JPH0356063Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a laminated insulation structure for cryogenic temperatures that prevents the generation of eddy currents.

(Prior art) A device that utilizes superconductivity, such as a superconducting coil, is housed together with liquid helium in the inner container of a double-structured container consisting of an inner container and an outer container. A vacuum is created in the space, and a layer of laminated insulation material is provided in that space to keep it cold.The laminated insulation material usually uses a plastic film with a metal such as aluminum vapor-deposited on the entire surface as a reflective film, and this reflective film and heat conduction. It has a structure in which spacers with a small ratio, for example, plastic net-like spacers are alternately stacked.

(Problems to be solved by the invention) Recently, devices using superconducting coils and superconducting elements that utilize alternating current electromagnetic fields, high-frequency electromagnetic fields, or pulsed electromagnetic fields have appeared. These devices are particularly sensitive to energy loss and unnecessary disturbance of electromagnetic fields, and to prevent these situations from occurring, the reflective coating of the laminated insulation material used to keep the devices cool is coated with metal. It is necessary to take measures to prevent eddy currents from occurring in the parts.

(Means and effects for solving the problem) Generally, changes in magnetic flux generated during equipment operation cause unnecessary eddy currents in surrounding conductors, causing energy loss, and the eddy currents also cause energy loss. This causes the inconvenience that the magnetic field is disturbed. The eddy current loss is
If the electromotive force that causes the eddy current is e and the electrical resistance of the eddy current path is r, then it is expressed as e ² /r. Therefore, increasing r reduces eddy current losses.
The present invention is an attempt to increase r.

In other words, the present invention provides an ultra-low temperature system in which a laminated insulation material layer formed by alternately stacking metal-deposited plastic films such as aluminum and spacers with low thermal conductivity is provided in the vacuum space between the inner container and the outer container. A laminated insulation material for eddy current, characterized in that slits that are not deposited are formed on one or both sides of the plastic film at appropriate intervals, and the slits are laminated so that the slits do not overlap above and below. The content includes a laminated insulation structure for extremely low temperatures that prevents this from occurring. A detailed explanation will be given below with reference to the drawings.

FIG. 1 shows an example of single-sided metal deposition, in which a reflective film 1 is a plastic film in which non-evaporated slits 3 form a striped pattern, and when laminating this and a spacer 4, the slits 3 do not overlap vertically. It is a perspective view of an example of the laminated heat insulating material of this invention which is laminated|stacked like this.

As a plastic material for low-temperature insulation, polyester film is desirable because of its heat resistance, cold resistance, low water absorption, and ease of handling. The slit portions 3 can be easily formed at appropriate intervals by masking or the like, where no metal is deposited. The slits 3 are preferably formed in a striped or lattice pattern over the entire surface of the plastic film. When laminating the reflective film, by making sure that the non-evaporated slits do not overlap on the upper and lower sides, it is possible to prevent radiation from passing through the laminated layers as much as possible, and to prevent changes in the magnetic field due to the presence of the slits. It is also possible to make it difficult for eddy currents to occur in the metal-deposited portion of the reflective film.

FIG. 2 is an example of a metal vapor deposited reflective film on both the front and back sides.
Slit portions 3, 3' with a non-evaporated striped pattern are formed on both the front and back surfaces. Moreover, it shows that the slit portion 3 on the front surface and the slit portion 3' on the back surface are prevented from overlapping. Figure 3 shows a reflective film with metal vapor deposited on both the front and back sides, with non-deposited grid pattern slits 3 on both the front and back sides.
3' is attached, and the slit portion 3 on the front surface and the slit portion 3' on the back surface do not overlap in the longitudinal direction.

In FIG. 4, only one reflective film 1 having non-evaporated striped pattern slits 3 in the laminated heat insulating material is shown for convenience. An eddy current 5 should be generated as shown by the dotted line, but in the present invention, due to the effect of the vapor-deposited slit portion 3, almost all of r→∞, and the generation of eddy current can be prevented. Although FIG. 5 shows only one reflective film having an undeposited striped pattern slit part in the hollow laminated heat insulating material surrounding the cylindrical container, the changing magnetic flux penetrates this hollow part, and the reflective film 1 By placing the non-evaporated slit portion 3 parallel to the magnetic flux, an eddy current 5 as shown by the dotted line would be generated along the circumference of the hollow cylinder in the case of conventional full-surface evaporation, but the slit portion 3 of the present invention Due to the effect, r becomes almost ∞, which prevents the generation of eddy current. In Figure 6, one reflection film 1 with a non-deposited lattice pattern is shown in the laminated insulation material surrounding the spherical container, but no matter which direction the changing magnetic flux passes through the laminated insulation material, the non-deposited lattice pattern remains The effect of the slit portion 3 can suppress the possibility of generation of eddy currents in all directions.

[Brief explanation of the drawing]

Figure 1 is a perspective view of a laminated insulation material according to one example of the present invention, and Figure 2
3 is an explanatory plan view of an example of a metal-deposited reflective film on both the front and back surfaces, and FIGS. 4, 5, and 6 are laminated insulation materials of the present invention (however, only one reflective film is shown). It is an explanatory diagram of the usage example of. 1... Reflective film, 2... Metal vapor deposition part, 3, 3'...
...Non-evaporation slit portion, 4...Spacer, 5...
Eddy current that should occur if there is no evaporation-free slit section.

Claims (1)

[Claims for Utility Model Registration] (1) Laminated heat insulation formed by alternately stacking metal-deposited plastic films such as aluminum and spacers with low thermal conductivity in the vacuum space between the inner container and the outer container. In a laminated insulation material for cryogenic use with a layer of plastic film, vapor-deposition-free slits are formed on one or both sides of the plastic film at appropriate intervals, and the slits are stacked so that they do not overlap above and below. A laminated insulation structure for extremely low temperatures that prevents the generation of eddy currents. (2) The laminated heat insulating structure according to claim 1, wherein the non-evaporated slit portions form a striped pattern or a lattice pattern. (3) In the case of metal vapor deposition on both the front and back surfaces of a plastic film, the laminated heat insulating structure according to claim 1 or 2, which is formed so that the undeposited slits do not overlap on the front and back surfaces.