2G Conductor Delivery for the Albany Cable Project HTS Solutions for a New Dimension in Power Superconductivity for Electric Systems 26 Annual DOE Peer Review
Next challenge: Delivery of nearly 1, m of 2G wire for the Albany Cable project SuperPower will provide nearly 1 km of 2G HTS conductor in 26 to build a 3 m long cable for the Albany Cable project, which will be the world s first 2G device. Largest single quantity of 2G delivery Minimum piece length requirement is 43 m not a delivery of tapes from laboratory runs! Excellent test for the reproducibility & manufacturing viability of our processes 3 m 2G cable segment 26 DOE Peer Review 24 Albany Cable project: National Grid, 35 m long cable. World s first in-grid cable, first underground HTS cable, first cable-to-cable joint. World s first 2G device (3 m)
Routine production of IBAD MgO now: 7 8 m per run Process length increased to ~ 77 m with two single-piece lengths Single piece lengths up to 57 m limited by substrate 25 production runs yielding 14,66 m of 12 mm wide IBAD MgO tapes produced in the last 5.5 months equivalent to 43,98 m of 4 mm wide tape 9 8 April onwards 7 6 # tapes 5 4 3 2 1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8+ IBAD Process length (m) 26 DOE Peer Review 25
Routine production of Homo-epi MgO & LMO buffers now 5 6 m lengths per run Process length has been typically 4 5 m. Now 5 6 m No change in process parameters since the beginning of production! Single piece length up to 57 m limited by substrate. 37 production runs yielding 12,52 m of 12 mm wide buffer tape equivalent to 37,56 m of 4 mm wide tape produced in the last 4 months # tapes 1 9 8 7 6 5 4 3 2 1 1-2 2-3 3-4 4-5 5-6 Buffer Process length (m) 26 DOE Peer Review 26
We are now routinely processing MOCVD tapes in lengths over 3 m 14 12 # tapes 1 8 6 4 2 May onwards 5-1 1-2 2-3 3-4 4-5 5-6 MOCVD Process length (m) 35% of tape produced by MOCVD are 2+m. 71% of tape produced since May are 2+ m and 43% are 3+ m 31 production runs yielding 5,72 m of 12 mm wide tape (= 17,16 m of 4 mm wide tape) 26 DOE Peer Review 27
Critical currents of 2 to 25 A/cm reproducibly achieved in long lengths from May onward 3 25 Average Ic (A/cm) 2 15 1 5 263 264 265 266 269 27 271 272 273 274 276 277 28a 28b MOCVD Run # #267 was damaged after MOCVD. #268 & # 275 were experimental runs Runs #278 & #279 were interrupted. 26 DOE Peer Review 28
More than 12, m of qualified tape in inventory for Albany Cable project Piece length required = 42.4 m 55% of tapes > 1 m piece length 27% of tapes > 2 m piece length # tapes 45 4 35 3 25 2 15 1 5 45-1 1-15 15-2 2-25 25-3 3-35 35-4 Tape length range (m) 26 DOE Peer Review 29
Higher Critical Currents HTS Solutions for a New Dimension in Power Superconductivity for Electric Systems 26 Annual DOE Peer Review
Thickness dependence of Jc of MOCVD films on IBAD YSZ & MgO; single pass vs. multipass MOCVD 35 3 3.5 3. 25 Ic ; IBAD YSZ, single pass 25 2.5 26 Ic ; IBAD MgO, multipass Ic (A/cm) 2 15 1 2. 1.5 1. Jc (MA/cm 2 ) 25 Jc ; IBAD YSZ, single pass 26 Jc ; IBAD MgO, multipass 5.5 1 1.5 2 2.5 3 MOCVD film thickness (microns) 26 DOE Peer Review 31 Multipass : Same tape used for sequential deposition of YBCO in multiple passes Ic increase with thickness of MOCVD films is similar on IBAD MgO & YSZ Similar results are obtained with multipass & single pass approaches. but multipass approach provides an option to modify process conditions in each pass & is also representative of multiwrap-processing with a helix. Jc at 1 micron is ~ 2 MA/cm 2 in both cases & is a limiting factor for thick films.5.
Ion milling experiments provided insight into factors limiting Jc in 1 micron thick MOCVD films Jc (MA/cm 2 ) Incremental Jc (MA/cm 2 ) 4. 3.5 3. 2.5 2. 1.5 1..5. 2.5 2. 1.5 1..5 72K 77K 82K 2 4 6 8 1 Thickness (nm). 2 4 6 8 1 Thickness (nm) 77K - T H = T Top layer is the low Jc region Fp / Fp,max 1. 1.3 μm.74 μm.8.55 μm.36 μm.16 μm.6.4.2 Fp (GN/m 3 ) 4.5 4. 3.5 3. 2.5 2. 1.5 1..5. 2 4 6 8 μ H (Tesla) 77K...2.4.6.8 1. H / H K Jc of 2 MA/cm 2 uniform in the bottom 2/3rds of the film. No dead layer at the bottom. Top layer is the low Ic region The lower Jc in the top layer is not due to loss of pinning! Data by Matt Feldman & David Larbalestier 26 DOE Peer Review 32
FIB & TEM analyses show that Ba-Cu-O phases could be a reason for current limitation in 1 micron thick films; Higher Jc by elimination of these phases from film interior FY5: 1 micron thick YBCO, Jc = 1.7 MA/cm 2 amorphous phase Ba-Cu-O rich phases could be remnant of possible liquid-assisted high-rate growth of MOCVD films These phases constitute ~ 2% of volume & could limit the Jc to < 2 MA/cm 2 in 1 micron thick films FY6:.7 micron thick, Jc = 3.3 MA/cm 2 YBCO YBCO Ba-Cu-O Si from sample holder 5 μm Ba-Cu-O Ba-Cu-O 2 nm.2 µm TEM by T. Holesinger TEM by X. Song, D.Larbalestier In FY6 tapes, Ba-Cu-O secondary phases are primarily seen at the surface will limit achievement of high Jc in thicker films produced in multiple passes 26 DOE Peer Review 33
MOCVD process optimized to further improve the microstructure & Jc of.7 micron thick films.7 micron thick, Jc range = 3.4 4.7 MA/cm 2 Voltage (microvolt) 16 14 12 1 8 6 4 2-2 77 K, self field.7 micron thick film Ic = 43 A = 335 A/cm Jc = 4.79 MA/cm 2 Ba-Cu-O rich phases have been essentially eliminated. Surface is clean except for occasional CuO regions suitable for depositing additional HTS layers in a multipass process. In addition, a high density of vertically oriented Y-rich secondary phases & horizontally-aligned (Y,Sm) oxide precipitates 26 DOE Peer Review are seen 34 5 μm 1 2 3 4 Current (A) TEM by T. Holesinger
Ic (A/cm) High critical currents achieved in thick MOCVD films based on first layer with improved microstructure 6 5 4 3 2 1 9% more!.5 1 1.5 2 2.5 3 MOCVD film thickness (microns) In a 2.1 micron film made in 3 passes, achieved Ic of 557 A/cm (Jc = 2.65 MA/cm 2 ) over 12 mm wide, 1 cm long tape. After patterning a 2.1 mm wide bridge, measured Ic of 63 A/cm (Jc = 3. MA/cm 2 ) 4.5 4. 3.5 3. 2.5 2. 1.5 1.. 26 DOE Peer Review 35 Jc (MA/cm 2 ) Voltage (microvolt) Ic, standard composition Ic, modified composition Jc, standard composition.5 Jc, modified composition -2 12 1 8 6 4 2 12 mm wide 1 cm long tape 5 cm voltage spacing 77 K, self field Ic = 668 A = 557 A/cm 2 4 6 8 Voltage (microvolt) 14 12 1 8 6 4 2 Current (A) 2.1 mm wide bridge 5 cm long tape 1 cm voltage spacing 77 K, self field Ic = 132 A = 63 A/cm -211 12 13 14 15 Current (A)
Ic-cm width [A/cm] Ic-cm width [A/cm] High Jc & Je measured in 2.1 micron high current conductor at 1 T, 75.5 K 6 1 1 3 25 2 15 1 5 T=75.5K H c α=.522.1.1 1 1 75.5 K bridge width=21.5μm Magnetic field [T] 1T 3T 5T 7T 3T 4mm tape -45 45 9 Angle between field and c-axis [deg] In-field measurements by B. Maiorov, S. Baily, F. Hunte, and L. Civale; TEM by T. Holesinger 26 DOE Peer Review 36 Vertically-oriented Y-rich secondary phases (same as in.7 μm film) 1+ A/cm conductor at 1 T, 75.5 K, B c! 1 T, 75.5 K B ~ a-b B c B c, 25 26 improvement Ic (A/cm) 294.4 116.7 61 9% Y map Layers of Y 2 O 3 precipitates at 7 degrees to a-b plane (same as in.7 μm film) Jc(MA/cm 2 ) 1.4.56.2 175% Je (ka/cm 2 ) 5.5 21.1 11 82% Significant improvement in in-field properties for a 45% increase in Ic at self field
High currents have been achieved by MOCVD over a range of conductor lengths Critical current (A/cm) Length (m) Ic (A/cm) Thickness (μm) Jc (MA/cm 2 ) 285 28 275 27 265 26 255 25 1.5 557 2.1 2.65 272 A/cm over 52 m 11 21 1 47 2.1 2.24 52 272 1. 2.72 31 Position (m) 157 263 1.2 2.19 41 227 246 1.2 2.5 51 26 DOE Peer Review 37 322 219 1.2 1.83 Critical current (A/cm) 3 28 26 24 22 2 Voltage (microvolt) 14 12 1 8 6 4 2-2 1 12 23 34 45 56 67 78 89 47 A/cm over 1.2 m 1 2 3 4 5 6 Current (A) 263 A/cm over 127 m Position (m) 1 111 122
Questions raised on the viability of MOCVD have been answered MOCVD stability High Ic by MOCVD Uniformity of Ic in long lengths MOCVD precursor cost From AMSC s whitepaper, Dec. 24 : A lower vacuum and therefore potentially lower cost technique is metal-organic chemical vapor deposition (MOCVD), which has been developed, particularly by Fujikura [Onabe 1997] and IGC-Superpower [Selvamanickam 21, 24a]. High performance up to 38 A/cm-width has been achieved in short centimeter-length samples. While the deposition rate is rapid, uniformity over large areas and the precursor cost, involving complex organic molecules, are still significant challenges. Wire lengths up to 6 m have been successfully processed by MOCVD [Selvamanickam 24b], but performance levels in these wires, around 1A/cmwidth, are still well below the low-cost MOD process Stability duration (hours) Uniformity in Ic Ic (A/cm) Precursor cost Over 1 m Over 2 m Over 3 m Over 1 m Over 2 m Over 3 m FY4 1 Longest length was 18 m 1% (baseline) FY5 7 4.2% 3.% 152 17 3% by scale by helix FY6 2 1.7% 2.6% 4.3% 263 246 219 6% 26 DOE Peer Review 38