Abstract
Comment on “Adiabatic excitation of longitudinal bunch shape oscillations”
Highlights
There is no discussion of the circumstances under which the adiabatic approach might be superior to a quarter period bunch rotation triggered by a sudden jump from low to high rf voltage
The reported experimental results from the alternating gradient synchrotorn (AGS) at Brookhaven National Laboratory are in qualitative agreement with a first-order perturbation treatment given in the subject paper
For a single bunch of 5 3 1012 protons, image current and space charge forces will influence the dynamics by a potential well distortion which varies as the bunch length changes
Summary
The basic premise of the subject paper [1] is that modulating the amplitude of the rf voltage in a synchrotron at a frequency near twice the synchrotron frequency with slow increase of the modulation percentage from near 0 to more than 50% can develop quadrupole mode (shape) oscillation without significant emittance growth. The desire to make very narrow bunches for, say, m collider is frustrated by the oscillation of the extended bunch in the nonlinear region of the rf bucket This problem can be addressed with a second harmonic rf system if the need justifies the cost. The purpose of the modeling reported below is to show that the means for answering many of the questions about the comparison of the analysis with the experiment are readily available. This comment does not address which are the interesting questions. The similarity between the simple model and the observations in the AGS is rather striking
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