Ultralow frequency kicking beam cavity fault point detection method based on contact resistance

Abstract

The invention provides an ultralow-frequency kicking beam cavity fault point detection method based on contact resistance, which is used for solving the technical problem that the contact resistance introduced by machining exists in an existing ultralow-frequency kicking beam cavity designed as a discrete component structure, and a technician is difficult to observe a fault point with the contact resistance through field detection and naked eyes. According to the ultralow-frequency kicking beam cavity fault point detection method based on the contact resistance, geometric modeling is carried out on all positions where the contact resistance possibly exists in an ultralow-frequency kicking beam cavity, resonant frequencies corresponding to all geometric models are simulated and calculated, and then the resonant frequencies are compared with actually measured resonant frequencies, so that the positions where the contact resistance exists can be rapidly determined, and the fault point detection accuracy is improved. Fault point detection of the ultra-low frequency kicking beam cavity is completed; meanwhile, the analysis of the influence of the contact resistance on the resonant frequency also provides important reference and guidance for mechanical forming and processing of an ultra-low frequency kicking beam cavity and resonant cavities with other frequencies.

Description

Technical Field

[0001] The present invention relates to a method for detecting fault points of an ultra-low frequency kick beam cavity for a high-intensity neutron source, and particularly to a method for detecting fault points of an ultra-low frequency kick beam cavity based on contact resistance. Background Art

[0002] A high-intensity neutron source device is essentially a charged particle acceleration device - a proton accelerator, which is a device for artificially generating high-energy charged particle beams. Particle accelerators were initially developed as an important means for people to explore atomic nuclei. As the exploration of the microscopic material structure gradually deepens to a new level of smaller dimensions, the requirements for particle accelerators have been pushed from the already achieved energy to a new and higher energy range.

[0003] Currently, the international forefront of proton accelerator technology mainly develops in two directions: high energy and high intensity. With the development of disciplines such as fast neutron physics and radiation hardening, high-intensity proton accelerators, as the key devices for generating high-intensity neutrons by bombarding targets, have gradually become a research hotspot in the field of particle accelerators. Among them, the multi-pulse compression technology based on path modulation, as one of the key technologies, can further improve the instantaneous beam intensity, realize the longitudinal compression of multiple micropulses before bombarding the target, and finally form a single short pulse width and small diameter proton bunch to achieve bombarding the target at the same time. The resonant cavity is applied to the multi-pulse compression system and serves as a key component at the entrance of the system. Its main function is to achieve lateral deflection of the micropulse bunches passing through before and after at different angles. The deflected micropulses are then finely adjusted through subsequent multiple magnetic paths. The paths of the front particles are longer, and the paths of the rear particles are shorter, so as to achieve the effect of compressing the pulse length and finally realize bombarding the target at the same time. Thus, it can be seen that the resonant cavity at the entrance realizing lateral beam kicking is a crucial link.

[0004] There are many studies on resonant cavities for realizing particle acceleration or deflection internationally, but most of them are high-frequency resonant cavities, and the frequency is generally above 100 MHz. For resonant cavities in this frequency band, the internal structure is relatively simple and generally has symmetry and integrity. For example: 500 MHz single-cell ellipsoidal superconducting resonant cavity, 1.3 GHz 9-cell tesla superconducting resonant cavity, 162.5 MHz radio frequency quadrupole resonant cavity (RFQ), 325 MHz spoke cavity (Spoke), etc. There are no discrete components inside these cavities, nor complex forming processes. Therefore, there are no obvious technical difficulties in mechanical design and processing. According to the design of the multi-pulse compression system of the high-intensity neutron source, the design index of the resonant cavity frequency for realizing lateral beam kicking at the entrance is 13.5 MHz. There are few studies on such low-frequency resonant cavities, and conventional cavity types cannot achieve it. Only by expanding the cavity size, theoretically, the cavity frequency can be reduced, but there are certain limitations because there is usually no infinite space reserved for the resonant cavity device in a particle accelerator device.

[0005] According to the existing research progress, the ultra-low frequency kicker cavity is designed as a discrete component structure, which consists of a metal outer cavity cylinder, a pair of deflection plates, a metal coil, a metal rod, and an insulating support. Since the resonant cavity can be equivalent to an RCL circuit, the introduction of the deflection plates increases the contribution of the equivalent capacitance, and the metal coil increases the equivalent inductance and capacitance. The resonant frequency of the resonant cavity is inversely proportional to the equivalent capacitance and inductance, resulting in a significant reduction in the resonant frequency. Although the discrete component structure can meet the requirements of low-frequency resonance, the introduction of the discrete component structure increases the parts that need mechanical welding and connection, and it is very easy to introduce contact resistance, making it difficult for the ultra-low frequency kicker cavity to accurately achieve the target resonant frequency. And whether the target resonant frequency can be accurately achieved is an important evaluation index for the ultra-low frequency kicker cavity. When the measured resonant frequency of the ultra-low frequency kicker cavity does not reach the target resonant frequency, it is very difficult for technicians to observe the fault point with contact resistance through on-site detection by the naked eye. Therefore, there is an urgent need for a method to quickly detect the fault points of the ultra-low frequency kicker cavity. Summary of the Invention

[0006] The present invention aims to solve the technical problem that the existing ultra-low frequency kicker cavity designed as a discrete component structure has contact resistance introduced by mechanical processing, and it is very difficult for technicians to observe the fault point with contact resistance through on-site detection by the naked eye. Therefore, a method for detecting the fault points of the ultra-low frequency kicker cavity based on contact resistance is provided.

[0007] To achieve the above object, the technical solution of the present invention is as follows:

[0008] A method for detecting the fault points of the ultra-low frequency kicker cavity based on contact resistance is characterized by including the following steps:

[0009] Step 1, determine the positions in the ultra-low frequency kicker cavity to be measured where contact resistance may exist;

[0010] Step 2, divide all the positions where contact resistance may exist into two groups in the way of permutation and combination, and obtain 2 n combination results, where n is the number of positions with contact resistance in the ultra-low frequency kicker cavity to be measured;

[0011] Step 3, use three-dimensional electromagnetic simulation software to establish geometric models for the 2 n combination results respectively. When modeling, establish a geometric model representing the non-contact state for the first group of each combination result, and establish a geometric model representing the contact state for the second group;

[0012] Step 4, simulate and calculate the resonant frequencies corresponding to all the geometric models, and the 2 nThe resonant frequencies corresponding to each geometric model are compared with the measured resonant frequency of the ultra-low frequency kick beam cavity to be measured. According to the geometric model that is closest to the measured resonant frequency of the ultra-low frequency kick beam cavity to be measured, the position where the contact resistance exists can be determined, and the fault point detection of the ultra-low frequency kick beam cavity to be measured is completed.

[0013] Further, in step 1, the position where the contact resistance may exist in the ultra-low frequency kick beam cavity to be measured is specifically determined as follows: The position where the contact resistance may exist in the ultra-low frequency kick beam cavity to be measured is determined according to the connection point positions between the discrete components in the ultra-low frequency kick beam cavity that need to be connected later.

[0014] Further, in step 4, the simulation calculation of the resonant frequencies corresponding to all geometric models is specifically as follows:

[0015] When the position where the contact resistance may exist in the first group of a combined result is one, directly simulate and calculate the resonant frequency of the geometric model corresponding to this combined result;

[0016] When the position where the contact resistance may exist in the first group of a combined result is multiple, simulate and calculate the resonant frequency of the geometric model corresponding to this combined result through the resonant frequency function based on polynomial regression.

[0017] Further, in step 3, the 3D electromagnetic simulation software is CST Microwave Studio software.

[0018] Further, in step 1, the ultra-low frequency kick beam cavity includes a metal outer cavity cylinder, a top flange and a bottom flange respectively arranged at the upper end and the lower end of the metal outer cavity cylinder, and an insulating support, a metal coil, a pair of deflection plates, a first metal rod, a second metal rod and a third metal rod arranged inside the metal outer cavity cylinder; The insulating support is coaxially arranged inside the metal outer cavity cylinder, and one end of it is connected to the bottom flange; The metal coil is embedded on the outer side wall of the insulating support; A pair of deflection plates are located at the other end of the insulating support, one of the deflection plates is connected to the top flange through the first metal rod, the other deflection plate is connected to the upper end of the metal coil through the second metal rod, and the lower end of the metal coil is connected to the bottom flange through the third metal rod; The connection between one of the deflection plates and the first metal rod, the connection between the other deflection plate and the second metal rod, and the connection between the lower end of the metal coil and the third metal rod are all of integrated design;

[0019] The positions where the contact resistance may exist in the ultra-low frequency kick beam cavity to be measured are three, including the connection position between the first metal rod and the top flange, the connection position between the second metal rod and the metal coil, and the connection position between the third metal rod and the bottom flange;

[0020] In step 2, the number of the combined results is 2 3 .

[0021] The beneficial effects of the present invention compared with the prior art are as follows:

[0022] 1. A method for detecting fault points of an ultra-low frequency kicker cavity based on contact resistance provided by the present invention geometrically models all possible positions with contact resistance in the ultra-low frequency kicker cavity, simulates and calculates the resonant frequencies corresponding to all geometric models, and then compares with the measured resonant frequencies, so as to quickly determine the positions with contact resistance and complete the detection of fault points of the ultra-low frequency kicker cavity; meanwhile, the analysis of the influence of contact resistance on the resonant frequency of the present invention also provides important reference and guidance for the mechanical forming and processing of ultra-low frequency kicker cavities and other frequency resonant cavities.

[0023] 2. The method for detecting fault points of the ultra-low frequency kicker cavity of the present invention has high repeatability and practicability, and is convenient for detection. It is also applicable to resonant cavities of other frequencies. Just by combining the model establishment method in the present invention, the positions with contact resistance in resonant cavities of any frequency can be quickly determined according to the different influences of contact resistance at different connection positions on the resonant frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic structural diagram of the ultra-low frequency kicker cavity to be detected in step 1 of an embodiment of a method for detecting fault points of an ultra-low frequency kicker cavity based on contact resistance of the present invention;

[0025] Figure 2 It is a schematic diagram of possible positions with contact resistance in the ultra-low frequency kicker cavity to be detected determined in step 1 of an embodiment of the present invention;

[0026] Figure 3 It is a schematic diagram of the resonant frequency curve of the ultra-low frequency kicker cavity to be detected when the connection position A between the first metal rod and the top flange is in different contact states in step 4 of an embodiment of the present invention;

[0027] Figure 4 It is a schematic diagram of the resonant frequency curve of the ultra-low frequency kicker cavity to be detected when the connection position B between the second metal rod and the metal coil is in different contact states in step 4 of an embodiment of the present invention;

[0028] Figure 5 It is a schematic diagram of the resonant frequency curve of the ultra-low frequency kicker cavity to be detected when the connection position C between the third metal rod and the bottom flange is in different contact states in step 4 of an embodiment of the present invention;

[0029] Figure 6 It is a schematic diagram of the resonant frequency curve of the ultra-low frequency kicker cavity to be detected when multiple positions are not in contact in step 4 of an embodiment of the present invention.

[0030] Specific reference numerals are as follows:

[0031] 1 - Deflection plate; 2 - Metal coil; 3 - Insulating support; 4 - First metal rod; 5 - Third metal rod; 6 - Metal outer cavity cylinder; 7 - Top flange; 8 - Bottom flange; 9 - Second metal rod. Detailed implementation manner

[0032] To make the advantages and features of the present invention clearer, the following further elaborates on the present invention in conjunction with the accompanying drawings and specific embodiments.

[0033] Existing ultra - low - frequency kick beam cavities achieve ultra - low frequencies through an optimized method of discrete components. The discrete components inside the ultra - low - frequency kick beam cavity need to be tightly connected by welding or assembly fixation. The areas where the discrete components are connected are high - incidence regions for generating contact resistance. The existence of contact resistance will cause the ultra - low - frequency kick beam cavity to be unable to achieve the target resonance frequency. Based on the different effects of contact resistance at different connection positions on the resonance frequency of the ultra - low - frequency kick beam cavity, the present invention realizes the precise detection of fault points.

[0034] A method for detecting fault points of an ultra - low - frequency kick beam cavity based on contact resistance specifically includes the following steps:

[0035] Step 1, determine the positions in the ultra - low - frequency kick beam cavity to be measured where contact resistance may exist.

[0036] In this embodiment, the target resonance frequency of the ultra - low - frequency kick beam cavity to be measured is 13.5 MHz, which belongs to an extremely low - frequency range for a resonant cavity. As Figure 1 shown, the discrete components of the ultra - low - frequency kick beam cavity to be measured include a metal outer cavity cylinder 6, a metal coil 2, a pair of deflection plates 1, an insulating support 3, a first metal rod 4, a second metal rod 9, and a third metal rod 5. A pair of deflection plates 1 and a metal coil 2 are the main structures of the ultra - low - frequency kick beam cavity. There is a deflection electric field in the gap between the pair of deflection plates 1, which provides a deflection force for the beam current. The beam current will pass through along the length direction of the deflection plates from the deflection plate gap, and the metal coil 2 provides a magnetic field; the insulating support 3 is used to support the metal coil 2 and the pair of deflection plates 1 to ensure the stable mechanical performance of the device; the metal outer cavity cylinder 6 forms a closed space, increasing the conductor surface area through which the current flows, thereby reducing conductor losses and avoiding radiation losses. The first metal rod 4, the second metal rod 9, and the third metal rod 5 connect the discrete components such as the pair of deflection plates 1, the metal coil 2, and the metal outer cavity cylinder 6, finally forming an equivalent RCL circuit. Compared with a conventional resonant cavity, the internal structure of the ultra - low - frequency kick beam cavity is complex, with more connection parts, and the mechanical welding and assembly parts are significantly increased, greatly increasing the risk of generating contact resistance. The method for detecting fault points of the ultra - low - frequency kick beam cavity based on contact resistance of the present invention is used to quickly find the positions where contact resistance appears due to improper mechanical welding or assembly, so as to ensure that the ultra - low - frequency kick beam cavity can accurately achieve the target resonance frequency.

[0037] The two ends of the metal outer cavity tube 6 are respectively provided with a top flange 7 and a bottom flange 8, one of the deflection plates 1 is connected to the top flange 7 of the metal outer cavity tube 6 through the first metal rod 4, the other deflection plate 1 is connected to the upper end of the metal coil 2 through the second metal rod 9, and the lower end of the metal coil 2 is connected to the bottom flange 8 of the metal outer cavity tube 6 through the third metal rod 5. One of the deflection plates 1 and the first metal rod 4, the other deflection plate 1 and the second metal rod 9, and the lower end of the metal coil 2 and the third metal rod 5 are all integrated designs, and there is no contact resistance problem.

[0038] In the present invention, the position where the contact resistance may exist in the ultra-low frequency kick beam cavity to be tested is determined according to whether the discrete components in the ultra-low frequency kick beam cavity to be tested need to be assembled and connected.

[0039] According to the internal structure of the ultra-low frequency kick beam cavity, the connection between the two discrete components, the deflection plate 1 and the metal outer cavity tube 6, needs to rely on the first metal rod 4 and the top flange 7. Considering the subsequent cold test of the ultra-low frequency kick beam cavity, the top flange 7 needs to meet the requirement of easy disassembly, so the connection between the top flange 7 and the first metal rod 4 should not be welded. Combined with the mechanical design of the ultra-low frequency kick beam cavity, an assembly fixation method is adopted here, and a positioning step is processed on the top flange 7 to ensure the connection between the first metal rod 4 and the top flange 7. Therefore, there is a risk of poor contact between the first metal rod 4 and the top flange 7.

[0040] The part where the metal coil 2 is connected to the second metal rod 9 is a quarter arc structure with a radius of 30 mm. According to the electromagnetic simulation results of the ultra-low frequency kick beam cavity, this area belongs to the strong field area. If the connected parts are not in good contact, it will not only easily generate contact resistance, but also affect the electromagnetic field distribution. These are all factors that affect the resonant frequency of the ultra-low frequency kick beam cavity.

[0041] The connection between the metal coil 2 and the metal outer cavity tube 6 needs to rely on the third metal rod 5 and the bottom flange 8. Like the top flange 7, considering the subsequent cold test of the ultra-low frequency kick beam cavity, the bottom flange 8 needs to meet the requirement of easy disassembly. Therefore, the bottom flange 8 and the third metal rod 5 are also assembled and fixed. A positioning step is processed to ensure the connection between the third metal rod 5 and the bottom flange 8. However, similarly, there is also a risk of poor contact between the third metal rod 5 and the bottom flange 8.

[0042] Therefore, it can be seen from the above analysis that there are three locations where contact resistance may exist in the ultra-low frequency kick beam cavity to be tested in this embodiment, such as Figure 2 As shown, it includes a connection position A between the first metal rod 4 and the top flange 7 , a connection position B between the second metal rod 9 and the metal coil 2 , and a connection position C between the third metal rod 5 and the bottom flange 8 .

[0043] In order to explore the influence of different contact states at the connection positions between two discrete components on the resonant frequency of an ultra-low frequency kick beam cavity, the present invention first uses CST Microwave Studio software to establish models for connection position A, connection position B, and connection position C respectively, that is, geometric models representing three different contact states of full contact, partial contact, and no contact are established for each connection position. At this time, other connection positions in the cavity are in a full contact state.

[0044] When establishing geometric models of three different contact states, the distance h between the contact surfaces of the two discrete components needs to be set as an independent variable, that is, when the distance h is at different values, the resonant frequency change curves under three different contact states of full contact, partial contact, and no contact are simulated and obtained.

[0045] The resonant frequency change curves under three different contact states obtained after establishing three geometric models for the connection position A between the first metal rod 4 and the top flange 7 are as Figure 3 shown. In the full contact state, that is, when the distance h is 0 mm, the resonant frequency f is always 13.508 MHz, that is, the frequency does not change; in the partial contact state, the average change rate Δf / Δh of the resonant frequency f with respect to the distance h is 0.01 kHz / mm, the change is not obvious, and the resonant frequency f basically fluctuates around 13.5 MHz, and the fluctuation range is very small and can be ignored; in the no contact state, the interval between the two contact surfaces is in the range of 0 - 20 mm, and the resonant frequency f fluctuates in the range of 13.508 - 14.164 MHz, and its average change rate Δf / Δh with respect to the distance h is 33 kHz / mm, and the resonant frequency increases.

[0046] The resonant frequency change curves under three different contact states obtained after establishing three geometric models for the connection position B between the second metal rod 9 and the metal coil 2 are as Figure 4 shown. In the full contact state, that is, when the distance h is 0 mm, the resonant frequency f is always 13.508 MHz, that is, the frequency does not change; in the partial contact state, the average change rate Δf / Δh of the resonant frequency f with respect to the distance h is 0.135 kHz / mm, the change is not obvious, and it basically fluctuates around 13.5 MHz, and the fluctuation range is very small and can be ignored; in the no contact state, the interval between the two contact surfaces is in the range of 0 - 20 mm, and the resonant frequency f fluctuates in the range of 13.508 - 16.418 MHz, and its average change rate Δf / Δh with respect to the distance h is 146 kHz / mm, and the change of the resonant frequency is obvious.

[0047] The resonant frequency change curves under three different contact states obtained after establishing three geometric models for the connection position C between the third metal rod 5 and the bottom flange 8 are as Figure 5As shown, in the fully - contact state, that is, when the spacing h is 0 mm, the resonant frequency f is always 13.508 MHz, which means the frequency does not change; in the partial - contact state, the average rate of change of the resonant frequency f with respect to the spacing h, Δf / Δh, is 0.045 kHz / mm, and the change is not obvious. Basically, it also fluctuates around 13.5 MHz, and the fluctuation range is very small and can be ignored; in the non - contact state, the distance between the two contact surfaces is in the range of 0 - 20 mm, and the resonant frequency f changes in the range of 13.508 - 20.083 MHz. Its average rate of change with respect to the spacing h, Δf / Δh, is 329 kHz / mm, and the resonant frequency increases significantly.

[0048] In summary, it can be seen that the resonant frequencies at connection position A, connection position B, and connection position C in the fully - contact state are basically in line with the target resonant frequency; the resonant frequencies in the partial - contact state change, but the change is not obvious and does not change significantly with the change of the spacing h; in the non - contact state, the resonant frequencies all change significantly, but they do not change greatly with the change of the spacing h. At the same time, it can be seen that the influences of connection position A, connection position B, and connection position C on the resonant frequency of the ultra - low - frequency kicker cavity in the non - contact state are quite different. Therefore, the present invention considers using the characteristic that the influence of the contact resistance at different connection positions on the resonant frequency of the ultra - low - frequency kicker cavity is significantly different to achieve precise detection of the fault point. At the same time, since the resonant frequencies in the partial - contact state and the fully - contact state are basically the same, for the sake of convenient description, they are collectively referred to as the contact state hereinafter.

[0049] Step 2: Arbitrarily divide the three positions of connection position A, connection position B, and connection position C, which may have contact resistance, into two groups in the way of permutation and combination, obtaining eight combination results. Specifically, in the first combination result, the first group includes connection position A, and the second group includes connection position B and connection position C; in the second combination result, the first group includes connection position B, and the second group includes connection position A and connection position C; in the third combination result, the first group includes connection position C, and the second group includes connection position A and connection position B; in the fourth combination result, the first group includes connection position A and connection position B, and the second group includes connection position C; in the fifth combination result, the first group includes connection position A and connection position C, and the second group includes connection position B; in the sixth combination result, the first group includes connection position B and connection position C, and the second group includes connection position A; in the seventh combination result, the first group includes connection position A, connection position B, and connection position C, and the second group is empty; in the eighth combination result, the first group is empty, and the second group includes connection position A, connection position B, and connection position C.

[0050] Step 3: Establish geometric models for all combination results.

[0051] CST Microwave Studio software is used to establish geometric models for all combination results. When modeling, a geometric model representing the non-contact state is established for the first group of each combination result, and a geometric model representing the contact state is established for the second group, that is, the discrete components corresponding to all connection positions (positions where contact resistance may exist) in the first group of each combination result are designed to be in a non-contact state, and the discrete components corresponding to all connection positions in the second group are designed to be in a contact state. In other embodiments of the present invention, other three-dimensional electromagnetic simulation software can also be used to perform geometric modeling on all combination results, and the spacing h value of all models varies within the range of 0 to 20 mm.

[0052] Step 4: simulate and calculate the resonant frequencies corresponding to all geometric models to complete the fault point detection of the ultra-low frequency kick beam cavity to be tested.

[0053] The position designed as a non-contact state in the first combination result is connection position A, and the positions designed as a contact state are connection positions B and connection positions C. The resonant frequency of the geometric model corresponding to the first combination result is simulated and calculated, that is, the resonant frequency of the ultra-low frequency kick beam cavity to be tested is simulated and calculated to vary in the range of (13.508, 14.164] MHz when the connection position A between the first metal rod 4 and the top flange 7 is in a non-contact state. It can be seen that when the connection position between the first metal rod 4 and the top flange 7 is in poor contact, the distance between the two contact surfaces is in the range of 0 to 20 mm, and the maximum deviation between the resonant frequency of the ultra-low frequency kick beam cavity and the target resonant frequency is 0.66 MHz.

[0054] In the second combination result, the position designed as a non-contact state is connection position B, and the positions designed as a contact state are connection position A and connection position C. The resonant frequency of the geometric model corresponding to the second combination result is simulated and calculated, that is, the resonant frequency of the ultra-low frequency kick beam cavity to be tested is simulated and calculated to vary in the range of (13.508, 16.418] MHz when the connection position B between the second metal rod 9 and the metal coil 2 is in a non-contact state. It can be seen that when the connection position between the second metal rod 9 and the metal coil 2 is in poor contact, the distance between the two contact surfaces is in the range of 0 to 20 mm, and the maximum deviation between the resonant frequency of the ultra-low frequency kick beam cavity and the target resonant frequency is 3 MHz.

[0055] In the third combination result, the position designed as a non-contact state is connection position C, and the positions designed as a contact state are connection positions B and connection positions C. The geometric model resonant frequency corresponding to the third combination result is simulated and calculated, that is, the resonance frequency of the ultra-low frequency kick beam cavity to be tested is about (13.508, 20.083] MHz when the connection position C between the third metal rod 5 and the bottom flange 8 is in a non-contact state. It can be seen that when the connection position between the second metal rod 9 and the metal coil 2 is in poor contact, the distance between the two contact surfaces is in the range of 0 to 20 mm, and the maximum deviation between the resonance frequency of the ultra-low frequency kick beam cavity and the target resonance frequency is as high as 6.6 MHz.

[0056] The positions designed as non-contact states in the fourth combination result include connection position A and connection position B, and the position designed as contact state is connection position C. For the situation where two positions in the fourth combination result are in non-contact state at the same time, during simulation calculation, geometric models of connection positions A and connection positions B in non-contact state are established at the same time, and geometric model of connection position C in contact state is established. Therefore, connection positions A and B affect the resonant frequency in the fourth combination at the same time. The resonant frequency of the combination is simulated using CST Microwave Studio software. The calculated resonant frequency is different from the frequency results when the single connection position A is not in contact (the first combination) or the single connection position B is not in contact (the second combination). Therefore, it is necessary to quickly lock whether the fault points affecting the resonant frequency are single or multiple through simulation and analysis. The present invention sets the frequency when the single connection position A is not in contact as the independent variable x1, the frequency when the single connection position B is not in contact as the independent variable x2, and the frequency under the joint influence of the connection position A and the connection position B being not in contact but the connection position C being in contact as y. According to the simulation results, the frequency change when the connection position A and the connection position B are not in contact is greater than the frequency change when the single connection position A and the single connection position B are not in contact, and is basically linearly related. The functional relationship of the resonant frequency can be obtained by polynomial regression: y=-42.394+3.919x1+0.221x2. When both connection position A and connection position B are not in contact at the same time, the contact surface spacing of the two positions is in the range of 0 to 20 mm, and the resonant frequency varies in the interval (13.508, 16.716] MHz, with a maximum deviation of 3.208 MHz from the target frequency. Figure 6 According to the resonant frequency measured by the kick beam cavity, it can be compared with the simulation results of the first three combinations. If there is a discrepancy in the comparison, it is necessary to consider that the fault point comes from two locations and compare it with the resonant frequency simulated under the joint action of the two fault points. Then, the test results, simulation results, and polynomial derivation calculation results are verified by polynomial calculation, and finally, multiple sources of fault points of contact resistance can be quickly determined.

[0057] The positions designed to be in a non-contact state in the fifth combined result include connection position A and connection position C, and the position designed to be in a contact state is connection position B. For the case where two positions are in a non-contact state simultaneously in the fifth combined result, during simulation calculation, a geometric model with connection position A and connection position C in a non-contact state and connection position B in a contact state is established simultaneously. Therefore, both connection position A and connection position C affect the resonant frequency under the fifth combination. The resonant frequency under this combination is simulated using CST microwave studio software, and the calculated resonant frequency is different from the frequency results when only connection position A is non-contact (the first combination) or only connection position C is non-contact (the third combination). Therefore, it is necessary to quickly lock whether the fault point affecting the resonant frequency is single or multiple through simulation and analysis. In the present invention, the frequency when only connection position A is non-contact is set as the independent variable x1, the frequency when only connection position C is non-contact is set as the independent variable x3, and the frequency under the combined influence of both connection position A and connection position C being non-contact but connection position B being in contact is set as y. According to the simulation results, the frequency change when both connection position A and connection position C are non-contact is greater than the frequency changes when only connection position A or only connection position C is non-contact, and it is basically linear. The functional relationship of the resonant frequency can be obtained through polynomial regression: y = 10.372 - 0.904x1 + 1.134x3. When both connection position A and connection position C are non-contact simultaneously, the contact surface spacing between the two positions is in the range of 0 - 20 mm, and the resonant frequency varies within the interval (13.508, 20.335] MHz, with a maximum deviation from the target frequency up to 6.827 MHz, as Figure 6 shown. According to the resonant frequency measured by the kicker cavity, it can be first compared with the simulation results in the first three combinations. If there are differences in the comparison, it is necessary to consider that the fault point comes from two positions, and compare it with the resonant frequency simulated under the combined action of the two fault points, and then use polynomial calculation to verify the test results, simulation results, and polynomial derivation calculation results. Finally, the sources of multiple fault points with contact resistance can be judged relatively quickly.

[0058] The positions designed to be in a non-contact state in the sixth combined result include connection position B and connection position C, and the position designed to be in a contact state is connection position A. For the case where two positions are in a non-contact state simultaneously in the sixth combined result, during simulation calculation, a geometric model with connection position B and connection position C in a non-contact state and connection position A in a contact state is established simultaneously. Therefore, both connection position B and connection position C affect the resonant frequency under the sixth combination. The CST microwave studio software is used to simulate the resonant frequency under this combination, and the calculated resonant frequency is different from the frequency results in the state where only connection position B is non-contact (the second combination) or only connection position C is non-contact (the third combination). Therefore, it is necessary to quickly lock whether the fault point affecting the resonant frequency is single or multiple through simulation and analysis. In the present invention, the frequency when only connection position B is non-contact is set as the independent variable x2, the frequency when only connection position C is non-contact is set as the independent variable x3, and the frequency under the combined influence of both connection position B and connection position C being non-contact but connection position A being in contact is set as y. According to the simulation results, the change in frequency when both connection position B and connection position C are non-contact is greater than the change in frequency when only connection position B or only connection position C is non-contact, and it is basically a linear relationship. The functional relationship of the resonant frequency can be obtained through polynomial regression: y = -6.569 + 0.394x2 + 1.103x3. When both connection position B and connection position C are non-contact, the contact surface spacing between the two positions is in the range of 0 to 20 mm, and the resonant frequency varies within the interval (13.508, 22.045] MHz, with a maximum deviation from the target frequency up to 8.537 MHz, as Figure 6 shown. According to the resonant frequency measured by the kicker cavity, it can be first compared with the simulation results in the first three combinations. If there is a discrepancy in the comparison, it is necessary to consider that the fault point comes from two positions, and compare it with the resonant frequency obtained by simulation under the combined action of the two fault points. Then, polynomial calculation is used to verify the test results, simulation results, and polynomial derivation calculation results. Finally, the sources of multiple fault points with contact resistance can be judged relatively quickly.

[0059] The positions designed as non-contact states in the seventh combination result include connection positions A, B, and C, that is, the three positions that may introduce contact resistance are all in a non-contact state. For this combination, when conducting simulation calculations, a geometric model of connection positions A, B, and C in a non-contact state is established at the same time. Therefore, connection positions A, B, and C affect the resonant frequency of the seventh combination at the same time. The resonant frequency under the combination is simulated using CST Microwave Studio software. The calculated resonant frequency is different from the frequency results in the states of single connection position A (the first combination), single connection position B without contact (the second combination) or single connection position C without contact (the third combination). Therefore, it is necessary to quickly lock whether the fault points affecting the resonant frequency are single or multiple through simulation and analysis. The present invention sets the frequency when the single connection position A is not in contact as the independent variable x1, the frequency when the single connection position B is not in contact as the independent variable x2, the frequency when the single connection position C is not in contact as the independent variable x3, and the frequency under the joint influence of the connection position A, the connection position B and the connection position C are not in contact as y. According to the simulation results, the frequency change when the connection position A, the connection position B and the connection position C are not in contact is greater than the frequency change when the single connection position A, the single connection position B and the single connection position C are not in contact, and is basically linear. The functional relationship of the resonant frequency can be obtained by polynomial regression: y=-1.770-0.355x1+0.277x2+1.215x3. When connection position A, connection position B and connection position C are not in contact at the same time, the contact surface spacing of the two positions is in the range of 0 to 20 mm, and the resonant frequency varies in the interval (13.508, 22.144] MHz, with a maximum deviation of up to 8.636 MHz from the target frequency. Figure 6 As shown. According to the resonant frequency measured by the kick beam cavity, it can be compared with the simulation results of the first three combinations. If there is a discrepancy between the comparisons, it is necessary to consider whether the fault point comes from two locations, and then compare it with the simulation results of the fourth, fifth, and sixth combinations. If there is a discrepancy between the comparisons, it is necessary to consider whether the fault point comes from three locations, and then compare it with the simulation results of the seventh combination. Then use polynomial calculations to verify the test results, simulation results, and polynomial derivation calculation results, and finally quickly determine the multiple sources of fault points of contact resistance.

[0060] By analogy, the resonant frequencies of the geometric models corresponding to the eight combination results can be obtained. Among them, since the first group of the eighth combination results is empty and the second group includes all possible locations where contact resistance may exist in the ultra-low frequency kick beam cavity to be tested, the resonant frequency of the geometric model corresponding to the eighth combination result can be used as the reference resonant frequency of the ultra-low frequency kick beam cavity to be tested, and compared with the target resonant frequency of the ultra-low frequency kick beam cavity to verify the simulation results.

[0061] Step 5: Compare the resonant frequencies corresponding to all the geometric models obtained from the simulation in Step 4 with the measured resonant frequency of the ultra-low frequency kicker cavity to be measured, and select the geometric model that is closest to the measured resonant frequency of the ultra-low frequency kicker cavity to be measured. The connection position in the first group of the corresponding combined results in the selected geometric model is the position where the contact resistance exists, and the fault point detection of the ultra-low frequency kicker cavity to be measured can be quickly completed.

[0062] The method for detecting the fault point of the ultra-low frequency kicker cavity based on the contact resistance according to the present invention can not only quickly and accurately detect the fault point according to the different influences of the contact resistance at different connection positions on the resonant frequency of the ultra-low frequency kicker cavity, but also provide guiding opinions for the machining of the ultra-low frequency kicker cavity. According to the resonant frequencies obtained from the simulation in Step 4 of this embodiment, for the case where a single position is not in contact, the connection position C between the third metal rod 5 and the bottom flange 8 has the greatest influence on the resonant frequency of the ultra-low frequency kicker cavity in the non-contact state, the connection position B between the second metal rod 9 and the metal coil 2 has the second greatest influence on the frequency in the non-contact state, and the connection position A between the first metal rod 4 and the top flange 7 has the least influence on the resonant frequency of the ultra-low frequency kicker cavity in the non-contact state; for the case where two or more positions are not in contact, the influence on the resonant frequency is the greatest when positions A, B, and C are all in the non-contact state. Therefore, the guiding opinions for machining formed are as follows: for the parts where welding cannot be adopted, the connection structure needs to be optimized, that is, when designing the positioning step at position C, the step depth needs to be optimized and good fixation needs to be achieved to ensure full contact of the two contact surfaces. For the parts where welding can be adopted, appropriate welding methods need to be selected according to different parts, and the welding quality needs to be strictly controlled to ensure full contact of the contact surfaces.

[0063] The above is only used to illustrate the technical solutions of the present invention and is not intended to limit it. For those of ordinary skill in the art, the specific technical solutions recorded in the above embodiments can be modified, or some of the technical features can be equivalently replaced, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions protected by the present invention.

Claims

1. A method for detecting fault points of an ultra-low frequency kicker cavity based on contact resistance, characterized in that, It includes the following steps: Step 1: Determine the positions in the ultra-low frequency kick beam cavity to be measured where contact resistance may exist; Step 2: Divide all the positions where contact resistance may exist into two groups in the way of permutation and combination, and obtain 2 n combination results, where n is the number of positions with contact resistance in the ultra-low frequency kicker cavity to be measured; Step 3: Use a 3D electromagnetic simulation software to establish geometric models for the 2 n combined results respectively. When modeling, establish a geometric model representing the non-contact state for the first group of each combined result, and establish a geometric model representing the contact state for the second group. Step 4: Simulate and calculate the resonant frequencies corresponding to all geometric models, and compare the resonant frequencies corresponding to the 2 n geometric models obtained from the simulation with the measured resonant frequency of the ultra-low frequency kicker cavity to be measured. Based on the geometric model that is closest to the measured resonant frequency of the ultra-low frequency kicker cavity to be measured, the location of the contact resistance can be determined, and the fault point detection of the ultra-low frequency kicker cavity to be measured can be completed.

2. A method for detecting fault points of an ultra-low frequency kick beam cavity based on contact resistance according to claim 1, wherein: In Step 1, determining the positions in the ultra-low frequency kick beam cavity to be measured where contact resistance may exist specifically includes: Determining the positions in the ultra-low frequency kick beam cavity to be measured where contact resistance may exist according to the connection point positions that need to be connected later between the discrete components in the ultra-low frequency kick beam cavity to be measured.

3. A method for detecting fault points of an ultra-low frequency kick beam cavity based on contact resistance according to claim 2, wherein: In Step 4, the specific method for simulating and calculating the resonance frequencies corresponding to all geometric models is: When there is one position where contact resistance may exist in the first group of a combined result, directly simulate and calculate the resonance frequency of the geometric model corresponding to this combined result; When there are multiple positions where contact resistance may exist in the first group of a combined result, simulate and calculate the resonance frequency of the geometric model corresponding to this combined result through a resonance frequency function based on polynomial regression.

4. A method for detecting fault points of an ultra-low frequency kick beam cavity based on contact resistance according to claim 3, wherein: In Step 3, the three-dimensional electromagnetic simulation software is CST Microwave Studio software.

5. A method for detecting fault points of an ultra-low frequency kick beam cavity based on contact resistance according to any one of claims 1-4, wherein: In Step 1, the ultra-low frequency kick beam cavity includes a metal outer cavity cylinder (6), a top flange (7) and a bottom flange (8) respectively arranged at the upper and lower ends of the metal outer cavity cylinder (6), and an insulating support (3), a metal coil (2), a pair of deflection plates (1), a first metal rod (4), a second metal rod (9) and a third metal rod (5) arranged inside the metal outer cavity cylinder (6); the insulating support (3) is coaxially arranged inside the metal outer cavity cylinder (6), and one end thereof is connected to the bottom flange (8); the metal coil (2) is embedded on the outer side wall of the insulating support (3); a pair of deflection plates (1) are located at the other end of the insulating support (3), one of the deflection plates (1) is connected to the top flange (7) through the first metal rod (4), the other deflection plate (1) is connected to the upper end of the metal coil (2) through the second metal rod (9), and the lower end of the metal coil (2) is connected to the bottom flange (8) through the third metal rod (5); the connection between one of the deflection plates (1) and the first metal rod (4), the connection between the other deflection plate (1) and the second metal rod (9), and the connection between the lower end of the metal coil (2) and the third metal rod (5) are all integrally designed; There are three positions in the ultra-low frequency kick beam cavity to be measured where contact resistance may exist, including the connection position between the first metal rod (4) and the top flange (7), the connection position between the second metal rod (9) and the metal coil (2), and the connection position between the third metal rod (5) and the bottom flange (8); In step 2, the number of the combined results is 2 3 .

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