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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]

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]

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]

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]

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]

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]

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]

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]

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]

We present a new phenomenon resulting from the interaction of magnetic beads with cancer cells in a laser trap formed on a slide containing a depression 16.5 mm in diameter and 0.78 mm of maximum depth. This phenomenon includes the apparent formation and expansion of a dark bubble that attracts and incinerates surrounding matter when it explodes, which leads to a plasma emitting intense radiation that has the appearance of a star on a microscopic scale. We have observed the star-like phenomenon for more than 4 years, and the intensity depends on the laser's power. Measuring the laser power of the dark bubble shows the entrapment of electromagnetic energy as it expands. [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]

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]

The rapid progress that plasma wakefield accelerators are experiencing is now posing the question as to whether they could be included in the design of the next generation of high-energy electron-positron colliders. However, the typical structure of the accelerating wakefields presents challenging complications for positron acceleration. Despite seminal proof-of-principle experiments and theoretical proposals, experimental research in plasma-based acceleration of positrons is currently limited by the scarcity of positron beams suitable to seed a plasma accelerator. Here, we report on the first experimental demonstration of a laser-driven source of ultra-relativistic positrons with sufficient spectral and spatial quality to be injected in a plasma accelerator. Our results indicate, in agreement with numerical simulations, selection and transport of positron beamlets containing N e + ≥ 10 5 positrons in a 5% bandwidth around 600 MeV, with femtosecond-scale duration and micron-scale normalised emittance. Particle-in-cell simulations show that positron beams of this kind can be guided and accelerated in a laser-driven plasma accelerator, with favourable scalings to further increase overall charge and energy using PW-scale lasers. The results presented here demonstrate the possibility of performing experimental studies of positron acceleration in a laser-driven wakefield accelerator. [ABSTRACT FROM AUTHOR]

In this work, a bi-stable behavior of laser ablation efficiency and quality was controlled by fluence and burst length. The plasma shielding of incoming laser radiation caused sudden jumps with a significant decrease in ablation efficiency for every even number of pulses in the burst. The attenuation of incoming laser radiation by plasma created by the previous pulse was incorporated into the toy model of burst ablation efficiency. The mathematical recurrence relation has been derived for the first time, binding ablation efficiency for the next pulse with the efficiency of the previous pulse, which predicts bi-stability, as well as sudden jumps occurring in ablation efficiency depending on the number of pulses in burst with the response to changes of the control parameter of peak laser fluence in the pulse. The modeling results using new recurrence relation showed stable and bi-stable ablation efficiency depending on burst fluence and the number of pulses, which agreed well with experimental data. The extremely efficient laser ablation has been achieved by optimizing the shielding effect using three pulses in the burst. [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]

This work reports the measurement of two-dimensional electron properties over a nanosecond scale integration time across a femtosecond laser-induced plasma filament in atmospheric pressure argon. Radial electron properties across the ∼ 100 μ m diameter filament are obtained at discrete axial locations at 2.5 mm steps by one-dimensional high-resolution laser Thomson scattering with a spatial resolution of 10 μ m. These measurements reveal plasma structural information in the filament. The Thomson spectral lineshapes exhibit clear spectral sidebands with an α parameter ∼ 1 , enabling the measurement of both electron temperature and density profiles. These measurements yield electron densities on the order of 10 22 /m 3 and electron temperatures of ∼ 2 eV. Heating from the probe laser due to inverse bremsstrahlung is taken into account to correct the Thomson scattering electron temperature measurements. Under these conditions, electron-neutral collision induced bremsstrahlung becomes the dominant laser-induced plasma heating process associated with the probe laser. The measurements reveal structural features of the filament, including an asymmetrically skewed density structure in the axial direction and reversed radial distributions of electron density and temperature. [ABSTRACT FROM AUTHOR]

Terahertz pulse generation from multiterawatt laser surface plasma near thick solid targets and thin foils has been studied. Pulses with energies up to 7 μJ were detected in the spectral region <3 THz in the direction of specular reflection from the surface of the CaF2 target. The dependence of the terahertz pulse energy on the laser pulse intensity can be approximated by the power function . For a fixed laser pulse duration and variable energy the power index lies in the range , while for a fixed energy and variable duration . [ABSTRACT FROM AUTHOR]

In certain conditions, plasma processes lead to the formation of a dispersed phase. A phase transformation is associated with the formation of a chemical bond and grouping of valence electrons of the surface and adsorbed atom, Pauli's principle being met. According to the experiment presented herein, nanoparticles generated from the plasma in laser-induced breakdown in a weak (80 mT) constant magnetic field, possess the smaller size than field-free nanoparticles. The paper studies processes affecting the nanoparticle size formed from the plasma in laser-induced breakdown in the weak constant magnetic field. [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]

The adoption of lightweight materials in engineering applications has become more popular over recent years, with adhesives replacing traditional joining methods such as bolts and rivets. Adhesion science and related technologies are arising as cleaner options for sustainable production in modern industry, with adhesive-bonded joints increasingly being used as design solutions in complex products and assemblies. However, the use of structural adhesives has several significant drawbacks, most of which are related to environmental impact, linked to the nature of the adhesive substance, as well as product disassembly/disposal deriving from the fact that adhesive joints are usually irreversible. Within this context, the goal of this paper is to study adhesive joints in mechanical assemblies from a life cycle perspective, offering more comprehensive analysis tools and assembly solutions suitable for industries such as automotive, aerospace, and assembly/packaging machinery. A methodological framework for the comprehensive characterization of bonded joints using effective surface activation techniques has been created and tested. The first phase encompasses the production of samples for mechanical testing under static and fatigue loading conditions. The second includes the characterization of inputs/outputs (life cycle inventory—LCI) for life cycle assessment (LCA) of mechanical assemblies employing adhesive joints and innovative surface activation techniques. The final phase provides a set of eco-design actions based on a critical analysis of the obtained results. The outcomes demonstrate how it is possible to achieve optimal adhesive-bonded joint properties under specific working conditions (e.g., static or fatigue loading) while maintaining a low environmental load using novel surface pre-treatments such as laser and plasma technologies. These outcomes are supported by a case-study in which adhesive joints are applied to the mechanical assembly of a bottle gripper for a food packaging machine. The adoption of eco-design rules in adhesive joint applications will help designers in the development of suitable solutions for lightweight applications from a complete life cycle perspective. [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]

The aspect of the detection of hydrogen isotopes in nuclear materials was analyzed in this review. Particular attention was paid to the spectroscopic methods for the detection of hydrogen isotopes in fusion reactor materials since their presence can induce severe problems in terms of material degradation and shortening of its lifetime. The main focus is on laser-induced breakdown spectroscopy, an optical emission method that is efficient, reliable, and fast. Recent results obtained at the VINCA Institute will also be presented. [ABSTRACT FROM AUTHOR]

An algorithm modeling a plasma in two-zone source approximation and its interface with the NLopt library for multiparameter optimization were established. In order to allow the spectrum modeling algorithm and the NLopt library to work together an abstraction layer that initializes both libraries in one action, calculates a given type of loss function, and transfers its value to the optimization algorithm is used. The joint use of these algorithms was tested on model data; convergence to the plasma parameters used to obtain the synthetic test spectrum was achieved. It was shown that the two-zone model can be used to describe both ionic and atomic lines correctly, including those that undergo self-reversal during evaporation of the aluminum alloys, while methods of "blind" optimization of the loss function can be used to estimate the temperature and electron density in the laser-induced plasma from its spectra. [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]

Laser wakefield acceleration (LWFA) of electrons is a highly promising and advanced technique within the field of laser plasma physics, which enables the generation of remarkably high-energy electron beams over a comparatively short distance. In this paper, we have used different Gaussian-like laser pulse profiles of the same amplitude of electric field and laser intensity in magnetized plasma. Generated wakefield and energy gain are calculated analytically by using equation of motion and Maxwell's equation. Our results show that generated wakefield and energy gain are greatly affected by the shape of laser electric field profile. Pulse with broader electric field profile produces more effective LWFA under identical conditions of other parameters. Energy gain by electrons increases slightly with increase in the strength of external magnetic field. Results show that for the broadest laser profile, the magnetic field has more influence on wakefield production and electron energy gain. The role of laser pulse length is also analyzed. In this study, we have obtained a maximum of 151.6 MeV energy gain with experimentally feasible parameters. Our findings will assist researchers in selecting the most energy-efficient pulse profile for LWFA. [ABSTRACT FROM AUTHOR]

An important theoretical approach is proposed for the resonant excitation of multiple and multifocal THz radiation fields via matching of the wavenumbers when there is an interaction of two skew coshyperbolic (cosh) Gaussian laser beams with a medium having graphite nanoparticles of spherical and cylindrical shapes in presence of an external periodic electrostatic field. Through the analytical treatment, we discovered that two additional transverse components of the nonlinear ponderomotive force and hence, nonlinear currents are generated during the interaction of beams and electrostatic field with the medium containing nanoparticles, leading to the emission of multiple THz radiation field. Two mechanisms are responsible for the resonant excitation of the THz fields: (1) the beating mechanism of two similar skew cosh laser beams and, (2) the coupling mechanism of the incident laser beams' electric field with the external periodic electric field. The additional components of the generated THz fields are termed as induced THz field, naming E → 0 I T H z 2 and E → 0 I T H z 3 . The external periodic electrostatic field and density ripples in the medium play an important role in matching of the wavenumbers for achieving multiple resonance conditions. These resonance conditions lead to frequency-tuneable radiation due to beating and coupling, occurring at ~ 8.2 THz and ~ 48 THz, for the longitudinal surface plasmon resonance and transverse plasmon resonance, respectively. The ratio of the two peaks increases with the magnitude of external electric field. A comparative theoretical study between the beating and induced fields and the effect of different beam parameters, shapes of nanoparticles, inter-particle distance, orientations of their basal planes with respect to incident lasers' field on the induced field has been investigated to uncover the significance of the external periodic field and the use of two kinds of nanoparticles. [ABSTRACT FROM AUTHOR]

The demand for industrial development toward advanced and precision manufacturing has sparked interest in ultrafast laser-based micromachining methods, particularly emerging advanced machining methods, such as laser-induced plasma micromachining (LIPMM). The main challenge in laser micromachining is finding the optimal process in a large process space to achieve a comprehensive improvement in processing efficiency and quality as approaches that rely on trial-and-error are impractical. In this work, we combined data-driven machine learning and physical model into a cycle design strategy, in order to efficient capture the comprehensive optimization process of LIPMM with high material removal rate and high microgroove depth. Based on the small sample dataset and additional physical variables provided by the physical model, the optimal process in the whole process space can be obtained using only four design cycles and dozens of data groups, and the material removal rate and microgroove depth of which are improved comprehensively compared with the original data. The design strategy integrated with physical model presented here could be applied in a wide range of fields, and thus shows the promise of accelerating the development of laser micromachining processes. [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]

Grid electrostatic lenses are often used in low-energy beam-transport systems to match accelerators. Modern computer technology and software allow us to consider a grid as a set of wires with a given diameter and cell size. The work presents the results of numerical simulation of a beam-extraction system of a laser plasma ion source and an electrostatic lens: matching systems with the I-4 linear accelerator and their comparison with experimental data. [ABSTRACT FROM AUTHOR]

Particle-in-cell (PIC) simulations are a widely-used tool to model kinetics-dominated plasmas in ultrarelativistic laser-solid interactions (dimensionless vectorpotential a0 > 1). However, interactions approaching subrelativistic laser intensities (a0 ≲ 1) are governed by correlated and collisional plasma physics, calling for benchmarks of available modeling capabilities and the establishment of standardized testbeds. Here, we propose such a testbed to experimentally benchmark PIC simulations of laser-solid interactions using a laser-irradiated micron-sized cryogenic hydrogen-jet target. Time-resolved optical shadowgraphy of the expanding plasma density, complemented by hydrodynamics and ray-tracing simulations, is used to determine the bulk-electron-temperature evolution after laser irradiation. We showcase our testbed by studying isochoric heating of solid hydrogen induced by laser pulses with a dimensionless vectorpotential of a0 ≈ 1. Our testbed reveals that the initial surface-density gradient of the target is decisive to reach quantitative agreement at 1 ps after the interaction, demonstrating its suitability to benchmark controlled parameter scans at subrelativistic laser intensities. Relativistic laser-solid interactions are simulated via particle-in-cell (PIC) approaches, while subrelativistic regimes rely on radiation-hydrodynamics formulations. To validate the methods at the transition from relativistic to subrelativistic laser intensities, the authors propose a testbed to experimentally benchmark PIC simulations. [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]

Laser–plasma acceleration of ions has been of interest for the past few decades. An effective way to enhance laser-driven proton acceleration is to improve laser absorption in plasmas. In this study, we show that lithium (Li) is the most promising candidate for accelerating protons with better absorption among target light weight materials used for ion acceleration. For this, two-dimensional particle-in-cell (PIC) simulations were performed to investigate the acceleration of ions and protons with a high-power laser (with an amplitude a0=10 and a pulse duration of 30 fs) to determine the optimal lithium target thickness for maximum energies. The maximum energy of Li ions is achievable with a target thickness of 40 nm, while the maximum proton energy can be achieved for a 30nm thickness of the target. Moreover, a series of PIC simulations were also performed with targets of different atomic numbers and thicknesses to understand lithium's performance for the acceleration of protons. Compared to other targets, such as Al (Aluminum), C (Carbon), and Be (Beryllium), the Li target has a significant enhancement in proton energy, which can be used as an alternative target to enhance proton and ion energies in future experiments. [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]

Clusters of active Brownian particles in gas-discharge plasma are considered as open systems with energy exchange with the environment. The evolution of a cluster of 19 active Brownian particles with a partially absorbing metal surface (so-called Janus particles) when exposed to intense laser radiation is shown. The formation of strongly correlated clusters of charged particles with increasing laser radiation power was observed experimentally. Based on an analysis of the trajectories of particles, the region of their localization, and changes in their kinetic energy, fractal dimension, and dynamic entropy for different values of laser radiation power density, the self-organization of a cluster of strongly interacting particles in the plasma of a high-frequency glow discharge is studied. [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]

Virtual machining simulation is becoming an essential and vital tool currently in traditional machining process. With it, a series of trial machining can be avoided. However, the situation is different for high-energy-beam cutting. Till today, there is no accurate virtual cutting simulation tool that can accurately simulate the physical cutting process. As a soft knife, whose shape is changing dynamically, it is a great challenge to accurately define the tool shape and build an accurate 3D geometrical model to be used as a virtual model for simulation. Aiming at abrasive water jet (AWJ) machining, a new method to build a soft knife profile based on energy distribution analysis has been explored in this paper. Through 3D point cloud data of kerf profile, a 3D model of the abrasive water jet profile has been built under different working conditions. To evaluate the effectiveness of the self-defined tool shape, the compensation strategy based on 3D AWJ profile has been carried out in the actual cutting process. The results show that 3D AWJ profile is beneficial to improve the machining accuracy. And this method can be generalized to other high-energy-beam cutting tools such as laser and plasma. [ABSTRACT FROM AUTHOR]

Selective laser processing of thin surface layers of metallic alloys selectively affects certain defective areas, such as stress concentrators, fracture nuclei, crack tips, and nanoscale particles. The rest of the material is practically unaffected. The method of selective laser processing increases both the microhardness and fracture toughness of, particularly, thin ribbons of hard and brittle amorphous- nanocrystalline metal alloys. It is essential that the initial amorphous-nanocrystalline structure of the material is preserved. The impact of a nanosecond laser pulse of high power density on the surface of a metal alloy is accompanied by laser-induced breakdown plasma, shock wave, and impulsive heating. The heating of the material is preceded by the passage of a compression shock wave capable of initiating local deformations and damages. The uneven heating of the material is primarily manifested in the defective areas and can lead to the relaxation of mechanical stresses due to plastic deformation. To study the interaction between the thermal front initiated by a laser pulse and defects in the surface layer of a metal alloy, it is necessary to improve the physical and mathematical models of these processes. [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]