JPS63192208A - Bobbin for superconducting coil - Google Patents

Abstract

PURPOSE:To avoid the local concentration of coil energy, and to prevent the burning of a coil by coating at least a coil contact surface in a bobbin body with a good thermal conductive inorganic insulating thin-film consisting of diamond, etc. CONSTITUTION:A bobbin type bobbin body 1 is composed of stainless, and coil contact surfaces, the outer surface of a winding drum 1a and the inner surfaces of both-end flanges 1b, are coated with a diamond thin-film 2. On a superconducting coil for ACs or pulses in which eddy current loss must be removed, the body 1 is formed by FRP, and the coil contact surfaces are coated with the diamond thin-film 2. Accordingly, the inorganic insulating thin-film being coated onto the coil contact surfaces in the body and having high thermal conductivity quickly transfers heat to other sections on the partial quenching of a coil and a quenching region is spread rapidly, thus preventing the generation of the local concentration of energy, then obviating the burning of the coil resulting from the local concentration.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for coils that is effective in preventing burnout of superconducting coils.

[Conventional technology]

As the winding frame for the Mi1tR coil, those made of stainless steel and those made of FRP made of glass fiber impregnated with epoxy resin are generally used.

The stainless steel winding frame was chosen for its mechanical strength and non-magnetic properties, and the contact surface with the coil is insulated with FRP sheets, Teflon sheets, etc.

On the other hand, in the case of AC magnets or pulsed magnets, if there is a metal object near the coil, eddy current loss will occur and performance will deteriorate, so FRP winding frames are often used as a countermeasure against eddy currents. , In the case of FRP@frame, no particular consideration is given to electrical insulation treatment between the winding wire and the winding frame.

[Problem that the invention seeks to solve]

In magnets, which are a typical application for superconducting coils, quenching occurs due to minute internal disturbances, such as subtle movement of the wire due to electromagnetic force or the generation of bubbles in liquid helium for cooling. If the quench occurs locally, the coil energy W - noise LI2 (L: coil inductance, ■ = coil current) is concentrated in such a local area, and the coil may be burnt out due to heat generation.

Therefore, in the case of superconducting magnets in particular, as a countermeasure against coil burnout, the heat locally generated during quenching is instantly propagated to the surrounding area to expand the quench area, and consideration must be given to prevent coil energy dissipation from being concentrated locally. It is desirable to do so.

However, the thermal conductivity of stainless steel is very low compared to other metals (several hundredths of that of copper), and that of FRP is even lower, several tenths of that of copper.

Therefore, in conventional superconducting coils using bobbins made of these materials, the propagation speed of local quenching depends on the amount and thermal conductivity of the copper used as a stabilizer in the superconducting wire. In many cases, the winding frame hardly contributes to the propagation of the quench, resulting in insufficient heat dissipation capacity and burnout.

[Means for solving problems]

This invention is characterized in that, in order to eliminate the above-mentioned problems, at least the coil contacting surface of the winding frame body is coated with a thin inorganic film of good heat conductivity such as diamond or alumina.

[Effect]

Recently, rapid progress has been made in coating techniques for thin films of artificial diamond, alumina, etc., using, for example, the chemical vapor deposition (CVD) method. These thin films have excellent electrical insulation properties (in the case of diamond, the insulation resistance is 1014Ω).
-1), and as can be seen from Figure 3, it has a characteristic that its thermal conductivity is much higher than that of copper. Therefore, in the winding frame of the present invention, the coating layer of diamond or the like provided on the coil contact surface of the main body plays a major role in heat propagation when local quench occurs.
Rapidly expand the quench area. As a result, local concentration of coil energy is avoided and burnout of the coil is prevented.

〔Example〕

Figure 1 shows a bobbin-type winding frame used in a superconducting solenoid coil for generating high magnetic fields for applications such as MRI (IF air resonance computer tomography imaging) and crystal pulling furnaces, and its main body 1 is made of stainless steel. Consists of. A diamond thin film 2 is coated on the coil contacting surfaces of the main body 1, that is, the outer surface of the winding drum 1a and the inner surfaces of the flanges 1b at both ends.

In the case of an AC or pulse superconducting coil that requires elimination of eddy current loss, the main body 1 is formed of the above-mentioned FRP, and the contact surface of the coil is coated with a diamond thin film 2.

Figure 2 shows a winding frame used for charged particle deflection magnets in large accelerators and SORs (Synchrotron Orbital Radiation Rings), where at least the coil contacts the cylindrical body 1' that straddles saddle-shaped dipole coils. The surface is coated with a diamond thin film 2.

The thin film 2 to be coated may be made of alumina, amorphous diamond, amorphous lumina, etc. The thermal conductivity of alumina is lower than that of diamond, but higher than that of stainless steel or FRP.

Alternatively, such a thin film may be coated over the entire surface of the bobbin.

〔effect〕

As described above, according to the present invention, the inorganic insulating thin film with high thermal conductivity coated on the coil contact surface of the main body rapidly transfers heat to other parts when the coil is locally quenched, thereby spreading the quench area. Since it is expanded quickly, local concentration of energy does not occur, and burnout of the coil due to the local concentration is prevented.

In addition, since the coating thin film is an excellent electrical insulator, there is no need for insulation treatment between the winding frame and the coil, which was previously required when the winding frame was made of metal, which improves the efficiency of coil assembly. do.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 and FIG. 2 are both perspective views showing one embodiment of the present invention, and FIG. 3 is a graph showing the thermal conductivity characteristics of diamond in comparison with copper. 1.1'... Main body of the winding frame, 1a... Winding barrel, 1b... Flange, 2... Diamond thin film. Patent applicant: Sumitomo Electric Industries, Ltd. Agent: Kama 1) Text: Two thermal conductivity
(W/ic)

Claims (3)

[Claims] (1) A winding frame for a superconducting coil, which is formed by coating at least the coil contacting surface of the winding frame body with an inorganic insulating thin film of good heat conductivity such as diamond. (2) A winding frame for a superconducting coil according to claim (1), wherein the main body is made of stainless steel. (3) The winding frame for a superconducting coil according to claim (1), wherein the main body is made of FRP.