2017/09/05 by V. Kornilov, Kornilov, Vladimir, Oliver Boine‐Frankenheim +1
Engineering · #Accelerator Physics (physics.acc-ph) #Acoustic Wave Phenomena Research #FOS: Physical sciences #Geophysics and Sensor Technology #Vibration Control and Rheological Fluids
paper · pdf · doi:10.48550/arxiv.1709.01425
openalex publication_date 2017/09/05 · openalex created_date 2017/09/15 · openalex updated_date 2026/07/28
Landau damping of head-tail modes in bunches due to spreads in the tune shift can be a deciding factor for beam stability. We demonstrate that the coherent tune shifts due to reactive impedances can enhance the space-charge induced damping and change the stability thresholds (here, a reactive impedance implies the imaginary part of the impedance of both signs). For example, high damping rates at strong space-charge, or damping of the k=0 mode, can be possible. It is shown and explained, how the negative reactive impedances (causing negative coherent tune shifts similarly to the effect of space-charge) can enhance the Landau damping, while the positive coherent tune shifts have an opposite effect. It is shown that the damping rate is a function of the coherent mode position in the incoherent spectrum, in accordance with the concept of the interaction of a collective mode with resonant particles. We present an analytical model, which allows for quantitative predictions of damping thresholds for different head-tail modes, for arbitrary space-charge and coherent tune-shift conditions, as it is verified using particle tracking simulations.