Coherent beam-beam modes in the LHC

by Maria Paz Zorzano (CERN)

Thursday 2 Mar 2000, 16:00 → 16:15 Europe/Zurich

SL Auditorium (CERN)

In colliding beam facilities where two counter rotating beams repeatedly cross each other, the electromagnetic fields of the two charge distributions have strong effects on the particle dynamics. This interaction is known as the beam-beam force and is the most important non-linearity at high energy. The beam-beam force can excite coherent modes of oscillations in the bunches. Landau damping can potentially damp these oscillation modes. For the LHC, experimental, analytical and tracking studies foresee that the collision of two beams with equal tunes, sizes and current ratio will excite two coherent dipole modes whose frequencies lie outside of the incoherent tune spread of the beam. This implies the loss of Landau damping of the coherent modes and may result in instability driven by any small impedance component of the vacuum chamber. The physics of these coherent modes and the mechanism of existence or lack of Landau damping are discussed and explained in detail. The implications for the operation of the LHC and possible cures to restore Landau damping are presented. The side effects and further consequences of the cures are evaluated and discussed. This seminar is intended for non-specialists.

Organiser(s): Werner Herr / SL Division

Note: Tea and coffee will be served at 15:30 in front of the Auditorium

more information more information