1. CARE steering September 17th 2008 1 NED Status Report Thierry Boutboul (CERN) CERN 17 September 2008

2. CARE steering September 17th 2008 2 CARE/NED JRA Following the 2003 EU peer review, the scope of the NED program was revised to focus on Nb 3 Sn 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).

3. CARE steering September 17th 2008 3 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).

4. CARE steering September 17th 2008 4 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).

5. CARE steering September 17th 2008 5 NED- CD: Status of the SMI contract (1) Following successful R&D step 2 including the cabling trial of a 40- strand Rutherford cable (LBNL), EAS/SMI was awarded the green light to launch the final strand production in fall 2007. Final strand manufacturing (12.7 km of strand overall) is currently underway and the full strand delivery to CERN has taken a few months delay (was expected by summer 2008). A first 1000 m long strand, B228, produced partly at Hanau (EAS) and partly at Enschede (SMI) delivered to CERN in April 2008 into 2 strand lengths (400 m + 600 m). A second strand, B230 (1650 m), was completely produced at Hanau, except final strand drawing to nominal diameter. This strand was delivered to CERN in July 2008 into 4 strand lengths (705 + 314 + 305 + 323 m). Since July 2008, equipment transfer from SMI to EAS was completed.

6. CARE steering September 17th 2008 6 NED- CD: Status of the SMI contract (2) An additional strand of 3.5 km is currently under fabrication at Hanau (final steps). It is expected to be delivered at the beginning of October 2008. The remaining 6.6 km of PIT strand are currently in early steps of production. They are expected to be delivered to CERN into two strand batches by the end of 2008. The strands B228 and B230 (partly) were used to produce at CERN a 14-strand cable (9.7 mm width and 2.2 mm thickness) for Short Model Coil (SMC) program. A 138 m long SMC cable was successfully produced in early September 2008.

7. CARE steering September 17th 2008 7 NED- CD: Status of the Alstom contract (1) During Step 2, Alstom considered two fabrication processes: one with cold work only (Way 1) and the second based on hot extrusion. With cold work method, Alstom produced a strand which included 78 sub-elements (~ 85 µm in diameter). This fabrication was characterized by workability problems (numerous breakages). This strand (binary Nb 3 Sn) showed a non-copper J c ~ 2000 A/mm 2 at 12 T and 4.2 K. The second way (extrusion) used to guarantee fair cohesion between Nb barrier and Cu can, especially important when increasing the number of sub-elements (to decrease filament size down to 50 µm, as requested by specification). Then, B1/63468 strand was produced into a single length of 1300 m, showing a very fair workability. This strand includes 246 sub- elements (~ 54 µm in diameter). In order to further check the strand workability, the B1/63468 was successfully drawn down to 0.8 mm diameter, corresponding to 35 µm in diameter sub-elements!!

8. CARE steering September 17th 2008 8 NED- CD: Status of the Alstom contract (2) However, disappointing critical current density for B1/63468: J c ~1500 A/mm 2 at 12 T and 4.2 K. Many efforts done at CERN to try to optimize heat treatment but without significant success (1600 A/mm 2 maximal value reached). The main reason for this low J c seems to be the big Nb 3 Sn grains observed by means of SEM (poor pinning). Therefore using Ta additions, leading to ternary Nb 3 Sn, should limit grain growth and then enhance J c (up to 40-50 %). Therefore, two billets currently fabricated by Alstom by cold drawing process with Nb-Ta filaments to get ternary Nb 3 Sn phase. Around 1.5 km long and 6 km long strands respectively expected by November and December 2008. Extrusion process continued in parallel (Ta-alloyed Nb 3 Sn). Raw material (especially Nb tubes) already ordered from supplier. 15-20 km of strand expected by March 2009.

9. CARE steering September 17th 2008 9 NED- CD: Planning of final strand delivery Firm Total [km] Delivered [km] 10/08 11/08 12/08 03/09 EAS/SMI12.72.63.5-6.6- Alstom24--1.5615-20

10. CARE steering September 17th 2008 10 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. This strand has 288 filaments (~ 50 µm), 84 h @ 675 o C: J c ~ 2500 A/mm 2. Heat treatment optimization studies at CERN: general trend was to decrease reaction temperature but increase duration to try to decrease Nb 3 Sn grain size. 320 h @ 625 o C: - 12 T and 4.2 K: I c > 1500 A, J c > 2700 A/mm 2, + 10 %!! - 15 T and 4.2 K: I c > 818 A (NED spec.), J c ~ 1500 A/mm 2 - RRR ~ 220 (vs 80 for 84 h @ 675 o C): much better for stability Reasonable cabling degradation of 5-6 % (as compared to 10-13 % for 84 h @ 675 o C).

11. CARE steering September 17th 2008 11 NED- CD: Conductor characterization (2) EAS/SMI B215 wire (continuation) Stringent NED specification fulfilled!! B c2 K = 26.3 T Courtesy of C. Senatore and R. Flukiger (Geneva Univ.)

12. CARE steering September 17th 2008 12 NED- CD: Conductor characterization (3) EAS/SMI B215 wire (end) SEM: Polished and fractured samples examined for standard and modified HT. 675 o C/84 h625 o C/320 h Un-reacted barrier ratio23 % of total filament25 % of total filament Sn content24.2 at. % Sn24.7 at. % Sn Coarse grain ratio~ 30 % of A15 phase Mean fine grain size~ 180 nm~ 160 nm Sample with optimized HT: less reacted Nb 3 Sn but with higher quality: higher Sn content, B c2 K, T c and smaller grain size (160 nm vs 180 nm) coarse grain (~ 1-2 µm)fine grain (~ 200 nm)

13. CARE steering September 17th 2008 13 NED- CD: Conductor characterization (4) EAS/SMI: characterization of final strands B228 strand: Strand diameter: 1.255 mm, Cu/non-Cu = 1.18 When reacted 120 h @ 650 o C, J c ~ 2450-2510 A/mm 2, RRR > 140 Very similar to B215 strand: EAS/SMI able to reproduce nice perf. !! B230 strand: Strand diameter: 1.254 mm, Cu/non-Cu = 1.25 For sake of saving strand length for SMC cable, I c and RRR shortly measured at CERN together with wires extracted from SMC cable. However, according to EAS measurements: J c = 2513 A/mm 2 at 4.2 K and 12 T (650 o C/120 h). If confirmed, indication of smooth technology transfer from SMI to EAS.

14. CARE steering September 17th 2008 14 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)

15. CARE steering September 17th 2008 NED conductor review4 Nov 2008 The aim of the review is twofold Firstly, the NED Nb 3 Sn conductor development program should be reviewed such that the achievements, the main difficulties and the limitations are brought out. Secondly, using the experience of this conductor program, the requirements for new dipoles and quadrupoles and the existing open issues ( eg. stability and stress sensitivity), recommendations for the next steps in Nb 3 Sn conductor development for accelerator magnets at CERN should be formulated. 15

16. CARE steering September 17th 2008 NED conductor review: program4 Nov 2008 1.History of the NED conductor programLuc Oberli 2.Results of the PIT conductor developmentThierry Boutboul 3.Results of the IT conductor developmentLuc Oberli 4.Results of the cable developmentThierry Boutboul 5.Guidelines on stabilityBernardo Bordini 6.Review on stress sensitivityRene Flukiger 7.Dipole conductor needs: examples for Fresca2Glyn Kirby 8.Quadrupole conductor needs: examples for HQ Helene Felice 16

17. CARE steering September 17th 2008 17 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 and cold mass design finished, winding tests with dummy Cu+Nb 3 Sn in progress by RAL-CERN team (with LBNL) Nb 3 Sn cable done (120 m ready: 3 poles). Tender for structure components called. First magnet foreseen to be tested in February 2009 at CERN (Courtesy P. Ferracin, LBNL)

18. CARE steering September 17th 2008 18 Deliverables NED25Final wire production (SMI)PrototypeWP3CERNSeptember 08 NED26Final report on wire characterization (SMI) reportWP3CERNSeptember 08 NED27Final cable production (SMI)PrototypeWP3CERNNovember 08 NED28Final report on cable performances (SMI) reportWP3CERNNovember 08 NED29Final wire production (MSA)PrototypeWP3CERNDecember 08 NED30Final report on wire characterization (MSA) reportWP3CERNDecember 08