A method for detecting leaks in medical cyclotron vacuum chamber

Abstract

The present invention relates to the technical field of leak detection, and specifically to a method for leak detection in a medical cyclotron vacuum chamber. The present invention first obtains the leakage risk prominence coefficient of each preset part according to the fluctuation deviation between the helium concentration curves corresponding to each preset part and other preset parts; then obtains the environmental pollution coefficient of each preset part during the helium leak detection process according to the time interval between adjacent helium leak detection processes, and the helium concentration before and during the measurement; further obtains the environmental fluctuation coefficient according to all environmental parameter curves; and finally obtains the leak credibility of each preset part. The present invention evaluates the leakage risk of different preset parts based on the changing characteristics of the helium concentration in the vacuum chamber during the helium leak detection process, and then analyzes the environmental interference in the helium leak detection process to compensate, thereby improving the accuracy of the leak detection results.

Description

Technical Field

[0001] The invention relates to the technical field of leak detection, and in particular to a leak detection method for a medical cyclotron vacuum chamber. Background Art

[0002] A medical cyclotron is a device that causes charged particles to perform cyclotron motion under the combined action of magnetic and electric fields. It is widely used in medical radiation diagnosis and treatment. The vacuum chamber is one of the core components of a medical cyclotron, responsible for maintaining the vacuum environment during particle acceleration to ensure the stability and efficiency of the particle beam. However, there may be leaks in the vacuum chamber, which will reduce the vacuum degree, thus affecting the particle acceleration process and may also cause radiation leakage, thus endangering life safety. Therefore, it is very important to detect leaks in the vacuum chamber of a medical cyclotron.

[0003] In the prior art, a helium leak detection method is usually used to detect whether a leak occurs at a leak point in a vacuum chamber. However, in a vacuum state, for very small leak points, due to the low density of the gas and its rapid diffusion, related instruments such as helium mass spectrometers are not sensitive enough to respond to small leaks. In addition, in the actual detection process, it is easily disturbed by environmental factors, such as changes in temperature and humidity, which may affect the diffusion rate of the gas or the sensor performance of the helium mass spectrometer. These factors may lead to misjudgment of vacuum chamber leak detection. Summary of the invention

[0004] In order to solve the technical problem of low accuracy of leak detection in the vacuum chamber of a medical cyclotron in the prior art, the present invention aims to provide a method for leak detection in the vacuum chamber of a medical cyclotron. The technical solution adopted is as follows:

[0005] During the helium leak detection process at each preset position of the medical cyclotron vacuum chamber, a helium concentration curve of the vacuum chamber and an environmental parameter curve under each environmental impact index are obtained; wherein the helium leak detection at each preset position is not synchronized; the pre-test helium concentration before the helium leak detection and the mid-test helium concentration during the helium leak detection process are obtained at each preset position;

[0006] Obtaining a leakage risk prominence coefficient for each preset location according to a fluctuation deviation between the helium concentration curve corresponding to each preset location and the helium concentration curve corresponding to other preset locations;

[0007] According to the time interval between the helium leak detection process corresponding to each preset position and the previous helium leak detection process, combined with the helium concentration before the test and the helium concentration during the test at each preset position, the environmental pollution coefficient of each preset position during the helium leak detection process is obtained; during the helium leak detection process at each preset position, the environmental fluctuation coefficient is obtained according to the fluctuation changes of all the environmental parameter curves;

[0008] According to the environmental fluctuation coefficient and the environmental pollution coefficient of each preset position during the helium leak detection process, combined with the corresponding leakage risk prominence coefficient, the credibility of the leakage point of each preset position is obtained.

[0009] Furthermore, the method for obtaining the leakage risk prominence coefficient includes:

[0010] According to the fluctuation characteristics of each helium concentration curve, obtaining the helium leakage parameter of the corresponding preset position;

[0011] Taking any preset part as the target part, taking the average of the differences between the helium leakage parameter of the target part and the helium leakage parameter of each non-target part as the helium leakage deviation of the target part;

[0012] After adding the preset non-zero positive parameter to the mean of the helium leakage parameters of all non-target parts, a reciprocal operation is performed, the reciprocal is used as the weight of the helium leakage deviation, and the weighted result is used as the leakage risk prominence coefficient of the target part.

[0013] Furthermore, the method for obtaining the helium leakage parameter includes:

[0014] The variance of the helium concentration in the helium concentration curve corresponding to each preset position is used as a concentration fluctuation parameter; according to the change trend of the helium concentration curve corresponding to each preset position, a concentration rising trend parameter is obtained; and the product of the concentration fluctuation parameter and the concentration rising trend parameter is used as the helium leakage parameter corresponding to the preset position.

[0015] Furthermore, the method for obtaining the concentration rising trend parameter includes:

[0016] A concentration parameter sequence and a time parameter sequence are acquired based on each of the helium concentration curves; and a normalized result of the correlation coefficient between the concentration parameter sequence and the time parameter sequence is used as a concentration rising trend parameter.

[0017] Furthermore, the method for obtaining the environmental pollution coefficient includes:

[0018] According to the difference between the helium concentration before measurement and the helium concentration during measurement at each preset part, and the helium concentration before measurement at each preset part, obtaining the helium residual parameter of each preset part;

[0019] The reciprocal of the time interval between the start time of the helium leak detection process corresponding to each preset position and the end time of the previous adjacent helium leak detection process is used as a purification failure parameter;

[0020] The helium residual parameter and the poor purification parameter are integrated to obtain the environmental pollution coefficient of each preset part during the helium leak detection process.

[0021] Furthermore, the method for obtaining the helium residual parameter includes:

[0022] The absolute value of the difference between the helium concentration before measurement and the helium concentration during measurement at each preset location is added with a preset non-zero positive parameter as the denominator; the helium concentration before measurement at each preset location is used as the numerator; and the fractional ratio is used as the helium residual parameter.

[0023] Furthermore, the method for obtaining the environmental fluctuation coefficient includes:

[0024] Taking the variance of the environmental parameters in each of the environmental parameter curves as the fluctuation index of the corresponding environmental parameter curve; fusing the fluctuation indexes of all environmental parameter curves to obtain a composite fluctuation parameter;

[0025] The product of the environmental parameters at the same time in different environmental parameter curves is used as the environmental composite index at the corresponding time; the average of all the environmental composite indexes at the same time is used as the weight of the composite fluctuation parameter, and the weighted result is used as the environmental fluctuation coefficient.

[0026] Furthermore, the method for obtaining the credibility of the leakage point includes:

[0027] Using the Euclidean norm of the environmental fluctuation coefficient and the environmental pollution coefficient as environmental interference parameters of the corresponding preset position during the helium leak detection process;

[0028] The environmental interference parameter is added to a preset minimum non-zero positive parameter and then a reciprocal operation is performed. The reciprocal is used as the weight of the leakage risk prominence coefficient corresponding to the preset location, and the weighted result is used as the leakage point credibility of the corresponding preset location.

[0029] Furthermore, the preset parts at least include each welding part, each connecting part and the valve of the vacuum chamber.

[0030] Furthermore, the environmental impact indicators include at least temperature and humidity.

[0031] The present invention has the following beneficial effects:

[0032] In the process of helium leak detection at each preset part of the vacuum chamber, the present invention obtains the helium concentration curve of the vacuum chamber and the environmental parameter curve under each environmental impact index, and obtains the pre-test helium concentration of each preset part before the helium leak detection and the mid-test helium concentration during the helium leak detection process, so as to provide data analysis preparation for the subsequent evaluation of the credibility of the leakage point of each preset part; according to the fluctuation deviation between the helium concentration curve corresponding to each preset part and the helium concentration curve corresponding to other preset parts, the leakage risk prominence coefficient of each preset part is obtained; according to the time interval between the helium leak detection process corresponding to each preset part and the previous helium leak detection process, the smaller the time interval, the greater the possibility that the helium is residual or not purified, and then combined with each preset part The helium concentration before and during the measurement of each preset position is measured, and the environmental pollution coefficient of each preset position during the helium leak detection process is comprehensively obtained. The environmental pollution coefficient reflects the degree of influence of the residual helium in the environment on the helium concentration curve, and indirectly reflects the interference effect on the assessment of leakage risk; further, in the helium leak detection process of each preset position, according to the fluctuation change of all environmental parameter curves, the environmental fluctuation coefficient is obtained. The environmental fluctuation coefficient reflects the influence of environmental impact indicators on the accuracy of helium detection, and also indirectly reflects the interference effect on the assessment of leakage risk; finally, according to the environmental fluctuation coefficient and environmental pollution coefficient of each preset position during the helium leak detection process, combined with the corresponding leakage risk prominence coefficient, the leakage point credibility of each preset position is obtained. The present invention evaluates its leakage risk based on the changing characteristics of the helium concentration in the vacuum chamber during the helium leak detection process of different preset positions, and then analyzes the environmental interference in the helium leak detection process for compensation, thereby improving the accuracy of the leakage point detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 A flow chart of a method for detecting leaks in a medical cyclotron vacuum chamber provided by one embodiment of the present invention;

[0035] Figure 2 A flow chart of a method for obtaining a leakage risk prominence coefficient provided by an embodiment of the present invention;

[0036] Figure 3 A flow chart of a method for obtaining an environmental pollution coefficient provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description of the specific implementation method, structure, features and effects of a medical cyclotron vacuum chamber leak detection method proposed by the present invention in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0038] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0039] The specific scheme of the medical cyclotron vacuum chamber leak detection method provided by the present invention is described in detail below with reference to the accompanying drawings.

[0040] See also Figure 1 , which shows a flow chart of a medical cyclotron vacuum chamber leak detection method provided by an embodiment of the present invention, specifically comprising:

[0041] Step S1, during the helium leak detection process at each preset position of the medical cyclotron vacuum chamber, obtain the helium concentration curve of the vacuum chamber and the environmental parameter curve under each environmental impact index; wherein the helium leak detection at each preset position is asynchronous; obtain the pre-test helium concentration of each preset position before the leak point detection and the mid-test helium concentration during the helium leak detection process.

[0042] In order to perform leak detection on the vacuum chamber of a medical cyclotron and ensure the normal operation of the medical cyclotron, the embodiment of the present invention will perform helium leak detection on each preset position of the vacuum chamber, thereby evaluating the credibility of the leak at each preset position.

[0043] Among them, in a preferred embodiment of the present invention, considering that the welding parts, interfaces and other positions of the vacuum chamber are common leakage parts, the preset parts at least include each welding part, each connection part and valve of the vacuum chamber; the implementer can also set the preset parts according to the actual situation, such as taking each suspected leakage part of the vacuum chamber as the preset part.

[0044] It should be noted that the helium leak detection of each preset position is not synchronous, that is, the helium leak detection process of each preset position is performed separately and sequentially to avoid the leakage of other preset positions interfering with the helium leak detection result of the preset position; the helium leak detection process is already a prior art well known to those skilled in the art, and the helium leak detection process of each preset position is consistent. Here, only the helium leak detection process and principle of any preset position are briefly described:

[0045] First, connect the helium mass spectrometer to the exhaust port of the medical cyclotron vacuum system, and try to ensure that the connection is tight and leak-free to monitor the helium concentration at the exhaust port; then start the vacuum pump system of the medical cyclotron to evacuate the vacuum chamber; when the vacuum state is stable for a period of time, use a helium spray gun to spray helium from the outside to the preset location; when there is a leak in the preset location, the sprayed helium will escape from the leak point into the vacuum chamber, and then the vacuum pump will extract the escaped helium to the exhaust port, so that the helium mass spectrometer can monitor the change in helium concentration at the exhaust port, so that it can be evaluated whether there is a leak in the preset location based on the change in helium concentration.

[0046] Considering that during the helium leak detection process at each preset location, by monitoring the helium concentration change at the exhaust port of the vacuum chamber, it can help evaluate whether the preset location is leaking; considering that during the helium leak detection process, environmental factors may affect the diffusion of helium or the measurement accuracy of the helium mass spectrometer, and the residual helium in the environment may escape into the vacuum chamber during the helium leak detection process at the preset location, thereby affecting the helium concentration monitoring result;

[0047] Therefore, in one embodiment of the present invention, during the helium leak detection process at each preset position, a helium concentration curve displayed in real time in the helium mass spectrometer is obtained; it should be noted that the helium mass spectrometer will automatically present the monitored helium concentration as a graphical curve, so it can be directly obtained; the implementer can also set the acquisition frequency by himself to construct the helium concentration curve;

[0048] At the same time, an environmental sensor is arranged in a local range of each preset position, such as within 0.5 meters, to collect environmental parameter curves under each environmental impact indicator; the environmental impact indicators include at least temperature and humidity, and the environmental sensors include temperature sensors and humidity meters, and the collection frequency is set to once per second, and the temperature data collected during the helium leak detection process is mapped to the corresponding timestamp to fit the temperature curve, and the humidity curve is fitted in the same way; the temperature curve and the humidity curve are used as the environmental parameter curves under the corresponding environmental impact indicators; the implementer can also set the type or number of environmental impact indicators by himself, such as adding air pressure, etc., and can also adjust the collection frequency by himself, which will not be repeated here;

[0049] Then, in the local range of each preset part, such as 0.5 meters, an additional helium mass spectrometer or related gas sensor is arranged, and the sampling frequency is set to once per second; before the helium leak detection at each preset part, the ambient helium concentration around the preset part within a preset time period is collected, wherein the preset time period can be set to 1 minute before the helium leak detection, and the average of all ambient helium concentrations collected within this minute is used as the helium concentration before the test; then, during the helium leak detection process, the ambient helium concentration around the preset part is collected, and the average of all ambient helium concentrations collected during the entire helium leak detection process is used as the helium concentration during the test;

[0050] Implementers can also define the preset time period by themselves, but they must ensure that the duration of the preset time period should be much shorter than the time interval between two adjacent helium leak detection processes to avoid the helium sprayed in the previous helium leak detection process interfering with the assessment of the helium concentration before the test; the sampling frequency can also be adjusted according to actual needs.

[0051] Step S2, obtaining the leakage risk prominence coefficient of each preset part according to the fluctuation deviation between the helium concentration curve corresponding to each preset part and the helium concentration curves corresponding to other preset parts.

[0052] Considering that during the helium leak detection process at each preset location, if the corresponding helium concentration curve fluctuates and shows an upward trend, it means that there may be a leak at the preset location, and the sprayed helium will escape from the leak point into the vacuum chamber, so that the helium concentration curve will fluctuate and rise over time;

[0053] Considering that during the helium leak detection process at each preset location, when helium is sprayed on a preset location, if there is a leak at an adjacent preset location, the sprayed helium may also flow to the adjacent preset location with the airflow, and then escape into the vacuum chamber. In this case, even if the preset location does not leak, the helium concentration curve may still show a fluctuating upward trend due to the leak at other adjacent preset locations. However, since the amount of flowing helium or the helium concentration is relatively low, the fluctuating upward trend caused in this case is relatively weaker than the fluctuating upward trend caused by the leak at the preset location itself.

[0054] Therefore, the embodiment of the present invention will evaluate the leakage risk prominence coefficient of each preset part based on the fluctuation deviation between the helium concentration curves corresponding to other preset parts; if the helium concentration curve of the preset part has a more obvious fluctuation rising trend compared with the helium concentration curves of other preset parts, it is more likely to be caused by its own leakage, and the leakage risk is more prominent.

[0055] Preferably, in one embodiment of the present invention, the method for obtaining the leakage risk prominence coefficient includes:

[0056] See also Figure 2 , which shows a flow chart of a method for obtaining a leakage risk prominence coefficient provided by an embodiment of the present invention, specifically comprising:

[0057] Step S201, obtaining helium leakage parameters corresponding to preset locations according to the fluctuation characteristics of each helium concentration curve.

[0058] Considering that leakage at the preset location will cause the helium concentration curve to show a fluctuating upward trend, the helium leakage parameters are first evaluated based on the fluctuation characteristics of the helium concentration curve; the more violent the fluctuation of the helium concentration curve and the upward trend, the larger the helium leakage parameter, in preparation for the subsequent evaluation of the prominent situation of the upward trend.

[0059] In a preferred embodiment of the present invention, considering that the variance can evaluate the fluctuation of data, the larger the variance, the more drastic the fluctuation; therefore, the concentration fluctuation parameter can be obtained based on the variance, and then the helium leakage parameter can be evaluated in combination with the change trend; therefore, the method for obtaining the helium leakage parameter includes:

[0060] The variance of the helium concentration in the helium concentration curve corresponding to each preset position is used as a concentration fluctuation parameter; according to the change trend of the helium concentration curve corresponding to each preset position, a concentration rising trend parameter is obtained; and the product of the concentration fluctuation parameter and the concentration rising trend parameter is used as the helium leakage parameter of the corresponding preset position.

[0061] Among them, in a preferred embodiment of the present invention, the method for obtaining the concentration rising trend parameter includes:

[0062] A concentration parameter sequence and a time parameter sequence are obtained based on each helium concentration curve; and a normalized result of a correlation coefficient between the concentration parameter sequence and the time parameter sequence is used as a concentration rising trend parameter.

[0063] As an example, the helium concentration in the helium concentration curve is taken as a sequence element, and the concentration parameter sequence is constructed in chronological order. The acquisition time corresponding to each helium concentration is taken as a sequence element to construct a time parameter sequence. Then, the Pearson correlation coefficient between the concentration parameter sequence and the time parameter sequence of each helium concentration curve is obtained, and the Pearson correlation coefficient is used as a function The x in the formula is used for positive correlation normalization, so that when the Pearson correlation coefficient is closer to 1, the normalized result is larger, indicating that the helium concentration shows an upward trend with the change of time parameters, and the larger the concentration rising trend parameter is.

[0064] Step S202 , taking any preset part as the target part, and taking the average of the difference between the helium leakage parameter of the target part and the helium leakage parameter of each non-target part as the helium leakage deviation of the target part.

[0065] In order to facilitate the analysis and expression of the fluctuation deviation between each preset part and the corresponding helium concentration curve of other preset parts, firstly, any preset part is taken as the target part, and the other preset parts except the target part are taken as non-target parts; then the target part is taken as the analysis object to evaluate its prominence relative to other non-target parts.

[0066] As an example, the helium leak deviation is calculated as: ; Wherein, e is the serial number of the target site; is the helium leakage deviation of the target part; n is the serial number of the non-target part; E is the total number of preset parts; is the helium leakage parameter of the target part; is the helium leakage parameter of the nth non-target part; is a linear normalization function.

[0067] In this example, the difference is specifically measured by the linear normalization result of the difference. When the difference between the helium leakage parameter of the target site and the helium leakage parameter of the non-target site is positive and the larger it is, the larger the normalization result is, indicating that the larger the helium leakage parameter of the target site is, and the larger the difference between the helium leakage parameters of all other non-target sites is, the larger the helium leakage deviation of the target site is, which indirectly reflects that it is more prominently abnormal relative to other non-target sites and has a greater leakage risk.

[0068] Step S203, after adding the preset non-zero positive parameter to the mean of the helium leakage parameters of all non-target parts, a reciprocal operation is performed, the reciprocal is used as the weight of the helium leakage deviation, and the weighted result is used as the leakage risk prominence coefficient of the target part.

[0069] Considering that when the helium leakage parameters of all non-target parts are smaller and the helium leakage deviation of the target part is larger, it further indicates that the more prominent the abnormality of the target part is relative to the other non-target parts, the greater the leakage risk.

[0070] As an example, the mean of the helium leakage parameters of all non-target parts is added with a preset non-zero positive parameter such as 0.001, and then a reciprocal operation is performed to avoid the reciprocal operation being meaningless without affecting the calculation result. Then, the reciprocal is multiplied by the helium leakage deviation of the target part, and the product is used as the leakage risk prominence coefficient of the target part.

[0071] At this point, the leakage risk prominence coefficient of the target part can be obtained; the target part is changed to obtain the leakage risk prominence coefficient of each preset part.

[0072] Step S3, according to the time interval between the helium leak detection process corresponding to each preset location and the previous helium leak detection process, combined with the helium concentration before and during the measurement of each preset location, obtain the environmental pollution coefficient of each preset location during the helium leak detection process; during the helium leak detection process of each preset location, obtain the environmental fluctuation coefficient according to the fluctuation changes of all environmental parameter curves.

[0073] Since there may be helium residue in the environment during two adjacent helium leak detection processes, it will affect the monitoring results of the helium concentration curve corresponding to each preset location, which may lead to low accuracy in the assessment of the leakage risk prominence coefficient of each preset location, and thus low accuracy in leak point detection.

[0074] However, considering that the residual helium usually dissipates gradually over time, its concentration usually decreases gradually, and the impact on the helium concentration monitoring during the next helium leak detection process will also gradually decrease, the time interval between two adjacent helium leak detection processes can evaluate the impact of the residual helium in the environment on the monitoring; considering the pre-test helium concentration in the environment before the helium leak detection and the helium concentration during the leak detection process, it can help evaluate the residual helium in the environment, and then facilitate the evaluation of the impact on the monitoring;

[0075] Based on this, the embodiment of the present invention will evaluate the environmental pollution coefficient of each preset location during the helium leak detection process based on the time interval between two adjacent helium leak detection processes, and then combine the helium concentration before and during the measurement of each preset location; the environmental pollution coefficient reflects the degree of influence of the residual helium in the environment on the helium concentration curve, so as to accurately determine the credibility of the leakage point in combination with the leakage risk prominence coefficient of each preset location in the future.

[0076] Preferably, in one embodiment of the present invention, the method for obtaining the environmental pollution coefficient includes:

[0077] See also Figure 3 , which shows a flow chart of a method for obtaining an environmental pollution coefficient provided by an embodiment of the present invention, specifically comprising:

[0078] Step S301, obtaining the helium residual parameter of each preset part according to the difference between the helium concentration before measurement and the helium concentration during measurement of each preset part, and the helium concentration before measurement of each preset part.

[0079] Considering that the greater the pre-measurement helium concentration of each preset location and the closer it is to the mid-measurement helium concentration, the greater the helium residue in the preset location and the greater the impact on subsequent monitoring results; based on this, the helium residue parameters can be evaluated.

[0080] In a preferred embodiment of the present invention, the method for obtaining the helium residual parameter includes:

[0081] The absolute value of the difference between the helium concentration before measurement and the helium concentration during measurement at each preset location plus a preset non-zero positive parameter is used as the denominator; the helium concentration before measurement at each preset location is used as the numerator; and the fractional ratio is used as the helium residual parameter.

[0082] As an example, the preset non-zero positive parameter is 0.001, and the absolute value of the difference between the helium concentration before the measurement and the helium concentration during the measurement is added to the preset non-zero positive parameter 0.001, so as to avoid affecting the calculation result and avoid the denominator being meaningless;

[0083] This embodiment comprehensively evaluates the helium residual parameter in the form of a ratio. When the numerator is larger and the denominator is smaller, it means that the helium concentration before measurement is larger and closer to the helium concentration during measurement, that is, the closer the helium concentration before measurement is to the helium concentration in the environment when helium is sprayed, the higher the helium residual degree is and the larger the helium residual parameter is.

[0084] Step S302: The reciprocal of the time interval between the start time of the helium leak detection process corresponding to each preset position and the end time of the previous adjacent helium leak detection process is used as a poor purification parameter.

[0085] When the time interval is smaller, it means that the helium leak detection process of the preset position is closer to the last helium leak detection process, and the possibility of helium being purified or dissipated is lower. Therefore, it is reciprocally calculated and the logic is adjusted so that the smaller the time interval is, the larger the purification poor parameter is, and the greater its residual impact is.

[0086] It should be noted that, since the helium leak detection process is not synchronized, the time interval between the start time of the helium leak detection process corresponding to each preset position and the end time of the previous adjacent helium leak detection process cannot be 0, so the countdown is meaningful.

[0087] Step S303, integrating the helium residual parameter and the purification failure parameter to obtain the environmental pollution coefficient of each preset position during the helium leak detection process.

[0088] As an example, the helium residual parameter and the poor purification parameter are multiplied and combined, and the product is used as the environmental pollution coefficient of the corresponding preset position during the helium leak detection process.

[0089] Considering that during the helium leak detection process, environmental factors may affect the diffusion of helium or the measurement accuracy of the helium mass spectrometer, for example, excessively high temperature will accelerate the diffusion of helium in the environment, thereby reducing the amount of helium escaping from the leak point at the preset location into the vacuum chamber; humidity will also affect the measurement accuracy of the helium mass spectrometer, resulting in unprepared helium concentration monitoring results; therefore, environmental factors will affect the monitoring results of the helium concentration curve corresponding to each preset location, which may result in low accuracy in the assessment of the leakage risk prominence coefficient of each preset location, and thus low accuracy in leak point detection;

[0090] Based on this, in the embodiment of the present invention, during the helium leak detection process at each preset location, the environmental fluctuation coefficient is obtained according to the fluctuation changes of all environmental parameter curves; the environmental fluctuation coefficient reflects the degree of influence of environmental impact indicators on the helium concentration curve, so as to accurately determine the credibility of the leakage point in combination with the leakage risk prominence coefficient of each preset location.

[0091] Preferably, in one embodiment of the present invention, considering that the higher the value of each environmental impact index is and the more violent the fluctuation is, the more the current helium spraying environment deviates from the ideal helium detection environment of constant temperature and humidity; and considering that the variance can evaluate the fluctuation of the data, the larger the variance is, the more violent the fluctuation is; therefore, the method for obtaining the environmental fluctuation coefficient includes:

[0092] The variance of the environmental parameters in each environmental parameter curve is used as the fluctuation index of the corresponding environmental parameter curve; the fluctuation indexes of all environmental parameter curves are integrated to obtain a composite fluctuation parameter;

[0093] The product of the environmental parameters at the same time in different environmental parameter curves is taken as the environmental composite index at the corresponding time; the average of all environmental composite indexes at the same time is taken as the weight of the composite fluctuation parameter, and the weighted result is taken as the environmental fluctuation coefficient.

[0094] As an example, the environmental impact indicators include temperature and humidity, and the calculation formula of the environmental fluctuation coefficient is:

[0095] ; Wherein, i is the serial number of the helium leak detection process of the preset position; is the environmental fluctuation coefficient during the helium leak detection process at the i-th preset position; f is the identifier of the environmental impact index corresponding to temperature; g is the identifier of the environmental impact index corresponding to humidity; is the fluctuation index of the temperature curve of the helium leak detection process at the i-th preset position; is the fluctuation index of the humidity curve of the helium leak detection process at the i-th preset position; is the composite fluctuation parameter of the helium leak detection process at the i-th preset position; is the mean value of the environmental composite index at all the same times during the helium leak detection process at the i-th preset position;

[0096] in, ; m is the sequence number of the moment in the helium leak detection process of the i-th preset position; M is the total number of moments in the helium leak detection process of the i-th preset position; is the temperature data at the mth moment in the temperature curve of the helium leak detection process at the i-th preset position; is the humidity data at the mth moment in the humidity curve of the helium leak detection process at the i-th preset position; It is the environmental composite index at the mth moment during the helium leak detection process at the i-th preset position.

[0097] In this example, the larger the variance of the temperature curve or the humidity curve, the larger its fluctuation index. Then, the fluctuation indexes of the two curves are multiplied and combined to obtain a composite fluctuation parameter. When the temperature data and humidity data at the same time are larger, the product is also larger, and the larger the environmental composite index at the corresponding time is, which means that the current time is more inclined to a high temperature and high humidity environment. Then, the mean of all environmental composite indexes at the same time is multiplied and combined with the composite fluctuation parameter to comprehensively evaluate the unstable changes in temperature and humidity during the helium leak detection process at the preset location to obtain the environmental fluctuation coefficient.

[0098] Step S4, obtaining the leak point credibility of each preset location according to the environmental fluctuation coefficient and environmental pollution coefficient of each preset location during the helium leak detection process, combined with the corresponding leakage risk prominence coefficient.

[0099] Since both the environmental fluctuation coefficient and the environmental pollution coefficient reflect the influence of environmental factors on the helium concentration curve, the leakage risk prominence coefficient of each preset location can be further adjusted in combination with the two, so as to accurately determine the credibility of the leakage point of each preset location.

[0100] Preferably, in one embodiment of the present invention, considering that the larger the environmental fluctuation coefficient and the environmental pollution coefficient are, the greater the interference to the accurate assessment of the leakage risk of the preset part is, the two can be integrated and the negative correlation can be mapped as the weight of the leakage risk prominence coefficient to compensate for the environmental factors of the leakage risk prominence coefficient of the preset part in the helium leak detection process; based on this, the method for obtaining the credibility of the leak point includes:

[0101] The Euclidean norm of the environmental fluctuation coefficient and the environmental pollution coefficient are used as the environmental interference parameters of the corresponding preset parts during the helium leak detection process. The environmental interference parameter is added with the preset minimum non-zero positive parameter and the reciprocal operation is performed. The reciprocal is used as the weight of the leakage risk prominence coefficient of the corresponding preset part, and the weighted result is used as the credibility of the leakage point of the corresponding preset part.

[0102] As an example, the calculation formula for leak confidence is: ; Wherein, i is the serial number of the helium leak detection process of the preset position; is the leak point credibility of the i-th preset position; is the hyperbolic tangent function, used for normalization; is the leakage risk prominence coefficient of the i-th preset location; is the environmental pollution coefficient during the helium leak detection process at the i-th preset position; is the environmental fluctuation coefficient during the helium leak detection process at the i-th preset position; is the environmental interference parameter in the helium leak detection process of the i-th preset position; To preset a minimum non-zero positive parameter, specifically 0.0001 is taken to avoid meaningless inverse calculation without affecting the calculation result.

[0103] In this example, when the environmental fluctuation coefficient and the environmental pollution coefficient are larger, the reciprocal is smaller, and the weight of the leakage risk prominence coefficient of the corresponding preset location is also smaller, so that the credibility of the leakage point is also lower. Then, the weighted result is normalized using the hyperbolic tangent, and the normalized result is used as the credibility of the leakage point of the corresponding preset location.

[0104] In one embodiment of the present invention, after obtaining the leak credibility of each preset part, considering that there may be inevitable accidental errors when only one helium leak detection is performed on each preset part, in order to eliminate the accidental errors, it is necessary to perform multiple helium leak detections on each preset part, and the average value of the leak credibility of each preset part evaluated during each helium leak detection process is used as the final leak credibility; the implementer can define the number of helium leak detections for each preset part according to actual needs to further improve the reliability of leak detection;

[0105] After obtaining the final leakage point credibility, the implementer can evaluate the possibility of each preset part being a leakage point based on the preset threshold. For example, when the final leakage point credibility of the preset part is greater than the preset threshold 0.3, it is considered that there is a leakage in the preset part; all preset parts can also be sorted in descending order according to the final leakage point credibility. The higher the leakage point credibility, the greater the leakage risk. Therefore, the preset parts with high leakage risk can be given priority, and then according to the location and size of the leakage point in the preset part, the appropriate repair technology can be selected, such as vacuum welding, spot welding, surface coating repair, etc. to repair the leakage, thereby improving the working performance of the medical cyclotron.

[0106] In summary, the present invention first obtains the leakage risk prominence coefficient of each preset part according to the fluctuation deviation between the helium concentration curves corresponding to each preset part and other preset parts; then obtains the environmental pollution coefficient of each preset part during the helium leak detection process according to the time interval between adjacent helium leak detection processes, and the helium concentration before and during the measurement; further obtains the environmental fluctuation coefficient according to all environmental parameter curves; and finally obtains the leakage point credibility of each preset part. The present invention evaluates the leakage risk of different preset parts based on the changing characteristics of the helium concentration in the vacuum chamber during the helium leak detection process, and then analyzes the environmental interference in the helium leak detection process to compensate, thereby improving the accuracy of the leakage point detection results.

[0107] It should be noted that the sequence of the above embodiments of the present invention is only for description and does not represent the advantages and disadvantages of the embodiments. The processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0108] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

Claims

1. A method for detecting leaks in a medical cyclotron vacuum chamber, characterized in that: The method comprises: During the helium leak detection process at each preset position of the medical cyclotron vacuum chamber, a helium spray gun is used to spray helium from the outside to the preset position, so that the helium mass spectrometer monitors the change of helium concentration at the exhaust port, and obtains the helium concentration curve of the vacuum chamber. At the same time, an environmental sensor is arranged in a local range of each preset position to collect the environmental parameter curve under each environmental impact index; wherein the helium leak detection at each preset position is not synchronized; the pre-test helium concentration of each preset position before the helium leak detection and the mid-test helium concentration during the helium leak detection process are obtained; Obtaining a leakage risk prominence coefficient for each preset location according to a fluctuation deviation between the helium concentration curve corresponding to each preset location and the helium concentration curve corresponding to other preset locations; According to the time interval between the helium leak detection process corresponding to each preset position and the previous helium leak detection process, combined with the helium concentration before the test and the helium concentration during the test at each preset position, the environmental pollution coefficient of each preset position during the helium leak detection process is obtained; during the helium leak detection process at each preset position, the environmental fluctuation coefficient is obtained according to the fluctuation changes of all the environmental parameter curves; According to the environmental fluctuation coefficient and the environmental pollution coefficient of each preset part during the helium leak detection process, combined with the corresponding leakage risk prominence coefficient, the credibility of the leakage point of each preset part is obtained; The method for obtaining the leakage risk prominence coefficient includes: According to the fluctuation characteristics of each helium concentration curve, obtaining the helium leakage parameter of the corresponding preset position; Taking any preset part as the target part, taking the average of the differences between the helium leakage parameter of the target part and the helium leakage parameter of each non-target part as the helium leakage deviation of the target part; After adding the preset non-zero positive parameter to the mean of the helium leakage parameters of all non-target parts, a reciprocal operation is performed, the reciprocal is used as the weight of the helium leakage deviation, and the weighted result is used as the leakage risk prominence coefficient of the target part.

2. A method for detecting leaks in a medical cyclotron vacuum chamber according to claim 1, characterized in that: The method for obtaining the helium leakage parameter comprises: The variance of the helium concentration in the helium concentration curve corresponding to each preset position is used as a concentration fluctuation parameter; according to the change trend of the helium concentration curve corresponding to each preset position, a concentration rising trend parameter is obtained; and the product of the concentration fluctuation parameter and the concentration rising trend parameter is used as the helium leakage parameter corresponding to the preset position.

3. A method for detecting leaks in a medical cyclotron vacuum chamber according to claim 2, characterized in that: The method for obtaining the concentration rising trend parameter includes: A concentration parameter sequence and a time parameter sequence are acquired based on each of the helium concentration curves; and a normalized result of the correlation coefficient between the concentration parameter sequence and the time parameter sequence is used as a concentration rising trend parameter.

4. A method for detecting leaks in a medical cyclotron vacuum chamber according to claim 1, characterized in that: The method for obtaining the environmental pollution coefficient includes: According to the difference between the helium concentration before measurement and the helium concentration during measurement at each preset part, and the helium concentration before measurement at each preset part, obtaining the helium residual parameter of each preset part; The reciprocal of the time interval between the start time of the helium leak detection process corresponding to each preset position and the end time of the previous adjacent helium leak detection process is used as a purification failure parameter; The helium residual parameter and the poor purification parameter are integrated to obtain the environmental pollution coefficient of each preset part during the helium leak detection process.

5. A method for detecting leaks in a medical cyclotron vacuum chamber according to claim 4, characterized in that: The method for obtaining the helium residual parameter comprises: The absolute value of the difference between the helium concentration before measurement and the helium concentration during measurement at each preset location is added with a preset non-zero positive parameter as the denominator; the helium concentration before measurement at each preset location is used as the numerator; and the fractional ratio is used as the helium residual parameter.

6. A method for detecting leaks in a medical cyclotron vacuum chamber according to claim 1, characterized in that: The method for obtaining the environmental fluctuation coefficient includes: Taking the variance of the environmental parameters in each of the environmental parameter curves as the fluctuation index of the corresponding environmental parameter curve; fusing the fluctuation indexes of all environmental parameter curves to obtain a composite fluctuation parameter; The product of the environmental parameters at the same time in different environmental parameter curves is used as the environmental composite index at the corresponding time; the average of all the environmental composite indexes at the same time is used as the weight of the composite fluctuation parameter, and the weighted result is used as the environmental fluctuation coefficient.

7. A method for detecting leaks in a medical cyclotron vacuum chamber according to claim 1, characterized in that: The method for obtaining the leak point credibility includes: Using the Euclidean norm of the environmental fluctuation coefficient and the environmental pollution coefficient as environmental interference parameters of the corresponding preset position during the helium leak detection process; The environmental interference parameter is added to a preset minimum non-zero positive parameter and then a reciprocal operation is performed. The reciprocal is used as the weight of the leakage risk prominence coefficient corresponding to the preset location, and the weighted result is used as the leakage point credibility of the corresponding preset location.

8. A method for detecting leaks in a medical cyclotron vacuum chamber according to claim 1, characterized in that: The preset positions at least include each welding position, each connecting position and the valve of the vacuum chamber.

9. A method for detecting leaks in a medical cyclotron vacuum chamber according to claim 1, characterized in that: The environmental impact indicators include at least temperature and humidity.

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