Distribution Of Radiation Intensity Research Articles

A numerical study on the influence of multiple nozzles on the infrared radiation signatures of liquid rocket exhaust plumes

A numerical study was conducted to examine the relationship between the infrared radiation characteristics of liquid rocket engine exhaust plumes under the same thrust conditions and the number and expansion degree of nozzles. This study used the Reynolds-averaged computational fluid dynamics method to simulate the flow field of multiple nozzles. A single-line group combined with the G-C approximation was used to calculate the molecular spectral properties, and a three-dimensional radiation transfer calculation model was established based on the line-of-sight method. The infrared radiation characteristics of the exhaust plume were calculated for single, double, three, and four nozzles. The radiation intensity of two typical bands, 2.7 μm and 4.3 μm, was studied, including spectrum, intensity, and radiation intensity distribution. The results show that the integrated infrared radiation intensity of the double-nozzle plume is 51.36 % lower than the average of the other three nozzle configurations under the over-highly under-expansion state. The radiation difference of the double nozzle reaches up to 38.3 % at different detection angles, whereas the differences between the three and four nozzles are below 10.5 % and 6.1 %, respectively, indicating that the radiation difference at each detection angle gradually decreases with the increase in the number of nozzles.

Image-based non-isotropic point light source calibration using digital fringe projection

Accurate light source calibration is critical in numerous applications including physics-based computer vision and graphics. We propose an image-based method for calibrating non-isotropic point light sources, addressing challenges posed by their non-radially symmetric radiant intensity distribution and the non-Lambertian properties of the calibration target. We deduce an image formation model, and capture the intensity of the calibration target at multiple poses, coupled with accurate 3D geometry acquisition using the digital fringe projection technique. Finally, we design an iterative computational framework to optimize all the light source parameters simultaneously. The experiment demonstrated the high accuracy of the calibrated light source model and showcased its application by estimating the relative reflectance of diverse surfaces.

ON THE ISSUE OF COMPREHENSIVE ASSESSMENT OF THE IMPACT OF THERMAL RADIATION AT WORKPLACES, TAKING INTO ACCOUNT AIR POLLUTION

Problem statement. The research demonstrates that existing methods for determining the distribution of thermal radiation intensity using nomograms and formulas contain significant errors. This is due to the adoption of a number of simplifications regarding numerous interdependent parameters, including the temperature inside furnaces, the size of openings and shafts, etc. As a result, there is a need for measurements of thermal radiation intensity at distances of 5−10 meters and beyond. The purpose of the article. The objective of the article is to propose a concept for a new experimental methodology to investigate the intensity of radiation exposure to workers at their workplaces. Simultaneously, in order to address the issues of thermal protection for workers, actual measurement data of thermal radiation levels are necessary for each workstation under real working conditions within the workspace. Conclusion. It is important to characterize the composition of the gas environment, as its impurities can distort the distribution of radiant energy through interference and diffraction effects, which need to be considered for microclimate optimization. The presence of dust particles complicates the straight-line heat transfer through scattering and scintillation of rays, requiring further improvement of models. Turbulence, impurities, and atmospheric heterogeneity are important factors that need to be further investigated and taken into account in heat transfer process modeling. Scintillation affects the quality of radiation transmission, necessitating further study of this phenomenon. Local atmospheric composition peculiarities require the development of models that consider these variations. The obtained experimental data will contribute to improving the accuracy of modeling and enhancing working conditions. Further refinement of measurement techniques is necessary for obtaining reliable information.

Multi-objective optimization design of aerodynamic and infrared characteristics of multi-stream serpentine nozzle

A multi-objective optimization design of multi-stream serpentine nozzle was carried out to improve the aerodynamic performance and reduce the infrared radiation signal. A numerical simulation was carried out to investigate the effects of nozzle pressure ratio (NPR), Aspect ratio (AR) and Ratio of length and diameter (L/D). Computational fluid dynamics (CFD) simulation was employed to study the aerodynamic performance of the multi-stream serpentine nozzle, and the narrow-band method with discrete transfer method were used to calculate its infrared radiation intensity distribution characteristics. A 3-factor, 21-level orthogonal table was designed based on the orthogonal experimental method, and multi-stream serpentine nozzle with different geometrical parameter and operating conditions were designed to obtain the aerodynamic performance and infrared radiation intensity data of each experimental sample point. Radial Basis Function (RBF) neural network and Multi-Objective Particle Swarm Optimization algorithm were used to optimize the geometry and operating conditions with better aerodynamic performance and weaker infrared signal. The result shows that the Pareto solutions obtained by the optimization have good accuracy compared with the numerical simulation results, with an aerodynamic performance error of 0.02% and an infrared radiation intensity error of 0.24%.

Modeling of Subwavelength Gratings: Near-Field Behavior

Subwavelength gratings have received considerable attention in the fields of photonics, optoelectronics, and image sensing. This paper presents simple analytical expressions for the near-field intensity distribution of radiation scattered by these gratings. Our proposed methodology employs a 2D point dipole model and a specialized version of perturbation theory. By validating our models via numerical techniques including boundary and finite element methods, we demonstrate their effectiveness, even for narrow slits.

Autonomous exploration for radioactive sources localization based on radiation field reconstruction

In recent years, unmanned ground vehicles (UGVs) have been used to search for lost or stolen radioactive sources to avoid radiation exposure for operators. To achieve autonomous localization of radioactive sources, the UGVs must have the ability to automatically determine the next radiation measurement location instead of following a predefined path. Also, the radiation field of radioactive sources has to be reconstructed or inverted utilizing discrete measurements to obtain the radiation intensity distribution in the area of interest. In this study, we propose an effective source localization framework and method, in which UGVs are able to autonomously explore in the radiation area to determine the location of radioactive sources through an iterative process: path planning, radiation field reconstruction and estimation of source location. In the search process, the next radiation measurement point of the UGVs is fully predicted by the design path planning algorithm. After obtaining the measurement points and their radiation measurements, the radiation field of radioactive sources is reconstructed by the Gaussian process regression (GPR) model based on machine learning method. Based on the reconstructed radiation field, the locations of radioactive sources can be determined by the peak analysis method. The proposed method is verified through extensive simulation experiments, and the real source localization experiment on a Cs-137 point source shows that the proposed method can accurately locate the radioactive source with an error of approximately 0.30 m. The experimental results reveal the important practicality of our proposed method for source autonomous localization tasks.

Assessment of the ITER divertor bolometer diagnostic performance

The ITER bolometer diagnostic will provide measurements of the total radiation emitted from the plasma, a part of the overall energy balance. It will consist of some 550 lines of sight (LOS) of bolometer detector, bundled in multiple individual cameras, which will be located in the gaps between blanket modules on the vacuum vessel wall, in five divertor cassettes, in two upper port plugs and in one equatorial port plug (Meister et al., 2017). The LOS are optimised as much as possible with design constraints to capture the details of different plasma regions in which the intensity and local distribution of radiation will vary over a large range. This is especially true in the divertor, where up to 70 % of the total thermal exhaust power from the core will have to be radiated during burning plasma operation. This radiation will be tightly concentrated meaning that not only will tomographic reconstruction of the distribution be challenging, but the bolometer cameras themselves need to be properly designed to handle the resulting heat fluxes. This paper first presents an assessment of the photonic heat fluxes falling on bolometers in the divertor region during high performance operation (where the heat fluxes will be highest). These heat fluxes are computed using ray-tracing from radiation distributions obtained with the SOLPS (plasma boundary region) and JINTRAC (plasma core region) codes and will serve as essential input to the thermal design studies of bolometers. The same SOLPS and JINTRAC simulations are used as models for the second focus of the paper which examines how closely the radiation distribution obtained from tomographic inversion of synthetic signals from the bolometer LOS matches the model input. Some effort has also been devoted to a study of how the reconstructions are affected by loss of individual LOS.

Bending Magnet Synchrotron Radiation Imaging with Large Orbital Collection Angles.

Synchrotron radiation (SR) from bending magnets, wigglers, and undulators is now extensively produced for users at storage ring based light sources, with unique properties in terms of average brightness and stability. We present a profound study of bending magnet SR intensity distribution in the image plane of a focusing optical system. Measurements of this intensity distribution at the MAX-IV low emittance storage ring are compared to theoretical predictions, and found to be in excellent agreement. This work shows upon the possibility of performing high resolution emittance diagnostics with visible or near-visible SR on upcoming low-emittance storage ring based light sources. As a byproduct of our study, we derive a closed analytical expression for the intensity distribution from a zero-emittance beam, in the limiting case of wide orbital collection angles. This expression finally allows us to demonstrate the meeting between classical electrodynamics applied to SR emission and focusing, and the Landau and Lifshitz prediction of radiation intensity distribution nearby a caustic.

Terahertz spin ratchet effect in magnetic metamaterials

We report on spin ratchet currents driven by terahertz radiation electric fields in a Co/Pt magnetic metamaterial formed by triangle-shaped holes forming an antidots lattice and subjected to an external magnetic field applied perpendicularly to the metal film plane. We show that for a radiation wavelength substantially larger than the period of the antidots array the radiation causes a polarization-independent spin-polarized ratchet current. The current is generated by the periodic asymmetric radiation intensity distribution caused by the near-field diffraction at the edges of the antidots, which induces spatially inhomogeneous periodic electron gas heating, and a phase-shifted periodic asymmetric electrostatic force. The developed microscopic theory shows that the magnetization of the Co/Pt film results in a spin ratchet current caused by both the anomalous Hall and the anomalous Nernst effects. Additionally, we observed a polarization-dependent trigonal spin photocurrent, which is caused by the scattering of electrons at the antidot boundaries resulting in a spin-polarized current due to the magnetization. Microscopic theory of these effects reveals that the trigonal photocurrent is generated at the boundaries of the triangle antidots, whereas the spin ratchet is generated due to the spatially periodic temperature gradient over the whole film. This difference causes substantially different hysteresis widths of these two currents.

Analyzing thermal radiation in cylindrical anisotropic scattering medium with element differential method

The spontaneous radiation combustion diagnosis technology has high requirements for obtaining the radiation intensity of highly directional resolution in a combustion system. Taking advantage of the numerical stability and easy implementation of the element differential method, this paper constructs a radiation model that can achieve the radiation intensity of spatial and angular high-resolution in cylindrical anisotropic scattering medium. In analyzing the radiation model, the radiation intensity is discretized in three dimensions. An upwind scheme is proposed to suppress the numerical oscillation of the strong convection characteristics of the radiation transfer equation. The double-layer node algorithm is used to capture the strong discontinuous singularities at the radiation boundary. The comparison with the analytical solution shows that the radiation model based on the element differential method can achieve the high-resolution description of radiation intensity with high-order accuracy. The accuracy and validity of the radiation model are verified through comparing with the results on the Monte Carlo method. The further description of the three-dimensional distribution of radiation intensity in angle and space proves that the up-wind scheme can effectively suppress numerical oscillation and realize stable calculation.

Dynamics of shaded areas in a typical-shaped solar greenhouse and their effects on tomato growth—A case study in winter

The side walls and fixed insulation quilt of a solar greenhouse helped reduce heat loss from the room at night but produced shadows on the greenhouse floor during the day, affecting the growth and development of crops. In the present study, a method to calculate the projected area of the side walls and fixed insulation quilt in the greenhouse was derived. Then, a typical-shaped solar greenhouse and tomatoes were used as experimental research objects to investigate the spatial and temporal variation of indoor solar radiation intensity and tomato growth. The results showed that: 1) The average absolute error between the calculated and measured values of the ground shade of the solar greenhouse on four typical sunny days was 1.12%, 2.65%, and 2.02%, respectively. The area of selected greenhouse was 450m2, the maximum shaded area could account for 20.3% of the total area of the greenhouse, the shaded area projected by the insulation onto the greenhouse floor remained constant at different times, and that projected by the wall decreased and then increased parabolically with time. 2) The average solar radiation intensity in the greenhouse at the winter solstice tended to increase and then decrease with time, with a maximum value of 41,374.0 Lux. The uniformity of solar radiation distribution was reduced in the morning, evening and midday hours. 3) The tomato plant height, stem diameter, leaf area index and yield were 36.9%, 14.7%, 63.1% and 125.4% higher, respectively, in the high than in the low solar radiation zone. The results of the study can provide a theoretical basis for clarifying the dynamics of shaded areas and the spatial and temporal distribution of solar radiation intensity in greenhouses, and for optimizing the structural parameters of solar greenhouses.

К вопросу о механизмах разогрева светодиодов на основе p-InAsSbP/n-InAs(Sb)

Three main reasons for a temperature increase in activated p-InAsSbP/n-InAs/n-InAsSbP and p-InAsSbP/n-InAsSb/n-InAs double heterostructures has been considered. Contribution of nonradiative Auger recombination, electron-phonon interaction and Joule heating to diode temperature increase in single element LEDs and flip-chip diode arrays (1×3) were evaluated at forward and reverse bias using data on spatial distribution of the mid-IR radiation intensity and current-voltage characteristics.

On heating mechanisms in LEDs based on p-InAsSbP/n-InAs(Sb)

Three main reasons for a temperature increase in activated p-InAsSbP/n-InAs/n-InAsSbP and p-InAsSbP/ n-InAsSb/n-InAs double heterostructures has been considered, contribution of nonradiative Auger recombination, electron-phonon interaction and Joule heating to diode temperature increase in single element LEDs and flip-chip diode arrays (1x3) were evaluated at forward and reverse bias using data on spatial distribution of the mid-IR radiation intensity and current-voltage characteristics. Keywords: IR LED, IR diode array, Joule heating, Auger recombination, electron-phonon interaction.

Spontaneous emission enhancement and directional emission by an optical nanonatenna array on a metallic mirror

Optical nanoantennas support surface plasmon polariton (SPP) with a confinement of light breaking through the diffraction limit, and thereby achieving an enhancement and regulation of electromagnetic field on a deep-subwavelength scale. In this paper, a periodic array of optical nanoantennas on a metallic mirror is proposed, where the antennas are gold nanocubes forming a two-dimensional periodic array, and a single point emission source is located in the nanogap between the antenna of gold nanocube and the gold mirror. The nanogap between the antenna and mirror can support gap surface plasmon, which results in an enhanced spontaneous emission rate. Meanwhile, the periodic array of nanoantennas can support the surface lattice resonance (SLR), which can achieve directional far-field radiation perpendicular to the substrate or in a specified direction by properly designing the array period. To design the antenna that can simultaneously achieve an enhancement of spontaneous emission rate and a directional radiation of far field, the calculation of the radiation field of a single point source in a periodic structure is transformed into the calculation of the radiation fields of a set of pseudoperiodic point-source arrays by combining the array scanning method (ASM) and full-wave rigorous numerical method, thus giving the spontaneous emission rate of the emitter and the near-field distribution of the antenna. Concerning the calculation of the angular distribution of far-field radiation intensity, we start from the Maxwell’s equations and provide a rigorous formulation and proof of the reciprocity-theorem method. This proof is different from those reported in existing literature and has a more rigorous applicability for infinite-extent periodic structures or has a lower amount of computational work. Based on the reciprocity-theorem method, the antenna parameters are designed so that the enhancement factor of far-field radiation intensity reaches a maximum value of 2756 in the direction perpendicular to the substrate, and simultaneously, the enhancement factors of total spontaneous emission rate and far-field spontaneous emission rate of the point source reach 1097 and 55.50, respectively. The proposed antenna has a simple structure that is easy to design and fabricate, and the proposed design method is intuitive and easy to implement, which can be used to guide the design of high-speed, high-brightness and directional-radiation light sources.

Silhouettes of Wormholes Traversed for Radiation

The problem of the passage of light through the mouth of a zero-mass wormhole and the possibility of observing the objects from another asymptotically flat space-time through the mouth of a wormhole are considered. It is shown that an individual star can have several images and the fact that the image of a flat Lambertian screen has a complex brightness distribution for an observer located on the opposite side of the throat. Images of two such screens visible inside the silhouette of a massless wormhole and the distribution of radiation intensity in their images are constructed.

Multi-Modal Non-Isotropic Light Source Modelling for Reflectance Estimation in Hyperspectral Imaging

Estimating reflectance is key when working with hyperspectral cameras. The modelling of light sources can aid reflectance estimation, however, it is commonly overlooked. The key contribution of this letter is a physics-based, data-driven model formed by a Gaussian Process (GP) with a unique mean function capable of modelling a light source with an asymmetric radiant intensity distribution (RID) and a configurable attenuation function. This is referred to as the light-source-mean model. Moreover, we argue that by utilising multi-modal sensing information, we can achieve improved reflectance estimation using the proposed light source model with shape information obtained by depth cameras. An existing reflectance estimation method, that solves the dichromatic reflectance model (DRM) via quadratic programming optimisation, is augmented with terms that allow input of shape information. Experiments in simulation show that the light-source-mean GP model had less error when compared to a parametric model. The improved reflectance estimation outperforms existing methods in simulation by reducing the error by 96.8% on average when compared to existing works. We further validate the improved reflectance estimation method through a multi-modal classification application.

Shot-to-shot two-dimensional photon intensity diagnostics within megahertz pulse-trains at the European XFEL.

Characterizing the properties of X-ray free-electron laser (XFEL) sources is a critical step for optimization of performance and experiment planning. The recent availability of MHz XFELs has opened up a range of new opportunities for novel experiments but also highlighted the need for systematic measurements of the source properties. Here, MHz-enabled beam imaging diagnostics developed for the SPB/SFX instrument at the European XFEL are exploited to measure the shot-to-shot intensity statistics of X-ray pulses. The ability to record pulse-integrated two-dimensional transverse intensity measurements at multiple planes along an XFEL beamline at MHz rates yields an improved understanding of the shot-to-shot photon beam intensity variations. These variations can play a critical role, for example, in determining the outcome of single-particle imaging experiments and other experiments that are sensitive to the transverse profile of the incident beam. It is observed that shot-to-shot variations in the statistical properties of a recorded ensemble of radiant intensity distributions are sensitive to changes in electron beam current density. These changes typically occur during pulse-distribution to the instrument and are currently not accounted for by the existing suite of imaging diagnostics. Modulations of the electron beam orbit in the accelerator are observed to induce a time-dependence in the statistics of individual pulses - this is demonstrated by applying radio-frequency trajectory tilts to electron bunch-trains delivered to the instrument. We discuss how these modifications of the beam trajectory might be used to modify the statistical properties of the source and potential future applications.

Interfacial Flows and Interfacial Shape Modulation Controlled by the Thermal Action of Light Energy

The review covers the research on thermocapillary convection caused by the thermal action of laser radiation in single-layer and bilayer liquid systems of capillary thickness. The advantages of using optical radiation are the instantaneous delivery of thermal energy to a place on demand (a bulk phase, interfaces); low radiation power required; concentrating heat flux on a spot of a few micrometers; the production of arbitrary spatial distributions of radiation intensity; and, as a result, corresponding thermal fields at a liquid interface and their fast reconfiguration. Thermocapillary stresses at the liquid interfaces lead to the transfer of the liquid and a change in the shape of the interface, in accordance with the distribution of the light-induced thermal field. Studies concerned with the methods of non-destructive testing of liquid media and solids, which are based on a photothermocapillary signal emitted by a laser-induced concave deformation of a thin layer, are considered. Features of thermocapillary deformation of a liquid–air interface caused by local heating of thin and thick (exceeding the capillary length) layers are demonstrated. A part of the review addresses the results of the study of thermocapillary rupture of films in the heating zone and the application of this effect in semiconductor electronics and high-resolution lithography. The works on the light-induced thermocapillary effect in bilayer (multilayer) liquid systems are analyzed, including early works on image recording liquid layer systems, liquid IR transducers, and nonlinear optical media.

Two-dimensional displacement sensors with angstrom-scale resolution based on optical slot antenna arrays

Optical displacement sensing with high resolution and noncontact detection plays an important role in nanometrology, nanofabrication, and super-resolution microscopy. However, displacement sensing along an arbitrary direction in a two-dimensional (2D) plane with angstrom-level precision remains challenging. Here, we propose a 2D displacement sensor composed of eight optical slot antennas. A tightly focused laser beam is illuminated upon the antennas. The amplitudes and phases of the output radiation of the antennas are controlled by geometries. The intensity distribution of the output far-field radiation, which strongly depends on the relative position between the focal spot of the incident light and the antennas, was used to retrieve the 2D coordinates of any location in a plane. A resolution as high as 0.88 nm was obtained. We also show a method for improving displacement sensitivity by designing the destructive interference among the radiation of the antennas. The angstrom-scale resolution and arbitrary point localization, along with the nanoscale size, pave the way for the development of high-performance sensing, integrated photonic circuits, and on-chip signal processing.

First demonstration of a novel single-end readout type position-sensitive optical fiber radiation sensor based on wavelength-resolved photon counting

In this study, a single-end readout type position-sensitive optical fiber radiation sensor was developed. Using the wavelength dependency of light attenuation inside the optical fiber, the incident position of radiation at the fiber can be estimated reversely. Instead of a spectrometer, we employed bandpass filters and photon-counting head as a photodetector to improve detection efficiency. The detection efficiency of a 10 m long plastic scintillation fiber at the 5 m position from the readout end was evaluated to be in the range of 0.08–0.12 % for 662 keV gamma-rays from 137Cs and 2.6–3.9 % for beta-rays from 90Sr/90Y when a bandpass filter transmitting photons with a wavelength of 500 nm was used. A basic measurement test of radiation intensity distribution was conducted using a 90Sr/90Y radioactive point source. A field test was also performed at the difficult-to-return zone in Fukushima Prefecture, and the estimated dose rate distribution roughly agreed with the survey meter measurement.