Design of Nb3Sn IR Quadrupoles with Apertures Larger than 120 mm

1. Design of Nb3Sn IR quadrupoles with apertures larger than 120 mm Paolo Ferracin and Ezio Todesco 1st HiLumiLHC / LARP Collaboration Meeting CERN 16-18 November, 2011

2. Introduction MQXC HQ Paolo Ferracin • Upgrade of the LHC IR quadrupoles • From Nb-Ti 70 mm bore (MQXA from Japan, MQXB from US) to larger apertures • Currently under development, 120 mm aperture quadrupoles • Nb-Ti: MQXC (CERN-CEA Collaboration) • Nb3Sn: HQ - MQXE (US LARP Collaboration) • Larger aperture under consideration for Nb-Ti (MQXD) and Nb3Sn (MQXF) • Preliminary design study of MQXF, a 140 mm aperture Nb3Sn quadrupole

3. Goals Paolo Ferracin • Investigate magnet parameters of an HQ-type quad. with the HQ cable and 140 mm aperture • How much do we lose in gradient? • How much do we increase the stress? • Analyse the potential benefits of using a wider cable than HQ

4. Outline Paolo Ferracin From HQ to MQXF Magnet parameters Stress analysis Conclusions

5. HQ • Five assemblies and tests at 4.4 K carried out • Max. grad. achieved: 170 T/m • 11.7 T estimated peak field • 86% of Iss at 4.4 K Paolo Ferracin • Shell-based support structure • Pre-loaded with bladders • OD 570 mm, 1 m long • Design focused on pre-load and alignment

6. From HQ to MQXFMagnetic design concept HQ MQXF_15mm MQXF_17mm Paolo Ferracin • Two cases considered: 15 and 17 mm wide cable • 2 layers with similar angles and 4 blocks • All harmonics below 1 unit at 2/3 of Rinand 80% Iss • Similar iron geometry with OD = 520 mm

7. From HQ to MQXFMechanical design concept HQ MQXF_15mm MQXF_17mm Paolo Ferracin • Same support structure concept as HQ • Same shell OD and thickness • Larger coil OD (aperture + thickness) • Collar-pad-yoke thickness reduced by 10 to 15 mm

8. Outline Paolo Ferracin From HQ to MQXF Magnet parameters Stress analysis Conclusions

9. Strand properties • 0.8 mm strand, 108/127 • 53% Cu -> Cu/Su: 1.13 • Extr. strand meas. (HQ coil 3-4) • Jc (4.2 K, 12 T) of 3070 A/mm2 with self field correction • This isconsidered a upperbound for a production • We assumed a Jc of 2800A/mm2with self field correction • This gives 2% reduction in gradient (3 T/m) w.r.t. 3070 A/mm2 Paolo Ferracin

10. Cable and coil parameters MQXF_15mm MQXF_17mm Paolo Ferracin • From HQ to MQXF_15mm • 11% more conductor • From MQXF_15mm to 17mm • 16% more conductor

11. Magnet parameters at 1.9 K MQXF_15mm MQXF_17mm Paolo Ferracin • From HQ to MQXF_15mm • Loss of 14% in gradient • 25% increase of stored energy • 15mm or 17mm ? • Increase of gradient +3% with 16% more conductor and 15% more stored energy

12. Fringe field at 500 mm from the center HQ MQXF_15mm MQXF_17mm 80% Iss Paolo Ferracin • W.r.t. Nb-Ti version, smaller yoke OD (520 mm) • Thicker shell (25 mm), and still missing the LHe vessel (5-10 mm thick) • From HQ to MQXF_15mm • Fringe field from 0.68 to 9.77 mT • From MQXF_15mm to 17mm • Fringe field increases to 18.55 mT • Is ittolerable ? Is shieldingnecessary ? Furtherstudiesneeded

13. Outline Paolo Ferracin From HQ to MQXF Magnet parameters Stress analysis Conclusions

14. Stress analysisThe HQ case at 169 T/m (80% of Iss) Paolo Ferracin • 2D comp. stress • Increase pre-load during cool-down • Pole turn always under pressure

15. Stress analysisThe HQ01e case: pole gauges measurements • Pole azimuthal stress vs. I2 duringtraining quench up to 170 T/m • Linear variation up to maximum current • No signs of unloading and pole-coil detachment Paolo Ferracin

16. Stress analysisThe HQ case at 169 T/m (80% of Iss) Paolo Ferracin • Coil peak stress located in inner layer • Pole turn during bladder-key operation • Pole turn after cool-down • Mid-plane turn during excitation

17. Stress analysisComparison at 80% of Iss Paolo Ferracin • From HQ to MQXF_15mm • IL Lorentz stress: +13% • Peak stress: +15 MPa • From MQXF_15mm to 17mm • Reduction of 10 MPa in peak stress

18. Axial forces and support Paolo Ferracin • From HQ to MQXF_15mm • Increase of axial force: 25% • From MQXF_15mm to 17mm • Increase of axial force : 15% • Axial support • Stainless steel end plate (50 mm thick) • Aluminum axial rods (34 mm diameter) • Maximum rod stress in MQXF • 350 (80% of Iss) to 500 MPa (100% of Iss)

19. Conclusions Paolo Ferracin • A preliminary design of the 140 mm bore Nb3Sn quadrupole magnet MQXF based on the HQ design has been carried out • From HQ to MQXF (in operational cond.) • Gradient: from 169 to 145 T/m • Stored energy: from 0.85 to 1.06 MJ/m • Fringe field: from 0.68 to 9.77 mT • Peak stress: from 140 to 150 MPa • According to a preliminary 2D mech. analysis, the HQ structure is capable provide pre-load to a 140 mm aperture coil up to Iss • Increasing the cable by 2 mm provides additional 4 T/m with a reduction of 10 MPa in coil peak stress, but 15% more conductor and stored energy • Next step • Further optimization of cable, coil, and support structure

20. Appendix Paolo Ferracin

21. Stress analysisComparison at 100% of Iss Paolo Ferracin • Similar conclusions as at 80% of Iss • Support structure • Bladder pressure • Up to 55 MPa • Shell max stress • Up to 340 MPa at 4.5 K • Iron maximum tension • Below 200 MPa

22. HQ parameters Paolo Ferracin

23. MQXF_15mm parameters Paolo Ferracin

24. MQXF_17mm parameters Paolo Ferracin

25. Stress analysisCoil stress in TQ & HQ with e.m. forces at 1.9 K Iss • Technology quadrupole TQ • 90 mm bore, 10 mm cable • Outer layer overcompressed by -60 MPa at max. gradient • High field quadrupole HQ • 120 mm bore, 15 mm cable • Inner and outer layer with low stress at max gradient 0 MPa 0 MPa 0 MPa -60 MPa Paolo Ferracin

26. Stress analysisThe HQ case at 169 T/m (80% of Iss) • Contact pressure (positive) coil-pole at 4.4 K • Contact pressure (positive) coil-pole with e.m. forces Paolo Ferracin

27. Saturation effect to Iss Paolo Ferracin

28. Support structure options Paolo Ferracin