TUAM1X —  Parallel Session   (05-Jul-16   09:00—09:25)
Chair: G. Franchetti, GSI, Darmstadt, Germany
Paper Title Page
TUAM1X01
 A Two Particle Model for Study of Effects of Space-Charge Force on Strong Head-Tail Instabilities.  
 
  • Y.H. Chin
    KEK, Ibaraki, Japan
  • M. Blaskiewicz
    BNL, Upton, Long Island, New York, USA
  • A. Chao
    SLAC, Menlo Park, California, USA
  • Y. Shobuda
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  
  In this talk, I present a new two particle model for study of strong head-tail instabilities in the presence of the space-charge force. It is a simple expansion of the well-known two particle model. No chromaticity effect is included. It leads to a formula for the growth rate as a function of the two dimensionless parameters: the space-charge tune shift parameter (normalized by the synchrotron tune) and the wake field strength, Υ. The 3-dimensional contour plot of the growth rate as a function of those two dimensionless parameters reveals stopband structures. Many simulation results generally indicate that a strong head-tail instability can be damped by a weak space-charge force, but the beam becomes unstable again when the space-charge force is further increased. The new two particle model indicates a similar behavior. In weak space-charge regions, additional tune shifts by the space-charge force dissolve the mode-coupling. As the space-charge force is increased, they conversely restore the mode-coupling, but then a further increase of the space-charge force decouples the modes again. This mode coupling/decoupling behavior creates the stopbands structures.  
slides icon Slides TUAM1X01 [9.087 MB]