1. ASC 2014Nb 3 Sn Block Coil Dipoles for a 100 TeV Hadron Collider – G. Sabbi 1 Performance characteristics of Nb 3 Sn block-coil dipoles for a 100 TeV hadron collider G. Sabbi, L.Bottura, D. Dietderich, D. Cheng, P. Ferracin, A. Godeke, S. Gourlay, M. Martchevskii, E. Todesco, X. Wang 2014 Applied Superconductivity Conference

2. ASC 2014Nb 3 Sn Block Coil Dipoles for a 100 TeV Hadron Collider – G. Sabbi 2 Collider Parameters (M. Benedikt) ParameterUnitBaselineAlt. CM EnergyTeV100 Circumferencekm10080 Dipole Field (Coll.)T1620 Dipole Field (Inj.)T1-1.2 Aperturemm40-50 T op (magnet)K4.5-1.9 T op (beam screen)K40-60 “Main focus is the 16 T Nb 3 Sn program as hadron collider baseline, representing a natural continuation of HL-LHC developments” We discuss the Nb 3 Sn block-dipole characteristics in this context

3. ASC 2014Nb 3 Sn Block Coil Dipoles for a 100 TeV Hadron Collider – G. Sabbi 3 Design Features 190 MPa 0 MPa Coil Stress @ B 0 = 16 T Flared coil ends Winding Pole Central support tube (tested with/without) Bore structural support Magnetic Field @ B 0 = 16 T 0T 16.9 T 0T 0 MPa 190 MPa 200 MPa (0T) 36 mm

4. ASC 2014Nb 3 Sn Block Coil Dipoles for a 100 TeV Hadron Collider – G. Sabbi 4 Experimental Reference 1.Coils assembled around a central tube for bore support (36 mm clear bore) HD2a & HD2b (coil 1&2); HD2c (coil 2&3) Highest B 0 on record for an accelerator dipole: 13.8 T (87% SSL) 2.Same coils 2&3 assembled without the central tube (43.3 mm clear bore) HD2d & HD2e: 13.4 T maximum field (-3%) but slower training 3.Coil design & process iteration aimed at correcting observed limitations HD3: similar quench patterns and slightly lower field than HD2 HD Models: 5 Coils, 6 Tests in 3 Phases: This study uses the HD experience as a basis to the extent possible We also incorporate feedback from the LARP models (TQ, HQ)

5. ASC 2014Nb 3 Sn Block Coil Dipoles for a 100 TeV Hadron Collider – G. Sabbi 5 Reference Design (single aperture) Performance parameters at B 1 =16 T Operating currentkA18.6 Peak fieldT16.9 Peak coil stress (0T)MPa200 Peak coil stress (16T)MPa190 Stored energyMJ/m0.77 Main geometrical parameters Strand diametermm0.8 Number of strands51 Cable widthmm22.0 Clear aperturemm36-43 No. turns (1 quadrant)54 Coil width at mid-planemm39 Minimum bending radiusmm12.78 Magnet cross-section Vertical aperture linked to cable width and strand diameter (cable aspect ratio) Coil stresses within the limits established by HD1, LARP TQ and HQ models Al shell (40 mm) Axial rods Load keys Iron Yoke

6. ASC 2014Nb 3 Sn Block Coil Dipoles for a 100 TeV Hadron Collider – G. Sabbi 6 Quench Performance and Margin Quench Locations (HD2a) All HD models limited to ~87% by localized quenches at the end of the straight section Need to incorporate a longitudinal pole gap to prevent excessive strain at reaction HD1 Coil Split-island with strain control gap 1 1

7. ASC 2014Nb 3 Sn Block Coil Dipoles for a 100 TeV Hadron Collider – G. Sabbi 7 Quench Performance and Margin (2) 1.9K Strand design: RRP 54/61 J c (12T,4.2K)= 3419 A/mm 2 J c (15T,4.2K)= 1880 A/mm 2 Cu/Sc ratio = 0.82 I c data corrected for self field 4.5K 4.2K (RW) 4.2K (XS) T= 1.9 K B pk = 18.1 T B 1 =17.1 T T= 4.5 K B pk = 16.4 T B 1 = 15.5 T * HD2c B pk =14.5 T B 1 =13.8T Magnetic Field [T] +1.7 T (12%) (optimization) +1.6 T (10%) (temperature)

8. ASC 2014Nb 3 Sn Block Coil Dipoles for a 100 TeV Hadron Collider – G. Sabbi 8 Coil Grading Benefits: higher field than HD2 with same conductor area (13.8 cm 2 /quadrant) Challenges: High Field cable: thickness +0.35 mm, winding radius -1 mm (should be ok) Low Field cable: (further) increased aspect ratio (may be beyond limits) Fabrication and splicing of the two sub-coils (a long list…) Cable ParametersHFLF Strand diameter [mm]1.00.65 No. Strands4164 No. turns (L1+L2)6+228+25 Conductor area [cm 2 ]2.5711.25 B 1 (SSL) [ T ]4.5K1.9K Reference (HD2)15.5217.15 Graded (*)16.6718.42 Dipole field increase+1.15+1.27 11.76 mm (*) I c scaled with strand area from HD2

9. ASC 2014Nb 3 Sn Block Coil Dipoles for a 100 TeV Hadron Collider – G. Sabbi 9 Two-in-one Configuration Geometrically the two coils can be brought in contact: 126 mm separation Field actually increases but field quality degrades due to left-right asymmetry This can be corrected with an asymmetric coil (same concept as for HiLumi D2) Satisfactory solution found for 150 mm separation: +75 -75 3 mm

10. ASC 2014Nb 3 Sn Block Coil Dipoles for a 100 TeV Hadron Collider – G. Sabbi 10 Compactness Compact arrangement has significant cost benefits 150 mm separation smaller than 194 mm in LHC Small beam separation allows small yoke OD 60 cm yoke OD to be compared with 55 cm LHC May be further reduced, need mechanical analysis Mechanical envelope will still be larger (shell) Short sample field is identical to single aperture: However, also need to consider other systems IR dipoles, RF etc. Short sample performanceI ss B 1 ss Temperature4.5K1.9K4.5K1.9K Single aperture (HD2)18.020.115.5217.15 Double aperture (2HD)17.819.715.4917.12

11. ASC 2014Nb 3 Sn Block Coil Dipoles for a 100 TeV Hadron Collider – G. Sabbi 11 Aperture Considerations HD2 bore design: Coil 45 x 47.2 mm Pole cutout OD 43.3 mm Bore tube ID 36 mm R21.65 Y=23.6 X=22.5 HD2d/e & HD3 w/o bore tube: 13.4 T (-3%) but slower training A thin support tube may be assumed as an optimal solution 50 mm aperture would require 1 mm strand (same aspect ratio) Same cable development as for grading (but cannot do both) Conductor scaling for this design is about linear with aperture +25% aperture will have a very significant impact on cost For same reason, optimization of internal bore structure is essential Integrate bore structural design with vacuum, cooling etc.

12. ASC 2014Nb 3 Sn Block Coil Dipoles for a 100 TeV Hadron Collider – G. Sabbi 12 Field Quality Considerations All cases optimized for low geometric harmonics (<1 unit at R=13 mm) As required in order to make meaningful comparisons HD2 was also optimized for low saturation (will work also for graded) For 2-in-1, we need some further improvement for low orders (n=2,3) Should be done together with mechanical analysis Large persistent current harmonics will require magnetic shim correction: HQ calculation and correctionHD2 calculation

13. ASC 2014Nb 3 Sn Block Coil Dipoles for a 100 TeV Hadron Collider – G. Sabbi 13 Conductor Properties Three cases representing actual wires used in HD and HQ models One set representing a possible FCC target (under discussion) Assumes shift of flux pinning curve with improved grain refinement Small D eff and increased Cu fraction Wire ParameterUnit54/6160/61108/127Target D eff mm77 53< 20 Non-Cu Fraction55615042 Heat TreatmentC/h665/48 TBD RRR28723070>200 J c (12T, 4.2K) (*)kA/mm 2 3419355227763552 J c (15T, 4.2K) (*)kA/mm 2 1880193514992772 I c (15T, 4.2K) (*)A520588376585 (*) From extracted strands; self-field corrected 4.2K

14. ASC 2014Nb 3 Sn Block Coil Dipoles for a 100 TeV Hadron Collider – G. Sabbi 14 Strategies for 16 T At 1.9K: 16 T goal requires improved conductor or graded coil At 4.5K: 16 T goal required improved conductor and graded coil B 1 (SSL) [ T ]4.5K1.9K 54/6115.517.1 60/6115.817.5 108/12714.516.0 Target17.5>19 Step 1: model magnet performance optimization Understand & remove 87% limitation - incorporate pole gap Optimize bore design for maximum aperture and fast training Based on this, we set an operating point at 85% of SSL Short sample target for 16 T at 85% is 18.8 T Assume graded coil will give +1 T Conductor options: