Dipole design at the 16 T frontier -Magnet R&D for a Future Circular Collider (FCC)
at Fermilab
Alexander ZlobinFermilab
FCC-hh Magnet target parameters
B / G(T) / (T/m)
Bpeak
(T)Bore(mm)
Length(units x
m)
MB 16 16.4 504500 x 14.3
MQ 450 13 50 800 x 6
MQX 225 13 100
D1 12 13 60 4x2 x 12
D2 10 10.5 60 4x3 x 10Inter-aperture distance ≈ 250 mmYoke diameter ≤ 700 mmStray field ≤ 100 mT
2015 FCC meeting Magnet R&D for a Future Circular Collider (FCC) at Fermilab 2
Present record – 13.8 T in ~35 mm aperture (HD2, LBNL, 2008)
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 Nb3Sn dipole, suitable for FCC, and 2 T HTS insert
Large-aperture 15 T Nb3Sn dipole and 5+ T HTS insert with stress management
Small-aperture 20 T accelerator dipole based on LTS (Nb3Sn) 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 meeting Magnet R&D for a Future Circular Collider (FCC) at Fermilab 3
Program Timeline
FY15-17:o Focus on 15 T Nb3Sn dipole demonstrator
2015 FCC meeting Magnet R&D for a Future Circular Collider (FCC) at Fermilab 4
VLHC HL-LHCLARP
FCC
Record field 13.8 T
HFDA HFDM-LM 43.5 mm Dipole mirror
10 T dipole
TQC TQM-LQM90 mm 200 T/m Quadrupole
quadrupole mirror
HFDC (R&W)40 mm 10 T dipole
MBHDP 60 mm 11 T dipole
MBHSP MBHSM60 mm 11 T dipole Dipole mirror
Magnet Design Choice
Coil design:o cos-thetao block-type o common coil
Technology: W&R, R&W Mechanical structure:
o with and w/o collaro 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 meeting Magnet 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
General considerations
Magnet field B ~ λJ×w Bmax~λJc(Bmax,T,…)×w
Small aperture dipole (~50 mm)oQuench protection: Coil enthalpy can absorb the stored energy in <50% of the coil volume with Tmax=250 K
oCoil maximum azimuthal stress is ~150 MPa
2015 FCC meeting Magnet 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
Jc(12T,4.2K)=3.5 kA/mm2
Strand and Cable
Strando RRP 127, 169 or 217 o Strand ID – 1 and 0.7 mmo Jc(12T, 4.2K) ~2700 A/mm2
Cableo N=28 (HFDA)o N=40 (MBH)o Ic degradation ~5%o stainless steel coreo cable prototypes are
available R&D
o increase Jc(15 T, 4.2 K)o increase strand D, cable
widtho reduce filament size
2015 FCC meeting Magnet R&D for a Future Circular Collider (FCC) at Fermilab 7
RRP-127 RRP-169 RRP-217
Coil Design Study
2015 FCC meeting Magnet R&D for a Future Circular Collider (FCC) at Fermilab 8
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
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
2015 FCC meeting Magnet R&D for a Future Circular Collider (FCC) at Fermilab 9
Optimized graded coil
Interim coil design
Mechanical Design
Lorentz forcesHorizontal support
Structure:Thin stainless steel coil-yoke spacerVertically split yoke Stainless steel clampsBolted skin (from 11 T dipole) Cold mass length: 1 mCold mass OD<610 mm (VMTF)
Protection heaters:Outer-layerInter-layer (2-3)Up to 80% of coil volume
2015 FCC meeting Magnet R&D for a Future Circular Collider (FCC) at Fermilab 10
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 sensitivityo operation margino quench protection
heater efficiency, radial quench propagation, coil quench temperature
o field quality geometrical harmonics, coil magnetization, iron saturation, dynamic effects
2015 FCC meeting Magnet R&D for a Future Circular Collider (FCC) at Fermilab 11
FNAL 15 T 2-in-1 Demonstrator Parameters
1 m diameter “cryostat” envelope
Number of apertures 2Aperture(mm) 60Aperture spacing (mm) 250Coil current (A) 11100Operating temperature (K) 4.3Max bore field at 4.3 K (T) 16.48Max coil field at 4.3 K (T) 16.96Margin along the load line 0Stored energy (MJ/m) TBDInductance (mH/m) TBDYoke ID (mm) 190.8Yoke OD (mm) 650
2015 FCC meeting Magnet R&D for a Future Circular Collider (FCC) at Fermilab 12
Is this magnet good for FCC?
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
2015 FCC meeting Magnet R&D for a Future Circular Collider (FCC) at Fermilab 13
B. Palmer (BNL), 2014
Conclusion
FCC needs cost-effective main dipole magnets with nominal operation fields of ~16 T based on Nb3Sn technologyo 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 2018o Design Bmax is above 17 T @1.9K with conservative Jco Accelerator quality features
Issues to be understood and resolved for FCCo demonstration of 15-16 T nominal field and accelerator
class parameters, improvement of magnet training, reduction of conductor degradation, magnet cost optimization
2015 FCC meeting Magnet R&D for a Future Circular Collider (FCC) at Fermilab 14
Infrastructure
Use the 11 T dipole components, tooling, and FNAL fabrication and test infrastructure => R&D cost and time reduction
2015 FCC meeting Magnet R&D for a Future Circular Collider (FCC) at Fermilab 15
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