Determination Of Attenuation Coefficients Research Articles

Determination of attenuation coefficients, thicknesses and effective atomic numbers for CuInSe2 semiconductor

The X-rays attenuation coefficients for Cu, In and Se in elemental state and the semiconductor CuInSe2 were measured at 15 different energies from 11.9 to 37.3keV by using the secondary excitation method. Monochromatic photons were obtained using the following secondary targets: Br, Sr, Mo, Cd, Te and Ba. 59.5keV gamma rays emitted from an annular 241Am radioactive source were used to excite secondary target and X-rays emitted from secondary target were counted by a Si(Li) detector with a resolution of 0.16keV at 5.9keV. A method to determine the thickness of thin film with XRF is described. Additionally, the effect of absorption edges on effective atomic numbers and their variation with photon energy in composite semiconductor sample was discussed. Obtained values were compared with calculated values.

Determination of attenuation coefficients of single mode optical fiber standards to be used in OTDR calibrations

The subject of this paper is the determination of attenuation coefficients of single mode optical fiber standards used in both loss and distance scales calibrations of OTDR instruments by applying “cut-back” method, and “loop transit time” measurements. In cut-back measurements a modified radiometer with InGaAs having 5 mm diameter active area, cooled to 77 K, was constructed and used. To derive attenuation coefficients after the completion of cut-back measurements, the loop transit time measurements were performed for standard fibers. Total expanded uncertainty was calculated as 3.30 × 10 - 3 for determination of attenuation coefficients.

Study of variance and covariance terms in linear attenuation coefficient measurements of irregular samples through the two media method by gamma-ray transmission

The two media method permits the application of Beer's law (Thesis (Master Degree), Universidade Estadual de Londrina, PR, Brazil, pp. 23) for the linear attenuation coefficient determination of irregular thickness samples by gamma-ray transmission. However, the use of this methodology introduces experimental complexity due to the great number of variables to be measured. As consequence of this complexity, the uncertainties associated with each of these variables may be correlated. In this paper, we examine the covariance terms in the uncertainty propagation, and quantify the correlation among the uncertainties of each of the variables in question.

Use of a new ICG-dye-enhanced diode laser for percutaneous laser disc decompression.

The lasers used today for Percutaneous Laser Disc Decompression (PLDD) can not selectively ablate the nucleus pulposus (NP). We hypothesized that if indocyanine green dye were injected into the NP, 805 nm diode laser irradiation would result in selective and safe removal of NP tissue without damaging nearby tissues. Twelve beagle dogs were used for three experiments, i.e., determination of attenuation coefficients of NP and AF, determination of weight of NP before and after laser irradiation, and histopathological study. The attenuation coefficient at 805 nm of NP which had been homogenized in the presence of ICG was 2521.3/cm. Upon application of the diode laser at a power of 1, 3, or 5 W (the intensity of laser irradiation: 0.353, 1.061, or 1.768 x 10(3) W/cm(2)) to NPs into which ICG had been injected, the weight of the NPs decreased by a mean 20, 45, and 65%, respectively. Macroscopic and microscopic examination of the discs after PLDD showed that only the NP where the tissues were stained by ICG were removed. These results indicated that the combined use of ICG and diode laser irradiation effectively and selectively ablates the NP with low laser power.

Interaction of photons with some solutions

The linear attenuation coefficients in aqueous solutions of some chlorides and sulphates, viz. MgCl 2·6H 2O, CaCl 2, SrCl 2·6H 2O, BaCl 2·2H 2O, Na 2SO 4, K 2SO 4 and MgSO 4·7H 2O were determined at 81, 356, 511, 662, 1173 and 1332 keV by the γ-ray transmission method in a good geometry setup. From the precision measured densities of these solutions, mass attenuation coefficients were then obtained which varied systematically with the corresponding changes in the concentrations (g/cm 3) of these solutions. A comparison between experimental and theoretical values of attenuation coefficients has shown that the study has potential application for the determination of attenuation coefficients of solid solutes from their solutions without obtaining them in pure crystalline form.

Two media method for gamma ray attenuation coefficient measurement of archaeological ceramic samples

This work reports the application of an alternative methodology for the linear attenuation coefficient determination of irregular shape samples, in such a way that it is not necessary to know the sample thickness. Based on this method, indigenous archaeological ceramic fragments from the region of Londrina, north of Parana State in Brazil, were studied. On the other hand, theoretical mass attenuation coefficient values were determined with the XCOM computer code. With the results obtained, it was concluded that the two media method works very well for the linear attenuation coefficient measurement of irregular-shaped ceramic samples, which makes it suitable, especially, for archaeometric studies.

Attenuation Measurements in Solutions of Some Carbohydrates

The linear attenuation coefficients in aqueous solutions of three carbohydrates, glucose (C6H12O6), maltose monohydrate (C12H22O11·H2O), and sucrose (C12H22O11), were determined at 81, 356, 511, 662, 1173, and 1332 keV by the gamma-ray transmission method in a good geometry setup. From the precisely measured densities of these solutions, mass attenuation coefficients were then obtained that varied systematically with the corresponding changes in the concentrations (g/cm3) of these solutions. The experimental results were used in terms of effective atomic numbers and electron densities. A comparison between experimental and theoretical values of attenuation coefficients has proven that the study has a potential application for the determination of attenuation coefficients of solid solutes from their solutions without obtaining them in pure crystalline form.

Factors affecting ultrasonic measurements in solid wood

The basis of the ultrasonic evaluation of the viscoelastic behaviour of wood is associated with measurements of velocities and of attenuation coefficients. The dispersion equation for anisotropic solids relates the complex elastic constants, the velocities and attenuations. The numerical significance of attenuation coefficients depends on the specific measurement situation. In this article we discuss the method of attenuation measurement in wood with the through-transmission technique and we relate some experimental factors that can affect the determination of attenuation coefficients. The factors affecting attenuation measurements are related to the geometry of the radiation field, and to the scattering and absorption of ultrasonic energy by the solid. The attenuation coefficients increase with frequency (from 0.1 to 1.5 MHz) either for longitudinal or shear waves. The lowest attenuation was obtained in the longitudinal direction and the highest attenuation was measured in the tangential direction.

Experimental determination of the attenuation coefficient of surface electromagnetic waves

The experimental determination of attenuation coefficients of surface electromagnetic waves (SEW) excited by using the evanescent wave coupling technique (two prism technique) proves to be elusive. In an experimental study of the SEW attenuation we could show that the electromagnetic surface modes are obscured by bulk electromagnetic waves. The influence of these bulk waves on the decoupled electromagnetic intensity was detected by its diffraction on a screen placed in front of the coupling prism. A simple half-quantitative description can be given in the framework of the Fresnel–Huyghens principle. The experimental arrangement modified by the additional screen allows the determination of the propagation lengths unambiguously. The measured propagation length for optically thick gold films agree with results obtained by infrared ellipsometric measurements.

Determination of attenuation coefficient for self-absorption correction in routine gamma ray spectrometry of environmental bulk sample

A simple method to determine γ-ray attenuation coefficients using Ba-133 γ-rays has been developed and applied to self-absorption correction in routine γ-ray spectrometry for environmental samples composed of unknown matrix elements. Experimental values of the mass attenuation coefficient obtained by the method agree well with calculated values for samples of known elemental composition which was determined by means of chemical analysis.

Low‐frequency attenuation in the North Pacific subarctic‐subtropical transition zone

The water mass regions in the North Pacific are relatively well defined. Kibblewhite et al. [J. Acoust. Soc. Am. 61, 1169–1177 (1977)] have shown that each water mass has a characteristic low frequency (below 200 Hz) attenuation. They find the highest attenuation to be in the Subarctic‐Subtropical Transition Zone and these values are the highest yet reported in any ocean for this frequency range. It has recently been reported by Focke et al. [J. Acoust. Soc. Am. 71, 1438–1444 (1982)] that such values of attenuation can be modeled using a frequency independent mechanism, exponentially decreasing from the surface, the origin of which is unspecified. We compare these results with attenuation coefficients we have obtained in this zone. The oceanographic and biological properties of this region are analyzed to determine possible scattering mechanisms and their distribution. The effect of the two frontal areas bounding this region on the determination of attenuation coefficients is also examined.

Phase insensitive ultrasonic attenuation coefficient determination of fresh bovine liver over an extended frequency range

The ultrasonic attenuation coefficient of fresh bovine liver was determined by the phase insensitive techniques of the radiation force balance at 1.37, 4.15, 6.90, and 9.65 MHz, and the scanning laser acoustic microscope (SLAM) at 100 MHz. A least squares fit of the ultrasonic attenuation coefficient (in Np/cm) vs ultrasonic frequency (in MHz) to the 1–10 MHz data yields A = 0.043 f1.266 (r**2 = 0.895) and to the 1–100 MHz data yields A = 0.043 f1.270 (r**2 = 0.954). The following observations can be made: the greatest frequency range (2 decades) over which ultrasonic frequency has been determined for the same specimens. (2) This is the first time it has been shown that the frequency dependence of attenuation remains essentially unchanged over this large frequency range. (3) The frequency dependence is slightly greater than has been observed from the various literature compilations. (4) The attenuation coefficient magnitudes are the lowest values yet determined for fresh liver. (5) The attenuation magnitudes are from 1.3 to 2.2 times greater than the ultrasonic absorption values in the same tissue.

Geometrical attenuation factors for directional correlation experiments

Experimentally determined values are given for the attenuation factors due to finite solid angle in directional correlation measurements. The method is applied to cylindrical NaI(Tl) detectors and Ge(Li) detectors. Experimental determination of attenuation coefficients is especially useful in the latter case due to the uncertainty regarding the position and extent of active volume of the Ge(Li) detector. The attenuation factors for escape peaks differ from those for the full-energy peaks of the Ge(Li) detectors. Results are given for specific detectors and geometries and verified experimentally.

Attenuation of Millimeter Wavelength Radiation by Gaseous Water

A theoretical computation and absorption by water vapor of radiation within the millimeter and submillimeter region of the electromagnetic spectrum permits the determination of attenuation coefficients for given vapor densities, pressures, and temperatures. The rigid asymmetrical top rotor approximation for all angular momentum quantum numbers J <or= 12 is used with a line shape derived from kinetic theory and half-widths calculated by Anderson's theory. An equation is given for extrapolating attenuation coefficients to pressures and temperatures other than those for which calculations were performed.