IPAC2012 - List of Authors (Silva, L.O.)

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).

WEPPR089	Experimental Progress: Current Filamentation Instability Study	3141
	B.A. Allen, P. Muggli USC, Los Angeles, California, USA M. Babzien, M.G. Fedurin, K. Kusche, V. Yakimenko BNL, Upton, Long Island, New York, USA C. Huang LANL, Los Alamos, New Mexico, USA J.L. Martins, L.O. Silva IPFN, Lisbon, Portugal W.B. Mori UCLA, Los Angeles, California, USA
	Funding: Work supported by: National Science Foundation and US Department of Energy. Current Filamentation Instability, CFI, is of central importance for the propagation of relativistic electron beams in plasmas. CFI has potential relevance to astrophysics, magnetic field and radiation generation in the afterglow of gamma ray bursts, and inertial confinement fusion, energy transport in the fast-igniter concept. An experimental study of this instability is underway at the Accelerator Test Facility, ATF, at Brookhaven National Laboratory with the 60MeV electron beam and centimeter length capillary discharge plasma. The experimental program includes the systematic study and characterization of the instability as a function of beam (charge, transverse and longitudinal profile) and plasma (plasma density) parameters. Specifically, the transverse beam profile is measured directly at the plasma exit using optical transition radiation from a thin gold-coated silicon window. Experimental results show the reduction of the beam transverse size and the appearance of multiple (1-4) filaments and are a function of the plasma density. We will present simulation and experimental results, provide discussion of these results and outline next steps in the experiment.

Paper

Title

Page

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).

WEPPR089

Experimental Progress: Current Filamentation Instability Study

3141

B.A. Allen, P. Muggli
USC, Los Angeles, California, USA
M. Babzien, M.G. Fedurin, K. Kusche, V. Yakimenko
BNL, Upton, Long Island, New York, USA
C. Huang
LANL, Los Alamos, New Mexico, USA
J.L. Martins, L.O. Silva
IPFN, Lisbon, Portugal
W.B. Mori
UCLA, Los Angeles, California, USA

Funding: Work supported by: National Science Foundation and US Department of Energy.
Current Filamentation Instability, CFI, is of central importance for the propagation of relativistic electron beams in plasmas. CFI has potential relevance to astrophysics, magnetic field and radiation generation in the afterglow of gamma ray bursts, and inertial confinement fusion, energy transport in the fast-igniter concept. An experimental study of this instability is underway at the Accelerator Test Facility, ATF, at Brookhaven National Laboratory with the 60MeV electron beam and centimeter length capillary discharge plasma. The experimental program includes the systematic study and characterization of the instability as a function of beam (charge, transverse and longitudinal profile) and plasma (plasma density) parameters. Specifically, the transverse beam profile is measured directly at the plasma exit using optical transition radiation from a thin gold-coated silicon window. Experimental results show the reduction of the beam transverse size and the appearance of multiple (1-4) filaments and are a function of the plasma density. We will present simulation and experimental results, provide discussion of these results and outline next steps in the experiment.