1. Precision Mechanics / Systems Aspects Case examples from LHC Trackers 1st EIROforum School on Instrumentation 11-15 May 2009 A. Onnela and A. Catinaccio CERN – PH/DT http://indico.cern.ch/conferenceOtherViews.py?view=standard&confId=43007 http://indico.cern.ch/conferenceOtherViews.py?view=standard&confId=43007 http://indico.cern.ch/conferenceOtherViews.py?view=standard&confId=43007

2. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 2 Intro: LHC Trackers and ‘precision’ Design Materials Analysis Manufacture, Assembly Transport, Installation Summary: Lessons learned

3. Intro: LHC Trackers Tracker in the heart of the experiment, next to the beam interaction point ESI 2009, 11-15 May 20093 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT

4. Intro: LHC Trackers Tracker: Measurement of particle track space points with 10-50 um precision ESI 2009, 11-15 May 20094 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT

5. Intro: LHC Trackers Measurement of particle track space points with 10-50 um precision Requirements on mechanical ‘precision’: Initially for geometry coverage and calibrations: Placing of individual measurement elements to an accuracy of 100-500 um During operation: Stability better than the measurement precision: 10-50 um ESI 2009, 11-15 May 20095 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT

6. Intro: LHC trackers ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 6 40 million times per second Find 4 straight tracks!

7. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 7 Intro: LHC trackers Here the 4 straight tracks + few other high momentum tracks

8. Intro: LHC Trackers ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 8 From individual sensor units (modules) via sub-assemblies up to the final Experiment

9. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 9 Intro: LHC Trackers and precision Design Materials Analysis Manufacture, Assembly Transport, Installation Summary: Lessons learned

10. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 10 To design correctly clarify: What is really needed? What ‘precision’ is needed? Establishing the requirements may be difficult and take many iterations, possibly late in the project, too Design: requirements

11. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 11 Design: What is really needed? Light weight, minimum material, “transparency” to particles Tight mechanical tolerances ( high initial accuracy) (a few tens of microns are required for the correct positioning of the detecting modules). High stability, high stiffness  high natural frequencies Short and Long term dimensional stability under load (low CTE, CME, creep) High radiation resistance Magnetic field: non-magnetic materials Low out-gassing and low gas permeability Example requirements from the LHC trackers:

12. But as it may be too difficult / too costly / too slow to reach, therefore try to get the real requirements on: Precision, Accuracy and Stability Yes, this is the preferred result! ESI 2009, 11-15 May 200912 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT Design: Requirements on Precision

13. Accuracy vs. Precision High accuracy but low precision High precision but low accuracy Graph: Pekaje Both influenced by the quality of manufacture and assembly, and by static loads ESI 2009, 11-15 May 200913 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT

14. Stability High momentary precision but low stability Stability influenced by dynamic loads, creep, vibration, temperature-, pressure-, humidity change, changing magnetic field, etc. ESI 2009, 11-15 May 200914 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT

15. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 15 Loads In addition to the ‘normal’, expected loads (gravitation, thermal, etc.) study also failure scenarios and related loads. Examples from the Atlas inner tracker: Transports and installation: Non-ideal support conditions or accidental loads (difficult to estimate!) Loss of thermal isolation of the LAr cryostat: Sudden move of tracker supports by 3 mm (far more than the displacements under normal conditions) Malfunctioning of cooling systems: fast heating or fast cooling of detectors (possibly severe thermal shocks)

16. Design for high precision Think up to the smallest details, e.g. connections are very important, and the error chain can be long (Modules  Sub-structures  Full Tracker  Installation into Experiment) Some examples on precision of (metallic) couplings: Illustrations: J. Huopana / U. Oulu Elastic averaging: ~5 um Pinned joints: ~5 um Kinematic coupling: ~0.5 um ESI 2009, 11-15 May 200916 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT

17. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 17 More and less interesting design subjects Modules & Layout Cooling & Services Structures & Interfaces Tracker: 1. This is where the attention naturally goes 2. Some attention goes to this, too 3. Little and late attention  Big problems Pay attention also to the less interesting subjects, already early on in the design process. Not fun, but very much necessary!

18. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 18 Intro: LHC Trackers and precision Design Materials Analysis Manufacture, Assembly Transport, Installation Summary: Lessons learned

19. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 19 Choice of materials Correct understanding of the design requirements enables Correct choice of materials Of the LHC tracker requirements… …all have a direct impact on the material choices. Light weight, minimum material, “transparency” to particles Tight mechanical tolerances (high initial accuracy) (a few tens of microns are required for the correct positioning of the detecting modules). High stability, high stiffness  high natural frequencies Short and Long term dimensional stability under load (low CTE, CME, creep) High radiation resistance Magnetic field: non-magnetic materials Low out-gassing and low gas permeability

20. Materials for a LHC tracker ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 20 For trackers a hybrid solution: Structures in CFRP, small support / cooling inserts in aluminium

21. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 21 Materials for a LHC tracker Documentation exists, e.g. “CERN: Compilation of radiation damage data” However, the products change, some materials are no longer available – some new materials are not tested yet (or not known by us)

22. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 22 CFRP (carbon-fibre reinforced polymers) much favoured as tailorable for high stiffness, good strength, low mass, near zero CTE, low CME, low creep –Typical carbon fibres: HT (high tensile e.g. T300) E = 200-255 GPa (235 for T300) IM (intermediate modulus e.g. T800) E = 255-315 GPa HM (high modulus e.g. M55J) E > 315 GPa UHM (ultra-high modulus e.g. GY-70, P120) E > 395 GPa (Note: Aluminum: 70 GPa, Steel: 210 GPa) –Typical matrix materials (resins): Epoxies Cyanate ester (10 times lower CME but usually costly) –Typical core materials: Nomex (aramid fibres) Aluminium New interesting possibilities with non-plastic matrices –Metal matrix composites (for thermal properties, but ‘heavy’) –Carbon-carbon composites (for thermal properties) Availability and (dis)continuity of commercial products can be a problem Materials for a LHC tracker

23. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 23 Intro: LHC Trackers and precision Design Materials Analysis Manufacture, Assembly Transport, Installation Summary: Lessons learned

24. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 24 Analysis Stability: analyse for high stiffness, thermal behaviour, vibrations & natural frequencies, support configuration, stress levels All boundary conditions must be well known (by experience) or large multipliers must be introduced (or risks taken!) Analyses must feedback to design at early stage Analyse carefully most stressed areas (local supports and connections) Allow time for analysis verification by extensive testing and prototype qualification (CFRP assemblies are often difficult to predict due to manufacturing and hybrid components) Typical analyses: Composite layup characterisation Static analysis (gravity loads, loads during transports) Sub modelling, local areas, supports and connections where the real problems can be. Buckling Thermal Modal analysis Random vibration Shock Analysis (transport and installation)

25. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 25 Examples of FEM calculations Rigid structures  high local stresses

26. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 26 Examples of FEM calculations ASIC power 5.3 W FEA Loads during handling can be much higher than the nominal operation loads

27. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 27 Examples of FEM calculations Vibration measurements for different accelerators Random vibration analysis on Atlas TRT barrel structure: Input power spectral density (PSD) 1  10 -8 g 2 /Hz and 5% damping ratio (frequency independent) results in 11 um displacements. 10x lower PSD results in 2x smaller displacement, still significant! ‘Fortunately’, finally a lot of cables, so a lot of damping too...

28. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 28 Intro: LHC Trackers and precision Design Materials Analysis Manufacture, Assembly Transport, Installation Summary: Lessons learned

29. Manufacture Example: Manufacture of this silicon module support frame ESI 2009, 11-15 May 200929 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT

30. Detector supports inserts (e.g. 11, 12, 13, and 14) Define parallel planes on which the detectors are mountedDefine parallel planes on which the detectors are mounted Planarity requirement 0.05 mmPlanarity requirement 0.05 mm 1.2 m ESI 2009, 11-15 May 200930 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT

31. Manufacture Metallic inserts Carbon fibre pieces in ‘1 mm precision’ Accurate gluing jig Applied concept: From modest accuracy components to assemblies of high accuracy ESI 2009, 11-15 May 200931 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT

32. Assembly 756x ESI 2009, 11-15 May 200932 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT

33. Measurements Geometrical precision of the module supports and positioning dowel pins measured to be better than 50  m over the whole area. 4% of assemblies found out of tolerances, and corrected. 24 module supports 12 dowel pins ESI 2009, 11-15 May 200933 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT

34. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 34 Manufacture

35. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 35 Measurements ASIC power 5.3 W FEA Photogrammetry ‘Robotic’ arm

36. Measurements ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 36

37. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 37 Example: Barrel Support Structure ASIC power 5.3 W FEA Measurements

38. And then the structures are loaded ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 38

39. Design hint: Choose carefully the color of the cables! ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 39

40. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 40 Intro: LHC Trackers and precision Design Materials Analysis Manufacture, Assembly Transport, Installation Summary: Lessons learned

41. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 41 Transport and installation

42. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 42 Transport and installation

43. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 43 Collision predicted from 3D measurements Installation adjusted accordingly Measurements up to the end

44. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 44 Intro: LHC Trackers and precision Design Materials Analysis Manufacture, Assembly Transport, Installation Summary: Lessons learned

45. ESI 2009, 11-15 May 2009 Precision Mechanics and Systems Aspects. A.Onnela, A.Catinaccio, CERN-PH/DT 45 Summary: Lessons learned Put effort into establishing clear specifications, be prepared to do many iterations and late modifications –Accuracy, precision, stability requirements –Load conditions –Electrical, magnetic, radiation, fluids, etc. Aim for simplicity and clarity in the design (e.g. supports). Enough of complications will come anyways! Do analysis early on to direct the design choices –Back-up with prototypes and tests where suitable data not available Plan and ‘design’ geometry measurements right from the beginning –References, survey targets, etc. And last, but not at all least: Take ‘services’ = Pipework and cabling into the main design effort right from the beginning –Remember to plan and design their testing too (leak tests, connectivity, etc.) The end