JP2001324554A - Measuring method and measuring device for eddy current generated magnetic field of metal duct in electromagnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new method for measuring the magnetic field generated by the eddy current flowing in a metal duct arranged between the magnetic poles of an electromagnet used for a circular accelerator or the like and to provide its measuring device. SOLUTION: The intensity of the magnetic field of the electromagnet 1 is changed at a varied time change rate, and a search coil 2 inserted in the metal duct arranged between the magnetic poles of the electromagnet is rotated. The search coil responds to the magnetic field component by the electromagnet 1 and the magnetic field component generated by the eddy current of the metal duct. Since the search coil responds to only the magnetic field component by the electromagnet when the metal duct 3 is removed, the magnetic field component generated by the eddy current of the metal duct can be determined by calculating the difference. The magnetic field generated by the eddy current of the metal duct can be determined from the difference between the output voltages of the search coil in the metal duct and the search coil outside the metal duct.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a magnetic field generated by an eddy current of a metal duct in an electromagnet used for, for example, a linear accelerator, a circular accelerator, etc. It concerns the device.

[0002]

2. Description of the Related Art FIG. 8 shows an apparatus for measuring the magnetic field of an electromagnet of this type disclosed in the specification of Japanese Utility Model Application No. 6-57000.
FIG. 8A shows a configuration of the electromagnet, and FIG. 8B shows a measurement circuit. The electromagnet 1 is a two-pole electromagnet and has a pair of opposed magnetic poles 11, and a metal duct 3 is arranged between the pair of magnetic poles. This metal duct 3 constitutes a passage of particles in a linear accelerator and a circular accelerator. The search coil 2 is arranged between the metal duct 3 and one magnetic pole 11. Reference numeral 4 denotes a driving power supply for the electromagnet, which is a pulse power supply for generating a sawtooth voltage. Reference numeral 5 denotes a search coil drive unit for positioning the search coil 2. The output voltage of the search coil 2 is converted into a digital signal by the A / D converter 61 and is taken into the computer 71 and stored. The fast Fourier transform calculator (FFT calculator) 72 takes in the output voltage waveform of the search coil 2 converted from the computer 71 into a digital signal, calculates the output voltage waveform, and outputs the magnetic field component of the search coil 2.

In this conventional apparatus, when the electromagnet 1 is driven by the pulse power supply 4, the strength of the magnetic field between the magnetic poles 11 of the electromagnet 1 changes with time, and a voltage is generated in the search coil 2 by the change in the magnetic field. Then, the output voltage waveform of the search coil 2 is calculated by the FFT calculator 72 to measure the magnetic field between the magnetic poles. When a DC power supply is used as the drive power supply 4, the output voltage of the search coil 2 is obtained by moving the search coil 2 and its waveform is calculated to measure the magnetic field between the magnetic poles.

[0004]

As described above, according to the conventional apparatus, the magnetic field between the magnetic poles 11 of the electromagnet 1 can be measured. However, when the eddy current flows through the metal duct 3 disposed between the magnetic poles, the eddy current can be measured. It is not possible to measure the magnetic field in metal ducts created by. For example, in a circular accelerator, when accelerating particles, the magnetic field of the electromagnet 1 changes in such a manner that the rate of change over time fluctuates. Therefore, an eddy current flows through the metal duct 3 disposed between the magnetic poles 11, and the magnetic field created by the eddy current By metal duct 3
The magnetic field inside changes. The change in the magnetic field due to this eddy current is
It is a cause of beam loss due to betatron resonance and the like, and the magnetic field due to the eddy current is a so-called error magnetic field, so it is important to measure and evaluate this magnetic field, but it cannot be measured by the conventional device. There were challenges. In the conventional device, the search coil 2 is arranged outside the metal duct, the driving voltage of the electromagnet is a sawtooth wave, and the time change rate of the magnetic field of the electromagnet is constant.
Since the eddy current generated in the metal duct 3 does not change over time, the magnetic field component generated by the eddy current does not change over time, and no voltage corresponding to the change occurs in the search coil.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and measures a magnetic field generated by an eddy current generated by a metal duct in an electromagnet, which measures a magnetic field generated by an eddy current flowing in a metal duct disposed between magnetic poles of the electromagnet. The aim is to propose a measurement method.

Another object of the present invention is to propose a novel measuring device for an eddy current generating magnetic field of a metal duct in an electromagnet for measuring a magnetic field generated by an eddy current flowing in a metal duct disposed between electromagnets.

[0007]

According to the present invention, there is provided a method for measuring an eddy current generating magnetic field of a metal duct in an electromagnet, the method comprising: The method includes rotating a search coil inserted in a metal duct disposed in the first position.

Further, according to the method for measuring an eddy current generating magnetic field of a metal duct in an electromagnet according to the present invention, the strength of the magnetic field of the electromagnet is changed in a manner that the rate of change with time changes, and the metal disposed between the magnetic poles of the electromagnet is provided. Rotating a search coil inserted into the duct to obtain a first output voltage corresponding to a first magnetic field component generated by the electromagnet and a second magnetic field component generated by an eddy current generated in the metal duct, from the search coil; And obtaining a second output voltage corresponding to the first magnetic field component from the search coil without being affected by the second magnetic field component, wherein the second output voltage is obtained based on a difference between the first output voltage and the second output voltage. This is a method for obtaining two magnetic field components.

Further, according to the method of measuring an eddy current generating magnetic field of a metal duct in an electromagnet according to the present invention, the strength of the magnetic field of the electromagnet is changed in such a manner that the rate of change with time changes, and the metal disposed between the magnetic poles of the electromagnet is provided. By rotating a first search coil inserted in the duct, an output voltage corresponding to a first magnetic field component generated by the electromagnet and a second magnetic field component generated by an eddy current generated in the metal duct is obtained from the first search coil. And obtaining an output voltage corresponding to the first magnetic field component from the second search coil without being affected by the second magnetic field component.
This is a method for obtaining the second magnetic field component based on a difference between output voltages of search coils.

Further, a method of measuring an eddy current generating magnetic field of a metal duct in an electromagnet according to the present invention is a method of driving the electromagnet with a sine wave voltage.

Further, according to the present invention, there is provided an apparatus for measuring an eddy current generating magnetic field in a metal duct in an electromagnet, wherein a driving power source for driving the electromagnet and a search coil for rotating a search coil are arranged in such a manner that the intensity of the magnetic field of the electromagnet varies with time. A coil drive mechanism, a computer that stores an output voltage waveform of the search coil, and a calculator that calculates a magnetic field component based on the output voltage waveform stored in the computer, wherein the search coil is arranged in the magnetic field of the electromagnet. Based on the output voltage waveform of the search coil in a state inserted in a metal duct and the output voltage waveform of the search coil in a state where the metal duct is removed and the search coil is inserted in the magnetic field of the electromagnet, The magnetic field component generated by the eddy current of the metal duct is obtained.

Further, according to the present invention, there is provided an apparatus for measuring an eddy current generating magnetic field of a metal duct in an electromagnet, wherein a driving power source for driving the electromagnet in a mode in which the strength of the magnetic field of the electromagnet varies with time changes; An arranged metal duct, a first search coil inserted in the metal duct, a second search coil inserted in the electromagnet magnetic field outside the metal duct, and a search coil for rotating the first and second search coils A drive mechanism, a computer that stores output voltage waveforms of the first and second search coils, and a calculator that calculates a magnetic field component based on the output voltage waveform stored in the computer, wherein an output of the first search coil is provided. A magnetic field component generated by an eddy current of the metal duct is obtained by the calculator based on a voltage waveform and an output voltage waveform of the second search coil. That.

[0013] In the measuring apparatus for eddy current generating magnetic field of a metal duct in an electromagnet according to the present invention, the driving power source drives the electromagnet with a sine wave voltage, and the intensity of the magnetic field of the electromagnet varies with time. It changes in an aspect.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 shows a first embodiment of a method and a device for measuring an eddy current generating magnetic field of a metal duct in an electromagnet according to the present invention. FIG. 1A shows a configuration of an electromagnet portion, and FIG. 1B shows a measurement circuit thereof. The electromagnet 1 is a two-pole electromagnet and has a pair of opposed magnetic poles 11. A metal duct 3 having a circular cross section is arranged between the magnetic poles 11, and a search coil 2 is inserted into an axis in the metal duct 3, and the output voltage is supplied to an amplifier 60. The metal duct 3 constitutes, for example, a path through which the particles pass while being incorporated in a circular accelerator.

FIG. 2 shows a cross section of the search coil driving mechanism 5. A motor 51 is provided on the outer periphery of the metal duct 3, and a rotating shaft 52 of the motor 51 extends into the metal duct 3 and is connected to a gear 53. The gear 54 meshes with the gear 53, and the shaft 55 extends on the axis of the metal duct 3, is coupled to the search coil 2 at a position sandwiched by the magnetic poles 11, and rotates the search coil 2 about the shaft 55. The electromagnet parts shown in FIGS. 1 and 2 are before being incorporated into a circular accelerator or the like. When incorporated into the accelerator, the drive unit 5, the motor 51, the shafts 52 and 55, the gears 53 and 54, and the search coil 2 are used. The particles are moved and retracted outside the beam region that does not hinder the passage of particles in the metal duct 3.

In FIG. 1B, reference numeral 41 denotes a drive power supply for driving the electromagnet 1, which is a pulse power supply for generating a sine wave voltage shown in FIG. 3B. The same voltage as that supplied to the electromagnet 1 is supplied to the A / D converter 62 as the sine wave voltage of the pulse power supply 41, and is converted into a digital signal. Reference numeral 8 denotes a trigger signal generator that generates the trigger signal shown in FIG. 3A based on the digital signal. Search coil 2
Is input to an A / D converter 61 via an amplifier 60, is converted into a digital signal, and is taken into a computer 71 and stored. Reference numeral 72 denotes a fast Fourier transform calculator (FFT calculator).

Next, the operation will be described. In FIG. 1, a pulse power supply 41 generates a magnetic field between the magnetic poles 11 of the electromagnet 1 whose time change rate changes with time. For example, when a sine wave voltage having an angular frequency ω ₁ as shown in FIG. 3B is supplied from the pulse power supply 4 and the search coil 2 is rotated at an angular frequency ω ₂ by the search coil driving unit 5, 3 (c) or (d) generates a sinusoidal voltage. In this case, since the strength of the magnetic field by the electromagnet changes in a manner that the time rate of change changes, the eddy current generated in the metal duct 3 changes with time, and the search is performed according to the change in the magnetic field due to the eddy current. A voltage is generated in the coil 2. In addition, since the search coil 2 is rotating, the temporal fluctuation of the eddy current can be captured in this sense.

FIG. 3C shows an output voltage waveform of the search coil 2 in a state where the metal duct 3 is arranged between the magnetic poles 11. The output voltage of this search coil 2 is
The signal is converted into a digital signal by the A / D converter 61 via the “0”. In this state, by using the trigger signal generating device 8 to generate a trigger signal shown in FIG. 3 (a), the output voltage waveform and a pulse search coils 2 of the time of the trigger signal several wavelengths as the initial time t ₀ The voltage waveform of the power supply 41 is taken into the computer 71. In this case, the eddy current flowing through the metal duct 3 changes with time, so that the output voltage waveform of the search coil 2 has a magnetic field component φ generated by the dipole electromagnet 1.
₁ and the magnetic field component φ ₂ created by the eddy current flowing through the metal duct 3
(See FIG. 3C). From the data of the output voltage waveform of the search coil 2 and the voltage waveform of the pulse power supply 41 taken into the computer 71, the search coil 2
The phase difference t ₁ between the output voltage waveform of the pulse power supply 41 and the voltage waveform of the pulse power supply 41 is calculated in advance.

Next, the metal duct 3 is removed from between the magnetic poles 11 so that only the search coil 2 exists between the magnetic poles 11.
In this state, the output voltage waveform of the search coil 2 when the sine wave voltage of the angular frequency ω ₁ is supplied to the electromagnet 1 and the search coil 2 is rotated at the angular frequency ω ₂ is
1 is taken into the computer 71 and their phase difference t ₂ is calculated in advance (see FIG. 3D). The voltage waveform of the search coil 2 in a state where the metal duct 3 is removed is not affected by the magnetic field component φ ₂ , and the magnetic field component φ ₁
Only respond to. Subsequently, a magnetic field component is obtained by performing a fast Fourier transform on the voltage waveform of FIG. 3C and the voltage waveform of FIG. FIG.
The voltage waveform of FIG. 3C responds to the magnetic field components φ ₁ and φ ₂ , and the voltage waveform of FIG. 3D responds only to the magnetic field component φ ₁ . When the difference is calculated, the magnetic field component φ _{2 of the} error magnetic field generated by the eddy current of the metal duct 3 is obtained.

In the first embodiment, the same search coil is used, and the magnetic field is measured when the metal duct 3 is present and when the metal duct 3 is removed. Therefore, two search coils are used in comparison with the case where two search coils are used. Accurate measurement can be performed without a decrease in measurement accuracy due to a difference in coil configuration. here,
For the magnetic field component of this error magnetic field, all the magnetic field components,
For example, in the case of using the two-pole electromagnet 1 according to the first embodiment, in order to obtain a magnetic field component corresponding to all the pole numbers, such as magnetic field components of 2, 6, and 10 poles, the sine wave voltage of the pulse power supply 41 is required. Angular frequency ω ₁ and rotational angular frequency ω of search coil 2
_{The two} need to be staggered, not equal.

Embodiment 2 FIG. FIG. 4 shows a configuration of an electromagnet part according to a second embodiment of the present invention. In the first embodiment, the electromagnet 1 is formed of a two-pole electromagnet. However, in the second embodiment, the electromagnet 1 is formed of a four-pole electromagnet and has a four-pole magnetic pole 12. The metal duct 3 is arranged at a center portion surrounded by the quadrupole magnetic poles 12, and the search coil 2 is inserted into an axial center portion thereof. Other configurations and measurement circuits are configured in the same manner as in the first embodiment. Similarly to the first embodiment, the electromagnet 1 is driven by a sine wave voltage and the search coil 2 is rotated to obtain a magnetic field component by the electromagnet 1 and a magnetic field component by an eddy current generated in the metal duct 3. By calculating the difference from the magnetic field component with 3 removed,
A magnetic field component generated by an eddy current generated in the metal duct 3 can be obtained.

Embodiment 3 FIG. FIG. 5 shows a configuration of an electromagnet part according to a third embodiment of the present invention. Embodiment 3
In this embodiment, the electromagnet 1 is constituted by a six-pole electromagnet and has a six-pole magnetic pole 13. The metal duct 3 is disposed at the center of the six-pole magnetic pole 13, and the search coil 2 is inserted at the axis thereof.
Other configurations and measurement circuits are the same as those of the first embodiment.
In the same manner, the magnetic field component generated by the eddy current generated in the metal duct 3 can be measured.

Embodiment 4 FIG. 6 shows a configuration of an electromagnet part according to a fourth embodiment of the present invention. Embodiment 3
In FIG. 1, the electromagnet 1 is formed of an eight-pole electromagnet and has an eight-pole magnetic pole 14. The metal duct 3 is arranged at the center of the eight-pole magnetic pole 14, and the search coil 2 is inserted at the axis thereof.
Other configurations and measurement circuits are the same as those of the first embodiment.
In the same manner, the magnetic field component generated by the eddy current generated in the metal duct 3 can be measured.

Embodiment 5 FIG. 7 shows a fifth embodiment according to the present invention. FIG. 7A shows a configuration of an electromagnet portion, and FIG. 7B shows a measurement circuit. In the fifth embodiment, the electromagnet 1 is configured as a two-pole electromagnet and has a two-pole magnetic pole 11. The metal duct 3 is disposed between the dipole poles 11. In the fifth embodiment, the first search coil 21 is inserted into the axis of the metal duct 3 in the same manner as the search coil 2 in FIG. A second search coil 22 is inserted between the metal duct 3 and one magnetic pole. These search coils 21 and 22 are rotated by search coil drive mechanisms 51 and 52 similar to the search coil drive mechanism 5 shown in FIG. 2, respectively. The output voltage of the search coil 21 is
0, digitized via the A / D converter 61 and taken into the computer 71. The output voltage of the search coil 22 is digitized via an amplifier 63 and an A / D converter 64 and is taken into a computer 71.

The electromagnet 1 is driven by a sine wave voltage having the angular frequency ω ₁ , and the search coils 21 and 22 are connected to the same angular frequency ω.
₂ , the output voltage of the search coil 21 depends on the magnetic field component φ ₁ generated by the electromagnet 1 and the magnetic field component φ ₂ generated by the eddy current generated in the metal duct 3, while the output voltage of the search coil 22 is Therefore, the magnetic field φ ₂ generated by the eddy current generated in the metal duct 3 is similarly obtained by performing a Fourier transform on the magnetic field component φ ₁ and calculating the difference between them by the FFT calculator 72. be able to.

According to the fifth embodiment, it is not necessary to remove the metal duct 3, and it is possible to easily obtain the magnetic field component generated by the eddy current generated in the metal duct 3. In addition, the trigger signal generator 8 shown in FIG. Also becomes unnecessary. In the fifth embodiment, the electromagnet 1 has four poles and six poles as shown in FIGS.
It is also possible to configure it with 8 poles.

[0027]

As described above, according to the present invention, the strength of the magnetic field of the electromagnet is varied in such a manner that the rate of change over time is varied, and the search coil inserted in the metal duct disposed between the magnetic poles of the electromagnet is rotated. This is a measurement method that includes measuring the eddy current generating magnetic field component of the metal duct.

Further, the intensity of the magnetic field of the electromagnet is changed in such a manner that the time rate of change fluctuates, and the search coil inserted in the metal duct disposed between the magnetic poles of the electromagnet is rotated to cause the first magnetic field component by the electromagnet to rotate. Obtaining a first output voltage from the search coil in accordance with the second magnetic field component generated by the eddy current of the metal duct and the first output voltage without being affected by the second magnetic field component
In the method including obtaining the second output voltage according to the magnetic field component from the search coil, the second magnetic field component can be accurately obtained using the same search coil.

Also, an output voltage is obtained from the first search coil inserted into the metal duct in accordance with the first magnetic field component generated by the electromagnet and the second magnetic field component generated by the eddy current of the metal duct. In a method including obtaining an output voltage corresponding to the first magnetic field component from the second search coil without being affected, the second magnetic field component can be easily obtained without the need for removing the metal duct or the like. .

The output voltage of the search coil in a state where the search coil is inserted in a metal duct arranged in the magnetic field of the electromagnet, and the output voltage of the search coil in a state where the metal duct is removed and the search coil is inserted in the magnetic field of the electromagnet. In the measuring apparatus for obtaining the generated magnetic field component of the eddy current of the metal duct based on the above, accurate measurement can be performed using the same search coil.

In the case of using the output voltage of the first search coil inserted into the metal duct and the output voltage of the second search coil outside the metal duct, the measurement can be easily performed without trouble such as removing the metal duct. can do.

[Brief description of the drawings]

FIG. 1 is a configuration diagram and a measurement circuit diagram of an electromagnet part according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a search coil driving mechanism according to the first embodiment of the present invention.

FIG. 3 is a measurement waveform chart according to the first embodiment of the present invention.

FIG. 4 is a configuration diagram of an electromagnet part according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram of an electromagnet part according to a third embodiment of the present invention.

FIG. 6 is a configuration diagram of an electromagnet part according to a fourth embodiment of the present invention.

FIG. 7 is a configuration diagram and a measurement circuit diagram of an electromagnet part according to a fifth embodiment of the present invention.

FIG. 8 is a configuration diagram and a measurement circuit diagram of an electromagnet portion showing a conventional device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Electromagnet 11, 12, 13, 14 Magnetic pole 2, 21, 22 Search coil 3 Metal duct 4,
41 Drive power supply 5 Search coil drive mechanism 71 Computer 72
FFT calculator

Claims (7)

[Claims] 1. A method according to claim 1, further comprising: changing a strength of a magnetic field of the electromagnet in such a manner that a rate of change in time varies, and rotating a search coil inserted in a metal duct disposed between magnetic poles of the electromagnet. A method for measuring the eddy current generating magnetic field of a duct. 2. The method according to claim 1, wherein the intensity of the magnetic field of the electromagnet is changed in such a manner that the rate of change with time fluctuates, and a search coil inserted in a metal duct disposed between the magnetic poles of the electromagnet is rotated to generate a second signal. Obtaining a first output voltage from the search coil according to one magnetic field component and a second magnetic field component generated by an eddy current generated in the metal duct; and
Obtaining from the search coil a second output voltage corresponding to the first magnetic field component without being affected by the magnetic field component;
A method for measuring an eddy current generating magnetic field of a metal duct in an electromagnet for obtaining the second magnetic field component based on a difference between the first output voltage and the second output voltage. 3. The electromagnet according to claim 1, wherein the intensity of the magnetic field of the electromagnet is changed in such a manner that the rate of change over time fluctuates, and a first search coil inserted in a metal duct disposed between the magnetic poles of the electromagnet is rotated. Obtaining from the first search coil an output voltage corresponding to a first magnetic field component generated by the first magnetic field and a second magnetic field component generated by the eddy current generated in the metal duct; and the first magnetic field component is not affected by the second magnetic field component. Obtaining an output voltage corresponding to a magnetic field component from a second search coil, and obtaining a second magnetic field component based on a difference between an output voltage of the first search coil and an output voltage of the second search coil. Method of measuring eddy current generating magnetic field. 4. The method for measuring an eddy current generating magnetic field of a metal duct in an electromagnet according to claim 1, wherein the electromagnet is driven by a sine wave voltage. 5. A drive power supply for driving the electromagnet in a manner in which the strength of the magnetic field of the electromagnet varies with time, a search coil drive mechanism for rotating a search coil, a computer storing an output voltage waveform of the search coil, And an arithmetic unit that calculates a magnetic field component based on the output voltage waveform stored in the computer, and an output voltage waveform of the search coil in a state where the search coil is inserted into a metal duct arranged in a magnetic field of the electromagnet. A metal duct in an electromagnet for obtaining a magnetic field component generated by an eddy current of the metal duct by the calculator based on an output voltage waveform of the search coil in a state where the metal duct is removed and the search coil is inserted into a magnetic field of the electromagnet. For measuring eddy current generated magnetic field. 6. A driving power supply for driving the electromagnet in a manner in which the strength of the magnetic field of the electromagnet varies with time, a metal duct arranged in the magnetic field of the electromagnet, and a first metal duct inserted in the metal duct. A search coil, a second search coil inserted in the electromagnet magnetic field outside the metal duct, a search coil driving mechanism for rotating the first and second search coils, and output voltage waveforms of the first and second search coils. A computer for storing, and a calculator for calculating a magnetic field component based on the output voltage waveform stored in the computer, wherein the computer calculates the magnetic field component based on an output voltage waveform of the first search coil and an output voltage waveform of the second search coil. An apparatus for measuring an eddy current generating magnetic field of a metal duct in an electromagnet, wherein a magnetic field component generated by the eddy current of the metal duct is calculated by a computer. 7. The eddy current of a metal duct in an electromagnet according to claim 5, wherein the driving power supply drives the electromagnet with a sine wave voltage and changes the strength of the magnetic field of the electromagnet in a manner that the rate of change with time changes. Measurement device for generated magnetic field.