A multi-channel low-error RF strip coupling position detection method and system

Abstract

The present invention discloses a multi-channel low-error RF strip coupling position detection method and system, the method comprising: connecting multiple RF strip coupling probes of a measurement system through a beryllium copper conductor to excite the RF signal, each RF strip coupling probe connection can excite the generation of four groups of RF signals, the four groups of RF signals are sent to their respective RF front ends to achieve filtering, gain adjustment, and down-conversion, the down-converted signal is an intermediate frequency signal, and is sent to an AD data collector, the AD data collector works under the drive of a synchronous clock separated from a signal source, and ensures that all the system acquisitions are phase referenced acquisitions. According to the principle of electromagnetic induction, a RF strip coupling probe is used to couple four RF signals, and accurate signal amplitude and phase information are extracted from the four RF signals to accurately obtain the position of the strip electrode relative to the beryllium copper wire, and then the deformation information of the connected low-temperature cavity to be measured is inverted.

Description

Technical Field

[0001] The present invention relates to the field of cryogenic vacuum technology and is used for deformation position measurement of superconducting equipment with high precision and low error, in particular to a multi-channel low-error radio frequency strip coupling position detection method and system. Background Art

[0002] A superconducting device is a device that uses the special properties of superconducting materials to work.

[0003] Superconducting materials can exhibit the characteristics of zero resistance and complete rejection of magnetic fields at low temperatures, which makes superconducting devices widely used in many fields.

[0004] In order to make superconducting materials exhibit the characteristics of zero resistance and complete magnetic field rejection at low temperatures, a warm superconducting cavity is designed to achieve this. However, low-temperature superconducting cavities and other equipment are prone to deviation during the cooling process, and the alignment requirements of the superconducting cavity at low temperatures cannot be guaranteed.

[0005] Therefore, how to propose a method to detect the deformation of the low-temperature superconducting cavity and provide reliable data for the subsequent calibration of the low-temperature superconducting cavity is a problem that needs to be solved at present. Summary of the invention

[0006] Purpose of the invention: To provide a multi-channel low-error RF strip coupling position detection method and system for realizing the pulsed low-energy particle continuous particle beam. The function of the cutter is to cut the beam into a pulse train for output, so as to solve the above-mentioned problems existing in the prior art.

[0007] Technical solution: A multi-channel low-error RF strip coupling position detection method, comprising:

[0008] Step 1: The processor controls the signal source to generate the required RF frequency, realizes amplitude and phase control, and generates multiple RF signals for continuous wave operation and pulse wave operation control;

[0009] Step 2: Send the signal to the feed end of the cryogenic container to be tested through a coaxial transmission line. The feed end has a matching transformation network to achieve the characteristic impedance of the measurement system composed of the 50 ohm impedance of the coaxial line and the RF strip coupling probe and the connecting pipe. Because of the change in the coaxial ratio of the inner and outer diameters, the impedance of the measurement system will be high. The matching transformation network here realizes a high transformation ratio function.

[0010] Step 3. The RF signal passes through the beryllium copper wire to excite the N RF strip coupling probes of the measurement system. Each RF strip coupling probe can excite and generate four groups of RF signals. These four groups of RF signals are sent to their respective RF front-ends to implement filtering, gain adjustment, and down-conversion (if down-conversion is not used, direct RF acquisition is required, which is also feasible). The down-converted signal is an intermediate frequency signal and is sent to the AD data collector. The AD data collector works under the drive of the synchronous clock separated from the signal source to ensure that all acquisitions of the system are phase-referenced acquisitions.

[0011] At the same time, the signal source also needs to generate the clock required for the processor to work, which is also a coherent operation.

[0012] Step 4: After the processor controls the AD data collector to complete the collection, it enters the process of processing the collection results;

[0013] Step 5: The measurement results of the RF strip coupling probe of the low-temperature superconducting cavity to be tested in the low-temperature container are detected for a long time. The measurement results can be accumulated according to the time distribution to form a data set of the offset of the RF strip coupling probe, and the data set can characterize the deformation of the low-temperature superconducting cavity to be tested with a certain size.

[0014] In a further embodiment, the processing of the collection results in step 4 includes:

[0015] Step 41, IQ demodulation;

[0016] The calculation relationship between sampling frequency and signal frequency is:

[0017] Among them, f IF is the intermediate frequency signal (IF signal) frequency of the sampled signal, m and n are arbitrary integers; the relationship between m and n represents the phase relationship between two samples:

[0018] At this time, the calculation relationship between I and Q satisfies the following formula:

[0019]

[0020]

[0021] Among them, x i Indicates the sampling data of AD.

[0022] In a further embodiment, the processing of the collection results in step 4 includes:

[0023] Step 42, Cordic algorithm obtains amplitude and phase information;

[0024] The CORDIC algorithm takes into account the requirements of speed, accuracy, and simplicity, and decomposes complex algorithms into some basic algorithms that are easy to implement in hardware, such as addition and shift. It meets the hardware's requirements for modularization and regularization of algorithms, and can give full play to the advantages of hardware and utilize hardware resources to achieve an optimization solution that combines hardware and algorithms.

[0025] In the amplitude modulation measurement system, the CORDIC algorithm uses the IQ signal after high-frequency signal demodulation to obtain the signal amplitude. Assume that there is a vector A(X a , Y a ), after rotating counterclockwise by angle θ, we can get vector B(X b , Y b ), then:

[0026]

[0027] One is used to obtain the amplitude and phase information of the sampling probe.

[0028] In a further embodiment, the processing of the collection results in step 4 includes:

[0029] Step 43: filtering;

[0030] The alpha-beta filter (αβ filter) is used to filter the amplitude and phase information. The filtering period T is relatively small. Assuming that the derivative (speed) v of the observed value remains constant during this period (the acceleration is or changes slowly), the filtering steps are as follows:

[0031] Step 431: According to the value at the last moment, press x k =x k-1 +Tv k-1 The equation predicts the value at the current moment:

[0032] Step 432: predict the derivative (speed value) of the value change at the current moment. Based on the assumption that the derivative value is constant, the derivative at the current moment is equal to the derivative at the previous moment.

[0033] v k =v k-1 ;

[0034] Step 433: There is an error r between the actual measured value z and the predicted value;

[0035] r k =z k -x k ;

[0036] Step 434, αβ filtering uses the selected α and β constants (the filter gets its name), uses α times the deviation r to correct the position estimate, and uses β multiplied by the deviation r to correct the velocity estimate, using T to normalize the size of β;

[0037] x k =x k +αr k

[0038]

[0039] To ensure the stability of the system, the values ​​of α and β are positive and less than 0.1;

[0040] Among them, x represents data, that is, amplitude or phase value; v represents the derivative of the numerical change of x (speed value); z represents the actual measurement value; k represents the kth data; k-1 represents the k-1th data (the data before k).

[0041] In a further embodiment, it also includes an offline three-coordinate calibration of the single RF strip coupling probe and an online calibration after the detection system is installed;

[0042] The single RF strip coupling probe offline three-coordinate calibration completes the calibration compensation of the offset of the mechanical center and the electrical center of the RF strip coupling probe itself, including:

[0043] Step 01: Use a level ruler to level the offline calibration platform;

[0044] Step 02, use a lever dial indicator to align the inner hole axis of the RF strip coupling probe with the rotation axis of the offline calibration platform; the rotation axis is the rotation axis of the rotating table;

[0045] Step 03: Use the theodolite to adjust the measuring wire to vertical;

[0046] Step 04: Use a dial indicator to measure the orthogonality of the electrode direction.

[0047] The RF strip coupling probe offline calibration platform includes:

[0048] Base;

[0049] The measuring station comprises a cross motion mechanism arranged on the base, a wire support frame mounted on the cross motion mechanism, and a measuring wire arranged at an end of the wire support frame;

[0050] The cross motion mechanism is a prior art and can be composed of an X-direction motion guide rail and a Y-direction motion guide rail to complete the cross-direction motion.

[0051] The mounting position comprises a rotating platform mounted on the base and a mounting seat arranged on the rotating platform;

[0052] The rotating table is a prior art, and can be composed of a motor installed on a base, and the motor drives the mounting base to rotate to complete the rotation function, and a manual turntable can also be designed to achieve this.

[0053] The detection system is calibrated online after installation to complete the calibration compensation of the mechanical position installation offset between multiple RF strip coupling probes, including:

[0054] Step 11, complete the online installation of the detection system, use the electronic level to level the RF strip coupling probe, the optical level to level the wire, and the theodolite to adjust the parallelism of the vertical line on the horizontal plane;

[0055] Step 22, at room temperature, generating an excitation signal and sending it to the feeding end of the cryogenic container to generate excitation for multiple RF strip coupling probes;

[0056] Step 33, the signal after being processed by the RF front end is collected by AD and then sent to the processor for calculation. For the calculation of the strip coupling signal, the compensation of the beryllium copper wire sag, the installation residual error of the RF strip coupling probe itself, and the mechanical deviation of the RF strip coupling probe are considered to calibrate the system error and record it in the error compensation parameter of the system data processing module;

[0057] The X and Y values ​​obtained by the difference and ratio method are relative values. The actual mechanical position data can only be obtained after the system error is corrected.

[0058] X real =K x ×X+X offset

[0059] Y real =K y ×Y+Y offset

[0060] Among them, X real and Y real is the actual position data, K x and K y is the sensitivity coefficient, X calc and Y calc is the calculated value, X offset and Y offset is the bias value.

[0061] A multi-channel low-error radio frequency strip coupling position detection system comprises: a mechanical unit, and an electronics unit connected to the mechanical unit;

[0062] The mechanical unit shown comprises:

[0063] A cryogenic container, a low-temperature superconducting cavity to be tested disposed in the cryogenic container, a plurality of detection units connected to the low-temperature superconducting cavity to be tested and connected to each other, and straightened beryllium copper wires disposed in the plurality of detection units;

[0064] Each group of detection units includes a connecting bracket and a radio frequency strip coupling probe mounted on the connecting bracket;

[0065] The electronics unit includes:

[0066] An AD data collector connected to a plurality of RF strip coupling probes;

[0067] A signal source and a processor are connected to the AD data collector and are interconnected;

[0068] A clock reference distribution module connected to the signal source and the processor;

[0069] A data display and processing module connected to the processor;

[0070] A matching transformation network module is connected to the feed-in terminal and the output terminal of the cryogenic container;

[0071] The coaxial transmission line is connected to the signal source and the feeding end of the cryogenic container.

[0072] In a further embodiment, one end of the beryllium copper wire is fixed at the feed end of the cryogenic container, and the other end is fixed at the output end of the cryogenic container; and a weight is applied to a wheel on the Endcap to straighten the beryllium copper wire.

[0073] In a further embodiment, the connection bracket includes a cavity hanging bracket connected to the low-temperature superconducting cavity to be measured, and a probe hanging bracket arranged on both sides of the cavity hanging bracket;

[0074] The radio frequency strip coupling probe is connected to the probe hanging bracket on any side;

[0075] Both ends of the RF strip coupling probe are connected with pipes, one end is a rigid pipe, and the other end is a flexible pipe. The inner diameter of the pipe is consistent with the inner diameter of the RF strip coupling probe, and the flexible pipe is connected with a corrugated pipe.

[0076] The rigid pipe is connected to a probe hanging bracket on one side which is far away from the installation of the radio frequency strip coupling probe.

[0077] Beneficial effect: The present invention discloses a multi-channel low-error RF strip coupling position detection method and system. Based on the principle of electromagnetic induction, the present invention utilizes a RF strip coupling probe to couple out four RF signals, and extracts accurate signal amplitude and phase information from the four RF signals to accurately obtain the position of the strip electrode relative to the beryllium copper wire, and then inverts the deformation information of the connected low-temperature cavity to be tested, providing data basis for the subsequent calibration of the low-temperature cavity to be tested. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 It is a schematic diagram of the system implementation principle of the present invention.

[0079] Figure 2 It is a schematic diagram of the principle of the radio frequency strip coupling probe of the present invention.

[0080] Figure 3 It is a specific schematic diagram of the radio frequency strip coupling probe of the present invention.

[0081] Figure 4 It is the amplitude simulation result of the sampling port at one position of the beryllium copper wire of the present invention.

[0082] Figure 5 It is the fitting result Mapping diagram of the present invention.

[0083] Figure 6 It is the result error diagram of two signal processing methods of the present invention.

[0084] Figure 7 It is a connection diagram of the radio frequency strip coupling probe and related pipelines of the present invention.

[0085] Figure 8 It is a block diagram of the collection part of the present invention.

[0086] Fig. 9 It is an off-line calibration platform for the radio frequency strip coupling probe of the present invention. DETAILED DESCRIPTION

[0087] The present application relates to a multi-channel low-error RF strip coupling position detection method and system, which is explained in detail below through specific implementation methods.

[0088] A multi-channel low-error radio frequency strip coupling position detection device, comprising:

[0089] Step 1: The processor controls the signal source to generate the required RF frequency, realizes amplitude and phase control, and generates multiple RF signals for continuous wave operation and pulse wave operation control;

[0090] Step 2: Send the signal to the feed end of the cryogenic container to be tested through a coaxial transmission line. The feed end has a matching transformation network to achieve the characteristic impedance of the measurement system composed of the 50 ohm impedance of the coaxial line and the RF strip coupling probe and the connecting pipe. Because of the change in the coaxial ratio of the inner and outer diameters, the impedance of the measurement system will be high. The matching transformation network here realizes a high transformation ratio function.

[0091] Step 3. The RF signal passes through the beryllium copper wire to excite the N RF strip coupling probes of the measurement system. Each RF strip coupling probe can excite and generate four groups of RF signals. These four groups of RF signals are sent to their respective RF front-ends to implement filtering, gain adjustment, and down-conversion (if down-conversion is not used, direct RF acquisition is required, which is also feasible). The down-converted signal is an intermediate frequency signal and is sent to the AD data collector. The AD data collector works under the drive of the synchronous clock separated from the signal source to ensure that all acquisitions of the system are phase-referenced acquisitions.

[0092] At the same time, the signal source also needs to generate the clock required for the processor to work, which is also a coherent operation.

[0093] Step 4: After the processor controls the AD data collector to complete the collection, it enters the process of processing the collection results;

[0094] Step 5: The measurement results of the RF strip coupling probe of the low-temperature superconducting cavity to be tested in the low-temperature container are detected for a long time. The measurement results can be accumulated according to the time distribution to form a data set of the offset of the RF strip coupling probe, and the data set can characterize the deformation of the low-temperature superconducting cavity to be tested with a certain size.

[0095] The processing process of the collection results in step 4 includes:

[0096] Step 41, IQ demodulation;

[0097] The calculation relationship between sampling frequency and signal frequency is:

[0098] Among them, f IF is the intermediate frequency signal (IF signal) frequency of the sampled signal, m and n are arbitrary integers; the relationship between m and n represents the phase relationship between two samples:

[0099] At this time, the calculation relationship between I and Q satisfies the following formula:

[0100]

[0101]

[0102] Among them, x i Indicates the sampling data of AD.

[0103] In a further embodiment, the processing of the collection results in step 4 includes:

[0104] Step 42, Cordic algorithm obtains amplitude and phase information;

[0105] The CORDIC algorithm takes into account the requirements of speed, accuracy, and simplicity, and decomposes complex algorithms into some basic algorithms that are easy to implement in hardware, such as addition and shift. It meets the hardware's requirements for modularization and regularization of algorithms, and can give full play to the advantages of hardware and utilize hardware resources to achieve an optimization solution that combines hardware and algorithms.

[0106] In the amplitude modulation measurement system, the CORDIC algorithm uses the IQ signal after high-frequency signal demodulation to obtain the signal amplitude. Assume that there is a vector A(X a , Y a ), after rotating counterclockwise by angle θ, we can get vector B(X b , Y b ), then:

[0107]

[0108] One is used to obtain the amplitude and phase information of the sampling probe.

[0109] The processing process of the collection results in step 4 includes:

[0110] Step 43: filtering;

[0111] The alpha-beta filter (αβ filter) is used to filter the amplitude and phase information. The filtering period T is relatively small. Assuming that the derivative (speed) v of the observed value remains constant during this period (the acceleration is or changes slowly), the filtering steps are as follows:

[0112] Step 431: According to the value at the last moment, press x k =x k-1 +Tv k-1 The equation predicts the value at the current moment:

[0113] Step 432: predict the derivative (speed value) of the value change at the current moment. Based on the assumption that the derivative value is constant, the derivative at the current moment is equal to the derivative at the previous moment.

[0114] v k =v k-1 ;

[0115] Step 433: There is an error r between the actual measured value z and the predicted value;

[0116] rk =z k -x k ;

[0117] Step 434, αβ filtering uses the selected α and β constants (the filter gets its name), uses α times the deviation r to correct the position estimate, and uses β multiplied by the deviation r to correct the velocity estimate, using T to normalize the size of β;

[0118] x k =x k +αr k

[0119]

[0120] To ensure the stability of the system, the values ​​of α and β are positive and less than 0.1;

[0121] Among them, x represents data, that is, amplitude or phase value; v represents the derivative of the numerical change of x (speed value); z represents the actual measurement value; k represents the kth data; k-1 represents the k-1th data (the data before k).

[0122] It also includes offline three-coordinate calibration of single RF strip coupling probes and online calibration after installation of the detection system;

[0123] The single RF strip coupling probe offline three-coordinate calibration completes the calibration compensation of the offset of the mechanical center and the electrical center of the RF strip coupling probe itself, including:

[0124] Step 01: Use a level ruler to level the offline calibration platform;

[0125] Step 02, use a lever dial indicator to align the inner hole axis of the RF strip coupling probe with the rotation axis of the offline calibration platform; the rotation axis is the rotation axis of the rotating table;

[0126] Step 03: Use the theodolite to adjust the measuring wire to vertical;

[0127] Step 04: Use a dial indicator to measure the orthogonality of the electrode direction.

[0128] The RF strip coupling probe offline calibration platform includes:

[0129] Base;

[0130] The measuring station comprises a cross motion mechanism arranged on the base, a wire support frame mounted on the cross motion mechanism, and a measuring wire arranged at an end of the wire support frame;

[0131] The cross motion mechanism is a prior art and can be composed of an X-direction motion guide rail and a Y-direction motion guide rail to complete the cross-direction motion.

[0132] The mounting position comprises a rotating platform mounted on the base and a mounting seat arranged on the rotating platform;

[0133] The rotating table is a prior art, and can be composed of a motor installed on a base, and the motor drives the mounting base to rotate to complete the rotation function, and a manual turntable can also be designed to achieve this.

[0134] The detection system is calibrated online after installation to complete the calibration compensation of the mechanical position installation offset between multiple RF strip coupling probes, including:

[0135] Step 11, complete the online installation of the detection system, use the electronic level to level the RF strip coupling probe, the optical level to level the wire, and the theodolite to adjust the parallelism of the vertical line on the horizontal plane;

[0136] Step 22, at room temperature, generating an excitation signal and sending it to the feeding end of the cryogenic container to generate excitation for multiple RF strip coupling probes;

[0137] Step 33, the signal after being processed by the RF front end is collected by AD and then sent to the processor for calculation. For the calculation of the strip coupling signal, the compensation of the beryllium copper wire sag, the installation residual error of the RF strip coupling probe itself, and the mechanical deviation of the RF strip coupling probe are considered to calibrate the system error and record it in the error compensation parameter of the system data processing module;

[0138] The X and Y values ​​obtained by the difference and ratio method are relative values. The actual mechanical position data can only be obtained after the system error is corrected.

[0139] X real =K x ×X+X offset

[0140] Y real =K y ×Y+Y offset

[0141] Among them, X real and Y real is the actual position data, K x and K y is the sensitivity coefficient, X calc and Y calc is the calculated value, X offset and Y offset is the bias value.

[0142] A multi-channel low-error radio frequency strip coupling position detection system comprises: a mechanical unit, and an electronics unit connected to the mechanical unit;

[0143] The mechanical unit shown comprises:

[0144] A cryogenic container, a low-temperature superconducting cavity to be tested disposed in the cryogenic container, a plurality of detection units connected to the low-temperature superconducting cavity to be tested and connected to each other, and straightened beryllium copper wires disposed in the plurality of detection units;

[0145] Each group of detection units includes a connecting bracket and a radio frequency strip coupling probe mounted on the connecting bracket;

[0146] The electronics unit includes:

[0147] An AD data collector connected to a plurality of RF strip coupling probes;

[0148] A signal source and a processor are connected to the AD data collector and are interconnected;

[0149] A clock reference distribution module connected to the signal source and the processor;

[0150] A data display and processing module connected to the processor;

[0151] A matching transformation network module is connected to the feed-in terminal and the output terminal of the cryogenic container;

[0152] The coaxial transmission line is connected to the signal source and the feeding end of the cryogenic container.

[0153] One end of the beryllium copper wire is fixed at the feeding end of the low-temperature container, and the other end is fixed at the output end of the low-temperature container; and a weight is applied to a wheel on the Endcap to straighten the beryllium copper wire.

[0154] The connecting bracket comprises a cavity hanging bracket connected to the low-temperature superconducting cavity to be tested, and a probe hanging bracket arranged on both sides of the cavity hanging bracket;

[0155] The radio frequency strip coupling probe is connected to the probe hanging bracket on any side;

[0156] Both ends of the RF strip coupling probe are connected with pipes, one end is a rigid pipe, and the other end is a flexible pipe. The inner diameter of the pipe is consistent with the inner diameter of the RF strip coupling probe, and the flexible pipe is connected with a corrugated pipe.

[0157] The rigid pipe is connected to a probe hanging bracket on one side which is far away from the installation of the radio frequency strip coupling probe.

[0158] The designed flexible pipe can facilitate the adjustment of the position of the RF strip coupling probe, and can also be used to eliminate the error caused by pipe processing so that the position of the RF strip coupling probe is adjusted to the designed ideal position.

[0159] The inner diameter of the pipe is consistent with the inner diameter of the RF strip coupling probe. Specific embodiment one:

[0161] When the RF signal passes through the internal pipe of the strip position detector, according to the principle of electromagnetic induction, the electrodes inside the detector will induce a corresponding current, forming an electromotive force (see Appendix Figure 2 As shown in the figure, a radio frequency strip coupling probe is used to couple out four radio frequency signals A, B, C, and D, and accurate signal amplitude and phase information are extracted from the four radio frequency signals to accurately obtain the position of the strip electrode relative to the beryllium copper wire, thereby inverting the deformation information of the connected low-temperature cavity to be tested.

[0162] When a RF sine wave is fed into the beryllium copper wire (a 325MHz sine wave is used in the example), and the position of the beryllium copper wire is changed, the voltage amplitude at each port is simulated as shown in the attached figure. Figure 3 As shown;

[0163] When the position of the beryllium copper wire shifts in a certain direction, the induced potential generated by the electrode in that direction will increase, while the induced potential of the electrode in the opposite direction will decrease. Therefore, the direction and degree of the deviation of the beryllium copper wire can be measured by comparing the electrical signals collected by the electrodes, thereby providing a basis for precise measurement of the position of the cryogenic cavity.

[0164] If the probe is installed at 45°, the position data (X, Y) of the beryllium copper wire is calculated by the difference and ratio method as follows:

[0165]

[0166]

[0167] If the probe is installed at 90°, the position data (X, Y) of the beryllium copper wire is calculated by the difference and ratio method as follows:

[0168]

[0169]

[0170] The length of the entire cryogenic cavity to be tested can reach several meters or even more than 10 meters. By arranging RF strip coupling probes at intervals, we use RF excitation signals and continuous measurement of multiple probes, multiple channels and multiple positions to obtain the deformation size parameters and corresponding position parameters of the entire cryogenic cavity to be tested.

[0171] In order to achieve accurate measurement, a high-order binomial fitting method is used to obtain the calculation coefficients of signal position conversion.

[0172] For example, due to the symmetry of the quadrant, the seventh-order binomial fitting formula is simplified as follows:

[0173] f x (x,y)=P 00 +P 10 x+P 30 x 3 +P 12 xy 2 +P 50 x 5 +P 32 x 3 y 2 +P 14 xy 4 +P 70 x 7 +P 52 x 5 y 2 +P 34 x 3 y 4 +P 16 xy 6

[0174] f y (x,y)=P 00 +P 01 y+P 21 x 2 y+P 03 y 3 +P 41 x 4 y+P 23 x 2 y 3 +P 05 y 5 +P 61 x 6 y+P 43 x 4 y 3 +P 25 x 2 y 5 +P 07 y 7

[0175] Substitute the measured electronic position signal (X, Y) and the corresponding actual beryllium copper wire position information to fit the seventh-order binomial calculation coefficient. According to the fitted calculation coefficient, the electronic position signal (X, Y) is transformed and the attached figure is drawn. Figure 5 The Mapping instance diagram shown, Figure 5 The left picture is the Mapping diagram after the position signal is converted by the difference ratio and signal processing method, and the right picture is the Mapping example diagram after the position signal is converted by the logarithmic ratio processing method. The above fitting theoretical results are of great significance to the subsequent experimental platform calibration work.

[0176] Further, the deviation distribution between the fitting position and the actual position within the range of ±5mm is shown in the figure below. The error of the two position signal processing methods can be kept within the range of 20μm, and the error distribution of the difference ratio and method is more concentrated and smaller, but both methods are within the acceptable error range.

[0177] Considering the attenuation of the RF signal fed into the carrier wire and the wire strength at liquid helium temperature, a carrier wire made of beryllium copper with a diameter of 0.5 mm is usually selected.

[0178] The radio frequency strip coupling probe is connected to the low temperature cavity through a connecting bracket.

[0179] Working principle description:

[0180] The processor controls the signal source to generate the required RF frequency, realizes amplitude and phase control, and generates multiple RF signals for continuous wave operation and pulse wave operation control;

[0181] Through the coaxial transmission line, it is sent to the feed end of the cryogenic container to be tested. There is a matching transformation network at the feed end to realize the characteristic impedance of the measurement system composed of the RF strip coupling probe and the connecting pipe from the 50 ohm impedance of the coaxial line. Because of the change in the coaxial ratio of the inner and outer diameters, the impedance of the measurement system will be higher. The matching transformation network here realizes a high transformation ratio function.

[0182] The RF signal passes through the beryllium copper wire to excite the N RF strip coupling probes of the measurement system. Each RF strip coupling probe can excite and generate four groups of RF signals. These four groups of RF signals are sent to their respective RF front-ends to implement filtering, gain adjustment, and down-conversion (if down-conversion is not used, direct RF acquisition is required, which is also feasible). The down-converted signal is an intermediate frequency signal and is sent to the AD data collector. The AD data collector works under the drive of the synchronous clock separated from the signal source to ensure that all system acquisitions are phase-referenced acquisitions.

[0183] At the same time, the signal source also needs to generate the clock required for the processor to work, which is also a coherent operation.

[0184] After the processor controls the AD data collector to complete the collection, it enters the process of processing the collection results;

[0185] The measurement results of the RF strip coupling probe of the low-temperature superconducting cavity to be tested in the low-temperature container for a long time can be accumulated according to the time distribution to form a data set of the offset of the RF strip coupling probe, which can characterize the deformation amount of the low-temperature superconducting cavity to be tested with a certain size.

[0186] The preferred specific embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above specific embodiments. Within the technical concept of the present invention, various equivalent transformations can be made to the technical scheme of the present invention, and these equivalent transformations all belong to the protection scope of the present invention.

Claims

1. A multi-channel low-error RF strip coupling position detection method, characterized in that: include: Step 1: The processor controls the signal source to generate the required RF frequency, realizes amplitude and phase control, and generates multiple RF signals for continuous wave operation and pulse wave operation control; Step 2, sending it to the feeding end of the low-temperature container to be tested through a coaxial transmission line; Step 3, the RF signal passes through the beryllium copper wire to stimulate multiple RF strip coupling probe connections of the measurement system. Each RF strip coupling probe connection can stimulate the generation of four groups of RF signals. The four groups of RF signals are sent to their respective RF front ends for filtering, gain adjustment, and down-conversion. The down-converted signal is an intermediate frequency signal and is sent to an AD data collector. The AD data collector works under the drive of the synchronous clock separated from the signal source to ensure that all the system acquisitions are phase-referenced acquisitions. At the same time, the signal source generates the clock required for the processor to work, which is also coherent work; Step 4: After the processor controls the AD data collector to complete the collection, it enters the process of processing the collection results; Step 5: Detect the measurement results of the radio frequency strip coupling probe of the low-temperature superconducting cavity to be tested in the low-temperature container for a long time, and accumulate a data set of the offset of the radio frequency strip coupling probe according to the time distribution, and the data set represents the deformation of the low-temperature superconducting cavity to be tested with a certain size; It also includes offline three-coordinate calibration of single RF strip coupling probes and online calibration after installation of the detection system; The single RF strip coupling probe offline three-coordinate calibration completes the calibration compensation of the offset of the mechanical center and the electrical center of the RF strip coupling probe itself, including: Step 01: Use a level ruler to level the offline calibration platform; Step 02: Use a lever dial indicator to align the inner hole axis of the RF strip coupling probe with the rotation axis of the offline calibration platform; Step 03: Use the theodolite to adjust the measuring wire to vertical; Step 04: Use a dial indicator to measure the orthogonality of the electrode direction; The detection system is calibrated online after installation to complete the calibration compensation of the mechanical position installation offset between multiple RF strip coupling probes, including: Step 11, complete the online installation of the detection system, use the electronic level to level the RF strip coupling probe, the optical level to level the wire, and the theodolite to adjust the parallelism of the vertical line on the horizontal plane; Step 22, at room temperature, generating an excitation signal and sending it to the feeding end of the cryogenic container to generate excitation for multiple RF strip coupling probes; Step 33, the signal after being processed by the RF front end is collected by AD and then sent to the processor for calculation. For the calculation of the strip coupling signal, the compensation of the beryllium copper wire sag, the installation residual error of the RF strip coupling probe itself, and the mechanical deviation of the RF strip coupling probe are considered to calibrate the system error and record it in the error compensation parameter of the system data processing module; The X and Y values ​​obtained by the difference and ratio method are relative values. After correcting the system error, the actual mechanical position data is obtained. ； in, and is the actual location data, and is the sensitivity coefficient, and is the calculated value, and is the bias value.

2. A multi-channel low-error RF strip coupling position detection method according to claim 1, characterized in that: The processing process of the collection results in step 4 includes: Step 41, IQ demodulation; The calculation relationship between sampling frequency and signal frequency is: ; in, is the intermediate frequency signal frequency of the sampling signal, m and n are arbitrary integers; the relationship between m and n represents the phase relationship between two samples: ; At this time, the calculation relationship between I and Q satisfies the following formula: ； in, Indicates the sampling data of AD.

3. A multi-channel low-error RF strip coupling position detection method according to claim 1, characterized in that: The processing process of the collection results in step 4 includes: Step 42, Cordic algorithm obtains amplitude and phase information; Using the IQ signal after high-frequency signal demodulation, the amplitude of the signal is obtained. Assume that there is a vector in the rectangular coordinate system , after a counterclockwise rotation of angle After that, we get the vector , then: ； One is used to obtain the amplitude and phase information of the sampling probe.

4. The multi-channel low-error RF strip coupling position detection method according to claim 1 is characterized by: The processing process of the collection results in step 4 includes: Step 43: filtering; The alpha-beta filter is used to filter the amplitude and phase information. The filtering period T is relatively small. Assuming that the derivative v of the observed value remains constant during this period, the filtering steps are as follows: Step 431: According to the value at the last moment, press The equation predicts the value at the current moment: Step 432: predict the derivative of the value change at the current moment. Based on the assumption that the derivative value is constant, the derivative at the current moment is equal to the derivative at the previous moment. ； Step 433: There is an error r between the actual measured value z and the predicted value; ； Step 434, αβ filtering uses the selected α and β constants, uses α times the deviation r to correct the position estimate, and uses β multiplied by the deviation r to correct the velocity estimate, and uses T to normalize the size of β; ； ； To ensure the stability of the system, the values ​​of α and β are positive and less than 0.1; Among them, x represents data, that is, amplitude or phase value; v represents the derivative of the numerical change of x; z represents the actual measured value; k represents the kth data; k-1 represents the k-1th data.

5. The detection system of the multi-channel low-error RF strip coupling position detection method according to claim 1, characterized in that: include: A mechanical unit, and an electronics unit connected to the mechanical unit; The mechanical unit shown comprises: A cryogenic container, a low-temperature superconducting cavity to be tested disposed in the cryogenic container, a plurality of detection units connected to the low-temperature superconducting cavity to be tested and connected to each other, and straightened beryllium copper wires disposed in the plurality of detection units; Each group of detection units includes a connecting bracket and a radio frequency strip coupling probe mounted on the connecting bracket; The electronics unit includes: An AD data collector connected to a plurality of RF strip coupling probes; A signal source and a processor are connected to the AD data collector and are interconnected; A clock reference distribution module connected to the signal source and the processor; A data display and processing module connected to the processor; A matching transformation network module is connected to the feed-in terminal and the output terminal of the cryogenic container; The coaxial transmission line is connected to the signal source and the feeding end of the cryogenic container.

6. The detection system of the multi-channel low-error RF strip coupling position detection method according to claim 5 is characterized by: One end of the beryllium copper wire is fixed at the feeding end of the low-temperature container, and the other end is fixed at the output end of the low-temperature container.

7. The detection system of the multi-channel low-error RF strip coupling position detection method according to claim 5 is characterized by: The connecting bracket comprises a cavity hanging bracket connected to the low-temperature superconducting cavity to be tested, and a probe hanging bracket arranged on both sides of the cavity hanging bracket; The radio frequency strip coupling probe is connected to the probe hanging bracket on any side; Both ends of the RF strip coupling probe are connected with pipes, one end is a rigid pipe, and the other end is a flexible pipe. The inner diameter of the pipe is consistent with the inner diameter of the RF strip coupling probe, and the flexible pipe is connected with a corrugated pipe.

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