JPH01130508A - Superconducting magnet device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] This invention relates to a superconducting magnet device for magnetic fields.

[Conventional technology]

Figure 3 [For example, IE Transactions on Magnetics (IEEE TRANS)
ACTIONS ON MAGNETIC8) 17)
The conventional superconducting magnet for generating a high magnetic field is shown in MAG-Volume 23 (1987), page 908. 1) In the figure.

Inside a first outer magnet (1) formed by winding an Nb-TL superconducting wire, a second outer magnet (2) formed by winding a (Nb, Tp)3Sn superconducting wire, and further inside thereof, Inner magnet made by winding V, Ga superconducting wire (3
) are placed. Inner magnet (3) is In5it
It consists of a V3Ga part (8a) (!3b) made by the method and a V, Ga part (8c) made by the SDP method. These outer magnets (1), (2) and inner magnet) (3) t'! , liquid helium (not shown) V
C: Immersion cooling. The outer magnets (1) and (2) are for generating a bias magnetic field, and the inner magnet (3) is for generating a high magnetic field.

Next, the characteristics of the above magnet system will be explained.

FIG. 4 is a diagram showing the operating characteristics of the first outer magnet (1) and the second outer magnet (2) shown on page 909 of the above-mentioned document at a liquid helium concentration of 4.2. That is, the first outer coil (1) generates a magnetic field of 6.9 T (Tesla) on the magnet center axis at an operating current of 1) 80 A. Similarly, the second outer coil (2) is on the center axis at the operating current of L180A.7. A magnetic field of B T is generated, and the combined magnetic field of both is L 4.2 on the central axis.
It becomes T. FIG. 5 shows the operating characteristics of the inner magnet (3) shown on page 910 of the above-mentioned document, and the In 5ftu V3Ga portions (8a) and (8b) of the inner coil (3) have an operating current of 1! Two magnetic fields at ll0A, 5DPV3
Ga, (3c) generates a magnetic field of 1.9 T on the central axis at the same operating current. Therefore, the first. The bias magnetic field from the second outer coil (L), (2) and the inner coil (3)
) can generate a total magnetic field of ts, t'r on the central axis.

In Figures 4 and 5, the construction. -H curve is a certain magnetic field (
In H), what is the upper limit current value (critical current IC) that can flow through the coil? : As shown. In both figures, is the critical current? It is designed to have a margin without setting it as the operating current. The reason for this is as follows. That is, when the operating current exceeds the critical current, a superconducting breakdown phenomenon called quench occurs. If a superconducting material is kept in a superconducting state, its electrical resistance is zero, but when superconductivity breaks down, its resistance increases by more than three orders of magnitude compared to metals such as copper.

On the other hand, superconducting magnets take advantage of the fact that the electrical resistance of superconducting wire is zero, and can be used to create a large army of Kanashi! (I) is flowing, so it's one! -It has a large amount of energy equivalent to L-engine 2. Here L is inductance. This energy is converted into Joule heat generation due to the high resistance of the part where the superconductor has broken down, causing the temperature to rise and lead to an accident in which the superconductor wire burns out. For the reasons mentioned above, superconducting magnets are generally designed so that the critical current is not set as the operating current, but about 50% of the critical current value is set as the operating current with some margin.

As a supplementary explanation, the magnetic field at which the critical current becomes zero is called a critical magnetic field.

[Problem that the invention seeks to solve]

Conventional superconducting magnet devices use V3Ga as the material for the inner coil of the high magnetic field generation part, but as shown in Figure 5, the critical current of V3Ga is .

It decreases rapidly on the magnetic field side higher than about 18T.

Either it is not possible to fabricate a coil for high magnetic fields higher than L8T, or it is necessary to lower the temperature of liquid helium to 1.8 K, as shown in the above literature (in this case, the critical magnetic field increases). Although it is possible to generate even higher magnetic fields, there is a problem in that the cryogenic cooling system has a complicated configuration.

This invention was made in order to solve the above-mentioned problems, and it is a superconducting magnet device that can generate a higher magnetic field at a normal 4.2 level without lowering the temperature of liquid helium. The purpose is to obtain.

Means for Solving Problem C] The superconducting magnet device according to the present invention uses an oxide-based superconductor such as a Y-Ba-Cu system, which is a so-called high-temperature superconductor, as a superconductor for an inner magnet for generating a high magnetic field. using the body.

[Effect]

In this invention, since the oxide-based superconductor has a large critical magnetic field of 80 T or more at liquid helium temperature, it is possible to manufacture a superconducting magnet with a central magnetic field exceeding 1874 T.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

In Figure 1, the outer magnets are
).

(2) Both constitute a bias magnetic field generating magnet (4) that generates a bias magnetic field. inner magneso)
(5) kZ A superconducting magnet for high magnetic fields is formed by winding a Y-Ba-Cu based oxide superconductor.

Next, the effect will be explained. Figure 2 is from the Japanese Journal of Applied Physics (JAPA).
81 JOURNAL OF APPLIED P
The Jc-B characteristics of the Y-Ba-Cu oxide shown on page L866 of HYSIC8) Volume 26 (1987) are shown, and the critical current density (Jc) with respect to the magnetic field (B) is shown.

From this figure, the critical current density (Jc) of the same material rapidly decreases as the magnetic field increases at a temperature of 77, but at a temperature of 4.2, the current density almost decreases due to the magnetic field for a magnetic field of about 2 T or more. do not. Article L475 of the above-mentioned document
Table 1 on page 1 shows that the critical magnetic field of the same material at 0 (zero) K is tto'r. From the above two literature descriptions, it is estimated that the critical magnetic field of the same substance at liquid helium temperature of 4.2 is 80T or more, and in the magnetic field region of 18T to 50T, it is sufficient to suppress the critical current by about 50%. It becomes possible to obtain an operating current for the superconducting inner coil with a sufficient margin.

In the above example, Y-B was used as the oxide superconductor.
For example, an a-Cu-based superconductor was mentioned.

Other oxide-based superconductors such as 5r-La-Cu-based superconductors may also be used.

Further, although the outer magnet has a two-layer structure and the high magnetic field superconducting magnet has a one-layer structure, both may have a multilayer structure. In addition, the bias magnetic field generating coil may be a copper coil provided in a room temperature space, or a variety of coils cooled with liquid nitrogen.

Furthermore, in the above embodiment, the coil for generating a high magnetic field has a simple winding structure, but as shown in FIG. That's true.

〔Effect of the invention〕

As described above, according to the present invention, since an oxide-based superconductor with a high critical magnetic field is used as a superconductor for a superconducting magnet for high magnetic fields, at the liquid helium temperature in 4.2, In the magnetic field region, without any reduction in critical current.

This has the effect of providing excellent high magnetic field characteristics.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention, with FIG. 1 being a sectional view and FIG. 2 being a critical current density characteristic diagram of an oxide superconductor. Are Figures 3 to 6 conventional superconducting magnet devices? show,
FIG. 8 is a sectional view, FIG. 4 is a characteristic diagram of a magnet for generating a magnetic field, and FIG. 5 is a characteristic diagram of a superconductor for high magnetic field use. (4)・Magnet for generating fist bias magnetic field, (5)・・
Superconducting magnet for high magnetic fields. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (3)

[Claims] (1) A superconducting magnet device comprising a magnet for generating a bias magnetic field and a superconducting magnet for generating a high magnetic field, which is provided inside the magnet for generating a bias magnetic field and uses an oxide superconductor as a superconducting material. (2) The superconducting magnet device according to claim 1, wherein the superconducting magnet for generating a high magnetic field is immersed and cooled in liquid helium. (3) The superconducting magnet device according to claim 1, wherein the oxide-based superconductor is a Y-Ba-Cu-based superconductor.