1. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 1 CERN European Organization for Nuclear Research Mechanical Engineering and Thermo-mechanical Analysis of LHC Collimators Alessandro Bertarelli TS – Materials and Mechanical Engineering Group External Review of LHC Collimator Project 01 July 2004

2. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 2 OUTLINE Project Requirements Project Requirements Design strategy Design strategy Technical design Technical design Thermal and Mechanical Calculations Thermal and Mechanical Calculations Conclusions Conclusions

3. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 3 Functional specification (Mechanical aspects): Functional specification (Mechanical aspects): – –High absorbed heat load (up to 32 kW) – –Very high precision (25  m on 1200mm) – –High robustness in accident cases (up to 700ºC) – –Low-Z, high conductivity materials for jaw (carbon based) – –Limited jaw temperature (<~50º C) for outgassing reasons – –Easy maintenance Schedule (see M. Mayer’s talk for details) – –Design Activity started in September 2003 – –First full prototype TCS by May 2004 PROJECT REQUIREMENTS

4. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 4 How to meet the challenging requirements ? Highest priority to Secondary Collimators (TCS) … Contribution of many experts … Wide exploitation of LEP experience … In-depth calculations carried out from the early stages of development (concurrent design) … Mix of traditional and edge technologies. Advanced Materials (C/C composites, GlidCop® …). Specific tests to validate most critical technologies (S. Calatroni’s talk) DESIGN STRATEGY

5. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 5 Main Features (TCS design) Multi-DoF internal alignment system. Monolithic jaw (1200mm) clamped to the support. Decoupling and compensation of thermal deformations. Cooling system. RF contacts for low impedance. Actuation system (2 step-motors per jaw). External alignment system and plug-in Electronic controls TECHNICAL DESIGN

6. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 6 TECHNICAL DESIGN Mechanical Assembly Beam axis Overall length: 1480mm Tank width: 260mm Vacuum Tank Main support and plug-in External adjustment motor Actuation system

7. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 7 TECHNICAL DESIGN Collimator Cross-section (1/2) Support Bar Clamping springs Jaw (25x80x1200 mm) Cooling Pipes Bellow Return Spring Stepper Motor Jaw stroke +30/-5 mm

8. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 8 TECHNICAL DESIGN Collimator Bloc 1. Jaws in C/C or graphite 2. Cooling Cu-pipes and plate pressed against the jaw, brazed to the bar. 3. GlidCop® support bar and clamping plates Low thermal contact resistance (P=3÷5 bar) Differential thermal expansion allowed Deformations minimized (compensation) 3 2 1

9. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 9 TECHNICAL DESIGN Actuating System 1. Jaw actuated by 2 stepper-motors via a roller screw (10  m/step) 2. Return spring for semi - automatic pullback and play recovery 3. Rack-pinion system to prevent misalignments 4. Vertical sliding of the jaw surface (  10mm) 1 1 2 2 3 3

10. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 10 TECHNICAL DESIGN Cooling System Jaw cooled by 2 Ø6 OFE- Cu pipes (3 loops each) Outer section squared (  9) to allow brazing to internal and external plates Water from general cooling circuit (Inlet temp. up to 27ºC) Water flow 5 l/min (20 l/min per collimator) leading to a 3 m/s velocity

11. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 11 THERMOMECHANICAL ANALYSIS Main problems to tackle in analysis and design … How to evacuate heat loads? How to evacuate heat loads? How to join graphite jaw and metal support? How to join graphite jaw and metal support? How to keep thermal deformations to a minimum? How to keep thermal deformations to a minimum?

12. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 12 Extensive analytical and numerical calculations. Extensive analytical and numerical calculations. Semi-analytical models for Thermal contact resistance, Convection, Thermal bending … Semi-analytical models for Thermal contact resistance, Convection, Thermal bending … Many FE models (ANSYS®) of the TCS were studied: Many FE models (ANSYS®) of the TCS were studied: –2- and 3-dimensional … –Different materials (C/C, C, Cu, Steel, Glidcop®)… –Input thermal load imported from FLUKA simulations … –Different load cases (nominal, accident, transient) –Complex boundary conditions … THERMOMECHANICAL ANALYSIS

13. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 13 THERMOMECHANICAL CALCULATIONS How to evacuate heat and allow free expansion … k Cu kGkG RMS Roughness R q Mean Asperity Slope  a P P EGEG Less than 1% of the interface surfaces is usually in contact …Less than 1% of the interface surfaces is usually in contact … Pressure is necessary to increase the effective contact surface …Pressure is necessary to increase the effective contact surface … Thermal conductance might be evaluated analyticallyThermal conductance might be evaluated analytically

14. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 14 THERMOMECHANICAL CALCULATIONS How to minimize thermal deformations … M1M1 M3M3 M2M2 u” i =  T/B  =u”L 2 /8 TT … the principle of compensation is used

15. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 15 THERMOMECHANICAL CALCULATIONS FEM Model for 3-D analysis Geom. B.C.: Hinged + Free expansion Contact elem. (friction + therm. Conductance) Preloaded Springs (5 bar) Convection (12360W/m2/K) + inlet temp. (27ºC) Temperature - dependent properties (when available) Deposited Heat Power (W/m 3 )

16. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 16 THERMOMECHANICAL CALCULATIONS Remarks on jaw materials Several materials were analyzed for the jaws: Several materials were analyzed for the jaws: –Snecma NB31 3-d C/C (Y max X min) –Snecma NB31 3-d C/C (Z max Y min) –SGL C1001 2-d C/C –Tatsuno AC150 2-d C/C –SGL R4550 “isotropic” graphite Out of these only AC150 and R4550 were retained since they present the best compromise in terms of deformations, strength and availability. Out of these only AC150 and R4550 were retained since they present the best compromise in terms of deformations, strength and availability.

17. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 17 THERMOMECHANICAL CALCULATIONS Thermal analysis Nominal Conditions 7 TeV 8e10 p/s Steady-state (p=5 bar) 2-D C/C AC150 TMax 47ºC Graphite R4550 TMax 51ºC

18. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 18 THERMOMECHANICAL CALCULATIONS Displacement analysis Nominal Conditions 7 TeV 8e10 p/s Steady-state 2-D C/C AC150  Max≈20  m Graphite R4550  Max≈14  m

19. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 19 THERMOMECHANICAL CALCULATIONS Displacement analysis Nominal Conditions 7 TeV 4e11 p/s Transient (after 10s) To be confirmed 2-D C/C AC150  Max≈30  m Graphite R4550  Max≈47  m

20. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 20 THERMOMECHANICAL CALCULATIONS Stress Analysis Nominal Conditions 7 TeV 8e10 p/s steady-state 2-D C/C AC150  Max≈7.8MPa Graphite R4550  Max≈5.8MPa

21. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 21 THERMOMECHANICAL CALCULATIONS Stress Analysis Accident case 7 TeV 9.1e11 p (200 ns) AC150 T max = 724º R4550 T max = 698º Courtesy A. Dallocchio

22. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 22 Notes: R=  adm (1- )/E  THERMOMECHANICAL CALCULATIONS Load case summary

23. 01.07.2004 A. Bertarelli – R. Perret CERN TS – MME Group 23 Based on the given requirements, technical layout is a mix between traditional and new solutions … Mechanical design was finalized … Feasibility confirmed by prototype manufacturing … Extensive thermo-mechanical analyses results predict that tough specification should be attained within reasonable limits, … … provided available data are correct (material characterization results are forthcoming) … … and new Fluka simulations confirm previous loads. In nominal conditions stresses are well below the limits. Special attention must be given to accident scenarios, where stresses come close to admissible limits … (see O. Aberle talk) CONCLUSIONS