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LEP dismantling

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102 quadrupoles cooled at 1.9 K, with gradients of 200 T/m ... FRESCA, 10 T, 88 mm. D. Leroy et al., 1999. R. Ostojic, LTC, 10 May 2006. 14. Summary ... – PowerPoint PPT presentation

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Title: LEP dismantling


1
General Considerations for the Upgrade of the
LHC Insertion Magnets
R. Ostojic CERN, AT Department
2
LHC Insertion Magnets
Final focus
Dispersion suppressor
Matching section
Separation dipoles
  • 154 superconducting magnets
  • 102 quadrupoles cooled at 1.9 K, with gradients
    of 200 T/m
  • 52 dipoles and quadrupoles cooled at 4.5 K, with
    fields of 4 T and gradients of 160 T/m

3
LHC Magnet Classes
  • MB class (MB, MQ, MQM)
  • (8.5 T, Nb-Ti cable at 1.9 K m-channel polyimide
    insulation)
  • 1b. MQX- class (MQXA, MQXB)
  • (8.5 T Nb-Ti cable at 1.9 K closed-channel
    polyimide insulation)
  • 2. MQY- class (MQM, MQY)
  • (5 T Nb-Ti cable at 4.5 K m-channel polyimide
    insulation)
  • 3. RHIC class (D1, D2, D3, D4)
  • (4 T Nb-Ti cable at 4.5 K closed-channel
    polyimide insulation)
  • 4. MQTL class (MQTL, MCBX and all correctors)
  • (3 T Nb-Ti wire at 4.5 K impregnated coil)
  • 5. Normal conducting magnets (MBW, MBWX, MQW)
  • (1.4 T normal conducting impregnated coil)

4
Upgrade of the Matching Sections and Separation
Dipoles
  • The present matching quadrupoles are
    state-of-the-art Nb-Ti quadrupoles which operate
    at 4.5 K.
  • The upgrade of the matching sections should in
    the first place focus on modifying the cooling
    scheme and operating the magnets at 1.9 K.
  • In case larger apertures are required, new
    magnets could be built as extensions of existing
    designs.
  • The 4 T-class separation dipoles should be
    replaced with higher field magnets cooled at 1.9
    K.
  • The MQTL-class should be replaced by magnets more
    resistant to high radiation environment.

5
The LHC low-b triplet
Q3
Q2
Q1
TASB
MQXA
MQXB
MQXA
MQXB
DFBX
6.37
5.5
5.5
6.37
2.985
2.715
1.0
MCSOX a3 a4 b4
MCBXA MCBXH/V b3 b6
MCBX MCBXH/V
MQSX
MCBX MCBXH/V
6
LHC low-b triplets
7
Limits of the present LHC triplets
  • Aperture
  • 70 mm coil
  • 63 mm beam tube
  • 60 mm beam screen ? b 0.55 m
  • Gradient
  • 215 T/m ? operational 205 T/m
  • Field quality
  • Excellent, no need for correctors down to b
    0.6 m
  • Peak power density
  • 12 mW/cm3 ? L 3 1034
  • Total cooling power
  • 420 W at 1.9 K ? L 3 1034

8
Aperture issue
  • The coil aperture was the most revisited magnet
    parameter of the low-b quadrupoles.
  • Aperture of 70 mm defined in the Yellow Book
    (1995, nominal b 0.50 m, ultimate 0.25 m).
  • Subsequent studies showed a need for increasing
    the crossing angle by a factor of two.
  • e-cloud instability ? introduction of beam
    screens.
  • Upgrade target remains a b of 0.25 m
    (irrespective of magnet technology).
  • Luminosity increase by a factor 1.5.
  • Higher luminosity implies substantially greater
    load on the cryogenic system.
  • feedback to the choice of aperture and magnet
    design.

9
Enabling operation of the LHCwith minimal
disruption
  • Maintenance and repair of insertion magnets
  • Large number of magnets of different type means
    limited number of spare magnets ready for
    exchange.
  • A facility is planned at CERN for repair/rebuild
    of matching section quadrupoles.
  • Particular problem low-beta quadrupoles and
    separation dipoles
  • Only one spare of each type (best magnets already
    in the LHC).
  • As of 2006, there will be no operating facility
    for repair and testing of these magnets.

10
Quadrupole-first layouts
Optimize the aperture and length of the
quadrupoles according to their position in the
triplet.
  • Use of aperture
  • Increase the aperture to reduce heat loads (peak
    and total)
  • Profit from better field quality to reduce the
    number of correctors and introduce stronger orbit
    correctors
  • Decrease b to complement other ways of
    increasing luminosity.

11
Large aperture quadrupoles using existing LHC
cables
12
Large aperture quadrupoles
Operating current at 80 of conductor limit
As the quadrupole aperture increases, the
operating gradient decreases by 20 T/m for every
10mm of coil aperture. To get a GL similar to the
present triplet, quadrupole lengths need to be
increased by 20-30. The Nb-Ti technology proven
for quadrupoles up to 12 m long.
13
RD directions for Nb-Ti quads
  • Technology and manufacturing issues are well
    mastered.
  • Relatively easy extension of main magnet
    parameters (aperture and length) without
    extensive RD.
  • Focus RD on magnet transparency
  • Cable and coil insulation
  • Thermal design of the collaring and yoking
    structures
  • Coupling to the heat exchanger

14
Summary
  • LHC contains several generations of Nb-Ti
    magnets. Extensive experience exists in building
    magnets of different aperture and length.
    Upgrading the magnets to a higher class should be
    considered as a first option.
  • Nb-Ti (1.9K) technology is a clear choice for
    upgrading the large number of magnets in the LHC
    insertions (dipoles and quadrupoles) of the 4 T
    class.
  • The availability of spare low-b triplets and
    separation dipoles is a serious concern. Any
    proposal for the upgrade must take this issue
    into account and provide an appropriate solution.
  • The shortest route for providing new magnets in a
    time frame compatible with LHC luminosity runs is
    to use Nb-Ti technology.
  • Nb-Ti (1.9K) technology has reached its limits
    for large series production with the LHC main
    dipoles improvements for small series are still
    possible.

15
Comment
  • It is generally accepted that a new generation of
    magnets (Nb3Sn, HTS,) will be required for the
    next hadron collider. CERN should take part in a
    wider effort to develop and demonstrate the
    feasibility of the new technology.
  • In the interest of LHC operation, we must have an
    alternative Nb-Ti technology can offer an
    appropriate intermediate solution.
  • The pitfalls in building Nb-Ti magnets should not
    be underestimated. There is a need to start
    design studies and development before LHC
    construction teams move on to other projects.
  • Initial experience from operating the LHC with
    beam is crucial for refining magnet parameters
    and making sure there are no unknown unknowns.
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