A stable and controllable heating method for hot cathode

Abstract

The present invention discloses a stable and controllable heating method for a hot cathode, which relates to the field of hot cathode electron emission technology and includes the following steps: S1, signal acquisition and processing; S2, signal conversion; S3, negative feedback workflow; S4, acquisition of electrical data across the hot cathode load; S5, constant temperature mode adjustment; S6, constant current mode adjustment. Based on a negative feedback circuit consisting of a triode, an amplifier, and a feedback resistor, the present invention achieves stable and precise control of the cathode heating current and heating temperature. The heating power supply can maintain high precision and stability under different load resistance values, solving the accuracy and real-time control issues existing in traditional designs. Furthermore, the present invention has the advantage of being easily controlled by a computer, providing users with greater operational flexibility and improving work efficiency and operational convenience.

Description

Technical Field

[0001] The present invention relates to the technical field of hot cathode electron emission, in particular to a stable and controllable heating method for a hot cathode. Background Art

[0002] As an important electron source, hot cathode is commonly used in various electron source devices and systems such as electron guns, vacuum tubes, X-ray tubes and emission probes. Among all hot cathode materials, refractory metal wires such as tungsten wire and rhenium wire are the most common and widely used materials. A very important problem in the practical application of this pure metal hot cathode is that it is usually accompanied by high thermal evaporation loss during operation, which leads to changes in hot cathode parameters such as hot cathode resistance, heating temperature and electron emission current. In almost all electron source components with hot cathode as the core, there are usually very high requirements for the stability of electron emission. According to Rich From the Jardson-Dushman formula, it can be seen that the main factor affecting the hot cathode electron emission current is the heating temperature of the hot cathode. Therefore, it is of great significance to achieve stable control of the hot cathode heating temperature. In addition, in the use of emission probes made of ultra-fine hot cathode filaments (diameter is usually in the micron level), special attention is paid to the stable control of the heating current and heating temperature of the hot cathode. Different emission probe measurement methods almost all require that the heating current or heating temperature of the filament is maintained unchanged. Therefore, in the use of emission probe devices, the research and development of a power supply that can achieve stable and controllable heating current output is an indispensable link.

[0003] There have been many studies on controlling the heating current of the hot cathode by adopting different negative feedback principles. One traditional method is to use analog technology to drive the hot cathode controller, but this has many limitations. It is not accurate enough, difficult to adjust and calibrate, and does not support computer interface. Another solution is to use a personal computer, commercial digital-to-analog converter, analog-to-digital converter and programmable power supply, but this method is expensive, bulky and has a slow response speed. Summary of the Invention

[0004] The object of the present invention is to provide a stable and controllable heating method for a hot cathode to solve the problems raised in the above background technology.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for stable and controllable heating of a hot cathode, comprising a core controller module, a DAC module, a negative feedback current control module, and a voltage / current acquisition module, the method comprising the following steps:

[0006] S1. Signal acquisition and processing: The core controller module receives the control instruction and transmits the instruction to the DAC module, and transmits the voltage signal and heating current signal collected on the hot cathode load R1 to the ADC module. The ADC module converts the analog signal into a digital signal and displays it in real time on the LCD screen. At the same time, the core controller module processes the collected voltage signal and heating current signal.

[0007] S2, signal conversion: The DAC module converts the digital signal processed and output by the core controller module into a continuous analog voltage or analog current signal;

[0008] S3, negative feedback workflow: the signal input terminal U of the negative feedback current control module i Connected to the output end of the DAC module, the signal output by the DAC module is converted into the heating current of the hot cathode load R1. The signal output end of the negative feedback current control module is the signal collection point for monitoring the working status of the hot cathode load R1.

[0009] S4. Collecting electrical data at both ends of the hot cathode load: The voltage / current acquisition module uses an in-phase proportional operation circuit to read the voltage at both ends of the hot cathode load R1 and collect the heating current of the hot cathode;

[0010] S5, constant temperature mode adjustment: compare the set hot cathode heating temperature and the real-time temperature of the hot cathode, and continuously monitor the state of the hot cathode and adjust the output voltage until the real-time temperature of the hot cathode is the same as the set hot cathode heating temperature, and finally output the hot cathode heating temperature. This value is used to monitor the working state of the hot cathode and ensure that the hot cathode operates stably at the set temperature;

[0011] S6. Constant current mode adjustment: The core controller module monitors and collects the hot cathode heating current in real time through the voltage / current acquisition module, and compares it with the set hot cathode heating current. By adjusting the voltage, the real-time hot cathode heating current and the set hot cathode heating current are kept at the same value, and finally the hot cathode is maintained in the set working state.

[0012] Preferably, in step S1, the core controller module communicates with the external device via a USB interface;

[0013] In step S2, the DAC module converts the digital signal into a continuous analog voltage or analog current signal.

[0014] Preferably, in step S3, the negative feedback current control module is composed of an amplifier, a transistor and a feedback resistor R2. The signal processed by the amplifier is input to the base of the transistor. The collector of the transistor is connected to the hot cathode load R1. The emitter of the transistor is connected to the feedback resistor R2. The signal input terminal U iConnected to the output end of the DAC module, the data output by the DAC module is converted into the heating current of the hot cathode load R1. The two signal output ends at the collector and emitter of the transistor are the first output end U o1 and the second output terminal U o2 , as the signal collection point for monitoring the working status of the hot cathode load R1, the two input terminals of the amplifier include the input terminal U i And the second output terminal U connected to the emitter of the transistor o2 When the transistor is in the on state, the emitter current of the transistor is supplied by the input terminal U i The ratio of the feedback resistor R2 is determined by changing the input terminal U i By changing the current flowing through the feedback resistor R2, the heating current of the hot cathode load R1 changes accordingly.

[0015] Preferably, in step S4, the voltage / current acquisition module uses an in-phase proportional operation circuit to input the signal to the signal input terminal U i With the first output terminal U o1 Connect to read the voltage across the hot cathode load R1 and input the signal to the U i With the second output terminal U o2 The core controller module calculates the heating current flowing through the hot cathode load R1 by reading the voltage across the feedback resistor R2.

[0016] Preferably, step S5 includes the following steps:

[0017] S501, input the set hot cathode heating temperature;

[0018] S502, then outputting a voltage signal through the DAC module to heat the hot cathode, and monitoring the current state of the hot cathode by collecting the heating current and heating voltage;

[0019] S503. Check the relationship between the emissivity and heating temperature of the hot cathode material, obtain the corresponding emissivity according to the set cathode heating temperature, calculate the real-time temperature of the hot cathode using the collected heating current, heating voltage and emissivity through the Stefan-Boltzmann law, then compare the set hot cathode heating temperature and the real-time temperature of the hot cathode, and continuously monitor the status of the hot cathode and adjust the output voltage of the DAC module.

[0020] Preferably, the step S5 further includes the following steps:

[0021] S504: if the set hot cathode heating temperature is lower than the real-time temperature of the hot cathode, increase the output voltage to heat the hot cathode;

[0022] S505: If the set hot cathode heating temperature is greater than the real-time temperature of the hot cathode, reduce the output voltage to lower the temperature;

[0023] S506: If the set hot cathode heating temperature is equal to the real-time temperature of the hot cathode, maintain the current output voltage.

[0024] Preferably, step S6 includes the following steps:

[0025] S601, input the set hot cathode heating current;

[0026] S602, the core controller module controls the DAC module to output an initial voltage signal to obtain a real-time hot cathode heating current;

[0027] S603 , the core controller module compares the real-time hot cathode heating current with the set hot cathode heating current, and dynamically adjusts the output voltage of the DAC module.

[0028] Preferably, the step S6 further includes the following steps:

[0029] S604: If the real-time hot cathode heating current is less than the set hot cathode heating current, the output voltage is automatically increased to increase the current;

[0030] S605: If the real-time hot cathode heating current is greater than the set hot cathode heating current, the output voltage is automatically reduced to lower the current;

[0031] S606: If the real-time hot cathode heating current is equal to the set hot cathode heating current, maintain the current output voltage.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The negative feedback circuit composed of a triode, an amplifier and a feedback resistor is used in the present invention to achieve steady and precise control of the hot cathode heating current and heating temperature. The heating power supply can maintain high precision and stability under different load resistance values. The fluctuation value of the heating temperature is less than 0.1% of the set value, and the fluctuation value of the heating current is less than 0.2% of the set value, which solves the accuracy and real-time control problems existing in traditional designs. In addition, the design of the present invention has the advantage of being easy to implement computer-side control, providing users with greater operational flexibility, improving work efficiency and convenience.

[0034] 2. The present invention automatically realizes stable control of hot cathode heating current and heating temperature through the software program on the external computer. The entire control process and user experience are convenient and efficient.

[0035] 3. The present invention is not only applicable to filamentous hot cathodes and pure metal hot cathodes, but also to hot cathodes of other shapes and materials, and has wide applicability;

[0036] 4. The present invention can automatically calculate the hot cathode heating temperature based on the hot cathode heating current and heating voltage collected in real time. Therefore, the present invention is not only suitable for places where the hot cathode heating temperature can be directly measured, but also suitable for many places where direct measurement of the hot cathode heating temperature cannot be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A schematic diagram of the overall method flow provided by an embodiment of the present invention;

[0038] Figure 2 A schematic flow chart of a method for adjusting a constant temperature mode according to an embodiment of the present invention;

[0039] Figure 3 A flow chart of a method for regulating constant current mode provided by an embodiment of the present invention;

[0040] Figure 4 A flowchart of the constant temperature mode software provided by an embodiment of the present invention;

[0041] Figure 5 A flowchart of the constant current mode software provided by an embodiment of the present invention;

[0042] Figure 6 A schematic diagram of the hardware structure of a steady-state heating power supply provided in an embodiment of the present invention;

[0043] Figure 7 A schematic diagram of a negative feedback output circuit in a constant heating power supply provided by an embodiment of the present invention;

[0044] Figure 8 A schematic diagram of a unidirectional proportional operation circuit in a steady-state heating power supply provided by an embodiment of the present invention;

[0045] Figure 9 A schematic diagram of the test results of the heating temperature output of the heating power supply provided by an embodiment of the present invention under different load resistances;

[0046] Figure 10 This is a schematic diagram of the heating current output test results of the heating power supply provided by an embodiment of the present invention under different load resistances. DETAILED DESCRIPTION

[0047] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0048] See also Figures 1 to 10 The present invention provides a technical solution: a method for stable and controllable heating of a hot cathode, comprising a core controller module, a DAC module, a negative feedback current control module, and a voltage / current acquisition module. The method comprises the following steps:

[0049] S1. Signal acquisition and processing: The core controller module receives the control instruction and transmits the instruction to the DAC module, and transmits the voltage signal and heating current signal collected on the hot cathode load R1 to the ADC module. The ADC module converts the analog signal into a digital signal and displays it in real time on the LCD screen. At the same time, the core controller module processes the collected voltage signal and heating current signal.

[0050] S2, signal conversion: The DAC module converts the digital signal processed and output by the core controller module into a continuous analog voltage or analog current signal;

[0051] S3, negative feedback workflow: the signal input terminal U of the negative feedback current control module i Connected to the output end of the DAC module, the signal output by the DAC module is converted into the heating current of the hot cathode load R1. The signal output end of the negative feedback current control module is the signal collection point for monitoring the working status of the hot cathode load R1.

[0052] S4. Collecting electrical data at both ends of the hot cathode load: The voltage / current acquisition module uses an in-phase proportional operation circuit to read the voltage at both ends of the hot cathode load R1 and collect the heating current of the hot cathode;

[0053] S5, constant temperature mode adjustment: compare the set hot cathode heating temperature and the real-time temperature of the hot cathode, and continuously monitor the state of the hot cathode and adjust the output voltage until the real-time temperature of the hot cathode is the same as the set hot cathode heating temperature, and finally output the hot cathode heating temperature. This value is used to monitor the working state of the hot cathode and ensure that the hot cathode operates stably at the set temperature;

[0054] S6. Constant current mode adjustment: The core controller module monitors and collects the hot cathode heating current in real time through the voltage / current acquisition module, and compares it with the set hot cathode heating current. By adjusting the voltage, the real-time hot cathode heating current and the set hot cathode heating current are kept at the same value, and finally the hot cathode is maintained in the set working state.

[0055] In step S1, the core controller module communicates with the external device via the USB interface;

[0056] In step S2, the DAC module converts the digital signal into a continuous analog voltage or analog current signal;

[0057] In step S3, the negative feedback current control module is composed of an amplifier, a transistor and a feedback resistor R2. The signal processed by the amplifier is input to the base of the transistor. The collector of the transistor is connected to the hot cathode load R1. The emitter of the transistor is connected to the feedback resistor R2. The signal input terminal U i Connected to the output end of the DAC module, the data output by the DAC module is converted into the heating current of the hot cathode load R1. The two signal output ends at the collector and emitter of the transistor are the first output end U o1 and the second output terminal U o2 , as the signal collection point for monitoring the working status of the hot cathode load R1, the two input terminals of the amplifier include the input terminal U i And the second output terminal U connected to the emitter of the transistor o2 When the transistor is in the on state, the emitter current of the transistor is supplied by the input terminal U i The ratio of the feedback resistor R2 is determined by changing the input terminal U i By changing the current flowing through the feedback resistor R2, the heating current of the hot cathode load R1 changes accordingly;

[0058] In step S4, the voltage / current acquisition module uses an in-phase proportional operation circuit to input the signal to the U i With the first output terminal U o1 Connect to read the voltage across the hot cathode load R1 and input the signal to the U i With the second output terminal U o2 The core controller module calculates the heating current flowing through the hot cathode load R1 by reading the voltage across the feedback resistor R2.

[0059] Step S5 includes the following steps:

[0060] S501, input the set hot cathode heating temperature;

[0061] S502, then outputting a voltage signal through the DAC module to heat the hot cathode, and monitoring the current state of the hot cathode by collecting the heating current and heating voltage;

[0062] S503. Query the relationship between the emissivity and heating temperature of the hot cathode material, obtain the corresponding emissivity based on the set cathode heating temperature, calculate the real-time temperature of the hot cathode using the collected heating current, heating voltage, and emissivity according to the Stefan-Boltzmann law, then compare the set hot cathode heating temperature with the real-time temperature of the hot cathode, continuously monitor the status of the hot cathode, and adjust the output voltage of the DAC module;

[0063] The calculation formula using the Stefan-Boltzmann law is:

[0064] U ht I ht =SξσT 4

[0065] Where U ht is the heating voltage of the hot cathode, I ht is the heating current of the hot cathode, S is the total surface area of ​​the hot cathode, ξ is the emissivity, and σ is the Stefan-Boltzmann constant, which is equal to 5.67*10 -8 Wm -2 K -4 , T is the operating temperature of the hot cathode;

[0066] Step S5 further includes the following steps:

[0067] S504: if the set hot cathode heating temperature is lower than the real-time temperature of the hot cathode, increase the output voltage to heat the hot cathode;

[0068] S505: If the set hot cathode heating temperature is greater than the real-time temperature of the hot cathode, reduce the output voltage to lower the temperature;

[0069] S506: If the set hot cathode heating temperature is equal to the real-time temperature of the hot cathode, maintain the current output voltage;

[0070] The constant temperature mode adjustment is applicable to electron source equipment where the relationship between the hot cathode and the heating temperature is known and the heating temperature cannot be directly measured. When the heating temperature of the hot cathode can be directly measured, the set temperature can be directly compared with the real-time temperature to control the heating current of the hot cathode.

[0071] As the resistance of the filament load increases, the filament load resistance shows a good step-like increasing trend. The temperature also jumps after the resistance jumps, but quickly returns to the set value. The circuit responds quickly and has a small delay. When the circuit is working stably, the filament operating temperature hardly changes over time. In the test, the temperature fluctuation was less than 0.1% of the temperature setting value, demonstrating the high precision and reliability of the stable and controllable heating power supply output temperature.

[0072] Step S6 includes the following steps:

[0073] S601, input the set hot cathode heating current;

[0074] S602, the core controller module controls the DAC module to output an initial voltage signal to obtain a real-time hot cathode heating current;

[0075] S603, the core controller module compares the real-time hot cathode heating current with the set hot cathode heating current, and dynamically adjusts the output voltage of the DAC module;

[0076] Step S6 further includes the following steps:

[0077] S604: If the real-time hot cathode heating current is less than the set hot cathode heating current, the output voltage is automatically increased to increase the current;

[0078] S605: If the real-time hot cathode heating current is greater than the set hot cathode heating current, the output voltage is automatically reduced to lower the current;

[0079] S606: If the real-time hot cathode heating current is equal to the set hot cathode heating current, maintain the current output voltage;

[0080] As the resistance of the filament load increases, the voltage across the filament load shows a nice step-like increasing trend. The circuit responds quickly and has little delay. When the circuit is working stably, the filament voltage hardly changes over time. In addition, changes in the filament load resistance do not change the measured heating current of the filament. In the test, the current fluctuation was less than 0.2% of the current setting value, demonstrating the high precision and reliability of the output current of the stable and controllable heating power supply.

[0081] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0082] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for stable and controllable heating of a hot cathode, comprising a core controller module, a DAC module, a negative feedback current control module, and a voltage / current acquisition module, characterized in that: The method comprises the following steps: S1. Signal acquisition and processing: The core controller module receives the control instruction and transmits the instruction to the DAC module, and transmits the voltage signal and heating current signal collected on the hot cathode load R1 to the ADC module. The ADC module converts the analog signal into a digital signal and displays it in real time on the LCD screen. At the same time, the core controller module processes the collected voltage signal and heating current signal. S2, signal conversion: The DAC module converts the digital signal processed and output by the core controller module into a continuous analog voltage or analog current signal; S3, negative feedback workflow: the signal input terminal U of the negative feedback current control module i Connected to the output end of the DAC module, the signal output by the DAC module is converted into the heating current of the hot cathode load R1. The signal output end of the negative feedback current control module is the signal collection point for monitoring the working status of the hot cathode load R1. S4. Collecting electrical data at both ends of the hot cathode load: The voltage / current acquisition module uses an in-phase proportional operation circuit to read the voltage at both ends of the hot cathode load R1 and collect the heating current of the hot cathode; S5, constant temperature mode adjustment: compare the set hot cathode heating temperature and the real-time temperature of the hot cathode, and continuously monitor the state of the hot cathode and adjust the output voltage until the real-time temperature of the hot cathode is the same as the set hot cathode heating temperature, and finally output the hot cathode heating temperature. This value is used to monitor the working state of the hot cathode and ensure that the hot cathode operates stably at the set temperature; S6. Constant current mode adjustment: The core controller module monitors and collects the hot cathode heating current in real time through the voltage / current acquisition module, and compares it with the set hot cathode heating current. By adjusting the voltage, the real-time hot cathode heating current and the set hot cathode heating current are kept at the same value, and finally the hot cathode is maintained in the set working state.

2. A method for controlling the heating of a hot cathode according to claim 1, characterized in that: In step S1, the core controller module communicates with the external device via the USB interface; In step S2, the DAC module converts the digital signal into a continuous analog voltage or analog current signal.

3. The method for a stable and controllable heating of a hot cathode according to claim 1, characterized in that: In step S3, the negative feedback current control module is composed of an amplifier, a transistor and a feedback resistor R2. The signal processed by the amplifier is input to the base of the transistor. The collector of the transistor is connected to the hot cathode load R1. The emitter of the transistor is connected to the feedback resistor R2. The signal input terminal U i Connected to the output end of the DAC module, the data output by the DAC module is converted into the heating current of the hot cathode load R1. The two signal output ends at the collector and emitter of the transistor are the first output end U o1 and the second output terminal U o2 , as the signal collection point for monitoring the working status of the hot cathode load R1, the two input terminals of the amplifier include the input terminal U i And the second output terminal U connected to the emitter of the transistor o2 When the transistor is in the on state, the emitter current of the transistor is supplied by the input terminal U i The ratio of the feedback resistor R2 is determined by changing the input terminal U i By changing the current flowing through the feedback resistor R2, the heating current of the hot cathode load R1 changes accordingly.

4. The method for a stable and controllable heating of a hot cathode according to claim 1, characterized in that: In step S4, the voltage / current acquisition module uses an in-phase proportional operation circuit to input the signal to the signal input terminal U i With the first output terminal U o1 Connect to read the voltage across the hot cathode load R1 and input the signal to the U i With the second output terminal U o2 The core controller module calculates the heating current flowing through the hot cathode load R1 by reading the voltage across the feedback resistor R2.

5. The method for a stable and controllable heating of a hot cathode according to claim 1, characterized in that: The step S5 comprises the following steps: S501, input the set hot cathode heating temperature; S502, then outputting a voltage signal through the DAC module to heat the hot cathode, and monitoring the current state of the hot cathode by collecting the heating current and heating voltage; S503. Check the relationship between the emissivity and heating temperature of the hot cathode material, obtain the corresponding emissivity according to the set cathode heating temperature, calculate the real-time temperature of the hot cathode using the collected heating current, heating voltage and emissivity through the Stefan-Boltzmann law, then compare the set hot cathode heating temperature and the real-time temperature of the hot cathode, and continuously monitor the status of the hot cathode and adjust the output voltage of the DAC module.

6. The method for a stable and controllable heating of a hot cathode according to claim 5, characterized in that: The step S5 further comprises the following steps: S504: if the set hot cathode heating temperature is lower than the real-time temperature of the hot cathode, increase the output voltage to heat the hot cathode; S505: If the set hot cathode heating temperature is greater than the real-time temperature of the hot cathode, reduce the output voltage to lower the temperature; S506: If the set hot cathode heating temperature is equal to the real-time temperature of the hot cathode, maintain the current output voltage.

7. The method for a stable and controllable heating of a hot cathode according to claim 1, characterized in that: The step S6 comprises the following steps: S601, input the set hot cathode heating current; S602, the core controller module controls the DAC module to output an initial voltage signal to obtain a real-time hot cathode heating current; S603 , the core controller module compares the real-time hot cathode heating current with the set hot cathode heating current, and dynamically adjusts the output voltage of the DAC module.

8. The method for a stable and controllable heating of a hot cathode according to claim 7, characterized in that: The step S6 further comprises the following steps: S604: If the real-time hot cathode heating current is less than the set hot cathode heating current, the output voltage is automatically increased to increase the current; S605: If the real-time hot cathode heating current is greater than the set hot cathode heating current, the output voltage is automatically reduced to lower the current; S606: If the real-time hot cathode heating current is equal to the set hot cathode heating current, maintain the current output voltage.

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