superconducting large bore sextupole for ilc vladimir kashikhin, fermilab

Superconducting Large Bore Sextupole for ILC

Vladimir Kashikhin, Fermilab

April 19, 2005 Vladimir Kashikhin - Superconducting Sextupole Magnet 2

Outline

• Magnet Parameters• 2D Magnetic Design• Magnet Manufacturing• Some Remarks• Summary


Main Parameters

Maximum field at 95 mm radius 4.3 T

Sextupole strength 510 T/m2

Effective length 2 m

Good field area diameter 10 mm

Clear aperture radius 95 mm

Coil inner radius 100 mm

Coil outer radius 133 mm

Iron core inner radius 150 mm

Iron core outer radius 250 mm

Collar structure thickness 15 mm

Beam pipe thickness 2.5 mm

Losses at 4.2 K < 10 W

Shell type coil sextupole with cold iron core

Design close to LHC IR Quadrupoles


2D Magnetic Design

Coil ampere-turns 343 kA

Current 7 kA

Calculated strength 519.2 T/m2

Coil maximum field 6.2 T

Iron core field (max) 3.8 T

Field energy 376 kJ/m

Lorentz force, Fx 56.5 t/m

Lorentz force, Fy -83.2 t/m

Number of turns 22(inner) + 27(outer)

NbTi Superconducting cable LHC IR inner

Jc at B=5 T, 4.2 2750 A/mm2

Strand diameter 0.808 mm

Field vectors and conductors shown

Large LHC cable margin provides design space for future cable and geometry optimization

Field quality better than 2*10-4 at 5 cm radius


Magnet Manufacturing

LHC IR Quadrupole cross-section (cables and collar structure)

The coils are wound using Rutherford- type NbTi cable, insulated with Kapton film coated by a polyimide adhesive. After winding coils are cured under pressure to a fixed size.

The coils are supported by stainless steel collars which locked in place using tapered steel keys.

The collared coil assembly is surrounded by a laminated two-piece low carbon steel yoke.

The iron yoke provides flux return and increase the aperture field.

The iron yoke is constrained by an 8 mm thick stainless steel shell which welded simultaneously in middle plane from both side to provide needed prestress.

Longitudinal coil support is provided by 50 mm thick end plates with bullets.


Some Remarks

• LHC IR cable is not optimal for this magnet. It capable carry 14 kA current at 7 T and 4.2 K and single layer coil looks visible.

• For stand alone magnet better move the design to low current and correspondingly more economic current leads. So, the volume of superconductor may be reduced.

• The magnet installation slot length (beam pipe distance from flange to flange) should be clarified. This is critical parameter for the magnet integrated strength.

• Maximum total vertical force component Fy generate less than 25 Mpa on ground insulation in the middle plane. This is low value but total stresses during magnet assembly, cooling down and full current should be carefully analyzed.

• Total magnetic energy 376 kJ/m is close to LHC IR quadrupole (294 kJ/m) and magnet quench protection is the same.

• Tevatron HTS current leads can be used as prototype.• FNAL has experience of production such type magnet for LHC.


Summary

• It is possible to build the sextupole with specified

parameters.• Shall type magnet is base line for the design.• Another approach with six racetrack coils should

be compared with proposed shell type.• Main advantage of proposed sextupole is that it

based on well-understood existing technology.

• It is possible to use Nb3Sn superconductor if the real losses will be larger or magnet shorter at the same integrated strength.

superconducting large bore sextupole for ilc vladimir kashikhin, fermilab

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