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Towards an extremely-flat beam optics with large crossing angle for the LHC

Warsaw, 25 th April 2012. Towards an extremely-flat beam optics with large crossing angle for the LHC. José L. Abelleira, PhD candidate EPFL, CERN Beams dep. Supervised by F. Zimmermann, CERN Beams dep.

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Towards an extremely-flat beam optics with large crossing angle for the LHC

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  1. Warsaw, 25th April 2012 Towards an extremely-flat beam optics with large crossing angle for the LHC José L. Abelleira, PhD candidate EPFL, CERN Beams dep. Supervised by F. Zimmermann, CERN Beams dep. Thanks to: S. Fartoukh, S.Russenschuck (CERN), D.Shatilov (BINP SB RAS,Novosibirsk), R. Tomas (CERN), C. Milardi, M. Zobov (INFN/LNF, Frascati (Roma))

  2. Contents Flat beam optics. Comparison. Double half-quadrupole Large Piwinski angle & crab-waist collisions Luminosity Future work, open questions Conclusions Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.

  3. Flat beam optics Local chromatic correction in Y. First time ever for LHC! Peak luminosity To increase luminosity: -Reduce both σx* and σ y* -Substantially reduce σy* sext1 sext3 sext2 βx*=1.5 m βy*=1.5 cm Crab –waist collisions Chromatic correction βx*βy*=15cmx15cm (nominal ATS optics with crab cavities) π/2 π/2 π/2 3π/2 π 5π/2 Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.

  4. Reference orbit 15σy 45 mm 2 mrad 15σx Minimum required according to beam-beam simulations. σx/ σy=10 Large crossing angle-> large Piwinski angle Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.

  5. Actual LHC optics IP The 2 beams see opposite gradients + + Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.

  6. Flat beam LHC optics IP The 2 beams see the same gradients - + How to produce opposite gradient in the same pipe? - + Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.

  7. Double half-quad S.Russenschuck NbTi g=115 T/m B0=-5.8 T Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.

  8. Kick due to the dipolar term Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.

  9. Matching Arc (MQ11) Arc (MQ11) βx=20 m βy=207 m Dx=0.6 m βx=127 m βy=21 m Dx=1.5 m FF MS DS Separation bending magnets Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.

  10. Large Piwinski angle Luminosity reduction through F but… 1-Decrease overlapping area. Lower βy decrease Hourglass effect limits βy decrease Head-on or small φ Large Piwinski angle ! Collision section (CS) 2-More particles N for the same beam-beam tune shift 3-It opens the possibility for crab-waist collisions Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.

  11. Crab-waist collisions With Large Piwinski Angle Collision Point ≠ Interaction Point P.Raimondi, D.Shatilov, M. Zobov Normal collision scheme Crab-waist collision scheme Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.

  12. Crab-waist collisions P.Raimondi, D.Shatilov, M. Zobov Sextupole strength In particular Conditions Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.

  13. Crab-waist simulations CW = 0 CW = 0.5 Dmitry Shatilov Mikhail Zobov Resonance suppression Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.

  14. Luminosity gain Luminosity (1034 cm-1s-1 ) Main limitation: the crossing angle due to the separation of the double half quad Further improvements in the double half-quad. design can reduce the crossing angle (Nb3Sn) θ/2= 2 mrad θ/2=1 mrad Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.

  15. Flat emittance εy ε ε βy* σhq βhq σhq βhq εx Limitation: aperture of the half quad Solution: reduce εy keeping constant εxεy • Squeeze of the emittance ellipse • βy increase in the half-quad.->reduction on σy*= sqrt(εyβy*) • βx decrease in the half-quad.->reduction of horizontal chromatic aberrations • ->increase on σx*= sqrt(εxβx*) • ->Geometric reduction factor increased F=(1+(ϴ/2)σz/σx)-1/2 • Luminosity increase through significant σy* reduction and F increase Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.

  16. Flat emittance Keep εxεy constant and vary εx/εy Θ=4 mrad N=2x1011 Luminosity Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.

  17. Work in the next months • Study of the aberrations • Rematch the dispersion • Improvement of the half-quad • Dynamic aperture • Beam-beam simulations Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.

  18. Open questions • Field quality of the double half-quad & correction scheme • Dispersion matching for the chromatic correction • 2nd order dispersion cancellation Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.

  19. Conclusions • An extremely-flat beam optics (βy*/βy*=100) is conceptual possible for LHC • Large Piwinski angle, to reduce the collision area and allow for a lower βy decrease • Local vertical chromatic correction • Possibility to have crab waist collisions that can increase luminosity and suppress resonances • Can accept higher brightness. • The performance of the new optics can be improved • Future half-quad designs (Nb3Sn) • Using a flat emittance • HE-LHC? Already flat emittance due to SR Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.

  20. Thank you… …For your attention Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.

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