Spectral Characteristics Of Radiation Research Articles

Simulation Analysis on the Characteristics of Aerosol Particles to Inhibit the Infrared Radiation of Exhaust Plumes

Aerosol infrared stealth technology is a highly effective method to reduce the intensity of infrared radiation by releasing aerosol particles around the hot exhaust plume. This paper uses a Computational Fluid Dynamics (CFD) two-phase flow model to simulate the exhaust plume fields of three kinds of engine nozzles containing aerosol particles. The Planck-weighted narrow spectral band gas model and the Reverse Monte Carlo method are used for infrared radiation transfer calculations to analyze the influencing factors and laws for the suppression of the infrared radiation properties of exhaust plumes by four typical aerosol particles. The simulation calculation results show that the radiation suppression efficiency of aerosol particles on the exhaust plume reaches its maximum value at a detection angle (ϕ) of 0° and decreases with increasing ϕ, reaching its minimum value at 90°. Reducing the aerosol particle size and increasing the aerosol mass flux can enhance the suppression effect. In the exhaust plume studied in this paper, the radiation suppression effect is best when the particle size is 1 μm and the mass flux is 0.08 kg/s. In addition, the inhibition of aerosol particles varies among different materials, with graphite having the best inhibition effect, followed by H2O, MgO, and SiO2. Solid particles will increase the radiation intensity and change the spectral radiation characteristics of the exhaust plume at detection angles close to the vertical nozzle axis due to the scattering effect. Finally, this paper analyzed the suppression effects of three standard nozzle configurations under the same aerosol particle condition and found that the S-bend nozzle provides better suppression.

Spectral Characteristics of Polarization Radiation in the Water Window Range

The high-intensity and monochromatic radiation sources in the water window spectral range are desirable for many applications. One of the potential candidates of soft X-ray sources is polarization radiation produced by a charged particle passing through a thin foil. In the soft X-ray range near the absorption edges of a target material, the real part of dielectric permittivity can exceed unity, and the Tamm–Frank criterion is fulfilled. Thus, two types of radiation are produced: transition and Cherenkov radiation. In this report, we theoretically investigated the spectral characteristics of radiation produced in both cases when the Tamm–Frank criterion is met or not met. We showed the dependences of the spectrum as a function of thickness and the incidence angle. To describe the properties of polarization radiation and the complex dielectric permittivity, the polarization current approach and Henke’s model were used, respectively.

Parametrical study on spectral radiation characteristics of solid fuel combustion medium for energy cascade utilization

From the perspective of cascade utilization of photo-thermal energy, this study investigated the effects of parameter variables including pressure, temperature, particle size and number density, and unburned ratio on the spectral radiation characteristics of solid fuel combustion. By coupling the radiative transfer equation with the accurate band model of gas radiation and the Mie theory of particle radiation, the radiation energy characteristics of the one-dimensional (1-D) combustion case were calculated parametrically. Results showed that temperature is the dominant factor. The spectral radiation proportion in the waveband of 0–2 μm accounts for 36.21 % at Ta = 1600 K. Increased pressure and particle number density enhance total radiation. The pressure mainly affects the wavebands of 0–2 μm and 3–4 μm, reaching saturation at 5 bar. Excessive particle number density hinders radiation transfer to the wall. Larger particle sizes increase the spectral radiation proportion of the short waveband. The increased unburned ratio also enhances radiation, but the promotion effect is limited. Optimization of combustion parameters plays a key role in regulating spectral radiation distribution and realizing cascade utilization of photo-thermal energy. This study provides guidance for the energy utilization of solid fuel combustion and the development of carbon neutrality technology.

Spectral and Temporal Characteristics of UHF Radiation Generated by a Miniature Electric Spark

Spectral and Temporal Characteristics of UHF Radiation Generated by a Miniature Electric Spark

Chemical sensors based on photonic colloidal crystals

Objectives. The paper analyzes the results of research into the formation of photonic crystal structures from polymer microspheres and the mechanisms of spectral shifts during selective reflection of non-monochromatic incident radiation from them in the visible and infrared light, as well as the use of polymer microspheres as sensors for detecting chemical substances having similar structures.Results. Research carried out at the Ya.K. Syrkin Department of Physical Chemistry in the Institute of Fine Chemical Technologies of the RTU MIREA is presented. Issues related to the detection of substances with similar chemical structure using sensors based on photonic crystals made of polystyrene microspheres 160–300 nm in size, are considered. Spectral shifts of the reflected radiation from the crystal surface are registered in the visible spectrum when substances in the liquid or gas phase are detected by the crystal surface.Conclusions. The method of electrophoretic deposition of colloidal particles in the form of polymeric microspheres on conducting surfaces can be used to create ordered structures over large areas. However, the detection of individual compounds by the optical method is impossible without controlling the kinetics of spectral shifts of reflected radiation from the surface of photonic colloidal crystals. The spectral characteristics of such radiation are directly related to the particle sizes that determine the period of the crystal lattice. The diffusion of chemical substances into a photonic crystal, which results in a swelling of the particles forming it and a shift in the spectrum of reflected radiation, is determined by a change in the period of the crystal lattice due to a change in the size of these particles A kinetic model of swelling polymer microspheres, which describes the diffusion of substances into porous polymer particles, is proposed. An excess amount of substance deposited on the surface of a photonic crystal above the limit is shown to lead to its degradation, which is manifested in the “fading” of the crystal surface and the concomitant disappearance of narrow peaks of reflected radiation.

Investigation on the ultraviolet spectral radiation characteristics of two-phase flow plume based on OH and alumina particles.

Ultraviolet detection has advantages over radar and infrared detection, such as low background radiation and high resolution. The UV spectral radiation characteristics of exhaust plume are of extremely great research significance as the main parameters for aircraft detection. We used the BEM-2 two-phase flow plume as the object of study, calculated the scattering characteristics of alumina particles and the UV absorption coefficient of OH in the plume based on the MIE theory and the line-by-line integration method, established the UV radiation transfer model of aircraft plume under gas-solid coupling, simulated the UV spectral radiation characteristics of the plume, and compared them with experimental results. The results show that due to the drastic changes of temperature and pressure at the Mach and non-Mach disks in the plume, the value of OH absorption coefficient fluctuates up and down along the axial direction with the position of the Mach disk; at 261nm, 282nm, and 306nm, the spectral radiation intensity of alumina particles accounts for approximately 96%, 85%, and 73% of the total spectral radiation intensity of the plume, respectively, which are much higher than the proportion of OH gas spectral radiation intensity, but in the infrared wave band, the influence of particle scattering characteristics on the spectral radiation intensity of the plume is much lower compared to the UV wave band; the overall radial range of the UV spectral radiation intensity of the plume is relatively narrow and its tail exhibits a converging shape, showing a good consistency with the experimental results.

Analysis and 3D Imaging of Multidimensional Complex THz Fields and 3D Diagnostics Using 3D Visualization via Light Field

We present a numerical platform for 3D imaging and general analysis of multidimensional complex THz fields. A special 3D visualization is obtained by converting electromagnetic (EM) radiation to a light field via the Wigner distribution function, which is known for discovering (revealing) hidden details. This allows for 3D diagnostics using the simple techniques of geometrical optics, which significantly facilitates the whole analysis. This simulation was applied to a complex field composed of complex beams emitted as ultra-narrow femtosecond pulses. A method was developed for the generation of phase–amplitude and spectral characteristics of complex multimode radiation in a free-electron laser (FEL) operating under various parameters. The tool was successful at diagnosing an early design of the transmission line (TL) of an innovative accelerator at the Schlesinger Family Center for Compact Accelerators, Radiation Sources, and Applications.

Spectral radiation characteristics of domestic liquid hydrocarbon fuels in mid-infrared band based on transmission method

Considering the influence of multi-reflection between packaged windows, the inversion model for optical constants of liquid hydrocarbon fuels is established based on double-thickness transmission method, while the transmittance spectra are obtained with the three-layer structure containing two packaged windows and the liquid sample under the background of empty sample compartment. Transmission measurements are operated on Bruker Vertex 70 FTIR spectrometer combined with a demountable liquid cell in the wavenumber range of 400–4000 cm−1. Distilled water is used as the standard material to verify the reliability of this method and the thicknesses are chosen as 0.1 mm and 0.2 mm in the wavenumber range of 2857–2273 cm−1 as its transmitted intensity is weak in the mid-infrared band. Based on the verification, the transmittance spectra of several domestic liquid hydrocarbon fuels are measured and analyzed, and the spectral radiation characteristics are determined under different temperatures, including 0# diesel, 93# gasoline and 97# gasoline with thicknesses of 0.5 mm and 1.0 mm. Results indicate that the absorption index of diesel is larger than that of gasoline in the researched band, and the maximum change rate of absorption index with temperature is 0.265 %/K for 0# diesel, which is less than that for gasolines, as they are 1.2 %/K for 93# gasoline and 2.0 %/K for 97# diesel.

Связанные с осадками события возрастания электромагнитной компоненты вторичных космических лучей: спектральные измерения и анализ

We report the measurement results of differential spectra of electromagnetic radiation in the range 0.1–4 MeV, which occurs in the atmosphere as a component of secondary cosmic rays. Spectral monitoring was performed using a spectrometer based on the Nai (TL) crystal in 2022–2023. The main purpose of the measurements was to determine spectral characteristics of the electromagnetic radiation during increase events, when the electromagnetic radiation flux from the atmosphere rises by tens of percent with respect to the background level. From a thorough analysis of the spectra of many dozens of events, we have drawn a conclusion that although the lines of natural radionuclides are present on the spectra and contribute their share, their total contribution to the increase events is ~0.1 of the total energy supplied during an increase. We unambiguously conclude that the effect of increasing electromagnetic radiation during precipitation is not due to the presence of radionuclides in precipitation.

Precipitation-related increase events of the electromagnetic component of secondary cosmic rays: Spectral analysis

We report the measurement results of differential spectra of electromagnetic radiation in the range 0.1–4 MeV, which occurs in the atmosphere as a component of secondary cosmic rays. Spectral monitoring was performed using a spectrometer based on the Nai (TL) crystal in 2022–2023. The main purpose of the measurements was to determine spectral characteristics of the electromagnetic radiation during increase events, when the electromagnetic radiation flux from the atmosphere rises by tens of percent with respect to the background level. From a thorough analysis of the spectra of many dozens of events, we have drawn a conclusion that although the lines of natural radionuclides are present on the spectra and contribute their share, their total contribution to the increase events is ~0.1 of the total energy supplied during an increase. We unambiguously conclude that the effect of increasing electromagnetic radiation during precipitation is not due to the presence of radionuclides in precipitation.

Calculation and Selection of Spectral Characteristics of Radiation of LED Luminaires for Operation Rooms

Many researchers considered improvement of colour discrimination an important factor of surgery illumination, but none of them provided data on colour contrast estimation. The article describes the results of an extensive search of spectrum that are the most preferable for application in surgery equipment using selected light emitting diodes (LED) of different types. The search was not also based on the qualitative characteristics recommended by the standard, but also on a previously non-considered parameter: colour contrast between human tissues K estimated in uniform-chromaticity systems. The programme developed in MATLAB environment allows to model the cumulative spectrum of a LED light source, to determine the proportions of LED radiation or crystals in LED providing the maximum value of LED general colour rendering index Ra at the set correlated colour temperature or the maximum value of averaged K in uniform-chromaticity systems both in presence of the limited Ra value of 85 and if there are no limitations. Such options of spectrum search allowed to evaluate the probability of K change and its maximum, as well as to identify three possible operating modes of surgery equipment when using the said LEDs. The first of them is following the existing recommendations for Ra with possible insignificant change of K, the second one is the priority of K assuming violation of the Ra recommendations to increase K, and the third option assumes switching between the modes if necessary. LED spectra are selected for such different modes. Other colour rendering indexes are also estimated, and the authors recommend using the new standard TM‑30–15 for standardisation of the colour rendering quality of light sources used in surgery luminaires. It is based on 99 samples and some of the tests have reflective properties close to those of human tissues.

The Role of Ferromagnetic Layer Thickness and Substrate Material in Spintronic Emitters.

In this article, we investigate optically induced terahertz radiation in ferromagnetic FeCo layers of varying thickness on Si and SiO2 substrates. Efforts have been made to account for the influence of the substrate on the parameters of the THz radiation generated by the ferromagnetic FeCo film. The study reveals that the thickness of the ferromagnetic layer and the material of the substrate significantly affect the generation efficiency and spectral characteristics of the THz radiation. Our results also emphasize the importance of accounting for the reflection and transmission coefficients of the THz radiation when analyzing the generation process. The observed radiation features correlate with the magneto-dipole mechanism, triggered by the ultrafast demagnetization of the ferromagnetic material. This research contributes to a better understanding of THz radiation generation mechanisms in ferromagnetic films and may be useful for the further development of THz technology applications in the field of spintronics and other related areas. A key discovery of our study is the identification of a nonmonotonic relationship between the radiation amplitude and pump intensity for thin films on semiconductor substrates. This finding is particularly significant considering that thin films are predominantly used in spintronic emitters due to the characteristic absorption of THz radiation in metals.

Investigation on the tunable spectral characteristics of a nanofacet-sandwiched structure

Spectral radiative characteristics of the nanofacet-sandwiched structure can be effectively tailored by tuning the geometric parameters. The finite-difference time-domain (FDTD) method for electromagnetics is employed to numerically predict the spectral transmittance and absorptance of a sandwiched structure with the nanofacets periodically distributed. Compared with the basic case (a classical three-layer planar configuration), changing the pertinent parameters can transform the radiative behavior from transmittance enhancement to absorptance enhancement. The effects of the width and thickness of the nanofacet, the gap between facets and the facet material are discussed respectively. The results indicate that at small facet thickness and width with large gap, the radiative characteristics exhibit a transmittance-enhancement mode (average transmittance of 0.83), and on the contrary, the absorptance-enhancement mode is achieved (peak absorptance of 0.97). The facet thickness, facet width and the gap between facets donate significant influences on the overall transmittance and absorptance, while the matrix thickness has little effect. Besides, the transmittance-enhancement mode is mainly dominated by the structural parameters, almost independent of the facet material. Whereas, the spectral absorptance presents different extra peaks while changing the facet material.

Flame propagation characteristics of premixed hydrogen–air deflagration with low concentration in a pipeline

This study used a visualized explosion propagation experimental system to investigate the flame propagation and hydroxyl (OH·) spectral radiation characteristics of hydrogen deflagration at the hydrogen concentration range of 7–17 vol%. The experimental results indicated that maximum flame propagation velocity, maximum explosion pressure, maximum flame temperature, and maximum relative spectral intensity of OH· gradually increased with hydrogen concentration. When concentration increased from 13 vol% to 17 vol%, the time to reach the maximum flame propagation velocity, the formation time of tulip flame, and the duration of the spectral radiation signal of OH· decreased by 52.9%, 55.6%, and 48.2%, respectively. In addition, flame propagation velocity oscillated when the tulip flame appeared, and maximum explosion pressure appeared later than the maximum temperature. Maximum flame propagation velocity, maximum explosion pressure, and maximum flame temperature positively correlated with maximum relative spectral intensity in the reaction system. These findings may serve as an essential reference for the safe and effective use of hydrogen and the research and development of radical targeted explosion suppressants.

Investigation of changes in the spectral characteristics of lamps of ultraviolet and infrared radiation: a review

The article describes the parameters of ultraviolet and infrared radiation, as well as their physical impact on organic and inorganic objects. The methods of using radiation, especially in agricultural activities, are characterized. The purpose of the study is to study the patterns of changes in the spectral characteristics of radiation depending on the choice of materials used. The parameters for finding IR radiation are given. Comparative results of radiation power depending on the brand of quartz glass are shown.

EVALUATION OF THE EM FIELD EXPOSURE IN THE RANGE OF 4G FREQUENCIES IN THE LABORATORY ENVIRONMENT

The aim of paper is to estimate the electromagnetic (EM) field radiation on the human body in the range of 4G operations. The analytical approach consists of application of concept of the equivalent cylindrical monopole antenna presenting grounded standing human. The analytical formulas, allowing to determine the EM field exposure are derived. The experimental setup, consisting of the spectrum analyzer USB-SA44B supplemented by the respective software, notebook for analysis of signals, transmitting-receiving antenna array designed of four microstrip antennas, the transmitting antenna operating in the frequencies 0.9 GHz, 1.8 GHz and 2.45 GHz, and signal generator SA6 are used for the measurements. The designed setup demonstrates the possibility to extract the spectral characteristics of radiation in the range of 4G operations that will used subsequently for the comparison with the modeling data. It is observed that the fixed strength of radiation depends on the sources of radiation. The perspective of design is evaluation of the SAR at the laboratory environment.

Backward Monte Carlo method for simulating spectral radiation characteristics of boost-gliding vehicle

The boost-gliding hypersonic vehicle possesses unique features of high Mach number, high stealth, and high maneuverability, becoming a new air defense threat. The detection of its spectral radiation characteristics is one of the early warning ways. The study of spectral radiation characteristics is essentially a process of solving the Radiative Transfer Equation (RTE). Backward Monte Carlo Method (BMCM) is the most accurate method to solve the RTE compared with other methods, such as the Finite Volume Method and Line-Of-Sight method. In this study, numerical simulations of spectral radiation characteristics of an HTV2-shaped aircraft, at three trajectory points of 70 km, 50 km, and 30 km, are conducted using the BMCM. The incoming flow around the aircraft is calculated by a two-temperature OpenFOAM solver. In particular, a long-range detection model for the BMCM is developed to improve simulation efficiency. The absorption coefficients are calculated by the Line-By-Line method. Eventually, a code termed Plume Work Station-Radiation is developed to obtain spectral radiation intensities of an HTV2-shaped aircraft in the range of 1−15μm. Simulation results indicate that the high-temperature aircraft surface makes a vital contribution to the total spectral radiation characteristics, while the external flow field only has a finite contribution at some sensitive bands. The spectral radiation intensity at 50 km is the highest among the three trajectory points. An intersection point appears between the spectral radiation intensities of 70 km and 30 km due to the localized high-temperature surface at 70 km. The wavelength of the intersection point varies with the detector direction, which is attributed to the variation of the projected area of the high-temperature surface with the detector direction.

Amplitude–Temporal and Spectral Characteristics of Pulsed UHF-SHF Radiation of a High-Voltage Streamer Discharge in Air under the Atmospheric Pressure

A special experimental setup with a three-electrode discharge gap was used to study the dynamic characteristics of the ultra-high- and super-high-frequency (UHF-SHF) electromagnetic radiation of a high-voltage discharge having the streamer form with reference to the dynamics of individual streamers at the nanosecond time resolution. We performed synchronous detection of the radiation waveforms using a wideband horn antenna, on the one hand, and high-speed photography of the discharge development in the discharge gap using an ICCD camera, on the other hand. It was found that the high-voltage discharge is a source of radiation in the frequency band up to 10 GHz, which is a series of individual ultrawideband (UWB) bursts having durations of less than 1 ns and leading fronts less than 100 ps long and appears when the streamers moving from the discharge anode (thin wire) meet the discharge cathode (plane). By the order of magnitude, the number of radiation bursts corresponds to the number of streamers that reach the electrode, according to the high-speed photography data. The qualitative data confirmed by simple theoretical estimations show that the sources of UWB radiation pulses are individual streamers at the moment of their contact with the electrode, and the radiation of the streamers can be regarded as transition radiation.

Spectral Radiation Characteristic Measurements of Absorption and Scattering Semitransparent Materials—A Review

The obtainment of spectral radiation characteristics of semitransparent materials mainly includes the use of a theoretical method or experimental method. As the experimental method can better characterize the real radiation transmission results inside the material, it is generally considered more reliable and used as the basis for the verification of theoretical results. In this paper, the absorbing and scattering semitransparent materials are taken as the analysis object to illustrate the research status and future development direction in the field of measurement and identification of spectral radiation characteristics. According to the physical quantities measured and the temperature range, research status is discussed for the spectral radiation characteristic measurements of absorbing and scattering semitransparent materials, which specifically involves the measurement principle, measuring system, measuring physical quantity, identification model and application range. This research will have guiding significance for the following research directions in the field of the acquisition of spectral radiation characteristic parameters of other new materials in the future.

Optimizing Spectral Waveband Selection for Spectral Radiation Detection of Hypersonic Vehicle

Space-based spectral radiation detection is one of the most effective approaches for detecting hypersonic vehicles. However, due to complex characteristics of the plasma sheath that is generated by aerodynamic thermal effect and envelopes hypersonic vehicle, space-based spectral radiation detection is still confronted with great challenges. Based on the mechanisms of spectral radiation and transmission, we establish a model to conduct optimal selection on spectral wavebands for detecting hypersonic vehicle. Through using the established model, we obtain the spectral radiation characteristics of plasma-sheath-enveloped vehicles (RAM-CII and HTV2) under different flight conditions (at 40–70-km altitude with 10–25-Mach velocity). The optimal spectral wavebands for space-based detection are analyzed and identified using the calculated spectral data, upon which the results reveal that significant differences exist in spectral radiation intensities of different flight status for those two vehicles. The overall radiation intensity of RAM-CII vehicle is higher than that of HTV2 vehicle, to which the optimized detection wavebands corresponding to velocity and altitude differ. Generally, at different altitudes, the optimal wavebands for both vehicles are 5.00–7.86, 2.59–3.44, and 1.81–2.10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> . At different flight speeds, the optimal bands are 0.78–1.13 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> and 99–130 nm, respectively. Combined with the optimized speed and height bands, the optimal detection bands of RAM-CII vehicle and HTV2 vehicle are 5.00–7.86 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ \mu \text{m}$ </tex-math></inline-formula> , 2.59–3.44 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> , and 99–130 nm. The above findings can provide useful data for in-depth study of space-based spectral radiation detection.