Analytical and numerical analysis of longitudinally coupled transverse dynamics of Pulse Picking by Resonant Excitation in storage rings serving timing and high-flux users simultaneously

Abstract

Abstract The pulse picking by resonant excitation (PPRE) method is applied at BESSY II to provide single bunch light to timing users while operating a multi-bunch filling pattern. This method can provide single bunch light to all beamlines simultaneously since the emittance of a selected bunch is increased by a quasi-resonant incoherent excitation close to the first synchrotron sideband of the betatron oscillation frequency. This gives high-flux to users by separating the synchrotron radiation from one horizontally enlarged bunch from the light of the multi-bunch beam. The properties of the excited bunch depend strongly on lattice parameters such as beta-functions and horizontal chromaticity, and the frequency and amplitude of the excitation signal. A theoretical interpretation by applying a linear transfer-matrix analysis based on the Liouville’s theorem is derived to illustrate a quantitative relation between the beam size and lattice parameters. In addition, measurements and numerical simulations show a monotonic increase of the timing bunch emittance as a function of the excitation amplitude at the first synchrotron sideband of the betatron oscillation frequency. The observed excitation-amplitude-dependent features of the transverse bunch size are confirmed by measurements with two independent diagnostics at BESSY II.