11T Dipole for the LHC Collimation upgrade A Case Study
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Transcript of 11T Dipole for the LHC Collimation upgrade A Case Study
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11T Dipole for the LHC Collimation upgrade
A Case Study
05/02/13
Chris Segal Agnieszka PriebeGiovanni TerenzianiHerve DzitkoMichele Bertucci
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Wire Parameters and CablingCu stabilizer matrix with Cu/non-Cu ratio of 1.5Strand diameter of 0.8 mm with filament diameter of 25 um
Strand Diameter = 0.8 mm
15.8 mm1.
42m
m
strand diameter 0.8 mmCu/SC ratio 1.5Pitch Angle 16.03 degCable Width 15.8 mmCable Thickness 1.42 mmInsulation Thickness 0.15 mmFilling Factor K 0.33
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12
3
56
4
7
Superconducting area (SC)
copper area (Cu)
1.5 : 1.0
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Load Line and Short Sample Conditions
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 200
500
1000
1500
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Nb3Sn, 1.9 KLoad LineNb3Sn 7 K
Field (T)
Criti
cal c
urre
nt d
ensit
y Jc
(A/m
m2)
1640
Jsc_ss 2,050 A/mm2
Jo_ss 677 A/mm2
Iss 17,838 ABpeak_ss 14.37 T
Bpeak_ss = 14.37 T 100% field in the coil
2050
Bpeak_op = 11.5 T
Jsc_op 1640 A/mm2Iop 14,300 AJo_op 541 A/mm^2B_peak_op 11.5 T
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Coil LayoutThe 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 oneEither layout removes the sextuple and decapole contributionInner layer needs more wedges since its closer to aperture
0)5sin()5sin()5sin(0)3sin()3sin()3sin(
123
123
α1
α3α2
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EM Forces, stress
2
31
3
2
200
3/
0_ 34
32rarrarJrdfplanemid
2
1231
31
1
232
200
63634ln
123
3632
232
aaaaaa
aJ
Fx
3
131
2
132
200
121ln
41
121
232 aa
aaaJFy
Fx = 2.53 MN/mFy = -2.25 MN/m
σ = -265 MPa
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Dimension iron yoke, collar, shrinking cylinder
iron yolk dimensions 172.43mmshrinking cylinder (support reaches 90% Iss) 6.32mmcollar 40mm
Dipole Section
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Limitation in Magnetic support structure design
• Iron can’t take more than 2T (Bsat)
• Thickness of iron yoke = 21cm
• Magnetic pressure on iron yoke
MPaBPM 200*2 0
2
satBtBr
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Compare Short sample, operational conditions, and margins with NbTi
0
5
10
15
20
0 10 20 30 40 50
Cen
tral f
ield
(T)
Coil width (mm)
r=28 mmr = 50 mmr = 75 mm
Nb3Sn 1.9 K
Nb-Ti 1.9 K
“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
11T (NbTi saturation)
“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.”
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Cos(θ) vs Block
• J ~ Cos(θ)
• Self supporting structure
• Circular opening, compact coil
• Easy winding, has long history of use
• 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
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High Pre-Stress vs Low Pre-Stress
• Less damage for the Sc parts.
•Optimal training
•Unloading but still good quench performance
• Stable plateau but small degradation
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Support StructureCollar-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.
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Advantages:• Proven coil positioning• Proven length scale-upR&D issues:• Deliver required pre-stress • Max. stress at assembly
Advantages:• Can deliver very high pre-stress• Large pre-stress increase at cool-down• Easily adjustableR&D issues:• Coil alignment accuracy• Length scale-up
Support Structure: Collar-based vs Shell-based
CoilAxial rod
ShellBladder
Key
YokePad
Filler
YokeGap
PreloadShim
ControlSpacer
Skin
Collar
YokeCollaringKey
Stress Relief Slotin inner pole
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Courtesy of Peter Lee, Florida State University
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Courtesy of Peter Lee, Florida State University
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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!