CN-122021344-A - Prediction method for conduction cooling superconducting cavity operable domain

CN122021344ACN 122021344 ACN122021344 ACN 122021344ACN-122021344-A

Abstract

The invention discloses a prediction method for an operable domain of a conduction cooling superconducting cavity, which comprises the steps of calculating field distribution under a target acceleration gradient according to electromagnetic characteristics of a vacuum domain of the superconducting cavity, calculating surface loss power density and dynamic thermal load under the target acceleration gradient based on the field distribution and actual surface resistance, reversely solving a secondary cold head temperature according to the total thermal load of the superconducting cavity, carrying out steady-state temperature field solving by taking the secondary cold head temperature as a thermal boundary condition of a cold head installation position to obtain temperature distribution of the surface of the cavity, updating parameters until heat balance according to the temperature distribution, constructing a constraint set according to the steady-state temperature field, inputting measurement data of the superconducting cavity into a prediction model, predicting margin of each steady-state temperature point, correcting the prediction model according to deviation between the prediction margin and actual measurement margin to obtain an online prediction model, inputting the operation data into the online prediction model to calculate margin of each steady-state temperature point, predicting the operable domain of the conduction cooling superconducting cavity, and giving action suggestions.

Inventors

GE RUI
SHA PENG
PAN WEIMIN
HE FEISI
Chang Zhengze
LIU XIAO
ZHOU JIANRONG

Assignees

中国科学院高能物理研究所

Dates

Publication Date: 20260512
Application Date: 20260407

Claims (10)

1. A method for predicting the operational domain of a conduction-cooled superconducting cavity, comprising the steps of: The method comprises the steps of a prediction model training stage, namely calculating field distribution under a target acceleration gradient according to electromagnetic characteristics of a vacuum space of a superconducting cavity, calculating surface loss power density and dynamic heat load under the target acceleration gradient based on the field distribution and actual surface resistance of the superconducting cavity, reversely solving the temperature of a secondary cold head on a cold quantity-temperature characteristic function of the secondary cold head adopted by a conduction cooling superconducting cavity vertical test system according to the total heat load of the superconducting cavity, carrying out steady-state temperature field solution by taking the temperature of the secondary cold head as a thermal boundary condition of a cold head installation position to obtain temperature distribution of the cavity surface, updating the actual surface resistance, the dynamic heat load and the total heat load according to the temperature distribution, repeating the processes until a heat balance convergence criterion is met, and constructing a constraint set according to the steady-state temperature field after heat balance convergence; The correction stage of the prediction model comprises the steps of inputting measurement data of the superconducting cavity into the prediction model, predicting the margin of each steady-state temperature point, determining a correction parameter set according to the deviation between the predicted margin and the actually measured margin, and correcting the prediction model to obtain an online prediction model of the superconducting cavity; and in the online prediction stage, operating data of the superconducting cavity are input into an online prediction model to calculate margin of each steady-state temperature point, the operable domain of the conduction cooling superconducting cavity is predicted, and action suggestions are given according to a constraint set.
2. The method of claim 1, wherein the vacuum domain of the superconducting cavity is subjected to electromagnetic signature analysis to obtain a characteristic frequency and a magnetic field distribution of the superconducting cavity, and the energy storage U 0 and the acceleration gradient E acc0 are extracted as reference values to calculate a field distribution under the target acceleration gradient E acc .
3. The method of claim 2, wherein the field distribution and actual sheet resistance based on the target acceleration gradient E acc Calculating surface loss power density under target acceleration gradient Obtaining dynamic thermal load 。
4. The method according to claim 2, characterized in that, according to Calculating a scaling factor According to the scaling factor The field distribution is scaled to obtain the field distribution under the target acceleration gradient E acc , E acc is the target acceleration gradient, L eff is the effective acceleration length, R/Q is the characteristic impedance parameter of the superconducting cavity, and f is the characteristic frequency of the superconducting cavity.
5. A method according to claim 1,2 or 3, wherein the actual sheet resistance Wherein, C T is a temperature factor, C Q is a coating quality factor, and R s is a theoretical surface resistance of the superconducting cavity.
6. The method of claim 1, wherein the power of the RF circuit is based on the power of the RF circuit Reflected power Calculating additional heating load entering low-temperature end of superconducting cavity by line attenuation coefficient 。
7. The method of claim 6, wherein the total heat load of the superconducting cavity is determined by Cold quantity-temperature characteristic function of secondary cold head adopted in conduction cooling superconducting cavity vertical test system Upper reverse solving for the temperature of the secondary cold head The temperature of the secondary cold head As the thermal boundary condition of the cold head mounting position, solving the steady-state temperature field to obtain the temperature distribution T (x, y, z) of the cavity surface, and updating the actual surface resistance according to the T (x, y, z) Dynamic thermal loading And total heat load Repeating the above steps until the heat balance convergence criterion is satisfied, and the total heat load , Is a static heat load.
8. The method of claim 7, wherein the set of constraints comprises: (1) Coldhead capability constraint ; (2) Hot spot temperature margin constraint Wherein, the method comprises the steps of, Is the maximum temperature of the key positions of the superconducting cavity and the heat conduction path, Is the superconducting material temperature limit in the superconducting temperature zone; (3) Reflected power ratio constraint Wherein, the method comprises the steps of, Setting a reflection threshold value allowed by the test system itself; (4) Temperature difference constraint across superconducting transition temperature zones Wherein To maximize the temperature differential across the superconducting cavity during the transition temperature region, Designing a limit value for the maximum allowable temperature difference of the cavity; (5) Frequency constraint ; Indicating the amount of frequency drift relative to the reference state.
9. The method of claim 8, wherein the action proposal is given based on a margin and a set of constraints for each steady state temperature point: (1) For fixed coupling conditions Solving the maximum reachable gradient of the current steady-state temperature point Outputting maximum allowable gradient Or maximum allowable incident power And giving a stepping strategy; when the dominant limiting factor is the reflection ratio Outputting a reflection early warning threshold value, suggesting to suspend power boosting and preferentially checking coupling matching, antenna attenuation and low-temperature end-attached heating load; When the dominant limiting factor is cold head capacity Or hot spot temperature Outputting an absolute margin of a cold head when the test is performed, and suggesting that if the subsequent test is continued to stay at the working point, the static heat load is reduced, the dissipation of an antenna is reduced or the contact thermal resistance is improved to be a preferential direction; (2) For adjustable coupling conditions Solving the maximum reachable gradient of the current steady-state temperature point Outputting maximum allowable gradient Or maximum allowable incident power Giving the coupling adjustment direction to make Maintain within a preset range, thereby reducing And expanding the runnable boundary; when the dominant limiting factor is When, it is preferred to adjust the coupling to reduce reflection; when the dominant limiting factor is Or (b) When it is recommended to limit the power step or rollback to a safe operating point while maintaining low reflection; if the dominant limiting factor is a detuning constraint Or when the reflection is obviously increased due to detuning, outputting a detuning early warning and suggesting to adopt a tuning strategy, reducing power stepping or waiting for thermal stabilization so as to avoid the rise of the reflected power caused by frequency drift; (3) And when the absolute margin of the cold head cold quantity approaches zero quickly or the absolute margin of a hot spot approaches zero quickly or the reflected power rises quickly in the power/gradient lifting process, judging to enter a quench high risk area and outputting early warning and power rollback suggestions.
10. The method of claim 9, wherein the reason for boundary formation is interpreted and the direction of test improvement is given with a constraint of minimal margin as a dominant limiting factor.

Description

Prediction method for conduction cooling superconducting cavity operable domain Technical Field The invention belongs to the field of radio frequency superconducting technology and low-temperature engineering, and relates to a prediction method for an operable domain of a conduction cooling superconducting cavity, which is suitable for the prediction and on-line evaluation of the operable domain of the vertical test of the conduction cooling superconducting cavity. Background The radio frequency acceleration module is a key core component of the accelerator and is responsible for providing power for particle beam. Compared with the normal temperature radio frequency technology, the superconducting radio frequency technology has the advantages of lower cost, less beam loss, stronger beam power and the like. The superconducting cavity, which is a core component of superconducting radio frequency technology, must operate in a superconducting temperature region. In order to maintain the low-temperature environment required by the superconducting cavity, a liquid helium soaking mode is generally adopted, and a complex and expensive liquid helium supply system is required to be matched, so that popularization and application of the superconducting radio frequency accelerator in the fields of medical treatment, industry and the like are not facilitated. With the continuous development of superconducting cavity technology, the quality factor (Q 0 value) of the superconducting cavity is continuously improved, and the dynamic heat load wattage of the superconducting cavity can be controlled to be in the order of units. The improvement of the Q 0 value of the superconducting cavity makes it possible to discard the traditional liquid helium soaking cooling scheme, and a novel cooling scheme based on a small refrigerator is adopted, and the heat load of the superconducting cavity is taken away by utilizing a heat conduction mode. According to the scheme, a liquid helium soaking environment is not required to be provided, peripheral helium compressor, low-temperature pipeline and other matched equipment are not required, so that the system volume is greatly reduced, the module structure is more compact, meanwhile, the maintenance is easy, the manufacturing and operating cost is reduced, and the scheme is easier to popularize and apply in the fields of industry, medical application and the like. However, the conduction cooling superconducting cavity still faces the following problems in vertical test and engineering operation that (1) the cold quantity of a cold head is obviously changed along with the temperature, the traditional superconducting cavity thermal simulation of a fixed wall temperature or a fixed heat flow boundary is difficult to reflect a real working point, and (2) in the conduction cooling vertical test, various static heat loads, contact thermal resistance and other affected factors of a test system are more, so that deviation occurs between temperature measuring point distribution and simulation prediction. The existing method mostly regards the deviation as a fixed assumption or experience margin, lacks a mechanism for carrying out on-line identification and correction on key thermal parameters based on measured data in the vertical test process, so that a high-precision prediction result of the boundary of the operable domain of the superconducting cavity is difficult to obtain, and (3) the existing method outputs a single superconducting cavity Eacc-Q 0 curve, lacks clear division and limiting factor interpretation of an operable area/non-operable area, and is difficult to guide a test strategy and on-line operation, and (4) lacks an on-line prediction tool linked with real-time data of a vertical test system, and is incapable of adaptively correcting a model and outputting an operable safety margin in the test process. Disclosure of Invention Aiming at the problems existing in the prior art, the invention aims to provide a prediction method for the operable domain of a conduction cooling superconducting cavity, which is an electromagnetic-thermal coupling performance prediction method for high-performance superconducting cavities such as Nb 3 Sn and the like under the conduction cooling condition, and is particularly suitable for vertical test, operable area assessment, instability risk judgment and online prediction and decision assistance of a test process of the conduction cooling superconducting cavity. The method is based on a cavity electromagnetic field scaling and surface resistance model, a multi-physical field coupling iterative solution of electromagnetic loss-heat conduction-cold head cold quantity/temperature characteristic is constructed, reflected power changes caused by cable loss and coupling deviation of a test antenna are brought into the heat balance of an overall system, and whether the cold head cold quantity-system heat load reaches the heat balance and whether other engineer