.W. Weijers1 Input also provided by Jun Lu1, Ulf Trociewitz2, Bob Walsh1, Denis Markiewicz1 Presented at KERI, Changwon July 15th 2009 1 Magnet Science & Technology, NHMFL 2 Applied Superconductivity Centre, NHMFL

  2. Outline • Introduction to NHMFL • YBCO, Nb3Sn wire and cable characterization capabilities within • Material Development & Characterization group • Systems Engineering group • Applied Superconductivity Center (brief) • Summary

  3. National Magnet Lab User Facility • Provides many of the world’s highest DC magnetic fields • 45T in hybrid, 38 mm warm bore • Purely resistive magnets: 35T in 38 mm warm bore, 31 T in 50 mm bore and 19T in 195 mm warm bore • Record bore size (105 mm warm bore) in 900 MHz NMR • Pulse magnets in 90-100 T range (Los Alamos) • 20 T SC magnet with mK capability • High B/T facility (Gainesville) Areal view of Tallahassee facilities

  4. Within the NHMFL • Magnet Science&Technology Division • Responsible for development and construction of in-house magnets and design and construction work for others • Typically mm to km length scale • Materials Development and Characterization group • Systems Engineering group • Large scale experiments including HTS coil and CICC testing • Applied Superconductivity Center • Responsible for Superconductor R&D • Typically nm-cm length scale

  5. Major projects Series connected hybrids NHMFL, HZB 32 T SC research magnet for NHMFL Nb3Sn CCIC Engineering data needed for: YBCO coated conductor YBCO for SNS? Bmax = 36 T (14 sc. + 22 res.) Imax = 20 kA Nb3Sn Jc> 2000 A/mm2 Transverse load: 280 kN/m Design #1 #2 Cold bore YBCO (mm) 40 40 Cold bore outer (mm) 200 200 YBCO conductor Length (m) 7347 4620 Cost at $50/m (k$) 367 231

  6. Devices for characterization of superconductors • Mostly YBCO, also BSCCO (77 & 4.2 K) • Stress-strain (also 300K) • Ic(B, strain) to 20 T • Angular dependence of Ic(B) to 35 T • Mostly Nb3Sn (4-10 K) • Axial strain-strain in strand and cable (also 300K) • Transverse load in strand and cable • Ic, Tc versus axial strain and transverse Lorentz-force cycling in 20 kA CICC • Stress-strain in Cable, conduit, CICC

  7. Materials Development & Characterization Group’s Superconductor Characterization Work Robert Walsh, Dustin McRae, Vince Toplosky, Yan Xin, Robert Goddard, Jun Lu, and Ke Han Magnet Science & Technology Division

  8. Versatile Materials Test Systems Designed for a wide array of materials test needs (structural, insulating and superconducting, etc.) Wide temperature range (400 K – 1.8 K) Fully Reverse Cycle Fatigue ASTM tensile specimen Nb3Sn Wire tensile specimen Capstan Grips Tape Tensile Test Racetrack Composite Tension Samples 100 kN Cryo-Test Machine Weld Fracture Toughness Specimen

  9. 4 K Tensile Tests of Nb3Sn composite wires

  10. CICC Mechanical Test Specimen • In-situ Tests allow determination of ; • Thermal Pre-strain caused by heat-treatment • Clamp force necessary to transmit equivalent strain • Estimate of Cable Modulus and Tensile Properties

  11. HTS Tape Tensile Test set-up Test temperatures 295 K, 77 K, and 4.2 K

  12. YBCO conductor tensile test results 20, 30, 50 mm Cu plating, 77 and 4.2 K, 3 batches (18, 20, 21) (secant)

  13. Participation in International Standards (VAMAS, ISO, and IEC) Round Robin Test Program 2008-2009 Standardized Tensile Tests of ; - Bi-2223 Laminate Tape (Brass or SS Clad) - Bi-2212 Silver Clad Round Wires • Additional Research; • Strain Measurement Method Comparison • Single wire extensometer (Shepic) • Set of (2) averaging extensometers (Nyilas)

  14. Setup used in recent IEC TC-90 WG-5 experiments Load cell Nyilas extensometer close up

  15. extensometer Copper Nb3Sn wire B Voltage taps Ic-strain apparatus • Measure ~100 mm straight wire, voltage taps ~ 40 mm. • 0 - 20 T, 195 mm bore resistive magnet at cell 4 of NHMFL • Max force = 5 kN. Backing plate thickness = 0.44-0.80 mm. no strain concentration T = 4.2 K

  16. Backing plate effectNb3Sn wire Mitsubishi-1400 wire at 4 K, 18 T

  17. IC , irreversibility strain of ITER high JC Nb3Sn strands extensometer Copper Nb3Sn wire B Voltage taps

  18. Ic-strain apparatusYBCO Ic vs. strain extensometer Copper YBCO tape T = 77 K YBCO tape x-section Voltage taps 40 mm Backing plate is 0.4 x 4 mm2 BeCu

  19. Results The irreversible limit is ~0.7% from the peak, comparable with published data.

  20. Modified stress-strain rig to allow in-situ Ic measurement of YBCO tape Vince Current contacts integrated with grips Voltage taps Reaction frame Under development now

  21. Ic strand versus transverse stress IC transverse stress device. The air cylinder applies transverse load via the pull rod and the end puck (not shown). The sample sits in a shallow groove which support the Lorentz force.

  22. Systems Engineering • Developing Walters spring (Markiewicz) • FEM work student project • Large scale CICC (Weijers) • Ic, Tc versus strain at 4-10 K, 12 T • Ic, Tc versus transverse load cycling • Nb3Sn Rutherford cable (Weijers, LBL) • Ic versus transverse load at 4 K, 12 T

  23. Walters Spring for Ic(e) to 31 T (Nb3Sn) • Walters Spring • Special Geometry • Applied Torque • Strain induced on conductor • 22mm Diameter ~25 mm tall

  24. Walters Spring DC Magnet Probe Small warm boreMotors must be kept away from high fieldTorque transmission through bore 50 mm warm bore

  25. Walters Spring Cross section view of circumferential strain

  26. Walters Spring Calculated strain along sample

  27. Large scale conductorsNb3Sn CICC and Rutherford cable • CICC for Series Connected Hybrids • Ic, Tcs versus B, Lorentz-force load cycling • Modern Rutherford cable for accelerator dipoles (LARP) • Ic versus transverse stress to 200 MPa at 12 T • Interested in YBCO cable • Desirable for future high-field magnet projects

  28. Ic, Tcs in CICC versus transverse stress • 3-5 bar supercritical helium, 4.5 to 10 K requires flow valves and heaters, He mass-flow meters, multiple thermometers, multi-channel DAQ • 12 T, 250 kN (~1 % strain), 20 kA HF:15 cm

  29. CICC sample construction

  30. CICC experiment • Sample is mounted to magnet, cooled down together • 20 kA from resistive magnet power supply • Sample in radial access slot, horizontal bore magnet • Load-bearing dewar wall

  31. Large scale conductorsNb3Sn CICC experimental setup(during setup, excuse the apparent lack of order) 250 kN actuator on cross head Load cell Pressurized helium dewar Magnet dewar Pressurized helium bottles LR280 refrigerators available in 2-3 years

  32. CICC example data

  33. Nb3SnRutherford cable under transverse pressure • In support of US LARP program (LBL) • Ic versus transverse load at 12 T, 4.2 K Superconducting DC transformer Range > ±30 kA Helium gas pressurized bellows drive a piston Range >200 MPa on cable Sample housing

  34. Ic(B,angle) at 4.2 K to 35 T (ASC) Sliding o-ring seal Driven by Kevlar wire Sample mounted on G-10 backing Sample narrowed to ~ 1mm bridge to keep Imax manageable

  35. Tensile test of conductor in the form of a thin coil • Hoop stress provides tensile load • Measures Ic(force) at 4.2 K, 20 T • Yield evens out between turns: much reduced “necking” • Proper terminal design is essential • Reproducible and reliable strain measurement is difficult • Magneto-resistance effects on strain gage • Mounting on curved Cu-plated surface is not trivial • Important step between short-sample data and larger coils

  36. Strain-limited thin coil(YBCO layer wound) Verification of both short sample properties and coil technology 20 T Inductive voltages 100 A = ~300 to 350 MPa

  37. Summary • An overview is presented of the capabilities at the NHMFL to measure electro-mechanical properties of HTS and LTS conductors and cables • Multiple set-ups cover a fairly large parameter space • Load: N to 500 kN • Temperature: 1.8-400 K • Magnetic field, angle: Ic(B) to 45 T, Ic(B,angle) to 31 T, Ic(B,e) to 20 T • Current: A to 20 kA at 700 V max, 35 kA SC transformer • Development of capabilities is driven by major projects • Series Connected Hybrid • High-field magnets with YBCO Coated Conductor

  38. Thank you for your attention!

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