Gamma-ray angular correlation measurement device and measurement method based on the device

Abstract

The present invention relates to a nuclear data measurement device, in particular to a gamma ray angle correlation measurement device and a measurement method based on the device, which solves the problems of time-consuming and labor-intensive measurement, inability to take into account both early and late measurements of nuclides with short half-lives, and difficulty in ensuring measurement accuracy when using the existing gamma ray angle correlation measurement device for measurement. The device is special in that it includes at least six detectors distributed in a circle along a detector placement ring; the central axis of each detector is located in the same plane and passes through the center of the detector placement ring; the detector placement ring is a virtual circle; among the angles between the central axes of every two detectors of at least six detectors, at least one angle is 90°; one angle is 180°; the sum of the number of angles that are greater than 90° and less than 180°, or greater than 90° and less than 180°, plus the number of angles that are greater than 90° and less than 180° after converting the angles greater than 0° and less than 90° according to the angle correlation symmetry principle, is greater than or equal to 8, and the 8 angles are not equal to each other.

Description

Technical Field

[0001] The invention relates to a nuclear data measuring device, in particular to a gamma ray angle correlation measuring device and a measuring method based on the device. Background Art

[0002] When an atomic nucleus transitions from an excited state to a ground state, it sometimes does so through multiple gamma transitions in succession, during which multiple gamma rays are emitted. The angular correlation between two cascade gamma rays is directly related to nuclear data such as the nuclear energy level structure, angular momentum, and transition order, and is one of the key parameters for nuclear data measurement.

[0003] See also Figure 1 The existing gamma-ray angular correlation measurement device adopts a dual-detector structure ([1] Gu Zainuer Aniva, Research on the method of simultaneous measurement of γ transition angular correlation by NaI detector, Master's thesis of Xinjiang University, 2017. [2] Zhang Gaolong et al., Angular correlation measurement of 60Ni cascade γ transition, University Physics, Vol. 33, No. 9, 2014.), and its structure includes a fixed detector 01 and a mobile detector 02. During the measurement process, the position of the fixed detector 01 remains unchanged, and the mobile detector 02 is rotated within a range of 90°, so that the central axis of the mobile detector 02 forms a different angle θ with the central axis of the fixed detector 01, and then the excited state nuclei are measured to obtain angular correlation data at different angles. The existing gamma-ray angular correlation measurement device using a dual-detector structure has the following defects:

[0004] (1) Since a multi-position time-sharing measurement method is used, to obtain a relatively complete angle correlation curve, at least 8 angles need to be selected for measurement, that is, at least 8 measurements are made, which is time-consuming and labor-intensive;

[0005] (2) Since each measurement needs to reach the rated statistical count, the measurement time must be long enough. For nuclides with short half-lives, most of the nuclides decay completely in the later period, so the early and late measurements are often not taken into account at the same time.

[0006] (3) When the mobile detector 02 is moved, the state of the mobile detector 02 changes. In particular, the influence brought by the change of electronic noise is not conducive to accurate measurement.

[0007] Although the above problem can be solved by deploying multiple detectors at the same time with the angle θ ranging from 90° to 180°, this will bring new problems: that is, under the premise of ensuring detection efficiency, only 4 to 5 detectors can be deployed due to crowded detector deployment, and 4 to 5 angle correlation data can be obtained at a time. However, only 4 to 5 angle correlation data cannot accurately draw the angle correlation curve. Summary of the invention

[0008] The purpose of the present invention is to provide a gamma-ray angle correlation measurement device and a measurement method based on the device, so as to solve the technical problems that when using the existing gamma-ray angle correlation measurement device for measurement, it is time-consuming and labor-intensive, it is impossible to take into account both the early and late measurements of nuclides with short half-lives, and it is difficult to ensure the measurement accuracy.

[0009] The technical solution adopted by the present invention is a gamma ray angle correlation measurement device, which is special in that:

[0010] Includes at least six detectors;

[0011] The at least six detectors are distributed in a circle along the detector placement ring, and the central axis of each detector is located on the same plane and passes through the center of the detector placement ring; the detector placement ring is a virtual circle;

[0012] Among the angles formed by the central axes of every two detectors of the at least six detectors, at least one angle is 90°; one angle is 180°; there are 8 angles that are all greater than 90° and less than 180°, or the number of angles that are greater than 90° and less than 180°, plus the number of angles whose equivalent angles are greater than 90° and less than 180° after conversion of angles greater than 0° and less than 90° according to the principle of angular association symmetry, the sum of which is greater than or equal to 8, and the angle values ​​of the 8 angles are not equal to each other.

[0013] Furthermore, the detectors are all cylindrical gamma-ray detectors.

[0014] Furthermore, the cylindrical gamma-ray detector is a high-purity germanium detector, a sodium iodide detector, a lanthanum bromide detector, or a cadmium zinc telluride detector.

[0015] Furthermore, in order to measure the angle correlation data required for drawing the angle correlation curve that meets the accuracy requirement and to minimize the number of detectors to save resources, the number of detectors is six.

[0016] Further, it is defined that the six detectors are respectively detector No. 1, detector No. 2, detector No. 3, detector No. 4, detector No. 5 and detector No. 6 in the counterclockwise direction; and it is defined that:

[0017] θ 1 is the angle between the central axis of the No. 5 detector and the No. 2 detector;

[0018] θ 2 is the angle between the central axis of detector No.5 and detector No.3;

[0019] θ 3 is the angle between the central axis of detector No. 4 and detector No. 6;

[0020] θ 4is the included angle between the central axes of the sixth detector and the third detector;

[0021] θ 5 is the included angle between the central axes of the fifth detector and the sixth detector;

[0022] θ 6 is the included angle between the central axes of the fifth detector and the first detector;

[0023] θ 7 is the included angle between the central axes of the first detector and the third detector;

[0024] θ 8 is the included angle between the central axes of the sixth detector and the second detector;

[0025] then the included angle between the central axes of the first detector and the second detector is 90°; the included angle between the central axes of the first detector and the fourth detector is 180°; θ 1 θ 2 θ 3 θ 4 θ 5 θ 6 θ 7 θ 8 Among θ

[0026] Furthermore, the diameter of the detector placement ring is 500 mm;

[0027] the θ 1 θ 2 θ 3 θ 4 θ 5 θ 6 θ 7 θ 8 are respectively equal to 168°, 123°, 115°, 160°, 37°, 102°, 135°, 155°.

[0028] The present invention also provides a gamma-ray angular correlation measurement method based on the above measurement device, which is characterized in that it includes the following steps:

[0029] Step 1: Determine the diameter size of the detector placement ring;

[0030] Step 2: Build a gamma-ray angular correlation measurement device

[0031] Step 2.1: Determine the number of detectors in the gamma-ray angular correlation measurement device to be built;

[0032] Step 2.2: According to the number of detectors in the gamma-ray angle correlation measurement device to be constructed determined in step 2.1, determine the angle between the central axes of the detectors;

[0033] Step 2.3: According to the diameter of the detector placement ring determined in step 1 and the angle between the central axes of the detectors determined in step 2.2, complete the construction of the gamma-ray angle correlation measurement device;

[0034] Step 3: Place the gamma-radioactive sample to be measured

[0035] Place the gamma-radioactive sample to be measured at the center of the detector placement ring in the gamma-ray angle correlation measurement device built in step 2;

[0036] Step 4: Measure the angle-related data and complete the measurement

[0037] At the same time, all detectors in the gamma-ray angle correlation measurement device built in step 2 are turned on to perform measurements, obtain angle correlation data of at least 10 different angles, and complete the measurement.

[0038] The beneficial effects of the present invention are:

[0039] (1) The gamma-ray angular correlation measurement device of the present invention cleverly utilizes the symmetrical properties of gamma-ray angular correlation and the circular distribution space, and sets at least six detectors at a certain angle on a circle, so as to simultaneously obtain angular correlation data of at least 10 detectors with different central axis angles, thereby avoiding the problems of time-consuming and labor-intensive measurement of nuclides with short half-lives, inability to take into account both early and late measurements, and difficulty in ensuring the accuracy of the measured angular correlation curve when moving the detector for measurement. Therefore, the present invention solves the technical problems of time-consuming and labor-intensive measurement of nuclides with short half-lives, inability to take into account both early and late measurements, and difficulty in ensuring the accuracy of the measured angular correlation curve when using the existing gamma-ray angular correlation measurement device.

[0040] (2) The gamma-ray angular correlation measurement device of the present invention measures angular correlation data greater than or equal to 10, which significantly improves the measurement accuracy of the angular correlation curve compared with the traditional method.

[0041] (3) The gamma-ray angle correlation measurement device of the present invention is provided with six detectors, which can simultaneously obtain at least 10 angle correlation data, greatly improving the cost-effectiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a structural schematic diagram of an existing angle correlation measurement device in the background technology;

[0043] Figure 1 The descriptions of the labels are as follows:

[0044] 01 - Fixed detector, 02 - Mobile detector.

[0045] Figure 2 is a schematic structural diagram of an embodiment of the present invention;

[0046] Figure 2 The descriptions of each label are as follows:

[0047] 1 - First detector, 2 - Second detector, 3 - Third detector, 4 - Fourth detector, 5 - Fifth detector, 6 - Sixth detector, 7 - Detector placement ring, 8 - Gamma radioactive sample to be measured. Specific embodiments

[0048] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0049] Refer to Figure 2 , a gamma - ray angular correlation measurement device of the present invention, the structure of which includes at least six detectors; the at least six detectors are circumferentially distributed along the detector placement ring 7, the central axes of each detector are located in the same plane, and all pass through the center of the detector placement ring 7; the detector placement ring 7 is a virtual circle, and its diameter size is determined by the designed detection efficiency. Among the angles formed by the central axes of every two of the at least six detectors, at least one angle is 90°; one angle is 180°; there are 8 angles that are all greater than 90° and less than 180°, or the number of angles greater than 90° and less than 180°, plus the number of angles greater than 90° and less than 180° after converting the angles greater than 0° and less than 90° according to the angular correlation symmetry principle, the sum is greater than or equal to 8, and the angular values of the 8 angles are not equal to each other. Preferably, the above - mentioned detectors are all cylindrical gamma - ray detectors.

[0050] In order to be able to measure both the angular correlation data required for drawing an angular correlation curve that meets the accuracy requirements and to minimize the number of detectors as much as possible to save resources, in this embodiment, the number of detectors is preferably six. Refer to Figure 2 , it is defined that: the six detectors are successively and counter - clockwise the first detector 1, the second detector 2, the third detector 3, the fourth detector 4, the fifth detector 5, and the sixth detector 6; and it is defined that: θ 1 is the angle between the central axes of the fifth detector 5 and the second detector 2; θ 2 is the angle between the central axes of the fifth detector 5 and the third detector 3; θ 3 is the angle between the central axes of the fourth detector 4 and the sixth detector 6; θ 4 is the angle between the central axes of the sixth detector 6 and the third detector 3; θ 5 is the angle between the central axes of the fifth detector 5 and the sixth detector 6; θ 6is the included angle between the central axes of the fifth detector 5 and the first detector 1; θ 7 is the included angle between the central axes of the first detector 1 and the third detector 3; θ 8 is the included angle between the central axes of the sixth detector 6 and the second detector 2; then the included angle between the central axes of the first detector 1 and the second detector 2 is 90°; the included angle between the central axes of the first detector 1 and the fourth detector 4 is 180°; θ 1 、θ 2 、θ 3 、θ 4 、θ 5 、θ 6 、θ 7 、θ 8 Among θ 1 、θ 2 、θ 3 、θ 4 、θ 5 、θ 6 、θ 7 、θ 8 are respectively equal to 168°, 123°, 115°, 160°, 37°, 102°, 135°, 155°; among which θ 5 After being converted according to the angular correlation symmetry principle, it is equivalent to 180° - 37° = 143°.

[0051] Using the gamma-ray angular correlation measurement device of the present invention, the method for measuring the gamma-ray angular correlation of the gamma radioactive sample 8 includes the following steps:

[0052] Step 1: Determine the diameter size of the detector placement ring 7

[0053] According to the requirements of the designed detection efficiency, determine the diameter size of the detector placement ring 7; the higher the requirement for the designed detection efficiency, the smaller the diameter size of the detector placement ring 7;

[0054] Step 2: Build the gamma-ray angular correlation measurement device

[0055] Step 2.1: According to the accuracy requirements for the angular correlation curve, determine the number of detectors in the gamma-ray angular correlation measurement device to be built; generally, the higher the accuracy requirements for the angular correlation curve, the more the number of detectors;

[0056] Step 2.2: According to the number of detectors in the gamma-ray angular correlation measurement device to be built determined in Step 2.1, determine the included angle between the central axes of each detector.

[0057] Step 2.3: Complete the construction of the gamma-ray angular correlation measurement device according to the diameter size of the detector placement ring 7 determined in Step 1 and the included angle between the central axes of each detector determined in Step 2.2;

[0058] Step 3: Place the gamma radioactive sample 8 to be measured

[0059] Place the gamma radioactive sample 8 to be measured at the center position of the detector placement ring 7 in the gamma-ray angular correlation measurement device constructed in Step 2;

[0060] Step 4: Measure the angular correlation data and complete the measurement

[0061] Simultaneously turn on all the detectors in the gamma-ray angular correlation measurement device constructed in Step 2 for measurement, obtain the angular correlation data of at least 10 different included angles, and complete the measurement.

[0062] In this embodiment, taking the measurement of the gamma radioactive sample 60 Co as an example, the above gamma-ray angular correlation measurement method includes the following steps:

[0063] Step 1: Determine the diameter size of the detector placement ring 7

[0064] According to the requirement of the designed detection efficiency, in this embodiment, determine the diameter size of the detector placement ring 7 to be 500 mm;

[0065] Step 2: Construct the gamma-ray angular correlation measurement device

[0066] Step 2.1: According to the accuracy requirement of the angular correlation curve, in this embodiment, determine the number of detectors in the gamma-ray angular correlation measurement device to be constructed to be six (in other embodiments, if the accuracy requirement for the angular correlation curve is increased, the number of detectors can be more than six); and the high-purity germanium detector in the cylindrical gamma-ray detector is selected. In addition to the high-purity germanium detector, a sodium iodide detector or a lanthanum bromide detector or a cadmium telluride detector can also be selected;

[0067] Step 2.2: According to the number of detectors in the gamma-ray angular correlation measurement device to be constructed determined in Step 2.1, determine the included angle between the central axes of each detector; in this embodiment, the included angle between the central axes of the first detector 1 and the second detector 2 is 90°; the included angle between the central axes of the first detector 1 and the fourth detector 4 is 180°; θ 1 、θ 2 、θ 3 、θ 4 、θ 5 、θ 6 、θ 7 、θ8 are respectively equal to 168°, 123°, 115°, 160°, 37°, 102°, 135°, 155°;

[0068] Step 2.3: Complete the construction of the gamma-ray angular correlation measurement device according to the diameter size of the detector placement ring 7 determined in Step 1 and the included angles between the central axes of the detectors determined in Step 2.2;

[0069] Step 3: Place the gamma radioactive sample 8 to be measured

[0070] Place the gamma radioactive sample to be measured 60 Co at the center position of the detector placement ring 7 in the gamma-ray angular correlation measurement device constructed in Step 2;

[0071] Step 4: Measure the angular correlation data to complete the measurement

[0072] Simultaneously turn on the 6 detectors in the gamma-ray angular correlation measurement device constructed in Step 2 for measurement, obtain angular correlation data at at least 10 different included angles, and complete the measurement.

[0073] The gamma-ray angular correlation measurement device of the present invention avoids the problem that when using the existing gamma-ray angular correlation measurement device for measurement, it is necessary to move the detector to change the angle and measure one by one, shortens the measurement time, and can measure the angular correlation data of nuclides with relatively short half-lives.

Claims

1. A gamma-ray angular correlation measurement device, characterized in that: it includes six detectors; the six detectors are circumferentially distributed along a detector placement ring (7), the central axes of each detector are all in the same plane, and all pass through the center of the detector placement ring (7); the detector placement ring (7) is a virtual circle; It is defined that: the six detectors are successively the first detector (1), the second detector (2), the third detector (3), the fourth detector (4), the fifth detector (5) and the sixth detector (6) in the counterclockwise direction; and it is defined that: θ 1 is the included angle between the central axes of the fifth detector (5) and the second detector (2); θ 2 is the included angle between the central axes of the fifth detector (5) and the third detector (3); θ 3 is the included angle between the central axes of the fourth detector (4) and the sixth detector (6); θ 4 is the included angle between the central axes of the sixth detector (6) and the third detector (3); θ 5 is the included angle between the central axes of the fifth detector (5) and the sixth detector (6); θ 6 is the included angle between the central axes of the fifth detector (5) and the first detector (1); θ 7 is the included angle between the central axes of the first detector (1) and the third detector (3); θ 8 is the included angle between the central axes of the sixth detector (6) and the second detector (2); Then the included angle between the central axes of the first detector (1) and the second detector (2) is 90°; the included angle between the central axes of the first detector (1) and the fourth detector (4) is 180°; the θ 1 , θ 2 , θ 3 , θ 4 , θ 5 , θ 6 , θ 7 , θ 8 are respectively equal to 168°, 123°, 115°, 160°, 37°, 102°, 135°, 155°.

2. The gamma-ray angular correlation measurement device according to claim 1, characterized in that: the detectors are all cylindrical gamma-ray detectors.

3. The gamma-ray angular correlation measurement device according to claim 2, characterized in that: the cylindrical gamma-ray detector is a high-purity germanium detector or a sodium iodide detector or a lanthanum bromide detector or a cadmium telluride detector.

4. The gamma-ray angular correlation measurement device according to claim 1, characterized in that: the diameter of the detector placement ring (7) is 500 mm.

5. A gamma-ray angular correlation measurement method based on the gamma-ray angular correlation measurement device according to any one of claims 1 to 4, characterized in that, it includes the following steps: Step 1: Determine the diameter size of the detector placement ring (7); Step 2: Build a gamma-ray angular correlation measurement device according to the diameter size of the detector placement ring (7) determined in Step 1; Step 3: Place the gamma-radioactive sample (8) to be measured Place the gamma-radioactive sample (8) to be measured at the center position of the detector placement ring (7) in the gamma-ray angular correlation measurement device built in Step 2; Step 4: Measure the angular correlation data and complete the measurement At the same time, turn on all the detectors in the gamma-ray angular correlation measurement device built in Step 2 for measurement, obtain angular correlation data at 10 different angles, and complete the measurement.

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