Distribution Of Radiation Intensity Research Articles

Mobile robot for radiation mapping in indoor environment

Radiation mapping is the process of measuring radiation intensity level at distributed sampling points in a predefined region of interest (ROI). This procedure is crucial in any radiological related emergency to locate contamination hotspot(s) or in routine inspections in any radiation facilities. When workers knowingly enter a high radiation zone to perform radiation mapping, they are exposed to the risk of radiation exposure. Mobile robot is a potential solution that could eliminate the health and safety risk and subsequently improve the measurement accuracy. This paper reports implementation of mobile robot for radiation mapping by using a commercial mobile robot platform, Turtlebot2 in conjunction with Robot Operating System (ROS). Mobile robot is capable to generate physical map of the targeted environment by using Simultaneous Localization and Mapping (SLAM). Simultaneously, Geiger Muller detector is utilized to perform radiation measurement. The radiation data is directly plotted on the physical map hence the radiation intensity distribution throughout the ROI could be assessed. Functionality of the radiation mapping robot is evaluated in real-world experiments and the results will be presented in the paper.

An In-situ and Direct Confirmation of Super-Planckian Thermal Radiation Emitted From a Metallic Photonic-Crystal at Optical Wavelengths

Planck’s law predicts the distribution of radiation energy, color and intensity, emitted from a hot object at thermal equilibrium. The Law also sets the upper limit of radiation intensity, the blackbody limit. Recent experiments reveal that micro-structured tungsten can exhibit significant deviation from the blackbody spectrum. However, whether thermal radiation with weak non-equilibrium pumping can exceed the blackbody limit in the far field remains un-answered experimentally. Here, we compare thermal radiation from a micro-cavity/tungsten photonic crystal (W-PC) and a blackbody, which are both measured from the same sample and also in-situ. We show that thermal radiation can exceed the blackbody limit by >8 times at λ = 1.7 μm resonant wavelength in the far-field. Our observation is consistent with a recent calculation by Wang and John performed for a 2D W-PC filament. This finding is attributed to non-equilibrium excitation of localized surface plasmon resonances coupled to nonlinear oscillators and the propagation of the electromagnetic waves through non-linear Bloch waves of the W-PC structure. This discovery could help create super-intense narrow band thermal light sources and even an infrared emitter with a laser-like input-output characteristic.

Numerical Study of the Discharge Spatial Characteristics Influence on the KrF Laser Generation

A self-consistent two-dimensional model of the discharge KrF laser on Ne/Kr/F2 gas mixtures is described. The model predictions are compared with the experimental results for a KrF laser with an excitation pulse duration of ~ 30 ns. An agreement within 10% for the discharge current and laser energy is obtained. Evolution of the discharge width and of the radiation intensity distribution between the electrodes over the time of a radiation pulse is demonstrated. In addition, the effect of the electrode radii on laser energy is analyzed.

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.

Analysis of the thermal efficiency of a compound parabolic Integrated Collector Storage solar water heater in Kerman, Iran

This paper presents an experimental study involving the design, manufacturing and testing of a prototype integrated collector storage (ICS) solar water heater (SWH) in combination with a compound parabolic concentrator (CPC). The thermal efficiency of the developed system is evaluated in Kerman (latitude 30.2907° N, longitude 57.0679° E), Iran. The developed system is intended to supply hot water for a family in remote rural areas. A 6-month experimental study was undertaken to investigate the performance of the ICS SWH system. The mean daily efficiency and overnight thermal loss coefficient of each experiment were analyzed to examine the appropriateness of these collectors for regions in Kerman. The results showed that mirror has the highest mean daily efficiency (66.7%), followed by steel sheet (47.6%) and aluminum foil (43.7%). The analysis of hourly and monthly operation diagrams for variations of water temperature for the developed ICS system showed that by increasing the amount of radiation entering the water heater, the thermal efficiency of the system decreases, such that the highest efficiency was in April and the lowest in July. With the distribution of radiation intensity in the months of August and September, the thermal efficiency of the system increased. This regional study illustrates how selecting a proper concentrator can increase the thermal efficiency of this solar-based system. It also shows how the temperature gradient between the ambient air and internal water in the storage tank can influence the performance of such systems, and how a controlled amount of hot water withdrawal can affect the system’s efficiency. Developing the ICSSWH system is an ideal sustainable solution in countries that benefit from a large amount of solar intensity.

A self-consistent model of second harmonic generation of laser radiation in the periodically poled nonlinear-optical crystal conditioned by its nonuniform heating

We introduce a self-consistent model that describes the process of the second harmonic generation (SHG) of the laser radiation in a nonlinear-optical crystal in conditions of its nonuniform heating induced by optical absorption. A periodically poled crystal pumped by the pulse laser radiation focused into its center was considered. The iteration procedure of solving the SHG problem relies on the interrelated solution of two equation systems describing the temperature dependent SHG and the heat conduction processes. The heat sources are represented by the absorbed power of both pump and generated radiations. Along with the absorption of pump and generated waves the diffraction effect was also taken into account. Eventually the resulting distribution of the crystal temperature should correspond to the radiation intensity distributions of pump and second harmonic.

The spatial and angular domain decomposition method for radiation heat transfer in 2D rectangular enclosures with discontinuous boundary conditions

To remedy discontinuous boundary conditions, we propose the spatial and angular domain decomposition approach for the solution of radiative transfer equation (RTE) in a two-dimensional rectangular enclosure. The RTE is angularly and spatially discretized. For each spatial node, the total solid angle 4π is decomposed into several angular sub-domains according to the distribution of discontinuous boundaries, and the quadrature weighting factors are recalculated for each angular sub-domain by using the compound trapezoidal integral scheme. For each angularly-discretized direction, the spatial domain is decomposed into a few spatial sub-domains according to the distribution of discontinuous boundaries. In each spatial sub-domain the distribution of radiative intensity is continuous, and the angularly-discretized RTE is solved for each spatial sub-domain. Two examples are employed to verify the performance of the domain decomposition method, and the results confirm its suitability and advantage for treating radiative transfer problem with discontinuous boundary conditions.

Study of reflectors for illumination via conformal maps

We present an approach for the study and design of reflectors with rotational or translational symmetry that redirect light from a point source into any desired radiant intensity distribution. This method is based on a simple conformal map that transforms the reflector's shape into a curve that describes light's direction after reflection. Both segmented reflectors and continuous reflectors are discussed, illustrating how certain reflector characteristics become apparent under this transformation. This method can also be used to study extended sources via translations.

A Smart Window for Angular Selective Filtering of Direct Solar Radiation

Abstract Thin-film grating coatings are proposed for smart windows to angular selective filtering of solar radiation. The gratings are formed by absorptive, reflective, or scattering parallel strips (made of chromogenic or other materials) alternating with directionally transmissive strips (untreated surface of pure glass) on two surfaces of the window pane(s). The smart window with grating optical filter has angular selective light transmission and partially or completely blocks the direct solar radiation in a preset angular range and transmits the scattered and reflected radiation without using the daylight redistribution devices. The results of numerical simulation and experimental confirmation of optimum slope angle of the strips on the pane(s), their widths, and relative position on two surfaces to minimize the directional light transmission of the window at the preset date and time of day taking into account orientation of the window to the cardinal, the latitude of the building, and the seasonal and daily distribution of the solar radiation intensity are demonstrated.

Measurements of Temperature and Emissivity Distributions on a High-Temperature Surface Using an Auxiliary Light Source Method

A method to simultaneously measure two-dimensional temperature and emissivity distributions on high-temperature diffuse surfaces is developed using an auxiliary light source. The high-temperature diffuse surface is irradiated from the hemispherical space with the auxiliary light source switched “on” or “off.” Two images of the effective radiation intensity are obtained in quick succession for the two states to determine the temperature and emissivity distributions. The measurement method and uncertainty models show that the effect of the unknown emissivity on the accuracy of the temperature field measurement can be eliminated. The optical pyrometer is a color charge coupled device (CCD) sensor with a quartz lamp array used as the auxiliary light source to illustrate the measurement method. An oxidized W–Ni–Fe alloy sample is heated at high temperatures of 600–1000 °C by a 700 W induction-heating device. The distributions of the effective radiation intensities from the sample surface during the “on” and “off” states of the lamp array are measured in the three color channels (R, G, and B channels) to calculate the temperature and emissivity distributions. The temperature measurement uncertainties are less than 4 °C for a temperature range of 600–900 °C. The temperature measurements are experimentally validated by the thermocouple method only with a small temperature difference. The emissivities calculated from the three color channels are very close with a range of 0.855–0.957. The relative uncertainties in the emissivities for channels R and G are less than 2.0%, while the relative uncertainty for channel B data was higher at 2.8% and 7.5% due to lower measurement signals in channel B. This analysis may provide a useful method for measuring the temperatures of high-temperature diffuse surfaces by successfully compensating for the effects of unknown or changing emissivities.

Experimental study of the filamentation phenomenon and measurement of filaments parameters

The article experimentally investigated the phenomenon of filamentation in the propagation of femtosecond laser radiation in transparent solid media. The experimental scheme for measuring the parameters of filaments using spherical and cylindrical optics was developed and assembled. A series of experiments on the spatial ordering of filaments was carried out. The sample was structured in the filamentation mode with a predetermined distribution of laser radiation intensity. The spatial redistribution of laser radiation passing through the formed structures in the quartz glass sample is also investigated.

Nanoparticle-based solar vapor generation: An experimental and numerical study

Steam generation by nanofluid under solar radiation has attracted intensive attention recently. Due to strong absorption of solar energy, nanoparticle-based solar vapor generation could have wide applications in many areas including desalination, sterilization and power generation. Steam generation of different concentrations of gold nanoparticle dispersions under focused sunlight of 5 sun and 10 sun were performed in this work. A numerical model combining radiative heat transfer, moisture transport, and laminar flow was established to investigate the temperature profile, evaporation rate above the surface and radiative intensity distribution inside the nanofluid. It was found that localized energy trapping at the surface of nanofluid was responsible for the fast vapor generation. To convert more solar radiative energy into latent heat of water (i.e., to vaporize water) at the surface, a new method was proposed to optimize the range of nanofluid concentration and optical depth for future solar vapor generator design.

Sun Simulator for Indoor Performance assessment of Solar Photovoltaic Cells

This paper presents systematic design procedure and features of a sun simulator developed for testing low concentrating linearly focusing solar photovoltaic concentrators. The designed solar simulator comprises of a xenon short arc lamp and paraboloidal reflector for uniform radiative flux distribution on focal plane at desired radiation intensity. Initial inputs to the design process include reflector geometry (shape and size), surface properties of the reflector surface (reflectivity), distance of the reflector aperture from the illuminated area, rated lamp power, lamp geometry and orientation. These specifications were inputted in a ray tracing analyzer using COMSOL Multiphysics. The angular distribution of radiative intensity from the lamp was also accounted for. The proposed design is able to deliver a radiative intensity of 500 W/m2 to test photovoltaic concentrators with aperture of up to 140 mm x 50 mm with a spatial non-uniformity of 4.5%.

Selecting the best piping arrangement for scaling-up an annular channel reactor: An experimental and computational fluid dynamics study

This study is focused on the selection of the best piping arrangement for a pilot scale annular channel reactor intended for the remediation of waters and wastewaters. Two annular channel reactors composed of a single UV lamp and distinct piping arrangements were considered: (i) a novel reactor with tangential inlet/outlet pipes – the FluHelik reactor, and (ii) a conventional Jets reactor. These two reactors were manufactured at lab scale and characterized in terms of residence time distribution (RTD), radiant power and ability to degrade aqueous solutions spiked with a model compound – 3-amino-5-methylisoxazole (AMI) – by H2O2/UVC and UVC processes. Computational fluid dynamics (CFD) simulations were used to assess the hydrodynamics, RTD and UV radiation intensity distribution of both reactors at pilot scale. In general, experimental results at lab scale revealed quite similar RTDs, radiant powers and AMI degradation rates for both reactors. On the other hand, CFD simulations at pilot scale revealed the generation of a helical motion of fluid around the UVC lamp in the FluHelik reactor, inducing: (i) a longer contact time between fluid particles and UV light, (ii) more intense dynamics of macromixing as a result of larger velocity gradients, turbulent intensities and dispersion of RTD values around the peak, and (iii) a more homogeneous UV radiation distribution. In addition, the design of the FluHelik reactor can favor the implementation of various reactors in series, promoting its application at industrial scale. The FluHelik reactor was chosen for scaling-up. A pre-pilot scale treatment unit containing this reactor was constructed and its feasibility was proven.

Optimized Angular Selective Filtering of Direct Solar Radiation

A method to optimize angular selective filtering of direct solar radiation by minimization of the directional light transmission of a window at preset date and time of day, taking into account the geographical coordinates of building, the trajectory of the sun, the seasonal and daily distribution of radiation intensity, and the azimuth of the window is proposed. The minimum light transmittance is ensured by application of an optical filter with two sloped surface gratings at the expense of optimum slope angle of filter’s gratings on the window pane(s), widths of transmissive and non-transmissive strips of both gratings, and their mutual arrangement. Results of determination of the optimum slope angles of filter’s gratings at the different dates, azimuths of the window, latitudes, refractive indices and distances between filter’s gratings are demonstrated.

Comparative Analysis of Errors in Monitoring the Earth’s Global Energy Budget by the Lunar Observatory and Orbiters

The errors in measurements of the energy of the reflected solar radiation and the thermal radiation emitted from Earth entering space in all directions from the top of the atmosphere are analyzed. The potentials of measurements onboard the Lunar Observatory (LO) and spacecraft (SC) on geostationary and solar-synchronous orbits and at the L1 Lagrange point of the Sun–Earth system (SEL1) are compared. To take into account the radiation from the edge of the Earth’s disk, which cannot be observed from a geostationary orbiter at all phase angles, theoretical models should be constructed. The intensity distribution of radiation reflected to space through all other directions in dependence on the surface type, the radiation incidence angle, and the observation angle is also modeled. The actual inaccuracy of these methods is approximately 1%. At the SEL1 point, a SC may simultaneously observe the whole surface of the planet only at a phase angle α = 0° and only in the periods when the Moon does not eclipse the Earth’s disk. To take into account the radiation reflected to space at all other phase angles, it is necessary to construct theoretical models. This fact, as well as the lack of observations during lunar eclipses of the Earth, is connected with large errors in the required quantities. The system of two optical robotic telescopes mounted on the LO will sequentially survey the Earth’s surface almost in all ranges of phase angles. The annual averages of the Bond albedo and the emitted thermal radiation of the Earth as a planet determined at the LO and the corresponding deviations of the annual average global energy budget of the planet from the equilibrium state will be almost an order of magnitude more accurate than those determined from the data of any orbiter.

Spectral radiative properties of skeleton inner structure of ceramic foam based on ordered opal structure model

In this work, three dimensional periodic ordered opal structures are used to model the inner structures of skeleton of porous ceramic foam. The radii of close-packed spheres range from 0.7 µm to 1.7 µm. The spectral radiative properties are predicted by applying the FDTD method to analyze the radiative transfer inside the skeleton. The characteristics of reflection spectra and transmission spectra with increasing incident wavelength are analyzed, including the different feature regions constituting the variation curves and the red shift of variation curve with growing size of close-packed spheres. The values and characteristics of absorption peaks surrounding the locations where size parameters are approximate to 1 are compared. The BSDF of scattering power are calculated further. The transformation of transmission in incident direction and reflection in mirror direction is shown. Then, the distribution of radiation intensity in cross sections parallel to the incident light are compared and the variety from uniform distribution to anisotropic periodic distribution is summarized. The prediction and analysis are benefit to further researches about the radiative transfer inside the porous ceramic foam.

Local burst model of CMB temperature fluctuations: luminescence in lines of primary para- and orthohelium

We have considered the formation of the luminescent subordinate HeI lines by the absorption of continuum radiation from a source in the lines of the main HeI series in the expanding Universe. It is suggested that at some moment of time, corresponding to the redshift z0, a burst of superequilibrium blackbody radiation with a temperature T + ΔT occurs. This radiation is partially absorbed at different z < z0 in the lines of the main HeI series and then converted into the radiation of subordinate lines. If νij is the laboratory frequency of the transition of some subordinate line originating at some z, then in the present time its frequency will be ν = νij/(1 + z). For different z (and, consequently, for different ν), the quantum yield for the subordinate lines of para- and orthohelium - the number of photons emitted in the subordinate line, per one initial excited atom and line profiles are calculated. Different pumping channels were considered. Spatial and angular distributions of radiation intensity of luminescent lines for the spherically symmetric radiation sources are presented. It is shown that for sufficiently large ΔT/T, the luminescent lines can be very noticeable in the spectrum of blackbody background radiation.

Optimized angular selective filtering of direct solar radiation.

A method to optimize the angular selective filtering of direct solar radiation by minimization of light transmission of a window at a preset date and time of day, taking into account the orientation of the window to the cardinal, the latitude of the building, and the seasonal and daily distribution of solar radiation intensity, is described. Optimization is carried out using an optical filter with two thin-film surface gratings with alternating transmissive and non-transmissive parallel strips. The optimal slope angle of the strips to horizontal, the widths of the strips, the shift of input and output gratings relative to each other, and the angular characteristics of light transmittance are calculated.

Study of the Filamentation Phenomenon of Femtosecond Laser Radiation

The filamentation phenomenon during propagation of femtosecond laser radiation in transparent solid media is experimentally studied. An experimental scheme for measuring the filament parameters using spherical and cylindrical optics is developed and assembled. The sample is structured in the filamentation mode, which makes it possible to obtain a specified distribution of laser radiation intensity.