1. Status on HQ Coil Design and Fabrication Helene Felice 11/16/2011 LARP Collaboration Meeting 17 1stHiLumi Collaboration Meeting CERN

2. HQ01 series Overview HQ01a HQ01b HQ01c HQ01d HQ01e Coils Test 1-2-3-4 April 2010 1- 4 -5-6 June 2010 1 -5-7-8 Oct. 2010 5-7-8-9 April 2011 5-7-8-9 July 2011 • 9 coils (54/61 or 108/127 RRP) • 5 tests at 4.4 K at LBNL HQ01a – 157 T/m – 79 % Iss – unusual ramp-rate HQ01b – 153 T/m – 77 % Iss – electrical failure HQ01c – 138 T/m – 70 % Iss – unusual ramp-rate HQ01d – 170 T/m – 86 % Iss - mechanical limit HQ01e – 170 T/m – 86 % Iss H. Felice - 1st HiLumi/ LARP Collaboration Meeting

3. Overview of HQ01 coil fabrication H. Felice - 1st HiLumi/ LARP Collaboration Meeting

4. HQ01b Electrical breakdown possible causes • Extensive mechanical analysis performed • ruled out the participation of the support structure • Autopsy of coil #6 • revealed origin of the short in the interlayer • pointed out end design weakness both Lead end and Return end • Review of the coil fabrication process: high compaction • Combination of these effects => electrical failure in HQ01b View of the return end Lead end H. Felice - 1st HiLumi/ LARP Collaboration Meeting

5. High compaction: a common symptom of HQ01 coils • 9 coils tested in HQ01 : same observations during fabrication • very high compaction after reaction • tendency to spring out of the reaction fixture (unlike TQ/LQ) • Broken strands in coil 10 • observed post-reaction Coil 3 • Some corrective actions taken to reduce the compaction • reduction of the radial • build-up of material in the • cavity Coil 10 • Coil / cavity size mismatch post reaction? Nb3Sn formation? • Not seen in TQ/LQ Coil 7 H. Felice - 1st HiLumi/ LARP Collaboration Meeting

6. Dimensional changes during heat treatment Study on unconfined cables Meas. performed at LBNL by J. Krishnan • axial contraction: 0.1 to 0.3 % • thickness increase: 1.4 to 4 % • width increase: 1.5 to 2 % Study on sections of LQ - TQ and HQ coils Thickness LQ and TQ: 5.6 and 6% of increase HQ: only 1 to 2 % of increase Width LQ and TQ => 1 to 2 % of increase HQ => 1 % of increase Meas. Performed at FNAL D. Bocian, M. Bossert width H. Felice - 1st HiLumi/ LARP Collaboration Meeting

7. What is different in HQ? • Comparison of the coil fabrication tooling between TQ/LQ and HQ • consistency with a constant cavity size at each step of the fabrication • Comparison of the coil cross-sections • difference in the nominal design insulation • 125 mm in LQ • 100 mm in HQ • Creating a buffer of 80 mm per turn in LQ ~ 6% of LQ cable thickness • Creating a buffer of 30 mm per turn in HQ ~ 2% of HQ cable thickness Effective insulation: 86 mm thick More room in the cavity required for radial and azimuthal expansion H. Felice - 1st HiLumi/ LARP Collaboration Meeting

8. Accounting for axial dimensional changes • Axial tension in the conductor ~ 5MPa => Relaxation due to winding tension • Contraction during reaction • Axial gaps in the pole pieces during winding Young modulus measured on various HQ unreacted cables: Winding relaxation estimated to 1mm/m Modulus (MPa) Measured by Brett Collins Total gap size 3 to 4 mm/m Axial contraction due to reaction estimated to be 2 to 3 mm/m Stress (MPa) H. Felice - 1st HiLumi/ LARP Collaboration Meeting

9. Test Coils • “Compaction theory” tested with test coils • Increase of the azimuthal space in the cavity • Still radial compaction • Unusual coil size => FNAL mirror test • Coil 13 – 54/61 – no core • By removing the mid-plane turn in both layers • ~5 % per turn of additional space • Axial gap increased from 0.8 mm to 2 mm • closed after reaction • contraction of ~ 3mm/m • Assembled in HQM02 tested at FNAL • 91 % of Iss at 4.6 K • 89 % of Iss at 2.2 K • Coil 12 – 54/61 – cored cable • By adjusting mid-plane shimming • ~3 % per turn of additional space • Assembled and tested in FNAL HQM01 • Limited by mid-plane turn • Improved performance at 150 A/s • => 82 % Iss Rodger Bossert & GuramChlachidze H. Felice - 1st HiLumi/ LARP Collaboration Meeting

10. HQ02 coils: reduced compaction • A new series of HQ magnets: HQ02 • Main requirement: using the same tooling as HQ01 • Interlayer insulation increased to 500 mm • Accounting for dimensional changes and interlayer insulation • Smaller cable with smaller strand => 0.778 mm => 14.8 mm x 1.375 mm • Axial gap size 4 mm/m • All coils made with 108/127 conductor • Revision of the end parts design • New approach for the magnetic cross-section • Reacted cable dimension based on some assumptions • on cable dimensional changes • Conductor alignment on the OD of the pole piece H. Felice - 1st HiLumi/ LARP Collaboration Meeting

11. Overview of HQ02 coil fabrication • Coil 14 post-reaction: • limited protrusion ~1.5 / 2 mm • Coil 15 post-curing: • Ongoing cored cable measurement to get reference numbers for cored cable dimensional changes • Total axial contraction: NA • Gap: 4 mm/m • 1 mm/m post curing • Total axial contraction: 3.5 mm/m • Gap: ~4 mm/m • 0.5 mm/m post curing H. Felice - 1st HiLumi/ LARP Collaboration Meeting

12. HQ persisting electrical weaknesses • Despite increased interlayer insulation • Despite outer layer end-shoe revision • Despite reduced compaction • Task force set up to address this issue • Possible revision in HQ and LHQ H. Felice - 1st HiLumi/ LARP Collaboration Meeting

13. Damaged insulation post-reaction Insulation fragmentation after reaction Possibly caused by the use of CTD binder Decision to stop using “precured” glass or Nextel ceramic for the interlayer insulation in the new generation of coils S-glass placed on the OD of the coil during reaction (combination of the brittleness and high compaction) Nextel ceramic interlayer insulation, not treated with binder H. Felice - 1st HiLumi/ LARP Collaboration Meeting

14. Summary • 11 coils fabricated with the HQ01 design • Observations: coil high compaction, electrical breakdown, somewhat limited performance • Possible cause of limitations • initial coil design – fabrication process: high compaction • 2 test coils with reduced compaction tested in FNAL mirror • HQ02 design implemented in coils 14 and 15 • 108/127 conductor, smaller cable, OL end-shoe revision • Introduction of SS cored cable in all coils starting with coil 15 H. Felice - 1st HiLumi/ LARP Collaboration Meeting

15. Some open questions • Electrical weaknesses observed in almost all the coils • Failure of the hipot coil to metallic components • Some insulation issues – compatibility with binder • Some uncertainties about the coil dimensional changes • Need to understand if the HQ somewhat limited performance come only from the coil high compaction • urgency to get HQ02 coils ready for test • Ongoing investigation • Dimensional changes in cored cables • Task force for end-shoe redesign and improvement H. Felice - 1st HiLumi/ LARP Collaboration Meeting