The invention relates to the field measurements of natural and artificial variations of elemental composition in conditions of high background radiation and (or) increased temperature in man-made objects and geological origin and can be used in emergency conditions of high radiation in the hot chamber or plants for the reprocessing of spent nuclear fuel in the remote control apparatus, for example, in boreholes or in probe space modules.

As a similar method x-ray fluorescence analysis [1], which includes the irradiation object energetic photons with the formation of atomic K-vacancies and subsequent measurement of the characteristic K-series of the analyzed elements. This method is based on the high resolution detector of x-ray photons and does not allow to analyze the elemental composition of the radioactive object or to perform elemental analysis in conditions of high background radiation, because it does not provide for a mechanism for priority registration of a useful signal in terms of the background, and the background is in a one-to-one.

As a prototype method for the selective measurement of the Compton profile For electrons [2], when the object is first irradiated by energetic photons (and poro is To give-a vacancy in the electron shell of the studied atom), and then, in time coincidence with the x-ray photons To the series, measure the energy distribution of photons scattered by the mechanism of the Compton effect. This method should be considered as non-destructive element analysis in conditions of high background radiation (which is generated due to excitation of atomic K-vacancy mechanism of the photoelectric effect). However, it is not suitable to perform multi-element analysis, because it does not provide the separation of the contributions from the different elements, and the energy width of the recorded Compton distribution of the photons is larger than the distance between the displacements of the x-ray K-lines of adjacent elements.

The aim of the invention is non-destructive multi-element analysis in conditions of high radiation background.

This objective is achieved in that in the known method of elemental analysis, including the irradiation object probing gamma-quanta with energy E₀and measurement of energy distribution of gamma rays scattered by the mechanism of Compton scattering in the regime of temporary coincidence with x-ray photons To the series, first select the list of analyzed elements in order of increasing atomic number Z1<Z2 <...<Zn and the corresponding list of the binding energies For electrons E(Z1)<E(Z2)<...<E(Zn), and calculates the placenta is therefore the ranges of scattering angles Δ ϕ₁that Δϕ₂, ...Δϕ_nprobing gamma rays, these rays are scattered after the initiation of the K-vacancy one additional K-series from the list E(Z1)<E(Z2)<...<E(Zn) in each of the ranges, and then placed inside each of the range detectors for detecting the scattered gamma rays, and the amplitude of the signal from each range increase and standardizes independently, and then accumulate the results of the simultaneous summation of the standardized amplitudes to amplitudes obtained from the detector that registers the x-ray photons of different K-series.

This goal is achieved by the fact that the device for elemental analysis, contains the emitter probe gamma-rays collimator holder of the object and a detector of gamma rays scattered by the mechanism of the Compton effect, the output of which is filed on the control circuit input line of the gate and detector of x-ray photons To the series, the output of which is submitted to the control input of the linear gate, the output of which is aligned with amplitude analyzer and drive pulses used several detectors of scattered gamma rays, which are located in the estimated ranges of scattering angle, and the output of each detector through independent amplitude Normalizer comes on the first input if anago adder, in response to the second input of the linear adder filed with the output from the detector of x-ray photons To the series, and the output of the linear adder agreed with the drive pulses.

Figure 1 shows a diagram of the Compton-fluorescent cell analyzer.

Consider the operation of the device 1 according to the list of analyzed elements in order of increasing atomic number

and its corresponding list of binding energies For electrons

in these atoms.

In the initial state of the device 1 Is turned off, the detection unit 3 are turned off, the detector 4, missing or blocked by protecting the emitter of gamma-quanta in the collimator 1.

When the device is gamma-quantum emitter 1 pass through the collimator and, after scattering in the object - 2 K-shells of an atom with atomic number Z1, fall into the detector 3g. Scattering at small angles is accompanied by a small energy transfer to the electron, so that the gamma rays scattered in sector g, ionize only the atoms with the lowest sequence number Z1. In the following sector f scattered photons capable of insulate already two kinds of atoms: Z1 and Z1+1, and so on, lists (1) and (2), where with increasing scattering angle in each subsequent sector of the scattered gamma-rays after ionization of all previous analyzed atoms list and one additional is on atom number greater per unit than in the previous sector.

The ionized atom with K-shell emits x-ray photons To series that are registered in the detector 4. The device 1 registers and stores the acts of simultaneous events the occurrence of the scattered photon in each of the sectors scattering a, b, ...g and x-ray photon in the detector 4. The division of information coming from different sectors of the scattering is achieved through a set of different amplification coefficients of the amplitudes of the standard signal in different amplifiers-formers 5 (a, b, ...g)belonging to different sectors of the scattering. This difference of coefficients gain select from the terms of such division total amplitude at the output of the linear adder 6 to be stored in different channels of the drive. In the set of statistics in various sectors recorded some number of pulses that satisfy the equations:

where N_gN_fN_e...N_athe number of counts detected in each of the sectors scattering.

In the system of linear equations (3) unknown coefficients a1, b1, b2,..., are determined by calibration measurements with a reference object, where known concentrations of all elements of n(Z)n(Z+1), ... then, using the obtained values A1, b1, b2, ... about Radelet desired concentration of elements in the studied object.

Upon irradiation of the object by gamma-quanta most intensively manifested two effects: the photoabsorption of the photon and the Compton scattering of a photon.

When the photoabsorption of a photon in the K-shell of an atom, the photon disappears and is formed atomic-vacancy, filling of which is accompanied only by the emission of characteristic x-ray K-series photons. Registration of characteristic photons allows to identify the atomic number of the excited atom, which is the basis of x-ray fluorescence method for the elemental analysis. The limitation of this method is due to the fact that for such identification of the atomic number, you must have x-ray detector that can distinguish between x-ray lines of the neighboring elements. Table 1 shows the values of energies of x-ray lines (eV) for the light elements from boron (Z=5) to silicon (Z=14), and lines belonging to neighboring elements, as well as lines belonging to the x-series single element, you cannot allow, for example, using a Ge(Li)detector.

TABLE 1.

When Compton scattering of the probing photon with energy E₀in the object 2 on the corner ϕ, 1 scattered photon receives energy, which is calculated by the formula A.

Compton:

where m is the electron mass, C is the speed of light, mc²˜511 Kev. In the scattering part of the photon energy E_e(E₀that ϕ) is transferred to the electron:

The binding energy of electrons in the K-shell atoms E_k(z) varies over a wide range (˜0.01-120 Kev), is determined by the law Mosley and to be confirmed experimentally. It is a function of the atomic number z. If E_e{E₀that ϕ)>E_k(z), then K-electron leaves the atom, where in the K-shell vacancy remains, and the scattered photon leaves at an angle ϕ, which is contained in the formula (4). If the binding energy of the electron in the K-shell is E_kthen the probing photons with energy E₀start insulate atom in the scattering on the critical angle ϕ_k:

Almost simultaneously with the appearance of the scattered photon (:10^-8s) each ionized atom fills this vacancy, emitting a characteristic x-ray photons To the series.

The essence of the invention lies in the fact that the selectivity for simultaneous registration of x-ray photon and the photon is scattered by the mechanism of the Compton effect is determined by the time resolution of the detectors, and this allows us not only to identify the atomic number of such elements which it is not possible to identify x-ray fluorescence method due to the energy resolution of the detector of the x-ray photons (see, e.g., Table 1), but also to suppress the background check cha the TIC. The expected effect is that the critical angle Compton scattering factor (6) shows a rather high sensitivity to energy due To the electron. The registration of the scattered photon is carried out in a range of angles between adjacent critical scattering angles ϕ_k(Z) and ϕ_k(Z+1)and the scattering contributions in various sectors of the scattering share through various normalized amplitudes "Compton" signal and the sum of these amplitudes (time match) with the amplitude of the signal from the detector of the x-ray photons.

Figure 2 shows the critical scattering angles (degrees)calculated by (6) for the items listed in Table 1.

Critical scattering angles φkSn designed for probing photon emitter^119mSn energy 23.875 Kev, and the ranges of scattering angles vary from ˜8° to 22°. Critical angles φkEu designed for probing photon emitter¹⁵¹Eu energy 21.6 Kev, and the angle range rasseiania change from ˜9° to -26°. Such ranges of scattering angles sufficient to identify the atomic number.

Compton elemental analyzer, 1, registers acts of simultaneous occurrence of x-ray photons K-series (detector 4) and Compton scattered photons (unit de is Ktorov 3) with schema linear adder (PA) 6, the temporal resolution which is usually worse: 10^-7sec.

In addition to the simultaneous summation of the amplitudes, the selectivity for elemental composition ensure due fulfillment of two conditions:

1. The energy width of the probing photons Eγ₀less than the measured energy shift ΔEγ₀<E_k(Δz)). This condition is satisfied for a large number of nuclear gamma-emitters.

2. The energy width of the recorded Compton scattered radiation ΔEϕ) less than the measured energy shift E_k(Δz):

where Δϕ effective angular dispersion that occurs when collimation probing and scattered photons (collimator detectors 3 are not shown, the beam is limited by the dimensions of each detector). This condition ensures the coordination of the energy width of the recorded Compton distribution and the range of the scattering angle.

From (4), (6) and (8) estimate valid, effective range of the scattering angle (sector scattering):

then specify its reasons Δϕ˜δ·Δϕ_k(Z)_minwhere Δϕ_k(Z)_min- minimum critical angular range, and δ, 0<δ<1 is the value of the permissible error if element is " analysis.

The estimation of the geometrical aperture for a narrow beam sensing is:

where Ω_x- the solid angle of reception of the x-ray photons.

1 shows a schematic diagram of the device, the aperture of which is small. Figure 3 presents the axial geometry of the same device, in which the geometrical aperture and the representativeness of the analysis increase by a factor To:

where a and b are the characteristic linear size of the object and detector x-ray photons in the "old" geometry Figure 1.

Figure 4 the table values for the binding energy of electrons in the K-shell E_k(Z) presents the calculation of the dependence of the critical angles ϕ_k(C) on the atomic number of the elements of Z for the two emitters:

Am²⁴¹E₀=59.54 Kev, T_1/2˜458 years and

Cd¹⁰⁹E₀=87.7 Kev, T_1/2˜453 days

From Figure 4 it follows that, using the emitter Am²⁴¹you can perform elemental analysis of light elements from Z=20 (calcium) to Z=32 (germanium), whereas the use of emitter Cd¹⁰⁹extends the list of analyzed elements up to Z=42 (molybdenum). When the atomic numbers Z>44 energy gamma-quanta Am²⁴¹and Cd¹⁰⁹not enough to ionize atoms on the mechanism of the Compton effect.

Evaluation angular diapason is, shown in Figure 4, show that with decreasing atomic number Z ranges of scattering angles in sectors scattering Δϕ_k(Z) for Am²⁴¹smoothly decreases from ˜21° to ˜4.4°and for Cd¹⁰⁹from ˜17.5° to ˜2.5°. Assessment of pulse rate (10) taking into account these values Δϕ_k(Z) for emitters activity 1-10 Curie points to the possibility of measuring the concentration of elements from CA to Mo with precision ˜0.1-0.01% of the time ˜10-100 hours (excluding factor (11), Figure 2).

When E0˜60-90 Kev, the analysis of light elements Z<20 is limited by two factors:

1. Reducing energy x-ray photons increases the probability of absorption within the object, and therefore reduces the likelihood of temporary matches.

2. Ionization of light atoms on the mechanism of the Compton effect occurs when small-angle scattering of photons, where the range of scattering angles decreases, and decreases the aperture ratio of the Desk light elements.

Emitters with lower energy gamma rays, such as^119mSn energy 23.875 Kev or¹⁵¹Eu energy 21.6 Kev, reduce atomic number of the analyzed elements, as shown previously for elements in the range 14>Z>5, table 1.

You can specify other long-lived emitters of gamma rays, suitable for use in the area is the first device, for example:

These isotopes emit two probe photons with different energies, which allows to extend the range of atomic numbers for the analyzed elements.

The operation of the device 1 with emitters Am²⁴¹and Cd¹⁰⁹not limited only to the analysis of elemental composition by light elements. If the object is heavier elements, Z>44, these elements are ionised by the mechanism of the photoelectric effect and available for (simultaneous with light elements) analysis mode x-ray fluorescence analysis. Because the ionization of elements on the mechanism of the photoelectric effect is not accompanied by the simultaneous emergence of the scattered photon, the energy threshold for this process is much higher and is determined by the inequality:

for emitter Am²⁴¹satisfied to Z=69 (thulium), and emitter Cd¹⁰⁹satisfied to Z=81 (thallium). If the radiator there is a start signal, and the mode of x-ray fluorescence analysis can also be protected from the Desk of background photons. For example, the collapse of the Am²⁴¹accompanied by radiation α-particles, then for the time ˜10^-8s child core Np²³⁷emits probe photon with energy Eγ₀=59.54 Kev:

In figure 1 the dashed line is m shown best in such case, the power-match 7 starting signal, registered from α-particles, and signal registered from the x-ray photon.

Let the average number of particles that fall into the first channel, is equal to n₁and the average number of particles that fall into the second channel, is equal to n₂and the corresponding duration of the signals (˜10^-7respectively equal to τ₁and τ₂. Then the probability of a double coincidence is estimated by the formula:

Let n₀₀the true number of double coincidences per unit time, and n₁=k₁·n₀₀n₂=k₂·n₀₀where k₁, k₂- the ratios of the average rate of appearance of the background above the average rate of appearance of true paired matches. Then the assessment of the contribution of random coincidences (15) with a typical value of n₀₀˜10³pulse/sec and k₁·k₂˜1 is in the range of 1-3%, which indicates a very efficient suppression of background signals.

The main difference and advantage of the proposed method is shown in the emergency situation (for example, increased radiation and (or) high temperature), when the use of the Ge(Li) detectors (require constant cooling to liquid nitrogen temperature) is not valid. The method can be used for elemental the analysis of radiation detectors, not with high energy resolution and does not require nitrogen temperatures, such as plastic scintillators, cesium iodide, cadmium telluride and other

LITERATURE

1. A.I. Abramov, Kazan Y.A., Matusevich Y.S. // basics of experimental methods of nuclear physics. M: Atomizdat, 1977.

2. Fukamachi T., Hosoya, S. Binding effect due to the K-electrons observed on a Compton Profile of Si. Separate measurement of the Compton Profile // Phys. Lett. A. 1972. v.41. P.5. ibid. P.416; Phys. Lett. V.38A. N5, p.341.

1. Method for the elemental analysis in the presence of background that includes the irradiation object probing gamma-quanta with energy E₀and measurement of energy distribution of gamma rays scattered by the mechanism of Compton scattering on bound electrons in the regime of temporary coincidence with x-ray photons To the series, wherein the first select list of the analyzed elements in order of increasing atomic number Z1<Z2 <...<Zn and the corresponding list of the binding energies For electrons E(Z1)<E(Z2)<...<E(Zn) and compute successive ranges of scattering angles Δϕ₁that Δϕ₂, ...Δϕ_nprobing gamma rays, these rays are scattered after the initiation of the K-vacancy one additional K-series from the list E(Z1)<E(Z2)<...<E(Zn) in each of the ranges, and then placed inside each of the range detectors for detecting scattered the Amma-ray moreover, the amplitude of the signal from each range increase and standardizes independently, and then accumulate the results of the simultaneous summation of the standardized amplitudes to amplitudes obtained from the detector that registers the x-ray photons of different K-series, while the selectivity for simultaneous registration of x-ray photon and the photon is scattered by the mechanism of the Compton effect, allows to identify the atomic number of elements, and the results of the simultaneous summation determine the desired concentration of elements in the studied object.

2. Device for elemental analysis according to claim 1, containing emitter probe gamma-rays collimator holder of the object and a detector of gamma rays scattered by the mechanism of the Compton effect, the output of which is filed on the control circuit input line of the gate and detector of x-ray photons To the series, the output of which is submitted to the control input of the linear gate, the output of which is aligned with amplitude analyzer and drive pulses, characterized in that used multiple detectors scattered gamma rays, which are located in the estimated ranges of scattering angle, and the output of each detector through independent amplitude Normalizer comes on the first input of the linear adder in response to the second input line is aqueous adder filed with the output from the detector of photons of x-ray K-series, and the output of the linear adder agreed with the drive pulses.