Search

High-Z dopants such as chlorine, bromine and silicon in carbon–hydrogen polymer (CH) targets play a crucial role during the ablation of inertial confinement fusion (ICF). These dopants can serve as diagnostic tools in experiments and mitigate hot electron preheating, but they also influence the laser ablation. In this paper, the process of high-power laser ablating doped CH targets has been studied through radiation hydrodynamic simulations. Our findings reveal that the laser absorption rate in the doped targets increase as a result of the increasing electron-ion collision frequency. This leads to the increase of the electron, ion and radiation temperatures. Furthermore, high-Z dopants contribute to a decrease in the ablation pressure, which tends to a constant. Moreover, the saturation phenomenon of the mass ablation rate has been found. For the targets with low doping ratios (e.g. 6.25%–12.5%), the mass ablation rate increases until reaching the saturation at a doping ratio of 18.75%, after which it decreases. This indicates that an appropriate doping ratio can increase the laser absorption and ablation. The results are helpful to comprehensively understand the effects of high-Z dopant on all stages of ICF. [ABSTRACT FROM AUTHOR]

In this paper we make an attempt to study the effect of a nanosecond prepulse on electron acceleration from microscopic solid particles. While standard scaling laws predict temperatures of ∼ 50 keV, our investigations showed an anomalous enhancement ( ∼ 200 keV) in electron temperatures from microscopic solids subjected to intense laser fields. Conventional isotropic expansion of the plasma target as a result of pre-pulse interaction is unable to explain the enhancement, prompting an experimental inquiry into the expansion form. Tentacle-like structures emerging from the spherical plasma are detected as an outcome of the pre-pulse interaction, with the region between the tentacles being targeted by the main laser pulse. We resort to PIC simulations to understand and predict the exact plasma condition that exists in this region. In this paper, we study a series of approximate pre-plasma conditions, particle shapes, and electron densities, examining them for their role in electron acceleration from this extended over-critical plasma target. [ABSTRACT FROM AUTHOR]

A silicon carbide (SiC) plasma has been produced by a Q-switched laser at 1064 nm, 3 ns pulse and 1010 W/cm2 intensity, in high vacuum to investigate the fundamental mechanisms of laser-semiconductor interaction. Although the high hardness and chemical stability restrain the SiC micromachining, it is a valuable semiconductor for devices working under extreme conditions.The plasma has been characterized by using time-of-flight (TOF) measurements of ions detected by an ion collector ring (ICR) and an ion energy analyzer (IEA). Fast CCD camera, quadrupole mass spectroscopy (QMS) and surface profiler have been employed to provide deep insights into the laser-SiC interaction mechanisms.Ion kinetic energies, charge states, plasma expansion velocity, ablation yield per laser pulse, plasma temperature and density have been measured.Applications of the laser-generated plasma are presented and discussed. [ABSTRACT FROM AUTHOR]

Multilayer interference structures acting as dispersion elements for a mirror spectrometer for a wavelength range of 7–30 nm have been calculated and synthesized. Three elements are implemented: for the range λ = 7–12 nm – multilayer structure Mo/B4C (number of periods N = 60, period thickness d = 6.5 nm); for the range λ = 11–18 nm – Mo/Be (N = 50; d = 9.83 nm) and for the range λ = 17–30 nm – Be/Si/Al (N = 40; d = 18.2 nm). For the entire spectral range, an efficiency of more than 10% was obtained at a wavelength resolution of 0.15–1.0 nm. [ABSTRACT FROM AUTHOR]

In this paper, the finite element model of molten pool flow-evaporation during laser micro-texture processing on metal surfaces was established by COMSOL software. The influence of surface tension, capillary force, and thermal capillary force on molten pool flow is considered in the numerical model, and the influence of recoil pressure generated by evaporating gas on molten pool flow and the solidification process is also fully considered. The numerical results show that with the increase of laser radiation time or laser power, the velocity and pressure of evaporating gas also increase gradually, and the diameter and depth of the formed texture also show an obvious upward trend. In addition, through the research of texture morphology characteristics and plasma formation during laser micro-texture processing, it can be found that when the laser power and radiation time increase to a certain extent, the plasma changes from a stable suspension phenomenon to a periodic evolution characteristic. Finally, the machining mechanism and reliability of laser micro-texture are revealed by comparing the simulation and experimental results. [ABSTRACT FROM AUTHOR]

The radiation spectra in the soft X-ray and extreme ultraviolet wavelength ranges of thin-film (0.15 μm) targets made of light materials (Si, C, Be) were studied when excited by a Nd:YAG laser pulse with a duration of 5.2 ns focused to an intensity of ~1012 W/cm2. Line spectra of BeIII, BeIV, CV, and SiV ions were recorded using a spectrometer based on a multilayer X-ray mirror. A comparison with the spectra of bulk solid-state targets of the same materials is carried out. In all cases, there was a decrease in the intensity of the lines of the soft X-ray spectrum of film targets compared to monolithic ones; the decrease was, depending on the material, from several tens of percent to several times, with more than an order of magnitude less mass of the vaporized substance. [ABSTRACT FROM AUTHOR]

An analysis of the luminescence spectra of plasma formed during laser ablation of a gold target immersed in superfluid helium at a laser radiation power density below the breakdown threshold of liquid helium showed that the ionization energy of the Au2+ ion should be no lower than 34 eV. [ABSTRACT FROM AUTHOR]

An analysis of the luminescence spectra of plasma formed during laser ablation of a gold target immersed in superfluid helium at a laser radiation power density below the breakdown threshold of liquid helium showed that the ionization energy of the Au2+ ion should be no lower than 34 eV. [ABSTRACT FROM AUTHOR]

The article considers the results of studying the emission radiation of Ar, Kr, CO2, CHF3, CF4 and N2 gas jets excited by pulsed laser radiation. The shape of the spectral dependence in the spectral range 2.3‒4.4 nm and the emission intensity of a number of lines in absolute units were studied. To excite the targets, a Nd:YAG laser, λ = 1064 nm, τ = 5.2 ns, Eimp= 0.8 J was used. A supersonic conical nozzle with dcr = 450 μm, 2α = 11°, L = 5 mm was used to form a pulsed gas jet. The pressure at the nozzle inlet was 25 bar, which corresponds to the developed condensation of molecular gases in gas jets. The spectra were deciphered and the ions emitting under the given experimental conditions were determined. [ABSTRACT FROM AUTHOR]

This paper describes the results of a laboratory experiment on the sub-Alfvén expansion of a quasi-spherical laser plasma cloud into a vacuum magnetic field in the regime of nonmagnetized ions. The role of Hall fields and currents in the anomalously fast dynamics of the magnetic field during the collapse phase of a diamagnetic cavity is considered. Detailed spatial measurements of the azimuthal Hall fields configuration are demonstrated and their relationship to diamagnetic cavity collapse is determined. As a result of the experiment, data were obtained confirming the hypothesis about the transfer of the main magnetic field by the movement of electrons associated with Hall currents. [ABSTRACT FROM AUTHOR]

Materials processing with ultrashort laser pulses is one of the most important approaches when it comes to machining with very high accuracy. High pulse repetition rates and high average laser power can be used to attain high productivity. By tightly focusing the laser beam, the irradiances on the workpiece can exceed 1013 W/cm2, and thus cause usually unwanted X-ray emission. Pulsed laser processing of micro holes exhibits two typical features: a gradual increase in the irradiated surface within the hole and, with this, a decrease in the local irradiance. This and the shielding by the surrounding material diminishes the amount of ionizing radiation emitted from the process; therefore, both effects lead to a reduction in the potential X-ray exposure of an operator or any nearby person. The present study was performed to quantify this self-shielding of the X-ray emission from laser-drilled micro holes. Percussion drilling in standard air atmosphere was investigated using a laser with a wavelength of 800 nm a pulse duration of 1 ps, a repetition rate of 1 kHz, and with irradiances of up to 1.1·1014 W/cm. The X-ray emission was measured by means of a spectrometer. In addition to the experimental results, we present a model to predict the expected X-ray emission at different angles to the surface. These calculations are based on raytracing simulations to obtain the local irradiance, from which the local X-ray emission inside the holes can be calculated. It was found that the X-ray exposure measured in the surroundings strongly depends on the geometry of the hole and the measuring direction, as predicted by the theoretical model. [ABSTRACT FROM AUTHOR]

The possibility was studied of creating thin-film gas-sensitive sensors using composite materials containing tin in their composition, which can significantly improve their characteristic. In addition, a layer-by-layer analysis of metals and multicomponent alloys was carried out under the action of dual laser pulses on a target in an air atmosphere. All experiments were carried out using a laser two-pulses multichannel atomic emission spectrometer LSS-1. In the course of this study, the processes of formation of a certain component composition of the near-surface laser plasma, as well as the influence of the defocusing parameter between doubled laser pulses upon their impact on the surface of the irradiated sample, were studied. Thus, this work illustrated the development of methods for obtaining nanoclusters of chemical elements during spectroscopic studies of laser plasma formed by the action of two successive pulses on a target and the possibility of obtaining nanofilms of both pure metals and composite alloys for subsequent practical application.

In this review, we attempt to provide a brief account of laser-induced breakdown spectroscopy (LIBS) methodology and technological developments. We also summarize various methods adopted for exploiting LIBS. Besides, a brief overview of combination of LIBS in conjunction with other methods is also given. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) are semiconductor nanocrystals with a size in the range of 1–10 nm. They are created on the basis of inorganic semiconductor materials Si, InP, CdSe, etc., and are coated with a stabilizer monolayer. QDs have unique optical, electrical, electrochemical, and catalytic properties. The crystal core of a quantum dot contains about 100–100 000 atoms. Quantum dot size is comparable to the wavelength in the material on the basis of which it is made. Inside a quantum dot, the potential energy of an electron is lower than outside it, and thus the motion of the electron is limited in all three dimensions. The energy levels of electrons inside a quantum dot are discrete and are separated by regions of forbidden states. The behavior and properties of these objects are described not by classical physics, but by quantum mechanics. The current review focuses on applications of QDs such as providing high-quality bioimaging of tumors in vitro and in vivo, visualization of drug transportation, targeted drug delivery, photothermal and photodynamic therapy, cell sorting activated by fluorescence, and use in biosensors. Emphasis is placed on the technology of accurate detection and inhibition of SARS-CoV-2 using quantum dots. [ABSTRACT FROM AUTHOR]

To study the spatial distribution of the soft X-ray radiation intensity of a laser-produced plasma, a new type of coded aperture was used. This aperture is a structure with a mutually perpendicular arrangement of opaque strips, the distances between which and their widths were calculated with the use of a random number generator. The radiation transmitted through such aperture gives an intricate pattern of the encoded image, which was recorded on a Fuji TR imaging plate without a protective coating. To reconstruct the spatial distribution of the plasma radiation intensity from this pattern, a mathematical algorithm was developed that is an iterative method for solving an ill-posed problem—the Fredholm integral equation of the first kind. It has been shown that the use of the coded aperture not only enhances the efficiency of the registration system by many times but also allows one to get a spatial resolution no worse than in the case of the use of a pinhole camera. It is established that the developed iterative method can be used both for sources which differ little from point sources and for spatially extended objects. [ABSTRACT FROM AUTHOR]

This publication presents an experimentally obtained video file for visualizing changes in the brightness of a radiation source based on a combination of continuous and repetitively pulsed optical discharges on a microsecond scale. The brightness was recorded with an electron-optical camera in the visible region of the spectrum in a nine-frame scan mode. A detailed description of the conditions and results of the experiments performed, the characteristics of the radiation source, as well as a discussion of the results obtained are published in [1, 2]. [ABSTRACT FROM AUTHOR]

We report results of experimental studies on spectral, temporal, energy and spatial characteristics of coherent radiation at a wavelength of 391.4 nm [ transition of molecular nitrogen ion]. Lasing occurs in pure nitrogen under pumping by a radiation pulse with a duration of 70 fs at a wavelength of 950 nm. The lasing parameters are studied as functions of nitrogen pressure, pump beam energy, and its focusing conditions. Optimal values of pump energy (6 mJ) and nitrogen pressure (30 mbar) are determined. It is found that the divergence of radiation decreases with increasing focal length of the lens and correlates with the geometric dimensions of the laser plasma. It is also shown that with increasing specific pump power, the pulse duration decreases and can be close to the transform-limited one (1.83 ps). [ABSTRACT FROM AUTHOR]

The reflection of a relativistically intense short laser pulse upon oblique incidence on solid-state targets of various thickness and density to find the parameters of targets in which the reflected radiation contains several ultrashort pulses of durations up to hundreds of zeptoseconds is considered. These pulses are generated due to oscillations of the reflecting electron layer in the target at a relativistic speed. The minimum achievable time duration of an individual reflected pulse for the currently experimentally accessible range of laser intensities up to ~1023 W/cm2 and the possibility of separating ultrashort pulses from the total electromagnetic signal of the reflected pulse are investigated. [ABSTRACT FROM AUTHOR]

The article describes Schlieren photography, realised using a laser plasma as a radiationsource. Optical systems prepared for visualisation of a stationary gas outflow and a pulsed gaseoustarget, produced in an atmosphere or vacuum environment are presented. A He-Ne laser beam orlaser plasmas were used as the light sources. Schlieren images of outflows of helium, carbon dioxide,krypton, nitrogen and sulphur hexafluoride, are presented. A comparison of various gas streams,formed in atmosphere, imaged using different light sources are shown. Schlieren images of a twostreamgaseous target formed in vacuum are also presented.Keywords: automation, electronics, electrical engineering and space technology, refraction, opticalsystem, laser plasma, schlieren photography

Using a multilayer mirror spectrometer of the extreme ultraviolet (EUV) range, the laser plasma emission spectra of bulk aluminum in the wavelength range of 8.0–18.0 nm were studied. Testing of thin film laser targets made of aluminum and comparative measurements of the intensity of EUV radiation of a film with a thickness of 100 nm and a bulk material target were carried out. [ABSTRACT FROM AUTHOR]

The prospects of application of high-power laser systems for the problems of nuclear photonics are discussed. By the example of the structure of the nuclear levels of the krypton isotope 83Kr having two isomeric states with energies of 9.4 and 41.6 keV, the possibility of their indirect excitation through the high-lying short-lived levels with the use of high-energy laser plasma radiation is described. It is shown that the cross section of photoexcitation of the 9.4-keV level by gamma-quanta with an exponential energy distribution increases by more than 100 times as the distribution temperature grows from 50 keV to 1 MeV at a constant amplitude. The estimates of the yields of the reactions of photoexcitation of 83Kr isomeric levels by plasma radiation generated by the petawatt-level laser system are performed for several values of the electron beam temperature and the thickness of the bremsstrahlung gamma-radiation converter. [ABSTRACT FROM AUTHOR]

Consideration has been given to the physical processes occurring in a laser-plasma source for deposition of nanocoatings using ion flows. In this source, a net is placed between a certain laser target and a copper substrate. A negative potential is applied to the net towards the target, and after it, a flow of charged particles predominantly made up of ions is formed. By applying a positive potential to the net towards the substrate, it is possible to control the energy of the ions moving to the substrate. In the net–substrate interval, ion flows of various ionization multiplicity have been found. It has been shown that with the potential of the electric field in the net–substrate interval of 100 V and over, the kinetic energy of ions is sufficient for the occurrence of secondary emission of ions from the substrate surface. The results of experiments make it possible to determine two substrate surface treatment regimes. With significant electric fields in the net–substrate interval, it is possible to clear the substrate surface using ion etching. At low electric field values, it is possible to deposit the laser target material on the substrate surface. [ABSTRACT FROM AUTHOR]

A technique for the absolute calibration of multichannel detectors based on CCDs using soft X-ray radiation from laser plasma is developed. The wavelength selection of radiation in an interval of λ = 2–10 Å is carried out using the monochromatization method (i.e., formation of quasi-monochromatic line X-ray radiation of laser plasma with a relatively large spatial angle of divergence). The proposed method is used to calibrate a Toshiba TCD 1304 CCD array: the absolute sensitivity of the detector is determined to be k0 = 0.08–0.2 photons/(pixel count), the quantum efficiency is QE = 0.4–1.0, the effective thickness of the sensitive layer is h = 16 ± 3 μm, and the detection limit of the detector is DL = 1–2 photons/pixel. The detector is used in a focusing crystal spectrometer for detection of X-ray spectra of laser plasma on the absolute intensity scale (multicharged ions of Mg and Ti). [ABSTRACT FROM AUTHOR]

We consider the results of computational experiments concerning the expansion of a plasma generated by laser radiation at the stage of a nanosecond prepulse ahead of the main femtosecond-range pulse. A series of plasmodynamic calculations are performed for various laser target materials. It is shown that in the considered problem statement, which corresponds to the typical conditions of full-scale experiments, the distribution of the laser plasma density as a whole is satisfactorily approximated by a simple three-parameter formula. [ABSTRACT FROM AUTHOR]

The reasons for the observed propagation velocities of stationary laser-supported combustion (LSC) waves in laser plasmatron scheme in argon and air to exceed the calculated ones in assumption of heat-conductive propagation mechanism are considered. Earlier obtained analytical solution of the hydrodynamic problem of flowing around model low density heated gas volume with step-like spherical boundary is used for interpretation experimental results. It is shown that when laser power is 2–3 times above LSC threshold power heat-conductive mechanism with correction factor predicted by the model gives satisfying description of the LSC wave velocities observed. At higher laser power radiative heat transfer factor should be taken into account. It is shown that flowing around spherical hot gas boundary model can also be applied to describe gas flow in thermal gravitational convection around continuous optical discharge (COD). An estimate is given for the pulsation frequency of the convective plume from COD, leading to the similarity relation common for optical discharges and flickering flames. [ABSTRACT FROM AUTHOR]

Low-temperature plasma production is possible as a result of photoionization using high-intensity extreme ultraviolet (EUV) and soft X-ray (SXR) pulses. Plasma of this type is also present in outer space, e.g., aurora borealis. It also occurs when high-velocity objects enter the atmosphere, during which period high temperatures can be produced locally by friction. Low-temperature plasma is also formed in an ambient gas surrounding the hot laser-produced plasma (LPP). In this work, a special system has been prepared for investigation of this type of plasma. The LPP was created inside a chamber filled with a gas under a low pressure, of the order of 1–50 mbar, by a laser pulse (3–9 J, 1–8 ns) focused onto a gas puff target. In such a case, the SXR/EUV radiation emitted from the LPP was partially absorbed in the low-density gas. In this case, high- and low-temperature plasmas (Te ~100 eV and ~1 eV, respectively) were created locally in the chamber. Investigation of the EUV-induced plasmas was performed mainly using spectral methods in ultraviolet/visible (UV/VIS) light. The measurements were performed using an echelle spectrometer, and additionally, spatial–temporal measurements were performed using an optical streak camera. Spectral analysis was supported by the PGOPHER numerical code.

BackgroundNuclear isomers are crucial in cosmic element synthesis and have potential applications in controlling nuclear energy release. Specifically, Europium (Eu) is significant in fundamental studies. For instance, 152Eu is used as a reference source for radioactive experiments, and its isomeric state 152m1Eu has a probability of 73% to produce cosmological p-nuclei 152Gd with β- decay. Therefore, 152m1Eu is a crucial nuclide in the nuclearsynthesis of p-nuclei 152Gd.PurposeThis study aims to realize the efficient excitation of 152m1Eu with a bremsstrahlung source generated by laser plasma.MethodsFirstly, the laser-plasma bremsstrahlung source was utilized to achieve the efficient excitation of 152m1Eu (45.6 keV, T1/2=9.31 h) in the experiment with yields of 8×104 particles/shot by this isotope. Then, numerical simulations of the yield of 152m1, m2Eu were performed using the Geant4-GENBOD program to get generation time, and peak excitation efficiency evolution with electron temperature.ResultsThe results demonstrate that when the electron temperature reaches 15 MeV, the yield of 152m1, m2Eu approaches saturation. When the incident electron charge is 17.6 nC, the yield of 152m1Eu is approximately 8×106 particles/shot, and that of 152m2Eu is approximately 2×105 particles/shot. The generation time of 152m1, m2Eu in the target is approximately 32 ps. When the electron temperature reaches 15 MeV, the peak excitation efficiency of 152m1Eu is expected to be ~1017 particles/s, and that of 152m2Eu is expected to be ~1016 particles/s.ConclusionsThe ultrashort ultrahigh intensity laser technology can significantly enhance the excitation efficiency of isotopes of the same nucleus, and this will provide an important research avenue for the study of cosmic element synthesis and nuclear energy release control applications.

Materials processing with ultrashort laser pulses is one of the most important approaches when it comes to machining with very high accuracy. High pulse repetition rates and high average laser power can be used to attain high productivity. By tightly focusing the laser beam, the irradiances on the workpiece can exceed 1013 W/cm2, and thus cause usually unwanted X-ray emission. Pulsed laser processing of micro holes exhibits two typical features: a gradual increase in the irradiated surface within the hole and, with this, a decrease in the local irradiance. This and the shielding by the surrounding material diminishes the amount of ionizing radiation emitted from the process; therefore, both effects lead to a reduction in the potential X-ray exposure of an operator or any nearby person. The present study was performed to quantify this self-shielding of the X-ray emission from laser-drilled micro holes. Percussion drilling in standard air atmosphere was investigated using a laser with a wavelength of 800 nm a pulse duration of 1 ps, a repetition rate of 1 kHz, and with irradiances of up to 1.1·1014 W/cm. The X-ray emission was measured by means of a spectrometer. In addition to the experimental results, we present a model to predict the expected X-ray emission at different angles to the surface. These calculations are based on raytracing simulations to obtain the local irradiance, from which the local X-ray emission inside the holes can be calculated. It was found that the X-ray exposure measured in the surroundings strongly depends on the geometry of the hole and the measuring direction, as predicted by the theoretical model.

An imaging (stigmatic) spectrograph consisting of a plane VLS grazing-incidence grating and a normal-incidence focusing broadband multilayer mirror (Mo/Be, 111–138 Å, Mo/Si, 125–250 Å) that determines the working spectral range has been designed and tested experimentally. Line emission spectra of multiply charged ions excited in the laser plasma have been obtained. The spectral and spatial resolutions of the instrument were limited by the pixel size (13 μm) of the detector in use and were ~ 103 and 26 μm, respectively. The stigmatism of the instrument makes it possible to use it for spectral diagnostics of plasmas with a high spatial resolution. The size of the instrument is about 1 m. [ABSTRACT FROM AUTHOR]

The issue of optimizing laser-plasma X-ray sources is still relevant. In this context, numerical simulation methods are very effective. A series of 2d PIC calculations using the EPOCH code were carried out. The laser pulse duration was 0.7 ps, the peak intensity was 3 × 1020 W/cm2, and silicon foil between 2 and 5 μm thick was used as a target. The conversion efficiency into the continuous X-ray spectrum was calculated. The results of comparison of numerical calculations with experimental measurements showed their satisfactory agreement. [ABSTRACT FROM AUTHOR]

The effect of the energy, the interval between the pulses, and the number of double laser pulses on the formation of the component and charge composition of laser plasma by laser spark spectrometry (LSS-1 spectrometer) was studied. The processes leading to the formation of mixed nanopowders of copper and aluminum oxides, precursors for the production of nanoceramics and films of CuAlO2 copper aluminates by the action of double laser pulses on a hybrid target consisting of cemented aluminum and copper plates, from AD1 and M2 alloys were investigated. It was shown that precursors for the manufacture of nanoceramics and nanofilms of CuAlO2 copper aluminates can be obtained by the successive action of a series of double laser pulses with energy of 53 mJ and an interval of 10 μs on a hybrid target. A closed glass weighing bottle containing the target was used for the products formed during interaction of the aluminum and copper ions with atmospheric oxygen. The size of the initial particles, determined by means of a high-resolution electron microscope, amounted to 30–45 nm. The particles were assembled into agglomerates and had a crystalline structure and spherical form. On account of the purely diffusion transfer mechanism of the fractals the size and amount of the fractal aggregates settling on the support situated at the bottom of the cuvette were several times greater than the amount of the products that settle on the side support. The main contribution to change in the intensity of the spectral lines for the Al and Cu atoms and ions and the AlO molecular bands comes from interaction of the second pulse with the condensation products formed in the channel after the action of the first pulse. With increase in the number of long-lived fractal aggregates in the air the intensity of molecular bands and lines decreases by ~1.5 times for Al III and by ~2 times for copper, which is due to active interaction of the long-lived large fractals that accumulate in the air with the incident radiation. [ABSTRACT FROM AUTHOR]

A layer-by-layer analysis of metals and alloys has been carried out, and the possibility of deposition of nanofilms containing tin in their composition on various types of surfaces (metal, glass) under the action of dual laser pulses on a target in an air atmosphere has been studied. The experiments were carried out using the laser two-pulse multichannel atomic emission spectrometer LSS-1. The advantages of the pulsed laser deposition as a method for producing clusters and fractals are: versatility in relation to the material, the ability to exclude impurities, the flexibility of the method, and the ability of controlling the formation of film structures. The performed spectroscopic studies of the laser plasma formed by the action of two successive pulses on a target illustrate the development of methods for obtaining nanoclusters of various chemical elements. This method can be used to obtain nanofilms of not only pure metals, but also composite alloys. The possibility of obtaining nanofilms for creating gas-sensitive sensors is shown.

The present work demonstrates the performance of a von Hámos high-energy-resolution X-ray spectrometer based on a non-conventional conical Si single-crystal analyzer. The analyzer is tested with different primary and secondary X-ray sources as well as a hard X-ray sensitive CCD camera. The spectrometer setup is also characterized with ray-tracing simulations. Both experimental and simulated results affirm that the conical spectrometer can efficiently detect and resolve the two pairs of two elements (Ni and Cu) Kα X-ray emission spectroscopy (XES) peaks simultaneously, requiring a less than 2 cm-wide array on a single position-sensitive detector. The possible applications of this simple yet broad-energy-spectrum crystal spectrometer range from quickly adapting it as another probe for complex experiments at synchrotron beamlines to analyzing X-ray emission from plasma generated by ultrashort laser pulses at modern laser facilities.

Parameters (thickness, electron density) of the laser target in the form of ultrathin foil are determined that provide maximum (~10%) conversion ratio of short relativistically intense laser pulses into a train of several coherent attopulses. Attopulse amplitude, duration are determined, conversion ratio of laser energy into the energy of attopulses is determined and the possibility of its increase using several successively located targets is shown. [ABSTRACT FROM AUTHOR]

The paper considers the emission spectra and dependences of the emission intensity of a number of carbon lines in absolute units for laser plasma generated by laser pulse on CO2, CHF3, and CF4 gas jets on the gas pressure at the nozzle inlet. A pulsed Nd:YAG laser, λ = 1064 nm, τ = 5.2 ns, Eimp = 0.8 J was used. Gas-jet targets were formed by a supersonic conical nozzle, the pressure at the nozzle inlet varied in the range of 5–25 bar. The emission spectra of the investigated gases were compared and the reasons for the different dependences of the radiation intensity on the gas pressure at the nozzle inlet were analyzed. [ABSTRACT FROM AUTHOR]

Copyright of Laser Technology is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, a computational-theoretical analysis of the possibilities of using the method of phase-contrast X-ray radiography for the study of low-contrast turbulent flows in laser plasma in experiments with astrophysical similarity is carried out. By modeling the passage of hard coherent X-ray radiation through test objects, we studied the parameters of a laboratory experiment that affect the contrast and resolution of the resulting phase-contrast images. The limiting scale for measuring the frequency-spatial spectrum of image power was determined, on which the manifestation of artifacts from the superimposition of diffraction effects from neighboring objects is not yet critical for the correct interpretation of the results. Optimal object-detector distances are found that provide resolution of the power spectrum of a turbulent flow on micron scales. These results are relevant for future laboratory experiments on the development of instabilities in plasma with astrophysical similarity up to the stage of energy dissipation. [ABSTRACT FROM AUTHOR]

A technique is described for achieving high accuracy (relative error up to ≈0.001%) for measuring the absolute wavelengths of the spectral lines of multiply charged ions with an average (Z = 17–25) by the nuclear charge, the spectra of which can be used for plasma diagnostics in laboratory astrophysics experiments. It is based on irradiation with subnanosecond laser pulses with an intensity of 1015–1016 W/cm2 targets with a multicomponent chemical composition, including atoms with both medium and low Z. The presence of the latter ensures the presence in the emission spectrum of the resulting laser plasma of lines of hydrogen-like ions used as references. An atomic-kinetic code was created, and the intensities of possible reference and investigated spectral lines were calculated. The principles of selecting the target material, the features of the implementation of the technique on the example of a focusing spectrometer with spatial resolution based on spherically curved mica and α-quartz crystals are considered, and specific parameters of spectrometer circuits and types of targets for precision measurement of the wavelengths of spectral lines of helium- and lithium-like ions with nuclear charges are given. Z = 13–25. The results obtained in this work will be used in the planning of fundamental X-ray spectral studies at the ELF laser facility being developed at MEPhI. [ABSTRACT FROM AUTHOR]

The constructed cylindrical and spherical models of a laser-plasma ion source of a portable neutron generator made it possible to analyze the dynamics of ion currents based on their representation in the form of the interaction of partial and limiting currents and to greatly simplify the numerical algorithm. For the selected parameters of the discharge gap and the laser, the values of ion currents at the cathode were obtained. The calculated values of ion currents were compared with experimental data. [ABSTRACT FROM AUTHOR]

In this paper, we consider an experimental procedure for searching for the stimulation of de-excitation of nuclear isomer (SDNI) of 186mRe (the isomer spontaneous half-life is T1/2 = 2 × 105 yr) in a high-current Z-pinch plasma. On the basis of the recently obtained results of observing SDNI for 186mRe in a laser plasma, the possibility of observing SDNI for 186mRe in a Z-pinch plasma with an electron temperature of ~1 keV at the Angara-5-1 setup is shown. The design of a liner, a set of metal wires with the 186mRe isomer whose electric explosion produces a Z-pinch, the method for introducing the 186mRe isomer into the liner, and the method for detecting SDNI for 186mRe in a Z-pinch plasma are discussed. [ABSTRACT FROM AUTHOR]

In this article, we present an overview of the application of X-ray self-emission methods for the imaging of hydrodynamic astrophysical phenomena in laboratory-scale experiments. Typical diagnostic approaches, their advantages, drawbacks, and application perspectives are considered. We show that X-ray imaging and spectroscopy methods with 2D and even 1D spatial resolution are valuable for numerous laboratory astrophysical problems. Furthermore, the methods revealed the hydrodynamic evolution, the spatial shape and structure, and spatial features of important parameters such as electron density and plasma temperature of astrophysical objects and related phenomena, which are also required for the verification of astrophysical models. [ABSTRACT FROM AUTHOR]

By now technologies, employing optical discharges find ever expanding applications in metering and diagnostic equipment in science, engineering and medicine. Based on the original experimental results authors look into some manifestations of spatial and temporal instabilities of the continuous and periodic pulse optical discharges (COD, POD). Set of the phenomena considered makes a great impact on a performance of laser produced plasmas essential for many applications, such as high brightness broadband light sources, for instance. Performance instability of continuous optical discharges followed by laser beam refraction on the refraction index gradients exhibit themselves first in spatial inhomogeneity of plasma thermal radiation luminosity and the other parameters related. Spatial inhomogeneity is accompanied by temporal instability of the plasma. The paper reports criteria for the appearance of instabilities related to the refraction followed by the limitations on supporting of elongated plasma. One of the main reasons of temporal instabilities of COD is thermal gravity convection. Instability of a heated gas zone surrounding optical discharge is followed by regular self-sustained oscillations leading in turn to pulsing of brightness and position of radiated plasma. Simple physical model proposed gives estimations correspondent to the observed pulse frequency dependence on gas pressure. In the case of periodic pulse optical discharges forced convection may be put forward as one of the main discharge instability reasons. Pulse optical discharge induces convective flows due to asymmetrical gas expanding following gasdynamic effect of the energy release zone shape determined by laser beam focusing system configuration. [ABSTRACT FROM AUTHOR]

In this work, the properties of carbon films fabricated upon the action of laser plasma on the simple gaseous hydrocarbons have been studied. The change in the properties of these films caused by subsequent thermal or laser treatment has been investigated. Carbon films deposited on a cold substrate have a complex nature, which is similar to the nature of tholins. These films contain carbon atoms in the sp2- and sp3-hybrid states in proportional amounts, as well as various structural fragments containing hydrogen and oxygen. Thermal annealing of carbon films leads to a decrease in the concentration of hydrogen and oxygen-containing structures, unification of the structure based on carbon atoms in sp3 hybridization and formation of a so-called diamond-like structure. It was shown that carbon films are formed by spherical particles with an average diameter of 7–8 nm. Laser annealing and fabrication of a film with direct constant laser exposure leads to formation of a graphene-like structure meaning sp2 hybridization of carbon. [ABSTRACT FROM AUTHOR]

We estimate theoretically the strong-field-modified vibrational parameters of three-atomic A B A molecules with D ∞ h symmetry in a laser-induced plasma. The linear CO 2 and CS 2 molecules in the X 1 Σ g state are considered as examples. We show that double degeneracy of the Π u mode is removed due to reduction of the A B A molecule symmetry by the laser field. The linear form of A B A molecule is preserved, the bond length being elongated. [ABSTRACT FROM AUTHOR]

In inertial confinement fusion using central ignition, the ignition hot spot is generated through self-heating during fuel compression. In contrast, fast ignition creates the hot spot through external heating. This difference allows the fast ignition approach to use a solid sphere as the fusion fuel shape. The implosion of a solid sphere is one form of laser-direct-drive slow implosion. Solid sphere fuel exhibits tolerance to hydrodynamic instability and can be mass-produced relatively easily, offering significant advantages for developing inertial fusion energy. Achieving high fuel peak and areal densities of with a solid sphere requires quasi-isentropic compression, which involves multiple shock waves. Our results show the critical role of uniform laser irradiation in initiating weak shock waves in the early phase, which is essential for forming a uniform and dense fuel core with solid spheres. Furthermore, dynamically adjusting the laser spot diameter could be crucial in optimizing the effectiveness of laser-direct-drive and fast ignition techniques when using solid sphere fuel. [ABSTRACT FROM AUTHOR]

The influence of the magnitude and type of defocusing of twin laser pulses on the purposeful formation of the component and charge composition of laser plasma under the influence of twin laser pulses on a target made of aluminum alloy AD1 (LSS-1 spectrometer) has been studied. It is shown that when defocusing is more than 1 mm, the intensity of the ion line Al III increases several times in comparison with zero defocusing, the intensity of the ion lines Al II, N II also increases more or less monotonously. At the same time, the intensity of the bands AlO practically becomes zero. At the 1 mm defocusing value, the processes of formation of mixed nanopowders were studied and, under the influence of successive series of double laser pulses with the energy of 54 mJ and the inter-pulse interval of the iss on an aluminum target placed in a closed rectangular glass cuvette, the size of primary Al2O3 particles estimated using high-resolution electron microscopy was mainly 30-40 nm, and Al– 45-60 nm. The particles are collected into agglomerates.