Development of a dosimeter for distributed body organs

Calculational methods for estimation of dose from external proton exposure of aribtrary convex bodies is briefly reviewed and all of the necessary information for the estimation of dose in soft tissue is presented. Special emphasis is on retaining the effects of nuclear reaction especially in relation to the dose equivalent

A study of heavy-heavy nuclear reactions

A simplified theory for heavy ion scattering shows good agreement with heavy ion absorption experiments. Theoretical implications on the complete coupled channel reaction equations are discussed

Proton tissue dose for the blood forming organ in human geometry: Isotropic radiation

A computer program is described which calculates doses averaged within five major segments of the blood forming organ in the human body taking into account selfshielding of the detailed body geometry and nuclear star effects for proton radiation of arbitrary energy spectrum (energy less than 1 GeV) and isotropic angular distribution. The dose calculation includes the first term of an asymptotic series expansion of transport theory which is known to converge rapidly for most points in the human body. The result is always a conservative estimate of dose and is given as physical dose (rad) and dose equivalent (rem)

A study of physical processes for space radiation protection

The determination of stopping power for monatomic molecules and water vapor is addressed. Intermediate and low energy protons are considered

Computer subroutines for the estimation of nuclear reaction effects in proton-tissue-dose calculations

Calculational methods for estimation of dose from external proton exposure of arbitrary convex bodies are briefly reviewed. All the necessary information for the estimation of dose in soft tissue is presented. Special emphasis is placed on retaining the effects of nuclear reaction, especially in relation to the dose equivalent. Computer subroutines to evaluate all of the relevant functions are discussed. Nuclear reaction contributions for standard space radiations are in most cases found to be significant. Many of the existing computer programs for estimating dose in which nuclear reaction effects are neglected can be readily converted to include nuclear reaction effects by use of the subroutines described herein

Elemental characteristics of aerosols emitted from a coal-fired heating plant

Size differentiated aerosols were collected downstream from a heating plant fueled with eastern coal and analyzed using particle induced X-ray emission technique. Based on aerosol masses collected in various size ranges, the aerosol size distribution is determined to be trimodal, with the three peaks centered at 0.54 microns, 4.0 microns, and 11.0 microns, respectively. Of the various trace elements present in the aerosols, sulphur is the only element that shows very strong concentration in the smallest size group. Iron is strongly concentrated in the 4.0 micron group. Potassium, calcium, and titanium also exhibit stronger concentration in the 4.0 micron group than any other group. Other trace elements - vanadium, chromium, manganese, nickel, copper, and barium - are equally divided between the 0.54 microns and the 4.0 microns groups. Apparently, all of the trace elements - except S - enter aerosols during the initial formation and subsequent condensation phases in the combustion process. Excess concentration of sulphur in the 0.54 microns group can only be accounted for by recondensation of sulphur vapors on the combustion aerosols and gas-to-particle phase conversion of sulfate vapors at the stack top

An investigation of electrical and optical properties of sputtered amorphous silicon nitride and germanium thin films

Low temperature preparation of thin amorphous Silicon Nitride and Germanium Films by direct RF sputter deposition was investigated. Influence of various sputtering parameters on film properties was studied. Infrared transmission spectrophotometry was used to evaluate optical properties of the films whereas electrical characteristics of the films were determined from current-voltage measurements of MIS structures. For Silicon Nitride films it was observed that the stoichiometry, as indicated by the IR transmission, dielectric constant and current density versus square root of electric field measurements, was a strong function of the sputtering gas composition and particularly the Ar/N ratio in the sputtering gas. It was established from the current-voltage relationship that the dominant conduction mechanism in these films is of PooleFrenkel type. The current-voltage characteristics of the MIS devices were observed to be independent of the electrode material, device area and the film thickness. It is concluded that the insulating films thus deposited were comparable to those deposited using any other deposition method and is anticipated that due to the low deposition temperatures, sputtering may emerge as a highly potential process for optoelectronic device passivation. Germanium Gamma-ray p-n junction detectors coated with 30 nm thick sputtered amorphous germanium exhibited improved surface stability. Hydrogenated amorphous germanium was also used and the result indicated that this material would have superior passivating properties than amorphous Germanium

An Investigation of Size-Dependent Concentration of Trace Elements in Aerosols Emitted from the Oil-Fired Heating Plants

Aerosols emitted from two oil-fired heating plants were aerodynamically separated into eight size groups and were analyzed using the photon-induced X-ray emission (PIXE) technique. It was found that Zn, Mo, Ag, and Pb, and (to a lesser extent) Cd, have a tendency to concentrate preferentially on the smaller aerosols. All of these elements, in certain chemical forms, are known to be toxic. Zinc and molybdenum, although present in low concentrations in the parent fuels, show the strongest tendencies to be concentrated in finer aerosols. Selenium, previously reported to show a very strong tendency to concentration in finer fly ash from coal-fired power plants shows little preference for surface residence. Vanadium, which occurs in significant concentration in the oil fuels for both plants, also shows little preference for surface concentration. Even though the absolute concentrations of the toxic elements involved are well below the safety levels established by the National Institute for Occupational Safety and Health (NIOSH), it would be advisable to raise the heights of the heating-plant exhaust chimneys well above the neighborhood buildings to insure more efficient aerosol dispersal