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.