The Effect of Non-Zero Closed Orbit on Electron-Cloud Pinch Dynamics

A study on the pinch dynamics of electron cloud during a bunch passage under the effect of a single arbitrary order multipole was presented at IPAC2011. The complexity of the pinch pattern is directly related to the order of the multipolar field. However, in a realistic situation, the proton beam will not be located in the center of the vacuum chamber. If the beam is offset a new pinch regime is encountered, where feed-down effects and asymmetry of pinch density render the dynamics more challenging. In this paper we discuss the pinch dynamics with orbit offset, including the resulting orbit variation along a bunch, and address their relevance for the incoherent effect of the electron cloud.