E. L. Haines

Pulse Height Defect and Energy Dispersion in Semiconductor Detectors

We have calculated the contributions of the atomic (screened Coulombic) scattering process to the pulse height defect and energy dispersion observed when heavy ions expend their energies in semiconductor detectors. Atomic scattering appears to account qualitatively for the pulse height defect observed for most heavy ions in both silicon and germanium detectors. Atomic scattering also contributes substantially to the energy dispersion.

Mineralogy, petrology, and chemistry of a Luna 16 basaltic fragment, sample B-1

Abstract Luna 16 sample B-1 was the largest fragment (62 mg) obtained in the sample exchange with the USSR. Petrologic, mineralogic, and chemical investigations have been made on this fragment in conjunction with Rb-Sr and40Ar/39Ar investigations by our colleagues. Sample B-1 is a fine-grained ophitic basalt but is distinguished from the Apollo samples by containing a single pyroxene, predominantly pigeonitic, an ilmenite content (7%) intermediate to that of the Apollo 11 and 12 samples, and subequal amounts of pyroxene (50%) and plagioclase (40%). Chemically it is distinguished by a high Sr content (437 ppm) and a high K/U value (4700). The K-content (1396 ppm) is higher than that of Luna 16 soil sample A-2.

Uranium concentration and distribution in six peridotite inclusions of probable mantle origin

Abstract Fission-track activation was used to investigate uranium concentration and distribution in peridotite inclusions in alkali basalt from six localities. Whole-rock uranium concentrations range from 24 to 82 ng/g (1ng= 10−9g). Most of the uranium is uniformly distributed in the major silicate phases — olivine, orthopyroxene, and clinopyroxene. Chromian spinels may be classified into two groups on the basis of their uranium content, having either less than 10 ng/g or 100–150 ng/g U. In one sample accessory hydrous phases, phlogopite and hornblende, contain 130 and 300 ng/g U, respectively. The contact between the inclusion and the host basalt is usually quite sharp. Glassy or microcrystalline veinlets found in some samples contain more than 1μg/g(1 μg= 10−6g). Very little uranium is associated with microcrystals of apatite. Our results agree with some earlier investigators, who have concluded that suboceanic peridotites contain too little uranium to account for normal oceanic heat flow by conduction alone.

Uranium-bearing minerals of lunar rock 12013

The U distribution in rock 12013 was studied by fission track and elemental mapping techniques. Major U-bearing phases are whitlockite, apatite, zircon, and phase β, which is a ZrTi mineral rich in Fe, Nb, Y, REE and containing up to 3.6% UO2, 4.7% ThO2, and 4.2% PbO. Calculated microprobe ages for phase β average 4.0 AE and are in reasonable agreement with RbSr and KAr ages. Phase β plays a significant role in the UThPb systematics of rock 12013 and may play a similar role in the model ages of lunar soil.

Measuring planetary hydrogen by remote gamma-ray sensing

Abstract A γ-ray spectrometer (GRS) orbiting about an airless or nearly airless planetary body may be used to detect and measure hydrogen concentration and the neutron leakage flux. The H concentration affects both the magnitude and energy spectrum of the neutron flux, while the neutron flux, in turn, determines the intensity of the observed H γ-ray line for a given concentration. Because of this interconnection, the dual measurement of both H and neutron flux enhances the accuracy of each, and assists in the measurement of other elements. Hydrogen is detected by means of its 2.223 MeV γ ray which arises from the capture of thermal neutrons producing deuterium. The 2.223 MeV H signal is observed in the γ-ray spectrum against an interference spectrum consisting of cosmic γ rays, planetary background emission, and a variety of γ rays arising from cosmic-ray particle interactions with the γ-ray spectrometer and spacecraft (SC). In addition, line interferences are generated by the interactions of neutrons with hydrogenous materials in the GRS and SC. In this paper the expected signal levels and the sources of continuum and line interference in the detection and measurement of H are assessed in terms of two possible missions, a lunar orbiter and a comet nucleus rendezvous. In lunar orbit, a 100 h observation at an altitude of 100 km should enable the detection of H at a level of 0.06% with an uncertainty of ∼ 0.02%. At a distance equal to the radius of a comets nucleus, in 100 h a GRS can detect H at a level of 0.07% and can measure H at expected cometary levels (∼ 6%) with an uncertainty of 0.06%.

Measuring planetary neutron albedo fluxes by remote gamma-ray sensing

Abstract A remote-sensing γ-ray spectrometer (GRS) is capable of measuring planetary surface composition through the detection of characteristic gamma rays. In addition, the planetary neutron leakage flux may be detected by means of a thin neutron absorber surrounding the γ-ray detector which converts the neutron flux into a γ-ray flux having a unique energy signature. The γ rays representing the neutron flux are observed against interference consisting of cosmic γ rays, planetary continuum and line emission, and a variety of gamma rays arising from cosmic-ray particle interactions with the γ-ray spectrometer and spacecraft (SC). In this paper the amplitudes of planetary and non-planetary neutron fluxes are assessed and their impact on the sensitivity of measurement is calculated for a lunar orbiter mission and a comet nucleus rendezvous mission. For a 100 h observation period from an altitude of 100 km, a GRS on a lunar orbiter can detect a thermal neutron albedo flux as low as 0.002 cm −2 s −1 and measure the expected flux of ∼ 0.6 cm −2 s −1 with an uncertainty of 0.001 cm −2 s −1 . A GRS rendezvousing with a comet at a distance equal to the radius of the comets nucleus, again for a 100 h observation time, should detect a thermal neutron albedo flux at a level of 0.006 cm −2 s −1 and measure the expected flux of ∼ 0.4 cm −2 s −1 with an uncertainty of 0.004 cm −2 s −1 . Mapping the planetary neutron flux jointly with the direct detection of H will not only provide a more accurate model for translating observed γ-ray fluxes into concentrations but will also extend the effective sampling depth and should provide a capability for simple stratigraphic modeling of hydrogen.

Whole‐rock uranium analysis by fission track activation

We report a whole‐rock uranium method in which the polished sample and track detector are separated in a vacuum chamber. Irradiation with thermal neutrons induces uranium fission in the sample, and the detector records the integrated fission track density. Detection efficiency and geometric factors are calculated and compared with calibration experiments.

Degradation of the Time Characteristics of Surface Barrier Detectors with Fission Fragment Dose

Differential energy losses of fission fragments in thin carbon films as function of mass and initial energy mapped by time of flight method

Use of Transformations in Multiparameter Data Sorting

A major problem in multiparameter data sorting is the excessive computer memory space required for all of the available information. This paper describes a sorting technique which is useful if the information in one parameter can be represented by a simple distribution which can be described by the coefficients of an appropriate transformation. It is possible to compute the coefficients without accumulating the data in spectral form. For example, consider a three parameter experiment where the events are characterized by x, y and f(x,y). Suppose that the purpose of the experiment is to map the amplitude, mean, standard deviation, skew and kurtosis of f(x,y) over the x-y plane. It is necessary to reserve only five words in the computer memory for each location in the x-y plane. During the sorting process, the quantities accumulated in these five registers are ?a0i, ?a1i, ?a2i, ?a3i, ?a4i, where ai is the digital value of f(x,y) for the ith event. Use of the Gauss-Hermite quadrature and the Fourier transformation are discussed and illustrated by an example (the measurement of secondary electron yields as a function of fission fragment mass and energy).

The Use of Local Linear Transforms to Reduce the Size of a Two-Dimensional Associative Memory

We discuss associative memory in the analysis of two-dimensional data where the variables are transformed before data accumulation. Local linear transforms reduce the number of associative locations required, while a two-dimensional search scheme shortens the search among the fewer locations. Application of these methods results in some saving of memory space and an appreciable saving in execution time.