New aspects of longitudinal instabilities in electron storage rings

• Published in: Scientific reports Vol. 8; no. 1; pp. 11918 - 8
• Main Authors: Blednykh, A., Bacha, B., Bassi, G., Cheng, W., Chubar, O., Derbenev, A., Lindberg, R., Rakitin, M., Smaluk, V., Zhernenkov, M., Chen-Wiegart, Yu-chen Karen, Wiegart, L.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 09.08.2018; Nature Publishing Group
• Subjects: 639/766/419; 639/766/419/1131; Energy; Humanities and Social Sciences; Laboratories; Light; multidisciplinary; PARTICLE ACCELERATORS; Radiation; Radiation measurement; Science; Science (multidisciplinary); Simulation
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-018-30306-y

Novel features of the longitudinal instability of a single electron bunch circulating in a low-emittance electron storage ring are discussed. Measurements and numerical simulations, performed both in time and frequency domain, show a non-monotonic increase of the electron beam energy spread as a function of single bunch current, characterized by the presence of local minima and maxima, where a local minimum of the energy spread is interpreted as a higher-order microwave instability threshold. It is also shown that thresholds related to the same zero-intensity bunch length depend linearly on the accelerating radio frequency voltage. The observed intensity-dependent features of the energy spread, confirmed by measurements with two independent diagnostics methods, i.e. horizontal beam profile measurements by a synchrotron light monitor and photon energy spectrum measurements of undulator radiation, are given a theoretical interpretation by applying a novel eigenvalue analysis based on the linearized Vlasov equation.