Design and Properties of SuperPower`s Practical 2G HTS Conductor for Electric Power Applications Venkat Selvamanickam

Transcription

1 Design and Properties of SuperPower`s Practical 2G HTS Conductor for Electric Power Applications Venkat Selvamanickam Y.Y. Xie, X. Zhang, Y. Qiao, and D. W. Hazelton Program funding from Title III and DOE through UT-Battelle, AFRL, & AFOSR HTS Solutions for a New Dimension in Power Applied Superconductivity Conference, Seattle, August 28 September 1, 26

2 SuperPower s 2G conductor is half as thick as 1G Substrate thickness = 5 microns Surround copper stabilizer = 2 microns all around Total conductor thickness is only.95 mm 2μm Cu 2 μm Ag 1 μm HTS ~ 3 nm LMO ~ 3 nm Homo-epi MgO ~ 1 nm IBAD MgO 5μm Hastelloy substrate 2μm Cu High-strength, non magnetic, highly resistive Hastelloy substrate is used 26 ASC 2

3 3+ m lengths of 2G conductor are routinely produced with high Ic and excellent uniformity at high throughput 35 MOCVD: 3 m/h in a single pass on high-throughput IBAD MgO buffered Hastelloy substrate Critical current (A) Critical Current * Length : 7,52 A-m Min Ic = 263 A = 219 A/cm over 322 m. Uniformity of 4.3% over 322 m. 77 K, Ic measured every meter over entire tape width of 12 mm Position (m) 26 ASC 3

4 2G conductor is now available in long lengths with Ic in the realm of 1G, & Je about 2x better than 1G End-to-end critical current of 4 mm wide 2G conductor slit from 12 mm wide tape 14 End-to-end Ic = 1 A over 27 μv/cm 12 Critical current (A) Position (m) Ic = 1 A in a 4 mm wide 2G conductor over 27 m! Je = 26.3 ka/cm 2 (for a 2 micron surround stabilizer i.e. 4 micron total) compared to a 1G Je of 13 ka/cm 2 to 17 ka/cm 2 26 ASC

5 Ic-cm width [A/cm] Ic-cm width [A/cm] Even higher Ic & Je demonstrated in short lengths T=75.5K H c α= K bridge width=21.5μm Magnetic field [T] 1T 3T 5T 7T 3T 4mm tape Angle between field and c-axis [deg] 1 T, 75.5 K Self field, 77 K B c, 1 T, 75.5 K B ~ a-b, 1 T, 75.5 K In-field measurements by B. Maiorov, S. Baily, F. Hunte, and L. Civale Voltage (microvolt) 26 ASC mm wide 1 cm long tape 5 cm voltage spacing 77 K, self field Ic = 668 A = 557 A/cm Ic (A/cm) Current (A) 2.1 micron thick YBCO Jc(MA/cm 2 ) Je (ka/cm 2 )

6 2G conductors are very mechanically robust: Can be slit to narrow widths & twisted to small twist pitches Twisting needs to be demonstrated in order for striated geometry to be fully effective in long lengths 2 mm 4 mm wide wide conductor, conductor, 1 full 4 full twists twists % Ic/Ic N-value Ic/Ic(Original) Number of full twist in 5 cm Twist Pitch - L/2 (cm) % original Ic retained at 5.5 full twists (Twist pitch = 9.4 cm) 26 ASC 6 95% original Ic retained even at 1 full twists (Twist pitch = 4.6 cm)

7 Use of high-strength 5 micron substrates yielded thin-profile 2G conductors with much higher tensile strain & critical tensile stress Conductor with 1 μm substrate Conductor with 5 μm substrate Stress (MPa) G with High-strength 5μm substrate 2G with 1μm substrate Strain (%) Tensile Stress (MPa) T = 76K Bare substrates (5 μm) Batch 1 Complete conductor (5 μm) Bare substrates (1 μm) Batch 3 Batch 2 Complete Conductor (1 μm) Tensile Strain (%) Critical Current (A) micron substrate conductor 1 1 micron substrate conductor 2 5 micron substrate conductor 1 5 micron substrate conductor Tensile Stress at R.T. (MPa) 2G conductor made with 1 micron substrate High-strength 5 micron substrate Yield strength at 77 K* 65 MPa 12 MPa Critical tensile stress at RT 35 MPa 55 MPa *Measurements Y. Zhou and K. Salama (U.Houston) N. Cheggour, D. Van der Laan, J. Ekin (NIST) 26 ASC 7

8 Bend performance significantly improved using thin-profile 2G conductors Ic/Ic(original) 1% 9% 8% 7% 6% 5% Bend at R.T. and Test While held on Mandrel 1 micron substrate 4 mm wide with 2 micron surround Cu 5 micron substrate 4 mm wide and surround Cu 5 micron substrate 12 mm wide no Cu Minimum bend dia reduced from 22 to 11 mm % Compressive Bend diameter (mm) Tensile 2x reduction in bend diameter using conductors with 5 micron substrates 26 ASC 8

9 Joints between 2G conductors show good electrical & thermo-mechanical properties Copper stabilizer solder HTS layer substrate 4 mm wide conductors each with 2 μm surround copper stabilizer Joint length = 3 cm Original tape thickness =.145 mm Thickness at joint =.32 mm No degradation in Ic (1 μv/cm) over the joint Resistivity over the joint is 38 nohm-cm 2 No degradation in Ic and resistivity when bent over down to 1.5 diameter and thermal cycled three times. Ic was tested at every thermal cycle When further bent over 1" mandrel, solder material failed. 26 ASC 9 Voltage (V) 2.5E-5 2.E-5 1.5E-5 1.E-5 5.E-6.E+ -5.E-6 Orginal Joint Bent over 2" dia, thermal cycled 3 times Bent over 1.5" dia, thermal cycled 3 times Crtiical Current (A)

10 Joints between thin-profile conductors show excellent mechanical & electrical performance Thickness at joint can be reduced from.32 mm to.22 mm by using thin-profile conductors (w/ 5 micron substrates) 4 mm wide conductors each with 2 μm surround copper stabilizer Joint length = 3 cm Original tape thickness =.95 mm Thickness at joint =.22 mm 1. Ic retention (%) Ic retention : High quality joint Ic retention : Low quality joint Joint resistivity : High quality joint Joint resistivity : Low quality joint Low quality joint High quality joint Resistivity (nω-cm 2 ) Voltage (μv) Current (A/cm) 26 ASC 1 Original 2" 1.5" 1" Bend Diameter Joint resistivity = 4 nωcm 2 Ic across joint & resistivity of joint are not affected down to a bend diameter of 1 Quality of joint primarily determines electrical & mechanical performance

11 Splices of thin-profile conductors show excellent mechanical & electrical properties Copper stabilizer solder HTS layer substrate Volatge (μv) Splice using a 3.5 cm long piece bent on 2" mandrel Bent over 1.5" mandrel Bent over 1" mandrel Two 4 mm wide,.95 mm thick (5 micron substrate, 2 micron surround copper stabilizer spliced with a similar piece 3.5 cm long. Splice Resistivity = 5 nωcm Current (A/cm) No Ic degradation when splice was bent down to 1 diameter. 26 ASC 11

12 Use of thin-profile 2G conductor enabled fabrication of high-field HTS coil In FY6, we demonstrated a 2G coil that generated.4 T at 77 K and.87 T at 64 K FY6 2G coil Coil ID (mm) Winding ID (mm) Winding OD (mm) Height (mm) 2G Tape Used (m) # Turns Avg Ic of Tape in Coil (A) 77K Coil Ic (A) 77K Amp Ic 64K Coil Ic (A) 64K Amp Ic 26 ASC , ,437 Central Field (kg) Central Field (kg) T Coil at 77 K! First Test Last Test model 77 K Current (A) 2.4 T at 64 K First Test Last Test 64 K Current (A)

13 New conductor geometries developed for ac loss reduction In order to benefit from patterning of YBCO, thick copper stabilizer also need to be striated Cu Ag HTS Tapes with striated YBCO & silver overlayer have been produced by several groups 1 μm substrate Cu 1 mm Very first demonstration of striation of a thick copper stabilizer Mechanical properties of fully-striated conductor need to be investigated 26 ASC 13

14 Thin profile 2G conductors enable higher Je & better mechanical properties High Je 26.3 ka/cm 2 in 322 m lengths (2x 1G) In self-field at 77 K, Je of 1, A/cm 2 in short tapes (with no Cu), 58.4 A/cm 2 for a 4 micron total copper stabilizer At 1 T at 75.5 K, 21.1 ka/cm 2 in short tapes (with no Cu), 12.2 ka/cm 2 for a 4 micron total copper stabilizer Better mechanical properties Bend diameter of 11 mm even with YBCO in tension with 95% Ic retention Low contact resistance & no Ic degradation of joints & splices when bent over 25 mm and thermal cycled 3 times from 77 K to RT Yield stress of conductor = 12 MPa (6-8 times 1G). Critical tensile stress > 55 MPa Twist pitch of 9.4 cm with 4 mm wide & 4.6 cm with 2 mm wide conductors High-performance devices Can pack more wire in a coil and wind it around small diameter. Coil generating 1.1 T at 77 K and 2.4 T at 64 K demonstrated 26 ASC 14