Abstract
In the article of Migliorati, Aumon, Koukovini-Platia, Huschauer, Metral, Sterbini and Wang [Phys. Rev. Accel. Beams 21, 120101 (2018)], hereafter the Article and the Authors, the long-standing qualification of the PS instability as the transverse mode-coupling instability, or TMCI, is not mentioned, while a model of the beam breakup (BBU) is discussed. Do the observations and modeling of the Article refute the long-standing idea that the PS instability is the TMCI?
Highlights
It was assumed, and not just at CERN, that when the coherent tune shift of a bunch is comparable with the synchrotron tune, the bunch becomes unstable due to the transverse mode coupling instability (TMCI), more or less independently of the space charge (SC)
This assumption appeared to be supported by measurements and simulations, so it seemed to be well justified to classify the transverse instabilities in CERN PS and SPS rings as TMCI
In that EPAC 2000 paper, the following was written about the PS instability: “... this instability is equivalent to the Transverse Mode Coupling instability of Kohaupt in terms of coupling of head-tail modes
Summary
It was assumed, and not just at CERN, that when the coherent tune shift of a bunch is comparable with the synchrotron tune, the bunch becomes unstable due to the transverse mode coupling instability (TMCI), more or less independently of the space charge (SC). This assumption appeared to be supported by measurements and simulations, so it seemed to be well justified to classify the transverse instabilities in CERN PS and SPS rings as TMCI. This conviction was expressed by CERN-associated authors many times when the instabilities were discussed, at least since the year 2000, when Ref.
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