Method for elemental analysis of media and apparatus realising said method
SUBSTANCE: fast neutron source is placed in a slowing unit; a γ-spectrometer employing a non-overload linear detection technique is used to detect instantaneous γ-quanta resulting from radiation capture of neutrons by nuclei of elements; calibration responses of separate elements making up the sample being identified are determined; apparatus spectra of γ-quanta are used to determine concentration of elements in the sample through weight coefficients of responses of elements, wherein chemical composition of the media is determined by: a priori determining the chemical composition - known chemical compounds - of the medium; determining calibration responses of compounds through the sum of calibration responses of elements making up the compounds; determining concentration of compounds and elements in the medium being identified; determining concentration of elements making up the compounds; establishing conformity of the obtained total concentration of elements of the medium, based on elements making up compounds of the medium being identified, concentration of elements of the medium obtained by identification decryption of only the elemental composition of the medium; in case of mismatch with a given error of the total concentration of elements of the medium, obtained by identification decryption based on elements making up the identified compounds of the medium, with concentration of elements of the medium, obtained by identification decryption of only the elemental composition of the medium, the procedure, starting from the a priori determining of the structure of compounds, is repeated.
EFFECT: faster elemental analysis, high resolution of identification of elements, high sensitivity of determining impurities in media.
3 cl, 13 dwg
The invention relates to the field of elemental analysis - qualitative detection and quantitative determination of elements and elemental composition of substances, materials and various objects. It can be liquid, solid materials, gases. Elemental analysis allows us to answer the question - what kind of atoms (elements) is analyzed substance.
Elemental analysis is one of the most important tasks in any industry, the purpose of which is to control the use of raw materials, production and finished products. Ferrous and nonferrous metallurgy, oil production and refining, farming, Geology, mining, and more practically impossible without the availability of analytical laboratories performing elemental analysis. Elemental analysis important in eco-analytical and sanitary-epidemiological control, analysis of food and feed, metals and alloys, inorganic materials, especially pure substances, polymeric materials, semiconductors, petrochemicals, explosives detection, and other medical and scientific research.
The effectiveness of elemental analysis depends largely on instrumental methods of analysis. Among the instrumental methods of analysis are widely distributed x-ray fluorescence, atomic emission is, atomic absorption spectrometry, spectrophotometry and fluorescence analysis, electrochemical methods (polarography, potentiometry, and others), mass spectrometry (spark, laser and others), different ways of activation analysis. When selecting the method and techniques of analysis take into account the structure of the analyzed materials, accuracy requirements determine the limit of detection elements, detection sensitivity, selectivity and specificity, and cost analysis, qualification of staff, speed of analysis, the level of required sample preparation and availability of necessary equipment.
It should be noted radioactivation analysis. Radioactivation analysis - a method of analysis of a substance according to the nature of the emission of radioactive isotopes produced by the bombardment of the analyte nuclear high energy particles. Radioactivation analysis has a high sensitivity and is used to determine impurities in metals, alloys, semiconductor materials, and other substances. Activation analysis is one of the major nuclear-physical methods of detection and determination of element content in different natural and man-made materials and objects in the environment. The method is based on the fundamental concepts and data about the structure of atomic nuclei, the cross section of the nuclear reactions, schemes and the probability of decay of radionuclides, the energy of the radiation, as well as modern methods of separation and pre-concentration of trace elements. Widespread activation analysis has received such advantages over other methods, such as low detection limits of elements (10-12-10-13g·cm-3), expressnet and reproducibility of the analysis, the possibility of non-destructive simultaneous determination of the sample 20 and more items. Common to all methods of activation analysis is the activation of substances neutrons, γ-rays or charged particles and the subsequent registration of the spectral composition of radiation of excited nuclei or formed radioactive isotopes. Most common first two methods. Activation analysis on charged particles, due to their low mileage in substance, is used mainly for the analysis of thin layers and in the study of surface effects.
The main disadvantage of these methods are high requirements for sample preparation and large or relatively long analysis time, and in some cases, as, for example, in the case of gamma activation analysis, bulkiness and lack of tooling.
For a wide range of tasks elemental analysis with acceptable accuracy, in which the limits of 10%, sensitivity and resolution of about 10-3÷10-4% of critical speed of elemental analysis and high penetrating ability of tools for the detection and control of elemental composition. This takes place when identifying the hidden bookmarks that are inaccessible for visual observation places, for example in containers large freight bookmarks from explosives, contraband on the posts of customs control, etc. in the Most optimal combination of features for identifying the elemental composition of the environments that are in these conditions, has a method (method) elemental analysis based on spectral analysis of instantaneous γ-rays created in the radiative capture of neutrons by the nuclei of elements.
Most fully this method developed and used by Rapiscan Systems www.rapiscansystems.com), in which the control of the quantitative composition of the medium (identification of the elemental composition) is carried out using neutron irradiation of materials by spectral analysis of γ-rays arising from the interaction of fast neutrons with the materials (substances). Elemental analysis is used to control large clade (containers).
In the method proposed in the present application, when the elemental analysis is also used SP is Chelny analysis of γ-quanta, occurs when the radiative capture of neutrons by the nuclei of elements. However, unlike the methods used by the company Rapiscan Systems, the proposed method analyzes the spectra of γ-ray, born during the capture of only neutrons do not interact with nuclei of the identifiable elements in the reaction inelastic scattering . In addition, the proposed method is identified not only the elemental composition and chemical (molecular) structure. Using a modified method of discrimination of time intervals significantly improves the characteristics neprekrashajushiesja spectrometer γ-quanta increases statistical precision and reduce bias. The measurement error is not more than 5÷15% for exposures (measurement intervals) is not more than a few tens of seconds and sensitivity to 10-5÷10-6g, for example, in samples of biological tissue volume V~1 cm3specific gravity of 1 g·cm-3. In General, the method allows to estimate the concentrations of elements and chemical compounds in the condensed and gaseous media up to 10-3÷10-4% with an error of less than 10%.
The authors of this application is very promising use of the proposals put forward in medicine and especially in the treatment of cancer. A new method of treating oncologists the definition of diseases, on which experts have high hopes, is neutron capture therapy (NRT). The essence of the NRT consists of the following: the tumor is injected with a drug containing boron-10 or gadolinium-157 and is exposed to its thermal neutron beam of great intensity. The drug has the ability to accumulate in the tumor, so the energy from the resulting nuclear reaction particles that destroy tumor cells occurs only in her, and healthy tissue is practically not damaged. For a complete cure with just one session NRT. Developing technology is the technology of choice for patients whom other methods of treatment to help not.
BNCT Boron Neutron Capture Therapy is one of the Central areas of modern non-surgical Oncology is not yet out of the discharge of the experimental treatment only because of a number of technical, financial and other factors. For example: a slight deviation from the relevant criteria of accuracy in determining the concentration of the drug with boron installed by specialists-oncologists, and, as a consequence, incorrect planning of treatment, can lead to loss of significant areas of healthy tissue or inadequate dose tumor tissue, requiring repeated procedures, and consequently, the danger of increased risk of session Le is to be placed. Therefore, the development of non-invasive methods of monitoring the content of boron in the field of tumor growth directly in the process of conducting NRT is a fundamentally important factor in the success of therapy. The proposed method and equipment for its realization on the identification of the elemental and chemical composition of environments to determine the concentration of boron-10 in a biological tissue within 10-40 µg/g when the relative weight of fabric ρ~1 g·cm-3with an error of no more than 10% during several tens of seconds and even units of seconds.
A known method for identifying the elemental composition on the spectral analysis of instantaneous γ-rays created in the radiative capture of fast neutrons is used in identifying plants Rapiscan Systems ' (www.rapiscansystems.com). The company now uses this method to control the elemental composition of large clade in closed freight containers. The disadvantage of this method is the ambiguity in the determination of the chemical composition environments due to the imperfection of the methods in the preparation of the calibration reference data identifying calibration measurements.
The known method [2, 3], adopted for the prototype, the identification of the elemental composition on the spectral analysis of instantaneous γ-quanta produced in the reactions of the radiative capture of neutrons by nuclei ELEH the clients. In this way [2, 3] mentions the possibility of identification of the chemical (molecular) structure of environments. However, the authors never describe how such identification is carried out. The disadvantage of this method is the large statistical uncertainty of the measurements and, therefore, prolonged exposure while taking measurements. In the application above mentioned disadvantages are absent.
The essence of the proposed method for determining the elemental composition is the following: the fast neutron source is placed in slowing down the block, γ-spectrometer using the method neprekrashajushiesja linear detection, record instant γ-quanta, born in radiative capture of neutrons by the nuclei of elements, determine the calibration response of the individual elements included in the identifiable sample, the apparatus spectra of γ-rays, determine the concentration of elements in the sample after weighting coefficients of the feedback elements, characterized in that the chemical composition of the media is determined according to the scheme: specify a priori the chemical composition of the well - known chemical compounds in the environment, determine the calibration feedback connections through amount the calibration response of the elements included in the composition of the compounds, determine the concentration of compounds and elements identified in the environment, determine the con is entrale elements, included in connections, establish the correspondence received total concentration of the elements of the environment, taking into account the elements included in the composition of the identified compounds in the environment, concentrations of the elements of the environment, the received identifying decoding only the elemental composition of the medium, if not the match for a given error total concentration of the elements of the environment, the received identifying decoding based on the elements included in the identified compounds in the environment, concentrations of the elements of the environment, the received identifying decoding only the elemental composition of the medium, the procedure starts with the a priori assignment of the structure of the compounds, repeat. When performing procedures identifying measurements are used γ-spectrometer using the method neprekrashajushiesja linear detection with the modified method of discrimination of time intervals or, more precisely, with the method of double discrimination of time intervals (see below, page 18).
The known device for identifying the elemental composition sold by the company Rapiscan Systems . The disadvantages of used devices are: the use of isotopic sources of fast neutrons; low resolution; low-speed elemental analysis, accuracy and sensitivity; the lack is a journey of reliable criteria for the chemical (molecular) structure of controlled environments. The disadvantages of the implemented setup should also include the following: identifying the installation is completed with various accessories, which makes it cumbersome and not always convenient. Weight can reach 20÷25 tons. Transportation installation is carried out in unsorted and disassembled sea or rail method.
The installation implemented the proposed method, these drawbacks are absent.
The prototype of the presented invention is a known device for identifying the elemental composition proposed in [2, 3]. The method of rapid identification and control, implemented by setting, based on the reception and decoding of the spectral composition and yield instant γ-rays produced by neutron irradiation of the nuclei. As neutron sources are pulsed neutron generators. The disadvantage of this device is the prototype, low statistical precision and, as a consequence, the long measuring exposure (several tens of minutes or more). Proposed in this application the device is devoid of this drawback.
The claimed method is implemented by using a device comprising a source of neutrons, a block of slow neutrons, γ-spectrometer using the method neprekrashajushiesja linearly is about detection, software unit, including a library of calibration characteristics (response γ-spectrometer in the form of arrays of measured spectra instant γ-rays created in the radiative capture of neutrons by the nuclei of different elements), measuring system for registering apparatus γ-spectra, block software system conversion weight contributions (weights) bitmap calibration characteristics in the concentration values of the atomic composition, the interface conversion measurement data in the values element-by-element concentrations in on-line mode, characterized in that the device implementing the method of the elemental and chemical analysis environments, installed γ-spectrometer using the method neprekrashajushiesja linear detection with the modified method of discrimination of time intervals or, more precisely, with the method of double discrimination of time intervals, allowing to decrease by several decimal orders of magnitude the time of the measurement procedure for the identification of the elemental and chemical composition environments, installed software unit conversion measurement data in the energy spectra of neutrons adapted to calculate the concentrations of chemical compounds and elements of the media based on measuring information and use modi is data identifying the calibration characteristics (response of the spectrometer), allows you to estimate the concentration of elements and chemical compounds in the condensed and gaseous media up to 10-3÷10-4% with an error of less than 10%, the device is in the stationary and mobile (portable) versions.
The implementation of the method and operation are explained in the following figures.
Figure 1. The block diagram of the fixed option identifies the conveyor installation type.
1 - pulsed neutron source; 2 - block of slow neutrons; 3 - radiation detectors (γ-spectrometer); 4 - Pentium I with software block for processing of experimental data in the on-line mode; 5 - measuring and recording system; 6 - briquette tbpo; 7 - pipeline.
Figure 2. The time dependence of the instant energy γ-ray radiation capture, absorbed in the detector, placed in the neutron spectrometer on the time of deceleration.
▲ - H, v - C --- - N, -··- - O, ···· - S, Δ - Cl, □ - Fe, - - Ni, -·- - Gd + -8U.
Figure 3. The pulse spectra of γ-rays.
1 - ▲▲▲ - a mixture of radionuclides (experiment); 2 - °°° - background; 3 - +++ -133Ba; 4 - *** -152Eu; 5 - ♦♦♦ -137Cs; 6 - ▲▲▲60Co.
Figure 4. The distribution of time intervals N(T).
Δ - calculation <n>=1549-1; ° - experiment <n>=1549-1detector - NaI(Tl)radiation - γ-quanta; • experiment <n>=1549-1detector - NaI(Tl)radiation - γ-quanta, the level of violence the purpose of time intervals T d=150 μs.
Figure 5. The detector operated in the linear mode of detection.
9 - n, γ; 10 - scintillation crystal; 11 - PMT; 12 - output of the photomultiplier, Ro>1000 PTO; 13 - storage capacitor, Withn; 14 - pre-amplifier, RI~1000 Megohms.
6. The original pulse spectrum φ(V) mixed flux of γ-rays from radionuclides137Cs and60Co. Experiment. Detector: single crystal - NaI(Tl).
7. Convolutional pulse spectrum γ-ray f(V) for <n>=0,01. The original pulse spectrum of γ-rays is presented on Fig.6.
Fig. The pulse spectra of γ-quanta. Radionuclides:94Nb;137Cs;60Co. Detector: a single crystal of NaI(Tl) height h=18 cm and a diameter of d=20 cm using discrimination of time intervals. ° -94Nb; × -137Cs+60With.
Fig.9. Pulse height spectrum of γ-quanta. Radionuclide94Nb. Detector: a single crystal of NaI(Tl) height h=18 cm and a diameter of d=20 cm Download - 540 kHz. Without discrimination of time intervals.
Figure 10. The distribution of time intervals N(T) <N>=10 MHz.
1 - T1; 2 - T2=TD;.
11. The block diagram of the spectrometer setup.
9 - γ-quanta; 10 - NaI(Tl) scintillation crystal; 11 - electronic photomultiplier optically coupled to the single crystal of NaI(Tl); 12 - died; 16 - electronic unit (aryadeva energy); 19 is a block with a controlled linear transmitter or linear gate; 22 - G5-78 - pulser; 25 - amplifier and shaper pulses coming from the line transmitter; 26 - single-Board analyzer SBS-60; 4 - Pentium I slot in which is inserted the blade pulse analyzer SBS-60; note: 15, 17, 18, 20, 21, 23, 24 - coaxial connectors through which switching with various electronic units spectrometric complex.
Fig. The block diagram of the charging unit.
27 - timer IMS; 28 of the front panel of the electronic unit; 11 - PMT; 12 - output dynode photomultiplier PMT(11); 15, 17, 18, 20, 23 - connector front panel; 16 - electronic unit (charge-energy); 19 - linear transmitter or linear gate; 22 - generator G5-78; 29 - repeater UDP; 30 input ("leg" 2) timer IS (1); 31 - repeater UDP; 32 - condenser; 33 - entrance ("leg" 4) timer IS (27); 34 - timer IS; 35 - repeater UDP; 36 - shaper IS; 37 - repeater UDP; 38 - repeater UDP; 39 - repeater UDP; 40 input ("leg" 2) timer IS (34); 41 - storage capacitor C2forming the output pulses of the timer IC 2 (61) of duration T=T1similar to the storage capacitor C1(42); 42 - cumulative capacitor C1involved in the formation of pulses at the output of the timer IS (34) of duration T=T0 ; 43 - conclusion ("leg" 6) timer (IM) (34); 44 - conclusion ("leg" 7) timer (IM) (34); 45 - conclusion ("leg" 3) timer (IM) (34); 46 - repeater UDP; 47 - shaper IS; 48 - repeater UDP; 49 switch P; 50 - repeater UDP; 51 - conclusion ("leg" 7) timer IS (27); 52 - conclusion ("leg" 3) timer IS (27); 53 - repeater UDP; 54-repeater UDP; 55 - repeater UDP; 56 - repeater UDP"; 57, 58 connectors front panel; 59 - repeater UDP; 60 - repeater UDP; 61 - timer IMS; 62 - access ("leg" 3) timer IMS (61); 63 repeater UDP; 64 - repeater UDP; 65 - shaper IS; 66 output (output) ("leg" 1) shaper IS (65); 67 output (output) ("leg" 6) shaper IS (65); 68 - amplifier UD1; 69 - repeater UDP; 70 - amp UD2; 71 - repeater UP.
Fig. Grouping events within the interval ΔT=T2-T1=70 NS.
Let us dwell in more detail on the method and equipment of the prototype due to the fact that the prototype covers basic usage of the principle of regularization A. N. Tihonov's when conducting both elemental and chemical analyses of the composition of the media. Installation developed two modifications:
- fixed option;
- "portable" mobile option.
Stationary version with dimensions of approximately 2×2×1.8 m, may in forced mode in terms of conveyor flow identifiable material provided is acity capacity up to 1000 t/day. When the control briquettes weighing 10÷20 kg ensures the identification of the elements under the concentration (by weight) of 0.5÷1% of the entire composition of a mixture of brick.
Background radiation when operating setting at a distance of 5÷10 m from the installation does not exceed the maximum permissible standards for the population at - irradiation during the year. On the idle setting background radiation is absent, since in the off state neutron generator does not emit neutrons.
The unit is mounted from standardized modules for 2.5÷3 hours. For the same time understands. Can be easily transported and installed practically anywhere, where you can provide the appropriate radiation safety.
Installation allows you to identify the elemental composition of the material environments in the presence of their own (material environments) background γ-quanta. Value (estimated) installation of not more than 150 thousand USD.
Analogous to the stationary variant are devices used by Rapiscan Systems www.rapiscansystems.com ). The advantage of installing, developed in [2, 3], is the best (in comparison with units designed by Rapiscan Systems) identifies resolution (10÷20 times) the ability of 2÷3 times less weight and cost of the installation itself. When this estimated speed scanning bulky bookmarks (containers)2÷3 times higher.
Considered in the prototype method is based on registration and identification of spectral composition and exit instant γ-ray, born in the capture of neutrons by the nuclei of elements. Pulsed neutron generator neutron energy En=14 MeV and pulse duration of the neutron τand=10-6to place in a grave that weakly absorb the moderator, which is a spatial environment, building to a specific point in time flows of neutrons with the distinguished strictly fixed average energy. Controlled material transport near environment, slowing down the neutrons. The rate of radiative capture of the slowing down of neutrons register output instant γ-rays generated in the radiative capture of neutrons by the material environment. The speed of the radiative capture of neutrons from the time of deceleration, and hence from the neutron energy f[fγ(En(t))], where t is the time of slow neutrons which are defined in the registration thread emissions instant γ-quanta differ significantly for different elements. Consider the functional dependency f[fγ(En(t))] as a function of the sensitivity of the slow block to the output of the γ-quanta depending on the atomic weight of elements of A. Then
g is e K(t,A)=f(f γ(t),A) is the kernel of the integral equation (1).
Define slowing down the block, together with the transport system submission and registration system instant γ-quanta, as identifying the installation. Then the kernel K(t,A) of equation (1) is the instrumental function of the response identifies install and fully identified by the sensitivity function f(fγ(t)). Solving equation (1)by instrumental temporal behavior of the output of γ-rays from nuclei of materials u(t) to estimate the initial concentration of elements φ(A), present in the mixture of materials.
The solution of the integral equation (1) (Fredholm equations of the 1st kind) perform in accordance with theory of regularization, developed Antionum  for solving essentially ill-posed problems type of Fredholm equations of the 1st kind. The solution of equation (1) is obtained by minimizing the smoothing functionality:
where α is the regularization parameter;- derivative of 1-th order of the desired range of concentrations of elements φ(A);- derivative of 1-th order priori spectrum concentration φ0(A); c1- pre-selected weighting factors; p(t) and q1(A) - defined weighting factors.
The actual set of parameters included in equation (1)has a discrete nature. Therefore, the in equation (1) is written in matrix form and solve the system of equations:
With respect to the operator equation (3) smoothing functional (2) can be written in the form:
where |P| and |Ql| is the weight matrix, |Rl| is the operator of differentiation of the 1st order.
The approach to decrypt the measurement data is widely used in neutron spectrometry for spectrometric systems of non-classical type. A typical example of spectrometric systems of non-classical type is multistory spectrometer , . In multisphere spectrometer has a set of fields from a material that effectively slow neutrons, for example, of polyethylene. Spheres of different diameter. Function sensitivity or response in multisphere spectrometer is the counting function of the neutron detector placed inside a freezing sphere, depending on the neutron energy incident on a sphere. For slowing spheres having different diameters, the accounting functional dependence will be different. In relation to multispinosa the spectrometer equation (1) can be written in the form:
where φ(E) spectrum of the neutrons incident on the retardation field; E - energy neutrons.
The spectrum of neutrons φ(E) is similar to the range of concentrations φ(A) in equation (1). Each sphere multisphere spectrometer, Otley is audacia from the others in their slowing down and scattering properties, similar chronoris at a particular time value t with a finite time interval Δt in the problem of the elemental composition of materials. However, unlike multisphere spectrometer, in which the actual number of fields is limited (usually not >10 spheres), in the problem about the elemental composition number of chronostop, practically, there is no limit on the upper bound of their number is determined by the achievable rank of matrix inverse |U|-1when solving the system of equations (3) and the criteria of the principle of regularization of the solution of incorrectly posed problems. For practical purposes this means that the simultaneous analysis of environments consisting of 50-100 items, is not a daunting task when determining the elemental composition of materials. Considered by the example of multisphere neutron spectrometer decryption method of measuring information has been tested during several decades and is characterized by stable reliability of the output of the experimental results. Therefore, this method is accepted as a basis for the algorithm for the determination of elemental and chemical composition of the identifiable materials, adapted in accordance with the ratios(1)÷(5).
The results of the research are presented in the papers [2, 3], using functional dependencies f(fγ(t))≡K(t,A)obtained by the calculation method is the Ontario-Carlo [9, 2], based on the method of regularization algorithm and software package for the calculation of the concentrations of chemical elements. Performed testing of the algorithm and software for the decoding of a mixture of medium prepared in the preset concentrations of the known elements, for example installation, is shown in figure 1. From pulse source 1 neutrons penetrate into heavy retarder 2. The neutron flux coming out of the retarder 2, falls on the briquette 6 (tbpo), located on the conveyor belt 7. As a result of interaction of neutrons with nuclei of the material environment briquette born 6 γ-quanta of radiation capture, which are recorded by the detectors of the spectrometer γ-ray 3. Measuring the information comes in the software unit 4 measurement and recording of complex 5, the output of which is in the on-line generated output information about the elemental and chemical composition of the briquette 6.
Function sensitivity was calculated by the Monte Carlo method  in geometry, simulating actual installation and the actual physical processes accompanying the interaction of instant γ-ray radiation capture with the detector environment. The detector is a scintillation detector, made in the form of plate-based scintillation crystal Bi3GeO12. Dimensions scintil is atora: 20×40×40 cm The parameter fγ(t), reflecting the behavior of sensitivity functions K(t,A)characterizes the full absorbed energy Eγinstant γ-ray radiation capture during their interaction with the scintillator in a time-dependent deceleration of neutrons in the lead moderator.
Identifiable sample represents the briquette in the form of a cube with side h=40 cm Briquette is located above the horizontal plane of heavy moderation. The distance between the plane of the bottom face of the sample and the plane of the retarder - 40 see the plane of the retarder practically plays the role of a flat neutron source with a diameter of about 100 cm Decrease in neutron flux planar source at a distance of 100 cm from the plane of the retarder is not more than 2-3 times. Such characteristics of the neutron flux above the plane of heavy retarder provided with a special configuration of channels and cavities within the volume of heavy moderation. The operating range of time intervals, within which is "measuring" the settlement procedure, is from 10 to 1000 μs, sometimes up to 2000÷3000 μs. This range of time intervals covers the range of neutron energies from about 1÷10 eV to 100 Kev. The energy resolution at any honorees within the specified energy (and time) interval, it is to rule, no worse than 50÷70%.
The sensitivity function f(fγ(t))≡K(t,A) is calculated by Monte Carlo method using the software complex MCNP  for the element: Cl, Fe, Gd, H, N, O, S. the Sizes of the brick - 40×40×40 cm of the above elements prepared homogeneous mixture having a density: ρ1=0.1 g·cm-3; ρ2=0.2 g·cm-3; ρ3=0.4 g·cm-3. Calculation functions (see (1)) φ(A)=Σibi·f(Eγ, t, Ai)characterizing the instantaneous output of γ-quanta mixture with pre-specified range of concentrations of the elements determined "weight" coefficients bi. Table 1 shows the results we have procedures described above.
|№ p/p||The elemental composition of the mixture||The concentration of elements in the mixture (Rel. units), (input information)||The concentration of elements in the mixture (Rel. units), (output - decoding)||The relative error of the results output, %|
|the density of the mixture ρ=0.1 g·cm-3; geometry mixture is a cube with side length l=40 cm; the mixture is homogeneous|
|the density of the mixture ρ=0.2 g·cm-3; geometry mixture is a cube with side length l=40 cm; the mixture is homogeneous|
|the density of the mixture ρ=0.4 g·cm-3; geometry mixture is a cube with side length l=40 cm; the mixture is homogeneous|
|6||Fe||0,20||0,1990||compared to 8.26|
|*)The data in table 1, obtained from monitoring the attenuation of the neutron flux in thickness identifiable samples.|
In the above embodiment, decryption measurement data in the initial data used by the function sensitivity with integral character. In each time interval range neutron deceleration is determined by the integral characteristic: total absorbed energy is released in the environment during its interaction is instantaneous γ-quanta of radiation capture. This approach is in the determination of the sensitivity functions provides high statistical precision in the exposure time of the measurement procedure within 1÷3 C. However, the relatively smooth behavior of the sensitivity functions and, therefore, "soft" distinction between them leads to substantial systematic errors. Therefore, the error output results of decoding, as a rule, amount to, on average, 5-10%.
To substantially reduce the systematic errors in the method of decoding the elemental composition was developed and experimentally tested a mobile (or portable) option identifies the installation. The informational basis of the mobile version are the pulse spectra of recoil electrons generated in the scintillator detector at the interaction environment of the scintillator with instant γ-quanta arising from the radiative capture of neutrons identifying environment.
In the mobile version of heavy retarder is not used. Use the moderator, the maximum weight is not more than 10 kg When using a pulsed neutron source with neutron energy En=14 MeV, the slowing down of neutrons in such a moderator is not more than 3÷5 ISS.
The pulse spectra or the amplitude of the stationary distribution of recoil electrons at the output of the scintillators N(E γEe-,V)≡N(V) are characterized by more pronounced irregularities that provides a much higher dependence of the corresponding matrices in the solution of equations of type (1), (2). Therefore, in the mobile version identify the units as a response or sensitivity functions are used amplitude hardware distribution N(V). More fully: N(V)≡N(EγEe-,V,A), where Eγ- instant energy γ-ray radiation capture, V is the amplitude distribution of recoil electrons with energy EeIs, A≡Ai- the i-th element is the source of birth instant γ-ray radiation capture.
In the mobile version performed experiments in a laboratory setup, simulating mobile version identifies the installation. In an experimental setup was absent neutron generator. As sources of γ-ray radiation capture figured simulators. Sources-imitators instant γ-ray radiation capture selected radionuclides included in the kit OSHI (exemplary spectrometry γ-sources). For experimental studies of selected γ-sources:137Cs;60Co;152Eu;133Ba. The fifth source is the location, the activity of which is from 10% to 50% of the activity of the sources set OSG is. The abbreviation of the fifth source is the background (fon). Figure 3 illustrates the pulse spectra of γ-rays of radionuclides: a mixture of radionuclides - 1; background - 2;133Ba - 3;152Eu - 4;137Cs - 5;60Co - 6.
The pulse spectra (Figure 3) measured using a single crystal of NaI(Tl), with dimensions: height h=18 cm; diameter d=20 see the Sources are located on the installation line and register the pulse height spectrum from a mixed stream of γ-quanta of the entire ensemble of the listed sources.
In one embodiment, the geometry of the experiment the proportion of the intensity of each source in the mixed flux of γ-rays incident on the scintillator from radionuclides137Cs;60Co;152En;133Ba; background: 0,160; 0,157; 0,466; 0,139; 0,078 respectively. The results of decoding the measurement information contained in the pulse height spectrum of γ-quanta mixture, produced by the method of statistical regularization and presented in table 2.
|№ p/p||Radionuclide||The relative intensity of the γ-emitting radionuclide in a mixture of radionuclides (input information)||The relative intensity of the γ-emitting radionuclide in a mixture of|
radionuclides(output - transcript)
|The relative error of the results output, %|
Table 2 shows the almost complete coincidence of input and output data. Input: a priori selected and tested experimentally, the proportion of γ-radiation intensity of each radionuclide in a mixture of all used γ-sources. Output: the proportion of the radiation intensity of each radionuclide in a mixture of all used γ-sources, estimated by the method of statistical regularization used with the eating of experimental data about hardware spectra of γ-quanta mixture and experimental data about the shape of the measured spectra of the original (reference) sources of γ-rays. Error results calculated data decryption, mainly located within 0,5÷1,5%. But the implementation of minor errors requires large exposures to perform measurement procedures in comparison with a stationary installation for the identification of the elemental composition. This is due to the increase in "weight" of statistical errors. To ensure statistical errors less than 3% is required in 10÷20-fold increase in exposure measurement procedures. In conditions similar to the above, for the case of fixed installation, the duration of the exposition will be no 1÷3, and ~20÷60 C. note: the results of decoding the elemental composition obtained for stationary installation, if necessary, can always be supplemented with data obtained under conditions typical for identifying mobile units. Moreover, using the same measuring equipment and without any additional setup operations.
The feature of the regularization method used when interpreting measurement data, such that it can successfully identify not only the element but also the chemical composition of materials and environments. This circumstance is used in the proposed in the present application is the method for determining the chemical is centred on the medium composition and device implements this method.
Table 3 shows examples in which the results of the analysis (identification) of the elemental and chemical (molecular) structure 2 different environments (mixtures), formed using the experimental data about the responses (instrumental spectra of γ-quanta) of the constituent elements and molecules. As in the results shown in table 2, imitators of the elements of the environment are relevant radionuclides. Similarly imitators ambient molecules are combinations of radionuclides, combined in a certain ratio. In response to the synthesized molecule is made not set responses of its constituent elements (radionuclides), and combined (superpositioning) total responses of its constituent ("molecule") "elements" (radionuclides). For example, consider the "molecule" type Cs2Ba1Co2≡Cs2BaCo2. The response of the molecule represents the pulse height spectrum of γ-rays, consisting of a mixture of fields γ-quanta "elements" Cs, Ba, Co, weights which should take into account the chemical composition of the "molecules" Cs2BaCo2taking into account the normalization on the molecular weight of the molecule Cs2BaCo2in the mixture. The table shows very good agreement between the input and output data analysis (identification) of the elemental and chemical composition of the media (the difference is substantially less regard is sustained fashion errors identifying analysis).
Table 4 presents the results of the analysis (identification) of the elemental and chemical composition of the media with the elemental composition similar to the composition of the environments listed in table 3 using the same response for elemental and molecular composition, as for cases environments, are presented in table 3. But in table 4, the molecular composition of intentionally erroneously changed. Results identification of the analysis show a complete mismatch (difference of the input and output data. Moreover, these differences are far beyond the relative errors identifying analysis.
|Wednesday||№ p/p||Radionuclides that mimic the elemental and molecular composition of the medium||The relative intensity of the γ-emitting radionuclides, imitating the elemental and molecular composition in a mixture of radionuclides (input information)||The relative intensity of the γ-emitting radionuclides, imitating the elemental and molecular composition in a mixture of radionuclides (output)||The relative error of the results output, %|
|Wednesday||№ p/p||Radionuclides that mimic the elemental and molecular composition of the medium||The relative intensity of the γ-emitting radionuclides, imitating the elemental and molecular composition in a mixture of radionuclides (input information)||The relative intensity of the γ-emitting radionuclides, imitating the elemental and molecular composition in a mixture of radionuclides (output)||The relative error of the results output, %|
Our proposed method for identifying the elemental and chemical composition of the implement with the help of the device based on the prototype described in [2, 3]. In the base of the device and measuring the complex with a scintillation detector, which is able to provide undistorted equipment spectra of γ-quanta with the downloads on the photocathode of the photomultiplier detector to 1000 MHz. However, the known device prototype has a significant drawback: despite the ability to provide high load on the photocathode of the PMT in some cases requires a long measurement procedures as the control channel sampling (discrimination) time intervals operates in the nonlinear regime. The problem is solved by using a modified method of discrimination of time intervals or the double discrimination of time intervals.
To understand the Ooty proposed in the present application is a modified method of discrimination of time intervals let us consider in more detail the features of the unmodified method of discrimination of time intervals, used in the prototype. Let us briefly consider the possibility scintillation spectrometer using the method of discrimination of time intervals and the method neprekrashajushiesja linear detection used in the prototype[10, 11, 12].
The method of discrimination of time intervals used in the prototype, is that the spectrometer is allocated an additional channel, which is formed by a range of time intervals (Figure 4). The impulses responsible for the formation of the spectrum of time intervals, is fed to the input of the integral discriminator, the discrimination threshold which is above Td. Range of time intervals below Tddistorted due to the effects of dead time and overlays. Pulses above the threshold (the level of Td) normalized integral discriminator and the output of the integral discriminator act on the control of linear gates. Linear input linear gate receives the pulses from the output of the spectrometric channel spectrometer. Pulses spectrometric channel are passed to the output line of the gate only if they correspond to the time intervals (in the spectrum of time intervals) above Td.
Method neprekrashajushiesja linear detection (prototype) is reduced to the non-use is not inany forming circuits commit analog information output from the detector of radiation. Figure 5 illustrates the method of linear detection on the example of the use of the scintillation detector of nuclear radiation. Nuclear radiation 9 (neutrons n and γ-quanta) is registered scintillation crystal 10. Scintillation flash at the output of the single crystal fall on the photocathode of the photomultiplier 11 (PMT). The resulting pulse currents i(t) from the output 12 of the photomultiplier tube 11 having an output resistance Ro>1000 PTO, proceed on the storage capacitor 13 (Cn). Time-varying charging of the capacitor Q(t) after the pre-amplifier 14, having an input resistance RI~1000 PTO, recorded subsequent recording equipment. The resulting information is presented in the form of measured spectra of voltage pulses U(t)=Q(t)/Cn. When implementing the described approach should satisfy the condition: Ro·Cn≥RI·n>>τandwhere τandthe pulse duration of the currents at the output of the photomultiplier tube 11, and hence the duration of the scintillation flashes formed in the single crystal 10 when registering nuclear radiation 9.
Developed spectrometric system in the study of Poisson event streams allows you to provide a number of unique features.
1. The processes accompanying the formation of u is of edeleny output storage capacitor after the corresponding transmitting device, amenable to simple analytical description.
2. The change in the length of the accumulation interval for cumulative condenser T provided any mode of operation of the recording system from the spectrometer to the integral.
3. In spectrometric mode may be loaded on the photocathode of the photomultiplier 10÷100 MHz.
4. In integrated mode, i.e. the mode register complete the absorbed energy in the time interval T, may be loaded on the photocathode of the photomultiplier to 100÷1000 MHz, 4÷5 orders of magnitude higher than the existing spectrometers.
Research has shown that for a Poisson stream of events equipment distribution equipment spectra), registered at the output of the accumulating capacitor Cnfor the time interval T, are described by the expression
where [φi(V)*φj(V)*...*φk(V)] - parcel “k”-th multiplicity; φ(V)=φi(V)=φj(V)=...=φk(V) - the original "single" pulse distribution apparatus or the spectra of γ-rays (or neutrons); P0P1Pkare coefficients whose values are determined by the Poisson formula
where m=0, 1, k; [Φi(V)*φj(V)*...*φk(V)] - convolution apparatus distributions φ(V) ratio "k".
The calculated and ksperimentalxnye research has shown, what distribution at the output of the accumulating capacitor Cnwhen the 2 extreme values of the parameter <n>, namely at <n> <<1 <n> >>1, have very important properties. When <n> <<1 convolutional equipment spectra f(V)practically coincide with the differential apparatus spectra φ(V)≡N(V), where N(V) by the channel analyzer recording setup registered by classical methods. For example, when the <n>=0,01 spectrum f(V)practically coincides with the spectrum of φ(V) (see Fig.6, 7). When <n> >>1, more precisely when <n> >10÷15 distribution f(V) are described by the Poisson distribution with parameter <n>qthat option <n> accurate to fractions of a percent connected
On Fig, 9 presents the pulse spectra of γ-rays measured using the method of discrimination of time intervals and without discrimination of time intervals. Measured the pulse spectra of radionuclides:94Nb, Eγ,1=0,702 MeV, Eγ 2=0,871 MeV;137Cs, Eγ=0,661 MeV;60Co, Eγ,1=1,173 MeV, Eγ 2=1,332 MeV (Fig). Download detector flow γ-ray radionuclide94Nb - 540 kHz; load detector flux of γ-rays Radion is Lidov ( 137Cs+60Co) to 1.5 kHz.
However, the method of discrimination of time intervals does not provide high statistics of the pulse spectra of γ-rays at high loads detectors and short-term exposures measurement procedures due to restrictions in forming the nodes of the control channel.
In the setup proposed in this application, the above drawback is eliminated, which allows a high statistical accuracy combined with minimum systematic errors. With sensitivity of 10-4÷10-6it is possible to provide the total error of the measurement results at the level higher than 10% for exposures of measurement procedures in just a few tens of seconds.
As noted above, the problem is solved by using a modified method of discrimination of time intervals or the double discrimination of time intervals.
The essence of a modified method of discrimination of time intervals or the double discrimination of time intervals, which are the subject of novelty proposed in this application will illustrate by example: on the photocathode photomultiplier tube (PMT) falling stream of optical photons produced in the scintillator by the registration of γ-quanta. Let intense the activity of the gamma is 10 MHz. In use as a scintillator single crystal of NaI(Tl). Limit values load (intensity registration) on the photocathode of the photomultiplier in modern spectrometers γ-rays were performed on single crystals of type NaI(Tl)is 1÷5 kHz . This is because the pulses of the emission of NaI(Tl) are, at best, two components: a quick τb~200 NS and slow τm~1 µs [1, 2]. In accordance with the expression(5), (6)  registration of emission of γ-rays using only the fast component of the decay τb~200 NS determines the ultimate load on the photocathode of the PMT about N=1÷5 kHz. Figure 10 presents the distribution of time intervals for the considered case the load on the photocathode of the PMT <N>=10 MHz.
Set the level of discrimination of time intervals equal to T1=0,4·10-6C=400 NS (1, Figure 10). The discrimination procedure performed using the charging device (charging unit), block-schematic of which is presented below on Fig. Install a second level of discrimination of time intervals equal to T2=Td=0,470·10-6with (2, Figure 10), i.e. the time interval for sampling the pulse spectrum of γ-rays on the scale of time intervals T of the distribution of time intervals N(T) will be δ td=T2-T1=0,7·10-7C=70 NS. Fast components is NT highlight NaI(Tl) is equal to about τ b~200 NS. Thus, recorded at the output of the spectrometer spectra recorded on the basis of the voltage pulses generated part (~30%) of the charge pulse currents decay.
Thus, the time interval between discriminations Td=70 NS. At Td=T1speed registration will be. At Td=T2speed registration will be. The average number of pulses within the interval δ td=70 NS, will be ΔN=(N1-N2)·Δ td=1,5·105·0,7·10-7~0,01=10-2times. At time Td1≈0,5·10-6with (3, Figure 10) charge the unit goes into the initial state and the mode of operation of the charging unit is repeated.
The count rate spectral pulses will be
When the number of channels of the analyzer NA=256, the number of counts in each channel of the analyzer will be:
During the time Δt≈100 with the number of counts in each channel will be ΔNA~104with-1.
As you can see, the statistical error in each channel will be δ~1%. The error due to the General dispersion of the entire spectrum, will be δg<<1%.
Experiments and calculations established [11, 12]that the distortion of the measured spectra of γ-quanta by recording radiation SPECT is ametramo, operating in the linear mode detection (Fig.7), negligible (error in the whole spectral range <<1%), if the condition: the number of pulse currents supplied to the storage capacitor Cnduring the time interval ∆ T1averaged over a large number of time intervals nT>>1, must satisfy the condition: <nq> <<1, or rather <nq> ≤0,01, where <nq> is the number of pulse currents supplied to the storage capacitor Cn. Observing this condition and using the algorithm of the method of double discrimination of time intervals described above, when using scintillators with faster times luminescence upon excitation of nuclear radiation, it is possible to provide a load on the photocathode of the PMT <N> ≥1000 MHz. For example, for plastic scintillators, which are characterized by only the fast component of the luminescence upon excitation of nuclear radiation, δb≈10-9with, when loading on the photocathode of the photomultiplier tube <N> ~103MHz, the speed of measurement procedures and quality measurement data will be similar, if <N> ~10 MHz, as discussed above in the example of a single crystal of NaI(Tl).
In the proposed in this application the device specified by the lack of "normal" method of discrimination of time intervals in the s resolved with the help of the developed electronic circuits, proven in the electronic unit 6, which is a part of a flowchart γ-spectrometer (11), is used as the host identifies the installation of the elemental and chemical composition environments. The spectrometer manufactured and tested in experimental prototype variant.
Let us briefly consider the interaction of electronic assemblies developed in the electronic unit, which is implemented by the ideology of the method of double discrimination of time intervals described above (Fig). From exit 10 (or 12 or another) dynode 12 photomultiplier PMT 11 current impulses of positive polarity is fed to the input connector 15 of the front panel 28 of the block 16. With the internal outlet connector 15 (inside block 16) the current pulses fed to the input 51 (pins 27 (IMS)) a normally open timer CR VI (IMS). From the output of the generator 22 (G5-78) pulses through the connector 23 of the block 16 and the follower 29 (UDP) is fed to the input 30 of the timer 27 (EMS) to control the timer. When entering from the output of the generator 22 (G5-78) of pulses of negative polarity (chain: connector 23 of the front panel 28 of the block 16, the follower 29 (UDP), repeater 31 (UDP)) to the input 30 of the timer 27 (IMS) trigger timer is turned over and the timer is closed. Capacitor 32 (C) starts the charge accumulationfor time T0before admission to the input 33 is of Aymara 27 (IMS) pulse lock negative polarity. Pulse lock negative polarity at the input 33 ("leg" 4) timer 27 (IMS), translates the trigger timer in a state in which the timer goes into an open state in which the capacitor 32 (C) is discharged and the accumulation of charge on it not happening. Pulse lock on the entrance 33 ("leg" 4) timer 27 (IMS) is generated by the timer 34 (IMS), which in the initial state is also open. Start the timer 34 (IMS) occurs almost simultaneously with the start of the timer 27 (IMS) through the repeater 35 (UDP) and the shaper 36 (IMS). The pulse of negative polarity and amplitude of 2.5÷3,0 B after repeaters 37 (UDP), 38 (UDP), 39 (UDP) are fed to the control timer 34 (IMS) (input 40 ("leg" 2)) and closes the timer 34 (IMS). Using current generator, performed on the variable resistance, the accumulation of charge on the storage capacitor 42 (C1) to a voltage equal to the reference set at the comparator timer 34 (IMS), which is connected to the output 43 ("leg" 6) timer 34 (IMS). Conclusion 43 ("leg" 6) timer 34 (IMS) connected to the terminal 44 ("leg" 7), which, in turn, is connected with the storage capacitor 42 (C1). When reaching at the storage capacitor 42 (C1voltage equal to the level of the reference voltage on the comparator timer 34 (IMS), the trigger timer 34 (IMS) tipped (Perek udaetsya in another state) and opens the key, connected to the output 44 ("leg" 7) timer. The timer opens, and the output 45 ("leg" 3) timer is allocated a rectangular pulse voltage of positive polarity and a duration of T0that is set by the resistance of the current generator timer 34 (IMS). Output output 45 ("leg" 3) timer - four branch outputs to the corresponding repeaters performed on operational amplifiers. One of these branches through the repeater 46 (UDP) pulses arrive on the shaper 47 (IMS) normalized signal duration - 0,5÷1,0 ISS, the leading edge which time corresponds to the trailing edge of the rectangular pulse at the output 45 of the timer 34 (IMS). From the output of the shaper 47 (IMS) voltage pulses of negative polarity and the output of the repeater 48 (UDP) through switch 49 (P), the repeater 50 (UDP) is fed to the input of the lock timer 27 (IMS) (output 33 of the timer 27 (IMS)). The accumulation of charge on the capacitor 32 (C) is terminated, because the timer 27 (IMS) goes to the original open state, and the output of the timer 27 (IMS) (pins 51, 52) are voltage pulses with a duration(3, Figure 10). Sawtooth voltage pulse of positive polarity ("saw") with a duration of T0allocated to the output 51 of the timer 27 (IMS), through repeaters 53 (UDP), 54 (UDP), 55 (UDP), 56 (ODP") postopia the weekend connectors 17, 18, 57, 58 block 16. Thus formed "saw" is the General.
In addition to running timer 34 (IMS), from the output of the shaper 36 (IMS) through repeaters 59 (UDP), 60 (UDP) start the timer 61 (IMS). Rectangular pulses of positive polarity and a duration of T1<T0from the output 62 of the timer 61 (IMS) are fed to the forming device, is now 63 (UDP), 64 (UDP), 65 (IMS), then through the amplifier 70 (UD2), the repeater 71 (UDP) and then through switch 49 (P) and the repeater 50 (UDP) to the input (pin 33) lock timer 27 (IMS). The output 62 of the timer 61 (IMS) and the output to the timer 27 (IMS) (pins 51 and 52) are voltage pulses of duration T1<T0. Output (output) 66 shaper 65 (IMS) generated pulses on the leading edge correspond to the trailing edge of the pulse T1. The pulses of positive polarity and duration δ t1=Δ tDwith an output (exit) 67 shaper 65 (IMS) after the amplifiers 68 (UD1) and 69 (UDP) are fed to the connector 20 of the front panel 28 of the block 16 and further to the control of linear transmitter (linear transmitter or linear gate 19).
Figure 11 presents a block diagram of the spectrometer complex of γ-quanta operating mode neprekrashajushiesja spectrometer γ-rays using the method of double discrimination of time and is of tervalon, γ-quanta 9 register with the scintillation crystal 10 (NaI(Tl)), optically coupled to the photocathode of the photomultiplier 11 (FEG-93). From the output of dynode 12 PMT 3 pulses of currents act on the connector 15 unit 16. From the output 17 of the block 16, the voltage pulses, the amplitude of which is directly proportional to the energy of the detected radiation and which registration is performed in the time interval ΔT=Td(Figure 10), is fed to the input 18 of the block 19 linear gate (or linear transmitter). Output connector 20 of the block 16 normalized voltage pulses of duration ΔT≤Td-T1(see the description of the charge unit, Fig) is fed to the input 21 of the control channel linear gate (or linear transmitter). The control pulses of duration ΔT≤Td-T1synchronized with the pulses coming from the output of the generator 22 (G5-78) for controlling the charge unit 16 connector (23). Output 24 of block linear gate 19, the voltage pulses are received at the amplifier-shaper 25, information on the spectral composition of which is fixed blade analyzer 26 SBS-60 and stored in the memory 4 PC Pentium I.
There is a very important factor that should be taken into account when registering spectra of pulse amplitudes spectrometric complex, see figure 11: possible distortions of the spectral composition of the pulse amplitudes of Nakonechny duration of the time interval ΔT≤T d-T1, i.e. the so-called boundary effects. For the considered case (parameters: <n>=0,01, <N>=10 MHz, ΔT=70 NS) made estimates of the probability of grouping the recorded events within the interval ΔT depending on time. On Fig illustrates the results of calculations performed on the basis of the convolution of three distributions: Poisson stream of events, binomial distribution and the distribution of time intervals within the interval of double discrimination ΔT≤Td-T1taking into account the above-mentioned parameters. The result is an almost 100%grouping acts events away from the boundaries of the interval. Experimental verification for the case of <n>=0,01 fully confirms this fact (Fig.7 [11, 12]).
Using γ-spectrometer block diagram of which is presented figure 11, using the method of double discrimination of time intervals performed experiments with radionuclides when loading on the photocathode of the photomultiplier tube <N> >540 kHz. The obtained results similar to those shown in Fig, but the length measuring exposure hundred times less than used in the experiment, the results of which are presented on Fig (exposure, respectively 40 and 4000).
The LIST of INFORMATION SOURCES
1. Vlasov N.A., Neutrons. M.: Nauka, 1971.
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3. Trykov O.A., Leonova OO, V.P. Semenov, Solov'ev N.A., Khachaturov N.G. Method and device for rapid determination of elemental composition of organic and inorganic substances. SSC RF IPPE. Problems of atomic science and technology. Series: Nuclear constants, 2007, S.
4. www.rapiscansystem.com. Internet pages Rapiscan Systems. Copyright © 2010.
5. Beckurts K., Wirtz K. Neutron physics. M: Atomizdat, 1968.
6. Tikhonov A.N. On the solution of ill-posed problems and the method of regularization // DAN SSSR, 1963. T, N3. P.501-504.
Tikhonov A.N. On the regularization of ill-posed problems // DAN SSSR, 1963. T, N1. 49-52.
7. Bramblett R.I., Ewing R.I., T.W. Bonner A new type of neutron spectrometer // Nuclear Instruments and Methods. Vol.9, No. 1. P.1-12.
8. Semenov, V.P., Trykov L.A., Mattresses N Some recovery methods spectra of neutrons from the results of measurements multisphere spectrometer: Preprint IPPE-507. Obninsk, 1974.
9. J.F. Briesmeister "MSNP-A General Monte Carlo N-Particle Code System, Version 4A". Los Alamos National Laboratory report LA-12625-M, 1993.
10. Trykov O.A. Method of discrimination of time intervals in spectrometry nuclear radiation: Preprint IPPE - 2796, Obninsk, 1999.
11. Leonov OO, V.P. Semenov, Solov'ev N.A., Trykov O.A., Khachaturov N.G. Neperegruzhayte scintillas the district spectrometer for fast neutrons and gamma-quanta. SSC RF IPPE. Problems of atomic science and technology. Series: Nuclear constants, 2008, ISSUE 1-2, P.87.
12. Leonov OO, V.P. Semenov, Solov'ev N.A., Trykov O.A., Khachaturov N.G. Neperegruzhayte scintillation spectrometer for fast neutrons and gamma-quanta. SSC RF IPPE. Nuclear Instrumentation. Metrology. Proceedings of SIC SNIIP, 2007.
13. Medvedev mathematical SCIENCES. Scintillation detectors. M: Atomizdat, 1977.
14. Trykov O.A., Mokhov A.S. Spectrometric method for measuring nuclear radiation and realizing its spectrometric system. Patent for invention No. 2269798 February 10, 2006
1. Method for the elemental analysis of environments, namely, that a fast neutron source is placed in slowing down the block, γ-spectrometer using the method neprekrashajushiesja linear detection, record instant γ-quanta, born in radiative capture of neutrons by the nuclei of elements, determine the calibration response of the individual elements included in the identifiable sample, the apparatus spectra of γ-rays, determine the concentration of elements in the sample after weighting coefficients of the feedback elements, characterized in that the chemical composition of the media is determined according to the scheme: specify a priori the chemical composition of the well - known chemical compounds in the environment, determine the calibration feedback connections through amount caliber is cnyh response elements, included in the composition of the compounds, determine the concentration of compounds and elements identified in the environment, determine the concentration of elements included in the composition of the compounds, establish the correspondence received total concentration of the elements of the environment, taking into account the elements included in the composition of the identified compounds in the environment, concentrations of the elements of the environment, the received identifying decoding only the elemental composition of the medium, if not the match for a given error total concentration of the elements of the environment, the received identifying decoding based on the elements included in the identified compounds in the environment, concentrations of the elements of the environment, the received identifying decoding only the elemental composition of the medium, the procedure starts with the a priori assignment of the structure of compounds I repeat.
2. The method according to claim 1, characterized in that when performing procedures identifying measurements are used γ-spectrometer using the method neprekrashajushiesja linear detection with the modified method of discrimination of time intervals or, more precisely, with the method of double discrimination of time intervals.
3. A device that implements the method according to claim 1, comprising a source of neutrons, a block of slow neutrons, γ-spectrometer using the method neprekrashajushiesja linear d is testirovanie, block software system that includes a library of calibration characteristics (response γ-spectrometer in the form of arrays of measured spectra instant γ-rays created in the radiative capture of neutrons by the nuclei of different elements), measuring system for registering apparatus γ-spectra, block software for converting the weight of contributions (weights) bitmap calibration characteristics in the concentration values of the atomic composition, the interface conversion measurement data in the values element-by-element concentrations in on-line mode, characterized in that the device has a γ-spectrometer using the method neprekrashajushiesja linear detection with the modified method of discrimination of time intervals or more precisely, with the method of double discrimination of time intervals, allowing to decrease by several decimal orders of magnitude the time of the measurement procedure for the identification of the elemental and chemical composition of the media unit installed software for converting measurement data in the energy spectra of neutrons adapted to calculate the concentrations of chemical compounds and elements of the media based on the measurement information and the use of identifying calibration features is to (response of the spectrometer), allows you to estimate the concentration of elements and chemical compounds in the condensed and gaseous media up to 10-3-10-4% with an error of less than 10%, the device implementing the method of the elemental and chemical analysis environments, performed in stationary and mobile (portable) versions.
SUBSTANCE: device has a source of monochromatic neutrons and accompanying monochromatic α-particles and an α-particle detector enclosed in a vacuum chamber, a γ-radiation detector and recording electronic circuitry. The device is in form of two portable units - an inspection unit and a control unit - connected to each other, wherein the inspection unit includes a source of labelled monochromatic neutrons and accompanying monochromatic α-particles, an α-particle detector, γ-radiation detectors and recording electronic circuitry; the γ-radiation detector is placed at an angle close to 45° from the direction of flux of the labelled monochromatic neutrons, perpendicular to the near plane of the unit, and is provided with protection from the flux of labelled monochromatic neutrons, wherein the device is provided with an additional external γ-radiation detector which is connected to the inspection unit; both γ-radiation detectors are based on BGO crystals; laser line generators are configured to indicate on the inspected object overall dimensions of the region exposed to flux of labelled monochromatic neutrons; spectrometer channels of both γ-radiation detectors are fitted with a thermal correction system consisting of thermal sensors mounted on BGO crystals in thermal contact with said crystals, an amplitude-digital converter and a single-board minicomputer, wherein the thermal sensors are connected by a communication line and a power line to the amplitude-digital converter, which is connected to the single-board minicomputer, which is connected to the power supply system of the device and the control unit.
EFFECT: high luminosity, sensitivity of the device, high energy resolution of the spectrometer channel for detecting gamma-radiation and fewer errors associated with thermal correction of gamma-spectra.
3 cl, 3 dwg
FIELD: measurement equipment.
SUBSTANCE: application: to survey or analyse materials with radiation methods measuring secondary emission with application of neutrons. The invention concept is as follows: it consists in the fact that a generator of tagged neutrons comprises a tight body, where the following components are installed - a source of ions, a source of gaseous deuterium and tritium, a system of accelerating and focusing electrodes, a tritium target, a deuteron absorber and a multi-channel α-detector, at the same time the tritium target is equipped with a cooling unit, which is joined in the place of thermal contact outside the vacuum volume of the generator, the accelerating electrode is made in the form of a cylinder, inside of which there is a circular grid, from one ring or more concentric rings fixed near the inlet edge of the accelerating electrode, in the accelerating electrode in direction of flight of α-particles and neutrons there are two holes, a high voltage isolator surrounded with a protective screen installed between the accelerating and focusing electrodes.
EFFECT: possibility to reduce a minimum recorded mass of a hidden substance, improved conditions of hidden substances identification, in particular, higher probability of hazardous substances identification and reduced probability of false alarms, higher accuracy of aiming a tagged neutron beam at a surveyed object.
SUBSTANCE: moss samples are collected from the bark of old aspen; the material obtained after homogenisation is divided into two parts, and each part is used to prepare 5-10 duplicate representative samples; one part of the representative samples undergoes atomic emission spectrometry to determine concentration of chemical elements in each sample; the other part of representative samples is exposed to a thermal neutron flux for not more than 5 hours; measurement of specific activity of each sample is carried out after activity decay of Na24 to a safe level; air pollution is determined by comparing the obtained concentrations of chemical elements in representative samples from the investigated territory with representative moss samples collected on a background territory with natural climatic conditions similar to those of the investigated territory, and lying at a distance of more than 100 km from industrial centres in a direction opposite to that of prevailing winds.
EFFECT: possibility of evaluating pollution of air in industrial centres and other vast areas by heavy metals and other chemical elements.
4 cl, 3 tbl, 4 dwg
SUBSTANCE: sealed housing of an inspection module is made from electrically insulating material and also has not less than three γ-ray detectors, wherein all detectors lie sideways from a neutron generator in form of a matrix having common protection from the stream of labelled monochromatic neutrons; line laser generators are mounted on the housing of the inspection module from the outside with possibility of removal and installation thereof and with possibility of indicating on the inspected object boundaries of exposure thereof to the stream of labelled monochromatic neutrons; the spectroscopic channel of the γ-ray detector is fitted with a thermo-correction system consisting of a thermal detector mounted on the chip of the γ-ray detector in thermal contact with it, an amplitude-to-digital converter (ADC) and a single-board computer. The thermal detector is connected by a communication line and a power line to the amplitude-to-digital converter, which is connected by a system bus to the single-board computer which is connected to the power supply system of the device and a control module.
EFFECT: achieving maximum possible intensity of the detected characteristic gamma-radiation, high time resolution of the system, high sensitivity of the gamma-detector, reduced number of errors associated with lack of compensation for change in ambient temperature, high accuracy of guiding and controlling the exposure area of the analysed object, as well as further reduction in the minimum detected mass of the concealed dangerous substance.
6 cl, 4 dwg
SUBSTANCE: analysed substance containing nitrogen and/or carbon is irradiated with a pulse of gamma-radiation. Secondary radiation from decay products formed by nitrogen-12 and boron-12 isotopes is picked up. The time spectrum of secondary radiation signals is recorded. The abundance ratio of nitrogen and carbon is determined from the obtained time spectrum analysis results. The analysed substance is identified based on its carbon and nitrogen composition through comparison with standard values from a data base. The time spectrum of the secondary radiation is recorded in a limited time interval, which starts from the end of the radiation pulse with time delay. The spectrum is processed by converting the measured differential time spectrum into an integral time spectrum. Determination of the abundance ratio of nitrogen and/or carbon in the sample is carried out for several time intervals of the measured spectrum. Accuracy of detecting substances containing nitrogen or carbon is determined by comparing values of abundance ratio of nitrogen and oxygen in the sample, calculated for different time intervals.
EFFECT: high accuracy and reliability of a photonuclear detector of explosive and narcotic substances with simultaneous increase in efficiency thereof.
3 cl, 3 dwg
SUBSTANCE: device for detection of hidden explosives and narcotic substances includes electron accelerator, slowing target and detector of secondary gamma radiation, wherein the electron accelerator used is the sectional microtron with the energy 55 MeV, and secondary radiation detector is the water Cherenkov counter.
EFFECT: increased speed, sensitivity and decreased possibility of false positives when searching for hidden explosives and narcotic substances.
1 dwg, 5 dwg
FIELD: scanning devices.
SUBSTANCE: invention is used to detect hidden substances with radiation methods. The γ-radiation detector is made on the base of LaBr3 crystal, the laser generators of the line are installed with the possibility to set a flux of monochromatic neutrons on the inspected object, the spectroscopic channel of the γ-radiation detector is fitted with a thermal correction system comprising a thermal sensor fixed on the LaBr3 crystal, in thermal contact with it, an amplitude-to-digital converter (ADC) and a single-board minicomputer. Furthermore, the thermal sensor is connected through a communication line and a supply line with the ADC, which is connected through a system bus to the single-board minicomputer, connected with the power source and the control unit.
EFFECT: the maximum possible registered distinctive gamma-radiation intensity is achieved; increased gamma-detector sensitivity; reduced the amount of errors caused by the lack of ambient temperature compensation; increased targeting accuracy and the radiation area of the inspected object; allowed the detection of smaller amount of dangerous hidden substances.
6 cl, 3 dwg
SUBSTANCE: detection system has a particle source (500) for generating a pulsed stream (140) of high-energy particles which includes neutrons and gamma-ray photons, and said stream is directed to the investigated object (600), where particles interact nuclei of atoms of the material(s) of the said object, a detector unit (400), having at least three detectors (411, 421, 431; 412, 422, 432; 413, 423, 433) which react to neutrons and gamma-ray photons in corresponding energy ranges coming from the object and incident on the detectors in response to the said stream of high-energy particles, where the detectors can operate in current detection mode in order to generate current signals representing gamma-ray photons and neutrons incident on the detectors with time, and a data processing unit (800) connected to outputs of detectors, which are adapted to form a distinctive characteristic from said signals obtained after directing the pulsed stream onto the object, including signal parameters which depend on time, and with possibility of comparing said characteristics with stored reference characteristics.
EFFECT: high efficiency of detecting common contraband as well as nuclear materials.
20 cl, 3 dwg
SUBSTANCE: stream of hydrogen nuclides is generated and modulated. Said nuclides are accelerated to a target where neutrons are generated. The inspected object is irradiated with neutrons. Gamma-ray quanta of the radiation capture or inelastic scattering are picked up and the arrival time of gamma-ray pulses with given energy distribution which corresponds to nuclei of elements making up a dangerous substance at the detector is recorded. The direction of flow of the accelerated hydrogen nuclides relative the initial direction is changed on the vertical and then on the horizontal. Detection of gamma-ray quanta and recording their arrival time at the detector is carried out after each measurement of the direction of the axis of symmetry of the neutron stream. Further, spatial coordinates of the unknown object in Cartesian coordinate system is determined using a corresponding system of equations.
EFFECT: rapid and easy measurement.
SUBSTANCE: device for determining content of elements in surface layer of a sample has a neutron source, an evacuated measurement chamber with an input neutron guide and an illuminated sample in the said chamber, a gamma-ray detector outside the measurement chamber. The neutron source is a source of ultracold neutrons. The measurement chamber is connected to an intermediate chamber and has an output neutron guide connected to an ultracold neutron detector. There is a butterfly valve in the input neutron guide. The flow section of the intermediate chamber is covered by an output vacuum slide valve mounted on a rod with possibility of movement, and the illuminated sample is attached to the rod with possibility of movement from the intermediate chamber to the measurement chamber.
EFFECT: wide range of analysed samples, high reliability of determining content of elements in a sample.
3 cl, 1 dwg
FIELD: detection of explosive in inspected subject.
SUBSTANCE: a camera provided with a radiation protection is irradiated by thermal neutrons, and at least by one detector of gamma-radiation, gamma-radiation is regustered by transformation of gamma quantums into electric pulses and comparison of their amplitudes with the threshold values, energy spectrum of gamma-radiation is determined at least within the interval of the energy of gamma-quantume, including the upper limit of the values of the energy of gamma-quantums emitted at interaction with thermal neutrons atom nucleus at least of one chemical element in composition of the materials of the chamber, radiation protection or detector of gamma radiation, the point of the maximum and the point of the decrease of the energy spectrum in the mentioned intervals of energy are determined, the amplitudes of the electric pulses are determined from gamma-quantums with energies corresponding to the energies of the points of maximum a decrease, corresponding to the energies of the points of maximum and decrease, ratings. Then the subject under inspection is placed in the chamber, the subject under inspection is irradiated by thermal neutrons, the gamma-radiation is registered, the lower and upper threshold values are determined, and a decision is taken on presence of explosive in the subject under inspection at an excess of the threshold value.
EFFECT: reduced probabilities of omission of explosive and false alarm.
FIELD: investigating or analyzing materials.
SUBSTANCE: method comprises radiating the object to be analyzed by the heat neutrons, recording the gamma-quanta emitted, and determining the number of background gamma-quanta with energy from the interval that includes 10.8 MeV by multiplying it by a correcting coefficient of the recorded background gamma-quanta.
EFFECT: enhanced reliability.
7 cl, 8 dwg
FIELD: technology for detecting explosive substance in a controlled object.
SUBSTANCE: device contains x-ray apparatus and apparatus for neutron-radiation analysis, including body with radiation protection, horizontal well made in body and radiation protection with one input aperture and chamber, formed by neutron reflectors in form of plates mounted in horizontal well, while upper and lower neutron reflectors are made of two immoveable elements and one moveable element positioned between them, equipped with motor and mounted with possible movement relatively to immoveable elements in horizontal direction, perpendicular to longitudinal axis of horizontal well. Also, device contains block for detecting gamma-radiation, positioned in the hollow of radiation protection oppositely to chamber behind neutron reflector, in form of at lest two gamma-radiation detectors, provided with collimators and mounted on moveable elements of upper and lower neutron reflectors on the side which is external relatively to chamber.
EFFECT: decreased probabilities of omission and false alarm when detecting an explosive substance, decreased value of minimal mass of explosive substance, which it is possible to detect by means of subject device for detecting explosive substance in controlled object, and also decreased dimensions and mass of apparatus for neutron-radiation analysis, included in composition of device.
5 cl, 10 dwg
FIELD: quality control engineering.
SUBSTANCE: device has optical fiber scintillators as radiation transportation channels united into package shaped as truncated cone or as truncated pyramid. Means for placing sample under study has projection objective, image intensifier, zooming objective and charge-bound matrix. Conic beam source is placed on transportation optical fiber channel axes intersection.
EFFECT: enhanced effectiveness and high spatial resolution not only in parallel but in conical beam as well; wide range of functional applications.
3 cl, 2 dwg
FIELD: quality control engineering.
SUBSTANCE: device has transportation channels being optical fiber scintillators composed from fiber filaments scintillating in various optical spectrum zones. The fibers are collected into truncated cone or truncated pyramid package. Means for placing sample under study is reciprocally movable or rotatable. Means for recording radiation has deflecting mirror and at least two optical channels manufactured as input projection objective having filter, image amplifier, zooming objective and charge-bound matrix.
EFFECT: enhanced effectiveness and high spatial resolution not only in parallel but in conical beam as well; wide range of functional applications in registering various types of penetrating radiation.
3 cl, 3 dwg
FIELD: quality control engineering.
SUBSTANCE: device has luminescent unit designed as optically transparent transformer-screen shaped as truncated cone or as truncated pyramid collected from luminescent fibers, which axes intersect at penetrating radiation source position. The optical system for recording radiation has deflecting mirror and in series connected input projection objective, image amplifier, zooming objective. Photoreceivers are designed as charge-bound matrix.
EFFECT: enhanced effectiveness and high spatial resolution not only in parallel but in conical beam as well; wide range of functional applications in registering various types of penetrating radiation.
2 cl, 1 dwg
SUBSTANCE: method comprises using conical beam of neutrons, amplifying extracted light beam, and directing the light beam to the matrix. The luminescence screen-converter is made of a plate whose surface is provided with capacitor or fiber-optic trancated cone, or trancated pyramid.
EFFECT: expanded functional capabilities.
5 cl, 3 dwg
FIELD: inspection of internal structure by means of radiation methods.
SUBSTANCE: radiography and tomography device ha penetrating radiation source, radiation optical registration system, which has screen-converter made in form of plate, deflecting mirror, objective, photoreceiver. There is lens condenser disposed behind screen-converter. Radiation optical registration system with deflecting mirror has input projective objective disposed in series with image amplifier, scaling objective, photoreceiver made in form of CCD-array. Conical penetration radiation source is disposed in point belonging to normal line to center of screen-converter where geometrical continuations of all light tracks come together, which tracks are created in screen-converter. Device also has aid for moving tested object, which aid is made for reciprocal and rotational movement.
EFFECT: increased spatial resolution; widened functional abilities; registration of different types of penetrating radiations as quick neutrons and/or thermal neutrons, and/or X-rays and gamma rays.
4 cl, 1 dwg
SUBSTANCE: vacuum chamber with a sample of pyrolytic graphite in it is degassed, vapours containing alkali metal atoms are fed to the chamber, and the sample is held at high temperature. Then the pyrolytic graphite sample with absorbed alkali metal atoms is exposed to neutron flow radiation in another container, thus converting alkali metal atoms into gamma-irradiating isotopes, and alkali metal atom quantity is further defined by gamma-ray spectrometry.
EFFECT: increased sensitivity and accelerated detection process for small quantities of alkali metal atoms.
FIELD: physics; measurement.
SUBSTANCE: application: for controlled object analysis for explosives. Substance: consists that controlled object is exposed to electromagnetic radiation invoking nuclear quadrupole atom resonance of at least one chemical element of explosive. Electromagnetic radiation emitted by controlled object is recorded, transformed to electric signal. Received effective electric signal is compared to related threshold value. If received effective electric signal exceeds related threshold value, the first plausibility ratio logarithm is defined for received effective electric signal. Thereafter controlled object is exposed to X-raying with X-ray imaging of controlled object. X-ray image helps to identify products of controlled object. Controlled object is exposed to thermal neutrons. Gamma-ray detectors record gamma-ray photons emitted by controlled object. Number of recorded gamma-ray photons is counted. That is followed by the second plausibility ratio logarithm definition for counted number of recorded gamma-ray photons. Then controlled object is considered to contain explosive, if total the first and second ratio logarithms exceed related threshold value.
EFFECT: higher probability of explosive detection and control speed.
9 cl, 2 dwg