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

Introduction 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 MQXC HQ Paolo Ferracin 06/02/2011

Goals 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 Paolo Ferracin 06/02/2011

Outline From HQ to MQXF Magnet parameters Stress analysis Conclusions Paolo Ferracin 06/02/2011

HQ Shell-based support structure Pre-loaded with bladders OD 570 mm, 1 m long Design focused on pre-load and alignment 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 06/02/2011

From HQ to MQXF Magnetic design concept 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 Rin and 80% Iss Similar iron geometry with OD = 520 mm HQ MQXF_15mm MQXF_17mm Paolo Ferracin 06/02/2011

From HQ to MQXF Mechanical design concept 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 HQ MQXF_15mm MQXF_17mm Paolo Ferracin 06/02/2011

Outline From HQ to MQXF Magnet parameters Stress analysis Conclusions Paolo Ferracin 06/02/2011

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 is considered a upper bound for a production We assumed a Jc of 2800 A/mm2 with self field correction This gives 2% reduction in gradient (3 T/m) w.r.t. 3070 A/mm2 Paolo Ferracin 06/02/2011

Cable and coil parameters MQXF_15mm MQXF_17mm From HQ to MQXF_15mm 11% more conductor From MQXF_15mm to 17mm 16% more conductor Units HQ MQXF_15 mm MQXF_17 mm Strand # 35 40 Thickness in/out mm 1.338/1.536 Width 15.150 17.314 Insulation thickness 0.100 Turns per oct. 46 51 52 Area supercond. per oct. mm2 380 422 491 Paolo Ferracin 06/02/2011

Magnet parameters at 1.9 K From HQ to MQXF_15mm 15mm or 17mm ? 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 MQXF_15mm MQXF_17mm Units HQ MQXF_15 mm MQXF_17 mm Temperature K 1.9 Loadline margin % 20 Gradient T/m 169 145 149 Peak field T 11.7 11.9 12.1 Stored energy MJ/m 0.85 1.06 1.22 Paolo Ferracin 06/02/2011

Fringe field at 500 mm from the center 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 it tolerable ? Is shielding necessary ? Further studies needed HQ MQXF_15mm MQXF_17mm 80% Iss Paolo Ferracin 06/02/2011

Outline From HQ to MQXF Magnet parameters Stress analysis Conclusions Paolo Ferracin 06/02/2011

Stress analysis The HQ case at 169 T/m (80% of Iss) 2D comp. stress Increase pre-load during cool-down Pole turn always under pressure Paolo Ferracin 06/02/2011

Stress analysis The HQ01e case: pole gauges measurements Pole azimuthal stress vs. I2 during training quench up to 170 T/m Linear variation up to maximum current No signs of unloading and pole-coil detachment Paolo Ferracin 06/02/2011

Stress analysis The HQ case at 169 T/m (80% of Iss) Coil peak stress located in inner layer Pole turn during bladder-key operation Pole turn after cool-down Mid-plane turn during excitation Paolo Ferracin 06/02/2011

Stress analysis Comparison at 80% of Iss 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 Units HQ MQXF_15 mm MQXF_17 mm IL OL Lorentz stress MPa -100 -120 -113 -128 -108 Paolo Ferracin 06/02/2011

Axial forces and support 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) Units HQ MQXF_15 mm MQXF_17 mm 80% Iss 100% Iss Axial force MN 0.85 1.32 1.06 1.63 1.22 1.87 Paolo Ferracin 06/02/2011

Conclusions 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 Paolo Ferracin 06/02/2011

Appendix Paolo Ferracin 06/02/2011

Stress analysis Comparison at 100% of Iss 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 Units HQ MQXF_15 mm MQXF_17 mm IL OL Lorentz stress MPa -154 -184 -173 -193 -167 -195 Paolo Ferracin 06/02/2011

HQ parameters Paolo Ferracin 06/02/2011

MQXF_15mm parameters Paolo Ferracin 06/02/2011

MQXF_17mm parameters Paolo Ferracin 06/02/2011

Stress analysis Coil 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 06/02/2011

Stress analysis The 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 06/02/2011

Saturation effect to Iss Paolo Ferracin 06/02/2011

Support structure options Paolo Ferracin 06/02/2011