CN109100664B - Method for measuring small space magnetic field - Google Patents

Abstract

The invention discloses a method for measuring a small space magnetic field, which sequentially generates more than three uniform strong magnetic fields with known strength in the direction of the small space magnetic field to be measured, wherein the strength is more than 30 times of the strength of a magnetic interference field; the method comprises the steps of measuring a total magnetic field value of a space after superposition every time through an optical pump magnetometer, constructing an equation set about the small magnetic field intensity to be measured, the uniform strong magnetic field intensity, the magnetic interference field intensity, the total magnetic field value of the space and an included angle between the magnetic interference field and the optical pump magnetometer in the direction of the small magnetic field to be measured along the axis of the optical pump magnetometer by utilizing trigonometric function relation, and obtaining the strength value of the small magnetic field to be measured in the space by solving the equation set. The invention can realize the measurement of the small magnetic field change to be measured in space.

Description

A method of measuring small magnetic field in space

technical field

The invention relates to the technical field of quantum precision measurement, in particular to a measurement method of a small magnetic field in space.

Background technique

In the field of space magnetic field detection, the optical pump magnetometer is the most widely used scalar magnetometer. It has the advantages of wide measurement range, high sensitivity, high precision and fast frequency response. The optical pump magnetometer has a blind spot in the measurement process, that is, only when the angle between the direction of the magnetic field to be measured and the optical axis of the magnetometer is within a certain range, the measurement can be performed normally, otherwise there is no signal.

When the optical pump magnetometer is mounted on a high-orbit satellite, due to the distance from the earth, the strength of the geomagnetic field is only about 100nT, while the magnetic interference of the satellite platform remains at the original level. Magnetic interference includes: (1) Soft magnetic interference, mainly generated by on-board equipment, such as wireless equipment interference, various electrical equipment interference, etc. The frequency of interference is generally high; (2) Hard magnetic interference, mainly related to satellite maneuvering and itself Depending on the material, the frequency of the interference is close to the frequency of the static magnetic field, and its intensity is many times greater than that of the soft magnetic interference. These magnetic interferences generated by the satellite platform are of different magnitudes and unstable directions, resulting in the combined direction of the combined field with the geomagnetic field to be measured is also not fixed. In particular, if the interference field is perpendicular to the geomagnetic field to be measured and much larger than the geomagnetic field to be measured, the contribution of the measured field to the total magnetic field will be much smaller than the resolution of the optical pump magnetometer. When the geomagnetic field to be measured is in the order of 100nT, and the satellite interference field is much larger than the geomagnetic field to be measured, reaching more than 30 times the geomagnetic field, the geomagnetic field can be called a small space magnetic field. Therefore, for the measurement of the small magnetic field in space, it is necessary to solve the problems of the working blind area of the optical pump magnetometer and the inability to measure the small magnetic field.

At present, the commonly used space magnetic measurement equipment mainly includes fluxgate magnetometer and optical pump magnetometer. Due to the limitation of the working principle, the fluxgate magnetometer has the problem of zero drift in the process of accumulation over time and in the process of temperature change, which will affect the accuracy of the magnetic measurement data. At this stage, the sensitivity required for magnetic field measurement is also very high, and it is necessary to measure the magnetic anomaly signal of the pT level or even lower. It is extremely difficult for a fluxgate magnetometer to have such a low sensitivity.

SUMMARY OF THE INVENTION

In view of this, the present invention provides a method for measuring the small magnetic field in space, which can realize the measurement of the change of the small magnetic field to be measured in space.

Specific embodiments of the present invention are as follows:

A method for measuring a small magnetic field in space, in which three or more uniform strong magnetic fields with known strengths are sequentially generated in the direction of the small magnetic field to be measured in space, and the strength is more than 30 times that of the magnetic interference field; The superimposed total space magnetic field value, the axis of the optical pump magnetometer is along the direction of the small magnetic field to be measured, and the trigonometric function relationship is used to construct information about the small magnetic field intensity to be measured, the uniform strong magnetic field intensity, the magnetic interference field intensity, the total space magnetic field value and The equation system of the angle between the magnetic interference field and the axis direction of the optical pump magnetometer can be obtained by solving the equation system to obtain the intensity value of the small magnetic field to be measured in space.

If the magnetic interference field is perpendicular to the direction of the small magnetic field to be measured, and a uniform strong magnetic field superimposed in the direction of the small magnetic field to be measured in the space is much larger than the magnetic interference field, the magnetic interference field can be ignored, and the superimposed space is measured by an optical pump magnetometer. The total magnetic field value, the axis of the optical pump magnetometer is along the direction of the small magnetic field to be measured, and the difference between the spatial total magnetic field value and the intensity value of the uniform strong magnetic field is the intensity value of the small magnetic field to be measured.

Further, the uniform strong magnetic field is generated in the direction of the small magnetic field to be measured by using a Helmholtz coil.

Further, the measurement system used in the measurement method includes: a Helmholtz coil, an optical pump magnetometer, a current source, a signal detection and processing module;

The axis of the Helmholtz coil is along the direction of the small magnetic field to be measured, the magnetic sensitive probe of the optical pump magnetometer is placed along the axis of the Helmholtz coil and placed in the center of the coil, and the current source is provided by the Helmholtz coil. The constant current, signal detection and processing module processes and analyzes the magnetic field voltage signal detected by the magnetic sensitive probe of the optical pump magnetometer to obtain the strength of the small magnetic field to be measured in space.

Beneficial effects:

The invention can measure the small magnetic field in space with the direction of the magnetic field determined, generate a uniform strong magnetic field with the same direction as the small magnetic field to be measured, and use the optical pump magnetometer to measure the total field value of the superimposed magnetic field, and can measure the magnetic field under the condition of large satellite magnetic interference. The small magnetic field in space meets the demand for magnetic field measurement in geosynchronous orbit, and is suitable for the magnetic field measurement of the optical pump magnetometer load of high-orbit satellites for the small magnetic field in space.

Description of drawings

Fig. 1 is the measuring system schematic diagram of the method of the present invention;

Figure 2 is a superposition of magnetic field vectors for constructing a system of equations.

Among them, 1-Helmholtz coil, 2-optical pump magnetometer magnetic sensitive probe, 3-current source, 4-signal detection and processing module.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

The optical pump magnetometer is a scalar magnetometer. The area near the magnetic field direction and its axis at 90 degrees is the working blind area, and the rest area is the working area. The area near the magnetic field direction and its axis at 0 degrees is its optimal working area. When the magnetic interference field is perpendicular to the optical axis of the magnetometer and is much larger than the small magnetic field to be measured, the superimposed field will be in the blind area of the optical pump magnetometer and cannot be measured, and the contribution of the field to be measured to the total field will be negligible, much less than Resolution of an optically pumped magnetometer. At this time, if a Helmholtz coil is used to generate a strong magnetic field far greater than the satellite magnetic interference field in the direction of the small magnetic field to be measured, according to the principle of superposition of magnetic field vectors, the direction of the total magnetic field will be pulled back to the working area of the optical pump magnetometer, thereby Measure the size of the total magnetic field of the small magnetic field to be measured in space, the satellite interference magnetic field, and the uniform magnetic field generated by the Helmholtz coil.

The invention provides a method for measuring the small magnetic field in space. If the magnetic interference field is perpendicular to the direction of the small magnetic field to be measured, that is, it is located in the blind area of the optical pump magnetometer, a Helmholtz coil is used to add a strong magnetic field in the direction of the small magnetic field to be measured. The strength of the strong magnetic field is more than 30 times that of the magnetic interference field, and the direction of the total magnetic field is always kept in the working area of the optical pump magnetometer. At this time, the contribution of the magnetic interference field perpendicular to the optical axis direction to the total field is almost zero, and the magnetic interference field It can be ignored that the magnitude of the small magnetic field to be measured is the variation relative to the uniform magnetic field generated by the coil, and the contribution of the small magnetic field to be measured can be detected by the optical pump magnetometer. Knowing the size and direction of the applied uniform strong magnetic field, the signal detection and processing module can finally give the strength value of the small magnetic field to be measured. Since the resolution of the optical pump magnetometer is in the order of pT, the measurement resolution of the small magnetic field in space mainly depends on the accuracy of the uniform magnetic field generated by the coil.

The magnetic field measurement system for measuring the small magnetic field in space consists of an optical pump magnetometer, a Helmholtz coil 1, a current source 3 and a signal detection and processing module 4, as shown in Figure 1. The Helmholtz coil 1 is two coaxially arranged coils with exactly the same radius and number of turns, the spacing is equal to the radius, and the middle is connected in series. The Helmholtz coil 1 can generate a uniform magnetic field in a large range near the midpoint of the shaft, and its strength is proportional to the current passing through the coil. The radius is 13cm and the number of turns is 70. When the current passing through the coil is 0.1A, a uniform magnetic field of 50000nT along the axis can be generated in the vicinity of the midpoint of its axis.

Optical Pump Magnetometer Magnetic Sensitivity Probe 2: It is used to sense the size of the superimposed field of the small magnetic field in space, the satellite magnetic interference field, and the uniform magnetic field generated by the coil.

The axis of the Helmholtz coil 1 is along the direction of the small magnetic field to be measured, and the current source 3 provides a steady current for the Helmholtz coil 1 . The magnetic sensitive probe 2 of the optical pump magnetometer is placed in the center of the Helmholtz coil 1, and its optical axis coincides with the axis of the Helmholtz coil 1, and the superposition of the uniform strong magnetic field generated by the Helmholtz coil 1 and the external magnetic field is total. The magnetic field is measured. Since the small magnetic field to be measured is almost in the same direction as the total magnetic field, the optical pump magnetometer can detect the change of the total magnetic field to be measured. At the same time, since the magnitude of the applied uniform strong magnetic field is known, the intensity of the small magnetic field to be measured in space can be obtained through the signal detection and processing module 4 .

If the magnetic interference field is not in the blind area of the optical pump magnetometer but in the working area, the superimposed fields of the two can still be detected by the magnetometer, and the magnetic interference field cannot be ignored. At this time, use the Helmholtz coil 1 to continuously generate three or more uniform strong magnetic fields with known strengths in the direction of the small magnetic field to be measured, measure the value of the total magnetic field each time, and use the cosine theorem to construct information about the strength of the small magnetic field to be measured in space, uniform and uniform. The equations of the strong magnetic field strength, the magnetic interference field strength and the angle between the magnetic interference field and the axis direction of the optical pump magnetometer are obtained by solving the equations to obtain the strength value of the small magnetic field to be measured in space.

The construction method of the equation system is as follows: As shown in Figure 2, assuming that the intensity of the small magnetic field to be measured in space is x, the intensity of the magnetic interference field is y, the axis of the optical pump magnetometer is along the direction of the small magnetic field to be measured, the magnetic interference field and the optical pump The included angle of the axis direction of the magnetometer is θ, and x, y, and θ are unknown quantities. The uniform strong magnetic field strengths generated by the Helmholtz coil 1 are respectively m ₁ , m ₂ , m ₃ , ···, m _n , and n≥3.

In the formula, a ₁ , a ₂ , a ₃ , _··· , an represent the total magnetic field value obtained by each measurement.

To sum up, the above are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (4)

1. a method for measuring a small magnetic field in space, characterized in that, in the direction of the small magnetic field to be measured in space, three or more uniform strong magnetic fields with known intensities are sequentially generated, and the intensity is more than 30 times the intensity of the magnetic interference field; The pump magnetometer measures the total spatial magnetic field value after each superposition. The axis of the optical pump magnetometer is along the direction of the small magnetic field to be measured, and the trigonometric function relationship is used to construct information about the small magnetic field strength to be measured, the uniform strong magnetic field strength, and the magnetic interference field strength. , the total magnetic field value in space and the equation system of the angle between the magnetic interference field and the axis direction of the optical pump magnetometer, and the intensity value of the small magnetic field to be measured in space is obtained by solving the equation system. 2. A method for measuring a small magnetic field in space, characterized in that if the magnetic interference field is perpendicular to the direction of the small magnetic field to be measured, and a uniform strong magnetic field superimposed in the direction of the small magnetic field to be measured in space is much larger than the magnetic interference field, the magnetic interference The field can be ignored, and the superimposed total spatial magnetic field value is measured by the optical pump magnetometer. The axis of the optical pump magnetometer is along the direction of the small magnetic field to be measured. The difference between the total spatial magnetic field value and the uniform strong magnetic field strength value is the value to be measured The strength value of the small magnetic field. 3 . The method for measuring a small magnetic field in space according to claim 1 , wherein the uniform strong magnetic field is generated in the direction of the small magnetic field to be measured by using a Helmholtz coil. 4 . 4. The method for measuring a small magnetic field in space as claimed in claim 1 or 2, wherein the measurement system used in the measurement method comprises: a Helmholtz coil, an optical pump magnetometer, a current source, a signal detection and processing module; The axis of the Helmholtz coil is along the direction of the small magnetic field to be measured, the magnetic sensitive probe of the optical pump magnetometer is placed along the axis of the Helmholtz coil and placed in the center of the coil, and the current source is provided by the Helmholtz coil. The constant current, signal detection and processing module processes and analyzes the magnetic field voltage signal detected by the magnetic sensitive probe of the optical pump magnetometer to obtain the strength of the small magnetic field to be measured in space.

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