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Magnet Systems. Jim Kerby 20 Apr 2007 With thanks to my colleagues. Current Program. Current focus: Demonstrate by the end of 2009 that Nb 3 Sn magnets are a viable choice for an LHC IR upgrade Known major issues Nb3Sn technology; Peak field on coil; Length; Consistency

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magnet systems

Magnet Systems

Jim Kerby

20 Apr 2007

With thanks to my colleagues

current program
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


[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] LHC Design Report

[2] R. Ostojic et al., PAC-05

[3] S. Caspi et al, MT-15

Quadrupole Designs for the LHC IR

From ASC06 HQ Paper

TQC and TQS Design Concepts





Axial rod




  • Stainless steel collars and skin
  • Control spacers to limit pre-load
  • End support plates, no pre-load
  • Aluminum shell over iron yoke
  • Assembly with bladders and keys
  • Aluminum rods for axial pre-load


SSL 3.2K

SSL 4.5K

TQC01 and TQS01 Quench Training

  • 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
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
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.

TQ Next Steps
  • Starting from TQ02, we are switching to RRP strand:
  • Higher current density, possibly different stress & stability characteristics




  • 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?
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
lq design study g ambrosio
LQ Design study – G. Ambrosio



Long Quad.

Design Study

Long Racetrack

Long mirror

Long Quadrupole

Practice coils

Goal: 4m long, G  200 T/m, F = 90 mm

long racetrack
Long Racetrack
  • Support structure assembled at LBNL with dummy coils
  • Tested at BNL at 77 K
  •  Ready to be used for LR01
lr coils lr01
LR coils – LR01


  • Coil impregnation – completed 4/ 16/ 07
  • Prep for assembly - underway


  • 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 May


  • Coil assembly – mid/ late May
  • Hang, wire, cool down – end of May
  • Cold test –start early June
lq mech design development
LQ Mech Design Development

With collars

With Al shell

Analysis of TQC with Ti coils: OK!

Hybrid concepts: SS shell + bladders

lq next steps
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
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?
Collar and pole locked with a key

Collar and pad locked with a key

FY07 progress:

  • Magnetic optimization of coil cross-section and ends
  • Mechanical design concepts with coil alignment
  • Detailed magnetic/mechanical analysis & comparisons
Summary of mechanical analysis

Model1= coil#i pole#i glued

20 MPa tension between pole and coil

rrp strand for larp
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
small magnet r d
Small Magnet R&D


  • 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
radiation study n mokhov
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!
rad hard insulation r d
Rad-Hard Insulation R&D

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

Rad-Hard Insulation Workshop

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

improved insulation for nb3sn cables in superconducting magnets
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 through

Conformation 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 properties

We 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?

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.
new initiatives p wanderer
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

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!