Progress in research and development of IBAD-MOCVD based superconducting wires V. Selvamanickam, I. Kesgin, A. Guevara, T. Shi, Y. Yao, Yue Zhang, Yangxin Zhang, and G. Majkic University of Houston, Houston, TX, USA
Y. Chen, Y. Qiao, S. Sambandam, G. Carota, A. Rar, Y. Xie, and J. Dackow SuperPower Inc., Schenectady, NY, USA Partially supported by U.S. DOE Office of Electricity & Energy Reliability and CRADAs with Oak Ridge, Argonne, and Los Alamos National Laboratories, and National Renewable Energy Laboratory Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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Dedicated in memory of Andrei Rar, 1961 – 2010 SuperPower’s Characterization Scientist A invaluable member of SuperPower Organization
Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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Superior wire features with IBAD-based substrates • Use of IBAD as buffer template provides the choice of any substrate • Advantages of IBAD are high strength, low ac loss (non-magnetic, high resistive substrates) and high engineering current density (ultra-thin substrates) • Fine grain size of superconductor on IBAD templates is very beneficial for multifilamentary wires for low ac losses • Amorphous alumina barrier layer enables superconductor processing at higher temperatures for high Ic.
< 0.1 mm
20µm Cu
2 µm Ag 1 µm YBCO - HTS (epitaxial) ~ 30 nm LMO (epitaxial) ~ 30 nm Homo-epi MgO (epitaxial) ~ 10 nm IBAD MgO
50µm Hastelloy substrate 20µm Cu
Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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MOCVD-based coated conductors are routinely produced in kilometer lengths 500 450
Critical Current (A/cm)
400 350 300 250 200 150 100
77 K, Ic measured every 5 m using continuous dc currents over entire tape width of 12 mm (not slit)
50 0 0
100
200
300
400
500
600
700
800
900
1000
Position (m)
• Minimum current (Ic) = 282 A/cm over 1065 m • Ic × Length = 300,330 A-m 4 Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
Wire price-performance is the key factor for commercialization • Today’s 2G wire : 100 A performance at 77 K, zero applied magnetic field, Price $ 40/m = $ 400/kA-m • At this price, cost of wire for typical device project (other than cable) > $ 1 M (more expensive than the typical cost of the device itself !) Cost of wire for a 500 km cable project = $ 20 M (~ cost of cable project itself !) Metric Price
Today $ 400/kA-m
Customer requirement < $ 100/kA-m*
For commercial market entry (small market)
< $ 50/kA-m*
For medium commercial market
< $ 25/kA-m*
For large commercial market
Four to 15-fold improvement in wire price-performance needed ! *at operating field and temperature Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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Objectives of UH-SuperPower program focused on meeting wire price-performance metrics • Higher self-field critical current in 2G wire by increasing film thickness – HTS is still only 1 to 3% of 2G wire compared with 40% in 1G wire and is the only process that needs to be changed in 2G wire for high Ic. • Significantly modify in-field critical current performance of 2G wire – Maximize potential of rare-earth, dopant, nanostructure modifications to tailor in-field critical current in device operating conditions • Reduce wire cost by high efficiency, simpler processes – Silver electrodeposition instead of sputtering – Substrate planarization instead of electropolishing + buffer – Improved MOCVD precursor conversion efficiency (only 15% now) • Reduce wire cost by increased yield – Develop new and enhanced on-line QA/QC tools • Added value to customer with advanced wire architectures – Multifilamentary wire for low ac loss Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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Improved pinning by Zr doping of MOCVD HTS wires • Systematic study of improved pinning by Zr addition in MOCVD films at UH. • Two-fold improvement in in-field performance achieved ! 5% 12.50%
70
1.6 1.4
60
1.2
50
1.0
40
0.8
30
0.6
20
0.4
10
1.0 T, 77 K
0.2
Standard Production wire
40 Critical current (A/4 mm)
2.5% 10%
Jc (MA/cm2)
Crtiical current (A/12 mm)
80
0% 7.50%
Enhanced Zr-doped production wire
30 c-axis
20
10 0 30 60 90 120 150 180 210 240 Angle between field and c-axis (°)
-30 0 30 60 90 120 150 180 210 240 270 300 330 360 Angle between field & tape normal (°)
Process for improved in-field performance successfully transferred to manufacturing Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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120
60
100
50
80
40
60
30
40
20
Ic at 0.52 T (A/ 4 mm width)
Self-field Ic (A/ 4 mm
Enhanced in-field performance of Zr-doped wires transitioned to long lengths
Standard undoped wire, self-field Ic Zr-doped wire self-field 10 Ic
20
Standard undoped wire, B || c-axis Standard undoped wire, min Ic angle
0
0
0
10
20
30
40
50
60
70
80
Zr-doped wire, B || c axis
90 100 110 120 130 140
Position (m)
Zr-doped wire min Ic angle
• Even with 16% lower self-field Ic, Zr-doped wire exhibits 80% higher Ic at B || c, and 71% higher Ic at min Ic angle compared with standard wire • Very uniformity of in-field Ic over 130 m of Zr-doped wire (~ 3%) Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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Benefit of Zr-doped wires realized in coil performance Coil properties
With Zr-doped wire
With undoped wire
Coil ID
21 mm (clear)
12.7 mm (clear)
Winding ID
28.6 mm
19. 1 mm
# turns
2688
3696
2G wire used
~ 480 m
~ 600 m
Wire Ic
90 to 101 A
120 to 180 A
Field generated at 65 K 2.5 T
2.49 T
Same level of high-field coil performance can be achieved with Zr-doped wire with less zero-field 77 K Ic, less wire and larger bore Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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2010 effort on Zr-doped MOCVD wires •
In 2009, we fixed the HTS film composition at Y0.6Gd0.6-Ba-Cu-O (based work on undoped compositions) and found optimum Zr doping to be 7.5%.
In 2010, we sought to determine •
If there is a rare-earth combination and content that works better with Zr-doped MOCVD wires (most BZO literature is on pure Y or pure Gd)
Fixing Zr dopant level at 7.5%, we investigated • influence of HTS film thickness • influence of Y : Gd ratio with a fixed (Y+Gd) value • influence of Y+Gd value at a fixed Y:Gd ratio Precursor is maintained at ambient conditions outside deposition chamber and numerous combinations can be studied in a single run.
Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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Improvement with Zr in thicker films 170
1.0 T, 77 K
120 70 20 60 90 120 150 180 210 240 270 300
Critical current (A/12 mm)
Angle between field and c-axis (°) 180 160 140 120 100 80 60 40 20
0% Zr, 2 passes
0% Zr, 3 passes
7.5% Zr, 1 pass
7.5% Zr, 2 passes
Critical current (A/12 mm)
Critical current (A/12 mm)
0% Zr, 1 pass
180 160 140 120 100 80 60 40 20
7.5% Zr, 3 passes
1.0 T, 77 K
60 90 120 150 180 210 240 270 300 Angle between field and c-axis (°)
1.0 T, 77 K
All samples were of composition Y0.6Gd0.6BCO Improvement in in-field critical current of Zr-doped wires increases with film thickness 60 90 120 150 180 210 240 270 300 Angle between field and c-axis (°) Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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Improvement in in-field critical current of Zr-doped wires increases with thickness Critical current at 1 T (A/12 mm) 1 pass
max near B || c 0% Zr 43 7.5% Zr 82 Improvement 91%
min Ic
max near B || a-b 32 85 39 71 22% -16%
2 passes 0% Zr 7.5% Zr Improvement
65 130 100%
43 67 56%
106 112 6%
0% Zr 7.5% Zr Improvement
77 177 130%
53 92 74%
128 151 18%
3 passes
Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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Influence of Y:Gd ratio
250 200
1.2 1.0 0.8
150
0.6
100
0.4
50
0.2
0
B || c, 77 K
0.0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
Magnetic Field (T)
Improved Ic retention at low fields, B || c (< 0.5 T) with decreasing Y:Gd ratio
Ic / Ic (B = 0)
Y1.2Gd0.0 Y0.8Gd0.4 Y0.6Gd0.6 Y0.2Gd1.0 Y0.0Gd1.2
300
1.2 1 0.8 0.6 0.4 0.2 0 350 300 250 200 150 100 50 0
5 4 3 2 1 0 0
0.2 0.4 0.6 0.8 Y content
1
Jc (MA/cm2)
All samples made in one run with 7.5% Zr. Y+Gd maintained at 1.2 but ratio of Y:Gd changed from 1.2:0 to 0:1.2 in steps of 0.2
Jc (MA/cm2)
Critical current (A/12 mm)
• •
Critical current (A/12 mm)
Gd content
1.2
Y1.2Gd0.0 Y0.6Gd0.6 Y0.2Gd1.0 Y0.0Gd1.2
1.0 0.8 0.6 0.4 0.2
B || c, 77 K 0.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
Magnetic Field (T)
Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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Influence of Y:Gd ratio Y1.0Gd0.2
Y0.8Gd0.4
Y0.6Gd0.6
Y0.4Gd0.8
Y0.2Gd1.0
1.0 T, 77 K
90
Y1.2Gd0.0 Y0.6Gd0.6 Y0.0Gd1.2
0.35
Y0.0Gd1.2
100
Y1.0Gd0.2 Y0.4Gd0.8
Y0.8Gd0.4 Y0.2Gd1.0
0.30
80
Ic / Ic (B = 0)
Critical current (A/12 mm)
Y1.2Gd0.0
70 60 50
0.25 0.20 0.15
40 30
0.10
20
0.05
1.0 T, 77 K 60
90
120 150 180 210 240 270 300 Angle between field and c-axis (°)
• •
60
90
120 150 180 210 240 270 300
Angle between field and c-axis (°)
Increasing Ic in the vicinity of B || a-b with decreasing Y:Gd ratio while Ic in the vicinity of B || c is constant at 25 to 30% retention Higher minimum Ic with decreasing Y:Gd ratio Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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Additional defect structure in Gd1.2BCO wires for better B || wire pinning Y1.2Gd0
Y0Gd1.2
BZO (111) particles
BZO rod
BZO epitaxial particle
BZO (111) particles along a-b plane in Gd1.2BCO
5 nm
TEM by C. Cantoni & A. Goyal, ORNL Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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Influence of Y:Gd changes at lower temperatures 1.4 10
6
92.5
65K, 5T 1.2 10
y = 88.893 + 2.9645x
Gd1.2 Y1.2 Y0.6Gd0.6
6
R= 0.97963
92 91.5 91
6
1 10
90.5 5
90
8 10
89.5 5
6 10
89 88.5 0
5
4 10
-50
0
50
Angle [deg]
100
0.2
0.4
0.6
Y
1.2-x
0.8
Gd
1
1.2
1.4
x
Measurements by Y. Zuev and A. Goyal, ORNL
• Best in-field performance switches from Gd1.2 to Y1.2 composition with decreasing temperature • Higher Tc of Gd1.2 composition could be a reason
Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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Influence of Y+Gd content 7.5% Zr in all samples Y content = Gd content Y+Gd content varied
zero-field Ic (A/12 mm)
330 110
310 290
90
270 70
250 1.2 1.3 1.4 1.5 1.6 Y + Gd content
Critical current (A/12 mm)
130
350
Y0.65Gd0.65 Ic at 1 T, || to tape (A/12 mm)
• • •
Y0.7Gd0.7
Y0.75Gd0.75
Y0.8Gd0.8
110 90 70 50 30
1.0 T, 77 K 10 60
90
120 150 180 210 240 270 Angle between magnetic field and c-axis ( )
300
Critical current can be tuned in desired orientation of magnetic field in application by modifying total rare earth content even with a fixed Zr % !
Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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Thicker (Gd,Y)2O3 precipitates along a-b plane in high (Gd,Y) wires
(Y,Gd)1.2
(Y,Gd)1.3
(Y,Gd)1.4
Ic / Ic (B=0)
0.4
(Y,Gd)1.5 1.0 T, 77 K
0.3
0.2
0.1 70
75
80
85
90
95
100
105
Angle beteweend field and c-axis (°)
TEM by Dean Miller, ANL
Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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In-field performance of Zr-doped films is drastically modified by rare earth content Zr content maintained at 7.5% in all three samples Y0.6Gd0.6
(Y,Gd)1.5
Critical current (A/12 mm)
140
Y1.2
Y1.2
1.0 T, 77 K
120 100 80
(Y,Gd)1.5
c-axis
60 40 20 60
90
120
150
180
210
240
270
300
Angle between field and c-axis (°) 20 nm Fewer defects along a-b plane in Y1.2 ; defects prominent along a-b plane in (Y,Gd)1.5 Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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Superior performance in recent Zr-doped MOCVD production wires Zr-doped wires with optimized rare-earth content transferred from R&D at Houston to SuperPower production operation. Production wire 1.1 µm thick HTS film Ic (77 K, 0 T) = 310 A/cm
60
40
Jc, MA/cm2
1000 Ic - 4mm width (A)
50
T=4.2K
30
20
10
0 0
20
40
60
80
T, K
Measurements by V. Braccini, J. Jaroszynski, A. Xu,& D. Larbalestier, NHMFL, FSU
100
undoped, B perp. wire undoped, B || wire FY'09 Zr-doped, B perp. wire FY'09 Zr-doped, B || wire FY'10 Zr-doped, B perp. wire FY'10 Zr-doped, B || wire
1
10 B (T)
Zr-doped production wires with new composition exhibit significantly improved critical current at 4.2 K in high magnetic fields up to 30 T ! Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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Substantial improvement in 2010 • 2009 : 28% self-field retention in Ic at 77 K, 1 T, B ⊥ wire in R&D wires 2010 : Achieved 39% retention in R&D wire. • Zr-doped MOCVD process fully transitioned to production and is routinely produced in kilometer lengths: now a standard product offering by SuperPower (‘ AP: Advanced Pinning’ wire)
Critical current (A/12 mm)
•
2010 : 25 – 30% self-field retention in Ic at 77 K, 1 T, B ⊥ wire routine in production wires 55 to 65% improvement in Ic over 2009 Zr-doped production wire at high fields 100%
39% retention at 1 T !
300 250
80%
200
60%
150
40%
100
20%
50
B ⊥ wire, 77 K
0 0.0
0.4
0.8
0%
1.2
Magnetic Field (T)
1.6
Zero-field Ic retention
•
Jc @ 4.2 K in field (A/4 mm)
FY’09
FY’10*
10 T, B ⊥ wire
201
310
20 T, B ⊥ wire
118
183
5 T, B || wire
1,219
1,893
10 T, B || wire
1,073
1,769
* Jc = 50 MA/cm2 at 4.2 K, 0 T
Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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Rapidly decreasing price of 2G HTS wire through technology advancements 100,000
10 m demo
77 K, self field
100 m demo
Price ($/kA-m)
10,000
1,000
First year of pilot production
100
30 K, 2 T
500 m demo
1,000 m demo
Creation of separate Manufacturing and R&D facilities
2 to 4x higher throughput
10 2004
2005
2006
2007
2008
2009
AP wire (Zr-doped) product introduction 2010
Year Wire price-performance improved by ~ 200% to ~ $ 100/kA-m for 30 K, 2 T applications Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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Goals for wire performance improvements • Two-fold improvement in in-field performance achieved with Zr-doped wires • Further improvement in Ic at B || c : Now 30% retention of 77 K, zero field value at 77 K, 1 T ; Goal is 50%. • Improvement in minimum Ic controlling factor for most coil performance : Now 15 to 20% retention of 77 K, zero field value at 77 K, 1 T ; Goal is first 30% and then 50% • Together with a zero-field Ic of 400 A/4 mm at 77 K, self field 200 A/4 mm at 77 K, 1 T in all field orientations. • Achieve improved performance levels at lower temperatures too (< 65 K) Goal
1000 800 600 400 200 0 0
1 2 3 Thickness (µm)
Critical current (A/4 mm)
Critical current (A/cmwidth)
200 Standard MOCVD-based HTS tape MOCVD HTS w/ self-assembled nanostructures
100
Goal
10x
77 K, 1 T
c-axis
10 0
30
60
90
120
150
180
210
240
Angle between field and c-axis (°) Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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350
100
300
90
250 200 150 100 50 0 0%
5%
10% Ta addition
15%
20%
Critical current (A/12 mm)
Critical current (A/12 mm)
Exploring other pathways to improve in-field performance : alternate dopants 0% Ta
7.5% Ta
10% Ta
12.5% Ta
15% Ta
17.5% Ta
1.0 T, 77 K
80 70 60 50 40 30 20 60
90
120
150
180
210
240
270
300
Angle between field and c-axis (°) • No impact by Ta addition on in-field properties • Double perovskite Ta compounds not formed ? Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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Double perovskite, Ba2(Y,RE)TaO6 nanorods observed in Ta-doped MOCVD films Why improvement in infield performance not seen in Ta-doped MOCVD films even with Ba2(Y,RE)TaO6 nanorods ? BYTO Gd2O3
Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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Exploring new pathways to improve in-field performance : directed assembly • In general, in-situ oxide nanostructures based on Zr, Nb, Ta created by selfassembly during HTS film growth have been used to improve in-field performance. • Epitaxial growth of HTS film simultaneously with self-assembly of nanorods has drawbacks : lack of control of size, distribution, and orientation of nanorods. • One approach is to direct the nucleation of self-assembled nanorods from predeposited nucleation sites on the LMO buffer surface
Pre-deposited nucleation sites
Pre-deposited nucleation site
BZO nanorod
LMO buffer LMO buffer Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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Exploring new pathways to improve in-field performance : prefabricated nanorods • Taking a step further, prefabricated nanorods on buffer surface followed by HTS epitaxial growth can allow for independent control of size, distribution and orientation of nanorods. • Three techniques developed for prefabricated nanorod growth on LMO on IBAD tapes.
Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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Electrodeposition of silver
Voltage (µv)
• Ag in 2G wire is a limiting factor in production capacity and wire cost • Electrodeposition is a lower-cost alternative to vacuum sputtering now used • Can be done in tandem with copper plating further increases production capacity HTS Cu Ag • Enabler for a low ac loss wire • Silver nitrate in organic solvent substrate • Contact resistivity ~ 4 µΩcm2 100 µm Cu • Over current capability with ~ 2 µm electrodeposited Ag = 400 Burn out at 207 A, 360 µV 20% more than Ic : comparable 350 with sputtered Ag 300 250 200 150 100 Ic = 171 A 50 0 0 100 200 Critical Current [A] Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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• Process scaled up to 100 m lengths at 60 m/h* even in a small research-scale system
Critical current (A/12 mm)
Scaled up electrodeposition of silver 300 200 As HTS deposited 100 0
0
20
40
60
80
100
Critical current (A/12 mm)
Tape Position (m)
300 200
After Ag Electrodeposition
100 0
0
20
40
60
80
100
Tape Position (m)
Critical current of HTS wire maintained over 100 m length after electrodeposition of silver & after oxygenation
Critical current (A/12 mm)
400 300 200 Electrodeposition + oxygenation
100 0
0
20
* 4mm wide equivalent Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
40
60
80
100
Tape Position (m) 29
400 300
Voltage (µV)
Critical current (A/12 mm)
Transport Ic measurement on 100 m long wire with electrodeposited silver
200 100 Transport Ic measured over 5 m 0
120 100 80 60 40 20 0
I-V curve measured over 5 m
-20 0
20
40
60
80
100
0
50 100 150 200 250 300
Tape position (m)
Current (A) • Transport Ic of 200 to 250 A/cm measured over 100 m through electrodeposited silver – Silver-HTS interface is good for current transfer – Silver surface is good enough for press electrical contacts
• ED Ag is able to sustain 10 to 20% more current beyond take-off current Silver electrodeposition is a scalable process for lower wire cost and is an enabler for multifilamentary 2G wire Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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HTS wire R&D is necessary to reach priceperformance requirements of commercial market Several R&D opportunities exist to improve critical current, in-field performance, reduce cost and increase throughput.
Price ($/kA-m)
1,000
77 K, 0 T, with R&D 77 K, 0 T without R&D 65 K, 3 T with R&D 65 K, 3 T, without R&D 50 K, 3 T with R&D 50 K, 3 T, without R&D commerical market
100
medium commercial market requirement large commercial market requirement
10 2009
2014
2019
2024
Commercial market requirements could be reached five to 10 years sooner with R&D. Applied Superconductivity Conference, Washington D.C., August 1 - 6, 2010
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