Analysis of statistical correlations and intensity spiking in the self-amplified spontaneous-emission free-electron laser

Krinsky, S.; Gluckstern, R.L.

doi:10.1103/physrevstab.6.050701

Cited by 51 publications

(36 citation statements)

References 26 publications

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“…(9) [21]. The spectral distribution of a single XFEL pulse is very spiky and random [22,37]. Averaged over many shots the spectral distribution can be taken as a normalized Gaussian [38,39],…”

Section: B Two-photon Ionization Cross Section For Chaotic Fieldsmentioning

confidence: 99%

Enhanced nonlinear response of Ne8+to intense ultrafast x rays

et al. 2012

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We investigate the possible reasons for the discrepancy between the theoretical two-photon ionization cross section, ∼10 −56 cm 4 s, of Ne 8+ obtained within the perturbative nonrelativistic framework for monochromatic light [S. Novikov and A. Hopersky, J. Phys. B 34, 4857 (2001)] and the experimental value, 7 × 10 −54 cm 4 s, reported in [G. Doumy et al., Phys. Rev. Lett. 106, 083002 (2011)] at a photon energy of 1110 eV. To this end, we consider Ne 8+ exposed to deterministic and chaotic ensembles of intense x-ray pulses. The time-dependent configuration interaction singles (TDCIS) method is used to quantitatively describe nonlinear ionization of Ne 8+ induced by coherent intense ultrashort x-ray laser pulses. The impact of the bandwidth of a chaotic ensemble of x-ray pulses on the effective two-photon ionization cross section is studied within the lowest nonvanishing order of perturbation theory. We find that, at a bandwidth of 11 eV, the effective two-photon ionization cross section of Ne 8+ at a photon energy of 1110 eV amounts to 5 × 10 −57 and 1.6 × 10 −55 cm 4 s for a deterministic ensemble and a chaotic ensemble, respectively. We show that the enhancement obtained for a chaotic ensemble of pulses originates from the presence of the one-photon 1s 2 -1s4p resonance located at 1127 eV. Using the TDCIS approach, we also show that, for currently available radiation intensities, two-photon ionization of a 1s electron in neutral neon remains less probable than one-photon ionization of a valence electron.

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Section: B Two-photon Ionization Cross Section For Chaotic Fieldsmentioning

confidence: 99%

Enhanced nonlinear response of Ne8+to intense ultrafast x rays

et al. 2012

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“…The pulses produced by the SASE process have a huge shot-to-shot fluctuation [43]of the pulse energy and spectrum and are characterized by low temporal coherence and a relatively large spectral bandwidth of around 1% in the soft x-ray regime [43,44]. The previous XRL experiments were performed in SASE operation, and we will hence characterize the XRL output for SASE pulses.…”

Section: Self-amplified Spontaneous-emission Pump Pulsementioning

confidence: 99%

Transient-gain photoionization x-ray laser

Weninger

Rohringer

2014

Phys. Rev. A

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We present a generalized theory based on one-dimensional Maxwell-Bloch equations to study the amplification process of an inner-shell photoionization-pumped atomic x-ray laser. Focusing an x-ray free-electron laser beam in an elongated neon-gas target results in a strong exponential amplification of Kα fluorescence, as recently demonstrated [N. Rohringer et al., Nature (London) 481, 488 (2012); C. Weninger et al., Phys.Re v .Lett.111, 233902 (2013)]. Here, we present an in-depth theoretical study of the amplification process that goes beyond the previous theory based on a rate-equation approach. We study the evolution of the pulse characteristics during the amplification process for transform-limited Gaussian and broadband self-amplified spontaneous-emission pump pulses. We discuss the impact of the gain-dependent group velocity on the emitted x-ray radiation and the resulting gain-guiding effects. A thorough analysis of the spectral and temporal properties of the emitted radiation is presented, including higher-order field-correlation functions, to characterize the ensemble of emitted x-ray pulses.

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“…To a good approximation the XFEL SASE pulses can be modeled as chaotic pulses with Gaussian statistics [18,32]. These pulses show a spiky pulse structure in the time and in the frequency domain as shown for a single SASE shot in Figs.…”

Section: Theoretical Approachmentioning

confidence: 99%

“…The ensemble average of the pulses is characterized by the average spectral bandwidth ω and the average pulse duration T . The temporal coherence (average width of a spike in the time domain) is related to the total spectral width T coh = √ π ω and the spectral coherence (average width of a spike in the frequency domain) is inversely proportional to the average pulse duration ω coh = 1 T [18,19]. Throughout the paper we assume a Gaussian power spectrum for the ensemble average with a bandwidth of ω = 7 eV (FWHM).…”

Section: Theoretical Approachmentioning

confidence: 99%

“…SASE pulses are characterized by a relatively broad bandwidth (typically 0.1% to 1% of the central photon energy) of limited longitudinal coherence. This results in emission spectra which vary on a shot-to-shot basis [17] and are very spiky in both time and frequency domain [18,19] (see Figs. 3(b) and 3(d) as an example for the temporal and spectral intensity envelope of a typical SASE pulse).…”

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confidence: 99%

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Stimulated resonant x-ray Raman scattering with incoherent radiation

Weninger

Rohringer

2013

Phys. Rev. A

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We present a theoretical study on stimulated electronic Raman scattering in neon by resonant excitation with an x-ray free electron laser (XFEL). This study is in support of the recent experimental demonstration [C. Weninger et al., Phys. Rev. Lett. (to be published)] of stimulated x-ray Raman scattering. Focusing the broadband XFEL pulses into a cell of neon gas at atmospheric pressure a strong inelastic x-ray scattering signal in the forward direction was observed, as the x-ray energy was varied across the region of core-excited Rydberg states and the K edge. The broadband and intrinsically incoherent x-ray pulses from the XFEL lead to a rich, structured line shape of the scattered radiation. We present a generalized Maxwell-Liouville-von Neumann approach to self-consistently solve for the amplification of the scattered radiation along with the time evolution of the density matrix of the atomic and residual ionic system. An in-depth analysis of the evolution of the emission spectra as a function of the Raman gain is presented. Furthermore, we propose the use of statistical methods to obtain high-resolution scattering data beyond the lifetime broadening despite pumping with incoherent x-ray pulses.

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Analysis of statistical correlations and intensity spiking in the self-amplified spontaneous-emission free-electron laser

Cited by 51 publications

References 26 publications

Enhanced nonlinear response of Ne8+to intense ultrafast x rays

Enhanced nonlinear response of Ne8+to intense ultrafast x rays

Transient-gain photoionization x-ray laser

Stimulated resonant x-ray Raman scattering with incoherent radiation

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