X-ray Spectroscopy of Hot Dense Plasmas: Experimental Limits, Line Shifts &amp; Field Effects

Renner, O.; Sauvan, P.; Dalimier, E.; Riconda, C.; Rosmej, F. B.; Weber, S.; Nicolaï, Philippe; Peyrusse, O.; Uschmann, I.; Höfer, Sebastian; Kämpfer, T.; Lötzsch, Robert; Zastrau, U.; Förster, E.; Oks, Eugene

doi:10.1063/1.3026477

Cited by 7 publications

(6 citation statements)

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“…The advent of such light sources stimulated rapid advances in many scientific disciplines ranging from atomic physics [6,7], study of molecules and chemical reactions [8,9], to clusters [10,11] and macroscopic objects [12-14] exposed to intense laser fields. They are actively used for creating and probing plasmas [15,16], hot dense matter [16][17][18] and warm dense matter [19,20]. Lower fluences of FELs are used to investigate structural changes within solid-state matter [12,[21][22][23][24].…”

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confidence: 99%

Femtosecond X-ray induced electron kinetics in dielectrics: application for FEL-pulse-duration monitor

Medvedev

2015

Appl. Phys. B

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regime of photon energy up to 24-25 keV with the pulse duration of a few tens of femtoseconds, possibly reduced further down to a few femtoseconds. The advent of such light sources stimulated rapid advances in many scientific disciplines ranging from atomic physics [6,7], study of molecules and chemical reactions [8,9], to clusters [10,11] and macroscopic objects [12-14] exposed to intense laser fields. They are actively used for creating and probing plasmas [15,16], hot dense matter [16][17][18] and warm dense matter [19,20]. Lower fluences of FELs are used to investigate structural changes within solid-state matter [12,[21][22][23][24]. These new light sources have also found a broad interest in the fields of nanophysics [25], molecular physics and biophysics [26].Insulators irradiated with femtosecond X-ray FEL radiation are observed to undergo a sequence of processes [12,27]. During the pulse, the photoabsorption excites electrons from the valence band, or deep atomic shells, to unoccupied conduction band states. The deep shell atomic holes then decay via Auger processes, which are the dominant relaxation channel for light elements (low-Z) [28]. An Auger decay promotes one more electron from the valence to the conduction band, following the relaxation of the deeper shell hole into the upper shells or the valence band. In case of heavy elements, with multiple shells, an intraatomic Auger cascade involving many steps over different shells is possible, ultimately ending up with multiple holes in the valence band. This process occurs typically on the few femtosecond timescale. The released photo-and Auger electrons scatter inelastically (so-called impact ionization of valence band or deep shell electrons of the material), or elastically (scattering on atoms or phonons without ionization of the target). Each impact ionization event excites one more electron into the conduction band. The impact ionization cascading typically occurs on the femtosecond Abstract Modern X-ray free-electron lasers (FELs) provide pulses with photon energies from a few tens of eV up to the tens of keV and durations as short as only a few femtoseconds. Experimental pump-probe scheme with a FEL pump and a visible light probe of a solid-state target can be used for the pulse-duration monitor on a shot-to-shot basis.To study the electron cascading in different materials used for pulse-duration monitor, XCASCADE, a Monte Carlo model of the X-ray-induced electron cascading within an irradiated target is developed. It is shown here that the electron cascade duration is sensitive to a choice of material. An appropriately selected target can significantly shorten the electron relaxation times. The grounds, upon which such a choice of the material can be made, are discussed. The results suggest that for photon energies of 24 keV, one could achieve direct monitoring of the pulse duration of 40 fs. Further deconvolution of the electron density into the contribution from the pulse itself and from the secondary cascading can increase the resolution up ...

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confidence: 99%

Femtosecond X-ray induced electron kinetics in dielectrics: application for FEL-pulse-duration monitor

Medvedev

2015

Appl. Phys. B

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“…The experimental configuration was based on a classic spectroscopic scheme with the detector placed at intersection of the central ray with the Rowland circle and the source-to-crystal and crystal-to-image distances fulfilling the focusing condition in the sagittal plane (decisive for its optimum one-dimensional spatial resolution - Renner et al, 2004). This setup provides the spectral Laser-driven ablation through fast electrons in PALS-experiment 181 resolution comparable with the intrinsic value λ/Δλ ≈ 10 4 following from the dynamical theory of X-ray diffraction at bent mica crystals (Renner et al, 2008). The spatially-resolved time-integrated spectra were recorded on X-ray film Kodak Industrex AA400.…”

Section: X-ray Measurementsmentioning

confidence: 96%

Laser-driven ablation through fast electrons in PALS-experiment at the laser radiation intensity of 1–50 PW/cm²

et al. 2014

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The paper is directed to the study of high-temperature plasma and ablation plasma formation as well as efficiency of the laser energy transfer to solid targets irradiated by laser pulses with intensities of 1–50 PW/cm2 and duration of 200–300 ps, i.e., at conditions corresponding to the characteristics of the laser spike designed to generate the igniting shock wave in the shock ignition concept. The experiments have been performed at Prague Asterix Laser System. The iodine laser delivered 250 ps (full width at half maximum) pulses with the energy in the range of 100–600 J at the first (λ1 = 1.315 µm) and third (λ3 = 0.438 µm) harmonic frequencies. The focal spot radius of the laser beam on the surface of Al or Cu targets made was gradually decreased from 160 to 40 µm. The diagnostic data collected using three-frame interferometry, X-ray spectroscopy, and crater replica technique were interpreted by two-dimensional numerical and analytical modeling which included generation and transport of fast electrons. The coupling parameter Iλ2 was varied in the range of 1 × 1014−8 × 1016 Wμm2/cm2 covering the regimes of weak to intense fast electron generation. The dominant contribution of fast electron energy transfer into the ablation process and shock wave generation was found when using the first harmonic laser radiation, the focal spot radius of 40–100 µm, and the laser energy of 300–600 J.

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“…It enables creating and probing plasmas, 14,15 hot dense matter, [15][16][17] and warm dense matter, 18,19 as well as the investigation of the interaction of low-fluence ultrafast laser pulses with matter, with applications to structural studies within solidstate physics, 11,[20][21][22][23] nanophysics, 24 molecular physics, and biophysics. 25 The presently operating free-electron lasers can produce laser pulses with durations of a few tens down to a few femtoseconds.…”

Section: Introductionmentioning

confidence: 99%

Nonthermal graphitization of diamond induced by a femtosecond x-ray laser pulse

2013

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Diamond irradiated with an ultrashort intense laser pulse in the regime of photon energies from soft up to hard x rays can undergo a phase transition to graphite. This transition is induced by an excitation of electrons from the valence band or from atomic deep shells of the material into its conduction band, which is followed by a transient rapid change of the interatomic potential. Such a nonthermal phase transition occurs on a femtosecond time scale, shortly after or even during the laser pulse. In this work we show that the duration of the graphitization depends on the incoming photon energy: the higher the photon energy is, the longer the secondary electron cascading which promotes the electrons into the conduction band will take. The transient kinetics of the electronic and atomic processes during the graphitization is analyzed in detail. The damage threshold fluence is calculated in the broad photon energy range and is found to be always ∼0.7 eV/atom in terms of the average dose absorbed per atom. It is confirmed that the temporal characteristics of a femtosecond laser pulse (at a fixed pulse duration and fluence) do not significantly influence the transient damage kinetics. Finally, the influence of an additional surface layer of high-Z material on the damage within diamond is discussed.

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X-ray Spectroscopy of Hot Dense Plasmas: Experimental Limits, Line Shifts & Field Effects

Cited by 7 publications

References 10 publications

Femtosecond X-ray induced electron kinetics in dielectrics: application for FEL-pulse-duration monitor

Femtosecond X-ray induced electron kinetics in dielectrics: application for FEL-pulse-duration monitor

Laser-driven ablation through fast electrons in PALS-experiment at the laser radiation intensity of 1–50 PW/cm²

Nonthermal graphitization of diamond induced by a femtosecond x-ray laser pulse

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X-ray Spectroscopy of Hot Dense Plasmas: Experimental Limits, Line Shifts & Field Effects

Cited by 7 publications

References 10 publications

Femtosecond X-ray induced electron kinetics in dielectrics: application for FEL-pulse-duration monitor

Femtosecond X-ray induced electron kinetics in dielectrics: application for FEL-pulse-duration monitor

Laser-driven ablation through fast electrons in PALS-experiment at the laser radiation intensity of 1–50 PW/cm2

Nonthermal graphitization of diamond induced by a femtosecond x-ray laser pulse

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Laser-driven ablation through fast electrons in PALS-experiment at the laser radiation intensity of 1–50 PW/cm²