Nb3Sn IR quadrupole R

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Nb3Sn IR quadrupole RD(wind and react)
US LHC Accelerator Research Program

brookhaven - fermilab - berkeley

• Alexander Zlobin, Fermilab
• For BNL-FNAL-LBNL Collaboration

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Magnet RD program goals

• Evaluate possibilities and limitations of
  luminosity upgrade related to the IR SC magnets
  (in collaboration with AP group)
• Develop high performance prototypes and
  technologies of SC magnets for high-luminosity
  inner triplets including
• Large-aperture, high gradient quadrupoles
• High-field beam separation dipoles and/or strong
  correctors
• Program focuses on Nb3Sn, large-aperture
  quadrupoles.
• Initial goal is to develop technologies, not
  specific designs.
• Specific design choices will be made after
  several years of magnet RD and related
  accelerator design studies.

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RD issues

• Proposed IR quadrupole RD program includes
  positive results obtained at UT, LBNL, BNL and
  Fermilab in the development of high field
  accelerator magnets.
• IR quadrupole RD will be performed in
  collaboration of three U.S. national Labs and
  CERN
• The RD program address the following issues
• Quadrupole design
• Technology
• Components
• Performance

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Conceptual design study

• FY2002-2004
• Establish quadrupole target parameters (with US
  and CERN AP groups).
• Develop and compare different design and
  technological approaches for IR quadrupoles.
• Generic IR quadrupole target parameters
• Large bore
• High field
• Excellent field quality
• High critical temperature
• Large operation margin
• Long lifetime

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NbTi Quads Field gradient

• Gmax(70mm)250-270 T/m _at_ 1.95K and
  Gmax(70mm)190-200 T/m _at_ 4.3K
• Gnom205-215 T/m _at_1.95K (limited by mechanics,
  quench performance)
• Scaling laws
• Gmax(D,Top)Gmax(70mm,Top)70/D
• an/bn1/Dn-1
• W?(G?D)2?D2 , Fr,? ?(G?D)?D (mechanics, quench
  performance, protection)

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Nb3Sn Quads Field gradient
90-mm design Gmax230-290T/m _at_1.95K and
220-345T/m _at_ 4.3K
70-mm design Gmax300-365T/m _at_1.95K and
285-345T/m _at_4.3K

• Nb3Sn quads 20-30 increase of G or D and
  possibility of Top4.3K.
• Gop275 T/m in 70-mm quads with Iop/Ic20
  (similar to MQXB) requires Nb3Sn strands with
  Jc(12T,4.2K)gt2.9 kA/mm2. Such strands are not
  available at present time.
• Gopgt205 T/m in 90-mm quads with Iop/Ic20
  requires Nb3Sn strands with Jc(12T, 4.2K)gt2.2
  kA/mm2. Such strands are commercially produced.

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Nb3Sn Quads Operation margin

• The maximum energy deposition in the coil at
  nominal LHC luminosity is 3.6 mW/cm3.
• NbTi quads
• factor of 2.5 operation margin with respect to
  the nominal heat deposition
• Nb3Sn quads
• factor of 2-3 higher temperature margin than for
  NbTi quads
• factor of 5-10 operation margin with respect to
  nominal heat deposition in the coil (if the heat
  transfer in the cryostat and cryogenics allow)

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Nb3Sn Quads Field quality
Systematic errors at Rref17 mm

• Iron saturation
• ??b6?lt0.01 similar to MQXB
• Coil magnetization
• ??b6?lt1 with passive correction or PIT Nb3Sn
  strands

• Systematic low-order harmonics could be provided
  on the same level as in MQXB in both 70-mm and
  90-mm Nb3Sn quadrupole designs

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Nb3Sn Quads Field quality
Random errors at Rref17 mm (?50 ?m random block
displacements)

• Only 90-mm or larger bore Nb3Sn IRQ designs
  provide random harmonics variation comparable
  with MQXB.
• Design and technology optimization for Nb3Sn
  magnets allow improvements of random field errors.

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Quadrupole target parameters and conditions

• Based on the preliminary studies the quadrupole
  main target parameters are (same or better than
  that for MQXB)
• Magnet (coil) bore 90 mm
• Nominal field gradient 205 T/m or higher
• Margin along the load line 15-20
• Temperature margin at list a factor of 3 wrt
  nominal luminosity
• Nominal temperature 1.9-2.0 K or 4.5 K
• Field quality as MQXB or better
• Life time gt5 years (operation, replacement)
• The following constraints were used in order to
  minimize the impact on the inner triplet systems
• - nominal current lt15-16 kA (current leads and
  feed boxes, bus bars, PS)
• - cold mass OD - lt 500 mm (cryostat, feed boxes,
  tooling, test facility)

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90-mm quadrupole for the LHC IR upgrade

• 90-mm single-aperture Nb3Sn IRQ
• 3-block coil design
• 90-mm coil bore
• Nominal gradient 205 T/m at 14.1 kA
• Operation temperature 1.9K or 4.5K
• Field quality as in present MQXB
• Ic margin 20 with the state of the art Nb3Sn
  strands
• Tc margin sufficient to withstand energy
  depositions 5-10 higher than nominal
• Iron yoke OD as in HGQ
• Large holes sufficient for effective longitudinal
  heat transfer
• Thick stand alone stainless steel collar

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Alternative coil designs

• Shel-type coils
• 2-layer vs. 4-layer design
• Block-type coils
• Racetrack vs. nested
• Criteria
• Magnet design (single or twin bore)
• Efficiency
• Field quality (body, ends)
• Operation margins
• Mechanics
• Quench protection
• technology

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Alternative magnet designs

• 2-in-1 quadrupole design
• Issues
• Optimal aperture size
• Minimum bore separation distance
• Parallel vs. non-parallel apertures
• Field quality
• Mechanics
• Longitudinal heat transfer
• Technology

Example VLHC 2-in-1arc quadrupole
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Design study summary

• The results of conceptual design study show
• Nb3Sn low-beta quadrupoles with 90-mm bore and
  Gnom205 T/m proposed for the LHC high-luminosity
  IR upgrade are feasible.
• Major magnet parameters meet the preliminary
  requirements. They can be safely operated at
  either 1.95 or 4.5 K at a factor of 5-10 higher
  level of radiation energy depositions
• The magnets have a lot of potential for the
  design optimization and require efforts for the
  development of their components and technologies.
  
• Some important parameters such as magnet
  training, training memory, field quality,
  reproducibility of main parameters from magnet to
  magnet, etc., that depend not only on magnet
  design but also on its technology as well as
  magnet long-term performance in real operation
  conditions have to be studied experimentally.

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Model magnet RD

• FY 2003-2005
• Fabrication and tests of 70 mm shell-type Nb3Sn
  quadrupole models using existing mechanical
  design and tooling for baseline IR quadrupoles.
• Fabrication and tests of 90 mm shell-type Nb3Sn
  quadrupole models based on D20 tooling.
• Fabrication and tests of simple Nb3Sn quadrupole
  models based on racetrack coils
• This is effective way to start program with
  restricted funds available in first 2-3 years.
• FY 2005-2009
• Development and study of final IR quadrupole
  short models.
• Long coil problem studies, life-time tests.

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70-mm quadrupole model

• We are starting new SC model magnet RD than
  accumulates and expand our experience with
  shell-type Nb3Sn coils and WR process
• 70-mm Nb3Sn coil in the MQXB collar
• Collars, iron laminations, skin and assembly
  tooling are available
• Magnet design and parameters
• Simplified 3-block geometry
• 42-strand cable
• Maximum gradient 280 T/m
• Geometrical field quality lt10-4

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90-mm quadrupole model

• Nb3Sn conductor jc2000 A/mm2 _at_ 12 T and 4.2 K.
• 250 T/m across a 90 mm bore.
• D20 dipole tooling
• Use keys and bladders during assembly
• 2-coils assembled with a quadrupole symmetry
• Reduce the amount of work by a factor of 2

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Full-scale prototypes

• FY 2009-2011
• Final quadrupole design decisions follow initial
  LHC operational experience.
• Fabrication and tests of large-aperture single or
  twin-aperture quadrupoles (final design and
  technology) full length in prototype cryostat.

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Conclusions

• Present 70-mm NbTi IR quads (MQXB)
• Gnom is restricted by mechanics and quench
  performance
• operation margin _at_Top1.95K and Iop/Iclt0.85 is
  only a factor of 2.5 wrt heat deposition at
  nominal luminosity
• Aperture increase reduces nominal field gradient
  and may lead to additional mechanical, quench
  performance and quench protection problems
• Nb3Sn IR quads with commercially produced Nb3Sn
  strands offer
• Gop205 T/m or higher at Top1.95-4.3K over 90 mm
  bore
• 20 critical current margin
• factor of 5-10 operation margin wrt to heat
  depositions in the coil at nominal luminosity
  with present inner triplet design
• field quality comparable with the field quality
  in MQXB or even better
• potential for the design optimization and require
  efforts for the development of their components
  and technologies.

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Summary

• Large-aperture Nb3Sn quads are a real option for
  the LHC IR upgrade
• RD program requires
• 6-7 years for short model RD and component
  development
• 2-3 years for the prototype development and
  reproducibility studies
• Total duration is 9-10 years based on the
  Fermilabs capabilities
• Wide collaboration helps to achieve the best
  results in the shortest time