JP3788648B2 - Cryostat - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cryostat having a liquid helium reservoir for immersing and cooling a superconducting coil independent of the outer container in an outer container of a cryostat that holds the superconducting coil at a cryogenic temperature.
[0002]
[Prior art]
In order to reduce the amount of liquid helium for cooling the superconducting coil and make the operation of the superconducting coil easier, a coil independent of this outer container is placed in the outer container of the cryostat that holds the superconducting coil at a cryogenic temperature. A cryostat having a liquid helium reservoir for immersion cooling has been proposed.
[0003]
In such a cryostat, the gas helium space is increased instead of reducing the volume of liquid helium, and the convection of gas helium is intense compared to a cryostat having no liquid helium reservoir.
[0004]
[Problems to be solved by the invention]
In a cryostat having a liquid helium reservoir for immersing and cooling a coil independent of this external container inside the cryostat's external container that holds the superconducting coil at a cryogenic temperature, the gas helium space increases and the convection of gas helium becomes intense. ing.
[0005]
For this reason, in such a cryostat, heat penetration due to gas helium convection between the outer container and the liquid helium reservoir increases. When the heat intrusion into the cryostat increases, there are problems such as an increase in the consumption of liquid helium, an increase in the load of the helium refrigerating machine connected to the cryostat, or a reduction in the continuous operation time.
[0006]
An object of the present invention is to solve the above-described problems, and is to provide a cryostat with less heat penetration into liquid helium by reducing gas convection itself or heat penetration due to gas convection. .
[0007]
[Means for Solving the Problems]
In the cryostat according to the first aspect of the present invention, the liquid helium reservoir is placed on a horizontal support member provided in the outer container, and between the outer container and the liquid helium reservoir and of the horizontal support member. A convection prevention plate for preventing helium gas convection is provided from the lower part to the upper part of the liquid helium reservoir . That is, the gas helium space can be subdivided by the convection prevention plate provided between the external container and the liquid helium reservoir. As a result, the temperature difference in the same space can be reduced, and the convection itself can be reduced.
[0010]
In the cryostat according to a second aspect of the present invention, a partition plate is provided along the inner surface of the outer container, and the evaporated helium gas from the liquid helium reservoir is evaporated between the partition plate and the inner surface of the outer container. It has a structure in which the inner surface of the outer container is cooled by being led out to the helium gas cooling channel through a lead-out pipe . With this structure, the liquid helium reservoir whose temperature has risen due to intrusion heat can be cooled by the sensible heat of the evaporated helium gas, so that the convection of the gas helium can be greatly relaxed.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
A cryostat according to a first embodiment of the present invention will be described with reference to FIG.
[0012]
In FIG. 1, reference numeral 1 denotes an external container of a cryostat, and a liquid helium reservoir 2 is disposed in the external container 1. Inside the liquid helium reservoir 2 are housed a superconducting coil 3 and liquid helium 4 for holding the superconducting coil 3 at a very low temperature. For this reason, the liquid helium reservoir 2 is maintained at substantially the liquid helium temperature.
[0013]
A heat insulating vacuum layer 5 is provided in the wall of the outer container 1, and the upper end opening of the outer container 1 is sealed by an upper flange portion 6. In the outer container 1, a plurality of convection prevention plates 7 are stacked in a shelf shape outside the liquid helium reservoir 2. The liquid helium reservoir 2 is mounted and fixed on a horizontal support member 14, and the horizontal support member 14 is connected to a vertical support member 15 suspended from the upper flange portion 6.
[0014]
Thus, the inner surface temperature of the outer container 1 becomes higher than that of the liquid helium reservoir 2 due to radiant heat through the heat insulating vacuum layer 5 and intrusion heat due to heat conduction from the cryostat upper flange portion 6. Due to this temperature difference, convection of the evaporated helium gas is induced inside the cryostat. Since the convection of helium gas increases the heat penetration into the liquid helium reservoir 2 or the liquid helium 4 itself, the evaporation of the liquid helium further increases.
[0015]
However, since the convection prevention plate 7 is provided between the cryostat outer container 1 and the liquid helium reservoir 2 in the present embodiment, the space between the cryostat outer container 1 and the liquid helium reservoir 2 is provided by the convection prevention plate 7. Subdivided and convection of gas helium is suppressed. Therefore, evaporation of the liquid helium 4 can be suppressed.
[0016]
Next, a cryostat according to a second embodiment of the present invention will be described with reference to FIG.
[0017]
In the present embodiment, as in the first embodiment, a liquid helium reservoir 2 is provided in the cryostat outer container 1, and a superconducting coil 3 and liquid helium 4 are accommodated in the liquid helium reservoir 2. The upper end opening of the liquid helium reservoir 2 is sealed with a lid 8. The liquid helium reservoir 2 is mounted and fixed on a horizontal support member 14, and the horizontal support member 14 is connected to a vertical support member 15 suspended from the upper flange portion 6.
[0018]
Thus, in the case where the lid 8 is not provided, convection of the evaporated helium gas is induced in the outer container 1, but by providing the lid 8 at the upper opening of the liquid helium reservoir 2 according to the present embodiment and closing it. The convection of the gas helium in the external container 1 is suppressed from coming into direct contact with the liquid helium 4 in the liquid helium reservoir 2, and the evaporation of the liquid helium 4 can be suppressed.
[0019]
Next, a cryostat according to a third embodiment of the present invention will be described with reference to FIG.
[0020]
In the present embodiment, a liquid helium reservoir 2 is disposed in an external container 1 of a cryostat, and a superconducting coil 3 and liquid helium 4 are accommodated in the liquid helium reservoir 2. The outer container 1 is provided with a heat insulating vacuum layer 5. A shield plate 9 is provided in the outer container 1 so as to surround the entire outside of the liquid helium reservoir 2. The liquid helium reservoir 2 is mounted and fixed on a horizontal support member 14, and the horizontal support member 14 is connected to a vertical support member 15 suspended from the upper flange portion 6.
[0021]
Here, the liquid helium reservoir 2 is maintained at substantially the liquid helium temperature. However, when the shield plate 9 is not provided, the inner surface temperature of the outer container 1 is the radiant heat through the heat insulating vacuum layer 5 or the cryostat upper flange portion. 6 is higher than that of the liquid helium reservoir 2 due to intrusion heat due to heat conduction or the like.
[0022]
However, according to the present embodiment, the temperature distribution in the outer container 1 is made uniform by the shield plate 9 provided between the liquid helium reservoir 2 and the outer container 1, so that convection of gas helium is suppressed, The direct contact of the gas helium with the liquid helium 4 is suppressed, and the evaporation of the liquid helium can be suppressed.
[0023]
Next, a cryostat according to a fourth embodiment of the present invention will be described with reference to FIG.
[0024]
In this embodiment, a liquid helium reservoir 2 is disposed in an outer container 1 of a cryostat, and a superconducting coil 3 and liquid helium 4 are accommodated in the liquid helium reservoir 2. The outer container 1 is provided with a heat insulating vacuum layer 5. The upper end opening of the liquid helium reservoir 2 is sealed with a lid 8. An outer container inner surface cooling mechanism 10 is provided between the outer container 1 and the liquid helium reservoir 2. The liquid helium reservoir 2 is mounted and fixed on a horizontal support member 14, and the horizontal support member 14 is connected to a vertical support member 15 suspended from the upper flange portion 6.
[0025]
The outer container inner surface cooling mechanism 10 includes a siphon-like outlet pipe 11 attached to the lid 8 and a partition plate 12 provided along the outer container inner face communicating with the outlet side of the outlet pipe 11. An evaporative helium gas cooling channel 13 is formed between the partition plate 12 and the inner surface of the outer container 1. The lid 8 is for preventing the convective gas helium from coming into direct contact with the liquid helium 4 in the liquid helium reservoir 2.
[0026]
According to the present embodiment, the evaporative gas in the liquid helium reservoir 2 flows out from the outlet pipe 11 of the external container inner surface cooling mechanism 10 and blows out to the evaporative helium gas cooling flow path 13 in the partition plate 12. The inner surface of the outer container 1 is cooled by flowing 13. Therefore, since the inner surface of the outer container 1 can be cooled by the evaporated helium gas from the liquid helium reservoir 2, the temperature difference between the inner surface of the outer container 1 and the liquid helium reservoir 2 is alleviated, and convection of gas helium is achieved. Can be greatly relaxed.
[0027]
【The invention's effect】
According to the first aspect of the present invention, the gas helium space can be subdivided by the convection prevention plate provided between the outer container and the liquid helium reservoir. Thereby, the temperature difference in the same space can be reduced, and the convection itself can be reduced.
[0030]
According to the invention of claim 2 , the convection of the gas helium can be greatly relaxed by cooling the inner surface of the outer container using the evaporated helium gas from the liquid helium reservoir.
[0031]
Thus, in the present invention, the consumption of liquid helium and the load on the helium refrigerating machine can be reduced by reducing the heat intrusion into the cryostat and the evaporation of liquid helium.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view schematically showing a part of a first embodiment of a cryostat according to the present invention.
FIG. 2 is a longitudinal sectional view schematically showing a part of a second embodiment of a cryostat according to the present invention.
FIG. 3 is a longitudinal sectional view schematically showing a part of a third embodiment of a cryostat according to the present invention.
FIG. 4 is a longitudinal sectional view schematically showing a part of a fourth embodiment of a cryostat according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... External container, 2 ... Liquid helium reservoir, 3 ... Superconducting coil, 4 ... Liquid helium, 5 ... Adiabatic vacuum layer, 6 ... Upper flange part, 7 ... Convection prevention plate, 8 ... Cover, 9 ... Shield plate, 10 ... External container inner surface cooling mechanism, 11 ... outlet pipe, 12 ... partition plate, 13 ... evaporative helium gas cooling channel, 14 ... horizontal support member, 15 ... vertical support member.

Claims (2)

In a cryostat having a liquid helium reservoir for immersing and cooling the superconducting coil independent of the external container in an external container of the cryostat that holds the superconducting coil at a cryogenic temperature, the liquid helium reservoir is provided in the external container. A convection prevention plate placed on the horizontal support member and preventing helium gas convection between the inside of the outer container and the liquid helium reservoir and from a lower portion of the horizontal support member to an upper portion of the liquid helium reservoir. Cryostat characterized by. In a cryostat having a liquid helium reservoir for immersing and cooling the superconducting coil independent of the outer container in the outer container of the cryostat that holds the superconducting coil at a cryogenic temperature, a partition plate is provided along the inner surface of the outer container. derives through the outlet pipe evaporated helium gas from the liquid helium reservoir to the evaporating helium gas cooling passage formed between the inner surface of the outer container and the partition plate to cool the inner surface of the outer container A cryostat characterized by that.

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