PAC2013 - List of Authors (Corde, S.)

Paper

Title

Page

A Betatron-Analysis Technique for Identifying Narrowband Trapped Charge within a Broadband Energy Tail in PWFA Experiments at FACET

147

C.E. Clayton, W. An, C. Joshi, K.A. Marsh, W.B. Mori, N. Vafaei-Najafabadi
UCLA, Los Angeles, California, USA
E. Adli, C.I. Clarke, S. Corde, J.-P. Delahaye, R.J. England, A.S. Fisher, J.T. Frederico, S.J. Gessner, M.J. Hogan, S.Z. Li, M.D. Litos, D.R. Walz, Z. Wu
SLAC, Menlo Park, California, USA
W. Lu
TUB, Beijing, People's Republic of China
P. Muggli
MPI, Muenchen, Germany

Funding: The work at UCLA was supported by DOE grant DE-FG02-92-ER40727 and NSF grant PHY-0936266. Work at SLAC was supported in part by Department of Energy contract DE-AC02-7600515.
Plasma accelerators driven by ultra-relativistic electron beams have demonstrated greater than 50 GeV/m acceleration gradients over a distance of a meter though the accelerated particles typically have had a 100% energy spread when a single drive bunch was used. However, it is known that by locally producing electrons via ionization within the beam-driven plasma wake, they can become trapped and accelerated so that high-energy, mono-energetic electron bunches can be produced. We propose a technique to help identify these bunches of electrons at the 10’s of pC level arising from the ionization injection of Ar electrons that may otherwise be lost or overlooked as part of the discrete betatron-focusing maxima or the maxima inherent the chromaticity of the imaging electron spectrometer.

MOPAC46

Suppression of the Transformer Ratio Due to Distributed Injection of Electrons in a Plasma Wakefield Accelerator

165

N. Vafaei-Najafabadi, W. An, C.E. Clayton, C. Joshi, W. Lu, K.A. Marsh, W.B. Mori
UCLA, Los Angeles, California, USA
E. Adli
University of Oslo, Oslo, Norway
E. Adli, C.I. Clarke, S. Corde, J.-P. Delahaye, R.J. England, A.S. Fisher, J.T. Frederico, S.J. Gessner, M.J. Hogan, S.Z. Li, M.D. Litos, D.R. Walz, Z. Wu
SLAC, Menlo Park, California, USA
W. Lu
TUB, Beijing, People's Republic of China
P. Muggli
MPI, Muenchen, Germany

Funding: The work at UCLA was supported by DOE grant DE-FG02-92-ER40727 and NSF grant PHY-0936266. Simulations used the UCLA Hoff man cluster. Work at SLAC was supported by DOE contract DE-AC02-7600515.
Evidence of beam loading due to distributed injection in Plasma Wakefield Accelerator experiments carried out at the FACET facility at SLAC during the year 2012 is presented. The source of the injected charge is tunnel ionization of Rb⁺ inside the wake, which occurs along the length of the interaction at each minima of envelope betatron oscillation. Rb was used specifically to mitigate the problem of head erosion, which limited the energy gain in earlier experiments using Li that were carried out at FFTB in SLAC. In the present experiment however, electrons produced via secondary ionization of Rb were injected in the wake and led to a severe depletion of the accelerating wake, i.e. beam loading, which is observed as a reduction of mean, i.e. measured, transformer ratio. This ‘‘dark current" limitation on the maximum achievable accelerating gradient is also pertinent to other heavier ions that are potential candidates for high-gradient PWFA.

THYAA2

Latest Plasma Wakefield Acceleration Results from the FACET Project

1101

M.D. Litos, E. Adli, C.I. Clarke, S. Corde, J.-P. Delahaye, R.J. England, A.S. Fisher, J.T. Frederico, S.J. Gessner, M.J. Hogan, S.Z. Li, D.R. Walz, G.R. White, Z. Wu, V. Yakimenko
SLAC, Menlo Park, California, USA
E. Adli
University of Oslo, Oslo, Norway
W. An, C.E. Clayton, C. Joshi, W. Lu, K.A. Marsh, W.B. Mori, N. Vafaei-Najafabadi
UCLA, Los Angeles, California, USA
P. Muggli
MPI, Muenchen, Germany

SLAC’s new FACET facility had its second user run in April–June, 2013. Several new milestones were reached during this run, including the achievement of beam driven plasma wakefield acceleration of a discrete witness bunch for the first time, and energy doubling in a noble gas plasma source. The FACET beam is a 20 GeV electron bunch with a charge of 3.2 nC that can be compressed and focused to a size of 20 μm × 20 μm × 20 μm rms. To create the two-bunch, drive/witness beam structure, a chirped and over-compressed beam was dispersed horizontally in a chicane and a bite was taken from its middle with a tantalum finger collimator, corresponding to a longitudinal notching of the beam due to the head-tail energy correlation. A new 10 terawatt Ti:Sapphire laser was commissioned and used during this run to pre-ionize the plasma source in order to increase the efficiency of energy transfer from the beam to the wake. Ultimately, a witness beam of hundreds of pC in charge was accelerated by a drive beam of similar charge in a pre-formed lithium plasma with a density of 5×10¹⁶ cm^−3, experiencing gradients reaching several GeV/m in magnitude.

Slides THYAA2 [22.217 MB]

THOCA1

X-ray Radiation and Electron Injection from Beam Envelope Oscillations in Plasma Wakefield Accelerator Experiments at FACET

1105

K.A. Marsh, W. An, C.E. Clayton, C. Joshi, W. Lu, W.B. Mori, N. Vafaei-Najafabadi
UCLA, Los Angeles, California, USA
E. Adli
University of Oslo, Oslo, Norway
E. Adli, C.I. Clarke, S. Corde, J.-P. Delahaye, R.J. England, A.S. Fisher, J.T. Frederico, S.J. Gessner, M.J. Hogan, S.Z. Li, M.D. Litos, D.R. Walz, Z. Wu
SLAC, Menlo Park, California, USA
W. Lu
TUB, Beijing, People's Republic of China
P. Muggli
MPI, Muenchen, Germany

Funding: The work at UCLA was supported by DOE grant DE-FG02-92-ER40727 and NSF grant PHY-0936266. The work at SLAC was supported by Department of Energy Contract DE-AC02-76SF00515.
Plasma wakefield accelerator experiments at FACET at the SLAC National Accelerator Laboratory have shown a correlation between ionization-injected electrons and the betatron x-ray yield. Emittance spoiling foils were inserted into the beam and the x-ray yield, excess charge, and beam energy loss was measured. The excess charge and x-ray yield are attributed to the beam envelope oscillations where at the minima, the field of the beam is strong enough to create secondary ionization, and at the electron oscillation maxima, the beam electrons spontaneously radiate x-rays. Large amplitude beam oscillations are expected to yield more x-rays and create more excess charge, but the results show beam head erosion strongly limits the wakefield excitation.

Slides THOCA1 [3.281 MB]

Paper	Title	Page
MOPAC38	A Betatron-Analysis Technique for Identifying Narrowband Trapped Charge within a Broadband Energy Tail in PWFA Experiments at FACET	147
	C.E. Clayton, W. An, C. Joshi, K.A. Marsh, W.B. Mori, N. Vafaei-Najafabadi UCLA, Los Angeles, California, USA E. Adli, C.I. Clarke, S. Corde, J.-P. Delahaye, R.J. England, A.S. Fisher, J.T. Frederico, S.J. Gessner, M.J. Hogan, S.Z. Li, M.D. Litos, D.R. Walz, Z. Wu SLAC, Menlo Park, California, USA W. Lu TUB, Beijing, People's Republic of China P. Muggli MPI, Muenchen, Germany
	Funding: The work at UCLA was supported by DOE grant DE-FG02-92-ER40727 and NSF grant PHY-0936266. Work at SLAC was supported in part by Department of Energy contract DE-AC02-7600515. Plasma accelerators driven by ultra-relativistic electron beams have demonstrated greater than 50 GeV/m acceleration gradients over a distance of a meter though the accelerated particles typically have had a 100% energy spread when a single drive bunch was used. However, it is known that by locally producing electrons via ionization within the beam-driven plasma wake, they can become trapped and accelerated so that high-energy, mono-energetic electron bunches can be produced. We propose a technique to help identify these bunches of electrons at the 10’s of pC level arising from the ionization injection of Ar electrons that may otherwise be lost or overlooked as part of the discrete betatron-focusing maxima or the maxima inherent the chromaticity of the imaging electron spectrometer.

MOPAC46	Suppression of the Transformer Ratio Due to Distributed Injection of Electrons in a Plasma Wakefield Accelerator	165
	N. Vafaei-Najafabadi, W. An, C.E. Clayton, C. Joshi, W. Lu, K.A. Marsh, W.B. Mori UCLA, Los Angeles, California, USA E. Adli University of Oslo, Oslo, Norway E. Adli, C.I. Clarke, S. Corde, J.-P. Delahaye, R.J. England, A.S. Fisher, J.T. Frederico, S.J. Gessner, M.J. Hogan, S.Z. Li, M.D. Litos, D.R. Walz, Z. Wu SLAC, Menlo Park, California, USA W. Lu TUB, Beijing, People's Republic of China P. Muggli MPI, Muenchen, Germany
	Funding: The work at UCLA was supported by DOE grant DE-FG02-92-ER40727 and NSF grant PHY-0936266. Simulations used the UCLA Hoff man cluster. Work at SLAC was supported by DOE contract DE-AC02-7600515. Evidence of beam loading due to distributed injection in Plasma Wakefield Accelerator experiments carried out at the FACET facility at SLAC during the year 2012 is presented. The source of the injected charge is tunnel ionization of Rb⁺ inside the wake, which occurs along the length of the interaction at each minima of envelope betatron oscillation. Rb was used specifically to mitigate the problem of head erosion, which limited the energy gain in earlier experiments using Li that were carried out at FFTB in SLAC. In the present experiment however, electrons produced via secondary ionization of Rb were injected in the wake and led to a severe depletion of the accelerating wake, i.e. beam loading, which is observed as a reduction of mean, i.e. measured, transformer ratio. This ‘‘dark current" limitation on the maximum achievable accelerating gradient is also pertinent to other heavier ions that are potential candidates for high-gradient PWFA.

THYAA2	Latest Plasma Wakefield Acceleration Results from the FACET Project	1101
	M.D. Litos, E. Adli, C.I. Clarke, S. Corde, J.-P. Delahaye, R.J. England, A.S. Fisher, J.T. Frederico, S.J. Gessner, M.J. Hogan, S.Z. Li, D.R. Walz, G.R. White, Z. Wu, V. Yakimenko SLAC, Menlo Park, California, USA E. Adli University of Oslo, Oslo, Norway W. An, C.E. Clayton, C. Joshi, W. Lu, K.A. Marsh, W.B. Mori, N. Vafaei-Najafabadi UCLA, Los Angeles, California, USA P. Muggli MPI, Muenchen, Germany
	SLAC’s new FACET facility had its second user run in April–June, 2013. Several new milestones were reached during this run, including the achievement of beam driven plasma wakefield acceleration of a discrete witness bunch for the first time, and energy doubling in a noble gas plasma source. The FACET beam is a 20 GeV electron bunch with a charge of 3.2 nC that can be compressed and focused to a size of 20 μm × 20 μm × 20 μm rms. To create the two-bunch, drive/witness beam structure, a chirped and over-compressed beam was dispersed horizontally in a chicane and a bite was taken from its middle with a tantalum finger collimator, corresponding to a longitudinal notching of the beam due to the head-tail energy correlation. A new 10 terawatt Ti:Sapphire laser was commissioned and used during this run to pre-ionize the plasma source in order to increase the efficiency of energy transfer from the beam to the wake. Ultimately, a witness beam of hundreds of pC in charge was accelerated by a drive beam of similar charge in a pre-formed lithium plasma with a density of 5×10¹⁶ cm^−3, experiencing gradients reaching several GeV/m in magnitude.
	Slides THYAA2 [22.217 MB]

THOCA1	X-ray Radiation and Electron Injection from Beam Envelope Oscillations in Plasma Wakefield Accelerator Experiments at FACET	1105
	K.A. Marsh, W. An, C.E. Clayton, C. Joshi, W. Lu, W.B. Mori, N. Vafaei-Najafabadi UCLA, Los Angeles, California, USA E. Adli University of Oslo, Oslo, Norway E. Adli, C.I. Clarke, S. Corde, J.-P. Delahaye, R.J. England, A.S. Fisher, J.T. Frederico, S.J. Gessner, M.J. Hogan, S.Z. Li, M.D. Litos, D.R. Walz, Z. Wu SLAC, Menlo Park, California, USA W. Lu TUB, Beijing, People's Republic of China P. Muggli MPI, Muenchen, Germany
	Funding: The work at UCLA was supported by DOE grant DE-FG02-92-ER40727 and NSF grant PHY-0936266. The work at SLAC was supported by Department of Energy Contract DE-AC02-76SF00515. Plasma wakefield accelerator experiments at FACET at the SLAC National Accelerator Laboratory have shown a correlation between ionization-injected electrons and the betatron x-ray yield. Emittance spoiling foils were inserted into the beam and the x-ray yield, excess charge, and beam energy loss was measured. The excess charge and x-ray yield are attributed to the beam envelope oscillations where at the minima, the field of the beam is strong enough to create secondary ionization, and at the electron oscillation maxima, the beam electrons spontaneously radiate x-rays. Large amplitude beam oscillations are expected to yield more x-rays and create more excess charge, but the results show beam head erosion strongly limits the wakefield excitation.
	Slides THOCA1 [3.281 MB]