Generation Of Radiation Research Articles

On some algorithms for comparing models of femtosecond laser radiation propagation in a medium with gold nanorods

The study of the features of the nonlinear optical interaction of laser radiation with various media is currently widely studied, including by mathematical modeling methods. In particular, the interaction of the laser pulse with the medium doped with nanorods leads to the melting of these nanorods and distortion of the laser pulse. In addition, the passage of a laser pulse through a medium with nanoparticles can lead to a change in the shape of the pulse and a significant distortion of its spectrum, as a result of which a number of undesirable effects may occur. The corresponding process can be described by the nonlinear Schrödinger equation. Analytical studies of the corresponding variants of the equation and numerical calculations have shown that the propagation of the resulting soliton subimpulses is characterized by the formation of a so-called nonlinear frequency chirp in the region of subimpulses. When considering the graphs of such a process, the following assumption arose: it is possible to measure the degree of nonlinearity by calculating the correlation coefficient between the frequency distribution in a linear and nonlinear medium. In the course of calculations using correlation analysis, we obtained statistical characteristics similar to those that were assumed in advance. At the same time, the most adequate variant of the pair correlation coefficient is obtained in the case of applying the algorithm proposed by us for its calculation.

Efficient generation of multi-order Raman radiation in aqueous solutions derived from -CH2 and -NH2 vibrations via cascaded four-wave mixing and Stokes processes

Efficient generation of multi-order Raman radiation in aqueous solutions derived from -CH2 and -NH2 vibrations via cascaded four-wave mixing and Stokes processes

Simulation of the impact of an additional corrugated structure impedance on the bursting dynamics in an electron storage ring

In the case of a single-digit picosecond bunch length, synchrotron light sources produce intense coherent radiation up to the THz range. The reduction of the bunch length by lowering the momentum compaction factor (low-α) gives rise to the microbunching instability, which is on the one hand a crucial roadblock in the x-ray range during to the resulting effective bunch lengthening, but on the other hand also an opportunity for the generation of intense THz radiation if it can be controlled appropriately. In the KIT storage ring KARA (Karlsruhe Research Accelerator), two parallel plates with periodic rectangular corrugations are planned to be installed as a proof of principle in an electron storage ring. These plates create an additional longitudinal impedance based on their geometry, which can affect the beam dynamics. The resulting impedance manipulation will be used to study and control the longitudinal electron beam dynamics and the emitted coherent synchrotron radiation. This paper presents the results of systematic studies in simulation of the impact of additional corrugated plate impedances on the longitudinal beam dynamics using the example of the KARA storage ring. If the periodicity of the wake function of the corrugated plates matches the size of the substructures in the longitudinal bunch profile, the instability threshold can be effectively manipulated. This extends intense THz radiation to different beam current regimes. Published by the American Physical Society 2024

Effect of heat generation on MHD Maxwell fluid flow on a stretching cylinder embedded in a porous medium along with impact of radiation

This study addresses the critical problem of understanding Maxwell fluids’ thermal and flow behavior in the occurrence of magnetohydrodynamics (MHD), radiation, and heat generation over a stretching cylinder, which is of significant importance in various industrial applications such as polymer processing and heat exchangers. The novelty of this work lies in its detailed exploration of the curvature parameter (αe) and its influence on the flow dynamics, extending beyond the scope of previous literature. The governing equations, incorporating the impacts of MHD, radiation, and heat generation, are derived and subsequently simplified using similarity transformations to convert them into ordinary differential equations. These equations are then solved numerically via the bvp4c solver in MATLAB. The results are presented through tables and graphical representations to deliver clear insights into the behavior of key non-dimensional parameters. Quantitative findings reveal that the temperature profile of the fluid increases with higher heat generation and radiation, with specific enhancements observed on both flat plates (curvature parameter αe = 0) and cylindrical surfaces (αe = 1). Our results are consistent with existing studies, validating the robustness of our numerical approach.

Radiative characteristics detection and generation mechanism analysis of soot and PAHs during the combustion process of raw coal and tar coal

Coal contains light volatiles, tar, and fixed carbon, among which the generation of soot during combustion process is most closely related to tar. In this study, the removal of light volatiles and the retention of tar in coal particles are achieved through physicochemical analyses and experiments, and the correlation between the radiative characteristic parameters and soot volume fraction is established from the perspective of combustion detection. Furthermore, the intrinsic mechanisms of soot precursor generation are revealed through mechanistic analysis. The results indicate that the combustion of raw coal has a longer combustion duration and higher flame height, whereas the combustion of tar coal shows higher spectral radiative intensity, flame temperature, and soot volume fraction. The A1 generation process includes both the odd-numbered C3 generation pathway and the even-numbered C2 + C4 generation pathway, and tar coal exhibits a higher generation rate on the pathways of A1 generation compared to raw coal. The generation of A2 is mainly attributed to the chemical reaction of phenyl and the synthesis of c-C5H5 molecules, and the generated benzene and naphthalene will undergo further reactions to generate tricyclic and tetracyclic aromatic hydrocarbons. In addition, the results of spectrometer detection show that the combustion of tar coal results in a higher concentration of soot precursors compared to raw coal. Among the soot precursors, A1 exhibits the highest concentration, while the concentrations of A2-A4 are lower than A1.

Terahertz Resonant Emission by Optically Excited Infrared-Active Shear Phonons in KY(MoO4)2.

The generation of monochromatic electromagnetic radiation in the terahertz (THz) frequency range has remained a challenging task for many decades. Here, the emission of monochromatic sub-THz radiation by optical phonons in the dielectric material KY(MoO4)2 is demonstrated. The layered crystal structure of KY(MoO4)2 causes infrared-active shear lattice vibrations to have energies below 3.7meV, corresponding to frequencies lower than 900GHz where solid-state-based monochromatic radiation sources are rare. Directly excited by a 5ps long broadband THz pulse, infrared-active optical vibrations in KY(MoO4)2 re-emit narrowband sub-THz radiation as a time-varying dipole for tens of picoseconds, which is exceptionally long for oscillators with frequencies below 1THz. Such a long coherent emission allows for the detection of more than 50 periods of radiation with frequencies of 568 and 860GHz. The remarkably long decay time together with the chemical stability of the employed material suggests a variety of possible applications in THztechnology.

Generation of CW Mid-Infrared radiation in the mW power range and tunable over 400 nm

Generation of CW Mid-Infrared radiation in the mW power range and tunable over 400 nm

Generation of broadband THz radiation by polariton parametric scattering in a LiNbO₃ waveguide

Generation of broadband THz radiation by polariton parametric scattering in a LiNbO₃ waveguide

Investigation of convective heat transport in a Carreau hybrid nanofluid between two stretchable rotatory disks

Abstract Hybrid nanofluids (HNFs) have outstanding energy transfer capabilities that are comparable to mono-nanofluids. Materials had appliances in obvious fields such as heat generation, micropower generation, and solar collectors. The objective of this study is to investigate the new aspects of convective heat transfer in an electrically conducting Carreau HNF situated between two parallel discs. In addition to the presumed stretchability and rotation of the discs, physical phenomena like nonlinear radiation, viscous dissipation, Joule dissipation, and heat generation and absorption are considered. The Cu and TiO2 nanoparticles dispersed in engine oil to understand the intricate phenomenon of hybridization. The Tiwari and Das nanofluid model is employed to model the governing partial differential equations (PDEs) and then simplified using boundary layer approximation. The suitable transformations of similarity variables are defined and implemented to change the set of formulated PDEs into ordinary differential equations. The reduced system is solved semi-analytically by the homotopy analysis method. The influences of involving physical parameters on the velocity and temperature are plotted with the help of graphical figures. This study brings forth a significant contribution by uncovering novel flow features that have previously remained unexplored. By addressing a well-defined problem, our research provides valuable insights into the enhancement of thermal transport, with direct implications for diverse engineering devices such as solar collectors, heat exchangers, and microelectronics.

Efficient Generation of X-Ray Radiation under Relativistic Laser Pulses Interaction with a Kr Cluster Jet

Efficient Generation of X-Ray Radiation under Relativistic Laser Pulses Interaction with a Kr Cluster Jet

Coherent high-power terahertz vortex generation with tunable orbital angular momentum based on transverse phase mask shaping

Abstract Terahertz (THz) radiation has become a significant tool in cutting-edge research due to its superior properties. THz vortices with tunable orbital angular momentum (OAM) are particularly attractive to the scientific community due to their well-defined discrete azimuthal phase around the propagation axis. However, the generation of high-power THz radiation with OAM remains a challenge for most existing technologies. In this paper, a new method for generating coherent high-power THz vortices with tunable OAM and frequency is proposed by combining frequency beating and transverse phase mask shaping techniques. Theoretical analyses and numerical simulations indicate that this method can generate coherent THz vortices with peak powers in the tens of megawatts and tunable topological charge numbers.

Comparative investigation on radiative and heat generation effects of ternary hybrid nanofluid flow over a curved permeable surface: Stability analysis

Comparative investigation on radiative and heat generation effects of ternary hybrid nanofluid flow over a curved permeable surface: Stability analysis

Significance of finite difference approach for application of Cattaneo-Christov theory conveying radiative ternary-hybrid nanofluids flow

This paper investigates the characteristics of ternary-hybrid nanoliquid for time-dependent Darcy-Forchheimer flow. Formulation is based for mixture of water subject to ternary nanoparticles with different shapes like (platelet, spherical and cylindrical). Heat transfer consists of convective condition, radiation and heat generation. Appropriate variables are used to generate dimensionless nonlinear system. Analysis is carried out for Cattaneo-Christov heat flux and variable thermal conductivity. Finite difference method (FDM) is utilized to construct solutions. Salient characteristics of sundry variables are discussed. Analysis is carried out for Nusselt number and skin friction. Present results may have relevance in renewable energy process, polymer extrusion and metallurgy.

679/339.5 nm radiation generation of pr: YLF laser pumped by fiber coupled blue laser diode module

679/339.5 nm radiation generation of pr: YLF laser pumped by fiber coupled blue laser diode module

The frequency spectrum and energy content in a pulse flux of terahertz radiation generated by a relativistic electron beam in a plasma column with different density distributions

This paper reports on the generation of a directed flux of electromagnetic radiation with an energy content of 10 J in the frequency range of 0.2—0.3 THz at a microsecond pulse duration in a beam-plasma system. The flux is generated when a relativistic electron beam (REB) pumps electron plasma waves in a magnetized plasma column. In the described experiments, this fundamentally new approach to generate terahertz radiation was carried out at the GOL-PET facility in the conditions of varying the beam current density and the plasma density in the appropriate ranges of 1—2 kA/cm2 and 1014—1015 cm−3. From the comparison of the flux energy spectrum measured experimentally in the frequency range 0.15—0.45 THz with the calculated one obtained using the previously proposed model of radiation generation in a beam–plasma system, it was shown that this process occurs through resonant pumping by REB of precisely the branch of upper-hybrid plasma waves. Mastering this new method to generate terahertz radiation opens the prospect of its use to obtain multi-megawatt radiation fluxes in the frequency range up to 1 terahertz and higher. For such a development approach the most promising beam for pumping plasma oscillations seems to be a kiloampere REB generated in a linear induction accelerator.

Spectral analysis of high-order harmonic generation in carbon plasma using linearly, radially, and azimuthally polarized femtosecond pulses

We demonstrate high-order harmonic generation in carbon plasma using linearly, radially, and azimuthally polarized beams from a femtosecond laser (1030 nm, 40 fs, 50 kHz). The conditions for carbon plasma formation during laser ablation were optimized by adjusting the heating pulse energy in the cases of the single-color (1030 nm) and two-color (1030 nm + 515 nm) pump schemes to generate harmonics up to the 39th order. The application of radial and azimuthally polarized annular single-color (1030 nm) beams at optimal conditions of plasma formation allowed the demonstration of the spectral division and inclination of the vector harmonics. An asymmetric distribution of harmonics was obtained using the vortex beam generated during the propagation of laser radiation through the quarter-wave plate and S-waveplate.

Possibility of the magnitude of the chiral vector having an effect on the terahertz radiation generation by hot electrons in zigzag carbon nanotubes driven by DC-AC fields

The possibility that the magnitude of a chiral or circumferential vector (Chv) influences the generation of terahertz radiations (T-rays) by hot electrons in zigzag carbon nanotubes (z-CNTs) driven by direct current (DC) and alternating current (AC) fields is taken into consideration. The study conducted a semiclassical theoretical analysis by using the Boltzmann kinetic equation to determine current density in relation to high AC field frequency (ω) and z-CNT circumference (|Chv|) when hot electrons were present. A numerical analysis was performed by varying the magnitude of the circumference of the tube at a fixed temperature and the strong hot electron injection rate at a predetermined value. When the circumference of the semiconducting zigzag carbon nanotubes (sz-CNTs) is increased, the current density's lowest and highest peaks are also enhanced (i.e., large amplitudes). This increases positive differential conductivity (PDC), necessitating enhanced domain suppression for higher potential generation of T-rays. In contrast, it was observed that reducing the tube's circumference in metallic zigzag carbon nanotubes (mz-CNTs) resulted in an increase in both the lowest and highest peaks of current density, which enhanced the PDC. These findings imply that larger circumferential sz-CNTs and smaller circumferential mz-CNTs may be more suitable candidates for a higher potential generation of T-rays with applications pertinent to modern science and technology.

Generation of terahertz radiation with a specified spectral profile from a mosaic combined organic crystal.

We present a method for the generation of terahertz (THz) pulses with a high optical-to-THz conversion efficiency and a smooth spectrum. The method is based on the optical rectification of near-infrared femtosecond laser pulses with a wavelength of 1240 nm in a mosaic combined crystal, consisting of two pieces of nonlinear organic crystals, OH1 and DSTMS. The mosaic combined crystal produces a relatively smooth spectrum in the 0.3-4.5 THz range with no pronounced absorption dips and with a maximum in a spectral amplitude at about 2 THz. The peak field strength is 9.6 MV/cm for an effective crystal diameter of 4.3 mm.

Laser-optical technologies for space debris removal

Technologies for the removal of space debris fragments of artificial (man-made) origin from near-Earth space is being proposed in order to provide the security of space flights. The fundamental principle of the proposed method is based on the utilization of intense solar radiation to direct and concentrate at space debris fragments with the aim of creating a plasma braking and transferring the fragment from a circular to an elliptical orbit following its subsequent burn up in the dense layers of the atmosphere. At the same time, the generation of substantial solar radiation is facilitated by a synthesized multi-aperture optical system situated in a heliosynchronous space orbit and permanently oriented towards the Sun.

Acoustically Induced Transparancy for Gamma-Ray Photons and Some of Its' Applications

In this paper, we consider the effect of the emergence of transparency of a resonantly absorbing medium for electromagnetic radiation due to the excitation of piston-like acoustic oscillations of the medium along the direction of radiation propagation – acoustically induced transparency. The physical mechanism and basic conditions for the implementation of the effect are discussed, as well as its application to reduce the propagation velocity of gamma-ray photons and on-demand recovery of an arbitrary part of a single-photon wave packet resonantly absorbed in the medium.