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Magnet SystemsJim Kerby

20 Apr 2007

With thanks to my colleagues

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Current Program

Current focus: Demonstrate by the end of 2009 that Nb3Sn magnets are a viable choice for an LHC IR upgrade

Known major issues– Nb3Sn technology; Peak field on coil; Length; Consistency

Three pronged approach: Predictable and reproducible performance

– TQ models (1m, 90mm bore, Gnom > 200 T/m, Bcoil > 12T)

Long magnet fabrication– LQ models (4m, 90mm bore, Gnom > 200 T/m, Bcoil > 12T)

Predictable and reproducible performance– HQ models (1m, 90+mm bore, Gnom ~ 250 T/m, Bcoil > 15T)

But several new initiatives are under discussion—slim Q0 options, for instance—we can not be completely locked in the box, and must be willing to contribute in the best way possible for LHC

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Quadrupole Designs for the LHC IR

100

150

200

250

300

350

50 70 90 110 130 150

Coil Aperture [ mm ]

Sh

ort

Sa

mp

le G

rad

ien

t [

T/m

]

Higher Performance

NbTi Upgrade CERN-HHH [2]

FNAL [4]-[5]

TQ [8]-[9]& LQ [10]

HQLBNL & INFN [3]FNAL [4]

KEK & FNALNbTi LHC IR

HQ-130

LBNL [6]

100

150

200

250

300

350

50 70 90 110 130 150

Coil Aperture [ mm ]

Sh

ort

Sa

mp

le G

rad

ien

t [

T/m

]

Higher Performance

NbTi Upgrade CERN-HHH [2]

FNAL [4]-[5]

TQ [8]-[9]& LQ [10]

HQLBNL & INFN [3]FNAL [4]

KEK & FNALNbTi LHC IR

HQ-130

LBNL [6]

[1] LHC Design Report[2] R. Ostojic et al., PAC-05[3] S. Caspi et al, MT-15

[4] T. Sen et al, PAC-01[5] A. Zlobin et al., EPAC 02[6] G. Sabbi et al., ASC-02

[8] R. Bossert et al., ASC-06[9] S. Caspi et al., ASC-06[10] G. Ambrosio et al., ASC-06

[1]

From ASC06 HQ Paper

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TQC and TQS Design Concepts

• Aluminum shell over iron yoke • Assembly with bladders and keys• Aluminum rods for axial pre-load

Axial rod

Shell Key

Yoke Pad

Filler

YokeGap

PreloadShim

ControlSpacer

Skin

Collar

YokeCollaringKey

Stress Relief Slotin inner pole

TQC TQS

• Stainless steel collars and skin• Control spacers to limit pre-load• End support plates, no pre-load

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TQC01 and TQS01 Quench Training

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5

7

9

11

13

15

0 10 20 30 40Quench Sequence

Que

nch

Cur

rent

[kA

]

4.5K Training

4.5K Ramp-Rate

Sub-Cooled (3.2K)

4.5K (2nd T.C.)

SSL 4.5KSSL 3.2K

TQS01TQC01

• TQC01: limited to 70% of short sample at 4.5K, but achieves 85% at 1.9K • TQS01: start training at 80% of 4.5 K short sample, limited to 87% in one coil• Maximum quench gradient was close to 200 T/m in TQC01 and TQS01

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TQS01b & TQS01c Test Results

• TQS01b: starts training at 75% of 4.5 K short sample, plateau at ~82% (1 coil)• TQS01c: Trained at and 4.5K and 1.9K, ~80% plateau is conductor-limited

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Field quality analysis:First TQ models show that the random coil block displacements are mostly within ± 50 microns which is factor of three larger than in production MQXB at the same fraction of coil aperture. This is an encouraging result given the differences between NbTi and Nb3Sn technologies and the fact that MQXB field quality was polished on many preceding short models.The measurements reveal opposite ramp-rate dependences in TQC01 and TQS01 transfer functions that may be related to different interstrand contact resistances.

Normal, 10-4 Skew, 10-4 n

TQC01 TQS01 MQXB TQC01 TQS01 MQXB 3 2.01 -1.46 -0.04±0.59 -1.72 4.41 0.01±1.00 4 -1.90 -0.52 0.13±0.13 0.62 -1.99 -0.22±0.40 5 0.58 3.06 0.00±0.17 -1.33 0.71 0.01±0.18 6 0.82 0.40 0.11±0.29 -0.10 -0.37 -0.10±0.18 7 0.07 0.07 -0.00±0.04 0.10 -0.11 -0.00±0.03 8 0.01 -0.11 -0.01±0.01 -0.03 -0.18 -0.00±0.03 9 0.04 0.02 0.00±0.01 0.08 -0.02 0.00±0.01 10 -0.06 0.06 0.02±0.01 0.00 0.00 -0.00±0.02

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TQ Next Steps

• Coils use new Ti pole pieces to confirm adequacy• Assembly to be completed by the end of April• Test in May at FNAL (4.5K & 1.9K)• Discussion: cause of the 80%-87% plateau & planned corrections

• Same coil design as TQC01 (bronze pole with stress relief cut)• Significantly higher collaring pre-load (addressing TQC01 problem)• Two coils possibly damaged during collaring (shim displacement) • Discussion: revise plan, minimize impact on schedule & milestones

• Converged on coil design (Ti poles and no stress-relief cut) • Need to start parts procurement & coil winding (after TQ02 spares)• Discussion: can we converge on a single structure for TQ03?

Starting from TQ02, we are switching to RRP strand:

• Higher current density, possibly different stress & stability characteristics

TQS02

TQC02

TQ03

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LQ Status & Plans

LQ “Design Study” is proceeding:

• Finalized coil envelope and design (TQ); structure decision in June 2007 (?)

• Feb 07 Workshop focused on integration with other program components

• TQ, LR, other supporting R&D and materials (conductor)

LQ “Task” FY07 plan: design & procure coil parts & tooling; start practice coils

• Winding/curing tooling design approved by internal review on April 9

• End parts will be same as TQ

Next steps: •Release drawings for winding & curing tooling•Confirm use of Ti pole pieces, determine length•Discuss reaction and impregnation tooling and procedures•Further clarify how/when feedback from rest of program will be integrated•Further clarify participation of LBNL and BNL

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LQ Design study – G. Ambrosio

TechnologicalQuadrupoles

Long Quad.Design Study

Long Racetrack Long mirror

Long Quadrupole

Practice coils

Goal: 4m long, G 200 T/m, = 90 mm

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Long Racetrack

Support structure assembled at LBNL with dummy coils Tested at BNL at 77 K Ready to be used for LR01

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LR coils – LR01

LRSC01: Coil impregnation – completed 4/ 16/ 07 Prep for assembly - underwayLRSC02 Coil reaction – heat cycle completed 4/ 19/ 07 Coil prep for impregnation – through end of April Coil impregnation – early/ mid May Prep for assembly – mid May1st LONG RACETRACK Coil assembly – mid/ late May Hang, wire, cool down – end of May Cold test –start early June

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LQ Mech Design Development

YokeGap

Collar-YokePreloadShim

ControlSpacer

Skin

Collar

YokeCollaringKey

Inner bronze polepiece with stressrelief slot

Bronze outerpole piece

Coil MidplaneShim

With Al shell

With collars

Hybrid concepts: SS shell + bladders

Analysis of TQC with Ti coils: OK!

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LQ: Next Steps

Conductor:

– TQ02 series results choice for LQ01 54/61 or 60/61 Coil Fabrication Technology:

– TQ02 series results Pole material (Ti or Bronze) Mechanical Design:

– Complete design of LQ with Al shell

– Analysis of TQC01b, TQ02s and TQ03s

– Generate mechanical design selection criteria Quench Protection:

– Design QP heaters for LQ, upgrade VMTF QP system

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HQ Status & Plans

HQ “Design Study”: goals, magnetic, mechanical, quench analysis reported at ASC

Main focus is on fundamental technology issues – HQ is not a prototype

4-layer coil w/TQ cable width – option of “standalone” test of outer double-layer• We need a “technology” HQ as part of the achieving the FY09 goal • HQ can be designed to facilitate the transition towards a prototype

Significant progress on mechanical design & analysis in recent months

FY07 HQ “task” plan is to get started on tooling design – requires radial envelope

Recently, more emphasis on “standalone” outer double-layer test (130 mm aperture)

Responding to CM7 comments, considered increasing cable width in outer layers• No significant advantage in terms of stress• Quench protection issues not analyzed yet – high priority• Strand diameter TBD based on materials feedback

We have confirmed the choice of a 10 mm cable – comments?

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FY07 progress: Magnetic optimization of coil cross-

section and ends Mechanical design concepts with coil

alignment Detailed magnetic/mechanical

analysis & comparisons

Collar and pole locked with a key

Collar and pad locked with a key

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HQ1 HQ2 HQ3 HQ1out HQ3out

Gradient SS (T/m) 312 319 308 185 205

Iss (A) 10600 12450 11010 13500 17030

Peak field ss (T) 15.74 16.03 15.49 14.54 15.37

Gradient comparison (T/m) 300 300 300 185 185 205

Peak field (T) 15.06 14.99 15.04 14.37 13.9 15.37

Fx (MN/m) 3.76 3.38 4.04 2.73 3.19 3.9

Fy (MN/m) -4.93 -4.62 -4.95 -3.48 -4.18 -5.14

at 4.2 K in high field (MPa) -165 -152 -136 -149 -153 -179

after excitation (MPa) -196 -177 -185 -194 -181 -219

Model1 = coil#i pole#i glued

20 MPa tension between pole and coil

Summary of mechanical analysis

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Nb3Sn Strand Specification Rev-D7/26/06

Process0.7 ± .003

≥ 2400

< 70

IS, A > 1000 A 47 ± 2 ≥ 10014 ± 2

350 ≥ 48

right-hand screwMinimum Piece length, mHigh temperature HT duration, h

Cu-fraction, %RRR (after full reaction)Twist Pitch, mmTwist Direction

Ternary RRP Nb3SnStrand Diameter, mm

J c(12 T) at 4.2 K, A/mm2

Ds, µm (sub-element diameter)

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RRP-54/61 Production 490 kg

0

2000

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6000

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10000

12000

1 2 3 4 5 6 7 8 9

No. of Pieces

Pie

ce L

engt

h, m

8220

8647

8648

8781

8817

8857

8879

8904

9420

9532

9533

9534

9560

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RRP Strand for LARP For FY08 LARP could use strands with the 127-stack

design– High Jc design has been achieved– Stability improves with decreasing sub-element

diameter– Smaller low field magnetization– Option to increase strand diameter wider cable

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Small Magnet R&D

SQ03: Fabrication and test of 4 new coils

– 108/127 strand• Possible candidate for LQ02

– Conductor evaluation in operational conditions similar to the TQ/LQ magnets• Cabling degradation

• Transverse stress degradation

• Short sample current

– Possibly use to address “bubbles”• Seen in TQs after 1.9K test

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Radiation study – N. Mokhov

Based on detailed MARS15 modeling and thorough analyses of coil apertures, distances to IP, low-Z spacers, stainless steel and high-Z liners, magnet splitting, and a set of TAS/TAN-type absorbers through final focus region, it is shown that dipole-first, and shell-type & block-type quad layouts are feasible for the LHC luminosity upgrade up to 1035 cm-2 s-1.

Work has started on design of radiation damage tests of materials for the superconducting magnets for the luminosity of 1035.

Q3-Q4 FY07 plans: further studies of block-type coil option; address a kW-scale heat loads in the triplet; (possibly) perform calculations on a slim dipole; design Rad-Dam beam tests in an emulated LHC-like environment.

We have everything to respond to all energy deposition Oliver’s requests, but need someone!

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Rad-Hard Insulation R&D

Goal: Develop insulation/impregnation scheme that can withstand the expected dose at Max luminosity

Plan A Plan B

FY07 Develop plans, schedule, cost

Select alternative materialFY08

Q1-Q2

Prepare samples and fixtures

FY08

Q3-Q4

Irradiation & tests Irradiation & tests

FY09 SQ and/or TQ

Rad-Hard Insulation Workshop

Fermilab, April 20, 2007 (1:30 – 6:00 pm)

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Improved insulation for Nb3Sncables in superconducting magnets

The result: robust insulation fabric with half the conventional thickness:

The silane sizing is stable through Nb3Sn heat treatment.The tight weave (80 ct) is strong and flexible, no broken yarns, no Cu show

throughConformation with cable is excellent, promotes easy coil winding.Silane survives heat treat, provides enhanced bonding with epoxy in final

coil.

New insulation has 20% higher shear strength!Good electrical propertiesWe could coordinate materials and braiding process

to make this new direct-braid insulation available to be applied to cable for LARP magnets.

Question: are you (we) interested?

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D2 challenges:•D2 apertures have the same polarity and negative coupling so most of the magnetic flux returns through the iron that needs to be relatively thick.•In spite of high current density, the quench field is ~10T and the operating field may probably be 9T instead of 14.1T quoted in the PAC03 paper. It extends magnet length from 10.0m to 15.7m.•The next optimization steps will attempt to reduce the yoke OR, while keeping the field quality at a reasonable level.

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New initiatives – P. Wanderer LHC/LARP can benefit from BNL experience in developing

– Slim magnets• “direct wind” CAD/CAM staff + machine produced NbTi magnets for:

– HERA IR upgrade (multielement)– BEPC IR upgrade (multielement)– ILC IR R&D (now underway)– Can we use this technology with Nb3Sn?

– Magnetized TAS• Discussions with R. Gupta High Temperature Superconductor for quad coil in TAS

– Basis: successful design, construction, operation of HTS superferric quadrupole for RIA R&D

– Fast-cycling superconducting magnets for PS2 and SPS upgrade• BNL modified RHIC dipole for GSI and fabricated and tested short model • Infrastructure for fast cycling magnet testing is available

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Closeout

New initiatives and participation…welcome!

Magnet tests exploring the phase space…as upgrades become more real, we will be able to suggest real phase space to operate in.

Proposal for new strand made….options for larger diameter as required

Continued R&D and studies on materials and cooling to make a real upgrade of LHC

Thanks to all collaborators on an active and open meeting!