Measurement Of Flux Distribution Research Articles

Optical characterization of a solar concentrating dish system

Solar dishes concentrate the quasi-collimated sun light towards a focal point. Typically, the optical characterization consists of experimental flux map measurements and Monte-Carlo ray-tracing (MCRT) simulations, which are fitted based on experimental data and serve for the prediction of the distribution of the irradiation in receivers or reactors. However, the MCRT simulations usually rely on idealized mirror geometries (i.e. parabolic mirrors), neglecting the actual dish geometry resulting from its construction method (such as petals, facets or segments). Thus, the parameter fitting might yield unrealistic parameters and local radiative flux peaks (“hot spots”), which are often experimentally detected behind the focal plane, cannot be predicted. Here, we characterized the 7m diameter solar dish at EPFL comprising 27 petals with a nominal focal length of 3.8 m and a rim angle of 50.3°. The measured peak concentration was 1781 suns and the received integrated solar power was 20.0 kW over an 18 cm diameter spot. We proposed an advanced geometry approach for the MCRT model considering the curvature of the dish, i.e. geometries mathematically described by a parabola with an exponent not equal, but close to 2. The advanced geometry approach was then applied for predicting experimentally measured flux distribution in focal and off-focus planes. The fitted reflectivities were 70% and 86% for the idealized and advanced geometry approach, respectively. The idealized geometry approach found an unrealistically low value whereas the advanced geometry approach’s value was within 1% of the manufacturer’s specification. The advanced geometry approach predicted a parabola exponent of 1.94, which emphasizes that the best geometry to describe the solar dish deviates from a perfect paraboloid. We conclude that MCRT models should consider non-perfect parabolic geometries for solar dishes in order to obtain more realistic values for the fitted parameters.

Measurement of flux distribution of an AmBe neutron source and estimation of two group integral capture cross-sections

Neutron capture cross sections of elements are of utmost importance in reactor physics, dosimetry applications and stellar nucleosynthesis studies. Manipal Centre for Natural Sciences (MCNS) possesses a 16Ci AmBe neutron source, which is housed inside a concrete structure. The neutrons undergo multiple scattering events in the concrete structure and surrounding materials; therefore, the neutron flux profile is unique to this source and structural material, which differs from the standard ISO spectrum. Using this AmBe source, experiments are being conducted to understand the neutron energy distribution in two groups to measure capture cross sections of various isotopes. In the present work, gold has been used as a flux monitor, and the indium cross-section has been measured in two groups. These foils (Gold and Indium) are irradiated with and without cadmium cover to understand the neutron spectra in two spectral regions as cadmium cutoffs neutrons of energy below 0.5 eV. Irradiated samples were counted in High-Pure Germanium (HPGe) detector, and the γ-spectra obtained were used to get the epi‑cadmium (0.5 eV and above) to total ratio of ⟨σ(E)ϕ(E)⟩. The neutron flux is estimated in two groups corresponding to thermal (thermal energy neutron extended up to 0.5 eV) and epi‑cadmium regions, and also the flux-weighted capture cross sections of 115In are determined.

Characterization and Deviation Analysis of a High-Flux Solar Simulator With Metal-Halide Lamps

Abstract Utilizing highly concentrated solar power for thermochemical processing as one of the extraterrestrial in situ resource utilization (ISRU) applications has been highlighted as an essential technique to support deep-space exploration in the future. Multi-source high-flux solar simulators (HFSSs) are widely employed to provide stable irradiance for indoor solar thermal experiments. Meanwhile, numerical modeling that can characterize the radiation transport mechanisms within the solar thermal system has been developed for performance evaluation before field trials. However, significant differences between simulated and measured flux distributions were shown for existing models developed based on the Monte-Carlo ray-tracing (MCRT) method, which has been attributed to only one or two specific reasons. In this paper, we proposed a comprehensive analysis of the concentration characteristics of a 42 kW metal-halide lamp HFSS, developed at Swinburne University of Technology, considering the effect of five aspects. The flux distribution, uniformity, and vector distribution under different configurations were compared to quantify the influence of these factors on receiving irradiance. The suitable arc size, reflector shape, and reflector surface properties of the existing HFSS have also been numerically determined to improve the model and reduce the root mean square error (RMSE) for the lamp array from 38.2% to 8.3%. This research provides a potential pathway to numerically predict the radiation transfer performance of HFSSs and determine the suitable configuration for desired solar thermochemical applications.

Axis-symmetric diesel spray flame model coupled with momentum flux distribution measurement and improved soot phi-T map

An axis-symmetrical diesel spray flame model coupled with momentum flux distribution measurement was developed as a tool for nozzle orifice development. Momentum flux distributions at several distances from the nozzle orifice exit are measured by a force sensor with a small-diameter aperture which traverses a cross-section. A theoretical momentum flux profile is determined by fitting with the measured momentum flux profile at the cross-section. The spray velocity profile and equivalence ratio profiles are quantified from the theoretical momentum flux profile. By interpolating the profiles of the measured cross-sections, the axis-symmetrical diesel spray flame model can calculate the equivalence ratio and other physical values as a function of the distance from the nozzle exit ( x) and the radius from the spray axis ( r). The equivalence ratio distribution in a cross-section involving the spray axis is converted into soot formation and oxidation distribution by coupling with the improved soot ϕ -T map. The conventional soot-NOx ϕ -T map did not show the borderline between the soot formation and oxidation. To quantify the residence time of the fuel element during soot formation, the narrow soot peninsula was expanded up to its maximum by replacing the soot yield with the soot particle diameter. Instead of contour lines for the of NO mole fraction, contour lines for the OH mole fraction were implemented to reveal the border between soot formation and soot oxidation on the ϕ -T map. The borderline appears clearly, consisting of a horizontal line in the lower-temperature region and a rising line in the higher-temperature region. The converted soot formation and oxidation regions in the axis-symmetric spray flame model exhibit a strong correlation with the measured soot distributions in a quasi-steady diesel spray flame. The shear-stress, which induces turbulence affecting soot formation/oxidation, is also quantified from the velocity distribution.

Euclid preparation

The European Space Agency's Euclid mission will provide high-quality imaging for about 1.5 billion galaxies. A software pipeline to automatically process and analyse such a huge amount of data in real time is being developed by the Science Ground Segment of the Euclid Consortium; this pipeline will include a model-fitting algorithm, which will provide photometric and morphological estimates of paramount importance for the core science goals of the mission and for legacy science. The Euclid Morphology Challenge is a comparative investigation of the performance of five model-fitting software packages on simulated Euclid data, aimed at providing the baseline to identify the best-suited algorithm to be implemented in the pipeline. In this paper we describe the simulated dataset, and we discuss the photometry results. A companion paper is focussed on the structural and morphological estimates. We created mock Euclid images simulating five fields of view of 0.48 deg2 each in the IE band of the VIS instrument, containing a total of about one and a half million galaxies (of which 350 000 have a nominal signal-to-noise ratio above 5), each with three realisations of galaxy profiles (single and double Sérsic, and 'realistic' profiles obtained with a neural network); for one of the fields in the double Sérsic realisation, we also simulated images for the three near-infrared YE, JE, and HE bands of the NISP-P instrument, and five Rubin/LSST optical complementary bands (u, g, r, i, and z), which together form a typical dataset for an Euclid observation. The images were simulated at the expected Euclid Wide Survey depths. To analyse the results, we created diagnostic plots and defined metrics to take into account the completeness of the provided catalogues, as well as the median biases, dispersions, and outlier fractions of their measured flux distributions. Five model-fitting software packages (DeepLeGATo, Galapagos-2, Morfometryka, ProFit, and SourceXtractor++) were compared, all typically providing good results. Of the differences among them, some were at least partly due to the distinct strategies adopted to perform the measurements. In the best-case scenario, the median bias of the measured fluxes in the analytical profile realisations is below 1% at a signal-to-noise ratio above 5 in IE, and above 10 in all the other bands; the dispersion of the distribution is typically comparable to the theoretically expected one, with a small fraction of catastrophic outliers. However, we can expect that real observations will prove to be more demanding, since the results were found to be less accurate for the most realistic realisation. We conclude that existing model-fitting software can provide accurate photometric measurements on Euclid datasets. The results of the challenge are fully available and reproducible through an online plotting tool.

Experimental Measurement of Solar Radiation Energy Flux Distribution on Curved Surfaces

Experimental Measurement of Solar Radiation Energy Flux Distribution on Curved Surfaces

Mountain Muon Tomography Using a Liquid Scintillator Detector

Muon tomography (MT), based on atmospheric cosmic rays, is a promising technique suitable for nondestructive imaging of the internal structures of mountains. This method uses the measured flux distribution after attenuation, combined with the known muon angular and energy distributions and a 3D satellite map, to perform tomographic imaging of the density distribution inside a probed volume. A muon tomography station (MTS) requires direction-sensitive detectors with a high resolution for optimal tracking of incident cosmic-ray muons. The spherical liquid scintillator detector is one of the best candidates for this application due to its uniform detection efficiency for the whole 4π solid angle and its excellent ability to distinguish muon signals from the radioactive background via the difference in the energy deposit. This type of detector, with a 1.3 m diameter, was used in the Jinping Neutrino Experiment (JNE). Its angular resolution is 4.9 degrees. Following the application of imaging for structures of Jinping Mountain with JNE published results based on the detector, we apply it to geological prospecting. For mountains below 1 km in height and 2.8 g/cm3 in the reference rock, we demonstrate that this kind of detector can image internal regions with densities of ≤2.1 g/cm3 or ≥3.5 g/cm3 and hundreds of meters in size.

Microstructures and properties of CrxFeNi(3-x)Al high-entropy alloys

Muon tomography (MT), based on atmospheric cosmic rays, is a promising technique suitable for nondestructive imaging of the internal structures of mountains. This method uses the measured flux distribution after attenuation, combined with the known muon angular and energy distributions and a 3D satellite map, to perform tomographic imaging of the density distribution inside a probed volume. A muon tomography station (MTS) requires direction-sensitive detectors with a high resolution for optimal tracking of incident cosmic-ray muons. The spherical liquid scintillator detector is one of the best candidates for this application due to its uniform detection efficiency for the whole $4\pi$ solid angle and its excellent ability to distinguish muon signals from the radioactive background via the difference in the energy deposit. This type of detector, with a 1.3~m diameter, was used in the Jinping Neutrino Experiment~(JNE). Its angular resolution is 4.9~degrees. Following the application of imaging for structures of Jinping Mountain with JNE published results based on the detector, we apply it to geological prospecting. For mountains below 1~km in height and 2.8~${\rm g}/{\rm cm}^3$ in the reference rock, we demonstrate that this kind of detector can image internal regions with densities of $\leq$ 2.1~${\rm g}/{\rm cm}^3$ or $\geq$ 3.5~${\rm g}/{\rm cm}^3$ and hundreds of meters in size.

Measurement and modeling of planar airblast spray flux distributions

A liquid sheet breaks up into drops by fast air streams at airblast type atomizers, which are widely utilized for jet engines. Fuel spray flux in space directly determines the local mass ratio of fuel to air inside a combustion chamber. However, it has been difficult to measure the quantitative spatial distribution of spray flux using laser techniques and mechanical patternators. Therefore, in the present study, we have developed a new shape of 3D printed patternator applicable to the measurement of spray flux distribution by a planar airblast atomizer, and quantitative data are presented at the conditions of gas velocity up to 100 m/s with changing atomizer configuration and liquid species as water and kerosene. Laser technique of Phase Doppler Anemometer and high-speed visualization are complementary conducted with theoretical investigation. The experimental results of spray flux distributions are consistently normalized by the proposed dimensionless injection condition based on the square root of momentum ratio of spreading drops to gas stream. The applicable limit of the present modeling framework is given by Weber number based on the ratio of inertia of gas stream to liquid surface tension.

Development of a special purpose LED ultraviolet lamp in a T8 flask

Fluorescent tubular ultraviolet lamps are used in medicine, industry, cosmetology, forensic science, and banking. During the development of the LED ultraviolet lamp in a T8 flask, a comparison of its lighting characteristics (power, energy flux, spectral distribution of radiation) with the parameters of special-purpose fluorescent lamps produced at industrial enterprises has been carried out. The design of the LED lamp includes a glass uviole tube with a diameter of 26 mm and a length of 322 mm (wall thickness is 1 mm, glass grade - SL97-3). For precise installation of the lamp in the irradiation facility and supplying electric power to it, plastic caps of the G13 pin type (the distance between the electrical contacts is 12.7 mm) are used. Measurements of electrical parameters, energy flux and spectral distribution of radiation have been carried out at nominal mains voltage on a Gooch &Housegophotocolorimetric measuring device. The developed LED lamp consumes seven times less electricity, has significantly longer (five times) expected service life and is a safer source of ultraviolet radiation, since it does not contain harmful vapors of mercury and its compounds. The LED ultraviolet lamp in a T8 flask can be used instead of the manufactured LUFT-10 lamps for special purposes, namely, in irradiators for carrying out technological processes (photochemical reactions, drying, curing), for attracting and disinsecting insects in traps, in photocopiers.

Stator End-Winding Thermal and Magnetic Sensor Arrays for Online Stator Inter-Turn Fault Detection

In this paper, two novel stator inter-turn fault sensing schemes, based on infrared (IR) thermopile sensor array (IRSA) and Hall-effect sensor array (HESA) are proposed. These circular sensing arrays are mounted along the inner wall of the stator's casing facing the end-winding region. This enables a direct measurement of temperature and magnetic flux distribution along the end-winding region in a non-contact way. Thus, the deviation in thermal and magnetic symmetry introduced by an inter-turn short circuit fault can be readily assessed. The proposed sensing schemes provides an intuitive and straight forward approach to inter-turn fault monitoring compared to the conventional methods, which depend on detecting fault induced secondary effects on external signals (motor currents, casing vibration, and temperature). The practicality and the diagnostic ability of the end-winding sensor array approaches in detecting the stator inter-turn faults is demonstrated using a 1.5 kW induction motor test rig. Compared to IRSA, HESA is found to be more versatile and with better early fault detection capability. Hence, an embedded online monitoring algorithm based on HESA is developed and demonstrated using the test rig.

Experimental study of jet fire radiation and a new approach for optimizing the weighted multi-point source model by inverse methods

The present study brings new experimental data on radiation from subsonic jet fires and proposes a new method for employing the inverse analysis technique to optimize the weighting coefficients of the multi-point model. First, detailed measurements of radiative heat flux distributions are obtained for different flame powers, injector diameters and sensor distances. All results fall onto a single curve with an adequate non-dimensionalization. A new correlation for the radiative heat transfer rate from these flames was obtained with a better performance compared to other options from literature. Then, an inverse method is employed to obtain the coefficients of the weighted multi-point model for predicting the radiative heat transfer from flames. By using the non-dimensional heat flux distributions, the inverse method became independent of the flame radiated fraction. A new optimization parameter that emerges from the non-dimensional model showed the consistency of the inverse method and leads to a correlation for the maximum heat flux as a function of the radial distance from the flame. Finally, the new weighting coefficients and the radiative heat transfer rate correlation were used to compute the dimensional radiative heat flux distributions. The comparison with the experimental data showed expressive improvements of the model prediction.

Optimizing solar dish performance using analytical flux distribution in focal region

In this paper, thermal performance analysis of 4 m2 solar dish collector is presented.The focal image characteristics of the solar dish are determined to propose the suitable design of a receiver. A flat plate was used for the receiver to measure flux distribution in the focal region. The measurement had been done in the midday. Intercept factor based on this distribution had been calculated and was obtained to calculate thermal efficiency after total heat loss was described. From the experiment, total heat loss was formed by conductive and radiative in the receiver. The results showed that the increase in total heat loss followed the increase in receiver temperature and it caused a decrease in thermal efficiency. On the peak of the measurement or in midday, receiver temperature can achieve 138°C and it gave around 1200-Watt heat loss and it was dominated by radiative heat loss for around 80%. The thermal efficiency of the system due to flux distribution measurement in the focal region was above 70% and it was classified as high average but we needed to cover this flux up so it did not lose a lot of heat. Cavity aperture would keep around 20% total heat loss and it minimized radiative heat loss from the flux. The design of cavity aperture was the next discussion to insulate thermal heat reflection of the parabolic dish system from high radiative heat loss.©2020. CBIORE-IJRED. All rights reserved

An adaptive dynamic programming method for torque ripple minimization of PMSM

<p style='text-indent:20px;'>The imperfect sinusoidal flux distribution, cogging torque, and current measurement errors can cause periodic torque ripple in the permanent magnet synchronous motor (PMSM). These ripples are reflected in the periodic oscillation of the motor speed and torque, causing vibration at low speeds and noise at high speeds. As a high-precision tracking application, ripple degrades the application performance of PMSM. In this paper, an adaptive dynamic programming (ADP) scheme is proposed to reduce the periodic torque ripples. An optimal controller is designed by iterative control algorithm using robust adaptive dynamic programming theory and strategic iterative technique. ADP is combined with the existing Proportional-Integral (PI) current controller and generates compensated reference current iteratively from cycle to cycle so as to minimize the mean square torque error. As a result, an optimization problem is constructed and an optimal controller is obtained. The simulation results show that the robust adaptive dynamic programming achieves lower torque ripple and shorter dynamic adjustment time during steady-state operation, thus meeting the requirements of steady speed state and the dynamic performance of the regulation system.

Polar Polarization Mode and Average Radical Flux Intensity Measurements Based on All Optical Spatial Communication Systems

Abstract This study presents the polar polarization mode and average radical intensity flux distribution measurements based on all optical spatial communication systems. The numerical technique that is applied with the simulation model is the diffraction fast Fourier integral transform. Spatial optical sources are used such as continuous wave (CW) laser and vertical cavity surface-emitting laser (VCSEL) with spatial connector and spatial aperture. Spatial temporal polarization effects are taken into account. Percentage encircled flux/average flux radical intensity and polar radical polarization are measured with spatial connector distance and spatial aperture width. The encircled flux is constant at 95 % of its value in the case of VCSEL laser source at a radical distance of exactly 10 μm. However, the encircled flux is constant at 92 %of its value in the case of CW laser source at a radical distance of exactly 6 μm. It is noticed that the encircled flux increases with increasing radial distance of spatial apertures that are used with two suggested light sources. The encircled flux is constant at 93 % of its value in the case of VCSEL laser source at a radical distance of exactly 10 μm.

Neutron flux distributions in the Large Helical Device torus hall evaluated by an imaging plate technique in the first campaign of the deuterium plasma experiment

The global flux distributions for thermal, epithermal and fast neutrons in the torus hall of large fusion devices were experimentally evaluated for the first time in the Large Helical Device (LHD) using the activation foil method measured by the imaging plate and high-purity germanium detector. It turned out that the thermal neutrons were effectively absorbed by borated polyethylene blocks placed beneath the LHD. This should reduce the radioactivity of the floor and would be beneficial in maintaining a good environment for radiation workers. Uniform distributions of epithermal and fast neutrons were observed near the LHD. In particular, the significant decrease in fast neutron flux with increasing distance from the LHD, due to the fast energy loss of fast neutrons, was observed.The neutron flux distribution measurement, with rough energy discrimination based on the threshold energy of the neutron activation foil, allows us to estimate the spatial radiation dose rate, as well as the radioactivity in components in the torus hall. The prediction of the radioactivity in the concrete floor indicated that radioactive isotope 55Fe will be a dominant source of radioactivity in the concrete after the nine-year deuterium experiment campaign finishes.

Fuel management code system against experimental measurements of the CMRR reactor

The China Mianyang Research Reactor (CMRR), with a thermal power of 20 MW, is an important high performance research reactor operated in China. In this paper, we introduced the fuel management (FM) computation toolbox and confirmatory experiments performed at this reactor. The toolbox system utilizes two roadmaps, the deterministic strategy as the standard method and the Monte Carlo (MC) strategy as the reference way. Interface glue-code packages for both roadmaps are developed to link the existing kernel codes to perform the input-file generation, data manipulation, and output data processing for fuel cycle analysis. In particular, a new MC based coupling strategy is proposed called the “burnup related nuclides list” method which can perform the FM engineering problem with high accuracy and speed. For the aspect of confirmatory experiments, we emphasize on the methods and instruments, including the control rods (CRs) critical position, the CR worth curve, and the thermal neutron flux distribution. We have developed a reactivity meter to perform the CRs worth measurement using the inverse kinetics method, and employed the Dy-Al foils to perform the thermal neutron flux distribution measurements. All three sets of experiments are performed after each refueling. With these data accumulated over years, our FM toolbox system is profoundly validated for various combinations of fuel burnup and core arrangement. It can be concluded that our FM toolbox and strategies, both the deterministic and the MC way, are satisfactory for the FM mission of our reactor.

Design and characterization of the non-uniform solar flux distribution measurement system

It is important to accurately measure the solar flux distribution on the heated surface for the utilization of solar energy. To this end, in this paper a new measurement system was proposed to measure the solar flux distribution of the absorber tube surface by taking advantage of the end loss effect. The new measurement system does not disturb the collected lights path and influence the operation of the solar collector. The solar flux distribution at different angles can be measured with a few number of heat flux gage by rotating the proposed solar flux measurement system. Compared with existing measurement techniques, the proposed solar flux measurement system has distinct advantages such as simple structure, flexible and reliable operation and easy application. An experimental platform was designed and constructed, and the solar flux distributions on the outer surface of the absorber under differentconditions are measured. The feasibility and effectiveness of the proposed measurement method are validated by comparing the experiment results and the numerical simulation results.

The Focal Heat Flux Distribution Measurement of High-times Concentrating Directional Transmission System

.

Space Weather Influence on Electromagnetic Geosynchronous Debris Perturbations Using Statistical Fluxes

AbstractDue to the space plasma and the Sun, spacecraft at geosynchronous Earth orbit can charge naturally negative tens of kV. This charging can cause arcing which can damage spacecraft electronics and solar panels. A charged spacecraft will also experience a perturbative force and torque due to Earth's electric and magnetic fields. These electromagnetic perturbations have recently been postulated to cause significant orbital changes for lightweight debris objects. This paper investigates the effects of electromagnetic perturbations by using a charging model that uses measured flux distributions to better simulate natural charging and includes the convection electric field. This is done for a calm space weather case of KP = 2−, a stormy case where KP = 8, and a worst possible case where the voltage is held at −30 kV the entire time. It is found that neglecting electromagnetic effects on lightweight Mylar debris can lead to 100 km displacements after only a one orbit, and the covariance associated with such objects must be increased during periods of high charging.