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Machine Plans for the LHC Upgrade

Machine Plans for the LHC Upgrade. Frank Zimmermann CERN, AB/ABP. Thanks to Ralph Assmann, Michael Benedikt, Rama Calaga, Ulrich Dorda, Angeles Faus-Golfe, Roland Garoby,Jean-Pierre Koutchouk, Javier Resta, Francesco Ruggiero, Rogelio Tomas, Walter Scandale . Large Hadron Collider (LHC).

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Machine Plans for the LHC Upgrade

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  1. Machine Plans for the LHC Upgrade Frank Zimmermann CERN, AB/ABP Thanks to Ralph Assmann, Michael Benedikt, Rama Calaga, Ulrich Dorda, Angeles Faus-Golfe, Roland Garoby,Jean-Pierre Koutchouk, Javier Resta, Francesco Ruggiero, Rogelio Tomas, Walter Scandale ATLAS Upgrade Workshop, 1 October 2006

  2. Large Hadron Collider (LHC) c.m. energy 14 TeV 7x Tevatron design luminosity 1034 cm-2s-1 ~100x Tevatron transverse beam energy density 1 GJ/mm2 ~1000x Tevatron nominal LHC already a very challenging machine! ATLAS Upgrade Workshop, 1 October 2006

  3. outline 1) motivation 2) pushing the luminosity 3) beam scenarios & upgrade schemes -luminous region -lifetime & integrated luminosity 4)IR upgrade 5) intensity limitations 6) injector upgrade 7) towards higher energy 8) questions to ATLAS 9) summary ATLAS Upgrade Workshop, 1 October 2006

  4. (1) motivation ATLAS Upgrade Workshop, 1 October 2006

  5. time scale of an LHC upgrade Jim Strait, 2003 radiation damage limit ~700fb-1 time to halve error integrated L L at end of year ultimate luminosity design luminosity (1)life expectancy of LHC IR quadrupole magnets is estimated to be <10 years due to high radiation doses (2) statistical error halving time exceeds 5 years by 2011-2012 → it is reasonable to plan a machine luminosity upgrade based on new low-b IR magnets around ~2014-2015 ATLAS Upgrade Workshop, 1 October 2006

  6. European Accelerator Network on November 2004: 1st CARE-HHH-APD Workshop (HHH-2004) on ‘Beam Dynamics in Future Hadron Colliders and Rapidly Cycling High-Intensity Synchrotrons’, Proc. CERN-2005-006 September 2005: 2nd CARE-HHH-APD Workshop (LHC-LUMI-05) on ‘Scenarios for the LHC Luminosity Upgrade’, Proc. CERN-2006-008 October 2006: 3rd CARE-HHH-APD Workshop (LHC-LUMI-06) ‘Towards a Roadmap for the Upgrade of the LHC and GSI Accelerator Complex’ .../LUMI-06/LHC-LUMI-06-invitation.pdf High Energy High Intensity Hadron Beams http://care-hhh.web.cern.ch/care-hhh/ ATLAS Upgrade Workshop, 1 October 2006

  7. upgrade stages • push LHC performance w/o new hardware luminosity →2.3x1034 cm-2s-1, Eb=7→7.54 TeV • LHC IR upgrade replace low-b quadrupoles after ~7 years peak luminosity →4.6x1034 cm-2s-1 • LHC injector upgrade peak luminosity →9.2x1034 cm-2s-1 • LHC energy upgrade Eb→13 – 21 TeV (15 → 24 T dipole magnets) ATLAS Upgrade Workshop, 1 October 2006

  8. (2) pushing the luminosity ATLAS Upgrade Workshop, 1 October 2006

  9. luminosity parameters that enter: ATLAS Upgrade Workshop, 1 October 2006

  10. there are many parameter constraints, for example e limited by arc aperture and field quality at injection b* limited by final triplet aperture & crossing angle & long-range beam-beam & collimation & chromatic correction (& beam lifetime) qc limited by geometric luminosity loss & long-range collisions & triplet aperture & triplet field errors nbNb ~ total current, limited by collimation, machine protection, beam dump nb limited by electron cloud heating Nb limited by image-current heating & collimation & pile-up events ATLAS Upgrade Workshop, 1 October 2006

  11. nominal crossing angle “at the edge” Piwinski angle luminosity reduction factor nominalLHC ATLAS Upgrade Workshop, 1 October 2006

  12. another important constraint is the (head-on) beam-beam tune shift total beam-beam tune shift at two IPs with alternating crossing DQbb < 0.01- 0.015, beam-beam limit for hadron colliders (from experience) ATLAS Upgrade Workshop, 1 October 2006

  13. for operation at the beam-beam limit luminosity equation can be rewritten as injector upgrade LHC+ injector changes LHC + injector changes IR upgrade ATLAS Upgrade Workshop, 1 October 2006

  14. (3) beam scenarios & upgrade schemes ATLAS Upgrade Workshop, 1 October 2006

  15. ATLAS Upgrade Workshop, 1 October 2006

  16. bunch structure plus: can use crab cavities event pile up tolerable more (&shorter) bunches nominal & ultimate LHC concerns: e-cloud LRBB impedance ~12.5 ns upgrade path 1 25 ns upgrade path 2 upgrade path 3 longer (&fewer) bunches 25 ns bigger (&shorter?) bunches 75 ns plus: no e-cloud? less current concerns: event pile up impedance concerns: impedance heating, LR compensation, may need 1-TeV injector plus: limited e-cloud limited pile up transitions by bunch merging or splitting; new rf systems required for cases 1 and 3 ATLAS Upgrade Workshop, 1 October 2006

  17. luminosity upgrade: baseline schemes 1.0 reduce sz by factor ~2 using higher frf & lower e|| (larger qc ?) 0.58 A qc>qmindue to LR-bb increase Nb increase Ff BBLR compen-sation yes bb limit? crab cavities reduce qc (squeeze b*) 2.3 no 0.86 A reduce b* by factor ~2 new IR magnets use large qc & pass each beam through separate magnetic channel 4.6 0.86 A if e-cloud, dump & impedance ok increase either nbor (Nb&e) by factor ~2 simplified IR design with large qc peak luminosity gain 9.2 beam current 1.72 A ATLAS Upgrade Workshop, 1 October 2006

  18. luminosity upgrade: backup scheme decrease Ff reduce b* by factor ~2 new IR magnets 1.0 increase szqc 0.58 A flatten profile increase Nb reduce #bunches by 1/3 to limit total current yes no 8.9 ? luminosity gain 1.0 A beam current ATLAS Upgrade Workshop, 1 October 2006

  19. due to the crossing angle, colliding long bunches does not mean the events are spread out over a large area rms length of luminous region luminous region is largest for nominal LHC ATLAS Upgrade Workshop, 1 October 2006

  20. optimum run time, integrated luminosity, etc. collisions, gas scattering intensity evolution for collisions only intrabeam scattering (IBS) growth burn-off collision lifetime with s~100 mbarn, nIP~2: Lpeak=1034 cm-2s-1 in 2808 bunches, Nb~1.15x1011: t~45 h (luminosity lifetime 22 h) Lpeak=1035 cm-2s-1 in 5616 bunches, Nb~1.7x1011: t~14 h (luminosity lifetime 7 h) tgas > 100 h (luminosity lifetime 50 h) tIBS~105 h (horizontal emittance growth time; luminosity lifetime 210 h) burn-off dominates over gas scattering and IBS ATLAS Upgrade Workshop, 1 October 2006

  21. luminosity time evolution average luminosity optimum run time → 6x 8x ATLAS Upgrade Workshop, 1 October 2006

  22. (4) IR upgrade ATLAS Upgrade Workshop, 1 October 2006

  23. IR upgrade T. Sen et al., PAC2001 T. Taylor, EPAC02 J. Strait et al., PAC2003 F. Ruggiero et al., EPAC04 goal: reduce b* by factor 2-5 options: NbTi ‘cheap’ upgrade, NbTi(Ta), Nb3Sn new quadrupoles new separation dipoles maximize magnet aperture, minimize distance to IR • factors driving IR design: • minimize b* • minimize effect of LR collisions • large radiation power directed towards the IRs • crab cavities or beam-beam compensators, • integration of elements inside detector • compatibility with upgrade path ATLAS Upgrade Workshop, 1 October 2006

  24. “open midplane s.c. dipole” (studied by US LARP) I R U P G R A D E “quadrupoles first” minimum chromaticity “dipole first” reduced # LR collisions; collision debris hits first dipole N. Mokhov et al., PAC2003 ATLAS Upgrade Workshop, 1 October 2006

  25. D0 dipole triplet magnets triplet magnets D0 dipole IR schemes with D0 dipole deep inside detector (e.g., ~3 m from IP) less LR collisions. no geometric lumi. loss not so short bunches & near head-on collision near head-on collision but large separation IR schemes with Q0 doublet deep inside detector (7.5 or 13 m from IP) triplet magnets triplet magnets Q0 doublet BBLR crab cavity triplet quads much easier, less Q’, could be combined with D0 short bunches & minimum crossing angle & BBLR Q0 doublet crab cavities & large crossing angle ATLAS Upgrade Workshop, 1 October 2006

  26. higher-luminosity IR optics web site http://care-hhh.web.cern.ch/care-hhh/SuperLHC_IRoptics/IRoptics.html Candidate solutions: Combined functionNbTi magnets with large l* (O. Bruning) Dipole first options with Nb3Sn (CERN & FNAL) Quad 1st Nb3Sn (T. Sen) Quad 1st“pushed” NbTi (O. Bruning, R. Ostojic, F. Ruggiero) Quad 1st with detector-integrated dipole (J.-P. Koutchouk) Quad 1st flat beam (S. Fartoukh) Quad 1st Nb3Sn or NbTi plus crab cavities (R.Tomas & F.Z.) Detector-integrated quadrupole doublet (E. Laface, W. Scandale, et al) Rating criteria: aperture, energy deposition, technology, chromatic correction, beam-beam compensation,…, risks, development time scales, operational difficulties ATLAS Upgrade Workshop, 1 October 2006

  27. (5) intensity limitations ATLAS Upgrade Workshop, 1 October 2006

  28. ultimate LHC intensity limitations • electron cloud • long-range & head-on beam-beam effects • collimator impedance & damage • injectors • beam dump & damage • machine protection • … ATLAS Upgrade Workshop, 1 October 2006

  29. electron cloud in the LHC schematic of e- cloud build up in the arc beam pipe, due to photoemissionand secondary emission [Courtesy F. Ruggiero] ATLAS Upgrade Workshop, 1 October 2006

  30. arc heat load vs. spacing, Nb=1.15x1011, ‘best’ model R=0.5 cooling capacity ATLAS Upgrade Workshop, 1 October 2006

  31. long-range beam-beam collisions • perturb motion at large transverse amplitudes, where particles come close to opposing beam • may cause high background, poor beam lifetime • increasing problem for SPS, Tevatron, LHC,... ATLAS Upgrade Workshop, 1 October 2006

  32. long-range beam-beam compensation by wire prototype wire compensator “BBLR” installed in the SPS ATLAS Upgrade Workshop, 1 October 2006

  33. crab cavities crab cavity 100-1000x more effective than bunch-shortening rf! crab voltage compared with bunch-shortening rf ATLAS Upgrade Workshop, 1 October 2006

  34. crab-cavity timing tolerance jitter tolerances (0.02 ps XFEL!) IP offset of 0.6 nm, ~5x10-5s* IP offset of 0.2 sx* tight jitter tolerance might prevent this scheme ATLAS Upgrade Workshop, 1 October 2006

  35. graphite collimator impedance renders nominal LHC beam unstable complex coherent tune shift plane + 43 collimators resistive wall & broadband stability border(s) from Landau octupoles LHC is limited to 40% of nominal intensity until “phase-2 collimation” Elias Metral ATLAS Upgrade Workshop, 1 October 2006

  36. LHC phase-2 collimation options • high chromaticity and/or transverse feedback (poor lifetime & emittance growth) • consumable low-impedance collimators (rotating metal wheels; prototype from US LARP / SLAC to be installed in 2008) • nonlinear collimation; pairs of sextupoles to deflect halo particles to larger amplitudes & open collimator gaps • use crystals to bend halo particles to larger amplitudes & open collimator gaps several proposed solutions ATLAS Upgrade Workshop, 1 October 2006

  37. U0 Channeled U0 θ1 θ1 U0 U0 Channeling in flat crystal ( Landau and Lifshitz, Mechanics) Y. Ivanov, PNPI ATLAS Upgrade Workshop, 1 October 2006

  38. U0 U0 Channeled θ3 U0 Reflected θ2 θ1 U0 U0 Channeling and reflection in bent crystal reflecting crystals could serve as primary collimators Y. Ivanov, PNPI ATLAS Upgrade Workshop, 1 October 2006

  39. crystal channeling & reflection demonstrated in SPS H8 -12.09.2006 Si-strip detector 65 m behind Crystal 400 GeV p 10-mrad reflection over 1 mm distance ↔ ~20000 T field! >99% efficiency unperturbed or scattered reflected channeled ATLAS Upgrade Workshop, 1 October 2006

  40. (6) injector upgrade ATLAS Upgrade Workshop, 1 October 2006

  41. injector upgrade - motivations raising beam intensity (higher bunch charge, shorter spacing etc.), for limited geometric aperture, L~eN, may be essential for alternative scheme reduction of dynamic effects (persistent currents, snapback, etc.) → improvement of turn-around time by factor ~2, effective luminosity by ~50% benefit to other CERN programmes (n physics, b beams,…) ATLAS Upgrade Workshop, 1 October 2006

  42. LHC injector upgrade SPS+ extraction energy450 GeV →1 TeV PS2 or PS2+ extraction energy26 GeV → 50 or 75 GeV LHC+ injection energy450 GeV → 1 TeV Super ISR is alternative to Super PS Superferric ring “pipetron” in LHC tunnel is alternative to Super SPS – issue: detector bypass ATLAS Upgrade Workshop, 1 October 2006

  43. parameter lists for new injectors under construction ATLAS Upgrade Workshop, 1 October 2006

  44. Upgraded CERN Complex fast cycling dipoles for Super-LHC injectors Super-LHC Super-SPS Super-Transferlines PS2 PS2? ATLAS Upgrade Workshop, 1 October 2006

  45. (7) towards higher energy ATLAS Upgrade Workshop, 1 October 2006

  46. ultimate LHC “upgrade”: higher beam energy 7 TeV→14 (21) TeV? R&D on stronger magnets ATLAS Upgrade Workshop, 1 October 2006

  47. Six institutes:CCLRC/RAL (UK), CEA/DSM/DAPNIA (France), CERN/AT (International), INFN/Milano-LASA & INFN/Genova (Italy), Twente University (the Netherlands), Wroclaw University (Poland). Three s.c. wire manufacturers (also contributing financially): Alstom/MSA (France),ShapeMetal Innovation (the Netherlands),Vacuumschmelze (now European Advanced Superconductors, Germany) • develop and construct a large-aperture (up to 88 mm), high-field (up to 15 T) dipole magnet model • that pushes the technology well beyond present LHC limits. Next European Dipole European Joint Research Activity proof-of principle & world record: 16 T at 4.2 K at LBNL (in 10 mm aperture). (S. Gourlay, A. Devred) ATLAS Upgrade Workshop, 1 October 2006

  48. proposed design of 24-T block-coil dipole for LHCenergy tripler P. McIntyre, Texas A&M, PAC’05 magnets are getting more efficient! ATLAS Upgrade Workshop, 1 October 2006

  49. (8) questions to ATLAS ATLAS Upgrade Workshop, 1 October 2006

  50. questions to ATLAS • is the back up solution with peak pile up of 500 events per crossing a viable option? • can “slim" s.c. magnets be installed deep inside the upgraded ATLAS detector, and, if so, under which boundary conditions, such as envelope, volume, material, or fringe field? ATLAS Upgrade Workshop, 1 October 2006

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