Engineering aspects of the Detector interface

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Engineering aspects of the Detector interface

• Knut Skarpaas VIII

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Detector interfaces

• Collider hall
• Final magnet supports
• Assembly Sequence

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Collider Hall Geometry

• Detector Size
• Currently modeling structure for small US design
• Small detector has a strong following
• Magnet support for last quads fairly rigid
• Compact package reduces deflections
• Detector group is further along on this design
• We are in continuous contact with many of the
  detector working groups

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Collider Hall /Detector Assembly Procedure

• Assembly staged during beamline commissioning
• Must shield detector assembly area from the beam
• Movable barrier
• Temporary support for beamline
• Must act like detector
• Final focus assembly dependent on magnet support
  method
• Cantilever
• Support tube
• Access to Detector Sub-components
• Vertex detector
• Central tracker
• Endcaps may be captive
• Segment endcaps

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Magnet support options

• Design goals for various support options
• Minimize deflections
• Minimize unsupported span
• Put support near critical deflection points
• Put support near massive items
• Current cantilever option has support near mask
  centroid
• Maximize moment of inertia (minimize sag)
• Tubular support advantageous
• Will need access ports to work on / install
  magnets
• Minimize mass supported by tube
• Some mask forces may be transferred to the doors

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Design goals for various support options cont.

• Material requirements
• Minimize radiation length of material near
  Interaction Point
• Cantilever design has no material at IP
• Radiation hard design
• Adhesives / polymers may degrade
• Interface with required detector components
• Vertex detector in bore (if support tube)
• If cantilever, support vertex detector from mask
  tips or from central tracker
• Masks (held by cantilever or inside support tube)
• Tungsten masks are massive
• 2500 lb requires support for door opening
• Central tracker hugs outer bore (or masks)
• Pass through steel in door

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Design goals for various support options cont.

• Door opening to be minimized to reduce Br near
  quads
• Clearances
• Assembly clearances
• Allow for gravitational deflections
• Current cantilever deflects .16 with door open
• Seismic clearance
• Site specific
• Services
• Vertex cables in bore (if support tube)
• Cooling for vertex detector
• Vertex detector requires 170k nitrogen gas
• Foam or vacuum insulated lines
• Foam lines are large (2)
• Luminosity monitor cables / cooling
• In bore for most options

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Assembly sequence

• Must be able to put detector together first time
• Must be able to access various components for
  servicing
• Minimize time to get to buried components
• Vertex servicing
• Central tracker servicing

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Allow for magnet positioning

• Coarse adjust
• First time alignment
• Remote alignment to remain within fine adjustment
  range
• Magnet Coarse Adjustment options
• Actuation
• Screw
• Ramp
• Cam
• Bellows or piston with liquid or gas
• Piezo
• Drive style
• Motor (stepper or servo)
• Can not be used in high magnetic field
• Drive shafts can transmit torque into bore
• Wind up problems can be eliminated with proper
  gear boxes
• May contribute too much heat / vibration
• Motor (hydraulic / pneumatic) (rotary or linear)
• Seals may be a problem in high radiation areas
• Gas may be too compressible

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Fine adjust

• Get to final magnet location
• Active positioning
• Needs to be radiation hard
• Non-magnetic
• Fine Adjustment Options
• Due to the fast response, and non-magnetic
  properties of piezo electric actuators, this is
  our current choice

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Interferometer compliant

• Several configurations possible
• Maximize stability / minimize detector
  penetrations
• Holes / windows in support allow sight to magnets
• Vacuum / gas transport lines
• Vacuum requires a joint to the stabilized object
• Transport lines can transmit vibration
• If vacuum is used with windows, windows may shift
  beam
• Gas is nice, but index of refraction changes with
  temperature
• Heat from electronics may shift beam

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Support tube

• Tube passes through detector
• Support styles possible
• Simple Simple
• Deflection is maximum stress is high in center
• The center is a bad place for high stress since
  it has a smaller moment of inertia and requires
  minimal material
• Fixed Rolling
• Deflection is smaller stress is high on ends
• Fixed-Intermediate Support- Intermediate
  Support-Rolling
• Tricky stress allocation
• Central tracker group does not like this option
• They would like to put detectors near the inner
  masks

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Cantilever

• Tube is installed from each tunnel
• May be mounted to a pier extending into pit
• While running, support is near mask CG
• Simple Simple
• Deflection is maximum when door is open
• Deflection good while running
• Fixed Simple
• Deflection is smaller but stress is high on one
  end

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Detector / final focus options

• Option 1
• SLD style detector
• Pro Quick access /easy detector shapes
• Con Large pit / unstable magnets
• Option 2
• SLD like detector with reduced door opening
• Concrete pillar under magnets (except last 2)
• Last 2 magnets on short cantilever or held by
  door
• Door supports trimmed on outside (doors may need
  counter weight)
• Pro Quick access /easy detector shapes
• All but last two magnets are on bedrock
• Con Last magnets rely on detector for stability
  (but could be actively isolated)

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Detector / final focus options cont.

• Option 3
• BaBar like detector split door
• Concrete pillar under magnets (except last 1)
• Cantilever last magnet and mask
• Door supports trimmed on outside (doors may need
  counter weight toward IP)
• Pro Quick access
• Con ECAL and HCAL must be split to remove (may
  require difficult rigging)
• Option 4
• SLD like detector (cut off outer feet)
• Key shaped pit
• Roll detector to open
• Fixture to open (to hold cantilever)
• Pro Stable / all but last magnet on bedrock
• Con Complicated pit / many cables to deal with
  / vac. dis-connect
• Long down time to get to vertex detector

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Detector / final focus options cont.

• Option 5
• Central detector spool package with Small
  detector layout
• Top splits in middle (iron and HCAL move to
  sides)
• Spool cranes out
• Shake spool
• Pro Stable
• Con Complicated pit / hard to get inside spool /
  vac. dis-connect / tricky wiring

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Assembly Procedures (Small detector /
cantilevered supports)

• Assemble detector on shielded side of pit
• Beam line commissioning happens using the real
  doublets on the other side of the pit with a
  temporary support
• Remove EM magnets on pier and pull doublet back
  into tunnel
• Rotate the detector to become parallel to the
  beam line
• Roll the detector into place (including doors)
• Slide cantilevered support tubes through doors
• Make up vacuum and transfer load of masks from
  detector to the support tube

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Vibration Issues

• Since the extent of vibration amplification
  varies widely with various geometries, emphasis
  until this point has been put on solidifying the
  detector geometry
• Detector revisions occur biannually
• As detector shapes and magnet styles become more
  stable, vibration isolation methods will be
  explored further
• Several possible vibration isolation scenarios
  are being considered
• Under all conditions, local noise must be
  isolated from the detector
• Local traffic minimized
• Pumps on isolators on separate slabs
• Well thought out plumbing and other services

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Vibration Issues Continued

• Find a stable site and make all components rigid
• Many problems could arise if we do not have a
  Plan B (and the site becomes noisy)
• Have a rigid detector and a floating (active /
  passive / both) magnet support
• A permutation of this option may be the most
  practical for a large detector
• Float the entire detector (or a large portion of
  it) on a gas suspension system
• A possible air system has been considered which
  incorporates a variable natural frequency which
  allows adjustment for detector mass changes
• Communication has begun with the LIGO group
• Work is currently being done at LIGO to stabilize
  a several hundred kilogram mass to 1 nm
• The LIGO system currently stabilizes a mass to a
  level several orders of magnitude better than NLC
  requirements. However, the system used is not
  currently practical for a physics detector.
  (Their frequency requirements are also different)

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Thermal Issues

• A high degree of positional stability requires a
  thermally stable environment
• Detector will most likely be under a thick (6
  thick) concrete lid for radiation protection
  reasons
• Large thermal masses should aid thermal stability
• Thermal excursions happen slowly and require a
  coarse adjustment range for the movers
• Tunnels which connect to pit are fairly cool at
  this point
• Should not be a large heat source (and may be
  sealed from pit)
• Tunnel temperature is set by local cooling tower
  capacities
• Have looked at wet bulb maximums at several sites

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Conclusions

• Detector design is still undergoing changes
• We are in contact with key people in many
  detector working groups
• One of the more popular detector choices is being
  structurally modeled currently
• Several issues will be studied and prototyped in
  the near future
• Vibration isolation options will be pursued