1. Stefano Redaelli, CERN, BE-ABP for the Collimation Project and HL-LHC-WP5 teams The LHC Collimation Baseline for HL-LHC 3 rd Joint HiLumi LHC-LARP Annual Meeting November 11 th -15 th, 2013 Daresbury Laboratory - Warrington, UK The HiLumi LHC Design Study is included in the High Luminosity LHC project and is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404.

2. S. Redaelli, 3rd HiLumi meeting 12/11/2013 2 Outline Introduction Where we are (140MJ@4TeV, 60cm β * ) OP feedback and upgrade plans Advanced collimator concepts Conclusions

3. S. Redaelli, 3rd HiLumi meeting 12/11/2013 3 Acknowledgements B. Salvachua, R. Bruce and ABP collimation team R. Losito, A. Lechner, F. Cerutti for the EN-STI team G. Stancari, A. Valishev (FNAL) A. Bertarelli (EN-MME) T. Markiewicz (SLAC), W. Scandale, D. Mirarchi (crystal studies) G.Arduini, O. Bruning, L. Rossi R. Appleby (Manchester) Core collimation team in the LHC accelerator physics group: R. Bruce, M. Cauchi, L. Lari, D. Mirarchi, E. Quaranta, M. Salvachua, A. Rossi, A. Marsili, G. Valentino. People who have recently left the team: R. Assmann, D. Wollmann, D. Deboy Many thanks to R. Assmann!

4. S. Redaelli, 3rd HiLumi meeting 12/11/2013 4 3 Introduction Superconducting coil: T = 1.9 K, quench limit ~ 15-50mJ/cm 3 LHC 2012: 145 MJ LHC design: 360 MJ HL-LHC: 500MJ! Factor 9.7 x 10 9 Aperture: r = 17/22 mm LHC “Run 1” 2010-2013: No quench with circulating beam, with stored energies up to 70 times of previous state-of-the-art!

5. S. Redaelli, 3rd HiLumi meeting 12/11/2013 5 LHC collimation layout Picture by C. Bracco Two warm cleaning insertions, 3 collimation planes IR3: Momentum cleaning 1 primary (H) 4 secondary (H) 4 shower abs. (H,V) IR7: Betatron cleaning 3 primary (H,V,S) 11 secondary (H,V,S) 5 shower abs. (H,V) Local cleaning at triplets 8 tertiary (2 per IP) Passive absorbers for warm magnets Physics debris absorbers Transfer lines (13 collimators) Injection and dump protection (10) Total of 108 collimators (100 movable). Two jaws (4 motors) per collimator! Momentum cleaning Betatron cleaning

6. S. Redaelli, 3rd HiLumi meeting 12/11/2013 6 Collimator gaps in 2012 Transverse cuts from H, V and S primary collimators in IR7 3σ beam envelope 2012: achieved the our design 7 TeV primary collimator setting! Secondary collimator retraction still above nominal (~2.5σ retraction instead than 1σ). Possible limitations: impedance and OP efficiency (more frequent alignments). 60 cm flat active length, gap = ± 1.05 mm σ v = 250 microns! L. Gentini Vertical primary collimators: 2012 settings 1 pound

7. S. Redaelli, 3rd HiLumi meeting 12/11/2013 7 Collimation cleaning at 4 TeV (β * =60cm) Off-momentum Dump TCTs Betatron 1/10000 0.00001 0.000001 Beam 1 Highest COLD loss location: efficiency of > 99.99% ! Most of the ring actually > 99.999% B. Salvachua Cleaning inefficiency [BLM/BLM tcp ] Cleaning defined here as:

8. S. Redaelli, 3rd HiLumi meeting 12/11/2013 8 Stability of cleaning Excellent stability achieved with 1 align- ment per year in IR3/6/7 (2x30 devices). New alignments are only repeated for new physics configurations (it remains crucial to be efficient!) ➙ PhD by G. Valentino: average alignment time < 5 min per collimator using the BLMs. B. Salvachua Setup time per collimator (2010-2012) G. Valentino p-p runs p-Pb/Pb-p runs

9. S. Redaelli, 3rd HiLumi meeting 12/11/2013 9 Outline Introduction Where we are (140MJ@4TeV, 60cm β * ) OP feedback and upgrade plans Advanced collimator concepts Conclusions

10. S. Redaelli, 3rd HiLumi meeting 12/11/2013 10 Why we need a collimation upgrade? LHC points Cleaning efficiency3, 7 Collimator impedance3, 7 Operational improvements, β*all Collimation in experiments (debris cleaning)1, 2, 5, 8 Halo control mechanisms4 Activation, full remote handlingall Collimator lifetime, consolidationall Collimation cleaning not enough to define the LHC performance: beam lifetime and quench limits at 7 TeV must be must be understood. Other important aspects: impedance contribution, settings hierarchy and β* reach. Physics debris collimation: high-luminosity experiments for protons + ion operation. Cannot cover all the topics - more focus on aspects covered by HiLumi-WP5 + US-LARP. Relying on many companion talks at this WS.

11. S. Redaelli, 3rd HiLumi meeting 12/11/2013 11 Minimum beam lifetime in 2012 Beam intensity versus time Minimum (assumed) beam lifetime Quench limit of SC magnets Collimation cleaning at limiting cold location Beam lifetime gives the loss rate on collimators. Cleaning η gives the peak losses in magnets. Collimator design: 500 KW! SQUEEZE ADJUST 1 hour 2012: Minimum lifetime with gaps equiv. to 7 TeV: 0.2 - 1 hour Beam lifetime [ h ] B. Salvachua See talk by E. Métral: to what extend this depends on collimators?

12. S. Redaelli, 3rd HiLumi meeting 12/11/2013 12 Collimation quench test 11 Gy/s at the TCP.B6R7.B2 in IR7 for a peak loss up to 1050 kW Beam 2 Achieved controlled losses of 5.8MJ, about 3 Tevatron full beams, in 15 s. Peak loss up to 1.05 MW, exceeding assumed quench limits by more than a factor 3 without quenching! Major effort undertaken to perform in Feb. 2012 quench tests with beam in operational conditions. Unfortunately, not possible with ion beams... B. Salvachua Ongoing work on different CERN working groups to understand this in detail. E. Skordis (fluka team)

13. S. Redaelli, 3rd HiLumi meeting 12/11/2013 13 Predicted intensity reach from cleaning Consider minimum lifetime of 0.2 h based on the 2012 experience - Perhaps pessimistic, but ~10% of fills reached τ b <0.5-1h! - Reviewers felt that it could get worse (25ns vs 50ns, higher E, larger impedance) Different models to scale losses to 6.5 TeV: Intensity reach from proton cleaning in IR7 is 3 to 6 times the nominal LHC (3.2x10 14 p). Less margin at 7 TeV (different for 2 available quench models). HL-LHC intensity goal reduce this window by a factor ~2. For more than a factor 2 above LHC design, we have to worry also about collimator robustness! We might have to set BLM thresholds to protect the collimators! Ions: ALICE luminosity upgrade target is at least a factor 2 above quench limits. Same limitations apply for IR1 and IR5 that have less priority for ion runs. No additional limitations in IR1/5 until LS3 from physics debris thanks to the use of 3 TCL collimators. Expect the same result for HiLumi, but need to prove this with final IR layouts. Backup slide in case more details are needed. See also talk by L.Esposito.

14. S. Redaelli, 3rd HiLumi meeting 12/11/2013 14 DS collimation: requirements by IR Until HL-LHC (before LS3) [L=2.5x10 34 cm -2 s -1, I tot =3.2x10 14 p] HL-LHC era (after LS3) (L=5x10 34 cm -2 s -1, I tot =6.2x10 14 p) ProtonsIonsProtonsIons IR7Betatron cleaning Needed? (unlikely) Needed TBC (ATS?) Needed? IR3 Momentum cleaning Not needed IR1/5ATLAS/CMSNot neededNeeded Needed? (unlikely) Needed IR2ALICENot neededNeededNot needed Needed IR8LHCbNot neededNot operatingNot neededNot operating Goal for the collimation project: have a solution available to address already in LS2 possible cleaning limitations revealed by the post-LS1 operation. Larger uncertainties for HL-LHC era, but more time to decide on DS collimation! Uncertainty on quench limits and performance, solved in 2015. Can we have 11 T dipoles in time? Do we need to consider alternative layouts (moving magnets)? Local collimation in DS addresses successfully limitations in all IRs!

15. S. Redaelli, 3rd HiLumi meeting 12/11/2013 15 Collimation review outcome https://indico.cern.ch/event/251588 External review panel: Mike Seidel (PSI, Chair), Giorgio Apollinari (FNAL), Wolfram Fischer (BNL), Marzio Nessi (ATLAS), Rudiger Schmidt (CERN/ESS), Carsten Omet (GSI). Main outcome on DS collimation:Due to the uncertainties on the extrapolations of beam lifetime and quench limits at 7 TeV, “The committee strongly encourages the development and prototyping of one 11 T (5.5 m) dipole magnet, and the cryogenic bypass collimator unit. … Build at least 4 units (1 unit consists of 2 magnets + bypass + collimator) since this would cover 2 possible cases…” Additionally: support for reduced impedance collimators and hollow elens works! The review panel recognized that DS collimation: - is needed for ions in IR2/1/5, already in LS2 (ALICE upgrade). - is probably not needed in LS2 but we cannot guarantee that at this stage. - is certainly beneficial for the HL-LHC era (ATS optics). - this technology will be clearly useful for the HL-LHC era Recommendation to work hard to achieve a minimum of 4 by LS2!

16. S. Redaelli, 3rd HiLumi meeting 12/11/2013 16 Progress towards final layouts R. Bruce Finalized layouts and lattices for IR2 and IR7 (IR1/5 ongoing) with 11 T magnets. Massive simulation campaigns (tracking + energy deposition) to understand the cleaning improvement and to determine key collimator parameters (length and material) ➙ specification for load cases are essentially ready. Updated collimator design taking new constraints into account. Provided inputs for the ongoing detailed integration studies. Starting iteration with WP11 for studying quench limits and magnet protection. This is part of the important HiLumi WP5 activity on the LHC collimation that will be discussed in details in the parallel WP5 section! Beam Improved design based on 80 cm length, EN-MEE

17. S. Redaelli, 3rd HiLumi meeting 12/11/2013 17 More pictures on DS collimators Lot of preparatory work done in preparation of the 2011 baseline solution base on moving magnets. Major re-design and integration work is needed, though. EN-MME, TE-MSC M. Karppinen for WP11

18. S. Redaelli, 3rd HiLumi meeting 12/11/2013 18 New collimator materials Main goal: reduce impedance of IR7 (and IR3) collimators, representing 90% of LHC impedance at top energy. See talks by E. Métral and N. Mounet for motivation! More robust tertiary collimators, might allow to push further beta* All new collimators will used improved mechanical design with integrated BPMS. LHC points Cleaning efficiency3, 7 Collimator impedance3, 7 Operational improvements, β*all Collimation in experiments (debris cleaning)1, 2, 5, 8 Halo control mechanisms4 Activation, full remote handlingall Collimator lifetime, consolidationall

19. S. Redaelli, 3rd HiLumi meeting 12/11/2013 19 Gain from new collimators N. Mounet The present collimators contribute to about 90% of the total machine impedance! The collimation contribution is reduced to 10 % if we consider a Mo coding (example here: Mo-Gr jaw coated by Mo). This is considered as a main show stopper to achieve the HL-LHC high intensity goal!

20. S. Redaelli, 3rd HiLumi meeting 12/11/2013 20 TCTP prototype assembly Timeline for new secondary collimators Our ambitious plan: - Build a machine-ready prototype for installation in the Christmas stop 2015! - Based on post-LS1 experience and results of prototyping, launch a production line for action during LS2! Many challenges ahead: - Finalize new collimator design - Production techniques for new materials, including coating - Beam validation of full scale prototype at CERN HiRadMat - Crucial tests of material properties under high irradiation Results expected from US-LARP (BNL) and Kurchatov See talk by N. Simos Cu-CD Fracture Analysis Mo-Gr composite Cu-CD composite

21. S. Redaelli, 3rd HiLumi meeting 12/11/2013 21 Outline Introduction Where we are (140MJ@4TeV, 60cm β * ) OP feedback and upgrade plans Advanced collimator concepts Conclusions

22. S. Redaelli, 3rd HiLumi meeting 12/11/2013 22 Hollow e-lens for the LHC Tevatron ➙ hollow beams allow to control selectively (by amplitude) the diffusion speed of halo particles ➙ control the “steady” tail population; decide when loosing halo (remove fast, erratic loss spikes); no affect on the beam core! Why do we need it? 1. If we are limited by quenches: Great advantage if we can control the time distribution of losses. This is the main motivation for the use of hollow e-lens for collimation! 2. If we do not quench: Design lifetime (0.2h) with the HL-LHC intensity we will cause losses exceeding the plastic deformation of primary/secondary collimators. 3. Halo population control critical for operation with crab-cavities CERN strategy, presented at the last US-LARP meeting: Focus present resources on achieving a conceptual design report by 2013, and a complete design report by end of 2014 to decide in 2015 about LHC installation. Beam population Diffusion speed Talk by G. Stancari on Thursday

23. S. Redaelli, 3rd HiLumi meeting 12/11/2013 23 Status of activities with US-LARP At CERN, we established links to achieve a design report by the end of 2014 Collimation (S. Redaelli), beam instrumentation (R. Jones) and engineering team (A. Bertarelli). Synergy with halo monitoring ➙ H. Schmickler. Planning now to setup an experimental test stand to characterize electron beams. We are very happy with the collaboration with the US-LARP team (G. Stancari, V. Valishev) and we wish that this could continue further. Recently we explored an exchange student program in collaboration with EPFL (L. Rivkin). Can we extend the Toohig fellow to PhD student? Giulio and Sasha suggested to consider the Fermilab joint PhD program as a model. Topics that we are going to address: - Analysis of Tevatron data relevant for LHC - Tracking simulations hollow e-lens excitation (continuation of V. Previtali, Toohig fellow) - Measurements of hollow beam in lab test stands (at Fermilab and CERN) - Analysis of diffusion model at the LHC (continuation of measurements done in 2012) V. Moens, Diploma thesis, Sep. 2013.

24. S. Redaelli, 3rd HiLumi meeting 12/11/2013 24 Crystal collimation studies Several open questions: - Can crystal collimation compete with the present very good cleaning system? - Uncertainty for the scaling to higher energy (e.g.: single diffractive losses). - Operational challenges for the complex operational cycle (ramp, squeeze, etc...). - Some outstanding machine protection concerns must be addressed. - Can we absorb more than 1 MW in one single block? Real need to improve the present system will be assessed in 2015 within the context of the collimation upgrade plans. PrimarySecondariesAbsorbers Bea m Standard collimation Bea m Absorbe r Crystal ??? Crystal-based collimation Promises of crystal collimation: 1. Improved DS cleaning in channeling; 2. Reduce impedance: less secondary collimators and larger gaps; 3. Much improved cleaning for ion beams. Note: only applicable to IR7 betatron cleaning, not useful for physics debris! Promising results at the SPS. Uncertainties on the extrapolation to unknown energy territories and operational challenges call for solid experimental validation before this technology can be relied upon for future designs.

25. S. Redaelli, 3rd HiLumi meeting 12/11/2013 25 Status of crystal proposal for LHC Converged on IR7 layouts for machine studies in horizontal and vertical planes. Existing secondary collimators to be used as absorbers during low-intensity MD’s only. Worked out preliminary settings that optimize cleaning of a crystal-based system. Identified locations of additional detectors. LHC engineering change request (ECR) under approval with the following proposal: Cabling for complete experiment; Installation of 2 goniometers; Space reservations for detectors. (nice to have but not essential for the initially feasibility demonstration) Talk by W. Scandale on Thursday!

26. S. Redaelli, 3rd HiLumi meeting 12/11/2013 26 Update on SLAC rotatory collimator Nice concept. Might be reconsider it in light of the recent material tests and updated safe limits? Cannot be considered as candidate until fully validated by beam tests (HRM, SPS?) A beam test strategy will be established as soon as we have the chance to test it at CERN! Being shipped to CERN now! See talk by T. Markiewicz on Thursday!

27. S. Redaelli, 3rd HiLumi meeting 12/11/2013 27 Scope of collimation consolidation “Optimistic” ballpark figures assuming that all upgrades discussed here are adopted for HL-LHC: - 22-30 new secondary collimators; - 4 more robust TCT collimators; - additional collimators in IR’s (new); - several DS collimator (new). THIS LEAVES IN THE MACHINE AT LEAST 70 HIGH-PRECISION COLLIMATORS THAT WILL HAVE MORE THAN 15 YEARS BY LS3! Several concerns: Mechanical wear in operation Challenging radiation environment Radiation wear of components Performance reduction from thermo-mechanical and electrical property degradation due from radiation. Talk by N. Simos tomorrow

28. S. Redaelli, 3rd HiLumi meeting 12/11/2013 28 Conclusions The LHC collimation upgrade is an integral part of HL-LHC The present upgrade baseline was discussed. We have solutions to address the main critical issues identified for the HL era! For us, important guidelines on upgrade strategy can only come in 2015, as also recognized by a recent external review that supported our baseline. From design to construction project: We are well advanced in terms of layouts, machine slots, space reservations. TCLD + 11T dipoles: converged on baseline layouts for critical IR’s. New collimator materials: slots essentially ready, further improved in LS1. Outstanding issue: integration of hollow e-lens in IR4 ➙ PLC! We set aggressive timelines to be ready for possible actions in LS2 Very challenging schedule for 11 T dipoles (DS collimators in the shade) Working hard to get a fully validated prototype for tests after 2015 to improve the LHC impedance. Solid solutions for the main challenges, but keep pushing new ideas: Advanced collimator concepts are more then ever on the table! Considering improved settings and operational conditions to address other limitations: some discussed in WP5 sessions, other in the pipeline.