1. Overview of FLUKA Energy Deposition and Design Studies for the LHC Overview of FLUKA Energy Deposition and Design Studies for the LHC M. Brugger, F. Cerutti, A. Ferrari, L. Lari, M. Mauri, L. Sarchiapone, G. Smirnov, V. Vlachoudis CERN AB/ATB/EET M. Magistris, A. Presland, M.Santana, K.Tsoulou

2. Workshop on Materials for Collimators and Beam Absorbers2 5th September 2007

3. Workshop on Materials for Collimators and Beam Absorbers3 5th September 2007 Overview What accelerator problems can be addressed with FLUKA Critical Quantities to be calculated  Heating/Cooling (ANSYS)  Quench protection  Dose to components  … Simulation Approach  Generic calculations  Benchmarks if needed/available  Detailed simulations  Interfaces with codes Related Uncertainties Needed Details  Clear definition of scenarios/configuration to be studied  Impact parameters, loss maps, magnetic fields,..  Required quantities and associated limits  Loss assumptions (results scale accordingly) Applications

4. Workshop on Materials for Collimators and Beam Absorbers4 5th September 2007 Multifold Structure

5. Workshop on Materials for Collimators and Beam Absorbers5 5th September 2007 Generic Study - Material Selection Different Cases 1. Graphite + 100  m Copper coating 2. 1cm Graphite plate on Copper 3. Block Materials C Cu C Single Module Prefire Total: 8 bunches Range: 5  – 10  =200  m  Proton/Bunch:1.05  10 11 pr Total: 9  10 11 pr

6. Workshop on Materials for Collimators and Beam Absorbers6 5th September 2007 New Simulation Strategy Dynamic FLUKA input generation with several ad-hoc scripts Detailed description of more than 20 prototypes located in a virtual parking zone Prototypes are replicated, rotated and translated according to the layout Magnetic field maps: Analytic + 2D Interpolated Dynamic generation of the DS and ARC (curved section) Optics test: Tracking up to 5  reproduce the correct beta function Input Files FLUKA input template Twiss files Object summary Prototype Info Scripts lattice,… Fluka Input (.inp) LATTICE definitions Curved Tunnel creation Magnetic Fields Intensity Scoring cards Fluka Executable LATTICE transformations Dynamic adjustment of collimator gaps Fortran Files Source routine Si Damage 1 MeV n eq. Magnetic Field History Tracking,…

7. Workshop on Materials for Collimators and Beam Absorbers7 5th September 2007 IR7 Collimation Simulation Allowed loss rates: 100 kW continuously 500 kW for 10s (1% of beam) 1 MW for 1 s Quench limits: Quadrupoles~1 mW/cm 3 Bending~5 mW/cm 3 Geometry Modeling 1.5 km tunnel Warm section (straight) 2 Dispersion suppressors (arc) >200 objects fully detailed ~50 Collimators with variable positioning of the jaws tilt changed runtime Cleaning Insertions MomentumBetatron

8. Workshop on Materials for Collimators and Beam Absorbers8 5th September 2007 Automatic Geometry Creation 1. Initial input file template 2. Space Allocation & Geometry Creation 3. Lattice generation 4. Magnetic Fields mapping

9. Workshop on Materials for Collimators and Beam Absorbers9 5th September 2007 Geometry of Dipoles Tesla 14m long objects with a field of 8.3 Tesla: 5mrad bend  ~3cm sagitta The superconducting dipoles (MB) are made out of 4 straight sections to accommodate the trajectory

10. Workshop on Materials for Collimators and Beam Absorbers10 5th September 2007 Magnetic Field Example MQW – Warm Quadrupole XY Symmetry Analytic 2D Interpolated

11. Workshop on Materials for Collimators and Beam Absorbers11 5th September 2007 Primary Inelastic collisions map Generated by the tracking code  3 general loss scenarios: Vertical, Horizontal and Skew  At injection at 450 GeV, as well as for 7 TeV low-beta beam FLUKA source: force inelastic interactions on the previously recorded positions Beam Loss Map For better visualization only, current results show higher contribution for the TCPs

12. Workshop on Materials for Collimators and Beam Absorbers12 5th September 2007 Reality is a Very Complex Issue !!! Collimators Only !!! Phase-I Only !!! ??? First Operation ??? ??? First Surprises ???

13. Workshop on Materials for Collimators and Beam Absorbers13 5th September 2007 LHC/IR7 Application Examples Primary material choice (generic studies)  heating studies assuming adiabatic conditions Geometry, extended details, verification of tracking, source definition Collimators – energy deposition studies  Jaws, RF fingers, cooling system  Followed-up by ANSYS calculations (TT40 Beam tests) Active absorbers to reduce the energy deposition in the cold magnets (DS, ARC) Passive absorbers to protect the warm magnets Accident scenarios, commissioning scenarios BLM detector design (cross-talk, thresholds) Dose to electronics (UJs, RRs) -> shielding design LHC Dump, injection protection (Window, CDQ, TCDS,… ) Phase-II design (SLAC & future) Scraper studies

14. Workshop on Materials for Collimators and Beam Absorbers14 5th September 2007 Secondary Collimator Example W Accurate geometrical representation of the actual collimator design Different particle loss scenarios Adopting respective jaw openings Detailed power load for each component 3D energy deposition maps for all collimators Detailed ANSYS studies (see Alessandro’s talk)

15. Workshop on Materials for Collimators and Beam Absorbers15 5th September 2007 Maximum power deposition in super-conducting coils: ~300 mW/cm 3  ~10.0 mW/cm 3  ~3 mW/cm 3  ~2 mW/cm 3 No absorbers 3 absorber 4 absorber5 absorber No absorbers 3 absorber 4 absorber5 absorber Active Absorber Layout Optimization Quench limit: 1-10 mW/cm 3 close to the expected limit

16. Workshop on Materials for Collimators and Beam Absorbers16 5th September 2007 New detailed FLUKA implementation Support post UPBEAM SST Support post DOWNBEAM SST Stub shaft Aluminum Jaw transition Aluminum Phase II Studies – SLAC Design

17. Workshop on Materials for Collimators and Beam Absorbers17 5th September 2007 F C B F C A A B E E D D TCSG Beam 1 Z X Y Sect. AA TCP D6L7 X Y Z 90 o Sect. BB TCP C6L7 X Y Z 0 o Sect. FF TCSM A5L7 X Y Z Sect. EE TCSM B5L7 Sect. DD TCSM A6L7 X Y Z 141.1 o 142.5 Sect. CC TCP B6L7 X Y Z 126.9 o 40.7 o 42.7 X Y Z 143.5 o 141.6 Fully integrated in the complex layout Applied to design studies Phase II Studies – SLAC Design

18. Workshop on Materials for Collimators and Beam Absorbers18 5th September 2007 Latest design changes Energy density peak cross- checked with former simulations based on a more simplified layout Detailed heating study possible z ~ 19 [cm] Lower left jaw z ~ 18 [cm] Upper right jaw ~ 76 [W/cm3] ~ 74 [W/cm3] z ~ 18 [cm] Lower left jaw ~ 78 [W/cm3] z ~ 16 [cm] Upper right jaw ~ 60 [W/cm3] z ~ 18 [cm] Lower left jaw ~ 28 [W/cm3] z ~ 17 [cm] Upper right jaw ~ 22 [W/cm3] Phase II Studies – SLAC Design

19. Workshop on Materials for Collimators and Beam Absorbers19 5th September 2007 A More Detailed Example Passive Absorber Design

20. Workshop on Materials for Collimators and Beam Absorbers20 5th September 2007 ~5 MGy/year, 10 years operation possible, but not guaranteed 4 spare magnets In case of repair need coil exchange rather straight forward Operating temperature ~50-55˚C (T-interlocks trip at 65˚C) Maximum acceptable temperature increase 10˚K (steady state): MBW=15 kW Separation Dipoles: MBW Magnets M. Karppinen

21. Workshop on Materials for Collimators and Beam Absorbers21 5th September 2007 Technical Drawing Separation Dipoles: MBW Magnets FLUKA Implementation

22. Workshop on Materials for Collimators and Beam Absorbers22 5th September 2007 Even 1 MGy/year, -> 10 years might be critical 4 Spare magnets (however, 3 out of them need repair!) 1 Set of spare coils, BUT Coil exchange not at all easy Operating temperature ~50- 55˚C (T-interlocks trip at 65˚C Stored heat is ~60 MJ, thus ~14 kW over 10 s could be enough to trip the T- interlock, if close to outlets Maximum acceptable temperature increase 10 K (steady state): MQW=10 kW Quadrupoles: MQW Magnets Injected coil shims likely to fail, thus first leading to coil movements and insulation damage M. Karppinen

23. Workshop on Materials for Collimators and Beam Absorbers23 5th September 2007 Quadrupoles: MQW Magnets Technical Drawing FLUKA Implementation

24. Workshop on Materials for Collimators and Beam Absorbers24 5th September 2007 Design Evolution Evolving IR7 Layout  60cm long primary collimators  Separation of D3, additional passive absorber (TCAPB)  Various loss scenarios Technical layout and integration  simple concept (simple block, no cooling)  first ideas (close aperture, cooling is needed)  more sophisticated (sandwich structure)  technically possible (Swiss cheese, but sufficient) Constraints, limitations, loss assumptions  Final loss assumptions  Magnets (esp. MQWs) might stand less than expected  Surprises aperture correction, alignment, mistake in coordinate system …

25. Workshop on Materials for Collimators and Beam Absorbers25 5th September 2007 Evolving FLUKA Designs (1) Starting Point(2) Conceptial Design (3) Technical Integration (4) Final Choice ??? Fe W Cu

26. Workshop on Materials for Collimators and Beam Absorbers26 5th September 2007 Impact on first MQW Most of the radiation passes through the beam pipe  The most important parameter is the inner radius.  Without passive absorbers the limit would be reached already in one year of operation`

27. Workshop on Materials for Collimators and Beam Absorbers27 5th September 2007 Protection of specific objects High radiation doses close to the collimators and downstream beam pipe.  Approved and tested equipement necessary!

28. Workshop on Materials for Collimators and Beam Absorbers28 5th September 2007 Passive Absorber Geometry Simple-Geo C. Theis Iron Shield Pipe Transition Copper Disks for Cooling Tungsten Inlets

29. Workshop on Materials for Collimators and Beam Absorbers29 5th September 2007 Simple-Geo C. Theis Passive Absorber Geometry

30. Workshop on Materials for Collimators and Beam Absorbers30 5th September 2007 Peak Location in the Absorber TCAPA – horizontal cut through the beam axis Peak: 140 W/cm 3 (TCAPC)

31. Workshop on Materials for Collimators and Beam Absorbers31 5th September 2007 MBW - Peak Location Peak is located at the front face of the MBW Directly above the beam pipe, within the first centimetres Peak Annual Dose: 3.4 MGy/y close to the expected limit`

32. Workshop on Materials for Collimators and Beam Absorbers32 5th September 2007 Peak is located inside the MQW Laterally at the closest distance to the beam pipe Peak Annual Dose: 1.2 MGy/y MQW –Peak Location above the expected

33. Workshop on Materials for Collimators and Beam Absorbers33 5th September 2007 ANSYS Studies – Maximum T Temperature in Tungsten remains below 300˚C Copper stays below 100˚C A. Bertarelli

34. Workshop on Materials for Collimators and Beam Absorbers34 5th September 2007 Intrinsic Uncertainties (Peaks) Even though statistical uncertainties of the FLUKA calculations are small (< percent level for the total power estimates, < 10% for the peak levels) it is important to consider the following SYSTEMATIC uncertainties:  Loss assumptions (at least 50%)  Important distances, grazing impacts on collimators (~40%)  Material transitions, i.e., dose to copper as compared to dose to the insulator (~20%)  FLUKA implementation and models (~30%, part. correlated)  Knowledge about considered “limits” and their translation into real lifetime (???) A total safety factor of 2-3 is realistic for peak values!!!

35. Workshop on Materials for Collimators and Beam Absorbers35 5th September 2007 Performed in laboratory conditions Dose-rate effect: Less degradation than from long-term irradiation. (Oxygen/humidity diffusion, dT) Depends on resin processing. MBW-resin MQW-resin e.g., Dose Limits M. Karppinen

36. Workshop on Materials for Collimators and Beam Absorbers36 5th September 2007 Simulation Accuracy - Summary Physics modeling:  Uncertainty in the inelastic p-A extrapolation cross section at 7 TeV lab  Uncertainty in the modeling used  30% on integral quantities like energy deposition (peak included) while for multi differential quantities the uncertainty can be much worse Layout and geometry assumptions & long distances  It is difficult to quantify, experience has shown that a factor of 2 can be a safe limit Grazing beam impacts at small angles on the surface of the collimators.  Including that the surface roughness is not taken into account  A factor of 2 can be a safe choice. Loss assumptions (results scale one to one!) Safety factor from the tracking programs is not included!

37. Workshop on Materials for Collimators and Beam Absorbers37 5th September 2007 Conclusion During the design of the collimation region FLUKA has been extensively used for various applications The design of components is an iterative and complex process starting from generic calculations and evolving to complex models When looking for almost microscopic quantities, tiny details in the implementation become important and might dominate the final results Clear defined interfaces are important for both, input and output quantities Uncertainties must be correctly considered and are mostly already dominated by external parameters, such as the assumption of loss parameters Only continuous code development and respective benchmark experiments can ensure high quality results and limit the range of known uncertainties

38. Workshop on Materials for Collimators and Beam Absorbers38 5th September 2007 Thank You