Spatial Distribution Of Radiation Research Articles

Studies of radiation background at the synchrotron light source DELTA

The 1.5-GeV electron storage ring of the synchrotron radiation source DELTA at TU Dortmund University is surrounded by a 1 m thick concrete radiation shielding wall with a height varying between 3.0 and 4.3 m and with open top. The installation of a new 7-T superconducting wiggler and tentative plans for a new building in the vicinity motivated recent studies of background radiation either directly escaping the open-topped radiation shield or being scattered by air or the roof of the hall (the so-called radiation skyshine). Spectra of gamma radiation were recorded under different conditions using a high-purity germanium detector. Long-term measurements were made with photoluminescence dosimeters. The paper presents the results together with calculations of the spectral distribution of wiggler radiation as well as a model for the spatial distribution of radiation emitted by the whole storage ring.

Computer-aided Optical Plasma Postprocessing Applied on Model Spark Gaps

Spark gaps are used as surge protective devices (SPD class 1) for low voltage grids protection against surge currents and overvoltages. For practical research of the narrow gap plasma of spark gaps, high-speed camera recordings are used in modified transparent test models. In this test setup, current densities of 1010 A/m2 are generated. In order to optimize and automate the evaluation process of camera recordings, an image analysis tool is developed further in this contribution. After basic image improvement and segmentation, this research optimizes a detection algorithm for plasma location and distribution. As a result, the known plasma distribution gives access to significantly more information about the plasma behaviour and the spatial distribution of radiation.

A microwave-driven deep-UV ZnI2 light source for degrading organic wastewater: comparison with mercury lamp

The traditional cathode low-pressure Hg lamp is the most mainstream UV light source in degrading organic wastewater but with significant limitations of short lifetime, environmental hazard and poor degradation efficiency. Here, we evaluate a self-designed microwave-driven ZnI2 deep-UV lamp on degrading Rhodamine B (RhB), methylene blue (MB), and p-nitrophenol (PNP). An electrodeless Hg lamp was used as control. First we investigated the emission wavelength, spatial radiation distribution, the effect of power on radiation intensity, and relative permittivity of ZnI2 lamp. Then the degradation rate, kinetics and energy yield on degrading RhB, MB and PNP as well as the cost were studied. ZnI2 lamp showed shorter wavelengths, approaching UVC radiation intensity, approaching attenuation factor and higher microwave coupling capability to Hg lamp. After treatment with ZnI2 lamp for 10, 6 and 15 min, 5 mg/L of RhB, MB and PNP can reach 100% removal rates. Moreover, higher degradation rate and kinetic constants of ZnI2 lamp for 3 compounds than the Hg lamp in this paper and in the literature were achieved. With the assistance of microwave and properties of environmental-friendly and low cost, ZnI2 lamp provides a new alternative to traditional Hg lamp and wastewater photochemical treatment method.

The Spatial Distributions of Radiation Emitted from a Sinusoidal Current Filament and a Dipole Antenna

While the analytical and numerical tools for determining the basic properties of a variety of antenna types have been long-established, there remains some continuing curiosity about how electromagnetic radiation is launched by such a simple antenna as a dipole. The following article discusses this problem in both the frequency domain and time domain. The sinusoidal current filament (SCF) is investigated first as a prototype of a wire dipole. The length-wise distribution of radiated power for the SCF is obtained from the distributed radiation resistance of Schelkunoff and Feldman, the induced electromotive force (IEMF) method, and the far-field analysis of radiation sources (FARS) developed by the author. The FARS approach is next used to analyze a frequency-domain numerical model of a dipole antenna, producing results similar to those for the SCF for a dipole of near-zero radius. Differentiating the decaying on-surface Poynting vector (PV) produces results comparable to those from FARS to explicitly demonstrate the power loss caused by radiation of the propagating current and charge. The lobed distributed radiated power is shown to be closely correlated with the square of the dipole current, confirming the cause of the radiation to be due to a partially reflected charge as the current and charge form standing waves on the dipole. Application of a time-domain version of FARS yields a smoothed length-wise distribution of radiated energy as opposed to the lobed variation of the frequency domain.

A microscale three-dimensional model of urban outdoor thermal exposure (TUF-Pedestrian).

Urban street design choices relating to tree planting, building height and spacing, ground cover, and building façade properties impact outdoor thermal exposure. However, existing tools to simulate heat exposure have limitations with regard to optimization of street design for pedestrian cooling. A microscale three-dimensional (3D) urban radiation and energy balance model, Temperatures of Urban Facets for Pedestrians (TUF-Pedestrian), was developed to simulate pedestrian radiation exposure and study heat-reducing interventions such as urban tree planting and modifications to building and paving materials. TUF-Pedestrian simulates the spatial distribution of radiation and surface temperature impacts of trees and buildings on their surroundings at the sub-facet scale. In addition, radiation absorption by a three-dimensional pedestrian is considered, permitting calculation of a summary metric of human radiation exposure: the mean radiant temperature (TMRT). TUF-Pedestrian is evaluated against a unique 24-h observational dataset acquired using a mobile human-biometeorological station, MaRTy, in an urban canyon with trees on the Arizona State University Tempe campus (USA). Model evaluation demonstrates that TUF-Pedestrian accurately simulates both incoming directional radiative fluxes and TMRT in an urban environment with and without tree cover. Model sensitivity simulations demonstrate how modelled TMRT and directional radiative fluxes respond to increased building height (ΔTMRT reaching -32°C when pedestrian becomes shaded), added tree cover (ΔTMRT approaching -20°C for 8m trees with leaf area density of 0.5 m2m-3), and increased street albedo (ΔTMRT reaching + 6°C for a 0.21 increase in pavement albedo). Sensitivity results agree with findings from previous studies and demonstrate the potential utility of TUF-Pedestrian as a tool to optimize street design for pedestrian heat exposure reduction.

Second-harmonic generation in the surface layer of a dielectric spheroidal particle: II. Analysis of the solution

The vectors used in the solution of the problem of second-harmonic generation in the surface layer of a dielectric spheroidal particle are explicitly expressed in terms of the basis vectors of the spherical, cylindrical, and Cartesian coordinate systems. Three-dimensional directivity patterns characterizing the spatial distribution of the generated radiation in the far-field region and its polarization are constructed. It is found that for a small size of a spheroidal particle, the directivity pattern due to each of the non-chiral components of the nonlinear dielectric susceptibility tensor has its own individual shape. A proportional increase in the linear dimensions of the particle leads to separation of several directions of predominant radiation with a high directivity in the directivity pattern. If the exciting radiation has a linear polarization, then the generated radiation due to one (any) of the independent components of the tensor is also linearly polarized. Mathematical properties characterizing the spatial distribution of the generated radiation in the far-field region and properties associated with the change of problem parameters are found for the functions used in the solution. A relationship between the symmetries of the directivity patterns of doubled-frequency radiation and the indicated properties is revealed. The conditions under which the generation of radiation does not occur and the conditions under which the generated radiation has a linear polarization are found. The above conditions are related to the features of the spatial distribution of the generated radiation and its polarization, illustrated in the directivity patterns. Methods for estimating the independent components of the nonlinear dielectric susceptibility tensor using these conditions are proposed. Keywords: second-harmonic generation, spheroidal dielectric particle, symmetry of the spatial distribution of radiation, conditions for the absence of generation, conditions for the generation of linearly polarized radiation.

Interconnected model with distributed thermal comfort for model based shading control

Modern buildings have a growing tendency to have large window fronts, with this design aspect leading to extensive solar heat gain and lighting in the rooms. Well-known thermal space models for control applications use simplifications of the spatial distribution of radiation and temperature. In this paper, a new modeling approach for efficient control of shading systems in rooms with large glass facades is presented and thermal comfort at multiple distributed positions in the room is more accurately captured. The idea of an interconnected system with submodels with lumped parameters and submodels with distributed parameters is introduced which can subsequently be used for model predictive control. With model-based shading control and the distributed thermal model presented, individual comfort control is possible at multiple positions in a room. The model is physically motivated, based on the material parameters and no calibration method is currently used, but realistic initial conditions are set for the simulations. Temperature variations due to incident solar radiation are included in the system part with distributed parameters and allow local thermal comfort measures. The resulting model is designed to be used in the context of model based shading control considering thermal comfort at multiple distributed locations. The introduced model is validated with simulations for temperature accuracy, distributed thermal comfort, and control characteristics. The main results are the interconnected model with additional benefits for distributed thermal comfort. Moreover, the presented modelling approach is designed for control applications, especially for model predictive control.

Nonlinear Thomson scattering of a relativistic elliptically polarized laser with varied incident pulse widths

Within the frame of classical electrodynamics, nonlinear Thomson scattering by a stationary electron of an elliptically polarized tightly focused laser has been investigated. The electron’s trajectory, energy gain, spatial radiation distribution and temporal characteristics are studied. Due to the properties of the elliptically polarized laser pulse, the energy curve is jagged and the trajectory of electrons is in an elliptical spiral shape. It is demonstrated that the net energy gain of the electron is nearly zero in the few-cycle domain, whereas the net energy gain increases as the laser has a larger pulse width. We describe a mechanism of electron energy gain variation during an elliptical polarized laser pulse. Furthermore, with pulse width increases, the spatial radiation distribution has more sets of local maxima and each set has four local maximums. Additionally, the results show that the electron has the potential to generate a single attosecond pulse when the laser has a few-cycle width pulse. The larger the pulse width is, the weaker the maximal radiation power will be.

First Application of an InfraRed Imaging Video Bolometer to Heliotron J Plasma

The spatial radiation distribution has been measured with an infrared imaging video bolometer (IRVB) in a neutral beam injected (NBI) plasma from the Heliotron J device. The temperature distribution on the IRVB foil is consistent with radiation simulated by the three-dimensional transport code, EMC3-EIRENE. The foil temperature increase is proportional to the radiation intensity measured with an Absolute eXtreme UltraViolet (AXUV) diode diagnostic. These results suggest that the IRVB can be used for plasma radiation measurements in small and medium size devices.

Spatial distribution of radiation from pulsed xenon gas-discharge lamps with different configurations of the plasma channe

The paper presents the results of studies of the spatial distribution of radiation from pulsed xenon lamps with a straight and U-shaped plasma channel configuration in the ultraviolet and near infrared spectral range. The dependence of the shape of the indicatrix on the design fea-tures of the flash lamp,the absorption coefficients of the plasma and the envelope limiting the discharge is shown.

Photometer for controlling the lighting parameters of LEDs

According to DSTU CIE 127:2017, control of characteristics of light-emitting diodes can be carried out in the laboratories of industrial or operational institutions with the use of working standards of radiation sources checked in the certified laboratories. The advantages of mass control of photometric characteristics of radiation sources are the following: higher speed and lower cost at a slightly lower but acceptable accuracy. In order to carry out mass control that meets the above requirements, in terms of production and operation, methods and technical means with a fairly high productivity, low cost of measurements and sufficient accuracy are required. The aim of the work is to solve an urgent problem – to increase the accuracy of measuring the light parameters of LEDs with a concentrated spatial distribution of luminous intensity and luminous flux for photometers without the use of rotating devices. It is shown that a photometer based on standard digital cameras, using a fiber optic focus and a correcting light filter, can provide sufficient accuracy in measuring the spatial distribution of radiation from directional light sources. Due to the use of a focon and matrix discrete photodetectors located in a plane perpendicular to the axial direction of radiation, it is possible to obtain an angular spatial distribution of light source radiation without rotating devices, which in turn reduces the cost of testing. The characteristics and ease of operation of modern digital cameras have allowed their use as a photodetector array, which simplifies the design of the photometer. The error of measuring the characteristics of sources with concentrated types of curves of light using a photometer in comparison with goniophotometric methods does not exceed 5%, which allows the use of such photometers for rapid control of such products in mass production and operating conditions.

Spatial distribution of radiation emitted by pulsed surface dielectric barrier discharge in air

The dynamics of radiation intensity at 337 nm emitted by the surface dielectric barrier discharge driven by 50 ns duration and 8 kV amplitude voltage pulse of both polarities has been analyzed experimentally and numerically. The calculations were performed in a 2D approach for experimental conditions to check the existing numerical models and understand what processes manage the discharge length and the spatial distribution of the discharge radiation intensity. Experimentally measured and numerically simulated profiles of radiation intensity along the discharge length notably differ from each other and the performed modification of the discharge physical model does not essentially change this difference. Radiation intensity from the discharge channel has been shown to be extremely sensitive primarily to the value of reduced electric field. We suppose that the discrepancy between experiment and numerical simulation could be due to 2D instead of 3D simulation and corresponding incorrect estimation of electric field distribution along the discharge channel. The numerical simulation of discharge length is in good agreement with experiment for the discharge stroke at the leading front of the voltage pulse and gives few times less values for the backward discharge at the trailing edge of the voltage pulse.

Uwarunkowania cyrkulacyjne ilości całkowitego promieniowania słonecznego docierającego do powierzchni ziemi w Polsce w latach 1986–2015 = Atmospheric circulation determinants of the amount of global solar radiation reaching the land surface in Poland in the years 1986–2015

Solar radiation is a key element of the Earth’s climate system and one of the most important variables in the energy balance of the active surface. The inflow of radiant energy to the Earth’s surface depends on the movement (circulation) of the atmosphere and on the associated changes in the amount of aerosols contained in the atmosphere as well as on cloudiness changes (which reduce the inflow of radiation to the Earth’s surface through reflection, dispersion and absorption processes). In that context, the work detailed in this paper had as its main aim a determination of the influence of atmospheric circulation on the amount of global solar radiation reaching the land surface in Poland. The research was based on source material from 1986–2015, originating from meteorological reanalyses and satellite products. Global solar radiation was analysed based on data from CM SAF satellite products, while atmospheric circulation types were designated with the use of modified version of the Lityński’s classification. Mean daily sums of radiation during individual circulation types, during A, 0, C macrotypes and on days with advection from particular directions were presented. Also the spatial distribution of radiation over the area of Poland during individual circulation types was shown. In the analyses special attention was paid to days with extremely large sums of solar radiation (above the 0.95 percentile). The largest daily sums of solar radiation are connected with anticyclonic circulation types, and the smallest ones – with cyclonic types. The largest mean daily sum of solar radiation occurs during south-western anticyclonic circulation, which is related to the significantly expanded Azores High. The smallest daily sums of solar radiation occur during cyclonic types, with advection of air masses from the north and east – in spring during NWC type, in autumn during EC type, in summer and winter during NEC type. The spatial distribution of solar radiation daily sums over the territory of Poland also depends on the circulation type. For most of the year, the circulation types with the northern and eastern components (N-NE-E) are associated with the reduction of the amount of solar radiation from north to south, while the inflow of air masses from the S-SW-W directions favours the reduction of radiation from south to north. Extremely large sums of solar radiation occur most probably during anticyclonic types with advection of air masses from SW, S and SE, and during the advectionless circulation 0A (conditional probability 0.13, 0.13, 0.11 and 0.10 respectively). The paper also demonstrates that the circulation type (i.e. prevailing pressure system) has a greater influence on daily sums of global solar radiation over Poland than the direction of air masses advection. The research results show that atmospheric circulation plays a significant role in determining the amount of solar radiation reaching the land surface in Poland.

Характеристики излучения короткодуговых ксеноновых газоразрядных ламп высокого давления

The paper is devoted to the study of changes in characteristics of ultra-high pressure short-arc xenon lamps when a tungsten layer is sprayed onto the quartz shell, as a result of heating and local electrode erosion. The paper analyzes the mechanisms of phenomena occurring in the super-high pressure xenon discharge and the cathode spot, which affect the sputtering of the electrode material. The main negative effects of tungsten deposits appearing on the lamp shell inner surface are considered: a decrease in the optical transparency and mechanical strength of quartz glass, an increase of the bulb temperature, a change in spectral characteristics and spatial distribution of radiation of a gas-discharge lamp. The original method developed for studying the parameters of radiation of a gas-discharge lamp and based on the superposition of the optical axis of the photometer with the axis of the lamp passing through the cathode spot and the considered shell segment, transparent or sprayed, allowed us to compare radiation characteristics of the lamp without changing the plasma parameters. The thermodynamic analysis carried out within the research confirmed the absence of chemical interaction of tungsten layer with quartz glass. Spectral distribution of xenon discharge radiation in the visible and IR ranges is different for a transparent bulb and the bulb with a tungsten spot, which is due to the size of tungsten layer particles on the lamp bulb. A study of spatial distribution of radiation from a gas-discharge lamp showed a decrease in the intensity of radiation in a solid angle bounded by a tungsten spot. At the same time, in this region, there was observed an increase in the temperature of the quartz shell, leading to the appearance of a longitudinal gradient of the temperature field of the gas-discharge lamp.

Speed of structured light pulses in free space

A plane monochromatic wave propagates in vacuum at the velocity c. However, wave packets limited in space and time are used to transmit energy and information. Here it has been shown based on the wave approach that the on-axis part of the pulsed beams propagates in free space at a variable speed, exhibiting both subluminal and superluminal behaviours in the region close to the source, and their velocity approaches the value of c with distance. Although the pulse can travel over small distances faster than the speed of light in vacuum, the average on-axis velocity, which is estimated by the arrival time of the pulse at distances z ≫ ld (ld is the Rayleigh diffraction range) and z > cτ (τ is the pulse width) is less than c. The total pulsed beam propagates at a constant subluminal velocity over the whole distance. The mutual influence of the spatial distribution of radiation and the temporal shape of the pulse during nonparaxial propagation in vacuum is studied. It is found that the decrease in the width of the incident beam and the increase in the central wavelength of the pulse lead to a decrease in the propagation velocity of the wave packet.

Radiation damage to undulator electronics at an electron accelerator

Experience gained from commissioning and operation of three elliptical polarization undulators (EPU) at the TPS taught us that undulator driving systems can behave erratically following a beam dump or loss. In this work, we discuss possible harmful radiation sources in a storage ring and analyse the effect of lack of electronic component radiation resistance in the system. According to measurements of spatial radiation distribution at the TPS, we propose solutions and an improved design for Phase-II EPUs.

EPR imaging of magnetic field effects on radiation dose distributions around millimeter-size air cavities

New hybrid radiotherapy treatment systems combining an MRI scanner with a source of ionizing radiation are being introduced in the clinic. The strong magnetic fields of MRI considerably affect radiation dose distributions, especially at tissue-air interfaces due to the electron return effect (ERE). Experimental investigation of the ERE within a sub-millimeter thick surface layer is still highly challenging.In the present work, we examine and quantify the magnetic field induced perturbations of dose distributions within a 0.5 mm layer surrounding millimeter-size air cavities by applying electron paramagnetic resonance imaging (EPRI).Air-filled fused quartz tubes (inner diameter 3 or 4 mm) mimic small air cavities and serve as model systems. The tubes were irradiated inside a PMMA phantom by a 6 MV photon beam. The irradiations were performed in the presence or absence of a transverse, magnetic field providing a magnetic field strength of 1.0 Tesla. The spatial distributions of radiation induced paramagnetic defects in the quartz tubes were subsequently determined by applying field-swept echo-detected EPRI and were then converted to relative dose distributions.The transverse magnetic field leads to considerable local dose enhancements and reductions (up to 35%) with respect to the mean dose within the quartz tubes. The experimentally determined dose distributions are in good quantitative agreement with Monte Carlo radiation transport simulations.The results of this work demonstrate the feasibility of field-swept echo-detected EPRI to measure magnetic field induced perturbations of dose distributions within a sub-millimeter thick surface layer at the dosimeter-air interface.

A Study of Plasmon-Coupled Fluorescence of Rhodamine 6G on Thin Nickel Films

Plasmon-coupled luminescence of rhodamine 6G dye molecules on a thin nickel film has been studied experimentally and theoretically. The spatial distribution of fluorescence of dye molecules, which is calculated using the transfer matrix method for describing flat-layered media, is in good agreement with the experimental diagrams obtained for the spatial distribution of radiation with different polarization. The coupling efficiency between the luminophore and nickel film plasmons is experimentally determined.

Goniometric complex for investigation the optical characteristics of radiation of luminescent structures

In this paper we describe an automated goniometric complex for investigation the optical characteristics and them spatial distribution of luminescent structures.On the market most instruments for measuring of the spatial distribution of radiation are designed for commercial light sources, such as LEDs, incandescent lamps, fluorescent lamps. Often scientific research requires measurements of the spatial distribution of emitted or scattered radiation upon excitation by external laser radiation. Therefore, the device for these measurements was designed and manufactured. In the article the design and principle of operation of the complex are described and its main technical characteristics are presented. During metrological certification specially developed five reference LEDs with different spectral characteristics were used to ensure traceability to the national measurement standards of the Republic of Belarus. The automated goniometric complex allows one to measure the spatial distribution of luminescence and scattering radiation with external laser excitation in the units of the spectral irradiance, luminous flux, chromaticity coordinates and correlated color temperature.The main metrological characteristics of the complex: spectral range — from 396 nm to 753 nm with a spectral resolution of 0.5 nm; power spectral density measurement range — from 3.5∙102 W/m3 to 1∙106 W/m3 in the spectral range from 400 nm to 750 nm with relative combined standard uncertainty of 7.8 %; chromaticity coordinate measurement range for coordinate x from 0.088 to 0.676, for coordinate y — from 0.160 to 0.715, with relative combined standard uncertainty of 5.5 % for coordinate x and 8.4 % for coordinate y; measurement range of correlated color temperature — from 2000 K to 7000 К with relative combined standard uncertainty of 9.3 %; luminous flux measurement range — from 0.6 lm to 35.0 lm with relative combined standard uncertainty of 9.3 %; rotation angle — from minus 90° to plus 90° in tangential direction and from minus 180° to plus 180° in radial direction with angular resolution of 0.5°.Measurement results are processed by specially developed software. Results can be presented in the form of three-dimensional diagrams for selected units of measurement or in form of a text file.

Effect of spatial radiation distribution on photocatalytic oxidation of methylene blue in gas-liquid-solid mini-fluidized beds

Radiation intensity is commonly assumed to be the same for simplification in a lab-scale photoreactor, however, the radiation along propagating direction attenuates exponentially owing to the absorption and scattering of photons by catalysts and bubbles. Hence, it is necessary to develop a model that can predict the spatial radiation distribution (SRD), which is a critical factor in designing industrial-scale photoreactors. In this study, a SRD model was developed to compute the radiation intensity as a function of the volume fraction of the medium and the distance between the observation point and the source. Subsequently, numerical simulations and analyses for the gas-liquid-solid mini-fluidized bed were performed by coupling the proposed SRD model with the reaction kinetic model based on a three-dimensional hybrid Euler-Lagrange method. The simulation results fit well with experimental data. Furthermore, the radiation intensity and the hydrodynamic factors exert different impacts on the degradation ratio with increasing reaction time, respectively. Under low concentration, the main influence on the degradation ratio is hydrodynamics, including reactant mass fraction, air volume fraction and catalyst volume fraction. The developed model is of potential value in industrial photocatalytic reactors.