A Special Nuclear Material Localization Method Based on Nuclear Resonance Fluorescence Feature Signals

Abstract

This invention discloses a method for locating special nuclear materials based on nuclear resonance fluorescence characteristic signals. The method includes the following steps: constructing a special nuclear material detection device; obtaining the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device; irradiating the special nuclear material to be tested with pulsed rays and recording the pulse emission time; obtaining the energy and time information of the characteristic rays of the special material to be tested based on the nuclear resonance fluorescence characteristic signal and the special nuclear material detection device; and obtaining the location result of the special nuclear material. The special nuclear material detection device constructed by this invention has a simple structure, reduces the number of detectors required for location, lowers costs, and shortens the location time of the special nuclear material by using this invention to obtain the location result.

Description

Technical Field

[0001] This invention relates to the field of nuclear material detection and localization, and specifically to a special nuclear material localization method based on nuclear resonance fluorescence characteristic signals. Background Technology

[0002] Given the serious harm caused by the smuggling of special nuclear materials, it is imperative to develop a set of special nuclear material detection and positioning technologies for use in ports and terminals. Traditional methods for detecting nuclear material smuggling in port and terminal containers typically utilize nuclear resonance fluorescence characteristic X-ray signals to identify the types of nuclides. Simultaneously, by adding a collimation limiting hole to the front of the detector, the spatial detection range of each detector is restricted to a specific area, treating each detector as a pixel. When a suspicious nuclear material is detected by a detector with a characteristic X-ray signal, the nuclear material is considered to be within the detection range of that detector. Spatial positioning of the nuclear material can be achieved by aligning the detector with the container area from different directions.

[0003] However, in order to achieve large-scale positioning and detection in the container area, the above-mentioned detection and positioning method requires a large number of detectors to meet the spatial positioning requirements. The construction cost of the detection system is high, and after adding a collimation limiting hole in front of each detector, it can only detect characteristic ray signals from a specific direction, which will greatly reduce the acquisition speed of characteristic signals and increase the detection and positioning time. Summary of the Invention

[0004] To address the aforementioned shortcomings in existing technologies, this invention provides a method for locating special nuclear materials based on nuclear resonance fluorescence characteristic signals. The constructed special nuclear material detection device has a simple structure, reduces the number of detectors required for location, lowers costs, and shortens the location time of special nuclear materials by using this invention to obtain location results.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0006] A special nuclear material localization method based on nuclear resonance fluorescence characteristic signals includes the following steps:

[0007] S1. Construct a special nuclear material detection device that includes at least four detectors, with the detectors positioned in a spherical shape and the measurement center of the detectors aligned with the center of the sphere;

[0008] S2. Obtain the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device;

[0009] S3. Irradiate the special nuclear material to be tested with pulsed rays and record the pulsed ray emission time. Based on the nuclear resonance fluorescence characteristic signal and the special nuclear material detection device, obtain the energy and time information of the characteristic rays of the special material to be tested.

[0010] S4. Based on the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device, the pulse emission time, and the energy and time information of the characteristic rays of the special material to be tested, obtain the localization result of the special nuclear material.

[0011] Furthermore, in step S1, the detector is a lanthanum bromide detector.

[0012] Furthermore, the special nuclear material detection device also includes a high-purity germanium detector.

[0013] Furthermore, in step S1, the detector is positioned at the rear corner of the direction of the pulse ray's propagation.

[0014] Further, in step S2, the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device is obtained. The specific process is as follows: a standard material is placed at the center of the special nuclear material detection device, and the standard material is irradiated with pulsed rays. Based on the nuclear resonance fluorescence characteristic signal and the special nuclear material detection device, the energy information and time information of the nuclear resonance fluorescence characteristic rays emitted by the standard material are detected. The emission time of the pulsed rays is used as the start signal, and the time when the nuclear resonance fluorescence characteristic rays of the standard material are detected is used as the end signal. The time difference between the start signal and the end signal is calculated to obtain the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device.

[0015] Furthermore, in step S3, the energy information of the special material to be tested is specifically the energy value of the characteristic ray acquired by the detector; the time information of the special material to be tested is specifically the time when the detector detects the characteristic ray.

[0016] Further, step S4 includes the following steps:

[0017] S41. Based on the energy information of the special material to be tested, obtain the superposition spectrum of the detector energy spectrum, and obtain the characteristic full-energy peak of the special nuclear material based on the superposition spectrum of the detector energy spectrum, so as to determine the type of special nuclear material.

[0018] S42. Based on the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device, the pulse emission time, and the time information of the special material to be tested, obtain the optical path difference between the detector and the special nuclear material;

[0019] S43. Based on the spatial position of the detector and the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device, the position of the special nuclear material is determined according to the optical path difference between the detector and the special nuclear material.

[0020] S44. Based on the type and location of the special nuclear material, obtain the location result of the special nuclear material.

[0021] The beneficial effects of this invention are as follows:

[0022] (1) This invention constructs a special nuclear material detection device, then obtains the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device, then uses pulsed rays to irradiate the special nuclear material to be tested and records the pulsed ray emission time, and based on the nuclear resonance fluorescence characteristic signal and the special nuclear material detection device, obtains the energy information and time information of the characteristic rays of the special material to be tested, and finally obtains the positioning result of the special nuclear material according to the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device, the pulsed ray emission time, and the energy information and time information of the characteristic rays of the special material to be tested. The constructed special nuclear material detection device has a simple structure, reduces the number of detectors required for positioning, reduces costs, and shortens the positioning time of the special nuclear material by using this invention to obtain the positioning result of the special nuclear material.

[0023] (2) By employing a lanthanum bromide detector, this invention can improve the accuracy of the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device and the time information of the special material to be tested, thereby improving the accuracy of the localization results of the special nuclear material.

[0024] (3) By setting a high-purity germanium detector in the special nuclear material detection device, the present invention can improve the accuracy of the energy information of the special material to be tested, thereby improving the accuracy of the detection of the type of special nuclear material;

[0025] (4) The present invention takes into account that there will be a strong scattering background in the direction of pulse ray propagation. By setting the detector at the rear corner position in the direction of pulse ray propagation, the scattering background is reduced.

[0026] (5) The present invention obtains the superposition spectrum of the detector energy spectrum by using the energy information of the special material to be tested, and obtains the characteristic full-energy peak of the special nuclear material based on the superposition spectrum of the detector energy spectrum, so as to determine the type of special nuclear material, which can shorten the time to determine the type of special nuclear material, and thus shorten the time to locate the special nuclear material.

[0027] (6) This invention obtains the optical path difference between the detector and the special nuclear material by using the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device, the pulse emission time, and the time information of the special material to be tested. Based on the spatial position of the detector, the position of the special nuclear material is determined according to the optical path difference between the detector and the special nuclear material, which can improve the positioning accuracy of the special nuclear material. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a special nuclear material localization method based on nuclear resonance fluorescence characteristic signals;

[0029] Figure 2 This is a schematic diagram showing the detector position setting of the present invention;

[0030] Figure 3 This is a flowchart of the nuclear resonance fluorescence detection process of the present invention;

[0031] Figure 4 This is a diagram illustrating the time information positioning process of the present invention. Detailed Implementation

[0032] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0033] like Figure 1 As shown, a special nuclear material localization method based on nuclear resonance fluorescence characteristic signals includes steps S1-S4, as detailed below:

[0034] S1. Construct a special nuclear material detection device that includes at least four detectors arranged in a spherical shape with the measurement center of the detectors aligned with the center of the sphere.

[0035] In an optional embodiment of the present invention, a lanthanum bromide detector is used. Lanthanum bromide detectors have high temporal resolution. By employing a lanthanum bromide detector, the present invention can improve the accuracy of the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device and the accuracy of the temporal information of the special material being tested, thereby improving the accuracy of the localization results of the special nuclear material.

[0036] The special nuclear material detection device also includes a high-purity germanium detector. The high-purity germanium detector has high energy resolution. This invention, by incorporating a high-purity germanium detector into the special nuclear material detection device, can improve the accuracy of energy information for the special material being tested, thereby improving the accuracy of detecting the types of special nuclear materials.

[0037] like Figure 2 As shown, the detector is positioned at the rear corner of the pulse ray's path. This invention takes into account the strong scattering background in the pulse ray's path; by positioning the detector at the rear corner of the pulse ray's path, the scattering background is reduced.

[0038] S2. Obtain the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device.

[0039] In an optional embodiment of the present invention, the present invention obtains the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device. The specific process is as follows: a standard material is placed at the center of the special nuclear material detection device, and the standard material is irradiated with pulsed rays. Based on the nuclear resonance fluorescence characteristic signal and the special nuclear material detection device, the energy information and time information of the nuclear resonance fluorescence characteristic rays emitted by the standard material are detected. The emission time of the pulsed rays is used as the start signal, and the time when the nuclear resonance fluorescence characteristic rays of the standard material are detected is used as the end signal. The time difference between the start signal and the end signal is calculated to obtain the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device.

[0040] like Figure 3 As shown, when pulsed gamma rays irradiate the nuclei of a standard material, and the pulsed gamma rays satisfy the resonance excitation conditions of the special nuclear material, the standard material is excited to an excited state. Based on the nuclear resonance fluorescence characteristic signal, the standard material in the excited state returns to the ground state by emitting a characteristic ray γ′, where the energy value of γ′ is the same as the energy value of the absorbed pulsed gamma rays. Therefore, this invention places the standard material at the center of a special nuclear material detection device, irradiates the standard material with pulsed rays, and obtains the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device based on the nuclear resonance fluorescence characteristic signal and the special nuclear material detection device.

[0041] This invention takes into account that the emission time of the pulsed rays originates from the pulsed ray emitting device and, after long-distance transmission, is not the moment when the pulsed rays strike the nuclei of the special nuclear material. Therefore, the difference between the emission time of the pulsed rays and the time when the detector detects the characteristic rays does not reflect the optical path difference of the characteristic rays. Therefore, before detecting the special nuclear material using the special nuclear material detection device, this invention places a standard material at the center of the sphere composed of detectors, allowing the pulsed ray beam to bombard the standard material. This calibrates the timing performance of the special nuclear material detection device, determining the time when the characteristic rays are detected by each detector when the standard material is at the center of the sphere.

[0042] S3. Irradiate the special nuclear material to be tested with pulsed rays and record the emission time of the pulsed rays. Based on the nuclear resonance fluorescence characteristic signal and the special nuclear material detection device, obtain the energy information and time information of the characteristic rays of the special material to be tested.

[0043] In an optional embodiment of the present invention, the energy information of the special material to be tested is specifically the energy value of the characteristic ray acquired by the detector; the time information of the special material to be tested is specifically the time when the detector detects the characteristic ray.

[0044] Specifically, pulsed rays are preferably pulsed photons or pulsed neutrons. Pulsed charged particle rays are also suitable for this method, but since pulsed charged particle rays have difficulty penetrating into the interior of the special material being tested, they can only detect characteristic signals near the surface of the special material being tested.

[0045] S4. Based on the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device, the pulse emission time, and the energy and time information of the characteristic rays of the special material to be tested, obtain the localization result of the special nuclear material.

[0046] In an optional embodiment of the present invention, the present invention determines the type of special nuclear material based on the energy information of the special material to be tested, determines the location of the special nuclear material based on the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device, the pulse emission time, and the time information of the special material to be tested, and finally obtains the location result of the special nuclear material based on the type and location of the special nuclear material.

[0047] Step S4 includes the following steps:

[0048] S41. Based on the energy information of the special material to be tested, obtain the superposition spectrum of the detector energy spectrum, and obtain the characteristic full-energy peak of the special nuclear material based on the superposition spectrum of the detector energy spectrum, so as to determine the type of special nuclear material.

[0049] This invention superimposes the energy values ​​of characteristic rays acquired by all detectors based on the energy information of the special material to be tested, obtains the superimposed spectrum of the detector energy spectrum, and obtains the full-energy peak of the characteristic rays of the special nuclear material based on the superimposed spectrum of the detector energy spectrum, so as to determine the type of special nuclear material. This can shorten the time for determining the type of special nuclear material, and thus shorten the time for locating the special nuclear material.

[0050] S42. Based on the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device, the pulse emission time, and the time information of the special material to be tested, obtain the optical path difference between the detector and the special nuclear material.

[0051] When the special nuclear material is located at the center of the sphere composed of the special nuclear material detection device, with the pulse emission time t0 as the reference time, the generation time t1 of the characteristic ray acquired by detector 1 = the generation time t2 of the characteristic ray acquired by detector 2 = the generation time t3 of the characteristic ray acquired by detector 3 = the time standard value t of the nuclear resonance fluorescence characteristic signal at the center of the sphere of the special nuclear material detection device. 中心 The optical path difference between the detector and the special nuclear material was found to be 0.

[0052] When the special nuclear material deviates from the center of the sphere composed of the special nuclear material detection device, the detectors at a greater distance detect the characteristic rays later, while the detectors at a closer distance detect the characteristic rays earlier. This invention calculates the degree to which the special nuclear material deviates from the center of the sphere based on the time difference between the time each detector detects the characteristic rays and the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the sphere, thereby obtaining the optical path difference between the detectors and the special nuclear material. For example... Figure 4 As shown, in this invention, detector 1 is designated as the reference detector, meaning that detector 1 is located at a spherical position with the special nuclear material to be tested as the center. Therefore, the generation time t1 of the characteristic rays acquired by detector 1 is equal to the time standard value t of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device. 中心 This invention obtains the time signal spectrum of detector 1 based on the pulse emission time t0 and the generation time t1 of the characteristic ray acquired by detector 1. It also obtains the time signal spectrum of detector 2 based on the pulse emission time t0 and the generation time t2 of the characteristic ray acquired by detector 2. Finally, it obtains the time signal spectrum of detector 3 based on the pulse emission time t0 and the generation time t3 of the characteristic ray acquired by detector 3. Then, this invention superimposes the time signal spectra of detector 1, detector 2, and detector 3 to obtain the total time signal spectrum of the detectors. The degree to which the special nuclear material deviates from the center position of the sphere composed of the special nuclear material detection device is calculated, thereby obtaining the optical path difference between the detector and the special nuclear material.

[0053] S43. Based on the spatial position of the detector and the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device, the position of the special nuclear material is determined according to the optical path difference between the detector and the special nuclear material.

[0054] S44. Based on the type and location of the special nuclear material, obtain the location result of the special nuclear material.

[0055] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A method for locating special nuclear materials based on nuclear resonance fluorescence characteristic signals, characterized in that, Includes the following steps: S1. Construct a special nuclear material detection device that includes at least four detectors, with the detectors positioned in a spherical shape and the measurement center of the detectors aligned with the center of the sphere; S2. Obtain the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device. The specific process is as follows: Place the standard material at the center of the special nuclear material detection device, irradiate the standard material with pulsed rays, and detect the energy and time information of the nuclear resonance fluorescence characteristic rays emitted by the standard material based on the nuclear resonance fluorescence characteristic signal and the special nuclear material detection device. Take the emission time of the pulsed rays as the start signal and the time when the nuclear resonance fluorescence characteristic rays of the standard material are detected as the end signal. Calculate the time difference between the start signal and the end signal to obtain the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device. S3. Irradiate the special nuclear material to be tested with pulsed rays and record the pulsed ray emission time. Based on the nuclear resonance fluorescence characteristic signal and the special nuclear material detection device, obtain the energy and time information of the characteristic rays of the special material to be tested. The energy information of the special material to be tested is specifically the energy value of the characteristic rays acquired by the detector; the time information of the special material to be tested is specifically the time when the detector detected the characteristic rays. S4. Based on the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device, the pulse emission time, and the energy and time information of the characteristic rays of the special material to be tested, obtain the localization result of the special nuclear material; Step S4 includes the following steps: S41. Based on the energy information of the special material to be tested, obtain the superposition spectrum of the detector energy spectrum, and obtain the characteristic full-energy peak of the special nuclear material based on the superposition spectrum of the detector energy spectrum, so as to determine the type of special nuclear material. S42. Based on the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device, the pulse emission time, and the time information of the special material to be tested, obtain the optical path difference between the detector and the special nuclear material; S43. Based on the spatial position of the detector and the time standard value of the nuclear resonance fluorescence characteristic signal at the center of the special nuclear material detection device, the position of the special nuclear material is determined according to the optical path difference between the detector and the special nuclear material. S44. Based on the type and location of the special nuclear material, obtain the location result of the special nuclear material.

2. The method for locating special nuclear materials based on nuclear resonance fluorescence characteristic signals according to claim 1, characterized in that, In step S1, a lanthanum bromide detector is used.

3. The method for locating special nuclear materials based on nuclear resonance fluorescence characteristic signals according to claim 1, characterized in that, Special nuclear material detection devices also include high-purity germanium detectors.

4. The method for locating special nuclear materials based on nuclear resonance fluorescence characteristic signals according to claim 1, characterized in that, In step S1, the detector is positioned at the rear corner of the direction of the pulse ray's propagation.

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