Vibrating sample magnetometer

Abstract

To provide a vibration sample type magnetometer capable of adopting a superconductive electromagnet as an exciting electromagnet, reducing power consumption more than before, and performing highly efficient operation.SOLUTION: In the vibrating sample magnetometer 1, the exciting electromagnet 102 is a superconducting electromagnet, and when the current supplied to the exciting electromagnet 102 is reduced, the magnetic energy of the exciting electromagnet 102 is returned to the battery 106 as a current by the regeneration circuit 110 disposed separately from the control circuit AMP, and the current flowing through the exciting electromagnet 102 is returned to the battery 106 by the control circuit AMP.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a vibrating sample magnetometer (VSM). [Background technology]

[0002] A known vibrating sample magnetometer has an exciting electromagnet and a detection coil that detects the induced voltage caused by the vibration of the measurement sample magnetized by the exciting electromagnet, arranged around the vibrating measurement sample, and a calculator that calculates M based on the equation V=kafM (V: detected voltage of the detection coil, a: excitation amplitude, f: excitation frequency, M: magnetic moment) (see Patent Document 1). In recent years, superconducting electromagnets have been used as the exciting electromagnets in vibrating sample magnetometers. Compared to conventional electromagnets, superconducting electromagnets are capable of passing large currents at low voltages and can generate extremely large magnetic fields. This means that the range of measurable magnetic moments is wider. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 5-172922 Summary of the Invention [Problem to be solved by the invention]

[0004] The exciting electromagnet implements a magnetic field variation pattern in which the magnetic field is gradually increased in the positive direction from a zero state, then gradually decreased back to zero, then gradually increased in the negative direction, then gradually decreased back to zero, then gradually increased again in the positive direction, then gradually decreased back to zero. Whether in the positive or negative direction, when the magnetic field is increased, the amount of current per unit time flowing through the exciting electromagnet (in this specification, when the term "amount of current" is used simply, it means the amount of current per unit time) is increased, and when the magnetic field is decreased, the amount of current is decreased.

[0005] The exciting electromagnet accumulates magnetic energy according to the amount of current flowing through it. Conventionally, when the amount of current is reduced in the above-mentioned magnetic field variation pattern, the magnetic energy accumulated in the exciting electromagnet is released as heat within the circuit. However, a superconducting electromagnet can pass a larger current than a conventional exciting electromagnet, so the magnetic energy that is accumulated is greater and the magnetic energy that is released is also greater. For this reason, releasing the magnetic energy accumulated in the exciting electromagnet as heat within the circuit not only causes the circuit to become too hot, but is also undesirable from the perspective of effective use of energy resources and environmental conservation.

[0006] The present invention attempts to solve these problems, and aims to provide a vibrating sample magnetometer that employs a superconducting electromagnet as an exciting electromagnet and is capable of highly efficient operation with reduced power consumption compared to conventional methods. [Means for solving the problem]

[0007] The first invention is a vibrating sample magnetometer having an exciting electromagnet that generates a magnetic field in a space in which a vibrating measurement sample is located, a detection coil that detects an induced voltage due to vibration of the measurement sample magnetized by the exciting electromagnet, a battery that supplies current to the exciting electromagnet, and a control circuit that controls the amount of current supplied from the battery to the exciting electromagnet, wherein the exciting electromagnet is a superconducting electromagnet, and in a normal state in which the magnetic properties of the measurement sample are measured, when the current supplied to the exciting electromagnet is reduced, a regenerative circuit arranged separately from the control circuit returns the magnetic energy of the exciting electromagnet to the battery as current, and the control circuit returns the current flowing through the exciting electromagnet to the battery.

[0008] According to the configuration of the first invention, when the current supplied to the exciting electromagnet is shifted from an increasing state to a decreasing state, and further, when the current supplied to the exciting electromagnet is being decreased, the current can be returned to the battery. When the current supplied to the exciting electromagnet is shifted from an increasing state to a decreasing state, the magnetic energy stored in the exciting electromagnet can be returned to the battery as current by the regenerative circuit. Furthermore, when the current supplied to the exciting electromagnet is being decreased, the amount of current earlier in time is greater than the amount of current later, so part of the earlier current becomes excess current. This excess current is returned to the battery by the control circuit. This enables highly efficient operation with reduced power consumption compared to conventional methods.

[0009] A second invention is a vibrating sample magnetometer according to the first invention, wherein the regeneration circuit and the control circuit are configured to control the current returned to the battery so as to satisfy a charging allowance condition for the battery.

[0010] To prevent damage to the battery or shortening its lifespan, there are charging allowance conditions for the battery, such as the amount of current per unit time, etc. In this regard, according to the configuration of the second invention, the regeneration circuit and control circuit are configured to control the current returned to the battery so as to satisfy the battery charging allowance conditions, so the battery is not damaged or its lifespan is not shortened.

[0011] A third invention is a vibrating sample magnetometer having the configuration of the first or second invention, wherein a low-pass filter is provided to block high-frequency components of the current returned to the battery.

[0012] According to the third aspect of the present invention, it is possible to eliminate current with high frequency components that are undesirable as charging current.

[0013] A fourth invention is a vibrating sample magnetometer having the configuration of the first or second invention, which includes a discharge circuit for discharging the magnetic energy of the exciting electromagnet as a current when the superconducting state of the exciting electromagnet is canceled.

[0014] According to the configuration of the fourth invention, for example, when the cooling medium (for example, helium) of the superconducting electromagnet leaks and the superconducting state is canceled, magnetic energy can be rapidly discharged as a current from the superconducting electromagnet.

[0015] A fifth invention is a vibrating sample magnetometer according to the first or second invention, wherein the regeneration circuit is formed by a flyback transformer, and is configured so that magnetic energy possessed by the exciting electromagnet is passed as a current through a primary coil of the flyback transformer and stored as magnetic energy in a core of the flyback transformer, and the magnetic energy of the core is returned as a current to the battery via a secondary coil.

[0016] A sixth invention is a vibrating sample magnetometer according to the fourth invention, further configured such that when the superconducting state of the exciting electromagnet is canceled, the regenerative circuit absorbs the magnetic energy of the exciting electromagnet.

[0017] According to the sixth aspect of the present invention, when the superconducting state of the exciting electromagnet is released, the magnetic energy stored in the exciting electromagnet can be released by the regenerative circuit in addition to the discharge circuit. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a vibrating sample magnetometer that employs a superconducting magnet as an exciting electromagnet and is capable of highly efficient operation with reduced power consumption compared to conventional methods. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic diagram showing the overall configuration of a vibrating sample magnetometer. [Figure 2] 1 is a schematic diagram showing the magnet structure of a superconducting electromagnet. [Figure 3] FIG. 2 is a schematic diagram showing a configuration related to an exciting electromagnet. [Figure 4] FIG. 2 is a conceptual diagram showing an example of current control by a control circuit. [Figure 5] FIG. 10 is a conceptual diagram showing an example of a current flow when an excitation current is increased. [Figure 6] 10A and 10B are conceptual diagrams showing an example of a coil current and a battery current when an excitation current increases. [Figure 7] 10 is a table showing an example of a relationship between a coil current and a battery current. [Figure 8] 10 is a graph showing an example of the relationship between a coil current and a battery current. [Figure 9] FIG. 10 is a conceptual diagram showing an example of a current flow when an excitation current is reduced. [Figure 10] 10A and 10B are conceptual diagrams showing an example of a coil current and a battery current when an excitation current is reduced. [Figure 11]FIG. 10 is a conceptual diagram showing an example of the current amount when the excitation current is constant. [Figure 12] FIG. 4 is a diagram conceptually showing the magnitude of a current in a normal operating state. [Figure 13] FIG. 4 is a conceptual diagram for explaining the operation of a regenerative circuit. [Figure 14] FIG. 2 is a conceptual diagram for explaining a condition for allowing charging of a battery. [Figure 15] FIG. 10 is a conceptual diagram for explaining a configuration for detecting an abnormality. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, modes for carrying out the present invention (hereinafter referred to as "embodiments") will be described. In the following description, similar components will be assigned the same reference numerals, and their description will be omitted or simplified. Note that description of components that can be implemented appropriately by a person skilled in the art will be omitted, and only the basic configuration of the present invention will be described.

[0021] <Outline of the Vibrating Sample Magnetometer> 1 is a schematic diagram showing a vibrating sample magnetometer 1 (hereinafter referred to as "magnetometer 1") according to an embodiment of the present invention. Magnetometer 1 has a high-temperature superconducting electromagnet 102 (hereinafter referred to as "magnet 102"), a vibration unit 200, a magnetization measurement unit 202, a magnetic field measurement unit 204, a recorder 300, a detection coil 302, and a Hall element 304. Hall element 304 is a magnetic flux density measurement probe for a gaussmeter 204a that constitutes magnetic field measurement unit 204.

[0022] The magnet 102 generates a magnetic field in the space where the measurement sample 310 is located. The magnitude of the magnetic field (magnetic flux density) generated by the magnet 102 is detected by a Hall element 304, where the magnetic flux density is expressed as a voltage. A gaussmeter 204a measures the magnetic flux density based on the output voltage from the Hall element 304. The output from the gaussmeter 204a is sent to a recorder 300.

[0023] The detection coil 302 is configured in a ring shape with a through-hole in the center. When the magnetized measurement sample 310 moves up and down through the through-hole of the detection coil 302, an induced current is generated in the detection coil 302, and is finally recorded in the recorder 300.

[0024] The excitation unit 200 includes an excitation coil 200a, a permanent magnet 200b, a vibrating body 200c, an excitation rod 200d, and an amplitude detection capacitor 200e. By controlling the AC current, the excitation coil 200a, which is disposed adjacent to the permanent magnet 200b, vibrates up and down. This causes the vibrating body 200c, which is disposed in contact with the excitation coil 200a, to vibrate, and the excitation rod 200d, which is connected to the vibrating body 200c, to vibrate up and down. This causes the measurement sample 310, which is connected to the excitation rod 200d, to move up and down through the through-hole of the detection coil 302.

[0025] The magnetization measurement unit 202 includes an oscillator 202 a, a power amplifier 202 b, a standard signal generator 202 c, an amplifier 202 d, an automatic gain controller 202 e, a phase shifter 202 f, an amplifier 202 g, a band-pass filter 202 h, a synchronous detection circuit 202 i, and a low-pass filter 202 j. The output of the magnetization measurement unit 202 is sent to a recorder 300.

[0026] Recorder 300 is an example of a recording device that records the magnetic properties of measurement sample 310 based on the detection results from magnetization measurement unit 202. Recorder 300 records the magnetic properties of measurement sample 310 indicated in the output from magnetization measurement unit 202 in association with the magnitude of the magnetic field in the space surrounding measurement sample 310 indicated in the output from gaussmeter 204a.

[0027] The magnetometer 1 measures the magnetic properties of the measurement sample 310 at a specific magnetic field magnitude. The magnetometer 1 performs a magnetic field variation pattern in which the magnetic field generated by the magnet 102 is gradually increased from zero in the positive direction, then gradually decreased back to zero, then gradually increased in the negative direction, then gradually decreased back to zero, then gradually increased again in the positive direction, then gradually decreased back to zero. Hereinafter, the state in which this variation pattern is performed is referred to as the "normal operating state." Whether in the positive or negative direction, the amount of current is increased when the magnetic field is increased, and the amount of current is decreased when the magnetic field is decreased. In the normal operating state, the magnet 102 maintains a superconducting state.

[0028] The detailed state of the magnetic field in the normal operating state is as follows: When the magnetic field generated by the magnet 102 is gradually increased from zero in the positive direction, the magnetometer 1 repeats the steps of increasing the current by a predetermined amount to increase the magnetic field by a constant magnitude, and maintaining the current at the predetermined amount to maintain the magnetic field at a constant magnitude. When the magnetic field generated by the magnet 102 is gradually decreased back to zero, the magnetometer 1 repeats the steps of decreasing the current by a predetermined amount to decrease the magnetic field by a constant magnitude, and maintaining the current at the predetermined amount to maintain the magnetic field at a constant magnitude. When the magnetic field generated by the magnet 102 is gradually increased in the negative direction, the magnetometer 1 repeats the steps of increasing the current by a predetermined amount to increase the magnetic field by a constant magnitude, and maintaining the current at the predetermined amount to maintain the magnetic field at a constant magnitude. In the stage of gradually reducing the magnetic field generated by the magnet 102 and returning it to zero, the magnetometer 1 repeats a step of reducing the current by a predetermined amount to reduce the magnetic field by a constant magnitude, and a step of maintaining the current at a predetermined amount to maintain the magnetic field at a constant magnitude. The magnetometer 1 measures the magnetic properties of the measurement sample 310 while the amount of current and the magnitude of the magnetic field are maintained at a constant magnitude.

[0029] The predetermined amount of current magnitude is, for example, 1 ampere (A). The magnetometer 1 increases the current in a positive direction by 1 ampere (A) at a time until it reaches +250 amperes (A). Next, the magnetometer 1 decreases the current from 250 amperes (A) by 1 ampere (A) at a time until it reaches 0 amperes (A). Next, the magnetometer 1 increases the current in a negative direction by 1 ampere (A) at a time until it reaches -250 amperes (A), and then decreases the current by 1 ampere (A) at a time until it reaches 0 amperes (A). The magnetometer 1 then again increases the current in a positive direction by 1 ampere (A) at a time until it reaches +250 amperes (A), and then decreases the current by 1 ampere (A) at a time until it reaches 0 amperes (A).

[0030] <Outline of the magnet structure of high-temperature superconducting magnets> FIG. 2 is a conceptual diagram illustrating an example of a magnet structure (hereinafter referred to as "magnet structure 400") including magnet 102. The magnet structure 400 has a housing 402, a heat insulating wall 404, and a cooling device 406. The cooling device 406 has a cooling section 406a, a refrigerant storage section 406b, a cooling tip section 406c, a heat conduction section 406d, and a cooling plate member 406e. Helium gas is used as the cooling medium. Helium gas is stored in the refrigerant storage section 406b, and is cooled by the cooling section 406a. Heat is then conducted to the cooling plate member 406e via the cooling tip section 406c and the heat conduction section 406d.

[0031] The magnet 102 is composed of high-temperature superconducting coils 102a. The high-temperature superconducting coils 102a are superconducting ceramic coils. A cooling plate member 406e is placed between the high-temperature superconducting coils 102a to cool the high-temperature superconducting coils 102a. The temperature of the high-temperature superconducting coils 102a during operation of the magnetometer 1 (normal operating state) is between minus 260 degrees Celsius and minus 250 degrees Celsius.

[0032] With the detection coil 302 (see FIG. 1) and the measurement sample 310 placed in the through-hole 400f, the measurement sample 310 vibrates up and down, and its magnetic properties are measured.

[0033] <Outline of power supply configuration> 3 is a diagram conceptually illustrating an outline of a configuration (hereinafter referred to as "power supply configuration 100") for controlling the current supplied to magnet 102. Power supply configuration 100 includes magnet 102, external power supply 104, battery 106, reactors 108a to 108d, AMP1, AMP2, and a regeneration circuit 110. Each component of power supply configuration 100 is controlled by power supply configuration control unit 200 (hereinafter referred to as "control unit 200").

[0034] The external power supply 104 is an AC commercial power source, which is converted to DC in the power supply configuration 100 before the current is sent to the battery 106 .

[0035] The battery 106 is, for example, a rechargeable lead battery. The battery 106 is, for example, a power supply of 72 volts (V) and 60 amperes (V) DC. Note that in the present invention, the battery is not limited to a lead battery as long as it is a rechargeable battery, and may be, for example, a lithium battery.

[0036] AMP1 and AMP2 are switch circuits that control current and voltage. AMP1 and AMP2 are bridge circuits. AMP1 and AMP2 are collectively referred to as "AMP." By having AMP1 and AMP2, the load on each of AMP1 and AMP2 can be reduced compared to when there is only one AMP.

[0037] By controlling the AMP and reactors 108a to 108d, the direction, magnitude, and voltage of the current from the battery 106 are adjusted, and the excitation current is sent to the magnet 102. The excitation current flowing through the magnet 102 is switched between a direction from one end 102a1 to the other end 102a2 of the magnet 102, or a direction from the end 102a2 to the end 102a1. When the current flowing to the magnet 102 is reduced, the current is returned to the battery 106 as regenerative current 1 by the AMP.

[0038] The regeneration circuit 110 is configured to return the electromagnetic energy stored in the magnet 102 to the battery 106 as an electric current. The regeneration path 100 includes a regeneration control switch 112, a flyback transformer 114, and a protection discharge circuit 116. In FIG. 3, the flyback transformer 114 is shown with its primary coil 114a and secondary coil 114b separated. In reality, the flyback transformer 114 has the primary coil 114a and secondary coil 114b arranged on a common core. The primary coil 114a and secondary coil 114b are insulated from each other but share the core.

[0039] A low-pass filter 120 composed of an inductor (L) and a capacitor (C) is arranged between the regeneration circuit 110 and the AMP and the battery 106. The regeneration current 1 and the regeneration current 2 are returned to the battery 106 with high-frequency components removed by the low-pass filter 120.

[0040] <Current control by the AMP> FIG. 4 is a conceptual diagram showing an example of current control by the AMP. The AMP has switches Q1 to Q8, and controls the direction, magnitude, and voltage of the current by connecting (ON) and disconnecting (OFF) the switches Q1, etc. The switches Q, etc. connect (ON) and disconnect (OFF) at, for example, 40 kilohertz (kHz). In each switch Q, etc., the ratio of the connection (ON) time to the total time of connection (ON) and disconnection (OFF) is called the "on-duty ratio".

[0041] For example, focusing on switches Q1 and Q5 that connect the positive terminal of the battery 106 to the end 102a1 of the magnet 102, when reducing the current (hereinafter referred to as "state A"), the connection (ON) time is made shorter than the disconnection (OFF) time. That is, the on-duty ratio is made less than 0.5. Switches Q1 and Q5 do not become connected (ON) simultaneously, and either one of them becomes connected (ON).

[0042] When a constant current is flowing (hereinafter referred to as "State B"), the connection (ON) time is made equal to the disconnection (OFF) time. In other words, the on-duty is set to 0.5. When the current is increased (hereinafter referred to as "State C"), the connection (ON) time is made longer than the disconnection (OFF) time. In other words, the on-duty is made greater than 0.5.

[0043] <Coil current and battery current> <<When the coil current increases>> 5 and 6, the state when increasing the current flowing through the magnet 102 (hereinafter referred to as the "coil current" or "excitation current") will be described. For ease of explanation, only AMP1 of the AMPs will be described. Also, the battery 106 is assumed to be 12 volts (V). The smoothing capacitor and losses in the circuit are not taken into consideration.

[0044] The inductance of the magnet 102 is assumed to be 1 Henry (H). Therefore, when a direct current that changes at a rate of 1 ampere per second is passed through the magnet 102, an electromotive force of 1 volt (V) is generated.

[0045] When the current flowing through the magnet 102 is increased, the battery 106 is discharged. As shown in FIG. 5, when the current flowing through the magnet 102 is increased, for example, the on-duty of the switches Q1 and Q4 is set to 0.54 (see FIG. 5(a)), and the on-duty of the switches Q2 and Q3 is set to 0.46 (see FIG. 5(b)). When the switches Q1 and Q4 are connected (ON), current flows from the battery 106 to the magnet 102. In contrast, when the switches Q2 and Q3 are connected (ON), current flows from the magnet 102 to the battery 106. Due to the difference in on-duty, the current flowing from the battery 106 to the magnet 102 is greater than the current flowing from the magnet 102 to the battery 106, so the current flowing through the magnet 102 increases over the predetermined time T.

[0046] For example, as shown in Fig. 6(a), in order to increase the current (coil current) flowing through the magnet (superconducting coil) 102 at a rate of increase of 1 A (ampere) per second, the current (battery current) from the battery 106 is controlled as shown in Fig. 6(b). As shown in Fig. 6(b), the average discharge current is determined by the difference in the on-duty of the current from the battery 106 and the current to the battery 106, and the average discharge current gradually increases.

[0047] 7 and 8 are a table and a graph showing the relationship between the coil current and the battery current. When the coil current increases, current is discharged from the battery 106. When the coil current decreases, current is charged to the battery 106.

[0048] For example, when the battery current is 1 A / s and a current of 10 A flows through the magnet 102, the average discharge current (Ibat) from the battery 106 is 10 / 12 amperes (approximately 0.83 amperes) according to the following equation 1. Formula 1: 1H×10A×1A / sec×Δt=12V×Ibat×Δt

[0049] When 200 A flows through the magnet 102, the average discharge current (Ibat) from the battery 106 is calculated as 200 / 12 amperes (approximately 16.7 amperes) according to the following equation 2. Formula 2: 1H×10A×1A / sec×Δt=12V×Ibat×Δt

[0050] The on-duty is varied by the ratio of the battery voltage (12V) to the inductance (1H) of the magnet 102. For example, when increasing the current, the on-duty is set to approximately 0.54, using the formula 0.5 x (1 + 1 / 12). This prevents over-discharge.

[0051] As shown in Figures 7 and 8, the increase or decrease in the coil current is greater than the increase or decrease in the battery current. Conversely, the increase or decrease in the battery current is smaller than the increase or decrease in the coil current. For example, when the battery current is 1 A / s, if the coil current decreases from 250 A to 200 A, the battery current decreases from 20.8 amperes to 16.7 amperes. This prevents over-discharge and over-charge.

[0052] <<When the coil current decreases>> When the current flowing through the magnet 102 is reduced, the battery 106 is charged. As shown in Figure 9, when the current flowing through the magnet 102 is reduced, for example, the on-duty of the switches Q1 and Q4 is set to 0.46 (see Figure 9(a)), and the on-duty of the switches Q2 and Q3 is set to 0.54 (see Figure 9(b)). When the switches Q1 and Q4 are connected (ON), current flows from the battery 106 to the magnet 102. In contrast, when the switches Q2 and Q3 are connected (ON), current flows from the magnet 102 to the battery 106. Due to the difference in on-duty, the current flowing from the magnet 102 to the battery 106 is greater than the current flowing from the battery 106 to the magnet 102, so the current flowing through the magnet 102 decreases over the predetermined time T.

[0053] For example, as shown in Figure 10(a), in order to reduce the current (coil current) flowing through the magnet (superconducting coil) 102 at a rate of decrease of 1 A (ampere) per second, the current (battery current) to the battery 106 is controlled as shown in Figure 10(b). As shown in Figure 10(b), the average charging current is determined by the difference in the on-duty of the current from the battery 106 and the current to the battery 106, and the average charging current gradually decreases.

[0054] When 10 A flows through the magnet 102, the average charging current (Ibat) to the battery 106 is −10 / 12 amperes (approximately −0.83 amperes) according to the following equation 3. Formula 3: 1H×10A×(-1A / sec)×Δt=12V×Ibat×Δt

[0055] When 200 A flows through the magnet 102, the average discharge current (Ibat) from the battery 106 is calculated as −200 / 12 amperes (approximately −16.7 amperes) according to the following equation 4. Formula 4: 1H×200A×(-1A / sec)×Δt=12V×Ibat×Δt

[0056] When the current is reduced, it is set to approximately 0.46 using the formula 0.5×(1−1 / 12), thereby preventing the battery 106 from being overcharged.

[0057] <<When the coil current is constant>> 11, when the excitation current is kept constant, for example, the on-duty of switches Q1 and Q4 is set to 0.50, and the on-duty of switches Q2 and Q3 is set to 0.50. When the excitation current is constant, a current equivalent to the excitation current flows between the AMP, magnet 102, and bypass capacitor (the capacitor of low-pass filter 120 in FIG. 3), and the current supply from battery 106 is limited to the amount of loss in the circuit, making it extremely small.

[0058] <<Current magnitude under normal operating conditions>> Fig. 12 is a diagram conceptually showing the magnitude of current in a normal operating state. Fig. 12(a) shows a state in which the excitation current is increased in a positive direction, reaches its maximum value in the positive direction, and then is decreased to 0 amperes (A) (hereinafter referred to as the "positive state"). Fig. 12(b) shows a state in which the excitation current is increased in a negative direction, reaches its maximum value in the negative direction, and then is decreased to 0 amperes (A) (hereinafter referred to as the "negative state").

[0059] As shown in FIG. 12(a), in the positive state, the magnetometer 1 gradually increases the current in the positive direction, and when it reaches its maximum value in the positive direction, it maintains the maximum value for a certain period of time and then gradually decreases it. As a result, the magnetic field gradually increases in the positive direction, and when it reaches its maximum value in the positive direction, it maintains the maximum value for a certain period of time and then gradually decreases it. In the step of gradually increasing the current in the positive direction, the magnetometer 1 repeats step (S1) of increasing the current by a predetermined amount and step (S2) of maintaining the current at the predetermined amount. In the step of gradually decreasing the current, the magnetometer 1 repeats step (S3) of decreasing the current by a predetermined amount and step (S2) of maintaining the current at the predetermined amount. The predetermined amount of current is, for example, 1 ampere (A), and the current is varied at a rate of 1 ampere (A) per second. The maximum value of the current in the positive direction is, for example, +250 amperes (A).

[0060] As shown in FIG. 12(b), in the negative state, the magnetometer 1 gradually increases the current in the negative direction. When it reaches its maximum value in the negative direction, it maintains the maximum value for a certain period of time and then gradually decreases it. As a result, the magnetic field gradually increases in the negative direction. When it reaches its maximum value in the negative direction, it maintains the maximum value for a certain period of time and then gradually decreases it. During the step of gradually increasing the current in the negative direction, the magnetometer 1 repeats step (S4) of increasing the current by a predetermined amount and step (S2) of maintaining the current at the predetermined amount. During the step of gradually decreasing the current, the magnetometer 1 repeats step (S5) of decreasing the current by a predetermined amount and step (S2) of maintaining the current at the predetermined amount. The predetermined amount of current is, for example, 1 ampere (A), and the current is varied at a rate of 1 ampere (A) per second. The maximum value of the current in the negative direction is, for example, -250 amperes (A).

[0061] In steps (S1) and (S4) where the excitation current is increased by a predetermined amount, the coil current and battery current fluctuate as shown in Figure 6. In steps (S3) and (S5) where the current is decreased by a predetermined amount, the coil current and battery current fluctuate as shown in Figure 10. In step (S2) where the excitation current is maintained, the coil current and battery current are maintained within a predetermined range as shown in Figure 11.

[0062] <Regenerative circuit operation> 13 is a conceptual diagram showing the operation of the regeneration circuit 110. The regeneration circuit 110 functions when the coil current changes from an increase to a decrease. More specifically, the regeneration circuit 110 functions when the coil current increases, remains constant, and then changes from that state to a decrease. When the coil current decreases, the regeneration circuit 110 recovers the energy stored in the coil 102 and regenerates current to the battery 106.

[0063] 13(a), when the regeneration control switch 112 is connected (Ton), electromagnetic energy stored in the magnet 102 flows as current i1 to the primary coil 114a and is stored as electromagnetic energy in the core 114c. Then, when the regeneration control switch 112 is disconnected (Toff), the electromagnetic energy stored in the core 114c is regenerated into the battery 106 as current i2.

[0064] 13(b), the time t2 until the electromagnetic energy stored in the core 114c is released as the current i2 is controlled to be longer than the time t1 until the current i1 is stored in the core 114c as the electromagnetic energy. The maximum value of the current i2 is controlled to be smaller than the maximum value of the current i1. This prevents excessive current from being regenerated in the battery 106.

[0065] The magnitude of the current regenerated by the flyback transformer 114 to the battery 106 is controlled by controlling the connection and disconnection of the regeneration control switch 112 .

[0066] When the superconducting state is lost during normal operation, the above-mentioned regeneration circuit 110 is actively operated in addition to the protective discharge circuit 116 described below to contribute to the release of current from the coil 102. That is, the electromagnetic energy stored in the coil 102 is passed as current to the primary coil 114a, and furthermore, the core 114c absorbs and stores it as magnetic energy.

[0067] <Battery charging conditions> As described above, when the current flowing through the magnet 102 is reduced, a current (regenerative current 1) is returned from the magnet 102 to the battery 106 via the AMP, and a current (regenerative current 2) is returned from the magnet 102 to the battery 106 via the regenerative circuit 110. At this time, the AMP adjusts the magnitude of the current and voltage (hereinafter referred to as "regenerative adjustment") so as to satisfy the charging allowance conditions of the battery 106. Note that an inductor (L) and a capacitor (C) are disposed between the battery 106 and the AMP, forming a low-pass filter 120. Regenerative current 1 and regenerative current 2 are pulse currents, but the low-pass filter 120 removes high-frequency components before returning them to the battery 106.

[0068] Fig. 14 is a conceptual diagram for explaining the allowable conditions for charging the battery 106. Generally, as shown in Fig. 14(a), the allowable conditions for normal charging are battery capacity x 1 / 10, and the allowable conditions for rapid charging are battery capacity x 1 / 1 to battery capacity x 1 / 2.

[0069] For example, as shown in Fig. 14(b), in the case where two sets of two 12V, 55Ah batteries connected in series are arranged in parallel, the charging current K is composed of the charging current K1 (regenerative current 1) from the AMP and the charging current K2 (regenerative current 2) from the regenerative circuit 110. That is, as shown in Fig. 14(c), K = K1 + K2. Therefore, as shown in Fig. 14(d), the power supply configuration control unit 200 (see Fig. 3) controls each part of the power supply configuration 100 so that K1 + K2 is smaller than the charging allowable value KM.

[0070] <Circuit and battery protection in emergency situations> During the normal operation described above, an emergency situation may occur, for example, when the cooling medium of the magnet structure 400 leaks and the superconducting state is lost (a so-called "quench"). When the superconducting state is lost, electrical resistance suddenly occurs, and there is a problem that the high-temperature superconducting coil 102a may be permanently destroyed due to heat generation. To avoid this problem, in an emergency, the electromagnetic energy stored in the magnet 102 is discharged (released) as an electric current by the protective discharge circuit 116 of the regeneration circuit 110.

[0071] FIG. 15 is a conceptual diagram illustrating the operation of the protective discharge circuit 116. As shown in FIG. 15(a), the high-temperature superconducting coil 102a can be thought of as having a coil resistance Rs. In the superconducting state, the coil resistance Rs is 0 ohms. Therefore, as shown in FIG. 15(b), if the rate of change of the current is constant, the coil voltage Vs generated across the high-temperature superconducting coil 102a is constant. In contrast, when the superconducting state is eliminated, the coil resistance Rs increases, and the coil voltage Vs increases, as shown in FIG. 15(c). The magnetometer 1 is configured to detect the increase in the coil voltage Vs as an abnormality signal, activate the protective discharge circuit 116, and discharge (emit) the electromagnetic energy accumulated in the high-temperature superconducting coil 102a as a current.

[0072] Unlike this embodiment, the magnetometer 1 may detect a quench by not only detecting an increase in the coil voltage Vs but also monitoring the coil temperature and outputting an abnormality signal if the temperature exceeds a predetermined temperature.

[0073] The present invention is not limited to the above-described embodiment, and any modifications and improvements that can achieve the object of the present invention are included in the present invention. [Explanation of symbols]

[0074] 1. Vibrating sample magnetometer 100 power configurations 102 High-Temperature Superconducting Magnet 104 External power supply 106 Battery 110 Regeneration circuit 112 Regeneration control switch 114 Flyback transformer 116 Protective discharge circuit 200 Power supply configuration control unit 400 magnet structure 406 Cooling device

Claims

1. an exciting electromagnet that generates a magnetic field in a space in which the vibrated measurement sample is located; a detection coil for detecting an induced voltage due to vibration of the measurement sample magnetized by the exciting electromagnet; a battery that supplies current to the exciting electromagnet; a control circuit for controlling the amount of current supplied from the battery to the exciting electromagnet; A vibrating sample magnetometer having the exciting electromagnet is a superconducting electromagnet, In a normal state in which the magnetic properties of the measurement sample are measured, when the current supplied to the exciting electromagnet is reduced, a regenerative circuit disposed separately from the control circuit returns the magnetic energy of the exciting electromagnet to the battery as a current, and the control circuit returns the current flowing through the exciting electromagnet to the battery. Vibrating sample magnetometer.

2. 2. The vibrating sample magnetometer according to claim 1, wherein the regenerative circuit and the control circuit are configured to control the current returned to the battery so as to satisfy a charging allowance condition of the battery.

3. a low-pass filter for blocking high frequency components of the current returned to the battery; 3. The vibrating sample magnetometer according to claim 1 or 2.

4. a discharge circuit for discharging the magnetic energy of the exciting electromagnet as a current when the superconducting state of the exciting electromagnet is released; 3. The vibrating sample magnetometer according to claim 1 or 2.

5. The regeneration circuit is configured to flow magnetic energy possessed by the exciting electromagnet as a current through a primary coil of the flyback transformer, store the magnetic energy in a core of the flyback transformer, and return the magnetic energy of the core as a current to the battery via a secondary coil.

3. The vibrating sample magnetometer according to claim 1 or 2.

6. 5. The vibrating sample magnetometer according to claim 4, further configured such that, when the superconducting state of said exciting electromagnet is released, said regenerative circuit absorbs magnetic energy possessed by said exciting electromagnet.

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