A. Keith Furr

Study of guinea pigs fed Swiss chard grown on municipal sludge-amended soil. Multi-element content of tissues.

Swiss chard, field-grown on soil amended with 100 dry tons per acre of municipal sewage sludge from Washington, DC, was fed to guinea pigs for 28 days. Control animals were fed Swiss chard grown on unfortified soi. Forty-one elements were determined in the sludge, the plant material, and liver, kidney, muscle, adrenal, and spleen tissues by neutron activation and other methods. Elevated concentrations of several elements found in the Swiss chard grown on the sludge-soil mixture also appeared at higher levels in certain of the animal tissues. These included antimony in adrenal, cadmium in kidney, manganese in liver tissues, and tin in several tissues. The animals showed no observable toxicological effects.

Time dependent deadtime and pile-up corrections for gamma ray spectroscopy

Abstract The losses of pulses in gamma spectroscopy due to the analog-to-digital (ADC) conversion process and due to pulse pile-up is a major problem in quantitative gamma ray spectroscopy. It is specially serious if the count rate varies significantly during the counting interval and if the nuclear events of interest are associated with an isotope with a half-life shorter than or comparable to the counting interval as is often the case for isotopes with half-lives of the order of 10 min or less. The count rates at which dead time losses become a problem depend upon the available equipment but, in the present work, the problem became acute at count rates in excess of 25 000 cps. A technique developed at VPI & SU is discussed in the present work which very satisfactorily corrects for both ADC and pile-up losses and is dependent upon the half-life of the decaying radioisotope.

Element content of mosses as possible indicators of air pollution.

Since mosses derive their nutrients largely from air, they may serve as possible indicators of the magnitude of air pollution. Samples ofSphagnum mosses were collected in the Adirondack region of northeastern New York and analyzed for 46 elements. High concentrations of barium, chromium, iron, lead, molybdenum, titanium and vanadium were found. Concentrations of aluminum and fluorine were correlated and may be related to aluminum and glass smelting activities in the area. The concentrations of a number of other element pairs in the mosses also indicated some correlation.

Proton Sputtering of Gold

Sputtering of gold by normally incident protons of energies between 500 eV and 8 keV has been studied. An ion source system delivering a magnetically analyzed proton beam to a target at a pressure of 5×10−8 Torr was utilized, and neutron activation established the quantities of sputtered material. The gold targets, consisting of microcrystals with preferred orientation, were sputtered predominantly on (100) and (110) planes, and the yields were not observed to depend perceptibly on the crystal orientation. The yield was a maximum of 0.022 atoms/proton at a proton energy of 4 to 5 keV, dropping off gradually at higher energies and sharply at lower ones. Analysis of the sputtered deposit spot patterns, using autoradiographs, indicated that focused collision sequences were of greater importance in proton sputtering than in sputtering by heavier ions. A readily detectable yield for sputtering by 500‐eV protons suggests a minimum atomic ejection energy of less than 10 eV for sputtering of gold.

Algorithm for computer processing and analysis of gamma ray spectra for large-scale laboratory operations

Abstract For large scale neutron activation analysis laboratories, computer analysis of data is necessary. This work discusses major features of the analytical program which has been developed and is currently being used at Virginia Polytechnic Institute and State University. Specific attention is drawn to fitting function choice, controlled fitting techniques, and methods of error analysis. In order to test the program, samples of standard reference material from the National Bureau of Standards were obtained and analyzed. The results of this analysis are given and demonstrate that the code is effectively doing its intended task.

A fast neutron spectrometer for reactor flux measurements

Abstract A neutron spectrometer has been constructed which may be employed in a collimated beam geometry for neutrons with energies from about 0.5 to 5.0 MeV. The design is a modification of a recoil proton telescope which employs a silicon surface barrier diode as a detector. Difficulties with neutron induced reactions in the diodes themselves from neutrons above 5 or 6 MeV which affect the performance of “sandwich-type” silicon diode neutron spectrometers are eliminated. A measurement of the neutron spectrum in a collimated beam from the V.P.I. reactor has been made which shows that the instrument provides a very satisfactory means of determining the neutron energy distribution in a non-mono-energetic flux.

Elemental content of vegetables and millet grown in potted soil amended with lignite fly ash

Vegetables and millet were grown to maturity in potted soil amended with 10% (by weight) of lignite fly ash. Analysis of the ash, soil, and crops for 40 elements showed Al, As, B, Mg, Mo, Rb, and Se to be absorbed at higher levels by the ash-grown plants than the controls in most instances. Selenium was of most concern, because of its toxicity and degree of plant uptake.

Neutron Activation Studies of the Roanoke River System

A study of an unusually compact and well defined river system containing many environmental factors leading to water pollution has been carried out by neutron activation analysis. Detailed baseline measurements of the levels of sodium, chlorine, magnesium, manganese, calcium, strontium, and aluminum were made and tests made above and below major effluent sources.

Apparatus for the Study of Proton Sputtering

An apparatus for the study of proton sputtering, consisting of a differentially pumped ultrahigh vacuum system, rf ion source, electrostatic lenses, and double focusing magnetic spectrometer has been designed and built. The system was capable of delivering a proton beam of energy from 500 eV to 8 keV, and average current density of 1.0 mA/cm2, to a target at 5×10−8 Torr.