11 T Dipole for the LHC Collimation upgrade

11 T Dipole for the LHC Collimation upgrade A Case Study Chris Segal Agnieszka Priebe Giovanni Terenziani Herve Dzitko Michele Bertucci 05/02/13

Wire Parameters and Cabling 1. 42 mm Cu stabilizer matrix with Cu/non-Cu ratio of 1. 5 Strand diameter of 0. 8 mm with filament diameter of 25 um 15. 8 mm Strand Diameter = 0. 8 mm strand diameter Cu/SC ratio Pitch Angle Cable Width Cable Thickness Insulation Thickness Filling Factor K 0. 8 mm 1. 5 16. 03 deg 15. 8 mm 1. 42 mm 0. 15 mm 0. 33

Superconducting area (SC) copper area (Cu) 7 6 5 4 3 2 1 1. 5 : 1. 0

Load Line and Short Sample Conditions Jsc_ss 2, 050 A/mm 2 Jo_ss 677 A/mm 2 Iss 17, 838 A Bpeak_ss 14. 37 T Jsc_op Iop Jo_op B_peak_op 1640 A/mm 2 14, 300 A 541 A/mm^2 11. 5 T 5000 4500 Critical current density Jc (A/mm 2) 4000 3500 3000 Nb 3 Sn, 1. 9 K Load Line 2500 2050 2000 1500 1640 1000 500 0 5 6 7 8 9 10 Bpeak_op = 11. 5 T 11 12 13 Field (T) 14 15 16 17 18 19 20 Bpeak_ss = 14. 37 T 100% field in the coil

Coil Layout The angles needed to cancel B 3 and B 5 are (48°, 60°, 72°) or (36°, 44°, 64°) There is a system of two equations, but with three unknowns, there is a degree of freedom allowing for a set of solutions rather than only one Either layout removes the sextuple and decapole contribution Inner layer needs more wedges since its closer to aperture α 3 α 1 α 2

EM Forces, stress Fx = 2. 53 MN/m Fy = -2. 25 MN/m σ = -265 MPa

Dimension iron yoke, collar, shrinking cylinder iron yolk dimensions shrinking cylinder (support reaches 90% Iss) collar Dipole Section 172. 43 mm 6. 32 mm 40 mm

Limitation in Magnetic support structure design • Iron can’t take more than 2 T (Bsat) • Thickness of iron yoke = 21 cm • Magnetic pressure on iron yoke

Compare Short sample, operational conditions, and margins with Nb. Ti “Every [superconductor] is a [great superconductor]. But if you judge [Nb. Ti] by “Everybody is a genius. But if you judge a fish by its ability to climb a its ability to [upgrade the LHC for high luminosity], it will live its whole life tree, it will live its whole life believing that it is stupid. ” believing that it is [a poor superconductor]. ” -Einstein 11 T (Nb. Ti saturation)

Cos(θ) vs Block • J ~ Cos(θ) • Self supporting structure • Circular opening, compact coil • Easy winding, has long history of use • Block cable is not keystoned, perpendicular to the mid plane • Additional internal structure needed • Ratio central field/current density is 12% lower less effective than cosθ • Bss is around 5% lower than by cosθ

High Pre-Stress vs Low Pre-Stress • Stable plateau but small degradation • Less damage for the Sc parts. • Optimal training • Unloading but still good quench performance

Support Structure Collar-based vs Shell-based • Low field: shrinking outer shell • High field: collars + outer shell • Very high field: bladders, intermediate coil supports. • If a magnet training does not improve from 4. 2 to 1. 9 K, there is a mechanical limitation.

Support Structure: Collar-based vs Shellbased Yoke Shell Advantages: • Proven coil positioning • Proven length scale-up R&D issues: • Deliver required pre-stress • Max. stress at assembly Bladder Pad Axial rod Key Coil Filler Advantages: • Can deliver very high pre-stress • Large pre-stress increase at cool-down • Easily adjustable R&D issues: • Coil alignment accuracy • Length scale-up

Courtesy of Peter Lee, Florida State University

Courtesy of Peter Lee, Florida State University

References CERN Accelerator School on Superconductivity lectures (2013): • Ezio Todesco, "Magnetic Design of SC Magnets" • Pierluigi Bruzzone, "Superconducting Cables" • Fernando Toral, "Mechanical Design of SC Magnets" Thanks for listening!