Angle Of Incident Radiation Research Articles

Effect of Textile Properties on the Bidirectional Solar-Optical Properties of Shading Fabrics

This paper presents an experimental approach to and preliminary results of measurements of bidirectional solar-optical properties of shading fabrics. Transmittance and reflectance profiles for three woven and three knitted fabrics are presented as a function of altitude and azimuth angle for selected incidence angles of simulated direct solar radiation. The woven fabrics exhibit transmittance profiles that are sharply peaked in line with the incident beam. At normal incidence, woven fabrics with transparent yarns result in high peak transmittance of approximately 41%, whereas opaque yarns and dense structures result in low peaks of 0.5–2%. All of the wovens tested exhibit low reflectances of 1–2%. Knitted fabrics also show sharply peaked transmittance profiles in line with the incident beam. However, the open knits have peak values of up to 63% at normal incidence, whereas opaque knits show peaks of only 1–4%. Peak reflectance values for all the knits were low at approximately 1–2%, even with metallized yarns.

Research on Sensitivity Characteristics of Thermoluminescence Dosimeters : Direction Dependence of MSO-S Type Detectors

The detectors for thermoluminescence dosimeters are made into smaller size than ionization chambers and scintillation deterctors. Furthermore, they are highly sensitive, they can do the measurement of radiation using many detectors at once and so on, accordingly they have been employed widely for medical treatment. However, since the shape of these detectors is bar type, there is the peculiarity in their sensitivity according to the angle of incident radiation into the detectors. In this research, further on the sensitivity characteristics due to the distance from a radiation source, the experimental examination was carried out by using MSO-S type detectors on the x-ray for diagnosis and cobalt gamma ray. As the result, it was elucidated that in the detectors used, there was the change of the sensitivity characteristics according to the distance from the radiation sources. The accuracy of measrement by using these detectors was researched, therefore it is reported.

Phantom for Calibrating and Type-Testing Individual Dosemeters

The suitability of two polyhedron phantoms for type-testing and calibrating individual dosemeters in connection with the introduction of the operational quantities H p (d) and H s (d) in individual monitoring is discussed. It is concluded that an icosahedron phantom with an edge length of 18.64 cm is preferable. It combines the advantages of a sphere phantom with those of a cube or slab phantom and allows a number of angles of radiation incidence to be used for a fixed radiation field. The expense of producing an icosahedron phantom is comparable with that of producing a sphere phantom

The solar cell output power dependence on the angle of incident radiation

The decrease in output power of silicon solar cells with increasing angle of incidence has been investigated theoretically and experimentally. Effective junction depth, reflection losses and surface photon distribution are modelled, taking into account the front surface recombination velocity. It is shown that the increase of power losses by surface recombination is dependent on the angle of incidence.

Progress towards the development of a CR-39 fast neutron personal dosemeter

The laboratoire de dosimetrie of the Centre de Radioprotection et de Sureté (CRS), Algiers, has been developing a fast neutron personal dosemeter using CR-39 detectors. Among track etch detectors used today, CR-39 remains the best available personal dosemeter for neutrons. Unfortunately, the drawbacks in using CR-39 as a neutron detector still exist especially the poor angular response of the flat dosemeter, the background reproducibility and the ageing of commercially available CR-39 materials. The response of the dosemeter using flat and cylindrical geometry, has been investigated using Cf-252 neutrons and neutrons beams of energies ranging from 144 keV up to 14.7 MeV at different angles of radiation incidence, i.e. 0°, 30° and 60°.

A Method for Determining Detector Efficiencies In-Situ by Variation of the Radiation Incidence Angle

en

Computation of the Optical Constants of a Thin Dielectric Layer from the Envelopes of the Transmission Spectrum, at Inclined Incidence of the Radiation

Abstract A mathematical expression for the transmission of a thin dielectric layer on a transmitting substrate is found. The finite dimensions of the substrate and its absorption are taken into account. The cases of inclined incidence of non-polarised, s- and p-polarised radiation to the layer are investigated. A way of determining the optical constants n(λ) and k(λ) of the layer from the envelopes of the transmission spectrum is offered. Computation of n(λ) and k(λ) of a model optical system at different angles of radiation incidence is performed as well as analysis of the results obtained.

Uncertainties in Dose Estimation Under Emergency Conditions and ESR Dosimetry with Human Teeth

Abstract There are uncertainties in estimating dose-effect relationships under emergency conditions. There may be a number of other noxious effects such as infection, various toxic substances and non-ionising radiations, in addition to radiological uncertainties, and also mental aspects. Therefore, the possibility of the combined effects of all direct factors and the indirect factors must be considered in interpreting the effects of a radiation accident, instead of ascribing all the effects solely to ionising radiation. The exact dose to a particular person is difficult to estimate, but is is also necessary to have some direct measurement of individual dose in order to confirm dose-effect relationships due to radiation. As a method of confirming the individual dose under emergency conditions, ESR dosimetry of tooth enamel has been carried out, not only to estimate the dose, but also to estimate the incident angle of radiation.

Uncertainties in Dose Estimation Under Emergency Conditions and ESR Dosimetry with Human Teeth

There are uncertainties in estimating dose-effect relationships under emergency conditions. There may be a number of other noxious effects such as infection, various toxic substances and non-ionising radiations, in addition to radiological uncertainties, and also mental aspects. Therefore, the possibility of the combined effects of all direct factors and the indirect factors must be considered in interpreting the effects of a radiation accident, instead of ascribing all the effects solely to ionising radiation. The exact dose to a particular person is difficult to estimate, but is is also necessary to have some direct measurement of individual dose in order to confirm dose-effect relationships due to radiation. As a method of confirming the individual dose under emergency conditions, ESR dosimetry of tooth enamel has been carried out, not only to estimate the dose, but also to estimate the incident angle of radiation.

Solar radiation induced natural convection in enclosures with conducting walls

Abstract A theoretical study is presented on combined heat transfer by conduction, convection and radiation in a rectangular cavity with an aspect ratio of 1 to 0.2. Constant flux solar radiation at a given incidence angle is transmitted through one of the vertical boundaries and they are absorbed by the enclosure walls. The temperature distribution within the cavity is computed in an iterative manner by the net radiation method, using solution results from the heat transfer by conduction and natural convection. It is found that the radiation and conduction have a significant effect on the flow field and heat transfer. The induced radiation has a stabilizing effect on the flow field with a tendency to make the secondary cells disappear. This effect increases with increasing solar radiation intensity and incidence angle and with decreasing aspect ratio. As a result, the net energy absorbed and transferred through the end wall is also increased. A correlation for combined heat transfer is also derived which can be used in passive solar wall collector design.

The use of carbon−loaded thermoluminescent dosimeters for the measurement of surface doses in megavoltage x‐ray beams

To determine the absorbed dose to the skin of patients undergoing radiotherapy with megavoltage radiations, it is necessary for the dose to be measured at shallow depths. This report assesses the suitability of carbon-loaded thermoluminescent dosimeters (manufactured by Vinten Instruments Limited) for this purpose. Measurements have been made of the effective measurement depth of the dosimeters, the linearity with dose, and the variation of sensitivity within a batch. The variation of surface dose with incident angle of radiation for 5-MV x rays has been measured using these disks; the results are compared with results obtained using a thin-windowed ionization chamber.

A Method for Evaluating Air Kerma and Directional Dose Equivalent for Currently Available Multi-Element Dosemeters in Radiation Protection Dosimetry

A method is outlined for estimating air kerma and directional dose equivalent from indications on multi-element dosemeters having energy and angle response functions that are different for at least two of the dosemeter's radiation-sensitive elements. The method employs dosemeter calibrations relating response of each element and the corresponding indication ratio(s) to radiation energy and angle of radiation incidence. Indications are measured in the usual way on the elements of each dosemeter irradiated under unknown conditions, and the ratio is formed of the indications of any two elements known to have different response functions. Using the calibration curves, energy-angle pairs are found that correspond to these indication ratios, and are then used to determine the corresponding response values - of which there are, in general, several per energy-angle pair. Finally, the response values corresponding to any given energy-angle pair are averaged, and air kerma or directional dose equivalent is computed from average response and the measured indication(s). The method is illustrated for a dosemeter for which photon calibration data were available.

A Method for Evaluating Air Kerma and Directional Dose Equivalent for Currently Available Multi-Element Dosemeters in Radiation Protection Dosimetry

A method is outlined for estimating air kerma and directional dose equivalent from indications on multi-element dosemeters having energy and angle response functions that are different for at least two of the dosemeter's radiation-sensitive elements. The method employs dosemeter calibrations relating response of each element and the corresponding indication ratio(s) to radiation energy and angle of radiation incidence. Indications are measured in the usual way on the elements of each dosemeter irradiated under unknown conditions, and the ratio is formed of the indications of any two elements known to have different response functions. Using the calibration curves, energy-angle pairs are found that correspond to these indication ratios, and are then used to determine the corresponding response values - of which there are, in general, several per energy-angle pair. Finally, the response values corresponding to any given energy-angle pair are averaged, and air kerma or directional dose equivalent is computed from average response and the measured indication(s). The method is illustrated for a dosemeter for which photon calibration data were available.

V-troughs with high concentration ratios for photovoltaic concentrator cells

Abstract V-troughs made of plane mirrors are used as solar concentrators with high concentration ratios assuming a normal incidence angle of solar radiation. Because of its uniform illumination, this type of concentrator is found to be suitable for photovoltaic concentrator cells. General analytical expressions for the concentrator's length, efficiency, reflector-to-aperture ratio and ideal and actual concentration ratios are derived. Comparison of the V-trough with the compound parabolic collector concentrator for the special case of normal incidence is presented. Design graphs using the experimental results are also discussed.

Errors Found in Expressions Given by Schaeffer and by Selph for Radiation Flux in Rectangular Straight Duct

Assuming the entrance of a rectangular straight duct to be uniformly covered with a film of radiation source, and the radiations to be emitted into the duct at Intensities proportional to cos2θ (θ: Angle of radiation incidence), the unscattered component of radiations along the duct axis is shown to be expressed by where φ0 is the total flux from the radiation source, while a, b are non-dimensional parameters representing the perspective angle of radiation source vertical and horizontal spreads. This consequently proves the fallacy of the expressions given by Schaeffer and by Selph for the same assumptions, i.e. and which are widely cited in textbooks, handbooks and reports.

Solar cell short-circuit current dependence on the angle of the incident radiation

The dependence of the photocurrent of n +p crystalline and pin amorphous silicon cells on the angle of incident radiation has been investigated theoretically and experimentally. It is found that for angles larger than about 30° from the normal to the surface the photocurrent is significantly smaller than expected from the cosine law. It is shown that the deviation is mainly due to increased reflection losses, the contribution from the increase in the effective junction depth being small.

Errors found in expressions given by Schaeffer and by Selph for radiation flux in rectangular straight duct.

Assuming the entrance of a rectangular straight duct to be uniformly covered with a film of radiation source, and the radiations to be emitted into the duct at Intensities proportional to cos2θ (θ: Angle of radiation incidence), the unscattered component of radiations along the duct axis is shown to be expressed by where φ0 is the total flux from the radiation source, while a, b are non-dimensional parameters representing the perspective angle of radiation source vertical and horizontal spreads. This consequently proves the fallacy of the expressions given by Schaeffer and by Selph for the same assumptions, i.e. and which are widely cited in textbooks, handbooks and reports.

Structural Changes Around Uranium at the Surface of Waste Glasses Caused by Leaching

AbstractStructural changes occurring at the surface of leached borosilicate glasses containing 3%wt of uranium have been investigated using fluores- cence EXAFS spectroscopy at grazing incidence. X-ray penetration depths between 30 Å and above 1000 Å are possible by varying the incidence angle of the X-ray monochromatic radiation in the vicinity of the critical angle for total external reflection, øc. This enables the surface and bulk structure to be compared. It is found that a local increase in uranium concentration takes place near the surface of the glass during the first 30 minutes of leaching time. Uranium is coordinated with oxygen and other uranium atoms. The local distribution can be modelled by a square planar island structure comprised of uranyl-type units. This structure changes with corrosion time. After 30 minutes of leaching there is evidence of partial removal of the surface layer.

A Survey of the Accuracies of Some Methods for the Determination of the Optical Constants of Thin Films

Abstract The optical constants n and k of a material in thin film form may be determined from measurements of two of the optical functions R, T, φR, , and φT in either the s or p state of polarisation. This paper discusses the inherent accuracies of a number of the possible combinations in terms of arrays of error parallelograms on an n-k diagram. The regions of high and low accuracy are identified and the changes produced by film thickness and angle of incident radiation are discussed. Particular attention is given to the photometric and ellipsometric functions.

Anomalous interaction of laser radiation with plasma

A physicomathematical model is used to describe the processes of resonance and parametric interaction of laser radiation with a plasma in the critical density region. The exceptionally strong influence of ponderomotive forces on the formation of the density profile close to the critical point is demonstrated. The parameters of the resultant gasdynamic flow are investigated over a wide range of intensities and incidence angles of the laser radiation and of plasma temperatures, the spatial structure of the plasma and electromagnetic waves is obtained, and the coefficients of the resonance and parametric absorption are given.