The XSQR technique uses nearly monoenergetic X-rays from the proton bombardment of a primary target to excite X-ray fluorescence for analytical purposes. With the proper choice of primary target, interferences from high concentration components in a matrix may be eliminated. An overview is given of the technique, the equipment it uses and its methodology. The application of the technique is described for the determination of Cr in steels using an Fe primary, Cu and Zn in gold objects using a Ge primary, multielemental analysis of geological and biological materials using primary targets such as Mo, Rh and Pd and Si in oils using a Ti primary target. The method serves as a useful complementary method to PIXE for the determination of the medium mass elements.
Triton-induced reactions on oxygen were studied with a view to using the prompt γ-rays for analytical purposes. Five γ-rays
were found to be potentially useful, of which three had a high intensity, the n(1, 0), n(2, 0) and p(1, 0) γ-rays, the other
two being the n(3, 0) and the unresolved pair α(1, 0)–α(2, 0). The γ-rays are labelled according to the conventions(a,b), wheres is the light prompt product and the γ-photon is emitted by de-excitation from levela tob in the heavy product nucleus. The method had a relative precision of 2 to 3.5% for surface oxygen concentrations from 50
to 3 μg/cm2. The sensitivity with 1 900 keV tritons was 0.13 μg/cm2 on surfaces of steel or copper which did not yield interfering γ-rays, but 0.45 μg/cm2 on aluminium where interfering γ-rays were emitted.
An activation analysis method has been developed for the routine determination of48Ca. The calcium is chemically separated, converted to the hydroxide, carbonate or chloride and activated for 30 min in the
γ-ray flux generated by a primary electron beam between 40 and 57 MeV and a current of about 50 μA. A large number of samples
can be activated simultaneously and the ratio of activities of47Ca and43K gives a measure of the isotopic concentration of48Ca. Naturally-occurring44Ca is used as an internal standard. The relative standard deviation is ±3.3%.
An overview of prompt nuclear analysis is presented in which the main areas of current interest are described. The various
approaches used for measuring concentration profile are illustrated. Some microprobe techniques are referred to, and applications
of prompt gamma-ray spectrometry from neutron and charged particle induced reactions are discussed. Topics currently receiving
attention are mentioned.
Boron was analysed in ore and glass samples by prompt proton spectrometry, using deuterons of 2.7 MeV to coincide with a region
where the excitation function of the10B(d, p)11B reaction did not vary appreciably with energy.
Targets of approximately 300 μg/cm2 thick of powdered samples were prepared by centrifugation. Concentrations down to 0.2% were determined. Possible interference
by other elements, particularly nitrogen, magnesium and titanium, was investigated.
Using the 871-keV16O p/1,0/ prompt -ray, oxygen was determined with a relative precision of ±3.8% at a concentration level of 120 g g–1. The sensitivity of the method is below 10 g g–1. 50 nm oxide layers on silicon wafers can be determined with a relative precision of 10%. A chamber for transporting targets sensitive to atmospheric gases and humidity is described.
The prompt gamma-rays of 2228 and 2230 keV from the reaction32S/p,p
/32S at Ep=5.0 MeV were measured during proton irradiation of 23 pure sulphur compounds of known composition. Elemental stopping powers were calculated from tables and used to compute the stopping power of the target material by Bragg's Law. Apparent discrepancies in the measured yield could point to deviations from Bragg's Law and hence to molecular effects. The value for any molecular effects was found to be 7.06%.
An assessment was made of the analytical potential of the exoergic reactions on boron, induced by3He+ beams. Possible interferences from C, N and O were studied. Gamma-rays originating from (3He, n), (3He, d), (3He, d), (3He, ) and Coulomb excitation were identified. Possible practical applications in boron studies are indicated.
Thin targets of rare earth fluorides were bombarded with 66 and 85 MeV protons. Measured cross sections for X-ray production agreed with PWBA calculations. Satellite X-rays from nuclear reactions were obtained for both (Z-1) and (Z+1) products from the bombardment of element Z. Interference-free sensitivities were of the order of tens of nanograms under bombardment with 1 mC of integrated charge. The technique was applied for the analysis of geological ores and standards.