Bremsstrahlung and line spectroscopy of warm dense aluminum plasma heated by xuv free-electron-laser radiation

Zastrau, U.; Fortmann, C.; Fäustlin, R. R.; Cao, Leifeng; Döppner, T.; Düsterer, S.; Glenzer, S. H.; Gregori, G.; Laarmann, Tim; Lee, H. J.; Przystawik, Andreas; Radcliffe, P.; Reinholz, H.; Röpke, G.; Thiele, R.; Tiggesbäumker, J.; Trường, Nguyễn Xuân; Toleikis, S.; Uschmann, I.; Wierling, A.; Tschentscher, Th.; Förster, E.; Redmer, R.

doi:10.1103/physreve.78.066406

Cited by 69 publications

(58 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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

View full text Add to dashboard Cite

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.

show abstract

Section: Introductionmentioning

confidence: 99%

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

2013

View full text Add to dashboard Cite

show abstract

“…2. In these experiments, carried out with a different set-up and a 29 µm focal spot 23 , the integrated spectra of 1,800 shots were measured (see Fig. 3).…”

mentioning

confidence: 99%

Turning solid aluminium transparent by intense soft X-ray photoionization

Nagler¹,

Zastrau²,

Fäustlin³

et al. 2009

Nature Phys

251

View full text Add to dashboard Cite

Saturable absorption is a phenomenon readily seen in the optical and infrared wavelengths. It has never been observed in core-electron transitions owing to the short lifetime of the excited states involved and the high intensities of the soft X-rays needed. We report saturable absorption of an L-shell transition in aluminium using record intensities over 10 16 W cm −2 at a photon energy of 92 eV. From a consideration of the relevant timescales, we infer that immediately after the X-rays have passed, the sample is in an exotic state where all of the aluminium atoms have an L-shell hole, and the valence band has approximately a 9 eV temperature, whereas the atoms are still on their crystallographic positions. Subsequently, Auger decay heats the material to the warm dense matter regime, at around 25 eV temperatures. The method is an ideal candidate to study homogeneous warm dense matter, highly relevant to planetary science, astrophysics and inertial confinement fusion. Saturable absorption, the decrease in the absorption of light with increasing intensity, is a well-known effect in the visible and near-visible region of the electromagnetic spectrum 1 , and is a widely exploited phenomenon in laser technology. Although there are many ways to induce this effect, in the simplest two-level system it will occur when the population of the lower, absorbing level is severely depleted, which requires light intensities sufficiently high to overcome relaxation from the upper level. Here, we report on the production of saturable absorption of a metal in the soft X-ray regime by the creation of highly uniform warm dense conditions, a regime that is of great interest in high-pressure science 2,3 , the geophysics of large planets 4,5 , astrophysics 6 , plasma production and inertial confinement fusion 7 . Furthermore, the process by which the saturation of the absorption occurs will lead, after the X-ray pulse, to the storage of about 100 eV per atom, which in turn evolves to a warm dense state. This manner of creation is unique as it requires intense, subpicosecond, soft X-rays. As such, it has not hitherto been observed in this region of the spectrum, owing both to the lack of high-intensity sources, and the rapid recombination times associated with such high photon energies. However, with the advent of new fourth-generation X-ray light sources, including the free-electron laser in Hamburg 8 (FLASH), soft X-ray intensities that have previously remained the province of high-power optical lasers can now be produced. Experiments at such high intensities using gas jets have already exhibited novel absorption phenomena 9 , and the possibility of irradiating solid samples with intense soft and hard X-rays has aroused interest as a possible means of producing warm dense matter (WDM) at known atomic densities 10,11 .We present the first measurements of the absorption coefficient of solid samples subject to subpicosecond soft X-ray pulses with intensities up to and in excess of 10 16 W cm −2 , two orders of magnitude higher than could ...

show abstract

“…This grid acts as a second grating which leads to Fourierimposed structures, especially in the pedestals of narrow, isolated lines [10,15].…”

Section: Xuv Dispersive Elementsmentioning

confidence: 99%

In-situ determination of dispersion and resolving power in simultaneous multiple-angle XUV spectroscopy

et al. 2011

View full text Add to dashboard Cite

We report on the simultaneous determination of non-linear dispersion functions and resolving power of three flat-field XUV grating spectrometers. A moderate-intense short-pulse infrared laser is focused onto technical aluminum which is commonly present as part of the experimental setup. In the XUV wavelength range of 10-19 nm, the spectrometers are calibrated using Al-Mg plasma emission lines. This cross-calibration is performed in-situ in the very same setup as the actual main experiment. The results are in excellent agreement with ray-tracing simulations. We show that our method allows for precise relative and absolute calibration of three different XUV spectrometers.

show abstract

Bremsstrahlung and line spectroscopy of warm dense aluminum plasma heated by xuv free-electron-laser radiation

Cited by 69 publications

References 43 publications

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

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

Turning solid aluminium transparent by intense soft X-ray photoionization

In-situ determination of dispersion and resolving power in simultaneous multiple-angle XUV spectroscopy

Contact Info

Product

Resources

About