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Dipole design at the 16 T frontier - Magnet R&D for a Future Circular Collider (FCC) at Fermilab Alexander Zlobin Fermilab. FCC-hh Magnet target parameters. Inter-aperture distance ≈ 250 mm Yoke diameter ≤ 700 mm Stray field ≤ 100 mT.
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Dipole design at the 16 T frontier -Magnet R&D for a Future Circular Collider (FCC) at FermilabAlexander ZlobinFermilab
FCC-hh Magnet target parameters Inter-aperture distance ≈ 250 mm Yoke diameter ≤ 700 mm Stray field ≤ 100 mT Present record – 13.8 T in ~35 mm aperture (HD2, LBNL, 2008) Magnet R&D for a Future Circular Collider (FCC) at Fermilab
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 • Develop accelerator magnets with world record parameters • Small-aperture 15 T Nb3Sn dipole, suitable for FCC, and 2 T HTS insert • Large-aperture 15 T Nb3Sn dipole and 5+ T HTS insertwith stress management • Small-aperture 20 T accelerator dipole based on LTS (Nb3Sn) and HTS (Bi-2212 or YBCO) coils • Perform magnet cost optimization studies. • Continue superconductor and structural material R&D for 15-20 T accelerator magnets. Magnet R&D for a Future Circular Collider (FCC) at Fermilab
Program Timeline • FY15-17: • Focus on 15 T Nb3Sn dipole demonstrator FCC Record field 13.8 T LARP HL-LHC VLHC MBHSP MBHSM 60 mm 11 T dipole Dipole mirror HFDA HFDM-LM 43.5 mm Dipole mirror 10 T dipole TQC TQM-LQM 90 mm 200 T/m Quadrupole quadrupole mirror MBHDP 60 mm 11 T dipole HFDC (R&W) 40 mm 10 T dipole Magnet R&D for a Future Circular Collider (FCC) at Fermilab
Magnet Design Choice • Coil design: • cos-theta • block-type • common coil • Technology: W&R, R&W • Mechanical structure: • with and w/o collar • Stainless Steel or Al shell • stress management • Field range: 10-13.8 T • 13.8 T - record since 2008 • Focus on the cos-theta (shell-type) design w/o collar D20 (LBNL), 13.4 T, 1997 HFDA (FNAL) 10 T, 2003-2006 MBHSP (FNAL) 11.6 T, 2012-2014 MBHDP (FNAL) 11.5 T, 2015 RD3c (LBNL), 10 T, W&R, 2003 DCC017 (BNL), 10 T, R&W, 2007 HFDC (FNAL), ~6 T, R&W, 2004 HD2 (LBNL), 13.8 T, 2008 Magnet R&D for a Future Circular Collider (FCC) at Fermilab
General considerations • Magnet field B ~ λJ×w Bmax~λJc(Bmax,T,…)×w • Small aperture dipole (~50 mm) • Quench protection: Coil enthalpy can absorb the stored energy in <50% of the coil volume with Tmax=250 K • Coil maximum azimuthal stress is ~150 MPa 150 mm bore Tmax=250 K 50 mm bore • Jc(12T,4.2K)=3.5 kA/mm2 P. Fessia et al., IEEE TAS, 19, 3, 2009. 1.9 K Magnet R&D for a Future Circular Collider (FCC) at Fermilab
Strand and Cable • Strand • RRP 127, 169 or 217 • Strand ID – 1 and 0.7 mm • Jc(12T, 4.2K) ~2700 A/mm2 • Cable • N=28 (HFDA) • N=40 (MBH) • Ic degradation ~5% • stainless steel core • cable prototypes are available • R&D • increase Jc(15 T, 4.2 K) • increase strand D, cable width • reduce filament size RRP-127 RRP-169 RRP-217 Magnet R&D for a Future Circular Collider (FCC) at Fermilab
Coil Design Study • Coil aperture: 60 mm • Coil cross-section: 4 layers, graded • Design parameters: Bmax, field quality, coil volume, az. stress • Design choice: 4L-5 – minimal coil size and stress 4L-1 4L-2 4L-3 4L-4 4L-5 Magnet R&D for a Future Circular Collider (FCC) at Fermilab
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/mm2 • Coil Bmax= 16.3/15.2 T at 4.3 K • Bore Bmax= 15.6/14.6 T at 4.3 K • + ~1.5 T at 1.9 K • Additional margin – higher Jc Optimized graded coil Interim coil design Magnet R&D for a Future Circular Collider (FCC) at Fermilab
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 Magnet R&D for a Future Circular Collider (FCC) at Fermilab
Test goals • Demonstration of 15-16 T field level • Study and optimization of • magnet quench performance • training, degradation, memory, effect of coil pre-load • ramp rate sensitivity • operation margin • quench protection • heater efficiency, radial quench propagation, coil quench temperature • field quality • geometrical harmonics, coil magnetization, iron saturation, dynamic effects Magnet R&D for a Future Circular Collider (FCC) at Fermilab
FNAL 15 T 2-in-1 Demonstrator Parameters 1 m diameter “cryostat” envelope Is this magnet good for FCC? Magnet R&D for a Future Circular Collider (FCC) at Fermilab
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 • Bop, Top B. Palmer (BNL), 2014 Magnet R&D for a Future Circular Collider (FCC) at Fermilab
Conclusion • FCC needs cost-effective main dipole magnets with nominal operation fields of ~16 T based on Nb3Sn technology • 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 qualitydipolefor FCC is a key milestone • FNAL has a promising dipole design and a plan to achieve this milestone by 2018 • Design Bmax is above 17 T @1.9K with conservative Jc • Accelerator quality features • Issues to be understood and resolved for FCC • demonstration of 15-16 T nominal field and accelerator class parameters, improvement of magnet training, reduction of conductor degradation, magnet cost optimization Magnet R&D for a Future Circular Collider (FCC) at Fermilab
Infrastructure Use the 11 T dipole components, tooling, and FNAL fabrication and test infrastructure => R&D cost and time reduction Magnet R&D for a Future Circular Collider (FCC) at Fermilab