1. on behalf of the CLIC active pre-alignment team
BDS alignment
H. MAINAUD DURAND
on behalf of the CLIC active pre-alignment team
Alignment strategy, status and next steps
BDS
MDI area

2. BDS: objective of pre-alignment
PRE-ALIGNMENT (beam off)
Mechanical pre-alignment
Active pre-alignment
Beam based alignment
Beam based feedbacks
Within +/- 0.1 mm (1s)
Within a few microns
Determination of the position of the components in a general coordinate system thanks to alignment systems =
Active pre-alignment +
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

3. 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

4. BDS: strategy Next steps No further studies needed between 2012-2016
Determination of the geodetic network on surface
Transfer of reference into tunnel
Determination of the geodetic network in tunnel
Distance < 2.5 km
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

5. BDS: strategy Metrological Reference Network (MRN)
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:
Precision at the bottom of the shaft of ± 2 mm
Calibration of metrological plates: ± 5 μm
Distance between pits: 3.5 km
Wires: 400m long
Deviation along 200m according to wire length ~ 3 to 5 μm

6. BDS: strategy (MRN) TT1 facility
Absolute alignment of the elements
(MRN)
TT1 facility
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!

7. 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
Romer arm
< 10 μm
Romer arm
Laser tracker: AT 401
Micro triangulation

8. BDS: strategy Support Pre-alignment Network (SPN)
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
Better knowledge of wires stretched over 500 m (TZ32 tunnel)

9. BDS: strategy Determination of the position Adjustment with cam movers
Active prealignment
Adjustment with cam movers
Next steps
Validation of the algorithms of repositioning
Adapt design to BDS components (weight and size?)
Improve the stiffness of the solution

10. 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:
Main difference concerns the MRN network (due to lack of space):
No overlapping of stretched wires in the last 250 m
No HLS system needed for the modeling of the sag, which will be extrapolated on the last 250 m.

11. 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
Capacitive sensor
QD0
QF1
Carbon bar with targets on both extremities
Development of special mechanics and sensors to displace the stretching device when QD0 is removed.
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.
Next steps
Propose a design for these solutions and integrate them
Validate prototypes on dedicated mock-ups 11

12. MDI area Left side w.r.t right side Next steps
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 12

13. 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:
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. RR
spoke
Line of sight for alignment systems
See next presentation by Harry van der Graaf
Next steps
Validation of spokes design and alignment systems at NIKHEF ( )
Validation of the concept on a mock-up at CERN ( ) 13

14. 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.
Improve accuracy of stretched wire solution
Go on with fiducialisation studies for objects longer than 2 m
Update propagation network simulations performed in 2009
Use TZ32 tunnel to have a better knowledge of wires stretched over 500 m.
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)
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
Concept proposed
Validation of spokes and alignment systems under NIKHEF
Validation of the whole concept CERN in

15. Thank you very much for your attention!15