1 / 35

Super-B-Factory

Super-B-Factory. John T. Seeman Assistant Director of the Technical Division Head of the Accelerator Department Caltech Meeting December 3, 2004. Beam Lines. SBF. SBF injector needs no changes. The PEP-II e + e - asymmetric collider. Location of new RF cavities. PEP-II HER RF cavities.

elina
Download Presentation

Super-B-Factory

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Super-B-Factory John T. Seeman Assistant Director of the Technical Division Head of the Accelerator Department Caltech Meeting December 3, 2004

  2. Beam Lines SBF SBF injector needs no changes

  3. The PEP-II e+e- asymmetric collider Location of new RF cavities

  4. PEP-II HER RF cavities

  5. Luminosity Equation • xy is the beam-beam parameter (~0.065) • Ib is the bunch current (1 to 3 mA) • n is the number of bunches (~1600) • by* is the IP lattice optics function (vertical beta) (10 mm) • E is the beam energy (3.1 and 9 GeV) • Luminosity (1033 cm-2 s-1)

  6. Higher Currents: • More rf power, cooling, injector • More HOM heating (more bunches) • Beam instabilities • Electron clouds, fast ions Smaller by*: • Smaller physical/dynamic aperture • Shorter lifetime, more background Shorter sz: • More HOM heating • Coherent synchrotron radiation • Shorter lifetime, more background Higher tune shifts: • Head-on collisions replaced by angled crossing • Degrades maximum tune shift unless crabbing cavities used Achieving Super B Luminosities

  7. The Roadmap Committee has studied the future of PEP-II and BaBar with a possible large upgrade at the end of the decade. A Super-PEP-II could produce 10 ab-1 per year with a peak luminosity of 7 x 1035/cm2/s. Accelerator parameter goals have been set and work towards a solid design has started. The long range time goal is to have a new upgraded accelerator running in 2011 or 2012. PEP-II/BaBar Roadmap: Super B-Factory Study

  8. Recommended PEP-II upgrades schemes Detector requirements depend on projecting backgrounds for luminosities that are >20 times larger than at present

  9. LER ring (no IR yet) Biagini 6 sextants, small negative momentum compaction,using present LER dipoles & quads (16 families), 3 sextupole families

  10. One sextant Biagini

  11. One half-arc + dispersion suppressor Biagini

  12. Super B-Factory Components Under Study IR SC magnets New Arc magnets New RF cavities New IR layout

  13. New IR magnet design (Parker)

  14. New IR magnet design Quadrupole, anti-solenoid, skew quadrupole, dipole and trims located in one magnet. All coils numerically wound on a bobbin.

  15. xy ◊ ◊ ◊ ◊ ◊ Activities towards luminosity upgrade • Crab crossing may boost the beam-beam parameter up to 0.2! (Strong-weak simulation) K. Ohmi Head-on(crab) (Strong-strong simulation) crossing angle 22 mrad • Superconducting crab cavities are under development, will be installed in KEKB in 2005. K. Hosoyama, et al

  16. Electron Cloud Instability & multipacting

  17. Antechambers Reduce Electron- Cloud-Instability High power photon stops LER aluminum vacuum system: limit at 4.5A Photon Stop limits 4.5 A at 3.1 GeV Total LER SR power = 2 MW

  18. Vacuum system for Super B Factory • Antechamber and solenoid coils in both rings. • Absorb intense synchrotron radiation. • Reduce effects of electron clouds. Circular-chamber Build-up of electron clouds Ante-chamber Ante-chamber with solenoid field

  19. HOM calculations: 476 MHz cavity S.Novokhotski Rbeam = 95.25 mm Total loss = 0.538 V/pC Loss integral above cutoff = 0.397 V/pC HOM Power = 203 kW @ 15.5A 476 MHz cavity with a larger beam opening

  20. HOM calculations: 952 MHz cavity S.Novokhotski Rbeam = 47.6 mm Total loss = 0.748 V/pC Loss integral above cutoff = 0.472 V/pC HOM Power = 121 kW @ 15.5A 952 MHz cavity with a larger beam opening

  21. Luminosity-dependent backgrounds PEP-II Head-On IR Layout • SR in bend & quadrupole magnets • Current dependent terms due to residual vacuum • Bhabha scattering at IP

  22. Higher Currents: • More rf power, cooling, injector • More HOM heating (more bunches) • Beam instabilities • Electron clouds, fast ions Smaller by*: • Smaller physical/dynamic aperture • Shorter lifetime, more background Shorter sz: • More HOM heating • Coherent synchrotron radiation • Shorter lifetime, more background Higher tune shifts: • Head-on collisions replaced by angled crossing • Degrades maximum tune shift unless crabbing cavities used Achieving Super B Luminosities

  23. Power Scaling Equations • Synch rad ~ I E4/r • Resistive wall ~ I2total/r1/frf/sz3/2 • Cavity HOM ~ I2total/frf/sz1/2 • Cavity wall power = 50 kW • Klystron gives 0.5 MW to each cavity • Magnet power ~ gap~r1

  24. Power scaling equations • Synch rad ~ I E4/r • Resistive wall ~ I2total/r1/frf/sz3/2 • Cavity HOM ~ I2total/frf/sz1/2 • Cavity wall power = 50 kW • Klystron gives 0.5 MW to each cavity • Magnet power ~ gap ~ r1

  25. 1.5x1034 2.5x1034 7x1034 Site power limits 476 MHz 952 MHz (Linac, PEP-II magnets and campus power = 40 MW)

  26. Recommended scenario: 5 to 7 x 1035 • Replace present RF with 952 MHz frequency over period of time. • Use 8 x 3.5 GeV with up to 15.5 A x 6.8 A. • New LER and HER vacuum chambers with antechambers for higher power (x 4). • Keep present LER arc magnets but add magnets to soften losses; replace HER magnets as well. • New bunch-by-bunch feedback for 6900 bunches (every bucket) at 1 nsec spacing. (Presently designing feedback system being 0.6-0.8 nsec spacing.) • Push by* to 1.5 mm: need new IR (SC quadrupoles) with 15 mrad crossing angle and crab cavities

  27. Important Factors in Upgrade Direction • Project is “tunable” • Can react to physics developments • Can react to changing geopolitical situation • Project anti-commutes with linear collider • Will emerge from BABAR and Belle, but could be attractive to wider community in context of other opportunities • As we learn more about machine and detector requirements and design, can fine tune goals and plans within this framework • Project has headroom • Major upgrades to detector and machine, but none contingent upon completing fundamental R&D • Headroom for detector up to 5 x 1035; with thin pixels beyond • Headroom for machine up to 8.5 x 1035; requires additional rf, which can be staged into machine over time

  28. Luminosity Equation • When vertical beam-beam parameter is limited. • xy ~ 0.06 in PEP-II and KEKB. • To raise luminosity: lower by*, raise I & xy.

  29. Early SBF with 3 x 1035 • E+ = 8 GeV • E- = 3.5 GeV • RF frequency = partial 476 and partial 952. • I+ = 5.3 A • I- = 12.0 A • by* = 3 mm • bx* = 25 cm • Emittance = 42 nm • Bunch length = 3.3 mm • Crossing angle = ~15. mrad • Beam-beam parameters = 0.11 • N = 3450 bunches • L = 3 x 1035 cm-2s-1 • Site power with linac and campus = ~90 MW.

  30. Final SBF with 8.4 x 1035 • E+ = 8 GeV • E- = 3.5 GeV • RF frequency = 952 MHz • I+ = 10.1 A • I- = 22.8 A • by* = 2 mm • bx* = 15 cm • Emittance = 39 nm • Bunch length = 2.2 mm • Crossing angle = ~15. mrad • Beam-beam parameters = 0.11 • N = 6900 bunches • L = 8.4 x 1035 cm-2s-1 • Site power with linac and campus = ~120 MW.

  31. Possible Timeline for Super B Program Construction of upgrades to L = 5-7x1035 Super B Operation Super-B Program R&D, Design, Proposals and Approvals 2001 2003 2005 2006 2008 2010 2011 2012 Construction Installation LOI CDR Commission P5 Planned PEP-II Program (June 30, 2003) (End 2006) (PEP-II ultimate)

  32. Simulation: head-on vs finite-crossing • Beam-beam limit is ~0.05 for finite-crossing collision from the both simulations. (Not much difference between 11 & 15 mrad) • Head-on collision much improves beam-beam parameter. • Discrepancy between Weak-Strong and Strong-Strong simulation is a factor of 2 for head-on collisions. Weak-Strong Strong-Strong 11 mrad = half crossing angle [bunch current] [bunch current]

  33. Coherent synchrotron radiation Energy change as a function of z/sz KEKB LER/ 2.6A (5120) chamber height dependence bunch length dependence • Numerical simulations with mesh (T.Agoh and K.Yokoya) • Analytic formula is not reliable due to strong shielding. • Loss factor estimation : • No synchrotron oscillation and no interference between bends. • 1 V/pC for 6 mm bunch length (LER) • 10 V/pC for 3 mm bunch length (LER) ⇔ 30~40 V/pC in the ring

  34. S-KEKB Choice of b*x, ex • b*x=30, 20, 15 cm • ex=24, 18, 12 nm Strong-Strong Beam-Beam Simulations by K. Ohmi Our choice Achievable beam-beam parameters depends on b*x and ex.

  35. Super KEKB machine parameters Beam-beam parameter is obtained from simulations: strong-strong (weak-strong)

More Related