CN109581474B - Method for detecting overlapping time windows accompanied by particle neutron detection - Google Patents
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Abstract
The invention provides a method for detecting an overlapping time window accompanied with particle neutron detection, which comprises the following steps: providing a labeled neutron generator; causing the labeled neutron generator to emit a neutron beam toward a detection object, and detecting gamma rays emitted by the detection object, wherein a plurality of time windows are provided for neutrons emitted by the neutron generator, and the neutrons are monitored according to the plurality of time windows, and each adjacent two time windows in the plurality of time windows have an overlapping portion. The detection method solves the problem of false negative caused by that a small amount of explosives are positioned at the adjacent position between the continuous time windows, and improves the sensitivity of the system for detecting the explosives.
Description
Technical Field
The invention relates to the field of contraband detection, in particular to a discontinuous time window imaging method for neutron detection of explosives.
Background
At present, terrorist events occur in the world, and terrorists hide explosives in packages and then initiate their missions at their opportunity is one of the common ways to carry out terrorist activities. In order to effectively detect hidden explosives, a detection method and related equipment capable of quickly and accurately identifying explosives are needed. The explosive nuclear detection technology mainly comprises an X-ray detection method, a neutron detection method, an electromagnetic measurement method and an electrochemical detection method.
Nowadays, X-ray fluoroscopy, X-ray-CT density detection, electric quadrupole detection, and the like are used internationally. X-ray imaging techniques can resolve the density of an item but cannot identify the elemental composition of the item and cannot confirm the presence of explosives in the package. The neutron detection technology can determine the element content of a detection area, is known as the 'fingerprint' technology in the field of explosive detection, and has the characteristics of high sensitivity and high accuracy. The neutron detection element analysis technology can directly analyze and detect the element composition proportion of an object to be detected, and can be used for detecting explosives, coal components, uranium ores and the like. The neutron explosive detection technology mainly comprises a thermal neutron method, a fast neutron method, a pulse fast thermal neutron method and a fast neutron-associated alpha particle imaging technology. The alpha particle imaging technology can realize three-dimensional space positioning detection of a detection area, effectively reduce the background of strong gamma radiation generated by 14MeV neutrons and the surrounding environment of a detected object in the detection process, have higher spatial resolution capability and stronger explosive identification capability, and have wide application prospect in the aspects of detecting hidden explosives and drugs.
When detecting packages by using a neutron-associated alpha particle imaging technology, continuous imaging of a detection object is required. In the prior art, a detection object is usually imaged in a continuous time window manner, that is, the detection object is imaged in a continuous time period, so that detection of small-volume contraband at a demarcation point of two time periods has uncertainty, and detection equipment has conditions of missed detection and missed report of the contraband.
Disclosure of Invention
In order to solve at least one of the above technical problems, an embodiment of the present invention provides an overlapping time window detection method accompanied with particle neutron detection, the method including the steps of: providing a labeled neutron generator; causing the labeled neutron generator to emit a neutron beam toward a detection object, and detecting gamma rays emitted by the detection object, wherein a plurality of time windows are provided for neutrons emitted by the neutron generator, and the neutrons are monitored according to the plurality of time windows, and each adjacent two time windows in the plurality of time windows have an overlapping portion.
According to a preferred embodiment of the method for detecting overlapping time windows with particle neutron detection according to the invention, each of said time windows corresponds to a distance interval traveled by said neutron in said package.
In another preferred embodiment of the method of overlapping time window detection with particle neutron detection according to the invention, the duration of said overlapping portion is 1/3 to 2/3 of the duration of each of said time windows.
According to still another preferred embodiment of the method of detecting overlapping time windows with particle neutron detection according to the invention, the duration of said overlapping portion is 1/2 times the duration of each of said time windows.
In a further preferred embodiment of the method for the detection of overlapping time windows with concomitant particle neutron detection according to the invention, the duration of the time window is between 1ns and 2 ns.
According to a further preferred embodiment of the method of overlapping time window detection with particle neutron detection according to the invention, the duration of the time window is 1.7 ns.
Compared with the prior art, the detection method solves the problem of false negative alarm generated when a small amount of explosives are positioned at the adjacent position between the continuous time windows, and improves the sensitivity of the system for detecting the explosives.
Drawings
Other objects and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings, and may assist in a comprehensive understanding of the invention.
FIG. 1 is a schematic diagram of a companion particle imaging neutron detection technique according to the present invention.
Fig. 2 is a schematic diagram of the detection of explosives using a continuous time window.
Fig. 3 is a schematic illustration of detection of explosives using time windows with overlapping portions in accordance with the present invention.
Fig. 4 is a coincidence measurement spectrum detected using the time window detecting method with overlapping portions according to the present invention.
It is noted that the drawings are not necessarily to scale and are merely illustrative in nature and not intended to obscure the reader.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings of the embodiments of the present invention. It should be apparent that the described embodiment is one embodiment of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention without any inventive step, are within the scope of protection of the invention.
Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs.
Aiming at the problems in the prior art, the invention provides a novel accompanied particle imaging neutron detection technology. In the prior art, the particle-associated neutron detection technology can mark emitted neutrons, and can effectively reduce the background of strong gamma radiation generated by 14MeV neutrons and the ambient environment of a detected object in the detection process. The specific process of the neutron detection technology accompanied with particle imaging according to the invention is shown in fig. 1, deuterium ions of a deuterium-tritium neutron generator are accelerated to strike a tritium target, a T (d, n) alpha reaction is generated, and alpha and n are emitted at the same time, wherein the directions of the alpha and the n are opposite. Firstly, marking the flight direction of neutrons by the flight direction of alpha particles measured by an alpha position sensitive detector (Si semiconductor detector); the change of gamma rays caused by alpha particles and neutrons along with time is measured, the flight distance of the neutrons can be determined according to the flight speed of the neutrons, and the space positioning detection of a detection area can be realized according to the flight direction and the distance of the neutrons. The invention provides a non-continuous time window reconstruction method based on the prior art.
The existing accompanying particle imaging neutron detection technology determines the depth range of neutron detection by setting time windows, wherein the size of each time windowTypically set to the time resolution of the system. Usually, a continuous time window setting method is adopted, and as shown in FIG. 2, adjacent first time windows tw1And a second time window tw2Is continuous, a first time window tw1After the end, the second time window t is openedw2. The continuous time window setting method is a method in which the time window set for a neutron is a continuous time window, that is, the entire detection period of the neutron is divided into a plurality of time windows which are sequentially continuous. Namely, the area where the object to be detected is located is continuously divided into a plurality of smaller detection units so as to improve the detection precision of the object to be detected. However, when the depth of a small quantity of explosive is at a position adjacent to a continuous time window, such as a depth of a small quantity of explosive at a first time window tw1And a second time window tw2The two adjacent detection areas at this position can only detect a part of the explosive, and if the volume of the explosive is small, the problem of false alarm may occur.
The invention provides a detection method which can solve the problem of false negative caused by that a small amount of explosives are positioned at the adjacent position of adjacent continuous time windows and greatly improve the sensitivity of a system for detecting the explosives. The method for detecting the overlapped time windows accompanied with particle neutron detection comprises the following steps: first, a labeled neutron generator is provided, and then, a neutron beam is emitted to a test object using the labeled neutron generator, and gamma rays emitted from the test object are detected. A plurality of time windows are set for neutrons emitted by the neutron generator, and the neutrons are monitored according to the plurality of time windows, and each adjacent two of the plurality of time windows have an overlapping portion.
As shown in fig. 3, by setting non-consecutive time windows, i.e. adjacent time windows having portions overlapping each other, i.e. a first time window tw1After starting, but before ending, a second time window t is openedw2Thereby enabling a first time window tw1And a second time window tw2With overlapping portions. This allows the detection of contraband such as explosives to be contained completely within a complete time window rather than being only partially exposed toA single time window, as shown, although a first time window tw1The whole body containing no explosive is possibly missed, but in the second time window tw2The explosive is contained in the whole body, so that the missing detection and the missing report can be avoided. Therefore, the overall detection and detection can be carried out on the contraband such as explosives and the like, so that the problem of missed detection or missed report caused by only detecting the local part of the explosives is solved.
Each time window corresponds to a distance interval traveled by neutrons in the detection object. That is, the time window may be set starting from the emission time of neutrons, and a plurality of time windows may be set during the travel of neutrons, where each time window corresponds to a certain section during the travel of neutrons, and the section is detected, so as to determine whether contraband such as explosives exists in the section.
The duration of the overlapping portions of adjacent time windows in the method of detecting overlapping time windows with accompanying particle neutron detection according to the present invention is 1/3 to 2/3 of the duration of each time window. If the length of the overlap portion is too short, the detection accuracy may be degraded or the detection and report omission may not be prevented, and if the length of the overlap portion is too long, the detection may be repeated and the detection efficiency may be too low. Controlling the duration of the overlapping portion to 1/3 through 2/3 at the duration of each time window enables higher detection efficiency to be maintained while ensuring detection accuracy and preventing missed detection. It is further advantageous to set the duration of the overlap to 1/2 of the duration of each time window.
Preferably, the time window in the overlapping time window detection method accompanying particle neutron detection according to the present invention has a duration of 1ns-2 ns. The time window duration can ensure the detection precision of the detection method and can keep certain detection efficiency. Further preferably, the duration of the time window is 1.7 ns. The detection method can improve the explosive detection precision of a single detection unit when the depth of a small amount of explosives is at the adjacent position of the continuous time window to a certain extent, and further improve the sensitivity of explosive detection.
Based on the overlapping time window detection method accompanied with particle neutron detection provided by the invention, a correlation detection test is carried out. Here, the detection system used includes a neutron generator, 2 sets of gamma detectors, and a shield. Wherein the neutron generator is an ING-27 type deuterium-tritium neutron generator produced by Russia, and the alpha particles are detected by a Si semiconductor detector; the gamma detector is a Lutetium Yttrium Silicate (LYSO) detector; the shield material is tungsten. The coincidence measurement spectra of TNT and milk powder samples shown in fig. 4 were obtained by setting the time windows using the overlapping time window reconstruction method according to the present invention. The abscissa in fig. 4 represents the track address, corresponding to the energy of the gamma-rays, and the ordinate represents the count, corresponding to the number of gamma-rays having the detected energy within a certain track (energy interval). The three curves represent measurements of three non-consecutive time windows selected, namely a first time window 39-45ns, a second time window 42-48ns and a third time window 45-51ns, respectively. As can be seen from the measurement results shown in fig. 4, the gamma detector will obtain different detection results under different discontinuous time window measurement conditions.
It should also be noted that, in the case of the embodiments of the present invention, features of the embodiments and examples may be combined with each other to obtain a new embodiment without conflict.
The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and the scope of the present invention is subject to the scope of the claims.
Claims (6)
1. A method of overlapping time window detection with particle neutron detection, comprising:
providing a labeled neutron generator;
causing the labeled neutron generator to emit a neutron beam toward a detection object; and
detecting gamma rays emitted from the inspection object,
it is characterized in that the preparation method is characterized in that,
a plurality of time windows are provided for neutrons emitted by the tagged neutron generator, and the neutrons are monitored in accordance with the plurality of time windows, with each adjacent two of the plurality of time windows having an overlapping portion.
2. The method of overlapping time window detection with concomitant particle neutron detection of claim 1,
each of the time windows corresponds to a distance interval traveled by the neutrons in the detection object.
3. The method of overlapping time window detection with concomitant particle neutron detection of claim 1,
the duration of the overlapping portion is 1/3 to 2/3 of the duration of each of the time windows.
4. The method of overlapping time window detection with concomitant particle neutron detection of claim 3,
the duration of the overlap portion is 1/2 times the duration of each of the time windows.
5. The method of overlapping time window detection with concomitant particle neutron detection of any of claims 1-4, characterized in that the duration of the time window is 1ns-2 ns.
6. The method of overlapping time window detection with concomitant particle neutron detection of claim 5, wherein the time window is 1.7ns in duration.
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| CN110764156B (en) * | 2019-11-11 | 2021-06-29 | 中国原子能科学研究院 | Suspicious object detection device |
| CN114236600A (en) * | 2021-11-25 | 2022-03-25 | 西北核技术研究所 | Neutron beam monitoring system based on silicon carbide detector |
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| CN102445706A (en) * | 2011-09-26 | 2012-05-09 | 华瑞科学仪器(上海)有限公司 | Neutron detector |
| CN103245680A (en) * | 2013-05-08 | 2013-08-14 | 中国原子能科学研究院 | Fast neutron imaging method and system based on time-of-flight method |
| CN104813436A (en) * | 2012-06-01 | 2015-07-29 | 拉皮斯坎***股份有限公司 | Methods and systems for time-of-flight neutron interrogation for material descrimination |
| CN206146858U (en) * | 2016-10-09 | 2017-05-03 | 中国原子能科学研究院 | Portable parcel explosive neutron detection device |
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| US3800150A (en) * | 1972-05-09 | 1974-03-26 | Mobil Oil Corp | Method and apparatus for radioactive well logging employing partially overlapping time windows for detection of radiation |
| US9939550B2 (en) * | 2013-03-15 | 2018-04-10 | Varex Imaging Corporation | Detection of special nuclear material and other contraband by prompt and/or delayed signatures from photofission |
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| US6393085B1 (en) * | 1997-10-17 | 2002-05-21 | Bruker Saxonia Analytik Gmbh | Analysis system for non-destructive identification of explosives and chemical warfare agents |
| CN102445706A (en) * | 2011-09-26 | 2012-05-09 | 华瑞科学仪器(上海)有限公司 | Neutron detector |
| CN104813436A (en) * | 2012-06-01 | 2015-07-29 | 拉皮斯坎***股份有限公司 | Methods and systems for time-of-flight neutron interrogation for material descrimination |
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