Real Time Process Control and Quality Control of Long-length …Spring+Sym.pdf · Materials...

Materials Research Society Spring Meeting, San Francisco, April 5 – 9, 20101


Real Time Process Control and Quality Control of Long-length Second-generation HTS Wires

A. Rar, Y. Xie, and J. Dackow, SuperPower Inc., Schenectady, NY, USA

V. SelvamanickamUniversity of Houston, Houston, TX, USA

1

Partially supported by U.S. DOE Office of Electricity & Energy Reliability and CRADAs with Los Alamos and Argonne National Laboratories



Piece lengths & critical current of 2G wire have been steadily improved over last five years

600+ m lengths with Ic > 300 A/cm1000+ m lengths with Ic > 250 A/cm



MOCVD-based coated conductors are routinely produced in kilometer lengths

3

0

50

100

150

200

250

300

350

400

450

500

0 100 200 300 400 500 600 700 800 900 1000

Crit

ical

Cur

rent

(A/

cm)

Position (m)

• Minimum current (Ic) = 282 A/cm over 1065 m • Ic × Length = 300,330 A-m

77 K, Ic measured every 5 m using continuous dc currents over entire tape width of 12 mm (not slit)


QC tools to qualify long wire requirements

Uniformity of critical current of long-length 2G HTS wires determines their yield which is the main factor that affects the economics

• On-line monitoring of superconductor film quality during MOCVD• Reel-to-reel in-field measurement system for 100+m wires• Qualify Ic uniformity across width for ROEBEL conductors


Critical current is strongly impacted by a-axis growth in MOCVD films

0

50

100

150

200

250

300

0 0.5 1 1.5

YBCO (200)/(006) ratio

Cri

tical

Cur

rent

(A/c

m)

a-axis grain

CuO

TEM by D. Miller, ANL


Long-length critical current uniformity is impacted by a-axis growth

0

50

100

150

200

250

300

1 31 61 91 121

151

181

211

241

271

301

331

361

391

Position (m)

Crit

ical

cur

rent

(A/c

m)

020406080

100120140160180

45.5 46 46.5 47 47.52 theta (degrees)

Inte

nsity

(arb

. uni

ts) tape center

tape front edgetape back edge

(006)

(200)0

10

20

30

40

50

60

45.5 46 46.5 47 47.52 theta (degrees)

Inte

nsity

(arb

. uni

ts)

tape centertape front edgetape back edge

(006)

(200)


Critical current limited by non/weak superconducting phases

y = 1.0007x - 0.0235R² = 0.8411

0

100

200

300

400

0 100 200 300 400Pr

edic

ted

criti

cal c

urre

nt (A

)

Measured critical current (A)

Ic=4.95*counts (006)-125

Critical current predicted based on (006) XRD peak intensity

Good correlation between measured Ic and XRD peak intensity


On-line XRD in new pilot-MOCVD system for real-time quality control

8


Real-time XRD data during long-length MOCVD HTS wire manufacturing

0102030405060708090

100

100 2100 4100

Ic o

r R

eBC

O (0

06)p

eak/

100

position (for XRD estimated)

Non contact Ic

XRD peak/100

(006)

(200)

Good correlation between real-time XRD data & critical current of long 2G HTS wires



In-field performance of long wires with Zr doping for improved pinning

40

50

60

70

80

90

100

110

120

-30 30 90 150 210 270 330

Crti

ical

cur

rent

(A/1

2 m

m)

Angle between field & tape normal (°)

5% 7.5% 10%

1.0 T, 77 K

Zr-doped MOCVD precursor recipe successfully transferred to manufacturing system.Is the enhanced pinning uniform over long lengths ?

Research MOCVD system at Houston Pilot MOCVD system at Schenectady, NY

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

10

20

30

40

50

60

70

80

-30 30 90 150 210 270 330J c

(MA

/cm

2 )

Crti

ical

cur

rent

(A/1

2 m

m)

Angle between field & tape normal (°)

0% 2.5% 5%

7.50% 10% 12.50%

1.0 T, 77 K


Reel-to-reel in-field measurement system set up based on technique developed at

LANL• LANL provided a magnet stage

(0.52 Tesla over 7.5 cm) for in-field measurement on long tapes at all field orientations (360°) & associated testing know-how.

• SP constructed a reel-to-reel system with sensors, controllers and software using this magnet stage.

11


Reel-to-reel system enables comparison of in-field performance of long wires

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

Improved pinning is uniform over 100+m lengths

0

10

20

30

40

50

60

0

20

40

60

80

100

120

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

I cat

0.5

2 T

(A/ 4

mm

wid

th)

Position (m)

Standard undoped wire, self-field IcZr-doped wire self-field IcStandard undoped wire, B || c-axisStandard undoped wire, min Ic angleZr-doped wire, B || c axisZr-doped wire min Ic angle

Self-

field

I c(A

/ 4 m

m


Meeting requirements for ROEBEL cables• ROEBEL cable is used for

low ac loss, high current applications

• Since current has to flow across the width, 2D Icuniformity is important.

• Previously, we patterned 12 mm wide 2G wire in multiple segments for measurements of Ic at different angles of current flow and found no discernible reduction in intermediate angles

0

50

100

150

200

250

300

-10 0 10 20 30 40 50 60 70 80 90 100Angle between curent and tape length (deg)

Ic (A

/cm

)

Tape 1Tape 2Tape 3

Buffer

Need a non destructive QC technique to evaluate 2D Ic non uniformity

Materials Research Society Spring Meeting, San Francisco, April 5 – 9, 2010 14

Non-destructive QC technique for 2-dimensional Ic uniformity analysis

A variety of techniques have been studied to measure the 2D uniformity of superconductors:

• Magneto-optical imagining: D. M. Feldmann, et al., Appl. Phys. Lett. 77, 2906 (2000); • Magneto scan: M. Zehetmayer, et al., Appl. Phys. Lett. 90, 032506 (2007); • Laser scanning: T. Kiss, et al., Applied Superconductivity, IEEE Transactions on, June

2005; • Magnetic imaging: G.W. Brown, et al., Mat. Res. Soc. Symp. Vol. 659 (2001); • Scanning Hall Probe: A. Oota, et al., Physica C 291, 188 (1997); • Magnetic Knife: J H¨anisch, et al., Supercond. Sci. Technol. 21 (2008) 115021

• Scalability over a practical conductor length has not been demonstrated yet.

• While some techniques are used to measure Ic uniformity along the transverse direction, the current flow is still along the tape length.

Fine resolution and measurement over long length are both needed to obtain data to determine the suitability of materials for certain applications


2D Uniformity Analysis using Tapestar Data• Non-magnetic nature of SuperPower 2G wire substrate allow evaluation of Ic with

magnetic technique such as Tapestar that provides 2D field profile every 1 mm tape using seven Hall sensor readings.

• Field penetration profile at every location along the tape reflects the uniformity across width.

• When non-uniformity across width exists, readings from Sensor 1 differs from that of Sensor 7– similarly Sensor 2 vs. Sensor 6 and Sensor 3 vs. Sensor 5

Tape width

Uniform Ic across width : Symmetrical field penetration profile

Non uniform Ic across width : Asymmetrical field penetration profile

1 2 3 4 5 6 7

Tape width


2D Uniformity Analysis using Tapestar Data• “Correlation Coefficient” calculated to determine

the degree of difference between a local field penetration and an ideal Bean profile.

• Relative gradient (RG) based on the readings from the two sensors at the opposite sides w.r.t. the center sensor shows how and how much a local profile differs from an ideal Bean profile.

1 2 3 4 5 6 7

Since Sensors 1 and 7 are located at the two edges, RG17 values typically indicates how well the Sensor array is aligned with the tape during the measurement.

(1)

100)47()41(

17(%)17 ×−+−

−=

SensorSensorSensorSensorSensorSensorRG

100)47()41(

26(%)26 ×−+−

−=


100)47()41(

35(%)35 ×−+−

−=



Field Penetration Profiles – Possible Scenarios

CaseRG35 (%)

RG26 (%)

RG17 (%) Note

Perfectly uniform 0 0 0 No difference between two sensor readings.

Extremely nonuniform - ∞ - ∞ - ∞

Left-hand side is ∞ times worse than the right-hand side

Typical - uniform 1.90 -2.28 -1.14 Quite uniform. Variation ~2%

Typical –nonuniform 16.46 4.12 -1.23

Very nonuniform between Sensors 3 and 5. There must be defects around Sensor 5 (positive value indicate better at left side - “polarity”)

15

20

25

30

35

40

-6 -4 -2 0 2 4 6

Sensor Position (mm)

Sens

or R

eadi

ng (m

T)

Perfectly uniform Extremely nonuniformTypical - uniform Typical - nonuniform


Minor variations in 2D Ic clear from RG analysis65 m long, 12 mm wide wire, min Ic = 314 A, av Ic = 316 A , 0.3% uniformity

18

0 10 20 30 40 50 60202224262830

Position (m)

Cent

er S

enso

r (m

T) -15-10-505

1015

Diff3

5 (%

)

-15-10-505

1015

Diff2

6(%

)

-15-10-505

1015

Wire1a

Diff1

7(%

)R

G35

(%)

RG

26 (%

)R

G17

(%)

62.5 63.0 63.5 64.0 64.5202224262830

Position (m)

Cent

er S

enso

r (m

T)

-15-10-505

1015

Diff3

5 (%

)

-10

-5

0

5

10

Diff2

6(%

)

-15-10-505

1015

Wire1a (62.5-64.5 m)

Diff1

7(%

) Left-hand side

Right-hand side

RG

17 (%

)R

G17

(%)

RG

26 (%

)R

G35

(%)

2D Ic analysis is an effective QC tool for wire selection for ROEBEL cables

Readings from all 7 sensorsMinor local variations not very visible

Relative gradient calculatedMinor local variations clear


Summary

Quality control tools have been established to assess uniformity in critical current along tape length, uniformity in-field performance over tape length and uniformity critical current across tape width

in long 2G HTS wires.

Uniformity of critical current of long-length 2G HTS wires determines their yield which is the main factor that improve the economics

19

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Real Time Process Control and Quality Control of Long-length …Spring+Sym.pdf · Materials...

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