Answers to the review committee G. Ambrosio, B.Bordini, P. Ferracin MQXF Conductor Review November 5-6, 2014 CERN

Stresses/strain Margin RRR Schedule 5/11/2014 Paolo Ferracin2

Mechanical analysis ≥2 MPa of contact pressure at up to 155 T/m (~90% of I ss ) Peak coil stress: -160/-175 MPa Strain effect not included in I ss computation Similar stress as HQ ~20% of margin 5/11/2014 Paolo Ferracin3 Inner layer Outer layer

HQ – QXF models for comparison 4 Additional step with SS shell for LHe containment QXF Aperture 150 mm Alu shell OD: 614 mm Alu shell thickness: 29 mm LHe vessel OD: 630 mm HQ Aperture 120 mm Alu shell OD: 570 mm Alu shell thickness: 25 mm 5/11/2014 H. Felice

Magnet parameters Temperature margin (K) Peak field (T) 5/11/2014 Paolo Ferracin5 4 K 5 K 12 T 10 T

Stress variations After cool-down, high stress in the pole turn At nominal field, low stress in the high field area, high stress in a lower field area 5/11/2014 Paolo Ferracin6

5/11/2014 H. Felice7

Test result of high stress TQ tests 8 93 % 91 % 88 % ~ 11.6 / 12.8 kA Only 5 % degradation from TQS03a to TQS03c [2] TQS03d did not recover => Permanent degradation All the plateau quenches located in the layer 1 multi-turn segment => highest stress with Lorentz forces ~ 12 / 13.2 kA ~ 12.3 / 13.5 kA [2] H. Felice et al., Performance of a Nb 3 Sn Quadrupole Under High Stress, IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 21, NO. 3, JUNE /11/2014 H. Felice

Higher range of pre-stress explored from HQ02a to HQ02b HQ02a performance(comparable with Nominal QXF operation) at cold and at maximum performance: 16.2 kA – 184 T/m HQ02b at maximum performance reached in HQ02b test (with increased preload) : 17.3 kA – 195 T/m 9  at 4.2 K  with Lorentz forces  at 4.2 K  with Lorentz forces 5/11/2014 H. Felice

Test Results HQ02a and HQ02b 10 [3] H. Bajas et al., Test Results of the LARP HQ02b Magnet at 1.9 K, submitted for publication HQ02b  with Lorentz forces HQ02a  with Lorentz forces 95% Iss at 1.9 K MPa azimuthal stress in HQ02b => No degradation - 95 % Iss reached 5/11/2014 H. Felice

Summary During the LARP program conductor strain has been investigated and minimized through material and design choices – Optimization of the pole piece material and gaps for HT Transverse stress is the control parameter for safe magnet pre-load, cooldown and energization – Experimental assessment of safe stress range – Shell-based support structure providing fine-tuned preload without pre-stress overshoot QXF level of azimuthal stress in the coil is lower than the level of stress in HQ highest performance. 11 5/11/2014 H. Felice

Stresses/strain Margin RRR Schedule 5/11/2014 Paolo Ferracin12

Margin I QXF-like coils may reach the SSL computed by testing extracted strands on ITER barrels Nov. 5, Max Iq vs SSL on load line SSL is based on extracted strands reacted with coils (criteria may be different) Coils in mirror structure CoilApertureMagn. lengthMax Iq vs SSLTemp. mmm%K TQM05901~ LQM01903~991.9 HQM

Margin II An Al-shell based magnet can reach similar values, with good coils and adequate pre-load: Nov. 5, Quadrupole with Al-shell structure MagnetAperture Magn. lengthMax Iq vs SSLTempComments mmm%K HQ02a HQ02b training stopped for limited test time

Margin III Most LARP magnets reached Iq > 90%, although they were still on the learning curve – TQS01/2/3 – LQS01/03 – LRS01b  After fine tuning of MQXF coil-fabrication and magnet assembly we expect the “magnet cloud” > 90%  Note: we have in the schedule 9 coils for 2 magnets Nov. 5,

Training Memory LQS01 – 90 mm aperture; ~3 m magnetic length HQ02 – 120 mm aperture; ~1 m magnetic length Nov. 5,

Nov. 5, LQS01 1 st & 2 nd Thermal Cycle

LARP/HL-LHC CM22, May 7-8, 2014HQ Program Update – G. Sabbi 18 HQ02a/b Quench Performance Significant improvement of training rate above 15 kA, reaching 95% of 1.9K SSL ~230 A/quench ~30 A/quench H. Bajas, G. Chlachidze, M. Martchevsky, F.Borgnolutti, D. Cheng, H. Felice, et al.

CERN – 5 th November 2014 Critical Current at 1.9 K 19 MQXF RRP-strand for Q2 – B. Bordini In order to accurately extrapolate the Magnet margin, I c measurements at 1.9 K were performed This wire is an ideal candidate because it has an I c just to specs  I c (4.22 K, 15 T)=362 A Round ‘Reduced Tin’ wire, billet (A01) reacted 50 hrs at 640 C.

CERN – 5 th November 2014 Values extrapolated from I c measurements of a round ‘Reduced Tin’ wire (billet 15914) reacted 50 hrs at 640 C. I c (4.22 K, 15 T) = 362 A Magnet Margin in Operating Conditions 20 MQXF RRP-strand for Q2 – B. Bordini 19.2 % Margin

Magnet parameters Temperature margin (K) Peak field (T) 5/11/2014 Paolo Ferracin21 4 K 5 K 12 T 10 T

Heat flow distribution - no helium channel in the mid-plane 85 % through the helium channels in the pole 15 % through the external insulation

Stresses/strain Margin RRR Schedule 5/11/2014 Paolo Ferracin23

Impact of RRR in magnet performance HQ02 reached 98% at 4.5K and “95%” at 1.9K – Coil 15 RRR: – Minimum in extracted strands: 50 LQS03 reached 91% at 4.5K and 82% at 1.9K – Temperature dependence almost flat – Limiting coil RRR: ~70 – Minimum in extracted strands: 50 Note: Current density higher in LQ than HQ Nov. 5,

CERN – 6 th November 2014 Magneto-Thermal Instability and Premature Quenches 25 Impact of RRR on Self-Field Instability– B. Bordini Magneto-thermal instabilities can cause premature quenches in a magnet (C and B)

CERN – 6 th November 2014 Instabilities in Magnets 26 Impact of RRR on Self-Field Instability– B. Bordini J.C. Perez et al. “The Short Model Coil (SMC) Dipole Performance Using the 11-T-dipole-type Nb 3 Sn Conductor” 4.3 K SS limit 1.9 K SS limit SMC Magnet wound with the 11 T cable (based on the RRP 108/127 wire)

CERN – 6 th November 2014 Effect of RRR on stability at 1.9 K 27 Impact of RRR on Self-Field Instability– B. Bordini 0.8 mm RRP ® Nb 3 Sn strand J c (12 T,4.3 K)≈2900 A/mm 2 RRR:

CERN – 6 th November 2014 Effect of RRR on stability at 1.9 K 28 Impact of RRR on Self-Field Instability– B. Bordini Laser Energy ≈ 3μJ RRP 0.7 mm J c (12 T,4.3 K)≈2800 A/mm 2

CERN – 6 th November 2014 Effect of RRR on stability 29 Impact of RRR on Self-Field Instability– B. Bordini Impact of the RRR on the high field instability of samples with different critical current density and of the copper to non copper ratio. For all the 4 cases an increase of RRR above 100 has not a large impact on the stability.

HQ02 RRR Note: Coil #15 extracted strands showed RRR as low as 50 Coil #15Coil #16 Coil #20Coil #17

Stresses/strain Margin RRR Schedule 5/11/2014 Paolo Ferracin31

MQXF project schedule 5/11/2014 Paolo Ferracin32 Short model program: 5 CERN-LARP models, – Coil fabrication starts in 02-03/2014 – First magnet test (SQXF1) in 07/2015 (3 LARP coils, 1 CERN coil) Long model program: 2 (CERN) + 3 (LARP) models, – Coil fabrication starts in 2015: 02 (LARP), 10 (CERN) – First magnet test in 08/2016 (LARP) and 07/2017 (CERN) Series production: 10 (CERN) + 10 (LARP) cold masses, – Coil fabrication starts in 01/2018 – First magnet test in 10/2019

Impact of cable dimensions optimization CERN MQXF current schedule 5/11/2014 Paolo Ferracin RRP short model 1 RRP short model 2 PIT short model 1 RRP long model 1 PIT long model 1