11 T Dipole Status and Plans at Fermilab Alexander Zlobin Fermilab

1. 11 T Dipole Status and Plans at FermilabAlexander ZlobinFermilab

2. Outline • 11 T Dipole Program status and plans • Field quality measurements in FNAL’s models 11 T Dipole status and plans

3. 11 T Dipole Motivation • CERN is planning to upgrade the LHC collimation system • ~3.5 m space can be provided by stronger (11 T) and shorter (11 m) special dipoles • Nb3Sn technology • the 11 T magnet must be compatible with the LHC lattice and main systems 11 T Dipole status and plans

4. 11 T Dipole R&D Program (FNAL) • The original plan for FY11-14 included 3 phases (FNAL-CERN): • Phase 1 (FY11-12): design and construction of a single-aperture 2 m long demonstrator dipole, delivering 11 T at the nominal LHC current of 11.85 kA and temperature of 1.9 K in a 60 mm bore with 20% margin • Phase 2 (FY13-14): fabrication and test of two 2 m long, twin-aperture demonstrator dipoles to confirm the final magnet design, demonstrate the magnet performance parameters and their reproducibility • Phase 3 (FY14-15): technology scale up by fabricating and testing a 5.5 m long twin-aperture dipole prototype • In FY13 the FNAL plan was modified to take into account the reduction of the HFM budget as well as CERN priorities and schedule for U.S. contributions to HL-LHC • the 3rd phase of the program has been cancelled • the scope of the 2nd phase has been optimized • the model length has been reduced from 2 m to 1 m to cut the cost of Nb3Sn cable and magnet parts (mainly collar and yoke) 11 T Dipole status and plans

5. Magnet Design and Parameters (FNAL) Challenges: high field, forces, stored energy! 0.7 mm Nb3Sn RRP strand 40-strand cable 2-layer coil Stainless steel collar 11 T Dipole status and plans

6. 11 T Dipole Fabrication and Test (FNAL) • Fabrication: from cable to magnet • Test: VMTF, quench performance, magnetic measurements, quench protection 11 T Dipole status and plans

7. Model Design Features (FNAL) MBHSP01 • MBHSP01: 2-m dipole demonstrator • RRP108/127 • Cable w/o core • Coils #2, 3 • MBHSP02: 1-m dipole model • RRP150/169 • Cable with 11.5 mm core • Coils #5, 7 • MBHSM01: 1-m dipole mirror • RRP108/127 (114/127) • Cable with 11 mm core • Coil #8 • Optimized pre-stress • MBHSP03: 1-m dipole model • RRP108/127 • Cable with 11 mm core • Coils #9, 10 – modified coil end parts (FNAL) • Modified collar, thicker protection shoe • Optimized pre-stress MBHSP02, 03 MBHSM01 11 T Dipole status and plans

8. Quench Performance Summary (FNAL) • MBHSP01: • limited quench performance • Bmax=10.4 T at 1.9 K, 50A/s • 78% of SSL • strong ramp rate sensitivity • holding quenches • MBHSP02: • improved quench performance • Bmax=11.7 T at 1.9 K • 97.5% of Bdes=12 T • low ramp rate sensitivity • holding quenches • MBHSM01: • Bmax=12.5 T at 1.9 K • ~100 (97)% at 4.5 (1.9) K of SSL • low ramp rate sensitivity • no holding quenches • MBHSP03: test in progress MBHSP02, 03 MBHSM01 MBHSP01 11 T Dipole status and plans

9. 11 T Dipole Plan for FY14-15 (FNAL) • Steps to be done in FY14 • Test single-aperture dipole model MBHSP03 • Assemble and test the 1st twin-aperture dipole model MBHDP01 • Finish MBH11 and MBH12 coil fabrication • Steps to conclude the 11 T dipole program in FY15 • Assemble and test the 2nd twin-aperture dipole model MBHDP02 • Performance reproducibility and improvement • Assemble and test mirror MBHSM01b or dipole MBHSP04 w/o collar • QP study, important for LARP QXF • Technology transfer to CERN MBHSP03 MBHDP01 MBHSP02+ MBHSP03 MBHDP02 MBHSP03+ Coils 11,12 MBHSP04 MBHSM01b B0(12 kA) = 11.6 T 11 T Dipole status and plans

10. 11 T Dipole Design (CERN) • Strand: RRP and PIT • Cable: insulation Mica/braided S2-glass • Coil: removable poles, ODS wedges, G11 saddle • Collar: round, thicker • Collar-yoke interface (nominal -20 µm interf.) 0.7 mm Nb3Sn strand 40-strand cable 2-layer coil Stainless steel collar Courtesy to M. Karppinen (CERN) 11 T Dipole status and plans

11. CERN Model Program Status and Plan: (May, 2014) MBHSM101 (May-June14) MBHSP101 (Aug 14) MBHDP101 (Feb 15) MBHSP102 (Nov 14) Courtesy to M. Karppinen (CERN)

12. MBHSM101 status Courtesy to D. Shmekens (CERN)

13. Magnetic Measurements Field harmonics definition: Rref=17 mm • right-handed coordinate system • z-axis pointing from RE to LE • MBHSP02: • 26 mm and 130 mm long, and 28 mm wide 16-layer PCB probes • Probe rotation speed is 1 Hz • The new probe increases sensitivity by a factor of 10-15 over the 2-layer PCB probe used in MBHSP01 11 T Dipole status and plans

14. Transfer Function • SC magnetization effect • Eddy current effect • The iron saturation effect: • measurement/calculations at 11.85 kA is less than 1.5% MBHSP01 MBHSP02 11 T Dipole status and plans

15. Field Harmonics MBHSP01 • SC magnetization effect - large • Eddy current effect – suppressed using cored cable • Iron saturation effect - small MBHSP02 11 T Dipole status and plans

16. Current Reset Effect • LHC Iinj=760 A (vertical dashed line) • For RRP108/127 strand, with Ires=100 A the LHC injection level corresponds to the minimum on b3 curve • simpler b3 correction • RRP-108/127 0.7 mm strand could be considered for use in the production 11 T dipole magnets MBHSP01 11 T Dipole status and plans

17. Effect of Temperature • Between 1 and 2 kA, ROXIE predicts ~7% increase of the hysteresis loop width for b3 at 1.9 K due to the increase of strand Jc • MBHSP01: • measurements show ~3% reduction of the b3 hysteresis loop width • MBHSP02: • the width of hysteresis loops in TF and b3 at 4.5 K is the same or slightly larger than the loop width at 1.9 K • Need explanation MBHSP01 MBHSP02 11 T Dipole status and plans

18. Dynamic Effects • MBHSP01: • measured b3 decay is small<2 units • MBHSP02: • current profile similar to the LHC with the injection current of 0.76 kA, non-linear current ramp after injection and the nominal current of 11.85 kA • injection plateau duration ~1000 s • b3 decay at injection porch is large~8 units • High repeatability of the effect • Need better understanding of this effect MBHSP01 MBHSP02 MBHSP02 11 T Dipole status and plans

19. Geometrical Harmonics • Geometrical harmonics defined at I=3.5 kA • Some improvement in MBHSP02 wrt MBHSP01 • Still large values of b3, a3 and b2 • coil shimming used to achieve the required coil pre-stress • coil cross-section deformations during magnet assembly • coil azimuthal misalignment inside the collar • Geometrical harmonics need to be optimized before moving to production 11 T Dipole status and plans

20. Azimuthal Coil Size Optimization (Being Built) MBHSP01 MBHSP02 MBHSM01 MBH02 445 mm from RE MBH05 479 mm from RE MBH08 447 mm from RE Mirror Block (1 box = 101.6 mm) MBH03 435 mm from RE MBH07 467 mm from RE FNAL-CERN management meeting

21. Summary • 10 short coils have been made • 2 new coils are in production • cable and parts for 2 coils • 3 short dipoles and 1 mirror have been fabricated and tested • Focus on quench performance • need to understand and reduce conductor degradation • Field quality measurements and quench protection studies • Some effects remain unexplained • All results are available for LARP and Hi-Lumi collaboration • Next steps • Fabrication and test of the first 2-in-1 dipole model • Technology transfer to CERN 11 T Dipole status and plans