Determination of boron, carbon, nitrogen and oxygen in nickel by charged particle activation analysis

Summary The determination of boron, carbon, nitrogen and oxygen in nickel by charged particle activation using the reactions ¹⁰B(d, n)¹¹C, ¹²C(d, n)¹³N, ¹⁴N(p, )¹¹C and ¹⁶O(³He, p)¹⁸F is studied. The interference of ¹¹B(p, n)¹¹C with the ¹⁴N(p, )¹¹C reaction is taken into account. ¹¹C, ¹³N and ¹⁸F are separated by oxygen combustion followed by trapping of ¹¹CO₂ in NaOH and by steam distillation of ¹³NH₃ and of H₂Si¹⁸F₆, respectively. The results obtained were 0.129±0.035 g g^–1 for boron, 86.4±8.3 g g^–1 for carbon, 1.077±0.037 g g^–1 for nitrogen and 8.91±1.00 g g^–1 for oxygen. The results for nitrogen and oxygen agreed satisfactorily with those of other analytical methods.Grateful acknowledgement is made to Prof. J. Hoste for his interest shown in this work, to J. Pauwels (B.C.M.N., Geel) for providing the samples, to B. F. Schmitt (Bundesanstalt für Materialprüfung, Berlin) for helpful information concerning the radiochemical separation of ¹¹C and to the NFWO and the IIKW for financial support.     

Determination of boron in the thin surface layer of a silicon wafer by instrumental charged particle activation analysis

Instrumental charged particle activation analysis (CPAA) for determining boron in a thin surface layer of silicon was developed. The nuclear reaction and incident energy were selected in order to minimize any interference from surface or bulk impurities. Thin boron film was used as a standard sample and its boron content was determined by neutron induced prompt -ray analysis. As a result, we were able to determine¹¹B and¹⁰B at 10¹⁵ atoms/cm² with an accuracy of better than 3% by 4 MeV proton and 7 MeV -bombardment, respectively. Each boron isotope could be determined down to 10¹³ atoms/cm². Our CPAA was applied to determine boron in a boron implanted silicon wafer of a SIMS standard sample.     

Determination of light elements in metals and semiconductors by charged particle activation analysis

The determination of boron, carbon, nitrogen and oxygen in metals and semiconductors by charged particle activation analysis (CPAA) is reviewed. It is shown that CPAA is a sensitive and accurate method suitable for the analysis of reference materials.     

Determination of rare earth elements by charged particle activation analysis in geological materials

The rare earth elements (REE), Pr, Sm, Eu, Gd, Ho, Er and Tm have been determined by charged particle activation analysis using 40 MeV a-particles through radiochemical approach. The radiochemical separation of REE as a group has been carried out from the bulk matrix. It has been shown from the theoretical computation that the products obtained from (a,xn) reactions (x = 1, 2, 3) are more suitable compared to those from (a,pyn) reactions (y = 0, 1, 2) due to the former having higher cross section (of the order of thousand millibarns).     

Standardization in charged particle activation analysis

Standardization methods in activation analysis with charged particles are studied critically. Several approximate standardization methods that do not require knowledge of the excitation function are compared with the “numerical integration method” using excitation function data from the literature. It is shown that these methods yield accurate results if the threshold energy of the considered reaction is high and if sample and standard have a comparable Z value. A method that gives a rapid estimate of the maximum possible error is also presented. It is shown that for the “numerical integration method” the accuracy of the excitation function data has only a small influence on the overall accuracy. The influence of the accuracy of stopping power data and of possible deviations from Bragg's rule for light element standards is also considered. “Bevoegdverklaard navorser” of the NFWO.     

Determination of impurities in single crystals of magnesium oxide by neutron activation analysis

The determination of some trace impurities in single-crystal magnesium oxide is described. Radiochemical separations of iron, cobalt, scandium, manganese and chromium by ion exchange and solvent extraction are applied in conjunction with γ-spectrometry. The impurities that give rise to long-lived γ-emitting isotopes are considered.     

On the determination of sulfur by charged particle activation analysis

An analytical method is described for the determination of trace amounts of sulfur by charged particle activation analysis. The method consists of proton irradiation followed by a rapid radiochemical separation of the product nuclide,^34m Cl. This procedure has been applied to a number of pure metal samples which range in sulfur content from 0.3 to 30 ppm. All analyses were repeated several times to ensure consistent results and to better evaluate experimental detection limits and systematic errors. The results indicate that sulfur determinations can be performed at a concentration of less than 1.0 ppm. Activation curves are presented for the reactions S(d,x)^34mCl, S(p,x)^34mCl, and the interfering reaction³⁵Cl(p, pn)^34mCl. In memoriam.     

Determination of oxygen impurity in high purity materials by charged particle activation analysis using alpha projectiles

40 MeV -particles have been used to determine oxygen impurity at ppm levels in silicon, copper, and stainless steel, through the radiochemical separation of¹⁸F from the matrix. The separation of¹⁸F has been carried out by two techniques, viz.(1) distillation of H₂SiF₆ and (2) precipitation of KBF₄ and some modification has been applied in the separation, depending on the nature of interferences from the matrix. Instrumental approach was also carried out to determine the oxygen impurity at 100 ppm in Si matrix because this approach is not possible in Cu and stainless steel samples due to matrix activity.     

Secondary effects in prompt charged particle activation analysis

The phenomenon of secondary excitation was observed during irradiation of thick targets of boron and gallium nitride with 2 MeV³He⁺ ions. This effect, though negligible during irradiation with protons or⁴He⁺ ions, becomes significant when highly exoergic reactions can occur.     

Determination of the wear of machine parts by charged particle surface activation

Surface activation with charged particles is a suitable method for the determination of wear in machine parts. Investigations of the dependence of the yield of major radioactive isotopes on particle energy and of the distribution of these isotopes along the depth of the activated layer are reported. Activation and activity measurement conditions for common materials of construction are suggested. Calculation procedures for converting activity values into absolute wear data and for evaluating methodical errors are given.     

Routine charged particle activation analysis of light elements

In order to develop a highly reliable method of routine charged particle activation analysis on a commercial basis by request of an outside company, (1) a new target holder was developed for brittle or low melting-point samples, (2) some modifications and improvements were introduced in the chemical separation, and (3) the reliability of the results was further examined. Oxygen, nitrogen, carbon, and boron in a greater variety of matrices have thus become analyzable with a higher reliability and efficiency.     

Determination of residual impurities in InP grown by the Czochralski method,using charged particle activation analysis

InP samples were analyzed by charged particle activation analysis. Proton activation at 12 MeV permits the nondestructive survey of 30 elements. The main impurities are Ti, Fe, Ga and Zn (10¹⁵ to 2·10¹⁶ at/cm³). Oxygen was analyzed separately by triton activation at 3 MeV; the oxygen concentration is normally less than 10¹⁶ at/cm³.     

Some problems of calibration technique in charged particle activation analysis

It is shown that three different approaches to calibration technique based on the use of average cross-section, equivalent target thickness and thick target yield are adequate. Using the concept of thick target yield, a convenient charged particle activation equation is obtained. The possibility of simultaneous determination of two elements impurities, from which the same isotope is formed, is pointed out. The calibration technique, in which thin standard is used but activation curve is not required, is discussed.     

Determination of nitrogen in boron carbide by instrumental photon activation analysis

Boron carbide is widely used as industrial material, because of its extreme hardness, and as a neutron absorber. As part of a round-robin exercise leading to certification of a new reference material (ERM-ED102) which was demanded by the industry we analysed nitrogen in boron carbide by inert gas fusion analysis (GFA) and instrumental photon activation analysis (IPAA) using the ¹⁴N(γ,n)¹³N nuclear reaction. The latter approach is the only non-destructive method among all the methods applied. By using photons with energy below the threshold of the ¹²C(γ,n)¹¹C reaction, we hindered activation of matrix and other impurities. A recently installed beam with a very low lateral activating flux gradient enabled us to homogeneously activate sample masses of approximately 1 g. Taking extra precautions, i.e. self-absorption correction and deconvolution of the complex decay curves, we calculated a nitrogen concentration of 2260 ± 100 μg g⁻¹, which is in good agreement with our GFA value of 2303 ± 64 μg g⁻¹. The values are the second and third highest of a rather atypical (non-S-shape) distribution of data of 14 round-robin participants. It is of utmost importance for the certification process that our IPAA value is the only one not produced by inert gas fusion analysis and, therefore, the only one which is not affected by a possible incomplete release of nitrogen from high-melting boron carbide. Figure Twin-Detector system for analyzing spatially extended samples     

The study of fundamental aspects of charged particle activation analysis

Two important problems are discussed: equations and data used for quantitation on one hand, diffusion under irradiation on another hand. It is suggested that recent semiempirical stopping power data for hydrogen and helium are sufficiently accurate to be used in any good calibration method, while for heavier ions it is preferable to use the “double reaction method”, which avoids the use of stopping power data. The problem of the additivity of the stopping powers in the case of compounds is also discussed and it is shown in a specific case that BRAGG-KLEEMAN's rule is valid. Deep diffusion under irradiation has sometimes been mentioned (e.g. F in Ge, Cu in Si): it can be an important source of errors in trace analysis. The possible deep diffusion of F in Ge has been studied: it is shown that such a diffusion does not occur, while surface contamination problems can lead to erroneous observations.     

Determination of boron in materials by cold neutron prompt gamma-ray activation analysis

An instrument for cold neutron prompt gamma-ray activation analysis (PGAA), located at the NIST Center for Neutron Research (NCNR), has proven useful for the measurement of boron in a variety of materials. Neutrons, moderated by passage through liquid hydrogen at 20 K, pass through a (58)Ni coated guide to the PGAA station in the cold neutron guide hall of the NCNR. The thermal equivalent neutron fluence rate at the sample position is 9 x 10(8) cm(-2) s(-1). Prompt gamma rays are measured by a cadmium- and lead-shielded high-purity germanium detector. The instrument has been used to measure boron mass fractions in minerals, in NIST SRM 2175 (Refractory Alloy MP-35-N) for certification of boron, and most recently in semiconductor-grade silicon. The limit of detection for boron in many materials is <10 ng g(-1).     

Determination of boron in a black mouse by prompt gamma activation analysis

In the boron neutron capture therapy, an accurate determination of the boron content in a biological sample is very important. The boron content was investigated with a standard solution of boron which was administered intraperitoneally with a dose of 750 mg/kg body weight into mice induced cancer cells and tumors. The boron content for two types of a sample was compared to the boronophenylalanine for the tumor and the ethylamine derivatives for the induced cancer cell, which were also investigated for their accumulation rate in each organ such as blood, spleen, liver, kidney and brain. An analytical quality control was carried out by using certified reference materials such as Peach Leaves, Apple Leaves and Spinach Leaves. The relative error of the measured values was in good agreement within 2% to the certified values.     

On the determination of phosphorus via charged particle activation analysis

The application of charged particle activation analysis to the determination of phosphorus in a variety of sample materials is discussed. The activity produced via the³¹P(, n)^34mCl reaction is quantitated either nondestructively or using postirradiation radiochemical separations depending on the characteristics of the sample matrices. Corrections which are necessary for the determination of phosphorus in pure tantalum metal due to spectral interferences are discussed.     

Determination of boron in borosilicate glasses by neutron capture prompt gamma-ray activation analysis

Major levels of boron in borosilicate glasses have been determined nondestructively by neutron activation analysis. In contrast to chemical methods for determining boron as a major component, the described nuclear method has few interferences and does not require chemical separation of boron prior to its quantitation. The effects of neutron self-shielding by boron (1 to 8% by weight) are examined, minimized by dilution of powdered samples with high purity graphite, and circumvented by comparative analyses. Results of the analysis of a series of glasses with increasing boron composition are 1.150±.005% and 7.766±.035% for the low and high members of the series. Accuracy of these results depends upon comparative analyses with the certified Standard Reference Material, SRM 93a (3.89±0.02% B). Once analyzed, the glasses are useful as secondary standards for alpha track counting, and also ion and electron microprobe analyses of glasses.     

Determination of magnesium in botanical reference materials by instrumental neutron activation analysis

Instrumental neutron activation analysis (INAA) was applied to the rapid determination of magnesium in the botanical reference materials Beech Leaves-100 and Spruce Needles-101. The magnesium content was quantitatively determined by measuring the gamma-ray photopeak at 1014 keV of the short-lived radionuclide²⁷Mg (9.46 m). The magnesium concentrations in the two materials were found to be 834.6±50.2 g·g^–1 dry weight and 618.6±36.2 g·g^–1, respectively. When assaying a 0.1 g sample under the same experimental conditions the limit of detection is 30 g of Mg.Work carried out at Risø National Laboratory, Isotopes Division, DK-4000 Roskilde, Denmark.