The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
S. H. Glenzer - One of the best experts on this subject based on the ideXlab platform.
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Two-color Thomson Scattering at FLASH
High Energy Density Physics, 2011Co-Authors: P. Sperling, S. H. Glenzer, R. Thiele, B. Holst, Carsten Fortmann, Sven Toleikis, Th. Tschentscher, Ronald RedmerAbstract:Abstract We propose a two-color pump–probe Thomson Scattering experiment at the FLASH facility in Hamburg to characterize warm dense matter states. The fundamental free electron laser wavelength of 40.5 nm is used to pump a liquid hydrogen jet that is subsequently probed with the third harmonic at 13.5 nm. We have considered the laser–target interaction in the pump and probe phase by using the radiation hydrodynamics code HELIOS. The calculation of the Thomson Scattering spectrum is based on the Chihara formula which is evaluated using the Born–Mermin approximation for the free electron dynamic structure factor and the Debye–Huckel static structure factor for the elastic Scattering part. We consider the full density- and temperature-dependent Thomson Scattering cross section throughout the inhomogeneous target. The results indicate that the electron–ion equilibration rate can be extracted by measuring the electron and ion feature with varying time delays between the pump and the probe pulse.
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Observation of relativistic effects in collective Thomson Scattering.
Physical review letters, 2010Co-Authors: Jason Ross, S. H. Glenzer, B B Pollock, D Price, John Palastro, Laurent Divol, George Tynan, Dustin FroulaAbstract:We observe relativistic modifications to the Thomson Scattering spectrum in a traditionally classical regime: v{sub osc}/c=eE{sub 0}/cm{omega}{sub 0}
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Thomson Scattering techniques in laser produced plasmas
2006Co-Authors: D H Froula, J S Ross, L Divol, A J Mackinnon, C. Sorce, S. H. GlenzerAbstract:Thomson Scattering has been shown to be a valuable technique for measuring the plasma conditions in laser produced plasmas. Measurement techniques are discussed that use the ion-acoustic frequency measured from the collective Thomson-Scattering spectrum to extract the electron temperature, ion temperature, plasma flow, and electron density in a laser produced plasma. In a recent study, they demonstrated a novel Thomson-Scattering technique to measure the dispersion of ion-acoustic fluctuations that employing multiple color Thomson-Scattering diagnostics. They obtained frequency-resolved Thomson-Scattering spectra of the two separate thermal ion-acoustic fluctuations with significantly different wave vectors. This new technique allows a simultaneous time resolved local measurement of electron density and temperature. The plasma fluctuations are shown to become dispersive with increasing electron temperature. Furthermore, a Thomson-Scattering technique to measure the electron temperature profile is presented where recent experiments have measured a large electron temperature gradient (Te = 1.4 keV to Te = 3.2 keV over 1.5-mm) along the axis of a 2-mm long hohlraum when heated asymmetrically.
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Dense matter characterization by X-ray Thomson Scattering
Journal of Quantitative Spectroscopy & Radiative Transfer, 2001Co-Authors: O. L. Landen, S. H. Glenzer, M. J. Edwards, Richard W. Lee, Gilbert Collins, R. C. Cauble, W. Hsing, B. A. HammelAbstract:Abstract We discuss the extension of the powerful technique of Thomson Scattering to the X-ray regime for providing an independent measure of plasma parameters for dense plasmas. By spectrally resolving the Scattering, the coherent (Rayleigh) unshifted Scattering component can be separated from the incoherent Thomson component, which is both Compton and Doppler shifted. The free electron density and temperature can then be inferred from the spectral shape of the high-frequency Thomson Scattering component. In addition, as the plasma temperature is decreased, the electron velocity distribution as measured by incoherent Thomson Scattering will make a transition from the traditional Gaussian Boltzmann distribution to a density-dependent parabolic Fermi distribution. We also present a discussion for a proof-of-principle experiment appropriate for a high-energy laser facility.
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A Thomson Scattering post-processor for the MEDUSA hydrocode
Journal of Quantitative Spectroscopy & Radiative Transfer, 2001Co-Authors: J. Hawreliak, S. H. Glenzer, D. M. Chambers, Robin Marjoribanks, M. Notley, Philip A. Pinto, O. Renner, P. Sondhauss, R. Steel, S. ToppingAbstract:Abstract In order to understand the physical processes that occur in laser-produced plasmas it is necessary to diagnose the time-dependent hydrodynamic conditions. Thomson Scattering is, in principle, an ideal diagnostic as it provides a non-intrusive method of measuring ion and electron temperature, electron density, plasma velocity, and heat flow. We describe here a post-processor for the MEDUSA hydrocode that simulates streak camera images of the Thomson spectra. The post-processor can be used in three ways: (1) creating simulated streak camera images that can be compared directly with experimental data, (2) evaluating experimental designs to determine the viability of the Thomson Scattering diagnostic, and (3) as an automated data analysis routine for extracting hydrodynamic parameters from a calibrated experimental streak camera image.
Dustin Froula - One of the best experts on this subject based on the ideXlab platform.
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Picosecond Thermodynamics in Underdense Plasmas Measured with Thomson Scattering.
Physical review letters, 2019Co-Authors: A. Davies, J. Katz, Wojciech Rozmus, John Palastro, Dan Haberberger, S. Bucht, Dustin FroulaAbstract:The rapid evolutions of the electron density and temperature in a laser-produced plasma were measured using collective Thomson Scattering. Unprecedented picosecond time resolution, enabled by a pulse-front-tilt compensated spectrometer, revealed a transition in the plasma-wave dynamics from an initially cold, collisional state to a quasistationary, collisionless state. The Thomson-Scattering spectra were compared with theoretical calculations of the fluctuation spectrum using either a conventional Bhatnagar-Gross-Krook (BGK) collision operator or the rigorous Landau collision terms: the BGK model overestimates the electron temperature by 50% in the most-collisional conditions.
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Mitigation of self-focusing in Thomson Scattering experiments
Physics of Plasmas, 2019Co-Authors: A. M. Hansen, David Turnbull, J. Katz, Dustin FroulaAbstract:A fundamental challenge associated with measuring Thomson Scattering comes from the small Scattering cross section associated with the interaction. To improve photon statistics, a powerful Thomson-Scattering probe laser is required. Ponderomotive self-focusing limits the maximum power in the Thomson-Scattering probe and was shown to limit the maximum achievable Thomson-Scattering signal-to-noise ratio. Operating the laser at powers above the self-focusing critical power was shown to cause beam degradation, which reduced the amount of collected Thomson-scattered light. Using a phase plate was shown to improve laser beam propagation and consequently improve the signal-to-noise ratio in the measured spectrum.
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Observation of Nonlocal Heat Flux Using Thomson Scattering.
Physical review letters, 2018Co-Authors: R. J. Henchen, J. Katz, Wojciech Rozmus, Mark Sherlock, D. Cao, John Palastro, Dustin FroulaAbstract:Nonlocal heat flux was measured in laser-produced coronal plasmas using a novel Thomson Scattering technique. The measured heat flux was smaller than the classical values inferred from the measured plasma conditions in regions with large temperature gradients and agreed with classical values for weak gradients. Vlasov-Fokker-Planck simulations self-consistently calculated the electron distribution functions used to reproduce the measured Thomson Scattering spectra and to determine the heat flux. Multigroup nonlocal simulations overestimated the measured heat flux.
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Observation of relativistic effects in collective Thomson Scattering.
Physical review letters, 2010Co-Authors: Jason Ross, S. H. Glenzer, B B Pollock, D Price, John Palastro, Laurent Divol, George Tynan, Dustin FroulaAbstract:We observe relativistic modifications to the Thomson Scattering spectrum in a traditionally classical regime: v{sub osc}/c=eE{sub 0}/cm{omega}{sub 0}
Young-dae Jung - One of the best experts on this subject based on the ideXlab platform.
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Effects of turbulence on the Thomson Scattering process in turbulent plasmas by the Scattering of electromagnetic waves
EPL (Europhysics Letters), 2013Co-Authors: Young-dae JungAbstract:The effects of turbulence on the Thomson Scattering process are investigated in turbulent plasmas. The Thomson Scattering cross section in turbulent plasmas is obtained by the fluctuation-dissipation theorem and plasma dielectric function as a function of the diffusion coefficient, wave number, and Debye length. It is demonstrated that the turbulence effect suppresses the Thomson Scattering cross section. It is also shown that the turbulence effect on the Thomson Scattering process decreases with increasing thermal energy. The dependence of the wave number on the total Thomson Scattering cross section including the turbulent structure factor is also discussed.This paper is dedicated to the late Prof. P. K. Shukla in memory of exciting and stimulating collaborations on effective interaction potentials in various astrophysical and laboratory plasmas.
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Electron-exchange and quantum screening effects on the Thomson Scattering process in quantum Fermi plasmas
Physics of Plasmas, 2013Co-Authors: Gyeong Won Lee, Young-dae JungAbstract:The influence of the electron-exchange and quantum screening on the Thomson Scattering process is investigated in degenerate quantum Fermi plasmas. The Thomson Scattering cross section in quantum plasmas is obtained by the plasma dielectric function and fluctuation-dissipation theorem as a function of the electron-exchange parameter, Fermi energy, plasmon energy, and wave number. It is shown that the electron-exchange effect enhances the Thomson Scattering cross section in quantum plasmas. It is also shown that the differential Thomson Scattering cross section has a minimum at the Scattering angle Θ=π/2. It is also found that the Thomson Scattering cross section increases with an increase of the Fermi energy. In addition, the Thomson Scattering cross section is found to be decreased with increasing plasmon energy.
Ju Gao - One of the best experts on this subject based on the ideXlab platform.
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Laser intensity measurement by Thomson Scattering
Applied Physics Letters, 2006Co-Authors: Ju GaoAbstract:We have examined the proposed idea [Ju Gao, Phys. Rev. Lett. 93, 243001 (2004)] of using Thomson Scattering to characterize the intensity profile of ultraintense laser fields(⩾1018W∕cm2) by calculating the nonlinear Thomson Scattering from single and multiple electrons in a Gaussian mode laser field. The results show a close correlation between the spectral features and local laser intensity. The effect may lead to a new scheme of characterizing laser intensity profiles.
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Nonlinear Thomson Scattering for Plasmaand Laser Characterization
IEEE Conference Record - Abstracts. 2005 IEEE International Conference on Plasma Science, 2005Co-Authors: Ju GaoAbstract:Summary form only given. One of the most powerful methods of diagnosing plasma is detecting the Scattering of electromagnetic radiation from the plasma. The process is described by the Thomson Scattering (TS) in which the electron radiates with the same frequency of the incident field. The radiation signal is proportional to the number of the electrons but the electron motion shifts the frequency by Doppler effects. Thomson Scattering then yields detailed information of both the electron density and speed distribution (temperature). TS typically has a very small cross-section, therefore it is advantageous to use more intense lasers. It is known for years that the electron acquires an additional energy in the high fields, known as the ponderomotive energy. Recent discussion shows that the electron also acquires a counterpart ponderomotive momentum. The ponderomotive momentum causes the electrons to drift along the laser propagation, which results in additional spectral shift. The effect is known as the nonlinear Thomson Scattering. Since the drift velocity is proportional to the laser intensity, a spread of the laser intensity results in spectral broadening. We have calculated detailed spectra of the Thomson Scattering from intense laser fields by solving the electron motion inside the intense laser field nonperturbatively and subsequently calculating the radiation spectra from electrodynamics theory. The spectral shift and broadening correlate with the laser properties and can exceed the Doppler shifts introduced by the electron speed, which suggests that deconvolution is necessary to remove the intensity effects from the laser and recover the true electron properties for the high intensity Thomson Scattering. Concurrently, this basic interaction between the plasma and high intensity laser opens up the possibility of using the nonlinear Thomson Scattering to characterize the laser fields, e.g. measure the absolute laser intensities in-situ and optically. The role of the electron in this case is thus changed from being a target to functioning as a probe
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Thomson Scattering from ultrashort and ultraintense laser pulses.
Physical review letters, 2004Co-Authors: Ju GaoAbstract:The Thomson Scattering in an ultraintense ( approximately 10(18) W cm(-2)) and ultrashort (20 fs) laser field is calculated that demonstrates different characteristics from those of the low-intensity field case. The electron trajectory no longer conforms to a figure-eight pattern, and the spectra demonstrate complex shifting and broadening to suggest that Thomson Scattering can be used for characterizing pulsed lasers. The initial phase at the electron entrance of the field can critically affect the Thomson Scattering, but its effect is weighted by the intensity profile of the field. As a result, the fourfold symmetry of the radiation pattern breaks down when the electron enters the field closer to the pulse peak. The relationship between the Thomson Scattering and Compton Scattering in the high field is analyzed.
Y.y. Lau - One of the best experts on this subject based on the ideXlab platform.
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Nonlinear Thomson Scattering: A tutorial
Physics of Plasmas, 2003Co-Authors: Y.y. Lau, Donald P. Umstadter, Richard KowalczykAbstract:Recent advances in table-top, ultrahigh intensity lasers have led to significant renewed interest in the classic problem of Thomson Scattering. An important current application of these Scattering processes is the generation of ultrashort-pulse-duration x rays. In this tutorial, the classical theory of nonlinear Thomson Scattering of an electron in an intense laser field is presented. It is found that the orbit, and therefore its nonlinear Scattering spectra, depends on the amplitude and on the phase at which the electron sees the laser electric field. Novel, simple asymptotic expansions are obtained for the spectrum of radiation that is backscattered from a laser by a counter-propagating (or co-propagating) electron. The solutions are presented in such a way that they explicitly show—at least in the single particle regime—the relative merit of using an intense laser and of an energetic electron beam in x-ray production. The close analogy with free electron laser/synchrotron source is indicated.
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Phase dependence of Thomson Scattering in an ultraintense laser field
Physics of Plasmas, 2002Co-Authors: Y.y. Lau, Donald P. Umstadter, T.s. StricklerAbstract:The Thomson Scattering spectra of an electron by an ultraintense laser field are computed. It is found that the electron orbit, and therefore its nonlinear Thomson Scattering spectra, depend critically on the amplitude of the ultraintense laser field and on the phase at which the electron sees the laser electric field. Contrary to some customary notions, the Thomson Scattering spectra, in general, do not occur at integer multiples of the laser frequency and the maximum frequency is proportional to the first instead of the third power of the electric field strength for the case of an ultraintense laser. The implications of these findings are discussed.
