CERN Phase II Collimation Conceptual Review Summary

1. US LHC Accelerator Research Program BNL - FNAL- LBNL - SLAC CERN Phase II Collimation Conceptual Review Summary 09 April 2009 LARP CM12 Napa, CA Tom Markiewicz/SLAC

2. Collimation News from LHC • “Cryo Collimators” proposed to bring LHC to ultimate luminosity: Conceptual Design Review 2-3 APR 2009 supports “continued engineering study” • The yet undesigned “Cryo Collimators” are modeled as warm 1m Tungsten adjustable jaws set at ~15s in the cold part of the ring on either side of the IR7 betatron collimation system • By protecting cold dipoles in the “dispersion suppressor” from “single diffractive protons” produced in primaries that miss all secondary collimators intensity limit in LHC improved by > x15-90 • Growing belief that transverse feedback will control impedance limit to LHC intensity and that this FB is aided in the low frequency region of interest by materials such as ceramics that lower the real part of the impedance and are robust • CERN Phase II secondary design is an improved version of Phase I with “cartridge” zone for placement of jaw material. • TT60 “High Radiation Material” test area a prerequisite to a material downselect. • Construction of TT60 supported by review committee • Desire for immediate development of electron lens with hollow e-beam profile for use as scraper Collimation Conceptual Review Summary - T. Markiewicz

3. Downstream of IR7 b-cleaning Halo Loss Map Losses of off-momentum protons from single-diffractive scattering in TCP halo cryo-collimators Upgrade Scenario See talk J. Jowett NEW concept transversely shifted by 3 cm without new magnets and civil engineering halo -3 m shifted in s +3 m shifted in s

4. 99.997 %/m  99.99992 %/m Proton losses phase II: Zoom into DS downstream of IR7 quench level Very low load on SC magnets  less radiation damage, much longer lifetime. T. Weiler Impact pattern on cryogenic collimator 2 Impact pattern on cryogenic collimator 1 Cryo-collimators can be one-sided! See talk T. Weiler R. Assmann, CERN R. Assmann, CERN

5. BPM integration Integration of BPMs into the jaw assembly gives a clear advantage for set-up time  Prototyping started at CERN BPM pick-ups BPM cables and electrical connections R. Assmann, CERN R. Assmann, CERN

6. Location of HiRadMat 3 possible locations of HiRadMat: former West AreaNeutrino Facility TT60 from SPS TI 2to LHC TT61 tunnel former T1 target area C. Hessler R. Assmann, CERN R. Assmann, CERN 3

7. The Tevatron e-Beam Lens See talk J. Smith. R. Assmann, CERN R. Assmann, CERN

8. Suggested Milestones I 2009 Review conceptual design, go ahead, refined WP’s. Start WP’s cryogenic collimation and hollow e-beam lens. Continue other WP’s. 2010 SPS: Beam test of collimator with in-jaw pick-ups (presently under construction), if we can install. Study results on in-jaw pick-up with Darmstadt/TEMF.LHC:Review beam experience with phase I collimation system. 2010/11 TT60:HiRadMat test facility installation. 2011 WP cryogenic collimation completed and hardware constructed.HiRadMat: Beam tests of advanced secondary collimators.HiRadMat: Material tests with beam shock impact.SPS: Beam tests of the hollow e-beam lens scraping. 2011/12 LHC: Modify SC dispersion suppressors around IR7 and IR3.LHC:Install collimators into the space created. R. Assmann, CERN R. Assmann, CERN

9. Suggested Milestones II 2012: LHC:Ready for nominal intensity.LHC: Parasitic beam tests of advanced secondary collimators.LHC: Parasitic tests of the hollow e-beam lens. Construction decision for phase II secondary collimators, decision for materials and concept (taking into account LHC beam experience, e.g. frequency of erroneous beam hits). 2013 LHC: Reduced beam tails and lower peak loss rate with scraping. Construction of phase II secondary collimators. 2013/14 LHC: Installation of advanced secondary collimators. 2014 LHC:Collimation with ultra-high efficiency, fast and non- destructive collimator setup and safe halo scraping. R. Assmann, CERN R. Assmann, CERN

10. Schedule for Discussion(ambitious and result-oriented “wish” schedule) R. Assmann, CERN 10

11. CHARGE to committee: •Review the conceptual solution of LHC collimation (phase II) for nominal/ultimate beam intensities. •Assess the urgency for phase II of LHC collimation. Committee recommends a staged approach to the overall upgrade the collimation system Work Package A (Dispersion Suppressor Collimators): Committee recommends to continue immediately with engineering design; prefer warm solution; Pro: seems a practicable solution (no show stoppers seen); activation in disp. suppressor section will rise with time; heat load in cold magnets/cryo system is fundamental problem; helps ion problems; unlikely that it will not be useful Con: relatively large effort required; unexpected new experiences from phase 1 operation might require other improvements;

12. CHARGE to committee: • •Assess if all expected collimation problems or solutions have been adequately addressed, including needs for the experiments. • clarify the time scale of possible performance degradation of the presently installed graphite collimators (data from Kurchatov Inst.) • better exploration of implications of activation in IR7 needed (may affect installation of cryo collimators) • study if fixed collimators in dispersion suppressor are feasible; this would simplify technical solution • clarify whether flexibility of beam optics in dispersion suppressor section is compromised by planned modifications • study advanced secondary collimator scheme with imperfections (beam optics, collimator alignment etc.) • understand the importance of irradiation test facility; we were not presented with a plan detailing the experiments, diagnostics and the uniqueness of this facility; positive experience with phase-I jaw tests is acknowledged

13. Continued: • spikes of loss rate are potentially very important; relying only on the hollow e-beam scraper is risky (beam core blowup; non-uniformity of hollow beam); committee recommends to also explore alternative schemes • integrated BPM`s are excellent idea; study impact of showers on integrated BPM • possibly weak point: detection of damage at primary collimators (observe degradation of cleaning efficiency but do not know origin; temperature measurement may not be conclusive) • study implementation of thin scattering tip at edge of primary collimators; increases local diffusion rate → larger impact parameter; might help collimation of heavy ions • HERA experience: dust falls into beam, causes extreme bursts of losses; e.g. from vertically movable Roman pots • experimental tests using SPS etc. are encouraged

14. RC 5 Year Plan: For Discussion Collimation Conceptual Review Summary - T. Markiewicz