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  • AIP Publishing  (25)
  • 1
    Online Resource
    Online Resource
    Nonlocal radiative forces in fully-ionized plasmas
    AIP Publishing ; 2000
    In:  Physics of Plasmas Vol. 7, No. 5 ( 2000-05-01), p. 1386-1396
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 7, No. 5 ( 2000-05-01), p. 1386-1396
    Abstract: The solution of the Fokker–Planck equation which contains the contribution of high-frequency electric fields is presented. For this, the projection operators of the Krook collision operator and the semicollisional propagator computed with the continued fractions were used. Both elastic and inelastic momentum transfer from the high-frequency electric field to electrons have been considered. The contributions of such high-frequency electric fields to the stress tensor and to the mean change of momentum due to electron–ion collisions are derived in the whole collisionality range. As a result, in the collisionless range, these contributions led to a new force which is 1.6 (instead of 4/3) more important than the Miller force. In the collisional range, the radiative force due to the inverse bremsstrahlung absorption is recovered and a new contribution which arises from the mean change of momentum due to collisions is found.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.873956
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2000
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  • 2
    Online Resource
    Online Resource
    Effect of electron collisions on transport coefficients induced by the inverse bremsstrahlung absorption in plasmas
    AIP Publishing ; 2005
    In:  Physics of Plasmas Vol. 12, No. 3 ( 2005-03-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 12, No. 3 ( 2005-03-01)
    Abstract: The transport coefficients of fully ionized plasmas under the influence of a high-frequency electric field are derived solving numerically the electron Fokker–Planck equation using a perturbation method, parametrized as a function of the electron mean-free-path λei compared to the spatial scales L. The isotropic and anisotropic contributions of the inverse bremsstrahlung heating are considered. Electron-electron collision terms are kept in the analysis, which allows us to consider with sufficient accuracy to describe plasmas with arbitrary atomic number Z. Practical numerical fits of the transport coefficients are proposed as functions of Z and the collisionality parameter λei∕L.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.1854155
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2005
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  • 3
    Online Resource
    Online Resource
    Theory of the thermal filamentation instability in the collisionless transport limit
    AIP Publishing ; 1999
    In:  Physics of Plasmas Vol. 6, No. 10 ( 1999-10-01), p. 4008-4014
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 6, No. 10 ( 1999-10-01), p. 4008-4014
    Abstract: The kinetic theory of the stationary and nonstationary thermal filamentation instability in fully ionized plasmas is presented. The collisionless transport limit is modeled by new transport coefficients corresponding to the convective heat flux and the temperature anisotropy. It is shown, in particular, that these effects decrease the instability growth rates by about a factor of 2, in conditions typical of current experiments. These two effects, combined with the collisional absorption of the light energy by the plasma electrons, lead to a thermal growth rate comparable to the one due to the ponderomotive drive. The comparison of the results obtained in this work with the principal results established in the literature, is also presented.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.873663
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1999
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  • 4
    Online Resource
    Online Resource
    Dispersion relation of quasi-static electromagnetic modes in relativistic plasmas
    AIP Publishing ; 2018
    In:  Physics of Plasmas Vol. 25, No. 1 ( 2018-01-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 25, No. 1 ( 2018-01-01)
    Abstract: Transverse quasi-static electromagnetic modes (ωkc≪1 , where ω and k are the mode frequency and the wavenumber, respectively, and c is the speed of light) are studied in laser heated relativistic plasmas, where the electron thermal energy could be comparable to or greater than the electron rest mass energy. A dispersion relation of these modes valid in the whole collisionality regime is derived with the use of the relativistic Vlasov-Landau and Maxwell equations. The dissipative part of the dispersion relation is calculated with the Maxwell-Boltzmann-Jüttner distribution function, as a function of the Knudsen number kλei, where λei is the electron mean-free-path. It is shown that the dissipative part exhibits a continuous transition from the collisional regime [∼kλei2] to the Landau collisionless one [∼kλei3] . The relativistic electrical conductivity is also deduced and compared with the results reported in the literature. Taking into account the anisotropy of the distribution function induced by the inverse bremsstrahlung absorption, the stability analysis of the electromagnetic modes is presented. It is found that for typical inertial confinement fusion plasmas, strong growing modes could be driven.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.4993589
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2018
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  • 5
    Online Resource
    Online Resource
    Transport coefficients in relativistic collisionless plasmas
    AIP Publishing ; 2004
    In:  Physics of Plasmas Vol. 11, No. 9 ( 2004-09-01), p. 4254-4260
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 11, No. 9 ( 2004-09-01), p. 4254-4260
    Abstract: The computation of the relativistic transport coefficients in collisionless plasmas is presented. The stationary relativistic Vlasov equation is analytically solved for perturbed plasmas with respect to the global equilibrium defined by the Maxwell–Boltzmann–Jüttner distribution function. The explicit expression of the distribution function is derived and the generalized collisionless transport coefficients are deduced for arbitrary plasma temperature. It is found that the relativistic effects tend to increase the value of the transport coefficients. In particular, in ultrarelativistic regimes the temperature anisotropy reaches its maximum value.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.1782192
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2004
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  • 6
    Online Resource
    Online Resource
    Analytic solution of the Vlasov equation and closed fluid equations
    AIP Publishing ; 1999
    In:  Physics of Plasmas Vol. 6, No. 5 ( 1999-05-01), p. 1500-1507
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 6, No. 5 ( 1999-05-01), p. 1500-1507
    Abstract: Using the projection operators, the analytic solution of the Vlasov equation linearized with respect to the global Maxwellian distribution function is presented. The expressions of the generalized quasistatic collisionless transport coefficients are computed, and in particular, a strong plasma temperature anisotropy and a convective heat flux are pointed out. The results obtained have been used to close the fluid equations. The spectral range validity of the collisionless fluid equations is also studied with the use of the plasma response function.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.873402
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1999
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  • 7
    Online Resource
    Online Resource
    Longitudinal dielectric function and dispersion relation of electrostatic waves in relativistic plasmas
    AIP Publishing ; 2017
    In:  Physics of Plasmas Vol. 24, No. 2 ( 2017-02-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 24, No. 2 ( 2017-02-01)
    Abstract: The longitudinal dielectric function is derived analytically from the relativistic Vlasov equation for arbitrary values of the relevant parameters z=mc2/T, where m is the rest electron mass, c is the speed of light, and T is the electron temperature in energy units. A new analytical approach based on the Legendre polynomial expansion and continued fractions was used. Analytical expression of the electron distribution function was derived. The real part of the dispersion relation and the damping rate of electron plasma waves are calculated both analytically and numerically in the whole range of the parameter z. The results obtained improve significantly the previous results reported in the literature. For practical purposes, explicit expressions of the real part of the dispersion relation and the damping rate in the range z & gt;30 and strongly relativistic regime are also proposed.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.4975668
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2017
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  • 8
    Online Resource
    Online Resource
    Numerical experiment to estimate the validity of negative ion diagnostic using photo-detachment combined with Langmuir probing
    AIP Publishing ; 2015
    In:  Physics of Plasmas Vol. 22, No. 7 ( 2015-07-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 22, No. 7 ( 2015-07-01)
    Abstract: This paper presents a critical assessment of the theory of photo-detachment diagnostic method used to probe the negative ion density and electronegativity α = n-/ne. In this method, a laser pulse is used to photo-detach all negative ions located within the electropositive channel (laser spot region). The negative ion density is estimated based on the assumption that the increase of the current collected by an electrostatic probe biased positively to the plasma is a result of only the creation of photo-detached electrons. In parallel, the background electron density and temperature are considered as constants during this diagnostics. While the numerical experiments performed here show that the background electron density and temperature increase due to the formation of an electrostatic potential barrier around the electropositive channel. The time scale of potential barrier rise is about 2 ns, which is comparable to the time required to completely photo-detach the negative ions in the electropositive channel (∼3 ns). We find that neglecting the effect of the potential barrier on the background plasma leads to an erroneous determination of the negative ion density. Moreover, the background electron velocity distribution function within the electropositive channel is not Maxwellian. This is due to the acceleration of these electrons through the electrostatic potential barrier. In this work, the validity of the photo-detachment diagnostic assumptions is questioned and our results illustrate the weakness of these assumptions.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.4926826
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2015
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  • 9
    Online Resource
    Online Resource
    Electronegative plasma diagnostic by laser photo-detachment combined with negatively biased Langmuir probe
    AIP Publishing ; 2018
    In:  Physics of Plasmas Vol. 25, No. 5 ( 2018-05-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 25, No. 5 ( 2018-05-01)
    Abstract: We propose a new technique for diagnosing negative ion properties using Langmuir probe assisted pulsed laser photo-detachment. While the classical technique uses a laser pulse to convert negative ions into electron-atom pairs and a positively biased Langmuir probe tracking the change of electron saturation current, the proposed method uses a negatively biased Langmuir probe to track the temporal evolution of positive ion current. The negative bias aims to avoid the parasitic electron current inherent to probe tip surface ablation. In this work, we show through analytical and numerical approaches that, by knowing electron temperature and performing photo-detachment at two different laser wavelengths, it is possible to deduce plasma electronegativity (ratio of negative ion to electron densities) α, and anisothermicity (ratio of electron to negative ion temperatures) γ−. We present an analytical model that links the change in the collected positive ion current to plasma electronegativity and anisothermicity. Particle-In-Cell simulation is used as a numerical experiment covering a wide range of α and γ− to test the new analysis technique. The new technique is sensitive to α in the range 0.5 & lt; α & lt; 10 and yields γ− for large α, where negative ion flux affects the probe sheath behavior, typically α & gt; 1.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.5024826
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2018
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  • 10
    Online Resource
    Online Resource
    Nonlinear propagation of ultraintense and ultrashort laser pulses in a plasma channel limited by metallic walls
    AIP Publishing ; 2006
    In:  Physics of Plasmas Vol. 13, No. 8 ( 2006-08-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 13, No. 8 ( 2006-08-01)
    Abstract: The nonlinear propagation of an ultraintense and ultrashort (UIUS) laser pulse in a metallic capillary is investigated using a classical model which takes into account the inverse bremsstrahlung absorption (IBA) in the formed plasma. The attenuation of the laser pulse due to the IBA in the plasma and to the laser energy dissipation in the metallic walls is shown. The guiding length and the twist of the laser pulse temporal envelope are presented for several values of the parameters of the plasma, the laser pulse and the metal. The numerical treatment shows that the guiding length increases when the pulse duration becomes shorter. This calculus shows also that in the case of moderate electronic densities, ne & lt;1017m−3, the formed plasma has a negligible effect compared to that of the metallic walls.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/1.2219431
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2006
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