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Baseline Scenario and Options for 3000 fb -1

Baseline Scenario and Options for 3000 fb -1. LHC Performance drivers LHC Performance limitations and challenges Operation experience from 2010 and 2011 HL Goals Upgrade considerations Potential HL- LHC Beam parameters. O . Brüning. 1. HL - LHC Public meeting 18. November 2011.

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Baseline Scenario and Options for 3000 fb -1

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  1. Baseline Scenario and Options for 3000 fb-1 LHC Performance drivers LHC Performance limitations and challenges Operation experience from 2010 and 2011 HL Goals Upgrade considerations Potential HL-LHC Beam parameters O. Brüning 1 HL-LHC Public meeting 18. November 2011

  2. Luminosity (round beams): • 1) maximize bunch intensity (brightness [Nb/en] if @ beam-beam limit) • 2) minimize beam size (constant beam power) • 3) maximize number of bunches • 4) compensate for ‘R’ • Operation at performance limit • choose parameters that allow higher than design performance • leveling mechanisms for controlling performance during run Performance optimization for the LHC O. Brüning 2 HL-LHC Public meeting 18. November 2011

  3. Bunch Intensity: • Beam-Beam interaction limit for beam brightness & crossing angle • Collective effects (e.g. TMCI)  ca. 3.5 1011 ppb • e-cloud effect  depends on bunch spacing and number of bunches •  see the next 2 transparencies • b*: • Aperture interaction with WP3 of the HL-LHC • Chromatic aberrations novel correction mechanisms • Event pile up and bunch luminosity limit detectors upgrade Performance Limitations & Challenges for the LHC (e.g. ATS S. Fartoukh) O. Brüning 3 HL-LHC Public meeting 18. November 2011

  4. Number of bunches: • Operation with more than 150 bunches • requires crossing angle; • Operation with for 25ns bunch spacing • and 2808 bunches implies ca. 30 long- • range beam-beam interactions /IP • 2) Electron cloud effect depends on bunch spacing (next transparency) • 3) Total beam power and cleaning efficiency (limit on total beam power) •  fewer bunches more performing for limited total current • dedicated task in HL-LHC project • for now we assume a limit of ca. 1 A per beam • 5) Injector performance depends on bunch spacing (higher brightness for 50ns) • maintain both bunch spacing options (25ns & 50ns) Performance Limitations & Challenges for the LHC O. Brüning 4 HL-LHC Public meeting 18. November 2011

  5. Performance Limitations & Challenges for the LHC F. Zimmermann, Chamonix 2011 Electron cloud effect: 25-ns bunch spacing 50-ns bunch spacing H. Maury e-cloud contribution acceptable for: 25ns and Nb = 2 1011 if dmax≤ 1.2 50ns and Nb = 4 1011 if dmax≤ 1.7 O. Brüning 5 HL-LHC Public meeting 18. November 2011

  6. effective cross section LHC Challenges: R Geometric luminosity reduction factor: Piwinski angle large crossing angle:  reduction of long range beam-beam interactions  reduction of head-on beam-beam parameter  reduction of the mechanical aperture  reduction of instantaneous luminosity  inefficient use of beam current (machine protection!)  opens the door for efficient luminosity leveling O. Brüning 6 HL-LHC Public meeting 18. November 2011

  7. LHC Challenges: Beam-Beam Interaction Tune spread due to head-on beam-beam interaction wox-ing: DQ ≈ 0.01 Long range interactions: Crossing angle configurations: Top Left: only head-on Top right: = 200mrad (≈ 7s) Bottom left: = 285mrad (≈ 10s) Bottom right = 400mrad (≈ 13s) Werner Herr et al, LPN 416 7 O. Brüning HL-LHC Public meeting 18. November 2011

  8. LHC Challenges: Beam-Beam Interaction Tune Footprint: Pacman bunches nominal beams alternating crossing planes all insertions Head-on & Long range DQy ≈ 0.01 DQx ≈ 0.01 Werner Herr 8 O. Brüning HL-LHC Public meeting 18. November 2011

  9. LHC Challenges: Resonances Qy LHC working point: n+m < 12 Qx = 64.31; Qy = 59.32 total tune spread must be smaller than 0.018 (SppS experience) keep dQ = 8 10-3 for operation tolerances and coupling! Qx 3/10 2/7 1/3 bunch intensity limited by beam-beam force: 3 head-on/bunch  xbeam-beam< 3.3 10-3 N < 1.2 1011 2 head-on/bunch  xbeam-beam< 5 10-3 N < 1.7 1011 9 O. Brüning HL-LHC Public meeting 18. November 2011

  10. Leveling:  successful for ALICE by parallel separation  to be confirmed with long-range beam-beam! Aperture  better than expected (b-beat, dispersion,tolerances) Emittance able to operate the LHC with 50% smaller than nominal beam emittances (aperture & brightness) beam-beam: able to collide beams with larger than nominal beam-beam parameters Operation Experience in 2010 and 2011: • ability to re-optimize beam parameters for higher performance • smaller beam emittance and larger beam-beam parameter 10 O. Brüning HL-LHC Public meeting 18. November 2011

  11. Preferred leveling mechanism: Crab Cavities Reservations: technology & MP & noise Supplementary tools for leveling: # crossing angle and Long-range and beam-beam wire compensators # transverse offsets at IP # dynamic b* squeeze • Operation at performance limit • choose parameters that allow higher than design performance • leveling mechanisms for controlling performance during run HL-LHC Performance Goals 11 O. Brüning HL-LHC Public meeting 18. November 2011

  12. Leveling by Crab Cavities Geometric luminosity reduction factor: Piwinski angle 12 O. Brüning HL-LHC Public meeting 18. November 2011

  13. Crab Cavities • Geometric luminosity • reduction factor: • CRAB cavity leveling is most • effective for small b* 13 O. Brüning HL-LHC Public meeting 18. November 2011

  14. Integrated luminosity: 200 fb-1 to 300 fb-1 per year Leveled peak luminosity: L = 5 1034 cm-2 sec-1 Total integrated luminosity: ca. 3000 fb-1 Virtual peak luminosity: L > 10 1034 cm-2 sec-1 HL-LHC Performance Goals 14 O. Brüning HL-LHC Public meeting 18. November 2011

  15. Upgrade Considerations: Beam Lifetime F. Zimmermann, Chamonix 2011 For given luminosity teff scales with total beam current N(t) = (1-t/teff) Ntot (s=100 mbarn) • argument for HL-LHC scenarios with maximum beam current • teff = 13.9 hours for 5 1014p/beam 15 O. Brüning HL-LHC Public meeting 18. November 2011

  16. Summary of LHC Intensity Limits (7 TeV) R. Assman @ Chamonix 2010 Chamonix 2011 R. Assmann • Lower Maximum Intensity of ca. 5 1014p/beam • (TMCI limit for 50ns!) • Upper Maximum Intensity of 6.5 1014p/beam • (e-cloud limit for 25ns!) •  Assume for now beam current limit of ca. 1 A / beam! 16 O. Brüning HL-LHC Public meeting 18. November 2011

  17. Upgrade Considerations: Beam Lifetime Run length assuming leveled luminosity: • virtual luminosity of k * 5 1034 cm-2 sec-1Tlevel = (1-1/√k) * teff • Assuming: 1.8 1011 ppb @ 25ns &3.5 1011 ppb @ 50ns ( ≈ 5 1014 p/beam) • teff = 13.9 hours for 5 1014p/beam: • # k = 2: Tlevel = 4.1 h • # k = 3: Tlevel = 5.9 h • # k = 4: Tlevel = 7.0 h 17 O. Brüning HL-LHC Public meeting 18. November 2011

  18. Upgrade Considerations: Integrated Luminosity Integrated luminosity: run with luminosity decay [StephaneFartoukh] • assuming no emittance growth over the fill  the emittance growth due to IBS and beam-beam is compensated by radiation damping • Lint = ca 0.4 fb-1 over 3 h for a luminosity decay to 2.5 1034 cm-2 s-1 18 O. Brüning HL-LHC Public meeting 18. November 2011

  19. Upgrade Considerations: Integrated Luminosity Integrated luminosity: leveling to constant luminosity Lint = Llevel*Tlevel • integrated luminosity directly proportional to total current • Lint = 0.4 + 0.73 fb-1 per fill for Ntot = 5 1014 ppb and k = 2 • Lint = 0.4 + 1.25 fb-1 per fill for Ntot = 5 1014 ppb and k = 4 (s=100 mbarn) 19 O. Brüning HL-LHC Public meeting 18. November 2011

  20. Upgrade Considerations: Integrated Luminosity • requires between 150 and 220 fills per year to reach 250 fb-1 per year! • implies 1 to 1.5 fills per day for previous scenario • (depending on virtual luminosity reach) Assume ca. 150 days / year for HL-LHC operation M. Lamont March 2011 LHC schedule 2011 v2.0 O. Brüning HL-LHC Public meeting 18. November 2011

  21. Upgrade Considerations: Integrated Luminosity HL-LHC running scenarios: • fill length between 7h and 10h for 5 1014 p/beam and ‘k’ = 2  4 • Turnaround time of ca. 5 hours • total fill time of ca. 12 and 15 hours • 1.5 fills (12h) per day (k = 2; virtual luminosity of 1035 cm-2 sec-1) • requires 75% machine efficiency! • 1 fill (15h) per day (k = 4; virtual luminosity of 2 1035 cm-2 sec-1) • requires 60% machine efficiency •  42% of time in stable beams with physics (= best performance in 2011)! What virtual performance levels (‘k’) are within reach for 5 1014 p/beam and 6 1014 p/beam? 21 O. Brüning HL-LHC Public meeting 18. November 2011

  22. HL LHC Upgrade: New scheme (ATS) for optics: -b* of 0.15m accessible for round beams @ 7 TeV  implies b-functions of > 20km inside triplet magnets!  limit of Field Quality and aperture -b* of 0.3m / 0.075m accessible for flat beams @ 7 TeV Limitations for b* at 7 TeV: Aperture & Chromatic aberrations • Aperture at 7 TeV: • interaction with WP3 of the HL-LHC • current aperture goals are consistent with b* of 0.15m and • 10 s separation Upgrade Considerations: Minimum b* values: S. Fartoukh 22 O. Brüning HL-LHC Public meeting 18. November 2011

  23. Bunch Intensity: • Collective effects (e.g. single bunch TMCI) ca. 3.5 1011 ppb • e-cloud effect  depends on bunch spacing •  2.2 1011 ppb at 25ns requires: dsec < 1.3 and • IRcryo upgrade • TMCI intensity limit for 50ns compatible with: dsec > 1.7 and • IRcryo upgrade • 3) Maximum bunch intensity always linked to beam emittance •  Injector complex performance after LIU Upgrade Considerations: Maximum Bunch Intensity: 23 O. Brüning HL-LHC Public meeting 18. November 2011

  24. Upgrade Considerations: Maximum Brightness Beam-Beam: limits maximum beam by brightness • DQ = 0.02 – 0.03 seems feasible based on 2010 - 2011 experience • maximum acceptable PA? Q > 2? (sync-betatron resonances) • Three experiments with head on collisions: x = 7.7 10-3 • assuming the same geometric reduction factor for x as for L (0.35 with alternating crossing) and assuming negligible contribution from long range: • en ≥ 2 mm for Nbunch = 3.5 1011 (50ns bunch spacing) • en ≥ 1 mm for Nbunch = 2.2 1011 (25ns bunch spacing) 24 O. Brüning HL-LHC Public meeting 18. November 2011

  25. nominal bunch length and minimum b*: ‘HL-LHC Kickoff+’ HL-LHC Performance Estimates minimum b* 5.6 1014 and4.6 1014 p/beam • sufficient room for leveling • with Crab Cavities: • Virtual luminosity for 25ns: • L = 7.4 / 0.37 1034 cm-2 s-1 • = 20 1034 cm-2 s-1 (‘k’ = 4) • Virtual luminosity for 50ns: • L = 8.4 / 0.37 1034 cm-2 s-1 • = 22.7 1034 cm-2 s-1 (‘k’ = 4.5) OK for HL goals (‘k’ = 4) (Even better if emittances can be further reduced: still a factor 1.2 to 2.5 wrt beam-beam limit) • Defines HL-LHC parameters for physics operation • still need to elaborate required • margins for losses during • acceleration and squeeze • LIU requires specifications for • LHC injection! (Leveled to 5 1034 cm-2 s-1) 25 O. Brüning HL-LHC Public meeting 18. November 2011

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