CN106290429B - A kind of PGNAA characteristic gamma rays power spectrum backoff algorithm - Google Patents
A kind of PGNAA characteristic gamma rays power spectrum backoff algorithm Download PDFInfo
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- CN106290429B CN106290429B CN201610886933.4A CN201610886933A CN106290429B CN 106290429 B CN106290429 B CN 106290429B CN 201610886933 A CN201610886933 A CN 201610886933A CN 106290429 B CN106290429 B CN 106290429B
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- power spectrum
- pgnaa
- gamma ray
- characteristic gamma
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/20—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by using diffraction of the radiation by the materials, e.g. for investigating crystal structure; by using scattering of the radiation by the materials, e.g. for investigating non-crystalline materials; by using reflection of the radiation by the materials
- G01N23/207—Diffractometry using detectors, e.g. using a probe in a central position and one or more displaceable detectors in circumferential positions
- G01N23/2076—Diffractometry using detectors, e.g. using a probe in a central position and one or more displaceable detectors in circumferential positions for spectrometry, i.e. using an analysing crystal, e.g. for measuring X-ray fluorescence spectrum of a sample with wavelength-dispersion, i.e. WDXFS
Abstract
The invention discloses a kind of PGNAA equipment characteristic gamma ray power spectrum backoff algorithms.The principle of the algorithm is the proportionality constant k by the way that measured matter is calculatedEi(i=1~1024), by the band information carrying N, the airborne signals N0 that are mounted on the ionisation chamber (6) on PGNAA equipment (1) subsequent controlled nucleon operated belt conveyor scale, operation is compensated to characteristic gamma ray power spectrum, solves the power spectrum distortion phenomenon caused by tested material own absorption characteristic gamma ray.For PGNAA equipment characteristic gamma ray during penetrating tested material arrival gamma-ray detector, part gamma ray can have the phenomenon that distortion by tested material own absorption, finally obtained characteristic gamma ray power spectrum.
Description
Technical field：
The present invention relates to a kind of power spectrum backoff algorithm, specifically a kind of PGNAA characteristic gamma rays power spectrum backoff algorithm.
Background technology：
Wink hair gamma neutron activation analysis technique (PGNAA) is a kind of quick, contactless multielement analysis technology, is being built
The industries such as material, coal, thermoelectricity, metallurgy, mine have obtained a large amount of application.Wink hair gamma neutron activation analysis technique principle be
With thermal neutron capture reaction occurs for tested material, generates characteristic gamma ray, and characteristic gamma ray passes through tested material to reach gal
Horse ray detector forms core pulse signal, and core pulse signal is transformed into digital signal by multiple tracks processor, ultimately forms spy
Levy gamma ray spectroscopy.Characteristic gamma ray while penetrating tested material, part ray can by tested material own absorption,
Cause final characteristic gamma ray power spectrum that cannot represent true characteristic gamma ray power spectrum, when tested material total amount becomes
When change, the attenuation of characteristic gamma ray can also change, and finally obtained gamma ray spectroscopy will have distortion phenomenon.
Invention content：
To solve characteristic gamma ray power spectrum problem of dtmf distortion DTMF, the present invention installs a nucleon additional after PGNAA equipment as shown in Figure 1
Belt conveyer scale, controlled nucleon operated belt conveyor scale by137Cs radioactive sources and ionisation chamber two parts are constituted, and the signal of ionisation chamber sends PGNAA equipment meters to
Calculate host.
Theoretically the tested material characteristic gamma ray that more multiphonon activation generates is also more, but due to material itself
Also there is attenuation, the characteristic gamma ray that detector is collected into can also decline with the e index that is added to of material gamma ray
Subtract：
IEi=I0Ei×exp(-μmEitm) (1)
IO in formula0iIt represents and generates energy as the intensity of the characteristic gamma ray of Ei, IEiEnergy is represented after material as Ei
Gamma ray intensity, μmEiExpression energy is mass attentuation coefficient of the characteristic gamma ray of Ei in material, with substance
Atomic number and ray energy are related, tmFor the mass thickness of material.By formula 1 it is found that if it is known that μmEiAnd tmIt can measure
Change Expressive Features gamma ray attenuation degree, to mathematically into be about to measure characteristic gamma ray amount be reduced to true spy
Levy the compensation operation of gamma ray amount.
The present invention is mounted with a controlled nucleon operated belt conveyor scale after PGNAA equipment, uses137Cs radioactive sources, ionisation chamber transmission knot
Structure, controlled nucleon operated belt conveyor scale follow following mathematical relationship：
N=N0 × exp (- μm0tm) (2)
N indicates that ionisation chamber counts when material in formula, and N0 indicates that ionisation chamber counts when empty belt, μm0It indicates137Cs radioactive sources
Corresponding mass attentuation coefficient can then be derivedBy tmIt brings formula 1 into, then can obtain：
In formulaWhen material composition composition transfer is little, this proportionality coefficient is approximately constant, this
Sample we only require to obtain constant kEi, the attenuation degree of characteristic gamma ray power spectrum is can be obtained by counting N, N0 of ionisation chamber,
Then power spectrum is modified.
Mass attentuation coefficient and linear absorption coefficient relationship are as follows：
μm=μ/ρ (4)
μ in formulamFor mass attentuation coefficient, μ is linear absorption coefficient, and ρ is material density.
The linear absorption coefficient μ of substance is defined as follows：
N in formulaiIndicate the atom number density of i-th kind of element in substance,For the gammaphoton and the element of i-th kind of element
Reaction cross-section, m indicate substance be made of m kind elements.
NiCalculation formula it is as follows：
M in formulaρIndicate the mass density of substance, MiIndicate Elements Atom amount, fiIndicate that i-th kind of element is shared in substance
Ratio (after normalization).
We are only it is to be understood that the substantially element constituent of measured matter in this way, according to the anti-of gammaphoton and various elements
The curve of section-gamma energy is answered, can be calculated by formula 4, formula 5, formula 6137The corresponding quality of Cs radioactive sources
Attenuation coefficient mum0With mass attentuation coefficient μ of the characteristic gamma ray in material that energy is EimEi, and then obtain proportionality constant
kEiWith the relation curve of gamma energy, N, N0 are counted according to ionisation chamber and formula 3 can be realized and be repaiied to the compensation of power spectrum
Just.
Advantageous effect：
Operation is compensated to the characteristic gamma ray power spectrum of PGNAA equipment using the present invention, characteristic gamma is solved and penetrates
The problem of line energy spectrum distortion, the accuracy of detection of PGNAA equipment can be promoted.
Description of the drawings：
Fig. 1 is schematic diagram of the present invention, and Fig. 2 is each element photon cross section curve graph, and Fig. 3 is proportionality constant k after calculatingECurve
Figure, Fig. 4 are the front and back characteristic gamma ray energy spectrum diagram of compensation.
1-PGNAA equipment, 2-PGNAA computing hosts, 3- belt conveyors, 4- tested materials, 5-137Cs radioactive sources, 6- ionization
Room.
Specific implementation：
This backoff algorithm specific implementation is made of two parts：Calculate proportionality constant kEiMatrix, compensation operation.
1, proportionality constant k is calculatedEiMatrix
Herein we assume that measured matter is cement slurry, it is assumed that characteristic gamma ray results from tested material thickness
At center, cement slurry is mainly by CaCO3、SiO2、Al2O3、Fe2O3、H2O is constituted, and each substance approximate composition is shown in Table 1, is then tested
Seven kinds of elements of H, C, O, Al, Si, Ca, Fe are mainly contained in material, and each element ratio f is calculated according to oxide componentsiIt is shown in Table 2,
Each element photon cross section curve graph is shown in Fig. 2.
1 raw ingredients of cement content table of table
| Substance | CaCO3 | SiO2 | Al2O3 | Fe2O3 | H2O |
| Mass ratio | 75% | 15% | 3% | 2% | 5% |
2 cement slurry Elements Atom ratio f of tablei
| Element | Ratio fi |
| Ca | 0.126127 |
| Si | 0.042042 |
| Al | 0.009892 |
| Fe | 0.004204 |
| H | 0.093427 |
| C | 0.126127 |
| O | 0.598181 |
According to known each element photon cross section data, each element atomic weight, each element ratio and formula 6, formula 5,
Formula 4 can calculate137The corresponding mass attentuation coefficient μ of Cs radioactive sourcesm0With energy be Ei characteristic gamma ray in material
Mass attentuation coefficient μmEi, and then obtain proportionality constant kEi(i=1~1024, corresponding 10keV~10.24MeV energy) matrix,
kECurve is shown in Fig. 3.
μm=μ/ρ (4)
2, compensation operation
Known features gamma ray spectroscopy IEi(i=1~1024), constant kEi(i=1~1024), ionisation chamber signal N,
N0, you can the characteristic gamma ray power spectrum I0 after compensation is calculated by formula 3Ei(i=1~1024).
In cement slurry detection application, the power spectrum region that we compare care is 2.8MeV~10.24MeV, therefore I
This subregion power spectrum only compensated into operation when calculating, as shown in figure 4, curve I is actual measurement cement slurry power spectrum
(2.8MeV~10.24MeV amplify 15 times), curve I0 be spectrum curve after compensation calculation (compensation calculation section be 2.8MeV~
10.24MeV, this interval curve amplify 15 times).
Claims (1)
1. a kind of PGNAA characteristic gamma rays power spectrum backoff algorithm, which is characterized in that include the following steps：
Step 1: according to measured matter elemental composition ratio, each element photon reaction cross-section and mass attentuation coefficient and linearly
Absorption coefficient relationship, substance linear absorption coefficient define and calculate separately energy in 2.8-10.24 with the atom number density of element
Mass attentuation coefficient of the gamma-rays of MeV in the various elements of measured matterWith137The γ of 0.662 MeV of Cs radioactive sources
Mass attentuation coefficient of the ray in the various elements of measured matter, according to formulaCalculate proportionality constant
kEi,Wherein i=1 ~ 1024 of Ei；
Step 2: on controlled nucleon operated belt conveyor scale137Cs radioactive sources are in ionisation chamber（6）Formed belt on have tested material band information carrying N and
It is the airborne signals N0 of sky on belt；
Step 3: PGNAA equipment measures the neutron activation Characteristic γ ray power spectrum I of tested material on beltEi, wherein i=1 of Ei
~1024；
Step 4: utilizing formulaCalculate the Characteristic γ ray power spectrum after compensating approachIts
I=1~1024 of middle Ei.
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| CN108645880B (en) * | 2018-05-11 | 2021-02-02 | 南京航空航天大学 | Energy spectrum analysis method for large-volume sample |
| CN112432965A (en) * | 2019-08-10 | 2021-03-02 | 丹东东方测控技术股份有限公司 | Method for on-line detection of sinter components |
| CN112392454B (en) * | 2020-11-16 | 2023-02-03 | 中国石油大学(华东) | Fracture bulk density quantitative calculation method based on neutron activation analysis self-shielding correction |
| CN115616010B (en) * | 2022-12-19 | 2023-03-21 | 合肥金星智控科技股份有限公司 | Material component detection method and detection device based on cross-belt neutron activation analysis |
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| CN1892252A (en) * | 2005-06-27 | 2007-01-10 | 通用电气公司 | Gamma and neutron radiation detector |
| CN204556840U (en) * | 2015-04-20 | 2015-08-12 | 清华大学 | Distinguish the on-line measurement device of uranium ore |
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