NED Status Report Arnaud Devred CEA/DSM/DAPNIA/SACM & CERN/AT/MAS CARE Steering Committee Meeting LPNHE 11 April 2006

CARE/NED JRA The Activity is 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).

Management & Communication (1/2) Steering Committee meetings – 23 February at CERN  1 June at CIEMAT HHH/AMT meeting – WAMDO: 3-6 April at CERN ESAC meeting  next fall, at the end of Step 2 of Conductor Development.

Management & Communication (2/2) 4 papers at ICEC 21/ICMC '06 (17–21 July, Prague, Czech Republic) – NED cryostat – Nano- and micro-hardness measurements – 2 papers on conventional insulation 6 papers at ASC (27 August–1 September, Seattle, WA) – Overview – Heat-transfer measurements – Quench computation on slot design – Wire FE model – NED reference design V2 – WGMDO comparison

NED/TSQP Work Package The TSQ Work Package includes two main Tasks – development and operation of a test facility to measure heat transfer to helium through Nb 3 Sn conductor insulation (CEA and WUT; Task Leader: B. Baudouy, CEA), – quench protection computation (INFN-Mi; Task Leader: G. Volpini).

Heat Transfer Measurement Task (1/2) The first part of the Task was to design and build a new He-II, double- bath cryostat. The cryostat was built by Kriosystem in Poland under the supervision of Wroclaw University according to specifications written by CEA. The cryostat was delivered to CEA on 20 September 2005 and has been rprepared for commissioning. Miscellaneous views of NED cryostat (Courtesy M. Chorowski, WUT)

Heat Transfer Measurement Task (2/2) The first cooldown was carried out on 14 February 2006 and it took ~7 hours to reach 1.5 K in the He II pressurized bath. First cooldown of NED cryostat at CEA (Courtesy B. Baudouy, CEA) The test was suspended due to a problem with a LHe level sensor that is a critical element of the control system. A new sensor has been ordered and the test is expected to resume in June Extensive measurement campaigns will follow.

NED Quench Computation Task INFN-Mi has carried a detailed analysis of the thermal and electrical behaviors of NED-like magnets during a quench. The computations were focused on the Reference 88-mm-aperture, cos , layer design and show that, magnets up to 10 m long can be operated safely, thereby justifying the choice of conductor parameters made early on. The Task is completed and a final report has been issued. Quench simulations for 10-m-long, 88-mm-aperture, cos , layer design (Courtesy M. Sorbi, INFN-Mi)

Complementary NED/TSQP Efforts Since the start of NED, two complementary efforts have been launched at CERN – Analysis of available LHC magnet test data at high ramp rate to determine how well the heat-transfer measurements at CEA correlate with actual magnet data, – Review of magnet cooling modes to estimate, on the cryogenics system point of view, what are the limitations on power extraction and to provide guidance on how to improve cooling of magnet coils (preliminary conclusions indicates that NED-like magnets may have to be operated in superfluid helium).

NED/CD Work Package The CD Work Package includes three main Tasks – conductor development (under CERN supervision; Task Leader: L. Oberli), – conductor characterization (CEA, INFN-Ge, INFN-Mi, and TEU; Task Leader: A. den Ouden, TEU), – FE wire model (to simulate cabling effects) (CERN and INFN-Mi; Task Leader: S. Farinon, INFN-Mi). It is the core of the Program and absorbs about 70% of the EU- allocated funding.

Conductor Development (1/2) Conductor specifications were derived from preliminary design studies carried out in at CERN; salient wire parameters are – diameter mm, – eff. filament diameter< 50  m, – Cu-to-non-Cu ratio1.25 ± 0.10, – filament twist pitch 30 mm, – non-Cu J C 1500 A/mm K & 15 T, – minimum critical current1636 A at 12 T, 818 A at 15 T, – N-value> 30 at 4.2 K and 15 T, – RRR (after heat treatment)> 200. (It is also requested that the billet weight be higher than 50 kg.)

Conductor Development (2/2) Based on these specifications, a call for tender was issued by CERN in June 2004 and two contracts (funded by CARE/NED) were awarded in November to 2004 to – SMI in The Netherlands (“Powder in Tube” Process) for 290 m of 40-strand cable, – Alstom/MSA in France (“Enhanced Internal Tin” process) for 580 m of 40-strand cable. After discussion with CERN, the two companies have agreed to work out their development program into two successive RD Steps (referred to as STEP 1 and STEP 2) followed by final cable production. Note that, since then, CERN has awarded in April 2005 a third contract for 580 m of 40-strand cable to Outokumpu OY (which is internally funded by CERN).

SMI Status (1/6) SMI STEP 1 was devoted to iterations on an existing 1-mm-ø strand design with 192 (NbTa) 3 Sn filaments. Several billets were produced with different powder compositions (B179 & B201) or outer Ta tubes around the Nb tubes to act as on anti- diffusion barrier. The best critical current results were obtained on B179 Diameter: 1.00 mm Filaments: 192 (50  m) Cu-to-non-Cu ratio = 0.73 I C = 1105 A at 12T (with 84 h at 675 °C) Non/Cu J C = 2410 A/mm 2 at 12 T

SMI Status (2/6) Following STEP 1, it was decided to produce another billet (B207), aimed at NED diameter, but keeping the same NbTa tubes and the same powder composition as for B179. The resulting wire is pretty good in terms of overall critical current but Cu-to-no-Cu ratio and critical current density are below expectations. Diameter: mm Filaments: 288 (50  m) Cu-to-non-Cu ratio = I C = 1313 A at 12T (with 84 h at 675 °C) Non/Cu J C = 2077 A/mm 2 at 12 T

SMI Status (3/6) The critical current of wire B207 has been fully characterized at INFN- Mi (7-13 T) and University of Geneva (15-19 T). Non-Cu J C = 2077 A/mm 2 at 12 T = 1118 A/mm 2 at 15 T INFN-Mi also performed stability current measurement, which did not show any instability up to 1800 A (14 to 18 mT/s).

SMI Status (4/6) INF-Mi also performed measurements on 2 deformed samples (0.35- mm deformation) yielding ~15-17% I C degradation. (Courtesy G. Volpini, INFN-Mi)

ø Nb = 55  m ø Nb3Sn = 44 mm Shielded volumes derived from m(T) 4.5 K, transverse field SMI Status (5/6) Magnetization measurements performed at INFN/Ge have confirmed the expected filament outer diameter. (Courtesy M. Greco, INFN-Ge)

SMI Status (6/6) The next step agreed upon by CERN is to produce a 10-kg billet similar to B207 (which was only 3 kg) with proper Cu-to-non-Cu ratio and a proper powder preparation (aimed at achieving a non-Cu critical current density greater than 2500 A/mm 2 at 4.2 K and 12 T)  should be ready by mid-June.

Alstom/MSA Status Alstom/MSA is developing the so-called enhanced internal-tin process based on a double-stacking billet design and cold drawing. STEP 1 has been devoted on optimizing billet design and assembly to obtain good workability. Workability problems have appeared more severe than anticipated and require a systematic study of main design and assembly parameters. Good progress, no show stoppers.

NED Conductor Characterization NED conductors are characterized by performing critical current and magnetization measurements. Critical current measurements represent a real challenge, given the expected performances (e.g., ~1600 A at 4.2 K and 12 T on a 1.25-mm-Ø wire, compared to ~200 A presently achieved on 0.8-mm-Ø ITER wires). To validate sample preparation and measurement processes, CEA, INFN-Mi and Twente University have carried out an extensive cross-calibration program and have now achieved a reasonable convergence.

FE Wire Model INFN-Ge has been working on a mechanical FE model (based on ANSYS ® ) to simulate the effects of cabling on un-reacted, Nb-Sn wires. To feed the model, CERN has supervised and/or carried out a series of nano-indentation and micro-hardness measurements to determine the mechanical properties of the materials making up the wire in the cold-work state where they are prior to cabling. Micro-hardness measurements on a X-cut of internal tin wire (courtesy C. Scheuerlein, CERN) FE model of internal tin wire (courtesy S. Farinon, INFN-Ge

NED/IDI Work Package (1/2) The IDI 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), – studies on “innovative” insulation systems relying on pre-impregnated fiber tapes and eliminating the need for a vacuum impregnation (CEA; Task Leader: F. Rondeaux).

NED/IDI Work Package (2/2) CCLRC/RAL is evaluating a polyimide-sized glass fiber tape that is able to sustain the required Nb 3 Sn heat treatment without degradation and which seems a promising solution to conventional insulation. The Innovative Insulation Task is built upon an ongoing R&D program at CEA which has demonstrated the feasibility of such a system, but which has been on hold for a year due to a lack of human resources; the program has now restarted and is gearing up to speed.

NED/MDO Working Group (1/4) The MDO Working Group is made up of representatives from CCLRC, CEA, CERN and CIEMAT (Chairman: F. Toral, CIEMAT). Its main charge is to address the following questions – How far can we push the conventional, cos , layer design in the aperture-central-field parameter space (especially when relying on strain-sensitive conductors)? – What are the most efficient alternatives, in terms of performance, manufacturability and cost? A number of magnetic configurations have been selected and are presently being evaluated.

NED/MDO Working Group (2/4) Common coil (CIEMAT) Ellipse-type (CEA/Saclay) Double helix (RAL) Cos  layer (CERN & RAL) Motor-type (CIEMAT) Cos  slot (CERN) (Courtesy F. Toral, CIEMAT)

NED/MDO Working Group (3/4) (Courtesy N. Schwerg, CERN) CERN has pursued the electromagnetic optimization of the baseline, 88-mm-aperture, cos  layer design with respect to – conductor geometry, – iron shape (to reduce saturation effects), – ferromagnetic shims (to compensate magnetization effects).

NED/MDO Working Group (4/4) (Courtesy P. Loveridge, CCLRC/RAL) CCLRC/RAL is developing a comprehensive (ANSYS ® -based) mechanical model of the baseline, 88-mm-aperture, cos  layer design throughout the various steps of manufacturing, cooldown and energization. STAINLESS- STEEL COLLAR LAMINATION LOWER COIL UPPER COIL IRON YOKE STAINLESS-STEEL SHRINKING CYLINDER

INFN/CANDIA Project (1/2) INFN has approved on 30 November 2004 a research project called CANDIA (Italian acronym for CAvi in Niobio- stagno per DIpoli ad Alto campo or niobium-tin cables for high field dipoles), involving teams from INFN-Frascati (LNF), INFN-Genova and INFN-Milano (LASA). The main goal of CANDIA is the development of a Nb 3 Sn conductor according to NED-like specifications. A call for tender was issued in the Fall of 2005 and a contract for the manufacture of 1500 m of wires was awarded on 15 December 2005 to Outokumpu Copper Superconductor Italy (OCSI).

INFN/CANDIA Project (2/2) The chosen technology is Internal Tin process. The expected delivery is Fall of Of course, close ties are maintained between CANDIA and NED.

What’s next? (1/2) 10 European Group Leaders/Managers and 2 US-LARP Managers have cosigned a contribution to the CERN Council Strategy Group This document outlines a strategy for European superconducting accelerator magnet R&D aimed at LHC luminosity upgrade, promoting the manufacturing of NED (in complement to LARP) and some well-focused R&D on cycled NbTi accelerator magnets.

What’s next? (2/2) The document will be extended to outline a world-wide strategy (with US and Japanese partners)  should be ready by mid-June. The strategy document will serve as a basis for a letter of intent to the European Strategy Group on Accelerator R&D (ESGARD) for FP7 proposals (due on 28 April 2006).

Letter of Intent for FP7 Transnational Access Test facilities for conductor characterization. Topics for JRA – NED manufacturing and test, – focused R&D on cycled NbTi accelerator magnets (conductor, supercritical helium study, quench protection study, extended test of FAIR-type prototype). Strategy on one or two JRA’s to be determined when the details of the call for proposal will be known.

Conclusion All NED Tasks are making good progress. The Activity will come to an end at the end of the year (first semester of 2007?). How to bridge the gap with FP7?