1. H. MAINAUD DURAND on behalf of the CLIC active pre-alignment team oWPS versus cWPS OUTLINE Introduction oWPS cWPS Results of inter-comparison tests o @ SLAC o On a CLIC test setup Summary and next steps

2. 2 Problem and solution proposed Solution proposed for CLIC CDR (from previous presentation) Sensors & actuators are associated to each support / articulation point of girder: As a summary: For CDR:- straight reference = stretched wires - sensors = Wire Positioning Sensors (WPS) More than 60 000 WPS needed!

3. 3 Problem and solution proposed More than 60 000 WPS needed! Requirements Precision< 2 μm Accuracy< 5 μm Range10 mm x 10 mm Radiation hard Installed in the LHC for the monitoring of the low beta triplets (relative measurements) Expensive but radiation hard Needed to be upgraded to fulfill the requirements cWPS New development especially to fulfill the CLIC demands oWPS

4. OUTLINE Introduction: CLIC project & active pre-alignment Presentation of oWPS Presentation of cWPS Intercomparison tests o @ SLAC o On the CLIC test setup Conclusion

5. 5 oWPS (1) Developed and manufactured by Open Source Instruments Inc. under GNU General Public License : http://www.opensourceinstruments.com/WPS/http://www.opensourceinstruments.com/WPS/ Design proposed in 2006 Version 1 in 2009 : oWPS1 Version 2 in 2011: oWPS2 Larger aperture Smaller exposure time PT1000 added Kinematic mounting surfaces (cone, conical chamfer and plane).

6. 6 oWPS (2) Principle Two CCD cameras mounted rigidly on a support with a kinematic mount CCD cameras take pictures of the wire from two different angles, under red light As the position and orientation of each camera has been determined previously in a calibration process, the position of the stretched wire is deduced in the same coordinate system Version 2 consists of: TC255 image sensors from Texas Instruments, 336x243 pixels, with 10 μm square pixels An array of 9 LEDs (each LED emitting 20 mW of 620 nm red light) A PT1000 glued on the sensor side A A3022 WPS head developed by OSI Inc.

7. 7 oWPS (3): stretched wires Carbon fiber wrapped by two thin plastic threads in PEEK Image of the wire Picture of the wire (-) Not antistatic (-) Transparent to infra-red (+) Smaller lineic mass, higher tensile strength (-) Non uniform longitudinally (-) Appearance of bright spots on images (+) Antistatic Multifilament yarn spun from liquid crystal polymer Metallization of Vectran wire by silver plasma coating

8. 8 oWPS (4) Validation tests Linearity tests Interchangeability tests Between 5 sensors: σ = ± 1.8 μm in radial σ = ± 5.8 μm in vertical Two high precision linear stages mounted at 90°, with a bidirectional repeatability of ± 0.2 μm Offsets between 2 calibrations of the same sensor

9. OUTLINE Introduction: CLIC project & active pre-alignment Presentation of oWPS Presentation of cWPS Intercomparison tests o @ SLAC o On the CLIC test setup Conclusion

10. 10 cWPS (1) Manufactured by Fogale Nanotech Prototype (1990)Version 1 in 1994Version 2 in 2000 Version 2 CERN New ways of fastening «gate» fastening solution tested on 17 sensors and 36 centering per sensors: -Radial repeatability ranging from 0.6 μm to 1.8 μm -Vertical repeatability ranging from 0.5 μm to 1.0 μm.

11. 11 cWPS (2) New calibration bench designed a a b c d a = reference sensors b = 2 displacement tables (resolution of displacement of 10 nm over 75 mm of stroke). c = Pelletier probe d = sensor to be calibrated Offsets between two calibrations of the same sensor Two high precision linear stages mounted at 90°, with a resolution of displacement of 10 nm

12. 12 cWPS (2) Associated stretched wire Each cWPS must be calibrated w.r.t. the type of wire:  There is a scale factor between carbon PEEK and carbon Kevlar wires: 50 μm per millimeter of range  There is a scale factor between carbon PEEK and carbon PES wires: 10 μm per millimeter of range  No scale factor between wires coming from the same manufacturing lot  Scale factor between same type of wire from different lots Carbon Kevlar Carbon PEEK/PES

13. OUTLINE Introduction: CLIC project & active pre-alignment Presentation of oWPS Presentation of cWPS Intercomparison tests o @ SLAC o On the CLIC test setup Conclusion

14. Inter-comparison at SLAC (From G. Gassner) Residuals < 1 μm Scale factor of 2% Residuals ~ 3 μm

15. 15 Description of module test setup at CERN Configuration:

16. Some first results… Noise Noise peak to peak < 2 μm Noise peak to peak ~ 6 μm

17. Some first results… Repeatability, Reproducibility, interchangeability Repeatability: Reproductibility: < 3 μm Interchangeability: cWPS: maximum offset of 10 μm, mean value ~3-4 μm oWPS: maximum offset of 14 μm, mean value ~6-8 μm

18. Some first results… Test of displacement of the wire cWPSoWPS Each wire is displaced, and the sensors should see displacements that are proportional to their longitudinal position along the wire  the offset between theoretical displacements and achieved displacements must be as small as possible.

19. Some first results… Short term stability measurements Zoom over 2 days of measurements (one value / minute, each value is the average of 40 readings) cWPS & oWPS see the same displacement of support, due to temperature variations Readings can not be compared: there is an effect of temperature variations to the oWPS itself  Compensation needed.

20. 20 Summary Performances of oWPS comparable to upgraded version of cWPS The Silver Vectran wire associated with oWPS is promising too, with a smaller linear mass and a stronger breaking tension. A conductive version is under development which could be associated to cWPS Next steps: perform tests concerning absolute measurements of oWPS and cWPS (latest results shown in previous presentation confirm that these measurements are within a few microns Develop a more compact version of oWPS, and a radiation hard version. oWPS (μm)cWPS (μm) Noise28 Repeatability< 1.5< 2 Reproducibility< 2< 3 Interchangeability6 - 83 - 4 Resolution< 0.5