A method for calibrating the constants of a three-axis magnetic field coil based on nuclear spin slowing-down factors

Abstract

A method for calibrating the coil constants of a three-axis magnetic field coil based on the nuclear spin slowdown factor. This method has a reasonable scheme and simple experimental operations, can accurately calibrate the coil constants of the three-axis magnetic field coil, and improves the accuracy of high-precision magnetic field measurement. It includes the following steps: Step 1, measure the precession frequency ω of alkali metal atoms in the SERF state. q ; Step 2, measure the precession frequency ω0 of alkali metal atoms in the non-SERF state; Step 3, calculate the nuclear spin slowdown factor q using ω q and ω0; Step 4, calculate the coil constant k in the direction of the measured coordinate axis using the nuclear spin slowdown factor q. x , k x and the relationship between q is as follows: #imgabs0# where B x is the magnetic field in the direction of the measured coordinate axis, g s is the Landé g-factor of the electron, μ B is the Bohr magneton, and I x is the magnitude of the current applied in the direction of the measured coordinate axis.

Description

Technical Field

[0001] The invention relates to the technical field of three-axis magnetic field coil constant calibration, in particular to a three-axis magnetic field coil constant calibration method based on a nuclear spin slowing factor. Background Art

[0002] With the development of quantum sensing technology, atomic magnetometers based on the interaction between magnetism, light and atoms have provided a revolutionary measurement method for non-invasive functional neuroimaging. Among them, spin-exchange relaxation-free (SERF) atomic magnetometers are expected to replace superconducting quantum interference devices (SQUID) magnetometers with their ultra-high sensitivity, movable and wearable flexible configuration advantages, and become the next generation of new brain magnetograph medical equipment, breaking through the problem of accurate measurement of weak neural signals that are difficult to achieve with traditional measurement methods, and opening up new methods for neuroscience and brain science research.

[0003] In ultra-high-sensitivity magnetic field measurement, it is necessary to use a three-axis magnetic field coil to compensate for the three-axis residual magnetism, and apply a modulated magnetic field and a calibration magnetic field to achieve the measurement of extremely weak magnetic fields. The precise calibration of the coil constant determines the precision and accuracy of the magnetic field measurement. At present, the flux gate is generally used to calibrate the coil constant of the three-axis coil, but this method cannot avoid the influence of the non-orthogonal angle of the coil, and the measurement result has a large error. Summary of the invention

[0004] The technical problem to be solved by the present invention is: to overcome the shortcomings of the prior art and propose a three-axis magnetic field coil constant calibration method based on the nuclear spin slowing factor. The method has a reasonable scheme and simple experimental operation, and can accurately calibrate the coil constant of the three-axis magnetic field coil, thereby improving the accuracy of high-precision magnetic field measurement.

[0005] The technical solution of the present invention is as follows:

[0006] A method for calibrating a three-axis magnetic field coil constant based on a nuclear spin slowing factor, characterized in that it comprises the following steps:

[0007] Step 1: Measure the precession frequency ω of the alkali metal atom in the SERF state q ;

[0008] Step 2: Measure the precession frequency ω of the alkali metal atom in the non-SERF state 0 ;

[0009] Step 3: Using ω q and ω 0 Calculate the nuclear spin slowing factor q;

[0010] Step 4: Use the nuclear spin slowing factor q to calculate the coil constant k in the direction of the measured coordinate axis. x , k x The relationship between and q is as follows:

[0011]

[0012] Where B x Magnetic field in the direction of the measured coordinate axis, g s is the electron's Lande g factor, μ B is the Bohr magneton, I x is the magnitude of the current applied in the direction of the measured coordinate axis.

[0013] The ω in step 1 q The results were obtained using a SERF atomic magnetometer without spin exchange relaxation.

[0014] The ω in step 2 0 The results were obtained using a SERF atomic magnetometer without spin exchange relaxation.

[0015] In step 3, q ​​= (2I + 1) ω 0 / ω q , where I is the nuclear spin angular momentum.

[0016] The technical effects of the present invention are as follows: the present invention provides a method for calibrating the constant of a three-axis magnetic field coil based on a nuclear spin slowing-down factor, which can accurately calibrate the coil constant of a three-axis magnetic field coil. It is only necessary to use an atomic magnetometer to measure the three-axis remanence, the precession frequency of alkali metal atoms in a SERF state, and the precession frequency of alkali metal atoms in a non-SERF state, respectively, calculate the nuclear spin slowing-down factor, and calculate the coil constant through the nuclear spin slowing-down factor.

[0017] The advantages of the present invention compared with the prior art are:

[0018] (1) The present invention obtains the precession frequency through the response of alkali metal atoms, thereby obtaining the nuclear spin slowing factor, and then calculating the coil constant of the three-axis coil. Compared with the existing method, the error caused by the non-orthogonal angle of the coil is avoided, and the accuracy of the result is guaranteed.

[0019] (2) The scheme of the present invention is simple to operate and can accurately calibrate the coil constant of the three-axis magnetic field coil, thereby improving the accuracy of high-precision magnetic field measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic flow chart of a method for calibrating a three-axis magnetic field coil constant based on a nuclear spin slowing factor for implementing the present invention. Figure 1The method comprises the steps of: 1, measuring the precession frequency of alkali metal atoms in the SERF state (using an atomic magnetometer to measure the precession frequency ω of alkali metal atoms in the SERF state); q , SERF is spin-exchange relaxation-free); Step 2, measure the precession frequency of alkali metal atoms in the non-SERF state (using an atomic magnetometer to measure the precession frequency ω of alkali metal atoms in the non-SERF state) 0 ); Step 3, calculate the nuclear spin slowing factor q (or nuclear slowing factor, using ω q and ω 0 Calculated); Step 4, calculate the coil constant k in the direction of the measured coordinate axis x . DETAILED DESCRIPTION

[0021] Below is the attached figure ( Figure 1 ) and Examples illustrate the present invention.

[0022] Figure 1 A schematic diagram of a method for calibrating the constants of a three-axis magnetic field coil based on a nuclear spin slowing factor for implementing the present invention. Figure 1 As shown, a method for calibrating the constant of a three-axis magnetic field coil based on a nuclear spin slowing factor is characterized in that it comprises the following steps: Step 1, measuring the precession frequency ω of an alkali metal atom in a SERF state q ; Step 2, measure the precession frequency ω of the alkali metal atom in the non-SERF state 0 ; Step 3, using ω q and ω 0 Calculate the nuclear spin slowing factor q; Step 4, use the nuclear spin slowing factor q to calculate the coil constant k in the direction of the measured coordinate axis x , k x The relationship between and q is as follows:

[0023]

[0024] Where B x Magnetic field in the direction of the measured coordinate axis, g s is the electron's Lande g factor, μ B is the Bohr magneton, I x is the magnitude of the current applied in the direction of the measured coordinate axis.

[0025] The ω in step 1 q The ω in step 2 is measured using a SERF atomic magnetometer without spin exchange relaxation. 0 The spin exchange relaxation-free SERF atomic magnetometer is used for measurement. In step 3, q ​​= (2I + 1) ω 0 / ω q, where I is the nuclear spin angular momentum.

[0026] The present invention relates to a three-axis magnetic field coil constant calibration method based on nuclear spin slowing factor, which can accurately calibrate the coil constant of the three-axis magnetic field coil. The method measures the nuclear spin slowing factor q and the measured coordinate axis direction coil constant k. x The coil constant of the measured coordinate axis direction is calculated by the relationship. The method of the invention is reasonable, the experimental operation is simple, and the coil constant of the three-axis magnetic field coil can be accurately calibrated, thereby improving the accuracy of high-precision magnetic field measurement.

[0027] like Figure 1 As shown, the technical solution of the present invention is a three-axis magnetic field coil constant calibration method based on nuclear spin slowing factor, comprising the following steps:

[0028] Step (1), measuring the precession frequency ω of the alkali metal atom in the SERF state q (Using atomic magnetometer to measure the precession frequency ω of alkali metal atoms in SERF state q , SERF stands for Spin-Exchange Relaxation-Free).

[0029] Step (2), measuring the precession frequency ω of the alkali metal atom in the non-SERF state 0 (Using atomic magnetometer to measure the precession frequency ω of alkali metal atoms in non-SERF state 0 ).

[0030] Step (3), calculate the nuclear spin slowing factor q.

[0031] Step (4), calculate the coil constant k in the direction of the measured coordinate axis x .

[0032] In step (3), the nuclear spin slowing factor q=(2I+1)ω 0 / ω q , where I is the nuclear spin angular momentum.

[0033] The coil constant k in the coordinate axis direction measured in step (4) is x The relationship between and the nuclear spin slowing factor q is as follows:

[0034]

[0035] Where B x Magnetic field in the direction of the measured coordinate axis, g s is the electron's Lande g factor, μ B is the Bohr magneton, I x is the magnitude of the current applied in the direction of the measured coordinate axis.

[0036] The contents not described in detail in the specification of the present invention belong to the prior art known to the professional and technical personnel in the field. It is pointed out here that the above description helps those skilled in the art to understand the invention, but does not limit the protection scope of the invention. Any equivalent replacement, modification and / or simplification of the above description without departing from the essence of the invention falls within the protection scope of the invention.

Claims

1. A method for calibrating the constants of a three-axis magnetic field coil based on the nuclear spin slowing factor. It is characterized in that The following steps are involved: Step 1: Measure the precession frequency ω of the alkali metal atom in the SERF state q ; Step 2: Measure the precession frequency ω of the alkali metal atom in the non-SERF state 0 ; Step 3: Using ω q and ω 0 Calculate the nuclear spin slowing factor q; Step 4: Use the nuclear spin slowing factor q to calculate the coil constant k in the direction of the measured coordinate axis. x , k x The relationship between and q is as follows: Where B x Magnetic field in the direction of the measured coordinate axis, g s is the electron's Lande g factor, μ B is the Bohr magneton, I x is the magnitude of the current applied in the direction of the measured coordinate axis.

2. The method for calibrating the three-axis magnetic field coil constant based on the nuclear spin slowing factor according to claim 1, It is characterized in that The ω in step 1 q Measured using a SERF atomic magnetometer without spin exchange relaxation.

3. The method for calibrating the three-axis magnetic field coil constant based on the nuclear spin slowing factor according to claim 1, It is characterized in that The ω in step 2 0 Measured using a SERF atomic magnetometer without spin exchange relaxation.

4. The method for calibrating the three-axis magnetic field coil constant based on the nuclear spin slowing factor according to claim 1, It is characterized in that In step 3, q ​​= (2I + 1) ω 0 ω q , where I is the nuclear spin angular momentum.

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