DE2138267C3 - Analyzer for measuring X-rays in a desired energy range with a filter, a main and an additional secondary radiator, as well as detectors for detecting the radiation emanating from the secondary radiators - Google Patents

Description

45 of the scattered radiation through the detector and a

Absorption of X-rays with above the

desired energy range of energy in the filter and conversion of this X-ray radiation into

The invention relates to an analyzer for measuring fluorescence radiation registered by the detector

th of X-rays in a desired 5 "filter material.

Energy range with a main secondary radiator The invention is based on the object of providing a

with the lower limit for the desired energy analyzer of the type mentioned at the beginning.

area defining absorption edge energy and form that he eliminates disruptive, outside

an additional secondary radiator, both of which are based on an X-ray located in the desired energy range

Filter with the upper limit for the desired 55 gene radiation with only one in a common

Absorption edges defining the energy range, the beam path, the filter, the secondary sir

energy lie in the beam path, as well as with one that is made possible by order.

Main secondary radiator outgoing radiation is detected. The task set is based on the invention Main detector and one of the additional detached by that for the main secondary radiator Secondary radiator outgoing radiation detecting 60 and the additional secondary radiator a common Additional detector, these detectors being provided with a filter and that the additional secondary are connected that one of the intensity of the X-ray emitters in the beam path after the main secondary radiation The emitter is arranged in the desired energy range and the same material is spoken Difference signal is formed. has the same composition as the filter.

An analyzer of this type is disclosed in US Pat. No. 65 The analyzer constructed in accordance with the invention 832. This known analyzer shows an increased sensitivity in practical operation a two-channel X-ray spectrometer and increased measurement accuracy for the with a different incident X-ray analysis in each channel. He enables one

Quantitative X-ray spectral analysis also of composed of a large number of elements Materials, and it also allows the use of relatively inefficient X-ray tubes, which is particularly advantageous for portable X-ray spectrometers.

An advantageous embodiment of the analyzer according to the invention, each with a two-layer design of filter and additional rear-view radiator is'

indicates the desired energy range (this electrical circuit is not shown),

At the first execution example! are the filter 1 and the additional secondary radiator 4 designed in one layer, while they are designed in two layers in a second embodiment, contains the first layer is a material with a K absorption channel, ie "with the upper limit de" desired energy range coincides, while »

characterized in that in the beam path of the io end the second layer contains a material with an incident X-ray radiation in the filter on an L-absorption edge, which between the first layer of a material with one of the
upper limit for the desired energy range

corresponding K-absorption edge a second

mentioned K-absorption edge and the K-absorption edge of a substance whose atomic number lies one smaller than that of the material of the first

Layer made of a material with a layer between the 15, When filter 1 is the layer of the K absorption edge for the material of the first K absorption edge defining material as

Layer on the one hand and the K absorption channels of a material with an atomic number lower by one on the other lying L-absorption edge follows, while-

Filter 1, the main secondary radiator 2 and the main detector 3 or through the filter 1, the additional secondary radiator 4 and the additional delector 5

first arranged in the beam path and with the additional secondary radiator 4 as second.

The embodiment according to FIG

rend in the additional secondary radiator these two layers- »» one main channel 6 and one behind this in the th additional channels lying in reverse order in the Sirahlengang of the beam path! 7 through the incident X-rays prefer ·.

In the following, the invention is explained in more detail with reference to the exemplary embodiments shown in the drawing explained; showing 35 are formed,

F i g. 1 shows a longitudinal section of an analyzer for The main secondary radiator 2 is in the form of

individual thin layers of material parallel to the filter 1.

In the main channel 6 protective screens 8 are housed, which allow direct incidence of the X-ray radiation in the main detector 3 after passing through the filter 1. In the case of the FIG. 1 shown Exemplary embodiments are as detectors 3 and 5 gas meters or proportional meters or Geiger

X-ray lines of chemical elements and the Absorp- 35 Müller counter, the wires of which are marked with 9, tion edges for the filter used for a second time. Entrance window 10 of the detectors 3

Measuring x-rays,

F i g. 2, the spectral characteristics for the main secondary radiator in an analyzer according to a first ^A, usführungsbeispiel,

F i g. 3 the spectral characteristics for the additional secondary radiator in the case of an analyzer according to the first exemplary embodiment,

F i g. 4 the mutual location of the characteristic

leadership example,

F i g. 5 <} '· ". Spectral characteristic for the main secondary radiator in an analyzer according to the second exemplary embodiment and

F i g. 6 the spectral characteristics for the additional secondary radiator in an analyzer according to the second embodiment.

The in F i g. 1 shown analyzer for measuring

and 5 are made of beryllium.

The analyzer is accommodated in a housing 11.

The illustrated analyzer for measuring X-rays works as follows:

The X-ray radiation incident in the direction of arrow A passes through the filter 1 (Fig. 1), which consists of a material whose absorption edges

of X-rays in a desired energy with the upper limit of the desired

area contains a filter 1, one in which coincides with an energy area, is determined by the fiI-

The direction of incidence indicated by the arrow / 4 is filtered, hits the main secondary beam

Radiation seen behind the filter 1 lying kr 2 and causes fluorescence radiation there,

Main secondary radiator 2 and a main detector which is registered by the main detector 3. By

gate 3, the radiation emanating from the main secondary radiator 2 50 entering the main secondary radiator 2

Radiation detected. reaches to the additional secondary radiator 4 and calls there

In addition, the analyzer contains ^{fluorescence radiation in the 1} S ¹ beam, which is generated by the additional detector

behind the main secondary radiator 2 an additional gate 5 is registered.

Secondary radiator 4 and an additional detector 5, the filter 1 absorbs mainly the

Radiation emanating from the additional secondary radiator 4, the energy of which is greater (but not by

lung recorded. more than 2 to 3 times) than the energy of

The filter 1 and the additional secondary sirahler 4 are the absorption edge of the filter 1. In the main secondary parts of a material whose absorption radiant heater 2 there is no fluorescence excitation of edge energy with the upper limit of the desired radiation, the energy of which is less than the energy range. The main part of the absorption edge of the main secondary jet secondary radiator 2 consists of a material which is 2. The stream will only fall in the desired energy range, the absorption edge energy of which lies with the lower one between the absorptive edges of the filter 1 and the limit of the desired energy range of the main secondary radiator 2. development in proportion ^; g not much through the filter I

The additional detector 5 is electrically weak with the 65, whereby a fluorescence of the main second main detector 3 connected in such a way that därstrahlers 2 is caused at the output, which leads to an

the analyzer produces a difference signal that shows the marked increase in the spectral response intensity of the measured X-ray radiation in geography (Iss main channel 6 in the desired energy

area E ₁ and E ₂ leads (Fig.2), where the radiation energy £ is plotted on the abscissa axis and the response sensitivity η of the radiation registration is plotted on the ordinate axis.

The presence of a very small responsive wedge of the main channel 6 is outside the desired energy range in the case of the one shown Analyzer due to the following three causes:

firstly by the partial passage of the radiation with one above the upper limit of the desired Encrgiebceichcs lying energy through the filter 1 with its subsequent conversion in the main secondary radiator 2 to its Fluorescence that is registered by the main detector 3,

second, through the partial transmission of radiation with one below the lower limit of the desired energy range through the filter 1 with the subsequent energy Scattering in the main secondary radiator 2 and registration of the radiation after the scattering by the main detector 3 and thirdly by the absorption occurring in the filter 1 the radiation with an energy above the upper limit of the desired energy range with its conversion into a fluorescence of the filter 1. The latter causes fluorescence in the main radiator 2 in some cases which is registered by the main detector 3.

The first two of these causes are also present in the additional channel 7, the one through the filter 1, the additional secondary radiator 4 and the additional detector 5 is formed. Therefore, the additional channel 7 also has a slight sensitivity outside of the desired energy range.

By choosing a suitable thickness for the main secondary radiator 2 in the main channel 6 and the additional secondary radiator 4 in the additional channel 7 can be an equality of the sensitivity for the Secure the main channel 6 and the additional channel 7 outside the desired energy range.

F i g. 3 shows the spectral response characteristics of the additional channel 7, with on the coordinate axes the same sizes as in FIG. 2 are applied. Since the energies of the absorption edges of the filter 1 and the additional secondary radiator 4 coincide, the additional channel 7 has no pronounced Increase in response sensitivity, as is the case for the main channel 6 (Fig.2).

Of course, the main channel 6 and the additional channel 7 can also be structurally separate. The results but are worse than with the analyzer described above.

When describing how the analyzer works according to FIG. 1 it was assumed that the filter 1 is made of a single material. The same was true for the additional secondary beam cr4.

Now, taking into account what has been said above, the mode of operation of the analyzer according to the second embodiment are considered, in which the material, its absorption edge energy coincides with the upper limit of the desired energy range and from which the filter 1 and the additional secondary radiator 4 are made, is designed in two layers.

In the analyzer according to the second exemplary embodiment, the third cause of the low sensitivity of the «analyzer to be eliminated outside the desired energy range.

Here is a specific example:
; The first layer in the beam path is ίο for filter 1 copper and the second thulium: Nickel is chosen as the material for the 'main secondary fahleri' in the main channel 6.

F i g. 4, where on the abscissa axis the energy E

and the absorption factor τ on the ordinate axis

* 5 plotted shows the mutual position of the

K absorption edges for copper (Cu) and the

L-absorption edge for thulium (Tm).

The fluorescence radiation of the CuK / r line produced in the copper layer of the filter 1 has an energy which is sufficient to cause secondary fluorescence of the main secondary radiator 2 made of nickel. But in the beam path of the CuK / r radiation is the thulium layer, which effectively absorbs the fluorescence line of the first Cu layer of the filter _{with its L 1n -KaHtC.} After passing through the main secondary radiator 2, the X-ray radiation arrives at the additional secondary radiator 4 in the additional channel 7, which is formed by the same materials as the filter 1. Here, the thulium layer faces the filter, while the copper layer is arranged as the second layer in the beam path.

In the thulium layer of the additional secondary radiator 4, a fluorescence is produced by the CuK ^ j line partially penetrating the filter 1. Through suitable Choice of the thickness of the thulium layer of the additional secondary radiator 4 can be a registration equality for the CuKjj line in the main channel 6 and in the additional channel 7.

Achieved when the radiation to be analyzed continues to pass through the additional secondary radiator 4 they the copper layer. In this there is also a scattering of the radiation that is not to be analyzed an energy lying below the K-absorption edge of copper and a fluorescence of the hard, radiation not to be analyzed. Here, the scattering and the fluorescence are due to the thickness of the additional secondary radiator 4 determined, which is chosen so that this scattering and fluorescence assume the same values as in the main channel 6. The reflection (fluorescence and scattering) from the copper layer of the additional secondary radiator 4 penetrates its thulium layer, where it is partially is weakened, and arrives at the additional detector 5. This weakening of the reflection in the Thulium layer of the additional secondary radiator 4 can by increasing the thickness of the copper layer of the Additional secondary radiator 4 can be compensated.

The application of the X-ray analyzer to quantitative chemical X-ray spectral analysis is considered below. The chemical element to be determined is zinc. It is further assumed that the object to be analyzed contains a number of other elements besides zinc, the characteristic X-ray lines of which _{lie next to the ZnK n} line. Copper and gallium are considered to be such elements. It is also assumed that the filter 1 made of copper and thulium, the main secondary radiator 2 in the main channel 6 made of nickel and the

Additional secondary radiator 4 in the additional channel 7 consists of thulium and copper.

In Fig.5 is the spectral response characteristic of the main channel 6 with the two-layer filter 1 made of copper and thulium and the mutual layer S of the characteristic X-ray lines for copper, zinc and gallium shown by an underperforming X-ray tube can be excited in the object to be analyzed. So can one Voltage at the X-ray tube of 2OkV and with a current flowing through the X-ray tube of 0.1 mA at the output of the main detector 3 in the main channel 6 when registering the fluorescence fine zinc can achieve a counting speed of 25,000 pulses / s.

From Fig. 5 it can be seen that one at the exit of the main detector 3 of the main channel 6 is practical only receives the zinc line.

F i g. 6 shows the spectral-response characteristic of the auxiliary channel 7 with the double-layered supplementary "0 Sekundärstrahlcr 4 from thulium and copper.

The additional detector 5, the from the additional

Secondary radiator 4 receives incident radiation is connected to the main detector 3 in such a way that a difference signal is obtained at the output of the analyzer, which shows the intensity of the X-ray radiation of Indicating zinc. The zinc concentration in the area to be analyzed is determined from this radiation intensity Object. (In FIGS. 5 and 6, the same values are on the coordinate axes as in FIGS. 2 and 3 applied.)

The presented analyzer for measuring X-ray radiation in a desired energy range enables quantitative X-ray spectral analysis of objects co-duplicated in terms of their elemental composition. The high light intensity of this analyzer makes it possible to use a low-power X-ray tube to excite the X-ray fluorescence in the object to be analyzed, which offers the possibility of making the X-ray spectrometer easily portable. The sensitivity ensured by the analyzer in the analysis of elements of the periodic table which are adjacent in terms of atomic number is at least 10 ~ ² %.

For this purpose 2 sheets of drawings 709808/141

Claims (2)

X-ray radiation is examined, it is in Claims: each of the two channels of this analyzer through "a filter with a higher atomic number and one, two- 1, analyzer for measuring X-ray radiation layers formed, secondary radiation lower young in a desired energy range with an atomic number between the absorption edges A main secondary radiation with the lower energy range of the same selected, the limit for the desired energy range fixed X-rays with a different energy underlay Absorption edge energic and one is pressing. The differ in the Additional secondary radiators, both of which are incident on one of the two channels Filter with the upper limit for the desired j ° of their energetic composition from each other, Energy range defining absorption edge and the later electrical !? Composition of energy lie in the beam path, as well as with an electridy triggered by these X-rays from the main secondary radiator outgoing see signals serves to reduce the influence of one in the Radiation detecting main detector and a beam path to be inserted sample for two different 15 dene energy ranges of the X-ray radiation impinging on it emanating from the additional secondary radiator Detecting additional detector, whereby to investigate gene radiation. From the U.S. PS These detectors are so interconnected, 3176 130 is further an analyzer for measuring that a differential range corresponding to the intensity of the X-ray radiation in the X-ray radiation in a desired energy range is known, in which in the path of the ffferenzsignal is formed, thereby characteristic 30 borrowed their energy in a selected energy indicates that the X-rays to be analyzed for the main secondary beam area are too ler (2) and the additional secondary radiator (4) in a radiation detector one after the other a filter, common filter (1) is provided and that the one material with the upper limit for the the additional secondary radiator (4) in the beam path selected energy range corresponding absorption arranged after the main secondary radiator (2) »5 contains an ionizing edge, and an incident X-ray is and the same material composition gene radiation excitable secondary radiator from one like the filter (1). Material with the lower limit for the specified 2. Analyzer according to claim 1, with in each case selected energy range of corresponding absorption two-layer Execution of filter and leading edge are inserted. When working with this trimmed secondary emitter, characterized in that 30 known analyzer shows that the detector that in the beam path of the incident X-rays also by incident X-rays with extra- 'Radiation in the filter (1) lying on a first layer from half of the desired energy range a material with an upper limit energy is affected. This essentially has There are three reasons for the desired energy range, namely a partial passage the K absorption edge is a second layer of 35 incident X-rays with one above the a material with a absorption edge between the K-Ab- upper limit of the desired energy range for the material of the first low energy through the filter with the following Layer on the one hand and the K-absorption edge conversion of this radiation into secondary radiators in a material with one order smaller - fluorescence radiation registered by the detector, On the other hand, L-absorption 40 a partial passage of the incident X-ray edge follows, while in the additional secondary radiator radiation with a below the lower limit of the (4) these two layers incline in the opposite direction to the desired energy range sequence in the beam path de, incident X-ray the filter with subsequent scattering in this X-ray radiation lying, gene radiation in the secondary radiator and registration