2G HTS Wire for High Magnetic Field Applications - SuperPower

2G HTS Wire for High
Magnetic Field Applications
Venkat Selvamanickam, Ph.D.
Department of Mechanical Engineering
Texas Center for Superconductivity
University of Houston, Houston, TX, USA
SuperPower Inc., Schenectady, NY, 12304 USA
1
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
1

2G HTS wire: Great potential for applications
• Second-generation (2G) high-temperature superconductor (HTS) is produced
by thin film vacuum deposition on a flexible nickel alloy substrate in a
continuous reel-to-reel process very different from mechanical deformation &
heat treatment techniques used for Nb-Ti, Nb 3
Sn and 1G HTS wires
– Only 1% of wire is the superconductor
– ~ 97% is inexpensive Ni alloy and Cu
– Automated, reel-to-reel continuous manufacturing process
– Quality of every single thin film coating can be monitored on-line
in real time !
40 μm Cu total
2 μm Ag
20μm Cu
1 μm YBCO - HTS (epitaxial)
100 – 200 nm Buffer
50μm Ni alloy substrate
20μm Cu
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
2

2G HTS wires provide unique advantages
• 2G HTS wires provide the advantages of high temperature operation at higher
magnetic fields.
• Mechanical properties of 2G HTS wires are also
20μm Cu
superior
YBCO (H//c) YBCO (H//ab) NbTi
Nb3Sn (Internal Sn)
100000
Nb3Sn (Bronze)
< 0.1 mm
50μm Hastelloy
20μm Cu
non-Cu Jc ( A/mm 2 )
10000
1000
100
0 5 10 15 20 25 30 35
Stress (MPa)
800
600
400
High Strength
1G HTS Low Je
SP 2G HTS
High Je
Applied Field ( Tesla )
200
0
Low Strength
1G HTSModerate Je
Nb3Sn
Moderate Je
0 0.1 0.2 0.3 0.4 0.5
3
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany Strain (%)

Advantages of IBAD MgO-MOCVD-based 2G
HTS wires
• Use of IBAD MgO as buffer template provides the choice of any substrate
– High strength (yield strength > 700 MPa)
– Non-magnetic, high resistive (both important for low ac losses)
– Ultra-thin (enables high engineering current density)
– Low cost, off-the-shelf
• High deposition rate and large deposition area by MOCVD
– enable high throughput
• Precursors are maintained outside deposition chamber
– Long process runs (already shown 50+ hours)
< 0.1 mm
20μm Cu
2 μm Ag
1 μm YBCO - HTS (epitaxial)
~ 30 nm LMO (epitaxial)
~ 30 nm Homo-epi MgO (epitaxial)
YBCO
~ 10 nm IBAD MgO
LaMnO 3
100 nm
50μm Hastelloy substrate
20μm Cu
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
MgO (IBAD + Epi layer)
Y 2 O 3
Al 2 O 3
Hastelloy C-276
4

Successful scale-up of IBAD-MOCVD-based 2G
HTS wires
• 500 m 2G HTS wire first
demonstrated in January 2007
(crossed 100,000 A-m)
• 1,000 m 2G HTS wire first
demonstrated in July 2008
(crossed 200,000 A-m)
• Crossed 300,000 A-m in July
2009 with 1,000 m wire.
• 1,400 m lengths are now
routinely produced.
• High throughput processing (>>
100 m/h* in IBAD & buffer
processes, > 100 m/h* in other
processes)
• Manufacturing capacity of few
hundred km/year
320,000
280,000
240,000
200,000
160,000
120,000
80,000
40,000
0
1 2 3
-0
*4 mm wide equivalent
v l-0
r-0
o u
J
a
N M
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
)
-m
(A
t
h
g
n
e
L
*
t
n
e
r
u
C
l
a
ic
r
it
C
90 A-m to
300,330 A-m
in seven
years
3
-0
v
o
N
4
-0
g
u
A
5
r-0
p
A
595 m
322 m 427 m
1 m 18 m 97 m 206 m
158 m
62 m
5
-0
c
e
D
6
-0
g
u
A
7
r-0
p
A
1,065 m
1,030 m
935 m
790 m
8
-0
n
a
J
8
-0
p
e
S
9
-
0
y
a
M
5

Meeting application requirements for HTS wire:
Superior performance in operating conditions
Application
Cables
Wind/Off-shore
Generators
Operating
Field (Tesla)
0.01 to 0.1 (ac)
0.1 to 1 (DC)
Operating
Temp. (K)
70 to 77
Key requirements
Low ac losses (ac)
High currents (dc)
Wire needed per
device (kA-m)
40,000 to
2,500,000
1 to 3 30 to 65 In-field I c 2,000 to 10,000
Transformers 0.1 65 to 77 Low ac losses 2,000 to 3,000
Fault current
limiters
0.1 65 to 77
Thermal recovery
High volts/cm
500 to 10,000
SMES 2 to 30 T 4 to 50 In-field I c 2,000 to 3,000
Automotive
motors
2 to 5 30 to 65
Aerospace 2 to 5 30 to 50
Low ac losses
In-field I c
500 to 1,000
Light weight
In-field I c
1,000 to 2,000
Magnets/coils 5 to 30 4.2 to 40 In-field I c 200 to 2,000
MRI, NMR, HEP,
Fusion reactors
5 to 30 4.2 K to 30
In-field I c
Long lengths
Persistent joints
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
2000 - 100,000+
6

SuperPower-UH 2G wire development strategy
• SuperPower’s technology operations consolidated in Houston which enabled total
focus on manufacturing in Schenectady.
Manufacturing objectives
• High yield, high volume
operation
• On-time delivery of highquality
wire
• Incorporate new technology
advancements
Technology objectives
• High performance wires
• Highly efficient, lower cost
processes
• Advanced wire architectures
• Successful transition to
manufacturing
Manufacturing
Operations in NY
SuperPower
Manufacturing at
Schenectady, NY
Customers
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
SP staff @
Houston
Technology
in Houston
National Labs
Best of both worlds : strong and concentrated emphasis on
technology development & manufacturing
UH research
staff
CRADAs
7

Improved pinning by Zr doping of MOCVD HTS
wires
5 nm sized, few hundred nanometer long BZO nanocolumns with
~ 35 nm spacing created during in situ MOCVD process
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
8

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 !
Process for improved in-field performance successfully
transferred to manufacturing at SuperPower
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
9

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 I c 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
I c , less wire and larger bore
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
10

Large improvements in in-field Ic of
Zr-doped wires at lower temperatures too
100 A/4 mm
All data from
production
wires
100 A/4 mm achieved at 65 K, 3 T in Zr-doped wire compared to 40 K, 3 T in undoped wire
165 A/4 mm achieved at 40 K, 5 T in Zr-doped wire compared to 18 K, 5 T in undoped wire
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
11

Large improvements in in-field Ic of
Zr-doped wires at lower temperatures too
Retention of 65 K
77 K, zero field I c
3 T
40 K
3 T
18 K
3 T
Undoped wire 0.27 1.02 2.13
Doped wire 0.73 1.99 3.50
Retention factor of
doped wire is higher by
2.7 1.9 1.6
77 K zero-field I c
of 2009 undoped wire = 250 A/cm
77 K zero-field I c of new doped wire = 340 A/cm
Retention factor of
doped wire including
higher zero field Ic is
higher by
3.71 2.64 2.23
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
12

Superior performance in recent Zr-doped
MOCVD production wires in high fields at 4.2K
60
50
40
Production wire
1.1 µm thick HTS film
I c
(77 K, 0 T) = 310 A/cm
1000
T=4.2K
Jc, MA/cm 2
30
20
10
0
0 20 40 60 80
T, K
J c
@ 4.2 K (A/4 mm) 2009 2010
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
I c
- 4mm width (A)
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)
Measurements by V. Braccini, J. Jaroszynski,
A. Xu,& D. Larbalestier, NHMFL, FSU
In-field performance of Zr-doped production wires
improved by more than 50% in high fields at 4.2 K
improved HTS4Fusion by more Workshop than • May 50% 26-27, 2011 in • high Karlsruhe, fields Germany at 4.2 K
13

High-Field Magnets demonstrated with 2G HTS
wire
• Coils fabricated
by SuperPower
and NHMFL
• Je ~ 300 A/mm 2
• Stress levels
300 – 400 MPa
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
14

Applications enabled by high-field performance:
Superconducting Magnetic Energy Storage (SMES)
• Energy storage with greater than 97% efficiency.
• Provides rapid response for either charge or discharge – amount of
energy available is independent of discharge rating – charge and
discharge sequence can repeat infinitely without degradation of magnet
• 2G HTS-based SMES being developed by ABB, SuperPower, UH and
BNL through $ 5.2M program funded by ARPA-E (GRIDS: Grid-Scale
Rampable Intermittent Dispatchable Storage)
• 20 kW ultra-high field SMES device with capacity of up to 3.4 MJ based
on HTS coils operating at magnetic fields of up to 25 T at 4.2K
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
15

Goals for further performance improvements
• Two-fold improvement in in-field performance achieved with Zr-doped wires
• Further improvement in I c
at B || c : Now 30% retention of 77 K, zero field value at
77 K, 1 T ; Goal is 50%.
• Improvement in minimum I c
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 I c
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)
Critical current (A/cmwidth)
1000
800
600
400
200
0
0 1 2 3
Thickness (µm)
Goal
Critical current (A/4 mm)
200
100
10
10x
Standard MOCVD‐based HTS tape
MOCVD HTS w/ self‐assembled nanostructures
Goal
77 K, 1 T c‐axis
0 30 60 90 120 150 180 210 240
Angle between field and c‐axis (°)
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
16

Multiple strategies to enhance in-field
performance: higher I c , more isotropic
• Superconductor process modification
– Chemical modifications in MOCVD to
modify defect density, orientation and
size.
• Influence of film thickness on in-field
I c
of Zr-doped films
• Influence of rare earth type and content
• Influence of Zr content at fixed
rare-earth type and content
• Influence of other dopants
• Influence of deposition rate
• Buffer surface modification buffer prior to superconductor growth
• Post superconductor processing modification such as post annealing
etc.
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
17

Opportunities with rare-earth modifications:
Influence of Y+Gd content
• 7.5% Zr in all samples
• Y content = Gd content
• Y+Gd content varied
Critical current can be tuned in desired orientation of magnetic field in
application by modifying total rare earth content even with a fixed Zr % !
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
18

Increased nanoscale (Gd,Y) 2 O 3 precipitates
along a-b plane with increased rare earth content
(Gd,Y) = 1.2
(Gd,Y) = 1.3
(Gd,Y) = 1.4
(Gd,Y) = 1.5
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
19

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 (Y,Gd)1.5
0.4
1.0 T, 77 K
I c / I c (B=0)
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
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
20

In-field performance of Zr-doped films is
drastically modified by rare earth content
Zr content maintained at 7.5% in all three samples
Y 1.2
c‐axis
(Y,Gd) 1.5
Multiple controls available to modify pinning performance of 2G HTS wires!
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
20 nm
21

Higher amperage wires using thicker films
7
6
Jc (MA/cm2)
5
4
3
Goal
2
0 1 2 3
Critical current (A/cmwidth)
1000
800
600
400
200
0
Thickness (µm)
0 1 2 3
Thickness (µm)
Goal
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
• 800 A/cm (= 320 A/4mm) already
demonstrated over 1 m by MOCVD
• 1000 A/cm (= 400 A/4mm) achieved
in 2 µm film in short samples using
microbridge by PLD at LANL.
22

Jc (MA/cm 2 )
Higher amperage wires using thicker films
8
7
6
5
4
3
2
1
0
SP
M3
-
714
0 0.5 1 1.5 2 2.5 3 3.5
HTS film thickness
Research MOCVD
Pilot MOCVD
Increasing Ic
2016 – 1000 A
2014 – 750 A/cm
2012 – 500 A/cm
Critical current (A/cmwidth)
1000
800
600
400
200
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
0
0 1 2 3
Thickness (µm)
Goal
• Address problems with decreasing
current density with thickness
• High currents without significantly
increasing film thickness by increasing
current density (Jc)
– Microstructural improvement (texture,
secondary phases, a-axis, porosity)
– Pinning improvement (interfacial &
bulk defects)
• Opportunity to reduce factor of two
difference between pilot and research
MOCVD systems
23
23

Another benefit with thicker films: better in-field
performance
All samples were of composition
Y 0.6
Gd 0.6
BCO
Improvement in in-field critical current of Zr-doped
wires increases with film thickness
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
24

Can high-field performance be improved with
higher Zr doping levels?
• Zero-field critical current drops beyond 7.5% Zr addition.
• Sharper drop in T c beyond 10% Zr addition (3 K from 10% to 25%)
• Transition width increases by 0.5 K beyond 15%
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
25

Superconductor quality degradation at high Zr
doping levels
• (Gd,Y)BCO lattice constant increases steadily with increasing Zr
• (Gd,Y)BCO peak intensity maximum at 7.5% Zr and reduces with
increasing Zr
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
26

In-field Performance at higher Zr doping levels
2009
0.4 µm film, Y 0.65 Gd 0.65 BCO
2010
0.9 µm film, Y 0.6 Gd 0.6 BCO
• Best performance at B || c with 7.5% Zr.
• I c at B || a-b increases at higher Zr content even with lower zero-field I c
• Opportunities with high Zr doping levels in B || a-b
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
27

New nanowire technologies being developed
to target large pinning enhancements
• 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.
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
28

Targeted improvements in in-field performance
of production wires through technology
• 10-fold improvement by combination of higher self-field critical current and
improved retention of in-field performance through technical innovations.
• Even at 4.2 K, 15 T, 2G HTS wire is comparable now with Nb 3
Sn wire.
Opportunity to improve to be 10X better than Nb 3
Sn !
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
29

Multfilamentary 2G HTS tapes for low ac loss
applications
• Filamentization of 2G HTS tapes is desired
for low ac loss applications.
• So far, there is no proven technique to
repeatedly create high quality mulfilamentary
2G tapes. Also, adds substantial cost.
ac loss (W/m)
2
1
100 Hz
0
0.00 0.01 0.02 0.03 0.04 0.05 0.06
B ac rms
(T)
unstriated
5.1 x
multifilamentary
4 mm
5-filament tape, 4 mm wide
(produced up to 15 m)
32-filament tape, 4 mm wide
(difficult to make even 1 m lengths)
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
30

Goals in multifilamentary 2G HTS wire fabrication
• Maintaining filament integrity uniform over long lengths (no Ic reduction)
• Striated silver and copper stabilizer (minimize coupling losses)
• Minimum reduction in non superconducting volume (narrow gap) and
fine filaments
Ag
HTS
Substrate
Cu
A fully filamentized 2G HTS wire would need to have 20 – 50 µm of copper
stabilizer striated !
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
31

Approach to make fully-filamentized 2G HTS wire
Cu Ag HTS
substrate
100 μm
Cu
1 mm
Fully-filamentized 2G HTS wire demonstrated, but still involves etching
X. Zhang and V. Selvamanickam, US 7,627,356
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
32

Etch-free process developed to fabricated
multifilamentary wire with fully striated stabilizers
12-filament wire with 10 µm thick
fully striated copper stabilizer
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
33

Significant ac loss reduction in multifilamentary
wire with fully striated stabilizers
• Critical current of standard
wire = 207 A
• Critical current of 12-
filament wire = 197 A
• Critical current of 12-
filament wire after 10 µm
copper stabilizer = 200 A
AC loss of 12-fiament wire at
60 Hz is 11 times lower than
that of unstriated wire without
copper stabilizer and 13 times
lower with copper stabilizer, at
higher fields
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
34

Significant ac loss reduction in multifilamentary
wire with fully striated stabilizers
• AC loss of 12-fiament wire at 300 Hz is 11 times lower than that of
unstriated wire with and without copper stabilizer
• AC loss of 12-filament wire unchanged with copper stabilizer unlike
standard wire; 11 to 13 times lower losses at all frequencies
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
35

Key 2G HTS wire metrics attractive for high
magnetic field applications
• Piece lengths:
– 1,000 m demonstrated with minimum Ic of ~ 300 A/cm
– 1,400 m routinely processed
– 100 – 300 m typical
• Critical current in production wires
– 325 A/cm available in long lengths (100 – 300 m)
– 810 A/cm (J e
= 810 A/mm 2 ) at 4.2 K,10 T, field perpendicular to wire
– 480 A/cm (J e
= 480 A/mm 2 ) at 4.2 K, 20 T, field perpendicular to wire
– 1855 A/cm (J e
= 1855 A/mm 2 ) at 4.2 K, 10 T, field parallel to wire
• Critical current in R&D wires
– 800 A/cm demonstrated in 1 m lengths
– Plenty of opportunities for 10x improvement in production wire performance
at low temperatures & high fields.
– Goal of J e
= 6000 A/mm 2 at 4.2 K, 15 T perpendicular to wire (~ 10x Nb 3
Sn
performance); 1000 A/mm 2 at 40 K, 15 T perpendicular to wire
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
36

Key 2G HTS wire metrics attractive for high
magnetic field applications
• Superior mechanical properties
– Yield strength > 700 MPa with superalloy-based 2G HTS wire
– Tensile and bend strains > 0.4% without performance degradation
– Intense R&D to improve transverse stress properties
• Joints
– Joint resistance of 50 – 100 nano-ohm cm 2 typical
– Opportunities for persistent joint fabrication (challenge is in
fabrication by magnet manufacturer in the field)
• AC losses
– Multfilamentary wires feasible way to reduce ac losses
– Scalable processes being developed for fully striated
multfilamentary wires
HTS4Fusion Workshop • May 26-27, 2011 • Karlsruhe, Germany
37