Transcript 150325j_FCCW15_Bruker_Conductors_Schlengax

Bruker response to the FCC specifications
Klaus Schlenga
Washington, March 25, 2015
Innovation with Integrity
Outline
 Bruker Nb3Sn wire portfolio and production statistics
 State of the Art PIT Performance
 Comparison of FCC conductor target list to current PIT performance
 Interplay filament diameter – Jc – RRR
 Requirements and ideas for improved PIT design
 Dedicated R&D program
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Nb3Sn Conductors at Bruker
 Bruker EAS has long time experience in development and
manufacturing of Nb3Sn superconductors.
 This comprises fabrication of Nb3Sn conductors by different
manufacturing routes:
o Internally Stabilized Bronze Route: 1970 - 2000
o Internal Tin Route: 1986 – 1990
o Outer Stabilized Bronze Route: 1980 – today
o Powder In Tube Route: 2004 - today
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Production Statistics
 Main focus of R&D at Bruker is to achieve highly reliable
performance levels of conductors. This can only been reached by
robust and controllable industrial fabrication processes.
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Production Statistics
 Main focus of R&D at Bruker is to achieve highly reliable
performance levels of conductors. This can only been reached by
robust and controllable industrial fabrication processes.
jc, fil + bronze / (A/mm²) (temp. corr.)
900
Fabrication of ≈ 38 t of Bronze Route Nb3Sn strand for ITER
880
860
840
820
811,0
800
780
760
740
Variation of total production
jc: average 811 A/mm², 3 σ < 7 %
720
700
0
100
200
300
400
500
01EE…
jc point
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jc tail
Average
± 3σ
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Production Statistics
 Main focus of R&D at Bruker is to achieve highly reliable
performance levels of conductors. This can only been reached by
robust and controllable industrial fabrication processes.
1600
400
1500
350
1400
300
1300
250
1200
200
1100
150
1000
100
RRR
jc (4.2 K, 15 T) / (A/mm²)
Fabrication of PIT192 – Ø = 1.00 mm
Billets delivered
jc (4,2 K, 15 T)
RRR
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State of Art Performance of
PIT Nb3Sn wires - spread
 Jc Performance of PIT192 NbTa filaments Ø = 1.00 mm
jc1/2 * B1/4 [103 * A1/2 * m-1 * T1/4]
Ic, max (4.2 K, 15 T) = 511 A; Cu / non Cu = 1.31, RRR = 177, Bc2* = 26.5 T
Ic, min (4.2 K, 15 T) = 453 A; Cu / non Cu = 1.33, RRR = 240, Bc2* = 26.4 T
120
3000
2500
jc non Cu /(A/mm²)
2000
1500
1000
500
100
80
60
40
20
0
10 12 14 16 18 20 22 24 26 28 30
B /T
0
11
12
13
14
15
16
17
B /T
jc -max
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jc -min
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Kramer -max
Kramer -min
Kramer Extrapolation
Kramer Extrapolation
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State of Art Performance of
PIT Nb3Sn wires - spread
 Jc Performance of PIT192 NbTa filaments Ø = 1.00 mm
after reaction
2500
reaction
front
jc non Cu /(A/mm²)
2000
powder
core
1500
outer
filament
contour
1000
500
0
11
12
13
jc1/2 * B1/4 [103 * A1/2 * m-1 * T1/4]
Ic, max (4.2 K, 15 T) = 511 A; Cu / non Cu = 1.31, RRR = 177, Bc2* = 26.5 T
Ic, min (4.2 K, 15 T) = 453 A; Cu / non Cu = 1.33, RRR = 240, Bc2* = 26.4 T
120
3000
100
80
60
40
20
Spread in electrical performance 0is an interplay
10 12 14 16 18 20 22 24 26 28 30
between jc and RRR. It can partially be explained
B /T
by different usage of the "real estate" of the
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16
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18
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Kramer -min
Kramer -max
filament
cross
section.
B /T
jc -max
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jc -min
Kramer Extrapolation
Kramer Extrapolation
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Target FCC specification for Nb3Sn strand
A. Ballarino, L. Bottura , ASC 2014, 3MSPa-06, to be published in IEEE TAS
Continuous reduction (NED-FRESCA2-HL-LHC) of strand diameters in
HEP specifications and reduction of filament diameters observed.
These reductions impact the feasibility of achieving the electrical targets.
The electrical performance data have now shifted to 16 T and
magnetization is introduced.
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Comparison of PIT192 Ø = 1. 00 mm strand
to target FCC specification
 Best performing PIT192
Ø = 1.00 mm strand
compared to target
specification.
3000
jc non Cu /(A/mm²)
2500
2000
Spec.
1500 A/mm²
1500

1000
1232
A/mm²
o The required increase in jc
(including margin!) needs
to be achieved having the
reduced filament
diameters and small
strand dimensions as
constraints.
+ 22 %
required
500
0
11
12
13
14
15
B /T
jc -max
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18
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o Robustness of strand for
cabling is required.
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Reduced filament diameter
 Reducing filament diameters means
(apart from desired decrease of magnetization):
jc PIT192 12102
jc PIT192 11403
jc PIT192 29995
jc PIT192 33053
400
2400
300
2200
RRR
jc (12 T, 4.2 K) / (A/mm)
2600
RRR PIT192 12102
RRR PIT192 11403
RRR PIT192 29995
RRR PIT192 33053
2000
200
100
1800
610 °C, 80 h + 630 °C, 80 h
1600
25
30
35
40
Ø filament / µm
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610 °C, 80 h + 630 °C, 80 h
0
45
50
25
30
35
40
45
50
Ø filament / µm
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RRR vs. Jc with small filament diameters
 … and will not only be a matter of heat treatment optimization!
250
Variation of heat treatments
applied to strands with 34 µm
and 29 µm respectively
200
RRR
150
100
50
0
2200
2250
2300
2350
2400
jc (12 T, 4.2 K) /(A/mm²)
34 µm
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2450
2500
29 µm
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Implications for current PIT design
 Reduction of strand and/or filament diameters of PIT wires with
standard layout will lead to
o More deformed filaments, due to grain size effects of the
materials involved
o Reduction of n value due to more inhomogeneous filaments
o Reduced reliability of diffusion barrier (unreacted Nb tube)
o More probable Sn contamination of the stabilizing Cu
o More sensitivity to cabling induced deformation
 Ic, n, RRR will suffer from these effects, thus new layouts become
mandatory to reduce their impact.
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Requirements for future PIT design
 Stabilizing Cu needs to be reliably protected
 Enhancing jc, non Cu by improved usage of the Nb3Sn area of
the filament cross section
 Enhancing the "quality" of the Nb3Sn by better
understanding/control of the reaction
 Extensive R&D and analytical work exclusively dedicated for this
application will be required to achieve the targets
 Reasonable margin above the specified values needs to be
assured for high yield
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R&D program for improved Nb3Sn strand
 FCC will be a unique challenge and opportunity for Nb3Sn
strand.
 Bruker EST will support this challenge but adequate funding
must be secured.
 To address FCC needs the strand manufacturer needs to have
enough degrees of freedom to play with.
 The more stringent the specification is, the less the chance to
develop a strand that enables the fabrication of magnets for FCC
on justifiable cost
 An iterative R&D program with milestones and possible
compromises and flexibility regarding performance along the
way might be necessary!
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Innovation with Integrity
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