Non-thermal evolution of dense plasmas driven by intense x-ray fields

Ren, Shenyuan; Shi, Yuanfeng; Berg, Q. Y. van den; Kasim, Muhammad; Chung, Hyun-Kyung; Fernandez-Tello, Elisa V.; Velarde, P.; Wark, J. S.; Vinko, S. M.

doi:10.1038/s42005-023-01216-x

Cited by 11 publications

(1 citation statement)

References 47 publications

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“…This extensive ionization and collisional process lead to a Maxwellian distribution. Recent research has revealed that the effect of non-thermalized electron distribution 40) on both population and emission spectra becomes significant at laser intensities over ∼10 17 W cm −2 . Given that the laser intensity employed here is up to 10 12 W cm −2 or so, and is much smaller by 5 orders of magnitude, any potential contribution from non-thermal electrons is expected to be negligible.…”

Section: Methodsmentioning

confidence: 99%

Study of population dynamics toward the development of atomic X-ray lasers in the 3–5 keV photon energies

Heo,

Kim

2024

Jpn. J. Appl. Phys.

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X-ray free-electron lasers (XFELs) are powerful tools for characterizing and probing the properties of matter at atomic resolution on the ultrafast timescale. However, they have certain limitations such as spectral fluctuation and poor temporal coherence. Atomic X-ray lasers offer the narrow bandwidth, longitudinal coherence, and spectral stability that can overcome these limitations. In this paper, we study the interaction of inner-shell vacancy states with high-intensity XFEL pulses. We show that it is possible to achieve population inversion between K-shell and L-shell vacancy states in calcium and titanium when pumped by high-intensity XFEL pulses. These states can be used to generate atomic X-ray laser emission in the 3–5 keV photon energy range.

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Section: Methodsmentioning

confidence: 99%

Study of population dynamics toward the development of atomic X-ray lasers in the 3–5 keV photon energies

Heo,

Kim

2024

Jpn. J. Appl. Phys.

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Transient absorption of warm dense matter created by an X-ray free-electron laser

Mercadier,

Benediktovitch,

Krušič

et al. 2024

Nat. Phys.

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Warm dense matter is at the boundary between a plasma and a condensed phase and plays a role in astrophysics, planetary science and inertial confinement fusion research. However, its electronic structure and ionic structure upon irradiation with strong laser pulses remain poorly understood. Here, we use an intense and ultrafast X-ray free-electron laser pulse to simultaneously create and characterize warm dense copper using L-edge X-ray absorption spectroscopy over a large irradiation intensity range. Below a pulse intensity of 1015 W cm−2, an absorption peak below the L edge appears, originating from transient depletion of the 3d band. This peak shifts to lower energy with increasing intensity, indicating the movement of the 3d band upon strong X-ray excitation. At higher intensities, substantial ionization and collisions lead to the transition from reverse saturable absorption to saturable absorption of the X-ray free-electron laser pulse, two nonlinear effects that hold promise for X-ray pulse-shaping. We employ theoretical calculations that combine a model based on kinetic Boltzmann equations with finite-temperature real-space density-functional theory to interpret these observations. The results can be used to benchmark non-equilibrium models of electronic structure in warm dense matter.

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Exploring relaxation dynamics in warm dense plasmas by tailoring non-thermal electron distributions with a free electron laser

Shi,

Ren,

Chung

et al. 2024

Physics of Plasmas

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Knowing the characteristic relaxation time of free electrons in a dense plasma is crucial to our understanding of plasma equilibration and transport. However, experimental investigations of electron relaxation dynamics have been hindered by the ultrafast, sub-femtosecond timescales on which these interactions typically take place. Here, we propose a novel approach that uses x rays from a free electron laser to generate well-defined non-thermal electron distributions, which can then be tracked via emission spectroscopy from radiative recombination as they thermalize. Collisional radiative simulations reveal how this method can enable the measurement of electron relaxation timescales in situ, shedding light on the applicability and accuracy of the Coulomb logarithm framework for modeling collisions in dense plasmas.

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Non-thermal evolution of dense plasmas driven by intense x-ray fields

Cited by 11 publications

References 47 publications

Study of population dynamics toward the development of atomic X-ray lasers in the 3–5 keV photon energies

Study of population dynamics toward the development of atomic X-ray lasers in the 3–5 keV photon energies

Transient absorption of warm dense matter created by an X-ray free-electron laser

Exploring relaxation dynamics in warm dense plasmas by tailoring non-thermal electron distributions with a free electron laser

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