IPAC2012 - List of Authors (Malone, R.)

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.

WEPPP051	Excitation of Plasma Wakefields with Designer Bunch Trains	2828
	P. Muggli MPI, Muenchen, Germany B.A. Allen, Y. Fang USC, Los Angeles, California, USA M. Babzien, M.G. Fedurin, K. Kusche, R. Malone, C. Swinson, V. Yakimenko BNL, Upton, Long Island, New York, USA
	Funding: Work supported by US Department of Energy. Plasma can sustain multi-GV/m longitudinal electric fields that can be used for particle acceleration. In the plasma wakefield accelerator, or PWFA, the wakefields are driven by a single or a train of electron bunches with length comparable to the plasma wavelength. A train of bunches resonantly driving the wakefields can lead to energy gain by trailing particles many times the energy of the incoming drive train particles (large transformer ratio). In proof-of-principle experiments at the Brookhaven National Laboratory Accelerator Test Facility, we demonstrate by varying the plasma density over four orders of magnitude, and therefore the accelerator frequency over two orders of magnitude (~100GHz to a few THz), that trains with ~ps period resonantly drive wakefields in ~10¹⁶/cc density plasmas. We also demonstrate energy gain by a trailing witness electron bunch that follows the drive train with a variable delay. Detailed experimental results will be presented.

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.

WEPPP051

Excitation of Plasma Wakefields with Designer Bunch Trains

2828

P. Muggli
MPI, Muenchen, Germany
B.A. Allen, Y. Fang
USC, Los Angeles, California, USA
M. Babzien, M.G. Fedurin, K. Kusche, R. Malone, C. Swinson, V. Yakimenko
BNL, Upton, Long Island, New York, USA

Funding: Work supported by US Department of Energy.
Plasma can sustain multi-GV/m longitudinal electric fields that can be used for particle acceleration. In the plasma wakefield accelerator, or PWFA, the wakefields are driven by a single or a train of electron bunches with length comparable to the plasma wavelength. A train of bunches resonantly driving the wakefields can lead to energy gain by trailing particles many times the energy of the incoming drive train particles (large transformer ratio). In proof-of-principle experiments at the Brookhaven National Laboratory Accelerator Test Facility, we demonstrate by varying the plasma density over four orders of magnitude, and therefore the accelerator frequency over two orders of magnitude (~100GHz to a few THz), that trains with ~ps period resonantly drive wakefields in ~10¹⁶/cc density plasmas. We also demonstrate energy gain by a trailing witness electron bunch that follows the drive train with a variable delay. Detailed experimental results will be presented.