RU2615711C1 - Multichannel x-ray analyzer - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: multichannel X-ray analyzer contains a source of X-ray or gamma radiation, a collimator and a primary beam filter, a specimen holder and analytical channels including collimators and secondary beam filters, a detecting device with detectors arranged in line and a registering equipment connected to the detector outputs, wherein the radiation source or the X-ray tube are used with the beam output at its end, the source or its focus is located on the circumference in the source axis plane or the electron beam (in the axial plane), the sample holder is adapted to install the sample with a flat or concave working surface on the said channel circumference, the detectors or the output openings of the secondary beam collimator are located on the line passing through the circumference point diametrically opposite to the source perpendicular to the channel, in addition, the analytical channels are located axially around the radiation source and contain the individual sample holders, and the openings are made in the primary beam collimator directed to the specimen holders.

EFFECT: providing performance capabilities of the analysis and the efficiency of the source usage, providing optimal conditions for analysing a wide range of items including the heaviest elements from thorium and above.

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Description

The present invention relates to spectrometers and analyzers for x-ray fluorescence analysis (XRF) of the composition of substances.

Known x-ray analyzers containing a radiation source and a semiconductor detector (PDD) (Bakhtiarov A.V. X-ray fluorescence analysis in geology and geochemistry. - L .: Nedra, 1985).

The disadvantage of an analyzer with PPD is that the performance and count rates in analyzers with one PDP are limited. The detectors from germanium and cadmium telluride have large emission peaks when recording radiation with energies above the absorption jumps. Silicon detectors, including drift detectors of the SDD type, are ineffective in detecting radiation with energies above 20-30 keV. Different types of PPD are optimal in limited energy ranges. To analyze different groups of elements, it is often necessary to repeat analyzes with different filters and other conditions.

The prototype is an X-ray analyzer containing an X-ray source, a collimator and a primary beam filter, a sample holder, two analytical channels with collimators and secondary radiation filters, detection devices with detectors arranged in a row and recording equipment connected to the outputs of the detectors (M.E. A. Robertson. US patent No. 5020084, 1991).

Used up to 12 detectors from high-purity germanium (OCH). Analytical channels are installed at angles of about 90 ° to the primary beam.

The disadvantage of the prototype is that the efficiency of using a powerful radiation source is small due to the limited aperture of the primary beam. In addition, when recording radiation at an angle of 90 °, the peak or maximum of the scattered bremsstrahlung coincides with the K _α lines of thorium and uranium and reduces the sensitivity of the analysis of these elements.

The technical result of the invention is to increase the productivity of analyzes and the efficiency of using the source, providing the possibility of simultaneous analysis of a wide range of elements in optimal conditions, including analysis with increased sensitivity of the heaviest elements from thorium and higher.

To achieve the specified technical result in a multichannel x-ray analyzer containing an x-ray or gamma radiation source, a collimator and a primary beam filter, a sample holder and analytical channels, including collimators and secondary beam filters, a detection device with detectors arranged in a row and recording equipment connected to the outputs of the detectors, according to the invention, a radiation source or x-ray tube with a beam exit from its end, the source or its focus p it is arranged on a circle in the plane of the axis of the source or electron beam (in the axial plane), the sample holder is arranged to mount the sample with a flat or concave working surface on the said channel circumference, the detectors or output openings of the secondary beam collimator are located on a line passing through a diametrically opposite source a circle point perpendicular to the channel, in addition, the analytical channels are axially located around the radiation source and contain separate sample holders and holes in the primary beam collimator are made directed to the sample holders.

The secondary beam collimator is made with slots between the walls or plates in axial planes.

One or two channels located on opposite sides of the channel source are configured to install a replaceable collimator with holes directed at a scattering angle above 140 ° from the sample position behind the source to channel detectors with this replaceable collimator.

The analyzer is schematically represented in the drawings:

FIG. 1 is a diagram in the axial plane passing along the axis of the source;

FIG. 2 is a top view along the axis of the source;

FIG. 3 is a diagram of the analysis of thorium-uranium in the axial plane;

FIG. 4 is a cross section of the secondary beam in a top view in the analysis of thorium-uranium.

A multichannel x-ray analyzer contains an x-ray tube with a wide panoramic beam at its end or isotopic and other gamma radiation sources, a collimator 2 and primary beam filters 3, sample holders 4 (Fig. 1) and analytical channels, for example channels, as a radiation source 1 6-9 (Fig. 2).

The analytical channel contains a collimator 10 and a secondary beam filter 11, a detection device 12 with detectors 13 arranged in a row, and recording equipment 14 connected to the outputs of the detectors.

The source 1 or its focus F ₁ is located on a circle in the plane of the axis FF _{1 of the} source or beam of e ^- electrons (in the axial plane).

The sample holder 4 is configured to mount the sample 5 with a flat or concave working surface on said channel circumference. The detectors 13 or the outlet openings 15 of the collimator 10 of the secondary beam are located on a line passing through a point F _{2 of a} circle perpendicular to the channel diametrically opposite to the source focus F ₁ .

In addition, the analytical channels are located axially around the radiation source and contain separate sample holders 4, and holes are made in the collimator 2 of the primary beam aimed at the sample holders.

The secondary beam collimator 10 can be made with slits formed by walls or plates 16 in axial (intersecting on the source axis) planes (Fig. 2).

One or two channels located on opposite sides of the channel source (for example, channels 6 and 8) are capable of installing replaceable collimators 17 with holes directed at a scattering angle θ _s above 140 ° from the sample position behind the source to channel detectors with this replaceable collimator ( Fig. 3).

The collimator 2 of the primary beams or a partition separate from this collimator can be made with a hole 18 in line with the holes of the collimators 17 (Fig. 1-3). To block the hole 18 with independent operation of the channels, you can enter the shutter 19.

Not shown nodes change sample and filter and other details.

Filters are selected depending on the power of the source and on which elements must be determined with minimal thresholds.

You can use collimators 10 to 90 ° with one or 2-3 slots and angles between the plates 16 from 5 to 15 °.

The collimator 17 for the analysis of thorium-uranium is made without dividing plates (Fig. 4), since at large distances from the sample to the detector the deviations from the axial plane are small, moreover, at large scattering angles, polarization does not play a significant role in suppressing the background.

The sample or point F ₃ can be shifted to points F ₁ or F ₂ , or tilt the diameter F ₁ F ₂ . With the same radii of the channels and the location of the points F ₂ at the same level with the point F _{1, the} angle θ _s is about 154 ° (Fig. 3).

Sample 5 can be poured into the cell 20. Non-flowing samples can be installed in the holder 4 without using the cell 20.

For analysis of relatively light elements, the scheme can be turned over. At the same time, cuvettes with a flat or slightly convex bottom are located below the circumference of the channels and the punch forms the surface of the sample.

Multichannel analyzer works as follows.

Samples are poured into a cuvette or mold, compacted or molded, irradiated, and the content of the elements is judged by the radiation spectrum. The calculation of the concentrations produced by known methods.

The analyzer works in automatic mode.

When running the analyzer, you can select the radius R _{1 of} the channel circumference 3-10 cm and the diameter of the image 3-7 cm. The radius R _{2 of the} concave surface of the sample or cuvette can be selected 1.5-2 times larger than the radius R ₁ . Detectors capable of operating at loads above 10 ⁵ pulses / s and x-ray tubes of 1-3 kW and above are preferred. In economical options with limited performance, you can use tubes with a power of 1 kW or less and channels with a small (1-4) number of detectors. In compact versions, isotopic sources of Co ⁵⁷ , Am ²⁴¹ , Cd ¹⁰⁹ , etc. can be used.

At the upper location of the sample, cuvettes with a slightly concave bottom made of plastic or aluminum with a thickness of 0.2-0.5 mm are used.

A multi-channel analyzer based on a powerful source can be performed with different channels and detectors that are optimal for analyzing different groups of elements.

In the analysis channels of heavy elements with atomic numbers Z above 56-60, you can install 4-12 OCH-detectors 3-5 mm thick or CdTe-detectors 1.5-2 mm thick. Heavy elements are determined at an accelerating voltage of 125-150 kV. In this case, tin filter 2 of a thickness of 4-5.5 mm forms the spectrum of the primary beam with a maximum in the region of 115-120 keV.

To analyze elements with Z less than 58-60, a channel with Si (Li) detectors 3-5 mm thick can be provided. Silicon detectors have less leak peaks and cleaner spectra. For the analysis of elements with Z less than 43-47, a channel with silicon drift detectors of the SDD type is possible.

For analysis of elements lighter than bismuth, collimators 10 by 90 ° and a filter 15 of the secondary beam of substances with an absorption edge above the line energy of those elements that must be determined with minimal thresholds, but less than the energy of the interfering elements or the peak of scattered radiation, are used. At an angle of 90 °, the peak of scattered radiation is located in the region of 93-100 keV, and the background under the Kα-lines of thorium-uranium is maximum.

For the analysis of thorium uranium with increased sensitivity in channels with FGG and CdTe detectors, replaceable collimators 17 are used, which are directed to the sample behind the source at a large angle θs 140-160 °, and open the screen 19 (Fig. 3). In this case, the peak of radiation scattered from the sample is shifted to the region of 83 keV, and the background under all thorium-uranium lines decreases. In this case, a filter 15 of lead and layers of lighter elements is used.

You can analyze samples with a flat or concave surface of a sphere, cylinder, torus or cone.

For analysis in the angle α 30-60 °, you can use samples with surfaces concave along the cylinder. You can also make samples and cuvettes with a concave surface along a torus or cone, capturing angles α above 60 °. In this case, the detectors can be located on a circle passing through the points F ₂ in the plane perpendicular to the axis FF _{1 of the} source.

Samples with concave concave surfaces that capture an azimuthal angle α of about 20-30 ° are preferred.

The analyzed areas of the sample are indicated by a dotted line in FIG. 2 and 4. During the rotation of the sample, its entire surface or entire volume is analyzed.

For small sample sizes and angles α, the deviations of the scattering angles from 90 ° and the planes of polarization are small, and the surface shape is not significant.

With semiconductor detectors, thresholds for detecting heavy (including gold, platinum, thorium, uranium, and rare-earth) elements are achievable at the level of ppm fractions in ores, rocks, and soils.

Contrast is increased due to filters, the use of polarization of bremsstrahlung, registration of radiation at 90 ° in the minimum of the scattering cross section, or due to the shift of the scattering peak at large angles in the analysis of thorium-uranium.

раз. При числе каналов k производительность растет пропорционально k*N (в десятки раз).With N detectors, overlays in the channel are reduced by N ² times, and the detection limit is more than

time. With the number of channels k, the performance grows proportionally to k * N (tens of times).

The proposed analyzer increases the productivity of analyzes and the efficiency of using the source, provides the possibility of simultaneous analysis of a wide range of elements in optimal conditions with different detectors and filters, including analysis with increased sensitivity of the heaviest elements from thorium and higher.

The claimed analyzer can be in demand in geology, ecology, mining and other branches of science and industry.

Claims (3)

1. A multi-channel x-ray analyzer containing an x-ray or gamma radiation source, a collimator and a primary beam filter, a sample holder and analytical channels including collimators and secondary beam filters, a detection device with detectors arranged in a row and recording equipment connected to the outputs of the detectors, characterized the fact that a radiation source or an x-ray tube is used with the beam exit from its end, the source or its focus is located on a circle in the plane of the axis of the source or electron beam (in the axial plane), the sample holder is configured to mount a sample with a flat or concave working surface on the mentioned channel circumference, the detectors or output holes of the secondary beam collimator are located on a line passing through a point of circle perpendicular to the channel diametrically opposite to the source, in addition, analytical channels are located axially around the radiation source and contain separate sample holders, and holes are made in the primary beam collimator I aimed at samples holders. 2. The analyzer according to claim 1, characterized in that the secondary beam collimator is made with slots between the walls or plates in axial planes. 3. The analyzer according to claim 1, characterized in that one or two channels located on opposite sides of the channel source are configured to install a replaceable collimator with holes directed at a scattering angle above 140 ° from the sample position behind the source to channel detectors with this replaceable collimator.

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