RU2356037C2 - Device for x-ray fluorescence analysis of substances - Google Patents

Abstract

FIELD: physics, measurements.

SUBSTANCE: proposed device is intended for X-ray fluorescence analysis of substances. The proposed device comprises a solid-state detector, sample holder, primary X-ray radiation source built-around the X-ray tube with two outlet openings arranged at 90° to each other and diffuser designed to polarise the primary X-ray radiation and representing two halves of a hollow cylinder. Note that the device comprises also one more outlet opening, arranged between the aforesaid two openings and at 45° to them, every outlet opening being furnished with the gates to block X-ray radiation coming out therefrom. Note also that the gates of the first two outlet openings are arranged to operate in phase and that the hollow cylinder halves are moved apart to allow radiation coming from the additional outlet opening gets directly onto the sample.

EFFECT: multi-purpose device for X-ray fluorescence analysis incorporating two X-ray optical measurement circuits using one X-ray tube.

2 dwg

Description

The invention relates to elemental analysis using X-ray fluorescence analysis spectrometers with energy dispersion and may find application in the processing industries, geology and metallurgy for the quantitative determination of elements in various materials.

X-ray fluorescence analysis using semiconductor detectors is increasingly used in the practice of the physical and chemical laboratories of industrial enterprises, due to the fact that it allows you to obtain valuable information about all the elements present in the sample.

With the advent of the so-called Si-PIN detectors, there was no need to cool semiconductor detectors with liquid nitrogen, which stimulated the widespread introduction of spectrometers with such detectors in various areas of analytical research.

The low detection limits of elements in X-ray fluorescence analysis with energy dispersion are achieved using a three-axis X-ray optical measurement scheme (ROSI), in which the X-ray characteristic radiation (XRP) from the sample is excited by polarized X-ray radiation that occurs when the radiation is incident on the secondary diffuser from the primary source of excitation. When using such an RSWI, the time required to collect the energy spectrum from the sample increases, because the intensity of the secondary X-ray radiation is several orders of magnitude lower than the primary radiation, therefore, they often deal with biaxial RSI.

All this poses the task of creating universal spectrometers in which both triaxial and biaxial ROSI can be implemented. This is especially necessary when solving analytical problems of various complexity, solved by express methods.

A device for X-ray fluorescence analysis of a substance is known that is implemented in an SPECTRO-HEPOS X-ray spectrometer (1), in which XRP is excited from a sample using polarized radiation from a secondary scatterer (three-axis ROSI). The disadvantage of this device is that it is impossible to implement the usual biaxial RSI, in which it is possible to carry out the rapid determination of elements in samples, solving simple analytical problems in short measurement times.

Closest to the proposed invention is a device for x-ray fluorescence analysis (2), in which the analyzed sample is irradiated by linearly polarized radiation from two output windows of the x-ray tube, which each fall on their secondary diffuser, made in the form of two halves of a hollow cylinder. The device implements a three-axis ROSI, and the primary x-ray radiation propagates from two output windows located at an angle of 90 ° to each other. Due to this, the intensity of CXR from the sample increases, since two X-ray optical beams from each of the windows take part in its occurrence. However, the device has its drawbacks. It is impossible to implement a biaxial ROSI in it, which provides the rapid execution of measurements to solve ordinary analytical problems.

The technical result achieved in the present invention is the creation of a universal device for x-ray fluorescence analysis, which can be implemented sequentially two RSI using one x-ray tube.

The required technical result is achieved in that the device for x-ray fluorescence analysis includes a semiconductor detector, a sample holder, a source of primary x-ray excitation based on an x-ray tube with two output windows located at an angle of 90 ° to each other and a diffuser for polarization of the primary radiation, made in the form of two halves hollow cylinder Along with this, it contains a third outlet window located between them at an angle of 45 to the other two. For the sequential implementation of two x-ray optical measurement schemes, each output window has a shutter for its overlap, and the shutters of the first two output windows have the ability to work synchronously. Using the third output window allows you to implement a two-axis ROSI in the device with the first two windows closed with shutters. In this case, the radiation from this exit window immediately enters the sample, causing XRD samples by primary excitation of the x-ray tube. The transition to a three-axis X-ray optical measurement scheme is carried out by closing the third output cone with a shutter and opening the first two windows. In this case, the primary radiation from the x-ray tube, leaving each output window, falls on its half of the scatterer, it is polarized and already the secondary x-ray radiation from the scatterer excites XRP from the test sample.

A general view of the proposed device is shown in FIG. 1. It consists of a semiconductor detector 1 with an input window 2. A collimator 4 is located on the path of XRD from sample 3. The excitation source is made in the form of an X-ray tube 5, in which there are two output windows 6 and 7, located at an angle of 90 ° to each other. In the middle of them, at an angle of 45 ° to them there is a third output window 8. Each of the output windows 6, 7 and 8 is equipped with shutters 9, 10 and 11, respectively. The dampers have openings and can in their guides (shown in figure 1, but not indicated) to make movements to overlap the output windows, to prevent the spread of x-ray radiation from them. The flaps of the first 6 and second 7 output windows are connected by an arm 12, which ensures their synchronous operation.

The secondary diffuser is made in the form of two halves 13 and 14 of the hollow cylinder, which are spaced so that they rely on the ends of the diameters, on which lie the center of the sample and the ends of the x-ray beams, reaching the surface of the diffuser, coming out of the outlet windows located at an angle of 90 ° to each other to a friend. This is done so that the beam incident from the X-ray tube and the beam scattered by the scatterer form an angle of 90 ° (as an angle based on the diameter), which corresponds to the conditions for the complete polarization of X-ray radiation.

Figure 2 shows an illustration of a three-axis ROSI, which shows the rays that come from each output window. Rays 15 and 16 belong to the first output window 6, and the rays 16 are primary and incident on the diffuser 13, and the rays 15 are secondary after the diffuser 13. The XRP from sample 3 is excited by primary x-ray rays polarized on the diffuser from the first window. For the second output window 7, the situation is similar. The rays 17 are primary and, incident on the diffuser 14, are polarized, and the secondary x-ray radiation enters the sample 3. The rays 18 are secondary polarized x-rays after the primary radiation is incident on the diffuser 14 from the output window 7. The rays 19 from the third output window 8 are directly distributed for sample 3. Pos. 20 indicates the direction of propagation of HXR from the sample, which enters the detector 1.

The proposed device operates as follows. The sample holder is placed in the position indicated by pos. 3. In the initial measurement, the shutter 11 overlaps the third output window 8 of the x-ray tube, and the shutters 9 and 10 connected by the bracket 12 are in a position in which the windows 6 and 7 are open. When a high voltage is applied to the x-ray tube 5 from the outlet windows 6 and 7, the primary x-ray radiation propagates as shown in pos. 16 for window 6 and pos. 17 for window 7. When it hits the diffuser, the primary x-ray radiation propagates as shown in pos. 15 for the first output window 6 and pos. 18 for the output window 7. Polarized x-ray radiation causes HRI from the sample fixed in the sample holder 3, which is taken by the collimator 4 of the detector 1 along the direction indicated by pos.20.

A semiconductor detector 1 connected to a spectrometric pulse processor (not shown in FIGS. 1 and 2) processes the radiation quanta entering it and converts them into numerical values of the element contents, thus showing the chemical composition of the sample. The personal computer used for this is not shown in FIG. 2 either.

After the registration of the energy spectrum using the three-axis ROSI, which uses two output windows 6 and 7 and two halves of the secondary diffuser 13 and 14, the high voltage from the x-ray tube 5 is removed and the shutters 9 and 10 together with the bracket 12 are moved so that they close the output windows 6 and 7. At the same time, the shutter 11 opens the output window 8. After that, high voltage is again applied to the x-ray tube 5, which leads to the appearance and propagation of primary x-ray radiation from the output window 8 eh direction indicated in Figure 2 poz.19. This radiation excites XRP from the sample placed in the sample holder 3, which is recorded by the detector 1 through the collimator 4 along the direction indicated by pos.20 in figure 2.

After the time has elapsed for measuring the energy spectrum from the sample for a biaxial ROSI realized using the output window 8 of the X-ray tube 5, the high voltage is removed and the sample is replaced in the sample holder 3. To carry out the measurement of the next sample, all operations are performed in the same sequence or the necessary This output (output) window (window) of the x-ray tube.

Thus, the use of the output window 8, the shutter on it and on other windows makes it possible to quickly carry out the transition from one RSI to another.

The proposed device is implemented on the basis of the BSV 28 X-ray tube in the third design (with four exit windows), one window being plugged with a lead stopper, and an opening was made between the two windows for the third exit window, where a 200-μm thick beryllium disk was glued. A compressible fitting was soldered into one of the unused windows for subsequent pumping of the x-ray tube to high vacuum. An X-ray tube with a molybdenum anode was used, and the necessary voltage was applied to it from a source of PUR-50 (NPO Burevestnik, St. Petersburg). To ensure the necessary operating modes (U = 40 kV, and I = 10 mA), cooling of the tube with running water was used. The BDER-KI-11K semiconductor detector (FSUE IFTP, Dubna) was used as a detector together with the SU-06P spectrometric device (RPC “Aspect”, Dubna), the last of which was connected to an IBM personal computer .

The proposed device is implemented in one of the models of the spectrometer x-ray fluorescence analysis, which has passed metrological certification as a means of measurement.

The operation of the device for the analysis of various samples showed its advantage over the analogue, namely that it was possible to realize a quick transition to a biaxial ROSI and to carry out express analysis with short exposure times for the analyzed ordinary samples, which is necessary under the conditions of the express laboratories requirement.

Literature

1. SPECTRO HEPOS: 10 years of experience using polarized X-rays to excite a spectrum in a benchtop spectrometer. R. Schramm, journal "Analytics and control", t.7, No. 2, 2003, pp. 139-141.

2. Preliminary patent of the Republic of Kazakhstan No. 13458, published in the Official Gazette "Industrial Property" No. 9, September 15, 2003, IPC G01N 23/223.

Claims (1)

A device for x-ray fluorescence analysis of a substance, consisting of a semiconductor detector, a sample holder, a source of primary x-ray radiation based on an x-ray tube with two output windows located at an angle of 90 ° to each other, and a diffuser for polarization of the primary x-ray radiation, made in the form of two halves of a hollow cylinder characterized in that it contains another outlet window located between two others at an angle of 45 ° to them, and each outlet window is provided with shutters for I was coming out of the overlapping of these X-rays, with the first two windows damper configured to operate synchronously, and the hollow cylinder halves apart and emission of the output window, which is located between the other two at an angle of 45 ° to them apply directly to the sample.

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