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S. Barber

First Name: Samuel

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Last Name: Barber

Full Name: S. Barber

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4 papers
title: Observation of redshifting and harmonic radiation in inverse Compton scattering
format: journal article
publisher:
year: 2015
21 authors: Y. Sakai | I. Pogorelsky | O. Williams | F.H. O'Shea | S. Barber | I. Gadjev | J. Duris | P. Musumeci | M. Fedurin | A. Korostyshevsky | B. Malone | C. Swinson | G. Stenby | K. Kusche | M. Babzien | M. Montemagno | P. Jacob | Z. Zhong | M. Polyanskiy | V. Yakimenko | J.B. Rosenzweig
abstract: Inverse Compton scattering of laser photons by ultrarelativistic electron beam provides polarized x- to γ-ray pulses due to the Doppler blueshifting. Nonlinear electrodynamics in the relativistically intense linearly polarized laser field changes the radiation kinetics established during the Compton interaction. These are due to the induced figure-8 motion, which introduces an overall redshift in the radiation spectrum, with the concomitant emission of higher order harmonics. To experimentally analyze the strong field physics associated with the nonlinear electron-laser interaction, clear modifications to the angular and wavelength distributions of x rays are observed. The relativistic photon wave field is provided by the ps CO2 laser of peak normalized vector potential of 0.5
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title: Beyond Injection: Trojan Horse Underdense Photocathode Plasma Wakefield Acceleration
format: conference proceeding
conference: AAC 2012 15th
year: 2012
18 authors: B. Hidding | J.B. Rosenzweig | Y.Xi | B. O'Shea | G. Andonian | D. Schiller | S. Barber | O. Williams | G. Pretzler | T. Königstein | F. Kleeschulte | M.J. Hogan | M. Litos | S. Corde | W.W. White | P. Muggli | D.L. Bruhwiler | K. Lotov
abstract: An overview on the underlying principles of the hybrid plasma wakefield acceleration scheme dubbed ”Trojan Horse” acceleration is given. The concept is based on laser-controlled release of electrons directly into a particle-beam- driven plasma blowout, paving the way for controlled, shapeable electron bunches with ultralow emittance and ultrahigh brightness. Combining the virtues of a low-ionization-threshold underdense photocathode with the GV/m-scale electric fields of a practically dephasing-free beam-driven plasma blowout, this constitutes a 4th generation electron acceleration scheme. It is applicable as a beam brightness transformer for electron bunches from LWFA and PWFA systems alike. At FACET, the proof-of-concept experiment ”E-210: Trojan Horse Plasma Wakefield Acceleration” has recently been approved and is in preparation. At the same time, various LWFA facilities are currently considered to host experiments aiming at stabilizing and boosting the electron bunch output quality via a trojan horse afterburner stage. Since normalized emittance and brightness can be improved by many orders of magnitude, the scheme is an ideal candidate for light sources such as free-electron-lasers and those based on Thomson scattering and betatron radiation alike.
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title: Harmonic radiation of a relativistic nonlinear inverse Compton scattering using two laser wavelengths
format: journal article
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year: 2011
9 authors: Y. Sakai | O. Williams | G. Andonian | A. Fukasawa | E. Hemsing | A. Marinelli | S. Barber | F.H. O'Shea | J.B. Rosenzweig
abstract: The use of two different wavelength lasers in the nonlinear regime of the inverse Compton scattering interaction is proposed in order to provide a new strategy for controlling scattered photon energy distributions in the x-ray to γ-ray spectral region. In this nonlinear interaction, the component of the relativistic electron’s trajectory driven by a longer-wavelength laser with the normalized vector potential aL∼1 is a large oscillatory figure-8; in the proposed scenario a rapid small-amplitude oscillation induced by a shorter-wavelength laser is superimposed upon this figure-8. Thus, the electron’s momentum is mainly supplied from longer-wavelength laser, while the high-frequency part of the acceleration is given by shorter-wavelength laser. In this way, the harmonics radiated at high frequency from the oscillating electron can be strongly modified by the nonlinear motion initiated by the low frequency, large aL laser resulting in the generation of the harmonics with the photon energy of 4γ2h̵(ωL,short+nωL,long). In this paper, the electron’s kinetics in the two-wavelength laser field and the concomitant emitted radiation spectrum are examined, with numerical illustrations based on a classical Lienard-Wiechert potential formalism provided.
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title: Dielectric Wakefield Acceleration of a Relativistic Electron Beam in a Slab-Symmetric Dielectric Lined Waveguide
format: journal article
publisher: Physical Review Letters
year: 15 June 2012
13 authors: G. Andonian | D. Stratakis | M. Babzien | S. Barber | M. Fedurin | E. Hemsing | K. Kusche | P. Muggli | B. O'Shea | X. Wei | O. Williams | V. Yakimenko | and J.B. Rosenzweig
abstract: We report first evidence of wakefield acceleration of a relativistic electron beam in a dielectric-lined slab-symmetric structure. The high energy tail of a ?60??MeV electron beam was accelerated by ?150??keV in a 2 cm-long, slab-symmetric SiO2 waveguide, with the acceleration or deceleration clearly visible due to the use of a beam with a bifurcated longitudinal distribution that serves to approximate a driver-witness beam pair. This split-bunch distribution is verified by longitudinal reconstruction analysis of the emitted coherent transition radiation. The dielectric waveguide structure is further characterized by spectral analysis of the emitted coherent Cherenkov radiation at THz frequencies, from a single electron bunch, and from a relativistic bunch train with spacing selectively tuned to the second longitudinal mode (TM02). Start-to-end simulation results reproduce aspects of the electron beam bifurcation dynamics, emitted THz radiation properties, and the observation of acceleration in the dielectric-lined, slab-symmetric waveguide.
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