davide tommasini nb3sn versus nbti in heii thermomag-07, paris 19 november 2007 typical insulations...

Davide Tommasini Nb3Sn versus NbTi in HeII THERMOMAG-07, Paris 19 November 2007

Typical insulations for Rutherford cablesTypical insulations for Rutherford cables

Heat transfer modelHeat transfer model

Heat flux comparison same operating Heat flux comparison same operating conditions conditions specific operating specific operating conditionsconditionsPotential for enhanced insulation for NbTiPotential for enhanced insulation for NbTi

Porosity checkerPorosity checker

Preliminary resultsPreliminary results

ConclusionsConclusions

NbNb33Sn vs NbTi in HeIISn vs NbTi in HeII


Typical Cable Typical Cable InsulationsInsulations

The first barrier to the removal of The first barrier to the removal of the heat generated in a coil is the the heat generated in a coil is the electrical insulation:electrical insulation:

~100-200 V between adjacent turns~100-200 V between adjacent turns

~5 kV to ground~5 kV to ground

up to 200 MPaup to 200 MPaNb-Ti:Nb-Ti:

All polyimide insulation: semi-All polyimide insulation: semi-permeablepermeable

to He IIto He II

NbNb33Sn (wind & react):Sn (wind & react):mineral fiber cloth wrapping & mineral fiber cloth wrapping &

EpoxyEpoxyresin impregnation: resin impregnation:

impermeable to impermeable to He IIHe II

Courtesy of F. Rondeaux (CEA)


NbTi : all PINbTi : all PI


Nb3Sn : S2 glass Nb3Sn : S2 glass +resin+resin

G.Dambrosio G.Dambrosio & &

D.Chichili D.Chichili


Heat Transfer ModelHeat Transfer Model

No He II reaches the strands No He II reaches the strands

Heat goes through solid Heat goes through solid conduction first, then to He II conduction first, then to He II

R InsulationKapton

R Kapitza Kapt.-He II.

Cab

le, T

c=T

b+T

He

II b

ath,

Tb=

1.9

1) Qa Vs Qb depends on insulation porosity2)Qa & Qb are non linear3)Qb has saturation level

R Kapitza Cu-He II

He II is in direct contact with the strandsHe II is in direct contact with the strands

Heat flux is shared by two parallel paths (Heat flux is shared by two parallel paths (aa & & bb). ).

Nb-Ti (porous insulation)Nb-Ti (porous insulation)

NbNb33Sn (sealed insulation)Sn (sealed insulation)

He I

I ch

an

nels

QQaa:: Solid Conduction

TTbb

TTCC

TTbb

TTCC

QQbb:: Superfluid Conduct.

QQaa

QQbb

QQ

R He IIChannel

Cab

le,

Tc=

Tb+

T

He

II b

ath,

Tb=

1.9

R insulationEp.+G.Fiber

R Kapitza Epoxy.-He II.

Q: Solid Conduction

a

b


Equivalent Thermal Equivalent Thermal ResistancesResistances

Bulk resistance of 0.1 Bulk resistance of 0.1 mm thick Kapton mm thick Kapton [7] ~2 ~2 times times larger than 0.2 mm larger than 0.2 mm thick epoxy+fiberglass thick epoxy+fiberglass [2]

Boundary resistanceBoundary resistance(Kapitza):(Kapitza):Kapton Kapton [8] (& Ep.+F.) (& Ep.+F.) ~6~6times larger than Cu times larger than Cu [9]

HE II channel HE II channel resistance: resistance: --depends depends on insulationon insulationporosity (channel porosity (channel lengthslengthsand cross-areas)and cross-areas)

--is always smaller than is always smaller than Kapton and Kapton and epoxy+fiberglass but is epoxy+fiberglass but is limited by saturationlimited by saturation


Experimental Experimental (B. Baudouy et al (B. Baudouy et al

Cryogenics 39, 921 (1999)

SSC dipole

LHC dipole

SolidConductionSuperfluid

Conduction

Predominance:


Comparison for Operating Comparison for Operating Conditions:Conditions:

SameSame or or SpecificSpecific

1.1. We consider two coils in a He II bath (We consider two coils in a He II bath (TTbb=1.9=1.9) :) :1.1. NbNb33Sn with Sn with sealed sealed insulationinsulation

2.2. Nb-Ti with Nb-Ti with porous porous insulationinsulation

2.2. We impose the We impose the samesame eng-eng-ineering current density ineering current density JJengeng

and operative peak field and operative peak field BB

3.3. We get the temperature margin We get the temperature margin T=TT=Tcc-T-Tbb we we combine it with the heat transfer correlations combine it with the heat transfer correlations and we obtain the corresponding heat fluxand we obtain the corresponding heat flux

2.2. We impose We impose JJ and and BBultult

specificspecific of their of their practical usepractical use


0 0.5 1 1.5 2 2.5 3 3.57

7.5

8

8.5

9

9.5

10

10.5

11

11.5

12

T Nb-Ti [K]

T

Nb 3S

n [K

]Temperature Margin (T=T

c-T

b) Comparison for 9 T Peak Field

J c,en

g [A

/mm

2 ]

0

103

205

307

409

511

613

715

817

919

Temperature Margin Temperature Margin Comparison for Comparison for Same B (9T) Same B (9T)

and Jand Jengeng

Tb=1.9

Cu/ScNb-Ti 1.5Nb3Sn 1


Maximum Heat Flux for Maximum Heat Flux for Same B (9T) and JSame B (9T) and Jengeng

0 500 1000 1500 2000 2500 30000

50

100

150

200

250

300

350

Jeng

[A/mm2]

Q [

W/m

]

IR Quad

LHC MainEnhanced

Bare

Nb3Sn

Cu/ScNb-Ti 1.5Nb3Sn 1

Bare cable asymptotic limit

Nb3 Sn Enhanced

SSC dipole

LHC dipole

SSC dipoleLHC dipoleEnhancedBare cableNb3Sn


Maximum Heat Flux for Maximum Heat Flux for SpecificSpecific ConditionsConditions

0 0.2 0.4 0.6 0.8 10

20

40

60

80

100

120

140

160

180

200

220

J/Jc(T

b,B

ult) [A/mm2]

Q [

W/m

]

Bare

cab

le a

symp

totic lim

it

Nb3 Sn

Enhanced

SSCLHC MainJ/Jc (Tb,Bult)

B= 9 T for NbTiB= 9 T for NbTi

B= 13.5 T for Nb3SnB= 13.5 T for Nb3Sn


it corresponds to ~ 220 mW/m per it corresponds to ~ 220 mW/m per cable cable

it corresponds to ~830 mW/m it corresponds to ~830 mW/m per cable per cable


Enhanced porosityEnhanced porosity


Porosity checker/1Porosity checker/1

Air enters the stack of cable longitudinally (A) and can Air enters the stack of cable longitudinally (A) and can exit longitudinally (C), without crossing the insulation exit longitudinally (C), without crossing the insulation or radially (B) crossing the insulation. or radially (B) crossing the insulation.

Insulation porosity is evaluated from the Insulation porosity is evaluated from the comparison between radial and longitudinalcomparison between radial and longitudinalflowflow

A C

BB

Flow out (B)

Flow in (A)

Flow out (C)


Porosity checker/2Porosity checker/2


Tests Results/1Tests Results/1

Vertical compression 10 MPa


Tests Results/2Tests Results/2


Heat transfer testsHeat transfer testsPower per cable edge (normalized to LHC inner layer ~ 2 mm) per meter of length

1.8

1.85

1.9

1.95

2

2.05

2.1

2.15

2.2

0 200 400 600 800 1000 1200 1400

Power [mW]

Tem

per

ature

[K

]

Enhanced (measurement D.Richter, to be published)LHC (measurement B.Baudouy Cryogenics 39, 1999)

SSC (measurement B.Baudouy Cryogenics 39, 1999)


ConclusionsConclusions For same For same BB and and JJengeng, Nb, Nb33Sn coils made by Rutherford Sn coils made by Rutherford

cables can draw one order of magnitude more heat than cables can draw one order of magnitude more heat than typical Nb-Ti coils typical Nb-Ti coils

For the same margin to critical surface (specific For the same margin to critical surface (specific operating conditions), Nboperating conditions), Nb33Sn coils made by Rutherford Sn coils made by Rutherford cables can draw three times more heat than typical LHC cables can draw three times more heat than typical LHC Nb-Ti coils Nb-Ti coils

……however…however…there is a large potential to increase the dimension of there is a large potential to increase the dimension of the cooling channels thus moving their saturation at the cooling channels thus moving their saturation at

higher heat fluxeshigher heat fluxes

The use of this potential in HeII provides a The use of this potential in HeII provides a spectacular increase of heat evacuation spectacular increase of heat evacuation

capabilities of NbTi coils competing/exceeding capabilities of NbTi coils competing/exceeding NbNb33Sn @ fields below 9 TSn @ fields below 9 T


ReferencesReferences

1. C. Meuris, B. Baudouy, D. Leroy, B. Slezess, Heat transfer in electrical insulation of LHC cables cooled with superfluid Helium, Cryogenics 39, 921 (1999)

2. L. Imbasciati et al.,Thermo-mechanical Characterization of Insulated and Epoxy-Impregnated Nb3Sn composites, IEEE Trans. on Appl. Supercond., Vol. 13, Issue 2, 1788 (2003)

3. D.S. Matsumoto, C.L. Reynolds Jr., A.C. Anderson, Thermal Boundary Resistance at Metal Epoxy Interfaces, Phys. Rev. B, Vol. 16 n.8, 15 Oct. 1977.

4. F. Rondeaux, P. Bredy, J.M. Rey, Thermal Conductivity Measurements of Epoxy Systems at Low Temperatures, Adv. Cryo. Eng. 48A (Materials), 197 (2002)

5. J. Gorter, J. H. Mellink, On the Irreversible Processes in Liquid Helium II, Physica 15, 285 (1949)

6. V. Arp, Heat transport through Helium II, Cryogenics 10, 96 (1970)7. J. Lawrence, A.B. Paterl, J.G. Brisson, The Thermal Conductivity of Kapton HN between

0.5 and 5 K, Cryogenics 40, 203 (2000)8. B. Baudouy, Kapitza Resistance and Thermal Conductivity of Kapton in Superfluid Helium,

Cryogenics 43, 667 (2003) 9. A. Kashani, S.W. Van Sciver, Kapitza Conductance of Technical Copper with Several

Different Surface Preparations, Cryogenics 25, 238 (1985)10. E. Todesco, J.P. Koutchouk, Scaling Laws for * in the LHC Interaction Regions, CARE

Workshop LUMI-06, 17th October 2006, Valencia, Spain.11. N. Kimura et al., Heat Transfer from Insulated Rutherford Type Cables Immersed in

Pressurized He II, Adv. Cryo. Eng. 43

davide tommasini nb3sn versus nbti in heii thermomag-07, paris 19 november 2007 typical insulations...

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