Method for measuring critical current density of superconducting material

Abstract

The invention discloses a method for measuring critical current density of a superconducting material. The specific steps include: (1) preparing a standard sample of a specific superconducting material, first using a four-lead method to measure currents of the standard sample under different magnetic field intensities and temperatures, then using a Campbell method to measure voltage signals output by the standard sample under the same magnetic field intensities and temperatures, and establishing an I / V-B-T standard curve of the standard sample; (2) making a sample to be measured into the same shape as the standard sample, then putting the sample to be measured in a Campbell method exploring coil, setting magnetic field intensity and temperature, measuring a voltage signal output by the sample to be measured through the Campbell method, and reading critical current of the sample to be measured through the I / V-B-T standard curve and then calculating critical current density of the sample to be measured. The method provided by the invention avoids equipment required by usage of the four-lead method, and solves the problems of many collected data and long time consumption of the Campbell method, magnetic measurement is relatively safe, and a measuring result is approximate to a measuring result of directly using the four-lead method.

Description

technical field [0001] The invention belongs to the technical field of electrical performance measurement of superconducting materials, and in particular relates to a method for measuring critical current density of superconducting materials. Background technique [0002] With the development and utilization of electric energy, the measurement of superconducting materials and their properties, which are closely related to the development of the electric power industry, is a must in industry and engineering. However, the research on the essence of superconducting materials is still in a developing state, and the research on the characteristics of superconducting materials and the field of performance measurement are even more immature. Among the several basic parameters of superconductivity, critical current is one of the basic properties of superconducting materials. Critical current is an important parameter for superconducting applications and a main indicator to measure t...

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Problems solved by technology

[0003] At present, there are several methods for measuring the critical current density of superconducting materials: the four-lead method is the most common electrical measurement method for measuring the critical current density of superconducting materials, and it is also a recognized method. The equipment used is simple, the measurement results are straightforward, and the measurement range is wide. However, the current in the process of superconducting power transmission is large, and it is easy to generate heat and damage the sample. In addition, a large current source is required; the DC magnetization method measures the hysteresis loop of the material, and then calculates the current of the material, which is safe and reliable.

And choose this kind of method to the second kind of superconductor, the weak point of the measurement result is that the measurement result precision is not high enough, can only reflect the regional current; The magnetic susceptibility coefficient is substituted into the model to estimate the current. This measurement method is difficult to determine the position when the imaginary part of the magnetic field is the largest, and it also changes with the frequency of the magnetic field, so the measurement result can only be estimated, but it can reflect the overall characteristics of the sample, and the frequency of the external field Without limitation, it is very convenient and fast to change the AC amplitude and frequency. This method is widely used to study the dynamic properties of magnetic flux; the mixed field measurement method includes the Campbell method and the third harmonic analysis method, and the external excitation field used in the Campbell method measurement The strength and frequency are limited, but it can reflect the overall characteristics of the material, especially the characterization of the impact of the microscopic characteristics on the results. It is also used in the study of the magnetic properties of materials, and is mostly used in the measurement of superconducting thin film materials; the third harmonic method is also derived from theoretical calculations. As a result, the accuracy of the results is relatively low, and the application range is not wide, but it can effectively supplement the Campbell method in the measurement of thin film materials, and can also express the effect of magnetic flux movement

[0004] These measurement methods have their own advantages and application ranges. The four-lead method, AC magnetization method, DC magnetization method and even the third harmonic method have relatively mature and extensive research and application. The Campbell method is a new research and application in recent years. method, but there are problems such as large amount of collected data, long time consumption, large amount of calculation, large error, and high requirements for stable signals.

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