Charged particle activation of medium Z elements

A survey has been made on the application of charged particle activation analysis for the detection of traces of medium Z elements (40≤Z≤58, 72, 74) using protons and deuterons of 20 MeV,³He and⁴He ions of 40 MeV. The product nuclides considered were γ-ray emitting radioisotopes with half lives ranging from 10 min to 3 days. Based on the thick target yields obtained, proton activation was found to provide an optimum compromise between sensitivity and selectivity.     

Determination of Ti,V, Zn and W traces by proton activation analysis

Procedures are described for determining traces of titanium in scandium, vanadium in titanium, zinc in copper and tungsten in tantalum, utilizing activation with 11 Me V protons. Experimental data on⁴⁸V,⁵¹Cr,⁶⁶Ga and¹⁸²Re yields and analytical sensitivities are reported.     

Determination of arsenic in refractory metals by radio-chemical charged-particle activation analysis

Arsenic is determined in tantalum and tungsten matrices via ⁷⁵As(p, n)⁷⁵Se and ⁷⁵As(d, 2n)⁷⁵Se reactions. Two ion-exchange procedures, with Dowex-1 columns, are described for the separation of the indicator radionuclides. Data on thick target yields for the ⁷⁵As(p, n)⁷⁵Se reaction are given. With 13-MeV proton or 15-MeV deuteron irradiation for 2 h at a current of 5 μA, the detection limit for arsenic is at the 10 μg kg^-1 level.     

Trace determination of zirconium using charged particle activation

Reaction yields on thick zirconium targets with proton, deuteron,³He and⁴He activation have been measured and compared. The most favorable reaction combining high sensitivity and selectivity was found to be Zr(p, xn)⁹⁰Nb. The absolute cross-section for this excitation function has been measured for proton energies up to 20 MeV. Analytical applications are illustrated with nondestructive zirconium analyses in glass. Yields from the thick target experiments indicate that the detection limit for this zirconium analysis method is ～1 ppb.     

Separation of tantalum from niobium in rock phosphates and its determination through neutron activation analysis

A simple solvent extraction procedure for an effective separation of traces of tantalum from rock phosphate samples has been developed and used in its determination through neutron activation analysis. The tantalum contents in the samples were found to be about 3.10⁻⁷%.     

Trace analysis of heavy metals in high purity materials by helium-3 activation analysis

A method is described to determine traces of V, Fe, Ni, Zn, Nb and Mo in high purity matrices of niobium, tantalum and tungsten by non-destructive 14 MeV³He activation analysis. The influence of nuclear and γ-ray interferences in the determination of these elements is discussed.     

Thin target 7Li(p, p'g)7Li inelastic gamma-ray yield measurements

Thin target angular distributions of inelastic gamma-ray yields resulting from ⁷Li(p, p'g)⁷Li interaction have been measured for incident proton energies between 1.0 and 1.8 MeV. McMaster 3 MV KN Van de Graaff accelerator facility primarily dedicated to in-vivo neutron activation measurements has been used to perform experiments using a thin lithium metal target and 7.62 cm × 7.62 cm, 12.7 cm × 12.7 cm NaI(Tl) scintillation detectors and HPGe detectors. The uncertainty in the relative yield determination is based on the statistics of the data, uncertainty in the 478 keV peak area determination due to other interfering reactions, and the uncertainty in the recording of the proton charge. The results for the angular distribution provide an evidence for anisotropic nature of the radiation as compared to the presumed isotropic nature. The total relative yield was determined from the angular distributions and then compared with the published total cross sections for the reaction. Thick target yields calculated from thin target yields were also found to be in good agreement with other studies.     

Proton activation analysis for chromium,nickel and copper

Proton activation analysis has been applied to develop a procedure for the simultaneous determination of chromium, nickel and copper. The procedure involves the bombardment of the sample with protons to induce⁵²Cr(p, n)^52mMn,⁶⁰Ni(p, n)⁶⁰Cu and⁶³Cu(p, n)⁶³Zn reactions. These reactions have been studied for proton energies from 11 MeV to 15 MeV. Thick target yields for the production of the indicator radionuclides as well as the sensitivities of the determination have been measured in this energy region and are compared with results obtained for other charged particle induced reactions. Detailed data are given on nuclear and instrumental interferences. The trace elements have been determined nondestructively and simultaneously in cobalt with a relative precision of 8 to 15%.     

Recovery of hafnium radioisotopes from a proton irradiated tantalum target

The^178m2Hf nucleus, with its long half-life (31 y) and high-spin isomeric state (16⁺) is desired for new and exotic nuclear physics studies. The Los Alamos Radioisotope Program irradiated a kilogram of natural tantalum at the Los Alamos Meson Physics Facility in early 1981. After fifteen years of decay, this target was ideal for the recovery of^178m2Hf. There was more than a millicurie of^178m2Hf produced during this irradiation and there has been a sufficient period of time for most of the other hafnium radioisotopes to decayed away. Traditionally, separation techniques for recovering hafnium isotopes from tantalum targets employ solvent extractions with reagents that are considered hazardous. These techniques are no longer condoned because they generate a mixed-waste (radioactive and hazardous components) that can not be treated for disposal. In this paper we describe a new and unique procedure for the recovery of hafnium radioisotopes from a highly radioactive, proton irradiated, tantalum target using reagents that do not contribute a hazardous waste component.     

Separation of Carrier-Free 176,177W and 176,177Ta Produced in 16O Irradiated Holmium Target

Carrier-free radionuclides of tungsten and tantalum, ^176,177W and ^176,177Ta have been produced by heavy ion activation of holmium target with 97 MeV ¹⁶O⁵⁺ beam. Radiochemical separation scheme has been developed to isolate tungsten and tantalum radionuclides from the holmium target matrix.     

The determination of tantalum and tungsten in rocks and meteorites by neutron activation analysis

A method for the determination of Sub-microgram amounts of tantalum and tungsten in rocks and meteorites by neutron activation analysis is described Radiochemical suparation from the components of the irradiated sample was employed to provide sources for measuring ¹⁸²Ta and ¹⁸⁷W by beta and gamma counting and by gamma spectrometry. Determinations of tantalum at the lower limit of 8.10^-10 g and tungsten at 2.10^-9 g have been made Amongst the materials examined using the method were the intercomparison rocks G₁ and W₁, rock samples from the Skaergaard Intrusion of East Greenland and a number of iron and stony meteorites In addition a number of standard steel samples of known tungsten content and one of known tantalum content were examined and good agreement was observed between the published results and those determined by activation analysis     

Production of carrier free192,193Hg and192,193Au in16O irradiated tantalum target and their separation by liquid-liquid extraction

Carrier-free radionuclides of mercury and gold^192,193Hg and^192,193Au have been produced by heavy ion activation of tantalum target with 95 MeV¹⁶O⁵⁺ beam obtained from an ECR ion source. An effective radiochemical separation scheme has been developed to isolate gold and mercury radionuclides from the tantalum target matrix.     

Preparation of actinide targets for the synthesis of the heaviest elements

The heaviest elements are synthesized in heavy-ion induced hot fusion reactions with various actinide targets. Because the actinide material is often available only in very limited amounts, a deposition method with high yields (~90 %) is needed. We report on the production of ²⁴⁴Pu, ²⁴³Am, ²⁴⁸Cm, ²⁴⁹Bk, and ²⁴⁹Cf targets on thin Ti backings by molecular plating. Different chemical purification steps using ion chromatographic techniques were applied for the purification of ²⁴⁹Cf and ²⁴⁴Pu. The deposition procedure applied for the production of ~0.4–0.8 mg/cm² thick targets is described. The deposition yield was determined either by α-particle or γ-ray spectroscopy. Furthermore, neutron activation analysis has been applied in the case of ²⁴⁴Pu, ²⁴³Am, and ²⁴⁸Cm. Information about the spatial distribution and homogeneity of the target layer was obtained by radiographic imaging.     

Criteria for selecting analytical wavelengths for multicomponent mixtures by the CPA matrix method and simultaneous spectrophotometric determination of niobium and tantalum

The reversed matrix representation of the Lambert-Beer law (CPA matrix method) is applied in simultaneous spectrophotometric determinations. Restrictions on the selection of analytical wavelengths in applying the CPA matrix method are investigated experimentally and theoretically. Four criteria for selecting suitable wavelengths are described. A spectrophotometric procedure for niobium and tantalum with salicylfluorone and cetyltrimethylammonium bromide in the presence of tartaric acid was developed and used for the simultaneous determination of niobium and tantalum by the CPA matrix method. The absorption maxima were at 520 and 513 nm, respectively. Measurements at six wavelengths in the range 500–530 nm provided data from which niobium (0.04–0.4 μm ml^?1) and tantalum (0.08–0.8 μg ml^?1) were evaluated, with relative standard deviations of <2.     

A micro-XRF spectrometer based on a rotating anode generator and capillary optics

The analytical characteristics of a laboratory-scale micro-X-ray fluorescence spectrometer, based on a rotating anode X-ray generator and capillary optics, are described. Usually, a microbeam 15 μm in diameter, derived from a copper or molybdenum anode operated at 45 kV, is used for sample irradiation. Elemental yields around the 1 count s⁻¹(μg cm⁻²)⁻¹ level are obtained, corresponding to absolute detection limits for thin samples in the 0.05–1 pg range and to relative MDL levels of 3–10 ppm for thick organic samples. The use of the instrument for studying (trace) element migration in Roman glass and for the nondestructive analysis of decorations on Japanese 18th century porcelain vases is described.     

Simultaneous determination of tantalum and hafnium in silicates by neutron activation analysis

A neutron activation procedure suitable for the routine determination of tantalum and hafnium in silicates is described. The irradiated sample is fused with sodium peroxide and leached, and the insoluble hydroxides are dissolved in dilute hydrofluoric acid-hydrochloric acid. After LaF₃ and AgCl scavenges, tantalum and hafnium are separated by anion exchange. Tantalum is obtained radiochemically pure; ²³³Pa and ⁹⁵Zr contaminants in the hafnium fraction are resolved by γ-ray spectrometry. The chemical yield of the procedure is detemined after counting by re-irradiation. Values for the 8 U.S. Geological Survey standard rocks are reported.     

Optimization of 89Zr production using Monte Carlo simulations

Zirconium-89 (⁸⁹Zr) can be produced in a cyclotron by focusing the proton beam on an yttrium-89 (⁸⁹Y) foil target. Optimal combination of beam energy and target assembly configuration enables maximum production of ⁸⁹Zr while minimizing the formation of contaminant nuclides such as ⁸⁸Zr and ⁸⁸Y to allow efficient and effective radiopharmaceutical labeling. Accurate modeling of the proton beam and the target is therefore an essential step to assure the best beam and target specification. We used the radiation transport code MCNPX to simulate the transport of protons through the irradiation assembly and the nuclear reaction code TALYS to obtain the production cross sections of various nuclides from proton-⁸⁹Y reactions. Results from simulating the irradiation of 14 mm diameter targets with aluminum (Al) degrader at 19.8 mA for 1 h suggested that the 0.15 mm thick one would produce 227 MBq while the 0.3 mm thick one would produce 413 MBq of ⁸⁹Zr with less than 1 % uncertainty. These results show excellent agreement with experimental work in literature. This work provides the basis for further experimental and theoretical assessments of the use of ⁸⁹Zr as radiopharmaceutical labels.     

Charged particle activation analysis coupled with X-ray counting

A survey is given on the analytical use of X-ray emitting radioisotopes produced by charged particle activation. Thirty-nine proton and deuteron reactions were considered on twentysix elements (34≤Z≤82). Thick target yields and sensitivity estimates are presented. The features and limitations of this method and the scope of non-destructive and destructive determinations are discussed. The main interest of this approach is to open an avenue for trace analysis with simplified data acquisition and reduction.     

Chemical separation procedure for the nuclide analysis of a tantalum target irradiated for 500 days with 800 MeV protons

A rapid radiochemical separation procedure has been developed for the determination of long-lived and stable nuclides produced by spallation and activation in a tantalum target irradiated for 500 days with 800 MeV protons. In this procedure the matrix element tantalum and simultaneously the¹⁸²Ta activity, built-up by activation of the matrix with themalized spallation neutrons is removed from many elements. About 50 mg of the sample is dissolved in a mixture of concentrated nitric and hydrofluoric acid. After dilution tantalum is extracted with a solution of 0.2M tetrahexylammonium bromide in methyl isobutyl ketone (MIBK). The residual amount of tantalum and the remaining¹⁸²Ta activity are 0.0003% and the recoveries of 27 investigated elements are in the range of 96.0–99.9%. A further 22 elements are quantitatively separated according to their chemical behavior. In the final aqueous fraction the separated long-lived and stable nuclides of 49 elements can be measured with high sensitivity by -ray spectrometry and mass spectrometry (ICP-MS).     

Hydrogen and deuterium analysis by heavy ion activation

The use of heavy ion activation as a method for the analysis of hydrogen and deuterium has been evaluated. Thick target yields from reactions of⁷Li,¹⁰B,¹¹B and¹⁹F on¹H and²H have been determined; activation curves for many of these reactions are presented and interferences are evaluated. Hydrogen has been determined in titanium via¹H(¹⁰B, α)⁷Be at the 100 and 33 ppm levels with relative precisions of 8 to 10%.