X-ray spectroscopic study of stopping dynamics for Ca<Superscript>6+</Superscript> ion in an aerogel target

Variation of the velocity of Ca⁶⁺ ions with initial energies of 5.9 and 11.4 MeV/nucleon has been experimentally studied in the course of ion stopping in a solid aerogel target. The method is based on measuring the Doppler shift in the K-shell spectrum of decelerated Ca¹⁹⁺ and Ca¹⁸⁺ ions. High spatial resolution (30–50 mm) in the direction of the ion beam propagation achieved simultaneously with high spectral resolution (λ/Δλ=1000–3000) in the X-ray wavelength interval of 2–4 Å allowed the ion beam dynamics in the solid target to be directly measured. By measuring variations in the relative intensity of spectral lines, it is possible to monitor the redistribution of the ions over charged states during their motion in the target.     

The investigation of the optics of shock-compressed strongly correlated plasma

Rare gas plasmas at high temperatures and pressures, produced by explosive shock fronts, are explored using laser diagnostics. The analysis of the response of a dense plasma to an electromagnetic wave of moderate-intensity proves successful for investigating properties and the validity of physical models describing the behaviour of dense and non-ideal plasmas. We present new experimental data for the reflectivity of oblique incidence of polarized electromagnetic waves on the front of shock-compressed xenon plasmas. The optical properties of strongly correlated plasma were studied in the near-infrared and green spectral regions at a plasma mass density ρ = 0.83 g/cm³ and temperature T = 32900 K. The spatial parameters of the plasma transition shock-front layer are determined by solving numerically the electromagnetic field equations.     

Dynamics of Time Evolution of Quantum Oscillator Excitation by Electromagnetic Pulses

Journal of Experimental and Theoretical Physics - The dynamics of time evolution of quantum oscillator excitation by electromagnetic pulses is investigated theoretically for an arbitrary field...     

Signature of externally introduced laser fields in X-ray emission of multicharged ions

Theory predicts that the presence of strong single-frequency electric fields results in appearance of satellite or dip structures in X-ray spectral lines emitted from hot dense plasmas. Emission from multicharged ions is measured to determine the effects of laser field. A ps-laser beam was split into two parts: the first created an expanding plasma, while the second, which was temporally synchronized, irradiated the plasma at a varying distances in a direction perpendicular to the target normal. The field introduced by the second beam perturbed the plasma environment in the vicinity of radiators. The spatially resolved X-ray spectra were recorded using the high-resolution toroidally bent crystal spectrometer combined with a CCD detector. Spectrally resolved features are observed in broadened Al Heβ line profiles that are consistent with predicted spectra. The predicted spectra are derived from a combination of hydrodynamic plasma modeling post-processed by theoretical models that include the effect of externally introduced laser fields. The possible mixing of higher-intensity fields is qualitatively explained by a combination of fluid and one-dimensional PIC simulations that indicate redistribution of the fields and density fluctuations due to a presence of parametric instabilities.     

Effect of the target density on the cross section of charge exchange between fast ions and atoms

When fast X^q+ X^{q^ + } ions collide with atomic or molecular targets, the total charge exchange cross section decreases with increasing target density. This is because the excitation levels of resulting X^{(q - 1)+} X^{(q - 1)^ + } ions are suppressed because of ionization by target atoms. The effect of target density on the total charge exchange cross section may amount to one order of magnitude or more depending on the charge and energy of an incident ion, as well as on the density and inner shell configuration of target atoms. Numerical calculations are performed for partial (in the principal quantum number n) cross sections σ(n) and total cross sections σ_tot=Σ_nσ(n) of charge exchange in the case of collisions of fast multiply charged ions having an energy E in the range 100 keV/u-10 MeV/u with gas or solid targets.     

Plasma emission spectroscopy of solids irradiated by intense XUV pulses from a free electron laser

The FLASH XUV-free electron laser has been used to irradiate solid samples at intensities of the order 10¹⁶ W cm^?2 at a wavelength of 13.5 nm. The subsequent time integrated XUV emission was observed with a grating spectrometer. The electron temperature inferred from plasma line ratios was in the range 5–8 eV with electron density in the range 10²¹–10²² cm^?3. These results are consistent with the saturation of absorption through bleaching of the L-edge by intense photo-absorption reported in an earlier publication.     

Quasi-isochoric ion beam heating using dynamic confinement in spherical geometry for X-ray scattering experiments in WDM regime

Extreme states of matter such as Warm Dense Matter “WDM” and Dense Strongly Coupled Plasmas “DSCP” play a key role in many high energy density experiments, however, creating WDM and DSCP in a manner that can be quantified is not readily feasible. In this paper, isochoric heating of matter by intense heavy ion beams in spherical symmetry is investigated for WDM and DSCP research: the heating times are long (100 ns), the samples are macroscopically large (millimeter-size) and the symmetry is advantageous for diagnostic purposes. A dynamic confinement scheme in spherical symmetry is proposed which allows even ion beam heating times that are long on the hydrodynamic time scale of the target response. A particular selection of low-Z target tamper and X-ray probe radiation parameters allows to identify the X-ray scattering from the target material and use it for independent charge state measurements Z* of the material under study.     

Radiation Emission of Fast Electrons in Collisions with “Ion‐Sphere” in Dense Plasmas

Radiative emission of fast electrons in collision with an “ion‐sphere” electron distribution in dense plasmas is under consideration. The electron structure of the ion sphere is calculated ab initio using self‐consistent solution of both bound and free electron distribution inside the sphere. Two radiation channels are included: emission of the colliding electron itself in static potential (conventional or static Bremsstrahlung) and the emission of “ion sphere” medium due to its polarization by the colliding electron (polarization Bremsstrahlung). The last one is calculated in the frame of local plasma density approximation. Interference between conventional and polarization Bremsstrahlung is taken into account. It is shown that spectral cross section of the process has characteristic features depending on plasma density and ionization stage of plasma ions. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Commissioning and early experiments of the PHELIX facility

At the Helmholtz center GSI, PHELIX (Petawatt High Energy Laser for heavy Ion eXperiments) has been commissioned for operation in stand-alone mode and, in combination with ions accelerated up to an energy of 13 MeV/u by the heavy ion accelerator UNILAC. The combination of PHELIX with the heavy-ion beams available at GSI enables a large variety of unique experiments. Novel research opportunities are spanning from the study of ion–matter interaction, through challenging new experiments in atomic physics, nuclear physics, and astrophysics, into the field of relativistic plasma physics.     

Spectral transitions from the Rydberg autoionization states of a Li-like Mg X ion

Satellite lines caused by radiative transitions from the Rydberg autoionization states of a Li-like Mg X ion in a plasma heated by radiation from a XeCl and a Nd laser are identified for the first time, and their wavelengths are measured precisely. Comparison of the experimental data with the atomic structures calculated by the method of relativistic perturbation theory shows that the accuracy of calculations of the energy of autoionization states is rather high even without the use of any semiempirical corrections and is of the order of 0.06%. The experimentally measured wavelengths can be used for a semiempirical estimate of the value of the leading order of perturbation theory among the orders that were neglected in calculations. It is shown that the simulation of the population kinetics of Rydberg autoionization states of Li-like ions in a dense plasma should take into account all possible channels of dielectronic capture, in particular, from the excited states of a He-like ion. The precision experimental wavelengths obtained for satellites of the He_ß and He_γ lines of the Mg XI ion make possible to use these satellites as reference lines in studies of complicated spectra of multielectron ions.