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Beam-beam simulations

Beam-beam simulations. M.E. Biagini, K. Ohmi, E. Paoloni, P. Raimondi, D. Shatilov, M. Zobov INFN Frascati, KEK, INFN Pisa, SLAC, BINP April 26th, 2006 UK SuperB Meeting, Daresbury. Outline. GuineaPig simulations & Automatization 2 beams scheme with asymmetric energies

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Beam-beam simulations

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  1. Beam-beam simulations M.E. Biagini, K. Ohmi, E. Paoloni, P. Raimondi, D. Shatilov, M. Zobov INFN Frascati, KEK, INFN Pisa, SLAC, BINP April 26th, 2006 UK SuperB Meeting, Daresbury

  2. Outline • GuineaPig simulations & Automatization • 2 beams scheme with asymmetric energies • Crab waist simulations: • DAFNE • SuperB

  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”: figure of merit is now L/log(eblowup/e) • Optimization of beam parameters must include Damping Ring optimization and Final Focus design

  4. First simulations • 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) in this first phase • Optimization of beam parameters for round beams case was performed interfacing GuineaPig with Mathematica • Round and flat, 2 and 4 beams studied

  5. GuineaPig to Mathematica E. Paoloni, 2nd SuperB LNF Workshop

  6. E. Paoloni, 2nd SuperB LNF Workshop Round case test • Tested first with round beams • Search of maximum L with a scan of parameters space L/log(eblowup/e) L/crossing Optimum region Scan of the bx,sx plane Scan of the sx,sz plane

  7. 4 Beams tests • 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 !!!!

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

  9. 2 beams asymmetric energies • Studied the 2-beams scheme with asymmetric energies for 4x7 GeV case: • Npart = 2.x1010 • I = 1.6 A (for a 3Km ring, 6000 bunches) • sx = 2.670 mm • sy = 12.6 nm • sz = 4. mm • bx = 2.5 mm • by = 80. mm • q= 2x25 mrad

  10. Study of emittance blow-up Symmetric E Asymmetric E (4x7 GeV) Y emittance blow-up: 4 GeV  5x10-3 7 GeV  3x10-3 Y emittance blow-up: 3x10-3

  11. 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

  12. 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  4x10-3 7 GeV  4x10-3

  13. Crab-waist simulations • The new idea by Pantaleo is being checked by several beam-beam codes: • Guinea-Pig: strong-strong , ILC centered • BBC (Hirata): weak-strong • Lifetrack (Shatilov): weak-strong with tails growths calculation • Ohmi: weak-strong (strong-strong to be modified for long bunches and large angles) Storage rings

  14. x e- e+ 2Sx/q q 2Sz*q z 2Sz 2Sx Vertical waist has to be a function of x: Z=0 for particles at –sx(- sx/2 at low current) Z= sx/2q for particles at + sx(sx/2 at low current)

  15. GuineaPig Collisions with uncompressed beams Crossing angle = 2*25 mrad Relative Emittance growth per collision about 1.5*10-3 eyout/eyin=1.0015

  16. DAFNE case (M.Zobov, LNF) • Hirata’s BBC code simulation(weak-strong, strong beam stays gaussian, weak beam has double crossing angle) • Np = 2.65x1010, 110 bunches • Ib = 13 mA (present working current) • sx = 300 mm, sy = 3 mm • bx = 0.3 m, by = 6.5 mm • sz = 25 mm (present electron bunch length) • q = 2x25 mrad • YIP = y+0.4/(q * x * y’) crabbed waist shift • Lo=2.33x1024 (geometrical) • L(110 bunches,1.43A) = 7.7x1032 • Lequil=6x1032

  17. n/q (Geometric) Luminosity Scan vs crab waist n/q Peak around 0.3/q Takes into account both bb interactions and geometric factor due to crab waist M.Zobov, LNF

  18. n/q n/q Vertical Tails (max amplitude after 10 damping times) Vertical Size Blow-up M.Zobov, LNF

  19. Present WP:nx = 0.11ny = 0.19Possible WP:nx = 0.057 ny = 0.097 Luminosity vs bunch current for 2 different working points M.Zobov, LNF

  20. Luminosity with shorter bunch and smaller sx (preliminary) 110 bunches M.Zobov, LNF

  21. Some resonances Crab waist No crab waist 1Qx = 2Qy (present with crossing angle only) 2Qx = 2Qy M.Zobov, LNF

  22. Ay = 90 Ay =45 Beam-Beam Tails (D.Shatilov, BINP) Without Crab Waist With Crab Waist Vertical tails growth Greatly reduced (A is the amplitude in number of beamsize s) Bunch core blowup also reduced

  23. SuperB LuminosityOhmi’s weak-strong code K2 is the strength of the sextupolar nonlinearity introduced to have crab waist

  24. SuperB vertical blow-up Ohmi’s weak-strong code

  25. Conclusions • For the asymmetric energies “equal blow up” can be obtained with transparency condition (asymmetric I, or sz) • The “crab waist” scheme has shown big potentiality and exciting results  LNF, BINP and KEKB physicists are working on the bb simulation with different codes to explore its properties and find the best set of parameters • This scheme is promising also for increasing luminosity at existing factories, as DAFNE, KEKB and possibly PEPII

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