JP2004259925A - Conduction cooling type superconductive magnet device for nuclear magnetic resonator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conduction cooling type superconductive magnet device for nuclear magnetic resonator, which hardly causes the quenching of a superconductive coil even upon power failure. <P>SOLUTION: The conduction cooling type superconductive magnet device is provided with a cryogenic refrigerating machine, a vacuum vessel, a heat radiation shielding chamber defined in the vacuum vessel by a heat radiation shielding plate, a superconductive coil arranged in the heat radiation shielding chamber, a heat transfer plate contacted thermally with the superconductive coil and the cryogenic refrigerating machine to conduct heat between both of them, and a cold storage material contacted thermally with the superconductive coil through the heat transfer plate. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a superconducting magnet apparatus used for a nuclear magnetic resonance apparatus, and more particularly to a conduction cooled superconducting magnet apparatus for a nuclear magnetic resonance apparatus, which cools a superconducting coil by a cryogenic refrigerator.
[0002]
[Prior art]
In the measurement of nuclear magnetic resonance, it is necessary to apply a strong static magnetic field to a sample in order to observe a nuclide having a nuclear spin in the sample. Therefore, conventionally, a superconducting magnet using liquid helium as a refrigerant as shown in FIG. 1 has been used.
[0003]
In the figure, 1 is a superconducting coil. The superconducting coil 1 is immersed in a helium tank 2 in which liquid helium is stored, and is maintained at an extremely low temperature. Further, in order to prevent the liquid helium in the helium tank 2 from evaporating and being lost, a nitrogen tank 3 storing liquid nitrogen for cooling the environment around the helium tank 2 is provided. The helium tank 2 and the nitrogen tank 3 are housed in a vacuum vessel 4 to prevent external heat from entering, and are placed so as to be thermally isolated from the outside.
[0004]
In recent years, conduction cooled superconducting magnet devices that do not use a refrigerant such as liquid helium or liquid nitrogen have been proposed (Non-Patent Document 1, Patent Document 1). The conduction-cooled superconducting magnet device uses a cryogenic refrigerator to cool the superconducting coil, maintaining the superconducting state of the superconducting coil using only electric power, even without liquid helium or liquid nitrogen. It was designed to be able to.
[0005]
FIG. 2 shows an example of a conduction cooled superconducting magnet apparatus for a nuclear magnetic resonance apparatus. In FIG. 2, this conduction-cooled superconducting magnet device for a nuclear magnetic resonance apparatus is provided with a heat source for further enhancing the heat insulating effect in a vacuum chamber 5 evacuated in order to avoid heat intrusion from the outside. A heat radiation shield chamber defined by the radiation shield plate 6 is provided, and the superconducting coil 7 is housed in the heat radiation shield chamber.
[0006]
Reference numeral 8 denotes a Gifford McMahon type refrigerator (GM refrigerator) as a cryogenic refrigerator for cooling the superconducting coil 7. The GM refrigerator 8 includes a first stage 8a and a second stage 8b. The first stage 8a is in thermal contact with the heat radiation shield 6 that defines the heat radiation shield chamber, and cools the heat radiation shield 6 to 40 to 50K. The two-stage stage 8b is in thermal contact with the heat transfer plate 9 and also through the heat transfer plate 9 with the superconducting coil 7 that is in thermal contact with the heat transfer plate 9, so that the superconducting coil 7 is , From the bottom to about 4K.
[0007]
Further, in the heat radiation shield room, a superconducting shim coil 10 which is indispensable for correcting distortion of a static magnetic field generated by the superconducting coil 7 at the time of measurement of nuclear magnetic resonance is in thermal contact with the heat transfer plate 9. , Is provided.
[0008]
In addition, outside the vacuum vessel 5, currents are supplied to a refrigerator power supply and a compressor 12, an excitation power supply 13 for exciting the superconducting coil 7, and a superconducting shim coil 10 necessary for operating the GM refrigerator 8. A superconducting shim power supply 14 for transmitting
[0009]
[Non-patent document 1]
Yukio Mikami, Junji Sakuraba, Keiichi Watarizawa et al., "Development of 15T refrigerator-cooled superconducting magnet", Magazine "Cryogenic Engineering" (Cryogenic Engineering Association / Cryogenic Engineering Society), Vol. 34, No. 5, 1999 Published on May 20, 2000, pages 200-205 [Patent Document 1]
JP 2001-77434 A
[Problems to be solved by the invention]
In such a situation, one of the biggest problems in putting the conduction cooling type superconducting magnet device into practical use is that if a power failure occurs while the device is operating, the refrigerator stops and the temperature of the superconducting coil rises. And quench occurred accordingly.
[0011]
An extremely high magnetic field stability of 10 ⁻⁹ / hour or more is required in a nuclear magnetic resonance apparatus. Therefore, once the superconducting magnet has quenched, it is excited after being brought to a stable state again. You have to wait for the magnetic field to stabilize for more than a few days. During that time, the device becomes unusable and the experiment stops.
[0012]
Excitation of the superconducting magnet is an extremely specialized operation, and is not an operation that can be handled by ordinary users. Therefore, every time a quench occurred due to a power outage, an expert had to be requested.
[0013]
SUMMARY OF THE INVENTION An object of the present invention is to provide a conduction-cooled superconducting magnet device for a nuclear magnetic resonance apparatus in which quenching of a superconducting coil does not easily occur even in the event of a power failure.
[0014]
[Means for Solving the Problems]
In order to achieve this object, a conduction-cooled superconducting magnet device for a nuclear magnetic resonance device according to the present invention is:
A cryogenic refrigerator,
A vacuum vessel,
In this vacuum vessel, a heat radiation shield chamber defined by a heat radiation shield plate,
A superconducting coil disposed in the heat radiation shield room;
A heat transfer plate for thermally contacting the superconducting coil and the cryogenic refrigerator, and conducting heat between the two;
The heat transfer plate is provided with a cold storage material that is in thermal contact with the superconducting coil via the heat transfer plate.
[0015]
In addition, a backup power supply for the superconducting coil is provided outside the vacuum vessel for controlling the current to reduce or eliminate the superconducting current flowing through the superconducting coil at the time of a power failure. .
[0016]
Further, a back-up liquid helium container that is in thermal contact with the heat transfer plate is provided in the heat radiation shield chamber, and liquid helium is always stored in the liquid helium container.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 3 shows an embodiment of a conduction cooled superconducting magnet device for a nuclear magnetic resonance apparatus according to the present invention. In FIG. 3, this conduction-cooled superconducting magnet device for a nuclear magnetic resonance apparatus is provided with a heat-insulating device in a vacuum chamber 5 evacuated in order to further prevent heat from entering from outside. A heat radiation shield chamber defined by the radiation shield plate 6 is provided, and the superconducting coil 7 is housed in the heat radiation shield chamber.
[0018]
Reference numeral 8 denotes a Gifford McMahon type refrigerator (GM refrigerator) as a cryogenic refrigerator for cooling the superconducting coil 7. The GM refrigerator 8 includes a first stage 8a and a second stage 8b. The first stage 8a is in thermal contact with the heat radiation shield 6 that defines the heat radiation shield chamber, and cools the heat radiation shield 6 to 40 to 50K. The two-stage stage 8b is in thermal contact with the heat transfer plate 9 and also through the heat transfer plate 9 with the superconducting coil 7 that is in thermal contact with the heat transfer plate 9, so that the superconducting coil 7 is , From the bottom to about 4K.
[0019]
Further, in the heat radiation shield room, a superconducting shim coil 10 which is indispensable for correcting distortion of a static magnetic field generated by the superconducting coil 7 at the time of measurement of nuclear magnetic resonance is in thermal contact with the heat transfer plate 9. , Is provided.
[0020]
A refrigerator power supply and a compressor 12 necessary for operating the GM refrigerator 8, a superconducting coil excitation power supply 13 for exciting the superconducting coil 7, and a superconducting shim coil are provided outside the vacuum vessel 5. A superconducting shim coil excitation power supply 14 for sending current to 10 is provided.
[0021]
The difference between this embodiment and the prior art is that a heat sink 15 made of a cold storage material is provided on the heat transfer plate 9 that is in thermal contact with the lower part of the superconducting coil 7. For the heat sink 15, a block of lead or copper, a block of a magnetic regenerator, or the like is used. Even if the GM refrigerator 8 stops operating due to a sudden power failure due to the presence of the heat sink 15, the heat invading from the outside of the vacuum vessel 5 is absorbed by the cooling power of the heat sink 15, and the superconducting coil 7. Prevent the temperature from rising rapidly.
[0022]
Thereby, at the time of a power failure, the temperature rise rate of the superconducting coil 7 can be made slower than the temperature rise rate when the heat sink 15 does not exist, and the quench of the superconducting coil 7 can be postponed.
[0023]
Next, FIG. 4 shows another embodiment of the conduction cooled superconducting magnet device for a nuclear magnetic resonance apparatus according to the present invention. The difference between this embodiment and the embodiment shown in FIG. 3 is that (1) a backup power supply is provided for the refrigerator power supply at the time of power failure, and (2) a backup power supply at the time of power failure is provided for the excitation power supply of the superconducting coil. (3) A backup power supply at the time of a power failure is provided for the excitation power supply of the superconducting shim coil.
[0024]
Generally, the power consumption of a refrigerator is considerably large (for example, 5 kW), and a large-scale power supply such as a generator is required for the backup. In order to avoid an increase in the cost burden for that purpose, in the previous embodiment, a heat sink was provided in the heat radiation shield room, and measures were taken to minimize the temperature rise of the superconducting coil during a power outage. Had been avoided.
[0025]
However, power outages include instantaneous power outages, power outages for several minutes due to lightning strikes, and power outages for several hours for electrical work. In the case of a power failure for a relatively short time, if a large temperature margin is provided for the superconducting magnet, the quench can be prevented by automatically returning the refrigerator after the power failure and restarting the cooling. However, in order to cope with a long-term power failure, it is inevitable to add backup equipment to the refrigerator power supply. This is the refrigerator backup power supply 16 shown in FIG.
[0026]
Also, when quench occurs, all the superconducting current becomes heat and raises the temperature of the superconducting magnet. The energy is quite large, raising the temperature of the superconducting magnet by tens of degrees. If this rise in temperature can be avoided, the cooling time of the superconducting magnet when the refrigerator resumes operation after the power failure can be shortened.
[0027]
In the superconducting magnet device employing the cooling method using a refrigerant as shown in FIG. 1, the current lead is removed for the purpose of preventing heat intrusion after the magnet is excited. Since the conduction magnet device uses current leads with little heat penetration, it can be always attached.
[0028]
By taking advantage of this advantage, monitor the temperature rise of the superconducting coil and the superconducting shim coil during a power outage, and reduce the superconducting current flowing through the superconducting coil and the superconducting shim coil when the temperature reaches just before the quench occurs, or If the current is controlled to be zero, it is possible to avoid a temperature rise of the superconducting magnet.
[0029]
In order to perform these operations, it is necessary to add backup power supplies to the control system of the superconducting magnet, the excitation power supply of the superconducting coil, and the excitation power supply of the superconducting shim coil, respectively. Since the power required for the operation is extremely small and the power consumption is small, it is not difficult to add the power. These are the backup power supply 17 for the superconducting coil excitation power supply and the backup power supply 18 for the superconducting shim coil excitation power supply shown in FIG.
[0030]
Next, FIG. 5 shows another embodiment of the conduction cooled superconducting magnet device for a nuclear magnetic resonance apparatus according to the present invention. In this embodiment, a liquid helium tank 19 that is in thermal contact with the heat transfer plate 9 is provided in a heat radiation shield chamber in addition to a heat sink that suppresses a temperature rise of the superconducting magnet at the time of a power failure.
[0031]
If the liquid helium is always stored in the liquid helium tank 19, the superconducting coil 7 and the superconducting shim coil 10 are cooled by the liquid helium even if the refrigerator 8 is stopped due to a power failure. It is possible to prevent the temperature of the superconducting coil 7 and the superconducting shim coil 10 from rising for a longer time than in the case of only 15.
[0032]
The liquid helium in the liquid helium tank 19 is maintained at a very low temperature by the refrigerator 8 during the operation of the refrigerator 8, so that the amount of evaporation is extremely small. Therefore, the size of the liquid helium tank 19 may be determined according to the capacity of the refrigerator 8 and the maintenance time at the time of power failure, and the superconducting coil is cooled only with the liquid helium without the refrigerator 8. Compared to the case, even a small liquid helium tank is sufficiently effective.
[0033]
【The invention's effect】
As described above, according to the conduction cooled superconducting magnet apparatus for a nuclear magnetic resonance apparatus of the present invention, a cryogenic refrigerator, a vacuum vessel, and a compartment formed by a heat radiation shield plate in the vacuum vessel. A heat radiation shield chamber, a superconducting coil disposed in the heat radiation shield chamber, and heat transfer for making thermal contact between the superconducting coil and the cryogenic refrigerator and performing heat conduction therebetween. A conduction cooling type superconducting magnet for a nuclear magnetic resonance apparatus, which is provided with a plate and a regenerator material that is in thermal contact with the superconducting coil via the heat transfer plate, so that quenching of the superconducting coil is unlikely to occur even when a power failure occurs. It has become possible to provide a device.
[Brief description of the drawings]
FIG. 1 is a view showing a conventional superconducting magnet device for a nuclear magnetic resonance apparatus.
FIG. 2 is a view showing a conventional conduction cooled superconducting magnet device for a nuclear magnetic resonance apparatus.
FIG. 3 is a view showing one embodiment of a conduction cooled superconducting magnet device for a nuclear magnetic resonance apparatus according to the present invention.
FIG. 4 is a view showing another embodiment of the conduction cooled superconducting magnet device for a nuclear magnetic resonance apparatus according to the present invention.
FIG. 5 is a view showing another embodiment of the conduction cooled superconducting magnet device for a nuclear magnetic resonance apparatus according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Superconducting coil, 2 ... Nitrogen tank, 3 ... Helium tank, 4 ... Vacuum container, 5 ... Vacuum container, 6 ... Heat radiation shield plate, 7 ... Super Conduction coil, 8: refrigerator, 8a: one stage, 8b: two stage, 9: heat transfer plate, 10: superconducting shim coil, 11: refrigerator power supply, 12 ... compressor, 13 ... superconducting coil excitation power supply, 14 superconducting shim coil excitation power supply, 15 ... heat sink, 16 ... refrigerator backup power supply, 17 ... superconducting coil excitation power supply Backup power supply, 18 ... Backup power supply for superconducting shim coil excitation power supply, 19 ... Liquid helium tank.

Claims (3)

A cryogenic refrigerator,
A vacuum vessel,
In this vacuum vessel, a heat radiation shield chamber defined by a heat radiation shield plate,
A superconducting coil disposed in the heat radiation shield room;
A heat transfer plate for thermally contacting the superconducting coil and the cryogenic refrigerator, and conducting heat between the two;
A conduction-cooled superconducting magnet device for a nuclear magnetic resonance apparatus, comprising: a regenerator material in thermal contact with the superconducting coil via the heat transfer plate. A backup power supply for the superconducting coil for controlling the current so as to reduce or eliminate the superconducting current flowing through the superconducting coil at the time of a power outage outside the vacuum vessel, wherein: 2. A conduction cooled superconducting magnet apparatus for a nuclear magnetic resonance apparatus according to claim 1. 3. A liquid helium container for backup, which is in thermal contact with the heat transfer plate, is provided in the heat radiation shield chamber, and liquid helium is always stored in the liquid helium container. A conduction-cooled superconducting magnet apparatus for a nuclear magnetic resonance apparatus as described in the above.

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