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Geology topics

P. W. Philbin

Publications and source records attributed to P. W. Philbin.

At least 19 recordsLinked to original sources
USGS1977

Importance of neutron energy distribution in borehole activation analysis in relatively dry, low-porosity rocks

To evaluate the importance of variations in the neutron energy distribution in borehole activation analysis, capture gamma-ray measurements were made in relatively dry, low-porosity gabbro of the Duluth Complex. Although sections of over a meter of solid rock were encountered in the borehole, there was significant fracturing with interstitial water leading to a substantial variation of water with depth in the borehole. The linear-correlation coefficients calculated for the peak intensities of several elements compared to the chemical core analyses were generally poor throughout the depth investigated. The data suggest and arguments are given which indicate that the variation of the thermal-to-intermediate-to-fast neutron flux density as a function of borehole depth is a serious source of error and is a major cause of the changes observed in the capture gamma-ray peak intensities. These variations in neutron energy may also cause a shift in the observed capture gamma-ray energy.

Geoexploration↗
USGS1977

In situ analysis of coal using a 252CF-Ge(Li) borehole sonde

A borehole sonde using a 252 Cf neutron source and a Ge(Li) gamma-ray detector was field tested in a coal bed in Belmont County, Ohio, to ascertain whether such a device could be useful as a coal-exploration tool. In continuous motion, the sonde was used to accumulate successive spectra over short time intervals. The intensities of the capture gamma rays from hydrogen and of the decay gamma rays from aluminum were determined simultaneously in each spectrum. A log of the intensities versus depth shows the depth and thickness of the coal bed. With the sonde stationary at points above, in, and below the coal bed, capture gamma rays were measured to show the variation in concentration of certain elements. From the spectrum recorded in the bed, a complete ultimate analysis, the percent ash content, and the heat content were determined without recourse to an external standard. With the sonde stationary at points above, in, and below the coal bed, capture gamma rays were measured to show the variation in concentration of certain elements. From the spectrum recorded in the bed, a complete ultimate analysis, the percent ash content, and the heat content were determined without recourse to an external standard. These experiments show that it is feasible to use a 252 CfGe(Li) borehole sonde as an aid in coal exploration.

Open-File Report↗
USGS1976

Intrinsic germanium detector used in borehole sonde for uranium exploration

A borehole sonde (~1.7 m long; 7.3 cm diameter) using a 200 mm 2 planar intrinsic germanium detector, mounted in a cryostat cooled by removable canisters of frozen propane, has been constructed and tested. The sonde is especially useful in measuring X- and low-energy gamma-ray spectra (40–400 keV). Laboratory tests in an artificial borehole facility indicate its potential for in-situ uranium analyses in boreholes irrespective of the state of equilibrium in the uranium series. Both natural gamma-ray and neutron-activation gamma-ray spectra have been measured with the sonde. Although the neutron-activation technique yields greater sensitivity, improvements being made in the resolution and efficiency of intrinsic germanium detectors suggest that it will soon be possible to use a similar sonde in the passive mode for measurement of uranium in a borehole down to about 0.1% with acceptable accuracy. Using a similar detector and neutron activation, the sonde can be used to measure uranium down to 0.01%.

Nuclear Instruments and Methods↗
USGS1976

Field experiments to test neutron interaction techniques in boreholes in relatively dry, low porosity rock

Depending on the technique, there are a number of problems associated with in situ neutron activation elemental analyses in boreholes. Several techniques of using delayed and capture gamma rays for in situ borehole spectral analysis were tried in a relatively dry gabbro. Using copper as a test element the best results using a delayed gamma-ray method were obtained by independent uniform neutron irradiation of the borehole followed by a delay time of about 16 hours before spectral analysis. The results obtained for several other elements measured by both delayed and capture gamma-ray methods, however, showed poor correlation with the chemical analyses. The change in the nonthermal compared with thermal neutron flux density in the rock appears to be the most serious cause of the poor correlation observed. This in turn affects the gamma-ray peak intensities and energies. Errors in the driller's log, poor correspondence between the core chemistry and the sample, and interstation interference also contributed substantially to the poor results.

Open-File Report↗
USGS1976

Intrinsic germanium detector used in borehole sonde for uranium exploration

A borehole sonde using a 200-mm 2 planar intrinsic germanium detector, mounted in a cryostat cooled by removable canisters of frozen propane, has been constructed and tested. The sonde is especially useful in measuring X- and low-energy gamma-ray spectra (40-400 keV). Laboratory tests in an artificial borehole facility indicate its potential for in-situ uranium analyses in boreholes irrespective of the state of equilibrium in the uranium series. Both natural gamma-ray and neutron-activation gamma-ray spectra have been measured with the sonde. Although the neutron-activation technique yields greater sensitivity, improvements being made in the resolution and efficiency of intrinsic germanium detectors suggest that it will soon be possible to use a similar sonde for measurement of the natural radiations of uranium in a borehole down to the 0.1 percent range with acceptable accuracy.

Open-File Report↗