11 T Dipole Experience M. Karppinen CERN TE-MSC On behalf of CERN-FNAL project teams The HiLumi LHC Design Study (a sub-system of HL-LHC) is co-funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement

11 T Nb 3 Sn 11 T Dipole for DS Upgrade  Create space for additional collimators by replacing 8.33 T MB with 11 T Nb 3 Sn dipoles compatible with LHC lattice and main systems.  kA (in series with MB)  LS2 : IR-2 o 2 MB => 4 x 5.5 m CM + spares  LS3 : IR-1,5 and Point-3,7 o 4 x 4 MB => 32 x 5.5 m CM + spares  180 x 5.5-m-long Nb 3 Sn coils M. Karppinen CERN TE-MSC  Joint development program between CERN and FNAL underway since Oct MB.B8R/L MB.B11R/L 5.5 m Nb 3 Sn 0.8 m Collim. 15,66 m (IC to IC plane) 14 February 2014

11 T Dipole Design Features 14 February 2014 M. Karppinen CERN TE-MSC  T at kA with 20% margin at 1.9 K  60 mm bore and straight 5.5-m-long coldmass  6-block coil design, 2 layers, 56 turns (IL 22, OL 34), no internal splice  Separate collared coils, 2-in-1 laminated iron yoke with vertical split, welded stainless steel outer shell

11 T Model Dipole Magnetic Parameters 14 February 2014 M. Karppinen CERN TE-MSC

Mechanical Design Concepts 14 February 2014 M. Karppinen CERN TE-MSC CERN FNAL Pole loading designIntegrated pole design Pole wedge Shim Filler wedge Loading plate Coil stress <150 MPa at all times up to 12 T design field Yoke gap closed at RT and remain closed up to 12 T

CERN 11 T Dipole Coil 14 February 2014M. Karppinen CERN TE-MSC Loading plate 2 mm 316LN SLS (Selective Laser Sintering) End Spacers with “springy legs” Braided 11-TEX S2-glass on “open-C” Mica sleeve ODS (Oxide Dispersion Strengthened) Cu-alloy Wedges Courtesy of D. Mitchell, FNAL OST RRP-108/ Ø0.7

 FNAL 2 m single-aperture model #1  RRP-108/127 strand, no core  B max =10.4 T at 1.9 K and 50 A/s (78% of SSL)  long training  irregular ramp rate dependence  Conductor degradation in coil OL mid-plane blocks and leads  lead damage during reaction - confirmed by autopsy MBHSP01 Quench Performance 14 February 2014M. Karppinen CERN TE-MSC A.V. Zlobin et al., ASC2012, Sept 2012 Quench history Ramp rate dependence

 FNAL 1 m single aperture model #2  RRP-150/169 strand, 25 µm SS core  Improved quench performance o B max = 11.7 T – 97.5% of design field B=12 T (78% of SSL at 1.9 K)  Field quality meets the present requirements  Issues to be addressed o Long training o Steady state B 0 = o Origin of conductor degradation in OL mid-plane blocks in coil fabrication or assembly process? MBHSP02 Quench Performance 14 February 2014M. Karppinen CERN TE-MSC Magnet training Ramp rate dependence Courtesy of G. Chlachidze, FNAL

MBHSM01 Mirror Magnet M. Karppinen CERN TE-MSC14 February 2014

MBHSM01 Quench Training M. Karppinen CERN TE-MSC 14 February 2014 Highest quench current at 4.5 K: 12.9 kA (92-100) % of SSL at 1.9 K: 14.1 kA (89-97) % of SSL About 4% degradation observed at 4.5 K after the 1.9 K training SSL at 4.5 K SSL at 1.9 K 4.5 K 1.9 K Courtesy of G. Chlachidze, FNAL

MBHSM01 vs. MBHSP01/02 M. Karppinen CERN TE-MSC 14 February 2014 Quench training in all 11 T magnets Courtesy of G. Chlachidze, FNAL

Lessons: Coil Parts  Nb 3 Sn Rutherford cable o Stainless steel core reduces eddy current effects o Limited compaction reduces mechanical stability o Winding tooling and process development o Braiding S2-glass over Mica-sleeve works well  End parts o SLS cost effective, flexible, and fast way of producing fully functional parts o 3-5 iterations required to get the shapes right, all manual modifications shall be minimised o Rigid metallic parts need features to make the “legs” flexible (“springy legs”, “accordeon”,..) o Dielectric coatings to develop: reactor paint, sputtering, plasma coating,.. o Epoxy-glass saddles (electrical insulation, softer for cable tails/splice, axial loading)  ODS wedges to minimise plastic deformation and distortion of the coil geometry M. Karppinen CERN TE-MSC 14 February 2014

 Min 3 Practice coils: Cu-cable, 2 X Nb3Sn  Mirror test to qualify coil technology  Tooling design o Modular tooling for easy scale-up o Understand (= measure) coil dimensional changes o Tight manufacturing tolerances require high precision quality control o Material selection and heat treatments (reaction tool) o First design the impregnation tool then reaction tool  Coil inspection: o E-modulus risky to measure o High modulus (wrt. Nb-Ti) means tight tolerances and require accurate dimensional control with CMM o Assembly parameter definition based on CMM data can be tricky.. Lessons: Coil Fabrication M. Karppinen CERN TE-MSC14 February 2014

To Develop: Heaters & Splicing  Outer layer heaters o Heaters and V-tap wiring integrated in polymide sandwich (“trace”) made as PCB o may not be enough to guarantee safe operation with redundancy o Inner layer “trace” difficult to bond reliably  Inter-layer heaters o Very efficient heat transfer to coils o Reaction resistant glass-Mica-St.St-Mica-glass sandwich o “Conventional” heaters with I-L splice  Inter-layer splice (within the coil i.e. high field) o Bring inner layer lead radially out and splice o Nb 3 Sn bridge (MSUT concept) o HTS bridge M. Karppinen CERN TE-MSC 14 February 2014