1. Engineering Department ENEN Collimator Robustness Studies with BCMS Beams Collimation Working Group 05.10.2015 F. Carra, A. Bertarelli, R. Bruce, P. Gradassi, A. Lechner, E. Quaranta 5 October 2015F. Carra – EN-MME1

2. Engineering Department ENEN  Goal of the study  FEA model & material properties  Results  Similarities with HRMT23  Conclusions Outlook 5 October 2015F. Carra – EN-MME2

3. Engineering Department ENEN  Goal: assess the consequences of a BCMS beam injection error on TCSG during Run II  BCMS beam is elliptic, FLUKA maps for this configuration not available  For this analysis: round beam  144 bunches and 288* bunches simulated  Two different beam sigmas: 0.61 and 1 mm  Total of 4 scenarios Goal of the study 5 October 2015F. Carra – EN-MME3 Simulated scenarios: summary of parameters Case 1Case 2 Energy (GeV)450 Beam sigma (mm x mm)0.61x0.61 ; 1x1 Bunch intensity (p)1.3E11 N. Bunches144288* Impact depth (sigma)11 * 288 bunches: not happening during Run II. Limited to 144 bunches by the TCDI in the transfer line. Intermediate scenario between Run II and Run III (which will feature higher bunch intensities).

4. Engineering Department ENEN Model and material properties 5 October 2015F. Carra – EN-MME4 Normal strains on CFC jaw Measured values CFC ultimate strain +x+x 2600  m/m  +y 850  m/m  +z 1800  m/m  –x -150000  m/m  –y -8000  m/m  –z -7500  m/m Glidcop yield stress  0.2 220 MPa CuNi 90/10 yield stress  0.2 120 MPa  CFC: elastic models  Static flexural and compressive tests at EN/MME at room temperature  Still, graphitic materials are not dramatically sensitive to temperatures of 5-600 ˚C and to the strain rate  Glidcop and CuNi mechanical data are also at room temperature, but the temperature increase on this two materials during the deposition is negligible  All thermal properties of the model are T-dependent

5. Engineering Department ENEN Results 5 October 2015F. Carra – EN-MME5 Simulated scenarios: summary of parameters Case 1Case 2 Energy (GeV)450 Beam sigma (mm x mm)0.61x0.61 ; 1x1 Bunch intensity (p)1.3E11 N. Bunches144288 Impact depth (sigma)11  Figures in the following slides related to Case 1 (nominal Run II), 0.61 x 0.61 sigma  A summary of the 4 cases is given at the end of the presentation  Simulation of impact + 20 s cool down + 1 s steady state analysis to determine the final jaw shape in case plastic deformation occurs  Last step duration (1 s) is “virtual”, because time integration was turned off

6. Engineering Department ENEN Case 1 Results: temperature 5 October 2015F. Carra – EN-MME6 CFC Glidcop CuNi Stainless steel

7. Engineering Department ENEN Case 1 Results: normal strains at the end of the impact 5 October 2015F. Carra – EN-MME7 CFC  x CFC  z CFC  y  Higher compressive strains in x direction: due to the higher CTE in that direction  During the impact, the problem is (mostly) controlled by the deformation  At longer times, it becomes more and more driven by the force (shockwave propagation) Y X Z Y X Z Y X Z

8. Engineering Department ENEN Case 1 Results: flexural oscillations, shockwaves and jaw permanent deformation 5 October 2015F. Carra – EN-MME8 Dynamic response of impacted jaw Jaw plastic deformation Shockwave propagation

9. Engineering Department ENEN Results summary 5 October 2015F. Carra – EN-MME9 Simulated scenarios: summary of results Case 1Case 2 Reference 0.611 1 CFC normal strains (tension and compression)  m/m] +x+x 650 70020002100 2600 +y+y 400 320800730 850 +z+z 400 320470440 1800  –x -2500 -2800-7600-7700 -150000  –y -180 -170-410-470 -8000  –z -80 -160-170 -7500 Plastic strain on jaw components 0000  The adopted elastic model neglects the damping typical of graphite materials…  …still, the uncertainty in the material properties would make it difficult to strongly conclude that Case 2 is safe by means of simulations only  Luckily, we have a recent experimental benchmarking! Y X Z

10. Engineering Department ENEN HRMT23 – “Jaws experiment” 5 October 2015 F. Carra – EN-MME10  Beam time: 24-31 July 2015  3 jaws impacted with SPS beam at increasing intensities  1 TCSP jaw included: same material as TCSG (CFC) with Glidcop taperings  BCMS-like beam was tested! (144 & 288 b,  = 0.61 mm)  Also, impact parameters very close to what simulated  Higher energy densities were also tested (  = 0.35 mm) TCSPM CuCD jaw TCSPM MoGr jaw TCSP CFC jaw

11. Engineering Department ENEN HRMT23 – “Jaws experiment” 5 October 2015 F. Carra – EN-MME11  In spite of the significant number of impacts at high intensities, no visible fracture has been observed! (online instrumentation, visual inspection) CFC after multiple impacts Simulations + Experimental confirmation = Safe scenario!

12. Engineering Department ENEN Conclusions (1/2) 5 October 2015 F. Carra – EN-MME12  The goal of the study was to simulate the BCMS injection error on a TCSG jaw  Four scenarios were analysed, with different beam size and intensity:  Case 1 – Nominal Run II (144 b, 0.61 & 1 mm sigma)  Case 2 (288 b, 0.61 & 1 mm sigma)  Material models are a key parameter of the simulation  Considerably more advanced than few years ago (e.g. CFC anisotropy and T/C asymmetry kept into account)  Nevertheless, phenomena like pseudo-plasticity, temperature/strain rate softening/hardening are still not included  Case 1: safety factors 2÷4  Case 2: safety factor just slightly higher than 1!

13. Engineering Department ENEN Conclusions (2/2) 5 October 2015 F. Carra – EN-MME13  Simulations alone were not enough to strongly conclude on the safety of BCMS beam with 288 impacting bunches  This conclusion is possible only combining the numerical results with the experimental observations done during HRMT23, in which a TCSP jaw was tested under similar (and more severe) beam parameters  Possible future analysis refinements discussed:  New Fluka simulations (correct BCMS elliptical beam)  Improved material parameters (pseudo-plasticity?) My PC after BCMS simulations EN/MME MechLab to the rescue

14. Engineering Department ENEN 5 October 2015F. Carra – EN-MME14

15. Engineering Department ENEN 5 October 2015F. Carra – EN-MME15