CN101629917B - Method and device for measuring effective atomic number of substance - Google Patents
Method and device for measuring effective atomic number of substance Download PDFInfo
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- CN101629917B CN101629917B CN 200810116760 CN200810116760A CN101629917B CN 101629917 B CN101629917 B CN 101629917B CN 200810116760 CN200810116760 CN 200810116760 CN 200810116760 A CN200810116760 A CN 200810116760A CN 101629917 B CN101629917 B CN 101629917B
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Abstract
The invention discloses a device for measuring an effective atomic number of a substance, which comprises an X ray source which emits X rays with different energy to a measured object, a Cerenkov detector which receives the X rays passing through the measured object and generates a first electrical signal, an energy depositing detector which receives the X rays passing through the measured object and generates a second electrical signal, and a processor which is used for acquiring the effective atomic number of the measured object according to the first electrical signal and the second electrical signal. The invention also discloses a method for measuring the effective atomic number of the substance. The method for measuring the effective atomic number of the substance by combining the Cerenkov detector and the energy depositing detector ensures that X-ray photons with high energy are more easy to form large signals during the detection of the Cerenkov detector compared with the X-ray photons with low energy, so the resolution effect of the acquired effective atomic number of the substance is enhanced.
Description
Technical field
The present invention relates to field of measuring technique, particularly relate to a kind of method and apparatus of measurement of species effective atomic number.
Background technology
At present, general using gases detector, scintillation detector and semiconductor detector in the radiant image field, the size of the signal that above-mentioned detector produces is directly proportional with the energy of ray in its sensitive volume.Two high low energy detectors of general now employing carry out the measurement of material effective atomic number, the approach of its realization adopts the detector of two energy deposition class character, the detector of measuring low energy X ray is placed near the one side of x-ray source and the one side of analyte, measure its back that is placed on of sigmatron, promptly X ray must pass the low energy detector earlier and reaches high energy detector then.
In realizing process of the present invention, the inventor finds that there are the following problems at least in the prior art: could arrive high energy detector because X ray must pass the low energy detector of front, the low energy detector of front has also absorbed the sigmatron of some when absorbing the X ray of relative low energy; Under the condition of determining, two detector sensitivities are restricted, and relative standard's variance of the output signal signal of these two detectors is bigger simultaneously; Thereby the resolving effect of the material effective atomic number that obtains is relatively poor.
Summary of the invention
The problem that the embodiment of the invention will solve provides a kind of method and apparatus of measurement of species effective atomic number, to overcome the relatively poor defective of resolving effect that causes the material effective atomic number that obtains in the prior art owing to the detector that adopts two energy deposition class character.
For achieving the above object, the technical scheme of the embodiment of the invention provides a kind of device of measurement of species effective atomic number, and described device comprises: x-ray source, to the X ray of testee emission different-energy; Cerenkov detector receives the X ray by described testee, and generates first electric signal; Energy deposition class detector receives the X ray by described testee, and generates second electric signal; Processor is used for obtaining the effective atomic number of described testee according to described first electric signal and second electric signal.
Wherein, described Cerenkov detector and energy deposition class detector are placed side by side, or described Cerenkov detector is placed on the rear of described energy deposition class detector.
Wherein, described Cerenkov detector comprises: the Cerenkov radiation body, be used to receive the X ray of incident, and produce Cherenkov's light; Photodiode generates first electric signal under the illumination of described Cherenkov's light; Reflectance coating is positioned at described Cerenkov radiation body periphery, is direct reflection; The lucifuge material separates described Cerenkov radiation body, photodiode and reflectance coating and the external world.
Wherein, the refractive index of described Cerenkov radiation body is selected according to x-ray source, and light transmission is that the visible light attenuation length is greater than 1 meter.
Wherein, the length range of described Cerenkov detector on described X ray incident direction determined according to environment for use.
Wherein, described processor comprises: the first electric signal receiving element is used to receive first electric signal that described Cerenkov detector generates; The second electric signal receiving element is used to receive second electric signal that described energy deposition class detector generates; Parameter storage unit, the intensity, power spectrum structure, the physical property of described Cerenkov detector and the physical property of described energy deposition class detector that are used to store described x-ray source; The effective atomic number acquiring unit is used for resolving described first electric signal and second electric signal according to described parameter storage unit stored parameters, obtains the effective atomic number of described testee.
Wherein, the medium of described Cerenkov detector is gas or printing opacity solid or liquid.
The technical scheme of the embodiment of the invention also provides a kind of method of measurement of species effective atomic number, said method comprising the steps of: x-ray source is to the X ray of testee emission different-energy; Cerenkov detector receives the X ray by described testee, and generates first electric signal; Energy deposition class detector receives the X ray by described testee, and generates second electric signal; Processor obtains the effective atomic number of described testee according to described first electric signal and second electric signal.
Wherein, in the step of the described effective atomic number that obtains testee, comprise: the X ray higher according to the Cerenkov detector relative energy is sensitive, this can distinguish bigger pair effect, and square relation that is directly proportional of pair effect and testee atomic number is resolved described first electric signal; According to energy deposition class detector relative energy lower can distinguish responsive, this can distinguish pair effect a little less than, and Compton effect accounts for leadingly, and the relation that the cross section of Compton effect is directly proportional with the atomic number of analyte is resolved described second electric signal; According to the analysis result of described first electric signal and second electric signal, obtain the effective atomic number of testee.
Technique scheme only is an optimal technical scheme of the present invention, have following advantage: the embodiment of the invention is by the method for measurement of species effective atomic number that Cerenkov detector and energy deposition class detector are combined, the photon of the X lower with respect to energy, x-ray photon bigger signal of easier formation when Cerenkov detector is surveyed that energy is higher, thus the resolving effect of the material effective atomic number that obtains strengthened.
Description of drawings
Fig. 1 is the structural drawing of device of a kind of measurement of species effective atomic number of the embodiment of the invention;
Fig. 2 is the cut-open view of B-B direction among Fig. 1;
Fig. 3 is the cut-open view of A-A direction among Fig. 2;
Fig. 4 is the process flow diagram of method of a kind of measurement of species effective atomic number of the embodiment of the invention.
Embodiment
Below in conjunction with drawings and Examples, the specific embodiment of the present invention is described in further detail.Following examples are used to illustrate the present invention, but are not used for limiting the scope of the invention.
The device of a kind of measurement of species effective atomic number of the embodiment of the invention comprises x-ray source, Cerenkov detector, energy deposition class detector and processor.Wherein, x-ray source is to the X ray of testee emission different-energy; Cerenkov detector receives the X ray by described testee, and generates first electric signal; Energy deposition class detector receives the X ray by described testee, and generates second electric signal; Processor is used for obtaining the effective atomic number of described testee according to described first electric signal and second electric signal.Cerenkov detector and energy deposition class detector are placed side by side, or Cerenkov detector is placed on the rear of energy deposition class detector, and the medium of described Cerenkov detector is gas or printing opacity solid or liquid.
Cerenkov detector comprises Cerenkov radiation body, photodiode, reflectance coating and lucifuge material, wherein the Cerenkov radiation body is used to receive the X ray of incident, produce Cherenkov's light, the refractive index of Cerenkov radiation body is selected according to x-ray source, and light transmission is that the visible light attenuation length is greater than 1 meter; Photodiode generates first electric signal under the illumination of described Cherenkov's light; Reflectance coating is positioned at described Cerenkov radiation body periphery, is direct reflection; The lucifuge material separates described Cerenkov radiation body, photodiode and reflectance coating and the external world.The length range of Cerenkov detector on described X ray incident direction determine according to environment for use, roughly on, the longer the better.
The processor first electric signal receiving element, the second electric signal receiving element, parameter storage unit and effective atomic number acquiring unit.Wherein the first electric signal receiving element is used to receive first electric signal that described Cerenkov detector generates; The second electric signal receiving element is used to receive second electric signal that described energy deposition class detector generates; Parameter storage unit is used to store intensity, power spectrum structure, the physical property of described Cerenkov detector and the physical property of described energy deposition class detector of described x-ray source; The effective atomic number acquiring unit is used for resolving described first electric signal and second electric signal according to described parameter storage unit stored parameters, obtains the effective atomic number of described testee.
The Cerenkov detector output amplitude is to the charged particle velocity correlation of incident, and threshold value is arranged, and promptly the speed of ray is lower than certain value, then can not produce signal.If the refractive index of Cerenkov detector sensitive volume is n, (less than c/n time) do not produce Cherenkov's light if the speed of charged particle is during less than the speed of light in medium, promptly can not produce signal, generally, the X ray energy is high more, the electronic secondary energy that X ray produces in the Cerenkov detector sensitive volume is high more, and the distance of walking in sensitive volume is big more, is easy to generate big signal more.After the photon energy of X ray is higher than 1.02MeV, interactional type takes place for X ray and material mainly is Compton scattering and pair effect, the cross section of Compton scattering reduces with the energy increase of photon, be directly proportional with the size of the atomic number that passes material, and the cross section of pair effect is with the increase when photon energy, with square being directly proportional of the atomic number of material, so X ray with certain power spectrum structure, for example, the accelerator x-ray source, when passing by the identical material of mass thickness, x-ray photon (for example 2MeV) number of relative low energy, little with the atomic number relation of forming this material, relative sigmatron photon (such as 5MeV), analyte is compared by the x-ray photon number of the material transmission of forming than the heavy atom ordinal number by the x-ray photon number and the analyte of the material transmission of forming than the light atom ordinal number, and number is more.
Similarly, when the X ray energy is lower than 1.02MeV, the interaction mode of X ray and material is photoelectric effect and Compton effect, with respect to Compton effect, photoelectric cross-sectional sizes is very sensitive to the atomic number of material, increase with its increase, when energy is low, mainly is photoelectric effect simultaneously, when energy is higher, mainly be Compton effect.Analyte is compared by the x-ray photon number of the material transmission of forming than the heavy atom ordinal number by the x-ray photon number and the analyte of the material transmission of forming than the light atom ordinal number, and number is more.
The structure of the device of a kind of measurement of species effective atomic number of the embodiment of the invention such as Fig. 1, Fig. 2 and shown in Figure 3, the Cerenkov radiation body 4 in actual use, with energy deposition class detector 3, placed side by side, line up detector array 5, have the X ray light that the x-ray source 1 of multiple X ray energy is launched,, reach detector 3 and 4 through tested object 3; Detector 3 and 4 is by corresponding sensing circuit, signal is converted into electric signal, at last by intensity, power spectrum structure and the detector 3 of known x-ray source and the physical property of detector 4, resolve the signal of detector 3 and detector 4, obtain the gray level image of tested object 3, and the information of the effective atomic number of tested object.
The flow process of the method for a kind of measurement of species effective atomic number of the embodiment of the invention may further comprise the steps as shown in Figure 4:
Step s401, x-ray source is to the X ray of testee emission different-energy.
Step s402, Cerenkov detector receives the X ray by described testee, and generates first electric signal.
Step s403, energy deposition class detector receives the X ray by described testee, and generates second electric signal.
Step s404, processor obtain the effective atomic number of described testee according to described first electric signal and second electric signal.Present embodiment is sensitive according to the higher X ray of Cerenkov detector relative energy, and this can distinguish bigger pair effect, and square relation that is directly proportional of pair effect and testee atomic number is resolved described first electric signal; According to energy deposition class detector relative energy lower can distinguish responsive, this can distinguish pair effect a little less than, and Compton effect accounts for leadingly, and the relation that the cross section of Compton effect is directly proportional with the atomic number of analyte is resolved described second electric signal; Therefore, for the tested object of specific thicknesses and specific atoms ordinal number, the signal relation of these two kinds of detector outputs is determined, by looking into database (or calculating), can determine the atomic number of tested object.
The embodiment of the invention is by the method for measurement of species effective atomic number that Cerenkov detector and energy deposition class detector are combined, the photon of the X lower with respect to energy, x-ray photon bigger signal of easier formation when Cerenkov detector is surveyed that energy is higher, thus the resolving effect of the material effective atomic number that obtains strengthened.
The above only is a preferred implementation of the present invention; should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the technology of the present invention principle; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.
Claims (9)
1. the device of a measurement of species effective atomic number is characterized in that, described device comprises:
X-ray source is to the X ray of testee emission different-energy;
Cerenkov detector receives the X ray by described testee, and generates first electric signal;
Energy deposition class detector receives the X ray by described testee, and generates second electric signal;
Processor is used for obtaining the effective atomic number of described testee according to described first electric signal and second electric signal.
2. the device of measurement of species effective atomic number according to claim 1 it is characterized in that described Cerenkov detector and energy deposition class detector are placed side by side, or described Cerenkov detector is placed on the rear of described energy deposition class detector.
3. the device of measurement of species effective atomic number according to claim 1 is characterized in that described Cerenkov detector comprises:
The Cerenkov radiation body is used to receive the X ray of incident, produces Cherenkov's light;
Photodiode generates first electric signal under the illumination of described Cherenkov's light;
Reflectance coating is positioned at described Cerenkov radiation body periphery, is direct reflection;
The lucifuge material separates described Cerenkov radiation body, photodiode and reflectance coating and the external world.
4. as the device of measurement of species effective atomic number as described in the claim 3, it is characterized in that the refractive index of described Cerenkov radiation body is selected according to x-ray source, light transmission is that the visible light attenuation length is greater than 1 meter.
5. the device of measurement of species effective atomic number according to claim 1 is characterized in that, the length range of described Cerenkov detector on described X ray incident direction determined according to environment for use.
6. the device of measurement of species effective atomic number according to claim 1 is characterized in that described processor comprises:
The first electric signal receiving element is used to receive first electric signal that described Cerenkov detector generates;
The second electric signal receiving element is used to receive second electric signal that described energy deposition class detector generates;
Parameter storage unit, the intensity, power spectrum structure, the physical property of described Cerenkov detector and the physical property of described energy deposition class detector that are used to store described x-ray source;
The effective atomic number acquiring unit is used for resolving described first electric signal and second electric signal according to described parameter storage unit stored parameters, obtains the effective atomic number of described testee.
7. as the device of claim 1 to 6 measurement of species effective atomic number as described in each, it is characterized in that the medium of described Cerenkov detector is gas or printing opacity solid or liquid.
8. the method for a measurement of species effective atomic number is characterized in that, said method comprising the steps of:
X-ray source is to the X ray of testee emission different-energy;
Cerenkov detector receives the X ray by described testee, and generates first electric signal;
Energy deposition class detector receives the X ray by described testee, and generates second electric signal;
Processor obtains the effective atomic number of described testee according to described first electric signal and second electric signal.
9. as the method for measurement of species effective atomic number as described in the claim 8, it is characterized in that, in the step of the described effective atomic number that obtains testee, comprising:
Sensitive according to the higher X ray of Cerenkov detector relative energy, this can distinguish bigger pair effect, and square relation that is directly proportional of pair effect and testee atomic number is resolved described first electric signal;
According to energy deposition class detector relative energy lower can distinguish responsive, this can distinguish pair effect a little less than, and Compton effect accounts for leadingly, and the relation that the cross section of Compton effect is directly proportional with the atomic number of analyte is resolved described second electric signal;
According to the analysis result of described first electric signal and second electric signal, obtain the effective atomic number of testee.
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| US8588370B2 (en) | 2010-06-30 | 2013-11-19 | Tsinghua University | Article inspection device and inspection method |
| CN102313752B (en) * | 2010-06-30 | 2014-07-23 | 清华大学 | Article detection equipment and method |
| CN103185734B (en) * | 2011-12-30 | 2015-11-25 | 同方威视技术股份有限公司 | Measure the method and apparatus of the effective atomic number of object |
| CN110333252B (en) | 2018-03-28 | 2021-12-17 | 同方威视技术股份有限公司 | Dual-energy detection method and device |
| CN109459452B (en) * | 2018-12-26 | 2021-10-22 | 上海联影医疗科技股份有限公司 | Effective atomic number calculating method, device and storage medium |
| CN110174693A (en) * | 2019-06-26 | 2019-08-27 | 中国工程物理研究院流体物理研究所 | A kind of stack multichannel Compton diode detector and measurement method |
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