U.S. patent application number 12/134741 was filed with the patent office on 2008-12-18 for cooling system for cryogenic storage container and operating method therefor.
Invention is credited to Hisashi Isogami, Norihide Saho, Hiroyuki TANAKA.
Application Number | 20080307801 12/134741 |
Document ID | / |
Family ID | 39760815 |
Filed Date | 2008-12-18 |
United States Patent
Application |
20080307801 |
Kind Code |
A1 |
TANAKA; Hiroyuki ; et
al. |
December 18, 2008 |
COOLING SYSTEM FOR CRYOGENIC STORAGE CONTAINER AND OPERATING METHOD
THEREFOR
Abstract
A cryogenic storage container is provided with a storage
container, a vacuum container containing the storage container, and
a heat shield. The cryogenic storage container is coupled to a
cooling source equipped with a cryogenic freezer via transport
piping so that the vibration of the cryogenic freezer cannot be
directly delivered to the cryogenic storage container. The
vibration can be further reduced by providing a bellows unit for
transport piping.
Inventors: |
TANAKA; Hiroyuki; (Mito,
JP) ; Saho; Norihide; (Tsuchiura, JP) ;
Isogami; Hisashi; (Ushiku, JP) |
Correspondence
Address: |
MATTINGLY, STANGER, MALUR & BRUNDIDGE, P.C.
1800 DIAGONAL ROAD, SUITE 370
ALEXANDRIA
VA
22314
US
|
Family ID: |
39760815 |
Appl. No.: |
12/134741 |
Filed: |
June 6, 2008 |
Current U.S.
Class: |
62/51.1 |
Current CPC
Class: |
G01R 33/3804 20130101;
G01R 33/3815 20130101; H01F 6/04 20130101 |
Class at
Publication: |
62/51.1 |
International
Class: |
F25B 19/00 20060101
F25B019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 8, 2007 |
JP |
2007-153015 |
Claims
1. A cooling system for a cryogenic storage container including a
cryogenic storage container having a storage container storing an
object to be cooled as soaked in a coolant, a vacuum container
provided around the storage container and forming a vacuum tank
between the vacuum container and the storage container, and a heat
shield provided in the vacuum tank, wherein coolant piping is fixed
to the heat shield, and a coolant passing through the coolant
piping is cooled by a cryogenic freezer, comprising: a cooling
source equipped with the cryogenic storage container; and coolant
transport piping for coupling the cooling source to the cryogenic
storage container, wherein the coolant cooled by the cryogenic
freezer is delivered to the cryogenic storage container through the
transport piping.
2. The cooling system for a cryogenic storage container according
to claim 1, wherein a bellows unit is provided for at least a part
of the coolant transport piping.
3. The cooling system for a cryogenic storage container according
to claim 1, wherein the coolant transport piping is configured by
coolant piping for passing a coolant inside, and a vacuum container
surrounding the piping, and a bellows unit is provided for at least
a part of the vacuum container.
4. The cooling system for a cryogenic storage container according
to claim 3, wherein the system is fixed to a floor at any portion
of the bellows unit provided for the vacuum container in the
coolant transport piping.
5. The cooling system for a cryogenic storage container according
to claim 3, wherein a bellows unit is provided for at least a part
of the coolant piping in the coolant transport piping.
6. The cooling system for a cryogenic storage container according
to claim 1, wherein: the cryogenic storage container has a portion
provided with two heat shields and a portion provided with one heat
shield between the storage container and the vacuum container; the
cooling source is provided with a second vacuum container which is
vacuum inside, the cryogenic freezer attached to the second vacuum
container, at least one heat exchange unit provided in the second
vacuum container and attached to a coolness generation unit of the
cryogenic freezer, at least one counterflow heat exchanger provided
in the second vacuum container, and second coolant piping passing a
coolant inside; the heat exchange unit and the counterflow heat
exchanger are coupled by the second coolant piping; the coolant
transport piping has third coolant piping passing a coolant inside,
and a third vacuum container forming a vacuum tank between the
third coolant piping and the third vacuum container; and coolant
piping fixed to the heat shield, the second coolant piping provided
for the cooling source, and the third coolant piping in the coolant
transport piping are coupled.
7. The cooling system for a cryogenic storage container according
to claim 6, wherein a vacuum container configuring the cryogenic
storage container is coupled to the second vacuum container
configuring the cooling source by the third vacuum container
configuring the coolant transport piping.
8. The cooling system for a cryogenic storage container according
to claim 1, wherein the heat shield provided between the storage
container and the vacuum container has a divided structure, and the
divided heat shields are coupled by a material having lower thermal
conductivity than the heat shield.
9. An operating method for the cooling system for a cryogenic
storage container according to claim 6, wherein: in the two
provided heat shields between the storage container and the vacuum
container configuring the cryogenic storage container, a heat
shield provided on the storage container side is first cooled by a
coolant cooled by the cooling source; the coolant whose temperature
has risen by the cooling is used as a low temperature source of the
counterflow heat exchanger in the cooling source to perform heat
exchange between the temperature-risen coolant and an opposite
coolant in the counterflow heat exchanger; the coolant whose
temperature has risen by the heat exchange cools the one provided
heat shield between the storage container and the vacuum container;
and the coolant whose temperature has risen by the heat exchange
with the one provided heat shield between the storage container and
the vacuum container cools a heat shield provided on the vacuum
container side in the two provided heat shields between the storage
container and the vacuum container.
10. An operating method for the cooling system for a cryogenic
storage container according to claim 6, wherein: in the two
provided heat shields between the storage container and the vacuum
container configuring the cryogenic storage container, a heat
shield provided on the storage container side is first cooled by a
coolant cooled by the cooling source; the coolant whose temperature
has risen by the cooling cools the one provided heat shield between
the storage container and the vacuum container; the coolant whose
temperature has risen by the heat exchange with the one provided
heat shield between the storage container and the vacuum container
is used as a low temperature source of the counterflow heat
exchanger in the cooling source and heat exchange is performed
between the temperature-risen coolant and an opposite coolant in
the counterflow heat exchanger; and the coolant whose temperature
has risen by the heat exchange cools a heat shield provided on the
vacuum container side in the two provided heat shields between the
storage container and the vacuum container.
11. A cooling system for a cryogenic storage container, comprising:
a cryogenic storage container having a storage container storing a
coolant and an object to be cooled, a vacuum container provided
around the storage container and forming a vacuum tank between the
vacuum container and the storage container, and a heat shield
provided in the vacuum tank, wherein the heat shield has a portion
having two heat shields between the storage container and the
vacuum container, and a portion having one heat shield between the
storage container and the vacuum container, coolant piping is fixed
to each of the two provided heat shields and the one provided heat
shield, a different coolant other than the coolant stored in the
storage container passes through the coolant piping, and the
coolant passing through the coolant piping cools the two provided
heat shield and the one provided heat shield; a cooling source
having a second vacuum container which is vacuum inside, a
cryogenic freezer provided in the second vacuum container, at least
one heat exchange unit provided in the second vacuum container and
attached to a coolness generation unit of the cryogenic freezer, at
least one counterflow heat exchanger provided in the second vacuum
container, and second coolant piping passing a coolant inside,
wherein the heat exchange unit is coupled to the counterflow heat
exchanger via the second coolant piping; and transport piping
having third coolant piping passing a coolant inside, and a third
vacuum container forming a vacuum tank between the third vacuum
container and the third coolant piping, wherein the coolant piping
fixed to the heat shield provided in the cryogenic storage
container is coupled to the second coolant piping provided in the
cooling source via the third coolant piping, and the vacuum
container in the cryogenic storage container is coupled to the
second vacuum container in the cooling source via the third vacuum
container.
12. An operating method for a cooling system for a cryogenic
storage container, comprising: a cryogenic storage container having
a storage container storing a coolant and an object to be cooled, a
vacuum container provided around the storage container and forming
a vacuum tank between the vacuum container and the storage
container, and a heat shield provided in the vacuum tank, wherein
the heat shield has a portion having two heat shields between the
storage container and the vacuum container, and a portion having
one heat shield between the storage container and the vacuum
container, coolant piping is fixed to each of the two provided heat
shields and the one provided heat shield, a different coolant other
than the coolant stored in the storage container passes through the
coolant piping, and the coolant passing through the coolant piping
cools the two provided heat shield and the one provided heat
shield; a cooling source having a second vacuum container which is
vacuum inside, a cryogenic freezer provided in the second vacuum
container, at least one heat exchange unit provided in the second
vacuum container and attached to a coolness generation unit of the
cryogenic freezer, at least one counterflow heat exchanger provided
in the second vacuum container, and second coolant piping passing a
coolant inside, wherein the heat exchange unit is coupled to the
counterflow heat exchanger via the second coolant piping; and
transport piping having third coolant piping passing a coolant
inside, and a third vacuum container forming a vacuum tank between
the third vacuum container and the third coolant piping, in which
the coolant piping fixed to the heat shield provided in the
cryogenic storage container is coupled to the second coolant piping
provided in the cooling source via the third coolant piping, and
the vacuum container in the cryogenic storage container is coupled
to the second vacuum container in the cooling source via the third
vacuum container, wherein: in the two provided heat shields
provided between the storage container and the vacuum container in
the coolant storage container, the heat shield provided on the
storage container side is first cooled by the coolant cooled by the
cooling source; the coolant whose temperature has risen by the
cooling is used as a low temperature source of the counterflow heat
exchanger in the cooling source to perform heat exchange between
the temperature-risen coolant and an opposite coolant in the
counterflow heat exchanger; the coolant whose temperature has risen
by the heat exchange is used in cooling the one provided heat
shield between the storage container and the vacuum container; and
using the coolant whose temperature has risen by the heat exchange
with the one provided heat shield provided between the storage
container and the vacuum container, the heat shield provided on the
vacuum container side in the two provided heat shields between the
storage container and the vacuum container is cooled.
13. An operating method for a cooling system for a cryogenic
storage container, comprising: a cryogenic storage container having
a storage container storing a coolant and an object to be cooled, a
vacuum container provided around the storage container and forming
a vacuum tank between the vacuum container and the storage
container, and a heat shield provided in the vacuum tank, wherein
the heat shield has a portion having two heat shields between the
storage container and the vacuum container, and a portion having
one heat shield between the storage container and the vacuum
container, coolant piping is fixed to each of the two provided heat
shields and the one provided heat shield, a different coolant other
than the coolant stored in the storage container passes through the
coolant piping, and the coolant passing through the coolant piping
cools the two provided heat shield and the one provided heat
shield; a cooling source having a second vacuum container which is
vacuum inside, a cryogenic freezer provided in the second vacuum
container, at least one heat exchange unit provided in the second
vacuum container and attached to a coolness generation unit of the
cryogenic freezer, at least one counterflow heat exchanger provided
in the second vacuum container, and second coolant piping passing a
coolant inside, wherein the heat exchange unit is coupled to the
counterflow heat exchanger via the second coolant piping; and
transport piping having third coolant piping passing a coolant
inside, and a third vacuum container forming a vacuum tank between
the third vacuum container and the third coolant piping, in which
the coolant piping fixed to the heat shield provided in the
cryogenic storage container is coupled to the second coolant piping
provided in the cooling source via the third coolant piping, and
the vacuum container in the cryogenic storage container is coupled
to the second vacuum container in the cooling source via the third
vacuum container, wherein: in the two provided heat shields
provided between the storage container and the vacuum container in
the coolant storage container, the heat shield provided on the
storage container side is first cooled by the coolant cooled by the
cooling source; the coolant whose temperature has risen by the
cooling cools the one provided heat shield between the storage
container and the vacuum container; the coolant whose temperature
has risen by the cooling is used as a low temperature source of the
counterflow heat exchanger in the cooling source to perform heat
exchange between the temperature-risen coolant and an opposite
coolant by the counterflow heat exchanger; and the coolant whose
temperature has risen by the heat exchange cools the heat shield
provided on the vacuum container side in the two provided heat
shields between the storage container and the vacuum container.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a cooling system for a
cryogenic storage container and its operating method, and more
specifically to a cooling system for a cryogenic storage container
by using a coolant such as a liquid helium for cooling at a
cryogenic temperature and its operating method.
[0003] 2. Description of Related Art
[0004] Recently, there is an increasing demand for a device
requiring a high magnetic field such as an MRI and an NMR. Such a
device uses a superconductive magnet for generating a high magnetic
field. In addition, a device using superconductivity is applied to
measure a weak magnetic field. These objects to be cooled are
cooled as soaked in a low temperature coolant, and normally liquid
helium having a boiling point of 4.2 K (-269.degree. C.) is used as
a coolant.
[0005] Liquid helium is low in evaporation latent heat, and the
evaporation latent heat of the liquid helium under an atmospheric
pressure is 20.7 [kJ/kg] which is not more than 1/100 of the
evaporation latent heat (2257 [kJ/kg]) of water under the
atmospheric pressure, and a large amount of liquid helium
evaporates by slight heat invasion. Therefore, in a cooling system
using liquid helium, it is necessary to periodically supply liquid
helium.
[0006] A well-known method to suppress the heat invasion into the
liquid helium stored in a cryogenic container is to provide a heat
shield in a vacuum tank between a container storing liquid helium
and a vacuum container, cool the heat shield down to the
intermediate temperature between the room temperature of the vacuum
container and the temperature of the liquid helium, and prevent the
radiant heat from the vacuum container at the room temperature from
directly being delivered to the liquid helium container (for
example, refer to JP-A-2002-232030 and JP-A-2002-232029).
[0007] Normally, two heat shields are provided, and the
high-temperature side heat shield provided on the vacuum container
side is about 77 K to 200 K, and the heat shield provided on the
liquid helium storage container side is about 4.2 K to 77 K.
[0008] The sensible heat of a helium gas evaporated from liquid
helium is commonly used as a cooling source of a heat shield. In
this case, when the amount of evaporation of the liquid helium
becomes low, the flow rate of the helium gas decreases, thereby
degrading the performance of cooling the heat shield, and raising
the heat shield cooling temperature.
[0009] To provide a heat shield, it is necessary to reserve a space
to suppress contact between the heat shield and the container
storing the liquid helium, and a space to suppress contact between
the heat shield and the vacuum container. When there are two heat
shields, it is further necessary to reserve a space to prevent
contact between the inner (low temperature side) heat shield and
the outer (high temperature side) heat shield, and the distance
between an object to be cooled and provided in a container storing
liquid helium and the surface of a vacuum container is long.
[0010] In the living body magnetic measurement, since the distance
between a superconductive device as an object to be cooled and the
surface of a vacuum container largely affects the sensitivity,
there is a request to shorten the distance between the object to be
cooled and the surface of a vacuum container as much as possible.
In addition, with the superconductive magnet generating a high
magnetic field, there is a request to utilize a higher magnetic
field by shortening the distance between a superconductive magnet
as an object to be cooled and the surface of a vacuum
container.
[0011] To fulfill the requests, it is desired to obtain the
structure of a cryogenic container with the shorter distance
between an object to be cooled and the surface of a vacuum
container. In JP-A-2002-232030, there is one heat shield to shorten
the distance between a storage container and a vacuum
container.
[0012] By cooling the heat shield at a low temperature, the amount
of evaporation of liquid helium can be reduced even with one heat
shield. Therefore, a method of cooling a heat shield using a
cryogenic freezer is well known.
[0013] When a freezer is not used, the cooling source of the heat
shield is the sensible heat of the helium gas evaporated from the
liquid helium. Therefore, when there is a small amount of
evaporation, the temperature at which the helium gas cools the heat
shield rises, and the amount of radiant heat from the heat shield
increases. Without a cryogenic freezer, the heat shield temperature
and the amount of evaporation of the liquid helium depend on the
balance between the temperature of the heat shield and the heat
shield cooling function of the evaporated helium gas.
[0014] However, by using the cryogenic freezer, the heat shield can
be cooled down to a lower temperature with a smaller amount of
evaporation of the liquid helium, thereby reducing the amount of
evaporation of the liquid helium.
BRIEF SUMMARY OF THE INVENTION
[0015] The insulating function of a cryogenic coolant storage
container is improved by utilizing a cryogenic freezer. However, a
cryogenic freezer necessarily generates a vibration although at
different levels depending on the difference in the structure of a
freezer and a cooling system. Therefore, it is difficult to apply
it to a living body magnetic measurement and a magnet for an NMR in
which a slight vibration can affect the sensitivity.
[0016] To enhance the sensitivity of a superconductive device as an
object to be cooled, or enhance the intensity of the magnetic field
on the surface of a vacuum container in a superconductive magnet,
it is necessary to shorten the distance from an object to be cooled
to the surface of a vacuum container. To realize this, the number
of heat shields provided for the vacuum tank between the storage
container and the vacuum container has been decreased to suppress
the space provided to prevent the contact between the heat shields
and shorten the distance between the storage container and the
vacuum container. However, there has been the problem with a
multi-channel superconductive device and a higher magnetic field of
a superconductive magnet that the surface area of the portion for
which only one heat shield can be provided becomes large, and the
radiant heat from the heat shield to the storage container
increases.
[0017] The object of the present invention is to provide a cooling
system for a cryogenic storage container capable of solving the
problem of the vibration occurring when a heat shield is cooled
using a cryogenic freezer, and an operating method for suppressing
the amount of evaporation of a coolant from a cryogenic storage
container.
[0018] The present invention is a cooling system for a cryogenic
storage container including: a storage container storing an object
to be cooled as soaked in a coolant; a vacuum container provided
around the storage container and forming a vacuum tank between the
vacuum container and the storage container; a heat shield provided
for the vacuum tank; a cryogenic storage container having coolant
piping fixed to the heat shield; a cooling source provided with a
cryogenic freezer for cooling a coolant passing through the coolant
piping; and coolant transport piping coupling the cooling source to
the cryogenic storage container, wherein the coolant cooled by the
cryogenic freezer is delivered to the cryogenic storage container
through the transport piping.
[0019] The present invention is also a cooling system for a
cryogenic storage container including:
[0020] a cryogenic storage container having a storage container
storing a coolant and an object to be cooled, a vacuum container
provided around the storage container and forming a vacuum tank
between the vacuum container and the storage container, and a heat
shield provided in the vacuum tank, wherein the heat shield has a
portion having two heat shields between the storage container and
the vacuum container, and a portion having one heat shield between
the storage container and the vacuum container, coolant piping is
fixed to each of the two provided heat shields and the one provided
heat shield, a different coolant other than the coolant stored in
the storage container passes through the coolant piping, and the
coolant passing through the coolant piping cools the two provided
heat shield and the one provided heat shield;
[0021] a cooling source having a second vacuum container which is
vacuum inside, a cryogenic freezer provided in the second vacuum
container, at least one heat exchange unit provided in the second
vacuum container and attached to a coolness generation unit of the
cryogenic freezer, at least one counterflow heat exchanger provided
in the second vacuum container, and second coolant piping passing a
coolant inside, wherein the heat exchange unit is coupled to the
counterflow heat exchanger via the second coolant piping; and
[0022] transport piping having third coolant piping passing a
coolant inside, and a third vacuum container forming a vacuum tank
between the third vacuum container and the third coolant piping,
wherein
[0023] the coolant piping fixed to the heat shield provided in the
cryogenic storage container is coupled to the second coolant piping
provided in the cooling source via the third coolant piping, and
the vacuum container in the cryogenic storage container is coupled
to the second vacuum container in the cooling source via the third
vacuum container.
[0024] The present invention is also an operating method for a
cooling system for a cryogenic storage container including:
[0025] a cryogenic storage container having a storage container
storing a coolant and an object to be cooled, a vacuum container
provided around the storage container and forming a vacuum tank
between the vacuum container and the storage container, and a heat
shield provided in the vacuum tank, wherein the heat shield has a
portion having two heat shields between the storage container and
the vacuum container, and a portion having one heat shield between
the storage container and the vacuum container, coolant piping is
fixed to each of the two provided heat shields and the one provided
heat shield, a different coolant other than the coolant stored in
the storage container passes through the coolant piping, and the
coolant passing through the coolant piping cools the two provided
heat shield and the one provided heat shield;
[0026] a cooling source having a second vacuum container which is
vacuum inside, a cryogenic freezer provided in the second vacuum
container, at least one heat exchange unit provided in the second
vacuum container and attached to a coolness generation unit of the
cryogenic freezer, at least one counterflow heat exchanger provided
in the second vacuum container, and second coolant piping passing a
coolant inside, wherein the heat exchange unit is coupled to the
counterflow heat exchanger via the second coolant piping; and
[0027] transport piping having third coolant piping passing a
coolant inside, and a third vacuum container forming a vacuum tank
between the third vacuum container and the third coolant piping, in
which
[0028] the coolant piping fixed to the heat shield provided in the
cryogenic storage container is coupled to the second coolant piping
provided in the cooling source via the third coolant piping, and
the vacuum container in the cryogenic storage container is coupled
to the second vacuum container in the cooling source via the third
vacuum container, wherein:
[0029] in the two provided heat shields provided between the
storage container and the vacuum container in the coolant storage
container, the heat shield provided on the storage container side
is first cooled by the coolant cooled by the cooling source;
[0030] the coolant whose temperature has risen by the cooling is
used as a low temperature source of the counterflow heat exchanger
in the cooling source to perform heat exchange between the
temperature-risen coolant and an opposite coolant in the
counterflow heat exchanger;
[0031] the coolant whose temperature has risen by the heat exchange
is used in cooling the one provided heat shield between the storage
container and the vacuum container; and
[0032] using the coolant whose temperature has risen by the heat
exchange with the one provided heat shield provided between the
storage container and the vacuum container, the heat shield
provided on the vacuum container side in the two provided heat
shields between the storage container and the vacuum container is
cooled.
[0033] Furthermore, the present invention is also an operating
method for a cooling system for a cryogenic storage container
including:
[0034] a cryogenic storage container having a storage container
storing a coolant and an object to be cooled, a vacuum container
provided around the storage container and forming a vacuum tank
between the vacuum container and the storage container, and a heat
shield provided in the vacuum tank, wherein the heat shield has a
portion having two heat shields between the storage container and
the vacuum container, and a portion having one heat shield between
the storage container and the vacuum container, coolant piping is
fixed to each of the two provided heat shields and the one provided
heat shield, a different coolant other than the coolant stored in
the storage container passes through the coolant piping, and the
coolant passing through the coolant piping cools the two provided
heat shield and the one provided heat shield;
[0035] a cooling source having a second vacuum container which is
vacuum inside, a cryogenic freezer provided in the second vacuum
container, at least one heat exchange unit provided in the second
vacuum container and attached to a coolness generation unit of the
cryogenic freezer, at least one counterflow heat exchanger provided
in the second vacuum container, and second coolant piping passing a
coolant inside, wherein the heat exchange unit is coupled to the
counterflow heat exchanger via the second coolant piping; and
[0036] transport piping having third coolant piping passing a
coolant inside, and a third vacuum container forming a vacuum tank
between the third vacuum container and the third coolant piping, in
which
[0037] the coolant piping fixed to the heat shield provided in the
cryogenic storage container is coupled to the second coolant piping
provided in the cooling source via the third coolant piping, and
the vacuum container in the cryogenic storage container is coupled
to the second vacuum container in the cooling source via the third
vacuum container, wherein:
[0038] in the two provided heat shields provided between the
storage container and the vacuum container in the coolant storage
container, the heat shield provided on the storage container side
is first cooled by the coolant cooled by the cooling source;
[0039] the coolant whose temperature has risen by the cooling cools
the one provided heat shield between the storage container and the
vacuum container;
[0040] the coolant whose temperature has risen by the cooling is
used as a low temperature source of the counterflow heat exchanger
in the cooling source to perform heat exchange between the
temperature-risen coolant and an opposite coolant in the
counterflow heat exchanger;
[0041] the coolant whose temperature has risen by the heat exchange
cools the heat shield provided on the vacuum container side in the
two provided heat shields between the storage container and the
vacuum container.
[0042] In the present invention, it is desired that the heat shield
provided between the storage container and the vacuum container of
the cryogenic storage container has a divided structure, and the
divided heat shields are coupled by a low thermal conductive
material.
[0043] It is also desired in the present invention, that a bellows
unit is provided at least in a part of the third vacuum container
in the coolant transport piping for coupling the cryogenic storage
container to the cooling source. It is also desired to provide a
bellows unit at least in a part of the third coolant piping in the
coolant transport piping.
[0044] It is further desired to provide a bellows unit at least a
part of the third vacuum container configuring the coolant
transport piping, and a part of the bellows unit is fixed to the
floor at any portion of the bellows unit.
[0045] The present invention can solve the problem of the vibration
occurring when a cryogenic freezer is used, and can suppress the
amount of evaporation of the liquid helium from the coolant storage
container on the cryogenic storage container.
[0046] Other objects, features and advantages of the invention will
become apparent from the following description of the embodiments
of the invention taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] FIG. 1 is a sectional view of the storage unit of the
cryogenic coolant storage container using a superconductive magnet
for an NMR according to the present invention;
[0048] FIG. 2 is a sectional view of the storage unit of the
cryogenic coolant storage container for a superconductive device
according to the present invention;
[0049] FIG. 3 shows the configuration of the cryogenic storage
container according to the present invention;
[0050] FIG. 4 is a sectional view of the structure of the heat
shield coupling unit according to the present invention;
[0051] FIG. 5 is a sectional view of the structure of the cooling
source according to the present invention;
[0052] FIG. 6 shows the cooling path according to an embodiment of
the present invention;
[0053] FIG. 7 shows the cooling path according to another
embodiment of the present invention; and
[0054] FIG. 8 is a sectional view of the transport piping according
to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0055] The embodiments of the present invention are described below
in detail with reference to the attached drawings, but the present
invention is not limited to these embodiments.
Embodiment 1
[0056] FIG. 3 shows the rough configuration of the cooling system
for a cryogenic storage container according to the present
invention. The cooling system for a cryogenic storage container
according to the present invention is configured by a storage unit
100, a cooling source 101, and a transport piping 102. The cooling
source 101 is equipped with a cryogenic freezer not shown in the
attached drawings. The cryogenic freezer is coupled to a compressor
not shown in the attached drawings via high pressure piping. Using
the cryogenic freezer eliminate the necessity to supply a coolant
such as liquid nitrogen, liquid helium, etc. In addition, the
coolness at or lower than the temperature of liquid nitrogen
occurring in the cooling stage of the cryogenic freezer can be
used.
[0057] In FIG. 3, a bellows unit 104 is provided for a part of the
transport piping 102. In the bellows unit 104, the bellows unit 104
is fixed to the floor using a support table 105 at any portion of
the bellows unit 104.
[0058] The cooling source 101 contains a cryogenic freezer for
generating a vibration. The cryogenic freezer provides a constant
vibration for the cooling source 101 to which the cryogenic freezer
is fixed. The vibration generated by the cooling source 101 is
delivered to the storage unit 100 through the transport piping
102.
[0059] By providing the bellows unit 104 for at least a part of the
transport piping 102, the vibration occurring in the cooling source
101 can be attenuated before reaching the storage unit 100. In
addition, in the bellows unit 104 provided for the transport piping
102, the bellows unit 104 can be fixed to the support table 105 on
the floor with high rigidity at any portion of the bellows unit,
thereby further reducing the vibration on the fixing unit of the
bellows unit 104. Furthermore, by the bellows unit 104 between the
fixed position of the bellows unit 104 on the floor and the storage
unit 100, the vibration to be delivered to the storage unit 100 can
be furthermore reduced. The fixing unit between the bellows unit
104 and the support table 105 can be a high rigidity stainless
steel pipe etc. However, in this case, it is desired to provide the
bellows unit at either ends of the fixing unit.
[0060] FIG. 1 is a sectional view of the storage unit of the
cryogenic coolant storage container using a superconductive magnet
for an NMR according to the present invention. The storage unit 100
is configured by a storage container 2 storing a coolant 5 and a
superconductive magnet 1a as an object to be cooled, a vacuum
container 3 for generating a vacuum tank 10 between the vacuum
container 3 and the storage container 2, double heat shields 7 and
8 provided around the storage container 2 in the vacuum tank 10,
one provided heat shield 9 between the storage container 2 and the
vacuum container 3 in the vacuum tank 10, and a coolant piping 11
passing a coolant for cooling each heat shield.
[0061] To effectively utilize a high magnetic field occurring in
the superconductive magnet 1a, it is necessary to shorten the
distance between the superconductive magnet 1a and the wall of an
access port 14 passing through the center of the magnet.
[0062] The storage unit 100 is commonly manufactured using
stainless steel and aluminum. Especially since the access port 14
has the problem of the magnetic properties of the material, it is
desired to use aluminum having low magnetic susceptibility.
[0063] In the double heat shields 7 and 8 provided around the
storage container 2 in the vacuum tank 10, the heat shield 8
provided on the vacuum container 3 side at the room temperature is
referred to as a high temperature shield, and the heat shield 7
provided on the storage container 2 side is referred to as a low
temperature shield.
[0064] The high temperature shield 8 receives radiation from the
vacuum container 3 at the room temperature, and the low temperature
shield 7 receives radiation from the high temperature shield 8. At
the portion where the double heat shields are provided, the storage
container 2 receives radiation from the low temperature shield
7.
[0065] On the other hand, the one provided heat shield 9 between
the storage container 2 and the vacuum container 3 in the vacuum
tank 10 receives radiation from the access port 14 at the room
temperature. At the portion where only one heat shield is provided,
the storage container 2 receives radiation from the heat shield 9
because there is the storage container 2 inside the heat shield
9.
[0066] The heat shields 7, 8, and 9 thermally contact the coolant
piping 11 through, for example, an aluminum tape, and are cooled by
heat exchange with a coolant cooled at a cryogenic temperature
passing in the coolant piping 11. The coolant piping 11 is formed
by a stainless steel pipe in a transportation region. The heat
contact portion between the heat shields 7, 8, and 9 and the
coolant piping 11 is connected by a copper pipe having high thermal
conductivity and intensity. When the contact area between the heat
shields 7, 8, and 9 and the coolant piping 11 can be sufficiently
reserved, the piping of the heat contact portion can be stainless
steel. However, it is necessary to decrease the thickness of the
piping.
[0067] The heat shield 7 provided as a double structure between the
storage container 2 and the vacuum container 3 in the vacuum tank
10 is divided, and each of the divided shields is provided with a
heat contact portion with the coolant piping 11. The division of
the heat shield 7 depends on the shield temperature of the divided
heat shield 7, and the shields to be cooled at the same temperature
can be coupled. Since the heat shield coupled to the coupling
portion (aperture) to the room temperature unit receives thermal
conduction from the room temperature, the temperature rises. To
reduce the high temperature portion of the heat shield, the heat
shield coupled to the coupling portion to the room temperature unit
is separated from another heat shield.
[0068] FIG. 4 shows the structure for fixing the heat shield
division part. When the heat shield is divided, and when there is
space between the heat shields, radiant heat occurs and passes
through the space. Therefore, a spacer 65 is interposed between
heat shields 61 and 62 to be cooled at different temperatures. By
using a glass fiber reinforced plastic (GFRP) having low thermal
conductivity as the material of the spacer 65, a temperature
difference can be made between the heat shields 61 and 62. At this
time, when the complete tight state is entered, the heat shield
cannot be vacuum inside. Therefore, it is necessary to provide
several exhaust holes 66. In addition, to prevent the radiant heat
passing through the exhaust holes 66, it is effective to enhance
the radiation rate on the inner surfaces of the holes, or cover the
surroundings of the exhaust holes with an exhaust shield 67.
[0069] Thus, by connecting the heat shields 61 and 62 by a material
of low thermal conductivity such as the GFRP etc., a temperature
difference between the heat shields can be provided.
[0070] The double heat shields 8 provided between the storage
container 2 and the vacuum container 3 in the vacuum tank 10 have
similar structures as the heat shield 7.
[0071] Since it is difficult to provide the coolant piping 11 for
the portion having thinner vacuum tank 10, piping is provided for
cooling between the double heat shields 7 and 8 between the storage
container 2 and the vacuum container 3 in the vacuum tank 10 with
respect to the one provided heat shield 9 between the storage
container 2 and the access port 14 in the vacuum tank 10.
[0072] It is desired that a laminated heat insuring material not
shown in the attached drawings is provided between the vacuum
container 3 and the high temperature shield 8 in the double heat
shields provided between the storage container 2 and the vacuum
container 3 in the vacuum tank 10 so that the radiant heat from the
vacuum container 3 at the room temperature to the high temperature
shield 8 can be reduced.
[0073] Similarly, it is also desired to provide a laminated heat
insuring material not shown in the attached drawings between the
access port 14 and the one provided heat shield 9 between the
storage container 2 and the access port 14 in the vacuum tank 10 so
that the radiant heat from the vacuum container 3 at the room
temperature to the heat shield 9 can be reduced.
[0074] FIG. 5 is a sectional view of the structure of the cooling
source according to the present invention. The cooling source 101
is configured by a second vacuum container 21, a cryogenic freezer
30 fixed to the second vacuum container 21, counterflow heat
exchangers 22 and 23 provided in the second vacuum container 21, a
heat exchange unit 41 thermally coupled to the first cooling stage
31 of the cryogenic freezer 30, a heat exchange unit 42 thermally
coupled to a second cooling stage 32 of the cryogenic freezer 30, a
heat shield 24 thermally coupled to the first cooling stage 31 of
the cryogenic freezer 30, and the coolant piping 11.
[0075] In FIG. 5, a Gifford-McMahon freezer (hereinafter referred
to as a GM freezer) is used as the cryogenic freezer 30. Although
there is only one GM freezer used in the present embodiment, there
can be a plurality of freezers depending on the cooling capacity.
If there is no problem with the cooling capacity, a pulse pipe
freezer generating a lower vibration than the GM freezer can be
applied.
[0076] A helium gas compressed by a compressor not shown in the
attached drawings is charged inside the coolant piping 11. The
coolant piping is made of stainless steel. The helium gas supplied
to the cooling source 101 from the compressor at the room
temperature is processed in heat exchange process with the opposite
helium gas when the helium gas passes through the counterflow heat
exchanger 22, and is cooled down to a low temperature. Next, the
gas is cooled down to the same temperature as the first cooling
stage 31 of the cryogenic freezer 30 by the heat exchange unit 41
thermally coupled to the first cooling stage 31 of the cryogenic
freezer 30. Next, when it passes through the counterflow heat
exchanger 23, it is processed in the heat exchange process with the
opposite helium gas, there by further reducing the temperature.
Then, the heat exchange unit 42 thermally coupled to the second
cooling stage 32 of the cryogenic freezer 30 cools down the gas to
the same temperature as the second cooling stage 32 of the
cryogenic freezer 30, and the gas is delivered to the storage unit
100 through coolant piping 11a provided in the transport piping
102.
[0077] After the temperature of the helium gas has risen by the
heat exchange with the heat shield as an object to be cooled in the
storage unit 100, the helium gas is fed back to the cooling source
101 through coolant piping 11b, and is used as a low temperature
source of the counterflow heat exchanger 23. The heat exchange is
performed between the gas and the opposite helium gas. The helium
gas whose temperature has risen is delivered to the storage unit
100 through coolant piping 11c. The helium gas whose temperature
has risen by the heat exchange with the heat shield as an object to
be cooled in the storage unit 100 is fed back to the cooling source
101 through coolant piping 11d, and is used as a low temperature
source of the counterflow heat exchanger 22. Then, the heat
exchange is performed with the opposite helium gas, and the helium
gas whose temperature has risen to the room temperature is returned
to the compressor not shown in the attached drawings.
[0078] Thus, by adopting the closed circulation system in which no
coolant is to be externally supplied, the internal temperature
fluctuation is reduced, and a long time continuous operation can be
performed.
[0079] The heat shield 24 thermally coupled to the first cooling
stage 31 of the cryogenic freezer 30 reduces the radiation to the
second cooling stage 32 of the cryogenic freezer 30 and the
counterflow heat exchanger 23. Between the vacuum container 21 and
the heat shield 24 thermally coupled to the first cooling stage 31
of the cryogenic freezer 30, a laminated heat insulating material
not shown in the attached drawings is provided to reduce the
radiant heat from the vacuum container 21 to the heat shield
24.
[0080] The vibration occurring from the cryogenic freezer 30 is
reduced by the attenuating mechanism not shown in the attached
drawings provided for the second vacuum container 21. The vibration
passing through the coolant piping 11 is decreased in the bellows
unit not shown in the attached drawings provided at a part of the
coolant piping 11. A part of the vacuum container of the transport
piping 102 has a bellows structure not shown in the attached
drawings, and reduces the vibration passing through the vacuum
container. By fixing at the bellows unit of the transport piping
102 to the floor with high rigidity, the vibration in the cooling
source 101 can be further prevented from being delivered to the
storage unit 100.
[0081] FIG. 6 shows a cooling path of the heat shield provided in
the storage unit 100 using a coolant cooled at a cryogenic
temperature by the cooling source 101.
[0082] In the heat exchange unit 42 thermally coupled to the second
cooling stage 32 of the cryogenic freezer 30 in the cooling source
101, the helium gas cooled down to the same temperature as the
second cooling stage 32 of the cryogenic freezer 30 is delivered to
the storage unit 100 through the coolant piping 11a, and the low
temperature shield 7 in the double heat shields between the storage
container 2 and the vacuum container 3 in the vacuum tank 10 is
cooled. Since there is the high temperature shield 8 around the low
temperature shield 7, radiant heat 202 received by the low
temperature shield 7 from the high temperature shield 8 is low, and
the rise of the temperature of the helium gas passing through the
coolant piping 11 is low.
[0083] The helium gas whose temperature has risen by the heat
exchange with the low temperature shield 7 is temporarily delivered
to the cooling source 101 through the coolant piping 11b, and is
used as a low temperature source of the counterflow heat exchanger
23. The heat exchange is performed between the gas and the opposite
helium gas, and the helium gas whose temperature has risen is
delivered again to the storage unit 100 through the coolant piping
11c, and the one provided heat shield 9 between the storage
container 2 and the vacuum container 3 in the vacuum tank 10 is
cooled.
[0084] Since the heat shield 9 receives radiant heat 204 from the
vacuum container 3 at the room temperature, the temperature of the
helium gas as a coolant rises. Using the helium gas whose
temperature has risen, the high temperature shield 8 in the two
provided heat shields between the storage container 2 and the
vacuum container 3 in the vacuum tank 10 is cooled. Since the high
temperature shield 8 receives radiant heat 201 from the vacuum
container 3 at the room temperature, the temperature of the coolant
is furthermore risen.
[0085] The helium gas whose temperature has risen by the heat
exchange with the heat shield 9 is delivered to the cooling source
101 through the coolant piping 11d, and is used as the low
temperature source of the counterflow heat exchanger 22.
[0086] As described above, the low temperature shield 7 in the
double provided heat shields between the storage container 2 and
the vacuum container 3 in the vacuum tank 10 is cooled down to
about 4.2 K to 10 K, and the high temperature shield 8 is cooled
down to about 70 K to 100 K, and the one provided heat shield 9
between the storage container 2 and the vacuum container 3 in the
vacuum tank 10 is cooled down to about 25 K to 45 K. Although the
storage container 2 receives radiant heat 203 from the heat shield
7, and radiant heat 205 from the heat shield 9, the amount of
evaporation of the liquid helium from the storage container 2 can
be suppressed because each heat shield temperature is low.
[0087] FIG. 8 is a sectional view showing the structure of the
transport piping 102. The transport piping 102 is configured by a
third vacuum container 301 and coolant piping 302 passing a coolant
inside. The bellows unit is used at least a part of the third
vacuum container 301 configuring the transport piping 102.
[0088] The vacuum container 3, the second vacuum container 21, and
a third vacuum container 301 are coupled to one another. Each
coolant piping provided in the vacuum container 3, the second
vacuum container 21, and the third vacuum container 301 is coupled
to realize the cooling path shown in FIG. 6.
Embodiment 2
[0089] FIG. 7 shows another example of a path for cooling a heat
shield provided in the storage unit 100 using a coolant cooled at a
cryogenic temperature by the cooling source 101. The entire
configuration is the same as shown in FIG. 3. The structure of the
storage unit 100 is also the same as the structure shown in FIG. 1.
The structure of the cooling source 101 is the same as the
structure shown in FIG. 5. The structure of the transport piping
102 is the same as the structure shown in FIG. 8.
[0090] The helium gas cooled down to the same temperature as the
second cooling stage 32 of the cryogenic freezer 30 by the heat
exchange unit 42 thermally coupled to the second cooling stage 32
of the cryogenic freezer 30 in the cooling source 101 is delivered
to the storage unit 100 through the coolant piping 11a, and cools
the heat shield 7 in the two provided heat shields between the
storage container 2 and the vacuum container 3 in the vacuum tank
10. Since there is the high temperature shield 8 around the low
temperature shield 7, the radiant heat 202 received by the low
temperature shield 7 from the high temperature shield 8 is low, and
the rise of the temperature of the helium gas passing the coolant
piping 11a is low.
[0091] The helium gas whose temperature has risen by the heat
exchange with the low temperature shield 7 cools the one provided
heat shield 9 between the storage container 2 and the access port
14 in the vacuum tank 10. Since the heat shield 9 receives the
radiant heat 204 from the access port 14 at the room temperature,
the temperature of the helium gas as a coolant rises. The helium
gas whose temperature has risen is temporarily delivered to the
cooling source 101 through the coolant piping 11b, and is used as a
low temperature source of the counterflow heat exchanger 23.
[0092] The helium gas whose temperature has risen by the heat
exchange with the opposite helium gas is delivered again to the
storage unit 100 through the coolant piping 11c, and cools the high
temperature shield 8 in the two provided heat shields between the
storage container 2 and the vacuum container 3 in the vacuum tank
10. Since the high temperature shield 8 receives the radiant heat
201 from the vacuum container 3 at a room temperature, it has a
large amount of received heat, and the temperature of the coolant
further rises.
[0093] The helium gas whose temperature has risen by the heat
exchange with the high temperature shield 8 is delivered again to
the cooling source 101 through the coolant piping 11d, and is used
as a low temperature source of the counterflow heat exchanger
22.
[0094] As described above, the low temperature shield 7 in the
double provided heat shields between the storage container 2 and
the vacuum container 3 in the vacuum tank 10 is cooled down to
about 10 K to 15 K, and the high temperature shield 8 is cooled
down to about 70 K to 100 K, and the one provided heat shield 9
between the storage container 2 and the vacuum container 3 in the
vacuum tank 10 is cooled down to about 20 K to 30 K.
[0095] According to the present embodiment, the amount of radiant
heat to the storage container 2 can be reduced. Although the
storage container 2 receives radiant heat 203 from the low
temperature shield 7, and radiant heat 205 from the heat shield 9,
the amount of evaporation of the liquid helium from the storage
container 2 can be suppressed because each heat shield temperature
is low.
[0096] The cooling system and its operating method of the present
invention are not limited to an application to a magnet for an NMR.
For example, it is also applicable to a magnet for an MRI.
Embodiment 3
[0097] FIG. 2 is a sectional view of the storage unit of the
cryogenic storage container storing a superconductive device. The
entire configuration of the cryogenic storage container is the same
as the configuration shown in FIG. 3. The structure of the cooling
source is the same as the structure shown in FIG. 5. The path for
circulating a coolant can be any of the circulation paths shown in
FIGS. 5 and 6. The structure of the transport piping is the same as
the structure shown in FIG. 8.
[0098] In the present invention, the superconductive device refers
to, for example, a superconducting quantum interference device
(SQUID) for measuring a weak magnetic field. The SQUID is a high
sensitive magnetic sensor capable of measuring a weak magnetic
field of 1/1,000,000 or less of the earth's magnetic field. To
realize a high sensitive measurement, it is necessary to reduce the
thermal noise occurring from the SQUID itself. Therefore, liquid
helium is used for cooling at a cryogenic temperature.
[0099] The distance from a superconductive device 1b to a
measurement surface 3a of the vacuum container 3 largely depends on
the measurement sensitivity, and the sensitivity is greatly
improved by shortening the distance.
[0100] The storage unit 100 stores the coolant 5, and is configured
by a storage container 2 storing the superconductive device 1b, the
vacuum container 3 for generating the vacuum tank 10 between the
vacuum container 3 and the storage container 2, the double heat
shields 7 and 8 provided around the storage container 2 in the
vacuum tank 10, the one provided heat shield 9 between the storage
container 2 and the vacuum container 3 in the vacuum tank 10, and
the coolant piping 11 passing a coolant for cooling each heat
shield. The vacuum container 3 is connected to the vacuum container
of the transport piping 102.
[0101] The storage unit 100 is generally manufactured by a
non-metal material and a non-magnetic material, and can be
manufactured using, for example, a GFRP. Since an eddy-current
occurring in the heat shield configuring a storage unit can affect
the measurement of the superconductive device 1b, there is no
coolant piping 11 around the superconductive device 1b. The joint
portion between the heat shield 9 and the coolant piping 11 is
provided with a sufficient distance kept to measure the
superconductive device. It is common to all heat shields.
[0102] The heat shield 9 is supported by a heat insuring support
unit 15 made of a material having thermal conductivity lower than
that of the heat shields 8 and 9, for example, a GFRP between the
heat shield 9 and the heat shield 8. By supporting the high
temperature shield 8 and the heat shield 9 by the heat insuring
support unit 15, a temperature difference can be made between the
high temperature shield 8 and the heat shield 9, thereby
successfully maintaining the heat shield 9 at a low
temperature.
[0103] It should be further understood by those skilled in the art
that although the foregoing description has been made on
embodiments of the invention, the invention is not limited thereto
and various changes and modifications may be made without departing
from the spirit of the invention and the scope of the appended
claims.
* * * * *