Coupling of Transverse and Longitudinal Collective Motions Due to Closed Orbit Distortion and Dispersion in a Two-Particle Model

摘要

In order to explain the large discrepancy between the measured transverse coherent tune shifts and analytical ones in a short bunch in PETRA, the effects of the closed orbit distortion y(sub co) and the dispersion eta on a beam instability is studied with a two-particle model. It follows the result which supports Kohaupt's previous results; they hardly contribute to real tune shift, while the momentum dependence of the wake force can make a beam unstable, with the growth rate which is proportional to the product of y(sub co) and eta. (ERA citation 14:003376)