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Dive into the research topics where R. Thiele is active.

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Featured researches published by R. Thiele.


High Energy Density Physics | 2007

Thomson scattering from near-solid density plasmas using soft x-ray free electron lasers

A. Höll; Th. Bornath; L. Cao; T. Döppner; S. Düsterer; E. Förster; C. Fortmann; S. H. Glenzer; G. Gregori; T. Laarmann; Karl-Heinz Meiwes-Broer; A. Przystawik; P. Radcliffe; R. Redmer; H. Reinholz; G. Röpke; R. Thiele; J. Tiggesbäumker; S. Toleikis; N. X. Truong; T. Tschentscher; I. Uschmann; U. Zastrau

We propose a collective Thomson scattering experiment at the VUV free electron laser facility at DESY (FLASH) which aims to diagnose warm dense matter at near-solid density. The plasma region of interest marks the transition from an ideal plasma to a correlated and degenerate many-particle system and is of current interest, e.g. in ICF experiments or laboratory astrophysics. Plasma diagnostic of such plasmas is a longstanding issue. The collective electron plasma mode (plasmon) is revealed in a pump-probe scattering experiment using the high-brilliant radiation to probe the plasma. The distinctive scattering features allow to infer basic plasma properties. For plasmas in thermal equilibrium the electron density and temperature is determined from scattering off the plasmon mode.


international conference on plasma science | 2005

Theory of X-ray Thomson scattering in dense plasmas

R. Redmer; Heidi Reinholz; Gerd Röpke; R. Thiele; A. Höll

For the diagnostics of dense plasmas, photons in the vacuum ultraviolet (VUV) or X-ray domain are required. First experiments have demonstrated the great capacity of X-ray Thomson scattering for the determination of plasma parameters such as density, temperature, and ionization state. For a reliable interpretation of the experimental data, the interaction of energetic photons with the plasma has to be considered. The cross section for Thomson scattering is related to the dynamic structure factor S(k,/spl omega/). We improve the usual random phase approximation by including collisions and calculate a dynamic collision frequency in Born approximation. We also study the influence of dynamic screening and the relation to the concept of dynamic local-field corrections to the dielectric function. We give results for a variety of plasma parameters and determine the region where collisions are of relevance.


New Journal of Physics | 2012

Dynamic structure factor in warm dense beryllium

K-U Plagemann; Philipp Sperling; R. Thiele; Michael P. Desjarlais; C. Fortmann; T. Döppner; Hae Ja Lee; S. H. Glenzer; R. Redmer

We calculate the dynamic structure factor (DSF) in warm dense beryllium by means of ab initio molecular dynamics simulations. The dynamic conductivity is derived from the Kubo-Greenwood formula, and a Drude- like behaviour is observed. The corresponding dielectric function is used to determine the DSF. Since the ab initio approach is so far only applicable for wavenumbers k = 0, the k-dependence of the dielectric function is modelled via the Mermin ansatz. We present the results for the dielectric function and DSF of warm dense beryllium and compare these with perturbative treatments such as the Born-Mermin approximation. We found considerable differences between the results of these approaches; this underlines the need for a first-principles determination of the DSF of warm dense matter.


Journal of Physics B | 2010

Probing near-solid density plasmas using soft X-ray scattering

S. Toleikis; T. Bornath; T. Döppner; S. Düsterer; R. R. Fäustlin; E. Förster; C. Fortmann; S. H. Glenzer; S. Göde; G. Gregori; R. Irsig; T. Laarmann; Hae Ja Lee; Bin Li; Karl-Heinz Meiwes-Broer; J. Mithen; B. Nagler; A. Przystawik; P. Radcliffe; H. Redlin; R. Redmer; H. Reinholz; G. Röpke; F. Tavella; R. Thiele; J. Tiggesbäumker; I. Uschmann; S. M. Vinko; T. Whitcher; U. Zastrau

X-ray scattering using highly brilliant x-ray free-electron laser (FEL) radiation provides new access to probe free-electron density, temperature and ionization in near-solid density plasmas. First experiments at the soft x-ray FEL FLASH at DESY, Hamburg, show the capabilities of this technique. The ultrashort FEL pulses in particular can probe equilibration phenomena occurring after excitation of the plasma using ultrashort optical laser pumping. We have investigated liquid hydrogen and find that the interaction of very intense soft x-ray FEL radiation alone heats the sample volume. As the plasma establishes, photons from the same pulse undergo scattering, thus probing the transient, warm dense matter state. We find a free-electron density of (2.6 ± 0.2) × 1020 cm−3 and an electron temperature of 14 ± 3.5 eV. In pump–probe experiments, using intense optical laser pulses to generate more extreme states of matter, this interaction of the probe pulse has to be considered in the interpretation of scattering data. In this paper, we present details of the experimental setup at FLASH and the diagnostic methods used to quantitatively analyse the data.


High Energy Density Physics | 2009

Thomson scattering in dense plasmas with density and temperature gradients

C. Fortmann; R. Thiele; R. R. Fäustlin; Th. Bornath; Bastian Holst; W.-D. Kraeft; V. Schwarz; S. Toleikis; Th. Tschentscher; R. Redmer

Abstract Collective X-ray Thomson scattering has become a versatile tool for the diagnostics of dense plasmas. Assuming homogeneous density and temperature throughout the target sample, these parameters can be determined directly from the plasmon dispersion and the ratio of plasmon amplitudes via detailed balance. In inhomogeneous media, the scattering signal is an average of the density and temperature dependent scattering cross-section weighted with the density and temperature profiles. We analyse Thomson scattering spectra in the XUV range from near solid density hydrogen targets generated by free electron laser radiation. The influence of plasma inhomogeneities on the scattering spectrum is investigated by comparing density and temperature averaged scattering signals to calculations assuming homogeneous targets. We find discrepancies larger than 10% between the mean electron density and the effective density as well as between the mean temperature and the effective temperature.


Proceedings of SPIE | 2009

Soft X-Ray Thomson scattering in warm dense hydrogen at FLASH

R. R. Fäustlin; S. Toleikis; Th. Bornath; T. Döppner; S. Düsterer; E. Förster; C. Fortmann; S. H. Glenzer; S. Göde; G. Gregori; R. Irsig; T. Laarmann; Hyesog Lee; B. Li; Karl-Heinz Meiwes-Broer; J. Mithen; A. Przystawik; H. Redlin; R. Redmer; H. Reinholz; G. Röpke; F. Tavella; R. Thiele; J. Tiggesbäumker; I. Uschmann; U. Zastrau; Th. Tschentscher

We present collective Thomson scattering with soft x-ray free electron laser radiation as a method to track the evolution of warm dense matter plasmas with ~200 fs time resolution. In a pump-probe scheme an 800 nm laser heats a 20 μm hydrogen droplet to the plasma state. After a variable time delay in the order of ps the plasma is probed by an x-ray ultra violet (XUV) pulse which scatters from the target and is recorded spectrally. Alternatively, in a self-Thomson scattering experiment, a single XUV pulse heats the target while a portion of its photons are being scattered probing the target. From such inelastic x-ray scattering spectra free electron temperature and density can be inferred giving insight on relaxation time scales in plasmas as well as the equation of state. We prove the feasibility of this method in the XUV range utilizing the free electron laser facility in Hamburg, FLASH. We recorded Thomson scattering spectra for hydrogen plasma, both in the self-scattering and in the pump-probe mode using optical laser heating.


Archive | 2009

Soft X-Ray Thomson Scattering in Warm Dense Matter at FLASH

R. R. Fäustlin; S. Toleikis; Th. Bornath; L. Cao; T. Döppner; S. Düsterer; E. Förster; C. Fortmann; S. H. Glenzer; S. Göde; G. Gregori; A. Höll; R. Irsig; T. Laarmann; H. J. Lee; K. H. Meiwes-Broer; A. Przystawik; P. Radcliffe; Ronald Redmer; H. Reinholz; G. Röpke; R. Thiele; J. Tiggesbäumker; N. X. Truong; I. Uschmann; U. Zastrau; Th. Tschentscher

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.


international conference on plasma science | 2009

Perspective for high energy density studies using x-ray free electron lasers

R.W. Lee; B. Nagler; U. Zastrau; R. R. Fäustlin; S. M. Vinko; T. Whitcher; R. Sobierajski; J. Krzywinski; L. Juha; A. J. Nelson; Sasa Bajt; T. Bornath; T. Burian; J. Chalupsky; Henry N. Chapman; Jaroslav Cihelka; T. Döppner; T. Dzelzainis; S. Düsterer; M. Fajardo; E. Förster; C. Fortmann; S. H. Glenzer; S. Göde; G. Gregori; V. Hajkova; P. Heimann; M. Jurek; F. Y. Khattak; A.R. Khorsand

A general overview of the potential for both warm and hot dense matter research for the future will be presented. First, a discussion of the regime defined as relevant to warm dense matter will be attempted in terms of the underlying physical phenomena that define the field. Next a categorization of the facilities to be included in the perspective will be given. With this as background a series of schematic experiments will be discussed with respect to the facilities where they will be pursued. Comments on the interaction amongst the various experiments and between the various facilities will be outlined.


Proceedings of SPIE | 2009

Perspective for high energy density studies on x-ray FELs

R.W. Lee; B. Nagler; U. Zastrau; R. R. Fäustlin; S. M. Vinko; T. Whitcher; R. Sobierajski; J. Krzywinski; L. Juha; A. J. Nelson; Sasa Bajt; K. Budil; R. Cauble; T. Bornath; T. Burian; J. Chalupsky; Henry N. Chapman; Jaroslav Cihelka; T. Döppner; T. Dzelzainis; S. Düsterer; M. Fajardo; E. Förster; C. Fortmann; S. H. Glenzer; S. Göde; G. Gregori; V. Hajkova; Philip A. Heimann; M. Jurek

We report on the x-ray absorption of Warm Dense Matter experiment at the FLASH Free Electron Laser (FEL) facility at DESY. The FEL beam is used to produce Warm Dense Matter with soft x-ray absorption as the probe of electronic structure. A multilayer-coated parabolic mirror focuses the FEL radiation, to spot sizes as small as 0.3μm in a ~15fs pulse of containing >1012 photons at 13.5 nm wavelength, onto a thin sample. Silicon photodiodes measure the transmitted and reflected beams, while spectroscopy provides detailed measurement of the temperature of the sample. The goal is to measure over a range of intensities approaching 1018 W/cm2. Experimental results will be presented along with theoretical calculations. A brief report on future FEL efforts will be given.


Physical Review Letters | 2007

Observations of Plasmons in Warm Dense Matter

S. H. Glenzer; O. L. Landen; Paul Neumayer; R.W. Lee; K. Widmann; S. W. Pollaine; R. J. Wallace; G. Gregori; A. Höll; T. Bornath; R. Thiele; Schwarz; W. D. Kraeft; R. Redmer

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C. Fortmann

University of California

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S. H. Glenzer

SLAC National Accelerator Laboratory

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R. Redmer

University of Rostock

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G. Röpke

University of Rostock

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T. Döppner

Lawrence Livermore National Laboratory

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U. Zastrau

SLAC National Accelerator Laboratory

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S. Göde

University of Rostock

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