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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