1. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 1 Nb 3 Sn IR Quadrupoles for HL-LHC BNL - FNAL - LBNL - SLAC GianLuca Sabbi for the US LHC Accelerator Research Program 2012 Applied Superconductivity Conference

2. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 2 High Luminosity LHC Physics goals: Improve measurements of new phenomena seen at the LHC Detect/search low rate phenomena inaccessible at nominal LHC Increase mass range for limits/discovery by up to 30% Required accelerator upgrades include new IR magnets: Directly increase luminosity through stronger focusing  decrease  * Provide design options for overall system optimization/integration  collimation, optics, vacuum, cryogenics Be compatible with high luminosity operation  Radiation lifetime, thermal margins Major detector upgrades are also required to take full advantage of SLHC

3. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 3 LARP Magnet Program Goal: Develop Nb 3 Sn quadrupoles for the LHC luminosity upgrade Potential to operate at higher field and larger temperature margin R&D phases: 2004-2010: 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 184 T/m gradient Current activities: Completion of LQ program: test of LQS03 to reproduce TQS03 result Optimization of HQ, fabrication of LHQ (technology demonstration) Design and planning of the MQXF IR Quadrupole development

4. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 4 MaterialNbTiNb 3 Sn Dipole Limit~ 10 T~ 17 T ReactionDuctile~ 675 0 C InsulationPolymideS/E Glass Coil partsG-10Stainless Axial StrainN/A~ 0.3 % Transverse stressN/A~ 200 MPa Transverse Stress (MPa) Cable Critical Current (kA) Brittleness: React coils after winding Epoxy impregnation Strain sensitivity: Mechanical design and analysis to prevent degradation under high stress Nb 3 Sn Technology Challenges

5. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 5 R&D Program Components SM TQS HQ  LR LQS LHQ   Racetrack coils, shell based structure Technology R&D in simple geometry Length scale up from 0.3 m to 4 m Cos2  coils with 90 mm aperture Incorporation of more complex layout Length scale up from 1 m to 4 m Cos2  coils with 120 mm aperture Explore force/stress/energy limits Nb 3 Sn Technology Demonstration

6. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 6 Overview of LARP Magnets SQ SM TQS LR LQS HQ TQC

7. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 7 Program Achievements - Timeline (1/3) Mar. 2006 SQ02 reaches 97% of SSL at both 4.5K and 1.9K Demonstrates MJR 54/61conductor performance for TQ Jun. 2007TQS02a surpasses 220 T/m at both 4.5K and 1.9K(*) Achieved 200 T/m goal with RRP 54/61 conductor Jan. 2008 LRS02 reaches 96% of SSL at 4.5K with RRP 54/61 Coil & shell structure scale-up from 0.3 m to 4 m July 2009TQS03a achieves 240 T/m (1.9K) with RRP 108/127(*) Increased stability with smaller filament size Dec. 2009 TQS03b operates at 200 MPa (average) coil stress(*) Widens Nb 3 Sn design space (as required…) (*) Tests performed at CERN

8. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 8 Program Achievements - Timeline (2/3) Dec. 2009 LQS01a reaches 200 T/m at both 4.5K and 1.9K LARP meets its “defining” milestone Feb. 2010TQS03d shows no degradation after 1000 cycles(*) Comparable to operational lifetime in HL-LHC July 2010 LQS01b achieves 220 T/m with RRP 54/61 Same TQS02 level at 4.5K, but no degradation at 1.9K Apr. 2011HQ01d achieves 170 T/m in 120 mm aperture at 4.5 K At HL-LHC operational level with good field quality Oct. 2011 HQM02 achieves ~90% of SSL at both 4.6 K and 2.2 K Special coil to test reduced compaction (*) Test performed at CERN

9. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 9 Program Achievements - Timeline (3/3) Apr. 2012 HQ01e-2 reaches 184 T/m at 1.9K (*) Despite using first generation coils, several known issues Above linear scaling from TQ (240/120*90=180 T/m) Jun. 2012HQM04 reaches 97% SSL at 4.6K and 94% at 2.2K Successful demonstration of revised coil design Single-pass cored cable, lower compaction Next Steps: Aug. 2012LQS03 test: reproduce TQS03 using 108/127 conductor Dec. 2012 HQ02a test: improve performance with 2 nd generation coils (*) Test performed at CERN

10. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 10 Summary – Technical Progress Steady advances in addressing technology issues that were initially perceived as potential show stoppers:  Conductor performance/stability, mechanical support, degradation due to stress and cycling, length scale-up, coil and structure alignment, field quality, quench protection, heat extraction and radiation lifetime Today, we can confidently say that there are no show stoppers However, we are behind in addressing a number of accelerator quality and production relevant issues, which affect the overall system performance, and ultimately the feasibility and success of the project:  Control of dynamic effects, insulation of long lengths of cable, increased electrical integrity, process documentation and QA, incorporation of rad- hard epoxies, evaluation and selection among candidate conductors Since last year we have significantly stepped up the pace in introducing these features. Results have been generally positive but we need to manage the risk associated with multiple/combined changes

11. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 11 Handling High Stress in Magnet Coils Titanium pole 1. Understand limits2. Optimize structure and coil for minimum stress TQ (90 mm, ~12 T)LQ (90 mm, ~12 T)HQ (120 mm, ~15 T) 4.5K, 0T/m SSL preload 4.5K, 0T/m SSL preload 4.5K, 0T/m SSL preload Key locationCoil geometry 200 MPa 170 MPa 190 MPa 170 MPa 180 MPa

12. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 12 Technology Quadrupole (TQ) Double-layer, shell-type coil 90 mm aperture, 1 m length Two support structures: - TQS (shell based) - TQC (collar based) Target gradient 200 T/m Winding & curing (FNAL - all coils)Reaction & potting (LBNL - all coils) TQC TQS

13. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 13 TQ Studies: Stress Limits Coil layer 1 stress evolution -   Systematic investigation in TQS03: TQS03a: 120 MPa at pole, 93% SSL TQS03b: 160 MPa at pole, 91% SSL TQS03c: 200 MPa at pole, 88% SSL Peak stresses are considerably higher Considerably widens design window 260 MPa @ 4.5K 255 MPa @ SSL Calculated peak stresses in TQS03c

14. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 14 TQS03d Cycling Test Reduced coil stress to TQS03b levels (160 MPa average)  Pre-loading operation and test performed at CERN Did not recover TQS03b quench current (permanent degradation) Performed 1000 cycles with control quenches every ~150 cycles No change in mechanical parameters or quench levels

15. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 15 High-Field Quadrupole (HQ) 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

16. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 16 Mechanical Design Space in HQ models Pole quenches and strain gauge data indicate insufficient pre-load Mid-plane quenches indicate excessive pre-load Narrow design and assembly window: ok for an R&D model designed to explore stress limits, may require optimization for production, in particular if the aperture is further increased Pole quenches (HQ01d)Pole stress during ramp to quench (HQ01d) Mid-plane Quenches (HQ01d)

17. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 17 Assembly Optimization in HQ01e HQ explores stress limits and test results confirm pre-load window is very narrow HQ01e: asymmetric loading for better stress uniformity P. Ferracin, H. Felice

18. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 18 Performance issues in early HQ Tests Time (s) Extraction Voltage (V) 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 HQ01b extraction voltage HQ01a-d Ramp Rate dependence M. Martchevsky

19. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 19 Initial Findings Conductor damage was traced to excessive strain during the coil reaction phase: No/insufficient gaps were included in pole segments to limit longitudinal strain Assumed less space for inter-turn insulation than TQ/LQ  higher compaction Electrical failures due to insufficient insulation and weaknesses at critical locations Compounded by lack of electrical QA Coil spring back in tooling (Over) size measurements of completed coil H. Felice, G. Ambrosio, R. Bossert, R. Hafalia, J. Schmalzle

20. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 20 Progress with new coil series Coil 15 was tested in HQM04 mirror, reaching 97% of SSL at 4.5K, 94% at 2.2K D. Dietderich, A. Godeke, R. Bossert, G. Chlachidze However, some issues are still appearing: Low compaction in coil 17 after curing  Gaps did not close after reaction – may or may not be related Many popped strands in coil 18 winding and (first in HQ) turn-to-turn short Process control issues or variability due to recent changes?

21. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 21 Field Quality Studies in HQ01d-e X. Wang Good start on geometric harmonics, showing size uniformity and alignment Persistent current effects are large but within limits set by design study Large dynamic effects indicate need to better control inter-strand resistance Eddy current harmonics for different ramp rates 12 kA, R.ref = 21.55 mm best fit d 0 = 29.6 µm. Analysis of geometric accuracy from random errors 0.2 µΩ – 3.6 µΩ in HQ01e << 20 µΩ for LHC magnets

22. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 22 Quadrupole Design Optimization High field technology provides design options to maximize luminosity

23. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 23 Scaling-up to 150 mm Aperture Based on results of LARP models at 90 and 120 mm, and preliminary studies for larger aperture, no serious difficulties are anticipated for the 150 mm aperture IR quadrupole design, but some optimization is required Conductor and cable: increase cable width from 14.8 mm to 18.5 mm to facilitate coil stress management and quench protection  Increase strand diameter from 0.778 to 0.85 mm to limit cable aspect ratio  Preliminary cable dimensions established for 0.85 mm wire: 18.5 mm width, 1.50 mm mid-thickness, 0.65 deg. keystone angle (D. Dietderich)  ~30 kg of 0.85 mm wire expected for mid-July, fabrication of prototype cable planned for this summer Electrical integrity: high voltage testing requirements were established, and an increase of cable insulation thickness from 0.1 mm to 0.15 mm is planned At this time, the key elements to start the cross-section design are available An increase of the cold mass diameter from 57 cm to 63 cm was also approved as baseline, providing a key parameter needed to start the mechanical design

24. ASC 2012Nb 3 Sn IR Quadrupoles for HL-LHC – G. Sabbi 24 Summary Acknowledgement A large knowledge base is available after 7 years of fully integrated effort involving three US Labs and CERN Demonstrated all fundamental aspects of Nb 3 Sn technology: - Steady progress in understanding and addressing R&D issues The remaining challenges have an increasingly programmatic flavor: design integration, production organization and processes HL-LHC IR Quads are a key step for future high-field applications Next few years will be critical and much work is still left to do - Integrate effort with CERN, EuCARD, KEK, US core programs