JP3100100B2 - Superconducting loop type magnetic field measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field measuring apparatus, and more particularly, to a magnetic field measurement in a minute area where a semiconductor type magnetic field sensor is difficult to insert or a continuous measurement of a strong magnetic field under radiation such as a fusion apparatus. The present invention relates to a simple magnetic field measuring device and a superconducting loop type magnetic field measuring device.

[0002]

2. Description of the Related Art Conventionally, a semiconductor magnetic sensor is generally used to measure a stationary magnetic field. That is,
It is measured as a voltage proportional to the magnetic field by a Hall element, or as an electric resistance value proportional to the magnetic field by a magnetoresistive element. It is also possible to rotate the coil in the magnetic field to be measured and measure the magnetic field by the electromotive force induced in the coil. However, under radiation, the semiconductor magnetic sensor loses its magnetoelectric conversion characteristics due to irradiation damage. In addition, a driving device such as a motor is required for the rotating coil, and there is a problem that the configuration is complicated. Further, there is a problem that the motor cannot be used in a strong magnetic field of several T (tesla).

In place of these, Japanese Patent Application Laid-Open No. Sho 63-282674 proposes a method for measuring a magnetic field using a permanent current of a superconducting loop. This conventional method will be described with reference to FIG. Superconducting loop 1 and superconducting loop 2 are connected by superconducting cable 3 to form a closed loop. Loop 1 is placed in a magnetic field to be measured, and loop 2 is placed in a place without a magnetic field. In a superconducting closed loop, all magnetic flux linking the loop is preserved. Therefore, assuming that the interlinkage magnetic flux is set to 0 in the initial state, as shown in FIG. 2, when an external magnetic field Φ0 is applied, a current I is induced. Occurs in loop 2. Here, assuming that the magnetic field linked to the superconducting cable 3 is Φ3,

[0004]

Φ0 + Φ1 + Φ2 + Φ3 = 0 (Formula 1) holds. Since the ratio of the magnitudes of Φ1 and Φ2 is uniquely determined by the size of the loop 1 and the loop 2, the value of Φ2 measured by the magnetic flux sensor 4 is obtained by setting the magnetic flux Φ3 linked to the superconducting cable 3 to zero. Can be obtained from

[0005]

The conventional superconducting loop type magnetic field sensor shown in FIG. 2 utilizes a magnetic field generated by a current I flowing when a loop 1 is inserted into a magnetic field φ0 to be measured. When the current I flows and the magnetic field Φ1 is generated, the loop 1
Is Φ0 + Φ1, which disturbs the magnetic field to be measured. For example, if the loops 1 and 2 have the same size, Φ1 is half the size of Φ0 (assuming Φ3 = 0, then Φ0 + Φ1 + Φ2 = 0 from equation 1). Φ2), and the magnetic field to be measured is reduced by half. Therefore, when measuring a magnetic field at several places spatially close to each other, there is a problem that accurate measurement cannot be performed.

Further, there is an upper limit of the current that can be passed through the superconducting loop in a strong magnetic field. As shown in FIG. 3, there is an upper limit in each of the temperature, the current density, and the magnetic field in the use region of the superconducting material. In FIG. 3, Tc, Hc and Jc are a critical temperature, a critical magnetic field and a critical current density, respectively. Although the superconducting state is maintained on the origin side with respect to the critical surface shown in FIG. 3, the superconducting state cannot be maintained outside the critical surface. Usually, the critical current density Jc
Is about 1 kA / mm ² . For example, in a fusion device, it is necessary to measure a magnetic field of about 1T.
Assuming that the diameter of the loop 1 is 2 cm and the wire diameter is 4 mm, the current I becomes 20 kA and the current density becomes J = 1.6 kA / mm ² , which exceeds the upper limit described above. Moreover, in the fusion device, since there is a magnetic field of several T or more orthogonal to the magnetic field of about 1T to be measured, the upper limit of the allowable current density is further reduced,
A conventional superconducting loop type magnetic field sensor cannot be used for a fusion device.

An object of the present invention is to provide a magnetic field measuring device and a superconducting loop type magnetic field sensor which can be used for measuring a magnetic field of a nuclear fusion device.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a detecting superconducting loop inserted into a magnetic field to be measured, and a measuring superconducting loop having a predetermined loop area ratio with the loop area of the detecting superconducting loop. A superconducting cable that connects the detection superconducting loop and the measurement superconducting loop to form a closed loop as a whole, a current detection unit that detects a current flowing in the closed loop when measuring a magnetic field, and the measurement superconducting loop. An exciting coil that generates a magnetic field that interlinks, a control unit that controls a current that flows through the exciting coil so that a current detected by the current detecting unit at the time of measuring the magnetic field has a predetermined value, and a magnetic field generated by the exciting coil. Magnetic field measuring means for measuring the magnitude; and the detecting superconducting loop based on the predetermined value, the loop area ratio, and the magnitude of the magnetic field measured by the magnetic field measuring means. A By providing the calculating means for calculating the magnitude of the magnetic field interlinking is achieved.

[0009]

The current flowing in the closed loop is measured, and the value of the closed loop current is controlled to be equal to or lower than the critical current density by the exciting coil and the control means. As a result, the superconducting state is constantly maintained, and the sensor can be used even in a strong magnetic field. If the closed loop current value is controlled to be 0, the magnetic field to be measured will not be disturbed at all. Therefore, there is no effect even in the proximity measurement. The positional relationship between the excitation coil and the superconducting loop for measurement,
Since the loop area ratio of the detection and measurement superconducting loops is known, the external magnetic field to be measured can be known from the current value flowing through the exciting coil and the linkage magnetic flux value of the superconducting loop.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a superconducting loop type magnetic field sensor which is a main part of a magnetic field measuring device according to one embodiment of the present invention. In this embodiment, the superconducting loop 1 and the superconducting loop 2 are connected by a superconducting cable 3 to form a closed loop. When an external magnetic field, that is, a magnetic field Φ 0 to be measured is applied to the loop 1, a current flows through the closed loop, and the current is measured by the current sensor 5. This current is referred to as I '
And In this embodiment, the current of the exciting coil 7 is controlled by the control power supply 6 so that the current I ′ becomes 0, and a magnetic field Φ 4 is applied to the superconducting loop 2. If the cable is configured so that the magnetic flux linked to the closed loop in the initial state is 0 and the magnetic flux Φ3 linked to the superconducting cable 3 is 0, Φ0 =
−Φ4 holds. Therefore, by measuring the magnetic flux Φ4 at which the current I ′ = 0 at the position of the loop 2 by the magnetic flux sensor 8, the external magnetic field Φ0 can be measured.

The principle of operation of this sensor will be described with reference to FIG. As shown in FIG. 4, when the magnetic flux Φ0 rises due to the external magnetic field, the current I is induced in the closed loop unless the current sensor 5, the control power supply 6, and the excitation coil 7 are operated.
A magnetic flux Φ1 in the loop 1 and a Φ2 in the loop 2 are generated in a direction to offset Φ0. In this embodiment, at this time, the current sensor 5
The operation time of the measurement control system is a dead time. However, when the control magnetic flux Φ4 is applied and the loop current I ′ becomes 0, if the loop 1 and the loop 2 have the same size, Φ4 And Φ1 are equal in size. Therefore, according to the present embodiment, since the external magnetic field can be measured with the current flowing through the closed loop kept at 0, the external magnetic field is not disturbed. In addition, the device can be used even in a strong magnetic field without being limited by the critical current density of the superconducting material.

FIG. 5 is a configuration diagram of a superconducting loop type magnetic field sensor which is a main part of a magnetic field measuring apparatus according to a second embodiment of the present invention. The feature of this embodiment is that the superconducting cable 3 connecting the superconducting loop 1 and the superconducting loop 2 is twisted. A loop 9 drawn from the superconducting cable 3 is a loop for measuring a current, and the current is measured by a current sensor 10 using a Hall element. In the present embodiment, the control power supply 6 is controlled so that the current of the loop 9 becomes 0 or becomes equal to or less than a preset value.
To control the magnetic field generated. The magnetic flux generated by the exciting coil 7 in the superconducting loop 2 is measured by a magnetic flux sensor 8. According to the present embodiment, since the superconducting cable 3 is twisted, the magnetic flux (that is, measurement noise) linked to the cable 3 can be extremely reduced, and the measurement accuracy can be improved. Furthermore, without disturbing the external magnetic field,
As in the first embodiment, there is no restriction on the critical current density of the superconducting material.

FIG. 6 is a configuration diagram of a superconducting loop type magnetic field sensor which is a main part of a magnetic field measuring apparatus according to a third embodiment of the present invention. In this embodiment, in order to further increase the measurement accuracy, the superconducting cable 11 is extended in parallel to the loop 1 in addition to the superconducting cable 3 (one closed loop is maintained as a whole without being connected to the loop 1). In FIG. 6, the superconducting cable 11 is the same as the superconducting cable 3 connecting the superconducting loops 1 and 2, and is laid in parallel. At this time, the superconducting cable 3 and the superconducting cable 11 are affected by exactly the same noise. Therefore, if the superconducting cable 3 and the superconducting cable 11 are provided so that the phases of the noises are reversed, the noise of the superconducting cable 3 can be completely canceled by the cable 11. Therefore, according to the present embodiment,
The noise from the superconducting cables 3 and 11 can be almost completely eliminated, and the accuracy of the magnetic field measurement by the loop 1 can be improved.

FIG. 7 is a configuration diagram of a loop type magnetic field sensor which is a main part of a magnetic field measuring apparatus according to a fourth embodiment of the present invention. In this embodiment, it is made of a normal conducting material. In this case, a cooling device for using the superconducting material becomes unnecessary. In FIG. 7, the loop 12 and the loop 13 are connected by a cable 14. The current I ′ flowing through the cable 14 is detected by the current sensor 5
The control power supply 6 and the exciting coil 7 are operated so that the current value becomes zero. The magnetic flux in the loop 13 is measured by the magnetic flux sensor 8. Further, the output from the current sensor 5 is integrated by the integrator 12 and added to the output of the magnetic flux sensor 8 in the arithmetic unit 13 to measure the external magnetic field φ0 as in the following equation.

[0015]

Φ 0 = −Φ 4 + ∫RI′dt (2) where R is an electric resistance including a loop and a cable.

According to this embodiment, since a normal conducting loop is used, a cooling device is not required, and the measurement can be performed without disturbing the external magnetic field. However, it is not suitable for long-time measurement because the integration operation is required.

FIG. 8 is a diagram showing an embodiment in which the present invention is applied to a plasma position / shape measuring device of a nuclear fusion device. FIG.
In, the plasma 17 is generated in the vacuum vessel 18,
The outer periphery of the vacuum container 18 for shielding radiation is surrounded by a shield 19. The magnetic field fluctuation around the plasma is measured by the pickup coil 20 and the integrator group 21. Although this measurement system is resistant to radiation, it can measure the magnetic field near the plasma, but is not suitable for long-time (low-frequency) measurement because of the integration operation. Therefore, the low-frequency side signal is cut by the high-pass filter 22 and used for measuring only the high-frequency component Bf.

Superconducting loop 23 and magnetic flux measuring device group 24
Constitute a plurality of superconducting loop type magnetic field sensors shown in FIG. This measurement system can measure for a long time,
Due to the electromagnetic shielding effect of the vacuum vessel 18 and the shield 19, it does not react to the high frequency components of the magnetic field due to the plasma. Therefore, the high-frequency side signal is cut by the low-pass filter 25 having substantially the same cut-off frequency as the high-pass filter 22, and is used for measuring only the low-frequency component Bs. In this way, high-frequency and low-frequency magnetic field components Bf and Bs are obtained as inputs to the plasma position and shape calculation device 26.
The plasma position and shape calculation device 23 reconstructs the magnetic flux around the plasma by the following equation.

[0019]

Φi = (Φf) i + (Φs) i (Formula 3) (Φf) i = Σ (Gf) ij · (Bf) j (Φs) i = Σ (Gs) ik · (Bs) k Here, i, j, and k indicate the points for obtaining the magnetic flux, the installation points of the pickup coils, and the installation points of the superconducting loop, respectively. Φi is the magnetic flux value at point i, (Φf) i and (Φs)
i indicates a high frequency component and a low frequency component of the magnetic flux value at the point i. (Gf) ij is a coefficient representing the correspondence between points i and j, and (Gs) ik is a coefficient representing the correspondence between points i and k. Since both depend only on the spatial coordinates, they can be calculated in advance. The position and shape of the plasma are uniquely determined as the contours of the magnetic flux distribution Φi thus obtained.

According to this embodiment, since both the high frequency component and the low frequency component of the magnetic flux around the plasma can be accurately calculated, the accuracy of the plasma position and shape measurement and control can be improved, and the continuous operation of the nuclear fusion device can be performed. Becomes possible.

FIG. 9 shows an embodiment of a magnetic field sensor for a nuclear fusion device. In FIG. 9, the superconducting loop 1 for the sensor unit, the superconducting loop 2 for measuring the magnetic field, and the superconducting loop 9 for measuring the current are all 1 cm in diameter and 1 mm in diameter of the superconducting wire. The diameter of the exciting coil 7 is also 1 cm, and the number of turns is 10. The loop 2 and the coil 7 are magnetically coupled by a ferrite core 27a having a relative magnetic permeability of 2500. Thereby, the leakage of the magnetic field can be prevented. A ferrite core 27b of the same type is also provided in the current measurement loop 9. A gap is provided in each of the two ferrite cores to embed the Hall elements 28a and 28b. The Hall element 28a is for measuring the magnetic field of the loop 2, and the Hall element 28b is for measuring the current flowing in the superconducting loop. Each Hall element is driven by constant current power supplies 29a and 29b. The output of the Hall element 28b is amplified by the amplifier 30, and the control power supply 6 is controlled by the exciting coil 7 so that this signal becomes zero.
To control the current. The resistor 31 is provided for adjusting the current change time constant of the exciting coil 7. The magnetic field to be measured appears as an output of the Hall element 28a, and is digitized by the AD converter 32.

As the specifications of the poloidal magnetic field measurement sensor of the nuclear fusion device, a measurement magnetic field of 1T, a measurement accuracy of 0.1%, and a time constant of 1 ms are set. First, the specifications of the control power supply 6 are estimated.
The magnetic flux linked to loop 2 for measurement is

[0023]

Φ4 = BS1 = 1 × π0.005 × 0.005 = 0.0000785 (Wb) (Equation 4) B: Measured magnetic field magnetic flux density (= 1T) S1: Cross section of loop 1 (= 0.0000785 m ² ) The coil current required at this time is

[0024]

Φ4 = μNS2J / l ∴ J = Φ4l / μNS2 = 1.0 (A) (Equation 5) μ: Permeability of ferrite core (= 0.00314H / m) N: Number of turns of exciting coil (= 10) S2 : Cross-sectional area of loop 2 (= 0.0000785 m ² ) l: Perimeter of ferrite core (= 0.0314 m) That is, 1A. The value R of the resistor 31 for setting the measurement time constant to 1 ms is

[0025]

R = L / τ = 3.9 (Ω) (Equation 6) L: Self-inductance of the exciting coil (= 0.0039H) τ: Time constant (= 0.001 s) Therefore, the capability of the control power supply 6 is as follows. Current 1A, Voltage 4
V, and those having such a specification are generally commercially available.

Next, the specifications of the constant current power supply 29a will be estimated. The product sensitivity of the Hall element is K = 300V / AT. Gallium arsenide Hall elements of this specification are commercially available at very low cost. Assuming that the output current of the power supply 29a is 0.01 A, when the measured magnetic field is 1 T, the output voltage of the Hall element is

[0027]

[Mathematical formula-see original document] 300 (V / AT) * 0.01 (A) * 1 (T) = 3 (V) (Expression 7), which is an appropriate value as an input of the AD converter. Therefore, the specification of the constant current power supply may be a current output of 0.01 A as described above. A voltage is hardly necessary, and a commercially available power supply is sufficient.

The measurement accuracy is determined by the measurement accuracy of the output voltages of the Hall elements 28a and 28b, assuming that the sizes of the loops 1 and 2 and the magnetic permeability of the ferrite core have been calibrated.
It is sufficiently possible to measure the output voltage of 28a shown in Expression 6 with an accuracy of 0.1% by using a 12-bit AD converter (bit error less than 0.03%). When the magnetic field to be measured changes by 0.001T, the output of the hall element 28b for loop current measurement instantaneously fluctuates by half, that is, 0.0005T. This is because most of the magnetic flux due to the current flowing in the superconducting loop is generated in the loops 2 and 9 having the ferrite core, and in the present embodiment, the two loops are equal in size. The voltage output will fluctuate by 1.5 mV from the same calculation as shown in the figure. If the output fluctuation of the Hall element, 1.5 mV, can be measured separately from 0 mV, it means that the accuracy of 0.1% in this part has been secured. No special device is required to distinguish a voltage of about 1.5 mV from 0 mV in a normal electronic circuit.
May be entered as is.

As described above, according to this embodiment, a 1T magnetic field can be continuously measured with a time constant of 1 ms and an accuracy of 0.1% using a commercially available power supply device.

[0030]

According to the present invention, since the magnetic field can be measured without disturbing the magnetic field to be measured, measurement at a plurality of spatially adjacent points becomes possible. In addition, since the current flowing in the superconducting loop can be controlled to be equal to or less than the critical current, measurement in a strong magnetic field becomes possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a superconducting loop type magnetic field sensor according to the present invention.

FIG. 2 is a diagram illustrating a configuration of a conventional superconducting loop type magnetic field sensor.

FIG. 3 is a diagram showing an allowable range of a superconducting state.

FIG. 4 is a diagram showing the operation principle of the superconducting loop type magnetic field sensor according to the present invention.

FIG. 5 shows a second embodiment of the superconducting loop type magnetic field sensor according to the present invention.
FIG. 3 is a diagram illustrating a configuration of an example of FIG.

FIG. 6 shows a third embodiment of the superconducting loop type magnetic field sensor according to the present invention.
FIG. 3 is a diagram illustrating a configuration of an example of FIG.

FIG. 7 is a diagram showing a configuration of a normal conducting loop type magnetic field sensor according to a fourth embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a plasma position / shape measuring device of a nuclear fusion device according to the present invention.

FIG. 9 is a diagram showing a configuration of a superconducting loop type magnetic field sensor using a ferrite core according to a fifth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Superconducting loop, 2 ... Superconducting loop, 3 ... Superconducting cable, 4 ... Flux sensor, 5 ... Current sensor, 6 ... Control power supply, 7 ... Exciting coil, 8 ... Flux sensor, 9 ... Current measuring loop, 10 ... Magnetic field Sensor, 11: Superconducting cable, 12: Normal conducting loop, 13: Normal conducting loop, 14: Normal conducting cable,
15 ... integrator, 16 ... adder, 17 ... plasma, 18 ... vacuum vessel, 19 ... shield, 20 ... pickup coil, 21 ... integrator group, 22 ... high-pass filter, 23 ... superconducting loop, 24 ... magnetic flux sensor group , 25: low-pass filter, 26: plasma position / shape calculation device, 27a, b: ferrite core, 28a, b: Hall element, 29a, b: constant current power supply, 30: amplifier, 31: resistor.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Akira Doi 7-2-1, Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. Energy Research Laboratory (56) References JP-A-63-282267 (JP, A) JP-A-2-47908 (JP, A) JP-A-64-73268 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01R 33/00-33/18

Claims (10)

(57) [Claims] 1. A superconducting loop for detection inserted into a magnetic field to be measured, a superconducting loop for measurement having a predetermined loop area ratio with a loop area of the superconducting loop for detection, and a superconducting loop for detection. A superconducting cable connected to the measuring superconducting loop to form a closed loop as a whole; current detecting means for detecting a current flowing in the closed loop during magnetic field measurement; and an excitation for generating a magnetic field interlinked with the measuring superconducting loop. A coil, control means for controlling a current flowing through the exciting coil so that a current detected by the current detecting means at the time of measuring the magnetic field has a predetermined value, and magnetic field measuring means for measuring a magnitude of a magnetic field generated by the exciting coil And a superconducting loop-type magnetic field measuring apparatus. 2. A superconducting loop for detection inserted into a magnetic field to be measured, a superconducting loop for measurement having a predetermined loop area ratio with a loop area of the superconducting loop for detection, and a superconducting loop for detection. A superconducting cable connected to the measuring superconducting loop to form a closed loop as a whole; current detecting means for detecting a current flowing in the closed loop during magnetic field measurement; and an excitation for generating a magnetic field interlinked with the measuring superconducting loop. A coil, control means for controlling a current flowing through the exciting coil so that a current detected by the current detecting means at the time of measuring the magnetic field has a predetermined value, and magnetic field measuring means for measuring a magnitude of a magnetic field generated by the exciting coil And calculating the magnitude of the magnetic field interlinked with the detection superconducting loop from the predetermined value, the loop area ratio, and the magnitude of the magnetic field measured by the magnetic field measuring means. A superconducting loop type magnetic field measuring apparatus, comprising: 3. A superconducting loop for detection inserted in a magnetic field to be measured, a superconducting loop for measurement having a predetermined loop area ratio with a loop area of the superconducting loop for detection, and a superconducting loop for detection. Two sets of superconducting cables connected to the measuring superconducting loop to form a closed loop as a whole, the superconducting cables being provided in parallel to cancel each other's noise phase, and detecting a current flowing through the closed loop when measuring a magnetic field Current detecting means, an exciting coil for generating a magnetic field linked to the measuring superconducting loop, and a current flowing through the exciting coil such that the current detected by the current detecting means at the time of measuring the magnetic field has a predetermined value. A superconducting loop-type magnetic field measuring apparatus, comprising: a control means; and a magnetic field measuring means for measuring a magnitude of a magnetic field generated by the exciting coil. 4. A superconducting loop for detection inserted into a magnetic field to be measured, a superconducting loop for measurement having a predetermined loop area ratio with a loop area of the superconducting loop for detection, and a superconducting loop for detection. Two sets of superconducting cables connected to the measuring superconducting loop to form a closed loop as a whole, the superconducting cables being provided in parallel to cancel each other's noise phase, and detecting a current flowing through the closed loop when measuring a magnetic field Current detecting means, an exciting coil for generating a magnetic field linked to the measuring superconducting loop, and a current flowing through the exciting coil such that the current detected by the current detecting means at the time of measuring the magnetic field has a predetermined value. Control means, magnetic field measuring means for measuring the magnitude of a magnetic field generated by the exciting coil, measurement of the predetermined value, loop area ratio, and magnetic field measuring means Calculating means for calculating the magnitude of the magnetic field interlinking with the detecting superconducting loop from the magnitude of the detected magnetic field. 5. The superconducting loop type magnetic field measuring apparatus according to claim 1, wherein the superconducting cable is twisted. 6. The superconducting loop type magnetic field measuring apparatus according to claim 1, wherein the measuring superconducting loop and the exciting coil are wound around a common ferrite core. 7. The superconducting loop type magnetic field measuring apparatus according to claim 1, wherein the predetermined value is zero. 8. A superconducting loop according to claim 1, wherein said current detecting means is configured to detect a current flowing through a current detecting loop provided on said superconducting cable. Type magnetic field measuring device. 9. A normal conducting loop for detection inserted into a magnetic field to be measured, a normal conducting loop for measurement having a predetermined loop area ratio with a loop area of the normal conducting loop for detection, A normal conducting cable that connects the normal conducting loop and the measuring normal conducting loop to form a closed loop as a whole, current detecting means for detecting a current flowing through the closed loop when measuring a magnetic field, and a chain connected to the measuring normal conducting loop. An exciting coil for generating an intersecting magnetic field, control means for controlling a current flowing through the exciting coil so that a current detected by the current detecting means at the time of measuring the magnetic field has a predetermined value, and a magnitude of a magnetic field generated by the exciting coil. Magnetic field measuring means for measuring the magnitude of the magnetic field measured by the magnetic field measuring means, integrating means for integrating the detection value of the current detecting means, and the magnitude of the magnetic field measured by the magnetic field measuring means. Magnetic field measurement comprising: calculating means for calculating the magnitude of a magnetic field interlinking with the normal conduction loop for detection and correcting the calculated value with the output value of the integrating means to calculate a magnetic field to be measured. apparatus. 10. A plasma position and shape measurement device of a fusion device having a magnetic field sensor for measuring a magnetic field around a plasma and an arithmetic unit for calculating a plasma position shape from an output of the magnetic field sensor. A device for calculating a plasma position shape using a measurement signal of the superconducting loop type magnetic field measurement device according to any one of claims 1 to 8, wherein the plasma position shape measurement device for a fusion device is provided. .