CLIC and HL-LHC alignment requirements

1. CLIC and HL-LHC alignment requirements H. MAINAUD DURAND

2. SUMMARY • CLIC project: • Introduction to the CLIC project • Alignment requirements • HL-LHC project: • Introduction to the HL-LHC project • Alignment requirements • Common alignment requirements of both projects

3. CLIC: introduction to the project Study for an e- e+ collider with a centre of mass energy of 3 TeV • Sub-µm beam size, down to a few nm at the IP • A number of challenges to be mastered, among which: • Very tight tolerances of alignment of components, to about 10 µm over a distance of 200m • Active stabilization of the quadrupoles in the nanometre range required

4. CLIC: introduction to the project

5. CLIC: introduction to the project • Based on a two beam acceleration concept • Each linac consists of more than 10 000 modules (with a 2m length)

6. CLIC: introduction to the project • Different types of components: • Quadrupoles : • MB quadrupoles: ~ 4000 • DB quadrupoles: ~ 42 000 • BPM: one per each quadrupole • Accelerating structures: ~ 142 800 • PETS components: ~ 71 000

7. CLIC: alignment requirements PRE-ALIGNMENT (beam off) Mechanical pre-alignment Active pre-alignment Beam based alignment Beam based feedbacks Within +/- 0.1 mm (1s) Within a few µm • Starting point = challenge concerning the pre-alignment of the CLIC components. • Requirements: • The zero of each component will be included in a cylinder with a radius of a few micrometers: • 10 µm (BDS components) • 14 µm (RF structures & MB quad BPM) • 17 µm (MB quad) • 20 µm (DB quad) • Active alignment consists of two steps: • Determination of the position by alignment sensors • Re-ajustment by actuators

8. SUMMARY • CLIC project: • Introduction to the CLIC project • Alignment requirements • HL-LHC project: • Introduction to the HL-LHC project • Alignment requirements • Common alignment requirements of both projects

9. HL-LHC: introduction to the project Objective: to extend the discovery potential of the LHC, by increasing its luminosity by a factor 10 beyond its design value • Key innovative technologies: • cutting-edge 13T superconducting magnets • Very compact and ultra precise superconductive cavities for beam rotation (crab cavities) • 300 m long high power superconducting links with zero energy dissipation

10. HL-LHC: introduction to the project

11. HL-LHC: introduction to the project

12. HL-LHC: Introduction to the project ATLAS CMS P. Fessia JP Corso and EN-MEF int. team

13. HL-LHC: introduction to the project

14. HL-LHC: introduction to the project

15. HL-LHC: alignment requirements Triplet Monitoring of the relative position Remote adjustment if needed Fiducialisation Within a few µm Initial alignment (absolute position) Smoothing Within +/- 0.1 mm ? (1σ) Monitoring of the position of the cold mass w.r.t. external fiducials Other components of the LSS Beam Within +/- 0.1 mm (1σ) Monitoring of the relative position Remote adjustment if needed Within +/- 0.1 mm ? (1σ) Within +/- 0.1 mm (1σ)

16. SUMMARY • CLIC project: • Introduction to the CLIC project • Alignment requirements • HL-LHC project: • Introduction to the HL-LHC project • Alignmentrequirements • Common alignment requirements of both projects

17. Common requirements between both projects • The determination of the position of the component can be divided (as an approximation) into two steps: • Determination of the “zero” of the component • In the referential frame of its mechanical support • In the referential frame of the sensor • Determination of the position of the referential frame of the sensor coupled to the component w.r.t a stretched considered as a straight reference Step 1 Step 2 Straight reference Magnet Sensor referential frame Mechanical support Step 1

18. Straight reference BDS: strategy Common requirements between both projects Sensor n sensors, with n > 100 • Sensor: • Biaxial sensor, providing radial and vertical offsets w.r.t alignment reference • Interchangeable at the micrometer level • Repeatability of measurements < 1 μm • Accuracy < 5 μm • Limited drift • Radiation hard, possibility of remote electronics • Frequency of acquisition: 20 Hz. • Straight reference: • - Length > 200 m • Stable, along time, according to environment conditions • Straight at a few micrometers

19. BDS: strategy Conclusion • Alignment requirements between both projects are quite different: • For HL-LHC: relative monitoring at the micrometer level, in a very severe environment • For CLIC: absolute alignment at the micrometer level • In both cases, we will need: • A straight alignment reference, stable along time and environment, over a length above 200 m • n sensors (n between 20 and 100), plugged on the components to be aligned, providing radial and vertical offset measurements w.r.t the alignment reference at a micrometric accuracy. • Can the laser beam be such a straight reference? • what about the stability of the beam, the stability of the laser source • Is vacuum needed on such distances? Which vacuum? Are there other solutions? • What is the impact of temperature, humidity and other parameters on the straightness of the laser beam? • How to be sure of the straightness of the beam?

20. BDS: strategy Conclusion • Concerning the sensors: • Which type of sensor can fulfil such requirements? • What is the impact of the diameter of the laser beam w.r.t. accuracy of the sensor? • How to attach the sensor to the component, and measure w.r.t. a laser beam under vacuum? • How to transfer the position of the laser beam outside the vacuum pipe without any constraints? • Are there rad hard sensors? • Which kind of algorithm for image processing should be used? • Then, once we have found a solution: how to validate the global solution? • These are a lot of questions! We hope to find a great number of answers during your presentations, and during the brainstorming.

21. SPARES SLIDES

22. BDS: strategy concerning the determination of position Solution proposed Installation and determination of the surface geodetic network Transfer of reference into tunnel Installation and determination of the tunnel geodetic network Absolute alignment of the elements Relative alignment of the elements Active prealignment Control and maintenance of the alignment

23. BDS: strategy concerning the determination of position Solution proposed Installation and determination of the surface geodetic network Transfer of reference into tunnel Installation and determination of the tunnel geodetic network Distance < 2.5 km • Combination of 3D triangulation and trilateration coupled with measurements 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)

24. BDS: strategy BDS: strategy concerning the determination of position Solution proposed Absolute alignment of the elements Metrological Reference Network Relative alignment of the elements • Propagation network simulations • Installed w.r.t the tunnel geodetic 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 • Std deviation of 3.6 μm over 200m of sliding window

25. BDS: strategy BDS: strategy concerning the determination of position Solution proposed Absolute alignment of the elements Relative alignment of the elements TT1 facility • Precision on a 140 m wire: better than 2 microns over 33 days • Standard error in the determination: 11 microns in vertical, 17 microns in radial. Can be improved!