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Summary and conclusions of the mini workshop on laser based alignment systems

Summary and conclusions of the mini workshop on laser based alignment systems. OUTLINE Overview of the workshop Presentations given during the workshop Conclusion. Introduction. CLIC project has very tight tolerances for the alignment of beam-related components

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Summary and conclusions of the mini workshop on laser based alignment systems

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  1. Summary and conclusions of the mini workshop on laser based alignment systems GUILLAUME STERN

  2. OUTLINE • Overview of the workshop • Presentations given during the workshop • Conclusion

  3. Introduction • CLIC project has very tight tolerances for the alignment of beam-related components • Requirement: 10 μm (at 1 σ) over a slidingwindow of 200 m • Solution based on stretched wires has some drawbacks (difficult implementation, cost) • Idea: replace stretched wire by laser beam

  4. Workshop goals • Many institutes throughout the world work on laser based alignment systems • Workshop goals • Reviewing existing systems • Sharing experience, problems • Talking about on-going developments, perspectives • Improving collaboration between institutes

  5. Workshop organisation • Participants (around 25 persons) • CERN • DESY (Germany) • KEK (Japan) • SPring 8 (Japan) • JINR (Russia) • ETHZ (Switzerland) • Agilent (Switzerland) • Program • Thursday 30th: Introduction + presentations • Friday 31st: Visit on CERN site + brainstorming + conclusion

  6. Presentation: Chao Zhang, Developing an Iris Diaphragm Laser Alignment System for Spring 8 Storage Ring Magnets • Principle: observing diffraction pattern of an iris • Goal: accuracy of 10 μm (at 2σ) over 10 m • Alreadyachieved: pointingstability of 8 μm (at 2σ) over 10 m

  7. QPre Ab Ae Laser Collimator Laser spot Presentation: Mikhail Lyablin, A Laser Based Fiducial Line For High-Precision Multipoint Alignment System • Principle: observing laser spot when laser beam propagates in a tube with atmospheric air • Goal: accuracy of 10 μm (at 1 σ) over a slidingwindow of 200 m • Already achieved: pointing stability of 1.5 μm (at 1σ) over 70 m Tube with atmospheric air Transparent windows

  8. Presentation: Tsuyoshi Suwada, Propagation and Stability Characteristics of a 500m Long Laser Based Fiducial Line For High-Precision Alignment of Long Distance Linear Accelerators stopper QPD sensor • Principle: observing laser spot with quadrant photodectectors (QPD) that are mechanically switched across the laser beam propagating in vacuum pipe • Goal: accuracy of 100 μm (at 1σ) over 500 m • Already achieved: pointing stability of 40 μm, estimatedaccuracy of 100 μm (at 1σ) over 500 m QPD sub-holder 130mmϕ QPD holder signal pick-up

  9. Presentation: Johannes Prenting, Status Report on the laser based Straight Line Reference System at DESY • Principle: observing diffraction pattern of spheres • Goal: accuracy of 300 μm (at 1σ) over 150 m • Estimated achievable accuracy: 100/200μm (at 1σ) over 150 m

  10. Original direction of the reflected beam QPR Laser Direction the reflected beam after tilt base θ ψ Base The surface of the liquid in case of horizontal basis Cuvette with a liquid The surface of the liquid with tilt base Presentation: Mikhail Lyablin, The Search For And Registration of the Superweak Angular Ground Motions • Principle: observing laser spot with quadrant photoreceiver (QPR) after reflection on water surface • Resolution: 5 nrad

  11. Presentation: Guillaume Stern, Laser Alignment Multipoint Based – Design Approach (LAMBDA project) • Principle: observing laser spot with camera/shutter assemblies that are mechanically switched across the laser beam • Goal: accuracy of 10μm (at 1σ) over 200 m • Already achieved: pointing stability of 10μm (at 1σ) over 3 m

  12. Presentation: SébastienGuillaume, Validation of Laser Alignment Systems by Systems Referred to Gravity • Many alignment systems refer to gravity (e.g. Hydrostatic Levelling Systems) • PhD thesis: determining the equipotential of gravity with respect to a straight line (part of the work: development of the deflectometer) • Possibility of performing inter-comparison between different alignment systems

  13. Conclusion • Two very intense days • Many institutes working on laser based alignment systems, though each of them with a different approach • So far, no institute has been able to meet CLIC requirements in terms of accuracy or resistance to radiation • Brainstorming highlighted following aspects • Necessity to work under vacuum • Quality of laser beam profile very important to guarantee a straight reference • Validation of the beam straightness through dedicated benches and through inter-comparison with other alignment systems • Collaborations for future work

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