JPH0744102B2 - Superconducting magnet device - Google Patents

Description

The present invention relates to a superconducting magnet device including a plurality of magnetically coupled superconducting magnets.

[Conventional technology]

A conventional device is shown in FIG. 2, and its configuration and excitation method will be described. The superconducting magnet device 1 comprises one main superconducting magnet 2 and two subsidiary superconducting magnets 3 and 3 ', and excitation power sources 4 and 4'are connected to the main and subsidiary superconducting magnets, respectively. It is possible to excite the sub-superconducting magnets 3 and 3'in series or to excite them independently by using another exciting power source.
Here, the former method will be described. In order to generate a desired magnetic field inside or outside the main superconducting magnet 2,
The auxiliary superconducting magnets 3 and 3'are constructed and arranged so that they can be assisted. For example, in order to improve the uniformity of the magnetic field distribution near the center of the main superconducting magnet 2, the sub-superconducting magnet 3
And 3'may be installed and excited according to the dimensions, positions to be arranged, and exciting current values calculated in advance. Further, in order to reduce the leakage magnetic field at the outer peripheral portion of the main superconducting magnet 2, the sub-superconducting magnets 3 and 3 ′ are designed in advance so as to generate a magnetic field in the opposite direction to the magnetic field generated by the main superconducting magnet 2. It can be placed at and excited.

In particular, when the secondary superconducting magnets 3 and 3'are used for the latter purpose, the exciting power source 4'can be omitted. That is, if the characteristics of superconductivity (zero resistance and magnetic susceptibility) are used, the purpose can be sufficiently achieved.

The superconducting magnet device as described above is disclosed in, for example, Japanese Patent Laid-Open No. 61-
No. 125109 is disclosed.

[Problems to be solved by the invention]

The above-mentioned conventional technique has been used without using the characteristics (zero resistance and magnetic susceptibility) of the superconducting magnet as a subordinate magnet, while making full use of its characteristics. There is a possibility that the excitation power supply can be omitted depending on the purpose of use.

An object of the present invention is to provide a superconducting magnet device which makes full use of the superconducting characteristics of the superconducting magnet and is simpler and more economical.

[Means for solving problems]

In order to achieve the above object, the sub-superconducting magnets 3 and 3'are composed of a superconducting closed circuit, and the sub-superconducting magnets 3 and 3'are
We added a means to switch them to superconducting state or normal conducting state. When the superconducting magnets 3 and 3'are wound with a superconducting wire, the lead wires are connected so that the superconductors have zero resistance.
In the case of a one-turn ring shape, it may be a closed-circuit sintered body made of a superconducting material or a forged body (or a cast body).

[Action]

The sub superconducting magnets 3 and 3'need to be magnetically coupled to the main superconducting magnet 2, and the closed superconducting magnets 3 and 3 '
When the magnetic field of the main superconducting magnet is applied, when they are in the superconducting state, it induces a current so as to cancel the applied magnetic field (support magnetism), and in the normal conducting state, the applied magnetic field is transmitted, and then the superconducting By returning to the state and setting the magnetic field of the main superconducting magnet 2 to zero, the transmitted magnetic flux is permanently captured (zero resistance). The present invention can be embodied by utilizing the above characteristics.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. As shown in the figure, in the present embodiment, the main superconducting magnet 2 is symmetrically positioned on both sides in a closed circuit shape (not connected or connected so as to have zero resistance even if there is a connection point) as previously designed. Install a secondary superconductor. A power supply 4 for exciting it is connected to the main superconducting magnet 2, and means (hereinafter, heaters) 5 and 5'for switching them to a superconducting state or a normal conducting state are connected to the subsuperconducting magnets 3 and 3 '. It is attached.

In the above structure, the sub-superconducting magnets 3 and 3'are heated by the heaters 5 and 5 ', and the main superconducting magnet 2 is excited until a predetermined magnetic field is reached while maintaining the normal conducting state. Subsequently, the heaters 5 and 5'are turned off to return the sub-superconducting magnets 3 and 3'to the superconducting state, after which the main superconducting magnet 2 is demagnetized and the power supply 4 is turned off. At this time, the leakage magnetic field of the main superconducting magnet 2 is still trapped in the subsuperconducting magnets 3 and 3 '. If the polarity of the power source 4 is reversed in this state and the main superconducting magnet 2 is excited until it reaches a predetermined magnetic field, a diamagnetic current is induced in the subsuperconducting magnets 3 and 3 ', and the already captured magnetic field is further strengthened. . At this time, the magnetic field distribution created by the entire superconducting magnet device 1 including the main superconducting magnet 2 and the subsuperconducting magnets 3 and 3'is uniquely reproduced according to the design value, and the magnetic field in the outer peripheral portion of the main superconducting magnet 2 is reproduced. And the magnetic field of 3'are weakened and the target leakage magnetic field can be reduced.

In the present embodiment, the superconducting magnet device having good symmetry is taken as an example, but naturally, depending on the purpose, the superconducting magnet device may have an asymmetrical arrangement, and the windings, shapes, dimensions, etc. of the sub-superconducting magnets 3 and 3'may be different. It may be different. The means for switching between the superconducting state and the normal conducting state need not be limited to the heater. Needless to say, it is not necessary to specify the main superconducting magnet and the subsuperconducting magnet, and the names may be reversed in FIG. Further, it is naturally conceivable for those skilled in the art to connect the secondary superconducting magnets in series.

〔The invention's effect〕

According to the present invention, the characteristics of superconductivity are fully utilized, and at least the excitation power source and power lead of the sub-superconducting magnet (not shown,
This eliminates the need for a current feeder, contributes to simplification of the superconducting magnet device, and is effective in cost reduction. In particular, when the present invention is applied to a superconducting MRI (Nuclear Magnetic Resonance Imaging) device which is currently attracting attention, an exciting power supply is unnecessary.
It is possible to provide an active shield coil capable of automatically magnetically shielding. Furthermore, if a sub-superconducting magnet is made of a recently discovered high-temperature superconductor (sintered body), not only the connection problem will be solved, but also the refrigerant used will change from conventional expensive liquid helium to inexpensive liquid nitrogen. Can be replaced, and the amount of use and consumption can be reduced, the manufacturing cost and the operating cost can be reduced, and the device can be inexpensive, have a simple structure, and have good operability, and secondary effects are expected. To be done.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram showing an embodiment of the superconducting magnet device of the present invention, and FIG. 2 is a diagram showing the configuration of a conventional example. 1 ... Superconducting magnet device, 2 ... Main superconducting magnet, 3, 3 '...
… Sub-superconducting magnet, 4 …… Excitation power supply for main superconducting magnet 2,
4 '... excitation power source for the secondary superconducting magnets 3 and 3', 5, 5 '...
heater.

Claims (2)

[Claims] 1. A superconducting magnet device comprising a sub-superconducting magnet magnetically coupled to a main superconducting magnet for the purpose of generating a magnetic field, wherein the sub-superconducting magnet has a closed circuit shape through which a permanent current can flow. A superconducting magnet device having means capable of maintaining a state or a normal conducting state and being excited by magnetic coupling with the main superconducting magnet. 2. The superconducting magnet device according to claim 1, wherein the main superconducting magnet is excited while keeping the sub-superconducting magnet in the normal conducting state, and the sub-superconducting magnet is returned to the superconducting state. A superconducting magnet device, characterized in that it is demagnetized and, subsequently, the main superconducting magnet is excited in the direction of the opposite polarity to that of the former so that the slave superconducting magnet can catch a desired magnetic field.