Plasma parameter transient terahertz wave transmission testing device, method and system

Abstract

The application discloses a plasma parameter transient terahertz wave transmission testing device, method and system, and relates to the technical field of plasma transmission testing.The device comprises a first microwave darkroom, a measured device, a second microwave darkroom, a vector network analysis module and an industrial computer, and the measured device is provided with plasma;the first microwave darkroom is provided with a first spread spectrum module, a transmitting horn antenna and a first lens, the second microwave darkroom is provided with a second spread spectrum module, a second lens and a receiving horn antenna, the transmitting horn antenna is connected with the first spread spectrum module, the receiving horn antenna is connected with the second spread spectrum module, and the vector network analysis module is connected with the first spread spectrum module, the second spread spectrum module and the industrial computer.The application obtains the terahertz wave transmission signal passing through the plasma, inverts the key parameters of plasma electron density and collision frequency, improves the accuracy of the model, does not need to intrude into the plasma, and is suitable for different processes and various application scenarios.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of plasma transmission testing, in particular to a plasma parameter transient terahertz wave transmission testing device, method and system. BACKGROUND

[0002] Plasma technology plays an irreplaceable role in large-scale manufacturing. For example, processes such as polysilicon etching and thin film deposition in the production of ultra-large scale integrated circuits used in the microelectronics industry need to be carried out in a plasma environment. In addition, the application research of plasma in the fields of environment, military, space, etc. is also gradually developed. Space vehicles such as space shuttles, satellites and missiles will generate a plasma sheath covering the surface of the vehicle when they pass through the earth's atmosphere at high speed. The plasma sheath will cause a communication blackout and interfere with the real-time communication of the vehicle.

[0003] The measurement of plasma parameters is the primary problem to be solved in the development of plasma technology and the solution to the communication blackout problem. It is also the primary problem to be solved in the development of new material processing, large-scale integrated circuit, photovoltaic and flat panel display manufacturing industries and key technologies in the aerospace defense field. Developing a testing method to measure plasma electron density, collision frequency and other parameters is of great significance to the development of related technologies and the solution to the communication blackout problem.

[0004] The commonly used plasma parameter testing methods include Langmuir probe method, optical spectrum method, microwave reflection method and microwave transmission method. Among them, the transmission method calculates the complex permittivity of the plasma by testing the phase and amplitude changes of the electromagnetic wave before and after passing through the plasma, and then calculates the electron density and collision frequency. Compared with the reflection method, the transmission method has the advantages of simple testing device, more concise signal processing procedure, strong adaptability, accurate measured data, fast measurement speed, low requirement on wave source and applicability to low temperature and high temperature plasmas, etc. It has important value for the research of plasma parameter testing technology.

[0005] The inventors found that the electromagnetic wave frequency selected by the current microwave transmission method is in the Ka band, which cannot be applied to the testing of a wide range of plasma parameters. It is necessary to further increase the electromagnetic wave frequency to the terahertz wave frequency band. In addition, the testing precision and dynamic testing capability of the existing microwave transmission technology are not high. Therefore, for a wide parameter range and dynamic plasma environment, how to use the terahertz wave transmission method to realize the plasma parameter testing has become a research focus. SUMMARY

[0006] The purpose of the present application is to provide a plasma parameter transient terahertz wave transmission testing device, method and system, which increases the testing frequency to the terahertz wave band, obtains the terahertz wave transmission signal through the plasma, inverses the key parameters such as the plasma electron density and collision frequency, improves the accuracy of the model and the precision of the algorithm, and at the same time, the measurement result of the transient measurement of the plasma is more accurate, the device with a testing window on the opposite side of the device does not need to invade the plasma, can be applied to different processes and various application scenarios, and solves the problems in the prior art.

[0007] To solve the above technical problems, the present application is realized by the following technical solutions:

[0008] The present application provides a plasma parameter transient terahertz wave transmission testing device in the first aspect.

[0009] The plasma parameter transient terahertz wave transmission testing device comprises a first microwave darkroom, a measured device and a second microwave darkroom arranged in sequence, wherein the measured device is provided with plasma; the first microwave darkroom is provided with a first spread spectrum module, a transmitting horn antenna and a first lens; the second microwave darkroom is provided with a second spread spectrum module, a second lens and a receiving horn antenna; the transmitting horn antenna is connected with the first spread spectrum module; the receiving horn antenna is connected with the second spread spectrum module; further comprising a vector network analysis module and an industrial computer; the first spread spectrum module and the second spread spectrum module are connected with the vector network analysis module respectively; the vector network analysis module is connected with the industrial computer; and air exists between the first microwave darkroom, the transmitting horn antenna, the plasma, the receiving horn antenna and the second microwave darkroom.

[0010] Preferably, the transmitting horn antenna is arranged at the focal point of the first lens, the receiving horn antenna is arranged at the focal point of the second lens, and the heights of the first lens and the second lens in the range of generating plane waves are both greater than or equal to the height of the measured plasma region.

[0011] The present application provides a testing method of the plasma parameter transient terahertz wave transmission testing device in the second aspect.

[0012] The testing method of the plasma parameter transient terahertz wave transmission testing device comprises the following steps:

[0013] An initial transmission transmission coefficient of the testing device when there is no to-be-measured plasma in the measured space is obtained;

[0014] Discrete receiving data is obtained;

[0015] Based on the initial transmission transmission coefficient and the discrete receiving data, only the terahertz wave electric field is considered, and the transmission transmission coefficient of the testing device changing with the sampling number is obtained;

[0016] Setting the attenuation constant and the phase constant of the terahertz wave in the plasma as linear functions of time, obtaining the eigen-transmission transmission coefficient of the test device based on an electromagnetic wave propagation model;

[0017] Based on the eigen-transmission transmission coefficient and the transmission transmission coefficient varying with the sampling number, constructing a target function;

[0018] Obtaining the minimum value of the target function, and based on the minimum value, obtaining the optimal values of the attenuation constant and the phase constant of the terahertz wave;

[0019] Based on the optimal values of the attenuation constant and the phase constant of the terahertz wave, obtaining the parameter values of the plasma electron density and the collision frequency.

[0020] Preferably, the initial transmission transmission coefficient of the test device when the to-be-measured plasma does not exist in the measured space is obtained, specifically:

[0021] When the to-be-measured plasma does not exist in the measured space, the radio frequency signal output by the vector network analysis module is multiplied by one frequency expansion module to form a terahertz wave signal, which is output by the transmitting horn antenna, forms a plane wave through a first lens, passes through air and a to-be-measured region respectively, is received by a receiving horn antenna, and is transmitted to the vector network analysis module through a second frequency expansion module. The industrial computer stores the received signal to obtain the initial transmission transmission coefficient S 21，0 .

[0022] Preferably, the discrete received data is obtained, specifically:

[0023] The receiving horn antenna receives the signal to obtain the discrete received signal Data:

[0024] Data=[Data(1),Data(2),Data(3),…Data(n)],(n=1,2…m)

[0025] Wherein, n represents the nth sampling, m is the total number of sampling points in the test time, and Data contains the terahertz wave propagation transmission transmission coefficient and sampling time information.

[0026] Preferably, the m discrete received data is divided into p single processing time periods, and each single processing time period includes q sampling points, that is

[0027]

[0028] Wherein, m=p×q.

[0029] Preferably, the transmission transmission coefficient of the test device varying with the sampling number is represented as:

[0030] S 21(n) = Data(n) / Data(1) · S 21,0

[0031] wherein, Data(n) is the discrete received data obtained by the n-th sampling, Data(1) is the discrete received data obtained by the 1st sampling, S 21,0 is an initial transmission transfer coefficient.

[0032] Preferably, the intrinsic transmission transfer coefficient is represented as:

[0033]

[0034] Preferably, the objective function F is represented as:

[0035]

[0036] wherein, is an intrinsic transmission transfer coefficient, S 21 (n) is a transmission transfer coefficient varying with the sampling number.

[0037] The third aspect of the present application provides a plasma parameter transient terahertz wave transmission test system.

[0038] The plasma parameter transient terahertz wave transmission test system comprises:

[0039] An initial transmission transfer coefficient acquisition module is configured to acquire an initial transmission transfer coefficient of the test device when no to-be-tested plasma exists in the measured space.

[0040] A discrete received data acquisition module is configured to acquire discrete received data.

[0041] An intrinsic transmission transfer coefficient acquisition module is configured to set the plasma electron density and the collision frequency as linear functions of time, and acquire the intrinsic transmission transfer coefficient of the test device based on the discrete received data.

[0042] A transmission transfer coefficient varying with the sampling number acquisition module is configured to acquire the transmission transfer coefficient of the test device varying with the sampling number based on the initial transmission transfer coefficient and the discrete received data, and only consider the terahertz wave electric field.

[0043] An objective function construction module is configured to construct an objective function based on the intrinsic transmission transfer coefficient and the transmission transfer coefficient varying with the sampling number.

[0044] An optimal parameter value acquisition module is configured to acquire a minimum value of the objective function, and acquire the optimal values of the terahertz wave attenuation constant and the phase constant based on the minimum value.

[0045] The plasma parameter value acquisition module is configured to acquire the plasma electron density and collision frequency parameter values based on the terahertz wave attenuation constant and the optimal phase constant value.

[0046] The present application has the following beneficial effects:

[0047] 1、The plasma parameter transient terahertz wave transmission testing device, method and system provided by the present application improve the model accuracy and algorithm precision by increasing the test frequency to the terahertz wave band, obtaining the terahertz wave transmission signal through the plasma, and inverting the key parameters such as plasma electron density and collision frequency.

[0048] 2、The plasma parameter transient terahertz wave transmission testing device provided by the present application can perform transient measurement on the plasma, and the measurement result is more accurate, and the plasma does not need to be intruded, and can be applied to different processes and various application scenarios; the testing device of the present application includes a terahertz wave antenna, a spread spectrum module, a vector network analysis module and an industrial computer, and can realize the terahertz wave propagation characteristics and plasma parameter testing in multiple application scenarios.

[0049] 3、The plasma parameter transient terahertz wave transmission testing method provided by the present application is an inversion algorithm of plasma parameters based on the terahertz wave propagation characteristics, and can realize high-time-resolution plasma parameter testing.

[0050] Of course, implementing any product of the present application does not necessarily need to achieve all the advantages described above at the same time. BRIEF DESCRIPTION OF DRAWINGS

[0051] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0052] Figure 1 It is a whole structure schematic diagram of the testing device of the first embodiment of the present application.

[0053] Figure 2 It is a transmission transmission coefficient calculation scheme schematic diagram of the system of the first embodiment of the present application.

[0054] Figure 3 It is a testing method flowchart schematic diagram of the second embodiment of the present application.

[0055] In the drawings, the components represented by the numbers are listed as follows: 1 is a first microwave darkroom, 2 is a measured device, 3 is a second microwave darkroom, 4 is a vector network analysis module, 5 is an industrial computer, 6 is a first spread spectrum module, 7 is a transmitting horn antenna, 8 is a first lens, 9 is a plasma, 10 is a second lens, 11 is a receiving horn antenna, and 12 is a second spread spectrum module. DETAILED DESCRIPTION

[0056] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0057] In the description of the present application, it should be understood that the terms "upper", "middle", "outer", "inner", "lower", "periphery" and the like indicate the orientation or positional relationship, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the indicated components or elements must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present application.

[0058] Embodiment one:

[0059] The embodiment discloses a plasma parameter transient terahertz wave transmission testing device.

[0060] Please refer to Figure 1 As shown in the figure, the present application is a plasma parameter transient terahertz wave transmission testing device, which comprises a first microwave darkroom, a measured device and a second microwave darkroom arranged in sequence, wherein the measured device is provided with a plasma; the first microwave darkroom is provided with a first spread spectrum module, a transmitting horn antenna and a first lens, the second microwave darkroom is provided with a second spread spectrum module, a second lens and a receiving horn antenna, the transmitting horn antenna is connected with the first spread spectrum module, and the receiving horn antenna is connected with the second spread spectrum module; the device further comprises a vector network analysis module and an industrial computer, the first spread spectrum module and the second spread spectrum module are connected with the vector network analysis module respectively, the vector network analysis module is connected with the industrial computer, and there is air between the first microwave darkroom, the transmitting horn antenna, the plasma, the receiving horn antenna and the second microwave darkroom.

[0061] In the embodiment, the vector network analysis module is connected with the first spread spectrum module, so as to realize transmission of the radio frequency signal output by the vector network analysis module to the first spread spectrum module; the vector network analysis module is connected with the second spread spectrum module, so as to realize reception of the signal received by the second spread spectrum module by the vector network analysis module; and the vector network analysis module is connected with the industrial computer, so as to realize information interaction between the vector network analysis module and the industrial computer.

[0062] Further, the transmitting horn antenna is arranged at the focal point of the first lens, the receiving horn antenna is arranged at the focal point of the second lens, and the heights of the first lens and the second lens in the range of the generated plane wave are greater than or equal to the height of the measured plasma.

[0063] Embodiment two:

[0064] Referring to Figure 3 The embodiment provides a test method of the plasma parameter transient terahertz wave transmission test device.

[0065] A test method based on the plasma parameter transient terahertz wave transmission test device in the above embodiment one, comprising the following steps:

[0066] Obtaining an initial transmission transmission coefficient of the test device when no to-be-measured plasma exists in a measured space;

[0067] Obtaining discrete receiving data;

[0068] Based on the initial transmission transmission coefficient and the discrete receiving data, only the electric field of the electromagnetic wave signal is considered, and a transmission transmission coefficient of the test device changing with a sampling number is obtained;

[0069] The terahertz wave attenuation constant and the phase constant in the plasma in a single processing time period are set as linear functions of time, and an intrinsic transmission transmission coefficient of the test device is obtained based on an electromagnetic wave propagation electromagnetic model;

[0070] Based on the intrinsic transmission transmission coefficient and the transmission transmission coefficient changing with the sampling number, a target function is constructed;

[0071] The minimum value of the target function is obtained, and based on the minimum value, optimal values of the terahertz wave attenuation constant and the phase constant are obtained;

[0072] Based on the optimal values of the terahertz wave attenuation constant and the phase constant, parameter values of the plasma electron density and the collision frequency are obtained.

[0073] Further, the initial transmission transmission coefficient of the test device when no to-be-measured plasma exists in the measured space is obtained, and specifically:

[0074] When there is no to-be-tested plasma in the to-be-tested space, the radio frequency signal output by the vector network analysis module is multiplied by the first frequency expansion module to become a terahertz wave signal, output by the transmitting horn antenna, forms a plane wave through the first lens, passes through the air and the to-be-tested region respectively, is received by the receiving horn antenna and transmitted to the vector network analysis module through the second frequency expansion module, and the industrial personal computer stores the received signal to obtain the initial transmission transmission coefficient S 21，0 .

[0075] Then, discrete reception data is obtained, specifically:

[0076] The to-be-tested plasma is tested, and the receiving horn antenna receives the signal to obtain discrete reception signal Data, that is, the received signal is a discrete quantity varying with time:

[0077] Data = [Data(1), Data(2), Data(3), … Data(n)], (n = 1, 2…m) (1)

[0078] Wherein, n represents the nth sampling, and m is the total number of sampling points in the test time. Here, Data contains the amplitude and phase information of the received signal.

[0079] The discrete reception data is divided into p single processing time periods, and each single processing time period includes q sampling points, that is,

[0080]

[0081] Wherein, m = p x q.

[0082] For the xth single processing time period, the yth data Data(x, y) is

[0083] n = (x-1) · q + y (3)

[0084] The transmission transmission coefficient T(n) of the entire system varying with the sampling number n is calculated below. If only the electric field of the electromagnetic wave signal is considered, the transmitting wave signal is E in , and the receiving wave signal is E out , the transmission transmission coefficient of the system can be expressed as:

[0085] S 21 (t) = E out / E in (4)

[0086] The initial value of S 21 before starting the plasma transient experiment can be expressed as:

[0087] S 21 (1) = E out (1) / Ein (1) = S 21,0 (5)

[0088] Since there is no plasma in the measured region at the beginning of the experiment, the transmission coefficient S 21 (1) of the system at the first sampling is equal to S 21,0 .

[0089] The emission wave signal remains unchanged throughout the test, so there is

[0090] E in (n) = E in (1) (6)

[0091] By combining equations (4) and (5), we get:

[0092] S 21 (n) = E out (n) / E in (1)·S 21,0 (7)

[0093] E out (n) can be obtained from the received signal data, so the calculation formula of S 21 (n) of the entire system changing with sampling time n is as follows:

[0094] S 21 (n) = Data(n) / Data(1)·S 21,0 (8)

[0095] According to the electromagnetic model of the system, the calculation formula of the transmission coefficient S 21 of the system can be expressed as a function

[0096] S 21 = T air1 ·T wall1 ·T air2 ·T wall2 (9)

[0097] Where T air1 , T wall1 , T wall2 , and T air2 are the transmission coefficients of the four interfaces between air and the front plasma device, the front plasma device and plasma, plasma and the rear plasma device, and the rear plasma device and air, respectively.

[0098] Here,

[0099]

[0100]

[0101]

[0102]

[0103]

[0104]

[0105]

[0106]

[0107]

[0108]

[0109]

[0110] Γ air2 = Z0 (21)

[0111] where k0represents the air wave number, ki represents the measured device wall electromagnetic wave number, k p represents the plasma wave number. di represents the measured device wall thickness, d p represents the measured plasma width. Z0represents the air wave impedance, Zi represents the measured device wall wave impedance, Z0represents the plasma wave impedance. R air1 , R wall1 , R wall2 , R air2 , respectively, are the reflection coefficients of the four interfaces of air and front plasma device wall, front plasma device wall and plasma, plasma and back plasma device wall, back plasma device wall and air. air1 , Γ wall1 , Γ wall2 , Γ air2 , respectively, are the input impedances of the four interfaces of air and front plasma device wall, front plasma device wall and plasma, plasma and back plasma device wall, back plasma device wall and air.

[0112] Here, k p = β - j·α is an unknown parameter related to the plasma parameters, β and α represent the attenuation constant and phase constant of the electromagnetic wave, respectively. Other parameters depend on the geometry and material properties of the test device.

[0113] For the xth single processing time period, β and α can be expressed as linear functions of time, i.e.

[0114] β = ax +b x t (22)

[0115] α=c x +d x t (23)

[0116] wherein a x and c x represent the initial value of the relative permittivity and loss of the plasma in a single processing time period, respectively, b x and d x represent the corresponding change rates thereof.

[0117] For the convenience of further analysis, the time is normalized with respect to a single processing time period. Let Δt represent the test time of a single data point, and the total test time is t m =m·Δt. If the time is normalized, the normalized value of the sampling time of the nth test data is (n·Δt) / (m·Δt)=n / m, and the above formula can be changed to

[0118]

[0119]

[0120] When x>1, there is

[0121]

[0122]

[0123] Since the plasma has not been generated in the measured region at the beginning of the experiment, when x=1, t

[0124]

[0125] c1=0 (29)

[0126] At this time, the only unknowns are b x and d x , and at this time, the intrinsic transmission transfer coefficient of the system can be expressed as:

[0127]

[0128] Based on the intrinsic transmission transfer coefficient of the entire system and the transmission transfer coefficient S 21 of the entire system varying with the sampling number n, a target function F x is constructed:

[0129]

[0130] The target function F xThe difference between the function calculation value representing the system transmission coefficient in a single processing time period and the actual transmission coefficient of the system is calculated by a direct method in b x and d x The feasibility of each iteration point is checked in the feasible region of b x and d x , and the variables b x and d x are continuously optimized to minimize the value of the objective function F, at which time the errors of the corresponding β x and α x are minimized, which are the optimal values under the corresponding test conditions.

[0131] β and α depend on the plasma frequency ω p and the collision frequency v, and have

[0132]

[0133]

[0134]

[0135] wherein ε0 represents the vacuum permittivity.

[0136] The optimal β and α values are brought into equations (32) and (33), and simultaneous equations are solved to obtain the plasma electron density n e and the collision frequency v in a single processing time period.

[0137] The embodiment provides a plasma parameter transient terahertz wave transmission test system.

[0138] The plasma parameter transient terahertz wave transmission test system comprises:

[0139] An initial transmission coefficient acquisition module is configured to acquire an initial transmission coefficient of a test device in a measured space when no to-be-measured plasma exists in the measured space;

[0140] A discrete reception data acquisition module is configured to acquire discrete reception data;

[0141] An intrinsic transmission coefficient acquisition module is configured to set the plasma electron density and the collision frequency as linear functions of time, and acquire an intrinsic transmission coefficient of the test device based on the discrete reception data;

[0142] A transmission coefficient acquisition module that changes with sampling times is configured to acquire a transmission coefficient of the test device that changes with sampling times based on the initial transmission coefficient and the discrete reception data, and only consider a terahertz wave electric field;

[0143] The objective function construction module is configured to construct an objective function based on the intrinsic transmission transfer coefficient and the transmission transfer coefficient varying with the sampling number;

[0144] The optimal parameter value acquisition module is configured to acquire a minimum value of the objective function, and acquire the optimal values of the terahertz wave attenuation constant and the phase constant based on the minimum value.

[0145] The plasma parameter value acquisition module is configured to acquire the plasma electron density and the collision frequency parameter values based on the optimal values of the terahertz wave attenuation constant and the phase constant.

[0146] In the description of the present specification, the description referring to the terms "one embodiment", "an example", "a specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0147] The preferred embodiments of the application disclosed above are only used to help explain the application. The preferred embodiments do not describe all the details of the application, and the application is not limited to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of the present specification. The present specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the application, so that those skilled in the art can well understand and utilize the application. The application is limited only by the claims and their full scope and equivalents.

Claims

1. A test method of a plasma parameter transient terahertz wave transmission test device, characterized in that, An plasma parameter transient terahertz wave transmission test device is adopted, the plasma parameter transient terahertz wave transmission test device comprises a first microwave darkroom, a device under test and a second microwave darkroom arranged in sequence, and a plasma is arranged in the device under test; a first spread spectrum module, a transmitting horn antenna and a first lens are arranged in the first microwave darkroom, a second spread spectrum module, a second lens and a receiving horn antenna are arranged in the second microwave darkroom, the transmitting horn antenna is connected with the first spread spectrum module, and the receiving horn antenna is connected with the second spread spectrum module; a vector network analysis module and an industrial computer are further included, the first spread spectrum module and the second spread spectrum module are connected with the vector network analysis module respectively, the vector network analysis module is connected with the industrial computer, and air exists between the first microwave darkroom, the transmitting horn antenna, the plasma, the receiving horn antenna and the second microwave darkroom; The transmitting horn antenna is arranged at the focal point of the first lens, the receiving horn antenna is arranged at the focal point of the second lens, and the heights of the first lens and the second lens in the range of generating a plane wave are greater than or equal to the height of the measured plasma; The test method of the plasma parameter transient terahertz wave transmission test device comprises the following steps: An initial transmission transmission coefficient of the test device when there is no to-be-measured plasma in a measured space is obtained; Discrete receiving data is obtained; Based on the initial transmission transmission coefficient and the discrete receiving data, only the terahertz wave electric field is considered, and a transmission transmission coefficient of the test device changing with a sampling number is obtained; The terahertz wave attenuation constant and the phase constant in the plasma are set as linear functions of time, and an intrinsic transmission transmission coefficient of the test device is obtained based on an electromagnetic wave propagation model; The intrinsic transmission transmission coefficient is expressed as: n denotes the nth sampling, m is the total number of sampling points within the test time, a x and c x respectively represent the initial value of the relative permittivity and loss of the plasma within a single processing time period, b x and d x respectively represent the change rate of the relative permittivity and loss of the plasma, t m is the total test time; Based on the intrinsic transmission transmission coefficient and the transmission transmission coefficient changing with the sampling number, a target function is constructed; The target function F is expressed as: wherein, S is the intrinsic transmission transfer coefficient, 21 (n) is the transmission transfer coefficient as a function of the number of samples; N is the number of sampling points within each single treatment time period; A minimum value of the target function is obtained, and based on the minimum value, optimal values of the terahertz wave attenuation constant and the phase constant are obtained; Based on the optimal values of the terahertz wave attenuation constant and the phase constant, parameter values of plasma electron density and collision frequency are obtained.

2. The test method of claim 1, wherein, The initial transmission transmission coefficient of the test device when there is no to-be-measured plasma in the measured space is obtained, specifically as follows: When there is no to-be-tested plasma in the to-be-tested space, the radio frequency signal output by the vector network analysis module passes through the first spread spectrum module to be multiplied into a terahertz wave signal, which is output by the transmitting horn antenna, forms a plane wave through the first lens, passes through the air and the to-be-tested region respectively, is received by the receiving horn antenna, and is transmitted to the vector network analysis module through the second spread spectrum module, and the industrial computer stores the received signal to obtain an initial transmission transmission coefficient .

3. The test method of claim 2, wherein, The discrete receiving data is obtained, specifically as follows: A signal is received by using the receiving horn antenna to obtain discrete receiving data Data: Wherein, n represents the nth sampling, m is the total sampling point number in the test time, and the Data includes the terahertz wave propagation transmission transmission coefficient and the sampling time information.

4. The test method of claim 3, wherein, The m discrete receiving data are divided into p single processing time periods, and each single processing time period includes q sampling points, that is, Wherein, m = p × q.

5. The method of claim 4, wherein the plasma parameter transient terahertz wave transmission test apparatus is characterized by, The transmission transmission coefficient of the test device changing with the sampling number is expressed as: where Data(n) is the discrete received data obtained at the nth sampling, Data(l) is the discrete received data obtained at the 1st sampling, S 21,0 is the initial transmission transfer coefficient.

6. A test method for a plasma parameter transient terahertz wave transmission test system using the plasma parameter transient terahertz wave transmission test device according to claim 1, characterized in that, It includes: An initial transmission transmission coefficient acquisition module is configured to obtain the initial transmission transmission coefficient of the test device when there is no to-be-measured plasma in the measured space; A discrete receiving data acquisition module is configured to obtain the discrete receiving data; The intrinsic transmission transmission coefficient acquisition module is configured to set the plasma electron density and the collision frequency as linear functions of time, and acquire the intrinsic transmission transmission coefficient of the test device based on the discrete received data; The transmission transmission coefficient acquisition module changing with the sampling number is configured to acquire the transmission transmission coefficient of the test device changing with the sampling number based on the initial transmission transmission coefficient and the discrete received data, and only consider the terahertz wave electric field; The objective function construction module is configured to construct an objective function based on the intrinsic transmission transmission coefficient and the transmission transmission coefficient changing with the sampling number; The optimal parameter value acquisition module is configured to acquire the minimum value of the objective function, and acquire the optimal values of the terahertz wave attenuation constant and the phase constant based on the minimum value; The plasma parameter value acquisition module is configured to acquire the plasma electron density and the collision frequency parameter values based on the optimal values of the terahertz wave attenuation constant and the phase constant.

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