Open AccessCollective effects in a diffraction‐limited storage ring
Author(s) -
Nagaoka Ryutaro,
Bane Karl L. F.
Publication year - 2014
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s1600577514015215
Subject(s) - storage ring , thermal emittance , beam (structure) , instability , physics , synchrotron radiation , synchrotron , diffraction , coupling (piping) , optics , scattering , transverse plane , electrical impedance , particle accelerator , materials science , mechanics , engineering , structural engineering , quantum mechanics , metallurgy
This paper gives an overview of collective effects that are likely to appear and possibly limit the performance in a diffraction‐limited storage ring (DLSR) that stores a high‐intensity ultra‐low‐emittance beam. Beam instabilities and other intensity‐dependent effects that may significantly impact the machine performance are covered. The latter include beam‐induced machine heating, Touschek scattering, intra‐beam scattering, as well as incoherent tune shifts. The general trend that the efforts to achieve ultra‐low emittance result in increasing the machine coupling impedance and the beam sensitivity to instability is reviewed. The nature of coupling impedance in a DLSR is described, followed by a series of potentially dangerous beam instabilities driven by the former, such as resistive‐wall, TMCI (transverse mode coupling instability), head–tail and microwave instabilities. In addition, beam‐ion and CSR (coherent synchrotron radiation) instabilities are also treated. Means to fight against collective effects such as lengthening of the bunch with passive harmonic cavities and bunch‐by‐bunch transverse feedback are introduced. Numerical codes developed and used to evaluate the machine coupling impedance, as well as to simulate beam instability using the former as inputs are described.