superior performance. powerful technology.
2G HTS Wire for Demanding Applications
and Continuous Improvement Plans
DW Hazelton
Tuesday, September 17, 2013  EUCAS-2013, Genova, Italy
SuperPower Inc. is a subsidiary of Furukawa Electric Co. Ltd.
Acknowledgements
•
We would like to acknowledge the contributions of the team at
SuperPower as well as collaborators from around the world.
•
In particular we would like to acknowledge the input from Toru
Fukushima, Paul Brownsey, Honghai Song*, Yifei Zhang, Justin
Waterman, Trudy Lehner, Hisaki Sakamoto, Ross McClure and Allan
Knoll.
•
The work presented here is supported in part from funding from the US
DOE Smart Grid Program and ARPA-E.
*currently at MSU-FRIB
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EUCAS 2013  Genova, Italy  September 17, 2013
2
Engineering progress drives 2G HTS adoption
Feature
Robust wire design
Mechanical strength
Approach
“Hastelloy” based substrate
supporting structure
Assessment
Tensile strength
Peel strength
Splicing stress
In-field performance Flux pinning with engineered
Critical current (Ic)
nanostructure
under magnetic field
Consistent & uniform process
Enhanced Ic at low (4.2-40K)
temp. and under perpendicular
field components (2-15T)
Alternative constructs Cable constructs
Bonded conductor designs
Higher operating
Alternative materials
currents
Special application
requirements
Higher operating currents
Stronger conductors with
application specific properties
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EUCAS 2013  Genova, Italy  September 17, 2013
3
HTS applications have a wide range of
demanding performance characteristics
Energy
Defense
Transportation
Industrial
Medical
Science/
Research
• Cable
• Motors
• Maglev
• Cables
• Motors
• Current
leads
• HF magnets
• FCL
• Induction
heaters
• Generators
• Directed
energy
weapons
• Rail engines
• Motors
• MRI
• Space
exploration
• Generators
• NMR
• SQUIDS
• Transformers,
incl. FCL
• Storage
– SMES
• Magnetic
separation
• High energy
physics
• Bearings
• Electronics
• Cell tower
base station
filters
– Flywheels
Courtesy of
Waukesha
Courtesy of
SuperPower
and Furukawa
Courtesy of Oswald
All Rights Reserved. Copyright SuperPower® Inc. 2013
EUCAS 2013  Genova, Italy  September 17, 2013
4
Wire performance critical to practical applications
•
•
•
•
•
•
•
Ic(B, T, )
– Temperature, magnetic field and field orientation dependence of Ic
– Minimum Ic at operating condition
Mechanical properties (electromechanical performance)
– Workability for fabrication into various devices
– Irreversible stress or strain limits under various stress condition, in terms
of Ic
Uniformity along length (Ic and other attributes)
Thermal properties (thermal expansion coefficient and thermal conductivity)
Quench stability (NZPV and MQE)
Insulation (material and method)
Splice
– Resistance (resistivity)
– Mechanical strength (tensile and bending)
Standards for 2G HTS wire property testing are under development
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EUCAS 2013  Genova, Italy  September 17, 2013
5
SuperPower’s ReBCO superconductor with artificial
pinning structure provides a solution for demanding
applications
•
•
•
•
Hastelloy® C276 substrate
• high strength
• high resistance
• non-magnetic
Buffer layers with IBAD-MgO
• Diffusion barrier to metal substrate
• Ideal lattice matching from substrate through ReBCO
MOCVD grown ReBCO layer with BZO nanorods
• Flux pinning sites for high in-field Ic
Silver and copper stabilization
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EUCAS 2013  Genova, Italy  September 17, 2013
6
Tensile strength predominately determined by substrate
20 µm Cu
40 µm Cu
100 µm Cu
Tensile stress-strain relationship of
as-polished Hastelloy substrate
(room temperature)
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Tensile stress-strain relationship of
SCS4050 wires with different Cu
stabilizer thickness (room temperature)
EUCAS 2013  Genova, Italy  September 17, 2013
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Tensile strength - effect of stress on Ic
Normalized Ic vs. room temperature tensile stress for a 12mm wide
wire with 100m Cu stabilizer
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EUCAS 2013  Genova, Italy  September 17, 2013
8
Delamination strength studied with peel test
P
90 peel test
Cu
Ag
Cohesive
REBCO
Buffer
Adhesive
Mixed mode
Hastelloy
Ag
Cu
P

Peeling Load (N)
T-peel test
Displacement (mm)
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Relationship between peel strength and
processing conditions established
EUCAS 2013  Genova, Italy  September 17, 2013
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Successful winding techniques demonstrated to
mitigate delamination issue
•
•
•
Decoupling of former from winding has been demonstrated to be
beneficial
– Eliminates radial tensile stress on the 2G HTS windings
– PET release layer incorporated at former:windings interface
– Lower thermal expansion formers (Ti, controlled expansion glassepoxy)
Alternative insulations/epoxy systems have been successfully
demonstrated
– PET shrink tube - NHMFL
– Electrodeposited polyimide - Riken
– Alternative epoxy system with filler - KIT
Use of cowound stainless steel as “insulation” with partial epoxy
application on coil sides
– Mitigates radial tensile stress on the 2G HTS
– Improves overall coil strength
– Negative impact on coil current density
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EUCAS 2013  Genova, Italy  September 17, 2013
1
0
Stainless steel insulation, partial epoxy application
on coil sides shows resistance to delamination
•
•
•
•
Very thin layer of epoxy
(transparent) after epoxy
is cured
Mechanical fix turn-turn
and layer-layer
Provides thermal link
between optional cooling
plates and windings
Seals the coil
1.00E-02
Five thermal cycles (77K), no degradation found
8.00E-03
TC#1
TC#2
Voltage (V)
6.00E-03
TC#3
TC#4
4.00E-03
TC#5
2.00E-03
0.00E+00
0
10
-2.00E-03
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EUCAS 2013  Genova, Italy  September 17, 2013
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30
40
50
Current (A)
11
Ic (B//c, T) / Ic (self field, 77 K)
Lift Factor defined as
Ic(B,T) / Ic(self field, 77K)
In-field critical current operating conditions vary
by application
4.2 K
14 K
22 K
10.00
33 K
45 K
Motors,
generators
50 K
65 K
77 K
HF
magnets,
SMES
1.00
0.10
Cables, FCLs,
transformers
0.01
0.0
2.0
All Rights Reserved. Copyright SuperPower® Inc. 2013
4.0
6.0
8.0
10.0
12.0
14.0
16.0
Applied Field B (T)
EUCAS 2013  Genova, Italy  September 17, 2013
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In-field performance:
Advantage of 2G HTS wire with flux pinning
Advanced MOCVD growth technology:
• Formation of dense & uniform nanorods
• Engineered growth properties
• Potential migration to new compositions
 Enhanced Artificial Pinning Effect
 Improved in-field critical current
 SuperPower’s “AP wire” recipe
BZO nanorod
Nanorods with BaZrO
Pinned flux
Superconductive current flow
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EUCAS 2013  Genova, Italy  September 17, 2013
13
Increased Zr doping in ReBCO layer for
improvement in critical current in the field
Increased Zr doping
Chen, et. al. ASC2012, Portland, Oregon, Oct. 2012
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EUCAS 2013  Genova, Italy  September 17, 2013
14
Lift factor performance tied to film composition
and growth conditions
30K, 3T
774A
373A
807A
795A
1037A
442A
Composition X
Precursor composition / Flow rate / Concentration / Chamber pressure, etc. etc.
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EUCAS 2013  Genova, Italy  September 17, 2013
15
Ic(B,T, Φ) characterization is critical to understanding
the impacts of processing on operational
performance
M3‐909‐3 Lift Factor vs. H//ab, T
50K
40 K
30K
20K
65 K
7
7
6
6
Lift Factor [ Ic(H,T)/Ic(sf, T) ] //ab
Lift Factor [ Ic(H,T)/Ic(sf, T) ] //ab
65 K
M3‐909‐3 Lift Factor vs. H//c, T
5
4
3
2
1
0
50K
40 K
30K
20K
5
4
3
2
1
0
0.0
2.0
4.0
6.0
8.0
10.0
0.0
2.0
Applied Field (Tesla)
4.0
6.0
8.0
10.0
Applied Field (Tesla)
Measurements made at the University of Houston
• Lift factor, Ic(B,T)/Ic(sf, 77K), particularly a full matrix of Ic(B,T, Φ) is in high demand.
• Frequently sought by coil/magnet design engineer, for various applications.
• Used to calculate local Iop/Ic ratio inside coil body, and design quench protection.
All Rights Reserved. Copyright SuperPower® Inc. 2013
EUCAS 2013  Genova, Italy  September 17, 2013
16
IcBT measurement system being built for
routine production sampling
Target operating conditions
– Temperature: 30K – 77K
– Field: 0 - 2T (65K)
• Higher field operation at 4K
– Field //c and //ab (rotatable 0-225
deg)
– Sample length in field – min 25
mm
– Maximum sample current 8001200A
• Full width samples to 4mm
wide
– Maximum coil current 400A
• 2G HTS background coils
– Enables testing of production
material in Schenectady (77K30K, 0-2T) to evaluate
consistency of lift factor.
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EUCAS 2013  Genova, Italy  September 17, 2013
1
7
Low temperature high field data being collected
at multiple sources
•
Internally at FEC’s Nikko facility in Japan (4 mm tape up to 17T)
•
Collaborators / customers facilities
– NHMFL (full tape, to 15T, YatesStar)
– Tohoku University (through FEC, bridge samples, to 15T)
– BNL (8T+)
– Other international high field test sites
– Customer facility (to 17T)
•
This data will be correlated with processing conditions to better
understand processing windows to result in more consistent uniform
product.
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EUCAS 2013  Genova, Italy  September 17, 2013
18
Ic uniformity along length (TapeStar)
Position (cm) (on a 12 mm wide wire)
•
•
•
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Magnetic, non-contact measurement
High spacial resolution, high speed, reel-to-reel
Monitoring Ic at multiple production points after MOCVD
Capability of quantitative 2D uniformity inspection
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EUCAS 2013  Genova, Italy  September 17, 2013
19
Ic (A, 77K, s.f.) and n-value
Ic uniformity along length
(four-probe transport measurement)
Position (m) (on a 4 mm wide wire)
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EUCAS 2013  Genova, Italy  September 17, 2013
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Engineering new wire innovations to address
customer requests and meet application requirements
•
Additional wire insulation methods
– Today: Kapton®/Polyimide wrapped
– Other options under development:
thinner profile, better coverage
•
Additional wire architectures under development
– Higher current carrying capability
• Multi-layer combinations
• Cable on Round Core (CORC)
• Plus others …
– Custom attributes
• FCL – normal state resistance feature
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EUCAS 2013  Genova, Italy  September 17, 2013
Courtesy: Advanced Conductor
Technologies
21
Demanding requirements for ROEBEL cable for
ac applications
•
•
ROEBEL cable is a known approach to produce low ac loss, high
current conductor/cable
Conductor exposed to severe mechanical cutting at sharp angles
ROEBEL cable made by KIT with SuperPower®
2G HTS Wire
No failure, no delamination
Only 3% loss in current from conductor to
ROEBEL cable
Cable engineering current density = 11,300 A/cm2
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EUCAS 2013  Genova, Italy  September 17, 2013
22
Capability for bonded conductors being developed
[higher amperage, specialty applications (FCL) ]
•
•
•
Bonded conductors offer the ability to achieve higher operating
currents
– LV windings of FCL transformer
– HEP applications
– High current bus applications
Bonded conductors offer higher strength
– FCL transformer fault currents
– High field HEP applications with high force loadings
Bonded conductors offer the ability to tailor application specific
operating requirements, i.e. normal state resistance for a FCL
transformer
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EUCAS 2013  Genova, Italy  September 17, 2013
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Reliable splices – low resistance and high strength
•
•
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Splicing / terminations required in
most applications
Splice properties are important
conductor performance and have
influences on dielectrics and
cryogenics as well
Low resistance and high
electromechanical strength are
basic requirements
Bridge joints between pancakes, Rtot = 10-7Ω
•
•
•
•
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Contact resistivity at REBCO/Ag interface has an effect on splice resistance
Splices fabricated via soldering at a temperature below 250C
Soldering temperature, pressure, duration time are important parameters
Ic retained across splices with no degradation through soldering
Splice resistance R ≤ 20 n for the lap joint geometry with a 10cm overlap
length
Splicing per customer request and each splice inspected
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EUCAS 2013  Genova, Italy  September 17, 2013
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Ic (d) / Ic (∞) or R (d) / R (∞) Ratio
Splice Ic and resistance vs. bending diameter
Bending Diameter (mm)
•
•
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Lap joint (HTS-HTS) of SCS4050 tapes with 40 µm Cu stabilizer
R(∞) = 6 ~ 20 n with 10 cm overlap length
Bent at room temperature and Ic measured at 77K
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EUCAS 2013  Genova, Italy  September 17, 2013
25
Summary
•
•
•
SuperPower 2G HTS conductor offers a flexible architecture to
address the broad range of demanding applications requirements.
SuperPower is engaging major resources in improving its
manufacturing capabilities to deliver a consistent, reliable, high
quality 2G HTS product
– Improved consistency of lift factor
– Improved piece length
– Improved current density
– Improved uniformity
Alternative conductor configurations are being developed to address
customer demand
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EUCAS 2013  Genova, Italy  September 17, 2013
26