Radiometric Units Research Articles

Angularly resolved photoluminescent emission from pulsed-laser-deposited ZnO films with different microstructures

Zinc oxide films with different microstructures have been produced using pulsed-laser deposition. Photoluminescence efficiency and angular emission patterns are characterized and reported in absolute radiometric units. Efficiencies between 0.6×10-6 and 7×10-6 were observed. In most cases, the angular emission pattern was lambertian, though the film microstructure produced an isotropic emission pattern in one case. A secondary peak, red-shifted 180 meV from the main ultraviolet ZnO emission peak, was observed for some films. The origin of the 180-meV red shift is tentatively attributed to zinc vacancies.

Uranium migration in a sedimentological phosphatic environment in Northern Palmyrides, Al-Awabed area, Syria

In previously published research, a factor analysis approach has been applied to airborne spectrometric data of the Al-Awabed area, Northern Palmyrides, Syria. A model of four factors (F1–F4) has proven to be sufficient to represent the acquired data, where 94% of the total data variance is explained. A scored lithological map including 11 radiometric units is established. Uranium migration trends have been determined for the first time through airborne spectrometric data of the study region, where different regional maps explaining the migration behavior have been established. A radioactive-geological model of such a migration is established and clearly shows that directions of uranium migration are strongly influenced by network drainage, topography, and fracturing systems in the region. Lithology of the 11 studied units also plays a dominant role in the rate of uranium migration. It was found that the four lithological phosphatic units P1–P4 are the main uranium sources in the study region, where the uranium migration is outward from these regions. The other seven lithological units C1–C3, M1–M4 are successively enriched by uranium during the geological evolution of the crust, where uranium migration is in an inward direction. It was also shown that uranium migration has occurred from its source for a short distance, limited by the boundaries of the lithological units which surround the phosphatic units. This finding is important from a prospecting and exploration point of view, and suggests that future uranium investigation activities are close to the phosphatic sources, if this process is creating the uranium distribution.

Identifying spectrometric signatures of phosphate deposits and enclosing sediments in Al-Awabed area, Northern Palmyrides, Central Syria, by the use of statistical factor analysis

In previous published research, a factor analysis approach has been applied to airborne spectrometric data of Al-Awabed area, Northern Palmyrides, Syria. A model of four factors (F1, F2, F3 and F4) has proven to be sufficient to represent the acquired data, where 94% of the total data variance is explained. A powerful tool for direct differentiation of various rocks units is obtained through the mapping of these four factors, where a scored lithological map including 11 radiometric units is established. Ninty nine rock samples have been taken according to the four factors to be analyzed by the γ-spectrometry technique in order to determine their content of eU, eTh and K%. The analysis of 65 samples according to F1 indicates that uranium concentration varies between 2.74 and 123.3 ppm with an average of 58.85 ppm and a standard deviation of 32.53 ppm. The analysis of 18 samples taken according to F2 indicates that K% concentration varies between 0.001 and 0.324 with an average of 0.145 and a standard deviation of 0.122. The analysis of 16 samples taken according to F3 indicates that K% concentration varies between 0.024 and 0.558 with an average of 0.227 and a standard deviation of 0.133. These γ-results are expected and fit very well with the results obtained by the factor analysis approach. Therefore, the validity and efficacy of the factor analysis approach, to be widely used as a guide in exploration and smart sampling for mining programs, are well demonstrated. The established phosphate maps show a width extension and distribution, and clearly indicate the potential of the research area, and it merits to be followed by economic exploration.

Linking fluorescence measurements to radiometric units

A general concept is presented to realize the traceability of fluorescence measurements to radiometric units based on a combination of suited physical and chemical transfer standards and a reference fluorometer as a linking unit. The standards comprise a newly designed spectral radiance transfer standard more closely adapted to the spectral radiance of typical fluorescent samples than conventional standard lamps and a set of easy-to-operate spectral fluorescence standards consisting of organic dyes. An example is given as to how the comparability of fluorescence spectra across instruments can be improved. Finally, the design and the calibration scheme of a new reference fluorometer is presented which is designed for the performance of relative and absolute fluorescence measurements with minimum uncertainty.

Linear color camera model for a skylight colorimeter with emphasis on the imaging pipeline noise performance

We develop a digital camera model with the purpose of simulating the performance of a sky radiance colorimeter, based on a single-sensor camera equipped with a charge-coupled device imager. To provide a color image, the sensor is covered with a Bayer color filter array (CFA). The model input is the radiance, expressed in radiometric units. Demosaicking of the CFA is performed using three common interpolation methods. Color characterization is performed by calculating 3×3 matrices, based on either the maximum-ignorance assumption or computer-generated sky radiance training sets. For the model to be reliable, we incorporate multiple noise sources. We also parameterize many critical characteristics of the simulated imager, for example, temperature-related dark-current generation and pixel size. Error propagation analysis is performed, including an analysis for the demosaicking methods. Colorimetric performance results, expected measurement accuracy, and validation of the derived noise propagation equations are presented.

Comparison of traceable calibration methods for primary photovoltaic reference cells

The calibration of photovoltaic reference cells used as primary laboratory standards for the calibration of photovoltaic devices needs to be traceable to international radiometric standards and SI units. As a contribution to the development of an international standard this paper describes three methods for the calibration of primary photovoltaic reference cells, establishing two independent traceability chains. The solar simulator method is traceable via a standard lamp to the international irradiance scale whereas the global sunlight method and the modified global sunlight method are traceable to the world radiometric reference. The calibration values obtained by the three methods agree with each other within their respective uncertainties and with the world photovoltaic scale within ± 0·8%. Copyright © 2005 John Wiley & Sons, Ltd.

Statistical factor analysis of aerial spectrometric data, Al-Awabed area, Syria: a useful guide for phosphate and uranium exploration

Factor analysis provides a quantitative interpretation for synthesizing and correlating data from airborne spectrometric surveys. Factor analysis is applied on such data of Al-Awabed area, Northern Palmyrides. The seven variables used in this research are: total radioactivity Ur 1 1 Unit of radioelement ( IAEA, 1976). , e U, e Th, K%, e U/e Th, e U/K and e Th/K. The analysis and interpretation show that a model of four factors (F1, F2, F3 and F4) is sufficient to represent them, where 94% of total data variance is interpreted. Mapping of these four factors proved to be a powerful tool for a direct differentiation of various rocks units, and a score lithological map of 11 radiometric units was established.

Caracterização geológica e estrutural através da interpretação do produto integrado TM-Landsat 5 e dados aerogamaespectrométricos, região de Alta Floresta - MT

Este artigo apresenta a caracterização geológica e tectono-estrutural de uma região da Província Aurífera de Alta Floresta, Mato Grosso, através da interpretação do produto integrado TM-Landsat 5 e de dados aerogamaespectrométricos (contagem total). O produto integrado TM-contagem total possui características importantes para a interpretação geológica: apresenta num único produto, feições estruturais fornecidas pela imagem TM, representadas pelos elementos de relevo e drenagem e os valores radiométricos (RGB) que contribuem de forma bastante satisfatória na discriminação das unidades litoestruturais. A geração do mapa geológico foi baseada na interpretação dos valores radiométricos de contagem total (levando-se em consideração quais fatores, tais como topografia e atividade antrópica, poderiam influenciar a reposta radiométrica), nas feições de relevo e drenagem (que auxiliam na caracterização tectono-estrutural) fornecidas pela imagem TM e também nos dados de campo. Como a área apresenta intensa atividade antrópica e relevo muito arrasado, o que prejudica a interpretação geológica das imagens de sensoriamento remoto, a geração do produto integrado TM-contagem total foi decisiva para a obtenção de dados necessários ao mapeamento. Como resultado final foi elaborado o mapa geológico da área, em escala 1:250.000, sendo delimitadas 10 unidades litoestruturais relacionadas diretamente às unidades radiométricas e às feições estruturais. Um importante trend de direção N60-70W e altos mergulhos relacionados às zonas de cisalhamento transcorrentes sinistrais dúcteis a dúcteis rúpteis foi caracterizado através da interpretação visual de produtos integrados e dados de campo.

Influence of the beam shape on aperture measurements with the laser beam scanning technique

The realization of a number of radiometric and photometric units requires one to measure accurately the area of precision apertures. The BIPM employs the laser-beam scanning technique which is based on the generation of a uniform irradiance by a two-dimensional superposition of many regularly spaced laser beams.The existing literature describes the formation of the uniform irradiance as a superposition of Gaussian laser beams and derives a condition for the largest allowable lattice spacing to obtain the necessary uniformity. In this paper we analyse the effect of the use of real laser beams which are almost, but not completely, Gaussian by applying Fourier analysis. Experimental results of aperture measurements with different spacings of the laser beams are also shown. The results of the calculations and the measurements show a characteristic dependence of the measured area on the grid spacing, even for spacings sufficiently small according to the condition based on Gaussian theory. This can be explained by very small deviations of the actual beam shape from a perfect Gaussian profile.

Mapping Monthly Distribution of Daily Light Integrals across the Contiguous United States

The daily light integral (DLI) is a measurement of the total amount of photosynthetically active radiation delivered over a 24-hour period and is an important factor influencing plant growth over weeks and months. Contour maps were developed to demonstrate the mean DLI for each month of the year across the contiguous United States. The maps are based on 30 years of solar radiation data for 216 sites compiled and reported by the National Renewable Energy Lab in radiometric units (watt-hours per m-2·d-1, from 300 to 3,000 nm) that we converted to quantum units (mol·m-2·d-1, 400 to 700 nm). The mean DLI ranges from 5 to 10 mol·m-2·d-1 across the northern U.S. in December to 55 to 60 mol·m-2·d-1 in the southwestern U.S. in May through July. From October through February, the differences in DLI primarily occur between the northern and southern U.S., while from May through August the differences in DLI primarily occur between the eastern and western U.S. The DLI changes rapidly during the months before and after the vernal and autumnal equinoxes, e.g., increasing by more than 60% from February to April in many locations. The contour maps provide a means of estimating the typical DLI received across the U.S. throughout the year.

Mars (matrix radiometric system) project

Abstract The MARS (Matrix Radiometric System) project is described. The instrument is intended to be used as a possible radiometric support to the ‘Cosmological Gene’ project. MARS is planned to be installed in the focal line of the RATAN-600 radio telescope. An input signal of two orthogonal linear polarizations is transferred via orthomode transducers, 128 units in line, to 256 radiometric modules. Each module of the system is an independent noise-added, gain-balanced straight-amplifier radiometer. The first prototype models of the radiometric module and of the noise generator unit design and test results are presented. MMICs and KEMT chip transistors as active components were applied. For one radiometric unit, 210 K noise temperature, 65 dB gain and 6 GHz bandwidth at 30 GHz centre frequency were measured.

Primary radiometric quantities and units

Methods used for the establishment and dissemination of primary radiometric quantities are reviewed together with the performance and use of filter radiometers, which are dominating advances in optical radiation measurement. The possibility is also discussed of using many of these advances in other metrological sectors, such as in thermal metrology to improve the realization and dissemination of the kelvin.

Radiometric unit for collimators used to reproduce differential radiances and differential radiation temperatures

A method is proposed for reproducing the values of the differential radiance and the differential radiation temperature for the certification of optoelectronic scanning equipment. The method is based on the application of an auxiliary source illuminating one of two radiance-equilized, diffusely reflecting plates mounted in the isothermal volume of a two-channel radiometric unit, which illuminates a mirror bar target in the collimator. The relationship between the total and spectral values of the radiation temperature is investigated.

Improvements to the German national primary standard of radiant power above 200 nm

The set of cryogenic radiometers in the Physikalisch-Technische Bundesanstalt (PTB) at Braunschweig was recently completed by the addition of a modified LaseRad II radiometer. The advantages of the improved facility for measurement of optical radiant power are described. The paper outlines the radiometric calibration chain of the PTB, including a cryogenic laser and broadband radiometer. The link of radiometric units to the International System of Units (SI) volt and ohm in the PTB is presented. Results of current direct international comparisons of cryogenic radiometers and an internal comparison are summarized. The results demonstrate the degree of international equivalence at the lowest level of uncertainty available. The international agreement is within 2 × 10-4.

The double-heatpipe black body: a radiance and irradiance standard for accurate infrared calibrations in remote sensing

Infrared remote sensing has become an important tool for studies of Earth resources, the environment and related issues. It is now well recognized that measurements in this field have to be accurately traceable to SI radiometric units in order to be comparable world-wide and reliable in the long term - in particular if the measurements are to detect small changes of key quantities. To provide a highly stable standard source of infrared radiation, the Physikalisch-Technische Bundesanstalt (PTB), Germany, has investigated the uncertainties of its double-heatpipe large-area black body for radiometric calibrations in the wavelength range from 1 µm to 50 µm. The spectral emission of the black body can be traced either to the International Temperature Scale ITS-90 or to the radiation thermometry cryogenic radiometer, with small uncertainties of about 50 mK at a black-body temperature of about 1000 C. The total relative standard uncertainty of the black body used as an irradiance standard in the infrared is less than 10-3 for wavelengths between 1 µm and 15 µm and at most a few times 10-3 for wavelengths up to 50 µm. With a more sophisticated treatment of diffraction corrections and cryogenic shielding of background radiation, the uncertainties can be reduced to a few parts in 104 for high-precision applications.

Design considerations for the construction of an absolute radiation detector at the NPL

An Absolute Radiation Detector (ARD) has been designed and constructed. After evaluation it will replace the existing UK primary national standard cryogenic radiometer, with an improved uncertainty. The ARD has been designed to measure black-body and laser radiation with an uncertainty approaching 10-5. From these measurements it will be possible to determine the fundamental constant, the Stefan-Boltzmann constant, confirming the radiometer as an absolute detector, and link this determination to the SI unit of luminous intensity, the candela, and other detector-based radiometric units. Thus source- and detector-based optical units will be tied to an invariant physical quantity ensuring their long-term stability. This paper describes some of the design considerations to enable the ARD to meet its objectives.

Pyrometric Particle Temperature Measurements in a Pressurized Fluidized Bed Gasification Reactor

Abstract A fiberoptic pyrometric technique for the measurement of the temperature of a fuel particle in a fluidized bed reactor is presented. In the fiberoptic pyrometry the thermal radiation emitted by bed and fuel particles is collected and transmitted to a radiometric unit by an optical lightguide immersed into the reactor. The radiation intensity is measured on two narrow wavelength bands and temperatures of the bed and individual fuel particles are determined from these signals. Experimental results obtained in an industrial pressurized fluidized bed gasificalion pilot plant of 15 MW of thermal power are reported. The temperature of the fluidized bed was 1140–1215 K and the pressure in the reactor was 1.6–2 MPa. A large number of fuel particles both hotter and colder than the surrounding bed were clearly detected. For the hotter particles the temperature elevation with respect to the bed was typically 40–100 K.

USING LOTUS 123 TO INTERCONVERT ILLUMINANCE, IRRADIANCE, AND PHOTON FLUX DENSITY VALUES

Because ASHS has adopted in their editorial policies the use of Systeme International (SI) units, it has become necessary to report light measurements in units other than footcandles. Since measurements using a radiometer can be tedious, tables providing values for different sources of light are often used to approximate required units. Using the tables provided by Thimijan and Heins [HortScience 18(6): 818-822], a Lotus 123 worksheet program was designed to interconvert photometric, radiometric, and quantum light units of measure. The worksheet is menu driven and can handle straight conversions or mixed conversions by entering requested information. Setup of the worksheet and instructions in its use will be provided at the meeting.

National Primary Radiometric Standards of the USSR

A versatile combined primary standard of the USSR has been established at VNIIOFI for the realization of radiometric units. The standard is based on two black bodies, operable at temperatures from 400 to 3000 K, and an absolute radiometer. Units of both spectral and broadband quantities are reproduced within the 0,2 μm to 25 μm range. A black-body radiator made of niobium carbide and graphite is used over the temperature range of 1500-3000 K, while that for the lower temperatures from 400 to 1200 K is a heat-pipe with a sodium heat-transfer medium. In order to determine the thermodynamic temperature T of the high-temperature black body, relative values of radiant flux Pe (Ti) and spectral radiance Leλ (λi, Ti) at several temperatures Ti are found. The method allows realization of radiometric and photometric quantities irrespective of the International Practical Temperature Scale (IPTS-68). The absolute radiometer used is of a special design and has a control system capable of maintaining the conical receiving cavity at constant temperature throughout the measurement process. The absolute radiometer is intended to realize radiometric units as well as to measure the spectral sensitivity of radiation receivers.

Ge photodiodes as transfer standards for radiant power measurements in the field of fibre optics

The demand for precise radiometric measurements in testing fibre-optical communication networks requires transfer standards of radiant power to fit the variety of available power meters to the radiometric units realised by the national standard laboratories. This paper is focused on Ge photodiodes as transfer standards covering the complete spectral range of interest, including the optical windows of fibre-optical communication at 850, 1300 and 1550 nm. Aspects of correct determination of the absolute spectral responsivity, temperature dependence, ageing, interreflections, inhomogeneity, non-linearity, and optimum detector size are discussed on the basis of measurements. Deviations from the ideal detector behaviour are explained by simple models. Some points of view on the use of Si and InGaAs photodiodes are also given.