Ray Spectrometers

The instrumentation used to measure y-rays from radioactive samples consists of a semiconductor detector, associated electronics, and a computer-based multichannel analyzer as shown in Fig. 6.3. 

For inter-comparison purposes of y-ray spectra or for testing the computer software for y-analysis, the IAEA has created a standard y-spectrum using the progeny of Ra i.e., decay chain products of Ra including Rn gas and other isotopes like Pb, Bi, °Pb, °Bi, etc. (Blaauw et al. 1997). 

T3q ical y-ray spectra from an irradiated pottery specimen are shown in Figs. 6.4 6.6 using two different irradiation and measmement procedmes. 

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X-ray spectrometer An apparatus used in the X-ray study of crystals in which a fine beam of monochromatic X-rays impinges at a measured angle on the face of a crystal mounted in its path, and in which the intensity of the X-rays diffracted in various directions by the crystal is measured with an ionization chamber mounted on an arm of the spectrometer table, or is recorded photographically. 

X-Ray Spectrometers. An x-ray spectrometer is an instmment that measures the fluorescence spectra of samples. The associated computer software then determines the quaUtative and quantitative elemental composition of the samples from the resulting spectra. 

At present the Bourevestnik, Inc. manufactures the following X-ray spectrometers and analyzers ... 

Over the last seventeen year s the Analytical center at our Institute amassed the actual material on the application of XRF method to the quantitative determination of some major (Mg, Al, P, S, Cl, K, Ti, Mn, Fe) and trace (V, Cr, Co, Ni, Zn, Rb, Sr, Y, Zr, Nb, Mo, Ba, La, Ce, Pb, Th, U) element contents [1, 2]. This paper presents the specific features of developed techniques for the determination of 25 element contents in different types of rocks using new Biaiker Pioneer automated spectrometer connected to Intel Pentium IV. The special features of X-ray fluorescence analysis application to the determination of analyzed elements in various types of rocks are presented. The softwai e of this new X-ray spectrometer allows to choose optimal calibration equations and the coefficients for accounting for line overlaps by Equant program and to make a mathematic processing of the calibration ai ray of CRMs measured by the Loader program. 

An energy-dispersive X-ray spectrometer and at least one wavelength-dispersive X-ray spectrometer... 

An optical microscope for precise positioning of the specimen relative to the X-ray spectrometers... 

Before the development of semiconductor detectors opened the field of energy-dispersive X-ray spectroscopy in the late nineteen-sixties crystal-spectrometer arrangements were widely used to measure the intensity of emitted X-rays as a function of their wavelength. Such wavelength-dispersive X-ray spectrometers (WDXS) use the reflections of X-rays from a known crystal, which can be described by Bragg s law (see also Sect. 4.3.1.3)... 

One of the early spectacular triumphs achieved with the x-ray spectrometer was the measurement by the elder Bragg33 of wavelengths for three L lines of platinum. By using a platinum target and the experi-... 

The discovery of the x-ray spectrometer changed x-ray research from a roughly quantitative to a highly precise activity. Barkla s discoveries, which owed so much to absorptiometry, were in the main confirmed, and the emphasis in x-ray research shifted from absorption to emission. 

Fig. 7-13. An example of a semiquantitati e application of the curved-crystal x-ray spectrometer used by Adler and Axelrod. By using chalcopyrite (CuFeS2) as a standard, the proper atomic ratios of copper to iron were obtained for bornite (Cu5FeS4) and cubanite (CuFe2S3). The Cu/Fe weight ratios in these minerals are 1.14 (chalcopyrite), 5.69 (bornite), and 0.57 (cubanite). (Courtesy of Adler and Axelrod, Norelco Reptr., 3, 65.)...

Curved-crystal x-ray spectrometers as needed for spectrum analysis and intensity measurement. 

Characterization methods. The 100 kV Vacuum Generator HB-5 STEM was used to mlcroanalyze samples. The HB-5 has a KEVEX SI(LI) energy dispersive X-ray spectrometer (EDS) and micro area electron diffraction (MAED) capabilities In conjunction with simultaneous bright and dark field Imaging capabilities. A more detailed explanation of the Instrumental operation can be obtained In a publication by C. Lyman(12). 

In a different example, traceability in the amount-of-substance analysis of natural potassium, thorium, and uranium by the method of passive gamma-ray spectrometry was demonstrated by Nir-El (1997). For an absolute quantitative determination, accurate values of two parameters were required (i) the emission probability of a gamma-ray in the decay of the respective indicator radionuclides, and (2) the detection efficiency of that gamma-ray. This work employed a number of CRMs in the critical calibration of the detection efficiency of the gamma-ray spectrometer and the establishment of precise emission probabilities. The latter results compared well with literature values and provided smaller uncertainties for several gamma-rays that were critical for the traceabUity claim. The amount-of-substance analytical results of the long lived naturally occurring radionucHdes K, Th, and... 

Fig. 8.28 External view of the MIMOS II sensor head without contact plate assembly (left) MIMOS II sensor head mounted on the robotic arm (IDD) of the Mars Exploration Rover. The IDD also carries the a-Particle-X-ray Spectrometer APXS, also from Mainz, Germany, for elemental analysis, the Microscope Imager MI for high resolution microscopic pictures ( 30 pm per pixel), and the RAT for sample preparation (brushing grinding drilling (< 1 cm depth)). Picture taken at Kennedy-Space-Center KSC, Florida, USA...

Thermal Emission Spectrometer) instrument indicated the metallic nature of the rock [340]. Observations made with the panoramic camera and the microscopic image revealed that the surface of the rock is covered with pits interpreted as regmaglypts and indicate the presence of a coating on the surface. The a-Particle-X-ray spectrometer (APXS) and the Mossbauer spectrometer were used to investigate the undisturbed and the brushed surface of the rock. Based on the Ni and Ge... 

The basic function of the spectrometer is to separate the polychromatic beam of radiation coming from the specimen in order that the intensities of each individual characteristic line can be measured. In principle, the wide variety of instruments (WDXRF and EDXRF types) differ only in the type of source used for excitation, the number of elements which they are able to measure at one time and the speed of data collection. Detectors commonly employed in X-ray spectrometers are usually either a gas-flow proportional counter for heavier elements/soft X-rays (useful range E < 6keV 1.5-50 A), a scintillation counter for lighter elements/hard X-rays (E > 6keV 0.2-2 A) or a solid-state detector (0.5-8 A). 

Simultaneous spectrometers consist of various combinations of analyser crystals and detectors, arranged around the sample at fixed angle settings. Use of a multichannel X-ray spectrometer with simultaneous determination of up to 24 elements can considerably increase the analysis speed (a few seconds to a few minutes). 

XRF nowadays provides accurate concentration data at major and low trace levels for nearly all the elements in a wide variety of materials. Hardware and software advances enable on-line application of the fundamental approach in either classical or influence coefficient algorithms for the correction of absorption and enhancement effects. Vendors software packages, such as QuantAS (ARL), SSQ (Siemens), X40, IQ+ and SuperQ (Philips), are precalibrated analytical programs, allowing semiquantitative to quantitative analysis for elements in any type of (unknown) material measured on a specific X-ray spectrometer without standards or specific calibrations. The basis is the fundamental parameter method for calculation of correction coefficients for matrix elements (inter-element influences) from fundamental physical values such as absorption and secondary fluorescence. UniQuant (ODS) calibrates instrumental sensitivity factors (k values) for 79 elements with a set of standards of the pure element. In this approach to inter-element effects, it is not necessary to determine a calibration curve for each element in a matrix. Calibration of k values with pure standards may still lead to systematic errors for unknown polymer samples. UniQuant provides semiquantitative XRF analysis [242]. 

Microprobe analysis was initially developed at the University of Paris by R. Castaing, who fitted an X-ray spectrometer to a converted electron microscope in the early 1950s, and the first commercial instrument, developed in France by the Cameca company, appeared in 1958. The following years saw commercial instruments produced in the UK, USA and Japan. 

The State of New Jersey has been able to correlate airborne radiation measurements to clusters of buildings with elevated indoor radon 49 In this study, researchers compared airborne y-ray spectrometer data with indoor radon data to see if any trends emerged. For the conditions in New Jersey,... 

Elemental analysis can also be performed on SEM samples using x-ray spectrometer attachments [55], The techniques are known as energy dispersive x-ray (EDX) analysis and wavelength dispersive x-ray (WDX) analysis and require installation of a detector in the sample chamber. 

Perkins [18] carried out radium and radiobarium measurements in seawater by sorption and direct multidimensional gamma-ray spectrometry. The procedure described includes the removal of radium and barium from water samples on sorption beds of barium sulfate impregnated alumina (0.5-1 cm thick) and direct counting of these beds on a multidimensional y-ray spectrometer. The radioisotopes can be removed at Unear flow rates of sample of up to 1 m/min. 

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