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

Abstract

The invention belongs to the technical field of vacuum measurement, and particularly discloses an ionization vacuum degree measurement method and device based on light intensity modulation. The light intensity of ultraviolet light is modulated through the modulator, the measured ion current signal is filtered and demodulated at the same time, the optimized ion current signal is obtained, the two are combined, the signal-to-noise ratio of the system is greatly improved, interference of environmental noise on a measurement result is effectively reduced, and the measurement accuracy is improved. And the accuracy and the reliability of vacuum degree measurement of the ionization vacuum gauge are obviously improved. Besides, according to different vacuum degree measurement scene requirements, the light intensity fluctuation frequency can be dynamically adjusted to obtain appropriate light current, accurate measurement can be achieved in a low-vacuum environment or a high-vacuum environment, and the application scene range is widened.

Description

Technical Field

[0001] The present application belongs to the field of vacuum measurement technology, and more specifically, to a method and device for measuring ionization vacuum degree based on light intensity modulation. Background Art

[0002] In modern science and technology and industrial production, accurate measurement of vacuum environment is crucial. Ionization vacuum gauge based on photoelectric effect is an important instrument for measuring vacuum degree in many scientific research and industrial production fields. Its working principle is to use the photoelectric emitter plate to emit electrons under light irradiation. These electrons collide with gas molecules in the ionization chamber to ionize them, and then measure the ion flow signal through the ion collector and convert it into an electrical signal to reflect the vacuum degree.

[0003] However, in practical applications, the photoelectric effect ionization vacuum gauge faces an important technical problem, that is, the low signal-to-noise ratio of the system. On the one hand, it is because the generated photocurrent is too small. The size of the photocurrent depends on many factors, including the intensity of the light source, the quantum yield of the photoelectric emitter plate material, etc. In many cases, due to the power limitation of the light source or the characteristics of the photoelectric emitter plate material itself, the generated photocurrent is often at a low level. On the other hand, in the actual measurement environment, there are various noise currents, which will interfere with the ion flow signal measured by the ion collector. When the ion flow signal is small, it is easily submerged by the environmental noise current. This situation will greatly reduce the accuracy and reliability of the measurement results of the ionization vacuum gauge.

[0004] At present, in order to solve the problem of low signal-to-noise ratio of photoelectric effect ionization vacuum gauge system, some methods focus on improving the photocurrent by improving the photoelectric emitter plate material, but the improvement effect is not ideal due to the limitation of material research and development cost and technical bottleneck. Other methods try to suppress noise from the circuit design, but in complex practical environment, it is difficult to completely eliminate the influence of noise on ion flow signal. The above methods have limitations. Summary of the invention

[0005] In view of the defects of the prior art, the purpose of the present application is to provide an ionization vacuum degree measurement method and device based on light intensity modulation, aiming to solve the problem of low signal-to-noise ratio of the existing photoelectric effect ionization vacuum gauge system.

[0006] The first aspect of the present application relates to an ionization vacuum degree measuring device based on light intensity modulation, the measuring device comprising: A semi-enclosed cavity structure probe is provided with an interface for the gas to be measured to enter, and a photoelectric emitter plate, an anode plate and an ion collecting plate are arranged in the cavity in sequence, and the three are connected to a first potential, a second potential and a third potential respectively, and 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 illuminate the photoelectric emitter plate to cause it to emit electrons through the photoelectric effect; A modulator, used for modulating the intensity of the emitted ultraviolet light so that it fluctuates in the form of a cosine wave; The processing unit is used to perform bandpass filtering and demodulation on the ion current on the ion collecting plate, wherein the center frequency of the bandpass filtering is the same as the angular frequency of the modulated cosine wave, to obtain an optimized ion current signal, comprehensively optimize the ion current signal and the ambient temperature, and calculate the ionization vacuum degree.

[0007] In some embodiments, it further includes: a current measurement component for measuring the ion current on the ion collecting plate and sending the current to the processing unit.

[0008] In some embodiments, it further includes: a temperature measurement component for measuring the ambient temperature in the probe cavity and sending it to the processing unit.

[0009] In some embodiments, the ultraviolet light source and the modulator are independent devices or integrated into one.

[0010] In some embodiments, the light intensity after modulation by the modulator is ,in, is the maximum light intensity of the UV light source, is the center frequency of the bandpass filter.

[0011] In some embodiments, the processing unit performs filtering through an ultra-narrow bandpass filter, whose response function is as follows:

[0012] in, is an imaginary unit, is the angular frequency, is the center frequency of the bandpass filter, is the bandwidth of the bandpass filter, which is smaller than the channel width.

[0013] In some embodiments, the processing unit calculates the ionization vacuum degree by the following formula: :

[0014] in, To optimize the ion current signal, is the Boltzmann constant, is the ambient temperature, is Planck's constant, is the speed of light in vacuum, is the absorption ratio of the photoemitter surface, is the ratio of the number of emitted photoelectrons to the number of photons absorbed by the photoemission plate surface, is the UV light power, is the probability of gas molecules being ionized to form positive ions and secondary electrons, is the average distance of secondary electrons from flying to being captured by the anode plate, is the probability of positive ions being captured by the ion collecting plate, is the basic charge, is the frequency of ultraviolet light.

[0015] A second aspect of the present application relates to a method for measuring ionization vacuum based on light intensity modulation, the method comprising: Modulating the intensity of the emitted ultraviolet light so that it fluctuates in the form of a cosine wave; Expose ultraviolet light to the photoemitter plate, causing it to emit electrons through the photoelectric effect; The escaped electrons are accelerated by the accelerating electric field and enter the ionization region with sufficient energy; The accelerated electrons collide with the gas molecules in the ionization region, causing the gas molecules to be ionized, generating positive ions and secondary electrons; Positive ions are captured under the action of the collecting electric field, forming an ion current; Performing bandpass filtering on the ion current signal, wherein the center frequency of the bandpass filtering is the same as the angular frequency of the modulated cosine wave; Then demodulate and restore the original signal to obtain the optimized ion current signal; The ion current signal and ambient temperature are comprehensively optimized to calculate the ionization vacuum degree.

[0016] In some embodiments, the modulated light intensity is ,in, is the maximum light intensity of the UV light source, is the center frequency of the bandpass filter.

[0017] In some embodiments, the ionization vacuum degree is calculated by the following formula: :

[0018] in, To optimize the ion current signal, is the Boltzmann constant, is the ambient temperature, is Planck's constant, is the speed of light in vacuum, is the absorption ratio of the photoemitter surface, is the ratio of the number of emitted photoelectrons to the number of photons absorbed by the photoemission plate surface, is the power of UV light, is the probability of the gas being ionized to form positive ions and secondary electrons, is the average distance that the secondary electrons travel before being captured by the anode plate, is the probability of positive ions being captured by the ion collecting plate, is the basic charge, is the frequency of ultraviolet light.

[0019] It can be understood that the beneficial effects of the second aspect can be found in the relevant description of the first aspect above, and will not be repeated here.

[0020] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the prior art: The present application discloses an ionization vacuum degree measurement device based on light intensity modulation, which modulates the light intensity of ultraviolet light through a modulator, and simultaneously filters and demodulates the measured ion current signal 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 vacuum. In addition, the present application can dynamically adjust the light intensity fluctuation frequency to obtain a suitable photocurrent according to the requirements of different vacuum measurement scenarios, and can achieve accurate measurement in both low vacuum and high vacuum environments, broadening the scope of application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of an ionization vacuum degree measurement device based on light intensity modulation provided in an embodiment of the present application.

[0022] Figure 2 This is a flow chart of an ionization vacuum degree measurement method based on light intensity modulation provided in an embodiment of the present application.

[0023] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1-ultraviolet light source, 2-modulator, 3-photoelectric emitter plate, 4-anode plate, 5-ion collecting plate, 6-entry interface, 7-temperature measurement component, 8-current measurement component, 9-processing unit. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0025] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0026] First, as Figure 1As shown, the present application discloses an ionization vacuum degree measuring device based on light intensity modulation, the measuring device comprising: A semi-enclosed cavity structure probe is provided with an interface 6 for the gas to be measured to enter, and a photoelectric emitter plate 3, an anode plate 4 and an ion collecting plate 5 are arranged in the cavity in sequence, and the three are connected to a first potential, a second potential and a third potential respectively, and the second potential> the first potential> the third potential, so as to form an accelerating electric field and a collecting electric field; The ultraviolet light source 1 is used to emit ultraviolet light and illuminate the photoelectric emitter plate 3, so that electrons escape through the photoelectric effect; Modulator 2, used for modulating the intensity of the emitted ultraviolet light so that it fluctuates in the form of a cosine wave; The processing unit 9 is used to perform bandpass filtering and demodulation on the ion current on the ion collecting plate, wherein the center frequency of the bandpass filtering is the same as the angular frequency of the modulated cosine wave, to obtain an optimized ion current signal, comprehensively optimize the ion current signal and the ambient temperature, and calculate the ionization vacuum degree.

[0027] Before the measurement, the probe cavity is vacuum. When preparing for the measurement, the probe is connected to the gas to be measured through the interface 6. If the vacuum degree needs to be continuously measured, the interface 6 is always connected to the device containing the gas to be measured. If not, it is closed.

[0028] In some embodiments, it further includes: a current measuring component 7 for measuring the ion current on the ion collecting plate and sending it to the processing unit 9.

[0029] In some embodiments, it also includes: a temperature measurement component 8 for measuring the ambient temperature in the probe cavity and sending it to the processing unit 9.

[0030] Preferably, considering that the center frequency of the filter may drift during actual operation, the processing unit 9 feedback controls the modulator 2 so that the frequency of the modulator is the center frequency of the filter.

[0031] In order to achieve an efficient photoelectric effect, a suitable light source needs to be selected. The present application uses ultraviolet light as a light source. Ultraviolet light has a higher photon energy and can more easily excite the photoelectric emitter plate to generate photoelectrons. Preferably, the present application also includes an optical path adjustment device for irradiating light onto the photoelectric emitter plate of the vacuum gauge.

[0032] The present application uses a modulator to accurately control the intensity of ultraviolet light at different times, so that the intensity of the light emitted by it fluctuates in the form of a high-frequency cosine wave.

[0033] When ultraviolet light shines on the photoelectric emitter plate in the vacuum gauge, the electrons in the photoelectric emitter plate will absorb the energy of photons and escape according to the principle of photoelectric effect. These escaped electrons become the initial electron source in the vacuum gauge.

[0034] The escaped electrons are accelerated under the action of the accelerating electric field (the accelerating electric field formed by the photoemitter plate connected to the first potential and the anode plate connected to the positive voltage), and obtain enough energy to enter the ionization region. The anode plate is a mesh structure made of fine metal wires, so most of the photoelectrons can pass through the anode plate and enter the ionization region. Since the ion collector plate is at a negative potential relative to the anode plate, the photoelectrons cannot reach the ion collector plate and are attracted back by the anode plate, moving back and forth between the photoemitter plate and the ion collector plate. When electrons collide with gas molecules in a vacuum environment, the gas molecules are ionized to produce cations and secondary electrons. Both secondary electrons and photoelectrons will eventually be captured by the anode plate.

[0035] Under the action of the collecting electric field (the ion collecting plate is connected to the third potential, and the anode plate is connected to the positive voltage to form the collecting electric field), the cations produced by ionization will be captured by the ion collecting plate to form an ion current.

[0036] The magnitude of the high-frequency ion current signal is measured by a current measuring unit (eg, an ammeter) and input into a signal processor.

[0037] The signal processor uses the high-frequency characteristics of the modulated signal and performs targeted filtering on the signal based on the good frequency selection characteristics and steep transition band of the high-frequency filter, effectively filtering out the noise, and then demodulating and restoring the original signal to obtain the optimized ion current signal, thereby measuring the pressure in the vacuum area.

[0038] It should be noted that by applying an appropriate electric field between the electrode plates, the electrons can be accelerated and given enough energy to ionize the gas molecules, thus improving the 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 photoemitter plate; a voltage of 160V is applied to the anode plate; and the ion collector plate is grounded.

[0039] In some embodiments, the ultraviolet light source and the modulator are independent devices or integrated into one.

[0040] In some embodiments, the light intensity after modulation by the modulator is ,in, is the maximum light intensity of the UV light source, is the center frequency of the bandpass filter.

[0041] In some embodiments, the processing unit performs filtering through an ultra-narrow bandpass filter, whose response function is as follows:

[0042] in, is an imaginary unit, is the angular frequency, is the center frequency of the bandpass filter, is the bandwidth of the bandpass filter, which is smaller than the channel width.

[0043] The ultraviolet light source produces a beam with a frequency of , power is The ultraviolet light is directed to the photoelectric emitter plate. Some photons are absorbed by the photoelectric emitter plate and then stimulate photoelectrons, while the other part of the photons are reflected and become invalid light beams. The absorption ratio of the photoelectric emitter plate surface is The ratio of the number of emitted photoelectrons to the number of photons absorbed by the photoemission plate surface is called the quantum yield. The photocurrent emitted by the photoelectric emitter plate can be obtained :

[0044] in, represents the elementary charge, is Planck's constant, Represents the speed of light in vacuum.

[0045] The electron flow emitted from the photoelectric emitter plate is accelerated by the electric field and enters the ionization region with a certain energy to bombard the vacuum chamber with a density of The gas molecules have a probability Ionized to form positive ions and secondary electrons, positive ions are captured efficiently The secondary electrons are collected by the ion collecting plate and fly at an average distance After being captured by the anode plate, the current detected by the ion collecting plate :

[0046] in, is a constant and depends on the gas type.

[0047] If the photocurrent is controlled is a certain value, then the ion current and the density of gas molecules Assuming the gas is an ideal gas, the equation , then we know and is proportional, that is:

[0048] in, is the ambient temperature, is the Boltzmann constant.

[0049] In other words, the gas pressure can be known by measuring the ion current. p .Right now:

[0050] The expression of pressure can be obtained as follows:

[0051] in, To optimize the ion current signal, is the Boltzmann constant, is the ambient temperature, is Planck's constant, is the speed of light in vacuum, is the absorption ratio of the photoemitter surface, is the ratio of the number of emitted photoelectrons to the number of photons absorbed by the photoemission plate surface, is the UV light power, is the probability of gas molecules being ionized to form positive ions and secondary electrons, is the average distance of secondary electrons from flying to being captured by the anode plate, is the probability of positive ions being captured by the ion collecting plate, is the basic charge, is the frequency of ultraviolet light.

[0052] Second, as Figure 2 As shown, the present application discloses a method for measuring ionization vacuum based on light intensity modulation, the measuring method comprising: Modulating the intensity of the emitted ultraviolet light so that it fluctuates in the form of a cosine wave; Expose ultraviolet light to the photoemitter plate, causing it to emit electrons through the photoelectric effect; The escaped electrons are accelerated by the accelerating electric field and enter the ionization region with sufficient energy; The accelerated electrons collide with the gas molecules in the ionization region, causing the gas molecules to be ionized, generating positive ions and secondary electrons; Positive ions are captured under the action of the collecting electric field, forming an ion current; Performing bandpass filtering on the ion current signal, wherein the center frequency of the bandpass filtering is the same as the angular frequency of the modulated cosine wave; Then demodulate and restore the original signal to obtain the optimized ion current signal; The ion current signal and ambient temperature are comprehensively optimized to calculate the ionization vacuum degree.

[0053] In some embodiments, the modulated light intensity is ,in, is the maximum light intensity of the UV light source, is the center frequency of the bandpass filter.

[0054] In some embodiments, the ionization vacuum degree is calculated by the following formula: :

[0055] in, To optimize the ion current signal, is the Boltzmann constant, is the ambient temperature, is Planck's constant, is the speed of light in vacuum, is the absorption ratio of the photoemitter surface, is the ratio of the number of emitted photoelectrons to the number of photons absorbed by the photoemission plate surface, is the power of UV light, is the probability of the gas being ionized to form positive ions and secondary electrons, is the average distance that the secondary electrons travel before being captured by the anode plate, is the probability of positive ions being captured by the ion collecting plate, is the basic charge, is the frequency of ultraviolet light.

[0056] Next, the signal-to-noise ratio before and after modulation is compared and analyzed.

[0057] Since there are various noise currents in the actual measurement environment, in most cases, the environmental current noise can be modeled by Gaussian white noise. These noise currents will interfere with the ion current signal measured by the ion collecting plate. When the ion current signal is small, it is easily submerged by the environmental noise current, resulting in a low signal-to-noise ratio of the ionization vacuum gauge system.

[0058] Ion current With light intensity is proportional to ,in, is a proportional constant. Therefore, the signal measured by the ion collecting plate (ion current signal and noise signal) is: Before light intensity modulation:

[0059] After light intensity modulation:

[0060] Generally speaking, the signal-to-noise ratio refers to the average power of the signal divided by the average power of the noise. For noise with infinite bandwidth, its power is infinite, so the noise power is generally only discussed within the processor bandwidth. The observation time of the signal is often limited, so this is a signal with limited energy, so the signal-to-noise ratio is generally discussed in the frequency domain energy spectrum. That is:

[0061] in, represents the power of the signal, represents the power of the noise, represents the power spectral density of the signal, represents the power spectral density of the noise, Represents the angular frequency.

[0062] First, the signal-to-noise ratio of the system before modulation is discussed.

[0063] right Perform Fourier transform and get ,in, represents the relationship between the ion current and the frequency domain before modulation, is the Dirac function.

[0064] Power spectral density of ion current signal pass Calculate and get .

[0065] The power of the ion current signal before modulation is (the signal frequency is greater than 0 and the bandwidth range is ):

[0066] White noise has the characteristic of uniformly distributing power spectrum density within the bandwidth, that is, .

[0067] The power of the current noise is .

[0068] In summary, the signal-to-noise ratio of the system before modulation is:

[0069] Secondly, the signal-to-noise ratio of the modulated system is discussed.

[0070] right Perform Fourier transform and get ,in, It represents the relationship between the ion current after modulation and the frequency domain.

[0071] The ion current signal is filtered through an ultra-narrow bandpass filter. The response function of the ultra-narrow bandpass filter is for:

[0072] in, represents the imaginary unit, represents the center frequency of the ultra-narrow bandpass filter, represents the bandwidth of the bandpass filter, and .

[0073] Get the output signal for:

[0074]

[0075]

[0076] The power spectral density of the ion current signal can be obtained .

[0077] The power of the modulated ion current signal is:

[0078] The power of the current noise is:

[0079] In summary, the signal-to-noise ratio of the modulated system is:

[0080] Finally, divide the post-modulation SNR by the pre-modulation SNR:

[0081] because It can be proved that the signal-to-noise ratio of the photoelectric effect ionization vacuum gauge system has been significantly improved through modulation technology.

[0082] It should be understood that expressions such as "including" and "may include" that may be used in the present 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 the present application, terms such as "including" and / or "having" may be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components, or combinations thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0083] In addition, in the present 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.

[0084] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. 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. Among them, "fixed connection" means that the relative position relationship after connection remains unchanged. "Rotational connection" means that the two are connected to each other and can rotate relative to each other after connection. "Sliding connection" means that the two are connected to each other and can slide relative to each other after connection. The directional terms mentioned in the embodiments of the present application, such as "top", "bottom", "inside", "outside", "left", "right", etc., are only reference directions of the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of the present application, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0085] In addition, in the embodiments of the present application, the mathematical concepts mentioned are symmetry, equality, parallelism, verticality, etc. These limitations are all for the current state of the art, rather than being absolutely strict definitions in a mathematical sense, and allow a small amount of deviation, approximation to symmetry, approximation to equality, approximation to parallelism, approximation to verticality, etc. are all possible. For example, A and B are parallel, which 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, which means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0086] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. An ionization vacuum degree measuring device based on light intensity modulation, characterized in that: include: A semi-enclosed cavity structure probe is provided with an interface for the gas to be measured to enter, and a photoelectric emitter plate, an anode plate and an ion collecting plate are arranged in the cavity in sequence, and the three are connected to a first potential, a second potential and a third potential respectively, and 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 illuminate the photoelectric emitter plate to cause it to emit electrons through the photoelectric effect; A modulator, used for modulating the intensity of the emitted ultraviolet light so that it fluctuates in the form of a cosine wave; The processing unit is used to perform bandpass filtering and demodulation on the ion current on the ion collecting plate, wherein the center frequency of the bandpass filtering is the same as the angular frequency of the modulated cosine wave, to obtain an optimized ion current signal, comprehensively optimize the ion current signal and the ambient temperature, and calculate the ionization vacuum degree.

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

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

4. The measuring device according to claim 1, characterized in that The ultraviolet light source and the modulator are independent devices or integrated into one.

5. The measuring device according to claim 1, characterized in that The light intensity after modulation by the modulator is ,in, is the maximum light intensity of the UV light source, is the center frequency of the bandpass filter.

6. The measuring device according to claim 1, characterized in that The processing unit performs filtering through an ultra-narrow bandpass filter, whose response function as follows: in, is an imaginary unit, is the angular frequency, is the center frequency of the bandpass filter, is the bandwidth of the bandpass filter, which is smaller than the channel width.

7. The measuring device according to claim 1, characterized in that The processing unit calculates the ionization vacuum degree by the following formula: : in, To optimize the ion current signal, is the Boltzmann constant, is the ambient temperature, is Planck's constant, is the speed of light in vacuum, is the absorption ratio of the photoemitter surface, is the ratio of the number of emitted photoelectrons to the number of photons absorbed by the photoemission plate surface, is the UV light power, is the probability of gas molecules being ionized to form positive ions and secondary electrons, is the average distance of secondary electrons from flying to being captured by the anode plate, is the probability of positive ions being captured by the ion collecting plate, is the basic charge, is the frequency of ultraviolet light.

8. A method for measuring ionization vacuum based on light intensity modulation, characterized in that: include: Modulating the intensity of the emitted ultraviolet light so that it fluctuates in the form of a cosine wave; Expose ultraviolet light to the photoemitter plate, causing it to emit electrons through the photoelectric effect; The escaped electrons are accelerated by the accelerating electric field and enter the ionization region with sufficient energy; The accelerated electrons collide with the gas molecules in the ionization region, causing the gas molecules to be ionized, generating positive ions and secondary electrons; Positive ions are captured under the action of the collecting electric field, forming an ion current; Performing bandpass filtering on the ion current signal, wherein the center frequency of the bandpass filtering is the same as the angular frequency of the modulated cosine wave; Then demodulate and restore the original signal to obtain the optimized ion current signal; The ion current signal and ambient temperature are comprehensively optimized to calculate the ionization vacuum degree.

9. The measuring method according to claim 8, characterized in that: The modulated light intensity is ,in, is the maximum light intensity of the UV light source, is the center frequency of the bandpass filter.

10. The measuring method according to claim 8, characterized in that: Calculate the ionization vacuum degree using the following formula : in, To optimize the ion current signal, is the Boltzmann constant, is the ambient temperature, is Planck's constant, is the speed of light in vacuum, is the absorption ratio of the photoemitter surface, is the ratio of the number of emitted photoelectrons to the number of photons absorbed by the photoemission plate surface, is the power of UV light, is the probability of the gas being ionized to form positive ions and secondary electrons, is the average distance that the secondary electrons travel before being captured by the anode plate, is the probability of positive ions being captured by the ion collecting plate, is the basic charge, is the frequency of ultraviolet light.

Images