NSLS-II Friday Lunchtime Seminar

Several instability thresholds and special waveform beam pattern have been observed during measurements of the electron beam energy spread σ_δ versus single-bunch current I_0 in NSLS-II. The experimental data have been collected from: the synchrotron light monitor (SLM) camera installed in a low dispersion area of the NSLS-II storage ring, the Full-Width Half-Maximum size of the In-Vacuum Undulator harmonic, the stripline kicker as a part of the bunch-by-bunch transverse feedback system and the large gap dipole chamber of Optical Extraction Beamline in NSLS-II. With mentioned measurement techniques we were able to confirm, that the microwave beam pattern behavior as a current dependent effect. The numerical simulations of the Vlasov-Fokker-Planck (VFP) equation with the longitudinal impedance budget simulated by the GdfidL code for a 0.3mm bunch length and the total longitudinal wakepotential W_(||,tot)(s), allowed us to reproduce the energy spread dependence on the single bunch current numerically for different lattices, bare lattice and regular operational lattice with all insertion devices magnet gap closed, including 3 damping wigglers. The present talk will be based on the results published in the Scientific Reports, 2018: A. Blednykh, B. Bacha, G. Bassi, W. Cheng, O. Chubar, A. Derbenev, R. Lindberg, M. Rakitin, V. Smaluk, M. Zhernenkov, Yu-chen Karen Chen-Wiegart and L. Wiegart, "New aspects of longitudinal instabilities in electron storage rings", Scientific Reports volume 8, Article number: 11918 (2018).