GLD experimental hall and detector assembly

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GLD experimental hall and detector assembly

• Y.Sugimoto
• KEK
• 3 Oct. 2006

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Background

• Experimental hall, detector assembly procedure,
  and iron yoke design are being re-considered
• Motivations are
• Conventional facility (CF) construction schedule
  shown in Vancouver
• Distance between beam line and a wall increased
  from 12m to 12.5m due to change of crossing angle
  (2mrad20mrad ? 14mrad 14mrad)
• Information about Air-pad

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CF schedule
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CF schedule

• Underground experimental hall gets ready for
  detector construction at tt04y11m
• ?It would be impossible to start experiment at
  tt07y
• Surface assembly hall can be ready at tt03y
• If detectors are assembled on surface, we could
  get ready for experiment earlier than underground
  assembly by 1.5y or more

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Surface assembly options

• Pure CMS-like assembly
• Detector is segmented into several large pieces (
  lt2000 ton /segment) (5 barrel rings and 3x2
  endcap disks in case of CMS)
• Detector assembly and test are done on surface,
  then disassembled again and lowered to the
  underground experimental hall by 2500 ton gantry
  crane
• The large segments are moved by air-pads
  underground (no large crane in the experimental
  hall)
• Modified CMS-like assembly
• Detector is segmented into few tens of medium
  size pieces (lt300 ton/segment) Barrel yoke will
  be segmented into 24 (12(f)x2(r)) pieces
• Detector segments are pre-assembled on surface
  and lowered to the u.g. exp. hall by 300 ton
  movable overhead crane
• Final assembly and checkout of the detector are
  done underground

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CMS
Barrel 5 rings Endcap 3 disks x2
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• Air pads for CMS

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Possible drawback of two options

• Pure CMS
• Solenoid is supported by the central barrel ring
  ? Thicker cryostat wall ? Larger detector size
• Gaps between rings ? More leakage field
• Precision of rings ? ? Uniformity of B-field ?
• More number of iron slabs and more muon detector
  modules ? Schedule and cost
• Job duplication on surface and underground ?
  Schedule and cost
• Larger access shaft (f20m) ? Schedule and cost
• Modified CMS
• More jobs underground ? Schedule?
• Final construction of iron return yoke
• Solenoid installation and test
• Muon detector installation
• 300 ton cranes both on surface and underground ?
  Cost
• Assembly procedure of heavy (300 ton) pieces ?

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Impact on detector/hall design

• Less jobs in the experimental hall than totally
  underground assembly scheme ? Smaller hall size
• For modified CMS-style assembly, less iron allows
  smaller crane
• Barrel of the DOD design 8300 ton ? 400 ton
  crane is necessary if divided into 24
  (12(f)x2(r))
• A new iron yoke design is made 6100 ton ? 300
  ton crane is OK
• Larger leakage field of the new design is
  compensated by additional coils

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New iron yoke design

• Barrel
• 4.5ltRlt7.2m, 8x25cm1x30cm iron 8x5cm gap
• Zlt4.45m (35cm shorter than DOD design)
• Endcap
• 0.4ltRlt7.2m with pole tip of 0.4ltRlt2.5m
• 4.5ltZlt7.5m with pole tip of 4.2ltZlt4.5m
• 10x25cm 1x30cm iron 10x5cm gap
• 5cm gap between barrel and endcap
• Leakage field
• 70 G (44 G for DOD design) at Z10m
• Compensation coils at Z10m and 12.5m can make it
  lt 50 G for Zgt10m

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New iron yoke design

• Air-pad developed for LHC experiments allows
  free movement of heavy detectors
• If the barrel part of GLD can move both in
  z-direction and x-direction,
• Experimental hall width can be smaller (32m?25m)
• Detector can be placed at the center of the hall
  (in z-direction)
• Because of smaller detector size and slightly
  larger distance between the beam line and a wall,
  endcaps can be open normally (not like a door),
  and consequently, endcap calorimeters can be
  supported by endcaps

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New iron yoke design
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New iron yoke design
Self Shielding
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New iron yoke design

• Compensation coils for leakage field

L1 Z10m, R1.5m, 6kAT L2 Z12.5m,
R2.45m, 4.5kAT
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New iron yoke design B-field

• FEA calculation by COMSOL
• Axial symmetric 2D calculation
• Permeability of iron
• Based on Yamaoka-sans data
• Slightly modified by hand
• Saturation magnetization 2.1T
• Solenoid
• Coil half length 4.08m
• Correction coil length 0.65m
• Field uniformity
• New requirement dB/Blt4.5x10-4 for Zlt0.5m (D.
  Peterson)

M
H
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Leakage B-field

• B field along r0

Without compensation coil
With compensation coils
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New experimental hall design

• Assumptions
• New GLD geometry (R7.2m, Z7.5m)
• Modified CMS-like assembly scenario
• Temporary floor of the beam line for the BDS
  pre-commissioning has a width of 3 m
• Width of concrete shield used for the
  pre-commissioning is 3 m
• Nothing should be placed at the bottom of the
  access shaft
• Five large segments (Barrel and 4 halves of
  endcap) should have gt1.5 m clearance around them
  for crane and human access

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Electronics huts
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Discussion on the hall size

• Hall width
• 25m width would be necessary
• 7.5m (detector) 2.5m (crane access for
  concrete shielding) 2.5m ( 3 cable chains (two
  for endcap halves and one for barrel)) x2 25m
• Hall height
• Less than 35m could be possible, depending on the
  shape of the vaulted ceiling
• This will be studied by CF group of GDE (Concept
  groups will provide information on the height of
  crane hook and crane capacity)

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• Cable chains for CMS