JP2000102517A - Cooling device for living body magnetographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the blocking of an exhaust pipe by dew condensation of the air penetrated from the outside of the exhaust pipe and surely prevent an accident by providing a means for detecting the pressure of the coolant gas layer within a low-temperature thermostat and detecting the freezing blocking of the exhaust pipe. SOLUTION: A pressure gauge 7 is constituted so as to introduce the pressure of a coolant gas tank 25 through a pressure conduit 6 inserted into the inner tank 1a of a low-temperature thermostat 1 through a baffle 2. Even if the outside air is penetrated into an exhaust pipe 5 through the release port of the exhaust pipe 5, cooled by the low-temperature coolant gas leaving the low- temperature thermostat 1, and frozen by dew condensation and coagulation on the inner wall of the exhaust pipe 5 to block the exhaust pipe 5 after the lapse of a long period, the blocking can be found through the pressure gauge 7, and an alarm is given on the basis of this, whereby the breakage of the low-temperature thermostat 1 can be prevented, and the safety of this kind of living body magnetographic device can be enhanced. On the basis of the alarm, the frozen part of the exhaust pipe 5 is thawed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling device for a biomagnetometer equipped with a low-temperature constant temperature bath using a liquid refrigerant such as liquid nitrogen or liquid helium.

[0002]

2. Description of the Related Art In recent years, a superconducting quantum interferometer (hereinafter, referred to as a superconducting quantum interferometer) capable of measuring a weak magnetic field has been developed.
nce Devices is abbreviated as SQUID)
A biomagnetism measurement device that measures a weak magnetic field generated by a magnetic current of the brain or heart and that is useful for medical diagnosis has been developed.

[0003] The above-mentioned SQUID is cooled by being housed in a low-temperature constant temperature bath into which a liquid refrigerant such as liquid nitrogen or liquid helium is introduced.

[0004] The low-temperature constant temperature bath is provided with an exhaust pipe for exhausting the evaporative gas of the liquid refrigerant, and a replenishing pipe for supplementing the evaporation of the liquid refrigerant.

[0005] As a cooling device of the SQUID measuring device, for example, as disclosed in Japanese Patent Application Laid-Open No. 4-321283, a coolant is supplied from a coolant container to a low-temperature constant-temperature bath containing a SQUID via a coolant supply conduit. Is introduced, a coolant is conducted to the SQUID holding structure in the low temperature constant temperature bath to indirectly cool the SQUID, and the cooling gas evaporated after cooling is exhausted through the operation valve and the exhaust pipe driven by the controller. Techniques are disclosed. This conventional coolant container incorporates a pressure holding valve for maintaining the overpressure of the evaporative gas in the container at least approximately constant.

[0006] In addition, although it is separated from the biomagnetic measurement device,
For example, as disclosed in Japanese Unexamined Patent Publication No. 61-73390, in a superconducting magnet device with a small refrigerator, the pressure in the liquid helium container accommodating the superconducting coil is controlled so as to keep the helium amount and the pressure in the container constant. There is a technique including a gauge and a liquid level gauge.

[0007]

The biomagnetism measuring device is
The SQUID and liquid refrigerant are housed in a low-temperature constant-temperature bath commonly called Dewar, and the evaporating gas of the liquid refrigerant in the low-temperature constant-temperature bath is constantly discharged to the atmosphere from the exhaust pipe. Was thought to never be.

However, since the exhaust pipe is connected to the outside through the discharge port to discharge the evaporative gas, the low-temperature refrigerant flowing from the discharge port into the exhaust pipe and coming out of the low-temperature constant temperature bath. After being cooled by the gas, the moisture in the air condenses and condenses on the inner wall of the exhaust pipe (so-called freezing phenomenon), and may block the pipe within a long period of time. When such a situation occurs, abnormal pressure is generated in the low-temperature oven, and in the worst case, the low-temperature oven may be ruptured. In such a situation, in a biomagnetism measuring apparatus for handling a human body, it is necessary to take measures to prevent such a situation from the viewpoint of protecting the safety of the human body.

[0009] In addition to the problem of the exhaust pipe being blocked as described above, when the evaporation amount of the refrigerant increases (boil-off) due to the breakage of the vacuum in the vacuum heat insulating layer of the low-temperature constant temperature bath, this problem must be solved early. It is important to discover and take countermeasures. That is, when used for magnetic measurement, measurement becomes impossible due to vibration due to boil-off, or the reliability of measured data decreases.

The present invention has been made in view of the above points, and has as its object the first object is to provide a cooling device for a biomagnetism measuring device in which air entering from the outside of an exhaust pipe which causes abnormal pressure in a low-temperature constant temperature bath. An object of the present invention is to detect an exhaust pipe blockage due to condensation and freezing (freezing) of the exhaust gas to surely prevent an accident.

A second object of the present invention is to provide a biomagnetism measuring device that detects a so-called boil-off phenomenon in addition to the above-described exhaust pipe blockage and further enhances safety.

[0012]

Means for Solving the Problems (1) With respect to the problem that air entering from the outside condenses (freezes) on the inner wall of the exhaust pipe and blocks the exhaust pipe, basically, the following problem is solved. Suggest a solution.

That is, a low-temperature constant-temperature bath containing a SQUID and a liquid refrigerant for cooling the SQUID, means for replenishing the low-temperature constant-temperature bath with the liquid refrigerant, and a refrigerant gas generated by evaporating the liquid refrigerant in the low-temperature constant-temperature bath. A cooling device for a biomagnetism measuring device having an exhaust pipe for exhausting, wherein a means for detecting a pressure of a refrigerant gas layer in the low-temperature constant temperature bath and detecting a freezing blockage of the exhaust pipe is provided. (First
Invention).

(2) Next, as an alternative to the above configuration (1), when the pressure of the refrigerant gas layer in the low-temperature constant temperature chamber becomes an abnormal pressure, a rupturable plate or an abnormal pressure that bursts to release the gas. (2nd invention).

(3) Means for responding to the problem of further improving the safety by detecting a so-called boil-off phenomenon in addition to the exhaust pipe blockage include the above-mentioned SQUID, low-temperature constant temperature bath, liquid refrigerant replenishing means, and exhaust pipe. In the cooling device of the biomagnetism measuring device, a liquid level meter for detecting a liquid level of the liquid refrigerant in the low-temperature constant temperature bath, a flow meter for detecting a flow rate of the refrigerant gas discharged through the exhaust pipe, and the flow rate Means for judging the presence / absence of boil-off of the liquid refrigerant from the detection value of the gas meter, and judging the presence / absence of freezing / clogging of the exhaust pipe from the detection value of the flow meter and the detection value of the liquid level gauge. (Third invention).

The operation of the invention described above will be described in the following embodiment of the invention.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a schematic vertical sectional view of a dewar (low-temperature constant-temperature bath) in a biomagnetism measuring apparatus according to an embodiment of the present invention.

The low-temperature constant temperature bath 1 is made of FRP (Fiber Reinforced P).
The side and bottom surfaces made of non-magnetic material such as (lastics: fiber reinforced plastic) have a double wall structure of the inner tank 1a and the outer tank 1b, and the space between the double walls 1a and 1b is an aluminum evaporated film. 20 are put in several layers and kept in a vacuum state (not shown). The reason why the low-temperature oven 1 is made of a non-magnetic material is as follows.
This is for use in magnetic measurement. In particular, when it is desired to eliminate the influence of the eddy current of the material of the bath itself for measurement of weak magnetism, a non-ferrous metal such as copper or aluminum should not be used. The vacuum between the inner tank 1a and the outer tank 1b is used to prevent heat from entering due to heat conduction and gas convection, and the aluminum vapor deposition film 20 is used to prevent heat from entering due to heat radiation. This is to prevent it.

A liquid refrigerant (for example, liquid helium) 21 is contained in the inner tank 1a, and a large number of SQUIS are contained in the liquid refrigerant.
A D (magnetic detection sensor) 22 is provided.

A baffle 2 for preventing heat from penetrating from the upper surface by heat conduction is provided on the upper portion of the inner tank 1a. The baffle 2 is made of a heat insulating material such as foamed styrene and urethane foam. The size (diameter) of the baffle 2 is set to be slightly smaller than the inner diameter of the inner tank 1a of the low temperature
a, An annular gap 23 is secured between the inner and outer circumferences of the baffle 2.

Signal line from SQUID 22 (not shown)
Is required to pass through the gap 23, and the gap 23 is formed between the inner diameter of the inner tank 1a and the outer diameter of the baffle 2 in consideration of the thickness of the flat cable used for the signal line and the workability of incorporating the baffle 2 into the tank. The difference from the diameter is desirably about 10 mm in diameter difference (5 mm in radius difference).

According to the gap 23 having such a degree, a relatively warm refrigerant gas (for example, 200 mm) near the upper part of the tank in the gap 23 is formed.
K) is prevented from flowing downward (for example, about 10K) by convection in the gap 23, and heat radiation due to a temperature difference between the top plate 24 disposed on the upper surface of the low temperature constant temperature bath 1 and the bottom surface of the bath 1 is prevented. It is prevented by the presence of the baffle 2 and the refrigerant gas contacts the wall surface of the inner bath 1a of the low-temperature constant temperature bath 1 as much as possible when the refrigerant gas flows upward from below the refrigerant gas layer 25 in the inner bath 1a. Then, heat exchange between the refrigerant gas and the inner tank 1a is promoted,
Therefore, it is configured to receive the invading heat from the outside via the wall of the inner tank 1a and then release (exhaust) by the refrigerant gas. Therefore, it is possible to suppress the heat that enters from the outside from thermally affecting the liquid refrigerant 21.

The guide tube 3 passes through the baffle 2 and the top plate 24 and passes through the sensor section 26 of the liquid level gauge 8 and the guide passes through a transfer tube 27 for supplying a liquid refrigerant such as liquid helium or liquid nitrogen. Tubes 4 are provided respectively.

The reason for providing these guide tubes 3 and 4 is as follows.
This is for preventing the sensor part 26 and the transfer tube 27 of the liquid level meter from being caught by the baffle 2 and the like when the sensor 26 and the transfer tube 27 are introduced into the low-temperature constant temperature bath 1 via the baffle 2 from outside.

The level gauge sensor 26 and the transfer tube 27 are fixed to the guide tubes 3 and 4 via Wilson seals 28 and 29 so as to seal the guide tubes 3 and 4. FIG. 2 shows an exploded cross-sectional view of the Wilson seal.
0, an O-ring 31 mounted therein, a tapered ring 32, and a female threaded sleeve 33 for tightening the tapered ring 32.

The inner diameters of the guide tubes 3 and 4 are set to be slightly larger than the outer diameters of the level gauge sensor section 26 and the transfer tube 27, and an annular shape formed between the level gauge sensor section and the transfer tube. Space is narrow.
This is for preventing the convection of the refrigerant gas and heat intrusion from above due to heat radiation. In addition, since no load is applied to the guide tubes 3 and 4 themselves, the tubes are made as thin as possible to reduce the cross-sectional area and prevent heat penetration due to heat conduction of the tubes themselves.
For example, since the outer diameter of the level gauge sensor section 26 is about 8 mm, the inner diameter of the level gauge guide tube 3 is preferably about 9 mm.
The material is stainless steel (thickness 0.1
FRP (thickness: 1 to 2 mm for manufacturing reasons), PET (polyethylene terephthalate, thickness: 1 mm or less) having a low thermal conductivity at a low temperature. The design concept such as the diameter and material of the guide tube 4 through which the transfer tube 27 passes is the same as in the case of the liquid level gauge guide tube 3.

Since the so-called air column vibration phenomenon is apt to occur in the guide tubes 3 and 4 due to the temperature difference between the upper end and the lower end, any side surface (tube wall) of the guide tubes 3 and 4 can be used to prevent this phenomenon. A hole (not shown) is provided. The hole diameter is φ1
It may be 5 mm. If at least one hole is provided, air column vibration can be prevented. However, if there is only one hole, there is no spare when the hole is closed, so it is preferable to provide a plurality of holes.

At the center of the top plate 24, there is provided an exhaust pipe 5 for discharging the evaporated refrigerant gas in the low-temperature oven to the outside of the low-temperature oven.

The exhaust pipe 5 is provided with an annular gap 2 around the baffle 2.
3 for discharging refrigerant gas (refrigerant gas evaporated in the low-temperature constant-temperature bath 1) to the outside through a plurality of gas passages 2a directed toward the center of the baffle 2 and a gas passage 2b provided at the center of the baffle 2. Things. Arrows indicate the flow of the refrigerant gas. The reason why such a series of refrigerant gas exhaust passage structures is adopted is that the refrigerant gas layer 2 above the liquid refrigerant in the low temperature oven 1
Rather than discharging the refrigerant gas to the outside at a low temperature through the guide pipe from 5 through the passage 23, it is more preferable to discharge the heat after invading the wall of the inner tank 1 a through the heat conduction through the passage 23.
This is because it is effective to reduce the amount of heat entering and reduce the amount of evaporation of the liquid refrigerant 21.

The reason why the exhaust pipe 5 is disposed at the center of the top plate 24 is that, when the exhaust pipe 5 is disposed eccentrically, the refrigerant gas closer to the wall of the inner tank 1a flows more (faster) and the refrigerant gas farther from the wall is closer to the wall. This is because heat exchange between the wall and the refrigerant gas cannot be sufficiently achieved because the gas flows less. Further, as shown in FIG. 1, the refrigerant gas flow path 2a passes through the second baffle from the top instead of the top baffle because the refrigerant gas passes between the baffle and the top plate. Then, the top plate is cooled, the top surface of the top plate is dewed, and the O-ring (not shown) between the top plate and the tank is cooled, and the sealing property of the O-ring is not secured,
This is because air enters the layer and water vapor freezes in the upper part of the tank.

Reference numeral 7 denotes a pressure gauge, which is an inner tank 1 of the low-temperature thermostat 1.
The pressure of the refrigerant gas tank 25 is guided through a pressure conduit 6 inserted through the baffle 2 into the inside a.

Although this pressure conduit 6 is directly introduced into the baffle 2 while maintaining airtightness, a guide pipe independent of the above-mentioned liquid level gauge guide pipe 3, refrigerant supply guide pipe 4, and exhaust pipe 5 is provided. (The design specification in the case of a guide tube is the same as that of the liquid level gauge guide tube 3 and the refrigerant supply guide tube 4).

The pressure conduit 6 is made of PET for manufacturing reasons.
If it is, the inner diameter is 2-3 mm, the wall thickness is about 0.1-0.5 mm, and if it is FRP, the inner diameter is 3-10 mm, the wall thickness is 1-3 m
m.

A low-temperature constant temperature bath made of FRP is usually used in a low temperature thermostat.
It has a design withstand pressure of about 5 atm (gauge) (hereinafter, pressure is expressed as gauge pressure). When supplying liquid helium, which is a liquid refrigerant, the liquid helium is pushed out from a helium tank (not shown) serving as a refrigerant supply source. Force is 0.2-0.3
Since it is considered that pressure of about atmospheric pressure has been applied, the value of the judgment of the danger of internal pressure on the tank side is 0.3 to
0.4 atm is preferred. When this value is exceeded, the pressure gauge 7
It is desirable to take an avoidance measure on the basis of the detection of that the exhaust system flow path is closed. Further, since the inside of the pressure conduit 6 is shut off from the outside air and the refrigerant gas does not flow, it is not necessary to attach the pressure gauge 7 to the low temperature constant temperature bath main body, and the pressure gauge 7 is drawn out of the magnetic shield room (not shown). Is also good. In this case, it is convenient to install the device near a console that is easy for the device operator to see during normal work.

The pressure to be measured by the pressure gauge 7 is a static pressure of at most about 0.5 atm under normal conditions. Therefore, the measurement range of the pressure gauge 7 is desirably about 1.0 atm or less. If the electronic pressure gauge has an external output port,
The system is configured such that when the pressure value exceeds a predetermined value (0.3 to 0.4 atmosphere in the above description), the CPU (controller) 10 issues a command to the alarm device 11 to issue an alarm. The CPU 10 also receives a signal from the liquid level gauge 8 to monitor the liquid level of the liquid refrigerant 21 in the low-temperature constant-temperature bath 1 and, if the liquid level falls below a predetermined value, a coolant tank (not shown). The liquid refrigerant is supplied into the low-temperature constant temperature bath 1 through the supply pipe 27 by driving the pump.

According to the present embodiment, external air enters the exhaust pipe 5 from the discharge port of the exhaust pipe 5 and is cooled by the low-temperature refrigerant gas coming out of the low-temperature constant-temperature bath. If the tube 5 is blocked by condensation or condensation during a long period of time, even if the tube 5 is blocked, the blockage can be detected via the pressure gauge 7 and an alarm based on this can be issued. Thus, the low-temperature thermostat can be prevented from being damaged in advance, and the safety of this type of biomagnetism measuring device can be improved. Based on this warning, for example, the thawing of the frozen portion of the exhaust pipe 5 is performed.

FIG. 3 relates to a second embodiment of the present invention and embodies the second aspect of the present invention. In the drawing, the same reference numerals as those in FIG. 1 indicate the same elements.

The present embodiment differs from the embodiment of FIG. 1 in that a rupturable plate 40 is provided at the end of the pressure conduit 6 instead of the pressure gauge 7. When the internal pressure of the tank 1 a rises due to the blockage of the exhaust pipe 5, the rupturable plate 40 ruptures, and the internal pressure can be released to the outside (outgassing) through the pressure conduit 6. The rupturable plate 40 is a diaphragm-type thin film formed of stainless steel or the like, and has a thickness and a size that can be ruptured at 0.3 to 0.4 atm and a diameter of the pressure conduit as described above. When the diaphragm 40 has a pressure equal to or higher than a predetermined pressure, the piercing tool 4 which is larger than the orifice diameter is selected.
It has a structure in which it is inverted to one side and bursts.

In this case, since the refrigerant gas flows only when the internal pressure is released, the pressure conduit 6 does not need to have a large inside diameter (as described above, the inside diameter of about 2 to 10 mm is sufficient).

In place of the rupturable plate 40, it is also possible to use a one-way valve to release gas when the pressure exceeds a predetermined value (not shown). On the other hand, the valve also has various operating pressures and orifice diameters, etc., but operates at 0.3 to 0.4 atm and the orifice diameter is larger than the inner diameter of the pressure pipe 6 (for example, 10 mm).
Degree) is sufficient. The advantage of using a one-way valve is that if the rupturable plate ruptures and the rupturable plate ruptures, the safe use of the low-temperature constant-temperature device will not be ensured until the installation of a new rupturable plate is completed again. After releasing the internal pressure to the outside, there is an advantage that the pressure is automatically restored. However, in this case, since the temperature of the passing refrigerant gas is low, the helical spring in the one-way valve may freeze or the ball may stick. To do so), place the valve away from the Dewar and allow the refrigerant gas to pass through the valve in a warmer state, or take measures such as providing a heater so that the valve does not freeze. (Not shown).

FIG. 4 shows another embodiment of the present invention. The present embodiment embodies the invention according to claim 3.
Since the basic structure of the low-temperature constant-temperature bath 1 is the same as that of FIG.

In this embodiment, in addition to the liquid level gauge 8 for detecting the liquid level of the liquid refrigerant in the low-temperature thermostat, the flow rate of the refrigerant gas discharged through a part of the exhaust pipe 5 through the exhaust pipe 5 is detected. A flow meter 9 is provided to constantly measure the flow rate of the refrigerant gas. It is desirable that the flow meter 9 has a function of checking upper and lower limits and an external output port.

This is because if there is no check function, the CPU 10 constantly monitors the flow value measured by the flow meter 9. For example, when the liquid helium evaporation rate of the low-temperature constant temperature apparatus is 2 liters / day, the flow rate is 2 × 700 / (24 ×
60) = 0.97 l / min (when the helium gas is at 0 ° C.), a flow meter with a full scale of 2 l / min is selected, and the operation guarantee range is 10 to the full scale.
In the case of ９０90%, it is conceivable to use the upper limit check set to 1.7 liters / minute, which is 85% of the full scale, and the lower limit check set to 0.3 liters / minute, which is 15%. Alternatively, it is conceivable that the upper limit value check is set to 4.25 liters / minute and the lower limit value check is set to 0.75 liters / minute with a flow meter of 5 liters / minute.

The operation of this embodiment will be described with reference to the flowchart shown in FIG.

When the detected flow rate value from the flow meter 9 falls below the lower limit, the liquid refrigerant has completely evaporated and no liquid refrigerant has been left in the low-temperature constant temperature bath, or the refrigerant gas containing the exhaust pipe 5 It is conceivable that the flow path has decreased due to blockage of the flow path. In this case, when the CPU 10 cannot confirm the liquid level in the low-temperature constant-temperature bath 1 based on the detection signal from the liquid level meter 8 in addition to the flow rate detection value, that is, recognizes that the liquid refrigerant has run out, Although there is no danger in the operation, the measurement cannot be performed as it is. Therefore, a warning is issued, not an alarm, to request the apparatus operator to replenish the liquid refrigerant.

Conversely, when the liquid level can be confirmed, the flow rate has decreased despite the presence of the liquid refrigerant, and it is considered that the flow path of the refrigerant gas is blocked. At this time, since the pressure in the low-temperature constant temperature bath is high, an alarm is issued to notify the operator of the possibility of danger, and a request is made to stop the measurement and to cope with the situation.

When the flow rate detection value from the flow meter 9 exceeds a predetermined upper limit, it can be recognized that the amount of evaporation of the liquid refrigerant has increased, and for example, the heat insulating performance of the vacuum heat insulating layer of the low-temperature constant temperature bath has decreased. Or the contents in the low-temperature constant-temperature bath are heated for some reason, etc., and if the operation is continued in this state, a situation where stable measurement data cannot be obtained can be assumed. An alarm is issued to alert the operator and the observer.

[0049]

According to the first and second aspects of the present invention, in a cooling device for a biomagnetism measuring device, even if air entering from the outside condenses and condenses on the inner wall of the exhaust pipe and freezes to block the exhaust pipe, the safety of the apparatus is maintained. Can be secured.

According to the third aspect of the invention, in addition to detecting the freezing and blocking of the exhaust pipe, a so-called boil-off phenomenon can be detected at an early stage to further enhance the safety.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a low-temperature constant temperature bath and peripheral devices according to a first embodiment of the present invention.

FIG. 2 is an exploded sectional view of a Wilson seal used in the first embodiment.

FIG. 3 is a schematic configuration diagram of a low-temperature constant temperature bath and peripheral devices according to a second embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a low-temperature constant temperature bath and peripheral devices according to a third embodiment of the present invention.

FIG. 5 is a flowchart for explaining the operation of the third embodiment.

[Explanation of symbols]

1. Low temperature thermostat, 2. Baffle, 3. Level gauge guide tube,
4 ... refrigerant supply guide pipe, 5 ... exhaust pipe, 6 ... pressure conduit, 7
... pressure gauge, 8 ... liquid level gauge, 9 ... flow meter, 10 ... CPU (exhaust pipe blockage, boil-off determination means), 40 ... bursting plate.

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[Procedure amendment]

[Submission date] October 22, 1998 (1998.10.
22)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

That is, a low-temperature constant-temperature bath containing a SQUID and a liquid refrigerant for cooling the SQUID, means for replenishing the low-temperature constant-temperature bath with the liquid refrigerant, and a refrigerant gas generated by evaporating the liquid refrigerant in the low-temperature constant-temperature bath. A cooling device for a biomagnetism measuring device having an exhaust pipe for exhausting, wherein a means for detecting a pressure of a refrigerant gas layer in the low-temperature constant temperature bath and detecting a freezing blockage of the exhaust pipe is provided. (First
Invention). Further, in place of the first aspect, a biomagnetic
In the cooling device of the measuring device, the liquid in the low-temperature constant temperature bath is
A liquid level gauge for detecting the liquid level of the refrigerant and the exhaust pipe.
A flow meter for detecting the flow rate of the refrigerant gas released by
From the detected value of the flow meter and the detected value of the liquid level gauge, the exhaust pipe
With means for determining the presence or absence of freezing blockage
(This is referred to as a second invention).

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

[0014] (2) Next, as an alternative to the configuration of (1) above, the rupture disk or abnormal pressure the pressure of the refrigerant gas layer of the low temperature thermostatic chamber ruptures because of the degassing becomes abnormal pressure A device provided with a responsive one-way valve is proposed ( third invention).

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

(3) Means for responding to the problem of further improving the safety by detecting a so-called boil-off phenomenon in addition to the exhaust pipe blockage include the above-mentioned SQUID, low-temperature constant temperature bath, liquid refrigerant replenishing means, and exhaust pipe. In the cooling device of the biomagnetism measuring device, a liquid level meter for detecting a liquid level of the liquid refrigerant in the low-temperature constant temperature bath, a flow meter for detecting a flow rate of the refrigerant gas discharged through the exhaust pipe, and the flow rate Means for judging the presence / absence of boil-off of the liquid refrigerant from the detection value of the gas meter, and judging the presence / absence of freezing / clogging of the exhaust pipe from the detection value of the flow meter and the detection value of the liquid level gauge. ( 4th invention).

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0049

[Correction method] Change

[Correction contents]

[0049]

According to the first, second and third aspects of the present invention, in the cooling device of the biomagnetism measuring apparatus, even if air entering from the outside condenses and condenses on the inner wall of the exhaust pipe and freezes the exhaust pipe to block the exhaust pipe. By detecting this, the safety of the device can be ensured.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0050

[Correction method] Change

[Correction contents]

According to the fourth aspect of the invention, in addition to detecting freezing and blocking of the exhaust pipe, a so-called boil-off phenomenon can be detected at an early stage to further enhance safety.

Claims (3)

[Claims] 1. A low-temperature constant temperature bath containing a superconducting quantum interference device for biomagnetism measurement and containing a liquid refrigerant for cooling the superconducting quantum interference device, and supplying the liquid refrigerant to the low-temperature constant temperature bath. Means, and a cooling device of a biomagnetism measuring device, comprising: an exhaust pipe for exhausting a refrigerant gas generated by evaporating a liquid refrigerant in the low-temperature constant temperature bath, wherein a pressure of a refrigerant gas layer in the low-temperature constant temperature bath is detected. A means for detecting freezing and closing of the exhaust pipe. 2. A low-temperature constant temperature bath containing a superconducting quantum interference device for biomagnetic measurement and containing a liquid refrigerant for cooling the superconducting quantum interference device, and supplying the liquid refrigerant to the low-temperature constant temperature bath. Means, and an exhaust pipe for exhausting a refrigerant gas generated by evaporating the liquid refrigerant in the low-temperature oven, wherein the pressure of the refrigerant gas layer in the low-temperature oven is an abnormal pressure. A cooling device for a biomagnetism measuring device, comprising: a rupturable plate which bursts to release gas or a one-way valve responsive to abnormal pressure. 3. A low-temperature constant temperature bath containing a superconducting quantum interference device for biomagnetism measurement and containing a liquid refrigerant for cooling the superconducting quantum interference device, and replenishing the low-temperature constant temperature bath with the liquid refrigerant. Means and an exhaust pipe for exhausting a refrigerant gas generated by evaporating the liquid refrigerant in the low-temperature oven, wherein a liquid level of the liquid refrigerant in the low-temperature oven is detected. A liquid level meter, a flow meter for detecting a flow rate of the refrigerant gas discharged through the exhaust pipe, and determining whether or not the liquid refrigerant is boiled off from a detection value of the flow meter, and a detection value of the flow meter. And means for judging the presence / absence of freezing / clogging of the exhaust pipe based on the detection value of the liquid level gauge.