Magnet Systems Overview

1. BNL - FNAL - LBNL - SLAC Magnet Systems Overview GianLuca Sabbi LARP Collaboration Meeting 17 November 16, 2011

2. LARP Magnet R&D Program Goal: Develop Nb3Sn quadrupoles for the LHC luminosity upgrade Potential to operate at higher field and/or larger temperature margin • R&D phases: • 2004-2009: technology development using the SQ and TQ models • 2006-2012: length scale-up to 4 meters using the LR and LQ models • 2008-2014: incorporation of accelerator quality features in HQ/LHQ • Program achievements to date: • TQ models (90 mm aperture, 1 m length) reached 240 T/m gradient • LQ models (90 mm aperture, 4 m length) reached 220 T/m gradient • HQ models (120 mm aperture, 1 m length) reached 170 T/m gradient • Current activities: • Completion of LQ program: assembly and test of LQS03 • Optimization of HQ models: accelerator quality, process control • Engineering design and tooling/parts procurement for LHQ

3. Program Organization

4. Program Components SM  LR • Racetrack coils, shell based structure • Technology R&D in simple geometry • Length scale up from 0.3 m to 4 m TQS  LQS • Cos2q coils with 90 mm aperture • Incorporation of more complex layout • Length scale up from 1 m to 4 m Reported by G. Chlachidze in PM session HQ  LHQ • Cos2q coils with 120 mm aperture • Explore force/stress/energy limits • Address accelerator quality requirements

5. High-Field Quadrupole (HQ) Design • 120 mm aperture, coil peak field of 15.1 T at 219 T/m (1.9K SSL) • 190 MPa coil stress at SSL (150 MPa if preloaded for 180 T/m) • Stress minimization is primary goal at all design steps (from x-section) • Coil and yoke designed for small geometric and saturation harmonics • Full alignment during coil fabrication, magnet assembly and powering

6. Contributions to the HQ Development • Cable design and fabrication LBNL • Magnetic design & analysis FNAL, LBNL • Mechanical design & analysis LBNL • Coil parts design and procurement FNAL • Instrumentation & quench protection LBNL • Winding and curing tooling design LBNL, FNAL • Reaction and potting tooling design BNL • Coil winding and curing LBNL, (CERN) • Coil reaction and potting BNL, LBNL, (CERN) • Coil handling and shipping tooling BNL • Structures (quadrupole & mirror) LBNL, FNAL, BNL • Assembly (quadrupole & mirror) LBNL, FNAL, (BNL, CERN) • Magnet test LBNL, FNAL, (CERN) • Accelerator Integration BNL, LBNL, FNAL, (CERN)

7. HQ Timeline, Issues and Progress 2008 July Selection of 120 mm quadrupole aperture for Phase 1 Nov. HQ design completed (cable, coil/tooling, structure) 2009 June Started winding of first coil 2010 May HQ01a test: reached 155 T/m @4.5K (~80%) June HQ01b test: coil damage due to inter-layer short Oct. HQ01c test: insulation OK, limited to 135 T/m by one coil Nov. Discovered broken strands in coil #10 after reaction Dec. Started design iteration and fabrication of special coils 2011 Apr. HQ01d test: reached 170 T/m (86%) by coil selection/QA May HQM01: promising results with lower compaction in coil 12 June New cable and coil design approved for lower compaction July HQ01e test: confirms HQ01d, magnetic measurements Sept. HQM02 test: best result to date with coil 13 (one less turn) Oct. Completed first coil with new cable design

8. HQ01a-e Quench Training NbTi operating target (120 T/m)

9. HQ Performance Issues • Mechanical issues: • Ramp rate dependence of first three models is indicative of conductor damage • Electrical issues: • Large number of insulation failures in coils, in particular inter-layer and coil to parts HQ01a-d Ramp Rate dependence HQ01b extraction voltage Extraction Voltage (V) Time (s)

10. Coil Analysis Findings • Both mechanical and electrical issues were traced to excessive compaction during the coil reaction phase: • HQ design assumed less space for inter-turn insulation than TQ/LQ • Reaction cavity limits radial & azimuthal expansion • No/insufficient gaps were included between pole parts to limit longitudinal strain (Over) size measurements of completed coil Coil spring back in tooling A detailed analysis will be presented by Helene Felice in the magnet parallel session

11. Individual Coil Tests in Mirror Structure • Mirror structure allows to test single coils: •  Efficient way to study design variations • Special coils bring special challenges • Two special coil were fabricated and tested: • #12-HQM01: larger cavity and cored cable • #13-HQM02: standard cavity, one less turn Ramp rate dependence • Coil 12 showed some performance limitations, probably related to splice fabrication oversight • Coil 13: best performing HQ coil to date, at 4.5K and 1.9K, using RRP54/61 • Details will be presented by Rodger Bossert and Guram Chlachidze in PM session

12. Design Revisions and Next Steps • Based on the analysis and tests results, the following changes were applied: • A new cable design was developed using smaller strand diameter (from 0.800 mm to 0.778 mm, to decrease compaction without changes in parts and tooling • Longitudinal gaps were progressively increased and 4mm/m was selected • Some end part modifications to increase insulation layers, avoid sharp points • Increased inter-layer insulation layer thickness to 0.5 mm • Next steps: • Test of coil 14 (first coil of the new design) in the mirror structure (Dec-Jan) • HQ01e test at CERN: evaluate 1.9K performance and perform independent magnetic measurements (Jan-Feb) • Test of coil 15 (new design and cored cable) in HQ or HQM (Mar-Apr) • A new effort is being organized to understand persisting electrical weaknesses (shorts in coil 14) and apply findings/corrections to both HQ and LHQ Presentations by Dan Dietderich, Helene Felice, Marta Bajko in PM session

13. Integration of HQ and LHQ Programs HQ/LHQ schedule integration was a key discussion topic at the last DOE review HQ LHQ Will be presented in detail by Giorgio Ambrosio during the magnet parallel session

14. Accelerator Quality in LARP Models

15. Accelerator Quality Requirements • Detailed specifications will be developed by the HL-LHC design study • Preliminary guidance was formulated by CERN in four areas: • Ramp rate: no quench at -150 A/s, starting from 80% of SSL • Requires control of eddy current losses, particularly in cables • Transfer function: < 1 unit reproducibility in the operating range • < 10 units spread for I< Imax/2 & <5 units for I>Imax/2 • Requires control of magnetization and eddy current effects • Persistent currents: injection |b6|<10 units, spread < 10 units • Requires control of conductor magnetization • Magnetic center: stable during ramp-up within ± 0.04 mm • Requires control of magnetization and eddy current effects

16. Current Accelerator Quality Developments • Structure optimization for alignment, uniform pre-load, minimal training • Field quality measurements and new design features to meet requirements • Structure development oriented toward magnet production and installation • Quench protection, rad-hard epoxy and cooling system studies PM session: Conductor and cable presentations by Arup Ghosh and Dan Dietderich Production structure and rad-hard epoxy discussion by Peter Wanderer

17. HQ Structure and Assembly Optimization • HQ explores stress limits and test results confirm pre-load window is very narrow • HQ01e: asymmetric loading for better stress uniformity • Could also be used to optimize geometric field quality

18. HQ01d-e Magnetic Measurements • Geometric harmonics are small, indicating good uniformity and alignment • Large persistent current effects indicate need for smaller filament conductors • Large dynamic effects indicate need to better control inter-strand resistance Eddy current harmonics for different ramp rates Geometric and persistent current harmonics Detailed presentation by Xiaorong Wang in the magnet parallel session

19. LARP Conductor Experience and Needs • In previous phases of the program, conductor has been adequate to meet the key magnet R&D goals: • RRP 54/61 for SQ, LR, and 1st generation TQ/LQ/HQ/HQM models • Enabled the 2009 milestone of >200 T/m in TQ and LQ • RRP 108/127 for optimized TQ, LQ, HQ/HQM, and LHQ • Smaller filament size, but needs further development • Accelerator requirements will be a priority in the next phase: • HQ02: evaluate cored cables for control of dynamic effects • HQM: evaluate coils made with larger RRP stacks and PIT • For construction project, key production issues need to be addressed: • Improve piece length (cable UL > 1km) and control of Jc, RRR • Production volume: ~15 tons in a 3-4 year period

20. Development of smaller filament wires • Work is currently underway to develop wires with smaller Deff • RRP 169 and 217 stacks under development at OST • PIT (192 tubes) under development by Bruker-AES • Both routes can in principle deliver < 40 mm at 0.8 mm • LARP plans – conductor procurement: • About 20 kg. of RRP 217 wire are currently available • Additional RRP 217 wire is expected from CDP contracts • PIT wire is expected from an exchange with CERN • LARP plans – conductor evaluation: • Fabricate and characterize HQ cables starting this year • If promising results are obtained, fabricate and test HQ coils

21. 12 T < Jc >= 2960 15 T < Jc >= 1550 Conductor Jc and RRR vs. Time RRP 54/61: 2002-2007 RRP 108/127: 2008-2011 Jc (12T, 4.2K) Both Jc and RRR for 108/127 are significantly lower than for 54/61, and no improvements are observed for increased production quantity Residual Resistivity Ratio

22. Conductor Piece Length • Cable UL for full scale magnets of 120 mm aperture will be ~1 km • (considerably higher if aperture is increased to 150 mm) • Cabling losses are large when strand piece length is comparable to cable UL • After optimization, RRP 54/61 achieved 1-2 pieces per billet (5-10 km range) • RRP 108/127 is still delivered in relatively short pieces, with min spec 550 m Sample piece lengths for RRP 108/127 billets procured by LARP Billet #

23. R&D and Construction Planning • A CERN-US working group was established in August 2010: • Following a request from last DOE review of LARP (7/2010) • Composition: 3 US (BNL, FNAL, LBNL) and 2 CERN members • Goals: • Discuss requirements and development plans for Nb3Sn • Present recommendations to LARP, DOE, CERN management • Main topics covered: • Magnet tests and success criteria for technology demonstration • Contributions from US and CERN in the next R&D phase • Infrastructure requirements for prototyping and production • Baseline and backup options for final design and production • Findings presented at the 2011 CERN-US meeting and DOE review

24. CERN and EU Participation • Several key contributions by CERN were discussed as part of this plan: • R&D and design phase: • HL-LHC Design Study: • Finalize basic requirements (esp. aperture) • Radiation and heat transfer studies • Conductor and materials development (with EU programs) • Participation in HQ model testing, assembly and fabrication (preparation for prototyping and production) • Infrastructure and prototyping phase: • Procure 10 m coil infrastructure at CERN • Full length prototype will be built at CERN by a combined US-CERN team with target completion by the end of 2015 • Production and installation phase: • CERN to participate in production & lead integration/installation

25. R&D and Construction Schedule As of June 2011 (DOE review) • Target date for installation of new IR Quadrupoles in LHC is 2021 • Target date for technology decision (Nb3Sn vs. NbTi) is 2014

26. Summary • Fundamental aspects of Nb3Sn technology have been demonstrated • R&D effort is now focusing on increased reliability, accelerator integration and production requirements • Systematic testing of LARP Nb3Sn models and CERN NbTi models will provide a direct comparison for the 2014 technology selection • Next few years will be critical and much work is still left to do • - Integrate R&D efforts with EuCARD, KEK, US core programs • - Need close participation and direct contributions by CERN Acknowledgement