Conceptual Design of the new D1 Magnet for HL-LHC upgrade - Present Status -

1. Conceptual Design of the new D1 Magnet for HL-LHC upgrade- Present Status - T. Nakamoto (KEK), Q. Xu (KEK/CERN) M. Iio (KEK), E. Todesco (CERN) 8 May 2012, LARP CM18/HiLumi LHC Meeting

2. Objective • For HL-LHC upgrade, needs for new Inner Triplet system at IR1 & IR5. • Large aperture HF Quadrupoles (120 or 140 mm), corrector package. • New beam separation dipole (D1) should be accommodated with large aperture IT Quads. • Replacement of current conventional magnets (nominal field 1.28T) by large aperture superconducting dipole magnets. • Conceptual design study is underway at KEK and CERN. Schematic layout of the LHC Current D1 (MBXW) at IR1 & IR5

3. Design Guideline for the new D1 • Coil ID: 150 mm for the 140 mm triplet 130 mm for the 120 mm triplet • Integrated field: 40 Tm, 50% larger than today (given by R. De Maria) • Operational margin: 70 % of the loadline (lot of radiation, margin needed) • Top: 1.9 K • Coil lay out: Two layers of 15 mm cable (thick coil to have larger field, lower stress, lower current density) • Conductor: Nb-Ti is baseline. (Leftover of LHC MB cables.) • Support structure: Collaring yoke structure (RHIC main dipole, MQXA, J-PARC SCFM) • Field homogeneity: ~ 10-4 at 2/3 bore radius • Cold mass OD: 570 mm (same as MB) >> Fringe fields will be an issue. • Radiation, energy deposition "order of 10 MGy, 1021 /m2, 10 W/m" ??

4. Design Parameters w/ NbTi LHC MB inner cable Bore diameter 150 mm Bore diameter 130 mm

5. MF Design with NbTi LHC dipole inner cable The dependence of b3 on the operating current caused by iron saturation and filament magnetization. Transfer function of the 2 cases with the collar width of 20 mm. Bore diameter: 130 mm b3 variation due to iron saturation & fringe field Collar thickness 20 mm

6. Fringe Field of the New D1 Magnet Stray field at the outer surface of the iron cryostat (ROXIE simulation results): 0.14 T at max. Magnetic field in the iron yoke and iron cryostat for 150 mm aperture and at nominal current (ROXIE simulation results) 90 o 0 o 180 o 270 o

7. Field Distortion Coupled w/ Stray Field (A) Optimized without iron cryostat • Stray field will be issues of environment. • Magnetic force between the cold mass and the iron cryostat must be considered. • Off-centered cold mass position in the current MB cryostat affects the field quality. (B) With an centered iron cryostat. (C) With an off-centered iron cryostat.

8. Measures for Stray Field: Increase of iron thickness Maximum fringe field at the outer surface of the cryostat with different sizes of iron yoke for 150 mm aperture (with 12 mm thick vacuum chamber and 20 mm thick collar) Maximum fringe field at the outer surface of the cryostat with different thickness of vacuum chamber for 150 mm aperture (with 550 mm iron yoke) Weight: 1.5 ton/m Weight: 4 ton/m

9. Measures for Stray Field: Shield coil method By using 6 turns of busbar (with the position angle of 22 degrees ) as the shield coil: the fringe field at the outer surface of the cryostat can be reduced from 0.14 T to ~ 0.04 T; The operating current is increased from 9.3 kA to 9.5 kA to keep the 70% load line ratio; the main field in the aperture is reduced from 6.35 T to 6.28 T. shield coil 90 o 180 o 0 o 270 o

10. Magnetic Field & Force on the Shield Coil Peak field of the main coil: 7.0 T Magnetic field Peak field of the shield coil: 2.1 T Lorentz force Shield coil Fx: 0.02 MN/m Fy: 0.02 MN/m Main coil Fx: 2.0 MN/m Fy: -1.0 MN/m

11. Position Dependence of the Shield Coil on b3 With optimized coil layouts for different position angles of the shield coil Target: Stray Field below 50 mT Operating current Injection

12. Field Quality for Each Case With optimized coil layout for each case to reduce multiples (b3 ~ b13) less than 1 unit Operating current Injection

13. Variation of Multipole Coefficients All available normal and skew multiples 150 mm aperture magnet with cryostat and shield coil (8 turns at 33°)

14. Mechanical simulation model in ANSYS • Collaring yoke structure (like RHIC main dipole, MQXA, J-PARC SCFM…) • 2D global model w/ tapered MP. • - The model w/ detailed key slot feature will be made later. • Simulation steps • Collaring • < 10 MPa pre-stress generated in coil by using a 0.1mm “virtual” gap between coil and mid-plane insulation; • Yoking (2 steps) • 1. load applied on the yoke shoulder to close the ~1mm gap between the top yoke (and spacer) and mid-plane; • 2. remove load, insert the lock-key. • Shell welding • Including stress from shell; • Cool-down to 2K • Excitation • Boundary conditions • Symmetry condition in X/Y direction: UX = 0 in line X = 0; UY = 0 in line Y = 0; • Friction coefficient of 0.2 for all internal interfaces; UX = 0 Stainless steel Shell Iron yoke Spacer Key Coil UY = 0 Gap thickness between top yoke and mid-plane: 0.95 mm (inner) / 1.23 mm (outer);

15. Stress intensity Yoking: load on the yoke shoulder 2.8 MN/m load applied on the shoulder of the iron yoke; The gap between top and bottom yokes closed at the inner end. The outer end is still opening. Boundary conditions UX = 0 Load: 2.8 MN/m Displacement in Y direction Yoke Spacer Coil Gap UY: 1 mm UY: 1.07 mm UY = 0

16. Stress distribution Excitation Including the Lorentz force transferred from the magnetic simulation results; The gap between top and bottom yokes closed at both ends. ~1.15 mm displacement in x direction Displacement in Y direction UX = 0 Fix the midline of the lock-key Yoke Spacer Coil UY: 0.95 mm UY: 1.16 mm UY = 0

17. Unit: Pa Coil Stress at Each Step Yoking with key Average coil stress in mid-plane Average coil stress in pole region Excitation at cold • Coil pre-stress at assembly: < 100 MPa • Compressive stress remains after cool-down and 110 % excitation. • Creep effect is not taken into account.

18. Radiation Resistant Materials After 1.9K (SUS plates) • Development of insulation coating technologies on metal parts (i.e. end spacers, wedges) • Ceramic spray • Polyimide coating by Vapor Deposition Polymerization technology. • Materials development using BT (BismaleimideTriazine) resin andCyanate Ester/Epoxy resin. • Epoxy: NG!! • Necessary for the new D1!! • Prepreg tape (curing at 150 °C) • GFRP Alumina plasma spray Polyimide coating BT resin: e irradiation (T. Sasuga, Polymer Vol. 27, 1986, 681) Materials have been developed. Irradiation tests up to 100 MGy are planned at JAEA Takasaki, KURI

19. To be addressed • Constraint of a unit cable length (leftover for MB) • 460m for inner cable, 780m for outer one. >> Start to design with the outer cable. • Structure with cooling capability to be implemented. • holes for internal HeII-HX (f80-100mm) • insulation for cables, collars. • Quench protection studies. • Coil end design: field optimization, stress. • Mechanical FEM analysis w/ detailed key slot feature. • Field quality adjustment: holes, collar. • Measure for stray field • Feasibility study of shield coil (ends, support structure) • Option of centered magnet wrt cryostat • Magnetic force affected by environments: cryostat, test-stand. • "Is field quality acceptable for the accelerator operation??" NbTi MQXC at CERN will be a good reference.

20. Backup

21. Higher Harmonics (other than b3) 130 mm aperture 150 mm aperture

22. Fringe field vs. turn no. of the shield coil

23. MF Design with NbTi LHC dipole inner cable Transfer function of the 2 cases with the collar width of 20 mm. The dependence of b3 on the operating current caused by iron saturation and filament magnetization. Bore diameter 150 mm Collar thickness 20 mm Bore diameter: 130 mm Bore diameter 130 mm Collar thickness 25 mm Bore diameter 130 mm Collar thickness 20 mm

24. Stress intensity Yoking – Key insertion Removeload from yoke shoulder and applied the same load on the lock-key; The gap between top and bottom yokes closed at both ends. Boundary conditions UX = 0 Displacement in Y direction Yoke Spacer Load: 2.8 MN/m Coil UY: 1 mm UY: 1.35 mm UY = 0

25. Stress intensity Shell welding Including the shell stress by inserting a virtual gap between yoke and shell; The gap between top and bottom yokes closed at both ends. UX = 0 Boundary conditions Displacement in Y direction Yoke Spacer Load: 2.8 MN/m Coil UY: 1 mm UY: 1.35 mm UY = 0

26. Stress intensity Cool-down to 2K The gap between top and bottom yokes closed at both ends. UX = 0 Boundary conditions Displacement in Y direction Yoke Spacer Load: 2.8 MN/m Coil UY: 1 mm UY: 1.35 mm UY = 0

27. Resource and Constraint • NbTi SC cable for MQXC (leftover of the LHC main dipole cable with new insulation system enhancing cooling capability) is the baseline. • Reuse of tooling, jigs, and facilities of the J-PARC SC Combined Function Magnets. • Yoke OD of 550 mm, same as the LHC main dipole. Yoke inner shape could be modified. • Press jig for collaring-yoke (3.6 m long) can be used as is.