MQXF Design and Conductor Requirements P. Ferracin MQXF Conductor Review November 5-6, 2014 CERN.

MQXF Design and Conductor Requirements

P. Ferracin

MQXF Conductor Review November 5-6, 2014

CERN

Outline

• Overview of MQXF design

• Baseline strand and insulated cable

• Coil design and magnetic analysis

• Magnet parameters

• Mechanical analysis and quench protection

5/11/2014Paolo Ferracin 2

Overview of MQXF design


• Target: 140 T/m in 150 mm coil aperture

• To be installed in 2023 (LS3)

• Q1/Q3 (by US LARP collaboration)– 2 magnets with 4.0 m of magnetic

length within 1 cold mass• Q2 (by CERN)

– 1 magnet of 6.8 m within 1 cold mass, including MCBX (1.2 m)

• Baseline: different lengths, same design– Identical short model magnets SQXF

by E. Todesco

20 40 60 80 100 120 140 160 180distance to IP (m)

Q1 Q3Q2a Q2b D1

Q1-3: 140 T/mMCBX: 2.2 T 2.5/4.5 T mD1: 5.6 T 35 T mD2: 4.5 T 35 T mQ4: 115 T/mMCBY: 3 T 4.5 T m

D2 Q4

From LARP HQ to MQXFStrand, cable and coil

• The aperture/cable width is approximately maintained– Aperture from 120 mm to 150 mm– Cable from 1.5 to 1.8 mm width– Similar stress with +30% forces

• Same coil lay-out: 4-blocks, 2-layer with same angle• Optimized stress distribution

• Strand increase from 0.778 mm to 0.85 mm– Same filament size from 108/127 to 132/169– Maximum # of strands: 40

• Lower Joverall from quench protection (from 580 to 480 A/mm2)


HQ MQXF

From LARP HQ to MQXFMagnet design

• Same structure concept • Pre-load capabilities of HQ design qualified and successfully tested

• Larger OD: from 570 to 630 mm• Additional accelerator features

• Larger pole key for cooling holes• Cooling channels• Slots for assembly/alignment • LHe vessel and welding blocks and slots


HQ MQXF



• OD: 630 m• SS shell, 8 mm for LHe

containment• Al shell, 29 mm thick• Iron yoke

– Cooling holes (77 mm) – Slots of assembly/alignment

• Iron Master plates – 58 mm wide bladder

• Iron pad• Al bolted collars

– Coil alignment with G10 pole key

• Ti alloy poles

MQXF magnet design


Outline







• 0.85 mm strand

• Filament size <50 μm• OST 132/169: 48-50 μm• Bruker PIT 192: 42 μm

• Cu/Sc: 1.2 0.1 55% Cu

• Critical current at 4.2 K and 15 T– 361 A at 15 T

MQXF strand(from CERN technical specification document)


Bruker PIT strand, 192

OST RRP strand, 132/169

MQXF baseline cable and insulation


MQXF baseline cable

• 40-strand cable• Mid – thickness after cabling

– 1.525 +/- 0.010 mm– Thin/thick edge: 1.438 /1.612 mm

• Width after cabling– 18.150 +/- 0.050 mm

• Keystone angle– 0.55 +/- 0.10 deg.

– Pitch length– 109 mm

– SS core 12 mm wide and 25 μm thick

• Assumed expansion during reaction– 4.5% in thickness: ~70 μm, same

keystone angle– 2% in width: ~360 μm

• Mid – thickness after reaction– 1.594 mm– Thin/thick edge: 1.505/1.682 mm

• Width after reaction– 18.513 mm


PIT

cable R

RP

cable

70 μm

360 μm

Dimensional changes during heat treatment• Unconfined cables and strands (RRP) at LBNL

– axial contraction: 0.1 to 0.3 %– thickness increase: 1.5 to 4 %– width increase: 1.5 to 2 %

• Data on PIT strands and cables (FRESCA2) – larger axial contraction, comparable cross-section increase

• In HQ01, only 1-2% space for expansion left in design– Clear signs of over compressed and degraded coils

• So in HQ02, reduction of strand diameter (0.8 0.778 mm)– Thickness: 4.5%, from 29 μm (HQ01) to 65 μm (HQ02)– Width: 2%– Very good HQ02 quench performance

• Same assumptions used for MQXF– No signs of over-compression in first coils– Work in progress: Ten stack measurements at CERN and MQXF LARP coil 1 cross-

section measurements at LBNL


Cable insulation

• AGY S2-glass fibers 66 tex with 933 silane sizing• 32 (CERN, CGP) or 48 (LARP, NEW) coils (bobbins)

• Variables: # of yarn per coil and of picks/inch• Target: 150 μm per side (145 5 μm) at 5 MPa, average 3 cycles


Sample Ins. Cable thickness (mm) Bare cable thick/ (mm) Insulation thick. (mm)

001_1 1.822 1.530 146

001_2 1.823 1.531 146

001_3 1.821 1.530 146

101_1 1.817 1.531 143

101_3 1.816 1.531 143

102_1 1.821 1.531 145

102_2 1.819 1.531 144

102_3 1.823 1.531 146

Tooling design

• Cable dimension after reaction and 150 μm thick insulation

• Coil cured in larger cavity

• Coil closed in reaction fixture in larger cavity

• Coil after reaction and during impregnation in nominal cavity

• Theoretical pressure ~5 MPa


Impact of cable dimensions optimization• Up to 20 μm of thickness increase with same

keystone angle– Compensated by insulation thickness

• from 150 to 140 μm 20 μm– “Transparent” modification, no impact on

schedule• More than 20 μm of thickness increase

and/or change of keystone angle– Example: from 0.55 to 0.4 deg., with same mid-

thickness• Thin edge from 1.438 to 1.462 mm 25 μm

– Considering 28 turns 700 μm on the outer layer– Change of wedges/pole/end-spacers

• ~10 months from new cable geometry to beginning of winding


22+28 = 50 turns

Outline







Coil design and magnetic analysis• Two-layer – four-block design, 22+28 = 50 turns• Criteria for the selection

– Maximize gradient and # of turns (protection) – Distribute e.m. forces and minimize stress

• All harmonics below 1 units at Rref = 50 mm

• 6 blocks in the ends• 1% peak field margin in the end (ss pad)


Persistent currents• Estimates using magnetization measurements of actual QXF

169 wires performed at Ohio State University• Harmonics are provided for second up-ramp following a pre-

cycle corresponding to the one used for strand measurements


Measured magnetization (OSU) Calculated b6 (after pre-cycle)

Persistent-current effect evaluation

• Effect of ±20% magnetization on b6, b10 included– Nominal b6 value of -10 units can be adjusted using current reset level

during pre-cycle– Dynamic aperture simulations have validated a persistent current b6 up

to 20 units at injection• Present value of magnetization average and spread are compatible

with field quality requirements

• For future study: assessment of the variability in wire magnetization and resulting uncertainty and random harmonics


Persistent current harmonics

b6 b10

Nominal D(+20%M) Nominal D(+20%M)

1.0 kA (injection) -10.0 -2.4 3.4 +0.8

17.5 kA (high field) -0.97 -0.12 -0.1 0.0

Coil design and magnetic analysisMagnet lengths


Magnetic length RT = 1198 mm

Coil design and magnetic analysisMagnet lengths


Short model Q1/Q3 (half unit) Q2

Magnetic length [mm] at 293 K 1198 4012 6820.5

Magnetic length [mm] at 1.9 K 1194.4 4000 6800

“Good” field quality [m] 0.5 3.3 6.1

Coil physical length [mm] at 293 K 1510 4324 7132.5

Iron pad length [mm] at 293 K 975 3789 6597.5

Yoke length [mm] at 293 K 1550 4364 7172.5

• Longitudinal thermal contraction = 3 mm/m (as LHC magnets)

Coil design and magnetic analysisConductor quantities


Short model Q1/Q3 (half unit) Q2

Cable length per coil [m] (Roxie) 126 407 687

Cable length per coil [m] (with margin) 150 450 710

Strand per coil [km] (with margin) 6.3 18.9 30.0

Strand per coil [kg] (with margin) 32 95 150

• Strand length = cable length * 40 * 1.05• 1 km of 0.85 mm strand: 5 Kg.

Outline







Superconductor propertiesVirgin strand, no self field correction

• Godeke’s parameterization


2450 at 12 T

1400 at 15 T

2040 at 15 T

3270 at 12 T

632 at 12 T

361 at 15 T

527 at 15 T

844 at 12 T

Ca1* 41.24 TCa2* = 1034 x Ca1* 42642 Teps_0,a 0.250% Bc2m*(0) 31.50 TTcm* 15.34 KC* 1541 TAp 0.5 q 2 Strain= -0.20%

Magnet parameters

• Self field corr. (ITER barrel)• 0.429 T/kA

• 5% cabling degradation• Operational grad.: 140 T/m

• Iop: 17.5 kA• Bpeak_op: 12.1 T

• 80-81% of Iss at 1.9 K• Gss: 171 T/m• Iss: 21.6 kA• Bpeak_ss: 14.7 T

• Stored energy: 1.3 MJ/m• Inductance: 8.2 mH/m


• Impact of higher Imax strand – +10% increase in critical

current about +3% in Iss

Magnet parameters

• Temperature margin (K) • Peak field (T)


Outline







Mechanical analysis• ≥2 MPa of contact pressure at up to

155 T/m (~90% of Iss)

• Peak coil stress: -160/-175 MPa

• Strain effect not included in Iss computation• Similar stress as HQ• ~20% of margin


Inner layer

Outer layer

Quench protection


• Protection studied in the case of 2 magnets in series (16 m) protected by one dump resistor (48 mΩ, 800 V maximum voltage)– Voltage threshold: 100 mV– Cu/Non-Cu: 1.2 – Validation time: 10 ms– Protection heaters on the outer and on the inner layer

• Hot spot T with 1.2 Cu/Non-Cu ratio: ~263 K

• Negligible effect of ~6-7 K from RRR (100-200) and Cu/non-Cu ratio (1.1 to 1.2)

Conclusions• Strand critical current of 361 A at 15 T

– Corresponding to current density of ~2500 A/mm2 at 12 T– ~80-81% of Iss

• Reasonable margin, probably the most critical parameter– 10% of critical strand current 3% of load-line margin

• Cu/non-Cu of 1.2– In HQ: 1.1-1.2

• Intermediate value between 0.85 (HD) and 1.6 (LHC) – Safe margin for protection

• Filament size <50 μm– Same filament size as one used in HQ02 successfully tested– Consistent with field quality requirements

• Cored cable required for reduction of dynamics effects (as in HQ02)

• Peak stress of ~170 MPa, similar to TQ/HQ series


Appendix


MQXF project schedule


• Short model program: 5 CERN-LARP models, 2014-2016– 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, 2015-2018– 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, 2018-2021– Coil fabrication starts in 01/2018– First magnet test in 10/2019

Impact of cable dimensions optimizationCERN MQXF current schedule


2014 2015 2016 2017 2018

RRP short model 1

RRP short model 2

PIT short model 1

RRP long model 1

PIT long model 1

MQXF Design and Conductor Requirements P. Ferracin MQXF Conductor Review November 5-6, 2014 CERN.

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Transcript of MQXF Design and Conductor Requirements P. Ferracin MQXF Conductor Review November 5-6, 2014 CERN.