Author: Silva, L.O.
Paper Title Page
WEPWA008 Measuring the Self-modulation Instability of Electron and Positron Bunches in Plasmas 2506
 
  • P. Muggli, O. Reimann
    MPI-P, München, Germany
  • E. Adli, V.K.B. Olsen
    University of Oslo, Oslo, Norway
  • J. Allen, S.J. Gessner, S.Z. Green, M.J. Hogan, M.D. Litos, B.D. O'Shea, V. Yakimenko
    SLAC, Menlo Park, California, USA
  • L.D. Amorim
    IST, Lisboa, Portugal
  • G. Andonian, C. Joshi, K.A. Marsh, W.B. Mori, N. Vafaei-Najafabadi, O. Williams
    UCLA, Los Angeles, California, USA
  • N.C. Lopes, L.O. Silva, J. Vieira
    Instituto Superior Tecnico, Lisbon, Portugal
  
  The self-modulation instability (SMI) * can be used to transform a long, charged particle bunch into a train of periodically spaced shorter bunches. The SMI occurs in a plasma when the plasma wake period is much shorter than the bunch length. The train of short bunches can then resonantly drive wakefields to much larger amplitude that the long bunch can. The SMI will be used in the AWAKE experiment at CERN, where the wakefields will be driven by a high-energy (400GeV) proton bunch. ** However, most of the SMI physics can be tested with the electron and positron bunches available at SLAC-FACET. *** In this case, the bunch is ~10 plasma wavelengths long, but can drive wakefields in the GV/m range. FACET has a meter-long plasma **** and is well equipped in terms of diagnostic for SMI detection: optical transition radiation for transverse bunch profile measurements, coherent transition radiation interferometry for radial modulation period measurements and energy spectrometer for energy loss and gain measurement of the drive bunch particles. The latest experimental results will be presented.
* N. Kumar et al., PRL 104, 255003 (2010)
** AWAKE Collaboration, PPCF 56 084013 (2014)
*** J. Vieira et al., PoP 19, 063105 (2012)
**** S.Z. Green et al., PPCF 56, 084011 (2014)
 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPWA008  
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MOPMA059 Lorentz boosted frame simulation of Laser wakefield acceleration using hybrid Yee-fft solver in quasi-3d geometry 691
 
  • P. Yu, A.W. Davidson, V.K. Decyk, W.B. Mori, A. Tableman, F.S. Tsung
    UCLA, Los Angeles, California, USA
  • F. Fiuza, L.O. Silva, J. Vieira
    IPFN, Lisbon, Portugal
  • R.A. Fonseca
    ISCTE - IUL, Lisboa, Portugal
  • W. Lu, X.L. Xu
    TUB, Beijing, People's Republic of China
  
  We present results from a preliminary study on modeling Laser wakefield acceleration (LWFA) with OSIRIS in a Lorentz boosted frame using a quasi-3D algorithm. In the quasi-3D algorithm, the fields and currents are expanded into azimuthal harmonics and only a limited number of harmonics are kept. Field equations in (r,z) space are solved for a desired number of harmonics in φ. To suppress the numerical Cerenkov instability (NCI) that inevitably arises due to the relativistic plasma drift in the simulation, we use a hybrid Yee-FFT solver in which the field equations are solved in (kz, r) space, where \hat{z} is the drifting direction. Preliminary results show that high fidelity LWFA boosted frame simulations can be carried out with no evidence of the NCI. Good agreement is found when comparing LWFA boosted frame simulations in the full 3D geometry against those in the quasi-3D geometry. In addition, we discuss how the moving window can be combined with the hybrid Yee-FFT solver to further speed up the simulation. The results indicate that unprecedented speed ups for LWFA simulations can be achieved when combining the Lorentz boosted frame technique, the quasi-3D algorithm, and a moving window.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA059  
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