A method for measuring the beam uniformity of a high-current ion beam based on a tungsten wire diagnostic target

Abstract

The application discloses a kind of based on tungsten wire diagnostic target's high-current ion beam beam uniformity measurement method, belong to high-current ion beam diagnostic technical field, comprising: the tungsten wire diagnostic target of ion source test platform is moved to specified position, and visible light camera parameter is set;Camera carries out the video acquisition of tungsten wire diagnostic target, determines background frame and frame to be handled;From background frame and frame to be handled, obtain the image of region to be analyzed;To the image of region to be analyzed, visible light image perspective transformation is carried out, and corrected image is obtained;According to corrected image, draw the three-dimensional visual distribution graph according to the size variation of gray value, process it, obtain the light intensity distribution in horizontal direction, the light intensity distribution in vertical direction and obtain filtered light intensity distribution;Filtered light intensity distribution is divided according to image coordinate axis direction, determines the beam uniformity of ion beam in vertical direction and horizontal direction.The application realizes the high efficiency of beam uniformity calculation.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of strong current ion beam diagnosis, and particularly relates to a strong current ion beam beam uniformity measurement method based on a tungsten wire diagnostic target. BACKGROUND

[0002] As one of the key parameters of the strong current particle beam (such as a neutral beam), the beam uniformity needs to be measured by a suitable method. The strong current particle beam beam uniformity diagnosis method includes taking a series of visible light images of the beam striking a TWC (Tungsten Wire Calorimeter, tungsten wire diagnostic target) by a visible light camera, processing the visible light images to obtain the beam uniformity. Due to the limitation of the angle of the visible light camera, the visible light front view image of the beam profile of the tungsten wire diagnostic target cannot be obtained, so the image needs to be denoised and distorted to obtain the beam profile, and the corrected image is converted into a gray image to obtain the light intensity distribution data for calculating the beam uniformity.

[0003] In actual ion beam diagnosis experiments, the prior art has the following problems: the video needs to be processed manually one by one, the batch processing capacity is insufficient, the efficiency is low, and errors are easy to occur; the background noise interferes with the image; the existing technology limits the shooting angle of the visible light camera, resulting in distortion of the tungsten wire diagnostic target image, and the beam profile cannot be accurately obtained; the tungsten wire mesh structure causes high-frequency noise in the image gray scale, the image gray scale curve fluctuates greatly, and the local peak and valley interference is serious; and there is a lack of reliable beam uniformity quantitative index. SUMMARY

[0004] To solve the above technical problems, the application adopts the following technical solution:

[0005] A strong current ion beam beam uniformity measurement method based on a tungsten wire diagnostic target, comprising:

[0006] Step 1, move the tungsten wire diagnostic target of the ion source test platform to a specified position, and set the visible light camera parameters;

[0007] Step 2, start the visible light camera to collect the video of the tungsten wire diagnostic target, play the recorded tungsten wire light-emitting video during the beam extraction experiment, and determine the background frame and the frame to be processed;

[0008] Step 3, obtain the image of the analysis area from the background frame and the frame to be processed of step 2;

[0009] Step 4, perform visible light image perspective transformation on the analysis area image of step 3 to obtain a corrected image;

[0010] Step 5, according to the corrected image obtained in step 4, draw a three-dimensional visualization distribution graph varying with the gray value;

[0011] Step 6: Process the 3D visualization distribution map from Step 5 to obtain the light intensity distribution in the horizontal direction and the light intensity distribution in the vertical direction;

[0012] Step 7: Filter the horizontal and vertical light intensity distributions obtained in Step 6 to obtain the filtered light intensity distribution;

[0013] Step 8: Divide the filtered light intensity distribution obtained in Step 7 according to the image coordinate axis direction to determine the beam uniformity of the ion beam in the vertical and horizontal directions.

[0014] The present invention has the following beneficial effects:

[0015] This invention solves the problem of insufficient batch processing capability in ion beam diagnostic experiments in the prior art by batch processing multiple video files and supporting independent frame selection and analysis for each video, thus achieving high efficiency in beam uniformity calculation.

[0016] This invention effectively suppresses background noise by subtracting the frame to be processed from the background frame, thus solving the problem in the prior art where background interference affects the accuracy of light intensity extraction in visible light images, thereby improving the signal-to-noise ratio of the light intensity signal.

[0017] This invention uses a perspective transformation algorithm to perform perspective transformation on images, thus solving the problem of image distortion caused by the limited shooting angle of existing cameras.

[0018] This invention uses grayscale processing combined with the SG (Savitzky-Golay) filtering algorithm to filter out high-frequency noise caused by the gaps in the tungsten wire mesh, thereby obtaining a smooth and stable light intensity distribution, which facilitates the calculation of subsequent beam uniformity.

[0019] This invention solves the problem of lacking reliable quantitative indicators for evaluating beam uniformity in the prior art by calculating the ratio of light intensity on the upper and lower sides and the ratio of light intensity on the left and right sides based on the light intensity distribution. It realizes the accurate evaluation of the uniformity of the tungsten wire diagnostic target beam in the vertical and horizontal directions, and provides data support for the optimization of ion source operating parameters. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a tungsten wire diagnostic target for calculating the bundle uniformity of the present invention;

[0021] Figure 2 This is a schematic diagram of the ion source testing platform of the present invention;

[0022] Figure 3 This is a schematic diagram of perspective transformation in the image correction method of the present invention;

[0023] Figure 4This is a schematic diagram of the beam uniformity calculation of the present invention, wherein 1-first beam spot, 2-second beam spot, 3-third beam spot, and 4-fourth beam spot. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0025] This invention proposes a method for measuring the uniformity of high-current ion beams based on tungsten wire diagnostic targets. By performing background denoising, perspective transformation, grayscale conversion, and SG filtering on batch images, the method enables batch calculation of beam uniformity, providing data support for optimizing ion source operating parameters.

[0026] The technical solutions, objectives, and beneficial effects of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. It should be noted that the embodiments described are only for better understanding and illustrating the technical content of the present invention, and are not intended to limit the scope of protection of the present invention. Equivalent substitutions or improvements obtained by those skilled in the art without creative effort, as well as reasonable combinations of various technical features without contradiction, should all fall within the scope of protection of the present invention.

[0027] For tokamak devices to achieve heating, the neutral beam must operate stably and reliably. In the field of neutral beams, parameters such as beam uniformity and beam divergence are key parameters for evaluating the stability and reliability of the neutral beam. Beam uniformity is obtained by analyzing visible light images captured by a visible light camera of the beam bombarding the surface of a tungsten filament diagnostic target.

[0028] like Figure 1 As shown, a 0.2 mm diameter tungsten filament emits visible light when bombarded by a high-energy beam of particles. The filament does not break even when the instantaneous beam temperature reaches 2000℃. The total dimensions of the tungsten filament diagnostic target are 1900 mm × 700 mm, with an effective filament length of 1750 mm along the Y-axis and 600 mm along the X-axis. At room temperature, the tungsten filament is taut. Even at temperatures reaching up to 2000℃, after linear expansion due to heat, the filament should remain taut. The filament should be subjected to tensile force throughout its entire lifespan, and this force should not exceed its withstand limit.

[0029] like Figure 2As shown, the ion source testing platform of the present invention includes a dual-drive ion source, an ion source electrode system, and a vacuum chamber arranged sequentially. Within the vacuum chamber, a tungsten filament diagnostic target, a visible light camera, and a beam cutoff target are arranged sequentially along the high-energy ion beam emission direction. The lens normal of the visible light camera forms a certain angle with the surface of the tungsten filament diagnostic target, and the high-energy ion beam transmission direction is perpendicular to the surface of the tungsten filament diagnostic target. The vacuum chamber provides a vacuum environment and support structure for the high-energy ion beam transmission. The high-energy ion beam generated by the ion source passes through the tungsten filament diagnostic target and is ultimately deposited on the beam cutoff target. The visible light camera captures a visible light image from the back of the tungsten filament diagnostic target.

[0030] The present invention provides a method for measuring the uniformity of a high-current ion beam based on a tungsten wire diagnostic target, comprising:

[0031] Step 1: Move the tungsten wire diagnostic target of the ion source test platform to the designated position and set the visible light camera parameters (such as exposure time and acquisition duration).

[0032] Step 2: Turn on the visible light camera to acquire video of the target (i.e., the tungsten filament diagnostic target) bombarded by the beam, play the tungsten filament luminescence video recorded during the beam extraction experiment, and determine the background frame and the frame to be processed.

[0033] Step 3: Obtain the image of the region to be analyzed from the background frame and the frame to be processed in Step 2; specifically:

[0034] If the video is a color video, the frame to be processed in step 2 is grayscaled and the background frame in the video is subtracted to remove background noise and obtain the net value image.

[0035] If the video is grayscale, the frame to be processed in step 2 is directly subtracted from the background frame in the video to remove background noise and obtain the net value image.

[0036] The preset analysis area is extracted from the net asset value image, that is, the part without image information is removed to obtain the image of the area to be analyzed.

[0037] Step 4: Based on the geometric position of the tungsten filament diagnostic target and the visible light camera, the image of the area to be analyzed in Step 3 is corrected after determining the four points of perspective transformation (performing visible light image perspective transformation) to obtain the corrected image.

[0038] Step 5: Based on the corrected image obtained in Step 4, draw a three-dimensional visualization distribution map showing the variation of gray values ​​to intuitively reflect the spatial distribution characteristics of the image gray values.

[0039] Step 6: Select M straight lines along the horizontal direction from the 3D visualization distribution map in Step 5, read the gray values ​​on these lines, accumulate them along the vertical direction, and then divide by M to obtain the light intensity distribution in the horizontal direction; similarly, select N straight lines along the vertical direction from the 3D visualization distribution map in Step 5, read the gray values ​​on these lines, accumulate them along the horizontal direction, and then divide by N to obtain the light intensity distribution in the vertical direction.

[0040] Step 7: Due to the gaps between adjacent tungsten filaments, the light intensity distribution in the beam spot profile fluctuates significantly, affecting subsequent processing. Therefore, SG filtering is applied to the horizontal and vertical light intensity distributions obtained in Step 6 to remove high-frequency noise and obtain the filtered light intensity distribution.

[0041] Step 8: Divide the filtered light intensity distribution from Step 7 according to the image coordinate axis: When the Y-axis of the image is used as the horizontal axis of the light intensity distribution, the left peak of the light intensity distribution corresponds to the upper part of the high-energy ion beam profile, and the right peak of the light intensity distribution corresponds to the lower part of the high-energy ion beam profile; when the X-axis of the image is used as the horizontal axis of the light intensity distribution, the left peak of the light intensity distribution corresponds to the left part of the high-energy ion beam profile, and the right peak of the light intensity distribution corresponds to the right part of the high-energy ion beam profile.

[0042] The average light intensity of each part (the upper part, lower part, left part, and right part of the high-energy ion beam profile) is calculated separately. The average light intensity of the upper part of the high-energy ion beam profile is compared with the average light intensity of the lower part, and the average light intensity of the left part is compared with the average light intensity of the right part, thereby determining the beam uniformity of the high-energy ion beam in the vertical and horizontal directions.

[0043] like Figure 3 As shown, in step 4, the process of the visible light image perspective transformation method includes:

[0044] Visible light image perspective transformation consists of two steps:

[0045] Step 4.1: Select four non-collinear reference points on the image plane of the region to be analyzed: And set the corresponding target plane rectangle coordinates: Establish the perspective transformation matrix between the original coordinates and the target coordinates, such as... Figure 4 As shown.

[0046] Step 4.2: Based on the perspective transformation matrix of the original coordinates and target coordinates established in Step 4.1, perform perspective transformation on the image to achieve perspective transformation of the visible light image.

[0047] Average light intensity distribution in the horizontal direction and the average light intensity distribution in the vertical direction The calculation formula is:

[0048] ;

[0049] in, This represents the distribution of light intensity along the i-th horizontal line. This represents the distribution of light intensity along the j-th vertical line.

[0050] X-axis beam uniformity of first beam spot 1 and second beam spot 2 and the Y-axis beam uniformity of the first beam spot 1 and the third beam spot 3 The calculation formula is:

[0051] , ;

[0052] in, The average value of the X-axis peak of the first spot 1. The average value of the X-axis peak of the second spot 2. The average value of the Y-axis peak of the first spot 1. The mean value of the Y-direction peak of the third spot 3.

[0053] like Figure 4 As shown, X represents the horizontal direction and Y represents the vertical direction. This represents the maximum value of the horizontal light intensity distribution. This represents the maximum value of the light intensity distribution in the vertical direction. This is the horizontal dividing point between the two peaks. At the vertical bimodal boundary point, a high-energy ion beam bombards a tungsten filament diagnostic target. The target emits light, forming a visible beam spot. After visible light image perspective transformation, grayscale processing, and SG filtering, the horizontal and vertical light intensity distributions are obtained. and These represent the mean values ​​of the X-direction peaks of the first spot 1 and the second spot 2, respectively. and This represents the mean peak value in the Y direction of the first beam spot 1 and the third beam spot 3. The ratio of the mean peak values ​​reflects the relative intensity of the beam in different regions, and is used to evaluate the beam uniformity of the region composed of the first beam spot 1 and the second beam spot 2 in the X direction, and the beam uniformity of the region composed of the first beam spot 1 and the third beam spot 3 in the Y direction. To analyze other regions (such as analyzing...), Figure 4 The uniformity of the bundles in the region consisting of the second bundle spot 2 and the third bundle spot 3, and the region consisting of the third bundle spot 3 and the fourth bundle spot 4, can be determined by following the method described above.

[0054] For beam uniformity calculation, given the four-point transformation coordinates and the frame to be processed and the background frame, the program can process dozens of experimental video files in batches at once and output the beam uniformity of all experiments uniformly. Researchers can then further analyze the changes in beam uniformity after changes in experimental conditions, thereby enabling the debugging and optimization of the ion source.

[0055] The above description is merely an embodiment of the present invention and does not limit the scope of the invention. Any equivalent structural or procedural transformations made based on the description and drawings of this invention, or direct or indirect applications in other related system fields, are similarly included within the protection scope of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A method for measuring the uniformity of a high-current ion beam based on a tungsten wire diagnostic target, characterized in that, include: Step 1: Move the tungsten wire diagnostic target of the ion source testing platform to the designated position and set the visible light camera parameters; Step 2: Turn on the visible light camera to acquire video of the tungsten filament diagnostic target, play the tungsten filament emission video recorded during the beam extraction experiment, and determine the background frame and the frame to be processed. Step 3: Obtain the image of the region to be analyzed from the background frame and the frame to be processed; Step 4: Perform visible light image perspective transformation on the image of the region to be analyzed to obtain the corrected image; Step 5: Based on the corrected image, draw a three-dimensional visualization distribution map showing the variation of grayscale values; Step 6: Process the 3D visualization distribution map: Select M straight lines along the horizontal direction, read the gray values ​​on the M straight lines, accumulate them along the vertical direction, and then divide by M to obtain the light intensity distribution in the horizontal direction; Select N straight lines along the vertical direction, read the gray values ​​on the N straight lines, accumulate them along the horizontal direction, and then divide by N to obtain the light intensity distribution in the vertical direction. Step 7: Perform SG filtering on the light intensity distribution in the horizontal and vertical directions to remove spatial high-frequency noise caused by the gaps in the tungsten filaments and obtain the filtered light intensity distribution. Step 8: Divide the filtered light intensity distribution into upper, lower, left, and right parts on the high-energy ion beam profile according to the image coordinate axis direction. Determine the beam uniformity of the ion beam in the vertical and horizontal directions by the ratio of the average light intensity of the upper and lower parts and the ratio of the average light intensity of the left and right parts.

2. The method for measuring the uniformity of a high-current ion beam based on a tungsten wire diagnostic target according to claim 1, characterized in that, In step 1, the ion source testing platform includes a dual-drive ion source, an ion source electrode system, and a vacuum chamber arranged sequentially. In the vacuum chamber, a tungsten wire diagnostic target, a visible light camera, and a beam cutoff target are arranged sequentially along the high-energy ion beam emission direction. The lens normal of the visible light camera has a certain angle with the surface of the tungsten wire diagnostic target, and the transmission direction of the high-energy ion beam is perpendicular to the surface of the tungsten wire diagnostic target. The vacuum chamber provides a vacuum environment and support structure for the transmission of the high-energy ion beam. The high-energy ion beam generated by the ion source passes through the tungsten wire diagnostic target and is finally deposited on the beam cutoff target. The visible light camera captures a visible light image from the back of the tungsten wire diagnostic target.

3. The method for measuring the uniformity of a high-current ion beam based on a tungsten wire diagnostic target according to claim 1, characterized in that, In step 3, the net asset value image is obtained from the tungsten filament emission video in step 2; specifically: If the video is a color video, the frame to be processed in step 2 is grayscaled and the background frame in the video is subtracted to remove background noise and obtain the net value image. If the video is grayscale, the frame to be processed in step 2 is directly subtracted from the background frame in the video to remove background noise and obtain the net value image.

4. The method for measuring the uniformity of a high-current ion beam based on a tungsten wire diagnostic target according to claim 1, characterized in that, In step 4, based on the geometric position of the tungsten filament diagnostic target and the visible light camera, the image of the area to be analyzed in step 3 is subjected to visible light image perspective transformation after determining the four points of perspective transformation, so as to obtain the corrected image.

5. The method for measuring the uniformity of a high-current ion beam based on a tungsten wire diagnostic target according to claim 4, characterized in that, In step 4, the visible light image perspective transformation includes: Step 4.1: Select four non-collinear reference points on the image plane of the region to be analyzed: And set the corresponding target plane rectangle coordinates: Establish the perspective transformation matrix between the original coordinates and the target coordinates; Step 4.2: Based on the perspective transformation matrix of the original coordinates and target coordinates established in Step 4.1, perform perspective transformation on the image to achieve perspective transformation of the visible light image.

6. The method for measuring the uniformity of a high-current ion beam based on a tungsten wire diagnostic target according to claim 1, characterized in that, In step 8, the filtered light intensity distribution from step 7 is divided according to the image coordinate axis direction, including: when the Y-axis of the image is used as the horizontal axis of the light intensity distribution, the left peak of the light intensity distribution corresponds to the upper part of the high-energy ion beam profile, and the right peak of the light intensity distribution corresponds to the lower part of the high-energy ion beam profile; when the X-axis of the image is used as the horizontal axis of the light intensity distribution, the left peak of the light intensity distribution corresponds to the left part of the high-energy ion beam profile, and the right peak of the light intensity distribution corresponds to the right part of the high-energy ion beam profile.

7. The method for measuring the uniformity of a high-current ion beam based on a tungsten wire diagnostic target according to claim 1, characterized in that, In step 6, the average light intensity distribution in the horizontal direction and the average light intensity distribution in the vertical direction The calculation formula is: ； in, This represents the distribution of light intensity along the i-th horizontal line. This represents the distribution of light intensity along the j-th vertical line; X-axis beam uniformity of the first and second beam spots and the Y-axis beam uniformity of the first and third beam spots The calculation formula is: ， ； in, The mean value of the X-axis peak of the first spot. The average X-axis peak value of the second beam spot. The average value of the Y-axis peak of the first spot. The mean value of the Y-axis peak of the third beam spot.

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