JPH01253690A - Magnetic shielding apparatus - Google Patents

Abstract

PURPOSE:To shield a ferromagnetic field effectively, by arranging a superconductor outside a magnet intended for magnetic shielding to cover the magnet while a magnetic body is arranged inside the superconductor. CONSTITUTION:A cylindrical superconductor 1 is arranged outside a magnet M such as electromagnet so as to wrap it M and disc-shaped superconductors 2 and 3 are joined at both ends of the superconductor 1. Inside the superconductors 1, 2 and 3, ring-shaped magnetic bodies 4 and 5 with a L-shaped section are fastened on corners respectively as joint between the superconductors 1 and 2 and that between the superconductors 1 and 3. In this case, the existence of the magnetic bodies 4 and 5 prevents increase in the demagnetization coefficient at the corners of the superconductors 1, 2 and 3. In other words, the magnetic bodies 4 and 5 with a high permeability attract lines of magnetic force l...l to guide thereby enabling effective shielding of a ferromagnetic body free from a local superconductive breakdown.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a magnetic shielding device, and is suitable for use in, for example, preventing leakage of a strong magnetic field generated by an electromagnet in an MR device to the outside. Regarding a shield device.

<Conventional technology> In order to shield the magnetic field generated by the magnet from the outside in devices that use magnets such as electromagnets, conventional techniques have been to cover the outside of the magnet with either a ferromagnetic material or a superconductor. Common.

<Problem to be solved by the invention> When a ferromagnetic material is used as a shielding material, for example, MR
In order to shield strong magnetic fields such as those used in I devices, there is a problem in that the device becomes larger and weighs more.

Furthermore, when using a superconductor, although there is no problem with increasing size or weight, superconductivity breakdown occurs at locations where the demagnetizing field coefficient is high due to its shape, etc., and that section becomes a normal conductor. There is a problem with magnetic field leakage.

The purpose of the present invention is to basically use a superconductor as a shield material to solve problems related to increase in size and weight, and to reliably shield magnetic fields without causing superconductor destruction due to its shape etc. The object of the present invention is to provide a magnetic shielding device that can do the following.

<Means for Solving the Problems> The configuration for achieving the above object will be described with reference to FIG. 1 which is an embodiment drawing. superconductor 1 to cover
, 2.3, and magnetic bodies 4, 5 are placed inside the superconductors 1, 2.3 and at positions where the demagnetizing field coefficient becomes high due to the magnetic field from the magnet M. characterized.

<Function> Generally, as shown in FIG. 3, when the magnetic field 1-[1MI, HIM□ emitted by the magnet is attempted to be shielded by the superconductor S, the demagnetizing field coefficient becomes high at the corner C and the like. That is, the magnetic fields H1, , Hl2 have components perpendicular to the shield wall H□, 1-1t, □, respectively,
The vertical component HIMIr+ HIM
IP and HIH2p remain as they are and form a strong magnetic field at corner C etc., destroying the superconducting state.

Therefore, as in the present invention, by providing the magnetic bodies 4 and 5 at positions where the demagnetizing field coefficient is high, such as the corner C, the lines of magnetic force generated from the magnet I-M are ! -°C is guided by the magnetic bodies 4 and 5 and does not concentrate at the corner C etc., and does not destroy the superconducting state.

<Example> Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a central vertical sectional view showing the structure of an embodiment of the present invention.

A cylindrical superconductor 1 is arranged outside a magnet (M) such as an electromagnet so as to wrap around the magnet (M), and disk-shaped superconductors 2 and 3 are connected to both ends of the superconductor 1, respectively. has been done.

Inside the superconductors 1, 2, and 3, link-shaped magnetic bodies 4 and 5 with cross-sections are located at the joints between superconductors 1 and 2 and at the corners where superconductors 1 and 3 are joined. It is fixed. As the magnetic bodies 4 and 5, it is desirable to use a ferromagnetic material such as iron.

According to the embodiments of the present invention described above, the presence of the magnetic bodies 4 and 5 does not increase the demagnetizing field coefficient at each corner of the superconductors 1, 2, and 3. That is, FIG. 2 is an explanatory diagram of the flow of magnetic force lines p ---z generated by the magnet M near the corners. Magnetic material 4 or 5 with high magnetic flux
We are drawn to and guided by this. As a result, the parallel components H1, .

It should be noted that the shape of the superconductor is not limited to the above embodiments, and the position of the magnetic material is not only the corner but also the position where the demagnetizing field coefficient is high due to the shape of the superconductor. Furthermore, it can be set at a position where the demagnetizing field coefficient of the superconductor becomes high due to the strength distribution of the magnetic field created by the magnet.

<Effects of the Invention> As explained above, according to the present invention, a magnet to be magnetically shielded is covered with a superconductor, and the demagnetizing field coefficient is increased inside the superconductor by the magnetic field from the magnet. Because a magnetic material is placed in the position, strong magnetic fields can be effectively shielded without increasing the size or weight of the device, and without causing localized superconductor breakdown due to the shape of the superconductor. can do.

[Brief explanation of the drawing]

Fig. 1 is a central vertical cross-sectional view showing the configuration of an embodiment of the present invention, Fig. 2 is an explanatory diagram of its operation, and Fig. 3 is related to the position where the demagnetizing field coefficient is high in a conventional magnetic shielding device using only superconductors. It is an explanatory diagram. 1.2.3...Superconductor 4.5...Magnetic material M...Magnet patent applicant Agent of Shimadzu Corporation
Patent Attorney Nishi 1) New-6~ Figure 3 Figure 2

Claims (1)

[Claims] A superconductor is placed outside the magnet to be magnetically shielded so as to cover the magnet, and a magnetic material is placed inside the superconductor at a position where the demagnetizing field coefficient is high due to the magnetic field from the magnet. A magnetic shielding device is installed.