PAC2013 - List of Authors (Fang, Y.)

Paper	Title	Page
MOPAC02	Electron and Positron Bunch Self-modulation Experiments at SLAC-FACET	84
	P. Muggli MPI, Muenchen, Germany E. Adli, S.J. Gessner, M.J. Hogan, S.Z. Li, M.D. Litos SLAC, Menlo Park, California, USA Y. Fang USC, Los Angeles, California, USA C. Joshi, K.A. Marsh, W.B. Mori, N. Vafaei-Najafabadi UCLA, Los Angeles, California, USA N.C. Lopes, L.O. Silva, J. Vieira Instituto Superior Tecnico, Lisbon, Portugal O. Reimann MPI-P, München, Germany
	A self-modulated proton-driven plasma wakefield acceleration experiment is being designed at CERN and will occur within 3-5 years. Uncompressed 20GeV lepton bunches currently available at SLAC-FACET could be used to test key physics of the CERN experiment (e.g. self-modulation instability (SMI), SMI seeding, ion motion, hosing, differences between electrons (e-) and positrons (e+), etc). The E-209 collaboration was formed to carry SMI experiments at SLAC-FACET. Here we show through full-scale Osiris simulations that electron self-modulation grows and saturates in less than 10cm. Wakefield excitation in the blowout regime leads to acceleration gradients in excess of 20GeV/m. The self-modulated e^- bunch then sustains stable wakefields over meter-long plasmas. As a result, 7(12)GeV e^- energy gain(loss) could be observed. In the blowout regime, most of the wakefield phase defocuses e+. Thus, uncompressed e⁺ bunches drive lower acceleration gradients, but still in excess of 10GeV/m, over 1m of plasma. We will discuss the experimental setup, diagnostics to measure SMI (e.g. CTR, energy spectrometer, OTR, etc) and expected results. First experimental results may also be available. J. Vieira et al., Phys. Plasmas 19, 063105 (2012).

MOPAC49	Possibility of Confirming SMI through Energy Spectrum with the 1nC ATF Electron Bunch	171
	Y. Fang, P. Muggli USC, Los Angeles, California, USA W.B. Mori UCLA, Los Angeles, California, USA P. Muggli MPI, Muenchen, Germany
	Funding: Work supported by US DOE We demonstrate experimentally for the first time the self-modulation seeding of a relativistic electron bunch in a plasma. The long (~3.2 ps) bunch available at BNL ATF drives wakefields with periods one to one sixth of the bunch length in plasmas of a 10¹⁵ to 10¹⁶ cm^-3 density range, which is observed as a periodic modulation of the bunch correlated energy spectrum after the 2 cm long plasma. OSIRIS* simulations show that electron bunches with a square temporal current profile seed effectively the wakefield and the development of the transverse modulation instability. Although the self-modulation instability (SMI) does not grow significantly over the 2cm-long plasma with a 50 pC bunch, simulations show that the SMI of the 1 nC bunch grows significantly and reaches saturation over the 2 cm propagation distance. We further examine the possibility of measuring the energy spectrum experimentally to confirm the development of SMI. Initial results show that due to dephasing between the bunch particles and the wakefields, the actual energy gain/loss by drive bunch particles is much lower than expected. ＊R. A. Fonseca et al., Lect. Notes Comp. Sci. vol. 2331/2002, (Springer Berlin/Heidelberg, (2002).

Paper

Title

Page

Electron and Positron Bunch Self-modulation Experiments at SLAC-FACET

84

P. Muggli
MPI, Muenchen, Germany
E. Adli, S.J. Gessner, M.J. Hogan, S.Z. Li, M.D. Litos
SLAC, Menlo Park, California, USA
Y. Fang
USC, Los Angeles, California, USA
C. Joshi, K.A. Marsh, W.B. Mori, N. Vafaei-Najafabadi
UCLA, Los Angeles, California, USA
N.C. Lopes, L.O. Silva, J. Vieira
Instituto Superior Tecnico, Lisbon, Portugal
O. Reimann
MPI-P, München, Germany

A self-modulated proton-driven plasma wakefield acceleration experiment is being designed at CERN and will occur within 3-5 years. Uncompressed 20GeV lepton bunches currently available at SLAC-FACET could be used to test key physics of the CERN experiment (e.g. self-modulation instability (SMI), SMI seeding, ion motion, hosing, differences between electrons (e-) and positrons (e+), etc)*. The E-209 collaboration was formed to carry SMI experiments at SLAC-FACET. Here we show through full-scale Osiris simulations that electron self-modulation grows and saturates in less than 10cm. Wakefield excitation in the blowout regime leads to acceleration gradients in excess of 20GeV/m. The self-modulated e^- bunch then sustains stable wakefields over meter-long plasmas. As a result, 7(12)GeV e^- energy gain(loss) could be observed. In the blowout regime, most of the wakefield phase defocuses e+. Thus, uncompressed e⁺ bunches drive lower acceleration gradients, but still in excess of 10GeV/m, over 1m of plasma. We will discuss the experimental setup, diagnostics to measure SMI (e.g. CTR, energy spectrometer, OTR, etc) and expected results. First experimental results may also be available.
*J. Vieira et al., Phys. Plasmas 19, 063105 (2012).

MOPAC49

Possibility of Confirming SMI through Energy Spectrum with the 1nC ATF Electron Bunch

171

Y. Fang, P. Muggli
USC, Los Angeles, California, USA
W.B. Mori
UCLA, Los Angeles, California, USA
P. Muggli
MPI, Muenchen, Germany

Funding: Work supported by US DOE
We demonstrate experimentally for the first time the self-modulation seeding of a relativistic electron bunch in a plasma. The long (~3.2 ps) bunch available at BNL ATF drives wakefields with periods one to one sixth of the bunch length in plasmas of a 10¹⁵ to 10¹⁶ cm^-3 density range, which is observed as a periodic modulation of the bunch correlated energy spectrum after the 2 cm long plasma. OSIRIS* simulations show that electron bunches with a square temporal current profile seed effectively the wakefield and the development of the transverse modulation instability. Although the self-modulation instability (SMI) does not grow significantly over the 2cm-long plasma with a 50 pC bunch, simulations show that the SMI of the 1 nC bunch grows significantly and reaches saturation over the 2 cm propagation distance. We further examine the possibility of measuring the energy spectrum experimentally to confirm the development of SMI. Initial results show that due to dephasing between the bunch particles and the wakefields, the actual energy gain/loss by drive bunch particles is much lower than expected.
＊R. A. Fonseca et al., Lect. Notes Comp. Sci. vol. 2331/2002, (Springer Berlin/Heidelberg, (2002).