An apparatus and method for calibrating pulsed high magnetic fields based on the optical rotation effect and proportional measurement

Abstract

The present invention relates to a pulsed high magnetic field calibration device and a calibration method based on the optical rotation effect and ratio measurement, which includes a light source part, a beam splitter, a constant magnetic field reproduction device, a pulsed magnetic field reproduction device, a detection device, a first crystal and a second crystal; wherein the light source part includes a laser and a polarizer, the detection device is composed of a light intensity meter and a differential comparator, the constant magnetic field reproduction device generates a constant magnetic field by a solenoid magnetic field coil, and the pulsed magnetic field reproduction device generates a pulsed magnetic field by a pulsed magnetic field coil; the length ratios of the crystals selected for the constant magnetic field and the crystals selected for the pulsed magnetic field are controlled in several combinations between 10:1 and 100:1. Compared with the prior art, it can avoid the problem of inaccurate measurement caused by uneven magnetic field distribution of parallel plates, and at the same time avoid the problem of accurate measurement of optical rotation parameters, realize the numerical comparison of the pulsed magnetic field and the constant magnetic field, and significantly improve the measurement uncertainty level.

Description

Technical Field

[0001] The present invention belongs to the technical field of pulsed magnetic field metrology and relates to a method for calibrating pulsed high magnetic field measuring tools. Background Art

[0002] Common pulsed high magnetic field measuring tools include sensors or measuring instruments such as Hall magnetometers, B-dot probes, TMR sensors, etc., which are used in occasions such as electron accelerators and high-voltage power transmission. A linear induction accelerator is a scientific instrument used to generate short-time, high-energy, and focused electron beams. Its components include an induction superposition type injector, several series-connected induction acceleration cavities, a pulsed power system, beam transport, a focusing system, and a control system, etc. In the research of linear induction accelerators, pulsed high magnetic field measuring tools such as magnetic probes and Hall magnetometers are widely used to analyze the magnetic field parameters of research devices, improve factors such as the magnetic lens focal length of the focusing system, the beam emission intensity and beam pulse width of beam transport, and achieve the purpose of improving the focusing effect. Therefore, it is necessary to ensure that the measurement accuracy of pulsed high magnetic field measuring tools reaches a higher level to ensure the consistency of the metrological characteristics of various pulsed high magnetic field measuring tools and the comparability of data. The method for calibrating pulsed magnetic field measuring tools based on a uniform pulsed magnetic field is mainly used for calibrating high-accuracy pulsed high magnetic field measuring tools with a measurement uncertainty level better than 5%.

[0003] Internationally, there is a relatively consistent understanding of the technical difficulty of calibrating pulsed high magnetic field measuring tools. It is generally believed that the reasons for this phenomenon are: one is that its sensitivity is related to frequency, and the other is that it is difficult to achieve high-frequency strong magnetic fields. At present, most of the traceability technologies for pulsed high magnetic fields at home and abroad adopt the standard magnetic field method in a coaxial TEM small chamber (such as DEF STAN 59-411 part3 issue 1 (par.6.22.1)). The standard magnetic field method in a coaxial TEM small chamber uses parallel plates in a transverse electromagnetic wave anechoic chamber (TEM) to establish a well-defined pulsed electromagnetic field, and compares the time-domain field waveform with the output of the field sensor to complete the calibration of the sensor parameters.

[0004] In this calibration method, the source of the magnetic field mainly depends on the distance h between the parallel plates, and its mathematical model is:

[0005]

[0006] According to relevant research reports, the typical value of the measurement uncertainty of this method is 9% - 12%, and it is difficult to calibrate high-accuracy pulsed high magnetic field measuring tools. The main reason is that the magnetic field distribution uniformity between the parallel plates is poor, and when the probe of the measuring tool to be calibrated is in different positions between the parallel plates, the output results have large differences. Therefore, it is necessary to design a calibration method mainly for calibrating high-accuracy pulsed high magnetic field measuring tools with a measurement uncertainty level better than 5%. Summary of the Invention

[0007] The object of the present invention is to overcome the defects of the prior art, and to solve the problem of improving calibration accuracy, and to propose a device and method for pulsed high magnetic field calibration based on the optical rotation effect and proportional measurement.

[0008] The present invention is achieved by the following technical solutions:

[0009] A pulsed high magnetic field calibration device based on the optical rotation effect and proportional measurement, which includes a light source part, a beam splitter, a constant magnetic field reproduction device, a pulsed magnetic field reproduction device, a detection device and a crystal; wherein the light source part includes a laser and a polarizer, the detection device is composed of a light intensity meter and a differential comparator, the constant magnetic field reproduction device generates a constant magnetic field by a solenoid magnetic field coil, and the pulsed magnetic field reproduction device generates a pulsed magnetic field by a pulsed magnetic field coil; the length ratios of the crystals selected by the constant magnetic field and the crystals selected by the pulsed magnetic field are controlled to be several combinations between 10:1 and 100:1.

[0010] Furthermore, the length ratio of the constant magnetic field crystal to the pulsed magnetic field crystal is controlled to be 100:1.

[0011] Furthermore, crystals with a higher Verdet coefficient are selected.

[0012] Furthermore, TGG crystals are selected.

[0013] Furthermore, the polarized laser generated by the light source part first passes through the crystal in the uniform constant magnetic field and then through the crystal in the uniform pulsed magnetic field. Relative to the laser propagation direction, the pulsed magnetic field and the constant magnetic field are in opposite directions.

[0014] A calibration method for a pulsed high magnetic field calibration device based on the optical rotation effect and proportional measurement, the specific steps of which include:

[0015] Step 1: Construct a calibration magnetic field: According to the peak magnetic induction intensity of the preset pulsed magnetic field and the magnetic induction intensity of the constant magnetic field, select the first crystal and the second crystal with a certain length ratio; the length ratio is controlled to be several combinations between 10:1 and 100:1;

[0016] Step 2: Reproduce a uniform constant magnetic field by the constant magnetic field coil, place the first crystal in the magnetic field uniform area therein, and the optical path direction of the polarized laser is the same as the magnetic axis direction of the reproduced constant magnetic field;

[0017] Step 3: Place the second crystal in the magnetic field uniform area of the pulsed magnetic field coil, and the optical path direction of the polarized laser is opposite to the magnetic axis direction of the reproduced pulsed magnetic field;

[0018] Step 4: Establish a measurement optical path, place the beam splitter between the constant magnetic field reproduction device and the pulsed magnetic field reproduction device, divide the beam of the light source part onto the two crystals by the beam splitter, and the light intensity meter and the differential comparator constitute the detection part;

[0019] Step 5: Generate no magnetic field in both the DC magnetic field and pulsed magnetic field reproduction parts, start the measurement optical path, detect the signal background value, and perform compensation and zero adjustment.

[0020] Step 6: Start the DC magnetic field part, adjust the magnetic field to 100 mT according to the design value, and observe the deviation of the detected signal from the zero position.

[0021] Step 7: Keep the DC magnetic field stable, start the pulsed magnetic field part, generate a pulsed magnetic field of 10 T, and observe whether the detected signal instantaneously returns to zero.

[0022] Step 8: If the detected signal does not return to the zero position, adjust the DC magnetic field, repeat Step 5 until it returns to zero, and record the loop current value of the DC magnetic field reproduction part and the reading of the calibrated pulsed magnetic field measuring tool in the pulsed magnetic field.

[0023] Step 9: Take out the crystal in the DC magnetic field coil, replace it with a Hall magnetometer probe with a measurement uncertainty better than 0.2% in the magnetic field uniform area. According to the loop current value recorded in Step 8, reproduce the DC magnetic field, record the reading of the Hall magnetometer, and calculate the reproduced magnetic field strength of the pulsed magnetic field according to the size ratio.

[0024] Step 10: Compare the reproduced magnetic field strength of the pulsed magnetic field calculated in Step 9 with the reading of the calibrated pulsed magnetic field measuring tool recorded in Step 8 to obtain the indication error of the magnetic induction intensity of the calibrated pulsed magnetic field measuring tool.

[0025] Furthermore, the DC magnetic field reproduction ability is 100 mT, and the pulsed magnetic field reproduction ability is 1 T - 10 T. According to the reproduction ability, the length ratio of the crystal is selected as 100:1, that is, the crystal length in the DC magnetic field is 100 mm, and the crystal length in the pulsed magnetic field is 1 mm.

[0026] Furthermore, the DC magnetic field is generated by a solenoid magnetic field coil.

[0027] Furthermore, the light source part is composed of an 895 nm laser and a polarizer.

[0028] In the calibration method of the present invention, polarized laser passes through a crystal in a uniform constant magnetic field and a crystal of the same material in a uniform pulsed magnetic field successively. Relative to the laser propagation direction, the pulsed magnetic field and the constant magnetic field have opposite directions. The lengths of the constant-field crystal and the pulsed-field crystal are measured. When neither the constant magnetic field nor the pulsed magnetic field exists, the polarization direction of the laser remains unchanged. After the constant magnetic field is applied, the light deflects. Subsequently, the pulsed magnetic field is applied. When the peak magnetic induction intensity of the pulsed magnetic field is the same as that of the constant magnetic field, the deflection amount of the light returns to the state without applied fields. At this time, the magnetic induction intensities of the constant magnetic field and the pulsed magnetic field are the same, and the measurement uncertainty mainly comes from the measurement uncertainty of the length, and a measurement uncertainty of 1% can be achieved.

[0029] The method of the present invention can avoid the problem of inaccurate measurement caused by uneven magnetic field distribution of parallel plates compared with the existing technology, and at the same time avoid the problem of accurate measurement of the optical rotation parameter, realize the numerical comparison between the pulsed magnetic field and the constant magnetic field, and significantly improve the measurement uncertainty level. Description of the Drawings

[0030] Figure 1 It is the standard magnetic field method in a coaxial TEM cell;

[0031] Figure 2 It is the schematic diagram of the embodiment of the present invention. Detailed Embodiments

[0032] The following will describe in detail the embodiments of the method of the present invention with reference to the drawings.

[0033] A pulsed high magnetic field calibration device based on the optical rotation effect and ratio measurement includes a light source part, a beam splitter, a constant magnetic field reproduction device, a pulsed magnetic field reproduction device, a detection device and a crystal; the light source part includes a laser and a polarizer, the detection device is composed of a light intensity meter and a differential comparator, the constant magnetic field reproduction device generates a constant magnetic field by a solenoid magnetic field coil, and the pulsed magnetic field reproduction device generates a pulsed magnetic field by a pulsed magnetic field coil; the length ratio of the crystal selected by the constant magnetic field and the crystal selected by the pulsed magnetic field is controlled at several combinations between 10:1 and 100:1. Preferably, the length ratio is controlled at 100:1.

[0034] Furthermore, a crystal with a higher Verdet coefficient is selected as the crystal, and preferably a TGG crystal.

[0035] The polarized laser generated by the light source part first passes through the crystal in the uniform and constant magnetic field, and then passes through the crystal in the uniform pulsed magnetic field. The direction of the pulsed magnetic field is opposite to that of the constant magnetic field with respect to the laser propagation direction. When neither the constant magnetic field nor the pulsed magnetic field exists, the polarization direction of the laser remains unchanged. After the constant magnetic field is applied, the light deflects. Subsequently, the uniform pulsed magnetic field is applied. When the peak magnetic induction intensity of the pulsed magnetic field is the same as that of the constant magnetic field, the deflection amount of the light returns to the state without magnetic field application. At this time, that is, when the magnetic induction intensities of the constant magnetic field and the pulsed magnetic field are the same, the measurement uncertainty mainly comes from the measurement uncertainty of the length, and a measurement uncertainty of 1% can be achieved.

[0036] A calibration method for a pulsed high magnetic field calibration device based on the optical rotation effect and ratio measurement, the specific steps of which include:

[0037] Step 1: Construct a calibration magnetic field: Select a crystal with a certain length ratio according to the peak magnetic induction intensity of the preset pulsed magnetic field and the magnetic induction intensity of the constant magnetic field. According to the reproducibility of the constant magnetic field being 100 mT and the reproducibility of the pulsed magnetic field being 1 T - 10 T, select the length ratio of the crystal, and control several combinations between 10:1 and 100:1. Preferably, in this example, a combination of 100:1 is selected for illustration, that is, the length of the crystal in the constant magnetic field is 100 mm, and the length of the crystal in the pulsed magnetic field is 1 mm. When other ratio combinations are selected, the measurement of other pulsed magnetic field strengths can be achieved.

[0038] Step 2: Reproduce a uniform and constant magnetic field by a constant magnetic field coil, such as a solenoid magnetic field coil. Place the 100 - mm crystal in the magnetic field uniform area therein, and the optical path direction of the polarized laser is the same as the magnetic axis direction of the reproduced constant magnetic field.

[0039] Step 3: Place a 1 - mm crystal in the magnetic field uniform area of the pulsed magnetic field coil, and the optical path direction of the polarized laser is opposite to the magnetic axis direction of the reproduced pulsed magnetic field. Note that the relationship between the pulsed magnetic field and the light passing direction here must be opposite to the relationship between the constant magnetic field and the light passing direction.

[0040] Step 4: Establish a measurement optical path, where an 895 - nm laser and a polarizer constitute the light source part. A beam splitter is placed between the constant magnetic field reproduction device and the pulsed magnetic field reproduction device to split the light beam onto two crystals, and a photometer and a differential comparator constitute the detection part.

[0041] Step 5: Neither the constant magnetic field nor the pulsed magnetic field reproduction part is powered on to generate a magnetic field. Start the measurement optical path, detect the background value of the signal, and perform compensation and zero adjustment.

[0042] Step 6: Start the constant magnetic field part and adjust it to a magnetic field of 100 mT according to the design value, and observe the deviation of the detection signal from the zero position.

[0043] Step 7: Keep the constant magnetic field stable, start the pulsed magnetic field part to generate a pulsed magnetic field of 10 T, and observe whether the detection signal instantaneously returns to zero.

[0044] Step 8: If the detection signal does not return to the zero position, adjust the constant magnetic field, repeat Step 5 until it returns to zero, and record the loop current value of the current reproduction part of the constant magnetic field and the reading of the pulsed magnetic field measuring tool to be calibrated in the pulsed magnetic field.

[0045] Step 9: Take out the crystal in the constant magnetic field coil, replace it with a Hall magnetometer probe with a measurement uncertainty better than 0.2% in the magnetic field uniform area, reproduce the constant magnetic field according to the loop current value recorded in Step 8, record the reading of the Hall magnetometer, and according to the size ratio, the reproduced field strength of the pulsed magnetic field can be calculated.

[0046] Step 10: Compare the reproduced field strength of the pulsed magnetic field calculated in Step 9 with the reading of the pulsed magnetic field measuring tool to be calibrated recorded in Step 8, and the indication error of the magnetic induction intensity of the pulsed magnetic field measuring tool to be calibrated can be obtained.

[0047] Thus, the calibration operation of the pulsed high magnetic field measuring tool based on the optical rotation effect and ratio measurement is completed.

[0048] In the calibration method of the present invention, by making polarized laser pass through the crystal in the uniform constant magnetic field and the crystal of the same material in the uniform pulsed magnetic field successively, relative to the laser propagation direction, the pulsed magnetic field and the constant magnetic field are in opposite directions, and the lengths of the constant field crystal and the pulsed field crystal are measured. When neither the constant magnetic field nor the pulsed magnetic field exists, the polarization direction of the laser does not change. After the constant magnetic field is applied, the light deflects. Subsequently, the pulsed magnetic field is applied. When the peak value of the magnetic induction intensity of the pulsed magnetic field is the same as that of the constant magnetic field, the deflection amount of the light will return to the state without applied field. At this time, the magnetic induction intensities of the constant magnetic field and the pulsed magnetic field are the same. The measurement uncertainty mainly comes from the measurement uncertainty of the length, and a measurement uncertainty of 1% can be achieved.

[0049] The method of the present invention can avoid the problem of inaccurate measurement caused by uneven magnetic field distribution of parallel plates compared with the existing technology, and at the same time avoid the problem of accurate measurement of the optical rotation parameters, realize the numerical comparison between the pulsed magnetic field and the constant magnetic field, and significantly improve the measurement uncertainty level.

[0050] Although the embodiments of the present invention are described in conjunction with the drawings, for those skilled in the art, several improvements can be made without departing from the principle of the present invention, and these should also be regarded as belonging to the protection scope of the present invention.

Claims

1. A pulsed high magnetic field calibration device based on the optical rotation effect and proportional measurement, characterized in that: The pulsed high magnetic field calibration device includes a light source part, a spectroscope, a constant magnetic field reproduction device, a pulsed magnetic field reproduction device, a detection device, a first crystal and a second crystal; the light source part includes a laser and a polarizer, the detection device is composed of a light intensity meter and a differential comparator, the constant magnetic field reproduction device generates a constant magnetic field by a solenoid magnetic field coil, and the pulsed magnetic field reproduction device generates a pulsed magnetic field by a pulsed magnetic field coil; the length ratio of the crystal selected by the constant magnetic field reproduction device to the crystal selected by the pulsed magnetic field reproduction device is controlled to be several combinations between 10:1 and 100:

1.

2. The pulsed high magnetic field calibration device according to claim 1, wherein: The length ratio of the crystal selected by the constant magnetic field reproduction device to the crystal selected by the pulsed magnetic field reproduction device is controlled to be 100:

1.

3. The pulsed high magnetic field calibration device according to claim 1, characterized in that: Crystals with higher Verdet coefficients are selected.

4. The pulsed high magnetic field calibration device according to claim 3, characterized in that: TGG crystals are selected.

5. The pulsed high magnetic field calibration device according to claim 1, wherein: The polarized laser generated by the light source part first passes through the crystal in the uniform constant magnetic field and then through the crystal in the uniform pulsed magnetic field. Relative to the laser propagation direction, the pulsed magnetic field and the constant magnetic field are in opposite directions.

6. A calibration method for a pulse high magnetic field calibration device based on the optical rotation effect and proportional measurement, characterized in that: The specific steps include: Step 1, constructing a calibration magnetic field: According to the peak magnetic induction intensity of the preset pulsed magnetic field and the magnetic induction intensity of the constant magnetic field, select a first crystal and a second crystal with a certain length ratio, and the length ratio is controlled to be several combinations between 10:1 and 100:1; Step 2, reproducing a uniform constant magnetic field by the constant magnetic field coil, placing the first crystal in the magnetic field uniform area therein, and the optical path direction of the polarized laser is the same as the magnetic axis direction of the reproduced constant magnetic field; Step 3, placing the second crystal in the magnetic field uniform area of the pulsed magnetic field coil, and the optical path direction of the polarized laser is opposite to the magnetic axis direction of the reproduced pulsed magnetic field; Step 4, establishing a measurement optical path, placing the spectroscope between the constant magnetic field reproduction device and the pulsed magnetic field reproduction device, splitting the beam of the light source part to the two crystals by the spectroscope, and the light intensity meter and the differential comparator constitute the detection part; Step 5, neither the constant magnetic field nor the pulsed magnetic field reproduction device is powered on to generate a magnetic field, start the measurement optical path, detect the background value of the signal, and perform compensation and zero adjustment; Step 6, start the constant magnetic field reproduction device, adjust the magnetic field to 100 mT according to the design value, and observe the deviation state of the detection signal from the zero position; Step 7, keep the constant magnetic field stable, start the pulsed magnetic field reproduction device, generate a pulsed magnetic field of 10 T, and observe whether the detection signal shows an instantaneous return to zero; Step 8, if the detection signal does not return to the zero position, adjust the constant magnetic field, repeat Step 5 until it returns to zero, and record the loop current value of the current constant magnetic field reproduction part and the reading of the calibrated pulsed magnetic field measuring tool in the pulsed magnetic field; Step 9, take out the crystal in the constant magnetic field coil, replace it with a Hall magnetometer probe with a measurement uncertainty better than 0.2% in the magnetic field uniform area, reproduce the constant magnetic field according to the loop current value recorded in Step 8, record the reading of the Hall magnetometer, and according to the size ratio, the reproduced magnetic field strength of the pulsed magnetic field can be calculated; Step 10, compare the reproduced magnetic field strength of the pulsed magnetic field calculated in Step 9 with the reading of the calibrated pulsed magnetic field measuring tool recorded in Step 8, and the magnetic induction intensity indication error of the calibrated pulsed magnetic field measuring tool can be obtained.

7. The calibration method according to claim 6, characterized in that: The reproduced field strength of the constant magnetic field is 100 mT, and the reproduced field strength of the pulsed magnetic field is 1 T to 10 T. The length ratio of the crystal is selected according to the reproduced field strength as 100:1, that is, the crystal length in the constant magnetic field is 100 mm, and the crystal length in the pulsed magnetic field is 1 mm.

8. The calibration method according to claim 6, wherein: The constant magnetic field is generated by a solenoid magnetic field coil.

9. The calibration method according to claim 6, characterized in that: The light source part is composed of an 895 nm laser and a polarizer.

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