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ATLAS Placement and Alignments. David Lissauer / BNL. Experimental Hall is very small compare to ATLAS Size. “Ship in a Bottle” Need to be aligned to the beam line to ~ mm and many of large Many envelopes have less than 20mm stay clear areasbetween moving Objects. Every Silly mm Counts!!!.

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atlas placement and alignments
ATLAS Placement and Alignments

David Lissauer / BNL

Experimental Hall is very small compare to ATLAS Size.

“Ship in a Bottle”

Need to be aligned to the beam line to ~ mm and many of large Many envelopes have less than 20mm stay clear areasbetween moving Objects.

Every Silly mm Counts!!!

Result of many discussions over the past year with:

Survey Team. LHC Machine and Civil Engineering.

Toroid and Muon Placement. Calorimeters: LAr/Tile.

Inner Detector. Beam Pipe.

EC Toroid, Shielding


atlas placement considerations
ATLAS Placement Considerations

Items under active consideration:

Floor Stability -- Monitoring on going

HO/HS Structures -- Accepted

Feet & Rail Placement -- Feet Accepted/Final Rail Aug ’05.

Barrel Toroid Placement -- Ongoing

Barrel Calorimeters/Solenoid -- Ongoing

EC Calorimeter -- Under study

ID Placement -- Preliminary agreement/Ongoing

Beam Pipe Placement -- Preliminary agreement/Ongoing

Small Wheel -- Under Study

EC Toroid -- Under Study

Big Wheels -- Under Study

EO Chambers -- Under Study

JF Shielding -- Under Study

lhc nominal beam and ip
LHC Nominal Beam and IP.
  • Nominal Beam Line:
    • Close orbit calculations uncertainty in the Nominal Beam Line (Geometrical line) is 3 mm. (I.e. actual beam vs. nominal beam line)

Uncertainty might be reduced by the time Barrel Calorimeter is installed (’05)

  • Beam Adjustments :
    • “Immediate”: < 1 mm by changing the magnetic field in the last magnet.
    • “Short term”: ~1 mm by adjusting the Jacks under the last triplet.
    • “Long term”: Re-align a string of magnets along the tunnel. Adjustments could be as much as 10-20 m.m. (K. Potter et al.)
  • Discussions with Machine, Survey: (K. Potter et al.)
    • Machine will be able to align itself to the ATLAS experiment to the level of 10-20 mm during a long shut down. The machine does not expect to be able to do this more than once every ~ 3 Years.
placement strategy
Placement Strategy
  • Stages I: Surface assemblies.
    • Placement of assemblies on the surface. Components need to be aligned and adjusted relative each other on the surface.
      • E.g: Barrel Cryostat Assembly: EM calorimeter, Solenoid magnet and Cryostat.
      • ID Barrel Assembly: Included TRT , SCT and Pixel Tube.
  • Stage II: Cavern assemblies.
    • Placement of Assemblies in the Cavern. Components need to be aligned and adjusted relative each other (Geometrical Beam line at the same time).
      • E.g: Barrel Cal Assembly: Tile and Barrel Cryostat Assembly are aligned relative to each other and the nominal beam line.
  • Stage III: Final placement.
    • Placement of assemblies relative to the nominal beam. (Usually)
      • E.g: Barrel Can Moves to final position and aligned relative to the Nominal Beam.
      • Barrel Toroid.
      • Due to the Floor movement we need to decide if we place the object at nominal position of “Off” nominal position expecting floor movement.

TC/Survey/Systems follow each of the “assemblies”

Working groups follow Placement specifications, and survey needs.

atlas exp hall floor movement
ATLAS Exp. Hall – Floor Movement
  • Civil Engineering expectation:

The existing calculation were done with simplifying assumptions.

          • Too large of a grid
          • Uniform Load on the floor
  • Floor Settlement:-2 mm from the time the concrete if poured and the time ATLAS got possession of the experimental hall. (No measurements to verify this)
  • ATLAS weight:-5.5 mm (Total –7.5 mm) due to the weight of the exp. Over ~ 6 month. Adiabatic as the weight is added.
  • Floor upward lift due to Hydrostatic Pressure:

~ + 1 mm / year due to hydrostatic pressure. Up To

~ 20 mm over 20 years.

grid monitoring floor movement
GRID Monitoring Floor Movement

A GRID of Survey “Rivets” has been installed at strategic position.

Monitoring of the floor stability is ongoing from July/August of ’03.

Expect to re-measure position every 2-6 month.

Accuracy : 0.3 mm – ‘datum point’: deep reference in the tunnel (same for machine and experiment geometry)

hydrostatic monitoring
Hydrostatic Monitoring

Hydrostatic System has been operating since June ’04.

(See TMB report by Hélène MAINAUD DURAND TS/SU/MTI)

Time span is small but measurements indicate movement of the floor. Higher on USA side than US side.

(For details see presentation by Jean-Christophe Gayde)

Relative height accuracy better than 100 Microns.

Absolute (relative to beam line 0.3 mm Sigma)

hydrostatic data quality
Hydrostatic data quality

Note Scale:

In Microns!!

Floor Stability – 8/03  9/04.

Precision (1 sigma)of the dZ = 0.2 mm

Floor and Bedplate Stability – 3D Model

From 25 June 04 to 08 Sept 04

Floor Movement uneven.

Possible combination of Hydrostatics lift and sage due to weight.

Need more time dependent data.

floor movement best estimate
Floor Movement – Best Estimate


Due to Cement

Contraction before

1st meas.

3 MM


Due to ATLAS


0.4 MM/year


Due to



Summary of the “pessimistic” prediction for the floor movements.

feet rails installed
Feet/ Rails: Installed.

Rail: Have been aligned and removed for Toroid installation.

Final alignment after Toroid is finished.

Feet : Have been placed in position.

All within Envelopes.

Bedplates: Have been placed in position.

toroid placement
Toroid Placement

Center of Toroid should co-inside with the Nominal Beam Line.

Assemble as Ellipse.

~20mm move due to Toroid weight.

~10 mm due to services and Muon chambers.

Position of First two Coils Fixes the center of the Toroid.

positioning of first 2 coils
Positioning of first 2 Coils

First Coils will fix the center of the Toroid.

Physics – Center of Toroid should be on the nominal beam line.

But can be as much as 20-30 mm off without affecting Muon trigger/Physics significantly.

Envelopes- require that the Toroid be within 10 mm envelope of nominal position.

We are more sensitive to down ward fluctuation than to Upward fluctuation.

summary conclusions
Summary & Conclusions
  • Toroid Assembly: Oval  Circle 0. +/- 3.5 mm
  • Five Years of Floor movements 3. +/- 3.0 mm
  • Floor Sag due to weight -3. +/- 2.0 mm
  • Placement Accuracy 0. +/- 2.0 mm
  • Total: 0. +/- 10.5 mm


place the Toroid Center at

– 5mm from Nominal Beam Line.

Final Decision Week of October 18th after latest input from Survey.

barrel calorimeter solenoid
Barrel Calorimeter/Solenoid

EM Calorimeter/Cryostat:

  • The EM Cal was placed so that it is below the

Cryostat IWV by ~ 4 mm.

Solenoid /Cryostat:

  • The Solenoid was placed so that it is below the

Cryostat IWV by ~ 2 mm.

Relative Placement:

  • of the EM calorimeter, Solenoid and the Cryostat IWV

are now fixed and can not be changed.

barrel calorimeter solenoid1
Barrel Calorimeter/Solenoid

Tile Calorimeter and Cryostat assembly is being done at Z=13.

After LAr if placed on the Tile on the Truck the relative position of the Tile/Cryostat IWV/Solenoid and EM position are fixed.

The Tile Calorimeter/Cryostat assembly will than be moved to Z=0.

The Barrel Calorimeter can be adjusted as a unit to the Nominal Beam line.

barrel calorimeter solenoid2
Barrel Calorimeter/Solenoid

We will align the Solenoid Axis with relation to the nominal Beam Axis. Resulting in the above relative loactions.

id installation
ID - Installation
  • TRT/SCT:
    • Are assembled on the Surface as a unit.
    • The TRT and SCT Axis have to be co-linear. There is a small gap between the TRT and SCT but it can not be reduced as it is part of the thermal shield and the construction tolerance.
  • Pixel Tube Installation:
    • Pixel Tube is installed first in the SCT/TRT module. On the Surface.
    • Pixel Tube can be installed “off” center by as much as 2-3 mm.

SCT /TRT Axis is Collinear.

No Possibility for adjustments of SCT relative to TRT.

Pixel Tube can be inserted off axis by as much as 2-3 mm.

Once inserted they can not be adjusted.

id installation1
ID - Installation
  • SCT/TRT/Pixel Tube:
    • The SCT/TRT/Pixel Tube are installed as a unit.
    • No relative adjustments of the individual components in possible in Situ.
    • The Module is support are adjusted on the surface so that the SCT/TRT axis will co inside with Barrel Cal IWV Axis.
    • At this stage there is some adjustment in Situ possible – (Max +/- 4 mm) but, ID aim will be to bring the Barrel IWV- TRT/SCT axis to co inside.
    • This requirement that the TRT/SCT axis coincide comes from the very tight space and the needed symmetry for the TRT/SCT Services.

The ID requires that the TRT/SCT axis co inside with the

IWV axis dues to the ID Services needs.

ATLAS thus agrees that the TRT/SCT Axis will be placed

2 mm off the nominal Beam Axis and off the Solenoid Axis.

id installation2
ID - Installation
  • Pixel Insertion:
    • The Pixel axis will co inside with the Pixel Tube Axis.
    • The Pixel Tube when placed (above ground) can be places so that its axis and the TRT/SCT Axis are off by 2-3 mm.
  • There are thus two options for the Pixel installation.
  • Place Tube Axis with SCT/TRT.
  • Place Tube Axis off by 2 mm to co-inside with Nominal beam.

The Present baseline is to install the Pixel to Co-inside

with the Nominal Beam Line

barrel muon system
Barrel Muon System
  • The Muon Support structure:
    • Rail System. First adjustments above ground (Local Coordinate system)
    • Final Adjustments in Situ before chambers are mounted.
    • Each Tower points to the Intersection region.
  • Individual Alignment/Placements for each chamber assembly needs are being defined.
    • MDT’s & RPC’s subassembly done on the Surface.
    • Once placed on the Rails no adjustments is possible.
  • Chamber Assembly Placement.
    • The specification on chamber placement needs to be defined. Survey Target position etc.
  • Alignment System.
barrel muon system1
Barrel Muon System




Reference plates for the alignment system

Reference points on the Toroid structure


Local reference frame of the small sector

Chamber rails

Local reference frame of the large sector

  • Floor Monitoring systems are in place.
  • ATLAS Placement has started. ATLAS has installed :Feet Rails, HS and HO structures. (Rails can still be readjusted )
  • This already has resulted in small change to detector envelopes and final placements. (e.g. HO chambers moved by 20 mm in Z.)
  • Some Subassemblies on the Surface already completer: Barrel EM/Solenoid/IWV completed, EC-C.
  • Agreement on Procedure and hierarchy for Barrel Calorimeter/Solenoid/ID placement.
  • Toroid Placement will start later this month.

Need to follow and re-optimize placement of detectors continuously.