Scenarios for the sLHC and the vLHC

1. Scenarios for the sLHC and the vLHC Walter Scandale, Frank Zimmermann CERN HCP2007 We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6 "Structuring the European Research Area" programme (CARE, contract number RII3-CT-2003-506395)

2. outline • LHC upgrade: why and when ? • beam parameters • the two selected scenarios for luminosity upgrade • features, • Bunch structure • IR layout, • merits and challenges • luminosity leveling ? • summary & recommendations for the sLHC • perspective for higher energy hadron collisions • VLHC at FNAL • dLHC and tLHC at CERN • R&D • possible plans

3. LHC luminosity upgrade: why and when? • How fast performance is expected to increase: • 4 y up to nominal L • 4 y up to nominal L & 2 y up to ultimate L • 4 y up to ultimate • IR quadrupole lifetime ≥ 8 years owing to high radiation doses • halving time of the statistical error ≥ 5 y already after 4-5 y of operation • luminosity upgrade to be planned by the middle of next decade

4. LHC luminosity upgrade: the LARP perspective Courtesy of V. Shiltsev - FNAL

5. baseline upgrade parameters 2001-2005 abandoned at LUMI’06 total heat 15.6 W/m >> 2.4 W/m (heat load induced by Sync.Rad + image current larger than the local heat load capacity)

6. New upgrade scenarios challenges injector upgrade Crossing with large Piwinski angle aggressive triplet compromises between # of pile up events and heat load

7. Luminosity at the beam-beam limit for operation at beam-beam limit with alternating planes of crossing at two IPs, luminosity equation can be written as 50 ns 50 ns 25 ns 50 ns where Qbb = total beam-beam tune shift (the change of Fh-g due to hourglass effect is neglected above) PAF/POFPA Meeting 20 November 2006

8. luminosity reduction factor from crossing angle Piwinski angle R  0.85 (nominalLHC)

9. 25-ns ultra-low- upgrade scenario • stay with ultimate LHC beam (1.7x1011 protons/bunch, 25 spacing) • squeeze * below ~10 cm in ATLAS & CMS • add early-separation dipoles in detectors, one at ~ 3 m, the other at ~ 8 m from IP • possibly also add quadrupole-doublet inside detector at ~13 m from IP • and add crab cavities (fPiwinski~ 0), and/or shorten bunches with massive addt’l RF  new hardware inside ATLAS & CMS,  first hadron-beam crab cavities (J.-P. Koutchouk et al)

10. CMS & ATLAS IR layout for 25-ns option l* = 22 m stronger triplet magnets D0 dipole Q0 quad’s Magnets embedded in the expt. apparatus small-angle crab cavity ultimate bunch intensity & near head-on collision (R1) PAF/POFPA Meeting 20 November 2006

11. 25-ns scenario assessment (accelerator view point) • merits: • negligible long-range collisions, • reduced geometric luminosity loss, • no increase in beam current beyond ultimate • challenges: • D0 dipole deep inside detector (~3 m from IP), • Q0 doublet inside detector (~13 m from IP & slim magnet technology), • crab cavity for hadron beams (emittance growth ?), • 4 parasitic collisions at 4-5 separation, • “chromatic beam-beam” Q’eff ~ z/(4*), • poor beam and luminosity lifetime ~ * PAF/POFPA Meeting 20 November 2006

12. 50-ns high intensity upgrade scenario • double bunch spacing • longer & more intense bunches with fPiwinski~ 2 • keep *~25 cm (achieved by stronger low- quads alone) • do not add any elements inside detectors • long-range beam-beam wire compensation  novel operating regime for hadron colliders Variant (not yet studied) • add early-separation dipoles, one at ~ 5 m, the other at ~ 9 m from IP • Reduce the current • Almost head-on crossing angle (W. Scandale, F.Zimmermann & PAF)

13. CMS & ATLAS IR layout for 50-ns option l* = 22 m stronger triplet magnets wire compensator long bunches & nonzero crossing angle & wire compensation PAF/POFPA Meeting 20 November 2006

14. 50-ns scenario assessment (accelerator view point) • merits: • no elements in detector, no crab cavities, • lower chromaticity, • less demand on IR quadrupoles (NbTi possible) • challenges: • operation with large Piwinski parameter unproven for hadron beams, • high bunch charge, • beam production and acceleration through SPS, • “chromatic beam-beam” Q’eff ~ z/(4*), • larger beam current, • wire compensation (established  last validation in RHIC) PAF/POFPA Meeting 20 November 2006

15. IR upgrade optics compatible with 50-ns upgrade path “compact low-gradient” NbTi,*=25 cm <75 T/m (Riccardo De Maria, Oliver Bruning) “modular low gradient” NbTi, *=25 cm <90 T/m (Riccardo De Maria, Oliver Bruning) “low max low-gradient” NbTi, *=25 cm <125 T/m (Riccardo De Maria, Oliver Bruning) standard Nb3Sn upgrade, *=25 cm ~200 T/m,2 versions with different magnet parameters (Tanaji Sen et al, Emmanuel Laface, Walter Scandale) + crab-waist sextupole insertions? (LNF/FP7) include sextupoles to compansate the glass-hours effect early separation with *=8 cm, Nb3Sn includes D0; either triplet closer to IP; being prepared for PAC’07 (Jean-Pierre Koutchouk et al) Use of Q0 being finalized for PAC’07 (E. Laface, W.Scandale) PAF/POFPA Meeting 20 November 2006

16. crab waist scheme realization: add sextupoles at right phase distance from IP initiated and led by LNF in the frame of FP7; first beam tests at DAFNE later in 2007 minimizes  at s=x/c Hamiltonian focal plane PAF/POFPA Meeting 20 November 2006

17. IP1& 5 luminosity evolution for 25-ns & 50-ns spacing • Turnaround time  10h • Optimized run duration 25 ns spacing 50 ns spacing average luminosity initial luminosity peak may not be useful for physics PAF/POFPA Meeting 20 November 2006

18. IP1& 5 event pile up for 25-ns and 50-ns spacing 50 ns spacing 25 ns spacing PAF/POFPA Meeting 20 November 2006

19. new upgrade bunch structures nominal 25 ns new alternative! ultimate & 25-ns upgrade 25 ns 50-ns upgrade, no collisions @S-LHCb! 50 ns new baseline! 50-ns upgrade with 25-ns collisions in LHCb 50 ns 25 ns PAF/POFPA Meeting 20 November 2006

20. S-LHCb collision parameters rms length of luminous region: PAF/POFPA Meeting 20 November 2006

21. luminosity leveling in IP1&5 experiments prefer more constant luminosity, less pile up at the start of run, higher luminosity at end how could we achieve this? 50-ns higher- scheme: dynamic  squeeze, and/or dynamic reduction in bunch length (less invasive) 25-ns low- scheme: dynamic  squeeze or Novel proposal under investigation based on the change the crossing angle (G. Sterbini) PAF/POFPA Meeting 20 November 2006

22. leveling equations beam intensity decays linearly length of run average luminosity PAF/POFPA Meeting 20 November 2006

23. assuming 5 h turn-around time PAF/POFPA Meeting 20 November 2006

24. IP1& 5 luminosity evolution for 25-ns & 50-ns spacing with leveling 25 ns spacing 50 ns spacing average luminosity PAF/POFPA Meeting 20 November 2006

25. IP1& 5 event pile up for 25-ns and 50-ns spacing with leveling 50 ns spacing 25 ns spacing PAF/POFPA Meeting 20 November 2006

26. summary • two scenarios of L~1035 cm-2s-1 for which heat load and #events/crossing are acceptable • 25-ns option: pushes *; requires slim magnets inside detector, crab cavities, & high gradient large aperture (Nb3Sn) quadrupoles and/or Q0 doublet; attractive if total beam current is limited; transformed to a 50-ns spacing by keeping only 1/2 the number of bunches • 50-ns option: has fewer longer bunches of higher charge ; can be realized with NbTi technology if needed ; compatible with LHCb ; open issues are SPS upgrade & beam-beam effects at large Piwinski angle; luminosity leveling may be done via bunch length and via * tuning

27. recommendations • luminosity leveling should be seriously considered in all cases: • more regular flow of events • moderate decrease in average luminosity • long-bunch 50-ns option entails less risk and less uncertainties; however with the drawback of the larger bunch population • 25-ns option is an optimal back up until we have gained some experience with the real LHC • concrete optics solutions, beam-beam tracking studies, and beam-beam machine experiments are needed for both scenarios

28. The VLHC versus the LHC energy upgrade

29. Design Study for a Staged Very Large Hadron Collider Fermilab-TM-2149 June 11, 2001 www.vlhc.org

30. The two Stages of the VLHC • Build a long tunnel. • Fill it with a “cheap” 40 TeV collider. • Later, upgrade to a 200 TeV collider in the same tunnel. • Spreads the cost • Produces exciting energy-frontier physics sooner & cheaper • Allows time to develop cost-reducing technologies for Stage 2 • vigorous R&D program in magnets and underground construction required. • This is a time-tested formula for success Main Ring  Tevatron LEP  LHC

31. Parameters of the VLHC

32. Cost drivers for the stage-1 (at FNAL) • Stage-1 at 40 TeV and 1034 luminosity • large tunnel to be build in the Fermilab area • total construction time ~ 10 years • Logistics and management complex • only 20 MW of refrigeration power, comparable to the Tevatron. • significant money and time saving by building the VLHC at FNAL • Cost estimate ~ 4 G$ • no detectors (2 halls included), • no EDI, • no indirect costs, • no escalation, • no contingency • 2001 prices and c.a. 2001 technology. • No cost reduction assumed from R&D • Cost almost independent of the choice of the B-field

33. vacuum chambers SC transmission line (100 kA) 30cm support tube/ vacuum jacket Cryo-lines 100kA return bus Transmission line magnet for Stage-1 • 2-in-1 warm iron • Superferric: 2T B- field • 100kA Transmission Line • Combined function dipole (no quadrupoles needed) • 65m Length • Self-contained including Cryogenic System and Electronics Cabling • Warm Vacuum System

34. Stage-2 • The Stage-2 VLHC can reach 200 TeV and 2x1034 or possibly significantly more in the 233 km tunnel. • A large-circumference ring is a great advantage for Stage-2 • A high-energy, high B-field (B > 12 T) VLHC in a small-circumference ring may not be realistic (too much synchrotron radiation). • To demonstrate feasibility and to reduce cost, there is the need for R&D in the following items • high-field magnet, • vacuum in presence of large radiated power • efficient tunneling • photon stopper.

35. Magnets for Stage-2 • Superconducting magnets based on Nb3Sn Stage-2 Dipole Single-layer common coil Stage-2 Dipole Warm-iron Cosine Q

36. Synchrotron radiation

37. Beam screen • There is an optimal size of the coolant pipe and of the beam screen temperature for a given synchrotron emission regime

38. Photon stoppers • Synchrotron radiation masks look promising. • Preliminary tests already performed at FNAL. • They will decrease refrigerator power and permit higher energy and luminosity. • They are practical only in a large-circumference tunnel.

39. Optimum Dipole Field Luminosity scale PSR<10 W/m/beam peak tL > 2 tsr Interaction per cross < 60 L units 1034 cm-2s-1 • The cutoffs are • field too low, not enough damping, • field too high, too much synchrad power so required aperture too large.

40. LHC energy doubler 14*14 TeV • dipole field Bnom = 16.8 T, Bdesign = 18.5-19.3 T (10-15% margin) • superconductor - Nb3Sn • 10-13 T field demonstrated in several 1-m long Nb3Sn dipole models • DLHC magnet parameters well above the demonstrated Nb3Sn magnet technology • R&D and construction time and cost estimates • 10+ years for magnet technology development and demonstration • Magnet production by industry ~ 8-10 years • High cost for R&D and construction (cost of dipoles > 3GCHF ?)

41. LHC energy tripler 21*21 TeV • dipole field Bnom = 25 T, Bdesign = 28-29 T (10-15% margin) • superconductor - HTS-BSCCO (low demand) or Nb3Sn • Magnet technology to be fully demonstrated • DLHC magnet parameters well above the demonstrated Nb3Sn magnet technology • Large aperture dipole to accommodate an efficient beam screen • R&D and construction time and cost/risk estimates • 20++ years for magnet technology development and demonstration • Extremely high R&D and construction cost and risk • SC cable to be developed, • Magnetic coil stress requires innovative dipole cross section • Magnet production by industry (?) ?? years

42. LHC, sLHC, DLHC perspective

43. VLHC perspective