Direct Transmission Measurements Research Articles

Direct analysis of 210Pb in sediment samples: Self-absorption corrections

A procedure for the direct γ-ray instrumental analysis of 210Pb in sediment samples is presented. The problem of dependence of self-absorption on sample composition is solved by making a direct transmission measurement on each sample. The procedure has been verified by intercalibrations and other tests.

Correlation between numerical predictions and measurements of single-mode fiber dispersion characteristics

Exact numerical solutions for the LP(01) propagating mode of the scalar wave equation are used to calculate propagation constants in single-mode fibers with arbitrary refractive-index profiles. The procedure is used to correlate predicted chromatic dispersion properties of single-mode fibers based on interferometrically measured profiles with direct transmission measurements vs wavelength. Resulting waveguide dispersion effects are used to design single-mode fibers that have minimum chromatic dispersion at desired wavelengths within the 1.3-1.6-microm region.

Optical properties and electronic structure of UO2

The near normal incidence reflectivity of UO2 single crystals has been measured in the photon energy range from 0.03 eV to 13 eV. From the reflectivity spectrum the complex dielectric function ε (ω) =ε1(ω)+iε2(ω) has been derived by means of the Kramers-Kronig relation. In addition the absorption coefficient was determined from a direct transmission measurement on thin single crystal plates in the weakly absorbing spectral region below the absorption edge. An energy level scheme is proposed which allows a self-consistent assignment of the structure in ε2 with optical transitions between maxima in the density of states. The energy gap found at 2.1±0.1 eV is attributed to a 5f2→5f16deg transition. A crystal field splitting 10Dq=2.8 eV is derived for the 6d conduction states. Good agreement is obtained within this model with XPS measurements and a recent molecular cluster approximation. It disagrees with a previous interpretation of reflectivity data.

Sound Absorption at 50 to 500 kc from Transmission Measurements in the Sea

The absorption coefficient of sound in sea water has been obtained by a series of direct transmission measurements at several moderately high frequencies in a sheltered deep water bay in Puget Sound. Advantage was taken of the isothermal and isosaline properties existing during certain seasons of the year in this location. The fluctuations normally encountered in such a measurement were minimized by the utilization of fixed buoys, a radio link for range determination by acoustic travel time, and a method of space averaging. Values obtained, in decibels per kiloyard at a temperature of 10°C and a salinity of 30 parts per thousand, are: 14.4±0.3 at 60 kc, 35.7±0.7 at 142 kc, 57±3 at 272 kc, and 101±3 at 467 kc. Although the frequency dependence of the absorption coefficient given by these measurements follows the normal relaxation law, the magnitudes are lower than those given by Del Grosso by 4 to 10 db/kyd.

Underwater Acoustic Transmission Variations Caused by Thermal Layers—Theoretical

A perturbation calculation on the eikonal equations by Bergmann [Phys. Rev. 70, 486 (1946)] is extended to apply to acoustic transmission in a medium with a single horizontal layer in which the deviation of the index of refraction from unity is very small. Numerical calculations for the sound level deviation for transmission in such a medium are presented. A temperature layer about 2 yd thick with a maximum temperature deviation from the surrounding water of 0.02°C can produce sound level variations of 2.2 db at 500-yd range. Excellent agreement is obtained in a comparison between these results and direct acoustic transmission measurements in an underwater medium closely approximating these assumptions. (This work was supported by the Bureau of Ordnance, U. S. Navy, under Contract NOrd 12937.)

Recent Field Measurements of the Absorption of Sound in Sea Water

The absorption coefficient of sound in sea water has been obtained by a series of direct transmission measurements at several moderately high frequencies in a sheltered, deep-water bay in Puget Sound. Advantage was taken of the essentially isothermal and isosaline properties existing during certain seasons of the year in this location. Utilization of fixed buoys, a radio link for range determination by acoustic travel time, and a method of space averaging minimized the fluctuations normally encountered in such a measurement. Values obtained, in decibels per kiloyard at 10°C and 30 parts per thousand salinity, are 14.4±0.7 at 60 kc, 36±1 at 142 kc, 57±2 at 272 kc, and 101±3 at 467 kc. Although the frequency dependence of the absorption coefficient given by these measurements follows the normal relaxation law, the magnitudes are lower than those given by Del Grosso (NRL Report 4279, Naval Research Laboratory, Washington, D. C., January 13, 1954) by 4 to 9 db/kyd. (This work supported by the Bureau of Ordnance, U. S. Navy, under Contract NOrd 12937.)

Optical and Photo-Electrical Properties of Indium Antimonide

Measurements have been made of the refractive index and absorption index of InSb by reflection methods with polarized radiation. Extensive studies of absorption constant have been made by direct transmission measurements. Both photovoltaic and photoconductive effects have been observed in InSb. At room temperature the photosensitivity extends to approximately 7.5μ, a considerably longer wavelength than for any other known material.