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High Field Magnet Made of Second Generation High Temperature Superconducting (2G HTS) Wire
Yimin Chen, Ph.D.Drew Hazelton, Venkat Selvamanickam
2008 International Conference on Electrical Machines and SystemsWuhan, China
2ICEMS, October 2008
Acknowledgements
• This work was partially supported by the Title III office, U.S. Department of Energy and the Air Force Research Laboratory
• The in-magnetic-field critical currents were measured by Y. Zhang at Oak Ridge National Laboratory under a CRADA
• The high magnetic field coil was tested by H. Weijers, D. Markewicz and D. Larbalestier at the US National High Magnetic Field Laboratory at Florida State University
3ICEMS, October 2008
Introduction to superconducting magnets
• Superconducting magnets have been an enabling technology for magnetic resonance imaging (MRI), particle accelerators and colliders and play an essential role in fusion devices
• The development of high magnetic field superconducting solenoids has been increasing the sensitivity and resolution of nuclear magnetic resonance (NMR) and opening opportunities for advancements in condensed mater physics, biology, chemistry, material sciences, physiology and psychology
• Superconducting magnets have some advantages over resistive electromagnets:
– The field is generally more stable, resulting in less noisy measurements– They can be smaller
4ICEMS, October 2008
Low temperature superconductors (LTS) are widely used in medical and high energy physics applications
Medical Devices: MRI
But, because of their low operating temperature, LTS have not found use in electric power applications
HEP: CERN – Particle Accelerator
5ICEMS, October 2008
Significant benefits of HTS in electric power industry
• Cleaner• More efficient• Safer• Smaller footprint• Lighter• Security benefits• Operation at LN2 temperatures (77K)
HTS Transformer
HTS Cable
HTS Fault Current Limiter HTS Motor
Conventional (copper)
2G HTS Cable
6ICEMS, October 2008
2G HTS wire is produced by advanced semiconductor-type manufacturing processes
2 μm Ag
20 μm Cu
20 μm Cu50 μm Hastelloy substrate
1 μm YBCO - HTS (epitaxial)
< 0.1 mm5 buffer layersTotal 160 nm
7ICEMS, October 2008
2G HTS will be the future of superconducting magnets
• Development of superconducting materials is driving the advancements of high field superconducting magnets
• LTS operate at low temperatures near 4K (LHe)• HTS operate at temperatures from 4K (LHe) to 77K (LN2)
• LTS: NbTi and Nb3Sn, 22.3 Tesla• 1G HTS: BSCCO-based, 25.05 Tesla• 2G HTS: REBCO-based, presented here
– REBCO is of high critical field ~70 T
8ICEMS, October 2008
High-field 2G HTS wire
• The applicability of a superconducting wire for a high field magnet is mainly determined by
– superconducting property Je(B) = Ic(B)/Ae – mechanical properties– lengths of the wire
9ICEMS, October 2008
Architecture Process method
20 μm Cu Electroplating
2 μm Ag Sputtering
1~ 5 μm ReBCO HTS MOCVD
30 nm LMO Sputtering
30 nm Homo-epi MgO Sputtering
10 nm IBAD MgO IBAD
7 nm Yttria Sputtering
80 nm Alumina Sputtering
50 μm metal alloy substrate Electrochemical-polish
20 μm Cu
Processes for long lengths of 2G wire• SuperPower 2G wire is manufactured with high throughput processes• The HTS layer is fabricated by Metal Organic Chemical Vapor Deposition
(MOCVD)– High rate, large area, high quality– Unique technology of SuperPower
10ICEMS, October 2008
77K, 0T 0
50100150200250300350400450
0 200 400 600 800 1000 1200
Position (m)
I c (A
/cm
-wid
th)
World record Ic-length performance of 2G wire
• The average Ic level of the 1205 m length was 384A/cm-width, but there were a few drops caused by defects
• 227A/cm over a length of 1030 meters -> 233,810 ampere-meter • There was a length of 540m with Ic above 337A/cm-width• The length with Ic above 302A/cm-width was 640m
11ICEMS, October 2008
Improved in-magnetic-field performance
• Approaches to higher Ic(B):
– The composition or the ratios of RE to Ba and RE to Cu is the key to achieving high Ic
– Substituting rare-earth in superconductor composition, such as Smand Gd, for Y in the YBCO film has been proved to be effective in improving in-magnetic-field properties
– Zr additions in REBCO films were shown to be effective pinning centers
12ICEMS, October 2008
0
2040
6080
100120
140160
180
-20 0 20 40 60 80 100 120
Angle (degree)
Criti
cal c
urre
nt (A
/cm
-wid
th) 0.7 micron SmYBCO
0.7 micron GdYBCO
0.7 micron Zr:GdYBCO
77K, 1T77K, 1T
0
50
100
150
200
250
300
350
400
450
-20 0 20 40 60 80 100 120
Angle (degree)
Criti
cal c
urre
nt (A
/cm
-wid
th) 3.5micron SmYBaCuO
2.8micron GdYBaCuO3.3micron Zr:GdYBCO
77K0.1
1
10
100
1000
0 2 4 6 8 10
Magnetic field B (Tesla)
Crit
ical
cur
rent
(A/c
m-w
idth
)
B//ab
B//c
Improved in-magnetic-field performance
77K0
200
400
600
800
1000
0 0.1 0.2 0.3 0.4 0.5
B//c (T)
I c (A
/cm
-wid
th)
3.5micron SmYBaCuO2.8micron GdYBaCuO3.3micron Zr:GdYBCO
Ic(B, θ=90ο) for different film compositions
Ic(B=1T, θ) for different film compositions Ic(B=1T, θ) for thick films
Ic(B, θ=90ο) and Ic(B, θ=0o) for Zr:GYBCO
13ICEMS, October 2008
SuperPower® 2G HTS wire has larger operating stress-strain window compared to other conductors
0
100
200
300
400
500
600
700
800
0 0.1 0.2 0.3 0.4 0.5
Strain (%)
Stre
ss (M
Pa)
"Low Strength" 1G HTS - Moderate Je
Nb3Sn - Moderate Je
SP 2G HTS - High Je
"High Strength" 1G HTS - Moderate Je
14ICEMS, October 2008
2G HTS has favorable thermal expansion characteristics
-0.004
-0.003
-0.002
-0.001
0.000
0.001
0.002
0 50 100 150 200 250 300 350
Temperature (K)
( ΔL
/ Lo
) 293
2G HTS (SCS4050) Iron / steel G10 warp 304 SS Copper Brass 70-30
15ICEMS, October 2008
High field insert magnet demonstrated
Coil ID 9.5 mm (clear)
Winding ID 19.1 mm
Winding OD ~ 87 mm
Coil Height ~ 51.6 mm
# of Pancakes 12 (6 x double)
2G wire used ~ 462 m
# of turns ~ 2772
Coil Je ~1.569 A/mm2 per A
Coil constant ~ 44.4 mT/A
Wire:Dimensions: 4 mm wide x
95 microns thickSubstrate: 50 micron Hastelloy
HTS: ~ 1 micron YBCO
Stabilizer: ~ 2 micron Ag on YBCO
~ 20 microns of surround copper stabilizer per side
Wire Ic 72 – 82 A, 77 K, sf
Coil Winding
Double Pancake Construction
Dry Wound (no epoxy)
Kapton polyimide insulation (co-wound)
Overbanding: 316 Stainless Steel
16ICEMS, October 2008
High field insert coil achieves record performance for highest HTS field, highest magnetic field by a superconducting magnet
Ic of Wires in Coil 72 A – 82 A (77K, sf)
4.2 K Coil Ic - self field 221 A
4.2 K Amp Turns @ Ic- self field
612,612
4.2 K Je @ Ic, self field 346.7 A/mm2
4.2K Peak Radial Field @ Ic, self field
3.2 T
4.2 K Central field – self field 9.81 T9.81 T
4.2 K Je @ Ic, 19 T background (axial)
274.6 A/mm2
4.2 K Peak Radial Field @ Ic, 19 T bkgd (axial)
2.7 T
4.2 K Coil Ic – 19 T background (axial)
175 A
4.2 K Amp Turns @ Ic – 19 T background (axial)
485,100
4.2K Central Field – 19 T background (axial)
26.8 T26.8 T
0.0
5.0
10.0
15.0
20.0
25.0
30.0
0 50 100 150 200
Current (A)
Cen
tral F
ield
(T)
19T background self field
17ICEMS, October 2008
Summary
• 2G HTS wire with high engineering critical current density has been manufactured and is available at a price that is rapidly decreasing
• In-magnetic field performance of 2G HTS wire has been remarkably improved through REBCO composition adjustment, high-Tc rare-earth element substitution, Zr-doping and growth condition optimization
• The mechanical properties of the wire are applicable for high field coils• A coil wound of 2G HTS wire generated 26.8 Tesla magnetic field in
2007• We have not yet reached the limit of 2G HTS capacity
– We believe that 30 Tesla and beyond is possible with the recently improved SuperPower 2G HTS wire
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