BDS alignment
H. MAINAUD DURAND
on behalf of the CLIC active pre-alignment team
Alignment strategy, status and next steps
 BDS
 MDI area
BDS: objective of pre-alignment
Objective of pre-alignment
PRE-ALIGNMENT (beam off)
Mechanical pre-alignment
Within +/- 0.1 mm (1s)
Active pre-alignment =
Active pre-alignment
Beam based alignment
Beam based feedbacks
Within a few microns
Determination of the position of the components in a general
coordinate system thanks to alignment systems
+
Re-adjustment thanks to actuators
The zero of each component will be included in a
cylinder with a radius of a few microns:
 10 µm (BDS components) OVER 500 m
(14 μm/17 μm for main linac components over 200 m)
Adjustment required: step size below 1 µm, 5 DOF
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BDS: strategy
Determination of the geodetic network on surface
Transfer of reference into tunnel
Determination of the geodetic network in the tunnel
Absolute alignment of the elements
Fiducialisation
Relative alignment of the elements
Active prealignment
Control and maintenance of the alignment
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BDS: strategy
Determination of the geodetic network on surface
Transfer of reference into tunnel
Determination of the geodetic network in tunnel

Combination of 3D triangulation and trilateration coupled with
measurements of on vertical plumb wires

Methods validated on an LHC pit in 2010 (depth of 65 m):
precision of 0.1 mm and accuracy of 0.5 mm

Hypothesis considered for CLIC: absolute position at the
bottom of each pit: ± 2 mm (depth > 100 m)
Next steps
No further studies needed between 2012-2016
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Distance < 2.5 km
BDS: strategy
Absolute alignment of the elements
Metrological Reference Network (MRN)
Propagation network simulations: max
deviation along the linac below 1 mm

Installed w.r.t the tunnel network

Overlapping stretched wires propagating the precision over
long distances

Simulations in 2009:
o
Precision at the bottom of the shaft of ± 2 mm
o
Calibration of metrological plates: ± 5 μm
o
Distance between pits: 3.5 km
o
Wires: 400m long
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Deviation along 200m according to
wire length ~ 3 to 5 μm
BDS: strategy
Absolute alignment of the elements
(MRN)
TT1 facility


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Precision on a 140 m wire: better than 2 microns over 33 days
Accuracy: 11 microns in vertical, 17 microns in radial. Can be improved!
BDS: strategy
Fiducialisation at the micron level

Fiducialisation and dimensional control of objects < 2m: CMM measurements
(Tolerances of measurement of Leitz Infinity: 0.3 μm + 1 ppm)

For objects > 2m or as control after transport or during specific tests:
combination of « mobile » means:
Instrument
Standard deviation between
instruments and CMM
measurements
AT401
< 5 μm
Micro
triangulation
< 5 μm
Romer arm
< 10 μm
Romer arm
Laser tracker: AT 401
Micro triangulation
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BDS: strategy
Relative alignment of the elements
Support Pre-alignment Network (SPN)

Sensors that are part to the component

Micrometric measurements between zero of the component and sensors interfaces
Summary:
Next steps
•
Improve accuracy of stretched wire solution (better calibration of sensors,
relative determination of the deflection of vertical, more accurate and precise
biaxial inclinometers)
•
Go on with fiducialisation studies concerning objects with a length > 2m
•
Update network propagation simulations performed in 2009
8•
Better knowledge of wires stretched over 500 m (TZ32 tunnel)
BDS: strategy
Active prealignment
Determination of the position
Adjustment with cam movers
Next steps
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•
Validation of the algorithms of repositioning
•
Adapt design to BDS components (weight and size?)
•
Improve the stiffness of the solution
MDI area
Determination of the position of QD0 w.r.t other components of the BDS (1)
Requirements:


Position of the zero of QD0 w.r.t ideal straight line of the 500 last meters of BDS: ± 10 μm rms
(including fiducialisation)
Longitudinal relative position between QD0 and QF1: ± 20 μm rms
Solutions:

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Main difference concerns the MRN network (due to lack of space):
o
No overlapping of stretched wires in the last 250 m
o
No HLS system needed for the modeling of the sag, which will be extrapolated on the last
250 m.
MDI area
Determination of the position of QD0 w.r.t other components of the BDS (2)

Longitudinal monitoring of QD0 w.r.t QF1: capacitive sensors coupled to each component
measuring w.r.t targets of a common carbon bar
QD0

QF1
Capacitive sensor
Carbon bar with targets
on both extremities
Development of special mechanics and sensors to displace the stretching device when QD0 is
removed.
o
Development of « opened » WPS sensors
Fixed part of stretched wire will have to displaced remotely, radially (get out the WPS
installed on QD0) and longitudinally (get out the support tube of QD0). Can not be
removed as it gives an alignment reference for all the BDS components over the last
500m.
o
Next steps
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•
Propose a design for these solutions and integrate them
•
Validate prototypes on dedicated mock-ups
MDI area
Left side w.r.t right side
Requirements:
Determination of left reference line w.r.t right reference line : within ± 0.1 mm rms
Monitoring of left reference line w.r.t right reference line : within a few microns
Monitoring of the position of left QD0 / right QD0 within ± 5 μm rms



Solutions:

Determination of left reference line w.r.t right reference line &monitoring of one BDS w.r.t other:
link stretched wires on both side by a common reference (as in the LHC), using the survey
galleries
Next steps
No further studies needed between 2012-2016
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MDI area
Left side w.r.t right side
Monitoring of the position of left QD0 /right QD0: Concept
4 Reference Rings (RR) located at each extremity of QD0, supported from outer tube
6 radial spokes per RR


In two steps:

RR
RR
RR
Next steps
RR

A monitoring of the position of QD0
w.r.t RR thanks to proximity sensors.
(initial calibration of their position
performed on a CMM)
A transfer of the position of RR
thanks to 6 spokes to alignment
systems. By combination of redundant
information, the position of the
center of 4 RR is computed.
See next presentation by Harry van der Graaf
•
Validation of spokes design and alignment systems at NIKHEF (2011-2012)
•
Validation of the concept on a mock-up at CERN (2012-2013)
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Summary

Same strategy of pre-alignment concerning BDS than for main linac

But tighter requirements in the determination of position, in the adjustment, which will require
dedicated prototypes and mock-ups, especially for the MDI area.
o
Improve accuracy of stretched wire solution
o
Go on with fiducialisation studies for objects longer than 2 m
o
Update propagation network simulations performed in 2009
o
Use TZ32 tunnel to have a better knowledge of wires stretched over 500 m.
o
Cam movers: adapt the design of MB quad to the BDS and MDI components (weight & size of
the components, loads not centered, 6 motorized DOF)
o
Special solutions required concerning longitudinal monitoring of final focus, and stretched
wire around QD0

Collaboration with NIKHEF concerning the monitoring of QD0 through the detectors
o
Concept proposed
o
Validation of spokes and alignment systems under progress @ NIKHEF
o
Validation of the whole concept foreseen @ CERN in 2012-2013.
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Thank you very much for your attention!
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