Lithium-drifted Germanium Detector Research Articles

Non-destructive elemental analysis of vertebral body trabecular bone using muonic X-rays.

Non-destructive elemental analysis with muonic X-rays was performed on human vertebral bone and lumbar torso phantoms. It can provide quantitative information on all elements in small deep-seated localized volumes. The experiment was carried out using the superconducting muon channel at TRIUMF in Vancouver, Canada and a lithium drifted germanium detector with an active area of 18.5 cm2. The muon channel produced backward-decayed negative muons with wide kinetic energy range from 0.5 to 54.2 MeV. The muon beam was collimated to a diameter of 18 mm. The number of incoming muons was about 4 x 10(6) approximately 5 x 10(7) per data point. In the measurements with human vertebral bones fixed with neutralized formaldehyde, the correlation coefficient between calcium content measured by muons and by atomic absorption analysis was 0.99 and the level of significance was 0.0003. In the measurements with lumbar torso phantoms, the correlation coefficient between calcium content measured by muons and by atomic absorption analysis was 0.99 and the level of significance was 0.02. The results suggest that elemental analysis in vertebral body trabecular bone using muonic X-rays closely correlates with measurements by atomic absorption analysis.

Measurements of atomic form factors at 4.283-Å-1 photon-momentum transfer.

Whole-atom differential cross sections for coherent scattering of 59.5-keV \ensuremath{\gamma} rays at 126\ifmmode^\circ\else\textdegree\fi{} by Ti, Ni, Zn, Se, Mo, Ru, Cd, Sn, Te, Gd, Dy, Yb, W, and Pb were measured using a high-resolution lithium-drifted germanium detector. Form factors were extracted from the measured cross sections and the results were compared with predictions of form-factor theories.

Analytical Sensitivities for Thirty-Six Elements in Cellulose Matrix by Means of High-Energy Photon Activation and Low-Energy Photon Detection

The analytical potentiality of the combined use of high-energy photon activation and low-energy photon detection has been investigated by irradiating 36 elements with 30-MeV bremsstrahlung. The characteristic X-rays and low-energy gamma-rays from the activation products were measured with an intrinsic high-purity germanium detector, and the experimental sensitivities have been estimated. A comparison was applied to the results with the conventional gamma-ray measurements with a lithium-drifted germanium detector. The attenuation of the low-energy photons due to a sample matrix was also considered. Practical detection limits for several elements were evaluated by analyzing a biological standard reference material, NIST Orchard Leaves. For Ba, Br, I, Ni, Mo, Pb, Sb and Zn, detection limits were lowered by low low-energy photon spectroscopy. From the results, applicability and versatility of this method have been demonstrated.

Determination of trace elements in Nigerian kola-nuts by instrumental neutron activation analysis

The trace elements content of Cola acuminata and three varieties of Cola nitida have been determined using neutron activation analysis. The samples have been irradiated at the Joint Universities Research Reactor, Risley, England for 71/2 hours in a neutron flux of 2.5·1012 n·cm−2s−1 and analysed using high resolution lithium drifted germanium detector coupled to a Canberra 35 microprocessor as a 4096 channel gamma spectrometer. The elements: Na, K, Br, W, Fe, Cs, Co, Zn, and Sc were detected.

Neutron-radiation analysis of ferromanganese concretions in the ocean

The authors describe a method and equipment for the neutron activation analysis of ferromanganese ores for purposes of surveying for these ores in the ocean floor. The neutron activation analyzer is based on a californium 252 spontaneous fission thermal neutron source and uses lithium-drifted germanium detectors for recording prompt gamma radiation spectra induced by the neutrons in the ores. The analyzer can work in a ship-borne laboratory and permits the immediate determination of the elements in the sample. Performance and resolution characteristics are included.

Actinium-228 in Natural Background Gamma Radiation Spectrum

The natural background γ-radiation was observed by 102.88 cc lithium drifted germanium detector. Twenty-five lines due to 228Ac were observed in the energy spectrum extending from 50 to 1.280 keV. Comparison with other workers led to identifying two unknown peaks and observing four new lines. A quantitative measurement of the peaks is given in terms of relative intensity of the observed γ-lines.

Actinium-228 in natural background gamma radiation spectrum.

The natural background γ-radiation was observed by 102.88 cc lithium drifted germanium detector. Twenty-five lines due to 228Ac were observed in the energy spectrum extending from 50 to 1.280 keV. Comparison with other workers led to identifying two unknown peaks and observing four new lines. A quantitative measurement of the peaks is given in terms of relative intensity of the observed γ-lines.

Ｇｅ（Ｌｉ）検出器の円板状面線源に対する全エネルギーピーク効率の形状補正

Ｇｅ（Ｌｉ）検出器の円板状面線源に対する全エネルギーピーク効率の形状補正

The Use of High Purity Germanium for the Detection of 20 to 200 MeV Light Ions

While lithium-drifted germanium detectors have become an accepted tool for high resolution gamma ray spectroscopy, they were also shown to be excellent charged-particle detectors as well. Their use for this purpose was limited, however, by the practical complexities of their handling and storage at liquid-nitrogen temperature, and consequent incompatability with typical nuclear research scattering chambers. Many of these difficulties were eliminated by the development of the high-purity germanium stopping detector in 1970, and by the more recent development of the transmission type high-purity germanium detectors in 1977. A variable geometry detector telescope system using these high-purity planar germanium detectors has been developed and used at intermediate energies at Indiana since 1976. A detailed description of the telescope system is presented, along with some practical experience of their use as light ion detectors. The effects of radiation damage and the radiation damage annealing procedures on detector properties and performance are emphasized.

Direct determination of 7Be in sediments

Cosmic-ray produced 7Be (53 days half-life) is directly measurable in freshly collected samples of river and coastal zone sediments using a lithium-drifted germanium detector. Calibration of the detector is discussed and an assessment of overall accuracy and sensitivity presented. The detection limit for a 250-g dry weight sediment sample contained in a Marinelli Beaker and counted for 200 minutes is approximately 0.4 pCi/g. Applications toward locating zones of rapid sedimentation as well as in understanding shallow-water sedimentation dynamics are suggested.

Separation of Macro-Quantities of Actinide Elements at Savannah River by High-Pressure Cation Exchange

Abstract Large-scale separation of actinides from fission products and from each other by pressurized cation exchange chromatography at Savannah River is reviewed. Several kilograms of 244Cm have been separated, with each run containing as much as 150 g of 244Cm. Dowex® 50W-X8 (Dow Chemical Co.) cation resin, graded to 30–70 micron size range, is used, and separation is made by eluting with 0.05M diethylenetriamine pentaacetic acid (DTPA) at a pH of 3. The effluent from the column is continuously monitored by a BF3 detector, a NaI detector, and a lithium-drifted germanium detector and gamma spectrometer to guide collection of product fractions. Operating the columns at 300 to 1000 psi pressure eliminates resin bed disruption caused by radiolytically produced gases, and operating at: increased flow rates decreases the radiolytic degradation of the resin per unit of product processed. A portion of the hot canyon of a production radiochemical separation plant was converted from a remote crane-operated facility to a master-slave manipulator-operated facility for separation and purification of actinide elements by pressurized cation exchange. It also contains an evaporator, furnaces, a calorimeter, and several precipitators and associated tanks. Actinide processing from target dissolution to packaging of purified product is planned in this facility.

Determination of selenium in environmental standard reference materials by a .gamma.-.gamma. coincidence method using lithium-drifted germanium detectors

A gamma-gamma coincidence technique is applied to the determination of low levels of selenium in NBS standard reference materials, using the /sup 75/Se (n,..gamma..) product. The method is shown to provide accurate determinations in a variety of materials. Removal of interfering ..gamma.. rays at 136 and 264 keV due to /sup 181/Hf and /sup 182/Ta and suppression of Compton background by three to four orders of magnitude are realized by the coincidence counting procedure. Selenium concentrations (..mu..g g/sup -1/) of 0.024, 0.065, 0.084, 0.053, 1.1, 2.6, and 8.8 were determined for SRMs 1570, 1571, 1573, 1575, 1577, 1632, and 1633, respectively. Two sigma Se detection limits were approximately 10 to 20 ng g/sup -1/ for biological reference materials, and 50 to 100 ng g/sup -1/ for fly ash and coal using the conditions reported. 2 tables.

Simultaneous determination of the noble metals in geological material by radiochemical neutron-activation analysis

A simple procedure is described for determining the noble metals in geological samples rich in chromium and copper. Powdered rock samples (0.1–0.3 g) are irradiated in an epithermal neutron flux, under a cadmium filter, to reduce interference from 51Cr and 64Cu. After digestion with a peroxide fusion, the noble metals are separated on Srafion NMRR ion-exchange resin. Activity from chromium(VI), retained on the resin, is eliminated by reduction to chromium(III) with iron(II) sulphate before separation. The gamma-ray activity is measured with a lithium-drifted germanium detector for palladium (109Pd), platinum (199Au), iridium (194Ir) and gold (198Au). The separation yield (iridium 40%, palladium 80%, gold 90%) is determined for each sample by irradiating the resin to activate a stable noble metal carrier. Multi-element noble metal standards (0.1–8 µg) are prepared from dilute solutions (100 µl) evaporated on resin (1 ml). The practical detection limits are 2.5 ng of palladium and platinum, 0.1 ng of iridium and 0.01 ng of gold. The reliability of the procedure was confirmed by analysing sulphide standards (PTM, PTC) and standard rocks (PCC-1, DTS-1). The method has been applied to the analysis of chrome-spinels.

Elastic scattering of 145 keV gamma rays

The differential elastic scattering cross sections of 145 keV gamma rays in Pb, Ta, Sn and Zr have been measured at angles ranging from 45 degrees and 115 degrees using a high-resolution lithium-drifted germanium detector. The experimental cross sections are compared with the available theoretical data. The present experimental results are in agreement with the theoretical results of Johnston et al. (1976) calculated using S-matrix theory of quantum electrodynamics. For medium- and low-Z elements the present experimental values are in agreement with the theoretical values compiled by Hubbell et al. (1975). At 45 degrees the experimental results for all elements are in agreement with the values calculated using Moilere's expression. The experimental results are in good agreement with the theoretical values of Smend et al. (1973) at all angles in high- and low-Z elements.

Simultaneous oxygen, carbon, nitrogen, sulfur and silicon determination in coal by proton induced gamma-ray analysis

The technique of gamma-ray analysis of light elements (GRALE) is extended to measure the concentration of carbon, nitrogen, oxygen, sulfur and silicon in coal samples. The composition of the sample is determined by analyzing the spectrum of gamma rays emitted following inelastic scattering of protons bombarding the target. A large volume lithium drifted germanium detector is used as a gamma-ray detector in this work. Coal samples are irradiated with 9.5 MeV protons in a helium atmosphere for 1000 sec. Results with standard coal samples indicate that the method has an accuracy of ∼5% of the concentration of each element and a precision of ∼4% for elements constituting at least 1% of the coal by weight.

Radioactive pollutant determinations using gamma-ray spectroscopy.

Qualitative and quantitative determination of radionuclide contamination in environmental samples is often complicated by the presence of uranium- and thorium-series radioelements as well as 40K. High resolution gamma-ray spectroscopy with lithium-drifted germanium detectors provides a method for the determination of man-made radio-nuclide contaminants in many matrices with a minimum of chemical separation. Methods have been studied for increasing the efficiency of such determinations by using large samples in reentrant beakers ("Merinelli beakers") and small samples inside the well of a recently developed Ge(Li) well detector. Specific examples for the determination of 129I(16 m.y. half-life) in the well detector and recent fall-out in grass samples are presented.

Radiochemical separation and determination of europium by Ge(Li) detector in biological tissues

A simple neutron activation method has been developed for the determination of europium in biological tissues and applied in the analysis of marine organism samples with ±9% precision at the nanogram level. The method is based on the separation, by ion-exchange, of the rare earth group from dry or ashed irradiated tissues and subsequent determination of152mEu, by γ-spectrometry using a lithium drifted germanium detector.152mEu, separated almost completely from other than rare earth elements, with better than 98% chemical yield, is counted on the 121.8 keV photopeak which then is practically free from any other γ-ray energy interfering in this counting.

Author index

The energies of seven low-lying excited levels of 90Zr, 91Zr, and 92Zr have been measured to within a few tenths of a keV. A high-intensity bremsstrahlung beam from a linear accelerator was used to create the radioactive niobium nuclei, 92Nb, 91Nb, and 90Nb by the (γ,n), (γ,2n), and (γ,3n) reactions on 93Nb. After the niobium nuclei decayed to the zirconium isotopes, 92Zr, 91Zr, and 90Zr, the energies of the transition γ-rays from these zirconium isotopes were measured with a high-resolution, lithium-drifted germanium detector and were used to determine the energy levels of the zirconium isotopes. The energy levels determined in this way are, for 90Zr, 2186·3, 2318·8, 3447·6, and 3590·4 keV; for 91Zr, 1205·0 keV; and for 92Zr, 934·3 and 1847·2 keV.

Simulation de la diffusion incohérente du rayonnement gamma par les électrons

The energy distribution of γ-rays incoherently scattered by the electrons of aluminium, tin, tungsten and lead is simulated by the Monte Carlo method. These electrons are regarded as free and in motion. The results are in good agreement with experimental distributions observed with a lithium-drifted germanium detector.

Fast Neutron Radiation Damage of High-Purity Germanium Detectors

Seven high resolution, high-purity planar germanium and two lithium-drifted germanium detectors have been exposed to fluences of monoenergetic fast neutrons of 1.4, 5.5 and 16.4 MeV to study radiation damage effects. Seven of the exposures were made at 5.5 MeV using detectors made from both LBL and General Electric Company material. Initial degradation of 60Co energy resolution was generally observed after fluences of 3 × 10+9 n/cm2. After fluences of 1010 n/cm2, the detector resolutions were all affected, and replacement would be required in most gamma ray spectrometry; these results are consistent with previous damage studies on germanium detectors. Considerable variability in neutron damage threshold between detectors was observed within this fluence range which must be attributable to a material parameter that is not yet fully determined. This is the major finding in this study. After irradiation, a significant increase in material resistivity was observed as a series resistance in the diodes undepleted region at low biases. The observations were made by capacitance effects and lengthened pulse rise time. Annealing of damage was observed during storage at LN2 temperature after irradiation; resulting, in some cases, in improvement of resolution and in others, further degradation. Drastic resolution degradation was observed on cycling detectors to dry ice temperatures, (200° K) with the loss of the high series resistance and an increase in acceptor concentration. Further cycling to room temperature for periods of hours resulted in improvement of the energy resolution compared with the 200° K value.