1. HL-LHC Corrector Magnet Design & Construction Activity Status Giovanni Volpini on behalf of the LASA team CERN, January 14 2014

2. summary Magnet specs requirements: integrated field, radiation loads & material certification operating features: operating currents, size Cross section design 2D from 2- to 6- pole Load lines, margins Superconducting wire choice, insulation & impregnation scheme, protection Mechanical issues assembly Problems waiting for us just round the (3D) corner… magnetic length cross-talk between magnets fringe field (“harmonics” at the magnet ends) forces between magnets Giovanni Volpini, CERN 14 January 20142

3. magnet specs & operating features Name Orientation Order Aperture Int strenght at radius = 50 mm Magnetic length Operating current Wire diameter Outer radius (construction) Stored energy Inductance TOTAL [-][mm][Tm][m][A][mm] [J][H] MCQSXS21501.000.7893000.7230.030412.80.676 MCSXN/S31500.060.1081500.5150.01200.50.107 MCOXN/S41500.040.1081500.5150.0654.20.058 MCDXN/S51500.030.1221500.5150.0588.70.052 MCTXN61500.090.4561500.5150.02649.40.235 MCTSXS61500.0150.0761500.5150.0441.60.039 Giovanni Volpini, CERN 14 January 20143

4. Cross-sections Giovanni Volpini, CERN 14 January 20144 yoke coil recooler pipe Sextupole Quadrupole bore

5. 2D cross sections: 4-pole Yoke radius = 230 mm Recooler bore D 50 mm @ r = 190 mm J eng (overall) ~ 300 A/mm² B peak iron = 2.43 T B peak coil = 2.82 T Warning: no stray field Giovanni Volpini, CERN 14 January 20145

6. 2D cross sections: 6-pole Yoke radius = 160 mm Recooler bore D 50 mm @ r = 190 mm, so it’s outside the yoke J eng (overall) ~ 260 A/mm² B peak iron = 3.7 T B peak coil = 2.0 T 03.12.2013 p 140 Giovanni Volpini, CERN 14 January 20146

7. 2D cross sections: 8- pole Yoke radius = 160 mm Recooler bore D 50 mm @ r = 190 mm, so it’s outside the yoke J eng (overall) ~ 260 A/mm² 8-pole B peak iron = 2.5 T B peak coil = 1.8 T Giovanni Volpini, CERN 14 January 20147

8. 2D cross sections: 10- 12- pole Yoke radius = 160 mm Recooler bore D 50 mm @ r = 190 mm, so it’s outside the yoke J eng (overall) ~ 260 A/mm² 12-pole B peak iron = 2.8 T B peak coil = 1.8 T 10-pole B peak iron = 2.65 T B peak coil = 1.8 T Giovanni Volpini, CERN 14 January 20148

9. SC wires Bruker-EAS NbTi for Fusion application Fine filaments PF wires Wire type 2 Cu:NbTi ≈ 2.30 Number of filaments 3282 Filament diameter≈ 8 μm @ 0.73 mm Two wire diameters: 0.5 and 0.7 mm S-glass insulation, An order for 8 km + 8 km will be issued in Jan 2014 Luvata Pori OK3900 Cu:NbTi ≈ 2.00 Number of filaments 3900 wire diameter 0.575 mm Filament diameter≈ 5.3 μm Bare wire An order for 20 km will be issued early in 2014 - Small wire (low operating current), but not too small (must be easy to handle, insulation should not reduce too much the Je); - High Cu content (again, low operating current, protection (4-pole)); - From the shelf product (season sale?): small amount required (10’s of kg); - Small filament (not a strict requirement, but these magnets are designed to operate in the whole range 0-Imax; Giovanni Volpini, CERN 14 January 20149

10. Quadrupole load line B @ r=50mm Design current = 300 A I c 350 A @ 5 T, 4.22 K T cs = 5.9 K 1.9 K 4.22 K B peak on coil Giovanni Volpini, CERN 14 January 201410

11. 6- and 12-pole load lines B peak on coil B @ r=50mm Design current = 150 A 4.22 K I c 179 A @ 5 T, 4.22 K Sextupole Dodecapole 1.9 K Sextupole Dodecapole Giovanni Volpini, CERN 14 January 201411

12. Field optimization Geometrical harmonics are controlled by changing the pole profile from the ideal hyperbolic profile; no action has been taken to control saturation harmonics. Small effect in case we use non circular iron yoke profile. We fear that much larger harmonics will appear at the magnet ends when the 3D computations are made. Design current = 150 A Design current = 300 A QuadrupoleSextupole a6a6 a 10 a 14 a9a9 a 15 a 21 Giovanni Volpini, CERN 14 January 201412

13. Magnet protection Quench protection is based on an external resistor dump. The maximum voltage V max is provisionally fixed at 100 V (6-pole to 12-pole) and 300 V (4-pole); any interest to keep V max 300 V? protection does not rely on quench heater; they could be considered for test purposes; the peak temperatures are computed in two limiting case: v quench → 0 (worst case) and v quench → ∞ (limiting the quench to one coil only); quench detection and switch operation time neglected; conclusion: quench does not seem a critical point –not obvious, but likely-; a more detailed quench computation with proper propagation speed has to be performed when the design reaches its final stage. nIop[A]T[K]R coil [Ω]R dump [Ω] v quench ∞0 2300119.4>3007.48>>1.000 315049.358.70.332<0.667 415037.839.30.089<<0.667 515035.936.90.065<<0.667 615076.9243.51.757>0.667 Giovanni Volpini, CERN 14 January 201413

14. Insulation & impregnation scheme Polyimide: Neither European company is able to provide kapton insulated wire, at least for such small supplies; could not identify an external supplier for dip coating, but only tape coating; doubtful behaviour during impregnation w.r.t. fiberglass: is polyimide porous enough and does it stick well to the resin? Fiberglass: one wire supplier will provide the wire already insulated with S-2 glass, with a 0.14 mm total (i.e. on diameter) thickness; discussions in progress with a specialized company to study the insulation procedure for the bare wire; Impregnation CTD-101K seems to be the most used and well known resin system. We understand that its radiation endurance properties are compliant with the design requirement. We are starting to develop the impregnation procedure with this resin. Giovanni Volpini, CERN 14 January 201414

15. Assembly The coils are not in contact with the pole. The spacer and the pole profile are tapered to match closely the coil to the pole, before tightening the screws of the wedge. coil pole wedge spacer Giovanni Volpini, CERN 14 January 201415

16. 3D design Yoke laminations machined by laser cut followed by EDM (final accuracy 1/100 mm) on the relevant surfaces: poles, coil slots, alignment slots. Assuming 5.8 mm thick iron; placing an order in parallel to CERN one? Sestupole preliminary design Giovanni Volpini, CERN 14 January 201416

17. interfaces & interferences Alternative iron design for 6-to-12 pole, allowing better alignment and/or connection with the 4-pole and other magnets. Impact on field quality negligible. Giovanni Volpini, CERN 14 January 201417 4-pole iron radius 6-8-10-12-pole iron radius recooler pipe Mechanical & electrical connection between magnets and LHe vessel to be defined, along with room for bus-bars etc. Iron radii used in the computations

18. Winding and impregnation tooling: first tests Giovanni Volpini, CERN 14 January 201418

19. open issues summary Questions to be answered as soon as possible… operating currents; outer iron diameter & shape; radiation hardness compliance, insulation & impregnation; field quality & fringe field; mechanical & electrical connection between magnets and LHe vessel to be defined, along with room for bus-bars etc.; …and, not to be forgotten: the MgB 2 solution (playground) other solutions (combined function magnet)? Giovanni Volpini, CERN 14 January 201419

20. Next steps Design Problems waiting for us just round the (3D) corner… magnetic length cross-talk between magnets fringe field (“harmonics” at the magnet ends) forces between magnets (March 2014) Residual magnetization at I=0 and impact on the harmonics Cross check COMSOL results w/ Roxie (March 2014) Mechanical design (May 2014) Construction & test Wind & impregnate a dummy coil (June 2014) Design the test cryostat Giovanni Volpini, CERN 14 January 201420

21. End (Episode I) Giovanni Volpini, CERN 14 January 201421 Acknowldgments Paolo Fessia Remi Gauthier Susana Izquierdo Bermudez Davide Tommasini …