Author: Vieira, J.
Paper Title Page
WEPPP037 Experimental Study of Self Modulation Instability of ATF Electron Beam 2807
 
  • Y. Fang
    USC, Los Angeles, California, USA
  • M. Babzien, M.G. Fedurin, K. Kusche, R. Malone, V. Yakimenko
    BNL, Upton, Long Island, New York, USA
  • W.B. Mori
    UCLA, Los Angeles, California, USA
  • P. Muggli
    MPI, Muenchen, Germany
  • L.O. Silva, J. Vieira
    Instituto Superior Tecnico, Lisbon, Portugal
 
  Funding: US. Department of Energy.
We demonstrate experimentally for the first time the self-modulation of a relativistic electron bunch in a plasma. This demonstration serves as a proof-of-principle test for the mechanisms of transverse self-modulation of particle bunches in plasmas. It indicates the possibility of using long electron or proton bunches as drivers for plasma based accelerators. The long (~5ps) bunch available at BNL-ATF is used in this experiment and in the particle-in-cell OSIRIS. We use the 2D version for cylindrically symmetric geometries. The energy of the beam particles is measured after the plasma exit in the experiment. The obvious energy gain and loss by electrons indicates the excitation of longitudinal wakefields, and hence of transverse focusing fields. Both simulations and experiments show that the electron beamlets are formed at the scale of the plasma wavelength, and the number of beamlets changes as the plasma density is varied. We also measured the variation in beam transverse size downstream from the plasma as well as the variations in coherent transition radiation energy to demonstrate the effect of transverse self–modulation.
 
 
WEPPP052 Self-modulation of Long Particle Bunches in Plasmas at SLAC 2831
 
  • P. Muggli
    MPI, Muenchen, Germany
  • Y. Fang
    USC, Los Angeles, California, USA
  • M.J. Hogan
    SLAC, Menlo Park, California, USA
  • W.B. Mori
    UCLA, Los Angeles, California, USA
  • L.O. Silva, J. Vieira
    IPFN, Lisbon, Portugal
 
  The transverse self-modulation (SM) of ultra-relativistic, long particle bunches can lead to the generation of large amplitude wakefields*. In this work we show that the physics of SM could be investigated with the long electron and positron bunches available at SLAC**. The propagation of SLAC electron and positron bunches in 1 meter plasmas was modeled with OSIRIS. 3D simulations reveal that hosing may limit SM, but that shaped bunches with a hard-cut front ensure that saturation of SM can be reached. Cylindrically symmetric simulations show that the blowout regime can be achieved using these shaped bunches. Accelerating gradients in excess of 20 GeV/m are generated, and up to 10 GeV energy gain and loss are observed in the simulations at the 1% charge level after one meter of plasma. Because the blowout regime is reached, positron driven wakes lead to accelerating gradients that can be less than half than those of electrons. Simulations results outlining the SM results expected with the SLAC-FACET beam parameters will be presented.
* N. Kumar et al., Phys. Rev. Lett. 104, 255003 (2010).
** J. Vieira et al., submitted (2011).