Analytical and numerical analysis of longitudinally coupled transverse Dynamics of Pulse Picking by Resonant Ecitation in storage rings serving Timing and high flux users simultaneously

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 I