Author: Li, S.Z.
Paper Title Page
TUPME050 Electron Bunch Self-modulation in Long Plasmas at SLAC FACET 1476
 
  • P. Muggli
    MPI, Muenchen, Germany
  • E. Adli, V.K.B. Olsen
    University of Oslo, Oslo, Norway
  • L.D. Amorim
    IST, Lisboa, Portugal
  • S.J. Gessner, M.J. Hogan, S.Z. Li, M.D. Litos
    SLAC, Menlo Park, California, USA
  • C. Joshi, K.A. Marsh, W.B. Mori, N. Vafaei-Najafabadi
    UCLA, Los Angeles, California, USA
  • N.C. Lopes, J. Vieira
    Instituto Superior Tecnico, Lisbon, Portugal
  • O. Reimann
    MPI-P, München, Germany
 
  Funding: This work performed in part under DOE Contract DE-AC02-76SF00515.
We study the physics of self-modulation instability (SMI) of long, when compared to the wake wavelength, electron and positron bunches in pre-formed plasmas at SLAC-FACET. Self-modulation is the result of the action of focusing/defocusing transverse wakefields on the bunch radius. Self-modulation leads to observables such as overall defocusing of the bunch, periodic modulation of the bunch radius at the wake period and multi-GeV energy gain/loss by drive bunch particles. Defocusing is observed from OTR images, radial self-modulation from CTR spectra and interferometric traces and energy gain/loss from energy spectra with sub-GeV resolution. The plasma density is varied by changing the vapor density ionized by a laser/axicon system. The bunch length, radius and charge can also be varied. The SMI can be seeded using a notch collimator system. Numerical simulations indicate that seeding the SMI mitigates the hose instability. Hose instability can also be seeded, for example by using the RF deflecting cavity to impart a tilt to the incoming bunch axis. The overall experimental plan as well as the latest experimental results obtained with electron bunches will be presented.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME050  
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