Germanium Semiconductor Detector Research Articles

Ge(Li) gamma-ray spectrometry as a pilot for NaI(Tl) gamma-ray spectrometry

Lithium-drifted germanium semiconductor detectors give much better resolution than do thallium-activated sodium iodide detectors, but much lower sensitivity. They can often advantageously be used in conjunction with NaI(Tl) detectors, to show whether corrections must be applied for activities other than the one to be measured and to provide the necessary information for calculation of the corrections.

Anomalous effect in a lithium-drifted germanium semiconductor detector

After the installation of a lithium-drifted germanium [Gel (Li)] gamma-ray detector in a vacuum cryostat at 77°K, a negative differential resistance was observed that was stable and measurable using d.c. methods. This letter describes the results and measured characteristics obtained so far.

A trace-element study of iron meteorites

The technique of neutron activation and γ counting on a lithium-drifted germanium semiconductor detector has been used in measuring concentrations of cobalt, copper, arsenic, gallium, iridium, and gold in 33 iron meteorites. Similar data on 25 other iron meteorites are available in the literature. These meteorites are grouped according to similarities in their trace-element content. Out of 23 samples classified as hexahedrites and coarse octahedrites, 22 can be assigned to three groups corresponding to the structural classifications as normal hexahedrites, coarse octahedrites, and a group intermediate between these two. Within these groups, as Ni increases, the elements Co, Cu, As, Ga, and Au increase while Ir decreases. This is thought to represent trace-element behavior during crystallization and crystal settling from a melt of a homogeneous chemical composition. A discontinuity involving the elements As, Au, Ga, and Ir exists between the coarse octahedrites and medium octahedrites. The medium octahedrites are also characterized by their heterogeneity. Only 8 out of 17 can be assigned to groups. Out of 10 fine octahedrites, 5 have uniform elemental compositions. This group differs from the medium octahedrites in Ni, Co, and Ga. These differences in trace-element abundance are ascribed to differences in composition of the Fe-Ni melt from which the meteorites crystallized. At least three melts, varying chiefly in Ni and Ga, are required to account for the compositions of all the iron meteorites. Six Ni-rich ataxites show no uniformity in their trace-element abundances. They probably represent the end stage of crystallization from several sources. Two structurally anomalous meteorites, Nedagolla and N'Goureyma, are unusually low in trace elements. This may have resulted from a remelting of a normal iron meteorite during break-up of the meteorite parent body.

Application of gamma ray spectrometry and computer techniques to the determination of the minimum detectable content of trace elements in neutron activated materials

A computer method has been developed in order to derive from the gamma ray spectrum of a neutron activated material the detection limits for a great number of trace elements. A “sensitivity spectrum” is calculated from the experimental data. The detection limit for 57 elements is then deduced using library data of specific activities. With this procedure it has been made possible to determine, in a sample of nuclear graphite, detection limits smaller than 1 ppm for about 40 elements. The performances of a 3″ × 3″ NaI(Tl) scintillator and of a lithium drifted germanium semiconductor detector for this particular application are compared. The computer program is written in FORTRAN-4 for the IBM 7090 computer.

Energy Levels ofBi211

The gamma-ray spectrum from the decay of ${\mathrm{Pb}}^{211}$ has been studied with NaI crystals (using singles, gamma-gamma coincidence, and sum-coincidence techniques) and with a germanium semiconductor detector. The energies and relative gamma-ray intensities are reported for 16 transitions in ${\mathrm{Bi}}^{211}$. The energy and relative intensity of 5 internal-conversion electron lines were measured with a precision magnetic betaray spectrometer. From the gamma-ray and internal-conversion transition energies and the gamma-gamma coincidence measurements a consistent level diagram for ${\mathrm{Bi}}^{211}$ is proposed which has levels at 404.84\ifmmode\pm\else\textpm\fi{}0.04, 766.34\ifmmode\pm\else\textpm\fi{}0.07, 831.83\ifmmode\pm\else\textpm\fi{}0.04, 1020\ifmmode\pm\else\textpm\fi{}3, 1076\ifmmode\pm\else\textpm\fi{}3, 1104\ifmmode\pm\else\textpm\fi{}2, 1188\ifmmode\pm\else\textpm\fi{}2, and 1265\ifmmode\pm\else\textpm\fi{}2 keV.

The Ge 73(n, α)Zn 70 reaction at 14 MeV observed in a lithium drifted germanium detector

The (n, α) reactions induced in germanium by 14 MeV neutrons have been observed in a germanium semiconductor detector. Values of the cross section of the ground-state transition of Ge 73(n, α)Zn 70 at 14.1 and 14.8 MeV are presented along with possible evidence for the existence of excited states of Zn 70 at 1.95±0.1 MeV and at 2.3±0.1 MeV. Evidence for a reduced response of the detector to the Zn recoil atoms is discussed.

A Rapid-Scan Infrared Spectrometer; Flash Photolytic Detection of Chloroformic Acid and of CF_2

A rapid-scan infrared spectrometer has been constructed and successfully applied to the study of short-lived intermediates produced by flash photolysis. A zinc-doped germanium semiconductor detector and a high-speed rotating Littrow mirror permit scan rates of 1000 cm−1/100 μsee through the region 5000–650 cm−1. Two transient species, chloroformic acid and CF2, have been identified, and lough estimates of their lifetimes have been obtained, 50–70 μsec and about 2.5 msec, respectively. This is the first spectroscopic detection of chloroformic acid.

The infrared detection of free radicals using flash photolysis methods

A rapid-scan infrared spectrometer has been constructed and successfully applied to the gas phase study of short-lived intermediates produced by flash photolysis. A zinc-doped germanium semiconductor detector and a Littrow mirror rotating at 10 000 rpm permit scan rates of 1 000 cm–1 /100 microseconds. Detector sensitivity extends over a wide spectral range, 2-40 μ. Two intermediates of short lifetime, chloroformic acid and CF2 , have been identified and rough estimates of their half-lives have been obtained, 50-70 microseconds and 2,5 milliseconds, respectively. The possibilities of infrared emission studies are suggested by the emission spectrum from a Cl2 — H2 explosion initiated by flash photolysis.