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The laser plasmas produced from the interaction of the high-power laser with the target surface are suitable sources for soft X-ray laser, which has many applications in industry and medicine. In order to create the maximum efficiency of the output soft X-ray laser, the parameters of the pump laser should be optimize. In a double-pulse pump laser, the intensity and width of the pre-pulse, the intensity and width of the main pulse and the delay time between the two pulses are effective parameters in the output X-ray production. In this research, by using a machine learning based on the multiple regression equation, the dependence of the gain coefficient on the pump pulse parameters are investigated and a statistical model for predicting the gain coefficient of soft x-ray laser based on the feature of the pump pulse is presented without the need to numerical solution of the complex hydrodynamic equations. [ABSTRACT FROM AUTHOR]

The hot plasma generated from the high-power pulse of the laser on the target surface is considered such as a suitable source for the amplification of soft X-ray lasers. The gain coefficient and output intensity of these types of lasers depend on the characteristics of the input pulse and the target material. Optimizing emission for practical purposes requires extensive numerical simulations based on hydrodynamic equations and equation of state, which is computationally difficult and complex. In this research, a solution to this problem is proposed by using a model based on machine learning to predict the gain value of soft X-ray laser with a multilayer perceptron neural network, which there is no need to directly numerically solve an emission model. Finally, it can be seen that the neural network can predict the gain coefficient of the soft X-ray laser relatively well using only the features of pumped pulse. The use of neural networks in soft X-ray laser emission produced from laser plasmas is a new approach that needs further investigations according to the extent of simulation and optimization algorithms. [ABSTRACT FROM AUTHOR]

Since a theory that can justify the condition of matching of the laser and plasma parameters to implement the relativistic self-trapping regime for laser light in a plasma, which is the most efficient for the acceleration of electrons, is still absent, doubts remain in the necessity of the corresponding extensive experimental studies, particularly in view of the lack of justification or completion of previous theories. The presented theoretical analytical approach, which includes the relativistic nonlinearity of the electron mass and electron cavitation in the plasma, allows one to overcome this problem and provides an analytical justification of the conditions of such matching for ultrarelativistic laser beams at the quantitative level, which is in agreement with the multidimensional numerical simulation. [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]

The present study describes the potential use of the Laser-induced breakdown spectroscopy (LIBS) coupled with the principle component analysis (PCA) for the discrimination/analysis of the precious gold alloy has been reported. It is very hard to discriminate between the Au-Alloys using conventional LIBS and it has been suggested that the use of multivariate methods assisted LIBS could solve the problem. Gold alloys of karats 18 K, 19 K, 20 K, 22 K, and 24 K with concentrations of 75, 79, 85, 93, and 99.9% have been tested and analyzed using LIBS. Plasma was generated on the surface of the target sample by focusing Nd: YAG laser under atmospheric pressure. Time-integrated emission spectra from plasma were collected in the range of 250–870 nm. The characteristic emission lines of constituents were identified using the NIST atomic spectra database. Normalized optical emission intensities of the detected elements were used as input data for principle component analysis (PCA). Five different three-dimensional clusters were observed, that belonged to five different karats of gold, suggesting the reliability of the model for the classification of precious alloy samples. The finding from this study showed that the LIBS coupled with PCA is an effective method for the classification of gold alloys with different percentages. [ABSTRACT FROM AUTHOR]

Laser processing has emerged as a pivotal technique for micro-hole fabrication owing to its exceptional efficiency and absence of tool wear. Nevertheless, certain imperfections persist in laser drilling. Consequently, this study presents a comprehensive analysis of the impact of laser processing parameters, methods, and physical field-assisted techniques on the quality and efficiency of laser drilling based on the characteristics desired for micro-holes. The findings reveal that selecting an appropriate laser wavelength and pulse width, coupled with meticulous adjustments to laser power, repetition frequency, and defocusing amount can enhance either processing efficiency or micro-holes quality; however, optimizing both aspects simultaneously remains challenging. By refining scanning strategies and implementing pulsed joint secondary repair approaches, heat accumulation is minimized while micro-holes quality is optimized; nevertheless, ensuring high processing efficiency poses difficulties. Ultrasonic assisted laser drilling enhances processing efficiency by facilitating the expulsion of molten materials, while magnetic field-assisted laser drilling improves processing efficiency by mitigating the attenuation of the laser caused by plasma clouds. Both techniques contribute to enhancing the quality of hole walls through their stirring effect. Water-based ultrasonic/magnetic field-assisted laser perforation combines heat dissipation and secondary flushing effects with ultrasonic/magnetic field assistance, resulting in superior micro-hole formation. Magnetic field-ultrasonic assisted laser perforation synergistically combines both effects. Furthermore, this study distinguishes between the promoting and inhibiting effects of rotating and static magnetic fields on molten metal flow, elucidating the impact of ultrasound and magnetic fields on molten metal from a melt dynamics perspective. Finally, we summarize the influence of each optimization method on micro-hole quality characteristics and processing efficiency while providing insights into future development trends. [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]

Low-pressure plasma processes are routinely used to grow, functionalize or etch materials, and thanks to some of its unique attributes, plasma has become a major player for some applications such as microelectronics. Plasma processes are however still at a research level when it comes to the synthesis and functionalization of nanoparticles. Yet plasma processes can offer a particularly suitable solution to produce nanoparticles having very peculiar features since they enable to: (i) reach particle with a variety of chemical compositions, (ii) tune the size and density of the particle cloud by acting on the transport dynamics of neutral or charged particles through a convenient setting of the thermal gradients or the electric field topology in the reactor chamber and (iii) manipulate nanoparticles and deposit them directly onto a substrate, or codeposit them along with a continuous film to produce nanocomposites or (iv) use them as a template to produce 1D materials. In this article, we present an experimental investigation of nanoparticles synthesis and dynamics in low-pressure microwave plasmas by combining time-resolved and in-situ laser extinction and scattering diagnostics, QCL absorption spectroscopy, mass spectrometry, optical emission spectroscopy and SEM along with a particle transport model. We showed for the first time the thermophoresis-driven dynamic of particle cloud in electrodless microwave plasmas. We showed that this effect is linked to particular fluctuations in the plasma composition and results in the formation of a void region in the bulk of the plasma surrounded by a particle cloud in the peripherical post-discharge. We also reveals and analyze the kinetics of precursor dissociation and molecular growth that result in the observed nanoparticle nucleation. [ABSTRACT FROM AUTHOR]

In this paper, an analytical formalism is developed for electron acceleration using two crossed and identical laser pulses in a plasma channel. The net electron energy is increased and the electron diffraction is decreased through the utilization of radially polarized (RP) crossed-focused laser pulses. The study investigates the impact of various parameters, such as laser amplitude, ion density, initial kinetic energy, injection angle, laser pulse duration, and spot size on electron energy gain within a preformed plasma ion channel. The presence of space-charge field confines the dynamic of electrons along the longitudinal direction. Consequently, the transverse component of the laser pulse vanishes along the propagation axis, whereas the longitudinal component provides a longitudinal force. This configuration leads to the observation of gain in energy of electrons in GeV at a laser intensity ∼ 10 19 W / cm 2 where the ion density is ∼ 10 23 m - 3 in plasma channel. [ABSTRACT FROM AUTHOR]

For CdZnTe crystals containing extended defects – coherent and incoherent twin boundaries, as well as lamellar systems of twins, we measure the propagation patterns of surface acoustic waves (SAW) in the gigahertz range excited by a sharply focused femtosecond laser pulse. Comparison of the calculated SAW radial velocities with experimental data allows us to determine the local crystallographic orientation of crystal regions with defects. We discover strong anisotropic scattering of SAW at twin boundaries and show that the structure of the twin boundary can be determined from the pattern of SAW scattering. Also, we demonstrate the non-reciprocal SAW propagation in lamellar twin systems, as well as quasi-waveguide SAW propagation along the lamellar twin layer. [ABSTRACT FROM AUTHOR]

A stand is described that is designed to study the emission properties of laser plasma in the extreme ultraviolet range (EUV) formed on liquid jet targets. To form a jet target, a pulse valve and capillaries of various diameters are used. A Nd:YAG laser is used (with a wavelength of 1064 nm, a pulse duration of 11 ns, a frequency of up to 10 Hz, and a pulse energy of 500 mJ) to excite laser plasma. To investigate the emission spectra, a mirror X-ray spectrometer calibrated in absolute units, an Aurora 4000 visible-range spectrometer, and a microscope operating in the EUV range are used. Photographing of the formed liquid jets is also provided. The design of the stand and its main parameters are presented. The results of the first experiments to study the processes of liquid outflow from various nozzles into vacuum are also presented. [ABSTRACT FROM AUTHOR]

To solve such global problems as climate stabilization and reducing greenhouse gas luminescences requires an integrated approach, including a strategic analysis of the problem and the development of criteria for selecting proposed solutions, a natural scientific research on the possibilities and ways to implement the assigned tasks, as well as an economic justification for the feasibility of implementing the developed measures. The present publication is an attempt to apply this approach to the problem of hydrogen energy via proposing the production of hydrogen by pyrolysis of natural gas in laser plasma as one of the ways to its solution. Therewith, the main attention is focused on the chemical processes that occur in laser plasma, as well as on the nature of the transformations that occur in the solid pyrolysis product. [ABSTRACT FROM AUTHOR]

Theoretical investigation on self-focusing of an elliptical q-Gaussian laser beam, carrying an intensity ripple over its cross section, in plasma with an axial density ramp has been presented. The optical nonlinearity of plasma has been modeled by the relativistic mass nonlinearity of plasma electrons in the field of a laser beam. Using the variational theory approach, semi-analytical solutions of the wave equations for the fields of the main beam and that of the ripple have been obtained. Emphasis has been put on the evolutions of the beam widths of the main beam and that of the ripple. [ABSTRACT FROM AUTHOR]

It is indispensable to accurately and sensitively identify and analyze the elemental composition of human blood serum. In the current study, human blood serums were analyzed for elements utilizing orthogonal dual pulse laser-induced breakdown spectroscopy (DP-LIBS) setup in He gas environment. Experimentally, a fundamental pulse Nd:YAG laser (1064 nm, 7 ns) was irradiated just above the material target to induce a luminous gas plasma. A third harmonic pulse Nd:YAG laser (355 nm, 7 ns) was subsequently focused on the material surface to initiate a target plasma to ablate the atoms from the blood serum film to be sent to the gas plasma region. Double pulse LIBS technique has been successfully applied to increase the LIBS signal intensity up to 8 folds of major, minor, and trace components in human blood serum. Furthermore, a number of emission lines that were indistinctly detected by single pulse LIBS were accurately identified with the use of the DP-LIBS. A variety of components from the human blood serum have been analyzed both qualitatively and quantitatively. Element concentrations measured in human blood are to be 8360 ppm, 219 ppm, 581 ppm, 785 ppm, 343 ppm, 293 ppm, and 12 ppm for C, Ca, K, Mg, P, Na, and Fe, respectively. The LIBS outcome results are in excellent agreement with the results acquired by applying the standard XRF technique. [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]

A method for recording the spatial distribution of radiation scattered from laser plasma in a wide angular range, up to 4π, using preexposed and developed photographic paper is proposed. This method makes it possible to obtain a radiation pattern of scattered radiation with a sufficiently high spatial and angular resolution. By calibrating the sensitivity of photographic paper, one can quantify the energy of scattered radiation in various directions and determine the integral value of the energy loss due to scattering in a wide spectral range from UV to IR. [ABSTRACT FROM AUTHOR]

This article discusses a measurement module of a dispersion interferometer based on a CO2 laser for integral plasma density measurements with a resolution of 4 × 1011 cm–2 with a time discreteness of 4 µs. Such characteristics of the device make it possible to use the results of its measurements in feedback loops for plasma density control. The main elements of the measurement module are crystals of analog-to-digital converters (ADCs) and a digital streaming data processing node based on a field-programmable gate array (FPGA). The algorithm for calculating the plasma density implemented in the digital node is based on the harmonic analysis of interferometer signals and is resistant to noise and changes in the modulation depth. The measurement module under consideration is a prototype of the system of monitoring and automatic control of plasma density at the Globus-M2 facility (St. Petersburg, Russia). [ABSTRACT FROM AUTHOR]

The methods of enhancement of the strong high-order harmonics of femtosecond pulses in laser-induced plasma are demonstrated. It comprises the application of the four techniques allowing the enhancement of harmonics in different spectral ranges. Among them are the selection of targets for ablation to create the conditions for resonance enhancement of single harmonic, formation of the quasi-phase-matching of a spectrally tunable group of harmonics, application of the two-color pump of plasma, and the formation of nanoparticles-contained plasmas. The number of generated coherent XUV photons increased in the region of single resonantly enhanced harmonic (62 nm) and the shorter-wavelength region (30–50 nm). The above techniques of harmonics enhancement allowed a significant (up to 50 times) growth in a whole harmonic yield in the case of indium plasma. We discuss the reasons preventing the joint implementation of the four methods of harmonics enhancement in the same spectral region. [ABSTRACT FROM AUTHOR]

This study explores the potential of utilizing microwaves to sustain the expansion of transient laser ablation plasma of Zr target. By application of microwaves on the plasma, we observe a significant enhancement with a two to three order of magnitude increase in the plasma emission intensity, and 18 times increase in the plasma's spatial volume. We investigate the temperature change of the plasma and observe that it decreases from 10,000 K to approximately 3000 K. Electron temperature decreased with volume expansion owing to increased surrounding air interaction, while the plasma can be sustained in air using microwaves. The increase in electron temperature during temperature drop is indicative of non-equilibrium plasma. Our results emphasize the contribution of microwaves in promoting enhanced emission and plasma formation at controlled, low temperature, thereby demonstrating the potential of microwaves to enhance the accuracy and performance of laser-induced breakdown spectroscopy. Importantly, our study suggests that microwaves could also mitigate the generation of toxic fumes and dust during ablation, a critical benefit when handling hazardous materials. The system we've developed is highly valuable for a range of applications, notably including the potential to reduce the possible emergence of toxic fumes during the decommissioning of nuclear debris. [ABSTRACT FROM AUTHOR]

A scheme for electron acceleration by self-focused q-Gaussian laser pulses in under-dense plasma has been presented. The relativistic increase in the mass of plasma electrons gives nonlinear response of plasma to the incident laser pulse resulting in self-focusing. Under the combined effects of the saturation nature of relativistic nonlinearity of plasma, self-focusing and diffraction broadening of the laser pulse, the beam width of the laser pulse evolves in an oscillatory manner. An electron initially on the pulse axis and at the front of the self-focused pulse, gains energy from it until the peak of the pulse is reached. When the electron reaches the tail of the pulse, the pulse begins to diverge. Thus, the deacceleration of the electron from the trailing part of the pulse is less, compared to the acceleration provided by the ascending part of the pulse. Hence, the electron leaves the pulse with net energy gain. The differential equations for the motion of electrons have been solved numerically by incorporating the effect of self-focusing of the laser pulse. [ABSTRACT FROM AUTHOR]

Laser wakefield acceleration (LWFA) continues to grow and awaken interest worldwide, especially as in various applications it approaches performance comparable to classical accelerators. However, numerous challenges still exist until this can be a reality. The complex non-linear nature of the process of interaction between the laser and the induced plasma remains an obstacle to the widespread LWFA use as stable and reliable particle sources. It is commonly accepted that the best wavefront is a perfect Gaussian distribution. However, experimentally, this is not correct and more complicated ones can potentially give better results. in this work, the effects of tuning the laser wavefront via the controlled introduction of aberrations are explored for an LWFA accelerator using the shock injection configuration. Our experiments show the clear unique correlation between the generated beam transverse characteristics and the different input wavefronts. The electron beams stability, acceleration and injection are also significantly different. We found that in our case, the best beams were generated with a specific complex wavefront. A greater understanding of electron generation as function of the laser input is achieved thanks to this method and hopes towards a higher level of control on the electrons beams by LWFA is foreseen. [ABSTRACT FROM AUTHOR]

The paper discusses the results of studying the emission spectra and absolute radiation intensities of laser plasma generated by laser pulse on a xenon gas-jet target. A Nd:YAG laser, λ = 1064 nm, τ = 5.2 ns, Epulse = 0.8 J was used. The spectral range 3–20 nm was studied. Gas-jet targets were formed by a supersonic conical nozzle. Emission spectra of laser plasma were obtained and interpreted. Absolute radiation intensities were determined in a number of spectral bands under various conditions of gas-jet target excitation. [ABSTRACT FROM AUTHOR]

In this study, the effect of environment gas and working pressure of laser-induced breakdown spectroscopy from ZnO: Al composite target (AZO) enhanced by an external magnetic field on the magnetized characteristics and emission spectra of plasma were investigated. The plasma was induced by a Q-switched nanosecond Nd: YAG laser at a constant pulse laser energy of 300 mJ at different pressures of 0.08, 0.2, 0.4, and 760 Torr in air and argon gas. The atomic and ionic emission lines increased in intensity directly with the working pressure. The plasma temperature (Te) and electron number density (ne) were determined at the different environmental conditions according to the intensity-ration method, and Stark broadening effect, respectively. Both ne and Te increased with increasing pressure and with the presence of magnetic field as a result of confining effect. The line profile appeared with high broadening at atmospheric pressure compared with vacuumed plasma. The Larmur radius and confinement factor β increased with working pressure. From another hand, using Ar instead of air caused slightly reduced ne at low pressure, while Te has the opposite behavior. [ABSTRACT FROM AUTHOR]

Various laser-produced metal plasmas were used for high-order sum and difference harmonic generation using the mixing of tunable mid-infrared pulses from optical parametric amplifier and 810 nm ultrashort pulses. We show that, regardless of non-optimal spatio-temporal overlap of two sources of radiation in the plasmas, the application of proposed technique allows a significant growth of harmonic yield and broadening of the number of different combinations of interacting waves in the extreme ultraviolet region, which could be useful for observation of the resonance induced enhancement of some frequency components. [ABSTRACT FROM AUTHOR]

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]

Ultra-intense lasers that ionize atoms and accelerate electrons in solids to near the speed of light can lead to kinetic instabilities that alter the laser absorption and subsequent electron transport, isochoric heating, and ion acceleration. These instabilities can be difficult to characterize, but X-ray scattering at keV photon energies allows for their visualization with femtosecond temporal resolution on the few nanometer mesoscale. Here, we perform such experiment on laser-driven flat silicon membranes that shows the development of structure with a dominant scale of 60 nm in the plane of the laser axis and laser polarization, and 95 nm in the vertical direction with a growth rate faster than 0.1 fs−1. Combining the XFEL experiments with simulations provides a complete picture of the structural evolution of ultra-fast laser-induced plasma density development, indicating the excitation of plasmons and a filamentation instability. Particle-in-cell simulations confirm that these signals are due to an oblique two-stream filamentation instability. These findings provide new insight into ultra-fast instability and heating processes in solids under extreme conditions at the nanometer level with possible implications for laser particle acceleration, inertial confinement fusion, and laboratory astrophysics. Ultrafast relativistic plasma instabilities accompany and influence laser matter interactions that accelerate particlebeams with potential applications in e.g radiotherapy or fussion fast ignition scenarios. Here, the authors use Small Angle X-ray Scattering to observe such instabilities on a femtosecond, tens of nanometer scale in solids, and draw conclusions on the underlying plasma dynamics. [ABSTRACT FROM AUTHOR]

Nanofilms of zinc, aluminum, lead, silver, and copper have been obtained by the laser-plasma method. The conditions of deposition of such films on substrates, providing the absence of metal particles on their surface, were determined. The threshold power densities of the laser radiation acting on a metal target, at which an intense evaporation of its material begins, were found experimentally. It is shown that the boiling temperature of the material of a target influences the surface relief of the metal nanofilms obtained. The conditions of obtaining fi lm coatings with small particles of the target material on their surface, which can be used for the realization of the giant Raman scattering, were determined. [ABSTRACT FROM AUTHOR]

When propagating inside dielectrics, an ultrafast Bessel beam creates a high aspect ratio cylinder of plasma with nanometric diameter that extends over several tens of micrometers to centimeters. We analyze the interaction between the intense ultrafast laser pulse and the plasma rod using particle-in-cell simulations. We show that electrons are heated and accelerated up to keV energies via transit acceleration inside the resonance lobes in the vicinity of the critical surface and compute their radiation pattern. [ABSTRACT FROM AUTHOR]

Terahertz radiation from two-color femtosecond laser-induced gas filament is investigated in a wide range of the ambient gas pressure from 0 to 606 kPa (i.e., 0–6 atm). We observed that the output energy of terahertz radiation first increased quickly to the strongest strength at the optimal pressure around 25 kPa then decreased gradually with increase of the gas pressure. We found a linear dependence of the time delay of the terahertz signals on increasing gas pressure under a wide range of gas pressure and nearly unchangeable plasma density profile of the filament in the high pressure range from ~ 50 kPa to 606 kPa if keeping the same pump laser energy. Our numerical simulation results reproducing the experimental dependence of decreasing terahertz strength on the increasing gas pressure in this high pressure range indicate that this dependence could be attributed mainly to the decreasing coupling of the two-color laser pulses in the plasma filament due to different changes of their propagating velocities in the ambient gas with increasing pressure. Our results would be helpful for understanding deeply the mechanism of terahertz radiation and remind a possible strategy for improvement of terahertz output under higher gas pressures and pumped by more laser energies. [ABSTRACT FROM AUTHOR]

We describe the experimental implementation of high-resolution soft X-ray spectrographs, which are stigmatic throughout their operating range. The optical configuration comprises a grazing-incidence plane VLS grating and a broadband normal-incidence focusing mirror with an aperiodic multilayer coating structure. The operating range is defined by the aperiodic multilayer mirror in use (Mo/Si: 12.5 – 25 nm; Mo/Be: 11 – 14 nm). The spectral resolution is determined by CCD detector resolution and is numerically equal to the product of the plate scale and the double pixel size. Vertically spaceresolved laser-produced plasma spectra of multiply charged ions are presented. The spatial resolution is equal to about 26 μm, the double pixel size. We discuss the prospect of extending high-resolution stigmatic spectral imaging below 11 nm and outline the data of numerical calculations of broadband normal-incidence mirrors based on aperiodic Ru/Sr and La/B4C multilayer structures. [ABSTRACT FROM AUTHOR]

An analytical formalism is developed to study the radiation pressure hole boring ion acceleration of a CH foil in an underdense upstream plasma. The laser quickly converts the foil into an overdense plasma and exerts a strong forward ponderomotive force on the electrons. The electrons are pushed to the rear and detach from the ions to form a thin electron layer, followed by a hydrogen ion layer and a distant carbon ion layer. The triple layer of electrons, protons and carbon ions is accelerated by the radiation pressure; the space charge field plays an intermediary role in accelerating the ions. In the frame of the electron layer, moving with velocity v f z ^ , the upstream protons appear to be moving backward with velocity - v f z ^ . They get reflected back in the fast moving intense space charge field of the triple layer, acquiring velocity v f z ^ . In the lab frame, these protons have a velocity nearly twice the velocity of the electron layer. For a Gaussian (in time) laser pulse, a parabolic density profile of the upstream plasma is seen to produce a proton beam with narrow energy spread. For a normalized laser amplitude a 0 = 10 , one may obtain 180 MeV protons in a parabolically decreasing density profile of scale length 40 μ m. [ABSTRACT FROM AUTHOR]

This work explores the enhanced spectroscopic characterizations of the soil plasma through the magnetic field-assisted laser-induced breakdown spectroscopy (LIBS) technique and its dependence upon laser fluence. The laser-induced soil plasma has been produced by the employment of Nd:YAG laser (1064 nm) on the surface of the pelletized river soil samples in the absence and presence of a magnetic field of 0.66 T at different laser fluences (30–61 J/cm2). Various elements particularly trace elements (arsenic, chromium, manganese, barium, titanium, cobalt, and strontium) were detected in the soil samples, where an enhancement factor of up to 6 times is achieved with the application of a magnetic field to LIBS. The plasma parameters like electron temperature (Te) and electron number density (ne) show an increasing trend with the laser fluence and then decline slightly after 51 J/cm2 laser fluence but with higher values of these parameters under the magnetic field. The better spectroscopic results are attributed to the magnetic confinement of the plasma, confirmed by the plasma parameter βt < 1. In addition, the threshold laser fluences have been estimated for the soil sample as ~ 6 J/cm2 and ~ 11 J/cm2 with and without magnetic field, respectively. The variation in Inverse Bremsstrahlung co-efficient and plasma frequency as a function of laser fluence is also reported. Improved spectroscopic results of magnetic field-assisted LIBS demonstrate it as a promising tool for the detection of multi-elements particularly trace elements in river soil samples. [ABSTRACT FROM AUTHOR]

In the work that is being presented here, the effect of sample thickness and laser irradiance on the reduction of the signal-to-background ratio SBG and the plasma parameters, specifically electron temperature and electron density, is being investigated using back-reflection-enhanced laser-induced breakdown spectroscopy (BRELIBS). Copper and silver discs that had been highly polished were attached to the back surface of the glass target, and the Nd-YAG laser beam that was focused on the front surface of the target was tuned to its fundamental wavelength. The thicknesses of the transparent glass samples that were analysed were 1 mm, 3 mm, and 6 mm. One is able to achieve a range of different laser irradiance levels by adjusting the working distance that exists between the target sample and the focusing lens. The end result of this is that the signal-to-background ratio in the BRELIBS spectra of thicker glass samples is significantly lower as compared to the ratio in the spectra of thinner glass samples. In addition, a significant influence of modifying the laser irradiance (by increasing the working distance on the SBG ratio) is seen at various glass thicknesses for both BRELIBS and LIBS, with BRELIBS having a better SBG. Nevertheless, the laser-induced plasma parameter known as the electron temperature has not been significantly impacted by the decrease in the glass thickness. [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 method is proposed for converting linearly polarized radiation of a single harmonic or a combination of high-order harmonics of an optical field, which form a train of subfemto-/attosecond pulses, into elliptically and, in particular, circularly polarized radiation in an optically modulated neon-like active medium of an X‑ray plasma laser. It is shown that this method can provide a high energy efficiency of radiation conversion due to the amplification of the harmonic field, and is also insensitive to changes in the number of high harmonics that form the amplified pulses. The possibility of experimental implementation of the method is considered on the example of an active plasma of neon-like Ti12+ ions with an unperturbed inverted transition wavelength of 32.6 nm. [ABSTRACT FROM AUTHOR]

This work presents an analytical and numerical study of the relativistic-ponderomotive effect on self-focusing of an intense cosh-Gaussian laser beam in a collisionless magnetized plasma by considering an external magnetic field in the direction of propagation of the laser beam. The nonlinear differential equation for the beam width parameter/intensity of a cosh-Gaussian laser beam in a magnetized plasma is obtained by Wentzel–Kramers–Brillouin (WKB) and paraxial-ray approximations. The self-focusing of the cosh-Gaussian beam at different values of the magnetic field parameter is investigated. The results have also been compared to relativistic nonlinearity. The results show that the self-focusing effect of cosh-Gaussian beam in magnetized plasma becomes stronger, when relativistic and ponderomotive nonlinearities acts together. In addition, the self-trapping of cosh-Gaussian beam in magnetized plasma has also been studied. Numerical results are presented for the well-established laser and plasma parameters. [ABSTRACT FROM AUTHOR]

The amplification in a free-electron laser undulator of a short-wavelength subattosecond pulse formed in a laser plasma upon its interaction with a relativistic electron bunch produced by a petawatt laser is considered. The aim of this work is to find the parameters of the system at which it is possible to amplify ultrashort pulses with a duration of up to hundreds of zeptoseconds. [ABSTRACT FROM AUTHOR]

Acceleration of laser-induced plasma created as a result of three-step photoionization of atomic vapor by pulsed radiation of dye lasers pumped by copper-vapor lasers is studied experimentally. The acceleration was achieved due to the alternating magnetic field appearing upon propagation of a current pulse through an inductor located in direct proximity from the area of laser protoionization of atomic lutetium vapor. [ABSTRACT FROM AUTHOR]

Dry reforming of methane (DRM) is a highly endothermic process, with its development hindered by the harsh thermocatalytic conditions required. We propose an innovative DRM approach utilizing a 16 W pulsed laser in combination with a cost-effective Mo2C catalyst, enabling DRM under milder conditions. The pulsed laser serves a dual function by inducing localized high temperatures and generating *CH plasma on the Mo2C surface. This activates CH4 and CO2, significantly accelerating the DRM reaction. Notably, the laser directly generates *CH plasma from CH4 through thermionic emission and cascade ionization, bypassing the traditional step-by-step dehydrogenation process and eliminating the rate-limiting step of methane cracking. This method maintains a carbon-oxygen balanced environment, thus preventing the deactivation of the Mo2C catalyst due to CO2 oxidation. The laser-catalytic DRM achieves high yields of H2 (14300.8 mmol h−1 g−1) and CO (14949.9 mmol h−1 g−1) with satisfactory energy efficiency (0.98 mmol kJ−1), providing a promising alternative for high-energy-consuming catalytic systems. Dry reforming of methane (DRM) is a highly endothermic process, often limited by the severe thermocatalytic conditions it demands. Here the authors introduce a novel DRM method that employs a 16 W pulsed laser along with a cost-effective Mo2C catalyst, allowing DRM to proceed under milder conditions. [ABSTRACT FROM AUTHOR]

The terahertz (THz) spectral zone is one of the most exciting but least explored domains of the electromagnetic spectrum. To extend the applicability of THz waves, the present objective is to develop an efficient, compact, durable, and low-cost THz emitter source. A spintronic THz emitter consisting of a ferromagnetic/nonmagnetic bilayer heterostructure is a promising innovation that can provide an alternative solution/replacement for conventional THz emitters. To further develop these spin-based THz emitters, we demonstrate an efficient and strong THz emission from a single layer of Co2MnGa with a large anomalous Hall effect (AHE) influenced by its Weyl semimetallic nature. Strong correlations among the THz emission, AHE, and chemical ordering of the full Heusler crystal structures for Co2MnGa are shown. Based on proper structural and chemical design, the topological nature of this material facilitates systematic optimization. Our initial findings provide a new design concept for the topological influences on spin-based THz emitters, and these emitters are expected to facilitate the further development of the intriguing Weyl physics. Our investigation delves into the pulse-laser-induced emission of THz waves from a single layer of Co2MnGa thin film, emphasizing its notable anomalous Hall effect (AHE) stemming from its Weyl semimetallic characteristics. We establish robust correlations between THz emission, AHE, and the chemical structure of Co2MnGa thin films. Significantly, Co2MnGa films exhibit much larger THz emission compared to conventional CoFeB films. These findings introduce an innovative approach to designing spin-based THz emitters and promise to deepen our understanding of Weyl physics. [ABSTRACT FROM AUTHOR]

Simultaneous measurements using two Intensified Charge-Coupled Device (ICCD) cameras with two bandpass filters on laser-induced air plasma have facilitated the illustration of a two-dimensional temperature distribution within the plasma. In each pixel, the intensity captured by the ICCD cameras could replace the intensity measurements using a spectrometer in the two-line ratio method for temperature measurement. The plasma was produced by a 532 nm pulse from a Q-switched neodymium-doped yttrium aluminum garnet laser. The two ICCD cameras with the two bandpass filters simultaneously captured the plasma to measure emission intensities at two wavelengths. The two-line ratio method using N II lines was applied in each pixel to examine the two-dimensional temperature distribution. Two laser energies and focal lengths were utilized to ensure spatially and temporally consistent temperature results considering the characteristics of the plasma temperature at the experiment conditions. The signal-to-noise ratio increased with increasing the incident energy and decreasing the focal length. The highest temperature was observed at the high incident energy and the short focal length. The location in the plasma with the maximum temperature varied over time. The temperature significantly reduced with time at the long focal length and low incident energy. The plasma temperature was measured using the two-line ratio method with a spectrometer. Average emission intensity images at the two wavelengths were used to examine the plasma temperature. The results of the three temperature measurement methods were compared to evaluate the accuracy of the methods. Generally, in the three methods, the temperature changes were similar along the x-axis of the plasma. The temperature difference between the two-filtered imaging method and the spectrometer was between 1 and 7%. The temperature difference between the average image method and the spectrometer was between 1 and 10%. The two-filtered imaging method simultaneously captures spectral emissions at two wavelengths and hence effectively shows a two-dimensional temperature distribution. [ABSTRACT FROM AUTHOR]

We report the optimization of the high-order harmonic generation (HHG) in the laser-induced gold plasma. It includes determination of the characteristics of heating pulses allowing formation of the gold plasma possessing suitable characteristics (plasma density, electron density, electron temperature, velocity of plasma), as well as determination of the optimal delay between heating picosecond pulses and driving femtosecond pulses. Time-resolved Au plasma spectra and images allowed determining the velocity of plasma spreading (2 × 104 m s-1), electron density (3 × 1016 cm-3), and electron temperature (0.8 eV) of gold plasma at the optimal fluence of heating 150 ps pulses allowing HHG up to the 53rd order at the conversion efficiency of 1 × 10− 5. We also report the modification of the blueshift of harmonics at different regimes of HHG and plasma formation. The harmonic splitting onto strong blue component and weak red component appeared at 3 × 1014 W cm-2 intensity of 806 nm pump. [ABSTRACT FROM AUTHOR]

Purpose: Postoperative urinary retention (PUR) is a common complication after prostate enucleation, which leads to an increased length of hospital stay and decreased postoperative satisfaction. This study determined the predictive factors of postoperative urine retention within 1 month after prostate enucleation and investigated whether PUR influences surgical outcomes at the 2-week, 3-month, and 6-month follow-up time points. Methods: Data were collected from the electronic medical records of 191 patients with benign prostatic obstruction (BPO) during October 2018 to September 2021. Of them, 180 patients who underwent thulium laser or plasma kinetic enucleation of the prostate (ThuLEP, PKEP) were separated into the PUR group (n = 24) and the non-PUR (NPUR) group (n = 156). Uroflowmetry and the International Prostate Symptom Score (IPSS) questionnaire were followed up at 2 weeks, 3 months, and 6 months postoperatively. Results: The PUR group had a significantly higher percentage of patients with type 2 diabetes mellitus (DM) than the NPUR group. Postoperatively, compared with the NPUR group, the PUR group had significantly less improvement in changes in the IPSS Quality of Life scores at 2 weeks, the total IPSS(International Prostate Symptom Score) at all follow-up times, the IPSS-S(IPSS storage subscores) at 2 weeks and 3 months, and the IPSS-V(IPSS voiding subscores) at all follow-up times. Predictive factors for PUR include lower preoperative maximum urinary flow (Qmax), lower preoperative total IPSS, and higher operation time. Conclusion: Lower preoperative Qmax, lower IPSS scores, and longer operation time were risk factors for PUR. Furthermore, PUR could be a prognostic factor for prostatic enucleation surgical outcomes. [ABSTRACT FROM AUTHOR]

High-order harmonic generation in laser-induced plasmas is analyzed from the point of view of presence of either molecular or atomic components. Comparison of boron carbide, carbon, and boron plasmas demonstrates the worsened characteristics of coherent extreme ultraviolet radiation in the case of B4C (smaller conversion efficiency, lower cutoff of generated harmonics, worsened stability). Similar features, alongside the disappearance of resonance-induced enhancement of harmonics and weakened quasi-phase-matching conditions, were observed in other molecular plasmas (Ag2S, GaAs, Cr3C2) compared with plasmas comprising atomic components (Ag, As, Cr). We discuss the reasons of worsening conditions in the case of high-order harmonic generation in few-atomic molecular species compared to the single-atomic ones. [ABSTRACT FROM AUTHOR]

The formation of a diamond-like carbon coating on a substrate as a result of the action of the radiation of an industrial laser (t ~ 20 ns, λ = 1.06 μm) on a target of the highly oriented pyrolytic UPV-1 graphite in a vacuum was investigated. It is shown that by changing the power density of the laser radiation on the surface of such a target, the velocity of scanning of the laser beam over the target surface, the laser pulse repetition frequency, and the temperature of the target, one can control the ratio between the sp2- and sp3-carbon bonds in the coating applied to a substrate. It was established that a diamond-like carbon coating with a predominant content of the sp3-bonded carbon is formed at a laser power density q ≥ 5.6∙108 W/cm2. In this case, it is advisable to select the laser pulse repetition frequency and the velocity of scanning of a laser beam over the surface of a target so that 10 to 14 laser pulses fall successively into one and the same area of the target surface. It is shown that, in the case where a target has a temperature T ≥ 423 K, the content of the sp3-linked carbon in the coating applied to a substrate decreases sharply, with the result that the properties of the coating deteriorate. [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]

A brief review of the results of experimental modeling of cosmic jets in superstrong magnetic fields of laser relativistic plasma is given. It is noted that the development of cyclotron instability with the generation of cyclotron radiation plays a key role in a number of processes in a plasma with a magnetic field: self-localization of plasma in the form of solitons, conversion of rotational motion of plasma into translational motion, cyclotron acceleration of charged particles, and separation (stratification) of a plasma jet into separate plasma formations. [ABSTRACT FROM AUTHOR]

In the paper, we demonstrate the application of X-ray spectroscopy with high spatial resolution to study magnetic reconnection in laboratory astrophysical experiments performed with nano- and pico-second duration laser facilities at a moderate laser density on the target of <1018 W/cm2. A brief overview of the commonly used experimental schemes is given. Atomic kinetic calculations for the L-shell spectra of Ne- and F‑like Fe ions (iron, Z = 26) demonstrate the high sensitivity of the measurements to changes in plasma parameters. The scope of the different diagnostic approaches to measure electron temperature and laser plasma density is discussed. It is shown that transitions in Ne-like ions are a universal tool for measuring plasma parameters, both in the region of laser interaction with the target and in the reconnection zone. [ABSTRACT FROM AUTHOR]

In this article, nanoparticles of neodymium oxide deposited on NaX zeolite powder were fabricated using a 3.5 kJ Mather-type plasma focus device. The NaX zeolite samples were exposed to the 10, 15, and 20 shot numbers of the plasma focus device at a distance of 14 cm from the anode tip and 0 angular positions concerning the anode axis. Parent NaX zeolite and NaX:Nd composites with different Nd2O3 percent weights were characterized using various techniques such as; XRF, XRD, SEM, FT‒IR, and UV‒vis. It is found from the XRD analysis that the structure of the NaX zeolite is not affected by the shots of the plasma focus device, but the crystallinity of the zeolite is changed slightly after increasing the device shots. It was also found from TF-IR spectra that the amount of Nd2O3 in the samples increases with the increase of the shot number. The SEM analysis revealed an irregular distribution of prose on the surface of the deposited zeolite. It was also deduced from the results that variations in amount of can have significant effects on the degree of the crystallinity and optical characteristics of the synthesized composite including refractive index, band gap energy, dielectric constant, and absorption coefficients. The finding results can be used to enhance the structural characteristics and optical properties of fabricated nano-clusters deposited on porous materials such as zeolite. [ABSTRACT FROM AUTHOR]