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R Loetzsch,
O Jäckel,
S Höfer,
T Kämpfer,
J Polz, I Uschmann,
M C Kaluza,
E Förster,
E Stambulchik,
E Kroupp,
Y Maron
[show abstract]
[hide abstract]
ABSTRACT: We developed a detection scheme, capable of measuring X-ray line shape of tracer ions in μm thick layers at the rear side of a target foil irradiated by ultra intense laser pulses. We performed simulations of the effect of strong electric fields on the K-shell emission of silicon and developed a spectrometer dedicated to record this emission. The combination of a cylindrically bent crystal in von Hámos geometry and a CCD camera with its single photon counting capability allows for a high dynamic range of the instrument and background free spectra. This approach will be used in future experiments to study electric fields of the order of TV/m at high density plasmas close to solid density.
The Review of scientific instruments 11/2012; 83(11):113507. · 1.52 Impact Factor
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U Zastrau,
A Sengebusch,
P Audebert,
E Brambrink,
R R Fäustlin,
T Kämpfer,
E Kroupp,
R Loetzsch,
Y Maron,
H Reinholz,
G Röpke,
E Stambulchik, I Uschmann,
E Förster
[show abstract]
[hide abstract]
ABSTRACT: We studied temperature and Ka yield radial profiles of thin titanium foils as a result of femtosecond high-power laser pulse irradiation at several 10 19 W/cm 2 by high-resolution x-ray spectroscopy. Laser-accelerated electrons heat the cold solid to bulk temperatures of up to 50 eV. The plasma strongly affects the shape of the emitted Ka doublet, which is surveyed by x-ray spectroscopy with both high spectral (E/DE ! 15,000) and 1D spatial (Dx 13.5 mm) resolutions. Temperature-dependent spectra modeled by line-shape calculations are compared with Abel-inverted experimental spectra and provide a radial temperature distribution. The radially resolved Ka yield shows a depletion of the Ka 1 -line at the position of the laser focus. The density gradients induced by prepulses are modeled by hydrodynamic simulations, and density-dependent line-shape models are applied. The x-ray yield as function of foil thickness is explained by partial refluxing of a multi-keV electron distribution inside the foil, supported by Monte-Carlo simulations. Finally, we derive parameters to optimize the peak brilliance of such a laser-driven thin foil x-ray source.
High Energy Density Physics 06/2012; 7(2):47-53. · 1.60 Impact Factor
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ABSTRACT: We present new results for laser excited semiconductor crystals probed by ultrashort x-ray pulses diffracted by the crystal
lattice. First we discuss acoustical phonons of semiconductors, i.e. indium antimonite and germanium, and then we describe
the temporal evolution of the laser-induced metal–semiconductor phase transition of samarium sulfide.
Applied Physics A 04/2012; 96(1):91-98. · 1.63 Impact Factor
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U. Zastrau,
T. Burian,
J. Chalupsky,
T. Döppner,
T.W.J. Dzelzainis,
R.R. Fäustlin,
C. Fortmann,
E. Galtier,
S.H. Glenzer,
G. Gregori, [......],
A.J. Nelson,
D. Riley,
F.B. Rosmej,
S. Toleikis,
T. Tschentscher, I. Uschmann,
S.M. Vinko,
J.S. Wark,
T. Whitcher,
E. Förster
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ABSTRACT: We report on experiments aimed at the generation and characterization of solid density plasmas at the free-electron laser FLASH in Hamburg. Aluminum samples were irradiated with XUV pulses at 13.5 nm wavelength (92 eV photon energy). The pulses with duration of a few tens of femtoseconds and pulse energy up to 100 µJ are focused to intensities ranging between 1013 and 1017 W/cm2. We investigate the absorption and temporal evolution of the sample under irradiation by use of XUV and optical spectroscopy. We discuss the origin of saturable absorption, radiative decay, bremsstrahlung and atomic and ionic line emission. Our experimental results are in good agreement with simulations.
Laser and Particle Beams 03/2012; 30(1):45. · 1.62 Impact Factor
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E Kroupp,
D Osin,
A Starobinets,
V Fisher,
V Bernshtam,
L Weingarten,
Y Maron, I Uschmann,
E Förster,
A Fisher,
M E Cuneo,
C Deeney,
J L Giuliani
[show abstract]
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ABSTRACT: The time history of the local ion kinetic energy in a stagnating plasma was determined from Doppler-dominated line shapes. Using independent determination of the plasma properties for the same plasma region, the data allowed for inferring the time-dependent ion temperature, and for discriminating the temperature from the total ion kinetic energy. It is found that throughout most of the stagnation period the ion thermal energy constitutes a small fraction of the total ion kinetic energy; the latter is dominated by hydrodynamic motion. Both the ion hydrodynamic and thermal energies are observed to decrease to the electron thermal energy by the end of the stagnation period. It is confirmed that the total ion kinetic energy available at the stagnating plasma and the total radiation emitted are in balance, as obtained in our previous experiment. The dissipation time of the hydrodynamic energy thus appears to determine the duration (and power) of the K emission.
Physical Review Letters 09/2011; 107(10):105001. · 7.37 Impact Factor
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ABSTRACT: We demonstrate that an ultrashort-pulse laser-driven x-ray diode can be used for time-resolved experiments on a picosecond timescale. Hence, acoustical phonons in germanium are observed after ultrashort laser-excitation and the results are compared with calculations according to a microphysical model. We also show the advantages of this kind of picosecond x-ray source compared to other sources on the basis of its properties.
Applied Physics Letters 04/2011; 98(14):141109-141109-3. · 3.84 Impact Factor
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A Lübcke,
F Zamponi,
R Loetzsch,
T Kämpfer, I Uschmann,
V Große,
F Schmidl,
T Köttig,
M Thürk,
H Schwoerer,
E Förster,
P Seidel,
R Sauerbrey
[show abstract]
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ABSTRACT: We investigate the structural response of SrTiO3 when Cooper pairs are broken in an epitaxially grown YBa2Cu3O7 top layer due to both heating and optical excitation. The crystal structure is investigated by static, temperature-dependent and time-resolved x-ray diffraction. In the static case, a large strain field in SrTiO3 is formed in the proximity of the onset of the superconducting phase in the top layer, suggesting a relationship between both effects. For the time-dependent studies, we likewise find a large fraction of the probed volume of the SrTiO3 substrate strained if the top layer is superconducting. Upon optical breaking of Cooper pairs, the observed width of the rocking curve is reduced and its position is slightly shifted towards smaller angles. The dynamical theory of x-ray diffraction is used to model the measured rocking curves. We find that the thickness of the strained layer is reduced by about 200 nm on a sub-ps to ps timescale, but the strain value at the interface between SrTiO3 and YBa2Cu3O7 remains unaffected.
New Journal of Physics 08/2010; 12(8):083043. · 4.18 Impact Factor
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F Zamponi,
A Lübcke,
T Kämpfer, I Uschmann,
E Förster,
A P L Robinson,
A Giulietti,
P Köster,
L Labate,
T Levato,
L A Gizzi
[show abstract]
[hide abstract]
ABSTRACT: Front and rear side x-ray emission from thin titanium foils irradiated by ultraintense laser pulses at intensities up to ≈5 × 10(19) W/cm2 was measured using a high-resolution imaging system. Significant differences in intensity, dimension, and spectrum between front and rear side emission intensity in the 3-12 keV photon energy range was found even for 5 μm thin Ti foils. Simulations and analysis of space-resolved spectra explain this behavior in terms of directional bremsstrahlung emission from fast electrons generated during the interaction process.
Physical Review Letters 08/2010; 105(8):085001. · 7.37 Impact Factor
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R R Fäustlin,
Th Bornath,
T Döppner,
S Düsterer,
E Förster,
C Fortmann,
S H Glenzer,
S Göde,
G Gregori,
R Irsig, [......],
F Tavella,
R Thiele,
J Tiggesbäumker,
S Toleikis, I Uschmann,
S M Vinko,
T Whitcher,
U Zastrau,
B Ziaja,
Th Tschentscher
[show abstract]
[hide abstract]
ABSTRACT: We investigate ultrafast (fs) electron dynamics in a liquid hydrogen sample, isochorically and volumetrically heated to a moderately coupled plasma state. Thomson scattering measurements using 91.8 eV photons from the free-electron laser in Hamburg (FLASH at DESY) show that the hydrogen plasma has been driven to a nonthermal state with an electron temperature of 13 eV and an ion temperature below 0.1 eV, while the free-electron density is 2.8x10{20} cm{-3}. For dense plasmas, our experimental data strongly support a nonequilibrium kinetics model that uses impact ionization cross sections based on classical free-electron collisions.
Physical Review Letters 03/2010; 104(12):125002. · 7.37 Impact Factor
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[show abstract]
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ABSTRACT: The displacive phase transition in SrTiO3 was investigated by means of x-ray diffraction. We used 4.5 keV photons thus probing only a very thin region near the surface. In the low temperature phase the lattice parameters evolve substantially different than in bulk material. We also investigated the phase transition under the influence of an epitaxial coating with YBaCu2O7 and found the nature of the phase transition changed. The near-surface region behaves like an epitaxial thin SrTiO3 film.
Applied Physics Letters 02/2010; 96(7):071901-071901-3. · 3.84 Impact Factor
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U Zastrau,
P Audebert,
V Bernshtam,
E Brambrink,
T Kämpfer,
E Kroupp,
R Loetzsch,
Y Maron,
Yu Ralchenko,
H Reinholz,
G Röpke,
A Sengebusch,
E Stambulchik, I Uschmann,
L Weingarten,
E Förster
[show abstract]
[hide abstract]
ABSTRACT: We study warm dense matter formed by subpicosecond laser irradiation at several 10(19) W/cm(2) of thin Ti foils using x-ray spectroscopy with high spectral (E/DeltaE approximately 15,000) and one-dimensional spatial (Deltax=13.5 microm) resolutions. Ti Kalpha doublets modeled by line-shape calculations are compared with Abel-inverted single-pulse experimental spectra and provide radial distributions of the bulk-electron temperature and the absolute-photon number Kalpha yield in the target interiors. A core with approximately 40 eV extends homogeneously up to ten times the laser-focus size. The spatial distributions of the bulk-electron temperature and Kalpha yield are strongly correlated.
Physical Review E 02/2010; 81(2 Pt 2):026406. · 2.26 Impact Factor
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Plasma Science, 2010 Abstracts IEEE International Conference on; 01/2010
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F Zamponi,
A Luebcke,
T Kaempfer, I Uschmann,
E Foerster,
A P L Robinson,
A Giulietti,
P Koester,
L Labate,
T Levato,
L A Gizzi
Physical Review Letters 01/2010; 105(26). · 7.37 Impact Factor
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L Labate,
E Foerster,
A Giulietti,
D Giulietti,
S Hoefer,
T Kaempfer,
P Koester,
M Kozlova,
T Levato,
R Loetzsch,
A Luebcke,
T Mocek,
J Polan,
B Rus, I Uschmann,
F Zamponi,
L A Gizzi
Laser and Particle Beams 12/2009; 27(4):643-649. · 1.62 Impact Factor
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S Betti,
C A Cecchetti,
E Foerster,
A Gamucci,
A Giulietti,
D Giulietti,
T Kaempfer,
P Koester,
L Labate,
T Levato,
A Luebcke, I Uschmann,
F Zamponi,
L A Gizzi
Physics of Plasmas 10/2009; 16(10). · 2.15 Impact Factor
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[show abstract]
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ABSTRACT: The emitted Kα-spectra of moderately ionized titanium radiators in a medium are used to determine plasma temperature and composition in electron heated target regions. A theoretical treatment of spectral line profiles using self-consistent Hartree–Fock and ion sphere model calculations to determine the influence of plasma polarization is applied. We confirm the importance of excited emitter states for line shape modeling.
Journal of Physics A Mathematical and Theoretical 05/2009; 42(21):214061. · 1.56 Impact Factor
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E Stambulchik,
L Weingarten,
E Kroupp,
D Fisher,
Y Maron,
U Zastrau, I Uschmann,
F Zamponi,
Eförster,
A Sengebusch,
H Reinholz,
Gröpke,
Yu Ralchenko
[show abstract]
[hide abstract]
ABSTRACT: Modeling of x-ray spectra emitted from a solid-density strongly coupled plasma formed in short-duration, high-power laser–matter interactions represents a highly challenging task due to extreme conditions found in these experiments. In this paper we present recent progress in the modeling and analysis of Kα emission from solid-density laser-produced titanium plasmas. The self-consistent modeling is based on collisional-radiative calculations that comprise many different processes and effects, such as satellite formation and blending, plasma polarization, Stark broadening, solid-density quantum effects and self-absorption. A rather strong dependence of the Kα shape on the bulk electron temperature is observed. Preliminary analysis of recently obtained experimental data shows a great utility of the calculations, allowing for inferring a temperature distribution of the bulk electrons from a single-shot measurement.
J. Phys. A: Math. Theor. 01/2009; 42.
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U Zastrau,
C Fortmann,
R R Fäustlin,
L F Cao,
T Döppner,
S Düsterer,
S H Glenzer,
G Gregori,
T Laarmann,
H J Lee, [......],
G Röpke,
R Thiele,
J Tiggesbäumker,
N X Truong,
S Toleikis, I Uschmann,
A Wierling,
T Tschentscher,
E Förster,
R Redmer
[show abstract]
[hide abstract]
ABSTRACT: We report the creation of solid-density aluminum plasma using free-electron laser (FEL) radiation at 13.5nm wavelength. Ultrashort pulses were focused on a bulk Al target, yielding an intensity of 2x10;{14}Wcm;{2} . The radiation emitted from the plasma was measured using an xuv spectrometer. Bremsstrahlung and line intensity ratios yield consistent electron temperatures of about 38eV , supported by radiation hydrodynamics simulations. This shows that xuv FELs heat up plasmas volumetrically and homogeneously at warm-dense-matter conditions, which are accurately characterized by xuv spectroscopy.
Physical Review E 01/2009; 78(6 Pt 2):066406. · 2.26 Impact Factor
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R. R. Fäustlin,
S. Toleikis,
Th. Bornath,
L. Cao,
T. Döppner,
S. Düsterer,
E. Förster,
C. Fortmann,
S. H. Glenzer,
S. Göde, [......],
P. Radcliffe,
R. Redmer,
H. Reinholz,
G. Röpke,
R. Thiele,
J. Tiggesbäumker,
N. X. Truong, I. Uschmann,
U. Zastrau,
Th. Tschentscher
[show abstract]
[hide abstract]
ABSTRACT: We present the attempt to diagnose electron temperature and density of a plasma via Thomson Scattering in the Warm Dense Matter
Regimew using soft x-ray Free Electron Laser radiation. A preliminary Self Thomson Scattering experiment has already been
conducted. In a current pump-probe experiment, together with an optical heating laser, we will record the temporal evolution
of the plasma achieving a resolution of approximately 250fs.
12/2008: pages 241-243;
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E.~Stambulchik,
E.~Kroupp,
D.~Osin,
V.~Bernshtam,
L.~Weingarten,
D.~Fisher,
Y.~Maron, I.~Uschmann,
F.~Zamponi,
U.~Zastrau,
E Förster,
A.~Sengebusch,
H.~Reinholz,
G.~Röpke,
Yu.~Ralchenko
International Conference on Strongly Coupled Coulomb Systems; 01/2008
