JPH11281723A - Method for monitoring refrigerant for superconducting quantum interference device sensor in biomagnetism measurement system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To observe a refrigerant state on the same computer display that controls biomagnetism measurement by measuring a quantity of the remaining refrigerant of a superconducting quantum interference device(SQUID) sensor in a dewar at optional times or periodically. SOLUTION: A dewar 4 filled with liquid helium as a refrigerant is placed above a chest part of a subject 2. A plurality of SQUIDs including SQUIDs and detection coils connected to the SQUIDs are stored in matrix form at a bottom part of the dewar 4. The liquid helium is continuously supplemented from an automatic supplementation device 5 outside a magnetic shield 1. A level gage is set along an inner wall of the dewar 4 to measured a level of the liquid helium. A quantity of the remaining refrigerant of a SQUID sensor in the dewar 4 can be confirmed on a screen of a computer 8 which executes biomagnetism measurement. The quantity of the remaining refrigerant can be measured optionally when it is desired. The quantity of the remaining refrigerant can be measured automatically at set times, or periodically, and the quantity and a decrease ratio can be confirmed on the screen of the computer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for monitoring a refrigerant for cooling a superconducting quantum interference device (hereinafter referred to as SQUID) sensor in a biomagnetic measurement system.

[0002]

2. Description of the Related Art Conventionally, for example, liquid level control of liquid helium, which is a refrigerant in a cryostat, is carried out in the cryostat by a continuous level gauge housed in the cryostat, a level gauge power supply for inputting a signal thereof, and an interlocking operation therewith. There is a liquid level control in a liquid helium supply device provided with a transfer tube valve which is operated in a controlled manner. A technique related to this is disclosed in Japanese Patent Application Laid-Open No. 60-70785. There is a problem in immediately applying the above-described conventional liquid level control device including a continuous liquid level gauge, a liquid level gauge power supply, and a transfer tube valve to, for example, a biomagnetic measurement system.

[0003]

The liquid helium level control device provided with the above-mentioned conventional continuous level gauge, level gauge power supply, transfer tube valve, etc. is often required to be immediately applied to, for example, a biomagnetic measurement system. There is a problem. First, the history of the liquid surface of liquid helium cannot be confirmed. Second, the rate of decrease in liquid helium cannot be predicted, and running costs cannot be reduced. Third, consideration for problems specific to the biomagnetic measurement system, for example, in the case of a magnetocardiograph, which cannot measure the liquid level of liquid helium because the measurement value is affected during biomagnetic measurement. There was no consideration.

The present invention takes into account the inability to confirm the history of the liquid surface of the conventional liquid helium, the prediction of the rate of decrease thereof, and the special problems in biomagnetism measurement. An object of the present invention is to provide a method for monitoring a SQUID refrigerant in a biomagnetic measurement system in which a state of a SQUID sensor refrigerant in a dual can be observed on a display of the same computer or a control device that controls the biomagnetic measurement. It is assumed that.

[0005]

The SQUID according to the present invention
The configuration of the monitoring method of the sensor refrigerant includes a dewar, a SQUID sensor in the dewar, a refrigerant for cooling the SQUID sensor, a liquid level meter for measuring a liquid level of the refrigerant, a refrigerant replenishing device, and the respective devices. In a method for monitoring a SQUID sensor refrigerant in a biomagnetic measurement system including a control device having a display device for controlling and displaying the refrigerant state on a screen, the control device measures the remaining amount of the refrigerant by the SQUID sensor in the Dewar. Is performed at an arbitrary time or at an arbitrary fixed period. In the refrigerant monitoring method for an SQUID sensor described in the preceding paragraph, the control device skips the measurement of the remaining amount of the refrigerant while collecting the measurement signal from the SQUID sensor. In the method for monitoring a SQUID sensor refrigerant described in the preceding paragraph, the history value of the remaining amount measurement of the refrigerant is displayed in a graph or a list on the display device. In the method for monitoring a SQUID sensor refrigerant described in the preceding paragraph, the latest residual value of the residual amount measurement of the refrigerant is displayed on a dedicated screen on the display device. In the method for monitoring a refrigerant of a SQUID sensor according to the preceding paragraph, the control device calculates a refrigerant reduction rate at regular time intervals from the history of the remaining amount of the refrigerant and displays the graph on a screen of the display device. is there. In the refrigerant monitoring method for the SQUID sensor according to the preceding paragraph, the lower limit setting value of the remaining amount is displayed on a graph of the history value of the remaining amount measurement of the refrigerant. In the method for monitoring a refrigerant of a SQUID sensor described in the preceding paragraph, an upper limit set value of the reduction rate is displayed on a history value graph display of the refrigerant reduction rate. SQUID described in the previous section
In the refrigerant monitoring method of the sensor, the measurement points are plotted on a graph of the history value of the refrigerant remaining amount measurement, and the measurement time can be confirmed from the plot. In the refrigerant monitoring method of the SQUID sensor according to the preceding paragraph, a warning is issued when the measured remaining amount of the refrigerant becomes lower than the lower limit set value or when the decrease rate of the refrigerant exceeds the upper limit set value. Is issued. In the refrigerant monitoring method of the SQUID sensor described in the preceding paragraph, an area in which the measured refrigerant remaining amount is lower than the lower limit set value is displayed in red. In the method for monitoring a refrigerant of a SQUID sensor described in the preceding paragraph, an area where the refrigerant reduction rate exceeds an upper limit set value is displayed in red. In the refrigerant monitoring method of the SQUID sensor described in the preceding paragraph, the display time range can be arbitrarily set in a graph display of the history value of the remaining amount measurement of the refrigerant. S described in the previous section
In the refrigerant monitoring method of the QUID sensor, even if the measurement of the remaining amount of the refrigerant is discontinuous, the history value of the remaining amount of the refrigerant is continuously displayed in a graph. In the refrigerant monitoring method of the SQUID sensor described in the preceding paragraph, the range of the displayed time can be arbitrarily set by a graph display of the refrigerant decreasing rate. SKU described in the previous section
In the refrigerant monitoring method of the ID sensor, the state of supply of the refrigerant is displayed on a screen of the display device while the refrigerant is being supplied from the refrigerant tank by the automatic supply device. In the refrigerant monitoring method for a SQUID sensor described in the preceding paragraph, the refrigerant monitoring program is automatically started by starting the control device. In the method for monitoring a refrigerant of a SQUID sensor according to the preceding paragraph, the display screen of the refrigerant state displays the refrigerant state in an uppermost title bar, an icon bar below the title bar, and a central part of the screen below the icon bar. The screen is divided into a display area, the latest helium remaining amount display box on the left side of the graph display area, and a cursor bar for display movement at the bottom, and the related button of the icon bar is pressed with a pointing device. This allows the refrigerant remaining amount to be measured, and displays the history value of the refrigerant remaining amount measurement within a predetermined range in the center portion of the screen, and physically matches the latest remaining amount of the refrigerant. A refrigerant management screen having a predetermined function of displaying a display area outside the predetermined range with a cursor bar and displaying a predetermined area on the display screen under a predetermined condition. It is characterized in. In the refrigerant monitoring method of the SQUID sensor according to the preceding paragraph, the history display screen of the refrigerant remaining amount displays the refrigerant remaining amount history value graph, plots the measurement points on the graph, and displays the refrigerant remaining amount lower limit value. In addition to displaying on the graph, a region where the refrigerant remaining amount is lower than the lower limit value is displayed in red. In the refrigerant monitoring method for a SQUID sensor according to the preceding paragraph, the refrigerant management screen having a predetermined function of opening and closing on the display screen includes an automatic measurement setting screen for managing an automatic measurement mode opened by pressing a button of the icon bar, and the refrigerant. A remaining amount warning notification screen that opens when the remaining amount is equal to or less than a predetermined lower limit value, and a decreasing rate warning notification screen that opens when the refrigerant decreasing rate is equal to or more than a predetermined upper limit value and a refrigerant helium automatic replenishment monitor screen that opens by pressing the button of the icon bar It is characterized by having.

A method for monitoring the refrigerant of the SQUID sensor having the above-described configuration will be functionally described. In the present invention, the sensor refrigerant remaining amount can be confirmed on the computer screen, and when the set time has elapsed, the helium remaining amount is automatically measured, and the remaining amount is equal to or less than the set value or the decrease rate is equal to or greater than the set value. If there is, a notification is made on the screen and the biomagnetism can be measured without worrying about the remaining amount of the refrigerant for each measurement, so that the biomagnetism measurement can be performed efficiently. Since the history of the remaining amount of helium and the decrease rate can be confirmed in a list or a graph on a computer, the degree of vacuum of Dewar can be confirmed.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present embodiment, in the biomagnetism measurement system shown in FIG. 1, the remaining amount of liquid helium is monitored on a screen on a control device (computer in this embodiment). . FIG. 1 is a schematic configuration diagram of a biomagnetometer that performs magnetocardiographic measurement according to an embodiment of the present invention. FIG. 2 is a Dewar cross-sectional view including a liquid level gauge mounting method of the biomagnetometer of FIG. FIG. 3 is an explanatory diagram of a graph display screen in the biomagnetism measuring device of FIG. 1, and FIG.
FIG. 5 is an explanatory view of a list display screen in the biomagnetism measuring apparatus of FIG. 1, FIG. 5 is an explanatory view of a decrease rate display screen in the biomagnetism measuring apparatus of FIG. 1, and FIG. 7, FIG. 7 is an explanatory view of a remaining amount warning notification screen in the biomagnetism measuring apparatus of FIG. 1, FIG. 8 is an explanatory view of a decreasing rate warning notification screen in the biomagnetic measuring apparatus of FIG. 1, FIG.
FIG. 10 is an explanatory diagram of a helium automatic replenishment monitor screen in the biomagnetism measuring apparatus of FIG. 1, and FIG. 10 is a flowchart of liquid helium automatic measurement in the case where the biomagnetism measurement of the biomagnetism measuring apparatus of FIG. 1 is performed.

Referring to FIG. 1, a biomagnetism measuring apparatus according to an embodiment of the present invention will be described. The biomagnetic measurement device is
In order to remove the influence of environmental magnetic noise, it is installed in a magnetically shielded room 101. The subject 102, which is a subject composed of a living body, is usually measured while lying on the bed 103, but may be measured while lying down.

[0009] It is assumed that the body surface of the subject (in the case of the chest, a plane generally parallel to the chest wall) is substantially parallel to the plane of the bed 103, and this plane is defined by the x-y coordinate system (x, y, z). y
Shall be parallel to the plane. Although the chest of the subject 102 has a curved surface and is inclined with respect to the surface of the bed 103, it is assumed to be substantially parallel to simplify the description.

A dewar 104 filled with liquid helium as a refrigerant is disposed above the chest of the subject 102, and the dewar 104 is a SQUID (Superc).
conducting Quantum Interfe
A plurality of SQUIDs 20-1... 27-8 shown in FIG. 2 (b) each including a detection device connected to the SQUID and a detection coil are shown in a matrix form. It is housed in the bottom 203. Liquid helium is continuously supplied from an automatic supply device 105 outside the magnetic shield 101. Liquid level meter 2
Numeral 02 is disposed along the inner wall of the Dewar 104 to measure the liquid level of the liquid helium. The liquid level gauge 202 is disposed in a cylinder of the liquid level gauge 202 shown in the drawing using, for example, a superconducting rod, and when cooled to liquid helium at a predetermined liquid level, the resistance of that part becomes zero. Become. By measuring the resistance of the superconducting rod, the liquid level of liquid helium can be obtained. A signal corresponding to the resistance of the superconducting bar is output. Hereinafter, it is called a resistance type superconducting liquid level gauge.

The SQUID 20-1... 27-
8 outputs a voltage generated from the subject 102 and having a specific relationship with the strength of the biomagnetic field detected by the detection coil, and the output is FLL (Flux Locked l).
(op) input to the circuit 106. The FLL circuit 10
6 is the SQUID so that the output of the SQUID is kept constant.
The change of the biomagnetic field input to the ID is canceled via the feedback coil. By converting the current flowing through the feedback coil (this is called a magnetic field lock) into a voltage, a voltage output having a specific relationship with a change in the biomagnetic field signal can be obtained. Since the detection is performed via the feedback coil as described above, a weak magnetic field can be detected with high sensitivity.

The output voltage is input to an AFA 107 comprising an amplifier, a filter, and an amplifier. The output is sampled, A / D converted, and taken into a computer 108. The computer 108 is composed of a personal computer, 108-1 is a display unit thereof, 108-
2 denotes a keyboard, and 108-3 denotes a mouse.
The mouse 108-3 is used to select a processing target by moving the cursor on the screen. This operation can also be performed by operating the keyboard. It is assumed that a printer is connected to the computer 108.

The AFA 107 has an input gain and an output gain that can be adjusted, a low-pass filter that passes a frequency signal that is lower than the first reference frequency, and a frequency that is higher than the second reference frequency that is lower than the first reference frequency. It includes a high-pass filter that passes signals and a notch filter that cuts off the frequency of the commercial power supply.

The computer 108 can perform various processes on the input signal, and the processing results can be displayed on the display unit 108-1. Note that the computer 108 shown in FIG. 1 shows one embodiment, and the present invention is not limited to this. For example, a display having a touch panel, or a device using a pointing device such as a trackball or a joystick instead of a mouse may be used instead of a mouse. Also,
In some cases, a computer connected via a public line may be used.

As the SQUID, for example, DC SQ
UID is used. When an external magnetic field is applied to the SQUID, a DC bias current (I bias) is applied to the SQUID so that a voltage (V) corresponding to the external magnetic field is generated.
Is shed. When the external magnetic field is represented by a magnetic flux Φ, a characteristic curve of V with respect to the magnetic flux Φ, that is, a magnetic flux Φ-voltage (V) characteristic curve is given by a periodic function. Prior to measurement, the offset voltage (VOFF) of the FLL circuit 6 must be
Is adjusted to adjust the DC voltage of the DC curve of the magnetic flux Φ-voltage (V) characteristic curve to the zero level.

The automatic measurement of liquid helium will be described with reference to the biomagnetism measuring device shown in FIG. 1 and the flowchart shown in FIG. In FIG. 10, when the computer 108 of FIG. 1 for measuring and analyzing a magnetic field generated from a living body and controlling each component device is started, a liquid helium management program is started at the same time, and the computer 108 is started.
The liquid helium management screen shown in FIG.

Here, creation of the liquid helium management screen of FIG. 3 will be described. To create the liquid helium management screen,
All operations are performed by the computer 8, and are operated by the display unit 8-1, the keyboard unit 8-2, and the mouse 8-3.
The computer 8 is equipped with appropriate software, for example, “Windows 95 Application”, and the computer 8 operates accordingly.

As shown in FIG. 2A, the liquid level gauge 202 provided in the Dewar 104 has a large number of holes formed in an outer cylinder, and the liquid helium in the Dewar 104 is discharged from the large number of holes. The liquid helium surface of the Dewar 104 and the detection liquid helium surface of the liquid level gauge 202 are made to enter the cylinder freely. As described above, the liquid level gauge 202 is a resistance type superconducting liquid level gauge, and the output is an analog signal.

The liquid level gauge 202 is always inserted into the Dewar 104, but when it is connected to an A / D converter (built in the AFA amplifier 7), the liquid level gauge 202 acts as an antenna. Since the influence of the external magnetic field is affected as noise when measuring the heart magnetism, when the liquid helium remaining amount measurement command is not output from the computer 8, it is disconnected by, for example, a relay switch. When the liquid helium remaining amount measurement command from the computer 8 is executed, the relay switch is connected, and the liquid level gauge 202 acquires the current analog value of the liquid helium remaining amount and passes through the A / D converter. , The computer 8
It is taken in. The fetched digital values are stored in a storage device (not shown) such as a hard disk provided in the computer 8.

The dynamic display using the stored measurement data will be described. As shown in the drawing, the keyboard 8-2 and the mouse 8-3 are operated to perform various arithmetic processings on signals stored in a storage device such as a hard disk based on software installed in the computer 8. , Dynamic display on the display. Hereinafter, the operation of the keyboard 8-2 and the mouse 8-3 will be complicated, and the description thereof will be omitted.

At the top of the screen, a title bar "helium management screen" is defined. Below this, an “icon bar” is displayed in which icons such as (measurement execution), (graph), (table), (decrease rate), (setting), and (automatic replenishment monitor) are displayed. In the icon bar,
(Measurement execution) 301 is a liquid helium remaining amount measurement execution button, (graph) 302 is a graph display switching button,
(Table) 303 is a list display switching button, (decrease rate) 304 is a reduction rate graph display switching button, (setting) 305 is an automatic measurement setting screen button, and (automatic replenishment monitor) 306 is an automatic replenishment monitor screen. Shows a display button. It should be noted that the display of the two is constant regardless of the change of the display screen.

A "graph display area" 32 is provided at the center of the screen.
The screen is divided into 0, the latest helium remaining amount display box 307 on the left side of the "graph display area" 320, and a "cursor bar for moving the graph display" at the bottom. The “graph display area” 320 counts clock interrupts from the computer 8 to perform time management, and the horizontal axis represents the time axis 317.
Set forth in In the drawing, the length is 24h from 16 to 15.

In response to the measurement signal indicating the liquid helium liquid level of the Dewar 104 from 0 to the maximum, the computer 8 calculates
It is converted to 100%, and the vertical axis is defined as the remaining liquid level axis 319.
The latest helium remaining amount display box 307 is determined to have the same shape as the Dewar 104 so as to have the same physical consistency as the liquid helium liquid level, and the computer 8 measures the liquid helium liquid level. Is subjected to image processing and the liquid level is displayed. Similarly, a screen of “cursor bar for moving graph display” is formed at the bottom.

The created screen is stored in a storage device such as a hard disk provided in the computer 8, and if necessary, a (graph) 302 of the icon bar is displayed.
Click to display. In order to illustrate that (graph) 302 in the icon bar is clicked, "shading" is displayed, so that the characters are not clear, but "graph" is displayed outside the table. The display of the other icon bars is the same.

Next, description will be given of a case where a graph of the history of the remaining amount of the refrigerant is described in the "graph display area" 320. On the time horizontal axis 317 on the graph display screen, the intersection of the time when the remaining amount was measured and the extension line of the remaining amount liquid level axis 319 of the remaining amount measured value, 309, 310, 311, 312, 31
Plot 3 Connect each point on this plot with a line. Next, a line 315 corresponding to the warning notification remaining lower limit value (remaining amount 20% in the figure) from the remaining liquid level axis 319 is displayed on the entire time axis 317. The measurement time can be confirmed on the screen, and the area 315 or less is displayed in red.

The latest helium remaining amount display box 307 is
The latest helium remaining amount is instructed, and a horizontal axis scale range input box 316 is provided below the latest helium remaining amount display box 307, which is one day in the figure. The display screen is moved left and right by the cursor 318 in the “cursor bar for moving the graph display” at the bottom, and a portion that is not displayed in the range of the horizontal axis time scale can be displayed.

Similarly to FIG. 3, the display screens shown in FIGS. 4, 5, 6, 7, 8, and 9 are also composed of a computer 8 equipped with appropriate software, a keyboard 8-2, and a mouse 8. -3
Is created by the same method by operation, and stored in a storage device such as a hard disk of the computer 8, and if necessary, is displayed by clicking a predetermined icon in the icon bar.

The method of monitoring the refrigerant in the magnetic field measuring device will be described with reference to the flowchart of FIG. Step 1
In step 001, on the graph display screen shown in FIG. 3, the mouse button 108-2 is used to click (hereinafter, press) the setting button 305 on the icon bar to open the automatic measurement setting screen shown in FIG. FIG. 6 is the same as FIG.
When the line 315 corresponding to the warning notification remaining lower limit value is displayed, the keyboard 108-2 displays the warning notification remaining lower limit value LI20.
% Is set in the frame. The automatic measurement setting screen in FIG.
Title bar automatic measurement setting screen, automatic measurement ON checkbox 601, automatic measurement cycle 604, warning notification remaining lower limit value 605, warning notification upper limit differential value 606, warning notification O
N box 602 and OK 607, warning sound ON box 6
03 and cancel 608 are displayed.

On the opened automatic measurement setting screen of FIG. 6, the automatic measurement mode is set by pressing the automatic measurement setting check box 601 for defining the measurement mode with the cursor of the mouse 108-3. Then, the keyboard 108-2 inputs the automatic measurement cycle time Δt to the automatic measurement cycle time input box 604 on the setting screen. For example, 1 is input and the automatic measurement cycle time is set to 1 hour.

In step 1002, the user sets “20”% in the input box 606 to set the decrease rate warning upper limit UI. The warning notification setting check box 602 is pressed with the cursor of the mouse 108-3 to set the warning notification mode, and then the warning sound setting check box 603 is pressed to set the warning sound mode. Here, the reduction rate (DV) is
The last helium remaining value-the current helium remaining value / the current measurement time-the previous measurement time.

With the above setting, the liquid helium remaining amount in the dur 104 is measured by the liquid level meter 202 at a cycle of one hour.
When the remaining amount of liquid helium becomes 20% or less, a warning sound is sounded, and a remaining amount warning notification screen shown in FIG. 7 is set to be opened, and the amount of reduction of liquid helium in the dewar 104 per hour is 20% or more. , A warning sound is emitted and a setting is made so that the decrease rate warning notification screen of FIG. 8 is opened.

As shown in the figure, the title bar is set as the remaining amount warning notification screen in the remaining amount warning notification screen shown in FIG. , Helium remaining amount is below the set value 701, current helium remaining amount:% 702,
An [OK] button 703 is set.

In the decrease rate warning notification screen of FIG. 8, the title bar is set as the decrease rate warning notification screen as shown in FIG.
Warning at the bottom screen! , Helium reduction rate has exceeded the set value 801, reduction rate:% (96 / Hou
r) 802, [OK] button 803 are set.

In step 1003, the current time
By adding t = 1, the next measurement time Nt is determined. 1 is entered in the horizontal axis scale range input box 316 on the graph display screen.
Is input, and the range of the horizontal axis 317 is input as 24, which is 24 hours. For example, 19
Since the automatic measurement cycle time 604 was set to one hour at 3:00 pm on August 27, 1997, the first measurement of the remaining amount of liquid helium was performed one hour later on August 2, 1997.
It is 4:00 pm on the 7th.

In step 1004, the current time and N
It is determined whether or not t matches. Current time and Nt
If they match, proceed to the next step. If they do not match, they return and wait until they do. In step 1014, the SQUID 20-1,.
There is a signal from 27-8, and it is determined whether or not biomagnetic measurement is being performed. If the measurement is in progress, the current time + Δt is added in step 1015 to make the next measurement time Nt. If the measurement is not being performed, the process proceeds to the next step 1005.

In step 1005, 1997
At 4:00 pm on March 27, Computer 1
08 acquires the value of the liquid level gauge 202. The value was, for example, 50% as shown in FIG. In the graph display area 320 of the graph display screen of FIG. 3, the liquid helium remaining amount CV 50% at 4:00 pm on August 27, 1997 is displayed as a point 309, and the latest liquid helium remaining amount display box 307 is displayed. Of the latest liquid helium balance CV3085
0% is indicated.

In step 1005, 1997
At 5:00 pm on March 27, Computer 1
08 acquires the value of the liquid level gauge 202. Its CV value is 25
%Met. In step 1006, the CV is compared with the LI set in step 1002, and CV ≦
The LI is determined. If CV ≦ LI, a warning sound is issued in step 1007, a remaining amount warning screen is opened in step 1008, liquid helium is supplied automatically or manually, and the condition of CV ≦ LI is eliminated. The quantity warning screen is closed. In step 1009, if the remaining amount warning screen is closed or if CV ≦ LI is not satisfied, step 1 is executed.
010.

In step 1010, the reduction rate DV
Is 50% liquid helium at 4:00 pm on August 27, 1997 and 5:00 pm on August 27, 1997.
From the liquid helium remaining amount of 25% at the minute, the reduction rate per hour is calculated as 25%. In step 1011, it is determined that DV ≧ UI. If DV ≧ UI is YES, that is, the set value is equal to or more than 20%, an alarm sounds in step 1012, and in step 1013, the decrease rate shown in FIG. A warning screen opens. Thereafter, when the liquid helium is replenished automatically or manually and the condition of DV ≧ UI is resolved, step 1 is executed.
At 014, the user can press the OK button 803 on the reduction rate warning notification screen in FIG. 8 to close the reduction rate warning notification screen.

In step 1011, when DV ≧ UI is NO or when the decrease rate warning screen of FIG. 8 is closed, the process proceeds to step 1015, where the current time + Δt is added, the next measured time Nt is set, and the process returns to step 1004. .

Here, the change by pressing the icon bar between the graph format display screen of FIG. 3 and the list display screens of FIGS. 4, 5, 6, and 7 will be described. This change can be made at any point from step 1001 to step 1005. However, since each step is complicated, the description will be omitted and the display screen will be mainly described.

Here, FIG. 4 will be described. In FIG. 4, the title bar and the icon bar are the same as described above without changing FIG. 3, and the description thereof is omitted. Further, as described above, the screen forming method is also the same as that in FIG. As shown in the figure, a liquid helium remaining amount list display area 414 is provided at the center of the screen, a cursor bar for moving the respective columns of the liquid helium remaining amount list display area 414 in the vertical direction at the left end, and a leftmost end at the left end. The screen is divided into the latest liquid helium remaining amount display box 407.

The liquid helium remaining amount list display area 41
4 is a table in which the horizontal direction is short, the vertical direction is a column in the longitudinal direction, and the horizontal direction is Date, Time, [%],
.. 409, 410, 411,... Are displayed sequentially every hour. The cursor bar and the latest liquid helium remaining amount display box 407 are the same as those in FIG.

Next, FIG. 5 will be described. In FIG. 5, the title bar and the icon bar are the same as in FIG. 3 without changing FIG. 3. As described above, the screen forming method is also the same as in FIG. The horizontal axis scale of the graph indicating the time at which the
h) Since the cursor 518 is also the same, the description will not be repeated and the description will be focused on its display.

As shown in the figure, the vertical scale (−10 in the figure) of the liquid helium reduction rate at the left end of the graph display area 515.
(From 0% to + 100%). In FIG. 5, 510 to 513 are graphs showing the decrease rates with respect to each time, and 514 is a line showing the set upper limit value of the warning notification differential value.

List display screen switching button 50 in FIG.
When 3 is pressed, a display screen is displayed in the list display area 414 in FIG. In the figure, the list display area 414 of the list display screen includes the top display area 4 of the list display screen.
09 is, for example, 4:00 pm on August 27, 1997.
50% of the liquid helium remaining amount CV 409 at the minute is displayed, and 50% of the latest liquid helium remaining amount CV 408 is displayed in the latest liquid helium remaining amount CV display box 407.

Further, when the steps proceed, August 1997
Helium remaining CV2 at 5:00 pm on March 27
5% is displayed, displayed in the display area 410, and 25% of the latest liquid helium remaining amount CV 408 is shown in the latest liquid helium remaining amount CV display box 407. When a button 402 for switching the display of the graph format on the screen is pressed, FIG.
The screen switches to the graph format display screen. Liquid helium balance CV at 5:00 pm on August 27, 1997
25% is displayed as point 310. The latest liquid helium remaining amount display box 307 shows 25% of the latest liquid helium remaining amount CV308.

Button 3 for switching the display of the decrease rate graph in FIG.
When the user presses the button 04 to switch to the decrease rate graph display screen of FIG.
The decrease rate of 25% at 5:00 pm on August 27, 2007 is displayed as a line 510 in the graph display area 515, and the latest liquid helium remaining amount display box 507 displays 25% of the latest liquid helium remaining amount 508. Is shown. An area 519 that is equal to or greater than the set warning notification decrease rate upper limit value line 514 is displayed as a portion painted in red.

List display screen switching button 50 in FIG.
When 3 is pressed, a display screen is displayed in the list display area 414 in FIG. In the figure, the list display area 414 of the list display screen includes the top display area 4 of the list display screen.
09 is, for example, 4:00 pm on August 27, 1997.
50% of the liquid helium remaining amount CV 409 at the minute is displayed, and 50% of the latest liquid helium remaining amount CV 408 is displayed in the latest liquid helium remaining amount CV display box 407.

Further, as the steps proceed, August 1997
Helium remaining CV2 at 5:00 pm on March 27
5% is displayed, displayed in the display area 410, and 25% of the latest liquid helium remaining amount CV 408 is shown in the latest liquid helium remaining amount CV display box 407. When a button 402 for switching the display of the graph format on the screen is pressed, FIG.
The screen switches to the graph format display screen. Liquid helium balance CV at 5:00 pm on August 27, 1997
25% is displayed as point 310. The latest liquid helium remaining amount display box 307 shows 25% of the latest liquid helium remaining amount CV308.

Button 3 for switching display of decrease rate graph in FIG.
When the screen is switched to the decrease rate DV graph display screen of FIG.
Reduction rate DV25% of 5:00 pm on August 27, 1997
Is displayed as a line 510 in the graph display area 515,
The latest liquid helium remaining amount display box 507 indicates that the latest liquid helium remaining amount 508 is 25%. Area 519 that is equal to or greater than the set warning notification decrease rate upper limit value line 514
Is displayed as a portion painted in red.

In step 1005, the next liquid helium remaining time measurement time is 6:00 pm on August 27, 1997.
Minutes, the computer 108 reads the level gauge 202
Get the value of. The value of the liquid level gauge 202 at this time is 20%
Met. Lower limit value 2 set in step 1006
Since it is 0% or less, a warning sound is emitted in step 1007, and the remaining amount warning notification screen of FIG. 7 is opened. While the remaining amount warning notification screen of FIG. 7 is being displayed, the display drawing of FIG. 5 is hidden. Thereafter, liquid helium is automatically or manually replenished. In step 1009, the user presses the OK button 703 on the remaining amount warning notification screen in FIG. 7 to close the remaining amount warning notification screen. The reduction rate display drawing of FIG. 5 reappears.

In step 1010, 199 of FIG.
From 25% liquid helium at 5:00 pm on August 27, 2007 and 20% liquid helium at 6:00 pm on August 27, 1997, the rate of decrease per hour Is calculated to be 5%. 5 is displayed as a line 511 in the graph display area 515 of the decrease rate graph display screen, and the latest liquid helium remaining amount display box 507 shows 20% as the latest liquid helium remaining amount CV 508.

When the graph display switching button 402 in FIG. 5 is pressed, the screen is switched to the graph display screen in FIG.
The liquid helium remaining 20% at 6:00 pm on August 27, 997 is displayed as a point 311, and the latest liquid helium remaining 20% is displayed as 308 in the latest liquid helium remaining display box 307. It is. In FIG.
When the list display switching button 303 is pressed, the screen is switched to the list form display screen of FIG. 4 and the remaining liquid helium 2 is displayed in the list display area 414 of the list form display screen of FIG.
0% is displayed as 411, and the latest liquid helium remaining amount display box 407 indicates the latest liquid helium remaining amount 20% as 408.

In step 1005, the next liquid helium remaining time measurement time is 6:00 pm on August 27, 1997.
Minutes, the computer 108 reads the level gauge 202
Get the value of. The value of the liquid level gauge (202) at this time is 2
It was 0%. In step 1006, since the set lower limit is 20% or less, a warning sound is emitted in step 1007, and the remaining amount warning notification screen of FIG. 7 is opened. In step 1014, the user presses an OK button 703 on the remaining amount warning notification screen shown in the figure to close the remaining amount warning notification screen.

In step 1010, 1997
25% liquid helium remaining at 5:00 pm on March 27
From the liquid helium remaining amount of 20% at 6:00 pm on August 27, 1997, the reduction rate per hour was calculated to be 5%, and the graph display area 5 of the reduction rate graph display screen of FIG.
15 is displayed as 511 and the latest liquid helium remaining amount display box 507 is displayed in the latest liquid helium remaining amount 20%.
Is shown as 508.

When the graph display switching button 402 in FIG. 3 is pressed, the screen switches to the graph display screen in FIG.
The liquid helium remaining amount 20% at 6:00 pm on August 27, 997 is displayed as 311 and the latest liquid helium remaining amount display box 307 displays the latest liquid helium remaining amount 2.
0% is shown as 308. When the list display switching button 303 is pressed, the screen is switched to the list display screen of FIG. 4 and the list display area 41 of the list display screen is displayed.
4, the remaining liquid helium remaining 20% 411 is displayed, and the latest liquid helium remaining display box 407 shows the latest liquid helium remaining 20%, 408.

In step 104B, the next liquid helium remaining time measurement time is 7:00 pm on August 27, 1997.
It is the minute and the time for automatic measurement.
Since the signal from the SQUID sensor at 016 was being measured, the liquid helium remaining amount measurement at 7:00 pm on August 27, 1997 is not performed. In step 1005,
Since it is 8:00 pm on August 27, 1997, which is the next liquid helium remaining time measurement time, the computer 108 acquires the value of the liquid level gauge 202. At this time, the value of the liquid level gauge 202 was 10%. In step 1006, the lower limit has become 20% or less, so in step 1007, a warning sound is emitted and the remaining amount warning notification screen of FIG. 7 is opened.

At step 1014, the OK button 703 on the remaining amount warning notification screen in FIG. 7 is pressed to close the remaining amount warning notification screen. In step 1010, the liquid helium balance at 6:00 pm on August 27, 1997
% And the liquid helium remaining amount of 10% at 8:00 pm on August 27, 1997, the reduction rate per hour is calculated as 5%.

The remaining liquid helium 10% is displayed as 412 in the list display area 414 of the list display screen of FIG. 4, and the latest liquid helium remaining value 10% is displayed in the latest liquid helium remaining display box 407. 408. Since the set value of the warning notification remaining amount lower limit is 20% or less, 10% 412 measured at 20:00 is painted in red. Note that the illustration is not shown in red because the drawing is complicated.

When the screen is switched to the reduction rate graph display screen of FIG. 5 by pressing the reduction rate graph display switching button 404, the reduction rate of 5% is displayed as 512 in the graph display area 515, and the latest liquid helium remaining amount display box is displayed. 50
In FIG. 7, the latest liquid helium remaining amount 25% is shown as 508.

When the graph display switching button 502 is pressed, the screen is switched to the graph display screen of FIG. 3, and the liquid helium remaining amount at 8:00 pm on August 27, 1997
% Is displayed as 312, and the latest liquid helium remaining amount 10% is displayed in the latest liquid helium remaining amount display box 307.
08.

Since the liquid helium remaining amount is 10%, the liquid helium automatic replenishing device 110
From 05, the supply of liquid helium to the Dewar 104 is started.
Pressing the automatic supply monitor button 306 opens the liquid helium automatic supply monitor screen of FIG. The liquid helium automatic supply monitor screen of FIG. 9 has a title bar defined as a helium automatic supply monitor screen, a helium automatic supply indicator below the title bar, and a liquid helium remaining area 901.
A liquid helium remaining amount 902 and a scale 903 are displayed, and a liquid helium remaining value 904 and an OK button 905 are displayed.

In this screen, the liquid helium remaining amount is acquired every minute, and the liquid helium remaining amount 902 and the liquid helium remaining value 904 in the liquid helium remaining amount display area 901 of the automatic replenishment monitor screen of FIG. Is updated until is 100%. At 100%, replenishment is over, so
Pressing an OK button 905 closes the automatic replenishment monitor screen of FIG.

Although the automatic measurement time has not yet come, the user wants to know the liquid helium remaining amount at 8:57 pm on August 27, 1997, and presses the measurement execution button 301. The computer 108 acquires the value of the liquid level gauge 202. The value obtained at this time was 100%. In step 1010, the liquid helium remaining amount of 10% at 8:00 pm on August 27, 1997 and the 8:57 pm on August 27, 1997
From 10% liquid helium remaining in minutes, the reduction rate per hour is calculated to be about -95%.

The liquid helium remaining amount 100% is displayed on the graph display screen of FIG. 3 as 313, and the latest liquid helium remaining amount display box 307 is displayed in the latest liquid helium remaining amount display box 307.
0% is shown as 308. An area 314 below the graph 315 with the set lower limit of 20% is displayed in red. When the screen is switched to the reduction rate graph display screen of FIG. 5 by pressing the reduction rate graph display switching button 304, the reduction rate of -95%
3 and the latest liquid helium remaining amount display box 507 displays the latest liquid helium remaining amount 100% as 508.
Is shown.

When the list display switching button 503 is pressed, the screen is switched to the list display screen of FIG. 4, and the liquid helium remaining amount 100% is displayed as 411 in the list display area 414 of the list display screen of FIG. Is done. The latest liquid helium remaining amount display box 407 indicates the latest liquid helium remaining amount 100% as 408.

[0067]

As described above in detail, according to the configuration of the present invention, the remaining amount of the skid sensor refrigerant in the Dewar can be confirmed on the screen of the computer for performing the biomagnetic measurement, and can be arbitrarily determined when it is desired to know the remaining amount. The remaining amount of refrigerant can be measured. Also, when the set time or the set cycle time comes, the helium remaining amount is automatically measured, and if the remaining amount is less than the set value or the decrease rate is more than the set value, a warning screen and a warning sound indicate that. Give me The history of the liquid helium remaining amount and reduction rate can be confirmed in a list or graph on the computer screen, and the measurement can be performed without paying attention to the remaining amount of the refrigerant every time the biomagnetism is measured. In addition, the biomagnetic measurement can be performed efficiently, and in addition, the degree of vacuum of Dewar can be estimated.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a biomagnetism measurement apparatus for performing magnetocardiography measurement according to an embodiment of the present invention.

FIG. 2 is a Dewar cross-sectional view including a method of attaching a liquid level gauge to the biomagnetism measuring apparatus of FIG. 1;

FIG. 3 is an explanatory diagram of a graph display screen in the biomagnetism measuring device of FIG. 1;

FIG. 4 is an explanatory diagram of a list display screen in the biomagnetism measuring device of FIG. 1;

FIG. 5 is an explanatory diagram of a reduction rate display screen in the biomagnetism measuring device of FIG. 1;

FIG. 6 is an explanatory diagram of an automatic measurement setting screen in the biomagnetism measuring device of FIG. 1;

FIG. 7 is an explanatory diagram of a remaining amount warning notification screen in the biomagnetism measuring device of FIG. 1;

FIG. 8 is an explanatory diagram of a reduction rate warning notification screen in the biomagnetism measuring device of FIG. 1;

FIG. 9 is an explanatory diagram of a helium automatic replenishment monitor screen in the biomagnetism measuring device of FIG. 1;

FIG. 10 is a flowchart of liquid helium automatic measurement when performing magnetocardiographic measurement by the biomagnetism measuring apparatus of FIG. 1;

[Explanation of symbols]

101: magnetic shield room, 102: subject, 103
... bed, 104 ... dure, 105 ... liquid helium automatic supply device and liquid helium tank, 106 ... FLL circuit, 107 ... filter circuit, 108 ... computer, 1
09 ... printer, 110 ... liquid helium automatic replenishing device,
201: cross section of Dewar, 202: liquid level gauge, 301: liquid helium remaining amount measurement execution button, 302: graph display switching button, 303: list display switching button, 3
04 ... reduction rate graph display switching button, 305 ... automatic measurement setting screen button, 306 ... automatic supply monitor screen display button, 307 ... latest helium remaining amount display box, 3
08: Latest helium remaining amount, 309 to 313: Graph showing remaining liquid helium amount measured at each time, 314: Area indicating lower than the set lower limit of warning notification, 315 ... Lower limit of set warning notification , 316: Horizontal axis scale range input box, 317: Horizontal axis scale of graph showing time when remaining amount of liquid helium is measured, 318 ... Cursor for displaying graph part where horizontal axis time scale is not displayed 319: vertical axis scale of the graph indicating the remaining amount of liquid helium, 320: graph display area, 401: liquid helium remaining amount measurement execution button, 402: graph display switching button, 403: list display switching button, 404
... Button for switching display of decrease rate graph, 405... Button for automatic measurement setting screen, 406... Button for displaying automatic replenishment monitor screen, 407...
... the latest liquid helium remaining amount, 409-413 ... the liquid helium remaining value for each measurement time, 414 ... the helium remaining amount list display area, 415 ... the cursor for displaying the part which is not displayed, 501 ... the liquid helium remaining amount Measurement execution button, 502: Graph display switching button, 503: List display switching button, 504: Reduction rate graph display switching button, 505: Automatic measurement setting screen button, 50
6 ... automatic replenishment monitor screen display button, 507 ... latest helium remaining amount display box, 508 ... latest liquid helium remaining amount, 509 ... horizontal axis scale range input box, 510
To 513: a graph showing a decrease rate with respect to each time, 514
... A line indicating the set upper limit value of the warning notification differential value, 515... A graph display area, 516...
Vertical axis scale indicating time, 518... A cursor for displaying a portion of the graph where the horizontal axis time scale is not displayed, 51
9: Area indicating the warning notification reduction rate upper limit or more, 6
01: Automatic measurement setting check box, 602: Warning notification setting check box, 603: Warning sound setting check box, 604: Automatic measurement cycle time input box, 6
05: warning notification remaining lower limit value input box, 606: warning notification upper limit differential value input box, 607: setting OK button, 608: setting cancel button, 701: warning message, 702: remaining liquid helium at the time of warning notification, 70
3 OK button, 801 warning message, 802 differential value at the time of warning notification, 803 OK button, 901 liquid helium remaining amount display area, 902 liquid helium remaining amount,
903: scale, 904: value of remaining liquid helium, 90
5 ... OK button, 1001 to 1016 ... Steps in the processing flow of liquid helium automatic measurement

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroyuki Suzuki 882 Ma, Hitachinaka-shi, Ibaraki Pref.Measurement Division, Hitachi, Ltd. Inside Engineering Co., Ltd. (72) Inventor Kazuhisa Machida 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside the Design Laboratory, Hitachi, Ltd.

Claims (20)

[Claims] 1. A dewar, a superconducting quantum interference device (SQUID) sensor in the dewar, a refrigerant for cooling the superconducting quantum interference device (SQUID) sensor, and a liquid level gauge for measuring a liquid level of the refrigerant Monitoring method for a superconducting quantum interference device (SQUID) sensor in a biomagnetic measurement system, comprising: a replenishing device for the refrigerant; and a control device having a display device for controlling the respective devices and displaying the state of the refrigerant on a screen. 3. The method of monitoring a refrigerant of a superconducting quantum interference device (SQUID) sensor according to claim 1, wherein the control device measures the remaining amount of the refrigerant in the Dewar at an arbitrary time or an arbitrary constant cycle. 2. The superconducting quantum interference device according to claim 1,
(QUID) sensor, wherein the control device skips the measurement of the remaining amount of the refrigerant while collecting the measurement signal from the superconducting quantum interference device (SQUID) sensor. Quantum interference device (SQUI
D) Monitoring method of sensor refrigerant. 3. The superconducting quantum interference device according to claim 1,
A method for monitoring a refrigerant of a superconducting quantum interference device (SQUID), wherein a history value of the remaining amount of the refrigerant is displayed in a graph or a list on the display device. Method. 4. The superconducting quantum interference device according to claim 1,
(QUID) sensor In the method for monitoring a refrigerant, the latest value of the remaining amount measurement of the refrigerant is displayed on the display device on a dedicated screen which is physically consistent with the refrigerant liquid level of the Dewar. Superconducting quantum interference device (SQUID)
How to monitor the refrigerant of the sensor. 5. The superconducting quantum interference device according to claim 1,
In the refrigerant monitoring method of the (QUID) sensor, the controller calculates a refrigerant reduction rate at predetermined time intervals from the history value of the remaining amount measurement of the refrigerant, and displays the graph on the screen of the display device. Superconducting quantum interference device (SQUID)
How to monitor the refrigerant of the sensor. 6. The superconducting quantum interference device according to claim 3,
In the method for monitoring refrigerant of a refrigerant (QUID) sensor, the lower limit set value of the remaining amount is displayed on a graph of a history value of the remaining amount measurement of the refrigerant, wherein the superconducting quantum interference device (SQUI) is displayed.
D) Method for monitoring refrigerant of the sensor. 7. The superconducting quantum interference device according to claim 5,
A method for monitoring a refrigerant of a superconducting quantum interference device (SQUI), wherein an upper limit set value of the reduction rate is displayed on a graph of a history value of the refrigerant reduction rate.
D) Method for monitoring refrigerant of the sensor. 8. The superconducting quantum interference device according to claim 3,
A method for monitoring a refrigerant of a superconducting quantum interference device (SQUID) sensor, wherein a measurement point is plotted on a graph of a history value of a remaining amount measurement of the refrigerant, and a measurement time can be confirmed from the plot. Refrigerant monitoring method. 9. The refrigerant monitoring method for a superconducting quantum interference device (SQUID) sensor according to claim 6 or 7,
A superconducting quantum, which issues a warning whenever the measured value of the remaining amount of the refrigerant becomes lower than the lower limit set value of the refrigerant or when the rate of decrease of the refrigerant exceeds the upper limit set value. A refrigerant monitoring method for an interference element (SQUID) sensor. 10. The refrigerant monitoring method for a superconducting quantum interference device (SQUID) sensor according to claim 6, wherein a region in which the measured refrigerant remaining amount is lower than the lower limit setting value is displayed in red. Monitoring method for a superconducting quantum interference device (SQUID) sensor. 11. The superconducting quantum interference device (SQUID) sensor according to claim 7, wherein a region in which the refrigerant reduction rate exceeds a set upper limit is displayed in red. Interference element (SQUI
D) Method for monitoring refrigerant of the sensor. 12. The refrigerant monitoring method for a superconducting quantum interference device (SQUID) sensor according to claim 3, wherein the measured remaining amount of the refrigerant is set to the lower limit of the remaining amount in a list display of the measured remaining amount of the refrigerant. A method for monitoring a refrigerant of a superconducting quantum interference device (SQUID) sensor, wherein a column lower than the value is displayed in red. 13. The refrigerant monitoring method for a superconducting quantum interference device (SQUID) sensor according to claim 3, wherein the display time range can be arbitrarily set in a graph display of a history value of the remaining amount measurement of the refrigerant. A method for monitoring a refrigerant in a superconducting quantum interference device (SQUID) sensor, the method comprising: 14. The refrigerant monitoring method for a superconducting quantum interference device (SQUID) sensor according to claim 1, wherein even if the remaining amount measurement of the refrigerant is discontinuous, the history value of the remaining amount measurement of the refrigerant is continuously displayed in a graph. A method for monitoring refrigerant in a superconducting quantum interference device (SQUID) sensor. 15. The refrigerant monitoring method for a superconducting quantum interference device (SQUID) sensor according to claim 5, wherein the range of the displayed time can be arbitrarily set in a graph display of the decrease rate of the refrigerant. Conduction quantum interference device (SKU
ID) A method of monitoring the refrigerant of the sensor. 16. The refrigerant monitoring method for a superconducting quantum interference device (SQUID) sensor according to claim 1, wherein while the refrigerant is being replenished from a refrigerant tank by an automatic replenishing device, the state of replenishment of the refrigerant is displayed on a screen of the display device. A method for monitoring a refrigerant of a superconducting quantum interference device (SQUID) sensor, which is displayed above. 17. The refrigerant monitoring method for a superconducting quantum interference device (SQUID) sensor according to claim 1, wherein a refrigerant remaining amount monitoring program is automatically started by starting the control device. Interference element (SQUI
D) Method for monitoring refrigerant of the sensor. 18. The refrigerant monitoring method for a superconducting quantum interference device (SQUID) sensor according to claim 1, wherein the display screen of the refrigerant state includes a top title bar, an icon bar below the title bar, The screen is divided into a display area for displaying the refrigerant state in the center of the screen at the bottom of the icon bar, a latest helium remaining amount display box on the left side of the graph display area, and a cursor bar for display movement at the bottom. By pressing a related button of the icon bar with a pointing device, the remaining amount of the refrigerant is measured.In the center of the screen, the history of the remaining amount of the refrigerant is displayed within a predetermined range, and It is displayed on a screen that is physically consistent with the latest remaining amount of the refrigerant, a display area outside the predetermined range is also displayed by a cursor bar, and is opened and closed under predetermined conditions on the display screen. A superconducting quantum interference device (SQUI) having a refrigerant management screen having a predetermined function.
D) Method for monitoring refrigerant of the sensor. 19. The refrigerant monitoring method for a superconducting quantum interference device (SQUID) sensor according to claim 18, wherein the history display screen of the remaining amount of the refrigerant displays the history value of the remaining amount of the refrigerant in a graph. A superconducting quantum interference device (SQUID) characterized in that the measurement points are plotted, the lower limit of the remaining amount of refrigerant is displayed on the graph, and a lower region of the remaining amount of refrigerant is displayed in red from the lower limit. ) Refrigerant monitoring method of the sensor. 20. The refrigerant monitoring method for a superconducting quantum interference device (SQUID) sensor according to claim 18 or 19, wherein a button on the icon bar is pressed on a refrigerant management screen having a predetermined function of opening and closing on the display screen. An automatic measurement setting screen that manages an automatic measurement mode that is opened and a remaining amount warning notification screen that opens when the remaining amount of refrigerant is equal to or less than a predetermined lower limit value, and a reduction rate warning notification screen that opens when the refrigerant reduction rate is equal to or higher than a predetermined upper limit value and A refrigerant monitoring method for a superconducting quantum interference device (SQUID) sensor, which is a refrigerant helium automatic replenishment monitor screen opened by pressing a button of an icon bar.