Measurement device and method for single-cavity operating frequency and inter-cavity coupling coefficient

Abstract

The present invention provides a measuring device for the single-cavity operating frequency and the inter-cavity coupling coefficient of a coupled resonator chain, comprising: a base; a support unit mounted on the base for fixing the coupled resonator chain; a probe unit mounted on the base and configured to feed incident microwaves into the coupled resonator chain and extract reflected microwaves; and a position adjustment unit provided on the base and connected to the probe unit, configured to adjust the horizontal position of the probe unit on the base. There is also provided a method for measuring the single-cavity operating frequency and the inter-cavity coupling coefficient of a coupled resonator chain by means of the above measuring device, and the measuring method reduces the frequency error caused by the probe extending into the resonator chain and improves the test accuracy and test efficiency.

Description

Technical Field

[0001] The present invention relates to the field of microwaves, and particularly to a measuring device and a measuring method for the single-cavity operating frequency and the inter-cavity coupling coefficient of a coupled resonator chain. Background Art

[0002] The accelerating tube is the core component of an electron linear accelerator, and its performance directly determines the stability and reliability of the whole machine. The accelerating tube accelerates electrons to a very high energy through microwave power. To ensure that electrons can obtain effective acceleration when passing through the accelerating tube, the inner wall of the accelerating tube on the electron passing path requires very high machining accuracy (±5μm) and good surface finish (▽10 or above). To verify the machining quality of the parts, it is necessary to measure their microwave parameters. Therefore, it becomes particularly important to accurately obtain the microwave parameters of the accelerating tube cavity chain.

[0003] The accelerating tube is a kind of coupled resonator chain. At present, the single-cavity frequency test of the coupled resonator chain mainly adopts the resonance method. There are usually two excitation methods for the resonance method, namely the blind plate short-circuit coupling loop excitation method (referred to as the coupling loop method) and the in-tube antenna probe excitation method (referred to as the antenna method).

[0004] As Figure 1 shown, in the coupling loop method, two small holes are opened on the metal blind plate, and coupling loops are respectively inserted. The input loop feeds in microwave power, and the output loop picks up the microwave and detects it through transistor detection. By changing the composition structure of the measured cavity chain, the frequencies corresponding to different modes can be measured.

[0005] As Figure 2 shown, in the antenna method, two metal pistons are respectively inserted at both ends of the coupled resonator chain, and an antenna probe is inserted along the central axis of the piston. The transmitting antenna feeds in microwave power, and the receiving antenna leads out for measurement. When two half-cavities are intercepted between the piston surfaces to sandwich a whole cavity, only the mode can be excited. If the number of cavities is changed, other modes can also be excited. However, no matter what method is used, the 0 mode and the π mode are suppressed. The amplitude and frequency of the resonance peak observed by the antenna method change with the deviation of the piston position. Only when the antenna is located at the accurate mid-section, the corresponding resonance frequency is the value to be measured.

[0006] According to the characteristics of the current two test methods, when the coupling loop method measures the single-cavity frequency of a certain mode of the cavity chain, it is necessary to replace the test cavity one by one and cannot perform continuous testing, so the test efficiency is relatively low. In the antenna method, the two half-cavities are not completely detuned during the test, and there will also be coupling with the whole cavity, which affects the accuracy of the whole-cavity frequency. Moreover, it has extremely high requirements for the probe position and the experience of the test personnel. Inaccurate probe position will cause a large error in the single-cavity frequency test result.

[0007] The content in the background art section is only the technology known to the applicant and does not of course represent the prior art in this field. Summary of the Invention

[0008] In view of at least one defect of the prior art, the present invention designs a measuring device and a measuring method for the single - cavity operating frequency and the inter - cavity coupling coefficient of a coupled resonator chain, reducing the influence of frequency drift caused by the probe extending into the cavity in the existing test method, thereby improving the test accuracy and efficiency.

[0009] The present invention provides a measuring device for the single - cavity operating frequency and the inter - cavity coupling coefficient of a coupled resonator chain, comprising: a base; a support unit, mounted on the base and configured to fix the coupled resonator chain; a probe unit, mounted on the base and configured to feed incident microwaves into the coupled resonator chain and extract reflected microwaves; and a position adjustment unit, provided on the base and connected to the probe unit, configured to adjust the horizontal position of the probe unit on the base.

[0010] According to one aspect of the present invention, the probe unit includes: a probe base, mounted on the base; and a probe, releasably clamped by the probe base, the probe including a magnetic probe and a detuning rod, and the diameters of both the magnetic probe and the detuning rod are smaller than the diameter of the beam hole of the coupled resonator chain.

[0011] According to one aspect of the present invention, the magnetic probe has a coaxial structure, including an inner conductor, an outer conductor surrounding the inner conductor, and an insulating layer located between the inner conductor and the outer conductor, and the inner conductor and the outer conductor are short - circuited at a predetermined distance from the end of the magnetic probe to form a coupling loop.

[0012] According to one aspect of the present invention, the base includes a scale - marked guide rail, the probe unit is mounted on the guide rail and can slide along the guide rail, and the position adjustment unit includes a gear - rack structure or a ball - screw structure, and the position adjustment unit is further configured to adjust the vertical height of the probe unit on the base.

[0013] According to one aspect of the present invention, the support unit includes a V - block for fixing the coupled resonator chain at a predetermined position.

[0014] According to one aspect of the present invention, a vector network analyzer is further included, the vector network analyzer can be connected to the probe, configured to output the incident microwaves and receive the reflected microwaves, and further configured to determine the single - cavity operating frequency and the inter - cavity coupling coefficient of the coupled resonator chain according to the reflected microwaves.

[0015] The present invention also provides a method for measuring the single - cavity operating frequency and the inter - cavity coupling coefficient of a coupled resonator chain based on the above - mentioned measuring device, comprising:

[0016] S101: Fix the coupled resonator chain on the support unit;

[0017] S102: Insert the probe unit into the beam hole of the coupled resonator chain through the position adjustment unit and adjust it to an appropriate horizontal position on the base;

[0018] S103: Feed incident microwaves into one of the cavities of the coupled resonator chain through the probe unit;

[0019] S104: Extract reflected microwaves from the coupled resonator chain through the probe unit;

[0020] S105: Obtain the single-cavity operating frequency and the inter-cavity coupling coefficient of the one cavity according to the reflected microwaves.

[0021] According to one aspect of the present invention, the probe includes a magnetic probe and a detuning rod. When the one cavity is a coupling cavity, step S102 includes: positioning the detuning rod and the magnetic probe on both sides of the coupling cavity respectively, so that the magnetic probe and the detuning rod detune the cavities other than the coupling cavity without affecting the coupling cavity.

[0022] According to one aspect of the present invention, the probe includes a magnetic probe and a detuning rod. When the one cavity is an accelerating cavity, step S102 includes: positioning the magnetic probe and the detuning rod on both sides of the accelerating cavity and an adjacent coupling cavity respectively, so that the magnetic probe and the detuning rod detune the cavities other than the accelerating cavity and the adjacent coupling cavity without affecting the accelerating cavity and the adjacent coupling cavity.

[0023] According to one aspect of the present invention, step S102 further includes: keeping the position of the magnetic probe close to the coupling cavity in the probe unit unchanged, moving the detuning rod in the probe unit into the accelerating cavity to detune the accelerating cavity, and then repeating steps S103 - S105.

[0024] According to one aspect of the present invention, the distance that the detuning rod close to the accelerating cavity in the probe unit is moved into the accelerating cavity is set so that the frequency difference generated by the movement is approximately one-thousandth of the operating frequency of the accelerating cavity.

[0025] According to one aspect of the present invention, step S105 includes: obtaining the double-peak frequencies of the reflected microwaves, and the double-peak frequencies include the 0-mode operating frequency and the π-mode operating frequency.

[0026] According to one aspect of the present invention, while keeping the position of the magnetic probe near the coupling cavity in the probe unit unchanged, the detuning rod near the accelerating cavity in the probe unit is moved into the accelerating cavity to more than three positions, and steps S103 - S105 are respectively repeated. Step S105 further includes: according to multiple groups of double-peak frequencies, obtaining the operating frequency of the accelerating cavity, the operating frequency of the adjacent coupling cavity, and the inter-cavity coupling coefficient between the accelerating cavity and the adjacent coupling cavity by fitting.

[0027] Through the measuring device and measuring method of the present invention, the position where the probe extends into the coupled resonator chain can be determined, and the test efficiency and accuracy can be improved. The test method combining the magnetic probe and the detuning rod can reduce the influence of the probe extending deep into the cavity on the test frequency and improve the test accuracy.

[0028] The features and advantages described in the specification are not all. In particular, in combination with the drawings and the specification, many additional features and advantages will be obvious to those of ordinary skill in the art. In addition, it should be noted that the terms used in this specification are mainly selected for readability and guidance purposes and may not be selected to describe or limit the inventive technical solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings forming a part of this disclosure are used to provide a further understanding of the disclosure. The schematic embodiments and descriptions thereof of the disclosure are used to explain the disclosure and do not constitute an improper limitation of the disclosure. In the drawings:

[0030] Figure 1 The schematic diagram of the test principle of the coupling loop method is shown;

[0031] Figure 2 The schematic diagram of the test principle of the antenna method is shown;

[0032] Figure 3a The first view of the measuring device provided by the present invention is shown;

[0033] Figure 3b The second view of the measuring device provided by the present invention is shown;

[0034] Figure 4 The schematic structural diagram of the magnetic probe is shown;

[0035] Figure 5 The flowchart of the measuring method provided by the present invention is shown;

[0036] Figure 6 The schematic diagram of the coupling cavity frequency test of the first embodiment is shown;

[0037] Figure 7 The schematic diagram of the accelerating cavity frequency and inter-cavity coupling coefficient test of the second embodiment is shown;

[0038] Figure 8 shows the S11 curve of the acceleration cavity of the second embodiment and its adjacent coupling cavity; and

[0039] Figure 9 shows a schematic diagram of the magnetic coupling RLC equivalent circuit of two resonant cavities. Detailed implementation manners

[0040] In the following, only some exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present invention. Therefore, the drawings and the description are considered to be exemplary in nature rather than restrictive.

[0041] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, 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. Therefore, it cannot be understood as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of the described features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0042] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "mounted", "connected", "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection: it can be a mechanical connection, an electrical connection, or can communicate with each other; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0043] In the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may include direct contact between the first and second features, or may include indirect contact between the first and second features through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "below" and "beneath" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the horizontal height of the first feature is lower than that of the second feature.

[0044] The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. To simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numerals and / or reference letters in different examples. Such repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those of ordinary skill in the art may be aware of the application of other processes and / or the use of other materials.

[0045] The present invention provides a measuring device for measuring the single-cavity operating frequency and the inter-cavity coupling coefficient of a coupled resonator chain. By a measuring method combining a magnetic probe with a detuning rod, a magnetic probe and a detuning rod are combined, and the single-cavity operating frequency and the inter-cavity coupling coefficient of the resonator chain are indirectly obtained through calculation. The measuring method reduces the frequency error caused by inserting the probe into the cavity and the influence on the inter-cavity coupling, and improves the test accuracy and test efficiency.

[0046] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not intended to limit the present invention.

[0047] Figure 3a The front view of a measuring device 10 according to an embodiment of the present invention is shown. The measuring device 10 includes: a base 11, a support unit 12, a probe unit 13, and a position adjustment unit 14.

[0048] The support unit 12 is mounted on the base 11, and is used to fix the coupled resonator chain as the cavity segment to be measured, and is configured to facilitate the replacement of the device under test. Figure 3bA perspective view of the measuring device 10 is shown, wherein the support unit 12 includes V-blocks 121, preferably two V-blocks 121, for fixing the cavity section 20 to be measured at a predetermined position to ensure that the center of the cavity section 20 to be measured and the center of the guide rail are in the same vertical plane. Preferably, the support unit 12 may further include a support disc 122, and the center of the support disc 122 has a stepped hole into which the cavity section 20 to be measured is inserted. Additionally, the support unit 12 or the support disc 122 may also include threaded fasteners for stably fixing the cavity section 20 to be measured thereon.

[0049] As Figure 3a shown, the probe unit 13 is mounted on the base 11 and configured to feed incident microwaves into the cavity section 20 to be measured and extract reflected microwaves. As Figure 3a and 3b shown, the probe unit 13 includes a probe base 131 and probes (including a magnetic probe 132 and a detuning rod 133). The probe base 131 is mounted on the base 11 through a position adjustment unit 14; the magnetic probe 132 and the detuning rod 133 are located on both sides of the cavity section 20 to be measured and are releasably clamped by the probe base 131. The diameters of the magnetic probe 132 and the detuning rod 133 are both smaller than the diameter of the beam hole of the cavity section 20 to be measured to ensure that the two probes can be adjusted into and out of the cavity section 20 to be measured without obstruction. As Figure 3a shown, the position adjustment unit 14 is provided on the base 11 and connected to the probe unit 13, and is configured to adjust the horizontal position of the probe unit 13 on the base 11, so as to adjust the magnetic probe 132 and the detuning rod 133 to different positions in the cavity section 20 to be measured and perform measurements.

[0050] According to a preferred embodiment of the present invention, in order to achieve precise positioning of the probe unit 13, the base 11 includes a guide rail with scales, and the probe unit 13 (or the position adjustment unit 14) may have a slider corresponding to the guide rail, so that the probe unit 13 is mounted on the guide rail and can slide along the guide rail. During testing, by recording the position or travel distance of the slider on the guide rail and comparing it with the length dimension of the cavity section 20 to be measured, the position of the probe unit 13 can be determined. Those skilled in the art can understand that the guide rail and the guide rail slider are only a transmission method, and other transmission methods can also be selected to achieve accurate determination of the position of the probe unit 13, and all should be included in the protection scope of the present invention.

[0051] As Figure 3aAs shown, the position adjustment unit 14 is arranged on the base 11 and connected to the probe unit 13, and is configured to adjust the horizontal position of the probe unit 13 on the base 11. According to a preferred embodiment of the present invention, the position adjustment unit 14 includes a rack and pinion structure or a ball screw structure. Taking the rack and pinion structure as an example, for example, a rack can be fixed on the guide rail, and a gear is arranged on the slider, and the gear and the rack are meshed together. By turning the gear with a knob, since the rack is fixed on the guide rail, the gear will roll left and right along the rack, and at the same time drive the slider and the probe unit 13 to move left and right along the guide rail and the rack to change its horizontal position. Those skilled in the art can understand that the rack and pinion structure or the ball screw structure is only a transmission method, and other transmission methods can also be selected, which should all be included in the protection scope of the present invention.

[0052] In addition, in addition to adjusting the horizontal position of the probe unit 13 on the base 11, the position adjustment unit 14 can be further configured to adjust the vertical height of the probe unit 13 on the base 11 to ensure that the probe unit 13 is directly opposite to the central beam hole of the cavity segment 20 to be measured.

[0053] Figure 4 The structural schematic diagram of the magnetic probe 132 according to an embodiment of the present invention is shown. The magnetic probe 132 is a coaxial line structure and can be modified on the basis of a common coaxial line. The magnetic probe 132 includes an inner conductor 1321, an outer conductor 1322 surrounding the inner conductor 1321, and an insulating layer 1323. The insulating layer 1323 is located between the inner conductor 1321 and the outer conductor 1322. The inner conductor 1321 and the outer conductor 1322 are short-circuited and connected at a predetermined distance at the end of the magnetic probe 132 to form a coupling ring, which can detect the magnetic field change during the test. Those skilled in the art can understand that the predetermined distance only needs to ensure the formation of the coupling ring.

[0054] As Figure 3a shown, the measuring device 10 may further include a vector network analyzer 15. The vector network analyzer 15 is connected to the probe unit 13. Specifically, as Figure 3b shown, the vector network analyzer 15 is connected to the magnetic probe 132, and is configured to output incident microwaves and receive reflected microwaves, and can determine the single-cavity operating frequency and the inter-cavity coupling coefficient of the coupled resonator chain according to the reflected microwaves. The specific calculation method will be described in detail below.

[0055] The measuring device 10 provided by the present invention has been described above. Next, the measuring method 100 provided by the present invention will be described in detail.

[0056] Figure 5The flowchart of the measurement method 100 provided by the present invention is shown, that is, the method 100 for measuring the single-cavity operating frequency and the inter-cavity coupling coefficient of a coupled resonator chain based on the above measurement device, where the coupled resonator chain is the to-be-measured cavity section 20, and the to-be-measured cavity section 20 includes a coupling cavity 21 and an accelerating cavity 22. The accelerating cavity 22 is used to establish an accelerating electromagnetic field to accelerate the electron beam entering it, and the coupling cavity 21 is used to couple the electromagnetic field between adjacent accelerating cavities. The method includes:

[0057] In step S101: Fix the to-be-measured cavity section 20 on the support unit 12. In step S101, first place the to-be-measured cavity section 20 on the support unit 12, ensure that the center of the to-be-measured cavity section 20 and the center of the guide rail are in the same plane, and then fix it.

[0058] In step S102: Insert the probe unit 13 into the beam hole of the to-be-measured cavity section 20 through the position adjustment unit 14 and adjust it to an appropriate horizontal position on the base 11. In step S102, adjust the probe unit 13 to an appropriate horizontal position on the base 11 and position the probe unit 13 on both sides of the cavity to be measured. By recording the position and travel distance of the slider on the guide rail and based on the length dimension of the to-be-measured cavity section 20, it can be determined which position the probe is in the to-be-measured cavity section 20, which helps to accurately position the probe on both sides of the cavity to be measured and prevent the probe position from being difficult to determine when the to-be-measured cavity section 20 is too long, thus affecting the test efficiency and the accuracy of the test results. Additionally, if necessary, the height of the probe unit 13 can be adjusted to be directly opposite to the central beam hole of the to-be-measured cavity section 20 by adjusting the position adjustment unit 14.

[0059] In step S103: Feed incident microwaves into one of the cavities of the to-be-measured cavity section 20 through the probe unit 13;

[0060] In step S104: Extract reflected microwaves from the to-be-measured cavity section 20 through the probe unit 13;

[0061] In step S105: Obtain the single-cavity operating frequency and the inter-cavity coupling coefficient of the one cavity according to the reflected microwaves.

[0062] Figure 6 The schematic diagram of the coupling cavity frequency test according to an embodiment of the present invention is shown. When the cavity to be measured is a coupling cavity, in step S102: Calculate the feed amount of each probe according to the length of each cavity of the to-be-measured cavity section, and then position the magnetic probe 132 and the detuning rod 133 on both sides of the coupling cavity to be measured respectively, so that the magnetic probe 132 and the detuning rod 133 detune the cavities other than the coupling cavity to be measured without affecting the coupling cavity to be measured, that is, the magnetic probe 132 and the detuning rod 133 are on both sides of the coupling cavity to be measured and close to the edge of the coupling cavity to be measured.

[0063] Then, in step S103: One end of the magnetic probe 132 in the probe unit 13 is connected to a port of the vector network analyzer 15. The vector network analyzer is set to read the S11 parameter, and then an incident microwave is fed into the measured coupling cavity through the probe unit 13.

[0064] In step S104: The vector network analyzer extracts the reflected microwave from the measured coupling cavity through the magnetic probe 132.

[0065] In step S105: According to the reflected microwave, the operating frequency of the measured coupling cavity is read from the vector network analyzer.

[0066] According to a preferred embodiment of the present invention, Figure 6 In the embodiment of, the detuning rod can also be replaced by a magnetic probe. The two ports of the vector network analyzer are respectively connected to two magnetic probes. An incident microwave is fed into the coupling cavity through one magnetic probe, and the microwave is extracted through the other magnetic probe. Then, the frequency value in the S21 curve of the vector network analyzer is read, which is the operating frequency of the coupling cavity.

[0067] Figure 7 Fig. shows a schematic diagram of the test of the accelerating cavity frequency and the inter-cavity coupling coefficient according to another embodiment of the present invention. The test preparation work is carried out in steps S101 and S102. The parts that are the same as those in the first embodiment will not be described again. Only the different parts will be described in detail below.

[0068] When the cavity to be measured is an accelerating cavity, in step S102: The detuning rod 133 and the magnetic probe 132 are respectively positioned on both sides of the measured accelerating cavity and an adjacent coupling cavity, so that the magnetic probe 132 and the detuning rod 133 detune the cavities other than the measured accelerating cavity and the adjacent coupling cavity without affecting the measured accelerating cavity and the adjacent coupling cavity. That is, the detuning rod 133 is positioned at the nose cone on one side of the measured accelerating cavity, and the magnetic probe 132 is positioned at the nose cone on the side of the adjacent coupling cavity far from the measured accelerating cavity.

[0069] In steps S103 and S104: One end of the magnetic probe 132 is connected to a port of the vector network analyzer 15. The vector network analyzer is set to read the S11 parameter, and then an incident microwave is fed into the measured accelerating cavity through the probe unit 13 and the reflected microwave is extracted from the measured accelerating cavity.

[0070] In step S105: The double-peak frequency of the reflected microwave at this position is read through the vector network analyzer, that is, the 0-mode operating frequency and the π-mode operating frequency. Figure 8 Fig. shows the S11 curve obtained by the vector network analyzer, where the two inverted peaks are the double-peak frequencies.

[0071] In the second embodiment, the operating frequency of the acceleration cavity under test cannot be directly read from the vector network analyzer. Instead, multiple sets of double-peak frequencies need to be recorded and then calculated according to a formula. Therefore, step S102 further includes: keeping the position of the magnetic probe 132 in the probe unit 13 close to the adjacent coupling cavity unchanged, moving the detuning rod 133 into the acceleration cavity under test to detune the acceleration cavity under test, and then repeating steps S103 - S105 to obtain multiple sets of double-peak frequencies.

[0072] According to a preferred embodiment of the present invention, the distance by which the detuning rod 133 in the probe unit 13 close to the acceleration cavity under test is moved into the acceleration cavity under test is set such that the frequency difference generated by the movement is approximately one-thousandth of the operating frequency of the acceleration cavity under test. That is, each time the detuning rod 133 is moved a small distance into the acceleration cavity under test to ensure that the frequency difference generated by each movement is a small amount. Those skilled in the art can understand that the small amount is not limited to one-thousandth of the operating frequency, as long as several sets of double-peak frequencies required for the calculation formula can be obtained.

[0073] Furthermore, keeping the position of the magnetic probe 132 in the probe unit 13 close to the coupling cavity adjacent to the accelerator under test unchanged, the detuning rod 133 in the probe unit close to the acceleration cavity under test is moved into the acceleration cavity under test to more than three positions, and steps S103 - S105 are respectively repeated to obtain multiple sets of double-peak frequencies. Step S105 further includes: according to multiple sets of double-peak frequencies, obtaining the operating frequency of the acceleration cavity under test, the operating frequency of the adjacent coupling cavity, and the inter-cavity coupling coefficient between the acceleration cavity under test and the adjacent coupling cavity by fitting a relationship curve.

[0074] The calculation method of the fitting curve is described in detail below.

[0075] Figure 9 Shows a schematic diagram of the magnetic coupling RLC equivalent circuit of two resonant cavities. The coupling between two cavities in a coupled resonant cavity chain can be equivalent to an RLC circuit. From relevant theories, it is easy to obtain the relationship formula between the coupling coefficient between two cavities and the frequency, as shown in formula (1). In the formula, f a and f c are respectively the frequencies of the acceleration cavity under test and the coupling cavity adjacent to it, k is the coupling coefficient between the two cavities, and f is the operating frequency in this operating mode. The solutions of formula (1) are the operating frequencies f 0 and f π, according to the relationship between the roots and coefficients, formulas (2) and (3) can be obtained. For the convenience of calculation, we introduce variables x and y, and the relationship between them is shown in formula (4). Since the detuning rod 133 continuously penetrates into the measured accelerating cavity and detunes the measured accelerating cavity, while the frequency of the adjacent coupling cavity remains unchanged, it can be seen from formula (4) that as the detuning rod 133 penetrates into the measured accelerating cavity by different distances, x and y satisfy a simple linear relationship. Thus, by continuously penetrating the detuning rod 133 into the measured accelerating cavity, several groups of different double-peak frequencies can be recorded, and the linear relationship between x and y can be obtained by fitting, and the values of a and b can be obtained. The coupling cavity frequency, the accelerating cavity frequency, and the coupling coefficient between the two are shown in formulas (5), (6), and (7).

[0076]

[0077]

[0078]

[0079]

[0080]

[0081]

[0082]

[0083] Combine the above calculation method with the test method 100 of the second embodiment. In step S102, move the detuning rod 133 a small amount into the measured accelerating cavity, read the double-peak frequency after the measured accelerating cavity is detuned, repeat it more than three times, obtain multiple groups of double-peak frequencies, and input the data into the table compiled according to formulas (1) to (7), then the relationship curve between x and y can be obtained by fitting, so as to obtain the working frequency of the coupling cavity and the working frequency of the accelerating cavity.

[0084] The working frequency of the coupling cavity calculated by the above method can be mutually verified with the directly measured working frequency of the coupling cavity in the first embodiment, ensuring the credibility of the results. At the same time, according to the linearity of the relationship curve between x and y obtained by fitting, the accuracy of the test result of the working frequency of the measured accelerating cavity can also be confirmed, and the method 100 can also obtain a relatively accurate test result for the side cavity that is not easy to measure accurately in the coupled resonant cavity chain.

[0085] The test method 100 provided by the present invention is applicable to various coupled resonant cavity chains, such as standing wave accelerating tubes with magnetic axis coupling, various side couplings, ring couplings, arrow-shaped coupling cavities, etc., and has good versatility.

[0086] Based on the measuring device 10 of the present invention, the sliding distance of the probe unit 13 can be recorded. Based on the length dimension of the cavity section 20 to be measured, it is convenient to determine the position of the probe in the cavity section 20 to be measured, improving the test efficiency and accuracy. The test method combining the magnetic probe and the detuning rod can reduce the influence of the probe position deep into the cavity on the test frequency, improving the test precision and test efficiency.

[0087] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A measuring device for the single - cavity operating frequency and the inter - cavity coupling coefficient of a coupled resonator chain, characterized in that, it includes: a base; a support unit, mounted on the base, for fixing the coupled resonator chain; a probe unit, mounted on the base, configured to feed incident microwaves into the coupled resonator chain and extract reflected microwaves, wherein the probe unit includes: a probe holder, mounted on the base; a probe, the probe is releasably clamped by the probe holder, the probe includes a magnetic probe and a detuning rod, the diameters of the magnetic probe and the detuning rod are both smaller than the diameter of the beam hole of the coupled resonator chain, wherein the magnetic probe is of coaxial structure, including an inner conductor, an outer conductor surrounding the inner conductor, and an insulating layer, the insulating layer is located between the inner conductor and the outer conductor, and the inner conductor and the outer conductor are short - circuited and connected at a predetermined distance from the end of the magnetic probe to form a coupling loop; and a position adjustment unit, arranged on the base and connected to the probe unit, configured to be able to adjust the horizontal position of the probe unit on the base, so as to adjust the probe to different positions within the coupled resonator chain for measurement.

2. The measuring device according to claim 1, characterized in that, the base includes a scale - equipped guide rail, the probe unit is mounted on the guide rail and can slide along the guide rail, the position adjustment unit includes a gear - rack structure or a ball - screw structure, and the position adjustment unit is further configured to be able to adjust the vertical height of the probe unit on the base.

3. The measuring device according to claim 1, characterized in that, the support unit includes a V - block, for fixing the coupled resonator chain in a predetermined position.

4. The measuring device according to claim 1, characterized in that, it further includes a vector network analyzer, the vector network analyzer can be connected to the probe, configured to output the incident microwaves and receive the reflected microwaves, and is further configured to be able to determine the single - cavity operating frequency and the inter - cavity coupling coefficient of the coupled resonator chain according to the reflected microwaves.

5. A method for measuring the single - cavity operating frequency and the inter - cavity coupling coefficient of a coupled resonator chain by using the measuring device according to any one of claims 1 - 4, characterized in that, it includes: S101: Fix the coupled resonator chain on the support unit; S102: Through the position adjustment unit, insert the probe unit into the beam hole of the coupled resonator chain and adjust it to an appropriate horizontal position on the base; S103: Through the probe unit, feed incident microwaves into one of the cavities of the coupled resonator chain; S104: Through the probe unit, extract reflected microwaves from the coupled resonator chain; S105: According to the reflected microwaves, obtain the single - cavity operating frequency and the inter - cavity coupling coefficient of the one cavity.

6. The method according to claim 5, characterized in that, The probe includes a magnetic probe and a detuning rod. When one of the cavities is a coupling cavity, step S102 includes: positioning the magnetic probe and the detuning rod on both sides of the coupling cavity respectively, so that the magnetic probe and the detuning rod detune the cavities other than the coupling cavity without affecting the coupling cavity.

7. The method according to claim 5, wherein, the probe includes a magnetic probe and a detuning rod. When one of the cavities is an accelerating cavity, step S102 includes: positioning the detuning rod and the magnetic probe on both sides of the accelerating cavity and an adjacent coupling cavity respectively, so that the magnetic probe and the detuning rod detune the cavities other than the accelerating cavity and the adjacent coupling cavity without affecting the accelerating cavity and the adjacent coupling cavity.

8. The method according to claim 7, wherein, step S102 further includes: keeping the position of the magnetic probe close to the coupling cavity in the probe unit unchanged, moving the detuning rod in the probe unit into the accelerating cavity, so that the accelerating cavity is detuned, and then repeating steps S103 - S105.

9. The method according to claim 8, wherein, the distance of moving the detuning rod close to the accelerating cavity in the probe unit into the accelerating cavity is set such that the frequency difference generated by the movement is one-thousandth of the operating frequency of the accelerating cavity.

10. The method according to claim 7, wherein, step S105 includes: obtaining the double-peak frequencies of the reflected microwave, and the double-peak frequencies include the 0-mode operating frequency and the π-mode operating frequency.

11. The method according to claim 10, wherein, keeping the position of the magnetic probe close to the coupling cavity in the probe unit unchanged, moving the detuning rod close to the accelerating cavity in the probe unit into different cavities within more than three of the coupling resonator chains respectively, and repeating steps S103 - S105 respectively, wherein step S105 further includes: according to multiple sets of double-peak frequencies, obtaining the operating frequency of the accelerating cavity, the operating frequency of the adjacent coupling cavity, and the inter-cavity coupling coefficient between the accelerating cavity and the adjacent coupling cavity by fitting.

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