1. 11T Dipole for the LHC Collimation upgrade
A Case Study
Chris Segal
Agnieszka Priebe
Giovanni Terenziani
Herve Dzitko
Michele Bertucci
05/02/13

2. Wire Parameters and Cabling
Cu stabilizer matrix with Cu/non-Cu ratio of 1.5
Strand diameter of 0.8 mm with filament diameter of 25 um
1.42mm
15.8 mm
Strand Diameter = 0.8 mm
strand diameter
0.8 mm
Cu/SC ratio
1.5
Pitch Angle
16.03
deg
Cable Width
15.8
Cable Thickness
1.42
Insulation Thickness
0.15
Filling Factor K
0.33

3. Superconducting area (SC)
copper area (Cu) 7 6 5 4 3 2 1
1.5 : 1.0

4. Load Line and Short Sample Conditions
Jsc_ss
2,050
A/mm2
Jo_ss
677
Iss
17,838 A
Bpeak_ss
14.37 T
Jsc_op
1640
A/mm2
Iop
14,300 A
Jo_op
541
A/mm^2
B_peak_op
11.5 T
2050
1640
Bpeak_op = 11.5 T
Bpeak_ss = T  100% field in the coil

5. Coil Layout
The angles needed to cancel B3 and B5 are (48°,60°,72°) or (36°,44°,64°)
There is a system of two equations, but with three unknowns, there is a degree of freedom allowing for a set of solutions rather than only one
Either layout removes the sextuple and decapole contribution
Inner layer needs more wedges since its closer to aperture α2 α3 α1

6. EM Forces, stress
Fx = MN/m
Fy = MN/m
σ = -265 MPa

7. Dimension iron yoke, collar, shrinking cylinder
iron yolk dimensions
172.43 mm
shrinking cylinder (support reaches 90% Iss)
6.32
collar 40
Dipole Section

8. Limitation in Magnetic support structure design
Iron can’t take more than 2T (Bsat)
Thickness of iron yoke = 21cm
Magnetic pressure on iron yoke

9. Compare Short sample, operational conditions, and margins with NbTi
“Every [superconductor] is a [great superconductor]. But if you judge [NbTi] by its ability to [upgrade the LHC for high luminosity], it will live its whole life believing that it is [a poor superconductor].”
-Einstein
“Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.”
11T (NbTi saturation)

10. Cos(θ) vs Block
Block cable is not keystoned, perpendicular to the mid plane
Additional internal structure needed
Ratio central field/current density is 12% lower  less effective than cosθ
Bss is around 5% lower than by cosθ
J ~ Cos(θ)
Self supporting structure
Circular opening, compact coil
Easy winding, has long history of use

11. High Pre-Stress vs Low Pre-Stress
Stable plateau but small degradation
Less damage for the Sc parts.
Optimal training
Unloading but still good quench performance

12. Support Structure Collar-based vs Shell-based
Low field: shrinking outer shell
High field: collars + outer shell
Very high field: bladders, intermediate coil supports.
If a magnet training does not improve from 4.2 to 1.9K, there is a mechanical limitation.

13. Support Structure: Collar-based vs Shell-based
Coil
Axial rod
Shell
Bladder
Key
Yoke
Pad
Filler
Advantages:
Can deliver very high pre-stress
Large pre-stress increase at cool-down
Easily adjustable
R&D issues:
Coil alignment accuracy
Length scale-up
Advantages:
Proven coil positioning
Proven length scale-up
R&D issues:
Deliver required pre-stress
Max. stress at assembly

14. Courtesy of Peter Lee, Florida State University

15. Courtesy of Peter Lee, Florida State University

16. Thanks for listening! References
CERN Accelerator School on Superconductivity lectures (2013):
Ezio Todesco, "Magnetic Design of SC Magnets"
Pierluigi Bruzzone, "Superconducting Cables"
Fernando Toral, "Mechanical Design of SC Magnets"
Thanks for listening!