SU934329A1 - X-ray differential filter - Google Patents

Description

This invention relates to an X-ray measurement technique, and more specifically to X-ray filters, designed to measure X-ray spectra emitted by, for example, laser electron-ion-beam plasma, plasma focus, linear 9 pinch devices, current maxima, X-ray tubes and guns.

X-ray diffraction spectrometers with crystals or riggers are known, which give good spectral resolution, but are narrowband, have a low luminosity and difficulties in resolving the spectrum. in time 1

 It is also known a device that uses absorption, in which X-rays are absorbed by a pair of foils made from different chemical elements or from a single element but of different thickness, located in the same plane. X-ray deflectors located behind the foil have the same spectral characteristics, and the x-ray emission spectrum is measured by the ratio of their output signals.

The control method used in this device is relatively simple, but requires knowledge of the type of spectrum in its application.

The closest to the proposed one is a Reitgei differential filter, two foils arranged next to one plane, made of different chemical elements, and the thickness of the foil from the lighter element is such that its transmission coincides with the transmittance of the foil from the heavier element K-edge absorption

15 of this foil f 3j.

The disadvantage of this filter is that the K-edges of the absorption of elements suitable for making plastics are unevenly distributed20 but with increasing atomic numbers and therefore there are wide energy digtazone in which the spectrum cannot be measured using a known device.

25

The purpose of the invention is to expand the field of spectral measurements and improve the accuracy of measuring the X-ray spectrum.

This goal is achieved by

Claims (3)

30 that in an x-ray differential filter containing two foils dispersed near one plane, made of different chemical elements, and the thickness of the foil of the lighter element is such that its transmission coincides with the transmission of the foil of the heavier element for its K-crabm absorption, the lighter element is selected from the condition that the radiation is completely absorbed by the foil from this element in front of its K-edge of absorption, and the thickness of the foil from the heavier element is chosen so that the width of the transmission spectrum in front of K-cr it uptake heavy element is measured emomu energy interval. Figure 1 shows the layout of the device in which the proposed filter is installed; Fig. 2 shows a schematic energy intensity distribution of the radiation after the foil passes from the lighter chemical element (dotted curve) and the foil from the heavier element (completely on the curve). The device for analyzing the X-ray spectrum, shown schematically in Fig. 1, contains two foils 1 of various chemical elements, directs the flow 2 of the analyzed X-ray radiation, two detectors 3 / mounted behind the plates, the outputs of which are connected to the inputs of the meter 4 of the difference signal. Measurement of the spectrum by means of a device containing the proposed differential filter, explains the graph shown in FIG. 2. The graph shows the dependence of the efficiency of x-ray detection (the product of foil transmission on the spectral sensitivity of the x-ray detector) on the energy of the x-ray quantum E for each of the detectors separately. The difference between the signals from the detectors (measured by device 4-) is proportional to the energy of the X-ray spectrum in the interval (E, EJL). This energy interval, as can be seen from the graph, is limited from the side of higher energy quanta to the K-edge of the element of a heavier foil, and from the side of lower energy quanta by passing this foil in front of the K-edge. The change in the thickness of the foil changes the width energy interval, increasing the thickness shifts the transmission of heavier foil in front of the K-edge closer to the K-edge and, thus, narrows the energy interval, reducing the thickness of the shifting transmission, on the contrary, further from the K-edge and, therefore, em em energy interval. To measure the energy of the spectrum in the interval 0.7 g –1.5b keV, you can use an At foil with thickness {yd {) 5 MKMV and Be from dgj. 290 microns. If the U and Be foils are 15 µm and 900 µm thick, respectively, the measured spectral range narrows to 1.1-1.56 keV. The spectrum energy in the range 1.6-4.5 keV can be measured using a filter of S.C and µm, Ae 5 µm). To narrow the interval to 3.0-4.5 keV, the foil thickness should be changed to 65 µm and 230 µm, respectively. The energy of the spectrum in the range of 3339 keV can be measured using the Ln foil filter (dj and Sn (dg |, 1 mm). The proposed technical solution covers the area of spectral studies, as it makes it possible to measure the x-ray spectrum in the energy range less than 4 keV, for which it is impossible to manufacture filters if you use the well-known solution. Invention X-ray differential filter containing two foils arranged with RIDOM in one plane, made of different chemical elements, and The thickness of the foil from the lighter element is such that its transmission coincides with the transmission of the foil from the heavier element beyond its K-edge absorption, characterized in that, in order to expand the range of spectral measurements and improve the accuracy of measurements, the lighter element is selected from the condition absorption of foil from this element in front of its K-edge of absorption, and the thickness of the foil of the same element is chosen so that the width of the transmission spectrum in front of the K-edge of absorption of a heavy element is equal to the measured energy cally interval. Sources of information that have been taken into account during the examination 1. L.Pr. X-ray spectroscopy of high-temperature plasma. UFN, 1976, t.119, issue 1, p. 49. 2. F.C. et aE. Continued Radiation in the X-ray and Visible Regions froma MagneticafEy Compressed Plasma. .Rev, 1960, 119, 3, p. 843-856. 3. D. Johnson, A system for recording the spectra of pulses emitted by plasma X-rays with a duration of the order of nanoseconds. Scientific Research Instrument 1974, 2, p. 47-51 (pototip).