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Accelerator Seminar


"Microbunching Instability in a Chicane:  Two-Dimensional Mean Field Treatment"

Gabriele Bassi






We study the microbunching instability in a bunch compressor by a parallel code with some improved numerical algorithms.  The two-dimensional charge/current distribution is represented by a Fourier series, with coefficients determined through Monte Carlo sampling over an ensemble of tracked points. This gives a globally smooth distribution with low noise.  The field equations are solved accurately in the lab frame using retarded potentials and a novel choice of integration variables that eliminates singularities.  We apply the scheme with parameters for the first bunch compressor system of FERMI@Elettra, with emphasis on the amplification of a perturbation at a particular wavelength and the associated longitudinal bunch spectrum.  Gain curves are in rough agreement with those of the linearized Vlasov system at intermediate wavelengths, but show some deviation at the smallest wavelengths treated and show the breakdown of a coasting beam assumption at long wavelengths.




Thursday, September 10, 2009

3:30 p.m. - 4:30 p.m.
CEBAF Center, Room L102/104

Talk Slides: (Slides)

Dr. Alex Bogacz or Anne-Marie Valente.