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BNL - FNAL - LBNL - SLAC. Magnet Systems Overview. GianLuca Sabbi LARP Collaboration Meeting 17 November 16, 2011. LARP Magnet R&D Program. Goal : Develop Nb 3 Sn quadrupoles for the LHC luminosity upgrade Potential to operate at higher field and/or larger temperature margin.
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BNL - FNAL - LBNL - SLAC Magnet Systems Overview GianLuca Sabbi LARP Collaboration Meeting 17 November 16, 2011
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
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
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
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)
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
HQ01a-e Quench Training NbTi operating target (120 T/m)
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)
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
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
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
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
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
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
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
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
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
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
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
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 #
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
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
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
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