CN115308788A - System for calibrating action depth of high-energy gamma ray in detector and using method - Google Patents
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Abstract
The invention relates to a system for calibrating the action depth of high-energy gamma rays in a detector and a using method thereof, gamma rays emitted by a high-energy gamma ray surface source pass through a collimation system with high ray blocking capacity and are incident from the side wall of the gamma ray detector, high-energy rays laterally penetrate through the detector, the planes of an anode and a cathode of the gamma ray detector are both parallel to a high-energy ray collimation slit determined by the height of a standard cushion block, the collimation system restrains high-energy rays and only laterally enter the detector from the collimation slit parallel to the cathode and anode planes of the gamma ray detector, a standard energy block supports the collimation system and adjusts the central plane position of the collimation slit, the standard cushion block supports the upper collimation system and determines the resolution of the depth direction of the detector, and a precision lifting platform is used for supporting the detector and adjusting the initial relative position of the high-energy ray detector and the collimation system; the invention realizes the experimental calibration of the depth of action of the high-energy gamma ray in the detector.
Description
Technical Field
The invention belongs to the technical field of gamma ray detection and imaging, and relates to a system for calibrating the action depth of high-energy gamma rays in a detector and a using method thereof.
Background
With the development of radiation detection technology, high-energy ray detection is widely applied to the fields of medical diagnosis and treatment, safety inspection, nuclear power monitoring and the like, and a large-size radiation detector becomes a main choice for high-end application of radiation detection due to the wide energy response range and high detection efficiency. The development of the ray signal analysis technology towards the direction of multi-dimensionality, refinement and high reliability gradually due to the expansion of the size of the detector, the improvement of the identification and resolution capability of the detector on high-energy rays and the full play of the advantages of large volume become the key for improving the performance of devices, and the development of a radiation detector with three-dimensional position resolution capability is the research front in the field of high-energy ray detection at present.
Generally, two-dimensional projection coordinates of a ray action site on an anode plane are determined through an anode electrode structure of the detector, and the action depth of rays in the detector, namely the third-dimensional coordinates of the ray action site, is calculated and obtained by substituting a cathode signal and an anode signal into a theoretical formula. The three-dimensional position resolution level greatly improves the acquisition capability of the detector on the energy and distribution information of the radioactive source, but the method for acquiring the third-dimensional coordinate of the ray action site through theoretical model calculation usually does not consider the influence of the properties of the detection crystal and an actual reading circuit, and the reliability of the calculated result needs to be improved. It is highly desirable to find a method of determining the third dimensional coordinates of the radiation action site that has high reliability and takes into account the inherent properties of the detection system.
Disclosure of Invention
Technical problem to be solved
In order to avoid the defects of the prior art, the invention provides a system for calibrating the action depth of high-energy gamma rays in a detector and a using method thereof, which include the influences of the nonuniformity of a detection crystal, the differences of ASICs (application specific integrated circuits) of different signal channels and a data processing circuit, and solve the uncertainty and the unreliability of the result obtained by adopting a theoretical calculation method in the past.
Technical scheme
A system for calibrating the action depth of high-energy gamma rays in a detector is characterized by comprising a high-energy gamma ray surface source 1, two high-energy ray collimation blocks 2, a precise lifting table 4, a standard gauge block 5 and a standard gasket 6; the two high-energy ray collimation blocks 2 are arranged on the precise lifting table 4, and a standard gasket 6 is arranged between the two high-energy ray collimation blocks 2, so that a high-energy ray collimation slit is formed between the two high-energy ray collimation blocks 2; the high-energy gamma ray surface source 1 is arranged at one side of the two high-energy ray collimation blocks 2, and the rays are directly opposite to the standard gasket 6 between the two high-energy ray collimation systems 2; the upper surface and the lower surface of the high-energy ray collimation slit are parallel to each other; the standard cushion blocks are configured in pairs and are placed on the upper surface of the lower collimating system which completely exposes the width of the ray incidence direction detector.
The high-energy ray collimating slit ensures that the intensity of gamma rays with energy not more than a specific value is attenuated to 95% of the incident intensity after passing through the collimating slit.
The length of the high-energy ray collimation slit is determined by the following formula:
the width of the high-energy ray collimation slit is that the height of the standard gauge block is matched with the depth resolution capability.
The height of the high-energy ray collimation block 2 is larger than the distance between the cathode and the anode of the detector to be detected.
The width of the collimator in the ray incidence direction of the high-energy ray collimation block 2 is as follows:
the width of the collimator in the ray incidence direction is not less than the width of the collimator in the ray incidence direction plus 2 times the width of the standard gasket
The high-energy ray collimation block 2 and the standard cushion block 6 are made of lead, pure copper, brass, red copper, tungsten or tungsten-nickel-iron.
The tolerance of the working sizes of the standard cushion block and the standard gauge block is less than 0.5 micron, and the adjustment precision of the precision lifting platform is less than 5 microns.
The use method of the system for calibrating the action depth of the high-energy gamma ray in the detector is characterized in that the thickness of the detected detector is more than 1.0cm, the detector is made of cadmium zinc telluride, and the electrode material is gold or indium or silver or aluminum; the application steps are as follows:
step 1: the following parameters are determined from the detector under test:
1. the intensity distribution of the high-energy gamma ray surface source 1 is similar to that of a uniform surface source, and the emergent area of gamma rays is larger than the lateral size vertical to the gamma ray detector; the energy of the gamma ray emitted by the radioactive source satisfies the following conditions:
2. determining the length of the collimation slit:
3. collimator width for determining ray incidence direction:
the width of the collimator in the ray incidence direction is more than or equal to the width of the collimator in the ray incidence direction plus 2 multiplied by the width of the standard gasket;
3. the height of the single collimator is larger than the distance between the cathode and the anode of the selected detector;
4. determining the width of a collimation slit according to the expected depth resolution of the detector, wherein the height of the standard gauge block is consistent with the depth resolution capability;
step 2: the detector to be detected is arranged on the other side of the high-energy ray collimation block 2 relative to the high-energy gamma ray surface source 1, and the number of layers of the standard gauge blocks is adjusted to adjust the collimation slit to be aligned with the side detection part of the detector;
the planes of the anode and the cathode of the gamma ray detector are parallel to the planes of the upper surface and the lower surface of the slit of the collimation system;
the arrangement plane of the radioactive sources is vertical to the plane of the center of the slit of the pure tungsten collimation system;
the distance from the radioactive source to the collimation system is far greater than the distance from the collimation system to the detector;
and step 3: testing the energy response and the time response of the detector at the initial position; the initial position is as follows: the plane of the anode/cathode of the detector is overlapped with the plane of the lower/upper surface of the collimation slit;
and 4, step 4: fixing the position of the detector unchanged, gradually increasing or decreasing the number of standard cushion blocks supporting the collimation system, and respectively testing to obtain signals of high-energy rays acting on the detector in different depths;
and 5: rays are incident from the side wall of the detector through a collimator system, an anode pixel electrode signal and a cathode plane electrode signal when each photoelectric effect event occurs are obtained through testing, and according to the ray depth principle, the cathode signal/the anode signal are in direct proportion to the ray incidence depth theoretically; calculating the ratio of the cathode signal to the anode signal in the test, and fitting the relation between the ratio of the cathode signal to the anode signal and the calibrated depth by using a linear function to obtain an actual depth calibration parameter;
the gamma rays which can be emitted by the radioactive source are attenuated by the detector, and the penetrating intensity is larger than 40%.
The resistivity of the cadmium zinc telluride material of the detector is 10 9 Omega cm or above, working leakage current less than 10nA, bare measurement 241 Am energy spectrum, the energy resolution ratio of gamma ray with energy of 59.5keV is less than 7%, and the inside of the crystal has no macroscopic defect, no crystal boundary and uniform tellurium inclusion distribution.
Advantageous effects
The invention provides a system for calibrating the action depth of high-energy gamma rays in a detector and a using method thereof, wherein the system comprises a high-energy gamma ray surface source, a high-energy gamma ray collimation system, a standard gauge block, a standard cushion block, a large-size high-energy gamma ray detector and a precise lifting table, gamma rays emitted by the high-energy gamma ray surface source pass through the collimation system with high ray blocking capacity and are incident from the side wall of the large-size gamma ray detector, the high-energy rays have higher probability of laterally penetrating the detector, the plane where an anode and a cathode of the large-size gamma ray detector are located is parallel to the high-energy ray collimation slit determined by the height of the standard cushion block, the collimation system restrains the high-energy rays from being laterally incident into the detector only in the collimation slit parallel to the cathode and anode planes of the gamma ray detector, the standard gauge block is used for supporting the collimation system and adjusting the central plane position of the collimation slit, the standard cushion block is used for supporting the upper collimation system and determining the resolution in the depth direction of the detector, and the precise lifting table is used for supporting the detector and adjusting the initial relative position of the high-energy gamma ray detector and the collimation system; the invention realizes the experimental calibration of the depth of action of the high-energy gamma ray in the detector.
The beneficial effects of the invention are:
firstly, obtaining a ray depth calibration parameter from measured data, wherein the ray depth calibration parameter takes the factors influencing a theoretical calculation model, such as the nonuniformity of a detection crystal, the difference of ASICs (application specific integrated circuits) of different signal channels and a data processing circuit, and the like into consideration. Compared with the experiment test without depth calibration, the experiment method can only obtain the plane two-dimensional coordinates of the ray action position, can determine the action depth of the gamma rays with different energies in the detector during vertical incidence, realizes the acquisition of the space three-dimensional coordinates of the ray action position, and provides data support for further performing accurate energy spectrum correction, device design optimization and high-energy ray Compton imaging according to the ray action depth.
Secondly, the experimental system designed by the invention can be used for various ray depth calibration experiments, the alignment regulation and the position regulation of each plane are realized through a high-precision standard gauge block, a standard gasket and a precision lifting table, the transportability, the diversity and the reliability of the experimental process and the testing method are higher, and the experiment and the testing cost are controllable.
Third, the experimental system related to the invention can obtain the special ray depth calibration parameters by performing a calibration experiment on one detector when the detector leaves the factory in principle, so that the experimental equipment is used as a prototype, further deeply developed by combining with an upper computer algorithm, and can be upgraded into a set of special detector parameter testing system.
Drawings
FIG. 1 is a schematic diagram of an experimental apparatus for calibrating depth of action of high-energy gamma rays in a large-size gamma ray detector;
FIG. 2 is a schematic diagram of a collimating system facing the direction of a high energy emitting surface source;
FIG. 3 is a schematic diagram of detector electrode dimensions;
FIG. 4 is a schematic size diagram of a collimation system;
description of the main part symbols: the method comprises the following steps of 1-high-energy gamma ray surface source, 2-high-energy ray collimation system, 3-large-size high-energy gamma ray detector, 4-precision lifting table, 5-standard gauge block and 6-standard gasket.
Detailed Description
The invention will now be further described with reference to the following examples, and the accompanying drawings:
unless otherwise defined, technical or scientific terms used herein shall have the ordinary meaning as understood by those skilled in the art. The terms "first," "second," "third," "fourth," and the like as used in the description and in the claims of the present application do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Thus, a feature defined as "first," "second," "third," or "fourth" may indicate or implicitly include one or more of that feature. In the description of the embodiments of the present application, the meaning of "a plurality" is two or more unless otherwise specified. "left", "right", "upper", "lower", "side", and like directional terms are defined with respect to the schematic latitude in the drawings, it is to be understood that these directional terms are relative concepts that are used for descriptive and clear relative to and which can be varied accordingly in accordance with the latitude in which the experimental device is placed, and do not indicate or imply that the device or element so referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore are not to be considered as limiting upon the present patent.
The embodiments of the present application will be described below with reference to the drawings. In the following description, reference is made to the accompanying drawings which form a part hereof and which show by way of illustration specific aspects of embodiments of the present application or which may be used to describe specific aspects of embodiments of the present application, and in which like or similar designations represent like or similar elements or elements having like or similar functionality throughout. It is to be understood that the embodiments of the present application are capable of use in other respects, and may include structural or logical changes not depicted in the attached drawings, the embodiments being illustrative and not restrictive of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present application is defined by the appended claims. In addition, it should also be understood that features of the various exemplary embodiments and/or aspects described herein may be combined with each other, unless explicitly stated otherwise.
The design idea of the invention is as follows:
the invention relates to a system for calibrating the action depth of high-energy gamma rays in a large-size detector.
The incidence direction of the ray, the distribution of the constrained ray and the alignment of the incidence direction of the ray and the depth of the detector to be calibrated need to be strictly defined. A high-energy gamma ray surface source, a high-energy gamma ray collimation system, a standard gauge block, a standard cushion block, a large-size high-energy gamma ray detector and a precision lifting table are used for building a test system. Gamma rays emitted by the high-energy gamma ray surface source pass through a collimation system with high ray blocking capacity and are incident from the side wall of the large-size gamma ray detector, and the high-energy gamma ray energy is selected to ensure that the detector can be laterally penetrated by a larger probability. The anode and cathode planes of the large-size gamma-ray detector are parallel to the high-energy ray collimating slit, so that the high-energy ray is restrained from being laterally incident into the detector only from the collimating slit parallel to the cathode and anode planes of the gamma-ray detector. The method comprises the steps of supporting a collimation system by using a standard gauge block, adjusting the position of a central plane of a collimation slit, supporting an upper collimation system by using a standard cushion block, determining the resolution ratio of the detector in the depth direction by using the thickness of the cushion block, supporting the detector by using a precise lifting table, and adjusting the initial relative position of a high-energy ray detector and the collimation system.
Gamma rays emitted by the high-energy gamma ray surface source pass through a collimation system with high ray blocking capacity and enter from the side wall of a large-size gamma ray detector, the high-energy rays can laterally penetrate through the detector with high probability, the planes of an anode and a cathode of the large-size gamma ray detector are parallel to a high-energy ray collimation slit determined by the height of a standard cushion block, the collimation system restrains the high-energy rays from being laterally incident into the detector only from the collimation slit parallel to the cathode and anode planes of the gamma ray detector, the standard gauge block is used for supporting the collimation system and adjusting the position of the center plane of the collimation slit, the standard cushion block is used for supporting the upper collimation system and determining the resolution in the depth direction of the detector, and the precision lifting platform is used for supporting the detector and adjusting the initial relative position of the high-energy ray detector and the collimation system; the invention realizes the experimental calibration of the depth of action of the high-energy gamma ray in the detector.
In one possible implementation, the material of the detector is cadmium zinc telluride, and the resistivity of the material is required to be 10 9 Omega cm or above, working leakage current less than 10nA, bare measurement 241 Am energy spectrum, the energy resolution ratio of gamma rays with the energy of 59.5keV is less than 7 percent, no macroscopic defect, no crystal boundary and uniform tellurium inclusion distribution are generated in the crystal; the electrode material of the detector is gold or indium or silver or aluminum; the electrode structure of the detector can ensure that the electric field in the detector is basically uniform when the detector works, and when the detection unit applies unit bias voltage, the weight potential curves of the cathode and the anode of the detector have difference.
In one possible implementation manner, the design rule of the high-energy ray collimation system for the length of the collimation slit is to ensure that the intensity of the gamma ray with the energy not exceeding a specific value after passing through the collimation slit is attenuated to 95% of the incident intensity, which is determined by the following formula:
in the high-energy ray collimation system, the upper surface and the lower surface of a collimation slit are parallel to each other, and the width of the collimation slit is determined by the depth resolution of an expected detector; in the high-energy ray collimation system, the height of a single collimator is greater than the distance between the cathode and the anode of the selected detector; in the high-energy ray collimation system, the width of a collimator in the ray incidence direction is determined by the following formula: the width of the collimator in the ray incidence direction is not less than the width of the collimator in the ray incidence direction plus 2 multiplied by the width of the standard gasket
The collimator is made of lead or pure copper or brass or red copper or tungsten-nickel-iron.
In one possible implementation manner, the intensity distribution of the radioactive source is similar to that of a uniform plane source, and the emergent area of gamma rays is larger than the lateral dimension perpendicular to the gamma ray detector; the radiation source is capable of emitting higher energy gamma rays.
In a possible implementation manner, the planes of the anode and the cathode of the gamma ray detector are both parallel to the plane of the upper and lower surfaces of the slit of the collimation system; the arrangement plane of the radioactive sources is vertical to the plane of the center of the slit of the pure tungsten collimation system; the distance from the radioactive source to the collimation system is far longer than the distance from the collimation system to the detector; the gamma ray emitted by the radioactive source has a high probability of penetrating the detector from the side direction, and a photoelectric effect energy deposition signal can be collected at any position in the transverse section of the detector, and the energy of the gamma ray emitted by the radioactive source meets the following requirements:
in one possible implementation manner, the standard cushion blocks are configured in pairs and are placed on the upper surface of the lower collimation system which completely exposes the width of the detector in the incident direction of the rays; the standard cushion block is made of lead, pure copper, brass, red copper, tungsten or tungsten-nickel-iron, and is made of the same material as the collimation system; the thickness of the standard gauge block is consistent with that of the cushion block, and the number of layers of the standard gauge block is adjusted to adjust the alignment of the collimation slit and the specific position of the side face of the detector; the tolerance of the working sizes of the standard cushion block and the standard gauge block is less than 0.5 micron, and the adjustment precision of the precision lifting platform is less than 5 microns.
The electrode structure of the detector can ensure that the electric field in the detector is basically uniform when in work, and when the unit bias voltage is applied to the detection unit, the weight potential curves of the cathode and the anode of the detector have difference. The design rule of the length of the collimating slit of the high-energy ray collimating system is to ensure that the intensity of gamma rays with the energy not exceeding a specific value after passing through the collimating slit is attenuated to 95% of the incident intensity. The intensity distribution of the radioactive source is similar to that of a uniform plane source, the emergent area of gamma rays is larger than the lateral dimension vertical to the gamma ray detector, the gamma rays with higher energy can be emitted, the detector can be penetrated by the lateral direction with higher probability, and photoelectric effect energy deposition signals can be collected at any position in the transverse section of the detector. The working dimension error or the adjusting precision of the standard cushion block, the standard gauge block and the precision lifting platform is high enough.
The invention is further illustrated by the following specific examples:
example 1: calibration 137 Cs/ 60 System and experimental method for acting depth of Co in large-size gamma ray detector
In this embodiment, the detector material is cadmium zinc telluride, and the resistivity of the material is required to be 10 9 Omega cm or above, working leakage current less than 10nA, bare measurement 241 Am energy spectrum, the energy resolution ratio of gamma ray with energy of 59.5keV is less than 7%, and the inside of the crystal has no macroscopic defect, no crystal boundary and uniform tellurium inclusion distribution. The electrode material of the detector is gold, the material of the collimation system enables partial material to be tungsten, the density of the device is more than 93%, and the density of the device is 18g/cm 3 The above.
In this embodiment, respectively use 137 Cs and 60 co two high energy gamma ray sources, the source size is about 10mm, and the position of the radioactive source is fixed in the experiment. The three-dimensional size of the detector is 22mm × 22mm × 15mm (length × width × height), and the detector electrode structure is a pixel type of 11 × 11. The collimation system consists of two pieces 30mm x 50mm x 20mm (length x width x height). The spatial resolution of the expected detector in the depth direction is 1mm, the working size of the standard gauge block is 1mm, the gauge block material is consistent with that of the collimator material, the working size of the standard cushion block is consistent with that of the standard gauge block, and the number of the standard cushion blocks is 15. By adjusting the precise lifting platform, when in an initial position,and the plane of the anode/cathode of the detector is overlapped with the plane of the lower/upper surface of the collimation slit, the energy response and the time response of the detector at the initial position are tested, and the test is stopped after the data volume of a certain time is recorded. The position of the detector is fixed and unchanged, the number of standard cushion blocks supporting the collimation system is gradually increased/decreased, signals of high-energy rays acting on the detector in different depths are respectively tested and obtained, and calibration parameters are obtained through calculation of an upper computer. Fig. 1 shows a schematic forward view of the experimental setup when the standard spacer of the collimation system is 9 during the test for calibration experiment. Fig. 2 is a schematic structural diagram of a collimation system composed of 2 standard gauge blocks and 2 collimators, which is aligned with the incident direction of the ray in the test process shown in fig. 1. The detector electrode dimensions are marked in fig. 3 and the collimation system dimensions are marked in fig. 4. Standard spacer and gauge tolerance<0.5 micron, the precision of the precision lifting platform is less than 5 microns. Tables 1 and 2 are respectively 137 Cs and 60 and calibrating the obtained linear function calibration data and the confidence interval thereof by the Co experiment.
TABLE 1 137 Cs linear calibration parameter and confidence
Note: NAN indicates that the pixel is de-enabled, with no test data.
TABLE 2 60 Co linear calibration parameter and confidence
Note: NAN indicates that the pixel is de-enabled, with no test data.
In summary, the above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A system for calibrating the depth of action of high-energy gamma rays in a detector is characterized by comprising a high-energy gamma ray surface source (1), two high-energy ray collimation blocks (2), a precision lifting table (4), a standard gauge block (5) and a standard gasket (6); the two high-energy ray collimation blocks (2) are arranged on the precise lifting table (4), and a standard gasket (6) is arranged between the two high-energy ray collimation blocks, so that a high-energy ray collimation slit is formed between the two high-energy ray collimation blocks (2); the high-energy gamma ray surface source (1) is arranged at one side of the two high-energy ray collimation blocks (2), and the rays are directly opposite to the standard gasket (6) between the two high-energy ray collimation systems (2); the upper surface and the lower surface of the high-energy ray collimation slit are parallel to each other; the standard cushion blocks are configured in pairs and are placed on the upper surface of the lower collimating system which is completely exposed to the width of the detector in the ray incidence direction.
2. The system for calibrating depth of action of high-energy gamma rays in a detector as claimed in claim 1, wherein: the high-energy ray collimation slit ensures that the intensity of gamma rays with energy not more than a specific value after passing through the collimation slit is attenuated to 95% of the incident intensity.
3. The system for calibrating the depth of action of high-energy gamma rays in a detector according to claim 1 or 2, wherein: the length of the high-energy ray collimation slit is determined by the following formula:
4. the system for calibrating the depth of action of high-energy gamma rays in a detector according to claim 1 or 2, wherein: the width of the high-energy ray collimation slit is that the height of the standard gauge block is matched with the depth resolution capability.
5. The system for calibrating depth of action of high-energy gamma rays in a detector as claimed in claim 1, wherein: the height of the high-energy ray collimation block (2) is larger than the distance between the cathode and the anode of the detector.
6. The system for calibrating the depth of action of high-energy gamma rays in a detector as set forth in claim 1 or 5, wherein: the width of the collimator in the ray incidence direction of the high-energy ray collimation block (2):
the width of the collimator in the ray incidence direction is more than or equal to the width of the collimator in the ray incidence direction plus 2 multiplied by the width of the standard gasket.
7. The system for calibrating the depth of action of high-energy gamma rays in a detector as set forth in claim 1 or 5, wherein: the high-energy ray collimation block (2) and the standard cushion block (6) are made of lead, pure copper, brass, red copper, tungsten or tungsten-nickel-iron.
8. The system for calibrating the depth of action of high-energy gamma rays in a detector as set forth in claim 1 or 5, wherein: the tolerance of the working sizes of the standard cushion block and the standard gauge block is less than 0.5 micron, and the adjusting precision of the precise lifting platform is less than 5 microns.
9. The use method of the system for calibrating the depth of action of the high-energy gamma rays in the detector is characterized in that the thickness of the detected detector is more than 1.0cm, the material of the detector is cadmium zinc telluride, and the material of the electrode is gold or indium or silver or aluminum; the use steps are as follows:
step 1: the following parameters are determined from the detector under test:
1. the intensity distribution of the high-energy gamma ray surface source (1) is similar to that of a uniform surface source, and the emergent area of gamma rays is larger than the lateral size vertical to the gamma ray detector; the energy of the gamma ray emitted by the radioactive source satisfies the following conditions:
2. determining the length of the collimating slit:
3. collimator width for determining ray incidence direction:
the width of the collimator in the ray incidence direction is more than or equal to the width of the collimator in the ray incidence direction plus 2 standard gasket widths;
3. the height of the single collimator is larger than the distance between the cathode and the anode of the selected detector;
4. determining the width of a collimation slit according to the expected depth resolution of the detector, wherein the height of the standard gauge block is consistent with the depth resolution;
and 2, step: the detector to be detected is placed on the other side, opposite to the high-energy gamma ray surface source (1), of the high-energy ray collimation block (2), and the number of layers of the standard gauge blocks is adjusted to adjust the collimation slit to be aligned with the detection part on the side face of the detector;
the planes of the anode and the cathode of the gamma ray detector are parallel to the planes of the upper surface and the lower surface of the slit of the collimation system;
the arrangement plane of the radioactive sources is vertical to the plane of the center of the slit of the pure tungsten collimation system;
the distance from the radioactive source to the collimation system is far greater than the distance from the collimation system to the detector;
and step 3: testing the energy response and the time response of the detector at the initial position; the initial position is as follows: the plane of the anode/cathode of the detector is overlapped with the plane of the lower/upper surface of the collimation slit;
and 4, step 4: fixing the position of the detector unchanged, gradually increasing or decreasing the number of standard cushion blocks supporting the collimation system, and respectively testing to obtain signals of high-energy rays acting on the detector in different depths;
and 5: rays are incident from the side wall of the detector through a collimator system, an anode pixel electrode signal and a cathode plane electrode signal when each photoelectric effect event occurs are obtained through testing, and according to the ray depth principle, the cathode signal/the anode signal are in direct proportion to the ray incidence depth theoretically; calculating the ratio of the cathode signal to the anode signal in the test, and fitting the relation between the ratio of the cathode signal to the anode signal and the calibrated depth by using a linear function to obtain an actual depth calibration parameter;
the gamma rays which can be emitted by the radioactive source are attenuated by the detector, and the penetrating intensity is larger than 40%.
10. The method of claim 9, wherein: the resistivity of the cadmium zinc telluride material of the detector is 10 9 Omega cm or above, working leakage current less than 10nA, and naked measurement 241 Am energy spectrum, the energy resolution ratio of gamma ray with energy of 59.5keV is less than 7%, and the inside of the crystal has no macroscopic defect, no crystal boundary and uniform tellurium inclusion distribution.
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| CN117250651A (en) * | 2023-11-07 | 2023-12-19 | 中国科学技术大学 | Planet element detection device based on pixel type tellurium-zinc-cadmium detector |
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| CN117250651A (en) * | 2023-11-07 | 2023-12-19 | 中国科学技术大学 | Planet element detection device based on pixel type tellurium-zinc-cadmium detector |
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