is aimed at the development of a large-aperture

Magnetization measurements as a tool for investigating the potential electrical transport properties of Nb3Sn superconducting wires.

Michela Greco, INFN-Genova

is aimed at the development of a large-aperture high field (up to 15 T) superconducting dipole magnet that will serve as a technology test bed for LHC luminosity upgrade

Development of a high-performance Nb3Sn wire (aiming at a non-copper critical current density of 1500 A/mm2 at 4.2 K and 15 T) is carried out.

A Working Group on Conductor Characterization (WGCC)

CEA, CERN, INFN-Genova, INFN-Milano, University of TwenteCEA, CERN, INFN-Genova, INFN-Milano, University of Twente

is aimed to define and carry out reliable, reproducible methods for the measurement of electromagnetic properties.

…In

tro

m(T

, B

)m

(B)

(B

,T)

sam

ple

sN

b?

M. Greco, INFN-Genova/ CARE05, CERN November 23, 2005

Genova coordinates three groups, having at disposal three facilities: a Vibrating Sample Magnetometer (VSM)

in Frascati, a DC-SQUID magnetometer and an AC susceptibility apparatus in Genova.

Intr

om

(T,

B)

m(B

)(

B,T

)sam

ple

sN

b?

…

Field orientation

Meas type

Applied Field

Info

Parallel m(T) Bdc=10 G, Bdc=100 G

Nb3Sn shielded volumeTc(B)

Parallel (T) Sample geometry, Nb3Sn homogeneity

Transverse m(T) Bdc=10 G, Bdc=100 G

Demagnetizing factor evaluation

Transverse (T) Sample geometry, Nb3Sn homogeneity

Transverse m(B) 0-3T, 0-8T Surface shielding, flux jumps, Jc

Pasquale Fabbricatore, INFN-Genova;Carlo Ferdeghini, CNR-INFM; Umberto Gambardella, INFN-Frascati


• Tc(B)

• Nb shielded volume

• Nb3Sn shielded volume

m= 0 ×Applied Field ×Sample Volume [Wb m] Conversion from cgs to SI units 1 emu=10-10/4 [Wb m]

Susceptibility 0 can be calculated using FEM. The samples measured can be assumed as cylinders

Parallel field, 0 ~1; Transverse field, 0 ~ 2

From the comparison of measurements in parallel and transverse field it is possible to evaluate demagnetizing

value N [Beff=B/(1-N)] and compare with FEM calculation.

m(T)

-0.0030

-0.0025

-0.0020

-0.0015

-0.0010

-0.0005

0.0000

0.0005

4 6 8 10 12 14 16 18 20

ma

gn

etic

mo

me

nt

(em

u)

T (K)

Tc Nb

3Sn=17.4 KT

c Nb

3Sn=17.4 K

Tc Nb=9.2 K

Nb3Sn shield: 0.00146 emu

total shield : 0.003 emu

Intr

om

(T)

m(B

)(

B,T

)sam

ple

sN

b?

…

Bdc=10 G, parallel field

-0.0060

-0.0050

-0.0040

-0.0030

-0.0020

-0.0010

0.0000

0.0010

4 6 8 10 12 14 16 18 20

ma

gn

etic

mo

me

nt

(em

u)

T (K)


Nb3Sn shield: 0.00249emu

Tc Nb

3Sn=17.4 K

Tc Nb=9.2 K


• Parallel and transverse field

• indication of shielding

• flux jumps at low fields

• Estimation of Jc(B) from m from meas in transverse field

m(B)

Intr

om

(T)

m(B

)(

B,T

)sam

ple

sN

b?

…

-1.5

-1

-0.5

0

0.5

1

1.5

-4 -3 -2 -1 0 1 2 3 4

mag

netic

mom

ent (

emu)

B (T)

m

comparison with Ic results

STBJNI

rrS

rd

rr

dlN

mTBJ

dlTBJN

m

),(

)(

2

/

)1(

3),(

)1( ),(3

scc,filc

2Sn

2SnNb

SnNb

SnNbSn

330fil

wirescc,

330scc,

filwire

3

3

3


(B,T)

Intr

om

(T)

m(B

)(

B,T

)sam

ple

sN

b?

…

tinn

nn eiBAB )(

1

prim

ary

coil

dual phase lock-in amplifier

reference

se

cond

ary

coils

s1

s2

)''χ'χ(χ1d/d

d/dχ 0

ext

itB

tB

0χ external susceptibility under conditions of perfect screening (Meissner state)

tiext eBB

0

"χ dissipated energy

The signal U at the pick-up coils s1 and s2 gives relevant information:U=Us1-Us2=N2/G mN= Turns in the pick-up coils, = frequency G= geometrical factor m= magnetic moment

normal state B=H, so ’=’’=0

perfect screening”=0M/B0


χ' stored energy

(B,T)

Intr

om

(T)

m(B

)(

B,T

)sam

ple

sJc

Ic

•Tc(B)

•Nb shielding volume

•Nb3Sn shielded volume

•Sharp transition

homogeneous material

•Smooth transition key of dishomogeneity

The peak becomes lower and smoother


Intr

om

(T)

m(B

)(

B,T

)sam

ple

sN

b?

…

First phase:

• Preliminary measurements on Internal TIN and “old” PIT samples

Calibrated the DCsquid /VSM/AC apparata and understand “different” results, if any

Verified the info that can be derived from different meas


Intr

om

(T)

m(B

)(

B,T

)In

t TIN

Nb

?…

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

-3 -2 -1 0 1 2 3

VSMSQUID

ma

gn

etic m

om

en

t (e

mu

)

Field (T)

Comparison of m-B measurements at 4.2 K with SQUID and VSM on two different

samples differing by 7.5% in length

-5 10-6

-4 10-6

-3 10-6

-2 10-6

-1 10-6

0

1 10-6

2 10-6

3 10-6

8 10 12 14 16 18

in-p

ha

se

Temperature (K)

-3*o

ut-

of-

ph

ase

’

-3”

Courtesy A. Devred, CEA/CERN

•Absence of flux-jumps at low field•20% difference between Nb3Sn geometrical and shielded volume values..hint of filament interconnection?

Extremely smooth Nb3Sn transitionpresence of several phases.

INTERNAL TINsample


Intr

om

(T)

m(B

)(

B,T

)P

ITN

b?

…

Samples: courtesy of A. Den Ouden & S. Wessel, UTwenteMicrograph:courtesy of Carlo Ferdeghini, CNR-INFM LAMIA

POWDER-in-TUBEsamples

Critical current measurements show high values of Jc for this kind of

Nb3Sn wires..but, unfortunately, all the samples measured up-to-now

show instabilities at low fields.

M. Greco, CARE05

-1.5

-1

-0.5

0

0.5

1

1.5

-4 -3 -2 -1 0 1 2 3 4

m (

em

u)

B (T)

-1.5

-1

-0.5

0

0.5

1

1.5

-4 -3 -2 -1 0 1 2 3 4

m (

em

u)

B (T)

-1.5

-1

-0.5

0

0.5

1

1.5

-4 -3 -2 -1 0 1 2 3 4

m (

em

u)

B(T)

Intr

om

(T)

m(B

)(

B,T

)P

ITN

b?

…

Powder-in-Tube sample

-1.5

-1

-0.5

0

0.5

1

1.5

-4 -3 -2 -1 0 1 2 3 4

m (

em

u)

B (T)

-1.5

-1

-0.5

0

0.5

1

1.5

-4 -3 -2 -1 0 1 2 3 4

m (

em

u)

B (T)

-1.5

-1

-0.5

0

0.5

1

1.5

-4 -3 -2 -1 0 1 2 3 4

m (

em

u)

B(T)

4.5 K 6 K 7 K

8 K 9 K 10 K

M. Greco, CARE05

Intr

om

(T)

m(B

)(

B,T

)P

ITN

b?

…

POWDER-in-TUBE sample

-1.5

-1

-0.5

0

0.5

1

1.5

-4 -3 -2 -1 0 1 2 3 4

1st time2nd time

m (

em

u)

B(T)

T=4.5 K, parallel field squid measurement

-1.5

-1

-0.5

0

0.5

1

1.5

-4 -3 -2 -1 0 1 2 3 4

1st time2nd time

m (

em

u)

B (T)

4.5 K

8 K

Reliability of repeated measurements in parallel field

with SQUID


Intr

om

(T)

m(B

)(

B,T

)sam

ple

sN

b?

…

Second phase:

• Measurements in parallel to the critical current cross-check program:

cross-check “different” results, if any of CEA, TWENTE and INFN-Milano

evaluation of wire degradation why flux jumps?


Intr

om

(T)

m(B

)(

B,T

)w

ire d

eg

rN

b?

…

B //B

Courtesy of Thierry Boutboul, CERN


Intr

om

(T)

m(B

)(

B,T

)w

ire d

eg

r.N

b?

…

B //B

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

-4 -2 0 2 4 6 8

virgindeformed

m (

em

u)

B(T)

10 K, parallel field

-1.5

-1

-0.5

0

0.5

1

1.5

-4 -2 0 2 4 6 8 10

virgindeformed

m (

em

u)

B(T)

4.5 K, transverse field

First results..


-0.0030

-0.0025

-0.0020

-0.0015

-0.0010

-0.0005

0.0000

0.0005

4 6 8 10 12 14 16 18 20

ma

gn

etic

mo

me

nt

(em

u)

T (K)

Tc Nb

3Sn=17.4 KT

c Nb

3Sn=17.4 K

Tc Nb=9.2 K

Nb3Sn shield: 0.00146 emu


m=0BaV

m=3*10-3 emu=3.77*10-12 Wb m1emu=4 10-10 Wb m

Ba=10 G

VshieldedNb=3.77 mm3

VshieldedNb3Sn=1.83 mm3

Nb3Sn=44m

VNb3Sn=0.98 mm3

Nb=65 m

There is a large amount of Nb in the conductor

Intr

om

(T)

m(B

)(

B,T

)P

ITN

b?

…

Why flux-jumps?

Parallel field

M. Greco, CARE05

Nb=65 m, Nb3Sn=44m

Enquire the role of Nb in the conductor

Intr

om

(T)

m(B

)(

B,T

)P

ITN

b?

…

B is the Nb3Sn area, corresponding to =50 m

M. Greco, CARE05

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

-3 -2 -1 0 1 2 3

ma

gn

etic

mo

me

nt

(em

u)

B (T)

VSM meas at 6.6 K

Is this a single flux-jump or rather the transition of the pure Nb phase? May this phase quench at 0.7 T?

Intr

om

(T)

m(B

)(

B,T

)P

ITN

b?

…

M. Greco, CARE05

According to this extrapolation, at 4.2 K we can have strong effects on magnetization due to this dirty Nb phase

0

2

4

6

8

10

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Tc(K

)B (T)

ac measurements in normal field

Intr

om

(T)

m(B

)(

B,T

)P

ITN

b?

Ic

M. Greco, CARE05

Intr

om

(T)

m(B

)(

B,T

)P

ITN

b?

…

M(B) on a not-reacted PIT sample in transverse field

-1.2

-0.8

-0.4

0

0.4

0.8

1.2

-0.4 -0.2 0 0.2 0.4

Hc2 not reachedHc2 reached

m (

em

u)

B(T)

Flux jumps…M. Greco, INFN-Genova/ CARE05, CERN November 23, 2005

Intr

om

(T)

m(B

)(

B,T

)P

ITN

b?

…

Magnetization measurements are a powerful tool

correlation with Jc meas

study of degradation

flux jumps

[..the presence of instabilities at low field is a strong limitation of application of Nb3Sn..

Modelization with FEM is in progress

No concluding word, for sure, but a warning on the importance of Nb in PIT Nb3Sn wires.]

is aimed at the development of a large-aperture

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