Point Source Geometry Research Articles

THE SPATIAL DISTRIBUTION OF LIGHT EMISSION FROM LIQUID PHASE BIO‐ AND CHEMILUMINESCENCE: VARIATIONS WITH CONTAINER TYPES, TURBIDITY AND CONTAINER FROSTING

Abstract— The spatial distribution of emitted light from liquid phase bioluminescence and chemiluminescent sources in three common types of containers has been evaluated. These sources, while theoretically isotropic, exhibit considerable anisotropy due to reflection and refraction effects at the interfaces between the solution, the container and the surrounding air. This anisotropy represents a considerable systematic error (>25%) in some values of quantum yields reported in the literature. The degree of asymmetry in spatial distribution depends on the solution volume, the refractive index, and the degree of light scattering in the solution. Quantitative evaluation of the projected image of these sources using a video camera system indicates that a major contribution to this asymmetry is due to reflection at the meniscus. Since container frosting removes the variability due to scattering, volume changes, refractive index differences and even, to some extent, use of different types of containers, it is recommended that quantum yields and comparative measurements be determined using frosted containers and point source geometry. The container of choice is a frosted, 1 ± 7.5 cm test tube.

Efficiency values of NaI well-type detectors in the γ-ray region 10–150 keV for point and needle-shaped source geometries

We have calculated the efficiency values of 2 × 2 in. and 3 × 3 in. NaI well-type detectors in the γ-ray region 10–150 keV for point- and needle-shaped source geometries. The diameter and the height of the well are 2.857 cm and 3.81 cm, respectively, for both detectors. γ-ray absorption in the aluminium mounting of the well has been taken into account.

Tables for the Determination of the Lateral Shielding Requirements of High Energy Electron and Proton Accelerators

Neutron dose-equivalent rate transmission tables for the lateral shielding of high-energy (> 0.8 GeV) electron and proton beams have been calculated to assist a shield designer who needs realistic shielding data in a short time, and who may be required to readjust his results frequently as machine design is modified. These tables give the dose-equivalent rate transmitted normally to a particle beam through an average shielding material equivalent in nuclear properties to aluminum with varying concentrations of water, and through iron. Though designed for use in cylindrical geometries, they can be applied to point-source geometries as well.

Shielding properties of the UPb 3 intermetallic compound

The objective of this paper is to illustrate the shielding properties of UPb 3. A review of the literature indicated that this composition would be the most desirable of the uranium-lead system for potential use as a shielding material. In calculating the shielding properties, a point source geometry was assumed, and an analytical expression for the dose rate was then derived. The absorption coefficients for the compound were determined from the weight fraction of each component, and its corresponding absorption coefficient. From these coefficients, an equivalent atomic number of 85.2 was found for UPb 3. Buildup factors for UPb 3 were then determined, using this equivalent atomic number. The results of this analysis demonstrated that UPb 3 should be a very effective shield against gamma radiation. In comparison with lead, UPb 3 will effect a substantial reduction in both size and weight of a shield. In addition, the high melting point of UPb 3 (1220°C) gives it a definite advantage over lead. Although fabrication costs were not included in this analysis, the literature indicates that UPb 3 can be produced on a price competitive basis.

Back-scattering of low-energy gamma rays

Experimental data are obtained on the spectral angular distribution of γ-rays back-scattered by different scatterers-paraffin wax, graphite, aluminium, iron, zinc, cadmium and lead (semi-infinite media) in an isotropic point source geometry. The energies of the primary y-rays were 0·145,0·190,0·279,0·320,0·396,0·661 and 0·765 MeV. The experimental values of the numerical and energy albedos A and AE are in good agreement with the calculated values obtained by the Monte Carlo method. The results of the work are presented in the form of tables and graphs of A, A E and A/IA E as functions of Z and E γ .