2. Vacuum, Surfaces & Coatings Group Technology Department Coating Options for IR2 and IR8 P. Costa Pinto, V. Baglin, J. Cave, S. Calatroni, P. Chiggiato, P. Cruikshank, C. Garion, B. Di Girolamo, M. van Gompel, L. Leggiero, H. Kos, N. Kos, H. Neupert, M. Sitko, M. Taborelli, I. Wevers Outline 1.Why and how to reduce e-cloud in IR2 & IR8 2.amorphous Carbon (a-C) coatings 3.Laser Engineered Surface Structures (LESS) 4.Planning 5.Summary & conclusions LHC Performance Workshop Chamonix 2016 2

3. Vacuum, Surfaces & Coatings Group Technology Department 1 – Why and how reduce e-cloud in IR2 & IR8 LHC Performance Workshop Chamonix 2016 3 Why? For the HL-LHC era, or earlier, the heat load to the beam screens of the LHC insertions may push to the limit the installed cooling capacity. Decrease heat load Lower the SEY <1.1 Reduce e-cloud Without scrubbing DeviceHeat-Load [W] 2015 Heat-Load [W] 2016 Heat-load LIU (SEY=1.2) [W] Limit 2015 Opening 80% [W] Limit 2016 Opening 100% [W] Limit Larger valve seat [W] IT/IR15110165330122185220 IT-D1/IR28100160320 117171194 Courtesy of G. Arduini

4. Vacuum, Surfaces & Coatings Group Technology Department 1 – Why and how reduce e-cloud in IR2 & IR8 LHC Performance Workshop Chamonix 2016 4 Why? For the HL-LHC era, or earlier, the heat load to the beam screens of the LHC insertions may push to the limit the installed cooling capacity. The study will investigate the feasibility of in-situ amorphous carbon (a-C) coating and in-situ Laser Engineered Surface Structures (LESS) for beam screen geometries of the LHC Insertions. How? a-C Low SEY based on the electronic properties of the material LESS Low SEY is a morphological effect

5. Vacuum, Surfaces & Coatings Group Technology Department 1 – Why and how reduce e-cloud in IR2 & IR8 LHC Performance Workshop Chamonix 2016 5 Why? For the HL-LHC era, or earlier, the heat load to the beam screens of the LHC insertions may push to the limit the installed cooling capacity. The study will investigate the feasibility of in-situ amorphous carbon (a-C) coating and in-situ Laser Engineered Surface Structures (LESS) for beam screen geometries of the LHC Insertions. How? a-C: Feasibility of in-situ technology by end of 2016 (plan A) LESS: proof of compatibility with HL-LHC by mid 2017 (plan B)

6. Vacuum, Surfaces & Coatings Group Technology Department 2 – a-C coatings LHC Performance Workshop Chamonix 2016 6 What we learned from the SPS (since 2008) Maximal secondary electron yield Low SEY carbon coatings can be produced by sputtering. The key parameter for low SEY is the hydrogen present in the plasma during the deposition. Stainless steel (UHV cleaned, not scrubbed) a-C carbon coating

7. Vacuum, Surfaces & Coatings Group Technology Department 2 – a-C coatings LHC Performance Workshop Chamonix 2016 7 What we learned from the SPS (since 2008) Robustness: after more than one year in air, just with aluminum foil protection, the SEY max is still below 1.06 The liner installed in the e-cloud monitors of the SPS since 2008 keeps its performance (no measurable e-cloud) in spite of several air venting periods.

8. Vacuum, Surfaces & Coatings Group Technology Department 2 – a-C coatings LHC Performance Workshop Chamonix 2016 8 What we learned from the SPS (since 2008) Particle counter: 2 StSt tubes measured in clean-room 1 coated with carbon 1 reference (in the lab. with plastic covers) both measured again in clean-room No increase after shaking and gentle hammering of the chamber. Dust: no difference between coated and uncoated beam pipes. No increase for a chamber left in air for months Pull test of adhesion (a-C on copper) shows an adhesion strength of 20-28 MPa even after 1GGy irradiation

9. Vacuum, Surfaces & Coatings Group Technology Department 2 – a-C coatings LHC Performance Workshop Chamonix 2016 9 What we learned from the SPS (since 2008) Extensively tested: e-cloud monitors, microwave transmission, vacuum, multipactor up to 2 Tesla, in-situ e-cloud and SEY in CesrTA, more than 100 meters of SPS coated with carbon during LS1, including COLDEX. No e-cloud activity registered on the pickup electrode I e < 5 10 -9 A Electronic noise I e ~5 10 -9 A If SEY ~ 1.10 => 2 10 -10 A If SEY ~ 1.25 => 2 10 -6 A (benchmarking with pyECLOUD) Measured heat load < 0.2 W/m Sensitivity 0.1 W/m In the past, scrubbed Copper gave 1.4 W/m Roberto Salemme, Build-up simulations for COLDEX and comparison with experimental data, Electron Cloud Meeting #20, CERN, March 13 th 2015 a-C coating

10. Vacuum, Surfaces & Coatings Group Technology Department 2 – a-C coatings LHC Performance Workshop Chamonix 2016 10 From SPS to HL-LHC: what else we need to know?  Effect of high irradiation dose: ok for 1 GGy of 150 keV protons @90K. (both SEY + adhesion)  SEY as a function of adsorbates @ low temperatures (on going)  Adhesion on beam screens after thermal cycling  How do we coat the triplets in situ?  RF impedance (B. Salvant et al): no significant impact expected.  Minimal required thickness (50 nm < thickness < 200 nm)  How do we control the quality of the coating in situ? (2017)

11. Vacuum, Surfaces & Coatings Group Technology Department 2 – a-C coatings LHC Performance Workshop Chamonix 2016 11 Development of coating technology ~ 45 meters Length to be coated: ~45 meters per “string” (Q1, Q2, Q3, DFBX & D1)

12. Vacuum, Surfaces & Coatings Group Technology Department 2 – a-C coatings LHC Performance Workshop Chamonix 2016 12 Development of coating technology Length to be coated: ~45 meters per “string” (Q1, Q2, Q3, DFBX & D1) Only 150 mm to insert a “coating device” 150 mm

13. Vacuum, Surfaces & Coatings Group Technology Department 2 – a-C coatings LHC Performance Workshop Chamonix 2016 13 Development of coating technology Length to be coated: ~45 meters per “string” (Q1, Q2, Q3, DFBX & D1) Only 150 mm to insert a “coating device” Change of cross section, RF fingers, BPMs… Beam screens annealed (Cu) @915 o C in 1 bar of H 2 High hydrogen outgassing during the coating!

14. Vacuum, Surfaces & Coatings Group Technology Department 2 – a-C coatings LHC Performance Workshop Chamonix 2016 14 Development of coating technology Develop a “modular sputtering source” that can be inserted in a 150 mm slot and pulled by cables all along a magnet. Coat each magnet individually (baseline). Start simple: DC diode sputtering? C arbon

15. Vacuum, Surfaces & Coatings Group Technology Department 2 – a-C coatings LHC Performance Workshop Chamonix 2016 15 Development of coating technology Develop a “modular sputtering source” that can be inserted in a 150 mm slot and pulled by cables all along a magnet. Titanium target pump hydrogen enhance adhesion Graphite target direction Start simple: DC diode sputtering? C arbon Coat each magnet individually (baseline). 100 mm

16. Vacuum, Surfaces & Coatings Group Technology Department 2 – a-C coatings LHC Performance Workshop Chamonix 2016 16 Development of coating technology Develop a “modular sputtering source” that can be inserted in a 150 mm slot and pulled by cables all along a magnet. Titanium target Graphite target Start simple: DC diode sputtering? C arbon Coat each magnet individually (baseline).

17. Vacuum, Surfaces & Coatings Group Technology Department 2 – a-C coatings LHC Performance Workshop Chamonix 2016 17 Development of coating technology Develop a “modular sputtering source” that can be inserted in a 150 mm slot and pulled by cables all along a magnet. Start simple: DC diode sputtering? C arbon Decreasing H 2 Coat each magnet individually (baseline).

18. Vacuum, Surfaces & Coatings Group Technology Department 2 – a-C coatings LHC Performance Workshop Chamonix 2016 18 Development of coating technology Develop a “modular sputtering source” that can be inserted in a 150 mm slot and pulled by cables all along a magnet. Decreasing H 2 Magnetron sputtering to increase deposition rate and reduce H fraction in the film? SPS quad in SMA18 Coat each magnet individually (baseline).

19. Vacuum, Surfaces & Coatings Group Technology Department Graphite target Beam screen (cut) QD (SPS) 2 – a-C coatings LHC Performance Workshop Chamonix 2016 19 Development of coating technology Develop a “modular sputtering source” that can be inserted in a 150 mm slot and pulled by cables all along a magnet. Decreasing H 2 Magnetron sputtering to increase deposition rate and reduce H fraction in the film? Coat each magnet individually (baseline).

20. Vacuum, Surfaces & Coatings Group Technology Department Graphite target Beam screen 2 – a-C coatings LHC Performance Workshop Chamonix 2016 20 Development of coating technology Develop a “modular sputtering source” that can be inserted in a 150 mm slot and pulled by cables all along a magnet. Decreasing H 2 Magnetron sputtering to increase deposition rate and reduce H fraction in the film? with B field from Quad Coat each magnet individually (baseline). field gradient 1 T/m

21. Vacuum, Surfaces & Coatings Group Technology Department Graphite target With permanent magnets inside 2 – a-C coatings LHC Performance Workshop Chamonix 2016 21 Development of coating technology Develop a “modular sputtering source” that can be inserted in a 150 mm slot and pulled by cables all along a magnet. Decreasing H 2 Magnetron sputtering to increase deposition rate and reduce H fraction in the film? with B field from Quad Coat each magnet individually (baseline).

22. Vacuum, Surfaces & Coatings Group Technology Department 2 – a-C coatings LHC Performance Workshop Chamonix 2016 22 Development of coating technology Develop a “modular sputtering source” that can be inserted in a 150 mm slot and pulled by cables all along a magnet. Decreasing H 2 Magnetron sputtering to increase deposition rate and reduce H fraction in the film? with B field from Quad with B field from permanent magnets Target with permanent magnets inside Photo: courtesy of V. Bellido-Gonzalez Gencoa Ltd. Coat each magnet individually (baseline).

23. Vacuum, Surfaces & Coatings Group Technology Department 2 – a-C coatings LHC Performance Workshop Chamonix 2016 23 Development of coating technology Develop a “modular sputtering source” that can be inserted in a 150 mm slot and pulled by cables all along a magnet. In parallel, develop pull system with feeding cables and differential pumping. Magnetron sputtering to increase deposition rate and reduce H fraction in the film? Coat each magnet individually (baseline).

24. Vacuum, Surfaces & Coatings Group Technology Department 2 – a-C coatings LHC Performance Workshop Chamonix 2016 24 Development of coating technology Develop a “modular sputtering source” that can be inserted in a 150 mm slot and pulled by cables all along a magnet. In parallel, develop pull system with feeding cables and differential pumping. Magnetron sputtering to increase deposition rate and reduce H fraction in the film? Coat each magnet individually (baseline). Next run: Coat > 4 meters with permanent magnets using high purity graphite targets

25. Vacuum, Surfaces & Coatings Group Technology Department LHC Performance Workshop Chamonix 2016 25 Technology proposed by UK institutes Laser treatment of metals (Nd:YVO4 Laser, just above ablation threshold) Potentially, the Laser + lensing system can be displaced along a pipe and treat the inner surface. 3 – LESS Courtesy Reza Valizadeh, ASTeC, STFC Daresbury Laboratory

26. Vacuum, Surfaces & Coatings Group Technology Department 3 – LESS LHC Performance Workshop Chamonix 2016 26 Type A Type B Type C Technology proposed by UK institutes 20  m Laser treatment of metals (Nd:YVO4 Laser, just above ablation threshold) Courtesy Reza Valizadeh, ASTeC, STFC Daresbury Laboratory

27. Vacuum, Surfaces & Coatings Group Technology Department 3 – LESS LHC Performance Workshop Chamonix 2016 27 Validation of LESS as a proof of concept by mid 2017 Tests on small flat samples: As received after 4 months in aluminium foil  SEY @RT and robustness 20 mm 20  m

28. Vacuum, Surfaces & Coatings Group Technology Department 3 – LESS LHC Performance Workshop Chamonix 2016 28  SEY @RT and robustness  Dust? (qualify as for a-C, 2016) Validation of LESS as a proof of concept by mid 2017 Tests on small flat samples: As received 20 mm 20  m

29. Vacuum, Surfaces & Coatings Group Technology Department 3 – LESS LHC Performance Workshop Chamonix 2016 29  SEY @RT and robustness  Dust? (qualify as for a-C, 2016)  Pump down @RT: ok Validation of LESS as a proof of concept by mid 2017 Tests on small flat samples: 20 mm

30. Vacuum, Surfaces & Coatings Group Technology Department 3 – LESS LHC Performance Workshop Chamonix 2016 30  SEY @RT and robustness  Dust? (qualify as for a-C, 2016)  Pump down @RT: ok Validation of LESS as a proof of concept by mid 2017 Tests on small flat samples:  RF impedance (2016) After LESS, RRR of the Cu on the beam screen decreases by a factor 1.8 Impact of roughness unknown RF impedance to be measured (Quadrupole Resonator) 20 mm

31. Vacuum, Surfaces & Coatings Group Technology Department 3 – LESS LHC Performance Workshop Chamonix 2016 31  SEY @RT and robustness  Dust? (qualify as for a-C, 2016)  Pump down @RT: ok Validation of LESS as a proof of concept by mid 2017 Tests on small flat samples:  RF impedance (2016)  e-cloud monitor in SPS (two installed) 20 mm

32. Vacuum, Surfaces & Coatings Group Technology Department 3 – LESS LHC Performance Workshop Chamonix 2016 32  SEY @RT and robustness  Dust? (qualify as for a-C, 2016)  Pump down @RT: ok Validation of LESS as a proof of concept by mid 2017 Tests on small flat samples:  RF impedance (2016)  e-cloud monitor in SPS (installed)  SEY in magnetic fields up to 10 Tesla (system under construction @BINP) 20 mm

33. Vacuum, Surfaces & Coatings Group Technology Department 3 – LESS LHC Performance Workshop Chamonix 2016 33  SEY @RT and robustness  Dust? (qualify as for a-C, 2016)  Pump down @RT: ok Validation of LESS as a proof of concept by mid 2017 Tests on small flat samples:  RF impedance (2016)  e-cloud monitor in SPS (installed)  SEY in magnetic fields up to 10 Tesla (system under construction @BINP)  Test tube in COLDEX (I e-cloud & heat load) (end 2016) 20 mm

34. Vacuum, Surfaces & Coatings Group Technology Department 4 – Planning LHC Performance Workshop Chamonix 2016 34 a-C coating 10 meters of beam screen + cold bore with permanent magnets (or Quad) 2016 2017 Demonstrate flawless adhesion Ti, ion bombardment Develop capability to etch the a-C coating in-situ O 2 plasma, UV photons + O 3 Develop in-situ quality control Construction & validation for other BS geometries Demonstration of LESS technology in long tubes Measure RF impedance Evaluate dust production (as it was done for the a-C coatings) LESS in COLDEX SEY in strong B (10 Tesla) @BINP a-C LESS Develop technology to bake beam screens up to 100 o C Vacuum @ cryogenic temperatures 2 Liners in SPS

35. Vacuum, Surfaces & Coatings Group Technology Department 5 – Summary & conclusions LHC Performance Workshop Chamonix 2016 35 Demonstrated a-C coating in beam screens with SEY max <1 Demonstrated displacement of a-C source along 4 m. No surprises expected when scaling to 10 m. COLDEX results are very encouraging for a-C @cryogenic temperature. LESS is promising: very low SEY and robustness against air exposure. LESS in long tubes still need to be demonstrated. Dust, RF impedance & Vacuum qualification at cryogenic temperatures to be investigated. Next important milestone for LESS: tube for COLDEX by end 2016. Both techniques potentially applicable to LHC arcs in case of need

36. Vacuum, Surfaces & Coatings Group Technology Department 36 Acknowledgements Herve Prin TE-MSC Pascal Catherine TE-MSC Benoit Salvant BE-ABP Carlo Zannini BE-ASR Roberto Salemme TE-VSC Giovanni Iadarola BE-ABP Anton Lechner EN-STI Ana Perez Fontenla EN-MME Daniel Berkovitz TE-CRG Elisa Vadivieso TE-VSC Valentin Nistor TE-VSC LHC Performance Workshop Chamonix 2016

37. Vacuum, Surfaces & Coatings Group Technology Department 37

38. Vacuum, Surfaces & Coatings Group Technology Department 38 Cleaning LESS

39. Vacuum, Surfaces & Coatings Group Technology Department LESS LHC Performance Workshop Chamonix 2016 39 Dust issues after UHV cleaning + Ultra Sounds As received Cleaned NGL + US As received after 4 months in aluminium foil Cleaned NGL+US 20 mm 20  m

40. Vacuum, Surfaces & Coatings Group Technology Department LESS LHC Performance Workshop Chamonix 2016 40 Dust issues after UHV cleaning + Ultra Sounds As received Cleaned NGL + US 20 mm 20  m Cu or Cu 2 O Cu +II CuO or Cu(OH) 2 Cu2p

41. Vacuum, Surfaces & Coatings Group Technology Department 41 CesrTA

42. Vacuum, Surfaces & Coatings Group Technology Department a-C @ CesrTA LHC Performance Workshop Chamonix 2016 42 SEY of samples measured in situ before and after conditioning The SEY of the carbon films (from CERN) remains low during the all test. It does not show conditioning (even with synchrotron radiation) since it has already an SEY of 1. IPAC2013 W.Hartung, J.Conway, C.Dennett, S.Greenwald, J.-S.Kim, Y.Li, T.Moore, V.Omanovic

43. Vacuum, Surfaces & Coatings Group Technology Department 43 UFOS

44. Vacuum, Surfaces & Coatings Group Technology Department UFOs LHC Performance Workshop Chamonix 2016 44

45. Vacuum, Surfaces & Coatings Group Technology Department UFOs LHC Performance Workshop Chamonix 2016 45 A. Lechner, B. Auchmann

46. Vacuum, Surfaces & Coatings Group Technology Department 46 porosity LESS

47. Vacuum, Surfaces & Coatings Group Technology Department LESS LHC Performance Workshop Chamonix 2016 47 DOUBLE PASSING OF LASER SEM images by A. Perez Fontenia (EN-MME-MM) – courtesy of S. Calatroni and I. Wevers Inclusion, laser induced cavities, trapped volumes ?

48. Vacuum, Surfaces & Coatings Group Technology Department 48 COLDEX R. Salemme

49. Vacuum, Surfaces & Coatings Group Technology Department COLDEX experiment (SPS) 49 Proton beam Mimics the LHC cryogenic beam vacuum in presence of LHC-type beams 2.2 m a-C coated copper Beam Screen in 316LN Cold Bore in drift space CB: 3 to 4.5 K; BS: 10 to 80 K Courtesy of R. Salemme

50. Vacuum, Surfaces & Coatings Group Technology Department Snapshot on COLDEX 2014-15 results 50 26 GeV/c, 25 ns, high intensity 450 GeV/c, 5+20 ns doublets 450 GeV/c, 5+20 ns doublets, slow ramp Vacuum activity on upstream/downstream gauges No pressure rise for a-C coated BS at 10K H 2 electron stimulated desorption below available sensitivity With 4x72 bunches, 25 ns, up to 1.5 ∙ 10 11 ppb: No significant heat load (≤0.2 W/m compared to 1.4 W/m for scrubbed Cu) → No significant current on pick-up ( 1000 nA for copper) → from benchmarking with pyECLOUD model simulations SEY < 1.25 SEY < 1.15 Courtesy of R. Salemme

51. Vacuum, Surfaces & Coatings Group Technology Department 51 COLDEX V. Baglin

52. Vacuum, Surfaces & Coatings Group Technology Department COLDEX (from V. Baglin @5th Joint HiLumi LHC-LARP Annual Meeting ) LHC Performance Workshop Chamonix 2016 52 The COLDEX program (LSS4 of SPS) is in progress, and will continue in LSS4 after EYETS (thanks to HL-LHC and CERN managements decision) : 40 K 50 K Thermal desorption spectroscopy Physisorbed / condensed H 2 is released from 400 nm thick a-C coating in the 40-50 K temperature range !  The temperature window 40-60 K is not appropriated  TBC in the coming year(s) if 50–70 K is an alternative H 2 adsorption isotherm a-C coating is a cryosorber ! At 10 K: capacity ~ 100 Cu but 1/10 of LHC cryosorber Characterisation with different gases and temperatures to be continued in 2016 R. Salemme Increasing T

53. Vacuum, Surfaces & Coatings Group Technology Department COLDEX (from V. Baglin @5th Joint HiLumi LHC-LARP Annual Meeting ) LHC Performance Workshop Chamonix 2016 53 COLDEX Studies with SPS beams: -A 2 m long LHC type cryogenic beam vacuum system -A beam screen temperature from 10 to 80 K and a cold bore temperature from 3 to 4.5 K In the 10 – 80 K range: Pressure rise < 10 -9 mbar, dominated by H 2 Heat load < 0.4 W/m Electron cloud activity < 2 10 -9 A/cm 2 H 2 condensation up to 3 10 16 H 2 /cm 2 do not strongly modify the behaviour Inconsistency Commissioning of COLDEX is not finished: Difficulties to keep the cryogenic settings Helium leak in the insulation vacuum Instruments to be repaired / calibrated / upgraded R. Salemme Many activities are planned during this YETS Several MDs are needed to consolidate the results and to continue the study

54. Vacuum, Surfaces & Coatings Group Technology Department 54 pyECLOUD G. Iadarolla

55. Vacuum, Surfaces & Coatings Group Technology Department Q1Q2Q3D1D2Q4Q5Q6Q7 ALICE IR2: BSIT_1 (19, 23.9) mm BSIT_2 (24, 28.9) mm BSD1 (33.7, 28.8) mm Inner triplets and D1 dipoles (IR2&8) Courtesy of G. Iadarola

56. Vacuum, Surfaces & Coatings Group Technology Department Q1Q2Q3D1 Inner triplets and D1 dipoles (IR2&8) Nominal LHC HL-LHC Courtesy of G. Iadarola

57. Vacuum, Surfaces & Coatings Group Technology Department Q1Q2Q3D1D2Q4Q5Q6Q7 ALICE IR2: Inner triplets and D1 dipoles (IR2&8) Similar considerations as for IR1&5: E-cloud suppression absolutely needed to operate with a reasonable heat load. a-C coating presently under test in COLDEX at the SPS looks very promising Clearing electrodes could be a valid alternative and add some margin Total heat load on the beam screen cooling circuit Courtesy of G. Iadarola

58. Vacuum, Surfaces & Coatings Group Technology Department 1 – Why and how reduce e-cloud in IR2 & IR8 LHC Performance Workshop Chamonix 2016 58 Why? For the HL-LHC era, or earlier, the heat load to the beam screens of the LHC insertions may push to the limit the installed cooling capacity. Q1Q2Q3D1D2Q4Q5Q6Q7 ALICE IR2: G. Iadarola, E. Metral, G. Rumolo, C. Zannini 4 th Joint HiLumi LHC - LARP Annual Meeting Total heat load on the beam screen cooling circuit Q1+Q2+Q3+D1 Decrease heat load 200 W installed cooling capacity Lower the SEY (1.1) Reduce e-cloud Without scrubbing

59. Vacuum, Surfaces & Coatings Group Technology Department 59 Measure DUST a-C

60. Vacuum, Surfaces & Coatings Group Technology Department 2 – a-C coatings LHC Performance Workshop Chamonix 2016 60 What we learned from the SPS (since 2008) Particle counter: 2 StSt tubes measured in clean-room 1 coated with carbon 1 reference (in the lab. with plastic covers) both measured again in clean-room No increase after shaking and gentle hammering of the chamber. Dust: no difference between coated and uncoated beam pipe. No increase for a chamber left in air for months Pull test of adhesion (a-C on copper) shows an adhesion strength of 20-28 MPa even after 1GGy irradiation

61. Vacuum, Surfaces & Coatings Group Technology Department 2 – a-C coatings LHC Performance Workshop Chamonix 2016 61 What we learned from the SPS (since 2008) Particle counter: 2 StSt tubes measured in clean-room 1 coated with carbon 1 reference (in the lab. with plastic covers) both measured again in clean-room Dust: no difference between coated and uncoated beam pipe. 3 µm < Size < 5 µm intake cycles 3µm < D <5µm Counting cycles N particles

62. Vacuum, Surfaces & Coatings Group Technology Department 62 XPS C1s

63. Vacuum, Surfaces & Coatings Group Technology Department XPS C1s line TE-TC June 2015

64. Vacuum, Surfaces & Coatings Group Technology Department Maximal secondary electron yield TE-TC June 2015

65. Vacuum, Surfaces & Coatings Group Technology Department 65 Al foil

66. Vacuum, Surfaces & Coatings Group Technology Department 66 Why aging is retarded by wrapping in a metal foil? Aging is strongly retarded by packaging in metal foil (aluminium or stainless steel), which is not tight to gas Molecule with low sticking coefficient Molecule with high sticking coefficient Metal foil sample A molecule with low sticking coefficient can go very far in a small conductance. A molecule with high sticking coefficient will adsorb immediately and never reach the sample surface. The metal foil protects from molecules with high sticking coefficient, like heavy hydrocarbons. NB: This is strictly valid only in molecular regime, but also in viscous flow in the absence of drag (if the collisions with the gas can be “mimicked” by a reduced sticking coefficient)

67. Vacuum, Surfaces & Coatings Group Technology Department 67 Cooling capacity D. Berkovitz

68. Daniel Berkowitz, TE-CRG-MLHL-LHC Heat Load Working Group16/11/201568 Capacity increase for the different magnet types Type Inventory Length [m] Q BS [W/m per aperture] Q BS increase (w.r.t. #0) #1 Open valve #2 Change sit #3 Change body #0 Op80% #1 Op100% #2 Change sit #3 Change body SAM Type 1Q5 L/R1Q5 L/R5Q6 L/R1 Q6 L/R5 8.23.17.315.5102.6 SAM Type 2 Q6 L/R4Q4 L/R6Q5 L/R6 6.93.79.218.5133.1 D3 L/R4 11.22.35.311.462.8 Q6 L/R2Q6 L/R3Q6 L/R7 Q6 L/R8 122.15.010.356.5 Q5L2Q5R2Q5L8Q5R8 132.04.69.550.2 Semi-SAM Q5D4L4D4Q5R4 16.73.37.413.833.9 Q4D2L1D2Q4R1Q4D2L5D2Q4R5 19.42.86.411.627.0 Q4D2L2Q4D2R2Q4D2L8Q4D2R8 22.82.45.49.721.1 IT IT L/R1IT L/R5 354.06.99.010.8 IT L/R2IT L/R8 453.05.06.47.2 Arc half cellall sectors 53.53.34.65.35.6 increase factor Gain in cooling capacity differs from case to case IT & ArcCells are limited by ∆p at the circuit → Parallelization of the BS channels proposed in previous slides SAMs and semi-SAMs present more margin to increase. Increase is very limited LSS2 & LSS8

69. Daniel Berkowitz, TE-CRG-MLHL-LHC Heat Load Working Group16/11/201569 Increase of BS by modifying the control valves Interesting as short-term solution only → Time for (better) middle/long term solutions to reach maturity. Conclusions Calculation model used so far will be refined (specially for ITs) As ∆p at the circuit seems becomes relevant Include pipe singularities (BS crossing, flexible hose, etc) in the model Model validation ongoing (!) Benchmark are estimations by L.Tavian (2014 in Evian)2014 in Evian General cooling availabiliy should not be forgoten If the modification is done along the whole LSS, then the refrigerators global capacity could become an issue. Control Valve ©Velan

70. Daniel Berkowitz, TE-CRG-MLHL-LHC Heat Load Working Group16/11/201570 Impedance calculations B. Salvant

71. Impedance considerations on the aC coating of the LHC beamscreen C. Zannini, B. Salvant Acknowledgments: N. Biancacci, S. Calatroni, E. Métral, G. Rumolo

72. Impedance model for analytical calculation Case with aC coating 5 layer structure 1 st layer (aC) 2 st layer (Ti) 3 st layer (Cu) 4 st layer (StSt) 5 st layer (Vacuum) Case without aC coating 3 layer structure 1 st layer (Cu) 2 st layer (StSt) 3 st layer (Vacuum) Materialσ el [S/m]εrεr Thickness [µm] aC coating4005.40.5 Titanium coating10 6 10.1 Copper10 9 150 Stainless steel1.35 10 6 11000 Vacuum01Infinity

73. Longitudinal impedance: effect of aC coating Significant effect on the imaginary part The effect on the real part is negligible No effect on beam induced heating (single beam) First order longitudinal impedance due to the weld No impact of aC coating (3D CST simulations) Two beams heating

74. Significant effect on the imaginary part The effect on the real part is negligible Coherent tune shift, TMCI thresholds Transverse impedance: effect of aC coating

75. Why the imaginary part depends on the aC coating? Case without aC coating 1 layer structure 1 st layer (Cu) Case with aC coating 2 layer structure 1 st layer (aC) 2 st layer (Cu) From transmission line theory one can derive the surface impedance seen by the beam The aC coating introduces an additional contribution to the imaginary impedance Coating thickness

76. Summary The aC coating, where applied, is expected to increase significantly the imaginary part of the resistive wall beam coupling effective impedance per unit length (about a factor 2) The effect on the full LHC longitudinal impedance is expected to be below 0.1 % (about 0.05%) The effect on the full LHC transverse impedance is expected to be well below 1% (about 0.2% in the worst case scenario) No impact is expected on the beam induced heating