MICE Mtg Oct 2002 Elwyn Baynham RAL 1
Focussing Absorber Magnet
Elwyn Baynham ; Tom Bradshaw
Iouri Ivaniouchenkov ; Jim Rochford
Applied Science Division
Rutherford Appleton Laboratory
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Scope of Presentation
Scope» Magnetic Modelling» Conductor specification » Force reaction » Cooling» Integration with absorber» Manufacturing routes
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Solenoid absorber assembly
Superconducting Coil
Liquid H2
19 K Window
300 K Window
He Gas Cooling
Coil Support Structure
380 mm Vacuum
40 K Shield
510 mm
350 mm
1310 mm
782 mm
15 liter Surge Tank
Hydrogen Vent
G-10 Absorber Support
G-10 Absorber Support
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Design Parameters
Inner radius mm 255Outer Radius mm 336
Z1 mm 125Z2 mm 342
Current density A/mm̂ 2 105Operating Current A 225
Peak Field T 6.04Ampere turns AT 1.85E+06Stored Energy MJ 2
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Design Parameters
Opera3d model Coil Pair at Z= 0 (mm) Radial cross section 255 to 336
(mm) Axial cross section 125 to 342
(mm) Current Density: +/-105.88
(A/mm2) Total current: 1.86E+06 (A) Peak fields 6.04T Stored energy 2 Mj
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Magnetic Modelling
Aspects modelled» Field Profiles» Peak Fields» Forces» Stored Energy/Inductance matrix
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Field Profile
Field Profile for central focusing pair
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Peak Field Profile
Peak Field Map
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Forces
Forces
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Stresses
Hoop stresses
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Stored Energy Computation
Stored Energy /Inductances
C1 F1 F1' C1'C1 338.55 4.62 -2.06 -4.11F1 4.62 50.54 -5.99 -2.06F1' -2.06 -5.99 50.54 4.62C1' -4.11 -2.06 4.62 338.55
C1 F1 F1' C1' TotalC1 7.25 0.10 -0.04 -0.09 7.22F1 0.10 1.08 -0.13 -0.04 1.01F1' -0.04 -0.13 1.08 0.10 1.01C1' -0.09 -0.04 0.10 7.25 7.22
Summary of spreadsheet calculations
Inductance matrix (H)
Energy matrix (Mj)
4 central coils only powered
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Protection Philosophy
Powering– 3 sets of focus coils to be powered in series – one pair of leads for each coil to allow field trimming
Protection– by resistor/diode bypass of each coil– energy dumped/coil is self energy – coupled energy is relatively small– no active protection is seen as necessary– modelling is not yet done
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Conductor Specification/Op margins
Iwire(5T,4.2K) I Wire Amps 760 760 760
Operating Current Iop A 225 248 272
Operating Field(Peak) Bop T 6 6.6 7.26Mev/c 200 220 240
Operating Temp Top K 4.5 4.5 4.5
Current Sharing temp Ts K 5.90 5.50 5.04
Temp Margin delT K 1.40 1.00 0.54
Ratio Iop/Ic @operating field @Top Iop/Ic 0.40 0.51 0.69
Operating Point along load line(Top) % 75 83 91
Overall Cu:Sc 4 4 4
Unit cell thickness mm 1.2 1.2 1.2
Unit cell width mm 1.8 1.8 1.8
J Overall A/mm 2̂ 105 115 127
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Cooling principles
Proposed cooling mode» 2-phase circulation in pipes - pumped
Established for detector magnets – Generally high stability – pure aluminium– Large deltaT > 2K
Advantages– No helium vessel– Small helium inventory – single magnet <10 litres
Disadvantages– Require some deltaP/deltaT for circulation – 0.2-0.3K
Transient stability is the same as a bath
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Preferred cooling sites
Force
Preferred cooling sites
Force
Cooling - force transfer principles
Cooling-force transfer in cold mass
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Force Transfer to the cryostat
Schematic of force control
150T 225T
Internal force restraint
Internal axial force restraint
Suspension
External axial force restraint
Between cryostats
75T
LH
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Integration and assembly
Principles» Solenoid cold mass main structural element
– cooled to 4K by 2 phase He– supported from vessel low heat leak supports– able to be pre-tested as a separate unit
» H2 Absorber mechanically mounted from the solenoid cold mass
– thermally isolating - G10– cooled by 14-18K He gas
» Modular design and assembly
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Design and Manufacture
Design– design of magnet coils and H2 absorber must be
integrated with design of cryostat
Manufacture – the coils are industry standard in terms of
conductor/size/stored energy– key issue is cooling and force constraint
field shape gives shear forces in coils
– margin of 1.5K is adequate for this type of magnet operation at the 20% higher field will depend on quality of
force support
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Solenoid absorber assembly