innovation with integrity klaus schlenga washington, march 25, 2015 bruker response to the fcc...
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Innovation with Integrity
Klaus Schlenga
Washington, March 25, 2015
Bruker response to the FCC specifications
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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Innovation with Integrity
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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Innovation with Integrity
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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Innovation with Integrity
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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811,0
700
720
740
760
780
800
820
840
860
880
900
0 100 200 300 400 500
jc, fi
l + b
ronz
e /
(A/m
m²)
(tem
p. c
orr.)
01EE…
jc point jc tail Average ± 3σ
Fabrication of ≈ 38 t of Bronze Route Nb3Sn strand for ITER
Variation of total productionjc: average 811 A/mm², 3 σ < 7 %
Innovation with Integrity
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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100
150
200
250
300
350
400
1000
1100
1200
1300
1400
1500
1600
RRR
jc (4
.2 K
, 15
T) /
(A/m
m²)
Billets deliveredjc (4,2 K, 15 T) RRR
Fabrication of PIT192 – Ø = 1.00 mm
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State of Art Performance of PIT Nb3Sn wires - spread
Jc Performance of PIT192 NbTa filaments Ø = 1.00 mmIc, max (4.2 K, 15 T) = 511 A; Cu / non Cu = 1.31, RRR = 177, Bc2* = 26.5 TIc, min (4.2 K, 15 T) = 453 A; Cu / non Cu = 1.33, RRR = 240, Bc2* = 26.4 T
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0
500
1000
1500
2000
2500
3000
11 12 13 14 15 16 17 18 19
jc n
on C
u /(
A/m
m²)
B /Tjc -max jc -min
0
20
40
60
80
100
120
10 12 14 16 18 20 22 24 26 28 30
j c1/2
* B1/
4[1
03*
A1/2
* m
-1 *
T1/
4 ]
B /T
Kramer -max Kramer -min
Kramer Extrapolation Kramer Extrapolation
Innovation with Integrity
State of Art Performance of PIT Nb3Sn wires - spread
Jc Performance of PIT192 NbTa filaments Ø = 1.00 mmIc, max (4.2 K, 15 T) = 511 A; Cu / non Cu = 1.31, RRR = 177, Bc2* = 26.5 TIc, min (4.2 K, 15 T) = 453 A; Cu / non Cu = 1.33, RRR = 240, Bc2* = 26.4 T
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0
500
1000
1500
2000
2500
3000
11 12 13 14 15 16 17 18 19
jc n
on C
u /(
A/m
m²)
B /Tjc -max jc -min
0
20
40
60
80
100
120
10 12 14 16 18 20 22 24 26 28 30
j c1/2
* B1/
4[1
03*
A1/2
* m
-1 *
T1/
4 ]
B /T
Kramer -max Kramer -min
Kramer Extrapolation Kramer Extrapolation
after reaction
powder core
reaction front
outer filament contour
Spread in electrical performance is an interplay between jc and RRR. It can partially be explained by different usage of the "real estate" of the filament cross section.
Innovation with Integrity
Target FCC specification for Nb3Sn strand
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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.
Innovation with Integrity
Comparison of PIT192 Ø = 1. 00 mm strandto target FCC specification
Best performing PIT192Ø = 1.00 mm strand compared to target specification.
o The required increase in jc (including margin!) needs to be achieved having the reduced filament diameters and small strand dimensions as constraints.
o Robustness of strand for cabling is required.
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0
500
1000
1500
2000
2500
3000
11 12 13 14 15 16 17 18 19
jc n
on C
u /(
A/m
m²)
B /Tjc -max
1232 A/mm²
Spec. 1500 A/mm²
+ 22 % required
Innovation with Integrity
Reduced filament diameter
Reducing filament diameters means (apart from desired decrease of magnetization):
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25 30 35 40 45 501600
1800
2000
2200
2400
2600
jc PIT192 12102 jc PIT192 11403 jc PIT192 29995 jc PIT192 33053
jc (
12
T,
4.2
K)
/ (A
/mm
)
Ø filament / µm
610 °C, 80 h + 630 °C, 80 h
25 30 35 40 45 500
100
200
300
400
610 °C, 80 h + 630 °C, 80 h
RRR PIT192 12102 RRR PIT192 11403 RRR PIT192 29995 RRR PIT192 33053
RR
R
Ø filament / µm
Innovation with Integrity
0
50
100
150
200
250
2200 2250 2300 2350 2400 2450 2500
RRR
jc (12 T, 4.2 K) /(A/mm²)
34 µm 29 µm
RRR vs. Jc with small filament diameters
… and will not only be a matter of heat treatment optimization!
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Variation of heat treatments applied to strands with 34 µm and 29 µm respectively
Innovation with Integrity
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 involvedo Reduction of n value due to more inhomogeneous filamentso Reduced reliability of diffusion barrier (unreacted Nb tube)o More probable Sn contamination of the stabilizing Cuo 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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Innovation with Integrity
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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Innovation with Integrity
R&D program for improved Nb3Sn strand
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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!
Innovation with Integrity
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