1. Superconducting Large Bore Sextupole for ILC
Vladimir Kashikhin, Fermilab

2. Vladimir Kashikhin - Superconducting Sextupole Magnet
Outline
Magnet Parameters
2D Magnetic Design
Magnet Manufacturing
Some Remarks
Summary
April 19, 2005
Vladimir Kashikhin - Superconducting Sextupole Magnet

3. Vladimir Kashikhin - Superconducting Sextupole Magnet
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
April 19, 2005
Vladimir Kashikhin - Superconducting Sextupole Magnet

4. Vladimir Kashikhin - Superconducting Sextupole Magnet
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
Field quality better than 2*10-4 at 5 cm radius
Large LHC cable margin provides design space for future cable and geometry optimization
April 19, 2005
Vladimir Kashikhin - Superconducting Sextupole Magnet

5. Vladimir Kashikhin - Superconducting Sextupole Magnet
Magnet Manufacturing
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.
LHC IR Quadrupole cross-section (cables and collar structure)
April 19, 2005
Vladimir Kashikhin - Superconducting Sextupole Magnet

6. Vladimir Kashikhin - Superconducting Sextupole Magnet
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.
April 19, 2005
Vladimir Kashikhin - Superconducting Sextupole Magnet

7. Vladimir Kashikhin - Superconducting Sextupole Magnet
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.
April 19, 2005
Vladimir Kashikhin - Superconducting Sextupole Magnet