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A possible approach to obtain a precise experimental data on the atomic structure of highly charged ions is considered. Since the key point determining measurement accuracy is the presence of reference lines with precisely known wavelengths, it is proposed first to to use hydrogen-like reference lines for precise measurements of the helium-like resonant transition and their dielectronic satellites. Then in turn these lines, which exist in the plasma over a wide temperature range, can be used as the reference in the wavelength measurement for other ions. The problems associated with the creation of the plasma conditions under which the reference and measured lines have comparable intensities are discussed. The irradiation of minerals with laser pulses, which, in terms of their chemical composition, are a set of elements with average 15 < Z < 30 and light Z < 15 nuclear charges, is proposed. Several experimental schemes to measure the wavelengths of the spectral lines of multiply charged calcium ions with an expected error of up to 0.125 mA are considered as an example.

In the paper, experimental results concerning the dynamics of the counter interaction of high-energy plasma flows in a magnetic field with an induction of up to 2 T are presented and discussed. Plasma flows with velocities (2–4) × 107 cm/s, ion density (2–4) × 1015 cm–3, and energy content of 70–100 kJ were formed by two electrodynamic coaxial accelerators with pulsed gas injection. Nitrogen and neon, as well as their mixtures with deuterium, were used as working gases. A description of the 2MK-200 facility, where the experiments were carried out, and diagnostic equipment are presented. Experimental results obtained in various operating modes of the facility are reported and discussed.

The use of targets with surface structures for laser-driven particle acceleration has potential to significantly boost the particle and radiation energies because of enhanced laser absorption. We investigate, via experiment and particle-in-cell simulations, the impact of micron-scale surface-structured targets on the spectrum of electrons and protons accelerated by a picosecond laser pulse at relativistic intensity. Our results show that, compared with flat-surfaced targets, structures on this scale give rise to a significant enhancement in particle and radiation emission over a wide range of laser–target interaction parameters. This is due to the longer plasma scale length when using micro-structures on the target front surface. We do not observe an increase in the proton cutoff energy with our microstructured targets, and this is due to the large volume of the relief.

Aims. EXor-type objects are protostars that display powerful UV-optical outbursts caused by intermittent and powerful events of magnetospheric accretion. These objects are not yet well investigated and are quite difficult to characterize. Several parameters, such as plasma stream velocities, characteristic densities, and temperatures, can be retrieved from present observations. As of yet, however, there is no information about the magnetic field values and the exact underlying accretion scenario is also under discussion. Methods. We use laboratory plasmas, created by a high power laser impacting a solid target or by a plasma gun injector, and make these plasmas propagate perpendicularly to a strong external magnetic field. The propagating plasmas are found to be well scaled to the presently inferred parameters of EXor-type accretion event, thus allowing us to study the behaviour of such episodic accretion processes in scaled conditions. Results. We propose a scenario of additional matter accretion in the equatorial plane, which claims to explain the increased accretion rates of the EXor objects, supported by the experimental demonstration of effective plasma propagation across the magnetic field. In particular, our laboratory investigation allows us to determine that the field strength in the accretion stream of EXor objects, in a position intermediate between the truncation radius and the stellar surface, should be of the order of 100 G. This, in turn, suggests a field strength of a few kilogausses on the stellar surface, which is similar to values inferred from observations of classical T Tauri stars.

In the paper, an X-ray spectroscopy-based approach on laser pulse temporal profile characterization is described. The structure of dielectronic satellites to H-like Ly&alpha, lines strongly depends on a plasma electron density, so it can be applied for diagnostics. These spectral lines are mainly emitted during initial stage of laser plasma expansion. It means that plasma parameters obtained via them characterizes matter conditions in a region surrounding a spot of laser-matter interaction. In the case when a laser contrast is high enough, the radiation interacts with cold matter, which had not been preliminary perturbed by a laser prepulse, and the satellites structure shape corresponding to high densities should be observed. It allows us to consider the satellites as a diagnostic tool for the laser temporal profile quality. In the paper dependencies of the dielectronic satellites structure on electron densities obtained from detailed kinetic calculations in the wide range of plasma parameter for different elements are under discussion. Fundamental theoretical aspects of plasma diagnostic based on the feature of satellite structures shape in hot dense plasma, which led to development of the proposed method, are also explained.

The shaping of astrophysical outflows into bright, dense, and collimated jets due to magnetic pressure is here investigated using laboratory experiments. Here we look at the impact on jet collimation of a misalignment between the outflow, as it stems from the source, and the magnetic field. For small misalignments, a magnetic nozzle forms and redirects the outflow in a collimated jet. For growing misalignments, this nozzle becomes increasingly asymmetric, disrupting jet formation. Our results thus suggest outflow/magnetic field misalignment to be a plausible key process regulating jet collimation in a variety of objects from our Sun’s outflows to extragalatic jets. Furthermore, they provide a possible interpretation for the observed structuring of astrophysical jets. Jet modulation could be interpreted as the signature of changes over time in the outflow/ambient field angle, and the change in the direction of the jet could be the signature of changes in the direction of the ambient field., Mass outflow is a common process in astrophysical objects. Here the authors investigate in which conditions an astrophysically-scaled laser-produced plasma flow can be collimated and evolves in the presence of a misaligned external magnetic field.

Density effects have great importance for studying the state of matter at high energy densities both for astrophysical and laboratory objects. At the moment, the question remains as to which model should be used for the description of the effect of ionization potential depression (IPD) in plasma with densities up to solid-state ones. Recent X-ray free-electron laser based researches claimed the adequacy of an early IPD model of Ecker and Kroll over the well-accepted model of Stewart and Pyatt, provided that these two models give significantly different predictions. Subsequent researches performed with optical lasers have received the opposite result. This work is intended to resolve the existing contradiction in conclusions of mentioned experiments. For the first time, the IPD effect for Si XIII ions of plasma generated by an ultrarelativistic optical laser pulse was described and quantified. We demonstrate the "disappearance" of electronic states up to the state with a principal quantum number of n = 4 (inclusively); the plasma density was varied from the critical to the near-solid one. A radiation-collision code PrismSPECT was used to distinguish different IPD models.

The formation of high energy density matter occurs in inertial confinement fusion, astrophysical, and geophysical systems. In this context, it is important to couple as much energy as possible into a target while maintaining high density. A recent experimental campaign, using buried layer (or "sandwich" type) targets and the ultrahigh laser contrast Vulcan petawatt laser facility, resulted in 500 Mbar pressures in solid density plasmas (which corresponds to about 4.6×10^{7}J/cm^{3} energy density). The densities and temperatures of the generated plasma were measured based on the analysis of x-ray spectral line profiles and relative intensities.

A developing application of laser-driven currents is the generation of magnetic fields of picosecond–nanosecond duration with magnitudes exceeding $B=10~\text{T}$ . Single-loop and helical coil targets can direct laser-driven discharge currents along wires to generate spatially uniform, quasi-static magnetic fields on the millimetre scale. Here, we present proton deflectometry across two axes of a single-loop coil ranging from 1 to 2 mm in diameter. Comparison with proton tracking simulations shows that measured magnetic fields are the result of kiloampere currents in the coil and electric charges distributed around the coil target. Using this dual-axis platform for proton deflectometry, robust measurements can be made of the evolution of magnetic fields in a capacitor coil target.

Results are presented from experimental studies of a pulsed source of soft X-ray (SXR) emission with photon energies in the range of 0.4–1 keV and an output energy of 2–10 kJ. SXR pulses with a duration of 10–15 μs were generated in collisions of two plasma flows propagating toward one another in a longitudinal magnetic field. The plasma flows with velocities of (2–4) × 107 cm/s and energy contents of 70–100 kJ were produced by two electrodynamic coaxial accelerators with pulsed gas injection. Nitrogen and neon, as well as their mixtures with deuterium, were used as working gases. The diagnostic equipment is described, and the experimental results obtained under different operating conditions are discussed. In particular, X-ray spectroscopy was used to study the high-temperature plasma produced in a collision of two plasma flows. The observed intensities of spectral lines are compared with the results of detailed kinetic calculations performed in a steady-state approximation. The calculations of the nitrogen and neon kinetics have shown that the electron temperature of a nitrogen plasma can be most conveniently determined from the intensity ratio of the resonance lines of He- and H-like nitrogen ions, while that of a neon plasma, from the intensity ratio between the resonance line of He-like Ne IX ions and the 3p−2s line of Li-like Ne VIII ions. In the experiments with plasma flows containing nitrogen ions, the electron temperature was found to be ≈120 eV, whereas in the experiments with plasma flows containing neon ions, it was 160–170 eV.

By driving hot electrons between two metal plates connected by a wire loop, high power lasers can generate multi-tesla, quasi-static magnetic fields in miniature coil targets. Many experiments involving laser-coil targets rely on proton deflectometry directed perpendicular to the coil axis to extract a measurement of the magnetic field. In this paper, we show that quantitative measurements using perpendicular probing are complicated by the presence of GV m−1 electric fields in the target that develop on sub-ns timescales. Probing parallel to the coil axis with fiducial grids is shown to reliably separate the electric and magnetic field measurements, giving current estimates of I ≈ 5 kA in 1 mm- and 2 mm-diameter wire loops. An analytic model of proton deflection in electric and magnetic fields is used to benchmark results from the particle-in-cell code and help deconvolve the magnetic and electric field deflections. Results are used to motivate a new experimental scheme that combines a single-plate target with axial proton probing and direct current measurements. This scheme has several important advantages over the traditional target and diagnostic set-up, enabling the robust measurement of coil magnetic fields and plasma properties, as well as making it easier to validate different theoretical models at a range of laser intensities.

The possibility of using the relative intensities of the 1snp 1P1–1s 2 1S0 transitions with n = 3–6 in He-like multicharged ions to diagnose plasma in a nonstationary ionization state is considered. The calculations performed for F VIII ions show that, at electron temperatures of T e = 10–100 eV, the intensity ratios are sensitive to the plasma electron density in the range of N e = 1016–1020 cm–3. The universal calculated dependences can be used to diagnose various kinds of recombining or ionizing plasmas containing such ions.

The interaction of high-power short lasers with solid density targets is an important application of modern solid state lasers. However, uncertainties in measurements due to lack of information on the laser pedestal-to-peak contrast limits the validity of many conclusions. We show that X-ray spectral measurements can provide a straightforward way for accessing the laser pedestal-to-peak contrast. The experiments use silicon targets and relativistic laser intensities of 3 × 1020 W/cm2 with a pulse duration of 1 ps. By not using or using a plasma mirror we compare low and high contrast measurements of the Ly-α line and its satellites to show that these lines are an effective laser contrast diagnostic. This diagnostic has potential to reduce uncertainty in future laser-solid interaction studies.

This work is devoted to the study of thermalization of plasma created by head-on collisions of high-energy plasma flows in a longitudinal magnetic field of 0.5–2 T. Hydrodynamic flows contained the energy of 200 kJ with velocities from 2 × 107 to 4 × 107 cm/s and ion density from 2 × 1015 to 4 × 1015 cm−3 were created inside the 2MK-200 facility by two electrodynamic plasma accelerators equipped by a system of pulsed gas injection. Nitrogen, neon and their mixtures with hydrogen and deuterium were implemented as working gases. A process of plasma creating was investigated by near-wall magnetic probes situated in different parts of the interaction chamber. Temporal evolution of the plasma electron temperature had been traced by x-ray photodiodes covered by different filters. It was discovered that the plasma electron temperature changed insignificantly during 6–8 μs after it reached the maximum value, which means that it ionization state can be considered as quasi-stationary.

X-ray absorption spectroscopy is a well-accepted diagnostic for experimental studies of warm dense matter. It requires a short-lived X-ray source of sufficiently high emissivity and without characteristic lines in the spectral range of interest. In the present work, we discuss how to choose an optimum material and thickness to get a bright source in the wavelength range 2 Å-6 Å (∼2 keV to 6 keV) by considering relatively low-Z elements. We demonstrate that the highest emissivity of solid aluminum and silicon foil targets irradiated with a 1-ps high-contrast sub-kJ laser pulse is achieved when the target thickness is close to 10 μm. An outer plastic layer can increase the emissivity even further.

The investigation of a recombining laser plasma is topical primarily because it can be used to simulate the interaction between plasma jets in astrophysical objects. It has been shown that the relative intensities of transitions of a resonance series of He-like multicharged ions can be used for the diagnostics of the recombining plasma. It has been found that the intensities of the indicated transitions for ions with the nuclear charge number Z n ~ 10 are sensitive to the plasma density in the range N e ~ 1016–1020 cm–3 at temperatures of 10–100 eV. The calculations performed for the F VIII ion have determined the parameters of plasma jets created at the ELFIE nanosecond laser facility (Ecole Polytechnique, France) in order to simulate astrophysical phenomena. The resulting universal calculation dependences can be used to diagnose different recombining plasmas containing helium-like fluorine ions.

The diffraction method is used to study the properties of laser radiation interacting with a gas-cluster plasma. Based on the simulation of propagation a laser beam with a wavelength 800 nm through a hexagon Cu-mesh and subsequently compared with the obtained experimental diffraction pattern, the contribution of the second harmonic to the laser radiation was considered. The capability of this method to reveal the spectral composition of laser radiation is discussed. Also, the dependence of the visibility of the diffraction pattern on the intensity of the laser beam is considered. Besides, the contribution of x-ray radiation generated from the laser-cluster interaction into the observed diffraction pattern signal was estimated.

X-ray absorption spectroscopy is proposed as a method for studying the heating of solid-density matter excited by secondary X-ray radiation from a relativistic laser-produced plasma. The method was developed and applied to experiments involving thin silicon foils irradiated by 0.5–1.5 ps duration ultrahigh contrast laser pulses at intensities between 0.5 × 1020 and 2.5 × 1020 W∕cm2. The electron temperature of the material at the rear side of the target is estimated to be in the range of 140–300 eV. The diagnostic approach enables the study of warm dense matter states with low self-emissivity.

The collimation of astrophysically-relevant plasma ejecta in the form of narrow jets via a poloidal magnetic field is studied experimentally by irradiating a target situated in a 20 T axial magnetic field with a 40 J, 0.6 ns, 0.7 mm diameter, high-power laser. The dynamics of the plasma shaping by the magnetic field are studied over 70 ns and up to 20 mm from the source by diagnosing the electron density, temperature and optical self-emission. These show that the initial expansion of the plasma is highly magnetized, which leads to the formation of a cavity structure when the kinetic plasma pressure compresses the magnetic field, resulting in an oblique shock [A. Ciardi et al., Phys. Rev. Lett. 110, 025002 (2013)]. The resulting poloidal magnetic nozzle collimates the plasma into a narrow jet [B. Albertazzi et al., Science 346, 325 (2014)]. At distances far from the target, the jet is only marginally magnetized and maintains a high aspect ratio due to its high Mach-number (M∼20) and not due to external magnetic pressure. The formation of the jet is evaluated over a range of laser intensities (1012–1013 W/cm2), target materials and orientations of the magnetic field. Plasma cavity formation is observed in all cases and the viability of long-range jet formation is found to be dependent on the orientation of the magnetic field.

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Diagnostics of the high-temperature plasma formed during plasma flow collisions by comparing observable intensities of various x-ray spectral lines to accurate kinetic calculation results is discussed. Kinetic calculations have shown that using the resonance line intensity ratio of He-like Ne IX and 3p–2s Li-like Ne VIII is the most convenient way to measure neon-containing plasma temperatures. Experimental research results of the pulse soft (0.1–1 keV) x-ray source with a total energy up to 50 kJ are shown. The radiation pulse is generated during a head-on collision of two low-temperature plasma flows immersed in a longitudinal magnetic field. The plasma flows with the velocities up to 4 × 107 cm/s and total energy up to 200 kJ are formed by a coaxial accelerator operating in pulse gas puffing mode. Neon was used as an inflating gas. Electron temperature for a plasma containing Ne ions is about 160–170 eV. Electron density around the collision region is in the range 1016–1017 cm−3.

While the plasma created by powerful laser expands from the target surface it becomes overcooled, i.e. recombining one. Improving of diagnostic methods applicable for such plasma is rather important problem in laboratory astrophysics nowadays because laser produced jets are fully scalable to young stellar objects. Such scaling is possible because of the plasma hydrodynamic equations invariance under some transformations. In this paper it is shown that relative intensities of the resonance transitions in He-like ions can be used to measure the parameters of recombining plasma. Intensity of the spectral lines corresponding to these transitions is sensitive to the density in the range of 1016-1020 cm-3 while the temperature ranges from 10 to 100 eV for ions with nuclear charge Zn ~ 10. Calculations were carried out for F VIII ion and allowed to determine parameters of plasma jets created by nanosecond laser system ELFIE (Ecole Polytechnique, France) for astrophysical phenomenon modelling. Obtained dependencies are quite universal and can be used for any recombining plasma containing He-like fluorine ions.

A stable complex of the chaperonins, cpn60 and cpn10 (Escherichia coli GroEL and GroES homologues), from the extremely thermophilic bacterium Thermus thermophilus has been isolated and crystallized. The crystals have dimensions up to 30 x 200 x 200 microns. Ultra-thin sections of the crystals estimated by electron microscopy showed a rectangular lattice with unit cell parameters of a = 17 nm, b = 27 nm, gamma = 90 degrees.

(1960). The Results and Tasks of Studies in Regional Economic Geography at the Institute of Geography of the Academy of Sciences of the USSR (1) Soviet Geography: Vol. 1, No. 1-2, pp. 33-40.