Accelerator Physics Seminar

Coherent beam-beam instability in collision with a large crossing angle

Start:2017/06/29 (Thu) 10:00 AM
End:2017/06/29 (Thu) 11:30 AM
Location:2nd buld, 1F, Meeting room, Middle

Speaker:Kazuhito Ohmi
Contact:K.Ohmi (PHS 4413)


In recent years the "crab waist collision'' scheme has become popular for circular e+e- colliders. The designs of several future colliders are based on this scheme. Until recently the beam-beam effects for collisions under a large crossing angle with or without crab waist were mostly studied using weak-strong simulations. We here present a strong-strong simulation result, in which a novel strong coherent head-tail instability is seen, which can limit the performance of proposed future colliders. We explain the underlying instability mechanism starting from the "wake force'' induced by the beam-beam interaction. Using this beam-beam wake, the beam-beam head tail modes are studied by an eigenmode analysis. The instability may affect all collider designs based on the crab waist scheme. We suggest an experimental verification at SuperKEKB during its commissioning Phase II.

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