A CNT cold cathode X-ray tube integrated with a panning gauge and a lifetime detection method thereof

Abstract

This application discloses a CNT cold cathode X-ray tube with an integrated Penning gauge and its lifespan detection method, relating to the field of vacuum electronic devices. The tube body is positioned between a first permanent magnet and a second permanent magnet; the X-ray tube anode is positioned on the top surface inside the tube body; the X-ray tube anode is connected to the positive terminal of an external power supply; the X-ray tube cold cathode is positioned on the bottom surface inside the tube body; the X-ray tube cold cathode is connected to the cathode of the external power supply; the Penning gauge anode is positioned on the inner wall in the middle of the tube body; the Penning gauge anode is connected to one end of an external high-voltage isolation measurement circuit; the Penning gauge cathode is positioned at the bottom of the tube body; the Penning gauge cathode is connected to the other end of the external high-voltage isolation measurement circuit. This application integrates a Penning gauge into the original X-ray tube without occupying additional space, thereby enabling accurate monitoring of the vacuum level during X-ray tube operation. Furthermore, it allows for lifespan prediction of the X-ray tube based on the vacuum level, achieving early warning and protection for failed X-ray tubes.

Description

Technical Field

[0001] This application relates to the field of vacuum electronic devices, and in particular to a CNT cold cathode X-ray tube with an integrated Penning gauge and a method for detecting its lifetime. Background Technology

[0002] Carbon nanotube (CNT) cold cathode X-ray tubes, due to their advantages such as room-temperature emission, low power consumption, fast response, and pulse-tunable emission, show broad application prospects in portable medical imaging, industrial non-destructive testing, security inspection, and scientific research. Compared with traditional hot cathode X-ray tubes, CNT cold cathode X-ray tubes do not require high-temperature heating, have a more compact structure, and are easier to miniaturize and integrate. However, X-ray tubes require extremely high internal vacuum levels during operation, typically maintained at [temperature missing]. The following points are relevant: Vacuum degradation can lead to unstable electron emission, anode target sputtering, decreased withstand voltage, and even irreversible failure, severely impacting tube lifespan and operational reliability. Therefore, real-time and accurate monitoring of vacuum levels during X-ray tube operation, and the subsequent assessment of tube health and prediction of remaining lifespan, has become a critical technical requirement for ensuring safe equipment operation. Currently, vacuum level detection largely relies on external, independent vacuum gauges, such as Penning gauges. These external gauges require additional vacuum interfaces and installation space, and measurement delays make it difficult to achieve continuous, in-situ monitoring of the actual operating conditions inside the tube.

[0003] Existing CNT cold cathode X-ray tubes lack internally integrated vacuum monitoring methods. External vacuum gauges not only occupy extra space, but also cannot characterize the dynamic changes in vacuum during tube operation in real time, resulting in the inability to detect vacuum deterioration and issue early warnings of failure in a timely manner. Summary of the Invention

[0004] The purpose of this application is to provide a CNT cold cathode X-ray tube with an integrated Penning gauge and a life detection method thereof. The Penning gauge can be integrated into the original X-ray tube without occupying extra space, so that the vacuum level can be accurately monitored during the operation of the X-ray tube, and the life of the X-ray tube can be predicted based on the vacuum level, so as to realize early warning and protection of the failed X-ray tube.

[0005] To achieve the above objectives, this application provides the following solution: In a first aspect, this application provides a CNT cold cathode X-ray tube with integrated Penning gauge, comprising: an X-ray tube anode, an X-ray tube cold cathode, a Penning gauge anode, a Penning gauge cathode, a tube body, a first permanent magnet, and a second permanent magnet; the tube body is disposed between the first permanent magnet and the second permanent magnet; the first permanent magnet and the second permanent magnet are used to generate a magnetic field perpendicular to the electric field direction along the axis of the tube body; the tube body is a vacuum cavity; the X-ray tube anode is disposed on the top surface inside the tube body; the X-ray tube... The tube anode is connected to the positive terminal of an external power supply; the X-ray tube cold cathode is disposed on the bottom surface inside the tube body; the X-ray tube cold cathode is connected to the cathode of the external power supply; the Penning gauge anode is disposed on the inner wall in the middle of the tube body; the Penning gauge anode is connected to one end of an external high-voltage isolation measurement circuit; the Penning gauge cathode is disposed at the bottom of the tube body; the Penning gauge cathode is connected to the other end of an external high-voltage isolation measurement circuit; the Penning gauge anode and the Penning gauge cathode are used to generate a potential difference by Penning discharge under the action of a magnetic field; the potential difference is used to characterize the vacuum level inside the tube.

[0006] Secondly, this application provides a lifetime prediction method for an integrated Penning gauge CNT cold cathode X-ray tube. This method is applied to the aforementioned integrated Penning gauge CNT cold cathode X-ray tube. The method includes: before power-on, applying a short pulse to the Penning cathode to induce ionization gas discharge; after power-on, controlling the X-ray tube cathode to emit an electron beam that bombards the X-ray tube anode, while simultaneously utilizing the Penning gauge anode and the Penning gauge cathode to induce ionization gas discharge. The ion discharge is self-sustaining under magnetic field confinement, continuously outputting ion current, and ion current monitoring data is obtained. The current pressure is calculated using the ion current monitoring data and a pre-calibrated logarithmic relationship, and the vacuum degree of the integrated Penning gauge CNT cold cathode X-ray tube is output. The vacuum degree change curve is plotted, and an adaptive lifetime prediction model is used to predict the lifetime of the integrated Penning gauge CNT cold cathode X-ray tube, and the lifetime prediction result is obtained. The adaptive lifetime prediction model is constructed based on a machine learning model. When the lifetime prediction result exceeds a threshold, a lifetime over-limit alarm is issued.

[0007] According to the specific embodiments provided in this application, the following technical effects are disclosed: This application integrates a Penning gauge into the existing X-ray tube. This allows for accurate monitoring of the vacuum level during X-ray tube operation, enabling lifespan prediction based on vacuum level, and providing early warning and protection against failed X-ray tubes. Furthermore, this application eliminates the need for an external independent vacuum gauge, saving internal tube space and reducing costs. Attached Figure Description

[0008] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0009] Figure 1 A schematic diagram of the structure of the integrated Penning gauge CNT cold cathode X-ray tube provided in the embodiments of this application.

[0010] Figure 2 A schematic diagram of the bottom structure of the integrated Penning gauge CNT cold cathode X-ray tube provided in the embodiments of this application.

[0011] Figure 3 An enlarged view of the Penning electrode provided in the embodiments of this application.

[0012] Figure 4 A schematic diagram of the structural connection between the integrated Penning gauge CNT cold cathode X-ray tube and the high-voltage isolation measurement circuit provided in the embodiments of this application.

[0013] Figure 5 A schematic flowchart illustrating the life testing method for CNT cold cathode X-ray tubes with integrated Penning gauges provided in this application embodiment.

[0014] Figure 6 A schematic diagram of the pressure-ion current calibration curve provided for an embodiment of this application.

[0015] Figure 7 This is a schematic diagram illustrating the operation flow of the adaptive lifetime prediction model provided in the embodiments of this application.

[0016] Reference numerals in the attached figures: 1. X-ray tube anode; 2. X-ray tube cold cathode; 3. Penning gauge anode; 4. Penning gauge cathode; 5. Tube body; 6. First permanent magnet; 7. Second permanent magnet. Detailed Implementation

[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0018] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] Example 1, as Figures 1-4 As shown, this embodiment provides a CNT cold cathode X-ray tube with integrated Penning gauge, which includes: X-ray tube anode 1, X-ray tube cold cathode 2, Penning gauge anode 3, Penning gauge cathode 4, tube body 5, first permanent magnet 6, and second permanent magnet 7.

[0020] 1) The tube body 5 is disposed between the first permanent magnet 6 and the second permanent magnet 7; the first permanent magnet 6 and the second permanent magnet 7 are used to generate a magnetic field perpendicular to the electric field direction along the axis of the tube body 5; the tube body 5 is a vacuum cavity.

[0021] Optionally, the tube body 5 is a vacuum-sealed tube body 5 (glass or metal shell), using a metal shell with a diameter of 30mm and a length of 150mm, and the interior is kept ≤ after baking, vacuum baking, and evacuation. High vacuum.

[0022] Optionally, both the first permanent magnet 6 and the second permanent magnet 7 are NdFeB permanent magnets, capable of providing an axial magnetic field B≈800Gs. The magnetic field direction is perpendicular to the cathode-anode electric field direction (E⊥B), achieving helical confinement of Penning discharge.

[0023] Furthermore, the magnetic field strength is between 100 Gs and 1000 Gs.

[0024] Optionally, the first permanent magnet 6 and the second permanent magnet 7, as magnetic field generating components, can also be miniature coils.

[0025] Furthermore, both the first permanent magnet 6 and the second permanent magnet 7 are miniature rare-earth magnetic sheets with self-supplied magnetic fields.

[0026] Furthermore, the tube 5 can maintain a state less than or equal to [a certain value] after vacuuming. The vacuum.

[0027] 2) The X-ray tube anode 1 is disposed on the top surface inside the tube body 5; the X-ray tube anode 1 is connected to the positive terminal of an external power supply; the X-ray tube cold cathode 2 is disposed on the bottom surface inside the tube body 5; the X-ray tube cold cathode 2 is connected to the cathode of an external power supply.

[0028] Furthermore, the X-ray tube cold cathode 2 is a vertical array.

[0029] Furthermore, the emitting area of ​​the X-ray tube cold cathode 2 is 5mm × 5mm.

[0030] Optionally, the X-ray tube cold cathode 2 (carbon nanotube cold cathode) serves as the electron emission source, arranged in a vertical array (approximately 2 × 10⁶ tubes) at the left end of the tube body 5. The X-ray tube cold cathode 2 generates an electron beam after being driven by a high voltage (-2.5 kV).

[0031] Optionally, the X-ray tube anode 1 (target material) is arranged opposite to the X-ray tube cold cathode 2.

[0032] 3) The Penning gauge anode 3 is disposed on the inner wall of the middle part of the tube body 5; the Penning gauge anode 3 is connected to one end of the external high-voltage isolation measurement circuit; the Penning gauge cathode 4 is disposed at the bottom of the tube body 5; the Penning gauge cathode 4 is connected to the other end of the external high-voltage isolation measurement circuit; the Penning gauge anode 3 and the Penning gauge cathode 4 are used to generate a potential difference by Penning discharge under the action of a magnetic field; the potential difference is used to characterize the vacuum degree inside the tube.

[0033] Furthermore, the Penning cathode 4 uses the same emission surface as the X-ray tube cold cathode 2, and is provided with a ring of micro-grooves, which are local cathodes for Penning discharge.

[0034] Furthermore, the Penning anode 3 is a ring anode.

[0035] Optionally, the ring anode is coupled in parallel to the low-voltage end of the high-voltage isolation measurement circuit via a 10nF high-voltage capacitor to prevent high-voltage impact on the amplifier. During measurement in the high-voltage isolation measurement circuit, the current signal is converted into voltage by a transimpedance amplifier (TIA) (gain 106V / A), and then sampled by a 12-bit ADC. DSP or FPGA: Reads the ADC data in real time and performs logarithmic conversion to obtain the pressure. Lifetime prediction is performed using real-time embedded algorithms.

[0036] Furthermore, the Penning anode 3 has an annular metal collecting ring (8mm in diameter) welded to the edge of its anode target material, which is electrically isolated from the tube body 5 by an insulating ceramic tube, serving as the ion collecting end.

[0037] Optionally, the Penning cathode 4 is connected to the cold cathode 2 of the X-ray tube or a miniature emission array is arranged on the surface of the cold cathode 2 of the X-ray tube. The Penning cathode 4 is used to emit electrons when a negative high voltage is applied. The Penning cathode 4 is directly connected in parallel with the cold cathode 2 of the X-ray tube, and the same -2.5kV voltage is applied.

[0038] The Penning gauge anode 3 serves as a dedicated collecting electrode for the X-ray tube anode 1, or a separate annular collecting electrode is provided on the anode side. The Penning gauge anode 3 is used to collect positive ions generated by gas ionization.

[0039] In practical applications, such as Figure 4 As shown, the high-voltage isolation measurement circuit mainly consists of the following parts: 1. A high-voltage isolation transformer or capacitive coupling circuit is used to isolate the ion current from the high-voltage anode side to the low-voltage measurement end.

[0040] 2. Current amplification / digital conversion unit, used to convert ion current signals into digital pressure values.

[0041] 3. Control and life prediction unit (CPU, FPGA, or dedicated chip) for real-time pressure reading. ; Calculate the cumulative damage index based on the preset model ;when An alarm signal is generated when the threshold is reached or the pressure changes abruptly; the predicted remaining lifetime L_rem is output.

[0042] In practical applications, the working process of a CNT cold cathode X-ray tube integrated with a Penning gauge is as follows: Before startup, a short pulse (3kV amplitude, 100μs width) is applied to the Penning cathode to help ignite the ionized gas and cause a discharge. Simultaneously with the emission of the electron beam from the X-ray tube, the Penning discharge is self-sustaining under magnetic field confinement, and the ion current I+ is continuously output. Sampling is performed every 0.1s, and calculations are performed... And update the cumulative damage index .like Exceeding the set threshold (e.g., > (Immediately issue an alarm signal and shut off the high voltage of the X-ray tube.)

[0043] Example 2, as Figures 5-7 As shown, this embodiment also provides a lifetime prediction method for CNT cold cathode X-ray tubes with integrated Penning gauges. The lifetime prediction method for CNT cold cathode X-ray tubes with integrated Penning gauges is applied to the aforementioned CNT cold cathode X-ray tubes with integrated Penning gauges. The lifetime prediction method for CNT cold cathode X-ray tubes with integrated Penning gauges includes: S1. Before energizing, apply a short pulse to the Penning cathode to ignite and discharge the ionized gas.

[0044] S2. After power is applied, the electron beam emitted from the cathode of the X-ray tube is controlled to bombard the anode 1 of the X-ray tube. At the same time, the Penning gauge anode 3 and the Penning gauge cathode 4 are used to perform Penning discharge. Under the constraint of the magnetic field, the discharge is maintained by itself and the ion current is continuously output to obtain the monitoring data of the ion current.

[0045] S3. For example Figure 6 As shown, the current pressure is calculated using the monitoring data of the ion current and the pre-calibrated logarithmic relationship, and the vacuum level of the integrated Penning gauge CNT cold cathode X-ray tube is output.

[0046] The pre-defined logarithmic relation is expressed as follows: .

[0047] in, It is the ion current; Due to current pressure.

[0048] S4. Plot the vacuum degree change curve and use the adaptive lifetime prediction model to predict the lifetime of the integrated Penning gauge CNT cold cathode X-ray tube to obtain the lifetime prediction result; the adaptive lifetime prediction model is constructed based on the machine learning model.

[0049] Optional, such as Figure 7 As shown, the prediction process of the adaptive lifetime prediction model is as follows: The vacuum degradation rate is determined to have an exponential relationship with the current pressure: .

[0050] Where D is the cumulative damage index, , This is the experimental calibration constant.

[0051] Temperature correction: Combined with cathode temperature monitoring of cold cathode X-ray tubes Introducing a correction factor : .

[0052] Set a failure threshold D_fail. When D(t) ≥ D_fail, the tube is considered to have entered the aging period, and the remaining lifetime is output: .

[0053] Collected during operation Actual pressure Calibration data is updated using the least squares method. Parameters are used to complete adaptive learning and improve prediction accuracy.

[0054] In practical applications, after long-term operation (>2000h), a machine learning method (recursive least squares) is used to regress the actual failure data (pipe replacement records, pressure at failure) against the measured I+, yielding the results. Parameters. The model can be updated to ensure that the lifetime prediction always reflects the latest tube aging status.

[0055] 1. Regression model construction.

[0056] The core of constructing a regression model is to establish the aging characteristics and lifespan parameters of the pipe. The mapping relationship needs to be established. Dynamic and static features need to be extracted from multi-source data, covering historical states, current states, and physical constraints, specifically including the following dimensions: time dimension, pressure dimension, measurement dimension, and state identifier. These features are integrated through multi-source data fusion (such as tube replacement records, failure pressure, and real-time ion current) to ensure that the model can reflect both cumulative damage and respond to sudden changes.

[0057] 2. The form of the regression model.

[0058] The regression model employs a hybrid approach combining physical mechanisms and data-driven methods to accommodate nonlinear aging processes. Basic lifetime model: Based on the power-law degradation model, assuming cumulative damage. satisfy: .

[0059] For real-time pressure, The cathode temperature, The parameter to be calibrated. When When the preset failure threshold is reached, the tube is determined to be faulty.

[0060] Parameter association framework: for linking parameters Associated with input features, using multiple linear regression: .

[0061] in, For the above input features (such as t, , wait), For regression coefficients, This represents the noise term. This form is fitted using the least squares method to ensure that the parameters are dynamically adjusted according to the aging data.

[0062] 3. Parameter update process.

[0063] The parameter update uses the Recursive Least Squares (RLS) algorithm to achieve online adaptive learning. The process is divided into two stages: initialization and iterative update. Initialization phase: Set the initial regression coefficient vector (Can be based on prior knowledge or random assignment).

[0064] Initialize the inverse covariance matrix P0 = ( Take the larger value, such as 10 3 (where I is the identity matrix).

[0065] Setting a forgetting factor (Values ​​range from 0.95 to 0.99, balancing the weights of historical and new data).

[0066] Iterative update (triggering condition: pipe failure or periodic collection of new data): Step 1: Construct input-output pairs. Extract the feature vector x(t) at the current time step, and output the parameter error. .

[0067] Step 2: Calculate the gain vector: .

[0068] Step 3: Update regression coefficients: .

[0069] Step 4: Update the inverse covariance matrix: .

[0070] Update cycle: every ΔT (e.g., 100 hours) or triggered by a failure event to ensure the model's real-time performance.

[0071] Termination occurs when equipment is decommissioned or requires manual intervention. This is achieved through feature normalization and... Optimize the model to enhance its robustness to operating condition fluctuations (such as sudden pressure changes); normalize it to Z-score normalization.

[0072] S5. When the life prediction result exceeds the threshold, issue a life limit over-limit alarm.

[0073] The technical effects of this application are as follows: This application integrates a Penning gauge into the original X-ray tube without occupying additional space, enabling real-time detection of vacuum leaks. The cold cathode structure and magnetic field confinement suppress gas re-adsorption, reducing maintenance frequency. Cumulative damage modeling allows for quantitative assessment of the remaining X-ray tube lifespan and early warning. Alarm signals can directly drive power shutdown or reduced-voltage operation, preventing catastrophic failures such as cathode sputtering and anode breakdown, thus improving safety and reliability. This application does not affect the geometry of the X-ray beam at all; it uses fiber optic transmission of ion current signals to achieve full electrical isolation; and pressure synchronization with the main cavity is compensated for through a calibration factor.

[0074] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0075] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A CNT cold cathode X-ray tube with integrated Penning gauge, characterized in that, The integrated Penning gauge CNT cold cathode X-ray tube includes: an X-ray tube anode, an X-ray tube cold cathode, a Penning gauge anode, a Penning gauge cathode, a tube body, a first permanent magnet, and a second permanent magnet; The tube is disposed between the first permanent magnet and the second permanent magnet; the first permanent magnet and the second permanent magnet are used to generate a magnetic field perpendicular to the electric field direction along the axis of the tube; the tube is a vacuum cavity; The X-ray tube anode is disposed on the top surface inside the tube body; the X-ray tube anode is connected to the positive terminal of an external power supply; the X-ray tube cold cathode is disposed on the bottom surface inside the tube body; the X-ray tube cold cathode is connected to the cathode of an external power supply. The Penning gauge anode is disposed on the inner wall of the middle part of the tube body; the Penning gauge anode is connected to one end of the external high-voltage isolation measurement circuit; the Penning gauge cathode is disposed at the bottom of the tube body; the Penning gauge cathode is connected to the other end of the external high-voltage isolation measurement circuit; the Penning gauge anode and the Penning gauge cathode are used to generate a potential difference by Penning discharge under the action of a magnetic field; the potential difference is used to characterize the vacuum degree inside the tube.

2. The integrated Penning gauge CNT cold cathode X-ray tube according to claim 1, characterized in that, The cold cathode of the X-ray tube is arranged in a vertical array.

3. The integrated Penning gauge CNT cold cathode X-ray tube according to claim 1, characterized in that, The emitting area of ​​the cold cathode of the X-ray tube is 5mm × 5mm.

4. The integrated Penning gauge CNT cold cathode X-ray tube according to claim 1, characterized in that, The Penning cathode uses the same emission surface as the cold cathode of the X-ray tube, and is provided with an additional ring of micro-grooves, which are local cathodes for Penning discharge.

5. The integrated Penning gauge CNT cold cathode X-ray tube according to claim 1, characterized in that, The Penning gauge anode is a ring anode.

6. The integrated Penning gauge CNT cold cathode X-ray tube according to claim 1, characterized in that, The Penning anode has an annular metal collecting ring welded to the edge of its anode target material, which is electrically isolated from the tube body by an insulating ceramic tube, serving as the ion collecting end.

7. The integrated Penning gauge CNT cold cathode X-ray tube according to claim 1, characterized in that, The magnetic field strength is between 100 Gs and 1000 Gs.

8. The integrated Penning gauge CNT cold cathode X-ray tube according to claim 1, characterized in that, Both the first permanent magnet and the second permanent magnet are miniature rare-earth magnetic sheets with self-supplied magnetic fields.

9. The integrated Penning gauge CNT cold cathode X-ray tube according to claim 1, characterized in that, The tube body can maintain a value less than or equal to 1 after vacuuming. The vacuum.

10. A method for predicting the lifetime of an integrated Penning gauge CNT cold cathode X-ray tube, wherein the method for predicting the lifetime of an integrated Penning gauge CNT cold cathode X-ray tube is applied to the integrated Penning gauge CNT cold cathode X-ray tube according to any one of claims 1-9, characterized in that, The lifetime prediction method for the integrated Penning gauge CNT cold cathode X-ray tube includes: Before energizing, a short pulse is applied to the Penning cathode to ignite and discharge the ionized gas. After being powered on, the cathode of the X-ray tube emits an electron beam to bombard the anode of the X-ray tube. At the same time, the Penning gauge anode and the Penning gauge cathode are used to perform Penning discharge, which is maintained by itself under the confinement of the magnetic field and continuously outputs ion current, thus obtaining monitoring data of ion current. The current pressure is calculated using the monitoring data of the ion current and the pre-calibrated logarithmic relationship, and the vacuum level of the integrated Penning gauge CNT cold cathode X-ray tube is output. A vacuum degree variation curve was plotted, and an adaptive lifetime prediction model was used to predict the lifetime of the integrated Penning gauge CNT cold cathode X-ray tube, and the lifetime prediction results were obtained; the adaptive lifetime prediction model was constructed based on a machine learning model. When the lifespan prediction result exceeds the threshold, a lifespan over-limit alarm is issued.

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