CN101329282A - Alignment method and device for radiation source and detector in non-destructive testing of large components - Google Patents

Abstract

The invention relates to the application field of nuclear technology, in particular to a method and a device for completing centering and positioning without a rigid connection between a radiation source and a detector during non-destructive testing of large components. The steps of the method for centering the radiation source and the detector when the present invention is used for non-destructive testing of large components are as follows: (a) approximately centering the radiation source and the detector; (b) rotating the centering shielding pattern to the shielding position; (c ) After imaging, check the position of the occlusion pattern; (d) adjust the radiation source to the position of the occlusion pattern within a certain imaging error, and complete the centering. The corresponding device includes a centering positioning plate, a shielding pattern and a shielding collimator, wherein the shielding pattern is arranged on the front end of the shielding collimator through the centering positioning plate. The invention realizes the accurate centering of the radiation source and the detector in the application of non-destructive testing of large and extra-large components, and can calculate the distance between the source point of the radiation source and the detector so as to meet the basic conditions of radiation imaging and complete the detection.

Description

Alignment method and device for radiation source and detector in non-destructive testing of large components

technical field

The invention relates to the application field of nuclear technology, in particular to a method and a device for completing the centering and positioning of a radiation source and a detector when there is no rigid connection between the radiation source and the detector during non-destructive testing of large components.

Background technique

Radiographic nondestructive inspection technology has been widely used in many fields such as airport, railway, port safety inspection and industrial quality inspection; in nondestructive inspection applications, the alignment of radiation source and detector is the basic condition for complete inspection. In traditional non-destructive testing applications, or there is a rigid connection between the radiation source and the detector, or the object to be detected is small, the radiation source and the detector can be aligned visually. However, during the non-destructive testing of large components or extra-large structures, the alignment of the radiation source and the detector becomes a problem due to the inability to rigidly connect or visually align. Therefore, there is an urgent need for a method and device that can ensure reliable alignment during non-destructive testing of large components.

Contents of the invention

In view of the defects of the above-mentioned detection methods, the present invention provides a method and device for centering the radiation source and the detector through radiation shielding in the non-destructive detection of large components.

The method for centering a radiation source and a detector for non-destructive testing of large components provided by the present invention includes the following steps:

(a) roughly aligning the radiation source with the detector;

(b) Rotate the centering blocking pattern to the blocking position;

(c) Check the position of the occlusion pattern after imaging;

(d) Adjust the radiation source to the imaging position of the occlusion pattern within a certain error, and complete the centering.

Wherein the centering device is a rotatable and movable heavy metal rectangular shielding ray pattern, its thickness is 1/5 to 2 times of the half-value layer thickness of the metal under the use of ray energy, and the center of the pattern is located at the shielding collimator center.

In step (d), if the position of the occlusion pattern deviates from the center, the distance from the source point of the radiation source to the detector and the deviation scale of the center of the two can be calculated through the size and deviation value of the image formed by the pattern, and the imaging is performed after adjustment. Until the adjustment is within a certain error, the centering step is completed.

The calculation method of the distance from the source point of the radiation source to the detector is as follows:

It is known that the distance between the shading pattern and the source point of the radiation source is L, the actual side length of the shading pattern is A, the side length of the formed image is i (pixels), each pixel of the image represents the actual length U, and the distance between the source point of the radiation source and the detector is M. then there is a geometric relationship $\frac{L}{m}=\frac{A}{\mathrm{iU}},$ It can be concluded $m=\frac{\mathrm{iUL}}{A},$ That is, the distance between the source point of the radiation source and the detector end under the current placement position.

The calculation method of the deviation scale is as follows:

The image formed by the known occlusion pattern deviates by h pixels from the center of the radiation field in the horizontal or vertical direction, and each pixel of the image represents the actual length U, so the actual offset H=hU.

Preferably, the radiation source is a portable high-energy ray source using an accelerator or radioactive isotopes; the detector is a DR imaging screen, a CR image screen, a flat scintillation screen combined with a CCD camera or an inflatable ionization chamber line array detector, a scintillator line The array detector and the semiconductor line array detector cooperate with one of the scanning devices.

Another aspect of the present invention is to provide a radiation source and detector centering device for non-destructive testing of large components, including a centering positioning plate, a shielding pattern and a shielding collimator, wherein the shielding pattern is positioned by centering The plate is arranged at the front end of the shielding collimator.

The centering device also includes positioning screws for fixing the centering and positioning plate on the shielding collimator, and the positioning screws fix the centering and positioning plate on the front end of the shielding collimator through the positioning screw holes at the four corners of the centering and positioning plate.

The shading pattern is a rotatable metal rectangular ray shading pattern, its thickness is 1/5-2 times of the half-value layer thickness of the metal under the ray energy, and the center of the pattern is located at the center of the shielding collimator.

Preferably, the shielding pattern is embodied as a left-right symmetric or up-down symmetric figure, such as a "Tian" shape, a "Wang" cross shape, an "X" cross shape, and the like.

Preferably, one side of the centering positioning plate has a rotation axis through which the shielding pattern is rotated. Rotating the shielding pattern to the shielding position can be used for centering; rotating to the outside is used for normal radiation imaging.

Through the present invention, in the application of non-destructive testing of large and extra-large components, the radiation source and the detector can be accurately aligned, and the distance between the radiation source and the detector can be calculated, so that it can meet the basic conditions of radiation imaging and complete detection.

The centering method and centering device of the present invention are used in the field of non-destructive testing of large components, such as columns, surfaces, beams, large boilers, nuclear power plant large pipes and Non-destructive testing of large and extra-large components such as containers, oil pipelines, natural gas pipelines and containers, large pipelines and containers of petrochemical processing enterprises. In addition, the centering method and centering device of the present invention can also be used in many fields such as traditional airports, railways, port safety inspections and industrial quality inspections.

Description of drawings

Fig. 1 is the front view when the king-shaped occlusion figure is in the centered state;

Fig. 2 is the front view of the king-shaped occlusion figure moving out of the occlusion position;

Fig. 3 is the front view of the square-shaped blocking figure in the centered state;

Fig. 4 is a front view of the matte block figure moving out of the block position.

In the figure: 1. Centering positioning plate; 2. Positioning screw; 3. Blocking pattern; 4. Rotation axis; 5. Shielding collimator; 6. Positioning screw hole.

Detailed ways

The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

The present invention provides a method and device for centering a radiation source and a detector by using radiation shielding, using an appropriate heavy metal shielding pattern at the exit of the cone beam radiation source collimator, through which the shielding pattern can be detected at the detector end The obtained radiation attenuation image is used to determine the relative position of the radiation source and the detector, and to solve the alignment problem between the radiation source and the detector.

As shown in Figures 1 to 4, the centering device consists of a centering positioning plate 1, a rotating shaft 4, and a blocking pattern 3 for centering. The hole 6 is positioned at the front end of the shielding collimator 5 . The blocking pattern 3 is a king-shaped (as shown in FIG. 1 and FIG. 2 ) or a field-shaped (as shown in FIG. 3 and FIG. 4 ), etc., which are vertically symmetrical or left-right symmetrical patterns that help centering. Rotating the centering shielding pattern to the shielding position can be used for centering (as shown in FIG. 13 and FIG. 2 ); rotating to the outside is used for normal radiation imaging (as shown in FIGS. 2 and 4 ). That is to say, the shading pattern is moved into or out of the shading position by means of translation or rotation, so as to perform centering of the radiation source and the detector and normal radiation imaging after centering. Wherein the radiation cone beam can be a cone beam or a quadrangular pyramid beam.

Certainly, those skilled in the art should know that the shielding pattern used for centering can also be moved into or out of the shielding position by means of hanging, buckling, etc., so as to realize radiation imaging after centering and centering.

In this embodiment, the radiation source is X-ray machine, accelerator, 60Co, 137Cs radioactive isotopes; the detector is an area array detector or a line array detector, which cooperates with the detector scanning device to complete plane scanning.

The radiation source can be an X-ray machine, an accelerator, or a radioactive isotope, and its energy is mono-energy, dual-energy or multi-energy, the energy range is 100KeV-9MeV, and the ray field angle is 15°-30°. The detector 3 is one of DR imaging screen, CR image screen, flat scintillation screen combined with CCD camera or gas-filled ion chamber line array detector, scintillator line array detector, semiconductor line array detector and scanning device.

In the present invention, the centering shielding pattern is made of heavy metal with a certain thickness, and the thickness value is 1/5 half-value layer to 2 half-value layers of the metal in the radiation source used, that is, the thickness is 1/5 of the metal in use. 1/5 to 2 times the half-value layer thickness under the ray energy, and the center of the pattern is located at the center of the shielding collimator. All surfaces of the shading pattern in the thickness direction are parallel to the rays radiating thereto, so the image formed by the shading pattern near the radiation source end is smaller than the image formed at the end far away from the radiation source. The radiation occlusion image covers more than 1/3 of the collimated radiation field.

The operation steps of the centering method in the present invention are as follows: roughly center the radiation source and the detector; rotate the centering blocking pattern to the blocking position; check the imaging position of the blocking pattern after imaging, if it is off-center, you can pass through the pattern The size (number of pixels) and deviation value (such as the number of pixels of deviation) of the formed image calculate the distance from the source point of the radiation source to the detector and the scale of the center deviation between the two, and then adjust the imaging until the adjustment is within the allowable error , to complete the alignment step.

The placement calculation process is as follows:

1. It is known that the shielding pattern is L from the source point of the radiation source, the actual side length of the shielding pattern is A, the side length of the formed image is i (pixels), each pixel of the image represents the actual length U, and the distance between the source point of the radiation source and the detector is M. then there is a geometric relationship $\frac{L}{m}=\frac{A}{\mathrm{iU}},$ It can be concluded $m=\frac{\mathrm{iUL}}{A},$ That is, the distance between the source point of the radiation source and the detector end under the current placement position.

2. The image formed by the known occlusion pattern deviates from the center of the radiation field by h pixels in the horizontal direction (or vertical direction), and each pixel of the image represents the actual length U, so the actual offset H=hU.

In a preferred embodiment of the present invention, the application of the cone beam is extended to the application of the flat beam, and the width of the line parallel to the flat beam in the occlusion pattern should be 1/5 to 2/3 of the width of the flat beam. In the flat beam application, the detector is a line array detector parallel to the flat beam. The radiation attenuation map with the occlusion pattern of the radiation source is obtained by the longitudinal movement of the detector relative to the radiation source, and the radiation source is calculated from the position and size of the occlusion pattern in this figure. The algorithm is the same as the cone beam scheme for the relative position of the detector.

Although the present invention has been shown and described in conjunction with a preferred embodiment, it will be understood by those skilled in the art that various changes may be made in both form and detail without departing from the spirit of the present invention. and scope of patent protection.

Claims (10)

1. A method for centering a radiation source and a detector when used for non-destructive testing of large components, characterized in that the method comprises the following steps: (a) roughly aligning the radiation source with the detector; (b) Rotate the centering blocking pattern to the blocking position; (c) Check the position of the occlusion pattern after imaging; (d) Adjust the radiation source to the imaging position of the occlusion pattern within a certain error, and complete the centering. 2. The method for centering radiation sources and detectors for non-destructive testing of large components according to claim 1, characterized in that the centering device is a rotatable and movable heavy metal rectangular shielding ray pattern, and its thickness is the 1/5 to 2 times the half-value layer thickness of the metal under the ray energy used. 3. The method for centering radiation sources and detectors for non-destructive testing of large components according to claim 1, characterized in that in step (d), if the position of the shielding pattern deviates from the center, the pattern can be used to Calculate the distance from the source point of the radiation source to the detector and the deviation scale between the two centers based on the size of the image and the deviation value, and then adjust the imaging until the adjustment is within a certain error to complete the centering step. 4. The method for centering the radiation source and the detector in the non-destructive testing of large components according to claim 3, characterized in that the calculation method of the distance from the source point of the radiation source to the detector is as follows: It is known that the distance between the shading pattern and the source point of the radiation source is L, the actual side length of the shading pattern is A, the side length of the formed image is i (pixels), each pixel of the image represents the actual length U, and the distance between the source point of the radiation source and the detector is M. then there is a geometric relationship $\frac{L}{m}=\frac{A}{\mathrm{iU}},$ It can be concluded $m=\frac{\mathrm{iUL}}{A},$ That is, the distance between the source point of the radiation source and the detector end under the current placement position. 5. The method for centering radiation sources and detectors for non-destructive testing of large components according to claim 3, characterized in that the calculation method of the deviation scale is as follows: The image formed by the known occlusion pattern deviates by h pixels from the center of the radiation field in the horizontal or vertical direction, and each pixel of the image represents the actual length U, so the actual offset H=hU. 6. The method for centering radiation sources and detectors for non-destructive testing of large components according to any one of claims 1 to 3, characterized in that the radiation source is a portable high-energy ray source using an accelerator or a radioactive isotope; The detector is one of DR imaging screen, CR image screen, flat scintillation screen combined with CCD camera or gas-filled ion chamber line array detector, scintillator line array detector, semiconductor line array detector and scanning device. 7. A centering device for radiation sources and detectors for non-destructive testing of large components, characterized in that the device includes a centering positioning plate (1), a shielding pattern (3) and a shielding collimator (5), wherein The shielding pattern (3) is arranged on the front end of the shielding collimator (5) through the centering and positioning plate (1). 8. The centering device for radiation sources and detectors used for non-destructive testing of large components according to claim 7, characterized in that it also includes a device for fixing the centering positioning plate (1) on the shielding collimator (5) The positioning screw (2) on the centering positioning plate is fixed on the front end of the shielding collimator (5) by the positioning screw (2) through the positioning screw holes at the four corners of the centering positioning plate. 9. The centering device for radiation sources and detectors for non-destructive testing of large components according to claim 7, characterized in that the shielding pattern (3) is a rotatable and movable metal rectangular shielding pattern, the thickness of which is It is 1/5 to 2 times of the half-value layer thickness of the metal under the ray energy used, and the center of the pattern is located at the center of the shielding collimator (5). 10. The centering device for radiation sources and detectors used in non-destructive testing of large components according to claim 7, characterized in that one side of the centering positioning plate (1) has a rotating shaft (4), which blocks the pattern (3) Rotating through the rotating shaft (4), rotating the shading pattern to the shading position can be used for centering; rotating to the outside is used for normal radiation imaging.

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