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  • 1
    Electronic Resource
    Electronic Resource
    High-quality electron beams from a laser wakefield accelerator using plasma-channel guiding (2004)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 431 (2004), S. 538-541 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Laser-driven accelerators, in which particles are accelerated by the electric field of a plasma wave (the wakefield) driven by an intense laser, have demonstrated accelerating electric fields of hundreds of GV m-1 (refs 1–3). These fields are thousands of ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature02900
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  • 2
    Electronic Resource
    Electronic Resource
    Observation of 20 eV x-ray generation in a proof-of-principle laser synchrotron source experiment (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 575-577 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A laser synchrotron source (LSS) [P. Sprangle, A. Ting, E. Esarey, and A. Fisher, J. Appl. Phys. 72, 5032 (1992)] was proposed to generate short-pulsed, tunable x rays by Thomson scattering of laser photons from a relativistic electron beam. A proof-of-principal (p.o.p.) experiment on this LSS configuration is performed. An intense laser pulse (λ0=1.053 μm) is Thomson backscattered from a focused relativistic electron beam. Time integrated x-ray signals from a photocathode/electron multiplier, at an electron beam energy of 650 keV and an x-ray photon energy of 20 eV, indicate an increase in the x-ray signals above the baseline by an amount comparable to the theoretically predicted value. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360644
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  • 3
    Electronic Resource
    Electronic Resource
    Laser wakefield acceleration and relativistic optical guiding (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 2146-2148 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An electron acceleration method is investigated which employs a short (τL ∼2πωω−1p ∼1 ps), high-power (P≥1015 W), single frequency laser pulse to generate large amplitude (E≥1 GeV/m) plasma waves (wakefields). At sufficiently high laser powers [P≥17(ω/ωp )2 GW], relativistic optical guiding may be used to prevent the pulse from diffracting within the plasma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100300
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  • 4
    Electronic Resource
    Electronic Resource
    Tunable, short pulse hard x-rays from a compact laser synchrotron source (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 5032-5038 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A compact laser synchrotron source (LSS) is proposed as a means of generating tunable, narrow bandwidth, ultra-short pulses of hard x rays. The LSS is based on the Thomson backscattering of intense laser radiation from a counterstreaming electron beam. Advances in both compact ultra-intense solid-state lasers and high brightness electron accelerators make the LSS an attractive compact source of high brightness pulsed x rays, particularly at photon energies beyond ∼30 keV. The x-ray wavelength is λ[A(ring)]=650 λ0[μm]/Eb2[MeV], where λ0 is the laser wavelength and Eb is the electron beam energy. For Eb=72 MeV and λ0=1 μm, x rays at λ=0.12 A(ring) (100 keV) are generated. The spectral flux, brightness, bandwidth, and pulse structure are analyzed. In the absence of filtering, the spectral bandwidth in the LSS is typically (approximately-less-than)1% and is limited by electron beam emittance and energy spread. Two configurations of the LSS are discussed, one providing high peak power and the other moderate average power x rays. Using present day technology, the LSS can generate picosecond pulses of x rays consisting of (approximately-greater-than)109 photons/pulse with a peak brightness of (approximately-greater-than)1020 photons/s mm2 mrad2 (0.1% BW) and photon energies ranging from 50 to 1200 keV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352031
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  • 5
    Electronic Resource
    Electronic Resource
    Propagation of radius-tailored laser pulses over extended distances in a uniform plasmaf| (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 1738-1743 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A Maxwell-fluid model is described, which allows simulation of laser pulses over extended distances (multiple diffraction lengths) in an underdense plasma. This model is used to simulate radius-tailored laser pulses, which can propagate over such distances with minimal distortion in a uniform plasma. Theoretical model equations governing the choice of radius tailoring are also given. A radius-tailored pulse has constant power approximately equal to the critical power for relativistic guiding over the length of the pulse and a spot size at focus that varies over the length of the pulse. A laser pulse configuration of this type can be constructed from a series of ultrashort Gaussian pulses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870678
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  • 6
    Electronic Resource
    Electronic Resource
    Laser-induced electron trapping in plasma-based accelerators : The 40th annual meeting of the division of plasma physics of the american physical society (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 2262-2268 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Trapping of plasma electrons in the self-modulated laser wakefield accelerator (LWFA) via the coupling of Raman backscatter to the wake is examined analytically and with three-dimensional (3-D) test particle simulations. The trapping threshold for linear polarization is much less than for circular and occurs for wake amplitudes of δn/n∼25%, which is well below wave breaking. Self-channeling provides continuous focusing of the accelerated electrons which, along with relativistic pump laser effects, can enhance the energy gain by a factor ≥2. The colliding pulse method for injecting electrons in the standard LWFA is examined. Simulations of test electrons in 3-D fields indicate the production of relativistic (≥25 MeV) high-quality electron bunches with ultrashort durations (a few femtoseconds), small energy spreads (a few percent), and low normalized emittances (1 mm mrad). © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873478
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  • 7
    Electronic Resource
    Electronic Resource
    Guiding of laser pulses in plasma channels created by the ignitor-heater technique : The 40th annual meeting of the division of plasma physics of the american physical society (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 2269-2277 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental and theoretical investigations of laser guiding in plasma channels are reported. Intense (〈5×1017 W/cm2), short (75 fs) laser pulses have been injected and guided in channels produced using a novel ignitor-heater technique, which uses two laser pulses. The ignitor, an ultrashort (〈100 fs) laser pulse, is brought to a line focus to ionize the gas jet. The heater pulse (160 ps long) is subsequently used to heat the existing spark via inverse Bremsstrahlung. The hydrodynamic shock expansion creates a channel. This technique allows the creation of slab or cylindrical channels in low atomic number gases, e.g., hydrogen. The channel profile was diagnosed with time resolved longitudinal interferometry. The effects of laser beam size and divergence mismatch at the channel entrance and leakage of the laser energy out of the channel are studied theoretically and experimentally in one and two transverse dimensions. An all-optical channel wake diagnostic based on Fourier domain interferometry is discussed, and a holographic-type inversion technique is proposed to increase the accuracy and reach of this method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873503
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  • 8
    Electronic Resource
    Electronic Resource
    Plasma wakefield generation and electron acceleration in a self-modulated laser wakefield accelerator experiment : The 38th annual meeting of the Division of Plasma Physics (DPP) of the American Physical Society (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 1889-1899 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A self-modulated laser wakefield accelerator (SM-LWFA) experiment was performed at the Naval Research Laboratory. Large amplitude plasma wakefields produced by a sub-picosecond, high intensity laser pulse (7×1018 W/cm2) in an underdense plasma (ne(approximate)1019 cm−3) were measured with a pump–probe coherent Thomson scattering (CTS) technique to last for less than 5 ps, consistent with the decay of large amplitude plasma waves due to the modulational instability. A plasma channel was observed to form in the wake of the pump laser pulse, and its evolution was measured with the pump–probe CTS diagnostic. The trailing probe laser pulse was observed to be guided by this channel for about 20 Rayleigh lengths. High energy electrons (up to 30 MeV) have been measured using an electro-magnetic spectrometer, with the energy spectra and divergence of lower energy (up to 4 MeV) electrons obtained using photographic films. Highly nonlinear plasma waves were also detected using forward Raman scattering diagnostics and were observed to correlate with the electron signals. Simulations of self-trapping of plasma electrons from the interaction of the laser wakefield with the slow plasma wave generated by Raman backscattering are also presented. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872332
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  • 9
    Electronic Resource
    Electronic Resource
    Gamma-neutron activation experiments using laser wakefield accelerators : The 42nd annual meeting of the division of plasma physics of the American Physical Society and the 10th international congress on plasma physics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 2510-2516 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Gamma-neutron activation experiments have been performed with relativistic electron beams produced by a laser wakefield accelerator. The electron beams were produced by tightly focusing (spot diameter (approximate)6 μm) a high power (up to 10 TW), ultra-short (≥50 fs) laser beam from a high repetition rate (10 Hz) Ti:sapphire (0.8 μm) laser system, onto a high density (〉1019 cm−3) pulsed gasjet of length (approximate)1.5 mm. Nuclear activation measurements in lead and copper targets indicate the production of electrons with energy in excess of 25 MeV. This result was confirmed by electron distribution measurements using a bending magnet spectrometer. Measured γ-ray and neutron yields are also found to be in reasonable agreement with simulations using a Monte Carlo transport code. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1352617
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  • 10
    Electronic Resource
    Electronic Resource
    Turbulent stabilization of the tearing mode in tokamak plasmas (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 200-211 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of turbulent electron diffusion from stochastic electron orbits on the stability of low-beta fluctuations is considered through the use of the normal stochastic approximation. A set of coupled, self-adjoint equations is derived for the fluctuation potentials φ˜ and A˜(parallel). Solutions to this set of equations describe both unstable finite-β drift waves when analyzed for high-m modes and the tearing mode when analyzed for low-m modes. For the tearing mode, it is shown that stability is obtained for sufficiently large values of the diffusion coefficient. Provided De∼1/n, this implies that a density threshold must be surpassed before the tearing mode is observed. Physically, turbulent electron diffusion prohibits the formation of a perturbed current within a finite region about the rational surface. At higher densities, the inclusion of a finite electrostatic potential φ˜ gives an additional stabilizing term to the dispersion relation, which physically represents ion inertial effects. This ion inertial effect implies that, in the absence of diffusion, the tearing mode is stabilized for ion betas βi above some critical value.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865977
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