High-sensitive elemental analysis using multi-parameter coincidence spectrometer: GEMINI-II

In this study, using neutron activation analysis with multi-parameter coincidence method which was developed at Japan Atomic Energy Agency (JAEA), a non-destructive, ultra-high sensitive multi-elemental determination has been realized. The multi-parameter coincidence method is carried out with an array of 19 germanium detectors, GEMINI-II. Using this system, very weak γ-rays emitted from trace amounts of elements can be detected. The iridium concentration has been determined by means of neutron activation analysis with multi-parameter coincidence method for Cuban sediment samples across the K/T boundary strata.     

Determination of trace elements using multi-parameter coincidence spectrometry

In this study, sensitive trace element analyses were carried out without chemical separation by the combination of neutron activation analysis and multi-parameter coincidence spectroscopy. A long-lived radioisotope ¹²⁹I in algae samples and iridium in geological samples were analyzed.     

New technique for the determination of trace elements using multiparameter coincidence spectrometry

Multiparameter coincidence g-ray spectrometry based on g-g coincidence is widely used in the field of nuclear structure studies, and has produced many succesful results. In this paper, feasibility of the method for neutron activation analysis of trace elements was studied. Particularly, a long-lived radioisotope ¹²⁹I (T_1/2 = 1.57^.10⁷ y) in algae samples and iridium in geological samples has been determined.     

Multiparameter Coincidence Spectrometry Applied to the Non-Destructive Neutron Activation Analysis of Meteorites

Abstract

A non-destructive method for the neutron activation analysis of chondritic meteorites by multiparameter coincidence spectrometry is described. Results for sodium, cobalt, nickel and iridium are presented, and agree with single coincidence spectrometry measurements. Scandium photopeaks are prominent in the multiparameter spectrum and this element could also be determined. The advantages of multiparameter spectrometry over single coincidence counting are outlined.     

William D. Ehmann, radioanalytical chemist and radiochemistry educator

Copper (Cu) is an essential element and is incorporated in many biomolecules that are involved in protecting the brain from oxidative damage. Many brain regions strongly affected by neurodegene rative diseases are small. A sensitive nondestructive procedure to determine Cu is desirable to preserve samples for additional studies. Copper is not easily determined by instrumental neutron activation analysis (INAA) due to high activity levels produced by major abundance elements such as sodium (Na) and chlorine (Cl), which produce a high Compton background. An INAA method involving a short epithermal neutron irradiation and counting with a Compton suppression system was developed to determine Cu in brain, via 5.1-min⁶⁶Cu. These short irradiation results are compared to those based on coincidence spectrometry of annihilation photons from positron emitting 12.7-h⁶⁴Cu after a long irradiation.     

Characteristic x-rays from (n, γ) products and their utilization in activation analysis

The possibility of using characteristic X-rays from radioactive elements in activation analysis was investigated during this work with particular emphasis on (n, γ) products. At least 27 of 56 elements investigated during this work were found to yield themselves to activation analysis employing characteristic X-rays from electron capture or internal conversion processes during isomeric transition. In presenting the results, a survey made of several elements and the limits of detection of 21 elements have been reported. Specific applications of this method were studied for the analysis of copper in a variety of samples (ores, minerals, steels, spent lubricants and human blood). The results of this investigation show that the use of characteristic X-rays in activation analysis has several advantages because the energies of these radiations are closely related to the periodicity of the elements themselves. Presented at the First IMR International Symposium, Trace Characterization—Chemical and Physical, National Bureau of Standards, USA (October, 1966).     

Photon and proton activation analysis of iron and steel standards using the internal standard method coupled with the standard addition method

The internal standard method coupled with the standard addition method has been applied to photon activation analysis and proton activation analysis of minor elements and trace impurities in various types of iron and steel samples issued by the Iron and Steel Institute of Japan (ISIJ). Samples and standard addition samples were once dissolved to mix homogeneously, an internal standard and elements to be determined and solidified as a silica-gel to make a similar matrix composition and geometry. Cerium and yttrium were used as an internal standard in photon and proton activation, respectively. In photon activation, 20 MeV electron beam was used for bremsstrahlung irradiation to reduce matrix activity and nuclear interference reactions, and the results were compared with those of 30 MeV irradiation. In proton activation, iron was removed by the MIBK extraction method after dissolving samples to reduce the radioactivity of⁵⁶Co from iron via⁵⁶Fe(p,n)⁵⁶Co reaction. The results of proton and photon activation analysis were in good agreement with the standard values of ISIJ.     

Determination of yttrium in rare earths by photon activation analysis

The determination of yttrium in the presence of large amounts of the rare earths by the thermal neutron reaction (89)Y(n, gamma)(90)Y is complicated because of frequent problems of sample self-shielding from major constituents of the sample, and the difficulty of separating (90)Y, a pure beta-emitter, from other elements which are very similar chemically. A non-destructive photon activation analysis method has been developed for this determination. Bremsstrahlung from a 35-muA beam of 35-MeV electrons induces the photonuclear reaction (89)Y(gamma, n)(88)Y. Optimum sensitivity is obtained by coincidence counting of the 0.90 and 1.84 MeV gamma-rays associated with the decay of (88)Y. The detection limit is less than 1 mug of yttrium.     

Rapid determination of molar ratios in binary systems by 14 mev neutron activation analysis

The 14 MeV neutron activation analysis method was applied for the rapid and non-destructive determination of the molar ratios of iron(III) oxide and zinc oxide in zinc ferrites. Iron was detected as⁵⁶Mn produced from⁵⁶Fe by the (n, p) reaction, and zinc as the sum of the coincidence counts of the annihilation radiations of the positrons emitted from⁶³Zn and⁶⁴Cu produced from⁶⁴Zn by the (n, 2n) and (n, p) reactions respectively. The ratios of the counts of⁵⁶Mn and the sum of the coincidence counts were not linearly related to the molar ratios of iron(III) oxide and zinc oxide in zinc ferrites. However, by corrections of the mutual contributions to the counts, linear relations were obtained between the ratios of the counts and the molar ratios when the corrected sum of the coincidence counts was used as an internal standard. The experimental and theoretical slopes of the analytical lines agreed within a difference of approximately 10%. The deviations between the results of the activation analysis and those of the chemical analysis were less than 5% of the chemical results.     

Multiple gamma-ray detection method and its application to nuclear chemistry

A new radionuclide quantification method is proposed on the basis of multiple gamma-ray detection, which is two or higher fold gamma-ray coincidence method. The coincidence method has so far been used for nuclear structure study. We apply this method for quantification of radioactive nuclei. The advantage of this method consists of high energy resolution and high sensitivity. It is successfully applied to nuclear waste analysis, neutron activation analysis and prompt gamma-ray analysis. The principle of the multiple gamma-ray detection method and future perspectives for an innovative pulsed neutron source and a new detector system will be presented.     

Multiparameter coincidence spectromety applied to the instrumental activation analysis of rocks and minerals

An instrumental method for activation analysis based on multiparameter coincidence spectrometry is described. Practical considerations of our X- and - coincidence systems are presented. The main applications of geochemical interest are the non-destructive determinations of tin in granitic rocks and iridium in ultra-basic rocks. Some other applications to the activation analysis are proposed.     

Comparison Method for Neutron Activation Analysis with γ-γ Matrix

A comparison method, utilizing neutron activation analysis followed by multidimensional spectrum analysis was proven to provide accurate quantification of the multi-element samples. In this study, 23 elements were detected simultaneously in a sample containing standard elements for neutron activation analysis. The method presented here can be applied for about 50 elements.     

Chemical analysis of precipitates in metallic alloys using coincidence Doppler broadening of positron annihilation radiation

Two-detector coincidence Doppler broadening (CDB) method of positron annihilation radiation is applied to the study of precipitates in metals. As the first step, the CDB spectra for many kinds of elements are measured to obtain the “fingerprint” of each element for the chemical analysis of the precipitates in metals. Utilizing the fingerprint of Cu, we made chemical analysis of nano-particles formed in the initial stage of thermal aging in a Fe–Cu alloy, and found that the particles are consisting of Cu only and free from vacancies, which demonstrates the usefulness of this method in the study of the precipitates.     

Coincidence counting for PGNAA applications: Is it the optimum method?

Summary One of the main advantages of γ-γ coincidence counting is the reduction of the background spectrum, pulse pile-up, and summing effects (for simple schemes). For prompt gamma-ray neutron activation analysis (PGNAA), the sources of background include the gamma-rays from the natural background, from surrounding materials, from the neutron source, and from detector neutron activation. While this counting approach effectively increases the signal-to-noise (S/N) ratio, it also decreases the signal counting rate. This adds some practical limitations to using this approach. In this work, two examples are presented for the efficient use of the coincidence counting approach.     

Simultaneous determination of Ir and Se in K-T boundary clays and volcanic sublimates

Our instrumental analytical method for an ultra-sensitive determination of Ir and Se in sediments and volcanic emission products is based on epithermal neutron activation analysis (ENAA) coupled with multiparameter coincidence spectrometry. An adequate setting of the energy paths and of the multiparameter coincidence spectrometry. An adequate setting of the energy paths and of the multiparameter analyzer allows a simultaneous counting of⁷⁵Se and¹⁹²Ir coincidences. This tool has been used to analyse different sediments sampled at the Cretaceous-Tertiary boundary (KTB) and volcanic samples in order to discuss the extra-terrestrial or volcanic origin of the Ir anomaly.     

The determination of Eu and Sm by application of X-ray spectrometry to isotope-source activation analysis

The use, for analysis, of K X-rays proceeding from metastable and beta-emitting radionuclides—produced by neutron activation—is an undeveloped aspect of activation analysis. Consequently, this study examines the feasibility of applying X-ray spectrometry to isotope source activation analysis and in particular the determination of Sm and Eu at low levels is described. Generally speaking, the sensitivity is seriously restricted by the thermal neutron flux of the source but in certain specific cases the analysis is favoured by the nuclear properties of the elements concerned. Therefore, the selection of elements was based largely on their demand for analysis and their ability to produce a practicable yield. Optimum signalto-noise ratios were attained by employing a detector that was particularly sensitive at energies below 150 keV. Analytical conditions are demonstrated for the elements of interest over a wide range of concentrations in small samples, and ultimately the applicability of the method was tested by the analysis of a typical monazite sample. The analytical potential of the method is thoroughly appraised and possible practical applications are discussed.     

The k 0 and relative INAA methods to determine elements in entire archaeological pottery objects

The advantages of instrumental neutron activation analysis applied to archaeological ceramics have been enhanced through the analysis of entire objects, using both the k ₀ method and the relative method, respectively, to determine the concentrations of chemical elements in aliquots of replicate objects used as comparators and in the sample object. Twenty-two chemical elements of archaeological importance were measured in mud figurines from Caral civilization (5000 year BC), irradiated inside a well-characterized radial channel facility of the nuclear research reactor at IPEN, Peru. The results showed less than 10 % of bias for most of the elements.     

Trennung von V,Cr und Mn aus Stahl und Aktivierungsanalyse der Legierungselemente mit 14 MeV-Neutronen

The elements are separated from iron by solvent-extraction. Cr, V and Mn are separated by ion-exchange chromatography with a strong acidic cation-exchanger. The elements are determined by 14 MeV-neutron activation analysis using γ-spectroscopy. The method is suitable for a concentration range of 0.05 to 5%.     

Compton suppression neutron activation analysis: Past,present and future

Conclusions In this work a review of the development of compton suppression is presented. It was shown that the application of Compton-suppression counting in instrumental NAA reduces the detection limits and improves the accuracy for a list of elements by substantial reduction of the background of the -spectroscopy. Results for certified reference materials obtained through the use of Compton suppression are normally more accurate and in agreement with the published values. Compton suppression is particularly helpful for low level concentrations in environmental samples to those elements which exhibit severe special interferences in the normal NAA counting. A list of the elements with isotopes having single or close to single -ray decay schemes and which could benefit from Compton-suppression counting is presented. Also, evaluation is made regarding the reliability of Compton suppression with increase in the overall dead-time of the counting. It was concluded that this method does not provide accurate quantification of the isotopes when the overall dead-time exceeds the 10% range. Investigation of the natural background was performed with Compton suppression for the purpose of neutron activation analysis application. The method presented proves to broaden the application of NAA and helps in its competition for simplicity, accuracy and reliability with the modern methods of elemental analysis. Future application of coincidence spectrometry in activation analysis should include better enclosing of the primary detector, utiliza5tion of x-ray and well type detectors, -, -, and -- coincidence techniques.     

Activation analysis with fast neutrons using a cyclotron

A systematic study of activation analysis with cyclotron-produced neutrons for (n, 2n), (n, p) and (n, α) reactions is presented. The limits of detection for elements of atomic number from 6 to 80 are given. The possibilities of optimization of irradiation conditions by the choice of the most suitable neutron spectrum are discussed. The potential of this fast neutron activation analysis method is compared with that of 14 MeV neutron activation analysis.