1. Preliminary ANSYS Studies for Tungsten Collimators
M. Cauchi,
R.W. Assmann, A. Bertarelli, R. Bruce, F. Carra,
A. Dallocchio, A. Rossi, D. Wollmann,
EN-MME Team
Collimation Working Group,

2. Acknowledgments
EN-MME department (F. Carra, A. Dallocchio, A. Bertarelli, N. Mariani) for providing the necessary tools (TCT model, material library, etc.) as well as for weekly training-on-the-job on thermo-mechanical simulations with ANSYS Workbench
FLUKA team (F. Cerutti, V. Boccone EN-STI) for providing several relevant FLUKA input files
H. Richter (DGS/RP) and D. Campanini (EN-MME) for developing and making available FLUKA-ANSYS interface
Collimation team – also F. Burkart, D. Deboy, S. Redaelli, G. Valentino
University of Malta supervisors (P. Mollicone, N. Sammut)
Marija Cauchi

3. Outline Introduction Simulation Conditions Flow of Analyses
Finite Element Modelling (ANSYS)
Geometry
Material Properties & Discretization
Loading & Boundary Conditions
Results & Conclusions
Future Work
Marija Cauchi

4. Introduction
TCTs – protection of the triplet against quenching & damage
During collimation setup, TCTs are very close to the beam - higher probability of being impacted
High energy & high intensity impacts
Materials involved subject to extreme conditions
Possibility to perform experimental tests is limited
Importance of developing reliable methods & accurate models to estimate the damage induced by an impact
Thermally-induced phenomena up to the melting point of metal can be reasonably well-treated with Standard FEM Codes (ANSYS)
Marija Cauchi

5. Simulation Conditions
Different cases derived through variations of energy and no. of impacting bunches
Assuming conservatively that all bunches have the same impact parameter (d=2mm), same charge (1.3 x 1011 p) and optical functions at TCTH.4R5B2
Case
Beam Energy [TeV]
Nominal Emittance [μm rad]
Beam Size σx x σy [mm]
Impacting Bunches
Bunch Spacing [ns]
Deposited Energy on Jaw [kJ]
TNT Equivalent [g] 1
3.5
3.50
0.51 x 0.32 -
38.6
9.2 2 5 7
0.60 x 0.38
56.2
13.4 3 25
111.3
26.6 4
216.1
51.6
Case 3 and Case 4 were simulated with the same FLUKA input file as Case 2 since effects due to different beam emittances (within a factor of 4) were found to be negligble (A. Bertarelli et al.)
Marija Cauchi

6. Flow of Analyses Transient thermal analyses performed sequentially
the first transient thermal analysis covers the impact duration of 1ns
the second transient thermal analysis a time period of 10s after the impact
Transient structural analysis performed sequentially to the thermal analyses
In the case of multi-bunch impact, attachment of multiple transient thermal analyses with the correct times (e.g. impact of 2 bunches: 1ns, 25ns, 1ns, 10s)
Marija Cauchi

7. Finite Element Modelling
Geometry
One TCTH.4R5B2 collimator jaw
Symmetrical approach - beam impact on collimator jaw should theoretically lead to a symmetrical energy deposition in the YZ plane (location of symmetry plane indicted by green)
Whole collimator structure in DesignModeler
Lower symmetrical half of collimator structure in DesignModeler
Beam Direction
Marija Cauchi

8. Finite Element Modelling
Material Properties
Assignment of research-based temperature-dependent material properties (material library)
Jaw material assumed to be pure tungsten (real material: INTERMET 180 – 95% W, 3.5% Ni,1.5% Cu)
Initial simulations excluding presence of screws (assumed to be perfectly bonded)
Water Cooling Pipe (Cu Ni10 Fe1 Mn)
Tungsten Block (x5) (20x17x200mm)
Block Support (Copper)
Support Beam (Glidcop Al-15)
Stiffener (Glidcop Al-15)
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9. Finite Element Modelling
Finite element discretization
Mesh size for the tungsten blocks: 1mm (transverse); 5mm (longitudinal)
Finest mesh close to beam impact (that is mainly on the W jaws)
Mesh density: importance of good compromise between accuracy and computational time
Mesh size: 1x1x5mm
Marija Cauchi

10. FLUKA-ANSYS Interface
Single impact parameters used to generate ANSYS input
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11. Finite Element Modelling
Loading conditions
Script generated by FLUKA-ANSYS interface inserted as a Command object under Transient Thermal Analysis
Creation of FLUKA plane to deposit energy correctly in accordance with script
Generation of table with energy deposition values and application of heat load
Boundary conditions
Speed of water in cooling pipes = 1.5m/s; inner diameter of cooling pipes = 0.006m
Water properties (kinematic viscosity, thermal conductivity)
Calculation of Reynolds number and Nusselt number (Dittus-Boelter equation)
Heat convection coefficient on the wet surface of the water pipes, h ≈ 7500 W/m2K
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12. Results
Temperature distribution during beam impact (1st transient analysis – duration of 1ns)
Beam Direction
Tmax = 2465oC
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13. Results Melting temperature of tungsten = 3370oC
High temperatures reached even with 1 bunch impact at 3.5TeV
Similar temperatures to those obtained in AUTODYN (A. Bertarelli et al.)
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14. Results Insufficient time duration for diffusion to take place
25ns bunch spacing
1ns impact
Insufficient time duration for diffusion to take place
Time [s]
Temperature [oC]
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15. Results Peak Power [MW/m2] Z-axis [m] – Along the beam direction
Jaw 1
Jaw 2
Jaw 3
Jaw 4
Jaw 5
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16. Results
Temperature distribution after beam impact (2nd transient analysis – duration of 10s)
Beam Direction
Distribution of deposited energy across structure
Some elements might be gone (eroded zone – not captured by ANSYS)
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17. Results Temperatures of structure after 10s
Differences on going from 3.5Tev to 5Tev
Differences on going from impact of 1 bunch to 2 bunches to 4 bunches
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18. Results Structural analysis Imported body temperature as a body load
Constrained as shown below
Carried out to obtain basis for future steady-state cases
Structural results not reliable since implicit codes (ANSYS) are not appropriate for accident scenarios (high temperatures lead to changes in density and phase which can be correctly simulated with explicit codes (AUTODYN))
Displacement A
X = 0, Y = 0, Z = free
Rotx = 0, Roty = 0, Rotz = free
Displacement B
X = 0, Y = free, Z = free
Marija Cauchi

19. Conclusions
Purpose of generation of these first basic simulations: to support the future developments through application of correct flow of analyses and usage of tools
High temperatures reached even with 1 impacting bunch at 3.5TeV
Under these conditions, change of density and change of phase (melting) are expected
Comparable thermal results between ANSYS and AUTODYN (any slight differences are due to different interpolation of mesh between FLUKA-ANSYS and FLUKA-AUTODYN)
Use of AUTODYN
Explicit code necessary for accident scenarios (impact conditions) to capture any changes in density and phase (also can simulate very short time durations)
To correctly simulate the thermo-mechanical response of the hit material, must take into account both the hyrdodynamic behaviour (through use of a dedicated EOS) and the deviatoric behaviour (using a dedicated material model)
Marija Cauchi

20. Future Work
Aim: to evaluate the thermo-mechanical behaviour & robustness of TCTs and TCLAs during different beam-impact scenarios
Impact of angles between jaw and beam (beam may not always be parallel to the jaw edge)
Beam energy up to 7TeV
Setup accident scenario (1 bunch during collimation setup)
Accident scenario during operation (more unlikely than setup accident scenario because it requires wrong TCT and TCDQ setup and asynchronous dump)
Asymmetrical impact (assume for example 8mm offset in horizontal jaw due to vertical crossing angle)
Inclusion of shift in impact transverse offset in case of multi-bunch impact scenario
Temperature sensors – simulations to observe how the sensors respond in case of an accident
Also, carrying out of simulations for steady-state conditions for the TCTx
Marija Cauchi

21. Thank you for your attention.
Questions?
Thank you for your attention.
Marija Cauchi