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Beam-beam simulations

Beam-beam simulations. M.E. Biagini, P. Raimondi LNF/INFN, SLAC 2 nd Workshop on SuperB, Frascati 16 th March 2006. Outline. Round or flat? 4 beams scheme 2 beams scheme with asymmetric energies Conclusions. BB simulations.

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Beam-beam simulations

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  1. Beam-beam simulations M.E. Biagini, P. Raimondi LNF/INFN, SLAC 2nd Workshop on SuperB, Frascati 16th March 2006

  2. Outline • Round or flat? • 4 beams scheme • 2 beams scheme with asymmetric energies • Conclusions

  3. BB simulations • Evolution of the SuperB layout is a consequence of the beam-beam studies • Both luminosity and beam blow-up are the parameters to “watch” • Optimization of beam parameters must include Damping Ring optimization and Final Focus design

  4. Round or Flat ? • An extensive campaign of beam-beam simulations has been carried out to find the best beam parameters set • GuineaPig code by D. Schulte (CERN) has been used (same as ILC studies) • Round and Flat beams have been considered • Optimization of beam parameters performed with Mathematica + GuineaPig (see next talk by E. Paoloni)

  5. 4 Beams Scheme • Option of colliding 4 beams in a “charge compensation” scheme considered • GuineaPig modified to allow 4 beams (many thanks to D. Schulte !!!) • 4 identical beams (energy, beam sizes, current) simulated • Parameters from optimization studies

  6. 7GeV e+ 2 GeV e+ injection 2GeV e+ DR e- IP 5 GeV e+ & 3.5GeV e- SC Linac 4 GeV e- 0.5GeV SCLinac e+ e- Gun e- Dump Linear SuperB Double Pass 1st LNF Workshop on SuperB, Nov. 2005

  7. Compressor Decompressor FF IP FF Optional Acceleration and deceleration Optional Acceleration and deceleration Compressor DeCompressor SuperB ILCDR-like ILC ring with ILC FF ILC compressor Colliding every 50 turn Acceleration optional Crossing angle optional

  8. Optimized Round case • EP parameter set: • Npart = 7.x1010 • I = 5.6 A (for a 3Km ring) • sx = sy = 0.916 mm • sz = 0.8 mm • bx = by = 0.55 mm

  9. x,x’ y,y’ z,dE/E y,y’ x,x’ x,x’ z,dE/E y,y’ z,dE/E Round case Phase space after collision (x,x’), (y,y’), (z,dE/E) 2 Beams 4 Beams

  10. 4 beams, Round case

  11. 2 beams, Round case

  12. Optimized Flat case • PR parameter set: • Npart = 2.x1010 • I = 1.6 A (for a 3Km ring) • sx = 2.670 mm • sy = 12.6 nm • sz = 4. mm • bx = 2.5 mm • by = 80. mm

  13. y,y’ z,dE/E x,x’ x,x’ y,y’ z,dE/E x,x’ y,y’ z,dE/E Flat Case Phase space after collision (x,x’), (y,y’), (z,dE/E) 2 beams 4 beams

  14. 4 beams, Flat case Large blow up of all 4 beams

  15. 2 beams, Flat case Smaller blow up of 2 beams

  16. 4 Beams conclusions • 4 beams are more unstable than 2 beams, highly disrupted, with larger emittance blow ups and give lower luminosity • Not exhaustive analysis not excluded we can find better working parameter set in the future • Shorter beams seem to work better • Larger horizontal beam size is better • Higher energy definitely works better Possible choice for ILC !!!!

  17. 2 beams asymmetric energies • Studied the 2-beams scheme with asymmetric energies • 4x7 GeV case • PR parameter set: • Npart = 2.x1010 • I = 1.6 A (for a 3Km ring) • sx = 2.670 mm • sy = 12.6 nm • sz = 4. mm • bx = 2.5 mm • by = 80. mm

  18. Symmetric energies Y emittance blow-up: 3.x10-3

  19. Asymmetric energies (4x7 GeV) Y emittance blow-up: 4 GeV  5x10-3 7 GeV  3x10-3

  20. Asymmetric energies (4x7 GeV)with transparency condition (I) • Np(4 GeV) = 2.65x1010 • Np(7 GeV) = 1.51x1010 • I(4 GeV) = 2.1 A • I(7 GeV) = 1.2 A Y emittance blow-up: 4 GeV  3.5x10-3 7 GeV  3.6x10-3

  21. Asymmetric energies (4x7 GeV)with asymmetric bunch lengths • Np(4 GeV) = 2x1010 • Np(7 GeV) = 2x1010 • I(4 GeV) = 1.6 A • I(7 GeV) = 1.6 A • sz(4 GeV) = 3.02 mm • sz(7 GeV) = 5.29 mm Y emittance blow-up: 4 GeV  4. x10-3 7 GeV  4. x10-3

  22. x e- e+ z Alternative scheme for beam-beam compensation of energy asymmetry • HER: larger by*, smaller ey,ex • LER: smaller by*, larger ey,ex • No need for high current in LER • Better for IBS, Touschek in LER • Work in progress, coordination with DR design

  23. Conclusions • More work is needed to understand if the 4 beams scheme can work at low energy • For the asymmetric energies “equal blow up” can be obtained with transparency condition (asymmetric I, or sz) • Alternative scheme is possible • Optimization work will continue to finalize the beam-beam parameters

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