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The use of crab cavities in colliders to increase luminosity

The use of crab cavities in colliders to increase luminosity. Graeme Burt Lancaster University / Cockcroft Institute. ILC Crab Cavity Collaboration. Cockcroft Institute : Graeme Burt (Lancaster University) Richard Carter (Lancaster University) Amos Dexter (Lancaster University)

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The use of crab cavities in colliders to increase luminosity

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  1. The use of crab cavities in colliders to increase luminosity Graeme Burt Lancaster University / Cockcroft Institute

  2. ILC Crab Cavity Collaboration Cockcroft Institute : Graeme Burt (Lancaster University) Richard Carter (Lancaster University) Amos Dexter (Lancaster University) Imran Tahir (Lancaster University) Richard Jenkins (Lancaster University) Philippe Goudket (ASTeC) Peter McIntosh (ASTeC) Alex Kalinin (ASTeC) Carl Beard (ASTeC) Lili Ma (ASTeC) Mike Dykes (ASTeC) • FNAL • Leo Bellantoni • Mike Church • Timergali Khabiboulline • Brian Chase • CERN • Daniel Schulte • Andrea Latina • SLAC • Chris Adolphson • Zenghai Li • Liling Xiao

  3. Effect of the crossing angle on luminosity Head-on collision Maximum luminosity Crossing angle introduced Reduced luminosity due to crossing angle Crossing angle with crab rotation Effective head-on collision

  4. Transverse deflecting dipole mode • The crab cavity imparts a transverse momentum to the bunch. • The bunch continues to rotate outside the cavity. Crab Cavity IP Separation from the Interaction Point ~15m ~0.12m/cell

  5. beam   magnetic field electric field   ● elliptical cavity TM110 dipole mode cavity • Use of the magnetic field of a TM110 dipole mode • The field gives a phase-dependant transverse momentum kick to the beam Magnetic field distribution of a TM110 mode

  6. Effect of distance between crab cavity and focusing quadrupole Angle given by crab kick a x1 QF1 QD0 Position of the crab cavity Trajectory of a particle at one end of the bunch Deflection x1>x2 x2 QF1 QD0 a

  7. Voltage Stability For optimum cell length qcrab is proportional to the maximum magnetic field in the cavity voltage error induces errors in bunch rotation θerror

  8. Bunch arrival time Jitter Late bunch without transverse kick Late bunch with transverse kick IP Collision point It is found that the crab cavity can correct for variation in bunch arrival time by providing a total transverse kick to early or late bunches, such that both bunch collide head-on.

  9. Absolute cavity phase error Collision point Dx IP displaced IP Absolute cavity phase error is not a major concern

  10. electron bunch Δx positron bunch Interaction point Phase Jitter Crabbed crossing angle with phase jitter Effective head-on collision

  11. Cavity Alignment If the cavity has a roll misalignment it will cause a small crossing angle in the vertical plane. This will significantly reduce luminosity.

  12. Higher Order Modes TM010 accelerating mode Higher order modes TM110v (SOM) Need to extract the fundamental mode TM011 (HOM) Extraction of the lower order mode and the higher order modes is essential to minimise disruption of the beam. frequency Beam-pipe cut-off The cavity design should allow for as much LOM/HOM damping as possible. TE111 (HOM) TM110h crabbing mode

  13. Transverse Wakefield • Collective Transverse Wakefields will kick the bunch similar to a phase error. • The collective effects have been simulated in MAFIA and the effects studied using a tracking code (PLACET). • These results have been used to place damping requirements on the higher order modes.

  14. ILC CC System Specification

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