Stability of coherent synchrotron oscillations with space charge

The stability of longitudinal dipole oscillations in Gaussian bunches is studied for different rf wave forms and with nonlinear space charge. In a previous study [O. Boine-Frankenheim and T. Shukla, Phys. Rev. ST Accel. Beams 8, 034201 (2005)], the space charge induced loss of Landau damping and the bunch response to rf phase modulations was analyzed for elliptic distributions. The present study investigates Landau damping of dipole modes with nonlinear space charge in Gaussian bunches. The stability boundary resulting from a dispersion relation is compared with stability scans performed within a self-consistent simulation scheme. The results are compared with numerically obtained beam transfer functions.