ISSN:0049-8246    

DOI:10.1002/xrs.1300120202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractExtensive use has been made of particle‐induced x‐ray emission (PIXE) analysis over the past several years. The optimization of its detection sensitivity calls for the judicious selection of several parameters including,inter alia, the beam energy used and the x‐ray window thickness. Thin windows are required in order to detect the light elements whose x‐ray energies are so low that they are heavily attenuated by any absorber material between the target and the detector. The choice of beam energy is dependant on the respective x‐ray production cross‐sections for elements of interest, the related background generated, as well as the associated beam energy degradation in the targets. These considerations often lead to a state where protons, elastically scattered from the target, have sufficient energy to penetrate the window and enter the x‐ray detector. The extent to which such protons and their related secondary electron production affect the energy spectrum resolution of intrinsic germanium and Si(Li) x‐ray detectors is demonstrated for a proton beam energy range from 2.1 to 3.5 MeV with a window thickness equivalent to the range of a

ISSN:0049-8246    

DOI:10.1002/xrs.1300120203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractA serpentine mineral specimen used for a standard in a Materials Analysis Company Model 400 electron microprobe equipped with a Kevex Model 5000A energy dispersive sperctrometer and an on‐line Hewlett–Packard 2100 computer, was repeatedly analysed during a study of serpentinization. The results of the repeated analyses were statistically analysed and show an acceptable level of accuracy and precision. The relative and absolute errors for the serpentine standard lie within the same ranges as the errors for the other standards (forsterite, enstatite, diopside, kyanite and kaersutite) used, although the standard deviations for the serpentine analyses are slightly greater. These results are within acceptable limits and indicate that serpentine can be routinely analysed by energy dispersed analysis, using a serpentine standard for magnesium and silicon determinations, with the same accuracy but with slightly lower precision than less hydrous silicates. Most elements were present in amounts between 2 to 63 wt% of the oxide in the standards used but 0.31 wt% Al2O3present in the serpentine standard was routinely determined with acceptable resu

ISSN:0049-8246    

DOI:10.1002/xrs.1300120204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractA new geometry for a radioactive source was developed for the XRF determination of trace elements in the range 0.1–50 μg in samples with diameters from 2–5 mm. The new set‐up was constructed with five241Am (45mCi each) point sources. The shielding and configuration of the source, as well as the choice of appropriate collimators in the optimal shapes and dimensions, were investigated in detail. The study was carried out to establish the conditions for obtaining maximum sensitivity. The count rates and signal‐to‐background ratios were compared with those obtained with an annular source and showed an improvement of a factor of ∼2 in the signal‐to‐background ratio and of a factor of 2–9 in the peak intensity for the elements st

ISSN:0049-8246    

DOI:10.1002/xrs.1300120205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractImprovements of the detection limits in photon induced x‐ray fluorescence analysis are obtained by the reduction of the radiation background using linear polarized x‐rays for excitation. A single crystal where Bragg reflection takes place at an angle 20 = 90° produces linear polarized and monochromatic x‐rays. The use of a single crystal instead of amorphous scattering materials increases the intensity of the polarized beam in some cases up to a factor 104. The use of curved crystals instead of standard flat crystal geometries shows a further increase in the intensity of the exciting beam in the focus line. The crystals in use for both geometries are described. Samples can be investigated in either form, liquid or solid, no special preparation technique is required. Detection limits are given for some elements, absolute amounts of 150 picogram can be detected in some

ISSN:0049-8246    

DOI:10.1002/xrs.1300120206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe control of brass composition and plating weight on brass‐plated steel wire and cord used as reinforcement in tyres is generally carried out by atomic absorption spectrometry, or by polarography. These methods require a mineralization of the sample and the analysis time is very long. On account of this, we have studied a direct analytical method on wires based on x‐ray fluorescence spectrometry. The mathematical method we use suppresses the influence of the cord construction and allows to calculate simultaneously the composition and thickness of the brass coating. The analytical performances, i.e. repeatability, accuracy and analysis time, are better than those prevailing with atomic absorption spectrometry or differential pulse polarography. Moreover, by dispensing with mineralization of the sample, XRFS is particularly well‐fitted for a routine control in produ

ISSN:0049-8246    

DOI:10.1002/xrs.1300120207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe study of the energy resolution and linearity of germanium, x‐ray detectors at very low energies is difficult due to the degradation of the spectral line shapes resulting from incomplete charge collection in the detectors's surface dead layer. The use of low‐energy, K escapes peaks obviates this difficulty as they are absorbed at depths characteristic of their full‐energy parent photons. Measurements have been performed using particle‐induced x‐ray emission analysis of targets having characteristic K and L x‐ray energies just above the Ge K‐edge. The escape peaks retain pure Gaussian shapes down to the noise level of the detector and open up the possibility of a selective field of high‐resolution escape‐

ISSN:0049-8246    

DOI:10.1002/xrs.1300120208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe linear relationship between the reciprocal of analyte‐line intensity, and the reciprocal of concentration has been applied to the determination of ten major and minor elements in silicate rocks and minerals. The analyses were carried out on fused specimens of 11 rock standards, with and without added La2O3, and with and without added NaNO3. The method requires no absorption matrix effect corrections, and is ideally suited to the analysis of geological materials with a wide range of chemical composition. It clearly has the advantage of simplicity and speed, and can be applied to the analysis of samples when suitable standards are not available. The results obtained in all cases are in excellent agreement with the literature. However, the discs with La2O3added yield results with better precision and accuracy than do those without La2O3. Na2O is normally determined on separately prepared rock powder pellets, but can be satisfactorily analysed by this method, using the La2O3added discs, together with all of the other major and minor elements. Na2O analyses are more readily obtained using discs without added NaNO3. We, therefore, recommend that the analysis of geological materials be carried out on fused glass discs with La2O3added and without NaNO

ISSN:0049-8246    

DOI:10.1002/xrs.1300120209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

ISSN:0049-8246    

DOI:10.1002/xrs.1300120213

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY