ned status report

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NED Status Report

Thierry Boutboul(CERN)

LPNHE9 April 2008

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CARE/NED JRA

•Following the 2003 EU peer review, the scope of the NED

program was revised to focus on Nb3Sn conductor and

insulation development. •The NED JRA has been articulated around four Work Packages

and one Working Group

1 Management & Communication (M&C),

2 Thermal Studies and Quench Protection (TSQP),

3 Conductor Development (CD),

4 Insulation Development and Implementation (IDI),

5 Magnet Design and Optimization (MDO) Working

Group. • It involves 7 institutes (8 laboratories)

• Total budget: ~2 M€; EU grant: 979 k€ (over ~3 years).

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NED/TSQP Work Package

• The Thermal Studies part of the TSQP Work Package was completed with the publication of the final report in December 2007 (CARE-Report-2007-033-NED)(CEA and WUT; Task Leader: B. Baudouy, CEA)

• The quench computation task was already completed before

(INFN-Mi; Task Leader: G. Volpini).

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NED-CD Work Package

• The CD Work Package includes two main Tasks – conductor development

two industrial contracts under CERN supervision: Alstom/MSA (F) and EAS/SMI (NL/D); Task Leader: L. Oberli

– conductor characterization (CEA, INFN-Ge, INFN-Mi, and TEU; Task Leader: A. den Ouden, TEU)

• It is the core of the Program and absorbs ~70% of the EU funding.

• It is complemented by two extensions of scope – FE wire model development to simulate cabling effects

(INFN-Ge & CERN; Task Leader: S. Farinon, INFN-Ge), – heat treatment study

(CERN; Task Leader: C. Scheuerlein).

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NED-CD: Status of the SMI contract

• EAS/SMI completed the step 2 with the successful cabling trial of a 40-strand Rutherford cable performed at LBNL in summer 2007, for which a critical current degradation of 4-8 % was measured at both CERN and Twente University for extracted strands.

• EAS/SMI was then awarded the green light to launch the final strand production.

• Final strand manufacturing (12.7 km of strand) is currently underway under the responsibility of EAS with part of process done at Hanau (EAS) and part at Enschede (SMI).

• The total strand is fabricated from 4 billets. The first length (~ 3 Km) expected to be completed by end of May 2008 (3 months of delay)

• The 3 remaining strand amounts expected by summer 2008.

• Part of the final strand (~ 1 length) will be used to produce at CERN a 14-strand cable for Short Model Coil (SMC) program.

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NED-CD: Status of the Alstom contract (1)

• During Step 2, Alstom produced a wire, B1/14508. This strand included 78 sub-elements and was processed by means of cold drawing only. B1/14508 strand was characterized by workability problems (numerous breakages), like B1/21204 wire (cold drawing as well). The best critical current densities obtained for B1/14508 are ~ 1900 A/mm2 (1.25 mm) and ~ 2100 A/mm2 (0.83 mm).

• Then, to ensure better workability, emphasis put on another process, based on hot extrusion to guarantee a fair cohesion between Nb barrier and copper can.

• Two final billets assembled with this sub-element material:1. One billet with 78 sub-elements, like previous strands

manufactured (~ 85 µm at nominal Φ)2. One billet with 246 sub-elements corresponding to ~ 50 µm

final sub-element diameter. First billet fulfilling NED specification.

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• Drawing of sub-elements and final billets were done by means of a new set of drawing dies, more suitable to Nb3Sn process. The final wires were achieved in January 2008.

• Drawing very successful:1. B1/63468 strand: 246 sub-elements, 1308 m in a lone

length!!2. B1/20124 strand: 78 sub-elements, 826 m + 402 m• In addition, sub-elements nicely shaped, as shown by the

micrograph:

B1/63468 cross-section

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• Drawing successfully 246 sub-elements very challenging!! As a comparison, the American company OST, after many years of development, is currently drawing kilometric strand lengths of up to 108 sub-elements, corresponding to ~ 80 µm final element diameter at NED strand nominal diameter (1.25 mm).

• B1/63468 strand: - 246 sub-elements - Strand diameter = 1.26 mm - Cu/non-Cu = 1.08 - Jcnon-Cu(12 T, 4.2 K) ~ 1450 A/mm2 (Alstom, 50 h @ 660 oC)• B1/20124 strand: 78 sub-elements, Φ1.26 mm, Cu/non-Cu =

1.53, Jcnon-Cu similar to B1/63468.• Other HT schedules tried without big success for time being,

max. Jc achieved: ~ 1600 A/mm2. SEM examinations at CERN showed Sn content at stochiometry (~ 25 at. % Sn) but big Nb3Sn grains, barrier not fully reacted (more details given in Characterization part).

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• HT optimization underway to react more barrier and to try reducing grain size.

• Relatively low Jc partly due to binary Nb3Sn compound. Ti or Ta additions (limit grain growth) should enhance Jc by ~ 50 %.

• Indeed solutions using Ta are currently implemented to achieve the Step 2. Alstom seems to be close to success although ~ 6 months are needed to produce strands.

• The final strand production would be launched in parallel to Step 2 completion and could not be completed by end of 2008. It would require a delay of several months.

• Meeting with Alstom people yesterday afternoon at CERN to discuss NED program completion. They will send to CERN very shortly a letter to express their commitment to finish the final strand production.

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NED-CD: Conductor characterization (1)

EAS/SMI B215 wire

• B215 is the successful prototype wire developed by SMI during Step 2. According to its design, the final strand is currently produced.

• 288 filaments (~ 50 µm), 84 h @ 675 oC: Jc ~ 2500 A/mm2, RRR ~ 80

• Heat treatment optimization studies at CERN: general trend is to decrease reaction temperature but increase duration to try to decrease Nb3Sn grain size.

• 320 h @ 625 oC: - Ic = 1496 A @ 12 T and 4.2 K (gain of ~ 100 A vs 84 h @ 675

oC) - Jc = 2665 A/mm2 !!! (gain of ~ 6 % !) - RRR ~ 220 (vs 80 for 84 h @ 675 oC): much better for stability• Impact of 320 h @ 625 oC HT schedule on cabling degradation

(both Ic and RRR) to be checked soon.

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Alstom B1/63468 strand

• Jc ~ 1440 A/mm2 for 50 h @ 660 oC (reacted and tested at Alstom)

• Several other HT schedules tried at CERN:50 h @ 645 oC, 25 h @ 660 oC, 50 h @ 620 oC and Ic measured at

CERN

• At Geneva University, Ic measured as function of longitudinal strain (to check stress impact).

• Jc measured at CERN or Geneva never exceeded 1590 A/mm2 (12 T).

• SEM/EDS examinations (CERN) showed that the Sn content is nearly stochiometric (~ 25 at. % Sn) and there is no Sn leak into copper (expected from high RRR values).

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• SEM examinations (CERN):1. The barrier not fully reacted 2. Numerous big grains (~ 300-

400 nm) Potential for more Jc even for low temperature

reaction (50h @ 620 oC ): bad for Jc.

B1/63468 micrograph (25h @ 660oC)

B1/63468 micrograph (50h @ 645oC)

• Currently in CERN oven: 200 h @ 660 oC. The goal: try to completely react the barrier

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NED-IDI Work Package (1)

• The Insulation Development and Implementation Work Package includes two main Tasks

– studies on “conventional” insulation systems relying on ceramic or glass fiber tape and vacuum-impregnation by epoxy resin (CCLRC/RAL; Task Leader: S. Canfer)

Completed with a final report in March 2007

– studies on “innovative” insulation systems relying on pre- impregnated fiber tapes and eliminating the need for a vacuum impregnation (CEA; Task Leader: F. Rondeaux).

Completed with a final report in December 2007(CARE-Report-2007-037-NED)

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Next Step: Short Model Coil SMC

• Participant funding only (formally outside FP6-CARE-NED )

• CCLRC/RAL, CEA and CERN have agreed to manufacture and test a series of LBNL-type Short Model Coils wound from NED-sub-cables so as to investigate – cable and insulation performances in real coil environment, – design limits for transverse and longitudinal loads.

• Coil design finished, cold mass design being finalized, winding tests with dummy in progress by RAL-CERN team (interactions with LBNL). Waiting for Nb3Sn strand from NED.First magnet foreseen to be tested in Sept-Oct at CERN

(Courtesy P. Ferracin, LBNL)

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Deliverables

NED 24 Final report on Heat Transfer Measurements

Report WP2 CEA-WUT

done Dec 07

NED 30 Report on innovative insulation report WP4 CEA done Dec 07

NED 25 Final wire production Prototype WP3 CERN Late 08

NED 26 Final report on wire characterization report WP3 CERN Late 08

NED 27 Final cable production Prototype WP3 CERN Late 08

NED 28 Final report on cable performances report WP3 CERN Late 08

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Publications in 2007

1. S. Farinon, T. Boutboul, A. Devred, D. Leroy, L. Oberli,NB3SN wire layout optimization to reduce cabling degradationMT20

2. T. Boutboul, A. den Ouden, A. Devred, P. Fabbricatore4, M. Greco, D. Leroy, L. Oberli, D. Pedrini and G. Volpini,Nb3Sn conductor development and characterization for NEDEUCAS 2007

3. M. Di Michiel, C. Scheuerlein,Phase transformations during the reaction heat treatment of powder-in-tube Nb3Sn superconductorsSupercond. Sci. Technol. 20, (2007) L55-L58

4. C. Scheuerlein, M. Di Michiel, A. Haibel,On the formation of voids in Nb3Sn superconductors", Appl. Phys. Lett., 90, 132510, (2007)

5. Polinski J., Canfer S., Ellwood G., Baudouy B.,Low Temperature Heat Transfer Properties of Conventional Electrical Insulation For The Next European Dipole.CEC-ICMC 2007

ned status report

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