1. Dipole design at the 16 T frontier - Magnet R&D for a Future Circular Collider (FCC) at Fermilab Alexander Zlobin Fermilab

2. FCC-hh Magnet target parameters B / G (T) / (T/m) B peak (T) Bore (mm) Length (units x m) MB 1616.450 4500 x 14.3 MQ4501350800 x 6 MQX22513100 D11213604x2 x 12 D21010.5604x3 x 10 Inter-aperture distance ≈ 250 mm Yoke diameter ≤ 700 mm Stray field ≤ 100 mT 2015 FCC meetingMagnet R&D for a Future Circular Collider (FCC) at Fermilab 2 Present record – 13.8 T in ~35 mm aperture (HD2, LBNL, 2008)

3. FNAL HFM Program  FNAL HFM R&D plan was coordinated with recent P5 recommendations and updated DOE-HEP GARD program Recommendation 24: “Participate in global conceptual design studies and critical path R&D for future very high-energy proton-proton colliders. Continue to play a leadership role in superconducting magnet technology focused on the dual goals of increasing performance and decreasing costs.”  In collaboration with the U.S. National laboratories, universities and industry o Develop accelerator magnets with world record parameters  Small-aperture 15 T Nb 3 Sn dipole, suitable for FCC, and 2 T HTS insert  Large-aperture 15 T Nb 3 Sn dipole and 5+ T HTS insert with stress management  Small-aperture 20 T accelerator dipole based on LTS (Nb 3 Sn) and HTS (Bi-2212 or YBCO) coils o Perform magnet cost optimization studies. o Continue superconductor and structural material R&D for 15- 20 T accelerator magnets. 2015 FCC meetingMagnet R&D for a Future Circular Collider (FCC) at Fermilab 3

4. Program Timeline  FY15-17: o Focus on 15 T Nb 3 Sn dipole demonstrator 2015 FCC meetingMagnet R&D for a Future Circular Collider (FCC) at Fermilab 4 VLHCHL-LHCLARP FCC Record field 13.8 T HFDA HFDM-LM 43.5 mm Dipole mirror 10 T dipole TQC TQM-LQM 90 mm 200 T/m Quadrupole quadrupole mirror HFDC (R&W) 40 mm 10 T dipole MBHDP 60 mm 11 T dipole MBHSP MBHSM 60 mm 11 T dipole Dipole mirror

5. Magnet Design Choice  Coil design: o cos-theta o block-type o common coil  Technology: W&R, R&W  Mechanical structure: o with and w/o collar o Stainless Steel or Al shell o stress management  Field range: 10-13.8 T o 13.8 T - record since 2008  Focus on the cos-theta (shell- type) design w/o collar 2015 FCC meetingMagnet R&D for a Future Circular Collider (FCC) at Fermilab 5 MBHSP (FNAL) 11.6 T, 2012-2014 MBHDP (FNAL) 11.5 T, 2015 HFDA (FNAL) 10 T, 2003-2006 D20 (LBNL), 13.4 T, 1997 HD2 (LBNL), 13.8 T, 2008 RD3c (LBNL), 10 T, W&R, 2003 DCC017 (BNL), 10 T, R&W, 2007 HFDC (FNAL), ~6 T, R&W, 2004

6. General considerations  Magnet field B ~ λJ× w B max ~λJ c (B max,T,…)×w  Small aperture dipole (~50 mm) o Quench protection: Coil enthalpy can absorb the stored energy in <50% of the coil volume with T max =250 K o Coil maximum azimuthal stress is ~150 MPa 2015 FCC meetingMagnet R&D for a Future Circular Collider (FCC) at Fermilab 6 Tmax=250 K 150 mm bore 50 mm bore P. Fessia et al., IEEE TAS, 19, 3, 2009. 1.9 K J c (12T,4.2K)=3.5 kA/mm 2

7. Strand and Cable  Strand o RRP 127, 169 or 217 o Strand ID – 1 and 0.7 mm o Jc(12T, 4.2K) ~2700 A/mm 2  Cable o N=28 (HFDA) o N=40 (MBH) o Ic degradation ~5% o stainless steel core o cable prototypes are available  R&D o increase Jc(15 T, 4.2 K) o increase strand D, cable width o reduce filament size 2015 FCC meetingMagnet R&D for a Future Circular Collider (FCC) at Fermilab 7 RRP-127 RRP-169 RRP-217

8. Coil Design Study 2015 FCC meetingMagnet R&D for a Future Circular Collider (FCC) at Fermilab 8  Coil aperture: 60 mm  Coil cross-section: 4 layers, graded  Design parameters: B max, field quality, coil volume, az. stress  Design choice: 4L-5 – minimal coil size and stress 4L-14L-24L-34L-4 4L-5

9. 15 T Dipole Demonstrator  Design concept: Coil bore: 60-mm Coil length: 1 m Optimized design: 4-layer graded coil Interim design: with 11 T coil Cold iron yoke  Design fields: Jc(15T, 4.2K)=1.35 kA/mm 2 Coil B max = 16.3/15.2 T at 4.3 K Bore B max = 15.6/14.6 T at 4.3 K + ~1.5 T at 1.9 K Additional margin – higher Jc 2015 FCC meetingMagnet R&D for a Future Circular Collider (FCC) at Fermilab 9 Optimized graded coilInterim coil design

10. Mechanical Design Lorentz forces  Horizontal support Structure:  Thin stainless steel coil-yoke spacer  Vertically split yoke  Stainless steel clamps  Bolted skin (from 11 T dipole)  Cold mass length: 1 m  Cold mass OD<610 mm (VMTF) Protection heaters:  Outer-layer  Inter-layer (2-3)  Up to 80% of coil volume 2015 FCC meetingMagnet R&D for a Future Circular Collider (FCC) at Fermilab 10

11. Test goals  Demonstration of 15-16 T field level  Study and optimization of o magnet quench performance  training, degradation, memory, effect of coil pre-load o ramp rate sensitivity o operation margin o quench protection  heater efficiency, radial quench propagation, coil quench temperature o field quality  geometrical harmonics, coil magnetization, iron saturation, dynamic effects 2015 FCC meetingMagnet R&D for a Future Circular Collider (FCC) at Fermilab 11

12. FNAL 15 T 2-in-1 Demonstrator Parameters 1 m diameter “cryostat” envelope Number of apertures2 Aperture(mm)60 Aperture spacing (mm)250 Coil current (A)11100 Operating temperature (K)4.3 Max bore field at 4.3 K (T)16.48 Max coil field at 4.3 K (T)16.96 Margin along the load line0 Stored energy (MJ/m)TBD Inductance (mH/m)TBD Yoke ID (mm)190.8 Yoke OD (mm)650 2015 FCC meetingMagnet R&D for a Future Circular Collider (FCC) at Fermilab 12 Is this magnet good for FCC?

13. Magnet Cost Reduction Cost reduction strategy: – Reduce magnet cross- section – cold mass (coil, structure) – cryostat – Increase magnet length – 15 m => 20 m – Reduce component cost – superconductor (use NbTi in low fields) – structural components – Reduce labor – number of coil layers – Improve performance – B op, T op 2015 FCC meetingMagnet R&D for a Future Circular Collider (FCC) at Fermilab 13 B. Palmer (BNL), 2014

14. Conclusion  FCC needs cost-effective main dipole magnets with nominal operation fields of ~16 T based on Nb 3 Sn technology o Special magnets with operation fields up to 20+ T based on HTS/LTS coils  Timely (by CDR in 2018) demonstration of 16-T-class accelerator quality dipole for FCC is a key milestone  FNAL has a promising dipole design and a plan to achieve this milestone by 2018 o Design Bmax is above 17 T @1.9K with conservative Jc o Accelerator quality features  Issues to be understood and resolved for FCC o demonstration of 15-16 T nominal field and accelerator class parameters, improvement of magnet training, reduction of conductor degradation, magnet cost optimization 2015 FCC meetingMagnet R&D for a Future Circular Collider (FCC) at Fermilab 14

15. Infrastructure Use the 11 T dipole components, tooling, and FNAL fabrication and test infrastructure => R&D cost and time reduction 2015 FCC meetingMagnet R&D for a Future Circular Collider (FCC) at Fermilab 15