CN-121142411-B - Weak magnetic induction intensity measuring device and method based on magnetic fluid Cotton-mountain effect

CN121142411BCN 121142411 BCN121142411 BCN 121142411BCN-121142411-B

Abstract

The application relates to the technical field of magnetic field measurement, in particular to a weak magnetic induction intensity measuring device and method based on a magnetic fluid Cotton-mountain effect. Comprising the following steps: a laser emitting module, a C-M effect container, a polarized light converter, a magneto-optical modulating module, a light intensity detector, the magnetic field intensity to be measured is measured and calculated by detecting the light intensity signal. The scheme is based on the Cotton-mountain effect of the magnetic fluid and combines a Senarmont compensation method and a Faraday magneto-optical modulation technology, so that high-precision measurement of weak magnetic induction intensity is realized.

Inventors

FAN DAIHE
YANG HONGYU
SHEN ZHENGHAN
REN ZHONGYUAN
SU JIAJIA
Yang Xindie
WEI YUN
JIA XINYAN
LIU QIJUN

Assignees

西南交通大学

Dates

Publication Date: 20260512
Application Date: 20251013

Claims (8)

1. The weak magnetic induction intensity measuring device based on the magnetic fluid Cotton-mountain effect is characterized by comprising: The laser emission module is used for generating incident polarized light with a first included angle with the first horizontal direction; the C-M effect container is internally provided with magnetic fluid liquid and is used for loading a magnetic field to be measured; The loading direction of the magnetic field to be measured is the same as the first horizontal direction, incident polarized light is injected into the C-M effect container along the second horizontal direction, the incident polarized light is elliptical polarized light under the action of magnetic fluid, and the first horizontal direction and the second horizontal direction are mutually perpendicular; the polarized light converter is arranged behind the second horizontal direction of the C-M effect container and is used for converting incident elliptical polarized light into emergent polarized light; the magneto-optical modulation module is arranged behind the second horizontal direction of the polarized light converter, and is used for carrying out high-frequency bias modulation on emergent polarized light and demodulating the emergent polarized light into a light intensity signal with light intensity alternating current variation; The light intensity detector is arranged behind the second horizontal direction of the magneto-optical modulation module and is used for measuring and calculating the magnetic field intensity to be measured by detecting the light intensity signal; the light intensity detector includes: The photodiode is used for detecting the light intensity signal and converting the light intensity signal into a weak current signal; a signal amplifier for amplifying a weak current signal into a voltage signal; the filter is used for filtering the voltage signal to obtain a characterization signal; the calculator calculates the magnetic field intensity to be measured according to the characterization signals; the calculator extracts the period of the high-amplitude signal from the characterization signal and the period T m of the characterization signal; Extracting the duration T s of the peak from the period of the high-amplitude signal; Calculating the magnetic field strength B to be measured according to the period T m and the duration T s ; c is a calculation constant related to the magnetic fluid parameter, and pi is a circumference ratio.
2. The weak magnetic induction intensity measuring device based on the magnetic fluid Cotton-Mouton effect according to claim 1, wherein: the magnetic fluid liquid was a 0.5% kerosene based Fe 3 O 4 solution.
3. The weak magnetic induction intensity measuring device based on the magnetic fluid Cotton-mountain effect of claim 1, wherein the filter extracts the fundamental frequency and the frequency doubling from the voltage signal.
4. The weak magnetic induction intensity measuring device based on the magnetic fluid Cotton-mountain effect of claim 1, wherein the magneto-optical modulation module comprises: the magneto-optical modulator is used for carrying out high-frequency bias modulation on the emergent polarized light to obtain a modulation signal, wherein the current introduced by the magneto-optical modulator is as follows: I m is the current magnitude introduced by the magneto-optical modulator, and I m0 is the current amplitude introduced by the magneto-optical modulator; And the analyzer is used for demodulating the modulated signal into a light intensity signal, and the included angle between the light transmission direction of the detector and the first horizontal direction is 3 pi/4.
5. The weak magnetic induction intensity measuring device based on the magnetic fluid Cotton-mountain effect of claim 1, wherein the first included angle is pi/4; The polarized light converter is a 1/4 wave plate, the included angle between the polarized light converter and the first horizontal direction is a second included angle, and the second included angle is pi/4.
6. The weak magnetic induction intensity measuring device based on the magnetic fluid Cotton-mountain effect of claim 1, wherein the light intensity detector further comprises a sampler; the sampler is used for The sampling rate captures the voltage signal for input to the filter.
7. The weak magnetic induction intensity measuring method is characterized in that the weak magnetic induction intensity measuring device based on the magnetic fluid Cotton-mountain effect is adopted to measure the magnetic field intensity, and the weak magnetic induction intensity measuring method comprises the following steps: step 1, generating incident polarized light E 1 with a first included angle with a first horizontal direction, wherein the first included angle is pi/4; Step 2, incident polarized light is injected into the magnetic fluid liquid to which the magnetic field to be measured is applied, so that the incident polarized light is converted into elliptical polarized light, and the phase difference of the long axis and the short axis of the elliptical polarized light can represent the strength of the magnetic field to be measured; Step 3, elliptical polarized light is injected into the polarized light converter, elliptical polarized light is converted into emergent polarized light, and the phase difference is converted into an included angle between the polarization direction of the emergent polarized light and the polarization direction of the incident polarized light; step 4, high-frequency bias modulation is carried out on the emergent polarized light, and the emergent polarized light is demodulated into a light intensity signal with alternating light intensity; And 5, converting the light intensity signal into a weak current signal, amplifying and converting the weak current signal into a voltage signal, sampling and filtering the voltage signal to obtain a characterization signal, and measuring the magnetic field intensity of the magnetic field to be measured based on the characterization signal.
8. The weak magnetic induction intensity measurement method according to claim 7, characterized in that: the light field of the incident polarized light is E 1 ; A is the electric field amplitude of the incident polarized light E 1 , For the jones matrix of incident polarized light E 1 , Representing matrix transposed symbols; the phase difference is delta; ; lambda is the wavelength of incident polarized light, d is the thickness of the magnetic fluid liquid, n 1 is the refractive index of the magnetic fluid liquid, c is the volume fraction of magnetic particles in the magnetic fluid liquid, χ x 、χ y respectively represents the x-axis direction polarization rate and the y-axis direction polarization rate of the magnetic fluid liquid in unit volume; The magnetic moment of the magnetic fluid is the magnetic moment corresponding to the magnetic particles in the magnetic fluid, k is the Boltzmann constant, T is the temperature of the magnetic fluid, B is the magnetic field strength of the magnetic field to be measured, coth is the hyperbolic cotangent function; The light field of emergent polarized light is E 2 ; ; the Jones matrix respectively represents a 1/4 wave plate and magnetic fluid liquid, e represents a natural constant, and i represents an imaginary unit; The optical field of the light intensity signal is E 3 ; ; jones matrix respectively representing analyzer and magneto-optical modulator; The light intensity I of the light intensity signal is: ; ; ; Representing a first intermediate parameter and a second intermediate parameter respectively, N 2 、R 2 、L 2 represents the number of turns, radius and length of the solenoid of the magneto-optical modulator respectively; I represents the light intensity of the light intensity signal, I 0 represents the amplitude of the light intensity signal, and I m0 represents the amplitude of the current fed into the magneto-optical modulator; The expression for amplifying, extracting and filtering the light intensity I of the light intensity signal to obtain the magnetic field B to be measured is as follows: ; T m represents the period of the ratio of I and I 0 , and T s represents the duration T s of peak extraction in the period of the high amplitude signal of the ratio of I and I 0 .

Description

Weak magnetic induction intensity measuring device and method based on magnetic fluid Cotton-mountain effect Technical Field The application relates to the technical field of magnetic field measurement, in particular to a weak magnetic induction intensity measuring device and method based on a magnetic fluid Cotton-mountain effect. Background Weak magnetic field measurement has wide and important application value in a plurality of key fields such as geophysical exploration, medical diagnosis (such as brain magnetic diagram), security assurance (such as contraband detection), basic physical experiment teaching and the like. Accurate detection of these weak magnetic field signals is critical for understanding natural phenomena, improving diagnosis and treatment level and guaranteeing public safety. Common weak magnetic field measurement techniques mainly include hall effect sensors, resonant magnetometers (such as proton magnetometers), and superconducting quantum interferometers (SQUIDs). Hall effect devices measure magnetic fields by electromagnetic conversion, resonant magnetometers utilize the resonant response of specific particles (e.g., protons) in a magnetic field, while SQUIDs detect changes in magnetic flux based on the josephson effect. The scheme has obvious limitations in the process of measuring the weak magnetic field, namely, the Hall device is greatly influenced by temperature, so that the weak magnetic field measurement precision is insufficient, the proton magnetometer has limited detection sensitivity to the weak magnetic field due to smaller proton magnetostriction, and the SQUID has extremely high sensitivity, but the SQUID must rely on expensive liquid helium or liquid nitrogen to maintain an ultralow temperature environment, so that the maintenance cost is high, and the wide application of the SQUID is limited. In view of the above, there is a lack of a low-cost and high-precision method for measuring a weak magnetic field. Disclosure of Invention The summary of the application is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. The summary of the application is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Some embodiments of the present application provide a weak magnetic induction intensity measuring device and method based on magnetic fluid Cotton-mountain effect to solve the technical problems mentioned in the background art section. As a first aspect of the present application, some embodiments of the present application provide a weak magnetic induction intensity measuring device based on a magnetic fluid Cotton-Mouton effect, including: The laser emission module is used for generating incident polarized light with a first included angle with the first horizontal direction; The loading direction of the magnetic field to be measured is the same as the first horizontal direction, and incident polarized light is injected into the C-M effect container along the second horizontal direction and is elliptical polarized light under the action of the magnetic fluid, and the first horizontal direction and the second horizontal direction are mutually perpendicular; the polarized light converter is arranged behind the second horizontal direction of the C-M effect container and is used for converting incident elliptical polarized light into emergent polarized light; the magneto-optical modulation module is arranged behind the second horizontal direction of the polarized light converter, and is used for carrying out high-frequency bias modulation on emergent polarized light and demodulating the emergent polarized light into a light intensity signal with light intensity alternating current variation; the light intensity detector is arranged behind the second horizontal direction of the magneto-optical modulation module and measures and calculates the intensity of the magnetic field to be measured by detecting the light intensity signal. The scheme is based on the Cotton-mountain effect of the magnetic fluid, and combines a Senarmont compensation method and a Faraday magneto-optical modulation technology to efficiently convert the magnetic fluid birefringence phase difference caused by the magnetic field to be detected into a detectable light intensity signal. By collecting and analyzing the light intensity signal, high-precision measurement of weak magnetic induction intensity is realized. The scheme has high measurement precision (optical phase difference sensitive conversion), relatively low cost (no ultralow temperature environment is needed), clear and visual structure (physical principle is clear and visible). Further, the method comprises the steps of, The magnetic fluid liquid was a 0.5% kerosene based Fe 3O4 solution. Through experimental measurement, the coal oil-based Fe 3O4 soluti