Abstract
Crab crossing scheme is an essential collision scheme to achieve high luminosity for the future colliders with large crossing angles. However, when bunch length of one or both colliding beams is comparable with the wavelength of the crab cavity voltage, the nonlinear dependence of the crabbing kick may present a challenge to the beam dynamics of the colliding beams and impact the beam quality as well as the luminosity lifetime. In this paper, the results of nonlinear dynamics in the crab crossing scheme are presented, using both analytical and numerical studies. The result indicates that higher-order synchro-betatron resonances may be excited in the crab crossing scheme with large crossing angle, which causes the beam quality deterioration and luminosity degradation. The studies also reveal possible countermeasures to suppress the synchro-beta resonance, hence mitigate the degradation of beam quality and luminosity.
Highlights
A crossing angle at the interaction region (IR) allows for a fast beam separation and smaller beta function at the interaction point (IP)
It is essential to study the beam dynamics consequence when kcσz ∼ 1. We refer to this as the finite bunch length effect, and will study the dynamics of such effect using an example with the parameters similar to that of the future Election-Ion Collider (EIC) which adopts the crab crossing scheme
In the situation of two interaction points (IPs) in the EIC rings, we will demonstrate that the first kind synchrobetatron resonances in Eq (33) can be cancelled or reduced by proper transformation between two IPs
Summary
A crossing angle at the interaction region (IR) allows for a fast beam separation and smaller beta function at the interaction point (IP). Our studies will focus on the dynamics for the electron-ion collision, which usually has much larger crossing angle and unsymmetric colliding beams. The bunch length of the beam, especially the ion beam, is usually not short enough, due to longitudinal dynamics and lack of an effective cooling method. It is essential to study the beam dynamics consequence when kcσz ∼ 1 We refer to this as the finite bunch length effect, and will study the dynamics of such effect using an example with the parameters similar to that of the future Election-Ion Collider (EIC) which adopts the crab crossing scheme.
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