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