Ionization vacuum degree measurement method and device based on light intensity modulation

Abstract

The application belongs to the technical field of vacuum measurement, and specifically discloses an ionization vacuum degree measurement method and device based on light intensity modulation. The light intensity of ultraviolet light is modulated by a modulator, and the measured ion current signal is filtered and demodulated to obtain an optimized ion current signal. The combination of the two greatly improves the signal-to-noise ratio of the system, effectively reduces the interference of environmental noise on the measurement results, and significantly improves the accuracy and reliability of the ionization vacuum gauge in measuring the vacuum degree. In addition, the application can dynamically adjust the light intensity fluctuation frequency according to different vacuum degree measurement scene requirements to obtain appropriate photoelectric current. Whether in a low vacuum or a high vacuum environment, accurate measurement can be achieved, and the application scene range is widened.

Description

Technical Field

[0001] This application belongs to the field of vacuum measurement technology, and more specifically, relates to a method and apparatus for measuring ionization vacuum degree based on light intensity modulation. Background Technology

[0002] In modern science and technology and industrial production, the accurate measurement of vacuum environments is crucial. Ionization vacuum gauges based on the photoelectric effect are important instruments for measuring vacuum levels in numerous scientific research and industrial production fields. Their working principle involves using a photoelectric emitting electrode to emit electrons under light irradiation. These electrons collide with gas molecules in the ionization chamber, ionizing them. The ion flow signal is then measured through an ion collecting electrode and converted into an electrical signal to reflect the vacuum level.

[0003] However, in practical applications, photoelectric ionization vacuum gauges face a significant technical challenge: a low signal-to-noise ratio. This is due, in part, to the small photocurrent generated. The magnitude of the photocurrent depends on several factors, including the light source intensity and the quantum yield of the photoemitting electrode material. In many cases, due to limitations in light source power or the inherent characteristics of the photoemitting electrode material, the generated photocurrent is often at a low level. Furthermore, various noise currents exist in the actual measurement environment, interfering with the ion current signal measured by the ion collecting electrode. When the ion current signal is small, it is easily overwhelmed by environmental noise currents. This situation leads to a significant reduction in the accuracy and reliability of the ionization vacuum gauge's measurement results.

[0004] Currently, to address the low signal-to-noise ratio of photoelectric ionization vacuum gauge systems, some methods focus on improving the photocurrent by modifying the photoemitting electrode material. However, limited by material development costs and technological bottlenecks, the improvement effect is not ideal. Other methods attempt to suppress noise through circuit design, but in complex real-world environments, it is difficult to completely eliminate the influence of noise on the ion current signal. All these methods have limitations. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this application is to provide a method and apparatus for measuring ionization vacuum degree based on light intensity modulation, aiming to solve the problem of low signal-to-noise ratio in existing photoelectric effect ionization vacuum meter systems.

[0006] The first aspect of this application relates to an ionization vacuum degree measuring device based on light intensity modulation, the measuring device comprising:

[0007] The probe has a semi-enclosed cavity structure with an interface for the gas to be measured to enter. Inside the cavity, there are a photoelectric emitting plate, an anode plate, and an ion collecting plate arranged in sequence. The three are connected to a first potential, a second potential, and a third potential, respectively, with the second potential > the first potential > the third potential, so as to form an accelerating electric field and a collecting electric field.

[0008] An ultraviolet light source is used to emit ultraviolet light and irradiate a photoelectrode, causing it to release electrons through the photoelectric effect.

[0009] A modulator is used to modulate the intensity of emitted ultraviolet light, causing it to oscillate in a cosine wave form.

[0010] The processing unit is used to perform bandpass filtering and demodulation on the ion current on the ion collecting electrode. The center frequency of the bandpass filter is the same as the angular frequency of the modulated cosine wave to obtain an optimized ion current signal. The ion current signal and the ambient temperature are combined to calculate the ionization vacuum degree.

[0011] In some embodiments, it also includes a current measuring component for measuring the ion current on the ion collecting plate and sending it to the processing unit.

[0012] In some embodiments, it also includes a temperature measurement component for measuring the ambient temperature inside the probe cavity and sending it to the processing unit.

[0013] In some implementations, the ultraviolet light source and the modulator are independent devices or integrated into one unit.

[0014] In some embodiments, the intensity of the light modulated by the modulator is ,in, This represents the maximum light intensity of the ultraviolet light source. This is the center frequency of the bandpass filter.

[0015] In some implementations, the processing unit performs filtering using an ultra-narrow bandpass filter, whose response function... as follows:

[0016]

[0017] in, The imaginary unit, Angular frequency, The center frequency of the bandpass filter. This is the bandwidth of the bandpass filter, which is less than the channel width.

[0018] In some embodiments, the processing unit calculates the ionization vacuum degree using the following formula. :

[0019]

[0020] in, To optimize the ion current signal, Boltzmann's constant, For ambient temperature, Let be Planck's constant. The speed of light in a vacuum. The absorption ratio of the photoemitting electrode surface. It is the ratio of the number of emitted photoelectrons to the number of photons absorbed by the surface of the photoelectrode. For ultraviolet light power, The probability that gas molecules are ionized to form positive ions and secondary electrons. This represents the average distance a secondary electron travels on its flight to be captured by the anode plate. This represents the probability that a positive ion is captured by the ion collecting plate. For elementary charge, The frequency is the ultraviolet light frequency.

[0021] The second aspect of this application relates to a method for measuring ionization vacuum degree based on light intensity modulation, the measurement method comprising:

[0022] The intensity of emitted ultraviolet light is modulated to make it oscillate in the form of a cosine wave.

[0023] When ultraviolet light is irradiated onto a photoelectrode, electrons are emitted from it through the photoelectric effect.

[0024] The emitted electrons are accelerated by the accelerating electric field and enter the ionization region with sufficient energy.

[0025] Accelerated electrons collide with gas molecules in the ionization region, causing the gas molecules to ionize and produce positive ions and secondary electrons;

[0026] Positive ions are captured under the action of the collecting electric field, forming an ionic current;

[0027] The ion current signal is subjected to bandpass filtering, wherein the center frequency of the bandpass filter is the same as the angular frequency of the modulated cosine wave.

[0028] The original signal is then demodulated to obtain the optimized ion current signal;

[0029] The ionization vacuum level is calculated by comprehensively optimizing the ion current signal and ambient temperature.

[0030] In some implementations, the modulated light intensity is ,in, This represents the maximum light intensity of the ultraviolet light source. This is the center frequency of the bandpass filter.

[0031] In some implementations, the ionization vacuum degree is calculated using the following formula. :

[0032]

[0033] in, To optimize the ion current signal, Boltzmann's constant, For ambient temperature, Let be Planck's constant. The speed of light in a vacuum. The absorption ratio of the photoemitting electrode surface. It is the ratio of the number of emitted photoelectrons to the number of photons absorbed by the surface of the photoelectrode. The power of ultraviolet light. The probability of a gas being ionized to form positive ions and secondary electrons. This represents the average distance a secondary electron travels before being captured by the anode plate. This represents the probability that a positive ion is captured by the ion collecting plate. For elementary charge, The frequency of ultraviolet light.

[0034] It is understandable that the beneficial effects of the second aspect can be found in the relevant descriptions in the first aspect above, and will not be repeated here.

[0035] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art:

[0036] This application discloses an ionization vacuum degree measurement device based on light intensity modulation. It modulates the intensity of ultraviolet light using a modulator, and simultaneously filters and demodulates the measured ion current signal to obtain an optimized ion current signal. The combination of these two methods significantly improves the system's signal-to-noise ratio, effectively reduces the interference of environmental noise on the measurement results, and significantly improves the accuracy and reliability of the ionization vacuum meter in measuring vacuum degree. Furthermore, this application can dynamically adjust the light intensity fluctuation frequency to obtain a suitable photocurrent according to different vacuum degree measurement scenarios, achieving accurate measurement in both low and high vacuum environments, thus broadening the range of application scenarios. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of an ionization vacuum degree measuring device based on light intensity modulation provided in an embodiment of this application.

[0038] Figure 2 This is a flowchart of an ionization vacuum degree measurement method based on light intensity modulation provided in an embodiment of this application.

[0039] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0040] 1-Ultraviolet light source, 2-Modulator, 3-Photoemitting electrode, 4-Anode plate, 5-Ion collecting electrode, 6-Inlet interface, 7-Temperature measurement component, 8-Current measurement component, 9-Processing unit. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0042] The embodiments of this application are described below with reference to the accompanying drawings.

[0043] Firstly, such as Figure 1 As shown, this application discloses an ionization vacuum degree measuring device based on light intensity modulation, the measuring device comprising:

[0044] The probe has a semi-enclosed cavity structure with an interface 6 for the gas to be measured to enter. Inside the cavity, there are a photoelectric emitting plate 3, an anode plate 4, and an ion collecting plate 5 arranged in sequence. The three are connected to a first potential, a second potential, and a third potential, respectively, with the second potential > the first potential > the third potential, so as to form an accelerating electric field and a collecting electric field.

[0045] Ultraviolet light source 1 is used to emit ultraviolet light and irradiate photoelectrode 3, causing it to emit electrons through the photoelectric effect;

[0046] Modulator 2 is used to modulate the intensity of emitted ultraviolet light, causing it to oscillate in the form of a cosine wave;

[0047] Processing unit 9 is used to perform bandpass filtering and demodulation on the ion current on the ion collecting electrode. The center frequency of the bandpass filter is the same as the angular frequency of the modulated cosine wave to obtain an optimized ion current signal. The ion current signal and the ambient temperature are combined to calculate the ionization vacuum degree.

[0048] Before measurement, the probe cavity is a vacuum. When preparing for measurement, connect to the gas to be measured via interface 6. If continuous vacuum measurement is required, interface 6 remains connected to the device containing the gas to be measured; otherwise, it is turned off.

[0049] In some embodiments, it also includes: a current measuring component 7 for measuring the ion current on the ion collecting plate and sending it to the processing unit 9.

[0050] In some embodiments, it also includes a temperature measurement component 8 for measuring the ambient temperature inside the probe cavity and sending it to the processing unit 9.

[0051] Preferably, considering that the center frequency of the filter may drift to zero during actual operation, the processing unit 9 provides feedback control to the modulator 2, so that the frequency of the modulator is the center frequency of the filter.

[0052] To achieve a high-efficiency photoelectric effect, a suitable light source must be selected. This application uses ultraviolet light as the light source, as ultraviolet light has high photon energy, which can more easily excite the photoemitting electrode to generate photoelectrons. Preferably, this application also includes an optical path adjustment device for illuminating the photoemitting electrode of the vacuum gauge with light.

[0053] This application uses a modulator to precisely control the intensity of ultraviolet light at different times, so that the intensity of the emitted light fluctuates in the form of a high-frequency cosine wave.

[0054] When ultraviolet light shines on the photoelectrode in the vacuum gauge, electrons in the photoelectrode absorb the energy of the photons and escape, according to the photoelectric effect. These escaped electrons become the initial electron source in the vacuum gauge.

[0055] The emitted electrons are accelerated by the accelerating electric field (the photoemitting electrode is connected to a first potential, and the anode plate is connected to a positive voltage, forming an accelerating electric field), gaining enough energy to enter the ionization region. The anode plate is a mesh structure made of fine metal wires, so most photoelectrons can pass through the anode plate and enter the ionization region. Because the ion collecting electrode is at a negative potential relative to the anode plate, the photoelectrons cannot reach the ion collecting electrode and are attracted back by the anode plate, moving back and forth between the photoemitting electrode and the ion collecting electrode. When electrons collide with gas molecules in the vacuum environment, they ionize the gas molecules, producing cations and secondary electrons. Both secondary electrons and photoelectrons are eventually captured by the anode plate.

[0056] Under the action of the collecting electric field (the ion collecting electrode is connected to a third potential and the anode plate is connected to a positive voltage, forming a collecting electric field), the cations generated by ionization will be captured by the ion collecting electrode, forming an ion current.

[0057] The magnitude of the high-frequency ion current signal is measured by a current measuring unit (e.g., an ammeter) and then input into a signal processor.

[0058] The signal processor utilizes the high-frequency characteristics of the modulated signal and, based on the excellent frequency selection characteristics and steep transition band of the high-frequency filter, performs targeted filtering on the signal to effectively remove noise. Then, it demodulates and restores the original signal to obtain an optimized ion current signal, thereby measuring the pressure in the vacuum region.

[0059] It should be noted that by applying an appropriate electric field between the electrode plates, electrons can be accelerated and given enough energy to ionize gas molecules, thus improving ionization efficiency. The strength and direction of the electric field should be designed according to the structure of the ionization chamber and the trajectory of the electrons. For example, a voltage of 60V is applied to the photoemitting electrode; a voltage of 160V is applied to the anode plate; and the ion collecting electrode is grounded.

[0060] In some implementations, the ultraviolet light source and the modulator are independent devices or integrated into one unit.

[0061] In some embodiments, the intensity of the light modulated by the modulator is ,in, This represents the maximum light intensity of the ultraviolet light source. This is the center frequency of the bandpass filter.

[0062] In some implementations, the processing unit performs filtering using an ultra-narrow bandpass filter, whose response function... as follows:

[0063]

[0064] in, The imaginary unit, Angular frequency, The center frequency of the bandpass filter. This is the bandwidth of the bandpass filter, which is less than the channel width.

[0065] An ultraviolet light source generates a beam with a frequency of Power is When ultraviolet light shines on a photoelectrode, some photons are absorbed by the photoelectrode and excited into photoelectrons, while the other photons are reflected as ineffective light. The absorption ratio of the photoelectrode surface is... The ratio of the number of emitted photoelectrons to the number of photons absorbed by the photoelectrode surface is called the quantum yield. The photocurrent emitted by the photoemitting electrode can be obtained. :

[0066]

[0067] in, Represents the elementary charge. Denotes Planck's constant. It represents the speed of light in a vacuum.

[0068] The electron stream emitted from the photoelectrode is accelerated by the electric field and enters the ionization region with a certain energy to bombard the vacuum cavity where the density is... Gas molecules, the gas with probability It is ionized to form positive ions and secondary electrons, with the positive ions having a high capture efficiency. Collected by the ion collecting plates, secondary electrons travel an average distance during flight. It is then captured by the anode plate, and the current is finally detected by the ion collecting electrode. :

[0069]

[0070] in, It is a constant and depends on the type of gas.

[0071] If the photocurrent is controlled If it is a constant value, then the ion current and gas molecule density Proportional. Assuming the gas is an ideal gas, through the equation... Then it can be known and Proportional, that is:

[0072]

[0073] in, For ambient temperature, is the Boltzmann constant.

[0074] In other words, the gas pressure can be determined by measuring the ion current. p .Right now:

[0075]

[0076] The combined expression for pressure is:

[0077]

[0078] in, To optimize the ion current signal, Boltzmann's constant, For ambient temperature, Let be Planck's constant. The speed of light in a vacuum. The absorption ratio of the photoemitting electrode surface. It is the ratio of the number of emitted photoelectrons to the number of photons absorbed by the surface of the photoelectrode. For ultraviolet light power, The probability that gas molecules are ionized to form positive ions and secondary electrons. This represents the average distance a secondary electron travels on its flight to be captured by the anode plate. This represents the probability that a positive ion is captured by the ion collecting plate. For elementary charge, The frequency is the ultraviolet light frequency.

[0079] Secondly, such as Figure 2 As shown, this application discloses a method for measuring ionization vacuum degree based on light intensity modulation, the measurement method comprising:

[0080] The intensity of emitted ultraviolet light is modulated to make it oscillate in the form of a cosine wave.

[0081] When ultraviolet light is irradiated onto a photoelectrode, electrons are emitted from it through the photoelectric effect.

[0082] The emitted electrons are accelerated by the accelerating electric field and enter the ionization region with sufficient energy.

[0083] Accelerated electrons collide with gas molecules in the ionization region, causing the gas molecules to ionize and produce positive ions and secondary electrons;

[0084] Positive ions are captured under the action of the collecting electric field, forming an ionic current;

[0085] The ion current signal is subjected to bandpass filtering, wherein the center frequency of the bandpass filter is the same as the angular frequency of the modulated cosine wave.

[0086] The original signal is then demodulated to obtain the optimized ion current signal;

[0087] The ionization vacuum level is calculated by comprehensively optimizing the ion current signal and ambient temperature.

[0088] In some implementations, the modulated light intensity is ,in, This represents the maximum light intensity of the ultraviolet light source. This is the center frequency of the bandpass filter.

[0089] In some implementations, the ionization vacuum degree is calculated using the following formula. :

[0090]

[0091] in, To optimize the ion current signal, Boltzmann's constant, For ambient temperature, Let be Planck's constant. The speed of light in a vacuum. The absorption ratio of the photoemitting electrode surface. It is the ratio of the number of emitted photoelectrons to the number of photons absorbed by the surface of the photoelectrode. The power of ultraviolet light. The probability of a gas being ionized to form positive ions and secondary electrons. This represents the average distance a secondary electron travels before being captured by the anode plate. This represents the probability that a positive ion is captured by the ion collecting plate. For elementary charge, The frequency of ultraviolet light.

[0092] Next, we will conduct a comparative analysis of the signal-to-noise ratio before and after modulation.

[0093] Because various noise currents exist in actual measurement environments, in most cases, ambient current noise can be modeled using a Gaussian white noise model. This noise current can interfere with the ion current signal measured by the ion collecting electrode. When the ion current signal is small, it is easily overwhelmed by ambient noise current, resulting in a low signal-to-noise ratio for the ionization vacuum gauge system.

[0094] Ion current With light intensity Proportional, that is ,in, It is a proportionality constant. Therefore, the signals measured by the ion collecting electrode (ion current signal and noise signal) are:

[0095] Before light intensity control:

[0096] After light intensity modulation:

[0097] The signal-to-noise ratio (SNR) we generally refer to is the average power of the signal divided by the average power of the noise. For noise with an infinite bandwidth, its power is infinite, so we typically only discuss noise power within the processor's bandwidth. Furthermore, the observation time of a signal is often finite, making it a signal with finite energy. Therefore, the SNR is generally discussed in the frequency domain energy spectrum. That is:

[0098]

[0099] in, Indicates the power of the signal. The power representing the noise. Represents the power spectral density of the signal. The power spectral density represents the noise. It represents angular frequency.

[0100] First, we discuss the signal-to-noise ratio of the system before modulation.

[0101] right Perform a Fourier transform to obtain ,in, This represents the relationship between the ion current before modulation and the frequency domain. This is the Dirac function.

[0102] Power spectral density of ion current signal pass Calculation, obtained .

[0103] The power of the ion current signal before modulation is (signal frequency greater than 0 and bandwidth range is...). ):

[0104]

[0105] White noise has the characteristic of uniformly distributing its power spectral density over a bandwidth, that is, .

[0106] The power of the current noise is .

[0107] In summary, the signal-to-noise ratio of the system before modulation is:

[0108]

[0109] Secondly, the signal-to-noise ratio of the modulated system is discussed.

[0110] right Perform a Fourier transform to obtain ,in, This indicates the relationship between the modulated ion current and the frequency domain.

[0111] The ion current signal is filtered through an ultra-narrow bandpass filter. The response function of the ultra-narrow bandpass filter is... for:

[0112]

[0113] in, Represents the imaginary unit. This indicates the center frequency of the ultra-narrow bandpass filter. This represents the bandwidth of the bandpass filter, and .

[0114] Obtain the output signal for:

[0115]

[0116]

[0117]

[0118] The power spectral density of the ion current signal can be obtained. .

[0119] The power of the modulated ion current signal is:

[0120]

[0121] The power of the current noise is:

[0122]

[0123] In summary, the signal-to-noise ratio of the modulated system is:

[0124]

[0125] Finally, divide the modulated signal-to-noise ratio by the unmodulated signal-to-noise ratio:

[0126]

[0127] because This demonstrates that the signal-to-noise ratio of the photoelectric effect ionization vacuum gauge system is significantly improved through modulation techniques.

[0128] It should be understood that expressions such as “comprising” and “may include” used in this application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In this application, terms such as “comprising” and / or “having” are to be interpreted as indicating a particular characteristic, number, operation, constituent element, component, or combination thereof, but not to exclude the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0129] Furthermore, in this application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0130] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. "Fixed connection" refers to a connection where the relative positional relationship remains unchanged after connection. "Rotary connection" refers to a connection where the components can rotate relative to each other after connection. "Sliding connection" refers to a connection where the components can slide relative to each other after connection. The directional terms mentioned in the embodiments of this application, such as "top," "bottom," "inner," "outer," "left," and "right," are only for reference to the directions in the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of this application, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0131] Furthermore, the mathematical concepts mentioned in the embodiments of this application, such as symmetry, equality, parallelism, and perpendicularity, are limitations specific to the current technological level, rather than absolute and strict mathematical definitions. Slight deviations are permissible; approximations of symmetry, equality, parallelism, and perpendicularity are all acceptable. For example, "A and B are parallel" means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. "A and B are perpendicular" means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0132] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A device for measuring ionization vacuum degree based on light intensity modulation, characterized in that, include: The probe has a semi-enclosed cavity structure with an interface for the gas to be measured to enter. Inside the cavity, there are a photoelectric emitting plate, an anode plate, and an ion collecting plate arranged in sequence. The three are connected to a first potential, a second potential, and a third potential, respectively, with the second potential > the first potential > the third potential, so as to form an accelerating electric field and a collecting electric field. An ultraviolet light source is used to emit ultraviolet light and irradiate a photoelectrode, causing it to release electrons through the photoelectric effect. A modulator is used to modulate the intensity of emitted ultraviolet light, causing it to oscillate in a cosine wave form. The processing unit is used to perform bandpass filtering and demodulation on the ion current on the ion collecting electrode. The center frequency of the bandpass filter is the same as the angular frequency of the modulated cosine wave to obtain an optimized ion current signal. The ion current signal and the ambient temperature are combined to calculate the ionization vacuum degree.

2. The measuring device as described in claim 1, characterized in that, Also includes: The current measurement component is used to measure the ion current on the ion collecting electrode and send it to the processing unit.

3. The measuring device as described in claim 1, characterized in that, Also includes: The temperature measurement component is used to measure the ambient temperature inside the probe cavity and send it to the processing unit.

4. The measuring device as described in claim 1, characterized in that, The ultraviolet light source and modulator are either independent devices or integrated into one unit.

5. The measuring device as described in claim 1, characterized in that, The intensity of the light modulated by the modulator is ,in, This represents the maximum light intensity of the ultraviolet light source. This is the center frequency of the bandpass filter.

6. The measuring device as described in claim 1, characterized in that, The processing unit performs filtering using an ultra-narrow bandpass filter, and its response function is... as follows: in, The imaginary unit, Angular frequency, The center frequency of the bandpass filter. This is the bandwidth of the bandpass filter, which is less than the channel width.

7. The measuring device as described in claim 1, characterized in that, The processing unit calculates the ionization vacuum degree using the following formula. : in, To optimize the ion current signal, Boltzmann's constant, For ambient temperature, Let be Planck's constant. The speed of light in a vacuum. The absorption ratio of the photoemitting electrode surface. It is the ratio of the number of emitted photoelectrons to the number of photons absorbed by the surface of the photoelectrode. For ultraviolet light power, The probability that gas molecules are ionized to form positive ions and secondary electrons. This represents the average distance a secondary electron travels on its flight to be captured by the anode plate. This represents the probability that a positive ion is captured by the ion collecting plate. For elementary charge, The frequency is the ultraviolet light frequency.

8. A method for measuring ionization vacuum degree based on light intensity modulation, characterized in that, include: The intensity of emitted ultraviolet light is modulated to make it oscillate in the form of a cosine wave. When ultraviolet light is irradiated onto a photoelectrode, electrons are emitted from it through the photoelectric effect. The emitted electrons are accelerated by the accelerating electric field and enter the ionization region with sufficient energy. Accelerated electrons collide with gas molecules in the ionization region, causing the gas molecules to ionize and produce positive ions and secondary electrons; Positive ions are captured under the action of the collecting electric field, forming an ionic current; The ion current signal is subjected to bandpass filtering, wherein the center frequency of the bandpass filter is the same as the angular frequency of the modulated cosine wave. The original signal is then demodulated to obtain the optimized ion current signal; The ionization vacuum level is calculated by comprehensively optimizing the ion current signal and ambient temperature.

9. The measurement method as described in claim 8, characterized in that, The modulated light intensity is ,in, This represents the maximum light intensity of the ultraviolet light source. This is the center frequency of the bandpass filter.

10. The measurement method as described in claim 8, characterized in that, The degree of ionization vacuum can be calculated using the following formula. : in, To optimize the ion current signal, Boltzmann's constant, For ambient temperature, Let be Planck's constant. The speed of light in a vacuum. The absorption ratio of the photoemitting electrode surface. It is the ratio of the number of emitted photoelectrons to the number of photons absorbed by the surface of the photoelectrode. The power of ultraviolet light. The probability of a gas being ionized to form positive ions and secondary electrons. This represents the average distance a secondary electron travels before being captured by the anode plate. This represents the probability that a positive ion is captured by the ion collecting plate. For elementary charge, The frequency of ultraviolet light.

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