JPH0511646B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a superconducting device, and particularly to a superconducting device suitable for a medical nuclear magnetic resonance computer tomography device (hereinafter referred to as an MRI device).

[Conventional technology]

It is generally known that when certain metals are brought to an extremely low temperature, they exhibit a so-called superconducting state in which the electrical resistance becomes zero. By utilizing this phenomenon, a strong and stable static magnetic field can be obtained without loss of power. Superconducting coils that take advantage of this feature have been adopted in various fields, and in particular, their application to medical MRI equipment, which requires a highly uniform and highly stable static magnetic field, has been in the spotlight. Among this type of devices, horizontal superconducting devices in which the center axis of the magnetic field is installed horizontally are widely adopted because of the ease of use of the generated static magnetic field space.
This is shown in FIG.

The superconducting coil 20 is immersed in liquid helium in the helium container 1 because it can operate stably for the first time in liquid helium (4.2K), which is a cryogenic refrigerant. This liquid helium must be kept at room temperature (300K) and thermally isolated from heat intrusion from the outside, and is usually kept in a helium container 1.
Around 20K gas helium shield plate 2,
It is covered with a liquid nitrogen shield plate 3 of approximately 80K, and is further housed in an insulated vacuum container 4, so that the amount of heat intrusion is suppressed by vacuum insulation, and the amount of evaporation of expensive liquid helium is suppressed as much as possible.

Further, since the liquid helium in the helium container 1 evaporates, it is necessary to replenish the decreased amount or to release the evaporated gas helium to the outside. Furthermore, in order to operate the superconducting coil 20, it is necessary to supply current from outside at room temperature. For this reason, measurement leads to measure the level of liquid helium, injection tubes to inject liquid helium, discharge tubes to release evaporated gas helium to the outside, and power leads for current flow are required. Therefore, a cryogenic refrigerant injection port 6 is configured. The above-mentioned measurement lead, liquid helium injection pipe, gas helium discharge pipe, and power lead are connected to the helium container 1 from outside at room temperature using this cryogenic refrigerant injection port 6.
The inner cylinder 7 to be introduced into the helium container 7 has a sufficiently large heat conduction length in order to reduce as much as possible the heat intrusion from the room temperature part (approximately 300K) to the helium container 1 in the cryogenic state.
Thermal anchor 8 from the 20K gas helium shield plate 2 and the approximately 80K liquid nitrogen shield plate 3,
There are 9.

Therefore, this cryogenic refrigerant injection port 6 makes it difficult to accommodate it in a narrow room such as a hospital. Therefore, the cryogenic refrigerant injection port 6 is inclined in the circumferential direction of the device as shown. However, the thermal anchors 8 and 9 were installed perpendicularly to the inner cylinder 7, as in the case where a cryogenic refrigerant injection port is formed vertically. This is the heat transfer distance from the outside at room temperature to the thermal anchor 9 at 80K, and
Heat transfer distance from 80K thermal anchor 9 to 20K thermal anchor 8, and further from thermal anchor 8
This is to maximize the heat transfer distance to the cryogenic part of 4.2K.

[Problems to be solved by the invention]

Since the conventional horizontal superconducting device had the above-mentioned configuration, the helium gas in the inner cylinder 7, which has a low physical temperature, accumulates in the downward vertical direction due to gravity, and from now on, the helium with a high temperature accumulates in the upper part. This was made clear through the study. Therefore, the temperature distribution of the inner cylinder 7 does not have isothermal lines perpendicular to the axis of the inner cylinder 7, but due to heat exchange with the gas helium, the temperature distribution In other words, it was found that there are isothermal lines in the horizontal direction. Therefore, in the case where the thermal anchors 8 and 9 are constructed in a direction perpendicular to the axis of the inner cylinder 7 as in the past, the thermal anchors 8 and 9 are connected by convection and heat exchange of gas helium from the portion located below in the vertical direction of gravity. The drawback was that heat could directly enter the cryogenic area.

Therefore, as shown in FIG. 6, the thermal anchors 8 and 9 of the inner cylinder 7 are installed in a substantially horizontal direction, and direct heat intrusion into the cryogenic part occurs due to the convection and heat exchange of gas helium within the inner cylinder 7. It has been proposed by the same applicant as the present application to avoid this.

However, as shown in FIG. 7, which is a cross-sectional view taken along the - line in FIG. was used as the gas helium discharge tube 21, so the diameter of the inner cylinder 7 was set to D.
In this case, there was a problem that ΔL would be longer than the conventional vertically installed cryogenic refrigerant injection port.

The present invention aims to solve this problem, and its purpose is to provide a superconducting device having a cryogenic refrigerant injection port that suppresses heat intrusion into the cryogenic part.

[Means for solving problems]

In order to achieve the above object, the present invention forms at least two inner cylinders smaller than conventional ones, and divides and arranges a power lead, a cryogenic refrigerant injection pipe, and a measurement lead in these inner cylinders. The present invention is characterized in that a gas discharge portion is formed between the cylinder and something disposed inside the cylinder, and a thermal anchor formed approximately horizontally is provided outside each of the inner cylinders.

[Effect]

Since the present invention has the above-described configuration, when the thermal anchor is formed almost horizontally on the outside of the inner cylinder divided into a plurality of parts, the part formed at the lower part of the thermal anchor in the vertical direction of gravity, that is, the conventional △L becomes small, and it is possible to suppress heat from entering the cryogenic part.

〔Example〕

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

FIG. 1 shows a horizontally placed superconducting device, which is similar in schematic structure to a conventional device.

The superconducting coil 20 is arranged so that the central axis of the magnetic field is substantially horizontal, and the superconducting coil 20
immersed in cryogenic refrigerant inside. A heat insulating shield plate consisting of a gas helium shield plate 2 and a liquid nitrogen shield plate 3 is provided to cover the periphery of the cryogenic refrigerant container 1, and this heat insulating shield plate allows the leakage of the cryogenic refrigerant from the room temperature outside into the cryogenic refrigerant container 1. heat intrusion is prevented. Furthermore, a heat insulating vacuum container 4 is arranged around the outer periphery. Cryogenic refrigerant container 1
The cryogenic refrigerant injection port 6 is inclined in the circumferential direction, and in this embodiment, the inclination angle is approximately 45°. This cryogenic refrigerant injection port 6 is provided with an inner cylinder whose details will be described later, and thermal anchors 8 and 9 that connect this inner cylinder and a heat insulating shield plate, and the thermal anchors 8 and 9 are placed almost horizontally. It is formed. This is an enlarged view of the main parts of FIG. 1 showing the detailed configuration of the inner cylinder, the power lead 11, the cryogenic refrigerant injection pipe 12, the measurement lead 13, the gas discharge part, and the thermal anchors 8 and 9 arranged inside the inner cylinder. This will be explained with reference to FIGS. 2 and 3.

In particular, as can be seen from FIG. 3, the inner cylinder connected to the thermal anchors 8, 9 on the outside has three inner cylinders 7a, 7b, 7c smaller than the conventional one. Each inner cylinder 7a, 7b, 7c has a power lead 1, respectively.
1. A cryogenic refrigerant injection pipe 12 and a measurement lead 13 are arranged, and the gap formed between these inner cylinders and what is arranged inside becomes a gas release part, that is, a conventional gas helium release pipe. There is. Therefore, the diameter D of each inner cylinder 7a, 7b, 7c is smaller than before, and if the thermal anchors 8, 9 are formed almost horizontally, △L will be smaller than before the improvement shown in FIG. becomes smaller. Therefore, the cryogenic refrigerant injection port 6 has approximately the same axial length as when its axis is substantially perpendicular, and an economical superconducting device with less evaporation of the cryogenic refrigerant can be achieved.

FIG. 4 is a cross-sectional view of a cryogenic refrigerant injection port 6 according to another embodiment of the present invention. As can be seen from a comparison with FIG. 3, in this embodiment, a power lead 11, a cryogenic refrigerant injection pipe 12, and a measurement lead 13 are arranged within the two inner cylinders 7a and 7b. Cryogenic refrigerant injection pipe 12 and measurement lead 13
are thinner than the power lead 11, so they are arranged together in one inner cylinder 7b.

As can be seen from this embodiment, it is sufficient if a plurality of inner cylinders are provided, and the power lead 11,
The cryogenic refrigerant injection pipe 12 and the measurement leads 13 may be arranged in a distributed manner. Generally, the measurement lead 13 and the power lead 11 have an insertion tube located inside the introduction tube, but they may be placed in the same insertion tube.

〔Effect of the invention〕

As explained above, in the present invention, a plurality of inner cylinders are provided, and the power lead, the cryogenic refrigerant injection pipe, and the measurement lead are arranged separately within these inner cylinders.
Even if the cryogenic refrigerant injection port is arranged diagonally and the thermal anchor is configured almost horizontally, the length of the lower part of the cryogenic refrigerant injection port can be suppressed, thereby reducing the amount of heat intrusion. At the same time, a superconducting device in which the amount of evaporation of cryogenic refrigerant is small can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a superconducting device according to the present invention;
2 is an enlarged view of the main part of FIG. 1, FIG. 3 is a sectional view taken along the - line in FIG. 2, and FIG. 4 is a sectional view of the main part of a superconducting device according to another embodiment of the present invention. 5 is a longitudinal cross-sectional view of a conventional superconducting device, FIG. 6 is a cross-sectional view of a main part of the previously proposed superconducting device, and FIG. 7 is a cross-sectional view taken along the line - in FIG. 6. 1...Cryogenic refrigerant container, 2...Gas helium shield plate, 3...Liquid nitrogen shield plate, 4...Insulated vacuum container, 6...Cryogenic refrigerant injection port, 7
a, 7b, 7c... Inner cylinder, 8, 9... Thermal anchor, 11... Power lead, 12... Cryogenic refrigerant injection pipe, 13... Measurement lead.

Claims (1)

[Claims] 1. A superconducting coil arranged so that the central axis of the magnetic field is in the horizontal direction, a substantially cylindrical cryogenic refrigerant container in which the superconducting coil is immersed in a cryogenic refrigerant, and A heat insulating shield plate that covers the periphery of the low temperature refrigerant container and thermally isolates it from the outside, a heat insulating vacuum container that houses the whole of these, an inner cylinder that communicates the cryogenic refrigerant container with the room temperature outside, the heat insulating shield plate and the inner cylinder. A cryogenic refrigerant injection port having a thermal anchor connected to a cylinder, a power lead, a cryogenic refrigerant injection pipe, and a measurement lead arranged in the inner cylinder, the cryogenic refrigerant injection port having a thermal anchor connected to the cylinder, In the superconducting device provided inclined in the circumferential direction of the refrigerant container, the thermal anchor is arranged substantially horizontally within the inclined cryogenic refrigerant injection port, and at least two inner cylinders are formed,
The power lead, the cryogenic refrigerant injection pipe, and the measurement lead are arranged separately in these inner cylinders,
A superconducting device characterized in that a gas discharge part is formed between each of the inner cylinders and something arranged inside the inner cylinder. 2. In the device described in claim 1, two inner cylinders are formed, and the power lead is disposed in one inner cylinder, and the cryogenic refrigerant injection pipe and the measurement tube are arranged in the other inner cylinder. A superconducting device characterized by the arrangement of leads.