Radiation Spectrum Research Articles

Microstructure building and thermal stability of cermet-based photothermal conversion coatings with layered structures

To enhance the thermal stability of cermet-based photothermal conversion coatings, the present paper proposes a novel strategy to replace the randomly distributed nanoparticles with layered structure. This kind of structure can not only suppress the agglomeration and rapid growth of nanoparticles, but also enhance the interaction between the absorber and sunlight. Thus, the thermal stability and selectivity can be simultaneously improved by this unique kind of structure. Then, a Cr/AlCrN/AlCrON/AlCrO multilayer cermet-based photothermal conversion coating is designed and fabricated by multi-arc ion plating. The microstructure, optical properties and thermal stability of the multilayer coating are studied in detail. The optical properties tests show that the absorptance and emittance of the as-deposited coating achieve 0.903 and 0.183, respectively. More importantly, after being annealed at 500 ℃ in air for 1000 h, the absorptance reaches 0.913 and the emittance arrives at 0.199, implying the enhanced selectivity and thermal stability, which are ascribed to the formation of nanolaminates, in which a series of alternating sublayers is observed in the AlCrON absorber. The nanolaminate is a two-phase composite structure composed of layered AlN and Cr<sub>2</sub>N nanoparticles distributed in amorphous dielectric matrix. According to the finite difference time domain (FDTD) simulations, this unique kind of microstructure can trap photons in the coating, which is beneficial to enhancing the interaction intensity and time between the sunlight and absorbing sublayer, and thus improving the absorption of sunlight. In addition, the reduction of particle spacing during annealing will lead to the red shift of extinction spectrum, which will better match the solar radiation spectrum. At the same time, this kind of structure can avoid the agglomeration of nanoparticles, which can simultaneously tune the optical properties and thermal stability.

Hawking radiation from a Reissner-Nordstrom-AdS black hole with integral monopoles in extended phase space

In recent years, thermodynamics and phase transitions of black holes in extended phase space have been extensively studied. The results show that the original first law of thermodynamics needs revising and new phase transitions will appear. However, so far, Hawking tunneling radiation has not been widely studied in the extended phase space. In particular, whether the tunneling radiation probability changes at this time is still uncertain. This work focuses on this topic, that is, to calculate the specific value of the tunneling probability in the extended phase space and ascertains whether the results obtained in the normal phase space are consistent with those in the extended phase space. The methods used herein are described below. Taking Reissner-Nordstrom-AdS black holes with global monopole for example, the cosmological parameters are regarded as dynamic variables, which is different from previous treatment methods that regard them as constants and ignore their contributions to the tunneling probability. In particular, cosmological parameters are introduced and regarded as thermodynamic pressure when the tunneling probability is calculated, and their contribution to the tunneling probability is considered. In the work the tunneling process of mass particles is mainly studied. The outgoing particles are viewed as spherical de Broglie waves, and then the relative phase velocity and group velocity are calculated. The geodesic equation is obtained according to the relationship between the two velocities, and the tunneling probability is calculated from the geodesic equation. It is concluded that the results show that the tunneling probability of the ingoing particles is proportional to the difference in the Bekenstein-Hawking entropy of the black hole before and after the particles tunnel, and the radiation spectrum deviates from the pure thermal spectrum, which is exactly the same as the case that the cosmological parameters are treated as constants. This means that the tunneling probability of particles can be obtained in the extended phase space, and the tunneling process does not depend on thermodynamic parameters. In addition, it is found that although the global monopole affects the dynamical behavior and thermodynamic quantity of the particle, it does not affect the entropy change or tunneling rate. In other words, the conclusion that the tunneling probability in extended phase space is exactly the same as that in normal phase space does not depend on the space-time topology.

Spectral emissivity of transition metals of the X group in the melting point region

An experimental study of the normal spectral emissivity of technical nickel, palladium and platinum in the solid polished and liquid phases near the melting points was carried out by the radiation method. The emission measurement was recorded by the bandwidth of the applied narrowband filters. The dependence of metal emission on the wavelength in the range of the radiation spectrum 0.26-10.6 μm is obtained. A comparative analysis with the literature data of other authors is carried out. A theoretical calculation of the emission is given according to the classical electromagnetic theory Hagen's formula and Rubens. Keywords: normal spectral emissivity, melting range, nickel, palladium, platinum, wavelength.

Radiation of extreme ultraviolet source and out-of-band from laser-irradiated low-density SnO<sub>2</sub> target

The extreme ultraviolet (EUV) lithography technology required for high-end chip manufacturing is the first of 35 “bottleneck” key technologies that China is facing currently. The high conversion efficiency EUV source and low out-of-band radiation play a significant role in the application of the EUV lithography system. In this work, the EUV source and out-of-band radiation are studied by using laser irradiated solid Sn target and low-density SnO<sub>2</sub> target. The result shows that a strong EUV radiation at a wavelength of 13.5 nm is generated when the laser irradiates the two forms of Sn targets. Owing to the self-absorption effect of the solid Sn target plasma, the maximum intensity of the wavelength is not located at the position of 13.5 nm, which is working wavelength of EUV lithography system. However, the peak radiation spectrum is located at the position of 13.5 nm with low-density SnO<sub>2</sub> target due to its weaker plasma self-absorption effect. In addition, the satellite lines are weaker in low-density SnO<sub>2</sub> target than in the solid Sn target, so that the spectrum efficiency of the EUV at 13.5 nm (2% bandwidth) is increased by about 20%. On the other hand, the experimental study of the out-of-band radiation is carried out. The out-of-band radiation spectral results show that the out-of-band radiation is mainly dominated by the continuum spectrum. Compared with the solid Sn target, the low-density SnO<sub>2</sub> target contains a part of the low <i>Z</i> element O (<i>Z</i> = 8), resulting in a low-intensity continuum spectrum. In addition, the collision probability of ion-ion and electron-ion both become low when the laser irradiates the low-density SnO<sub>2</sub> target, resulting in a short out-of-band radiation duration time. Therefore, the out-of-band radiation generated by the laser irradiated on the low-density SnO<sub>2</sub> target is weak based on the above reasons. The angular distribution of out-of-band radiation measurement results shows that the intensity of out-of-band radiation decreases with the angle increasing. A cosine function <inline-formula><tex-math id="M2">\begin{document}$A \cos ^\alpha \theta$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20222385_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20222385_M2.png"/></alternatives></inline-formula> can fit the angular distribution of the total radiation.

Роль спектральных характеристик источников излучения в формировании урожая салата при выращивании методом гидропоники

Growing plants indoors in the controlled environment involves the use of LED systems with an adjustable spectrum and intensity with manual or remote control. The aim of the study was to determine the role of different LED emission spectra in growth, development, and yield of lettuce cultivated hydroponically to develop requirements for the LED irradiator design. Studies were carried out in a growth chamber with periodic flooding hydroponics when irradiating lettuce plants of Kuk, Afitsion, and Khrizolit varieties under multispectral irradiators. The first irradiator has a radiation spectrum coinciding with the spectral distribution function of relative photosynthetic activity of solar radiation (control). The radiation of the second one coincides with the function of the spectral sensitivity of plants according to K.J. McCree. The third irradiator has an adjustable spectrum by three control channels for three parts of the spectrum coinciding with chlorophyll synthesis functions. It was found that the response of different lettuce varieties to the spectral composition of irradiation is specific. The maximum yield of the Kuk variety (4.45 kg/m2 ) was obtained under the first irradiator, that of lettuce Afitsion (4.7 kg/m2 ) and Khrizolit (6.55 kg/m2 ) - under the second one. Based on the results obtained the authors made requirements and designed an LED irradiator, which combines all the advantages of LED and digital technologies and provides for the implementation of the required radiation functions for laboratory research and in-vitro plant cultivation. It is noted that the LED module of the irradiator should include LEDs of violet, blue, red, dark red, and far red radiation, as well as LEDs of warm and cool white light colours.

Effects of Mesoscale Stirring on Phytopigment Determinations in the Photic Water Layer from Multispectral Ocean Color Data (The Case of the Tasman Sea)

The inconstancy of phytopigment composition during intensive mesoscale mixing of the Tasman Sea photic layer was investigated using MODIS images of its surface. To do this, each pixel of such an image is assigned a WRM index equal to the sum of the wavelengths of the minima in the reflectance spectrum of the water surface within the boundaries of a pixel on the ground (Spectral Indexing of Pixels, or SIP approach). WRM is acceptable as an indicator of phytopigment composition variability in the water column, since the attenuation of light by water as a solvent and by its admixtures of other nature is inferior to light absorption by phytopigments in spectral selectivity, while the composition of phytopigments in the aquatic environment depends on the species composition of local phytoplankton. A co-analysis of WRM distributions and characteristics of Tasman Sea waters showed that with increased mesoscale variability in open ocean waters, phytopigment content in the near-surface layer reaches levels at which minimums of pigment origin at 400–550 nm, discernible by multispectral ocean color scanners, occur in the backscattered solar radiation spectrum. This phenomenon is ignored by common algorithms for chlorophyll determination based on the data of multispectral ocean color scanners (band-ratio algorithms) and, apparently, is one of the reasons for the known tendency of such algorithms to overestimate chlorophyll concentration relative to its real content in the water column. The conclusion is applicable to any ocean basins if they, like the Tasman Sea, are not affected by external sources of optically significant admixtures in water.

Conducting fundamental scientific research and exploratory scientific research

The work is devoted to the study of the characteristics of a low-temperature plasma of a high-frequency (HF) discharge (f=13.56 MHz) ignited between metallic and electrolytic electrodes at atmospheric pressure. Burning of an RF discharge in a diffuse (volumetric) form is observed at the interface between the media between the electrodes. Numerical calculations of the electric field strength and the distribution of the volumetric power density of the Joule heat release before breakdown in a vapor-gas mixture near a metal electrode are presented. The discharge radiation spectrum, plasma composition, and electron density were studied by optical emission spectroscopy. The thermograms of the electrode surface under the conditions of an RF discharge are considered. Keywords: Plasma-liquid systems, high-frequency discharge, electrolytes, numerical methods.

Влияние изотопного состава особо чистого германия на характеристики процессов взаимодействия с потоком нейтронов

The possibility of varying the properties of semiconductor materials is relevant for the development of microelectronics and creation of semiconductor materials with improved properties. In this study, we set out to investigate the mechanisms of interaction of neutron radiation with high-purity germanium (HPG). This semiconductor material can be used as part of detecting structures in the development of high energy-resolution measuring equipment designed to analyze complex radiation spectra.

Обоснование параметров системы искусственного светодиодного освещения животноводческих помещений

Lighting of livestock buildings affects the productivity of animals. The system of artificial LED lighting provides the reduction of energy costs in the livestock production at agro-industrial enterprises. A mathematical model is presented to substantiate the parameters of the system of artificial LED lighting of livestock premises. The system of artificial LED lighting should provide regulation of illumination depending on breed and light perception channels of an animal, use control programs of radiation spectrum and illumination duration. The results of mathematical analysis determined that illuminance, uniformity of illumination in livestock premises and power consumption of the LED system depends on the mounting height of lighting devices, as well as the type of light intensity curve, which are determined by the geometric features of LED lighting devices. The emission spectrum is determined by the type of LED light sources, while the duration and periodicity of the daylight hours is provided by the LED software devices. The development of new design solutions of lighting devices will increase the livestock productivity and reduce energy costs.

Simulation of coloured particles radiation spectra from black holes

The Journal of the National Science Foundation of Sri Lanka publishes the results of research in all aspects of Science and Technology. The journal also has a website at http://www.nsf.gov.lk/. 2021 Impact Factor: 0.682The JNSF provides immediate open access to its content on the principle that making research freely available to the public supports a greater global exchange of knowledge.Cover :Leatherback (a), green (b - adult & f - hatchling), hawksbill (c) and olive ridley (d) turtles who nest in Sri Lankan beaches, green turtle crawl marks (e) and by-catch of sea turtles in fisheries (c & d)Photo credits: SJ Perera (a & c), WPN Perera (b & e), K Ekaratne (d & f)

MEASUREMENT OF THERMAL RADIATION OF MOXA PHYSIOTHERAPEUTIC REGIME

Thermal radiation from various sources is widely used in medical therapy procedures. Sources of artificial and natural origin are used to create thermal radiation. The latter are of the greatest interest, as they form a wide spectrum of radiation, most comparable to a person's own radiation. The use of wormwood cigars (mox) became widespread. With their help, sessions of one of the most popular methods of Chinese folk medicine, moxatherapy (burning, thermopuncture, "jiu" therapy) are conducted. The authors conducted studies of the thermal radiation of a wormwood cigar in the wavelength range of 800…1000 nm. "Qiaitiao" No. 6 cigars from the standard treatment set were used for experimental research.
 The purpose of the conducted research is to determine the power of thermal radiation of moxa and evaluate the dynamics of its changes during the course of a treatment session. A high-precision OM3-65 absorbing power wattmeter with an optoelectronic converter was used for measurements. Studies have shown that the maximum power of thermal radiation is formed immediately after the wormwood cigar begins to smolder. Its value is within (1.5...2.0) 10-4 W. When a cigar burns for 2.5 minutes, the intensity of heat radiation decreases by more than an order of magnitude. This is due to the fact that in the process of smoldering moxa, a layer of ash is formed between the burning and irradiation zones, which partially absorbs the flow of thermal radiation. In addition, during decay of fixed moxa, the irradiation zone gradually moves away from the irradiated surface.
 Removing the ash layer and placing the moxa at the previous distance leads to the restoration of the initial power level. Approximate expressions were obtained, which, based on experimental data, describe the change in the heat radiation power of a wormwood cigar.
 The features revealed during the study of the thermal radiation of the wormwood cigar will be useful for specialists engaged in practical thermotherapy and will contribute to increasing its effectiveness.

Superradiant parametric x-ray emission

We compute a spectrum of parametric x-ray radiation inside a crystal from a bunch of electrons, which is periodically modulated in density. We consider that the bunch of electrons is exiting from an x-ray free-electron laser (XFEL) channel. We demonstrate that in the case of a resonance between the frequency of parametric x-ray radiation and a frequency of modulation of an electron bunch, the sequence of strong quasimonochromatic x-ray pulses is formed---superradiant parametric x-ray emission (SPXE) with frequencies that are multiples of the modulation frequency. The number of photons in the pulse of SPXE in the case of extremely asymmetric diffraction is comparable with the photon number in the pulse of an XFEL. Moreover, the SPXE is directed under the large angle to the electron velocity and every harmonic in the spectrum is emitted under its own angle.

Optical study of the effects arising from the interaction of a CO2-laser with the powder in a coaxial nozzle for laser cladding

Experimental studies of the NiCr powder interaction with the CO2-laser radiation in the conditions of free jets of a coaxial nozzle for laser cladding are carried out. Optical diagnostics is used with the video recording of moving particles and registration of the radiation spectrum. The influence of the type of working gas, i.e., air and argon, as well as laser operation modes – the continuous CW and pulse-periodic PP on plasma ignition – is studied. An increase in the average particle velocity from 3 m/s in a cold flow to 10 m/s, when exposed to a laser, was found and the maximum velocity values at the level of 50-60 m/s were registered. The phenomena of particle break-up and plasma plume formation on their surface are described. It is shown that particles rotating with a frequency of 30-40 kHz are present in the powder flow. The continuous thermal radiation of particles and the spectral lines of plasma radiation in the range of 400-900 nm are analyzed.

AnaBHEL (Analog Black Hole Evaporation via Lasers) Experiment: Concept, Design, and Status

Accelerating relativistic mirrors have long been recognized as viable settings where the physics mimic those of the black hole Hawking radiation. In 2017, Chen and Mourou proposed a novel method to realize such a system by traversing an ultra-intense laser through a plasma target with a decreasing density. An international AnaBHEL (Analog Black Hole Evaporation via Lasers) collaboration was formed with the objectives of observing the analog Hawking radiation, shedding light on the information loss paradox. To reach these goals, we plan to first verify the dynamics of the flying plasma mirror and characterize the correspondence between the plasma density gradient and the trajectory of the accelerating plasma mirror. We will then attempt to detect the analog Hawking radiation photons and measure the entanglement between the Hawking photons and their “partner particles”. In this paper, we describe our vision and strategy of AnaBHEL using the Apollon laser as a reference, and we report on the progress of our R&D concerning the key components in this experiment, including the supersonic gas jet with a graded density profile, and the superconducting nanowire single-photon Hawking detector. In parallel to these hardware efforts, we performed computer simulations to estimate the potential backgrounds, and derived analytic expressions for modifications to the blackbody spectrum of the Hawking radiation for a perfectly reflecting point mirror, due to the semi-transparency and finite-size effects specific to flying plasma mirrors. Based on this more realistic radiation spectrum, we estimate the Hawking photon yield to guide the design of the AnaBHEL experiment, which appears to be achievable.

Perfect Nonradiating Modes in Dielectric Nanoparticles

A hypothesis of the existence of perfect nonradiating modes in dielectric nanoparticles of an arbitrary shape is put forward. It is strictly mathematically proved that such modes exist in axisymmetric dielectric nanoparticles and have unlimited radiation Q factors. With the smart tuning of the excitation beams, perfect modes appear as deep minima in the scattered radiation spectra (up to complete disappearance), but at the same time, they have a substantial amplification of the fields inside the particle. Such modes have no analogs and can be useful for the realization of nanosensors, low threshold nanolasers, and other strong nonlinear effects in nanoparticles.

Achieving Persistent Luminescence Performance Based on the Cation-Tunable Trap Distribution.

Deep-red persistent luminescence (PersL) materials have promising applications in fluorescence labeling and tracking. PersL spectral range and PersL duration are considered to be the key factors driving the development of high-performance deep-red PersL materials. To address these two key issues, the performance of PersL materials was continually optimized by doping with cations (Si4+ and Al3+ ions), relying on the material of Li2ZnGe3O8:Cr3+ from the previous work of our group, and a 4.8-fold increase in PersL radiation spectrum intensity and more than twice the PersL duration was achieved (PersL duration up to 47 h). Ultimately, the obtained PersL materials are used to demonstrate their potential use in multi-level anti-counterfeiting, tracking and localization, respectively. This study provides a unique and novel entry point for achieving high-performance PersL materials by optimizing the PersL material host to modulate the electronic structure.

Large-area 1D selective emitter for thermophotovoltaic applications in the mid-infrared

Two- or three-dimensionally patterned subwavelength structures, also known as metamaterials, have the advantage of arbitrarily engineerable optical properties. In thermophotovoltaic (TPV) applications, metamaterials are commonly used to optimize the emitter’s radiation spectrum for various source temperatures. The output power of a TPV device is proportional to the photon flux, which is proportional to the emitter size. However, using 2D or 3D metamaterials imposes challenges to realizing large emitters since fabricating their subwavelength features typically involves complicated fabrication processes and is highly time-consuming. In this work, we demonstrate a large-area (78 cm2) thermal emitter. This emitter is simply fabricated with one-dimensional layers of silicon (Si) and chromium (Cr), and therefore, it can be easily scaled up to even larger sizes. The emissivity spectrum of the emitter is measured at 802 K, targeting an emission peak in the mid-infrared. The emissivity peak is ∼0.84 at the wavelength of 3.75 μm with a 1.2 μm bandwidth. Moreover, the emission spectrum of our emitter can be tailored for various source temperatures by changing the Si thickness. Therefore, the results of this work can lead to enabling TPV applications with higher output power and lower fabrication cost.

High performance foreign-dopant-free ZnO/AlxGa1−xN ultraviolet phototransistors using atomic-layer-deposited ZnO emitter layer

High-performance foreign-dopant-free ZnO/AlxGa1−xN heterojunction ultraviolet (UV) phototransistors were fabricated and characterized. The ZnO layer with high electron concentration was grown as emitter by atomic layer deposition, while the AlxGa1−xN/GaN heterostructure was epitaxied as base and collector by metal organic chemical vapor deposition. A linearly upgraded/downgraded AlxGa1−xN layer was used as polarization-induced n/p type layer without dopant. The prominent feature of the resulting n+-p-n ZnO/AlxGa1−xN phototransistors is a three-stage rising spectral response matching the biological action spectrum of solar UV radiation. Moreover, the phototransistors demonstrate a low dark current of less than 1 pA at 2 V, a maximum responsivity of ∼8.7 A/W at 5 V and 300 nm, a normalized detectivity of ∼1 × 1013 Jones, and a high response speed with a rise/fall time of 3.5 μs/450 μs. This work shows a feasible and simple-process approach for developing high-performance multiband spectral response photodetectors based on different wide band gap material systems.

Pulsars in AstroSat-CZTI: detection in sub-MeV bands and estimation of spectral index from hardness ratios

The Cadmium Zinc Telluride Imager (CZTI) onboard AstroSat, an open detector above \(\sim \)100 keV, is a promising tool for the investigation of hard X-ray characteristics of \(\gamma \)-ray pulsars. A custom algorithm has been developed to detect pulsars from long integration (\(\sim \)years) of archival data, as reported by us earlier. Here, we extend this method in the analysis to include additional \(\sim \)20% of the CZTI pixels that were earlier ignored due to their lower gain values. Recent efforts have provided better and more secure calibration of these pixels, demonstrating their higher thresholds and extended energy range up to \(\sim \)1 MeV. Here, we use the additional information provided by these pixels, enabling the construction of pulse profiles over a larger energy range. We compare the profiles of the Crab pulsar at different sub-bands and show that the behavior is consistent with the extended energy coverage. As detailed spectroscopy over this full band remains difficult due to the limited count rate, we construct hardness ratios which, together with AstroSat mass model simulations, are able to constrain the power-law index of the radiation spectrum. We present our results for the phase-resolved spectrum of PSR J0534\(+\)2200 and for the total pulsed emission of PSR J1513−5908. The recovered photon indices are found to be accurate within \({\sim }20\)%.

Arrays of combined antennas with equal-amplitude distribution of bipolar voltage pulses

The paper presents the comparative characteristics of the radiation pattern of the combined antenna arrays excited by a bipolar pulse and harmonic oscillations near the central frequency of the spectrum of ultrawideband radiation. Particular attention is paid to the 3x3 array radiation source with maximum efficiency.