towards a nb3sn conductor for fcc...group of applied superconductivity department of quantum matter...

Group of Applied SuperconductivityDepartment of Quantum Matter Physics

University of Geneva, Switzerland

Towards a Nb3Sn conductor for FCCMaterial development and electromechanical studies

Florin BUTA, Luc GAMPERLE, Christian BARTH, José FERRADAS, Carmine SENATORE

http://supra.unige.ch

OutlineInvestigations on the enhancement of Jc in (Nb,X)3Sn superconductors by internally oxidized ZrO2 particles

H2020 EuroCirCol WP5 Task 5: Conductor studies

Florin BUTA

@ CERN : Simon HOPKINS, Bernardo BORDINI, Amalia BALLARINO

@ CERN : Bernardo BORDINI, Davide TOMMASINI

Luc GAMPERLE Christian BARTH José FERRADAS

Addendum FCC-GOV-CC-0112 (KE3545/ATS)

Electromechanical studies – effects of the transverse stress

Performance target non-Cu Jc(4.2K,16 T) = 1500 A/mm2

Mt 2;10 When they saw the star, they rejoiced exceedingly with great joy

12 14 16 18 20 220

500

1000

1500

2000

2500

3000

FCC Target

no

n-C

u J

c [A

/mm

2]

B [T]

@ 4.2 K

12 14 16 18 20 220

500

1000

1500

2000

2500

3000

FCC Target

no

n-C

u J

c [A

/mm

2]

B [T]

@ 4.2 K

12 14 16 18 20 220

500

1000

1500

2000

2500

3000

FCC Target

no

n-C

u J

c [A

/mm

2]

B [T]

PIT - BKr

= 26.5 T

RRP - BKr

= 24.9 T

@ 4.2 K

J. Parrell et al., AIP Conf. Proc. 711 (2004) 369

T. Boutboul et al., IEEE TASC 19 (2009) 2564


Laboratory for the development of superconducting wires @ UNIGE

An (almost) unique equipment

Wire drawing bench 1.5t

Wire drawing bull-block 0.3t

Wire drawing dies from 15 to 0.2 mm

Hot-rolling mill and hot-rolling groove roller

Rolling mill with tungsten carbide rollers

Powered turks head machine

Two swaging machines

250t hydrostatic hot extrusion machine

R&D of internal Sn Nb3Sn conductors A collaboration between UNIGE and Bruker BioSpin funded by (2007-2010)

Cu/Nb-Ta rod Sub-element bundle

Sub-element with pure Sn core

Final wire109 sub-elements

F. Buta, R. Flükiger, CTI 9049.1 PFIW-IW final report, 2011

12 14 16 18 20 220

500

1000

1500

2000

2500

3000 Internal Sn UNIGE - B

Kr= 24.6 T

FCC Target

no

n-C

u J

c [A

/mm

2]

B [T]

@ 4.2 K


Internal oxidation and grain refinement in Nb3Sn

Idea from Benz (1968) to form fine precipitates in Nb to impede the A15 grain growth

Use of a Nb-Zr alloy: Zr has stronger affinity to oxygen than Nb

Oxygen supply added to the composite: oxidation of Zr and formation of nano-ZrO2

X. Xu et al., APL 104 (2014) 082602

X. Xu et al., Adv. Mat. 27 (2015) 1346

Average grain size is reduced down to < 50 nm

Greatly enhanced pinning in binary Nb3Sn

@ Ohio State University

M.G. Benz, Trans. Metall. Soc. AIME, 242 (1968) 1067-1070

R&D on internal oxidation in Nb3Sn @ UNIGE

• Explore routes leading to the increase of the critical current densities in Nb3Sn by reducing the grain sizes and increasing the upper critical field

• Evaluate different oxygen sources for the internal oxidation of Zratoms present in the Nb filaments

• Addition of suitable dopants to enhance the upper critical field

• Optimize wire configurations and heat treatments

Ohio State Univ. Configuration

Oxide powder Nb-Zr alloy

Cu

Sn

UNIGE configuration

Oxide powder Nb-Zr alloy

Sn

Cu

R&D on internal oxidation in Nb3Sn @ UNIGE

Filament material - oxygen source combinations

Nb alloy Metal oxide Status

Nb-7.5wt%Ta none

Nb-7.5wt%Ta MoO3

Nb-7.5wt%Ta SnO2 planned

Nb-1wt%Zr MoO3

Nb-1wt%Zr SnO2

Nb-1wt%Zr CuO being drawn

Nb-7.5wt%Ta-1wt%Zr SnO2 being drawn


Filament material - oxygen source combinations

Nb alloy Metal oxide Status

Nb-7.5wt%Ta none

Nb-7.5wt%Ta MoO3

Nb-7.5wt%Ta SnO2 planned

Nb-1wt%Zr MoO3

Nb-1wt%Zr SnO2

Nb-1wt%Zr CuO being drawn



How to select the oxygen source ?

• high Gibbs free energy of formation

• low hardness that would make it compatible with wire fabrication

• the metal resulting from the reduction has not to affect superconductivity

Sample fabrication

• The Nb alloy wire was then electroplated successively with: Cu, Sn, Cu

• The deposit thicknesses were varied to achieve different Cu/Sn and Nb/Sn ratios

• Oxygenation treatment was performed on the Nb alloy wire prior to the electroplating or on the full wire prior to the A15 formation

0.22 mm diameter wires of Nb alloy were prepared by cold deformation of a 12 mm diameter rod with nano-sized powders compacted in a central hole

1 2 3 4 5 6 70.0

5.0x103

1.0x104

1.5x104

2.0x104

2.5x104

Ind

uct

ive

Jc [

A/m

m2]

Magnetic field [T]

Nb7.5Ta, no oxygen source

Nb1Zr, MoO3

Nb1Zr, SnO2

Oxidation treatment @ 500°C/50h

Sn

O

Critical current density

Nb3Sn

Nb1Zr

Nb7.5Ta Nb1Zr + SnO2

FpMAX(4.2 K) 28.3 GN/m3 62.4 GN/m3

BKramer(4.2 K) 27 T 23.4 T

@ 4.2 K

Nb7.5Ta Reference

Grain morphology

Nb1Zr + SnO2

Oxidation @ 500°C/300h

0 50 100 150 200 250 300 3500.0

0.2

0.4

0.6

0.8

1.0

Fr

acti

on

of

grai

ns

grain size [nm]

Nb7.5Ta, no oxygen source

Nb1Zr + SnO2, 500°C/300h

Median grain size153 nm

Median grain size88 nm

Pinning force

0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

0.6

0.8

1.0

no

rmal

ize

d p

inn

ing

forc

e

normalized field

T = 4 K

T = 6 K

T = 8 K

T = 10 K

T = 12 K

T = 14 K

T = 16 K

Nb7.5Ta

0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

0.6

0.8

1.0

no

rmal

ize

d p

inn

ing

forc

e

normalized field

T = 4 K

T = 6 K

T = 8 K

T = 10 K

T = 12 K

T = 14 K

T = 16 K

Nb1Zr + SnO2

Nb7.5Ta Reference Nb1Zr + SnO2

0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

0.6

0.8

1.0

no

rmal

ize

d p

inn

ing

forc

e

normalized field

T = 4 K

T = 6 K

T = 8 K

T = 10 K

T = 12 K

T = 14 K

T = 16 K

Nb7.5Ta

0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

0.6

0.8

1.0

no

rmal

ize

d p

inn

ing

forc

e

normalized field

T = 4 K

T = 6 K

T = 8 K

T = 10 K

T = 12 K

T = 14 K

T = 16 K

Nb1Zr + SnO2


Pinning force

0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

0.6

0.8

1.0

no

rmal

ize

d p

inn

ing

forc

e

normalized field

T = 4 K

T = 6 K

T = 8 K

T = 10 K

T = 12 K

T = 14 K

T = 16 K

Nb7.5Ta

0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

0.6

0.8

1.0

no

rmal

ize

d p

inn

ing

forc

e

normalized field

T = 4 K

T = 6 K

T = 8 K

T = 10 K

T = 12 K

T = 14 K

T = 16 K

Nb1Zr + SnO2

Nb7.5Ta Reference Nb1Zr + SnO2

0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

0.6

0.8

1.0

no

rmal

ize

d p

inn

ing

forc

e

normalized field

T = 4 K

T = 6 K

T = 8 K

T = 10 K

T = 12 K

T = 14 K

T = 16 K

Nb7.5Ta

0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

0.6

0.8

1.0

no

rmal

ize

d p

inn

ing

forc

e

normalized field

T = 4 K

T = 6 K

T = 8 K

T = 10 K

T = 12 K

T = 14 K

T = 16 K

Nb1Zr + SnO2


GB pinning max @ b = 0.2point pinning max @ b = 0.33

0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

0.6

0.8

1.0

no

rmal

ize

d p

inn

ing

forc

e

normalized field

Nb7.5Ta

Nb1Zr + SnO2

OutlineInvestigations on the enhancement of Jc in (Nb,X)3Sn superconductors by internally oxidized ZrO2 particles

H2020 EuroCirCol WP5 Task 5: Conductor studies

Florin BUTA

@ CERN : Simon HOPKINS, Bernardo BORDINI, Amalia BALLARINO

@ CERN : Bernardo BORDINI, Davide TOMMASINI

Luc GAMPERLE Christian BARTH José FERRADAS

Addendum FCC-GOV-CC-0112 (KE3545/ATS)

Electromechanical studies – effects of the transverse stress


12 14 16 18 20 220

500

1000

1500

2000

2500

3000

FCC Target

no

n-C

u J

c [A

/mm

2]

B [T]

PIT - BKr

= 26.5 T

RRP - BKr

= 24.9 T

@ 4.2 K

T. Boutboul et al., IEEE TASC 19 (2009) 2564

12 14 16 18 20 220

500

1000

1500

2000

2500

3000

FCC Target

no

n-C

u J

c [A

/mm

2]

B [T]

PIT - BKr

= 23.2 T @ 200 MPa

RRP - BKr

= 23.8 T @ 200 MPa

@ 4.2 K, 200 MPa

J. Parrell et al., AIP Conf. Proc. 711 (2004) 369

and 200 MPa

Degradation upon transverse loads

The 16 T FCC dipoles are being designed with a peak stress of 200 MPaat operation

Nb3Sn Rutherford cable for HL-LHC, 40 strands

Are the Nb3Sn wires in the cable able to withstand such a high stress level? Which degradation is tolerable?

• Nb3Sn wires are deformed during cabling

• Cables are braided with glass fiber

• The winding is impregnated with resin

Is it possible to extrapolate the behaviour of the cable from a single wire experiment?

The WASP concept for Ic vs. transverse stress

4-WALL + impregnation

Pulling force

3 groove widths

1.30 mm

1.15 mm

1.00 mm

Resin

Sample

CERN-UNIGE collaboration agreement K1629/TE (2009-2012)

The irreversible limit of the wire under transverse stress is influenced by several parameters

• the type of impregnation (the elastic modulus of the resin)

• the redistribution of the applied stress on the wire

Rolled wire to simulate the deformation during cabling

• the type of wire

Ic vs. transverse stressPIT 192 + epoxy L

0 5 10 15 20 25 30 350.2

0.4

0.6

0.8

1.0

@ 4.2K, 19 T

I c / I c0

Transverse force [kN]

#31712-1 unload

95% Ic0

0 30 60 90 120 150 180 210 240Transverse stress [MPa]

ForceStress

groove length groove w th id

irr = 110 MPa

The corresponding irreversible stress limit is

where

The irreversible limit is defined at the force level leading to a 95% recovery of the initial Ic after unload

Here Firr = 16 kN

60 80 100 120 140 160 180

0.0

0.5

1.0

1.5

2.0

2.5

F = 0.5 kN

F = 15 kN

unload to 0.5 kN

@ 4.2 K, 19 T

Elec

tric

fie

ld [

V/c

m]

Current [A]

Epoxy L

Sample

Glass fiber

Ic vs. transverse stress: wire in a glass fiber sleeve

The wire with glass fiber sleeve was measured in a larger groove (1.30 mm vs 1.15 mm)

0 30 60 90 120 150 180 210 2400.2

0.4

0.6

0.8

1.0

PIT #31712 Ø = 1.0 mm

@ 4.2K, 19 T

95% Ic0

Transverse stress [MPa]

I c / I c0

sample #1 round

with glass fiber sleeve

PIT #14310 Ø = 1.0 mm

Shift of irr by > 50 MPa

Ic vs. transverse stress: epoxy L vs. stycast

0 5 10 15 20 25 30 350.2

0.4

0.6

0.8

1.0

PIT #31712 Ø = 1.0 mm

@ 4.2K, 19 T

I c / I c0

Transverse force [kN]

epoxy impregnation

stycast impregnation

95% Ic0

0 30 60 90 120 150 180 210 240


The change of resin, from epoxy to stycast, leads to an increase of irr by > 50 MPaThe result is comparable to the value found with epoxy + glass fiber sleeve

Ic vs. transverse stress on 15% rolled wires

0 50 100 150 200 250

60

80

100

120

140

160

180

sample #1 round

sample #2 15% rolled


PIT #31712 Ø = 1.0 mm

@ 4.2K, 19 T

I c [A

]

50 100 150 200 250

60

80

100

120

140

160

180

@ 4.2K, 19 T

95% Ic0


I c [A

]

sample #1 round

sample #2 15% rolled

RRP 132/169 #114163 Ø = 1.0 mm

PIT 192 RRP 132/169

~7.5% Ic reduction by rolling

Shift of irr by ~ 40 MPa

NO Ic reduction by rolling

Shift of irr by ~ 15 MPa

…more details in the poster (#256) of José FERRADAS

Summary

• Observed a refinement of the Nb3Sn grains but the process is still under optimization

• NbTaZr alloys: The goal is to produce material with refined grains (ZrO2 dispersion) and enhanced Bc2 (Ta-doping)

• Explored the irreversible stress limit of PIT and RRP wires in different load conditions

Thank you for the attention !

Carmine SENATORE

[email protected]

http://supra.unige.ch

towards a nb3sn conductor for fcc...group of applied superconductivity department of quantum matter...

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