Superconducting Large Bore Sextupole for ILC Vladimir Kashikhin, Fermilab

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

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

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

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

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

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