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20-24 October 220-24 October 2003003 Superconducting Magnet

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CERNSlide Slide 11/14/14

[email protected] [email protected] [email protected]@lbl.gov

Fabrication and Performance of Nb3Sn Fabrication and Performance of Nb3Sn Rutherford-type Cable with Cu Added Rutherford-type Cable with Cu Added

as a Separate Componentas a Separate Component

1818thth Conference on Magnet Technology Conference on Magnet Technology October 20 - 24, 2003October 20 - 24, 2003

Mirco CoccoliMirco Coccoli


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OutlineOutline

• IntroductionIntroduction

• Mixed-strand Cable Manufacturing and TestingMixed-strand Cable Manufacturing and Testing

• MC Power Losses MeasurementMC Power Losses Measurement

• A more general approach: Copper Added as a A more general approach: Copper Added as a Separate Component Separate Component

• Quench Propagation Performance SimulatedQuench Propagation Performance Simulated

• ConclusionsConclusions


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IntroductionIntroduction

• Foreseeing future Hadron Colliders, such as a 35km Foreseeing future Hadron Colliders, such as a 35km radius VLHC, it is desirable to investigate low cost radius VLHC, it is desirable to investigate low cost (conductor) solutions(conductor) solutions

• From the stand point of overall conductor cost, it is From the stand point of overall conductor cost, it is desirable to minimize the amount of copper that is desirable to minimize the amount of copper that is co-processed with the superconductor during strand co-processed with the superconductor during strand fabrication.fabrication.

• A possible solution is to add a copper fraction at A possible solution is to add a copper fraction at final, ie cabling stagefinal, ie cabling stage


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MC ManufacturingMC Manufacturing

• Two Mixed-strand Cables (MC) have been fabricated, winded in Two Mixed-strand Cables (MC) have been fabricated, winded in coils and testedcoils and tested

• The first difficulty has been the matching of the elongation between The first difficulty has been the matching of the elongation between the two types of strand, resulting in a mechanically instable cable the two types of strand, resulting in a mechanically instable cable (popped strands) (popped strands)


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MC Electrodynamic StudyMC Electrodynamic Study

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- Less eddy current loops - Less eddy current loops Smaller power loss Smaller power loss

- This feature has been measured (- This feature has been measured (M. D. Sumption et al, “AC Loss of M. D. Sumption et al, “AC Loss of Nb3Sn-based Rutherford Cables with Internally and Externally Added Nb3Sn-based Rutherford Cables with Internally and Externally Added Cu” ASC02) Cu” ASC02) on the tested cable and in agreement with the formulaon the tested cable and in agreement with the formula

NNssNNs,scs,sc


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Mixed Strand Test in SMTF (1)Mixed Strand Test in SMTF (1)

• The mechanical problem noticed during the cable The mechanical problem noticed during the cable fabrication have been shown by the tests performed in the fabrication have been shown by the tests performed in the Subscale Magnet Test Facility (SMTF) at Berkeley LabSubscale Magnet Test Facility (SMTF) at Berkeley Lab

• Two coils have been wounded out of Mixed Strand cablesTwo coils have been wounded out of Mixed Strand cables– Simple mixed strand– Mixed strand cable with SS core for mechanical stability

• Results of the Power tests have not been satisfactory (40% Results of the Power tests have not been satisfactory (40% and 70% of ss limit) leading to the conclusion that a good and 70% of ss limit) leading to the conclusion that a good compaction in these coils is too difficult to achievecompaction in these coils is too difficult to achieve


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Mixed Strand Test in SMTF (2)Mixed Strand Test in SMTF (2)

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ench

/Iss

• Short Sample Short Sample limit reached limit reached in Nb3Sn coilin Nb3Sn coil

• MC 1 reached MC 1 reached ~40% ss~40% ss

• MC 2 reached MC 2 reached ~70% ss~70% ss

• New SolutionNew Solution


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Copper Added as a Separate Copper Added as a Separate ComponentComponent

• Add the copper as a coreAdd the copper as a core– Pure copper cored poor quality– SS-Cu strip assembled in a “sandwich stile” ss-cu-ss

– Most likely alternative: cu-ss-cu good mechanical stability

Ready a coil Ready a coil

to be tested in SMTFto be tested in SMTF

Ready a coil Ready a coil

to be tested in SMTFto be tested in SMTF


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Quench Speed Simulations: Quench Speed Simulations: MC vs TradMC vs Trad

• Copper Added Copper Added separately as a core separately as a core means no advantage for means no advantage for the power losses (~)the power losses (~)

• Protection Protection

10 times faster quench10 times faster quench

• Subject to verification Subject to verification in magnet tests (LBNL)in magnet tests (LBNL)

• No quench heaters in No quench heaters in Future Accel Magnets?Future Accel Magnets?

1

10

100

1000

65% 70% 75% 80% 85% 90%Imag/Iss

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nch

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Mixed Strand Baseline


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Quench Speed Simulations: Quench Speed Simulations: GelGel

• Two “wires” modelTwo “wires” model• Simulated the Simulated the

dependence from the dependence from the electrical conductance electrical conductance between the sc strand between the sc strand and the cu stripand the cu strip

• Quench speeds in the Quench speeds in the 1km range1km range

• To be measured in a To be measured in a test…test…

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200

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65% 75% 85%

Gel 200 SC-RRR40 Gel 100 SC-RRR40 Gel 10 SC-RRR40


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Quench Speed Simulations: Quench Speed Simulations: added copper RRRadded copper RRR

• Added copper RRR Added copper RRR effect on quench speedeffect on quench speed

• Small effect Small effect one one degree of freedom added degree of freedom added to the cable design to the cable design

• High Copper RRR High Copper RRR better heat conduction better heat conduction property property lower peak lower peak temperaturestemperatures

• Simulations and practical Simulations and practical test are foreseentest are foreseen

100

150

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65% 75% 85% Imag/Iss

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nch

(m/s

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Gel 100 Cu-RRR400 Gel 100 Cu-RRR200 Gel 100 Cu-RRR50


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Quench Speed Simulations:Quench Speed Simulations:SC strand RRRSC strand RRR

• Effects of Sc strand RRREffects of Sc strand RRR

• Good for low RRRGood for low RRR

• Of course there is a lower Of course there is a lower limitlimit

• Typical choice ~ 40 Typical choice ~ 40 good enough for quench good enough for quench speedspeed

• Stability must be addressed Stability must be addressed as a next step of this studyas a next step of this study

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65% 75% 85%

Gel 100 SC-RRR40 Gel 100 SC-RRR300 Gel 100 SC-RRR150


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Quench Velocity ModelQuench Velocity Model

• The current redistributes in the nearby copper The current redistributes in the nearby copper passing trough the Gel passing trough the Gel initial hot spot initial hot spot

• The current flows in the pure copper and The current flows in the pure copper and redistributes back to the sc strandredistributes back to the sc strand

Normal Zone Superconducting Zone

GelGel Gel Gel Gel Gel

R (z)

R (z)

I2(z0)

I1(z0)

I2(z)

I1(z)

z


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ConclusionsConclusions

• Several alternative methods for adding Cu to a Rutherford-type Several alternative methods for adding Cu to a Rutherford-type superconducting cable have been investigatedsuperconducting cable have been investigated

• This cabling technique begun as a cost effective approach to This cabling technique begun as a cost effective approach to conductor/cabling in view of future HEP accelerator magnets (VLHC)conductor/cabling in view of future HEP accelerator magnets (VLHC)

• The hypothesis of protection advantages related to quench propagation The hypothesis of protection advantages related to quench propagation velocity is being investigatedvelocity is being investigated

• The thermal conduction channel represented by the separately added The thermal conduction channel represented by the separately added fraction of copper has been measured to be a mean of stability against fraction of copper has been measured to be a mean of stability against “external” heat/energy sources “external” heat/energy sources more test needed more test needed

• Good performance in actual magnet coils has not yet been Good performance in actual magnet coils has not yet been demonstrated (<first half of 2004 at LBNL?)demonstrated (<first half of 2004 at LBNL?)

• Testing in the Subscale Magnet Test Facility is neither a trivial nor an Testing in the Subscale Magnet Test Facility is neither a trivial nor an expensive taskexpensive task


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EndEnd


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