JP5513783B2 - Measuring device and fuel cell system - Google Patents

Description

  The present invention relates to a measuring apparatus and a fuel cell system.

Conventionally, a measuring apparatus for measuring the amount of solvent in a sample, the mobility of solvent molecules, and the like using a nuclear magnetic resonance method has been proposed (see Patent Documents 1 and 2).
In such a measuring apparatus, for example, an excitation oscillating magnetic field is applied to a specific portion of a sample placed in a static magnetic field using a small RF coil smaller than the sample, and an NMR ( Nuclear magnetic resonance) signal is acquired. Based on the NMR signal acquired by the small RF coil, the amount of solvent in the sample, the mobility of solvent molecules, and the like are calculated.

  In such a measuring apparatus, the amount of solvent and the like can be measured by detecting the movement of nuclear magnetization as an NMR signal by the spin resonance phenomenon of a nucleus placed in a magnetic field.

Pamphlet of International Publication 2006/109803 Pamphlet of International Publication 2008/041361

It has been found that the following problems occur in the measuring apparatus as described above.
First, the first problem will be described.
In the measuring apparatus as described above, as shown in FIG. 64, the small RF coil and the static magnetic field application unit are arranged so that the direction of the static magnetic field H ₀ from the static magnetic field application unit and the direction of the axis of the small RF coil are orthogonal to each other. Is arranged.

This is because the direction of the static magnetic field H _{0 and the} direction of the oscillating magnetic field H ₁ applied from the small RF coil must be orthogonal to each other.
More specifically, it is necessary to excite nuclear magnetization when performing measurement with the above-described measurement apparatus. Exciting the nuclear magnetization and rotating in a state where the nuclear magnetization is tilted at a constant angle with respect to the static magnetic field, that is, the nuclear magnetization precesses, so that the time change of the magnetic flux passing through the small RF coil occurs, and the small RF coil Can be detected as an NMR signal.
Nuclear magnetization in thermal equilibrium is directed in the direction of the static magnetic field H _0, and there is no time change in the magnetic flux passing through the small RF coil. In order for a small RF coil to receive an NMR signal, it is necessary to excite nuclear magnetization and cause precession about the direction of the static magnetic field H ₀ as the center of rotation. To excite nuclear magnetization by applying excitation oscillating magnetic field perpendicular to the static magnetic field H ₀ direction, it is necessary to tilt the nuclear magnetization to the static magnetic field H ₀ direction. That is, for excitation of nuclear magnetization, the outer product of the nuclear magnetization vector facing the static magnetic field H ₀ direction and the oscillating magnetic field vector for excitation must be sufficiently large and have a significant value.
Therefore, the direction of the static magnetic field H _{0 and the} direction of the oscillating magnetic field H ₁ for excitation generated by the small RF coil need to be orthogonal to each other.
Static and the magnetic field H ₀ direction, in order to orthogonal to the direction of the excitation oscillating magnetic field H ₁ from small RF coil, a static magnetic field H ₀ direction, it must be perpendicular to the axial direction of the small-sized RF coils. Therefore, for example, as shown in FIG. 65, when measuring a film-like sample 511, it is necessary to arrange the surfaces of the pair of magnetic poles 113A and 113B and the surface of the sample 511 to be orthogonal to each other. Therefore, when trying to measure a sample having a large area, it is necessary to increase the dimension between the pair of magnetic poles, resulting in an increase in the size of the measuring apparatus.
In FIG. 65, reference numeral 914 indicates a small RF coil.

Next, the second problem will be described.
When performing measurement with the above-described conventional measuring apparatus, a very thin sample may be measured. And it may be required to measure the state on the front surface side or the state on the back surface side of this very thin film. For example, the sample is a solid polymer electrolyte membrane used in fuel cells, and it is required to measure the water content of the solid polymer electrolyte membrane on the hydrogen electrode side and the water content of the solid polymer electrolyte membrane on the oxygen electrode side May be. At this time, when the small RF coil has a large inner diameter and the small RF coil has a deep measurement depth, both the hydrogen electrode side and the oxygen electrode side of the solid polymer electrolyte membrane are included in the measurement region. It becomes impossible to distinguish the water content and the water content on the hydrogen electrode side.
In order to solve such problems, it is conceivable to reduce the inner diameter of the small RF coil. This is because the measurement depth becomes shallower in proportion to the inner diameter of the small RF coil. However, in this case, the NMR signal intensity decreases, and accurate measurement becomes difficult.

First, the first invention for solving the first problem will be described.
According to the first aspect of the present invention, there is provided a measuring apparatus that applies an excitation oscillating magnetic field to a film-like or flat plate-like sample containing a protic solvent and detects an NMR signal corresponding to the excitation oscillating magnetic field. And
A pair of magnetic poles having different polarities arranged opposite to each other, and a static magnetic field applying unit that applies a static magnetic field to the film-like or flat sample arranged between the magnetic poles;
A planar RF coil for applying an excitation oscillating magnetic field to the sample and acquiring an NMR signal corresponding to the excitation oscillating magnetic field;
Between the pair of magnetic poles of the static magnetic field application unit, the sample is arranged so that the direction of the static magnetic field formed by the pair of magnetic poles penetrates the front and back surfaces of the sample vertically,
The planar RF coil is wound in an annular shape so as to surround one axis, and the planar RF coil is disposed on the sample so that the axis is orthogonal to the sample front and back surfaces. A measuring apparatus is provided in which the axis of the planar RF coil is parallel to the direction of the static magnetic field formed by the static magnetic field application unit.

According to this invention, the sample is disposed between the pair of magnetic poles so that the direction of the static magnetic field formed by the pair of magnetic poles penetrates the front and back surfaces of the sample vertically. The planar RF coil is arranged with respect to the sample so that its axis is orthogonal to the sample front and back surfaces, and the axis of the planar RF coil is parallel to the direction of the static magnetic field formed by the static magnetic field application unit. It is.
Since the surface of the sample is disposed so as to face the pair of magnetic poles, the distance between one magnetic pole may be at least the thickness of the sample. Therefore, even when measuring a sample having a large area on the front and back surfaces, it is not necessary to increase the distance between the pair of magnetic poles, and an increase in the size of the measuring apparatus can be suppressed.
Here, the front and back surfaces of the sample are surfaces orthogonal to the thickness direction of the sample.

Next, a second invention for solving the second problem will be described.
According to the second invention,
A measurement device that applies an excitation oscillating magnetic field to a sample containing a protic solvent and detects an NMR signal corresponding to the excitation oscillating magnetic field,
A static magnetic field application unit that applies a static magnetic field to the sample;
A planar RF coil for applying an excitation oscillating magnetic field to the sample and acquiring an NMR signal corresponding to the excitation oscillating magnetic field;
The planar RF coil has a pair of first portions extending substantially parallel to each other, and a second portion connecting between opposing ends of the pair of first portions,
The distance between the pair of first parts is Ds,
When the distance between a pair of intersections extending in parallel with the first part and passing through a center point of the distance between the pair of first parts intersects with the pair of second parts is Dl,
A measuring device having Dl / Ds of 2 or more is provided.

In the present invention, Dl / Ds of the planar RF coil is set to 2 or more. As a result, it is possible to reduce the signal strength while reducing the measurement depth.
Furthermore, in the present invention, a solid polymer electrolyte membrane containing a protic solvent, a fuel electrode disposed on one side of the solid polymer electrolyte membrane, and a solid polymer electrolyte membrane disposed on the other side of the solid polymer electrolyte membrane. A fuel cell having an oxidizer electrode;
A fuel cell system including a measuring device, wherein the measuring device is any of the measuring devices described above.

According to 1st invention, the measuring apparatus which can suppress the enlargement of a measuring apparatus is provided.
According to the second aspect of the invention, there is provided a measuring apparatus that can reduce the signal strength while reducing the measurement depth.

It is a figure which shows the fuel cell system of 1st embodiment of this invention. It is a figure which shows a fuel cell. It is a top view of a small RF coil. It is a figure which shows a magnet and a fuel cell. It is a block diagram which shows the structure of the control part of a measuring device. It is a figure which shows the structure of a part of measuring device in embodiment. It is a figure which shows an example of LC circuit which performs the application of the oscillating magnetic field for excitation of a measuring apparatus in embodiment, and the detection of a NMR signal. It is a schematic diagram which shows arrangement | positioning of G coil. It is a figure explaining the shift | offset | difference of the phase difference of a NMR signal. It is a figure which shows the intensity | strength of the spin echo signal measured using the solenoid coil. It is a figure which shows the principal part of 2nd embodiment of this invention. It is a figure which shows the principal part of 3rd embodiment of this invention. It is a figure which shows the modification of this invention. 4 is a diagram showing a small RF coil (track-shaped coil) used in Experimental Example 1 of Example 1. FIG. It is a figure which shows the positional relationship of a track shape coil and water. It is a figure which shows the spin echo signal intensity | strength acquired when the angle (theta) which the axis | shaft of a track-shaped coil and a static magnetic field make is 0 degree, 45 degrees, and 90 degrees. 6 is a diagram of a circular coil used in Experimental Example 1 of Example 1. FIG. It is a figure which shows the spin echo signal intensity | strength acquired when the angle (theta) which the axis | shaft of a circular coil and a static magnetic field make is 0 degree, 45 degrees, and 90 degrees. It is a figure which shows the positional relationship of a track shape coil and water. It is a figure which shows the MR image of (theta) = 90 degrees and excitation pulse output TX = 7.0. It is a figure which shows the MR image of (theta) = 90 degrees and excitation pulse output TX = 8.0. It is a figure which shows the MR image of (theta) = 90 degrees and excitation pulse output TX = 8.6. It is a figure which shows the positional relationship of a track shape coil and water. It is a figure which shows the MR image of (theta) = 0 degree and excitation pulse output TX = 7.0. It is a figure which shows the MR image of (theta) = 0 degree and excitation pulse output TX = 8.0. It is a figure which shows the MR image of (theta) = 0 degree and excitation pulse output TX = 9.0. It is a figure which shows a track shape coil and a coordinate. It is a figure which shows yz distribution of the spin-echo signal intensity | strength at the time of (theta) = 90 degrees and the excitation angle (alpha) in a sample surface (z = zs) being 90 degrees. It is a figure which shows yz distribution of the spin echo signal intensity | strength when the excitation angle (alpha) in the sample surface (z = zs) is 180 degrees (theta) = 90 degrees. It is a figure which shows yz distribution of the spin echo signal intensity | strength at the time of (theta) = 0 degree and the excitation angle (alpha) in a sample surface (z = zs) being 90 degrees. It is a figure which shows yz distribution of the spin echo signal intensity | strength when (theta) = 0 degree and the excitation angle (alpha) in a sample surface (z = zs) is 180 degrees. It is a figure of the track shape coil used in Example 2. FIG. It is a figure which shows the temperature change of a fuel cell. It is a figure which shows the relationship between the water content of a solid polymer electrolyte membrane, and the intensity | strength of a spin echo signal. The normalized spin echo signal intensity obtained by the coil on the hydrogen electrode side is shown. The normalized spin echo signal intensity obtained by the coil on the oxygen electrode side is shown. The normalized spin echo signal intensity obtained by the coil on the hydrogen electrode side is shown. The normalized spin echo signal intensity obtained by the coil on the oxygen electrode side is shown. FIG. 6 is a diagram showing a fuel cell system used in Example 3. It is a figure which shows a track shape coil and a circular coil. It is a figure which shows the positional relationship of a coil and water. It is a figure which shows the spin echo signal strength acquired with each coil. It is a figure which shows the measurement depth of a coil, and a spin echo signal strength. It is a figure which shows the relationship between the converted signal strength and the measurement volume of a coil on the basis of ID0.6mm circular coil. It is a figure which shows the relationship between the converted signal strength and the measurement depth of a coil on the basis of ID0.6mm circular coil. It is a figure which shows the internal diameter of a circular coil, and Ds and Dl of a track shape coil. It is a figure which shows a track shape coil and a coordinate. It is a figure which shows the spatial distribution of the magnetic field Hz (x, 0, z) which a track shape coil produces in xz plane. It is a figure which shows the spatial distribution of the magnetic field Hz (0, y, z) which a track shape coil produces in a yz plane. It is a figure which shows the spatial distribution of the magnetic field Hz (x, y, 0) which a track shape coil produces in an xy plane. It is a figure which shows the spatial distribution _SFID (x, 0, z) of the FID signal strength in xz plane. It is a figure which shows distribution _FID (0, 0, z) of the FID signal strength on az axis. It is a figure which shows distribution _SFID (x, 0, 0) of the FID signal strength on the x-axis. FIG. 6 is a diagram showing a spatial distribution S _SpinEcho (x, 0, z) of spin echo signal intensity in the xz plane. It is a figure which shows distribution S _SpinEcho (0, 0, z) of the spin echo signal intensity on az axis. FIG. 5 is a diagram showing a spin echo signal intensity distribution S _SpinEcho (x, 0, 0) on the x-axis. FIG. 6 is a diagram showing an intensity distribution S _SpinEcho (x, y, 0.16 mm) in the xy plane of a spin echo signal. It is a figure which shows intensity distribution of the spin echo signal of a y-axis direction. It is a figure which shows intensity distribution of the spin echo signal of a x-axis direction. FIG. 6 is a diagram showing an intensity distribution S _SpinEcho (x, y, 0.16 mm) in the xy plane of a spin echo signal. It is a figure which shows intensity distribution of the spin echo signal of a y-axis direction. It is a figure which shows z-axis direction distribution of a FID signal. It is a figure which shows z-axis direction distribution of a spin echo signal. It is a figure which shows the static magnetic field direction in the conventional measuring apparatus, and the oscillating magnetic field direction for excitation. It is a figure which shows the arrangement | positioning relationship between the magnet and sample in the conventional measuring apparatus. It is a figure which shows the modification of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In all the drawings, common constituent elements are denoted by the same reference numerals, and description thereof is omitted as appropriate.
(First embodiment)
FIG. 1 shows a fuel cell system 1 of the present embodiment.
The fuel cell system 1 includes a fuel cell 5 and a measuring device 100 that measures the operating state of the fuel cell 5.
(Configuration of fuel cell)
As shown in FIG. 2, the fuel cell 5 includes a membrane electrode assembly 51 having a solid polymer electrolyte membrane 511, a pair of diffusion layers 52 and 53, and separators 54 and 55.
The membrane electrode assembly 51 includes a solid polymer electrolyte membrane 511 and catalyst layers 512 and 513 provided on both sides of the solid polymer electrolyte membrane 511.

The solid polymer electrolyte membrane 511 contains a protic solvent (water in this embodiment), and is a membrane capable of conducting ions in a state containing this water. For example, Nafion (registered trademark) can be used as the solid polymer electrolyte membrane 511.
Of the pair of catalyst layers 512 and 513, one catalyst layer 512 is provided so as to be in contact with one surface of the solid polymer electrolyte membrane 511, and the other catalyst layer 513 is the other of the solid polymer electrolyte membrane 511. It is provided so as to be in contact with the surface. The catalyst layers 512 and 513 are formed, for example, by laminating a surface of the solid polymer electrolyte membrane 511 with a platinum particle supported on the surface of carbon particles.
One catalyst layer 512 functions as an oxidant electrode (oxygen electrode, cathode). The other catalyst layer 513 functions as a fuel electrode (hydrogen electrode, anode). During operation of the fuel cell 5, the current moves from the hydrogen electrode (catalyst layer 513) to the oxygen electrode (catalyst layer 512) through the electric circuit (electronic load device) 57.

The diffusion layer 52 is provided on the surface of the catalyst layer 512 opposite to the surface on the solid polymer electrolyte membrane 511 side. Similarly, the diffusion layer 53 is provided on the surface of the catalyst layer 513 opposite to the surface on the solid polymer electrolyte membrane 511 side. As the diffusion layers 52, 53, for example, water-repellent carbon paper can be used. The water present in the membrane electrode assembly 51 is discharged to the outside through the diffusion layers 52 and 53.
Note that current collecting electrodes (current collectors) 56 for taking out the current generated by the fuel cell 5 are attached to the diffusion layers 52 and 53, respectively.

The separators 54 and 55 are insulating materials having flow paths 541 and 551, which are plate-like bodies made of polycarbonate in this embodiment. The gas passing through the flow paths of the separators 54 and 55 contacts the catalyst layers 512 and 513 through the diffusion layers 52 and 53.
In addition, you may comprise the separators 54 and 55 with an electroconductive material.

(measuring device)
First, with reference to FIG. 1, the outline | summary of the measuring apparatus of this embodiment is demonstrated.
The measuring apparatus 100 of this embodiment applies an oscillating magnetic field for excitation to a film-like or flat plate-like sample containing a protic solvent (in this embodiment, a solid polymer electrolyte membrane 511 which is a film-like sample). In addition, an NMR signal corresponding to the oscillating magnetic field for excitation is detected.
The measuring apparatus 100 includes a pair of magnetic poles 113A and 113B having different polarities arranged opposite to each other, and a static magnetic field applying unit 113 that applies a static magnetic field to a sample 511 disposed between the magnetic poles 113A and 113B.
A planar RF coil (hereinafter also referred to as a small RF coil) 114 that applies an excitation oscillating magnetic field to the sample 511 and acquires an NMR signal corresponding to the excitation oscillating magnetic field is provided.
Said pair of magnetic poles 113A of the static magnetic field applying unit 113, between 113B, a pair of magnetic poles 113A, so that the direction of the static magnetic field _{H 0} formed by 113B penetrates vertically the front and back surfaces of the sample, the sample 511 Be placed.
The planar RF coil 114 is wound in an annular shape so as to surround one axis, and is arranged with respect to the sample 511 so that the axis Ax is orthogonal to the front and back surfaces of the sample. An axis Ax of the planar RF coil 114 is parallel to the static magnetic field H ₀ direction formed by the static magnetic field application unit 113.

Further, as shown in FIG. 3, the planar RF coil 114 has a pair of first portions 1140 and 1141 extending substantially in parallel with each other and between the opposing ends of the pair of first portions 1140 and 1141. And second portions 1142 and 1143 to be connected. A distance between the pair of first portions 1140 and 1141 is Ds, and a second straight line extending in parallel with the first portions 1140 and 1141 while passing through the center point of the distance between the pair of first portions 1140 and 1141. When the distance between the intersections with the portions 1142 and 1143 is Dl, Dl / Ds is 2 or more.
Note that the first portions 1140 and 1141 may not be completely parallel, and may be slightly deviated from parallel if the measurement depth can be accurately grasped.

  In addition, the measuring apparatus 100 includes a gradient magnetic field application unit 251, an RF oscillator 102, a modulator 104, an RF amplifier (RF amplification unit) 106, a preamplifier 112, a detector 140, an A / D converter 118, and a switch unit 170. , A control unit 150, a timing unit 128, a sequence table 127, a data reception unit 120, an output unit 135, and the like.

Next, the measuring apparatus 100 of this embodiment will be described in detail.
The measuring device 100 measures the current at a specific location of the solid polymer electrolyte membrane 511, measures the amount of water, and measures the mobility.

The static magnetic field application unit 113 applies a static magnetic field to the solid polymer electrolyte membrane 511. An excitation oscillating magnetic field is applied to the solid polymer electrolyte membrane 511 in a state where the static magnetic field is applied, and current measurement, moisture content measurement, and mobility measurement are performed.
In the present embodiment, the static magnetic field application unit 113 is configured to include a pair of magnetic poles (magnets) 113A and 113B arranged to face each other with a predetermined interval. Each of the magnets 113A and 113B is a plate-like permanent magnet, and is arranged so that the surfaces thereof (surfaces orthogonal to the magnet thickness direction) face each other. As shown in FIG. 4, the surface shape of the magnets 113A and 113B is larger than that of the fuel cell 5, and the fuel cell 5 is arranged so that the fuel cell 5 does not protrude from the space between the magnets 113A and 113B. .
Further, the fuel cell 5 is arranged so that the surfaces of the magnets 113A, 113B and the surface (back surface) of the fuel cell 5 face each other. That is, the fuel cell 5 is disposed so that the direction of the static magnetic field formed by the magnets 113A and 113B penetrates the front and back surfaces of the fuel cell 5 (that is, the front and back surfaces of the solid polymer electrolyte membrane 511) vertically.

  The small RF coil 114 applies an excitation oscillating magnetic field to a specific portion of the solid polymer electrolyte membrane 511 and acquires an NMR signal corresponding to the excitation oscillating magnetic field. Specifically, the excitation oscillating magnetic field is a high-frequency pulse emitted from a small RF coil to the surroundings.

The small RF coils 114 are planar RF coils, and a plurality of small RF coils 114 are arranged along the surface direction of the solid polymer electrolyte membrane 511 as shown in FIG. In FIG. 1, only one small RF coil 114 is shown, and the description of the other small RF coils is omitted. Furthermore, in FIG. 1, only the solid polymer electrolyte membrane 511 and the diffusion layers 52 and 53 of the fuel cell 5 are shown, and the description of the other members is omitted.
The small RF coil 114 is arranged such that the axis Ax is orthogonal to the front and back surfaces of the solid polymer electrolyte membrane 511.
The small RF coil 114 is disposed between the diffusion layer 52 and the solid polymer electrolyte membrane 511 and between the diffusion layer 53 and the solid polymer electrolyte membrane 511.
A plurality of small RF coils 114 are arranged along the front and back surfaces of the solid polymer electrolyte membrane 511 so that the axis Ax of the small RF coil 114 is parallel to the direction of the static magnetic field formed by the magnets 113A and 113B.
The measurement region of the small RF coil 114 is from the surface of the solid polymer electrolyte membrane 511 to the middle position of the thickness of the solid polymer electrolyte membrane 511. And the measurement area | region of the small RF coil 114 arrange | positioned between the diffusion layer 52 and the solid polymer electrolyte membrane 511, and the small RF coil 114 arrange | positioned between the diffusion layer 53 and the solid polymer electrolyte membrane 511 are shown. It does not overlap with the measurement area. Furthermore, the measurement areas of adjacent small RF coils 114 do not overlap.

The small RF coil 114 is preferably ½ or less, more preferably 1/10 or less of the entire size of the solid polymer electrolyte membrane 511. With such a size, the current value, the amount of protic solvent (water), and mobility in the solid polymer electrolyte membrane 511 can be accurately measured in a short time.
The size of the solid polymer electrolyte membrane 511 is the size of the surface of the solid polymer electrolyte membrane 511. By setting the exclusive area of the small RF coil 114 to preferably 1/2 or less, more preferably 1/10 or less of the solid polymer electrolyte membrane 511, accurate measurement can be performed in a short time. The size of the small RF coil 114 is preferably, for example, 10 mm or less in diameter.

As shown in FIGS. 2 and 3, the small RF coil 114 is formed by winding a conducting wire in an annular shape so as to surround one axis Ax. In other words, the small RF coil 114 does not have a plurality of coils each surrounding around two or more axes such as a planar-type 8-shaped coil (sometimes referred to as a butterfly coil, a double-D coil, or the like). .
The small RF coil 114 includes a pair of first portions 1140 and 1141 extending substantially parallel to each other, and second portions 1142 and 1143 connecting between the opposing ends of the pair of first portions 1140 and 1141. Have The distance between the pair of first portions 1140 and 1141 (here, the length of the first straight line that is the shortest straight line connecting the pair of first portions 1140 and 1141) is Ds, and passes through the center of the first straight line. When the distance between the intersections at which the second straight line L extending in parallel with the first portions 1140 and 1141 intersects the second portions 1142 and 1143 is D1, Dl / Ds is 2 or more, preferably 3 or more. is there.
In addition, Dl / Ds is preferably 15 or less, more preferably 10 or less, and particularly preferably 7 or less, from the viewpoint of moldability, shape retention, and handleability of the small RF coil 114. If a film or the like is applied to the coil and the shape is maintained (for example, the entire coil is sandwiched between polyimide films or the like so that the shape can be easily maintained), Dl / Ds can be set to 100 or less. However, since there is a possibility that gas permeation may be suppressed by the coil, it is not preferable to attach a film or the like in the measurement of the fuel cell, and it is preferable to set Dl / Ds to 10 or less.

Here, the effect of setting Dl / Ds to 2 or more will be described.
The measurement region (measurement volume) by the small RF coil depends on the area of the region surrounded by the small RF coil × the measurement depth of the small RF coil. When a small RF coil having a circular outer shape is used, the measurement volume depends on ID ³ (ID is the inner diameter of the circular small RF coil). In order to reduce the measurement depth, the ID may be reduced, but the measurement volume is reduced, the signal intensity is reduced, and the signal-to-noise ratio is reduced.
On the other hand, even when the small RF coil 114 of the present embodiment is used, the measurement volume depends on the area of the region surrounded by the small RF coil 114 × the measurement depth of the small RF coil 114.
Here, as a result of intensive studies by the present inventors, the shape of the small RF coil 114 is changed to a pair of first portions 1140 and 1141 extending substantially parallel to each other, and the pair of first portions 1140, It has a second portion 1142 and 1143 connecting the opposite ends of 1141, and by setting Dl / Ds to 2 or more, the measurement depth is reduced and the signal-to-noise ratio is prevented from being lowered. I knew it was possible. Since it was found that the measurement depth is proportional to Ds of the small RF coil 114 (see Example 3 described later in detail), while increasing Dl and decreasing Ds, the measurement depth is reduced, and It was found that the signal-to-noise ratio can be prevented from decreasing.
Here, Dl is preferably about 0.1 mm or more and 20 mm or less from the viewpoint of moldability, shape retention, and handleability, and Ds is preferably about 0.01 mm or more and 10 mm or less from the viewpoint of measurement depth.

The external shape of the small RF coil 114 is a flat shape, and examples thereof include a rectangle and a track shape.
As shown in FIG. 3, the track shape is a shape in which the first portions 1140 and 1141 are linear and the second portions 1142 and 1143 are curved to draw an arc.

Next, application of an oscillating magnetic field for excitation by the small RF coil 114 will be described.
As shown in FIG. 1, the oscillating magnetic field (exciting oscillating magnetic field) applied by the small RF coil 114 is an RF oscillator 102, a modulator 104, an RF amplifier 106, and a pulse controller 151 in the controller 150 (see FIG. 5). ), The switch unit 170, and the small RF coil 114 in cooperation. In the present embodiment, the RF pulse generation unit that generates an RF pulse for generating an oscillating magnetic field for excitation in the small RF coil 114 includes the RF oscillator 102, the modulator 104, and the RF amplifier 106. The excitation oscillating magnetic field oscillated from the RF oscillator 102 is modulated by the modulator 104 based on the control by the pulse control unit 151 in the control unit 150 to become a pulse shape. The generated RF pulse is amplified by the RF amplifier 106 and then transmitted to the small RF coil 114.
Although not shown, an RF pulse generator is provided corresponding to each small RF coil 114, and the plurality of RF pulse generators are connected to the controller 150.

  The frequency of the oscillating magnetic field for excitation substantially coincides with the resonance frequency of the NMR signal in a state where no current flows in the static magnetic field. The RF oscillator 102 stores this resonance frequency.

As shown in FIG. 5, the control unit 150 includes a pulse control unit 151, a first measurement mode for measuring the current of the solid polymer electrolyte membrane 511, and a second for measuring the water content in the solid polymer electrolyte membrane 511. A switching unit (mode switching control unit 152) that switches between a measurement mode and a third measurement mode for measuring the ease of movement (movability) of water in the solid polymer electrolyte membrane 511;
The operation signal accepting unit 129 connected to the mode switching control unit 152 accepts the operator's request for the measurement mode. Then, the operation signal receiving unit 129 sends this request to the mode switching control unit 152.

  The pulse control unit 151 controls the above cooperation so that the excitation oscillating magnetic field applied to the solid polymer electrolyte membrane 511 by the small RF coil 114 is executed according to the above pulse sequence.

  The pulse control unit 151 is connected to the sequence table 127 and the time measuring unit 128, and generates a high frequency pulse based on the sequence data acquired from the sequence table 127 and the measurement time in the time measuring unit 128. The sequence table 127 stores high-frequency pulse sequence data when current is measured. Specifically, the sequence table 127 stores a timing diagram in which the generation time and interval of the high frequency pulse are set, and the intensity and phase of the high frequency pulse applied based on the timing diagram.

  The small RF coil 114 applies this RF pulse to a specific portion of the solid polymer electrolyte membrane 511. Then, the small RF coil 114 acquires the NMR signal of the applied RF pulse. The NMR signal is, for example, an echo signal corresponding to the excitation oscillating magnetic field.

In the first measurement mode, the excitation oscillating magnetic field applied by the small RF coil 114 to the solid polymer electrolyte membrane 511 is, for example,
(A) a 90 ° pulse, and
(B) A pulse sequence composed of 180 ° pulses applied after the elapse of time τ of the pulses in (a).

In the second measurement mode, the excitation oscillating magnetic field applied by the small RF coil 114 to the solid polymer electrolyte membrane 511 is, for example,
(A) 90 ° pulse,
(B) 180 ° pulse applied after time τ of pulse (a), and (c) n 180 ° applied at intervals of time 2τ, starting from time 2τ of pulse (b). Pulse (n is a natural number)
It is.

Further, in the third measurement mode, the excitation oscillating magnetic field applied to the solid polymer electrolyte membrane 511 by the small RF coil 114 is excited by the pulse sequence including the following (a) to (d). Apply oscillating magnetic field.
(A) a 90 ° pulse of an oscillating magnetic field for excitation,
(B) A gradient magnetic field pulse that starts after the elapse of the pulse time of (a) and is applied for a fixed time d,
(C) a 180 ° pulse of an oscillating magnetic field for excitation applied after elapse of time τ of the pulse of (a), and
(D) A gradient magnetic field pulse that starts after the elapse of the pulse time of (c) and is applied for a predetermined time d.

Next, detection of NMR signals will be described.
The NMR signal detection unit detects the NMR signal acquired by the small RF coil 114 and sends the NMR signal to the calculation unit 130. The NMR signal detector includes a preamplifier 112, a detector 140, and an A / D converter 118. The detected NMR signal is amplified by the preamplifier 112 and then sent to the detector 140.
Although not shown, an NMR signal detection unit is provided corresponding to each small RF coil 114, and a plurality of NMR signal detection units are connected to the data receiving unit 120.

The detector 140 is configured to detect a real part and an imaginary part of the NMR signal by a phase sensitive detection method. In order to accurately separate the NMR waveform acquired by the detector 140 into a real part and an imaginary part, the phase difference between the sine wave and the cosine wave of the fundamental wave that is the source of demodulation is strictly 90 degrees. It is preferable to adjust. By adjusting so that the two fundamental waves have a phase difference of exactly 90 degrees, the phase difference can be calculated more accurately using tan ⁻¹ of the real part and the imaginary part described later. The reference wave that is the source of demodulation is generated by a 90 ° hybrid described later with reference to FIG. 6, for example.

  The detector 140 sends the detected real part and imaginary part to the A / D converter 118. The A / D converter 118 A / D converts the NMR signal and then sends it to the data receiving unit 120. The calculation unit 130 acquires data sent to the data reception unit 120.

  The application of the excitation oscillating magnetic field and the detection of the NMR signal have been described above. However, these can be realized by an LC circuit including a small coil.

  FIG. 7 is a diagram illustrating an example of such an LC circuit. In FIG. 7, the coil portion (inductance portion) of the resonance circuit is configured by a small RF coil. In the nuclear magnetic resonance (NMR) method, the motion of nuclear magnetization is detected as an NMR signal by the spin resonance phenomenon of a nucleus placed in a magnetic field. The spin resonance frequency in a magnetic field of 1 Tesla is about 43 MHz, and an LC resonance circuit as shown in FIG. 7 is used to selectively detect the frequency band with high sensitivity.

Returning to FIG. 1, the switch unit 170 is provided in a branch unit that connects the small RF coil 114, the RF amplifier 106, and the preamplifier 112.
A first state in which the small RF coil 114 and the RF signal generator (RF amplifier 106) are connected; and
It has a function of switching the second state in which the small RF coil 114 and the NMR signal detector (preamplifier 112) are connected.
That is, the switch unit 170 serves as a “transmission / reception switching switch”. The role is to transmit the excitation pulse amplified by RF power-amp to the small RF coil 114 to separate the preamplifier 112 of the receiving system and protect it from a large voltage, and to receive the NMR signal after excitation. In other words, the noise generated by the large amplification transistor leaking from the RF amplifier 106 is blocked from being transmitted to the preamplifier 112 of the receiving system. When measurement is performed using the small RF coil 114, the switch unit 170 is necessary to handle a weak signal. A plurality of switch units 170 are provided corresponding to each small RF coil 114.

  Furthermore, the measuring apparatus 100 includes a gradient magnetic field application unit (a pair of G coils 251) that applies a gradient magnetic field to the solid polymer electrolyte membrane 511 and a current driving power source 159 that supplies a pulse current to the pair of G coils 251. Further prepare.

  The pair of G coils 251 are gradient magnetic field application coils that are spaced apart from the small RF coil 114. As shown in FIG. 1, the pair of G coils 251 are arranged so that a gradient magnetic field can be applied to the solid polymer electrolyte membrane 511. Two G coils 251 are arranged with respect to one small RF coil 114, and are opposed to each other with the small RF coil 114 interposed therebetween.

Various shapes can be adopted for the G coil 251, but a flat coil is used in this embodiment. In FIG. 1, the G coil 251 is disposed so as to sandwich the front and back surfaces of the solid polymer electrolyte membrane 511, but is not limited thereto. As shown in FIG. 66, a G coil 251 may be arranged. Furthermore, the G coil 251 may be, for example, a half moon as shown in FIG. FIG. 8 illustrates the case where a plurality of small RF coils 114 are arranged for one solid polymer electrolyte membrane 511 and a pair of G coils 251 are arranged for the plurality of small RF coils 114. FIG. 8 illustrates a case where a pair of G coils 251 is arranged for each small RF coil 114.
Note that the pair of G coils 251 may not be arranged for each small RF coil 114, and may be arranged such that the entire fuel cell 5 is sandwiched between the pair of G coils, for example.

The apparatus configuration around the solid polymer electrolyte membrane 511 has been described above. Next, an NMR signal processing block will be described.
Returning to FIG. 1, the real part and the imaginary part of the NMR signal (echo signal) detected by the detector 140 are acquired by the data receiving unit 120 and sent to the calculation unit 130. The calculation unit 130 includes a first calculation unit 130A that calculates a current value, a second calculation unit 130B that calculates a moisture content, and a third calculation unit 130C that calculates mobility.
In the first measurement mode, the first calculation unit 130A acquires the real part and the imaginary part of the echo signal detected by the detector 140, and uses them to calculate the phase difference between the echo signal and the excitation oscillating magnetic field. The frequency difference (frequency shift amount) Δω based on the frequency of the echo signal and the frequency of the excitation oscillating magnetic field is calculated from the time change of the phase difference.
The frequency of the echo signal changes from the frequency of the excitation oscillating magnetic field, which is the reference frequency, due to the magnetic field formed by the flow of current. For this reason, the current flowing through the solid polymer electrolyte membrane 511 is obtained from the difference in frequency of the measured echo signal by acquiring the relationship between the frequency change amount (difference) and the current value in advance. The frequency difference is obtained by converting the amount of phase change at a certain time interval per unit time.

Specifically, the phase is calculated by tan ⁻¹ (Re / Img) from the detected real part and imaginary part signals. This value is calculated as a phase difference ΔΦ [rad] at each time of the NMR signal obtained as a time series. As shown in FIG. 9, ΔΦ is a difference between a reference wave traveling at a frequency that does not change with time (the phase at a certain time is Φ ₀ ) and the phase of the NMR signal measured at the same time. Here, the reference frequency is set in advance to the resonance frequency of the NMR signal when no current flows.

The first calculation unit 130A of the calculation unit 130 obtains Δω by converting the amount of change per unit time based on the phase difference ΔΦ obtained in time series. Then, the value of the current of the solid polymer electrolyte membrane 511 at the measurement location is calculated by referring to the relationship between Δω and the current. As an example of a specific method for obtaining the relationship between Δω and current, the magnetic field strength formed at the coil position is theoretically analyzed assuming the shape of the fuel cell and the distribution of the flowing current. There is a method of converting to a frequency shift amount using the fact that the frequency of the signal is directly proportional. Of course, the relationship between the two may be obtained experimentally in advance. The first calculation unit 130A may calculate the current density as a value obtained by dividing the obtained frequency shift amount by the area in which the current flows.
The relationship between Δω and current is stored in the first storage unit 191 of the storage unit 190. The first storage unit 191 stores, for example, data on the correlation between the frequency difference Δω obtained experimentally and the current. More specifically, this is calibration curve data of the frequency difference Δω and the current. The first calculation unit 130A in the calculation unit 130 acquires calibration curve data from the first storage unit 191 of the storage unit 190, and calculates a current corresponding to the frequency difference Δω based on the calibration curve data.

In the second calculation unit 130B, the amount of moisture at a specific location of the sample 511 is calculated from the intensity of the NMR signal obtained by applying an excitation oscillating magnetic field to the sample 511. In the second calculation unit 130B, a T ₂ relaxation time constant is calculated from the received NMR signal, and a moisture content is calculated from the calculated T ₂ relaxation time constant.
In the second calculation unit 130B, the T ₂ relaxation time constant is calculated, the moisture amount corresponding to the calculated T ₂ relaxation time constant is read from the data stored in the second storage unit 192, and the moisture amount is calculated.
The second storage unit 192 stores a T ₂ relaxation time constant and a water amount corresponding to the T ₂ relaxation time constant.
Here, when calculating the amount of the protic solvent (water), the necessary “intensity of the NMR signal” is based on the Real and Imaginary components acquired by the detector 140.
(Real ^ 2 + Imaginary ^ 2) ^ 1/2
Can be converted to that intensity. That is, this calculation corresponds to obtaining the radius of the circle in FIG.

The third calculation unit 130C calculates mobility. The mobility is a physical property value indicating the ease of movement of the protic solvent in the sample, and includes, for example, a self-diffusion coefficient, mobility, etc. In this embodiment, the self-diffusion coefficient is used as the mobility. Is calculated.
The third calculation unit 130C specifies the sample 511 based on the NMR signal obtained by applying the excitation oscillating magnetic field to the sample 511 and the NMR signal obtained by applying a different gradient magnetic field. Calculate the self-diffusion coefficient of water molecules at the location.
The third calculation unit 130C calculates a self-diffusion coefficient from the acquired NMR signal using the following formula (I).
The peak intensity S of the NMR signal depends on the applied pulse gradient magnetic field intensity Gz [gauss / m], the application time d, and the pulse interval Δ, and the self-diffusion coefficient Dz [m ² / s].
ln (S / S ₀ ) = − γ ² DzΔ ² dGz ² (I)

In the above formula (I), d, Δ, and Gz represent the pulse width of the gradient magnetic field pulse, the time interval between the pair of gradient magnetic field pulses, and the magnetic field gradient of the gradient magnetic field pulse, respectively. S ₀ is the peak intensity of the NMR signal when Gz = 0 when no gradient magnetic field is applied, γ is the nucleus to be measured, here the magnetorotation ratio of the hydrogen nucleus ¹ H is 42.577 × 10 ² [1 / gauss · s]. Using this formula (I), the third calculation unit 130C calculates the self-diffusion coefficient from the acquired NMR signal.

  Next, referring to FIG. 6, the RF oscillator 102, modulator 104, RF amplifier 106, pulse control unit 151, switch unit 170, small RF coil 114, preamplifier 112, detector 140, and A / D converter 118 Explain the cooperation.

  In FIG. 6, the modulator 104 includes a mixer 177, a mixer 179, and a synthesizer 181. The detector 140 includes a mixer 183, a mixer 185, and a distributor 187. The A / D converter 118 includes a first A / D converter 118A and a second A / D converter 118B.

  In FIG. 6, a 90 ° hybrid 171 and a distributor 173 are further arranged in this order between the RF oscillator 102 and the modulator 104, and a distributor 175 is further provided between the 90 ° hybrid 171 and the detector 140. Is arranged.

  In this configuration, the waveforms output from the RF oscillator 102 are made into two waveforms having the same frequency but different phases by 90 ° by the 90 ° hybrid 171. Based on these two reference waveforms, the NMR signal is detected and becomes Real and Imaginary components.

  Here, the two waveforms output from the 90 ° hybrid 171 are specifically a sine wave and a cosine wave, and it is important for obtaining the phase that the two waveforms are accurately orthogonal to each other. is there.

  In FIG. 6, the names of the signals in the A / D converter 118 are given as Real and Imaginary, but this is a representation for convenience and may be opposite to Imaginary and Real. In the opposite case, the phase obtained by arctan is merely shifted by ± 90 °, and this is not a problem when obtaining the “phase change amount” that increases and decreases with time.

Next, the effect of this embodiment is demonstrated.
A pair of magnetic poles 113A, the inter-113B, a pair of magnetic poles 113A, the static magnetic field _{H 0} is formed by 113B so as to penetrate the front and back surfaces of the sample 511 vertically, the sample 511 is placed. The planar RF coil 114 is disposed with respect to the sample 511 so that its axis Ax is orthogonal to the front and back surfaces of the sample 511, and the axis Ax of the planar RF coil 114 is statically formed by the static magnetic field applying unit 113. it is parallel to the magnetic field _{H 0} direction.
Since the surface of the sample 511 is disposed so as to face the pair of magnetic poles 113A and 113B, the distance between the magnetic poles 113A and 113B may be at least the thickness of the sample 511. Therefore, even when measuring the sample 511 having a large area on the front and back surfaces, it is not necessary to increase the distance between the pair of magnetic poles 113A and 113B, and an increase in the size of the measuring apparatus 100 can be suppressed.

Here, the conventional technical level will be described.
As explained in the background art section, in the conventional measuring apparatus, the small RF coil and the static magnetic field application unit are arranged so that the direction of the static magnetic field from the static magnetic field application unit and the direction of the axis of the small RF coil are orthogonal to each other. Has been.
The reason for this arrangement is that the direction of the static magnetic field and the direction of the oscillating magnetic field for excitation applied from the small RF coil must be orthogonal to detect the NMR signal. Therefore, it has been usual to arrange the small RF coil and the static magnetic field application unit so that the direction of the static magnetic field from the static magnetic field application unit and the direction of the axis of the small RF coil are orthogonal to each other. This is not limited to a measuring device for measuring the moisture content of a solid polymer film or the like, and is the same for a general NMR device. That is, in order to detect NMR signals, the axis of the coil and the direction of the static magnetic field from the static magnetic field application unit are arranged orthogonally. For example, pages 144 and 148 of “Corona Corp., Medical Image Diagnostic Equipment-Centering on CT and MRI-” also disclose that the direction of the static magnetic field is orthogonal to the axis of the coil. ing.
In order to excite nuclear magnetization, it is necessary to apply an excitation oscillating magnetic field from a direction orthogonal to the static magnetic field direction and tilt the nuclear magnetization with respect to the static magnetic field direction. If the direction of the oscillating magnetic field has to be orthogonal, and the static magnetic field direction and the axis of the coil are arranged in parallel, the nuclear magnetization cannot be effectively tilted with respect to the static magnetic field direction. It was thought that no signal could be obtained.

FIG. 10 shows an example in which a spin echo signal is detected using a solenoid coil.
This is measured by using a small RF coil 114 of the measuring apparatus 100 shown in FIG. 1 as a solenoid coil, and a sample in which water is sealed in a polypropylene tube having an outer diameter of 2 mm.
The solenoid coil has a wire diameter of 0.1 mm and a winding number of 19 turns, and is arranged so as to surround the circumference of the polypropylene circular tube. When the angle between the solenoid coil axis and the direction of the static magnetic field is θ, and the angle θ between the static magnetic field H ₀ and the excitation magnetic field H ₁ (solenoid coil axis) is 90 °, 45 °, and 0 ° FIG. 10 shows the spin echo signal intensity obtained in FIG.

  TX on the horizontal axis is a value indicating the excitation pulse output output from the transmitter, and shows the reading value of the output adjustment dial as it is. The greater the dial reading TX, the greater the excitation pulse output, and the power increases exponentially with respect to TX. The value on the vertical axis is the intensity of the echo signal, and the value obtained by reading the voltage of the received signal with a 16-bit AD converter is shown as it is.

The measurement conditions are as follows.
The irradiation time of the first excitation pulse is 40 μs, the irradiation time of the second excitation pulse is 80 μs, and the amplitudes of the first excitation pulse and the second excitation pulse are equal. The interval between the first excitation pulse and the second excitation pulse is 5 ms (the spin echo time TE is equivalent to 10 ms), the repetition time TR of the first excitation pulse is 20 seconds, the dummy measurement is 4 times, and the signal is integrated once. The FID signal was spoiled by applying a gradient magnetic field of 1 ms after irradiation of the second excitation pulse. The amplifier gain (amplification factor) of the receiver was the same for all measurements.

From FIG. 10, the spin echo signal is large when the angle θ between the static magnetic field H ₀ and the excitation magnetic field H ₁ is 90 °, while the signal is very small when the angle θ is 0 °, It can be seen that the signal is not clearly observable. It can be seen that when the angle θ is 45 °, the signal intensity is smaller than that of 90 °, and the echo signal intensity decreases as the angle θ decreases. When the angle θ is 90 °, the excitation pulse output TX at which the spin echo signal is maximum is about 7.0, but increases to about 7.8 when the angle θ is 45 °. This is because the value of H ₀ × H ₁ decreases as the angle θ decreases, in other words, the component perpendicular to H ₁ decreases with respect to H ₀ , and a larger excitation pulse must be applied. In other words, it can be said that the magnetization vector is not excited up to the condition of strongly emitting the spin echo signal.
Also from this result, the direction of the static magnetic field and the direction of the excitation oscillating magnetic field applied from the coil must be orthogonal, and if the static magnetic field direction and the axis of the coil are arranged in parallel, the nuclear magnetization It can be seen that it is normal to think that can not be tilted with respect to the direction of the static magnetic field.

  In contrast, as a result of intensive studies, the present inventors have found that an NMR signal can be detected even when the axis of the small RF coil 114 is parallel to the static magnetic field direction. (For details, see Examples 1 and 2 described later). Thereby, even when measuring a sample having a large area on the front and back surfaces, it is not necessary to increase the distance between the pair of magnetic poles, and an increase in the size of the measuring apparatus can be suppressed.

Next, the second effect of this embodiment will be described.
In some cases, measurement of the moisture content and the like on the front side and the back side of the sample to be measured is required.
For example, in the operation of the fuel cell 5, the moisture content, mobility, and power generation amount on the front and back surfaces of the solid polymer electrolyte membrane 511 are very important factors. In the fuel cell 5, hydrogen is humidified and sent to the solid polymer electrolyte membrane 511. In the solid polymer electrolyte membrane 511, hydrogen from the hydrogen electrode side reacts with oxygen from the oxygen electrode side to generate water. Since this water is discharged from the oxygen electrode side, if water accumulates too much on the oxygen electrode side, the water will cover the catalyst and oxygen will not reach the solid polymer electrolyte membrane 511. On the other hand, when the humidification amount of hydrogen supplied to the hydrogen electrode side is too small, the solid polymer electrolyte membrane 511 is dried by water molecules moving to the oxygen electrode side together with hydrogen ions, and the solid polymer electrolyte is dried. The ion conductivity in the film 511 is deteriorated.
In order to operate the fuel cell 5 efficiently, it is necessary to keep the water content on the oxygen electrode side and the water content on the hydrogen electrode side at a certain level. It is necessary to accurately grasp the amount, mobility, and power generation amount.
Here, the solid polymer electrolyte membrane 511 is very thin, and its thickness is about 20 μm to 50 μm. Thus, it is very difficult to accurately measure the moisture content and the like on the front and back sides of the very thin solid polymer electrolyte membrane 511.

The reason for this will be described below.
Conventionally, circular coils have been used as small RF coils. The reason is considered to be as follows.
(I) Considering the manufacturing yield and ease of manufacturing, a circular shape is most easily created.
(Ii) A circular coil can be arranged without considering the arrangement direction of the circular coil and the like because the part that becomes the measurement region, that is, the part surrounded by the circular coil is circular. Are better.
(Iii) Since the circular coil is circular, it has high mechanical strength against deformation and high shape retention.
Therefore, as a conventional small-sized RF coil, a circular coil having an outer shape is used, and a circular coil having a ratio of a major axis to a minor axis of about 1.1 to 0.9 is considered even if manufacturing errors are taken into consideration. It is thought that it is used.
However, when such a circular coil is used to measure the moisture content and the like on the front and back surfaces of the solid polymer electrolyte membrane 511, the diameter of the circular coil needs to be reduced. If the diameter of the circular coil is reduced, the measurement volume becomes very small, so that the signal-to-noise ratio is lowered and accurate measurement cannot be performed.
Therefore, with the conventional technique, it is very difficult to accurately measure the moisture content and the like on the front side and the back side of the very thin solid polymer electrolyte membrane 511.
In contrast, the inventors of the present invention have a pair of first portions 1140 and 1141 that extend the small RF coil 114 substantially in parallel with each other and between the opposing ends of the pair of first portions 1140 and 1141. It has the 2nd part 1142 and 1143 to connect, and Dl / Ds was set to 2 or more. This makes it possible to reduce the measurement depth and prevent a decrease in the signal-to-noise ratio, and to reduce the water content, the mobility of water molecules, and the power generation amount on the front and back sides of the solid polymer electrolyte membrane 511. It can be measured reliably (for details, see Example 3 described later).

  Further, by providing the small RF coil 114 with a pair of parallel first portions 1140 and 1141, variation in measurement depth in the longitudinal direction of the small RF coil 114 can be suppressed.

(Second embodiment)
A second embodiment of the present invention will be described with reference to FIG.
In the embodiment, the static magnetic field application unit 113 has a pair of magnetic poles 113A and 113B, and the static magnetic field application unit 113 is a permanent magnet. On the other hand, the static magnetic field application unit 213 according to the present embodiment is composed of an electromagnet, and includes a pair of magnetic poles 213A and 213B arranged to face each other and another pair of magnetic poles 214A and 214B arranged to face each other. Other points are the same as in the above embodiment. Note that the measurement apparatus of this embodiment also includes a plurality of small RF coils as in the above embodiment, but only one small RF coil 114 is shown in FIG. FIG. 11 shows only the solid polymer electrolyte membrane 511 and the diffusion layers 52 and 53 of the fuel cell 5, and the other members are not shown.

Pole 213A, 213B, 214A, 241B is flat, a pair of magnetic poles 213A, the inter-213B, a pair of magnetic poles 213A, the direction of the static magnetic field _{H 01} which is formed by 213B through the front and back surfaces of the sample 511 vertically Thus, the sample 511 is arranged. On the other hand, a pair of 214A, the inter-214B, a pair of magnetic poles 214A, a sample 511 such that the direction of the static magnetic field _{H 02} is parallel to the front and back surfaces of the sample formed by 214B is disposed.
In other words, the axis Ax of the small-sized RF coils, pole 213A, by 213B, is parallel to the static magnetic field _{H 01} direction is formed, the magnetic poles 214A, perpendicular to the direction of the static magnetic field _{H 02} which is formed by 214B.
Such a measuring apparatus includes switching means for switching between the timing for generating the static magnetic field H ₀₁ between the pair of magnetic poles 213A and 213B and the timing for generating the static magnetic field H ₀₂ between the pair of magnetic poles 214A and 214B. The measurement is performed by switching between the timing for generating the static magnetic field H ₀₁ between the magnetic poles 213A and 213B and the timing for generating the static magnetic field H ₀₂ between the pair of magnetic poles 214A and 214B. The static magnetic field H ₀₁ and the static magnetic field H ₀₂ are alternately applied to the sample 511 and are not applied simultaneously.
Although details will be described later in the Examples, a pair of magnetic poles 213A, and the measurement area of the small-sized RF coil 114 when measured by generating a static magnetic field _{H 01} in 213B, a pair of magnetic poles 214A, the static magnetic field _{H 02} among 214B This is different from the measurement region of the small RF coil 114 when it is generated.
Therefore, according to the present embodiment, different areas can be measured in one small RF coil 114.

In the present embodiment, the application direction of the static magnetic field is switched using an electromagnet. However, the present invention is not limited to this, and the application direction of the static magnetic field may be switched by moving the sample 511 and the small RF coil 114. In addition to the electromagnet, the direction of the static magnetic field applied to the sample may be changed by rotating a permanent magnet.
Further, the G coil 251 may be arranged so that the solid polymer electrolyte membrane 511 is sandwiched from the front and back sides as in the first embodiment.

(Third embodiment)
A third embodiment of the present invention will be described with reference to FIG.
In the first embodiment, the static magnetic field application unit 113 has a pair of magnetic poles 113A and 113B. On the other hand, the static magnetic field application unit 313 of this embodiment includes a plurality of pairs of magnetic poles 113A and 113B. Other points are the same as in the first embodiment.
In the plurality of pairs of magnetic poles 113A and 113B, one magnetic pole 113A is disposed on the front surface side of the sample 511 along the surface of the sample 511, and the other magnetic pole 113B is disposed on the rear surface side of the sample along the back surface of the sample 511. The magnetic poles 113A and the magnetic poles 113B are spaced apart.
Each of the magnetic poles 113 </ b> A and 113 </ b> B has a flat plate shape, but is smaller in size (area of the surface facing the sample 511) than the front surface or the back surface of the sample 511.
By doing in this way, even if it is the very big sample 511, the moisture content etc. in the sample 511 surface can be measured.
In the conventional measuring apparatus, since it is necessary to arrange the sample so that the direction of the static magnetic field and the surface direction of the sample are parallel, the width in the surface direction of the sample is inserted between the space of the pair of magnetic poles. It was necessary to make a large space between the pair of magnetic poles. Therefore, the static magnetic field application unit becomes very large, the apparatus becomes large, and the apparatus becomes expensive.
On the other hand, even if the sample 511 is very large as in this embodiment, it is only necessary to use a plurality of pairs of magnetic poles 113A and 113B, so there is no need to prepare a very large static magnetic field application unit. The increase in the size of the apparatus and the increase in cost can be suppressed.

It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
For example, in the embodiment, the measurement apparatus 100 measures one piece of the solid polymer electrolyte membrane 511. However, the present invention is not limited to this, and the fuel cell 5 is stacked to correspond to each solid polymer electrolyte membrane 511. Then, each solid polymer electrolyte membrane 511 may be measured using the small RF coil 114.
If the solid polymer electrolyte membrane 511 is much larger than the magnets 113A and 113B of the static magnetic field application unit, as shown in FIG. 13, the static magnetic field formed by the magnets 113A and 113B of the static magnetic field application unit While maintaining the state of vertically penetrating the front and back surfaces of the solid polymer electrolyte membrane 511, the sample 511, that is, the fuel cell is moved up and down in the direction of the arrow in FIG. 13A, or the depth direction in FIG. Alternatively, the fuel cell 5 may be moved in the direction of the arrow 13 (B) to measure the water content or the like at a specific location of the solid polymer electrolyte membrane 511.
Further, the magnets 113A and 113B are moved to the solid polymer electrolyte membrane 511 while maintaining the state in which the static magnetic field formed by the magnets 113A and 113B of the static magnetic field application unit vertically penetrates the front and back surfaces of the solid polymer electrolyte membrane 511. You may move relatively.
In any case, the measuring apparatus includes a solid polymer electrolyte membrane 511 and moving means for moving the magnets 113A and 113B.
13A is a diagram viewed from the side surface direction of the sample 511, and FIG. 13B is a diagram viewed from the surface side of the sample 511.
Furthermore, in the said embodiment, although the measuring object by the measuring apparatus was set as the solid polymer electrolyte membrane 511 of the fuel cell 5, it is not restricted to this. Any sample containing a protic solvent may be used.
Hereinafter, examples of the reference form will be added.
1. A measurement device that applies an excitation oscillating magnetic field to a film-like or flat sample containing a protic solvent and detects an NMR signal corresponding to the excitation oscillating magnetic field,
A pair of magnetic poles having different polarities arranged opposite to each other, and a static magnetic field applying unit that applies a static magnetic field to the film-shaped or flat-shaped sample disposed between the pair of magnetic poles;
A planar RF coil for applying an excitation oscillating magnetic field to the sample and acquiring an NMR signal corresponding to the excitation oscillating magnetic field;
Between the pair of magnetic poles of the static magnetic field application unit, the sample is arranged so that the direction of the static magnetic field formed by the pair of magnetic poles penetrates the front and back surfaces of the sample vertically,
The planar RF coil is wound in an annular shape so as to surround one axis, and the planar RF coil is disposed on the sample so that the axis is orthogonal to the sample front and back surfaces. The measuring device in which the axis of the planar RF coil is parallel to the direction of the static magnetic field formed by the static magnetic field application unit.
2. 1. In the measuring apparatus described in
The planar RF coil has a pair of first portions extending substantially parallel to each other, and a second portion connecting between opposing ends of the pair of first portions,
The distance between the pair of first portions is Ds,
When the distance between a pair of intersections extending in parallel with the first part and passing through a center point of the distance between the pair of first parts intersects with the pair of second parts is Dl,
A measuring device having Dl / Ds of 2 or more.
3. 1. Or 2. In the measuring apparatus described in
Comprising a plurality of planar RF coils;
The planar RF coil is a measurement device that is spaced apart along the surface of the sample.
4). 1. To 3. In the measuring apparatus according to any one of
In a state where the direction of the static magnetic field formed by the pair of magnetic poles maintains a positional relationship perpendicularly penetrating the front and back surfaces of the sample, the sample and the pair of magnetic poles of the static magnetic field application unit are relatively A measuring apparatus comprising moving means for moving.
5). 1. To 4. In the measuring apparatus according to any one of
A measuring apparatus comprising switching means for switching a static magnetic field application direction or an arrangement direction of the sample with respect to the static magnetic field application unit so that a static magnetic field direction from the static magnetic field application unit is orthogonal to an axis of the planar RF coil. .
6). 1. To 5. In the measuring apparatus according to any one of
The static magnetic field application unit has a plurality of pairs of the pair of magnetic poles,
In the plurality of pairs of magnetic poles, one magnetic pole is spaced apart along the sample surface on the sample surface side, and the other magnetic pole having a polarity different from that of the one magnetic pole is disposed along the sample back surface on the sample back surface side. Measuring device.
7). A measurement device that applies an excitation oscillating magnetic field to a sample containing a protic solvent and detects an NMR signal corresponding to the excitation oscillating magnetic field,
A static magnetic field application unit that applies a static magnetic field to the sample;
A planar RF coil for applying an excitation oscillating magnetic field to the sample and acquiring an NMR signal corresponding to the excitation oscillating magnetic field;
The planar RF coil has a pair of first portions extending substantially parallel to each other, and a second portion connecting between opposing ends of the pair of first portions,
The distance between the pair of first parts is Ds,
When the distance between a pair of intersections extending in parallel with the first part and passing through a center point of the distance between the pair of first parts intersects with the pair of second parts is Dl,
A measuring device having Dl / Ds of 2 or more.
8). 7). In the measuring apparatus described in
A measuring apparatus having Dl / Ds of 10 or less.
9. 7). Or 8. In the measuring apparatus described in
A measuring apparatus in which an outer shape of the planar RF coil is a track shape.
10. 7). To 9. In the measuring apparatus according to any one of
Comprising a plurality of planar RF coils;
The planar RF coil is a measurement device that is spaced apart along the surface of the sample.
11. 1. To 10. In the measuring apparatus according to any one of
The measurement apparatus is a solid polymer electrolyte membrane.
12 1. To 11. In the measuring apparatus according to any one of
A measuring apparatus having a calculating unit that calculates the amount of protic solvent in the sample based on a nuclear magnetic resonance signal acquired by the planar RF coil.
13. 1. To 12. In the measuring apparatus according to any one of
A gradient magnetic field application unit for applying a gradient magnetic field to the sample;
A controller that executes application of the gradient magnetic field and the excitation oscillating magnetic field according to a predetermined pulse sequence;
A second calculation unit,
The planar RF coil acquires NMR signals corresponding to the excitation oscillating magnetic field and the gradient magnetic field,
The second calculation unit is a measurement device that calculates the mobility of the protic solvent at a specific location of the solid sample based on NMR signals obtained corresponding to different gradient magnetic fields and acquired by the planar RF coil.
14 1. Thru 13. In the measuring apparatus according to any one of
The sample is one in which current is generated in the sample,
A measurement apparatus having a third calculation unit that calculates a difference between the frequency of the NMR signal acquired by the planar RF coil and the frequency of the oscillating magnetic field for excitation, and calculates a current at a specific location of the sample from the difference. .
15. A solid polymer electrolyte membrane containing a protic solvent; a fuel electrode disposed on one side of the solid polymer electrolyte membrane; and an oxidant electrode disposed on the other side of the solid polymer electrolyte membrane. A fuel cell having
A fuel cell system including a measuring device,
The measuring apparatus is 1. To 14. A fuel cell system, which is the measuring device according to any one of the above.

Next, examples of the present invention will be described.
In the examples below,
I. Examination when the axis of a small RF coil is parallel to the static magnetic field direction
II. Two studies were conducted on the external shape of the small RF coil.
First, I will be described.

<I. Study when the axis of a small RF coil is parallel to the static magnetic field direction>
Example 1
In Example 1, the following Experimental Examples 1 and 2 were performed, and MR image analysis and magnetic field distribution analysis were performed.
(1) Experimental example 1
The spin echo signal was detected using the measuring apparatus shown in FIG.

(Small RF coil (track shape coil))
FIG. 14 shows a photograph of the small RF coil used. The small RF coil has a track shape and is formed by winding a polyurethane-coated copper wire having a wire diameter of 0.04 mm three times around one axis. This small RF coil (hereinafter sometimes referred to as a track-shaped coil) is a planar coil having Ds of 0.5 mm and Dl of 3.5 mm.

(Measurement sample)
Distilled water was put into a sample container, and a track-shaped coil was attached to the surface of the container with Kapton tape and fixed.
The region in which the water in the sample container can be enclosed is a rectangular parallelepiped shape, is square in plan view and has a side length of 14 mm. The depth is 5 mm. A cover glass having a thickness of 0.16 mm was pasted on the surface of the sample container where the track-shaped coil was in contact, thereby forming a container. Distilled water was sealed in the container. FIG. 15 shows the positional relationship between the track-shaped coil and water. Water is at position zs, 0.16 mm away from the track-shaped coil.

(An angle θ formed by the axial direction of the track-shaped coil and the static magnetic field H ₀ )
The LC resonance circuit was assembled with a track-shaped coil, and the resonance frequency was 44.2 MHz. In this measuring device, you can rotate the track shape coil and the sample to the static magnetic field H ₀ in both.

(Spin echo signal acquisition result)
FIG. 16 shows the spin echo signal intensity obtained when the angle θ formed by the axis of the track-shaped coil and the direction of the static magnetic field is 0 °.
The measurement conditions are as follows.
The irradiation time of the first excitation pulse is 40 μs, the irradiation time of the second excitation pulse is 80 μs, and the amplitudes of the first excitation pulse and the second excitation pulse are equal. The interval between the first excitation pulse and the second excitation pulse is 5 ms (the spin echo time TE is equivalent to 10 ms), the repetition time TR of the first excitation pulse is 20 seconds, the dummy measurement is 4 times, and the signal is integrated once. The FID signal was spoiled by applying a gradient magnetic field of 1 ms after irradiation of the second excitation pulse. The amplifier gain (amplification factor) of the receiver was the same for all measurements.
For reference, measurement results when the angle θ is 45 ° and 90 ° are also shown.
From FIG. 16, it can be seen that even when the angle θ is 0 °, the spin echo signal is acquired and its intensity is larger than that when it is 90 °. As the angle θ decreases, the excitation pulse output TX that maximizes the spin echo signal increases, and the intensity of the spin echo signal also increases.
When a small RF coil is used, the value of H ₀ × H ₁ does not become zero even when the angle θ changes, indicating that a spin echo signal can be acquired.

(2) Experimental example 2
In Experimental Example 1, a small RF coil having a track shape was used, but here, a planar circular coil (hereinafter also referred to as a circular coil) was used as the small RF coil.
FIG. 17 shows a photograph of the circular coil used. The circular coil was manufactured by winding a polyurethane coated copper wire with an inner diameter of 1.0 mm and a wire diameter of 0.04 mm 10 times in a plane.
The other points are the same as in Experimental Example 1.
The spin echo signal intensity when the angle θ is 0 ° is shown in FIG. For reference, the measurement results when the angle θ is 45 ° and 90 ° are also shown. As can be seen from FIG. 18, the spin echo signal is acquired even when the angle θ is 0 °, and the intensity thereof is almost the same at any angle regardless of the angle θ. However, it is a feature of this circular coil that the excitation pulse output TX at which the spin echo signal becomes maximum increases as the angle θ decreases.

  From the above experimental examples 1 and 2, it was confirmed that even when the angle θ was 0 °, NMR signals could be detected by using a planar RF coil such as a track-shaped coil or a circular coil.

(3) Analysis of MR Image Using the small RF coil (track-shaped coil) of Experimental Example 1, MR images were obtained when the angle θ was 0 and 90 °. The MR image represents the spatial distribution of the NMR signal intensity, and it can be seen from which region the NMR signal is emitted with what intensity. A typical example of MR measurement is the spatial distribution of water concentration.
Excitation pulse is 90 ° -180 ° condition (nuclear magnetization vector is excited by the first excitation pulse so that the angle α [deg] from the static magnetic field H ₀ direction is tilted by 90 °, and then further by the second excitation pulse. In the case where the spin echo signal is acquired by satisfying the condition of being excited only by 180 degrees, the intensity S _SE (α = 90 °) of the spin echo signal is expressed by the following equation (A).

Where A is a device constant, ρ (x, y, z) is the x, y, z direction distribution of water concentration, TR is the 90 ° excitation pulse repetition time, TE is the echo time, and T1 is the spin-lattice relaxation time. The constant, T2, is a spin-spin relaxation time constant.
If measurement is performed under the same conditions of A, TR, TE, T1, and T2, the spatial distribution of the spin echo signal intensity represents the spatial distribution of the water concentration.

On the other hand, when the excitation pulse is not in a 90 ° -180 ° condition (although the output of the first excitation pulse and the second excitation pulse has a one-to-two relationship, the first excitation pulse causes a static magnetic field H ₀ to If the nuclear magnetization vector falls by an angle α [deg] and α is not necessarily 90 °), the intensity of the spin echo signal is S _SE
S _SE (α) = B sin ³ (α) Formula (B)
Represented by B is a constant determined by the apparatus constant, the sample volume, the reception sensitivity of the coil, and the like.
When water is used as a sample and the distribution is uniform (ρ is uniform) at a spatially uniform concentration and MR images are acquired under the same conditions of TR, TE, T1, and T2, signals are output to the MR image. If a spatial distribution of intensity appears, the spatial distribution is a spatial distribution of the excitation angle α of the nuclear magnetization vector, which is represented by the equation (B). (On the other hand, when an MR image is acquired with a solenoid coil that can excite a nuclear magnetization vector at a spatially uniform excitation angle α, the MR image of water inserted into the solenoid coil is spatially uniform. (The signal strength will vary.)
Thus, if an MR image of a water sample is acquired using a small RF coil, the spatial distribution of the excitation angle α can be known. That is, the angle θ between the axial direction of the small RF coil and the direction of the static magnetic field H ₀ is 90 ° and 0 °, and each MR image is acquired, and the angle θ is changed by looking at the spatial distribution of the signal intensity. It is possible to know the spatial distribution of the excitation angle α of the small RF coil at the time.

MR images were measured under the following conditions.
The time interval between the first excitation pulse and the second excitation pulse is 7 ms (echo time TE is 14 ms), the output of the first excitation pulse and the second excitation pulse is one-to-two, and the repetition time of the first excitation pulse is The MR image is integrated in the thickness direction without slicing for 5 seconds, the number of integration is one, the pixel size of the MR image is a square of 0.0625 mm on a side. MR images were acquired at three TXs by changing the output TX of the excitation pulse.

MR images were displayed in the positional relationship shown in FIG. In the MR image, only the NMR signal emitted from the region of the water sample is imaged. The cover glass is not reflected.
Further, it can be considered that the spin echo signal intensity shown in FIG. 16 corresponds to a value obtained by integrating the signal intensity of the acquired MR image in the entire space. However, they do not match completely. The reason is that in MR image acquisition, TE is as long as 14 ms, and the gradient magnetic field applied time (about 3 times) and strength (about 2 times) applied when performing frequency / phase encoding are greatly different. This is due to the fact that phase dispersion is caused by water self-diffusion and the signal is lowered.

(3-1) When the angle θ is 90 ° and the excitation pulse output TX is 7.0, the angle θ formed by the axis Ax direction of the track-shaped coil and the direction of the static magnetic field H ₀ is 90 °, and the excitation pulse output TX FIG. 20 shows an MR image obtained when the value is set to 7.0 as an isoline diagram of signal intensity. The excitation pulse output of TX = 7.0 is a case where the spin echo signal intensity integrated in the whole space is smaller than TX (about 8.0) shown in FIG. In the figure, the position of the coil is added to make the positional relationship easy to understand.

  From FIG. 20, it can be seen that in the MR image in which TX is measured with a value smaller than 8, the signal intensity is strong in the inner region of the track-shaped coil, and it is semicircular. The signal intensity has a maximum value in a region on the central axis of the track-shaped coil and close to the track-shaped coil plane. The signal strength decreases with distance from the central axis and closer to the track-shaped coil conductors, and on the other hand, with decreasing distance from the track-shaped coil plane. Considering this signal intensity and the formula (B), the excitation angle α in the region near the track-shaped coil plane on the central axis of the track-shaped coil is close to 90 °, and away from the central axis, It can be seen that the excitation angle α decreases as the conductor is approached, and the excitation angle α decreases as the distance from the track-shaped coil plane increases.

(3-2) When the angle θ is 90 ° and the excitation pulse output TX is 8.0 The MR image obtained when the excitation pulse output TX is 8.0 (maximum value of signal intensity in FIG. 16) 21. Similar to FIG. 20, the signal intensity is strong in the inner area of the track-shaped coil, but as a whole, the area where the signal intensity is strong is shaped to be pushed away. If you look in detail, the signal intensity is small on the central axis of the track-shaped coil and in the region close to the track-shaped coil plane (the portion shown as region A in the figure), and it is a little away from the track-shaped coil plane. The signal is at the maximum value at that position. The reason for this is considered to be that the excitation pulse output in the region A becomes too large, the excitation angle α of the nuclear magnetization vector exceeds 90 °, the value of the equation (B) becomes small, and the signal intensity decreases. . Thus, the increase / decrease in the excitation pulse output changes the region where the NMR signal is mainly emitted.

(3-3) When the angle θ is 90 ° and the excitation pulse output TX is 8.6 MR images when TX is further increased are shown in FIG. In the area A, the excitation angle is further increased by irradiation with a large excitation pulse, and finally reaches 270 °, and the signal intensity increases again. On the central axis of the track-shaped coil, the excitation angle gradually decreases as the distance from the track-shaped coil increases, and the signal intensity has a distribution that repeatedly increases and decreases.
Thus, when the angle θ formed by the axial direction of the track-shaped coil and the direction of the static magnetic field H ₀ is 90 °, the inner region of the coil is excited and the NMR signal is acquired from that region. I understand. It can also be seen that by changing the excitation pulse output TX, the emission region of the main NMR signal becomes far from or near the track-shaped coil plane.

(3-4) MR image when the angle θ is 0 ° As shown in FIG. 23, the angle formed between the axis Ax of the track-shaped coil and the direction of the static magnetic field H ₀ as shown in FIG. MR images were acquired with θ being 0 °.

(3-4-1) When the angle θ is 0 ° and the excitation pulse output TX is 7.0)
The MR image obtained when the angle θ formed by the axis Ax of the track-shaped coil and the direction of the static magnetic field H ₀ is 0 ° and the excitation pulse output TX is 7.0 is shown as an isoline diagram of signal intensity in FIG. Show. The excitation pulse output of TX = 7.0 is a case where it is considerably smaller than TX (about 8.4) in which the spin echo signal intensity integrated in the entire space is maximized as shown in FIG. In addition, the position of the track-shaped coil is added in the figure to make the positional relationship easy to understand.
From FIG. 24, it can be seen that when the angle θ is 0 °, NMR signals are emitted from two regions near the conductor of the track-shaped coil, and the signal near the center axis of the track-shaped coil is weak. The signal intensity distribution in FIG. 24 is significantly different from the semicircular distribution shown in FIG. 20, and it can be seen that the signal emission region can be changed by changing the angle θ.

(3-4-2) When the angle θ is 0 ° and the excitation pulse output TX is 8.0 FIG. 25 shows an MR image when the excitation pulse output TX is 8.0. It can be seen that the region to be excited spreads and the signal is maximized in a region slightly further from the track-shaped coil plane. That is, it is presumed that the excitation angle exceeds 90 ° and the signal is small in the region near the track-shaped coil.

(3-4-3) When the angle θ is 0 ° and the excitation pulse output TX is 9.0 An MR image when the excitation pulse output TX is 9.0 is shown in FIG. It can be seen that the region emitting the NMR signal is further widened and away from the coil plane.
Accordingly, when the angle θ formed by the axial direction of the track-shaped coil and the direction of the static magnetic field H ₀ is 0 °, the region near the coil conductor is excited, and the NMR signal from this region is strongly measured. The signal from the region on the track-shaped coil central axis Ax is weak.

From the above, it was found that the region of the NMR signal excited and acquired by the track-shaped coil is changed by changing the angle θ formed by the axial direction of the track-shaped coil and the direction of the static magnetic field H ₀ to 0 ° and 90 °. . The region also depends on the excitation pulse output, and it can be said that the NMR signal is mainly acquired from the region near the track-shaped coil plane when weakened and the region away from the track-shaped coil plane when strengthened.

(4) Analysis of magnetic field distribution generated by track-shaped coil when angle θ is changed to 0, 90 ° Next, the magnetic field distribution generated by the track-shaped coil when angle θ is changed was analyzed.

Analysis method The following assumptions were made about the coil geometry.
・ The coil wire diameter shall be zero. (Infinitely small wire diameter)
・ There is no skin effect during conduction. (Because the wire diameter was zero, the effect of current flowing only on the coil surface was ignored.)
-In a three-turn coil, three circles with different diameters are arranged concentrically. (Do not spiral.)
-The coil is made of only conductive wire, and the coating film is ignored. (The dielectric constant and permeability use vacuum values.)
・ There is no sample. (Vacuum values are used for permittivity and permeability throughout the space.)
・ Lead parts (wiring parts other than circular coils) are ignored.

Small RF coils produce magnetic excitation field _{H z (x p, y p} , z p) magnetic field H analysis method current flowing in the theoretical analysis conductor based on Biot-Savart law I make of the basis of the Biot-Savart law Can be calculated. When the surface coil is placed in a vacuum (permeability 4π × 10 ^-7 N / A ² ), the magnetic field H (x _p , y _p ) created by the surface coil at the position (x _p , y _p , z _p ) , z _p ) is expressed by equation (1). The coordinate system in this equation is as shown in FIG. The oscillating magnetic field Hz is the magnetic field strength in the z-axis direction of the coil.

H: Magnetic field strength at position r [A / m] (vector)
r: Position of point P in space (x _p , y _p , z _p ) [m] (vector)
r ': Position of point Q on the coil (x _q , y _q , z _q ) [m] (vector)
I: Current [A] (scalar)
t: unit vector representing the direction of current flow (representing the shape of the coil at the point Q. In FIG. 27, when the angle α between the point Q and the x-axis is assumed, t is t = (sin α, cos α, 0) Yes.) [-] (Vector)
Meaning of integration: Line integration is performed over the entire circumference of the coil. (The magnetic field generated at the point P is obtained by moving the point Q on the coil along the coil and integrating the magnetic field generated at the position of each point Q over the entire circumference of the coil (taking the sum). )

The center of the track-shaped coil (track-shaped coil used in Experimental Example 1) was used as the origin of Cartesian coordinates (xyz coordinate system). The axial direction of the track-shaped coil was taken as the z-axis direction, the long-axis direction of the small RF coil was taken as the x-axis direction, and the short-axis direction was taken as the y-axis direction. The static magnetic field is H ₀ , and the magnetic field created by passing a current through the coil is H ₁ . The x, y and z directions are shown after those symbols. This analysis was performed only on the yz plane where x = 0. The reason is that the yz plane is considered to be a plane representing the excitation phenomenon of the track-shaped coil.
As shown in FIGS. 27A and 27B, the axial direction of the track-shaped coil is fixed in the z-axis direction, and the application direction of the static magnetic field H ₀ depends on two cases where the angle θ is 0 ° and 90 °. changed. When the angle θ between the axial direction (z) of the small RF coil and the static magnetic field H ₀ is 90 °, the static magnetic field H ₀ is directed in the y-axis direction and only H ₀ _y is applied. When the other angle θ is 0 °, the static magnetic field H ₀ is directed in the z-axis direction, and only H _{0 —} z is applied.

(4-1) Distribution of spin echo signal intensity when the angle θ is 90 ° When the angle θ between the axial direction (z) of the track-shaped coil and the static magnetic field H ₀ is 90 °, a current I was passed through the coil. The magnetic field strength formed during the theoretical analysis was analyzed. At this time, the oscillating magnetic field direction related to the excitation of the nuclear magnetization vector is H1_z in a direction perpendicular to H0_y. The x direction is the short axis direction, and in most of the small RF coil, H1_x is small compared to H1_z, and the contribution to the spin echo signal is small.
FIG. 28 shows the yz distribution of the spin echo signal intensity when the excitation angle α on the sample surface (z = zs) is 90 °. In this figure, it is standardized with reference to the region of maximum signal intensity. It can be seen that the distribution of this figure is very similar to the signal intensity distribution of the MR image of FIG. (Because the display method of the figure is different, it is rotated by 90 degrees in FIGS. 20 and 28.)
Next, FIG. 29 shows the yz distribution of the spin echo signal intensity when the excitation angle α on the sample surface (z = zs) is 180 °, corresponding to the increase in the excitation pulse output. From this figure, it can be seen that when the excitation pulse output is increased, the region where the signal intensity becomes strong becomes a region far away from the plane of the coil. This result is the same result as FIG. 21 of the MR image obtained by increasing the excitation pulse output. From the above results, the angle θ between the axial direction of the track-shaped coil and the direction of the static magnetic field H ₀ is 90 °. It can be seen that the nuclear magnetization vector is excited by the magnetic field H1_z in the z direction created by the coil, and an NMR signal (spin echo signal) is observed.

(4-2) Distribution of spin echo signal intensity when the angle θ is 0 ° When the angle θ between the axial direction (z) of the track-shaped coil and the static magnetic field H ₀ is 0 °, it is related to the excitation of the nuclear magnetization vector. The direction of the oscillating magnetic field is H1_y in the direction perpendicular to H0_z. As in the previous section, H1_x is small and the contribution to the spin echo signal is small and ignored.
FIG. 30 shows the yz distribution of the spin echo signal intensity when the excitation angle α on the sample surface (z = zs) is 90 °. FIG. 31 also shows the results when the excitation angle α is 180 °.
FIG. 30 shows the MR image in FIG. 24, and FIG. 31 shows the MR image in FIG. 25, together with the spatial distribution of the signal intensity, the change in the distribution shape with respect to the excitation pulse output (the region where the signal intensity is strong from the coil plane goes far away. The phenomenon is very similar.
Thus, when the angle θ between the axial direction (z) of the track-shaped coil and the static magnetic field H ₀ is 0 °, the nuclear magnetization vector is excited by the oscillating magnetic field H1_y in the y direction perpendicular to the axial direction of the coil. I understood.
From the comparison of the above analysis results and the MR image, the following was found.
When the angle θ between the axial direction (z) of the small RF coil and the direction of the static magnetic field H ₀ is 90 °, the nuclear magnetization vector is excited by the magnetic field H1_z in the z direction created by the coil.
When the angle θ between the axial direction (z) of the small RF coil and the static magnetic field H ₀ is 0 °, the nuclear magnetization vector is excited by the oscillating magnetic field H1_y in the y direction perpendicular to the axial direction of the coil.

(Example 2)
Using the fuel cell system shown in FIG. 1, the water content in the solid polymer electrolyte membrane was measured.
FIG. 32 shows a photograph of the planar track-shaped coil (small RF coil) used. This track-shaped coil has Ds of 0.3 mm, Dl of 1.5 mm, a wire diameter of 0.06 mm, and three turns. This coil was inserted between GDL (diffusion layer) and PEM (solid polymer electrolyte membrane). There are eight track-shaped coils arranged in a line at equal intervals. There are a total of 16 on the hydrogen electrode side and 8 on the air electrode side (see FIG. 2).
For GDL, a carbon mesh having a thickness of 400 μm was used. The generated current flows through this GDL, flows through the collector electrode, and is consumed by the electronic load device. The gas flow path attached to the separator is a serpentine type (single stroke) flow path of 1.5 mm wide, 2 mm deep, 3.5 mm pitch on both the hydrogen and air sides. Hot water was allowed to flow through the separator so that the temperature of the fuel cell was 50 ° C.
As the PEM (solid polymer electrolyte membrane), a Nafion 117 membrane having a thickness of 178 μm was used. A platinum catalyst was fused to this PEM by a hot press method to obtain an MEA. The area of the platinum catalyst is 50 mm x 50 mm. This dimension is the power generation area.

FIG. 2 shows the cell structure of the fuel cell used in this experiment. A track-shaped coil was inserted between the MEA and GDL. The axial direction (direction perpendicular to the plane) of these track-shaped coils is the z-axis direction. Direction of the static magnetic field H ₀ is set to the z-axis direction. The angle θ between the axis Ax of the track-shaped coil and the static magnetic field H0 was set to zero.

  Hydrogen gas was supplied at a flow rate of 60 ml / min, passed through a bubbler at 45 ° C. and humidified. The air was supplied at a flow rate of 150 ml / min, humidified through a bubbler at 45 ° C., and supplied to the cell. The fuel cell was maintained in this state before power generation and measured after it was in a steady state.

(1) Measurement result of change in water content of PEM during drying process by increasing the cell temperature The initial temperature of the fuel cell was set to 50 ° C, and the temperature control water was increased to 60 ° C (see Fig. 33). The signal intensity of PEM was measured when the relative humidity was reduced. The water vapor concentration of the feed gas is determined at the bubbler temperature of 45 ° C, which is constant, but the relative humidity of the feed gas is determined by the cell temperature, and when the cell temperature is 50 ° C, the relative humidity is 79% and the cell temperature is The relative humidity at 60 ° C. is 50%. Increasing the cell temperature reduces the relative humidity of the fuel cell. In this process, the PEM gradually dries over time. In this experiment, the water content of PEM during the drying process was measured. Here, since the intensity of the spin echo signal of the PEM and the water content are in a substantially direct relationship (see FIG. 34), it is considered that the water content of the PEM is decreased due to the decrease of the signal intensity.
The measurement conditions of the NMR signal are as follows. The echo time (TE) was 10 ms, the 90-degree excitation pulse repetition time (TR) was 10 seconds, and a 1-ms gradient magnetic field was applied before and after the 180-degree excitation pulse to spoil the FID signal. The echo signal intensity was an average value at three consecutive times (three points at 10-second intervals) in order to reduce variation.

FIG. 35 shows the normalized spin echo signal intensity obtained with the coil on the hydrogen electrode side and FIG. 36 with the coil on the oxygen electrode side.
Coil B in FIG. 35 is the small RF coil 114B in FIG. 2, Coil D is the small RF coil 114D in FIG. 2, Coil F is the small RF coil 114F in FIG. 2, and Coil H is in FIG. 2 small RF coil 114H. In addition, Coil J in FIG. 36 is the small RF coil 114J in FIG. 2, Coil L is the small RF coil 114L in FIG. 2, Coil N is the small RF coil 114N in FIG. 2, and Coil P is This is the small RF coil 114P of FIG.

35 and 36, although there is some variation, the signal strength after 700 seconds when the temperature of the fuel cell has reached approximately 60 ° C is lower than the signal strength before that in almost all coils. It can be said that the water content of PEM was lowered and dried.
As a result, even if the angle θ between the axial direction of the small RF coil and the direction of the static magnetic field is 0 °, the moisture content of the PEM in the fuel cell can be measured, and the moisture content of the PEM decreases during the drying process. I understood that it was captured.

(2) Change in water content of PEM during power generation When the fuel cell temperature is 50 ° C (relative humidity 79%) and the power generation current is 3A, the PEM content on the hydrogen electrode side and air electrode (oxygen electrode) side The amount of water was measured. Here, similarly to the above (1), the echo signal intensity is obtained, and the echo signal intensity and the water content are directly proportional to each other, and the water content of the PEM is increased or decreased. The gas flow rate, bubbler temperature, NMR measurement conditions, etc. are all the same as in the above experiment (1).
There was a concern that the echo signal during power generation caused a frequency shift due to the current flowing through the GDL, which affected the spin echo signal intensity. Therefore, power generation and stoppage were repeated at 50 second intervals, and only the spin echo signal intensity at the time of power generation stoppage was extracted to organize the measurement results. FIG. 37 shows a normalized spin echo signal on the hydrogen electrode side, and FIG. 38 shows a normalized spin echo signal on the air electrode side. Coil B in FIG. 37 is the small RF coil 114B in FIG. 2, Coil D is the small RF coil 114D in FIG. 2, Coil F is the small RF coil 114F in FIG. 2, and Coil H is 2 small RF coil 114H. Further, Coil J in FIG. 38 is the small RF coil 114J in FIG. 2, Coil L is the small RF coil 114L in FIG. 2, Coil N is the small RF coil 114N in FIG. 2, and Coil P is This is the small RF coil 114P of FIG.
From FIG. 37 showing the water content on the hydrogen electrode side, it seems that the water content gradually decreases as the power generation time becomes longer.
From FIG. 38 showing the water content of the other air side electrode, it can be seen that as the power generation time becomes longer, drying progresses upstream (coils J, L), and wetting progresses downstream (coils N, P). appear.
In FIGS. 37 and 38, it is considered that the reason why the change in the water content was not clear is that the power was generated with a relative humidity as high as 79%. The basis for this is that, in other experiments, when the PEM with a relative humidity of about 30% is generated in a dry state, the water content in the PEM is different between the hydrogen electrode side and the oxygen electrode side. This is because the was not seen.

<II. Study on external shape of small RF coil>
Next, the external shape of the small RF coil II described above was examined.

(Example 3)
Here, the superiority of the small RF coil 114 (hereinafter referred to as a track-shaped coil) over the circular coil was examined.
As a measuring apparatus, the apparatus shown in FIG. 39 was used. In this apparatus, the axial direction of the small RF coil 114 and the static magnetic field direction are orthogonal to each other. Other points are the same as those of the measurement apparatus 100 of the above embodiment.
FIG. 40 shows photographs of the track-shaped coil and the circular coil used. Two types of track-shaped coils and three types of circular coils (inner diameter 0.6 mm, 0.8 mm, 1.0 mm) were used. Tables 1 and 2 summarize the detailed dimensions and number of turns of the coil.
FIG. 40A shows a track-shaped coil, in which a copper wire with a wire diameter of 0.04 mm is wound three times, Ds is 0.5 mm, and Dl is 3.5 mm.
FIG. 40B is also a track-shaped coil, in which a copper wire with a polyurethane film having a wire diameter of 0.06 mm is wound three times, Ds is 0.39 mm, and Dl is 1.29 mm.
On the other hand, FIG. 40C shows a circular coil in which a polyurethane coated copper wire having a wire diameter of 0.04 mm is wound five times and an inner diameter ID is 0.6 mm.
Here, the track-shaped coil is wound three times and the circular coil is wound five times, and the difference in the number of turns gives a difference in the reception sensitivity of the NMR signal. The higher the number of turns, the higher the reception sensitivity. This can be understood by considering the strength of the magnetic field formed when the same current is passed through the coil. A coil with a large number of turns has a higher magnetic field strength. In order to make a quantitative discussion, it is only necessary to theoretically analyze the strength of the magnetic field generated when a predetermined current (for example, 1 A) is passed through the coil and convert it to reception sensitivity. Similarly, the reception sensitivity depends on the coil shape. By giving the coil shape and the number of turns and conducting a theoretical analysis, the reception sensitivity depending on the shape and the number of turns can be quantitatively evaluated.

(Measurement sample)
Water was put into a sample container, and a coil was attached to the surface of the container with Kapton tape and fixed. The container was manufactured using two cover glasses with a thickness of 0.16 mm, with a gap of 0.58 mm, and water was put into the gap. FIG. 41 shows the positional relationship between the coil and water. Water is at position zs, 0.16 mm away from the coil.
Spin echo signals were obtained using the coils shown in Tables 1 and 2 and the water sample shown in FIG. The measurement conditions are as follows. The static magnetic field strength was 1 T, the 90-degree excitation pulse repetition time TR was 20 seconds, the echo time TE was 10 ms, and a gradient magnetic field was applied for 3 ms before and after the 180-degree excitation pulse. The dummy count before the measurement is four times, and one-shot measurement without integration. The amplifier gain, the filter frequency band, etc. after receiving the NMR signal by the RF coil were all set to the same signal acquisition conditions.
The spin echo signal intensity acquired by each coil is shown in FIG. The vertical axis is the value of the AD converter reading itself. (Because it increases or decreases depending on the amplifier gain, it is described in an arbitrary unit. However, since the signal acquisition conditions are all the same as described above, they can be compared with each other.)
FIG. 43 is a graph in which the horizontal axis of FIG. 42 is converted into “measurement depth”. The measurement depth is a value obtained by multiplying the inner diameter ID of the circular coil by 0.32. In the case of a track-shaped coil, a value obtained by multiplying Ds by 0.37 was used (the explanation of numerical values of 0.32 and 0.37 will be described later).
From these figures, it can be seen that Ds of the track-shaped coil is smaller than that of the circular coil having an inner diameter of 0.6 mm and 0.8 mm, the measurement depth is shallow, but the signal intensity is large.

(1) Receiving sensitivity correction method based on coil shape, number of turns, etc. As shown in Tables 1 and 2, the number of turns of the track-shaped coil is different from the number of turns of the circular coil. Not equal. If the number of turns of the track-shaped coil is set to 5, the received signal strength may further increase. Also, the reception sensitivity increases or decreases depending on the shape of the coil. Furthermore, the reception sensitivity increases and decreases depending on the electric resistance value of the coil. For this reason, it is necessary to eliminate the effect of the reception sensitivity due to the shape, number of turns, and electrical resistance of the coil, and to compare the signal strength based on the same reference. By comparing with the same standard, the difference in signal strength between the circular coil and the track-shaped coil can be evaluated regardless of the number of turns of the coil, etc., and as a result, it shows that it depends on the measurement volume it can. Below, the correction coefficient used in order to compare signal strength by the same reference | standard is demonstrated.
The standard was a circular coil with an inner diameter ID of 0.6 mm.

(1-1) Correction coefficient based on the electrical resistance value of the coil (this is called correction coefficient 1)
An NMR signal is received by inducing a current in a coil by a fluctuating magnetic field generated by an excited magnetization vector in a sample. At this time, the length of the conductive wire of the coil varies depending on the shape and the number of turns of the coil, and the electrical resistance value of the coil increases and decreases, and the induced current value also increases and decreases accordingly. The relationship between the electrical resistance value of the coil and the reception sensitivity depends on the following relationship.
The reception sensitivity of the coil depends on the square root of the ratio of the electrical resistance values of the coils. That is, the correction coefficient 1 when the electrical resistance value of the ID 0.6 mm circular coil is used as a reference is expressed by the following equation.
The reason why the square root correction coefficient 1 of the correction coefficient 1 = (electric resistance value of the coil) / (electric resistance value of the reference ID 0.6 mm circular coil) is expressed by the above equation is shown below.
A current is induced in the coil by the fluctuating magnetic field, which becomes energy E for resonating the LC resonance circuit including the coil. In this LC resonance circuit, it is assumed that the electric resistance value of the thin conductor portion forming the coil is the largest, and the resonance energy E is consumed by the electric resistance of the coil. At this time, if the effective current flowing in the coil is I and the effective voltage applied to both ends of the coil is V, the resonance energy E is VI. If this is rewritten with the electric resistance value R = V / I, E = RI ² is obtained.
When the electric resistance value of the coil ₁ is written as R ₁ and the current induced in the coil is I ₁ , the resonance energy is E = R ₁ I ₁ ² . Similarly, E = R ₂ I ₂ ² for the coil 2.
Assuming that the resonance energy E given to the LC resonance circuit is determined by the variable magnetic field generated by the magnetization vector, and E is equal in coils 1 and 2, R ₁ I ₁ ² = R ₂ I ₂ ² The current ratio is
I ₂ / I ₁ = (R ₂ / R ₁ ) ^1/2
Here, if the coil 1 is a reference ID 0.6 mm circular coil, the equation of the correction coefficient 1 is obtained.

(1-2) Correction coefficient based on the magnetic field intensity generated by the coil (this is called correction coefficient 2)
The strength of the magnetic field generated by the coil varies depending on the shape and number of turns of the coil. When a current of 1 A is passed through the coil, the more turns the coil has, the stronger the magnetic field it creates. This means that the more the shape and the number of turns the coil can create a strong magnetic field, the stronger the current is induced in the coil by the varying magnetic field, and the higher the receiving sensitivity of the coil.
If the reception sensitivity of the coil is a low frequency of about 43 MHz, it is considered that it is proportional to the strength of the magnetic field formed when a steady current is passed. Therefore, by simulating the shape of the coil and theoretically analyzing the magnetic field strength Hz at the sample surface (z = zs) on the central axis of the coil formed when a steady current of 1 A was passed through it, the magnetic field strength Hz (z = zs) is assumed that the correction coefficient 2 is proportional. In other words, the correction coefficient 2 is expressed by the following equation based on the magnetic field strength created by the circular coil having an inner diameter of 0.6 mm.
Correction factor 2 = (Magnetic field strength Hz created by coil at z = zs) / (Magnetic field strength Hz created by z = zs by standard ID 0.6mm circular coil)

As described above, the converted signal intensity I using the two correction coefficients 1 and 2 is expressed by the following equation.
I = Iexp × (correction coefficient 1) × (correction coefficient 2) / (signal intensity Iexp of ID 0.6 mm circular coil) Expression (A)
Here, Iexp indicates the measured spin echo signal intensity.

  As an interpretation of the above formula (A), the correction coefficient 1 is a coefficient for correcting the difference in the current value induced in the coil by the electric resistance value, and the correction coefficient 2 is the magnetic field strength formed by the coil shape and the number of turns. It may be considered that the coefficient corrects the difference. This correction corrects differences in the shape, number of turns, and electrical resistance value of the coil.

(1-3) Comparison of Signal Intensity Converted with Reception Sensitivity Correction Factor FIGS. 44 and 45 show the results when the signal intensities in FIGS. 42 and 43 are converted by equation (A).
This figure also shows the measurement volume curve calculated by the following equation.

Measurement volume of the circular coil = (inner area of the coil = ID ^2/4) × (measurement depth = ID × 0.32) · · · formula (B1)
Measurement volume of track shape coil = (inner area of the coil = Ds × (Dl-Ds) + Ds 2/4)
× (Measurement depth = Ds × 0.37) Expression (B2)
Here, ID, Ds, and Dl are shown in FIG.

Further, 0.32 and 0.37 in the formula (B2) are derived from Table 3 described later (details will be described later).
Further, when these measurement volumes are shown in FIGS. 44 and 45, the measurement volume of a circular coil having an inner diameter of 0.6 mm is shown as a reference 1.

  From the formula (B1), in the case of a circular coil, the measurement volume increases with the cube of the inner diameter, while from the formula (B2), in the case of a track-shaped coil, it increases with the square of Ds. . In the case of a track-shaped coil, D1 is provided as another shape parameter as the measurement volume.

From FIG. 44, it can be seen that the increase rate of the converted signal intensity of the circular coil coincides with the increase rate of the measurement volume indicated by the broken line. Therefore, it can be said that the increase in signal intensity is proportional to the increase in measurement volume.
On the other hand, in the track shape coil, there are two shape parameters of the track shape coil, Ds and Dl. FIG. 44 shows the increase ratio of the measurement volume when the ratio Dl / Ds between them is 2, 3, and 7. The track-shaped coil used in the experiment is Dl / Ds = 7, 3.3. The converted signal strength of Dl / Ds = 7, 3.3 and the measurement when calculated as Dl / Ds = 7, 3.3 It can be seen that the solid volume line is in good agreement. From this figure, it is understood that the signal intensity is proportional to the measurement volume in the track-shaped coil as well as the circular coil.

FIG. 45 is a diagram in which the result of FIG. 43 is rearranged with the measurement depth, with the vertical axis representing the converted signal intensity, similarly to FIG. From this figure, although the track-shaped coil has a measurement depth of about 0.2 mm, which is similar to the circular coil with an inner diameter of 0.6 mm, the converted signal strength is very large compared to the circular coil. I understand that.
It can also be seen that when Dl / Ds is 2 or more, the track-shaped coil has a remarkable effect of increasing the signal intensity while keeping the measurement depth shallow.
From the above results, it can be said that the track-shaped coil can increase the signal intensity while keeping the measurement depth shallow.

(2) Method for Analyzing Magnetic Field and Signal Strength Here, a method for deriving the above-described equation (B2) by analyzing the measurement region and measurement depth when using a surface coil will be described.

Analysis method The following assumptions were made about the coil geometry.
・ The coil wire diameter shall be zero. (Infinitely small wire diameter)
・ There is no skin effect during conduction. (Because the wire diameter was zero, the effect of current flowing only on the coil surface was ignored.)
-In a three-turn coil, three circles with different diameters are arranged concentrically. (Do not spiral.)
-The coil is made of only conductive wire, and the coating film is ignored. (The dielectric constant and permeability use vacuum values.)
・ There is no sample. (Vacuum values are used for permittivity and permeability throughout the space.)
・ Lead parts (wiring parts other than coils) are ignored.

Under the above assumption, the magnetic field H generated by the current I flowing through the conductor was calculated based on Bio-Savart's law. When the surface coil is placed in a vacuum (permeability 4π × 10 ^-7 N / A ² ), the magnetic field H (x _p , y _p ) created by the surface coil at the position (x _p , y _p , z _p ) , z _p ) is expressed by equation (1). The coordinate system in this equation is as shown in FIG. The oscillating magnetic field Hz is the magnetic field strength in the z-axis direction of the coil.

H: Magnetic field strength at position r [A / m] (vector)
r: Position of point P in space (x _p , y _p , z _p ) [m] (vector)
r ': Position of point Q on the coil (x _q , y _q , z _q ) [m] (vector)
I: Current [A] (scalar)
t: unit vector representing the direction of current flow (representing the shape of the coil at point Q. In FIG. 47, when the angle α between point Q and the x-axis is taken, t is t = (sin α, cos α, 0) Yes.) [-] (Vector)
Meaning of integration: Line integration is performed over the entire circumference of the coil. (The magnetic field generated at the point P is obtained by moving the point Q on the coil along the coil and integrating the magnetic field generated at the position of each point Q over the entire circumference of the coil (taking the sum). )
As shown in FIG. 47, the center of the small RF coil (track-shaped coil) is the origin of Cartesian coordinates (xyz coordinate system). The axial direction of the small RF coil was taken as the z-axis direction, the long axis direction of the small RF coil was taken as the x-axis direction, and the short axis direction was taken as the y-axis direction.

(2-1) Signal Strength Analysis Results (2-1-1) Magnetic Field Hz (x, y, z) Distribution Formed When Current 1 A Flows through the Track-Shaped Coil FIG. Shows the spatial distribution of the magnetic field Hz (x, 0, z) created by the track-shaped coil in the xz plane when a current of 1 A is applied. From this figure, it can be seen that the magnetic field Hz in the major axis (x) direction is almost uniform. That is, the NMR signal can be excited and acquired almost uniformly in the long axis (x) direction in the range inside the track-shaped coil.
FIG. 49 shows the magnetic field Hz (0, y, z) in the yz plane, and FIG. 50 shows the spatial distribution of the magnetic field Hz (x, y, 0) in the xy plane.
FIG. 51 shows the spatial distribution S _FID (x, 0, z) of the FID signal intensity on the xz plane. 52 shows the FID signal intensity distribution S _FID (0, 0, z) on the z-axis, and FIG. 53 shows the FID signal intensity distribution S _FID (x, 0, 0) on the x-axis. .
FIG. 54 shows the spatial distribution S _SpinEcho (x, 0, z) of the spin echo signal intensity in the xz plane. 55 shows the spin echo signal intensity distribution S _SpinEcho (0, 0, z) on the z axis, and FIG. 56 shows the spin echo signal intensity distribution S _SpinEcho (x, 0, 0) on the x axis. Indicates.
From FIG. 49 to FIG. 56, the signal intensity in the x-axis direction is almost uniform in the range inside the track-shaped coil, and the signal intensity in the z-axis direction is narrower in the spin echo signal than in the FID signal. I understand.

(2-1-2) Spatial distribution of signal intensity acquired by track-shaped coil (when excitation angle is 90 degrees on sample surface)
FIG. 57 shows the intensity distribution S _SpinEcho (x, y, 0.16 mm) in the xy plane of the spin echo signal when the surface of the sample is at position z = 0.16 mm and the excitation angle at that position is 90 degrees. Show. 58 and 59 show signal intensity distributions in the y-axis direction and the x-axis direction. 57 to 59, it can be seen that the NMR signal can be acquired with a substantially uniform signal intensity within the range inside the track-shaped coil.

(2-1-3) Spatial distribution of signal intensity acquired by circular coil (when excitation angle is 90 degrees on sample surface)
As a comparison, a circular coil with an inner diameter of 0.6 mm was also analyzed. In the circular coil, assuming that the surface of the sample is at position z = 0.16 mm, and the intensity distribution S _SpinEcho (x, y, 0.16 mm) on the xy plane of the spin echo signal when the excitation angle at that position is 90 degrees As shown in FIG. FIG. 61 shows a signal intensity distribution in the y-axis direction.

(2-1-4) Comparison between track-shaped coil and circular coil In order to compare the measurement depth between the track-shaped coil and the circular coil, it is assumed that there is a sample in the entire area around the coil, and the excitation angle at the coil center is 90. The signal intensity distribution was analyzed. 62 shows the z-axis direction distribution of the FID signal, and FIG. 63 shows the z-axis direction distribution of the spin echo signal. In these analyses, geometrical similarity holds, so these figures are normalized by Ds for track-shaped coils and by ID for circular coils.
62 and 63, a position where the signal intensity is halved is defined as a measurement depth. From these figures, the measurement depths were read, and Table 3 summarizes the measurement depths for the track-shaped coil and the circular coil.
From this result, the measurement depth is 0.46 when the FID signal is acquired and 0.37 when the spin echo signal is acquired, with D _{s of the} track-shaped coil as a reference. In the case of a circular coil, the inner diameter ID is 1 as a reference, and is 0.38 when the FID signal is acquired and 0.32 when the spin echo signal is acquired. It can be seen that the track-shaped coil is slightly deeper than the measurement depth (0.38 for FID, 0.32 for SE) of the circular coil (inner diameter ID = 0.6mm, wire diameter 0.08mm, 5 turns).

From this result, it can be seen that in the above-described equation (B2), the measurement depth at the time of detecting the spin echo signal is Ds × 0.37 or ID × 0.32.
As described above, it was found from FIGS. 44 and 45 that the value calculated by the calculation formula (B2) and the experimental data substantially coincide.

  Table 3 also shows the area inside the coil (the area surrounded by the coil). When there is a sample in the entire space, the signal intensity is considered to be approximately proportional to the inner area of the coil, and therefore the signal intensity can be estimated by the ratio of the areas. The signal strength obtained with the track-shaped coil is estimated to be about 6 times that of the circular coil.

  In Table 4, the measurement area was calculated based on the results of FIGS. 57 and 60 of the xy plane distribution of the spin echo signal intensity obtained when the excitation angle was 90 degrees at the sample surface position z = 0.16 mm. Results are shown. The area ratio between the measurement area of the track-shaped coil and that of the circular coil is 4.8 times, and it is presumed that there is a difference in signal intensity of this level even in actual measurement.

DESCRIPTION OF SYMBOLS 1 Fuel cell system 5 Fuel cell 51 Membrane electrode assembly 52, 53 Diffusion layer 54, 55 Separator 100 Measuring apparatus 102 RF oscillator 104 Modulator 106 RF amplifier 112 Preamplifier 113 Static magnetic field application part 113A, 113B Magnetic pole 114 Small RF coil (plane RF coil)
114A to 114P Small RF coil 118 A / D converter 118A Converter 118B Converter 120 Data receiving unit 127 Sequence table 128 Timing unit 129 Operation signal receiving unit 130 Operation unit 130A First calculation unit 130B Second calculation unit 130C Third calculation Unit 135 output unit 140 detector 150 control unit 151 pulse control unit 152 mode switching control unit 159 current drive power supply 170 switch unit 171 hybrid 173 distributor 175 distributor 177 mixer 179 mixer 181 combiner 183 mixer 185 mixer 187 distributor 190 Storage unit 191 First storage unit 192 Second storage unit 213 Static magnetic field application unit 213A, 213B Magnetic pole 214A, 214B Magnetic pole 251 Gradient magnetic field application unit 251 G coil 313 Static magnetic field application unit 511 Solid polymer electrolyte membrane 512 513 catalyst layer 541 and 551 flow path 914 sized RF coils 1140 and 1141 the first portion 1142 and 1143 second portion Ax axis

Claims (11)

A measurement device that applies an excitation oscillating magnetic field to a film-like or flat sample containing a protic solvent and detects an NMR signal corresponding to the excitation oscillating magnetic field,
A pair of magnetic poles having different polarities arranged opposite to each other, and a static magnetic field applying unit that applies a static magnetic field to the film-shaped or flat-shaped sample disposed between the pair of magnetic poles;
A planar RF coil for applying an excitation oscillating magnetic field to the sample and acquiring an NMR signal corresponding to the excitation oscillating magnetic field;
Between the pair of magnetic poles of the static magnetic field application unit, the sample is arranged so that the direction of the static magnetic field formed by the pair of magnetic poles penetrates the front and back surfaces of the sample vertically,
The planar RF coil is wound in an annular shape so as to surround one axis, and the planar RF coil is disposed on the sample so that the axis is orthogonal to the sample front and back surfaces. The measuring device in which the axis of the planar RF coil is parallel to the direction of the static magnetic field formed by the static magnetic field application unit. The measuring apparatus according to claim 1,
The planar RF coil has a pair of first portions extending substantially parallel to each other, and a second portion connecting between opposing ends of the pair of first portions,
The distance between the pair of first portions is Ds,
When the distance between a pair of intersections extending in parallel with the first part and passing through a center point of the distance between the pair of first parts intersects with the pair of second parts is Dl,
A measuring device having Dl / Ds of 2 or more. The measuring apparatus according to claim 1 or 2,
Comprising a plurality of planar RF coils;
The planar RF coil is a measurement device that is spaced apart along the surface of the sample. In the measuring apparatus in any one of Claims 1 thru | or 3,
In a state where the direction of the static magnetic field formed by the pair of magnetic poles keeps a positional relationship perpendicularly penetrating the front and back surfaces of the sample, the sample and the pair of magnetic poles of the static magnetic field application unit are relatively A measuring apparatus comprising moving means for moving. In the measuring apparatus in any one of Claims 1 thru | or 4,
A measuring apparatus comprising switching means for switching a static magnetic field application direction or an arrangement direction of the sample with respect to the static magnetic field application unit so that a static magnetic field direction from the static magnetic field application unit is orthogonal to an axis of the planar RF coil. . In the measuring apparatus in any one of Claims 1 thru | or 5,
The static magnetic field application unit has a plurality of pairs of the pair of magnetic poles,
In the plurality of pairs of magnetic poles, one magnetic pole is spaced apart along the sample surface on the sample surface side, and the other magnetic pole having a polarity different from that of the one magnetic pole is disposed along the sample back surface on the sample back surface side. Measuring device. In the measuring apparatus in any one of Claims 1 thru | or 6 ,
The measurement apparatus is a solid polymer electrolyte membrane. In the measuring apparatus in any one of Claims 1 thru | or 7 ,
A measuring apparatus having a calculating unit that calculates the amount of protic solvent in the sample based on a nuclear magnetic resonance signal acquired by the planar RF coil. The measuring apparatus according to any one of claims 1 to 8 ,
A gradient magnetic field application unit for applying a gradient magnetic field to the sample;
A controller that executes application of the gradient magnetic field and the excitation oscillating magnetic field according to a predetermined pulse sequence;
A second calculation unit,
The planar RF coil acquires NMR signals corresponding to the excitation oscillating magnetic field and the gradient magnetic field,
Wherein in the second calculation unit, different gradient field obtained corresponding, on the basis of the plane NMR signal acquired by the RF coil, prior Ki試 charge measuring device for calculating the mobility of the protic solvent in a specific portion . The measuring apparatus according to any one of claims 1 to 9 ,
The sample is one in which current is generated in the sample,
A measurement apparatus having a third calculation unit that calculates a difference between the frequency of the NMR signal acquired by the planar RF coil and the frequency of the oscillating magnetic field for excitation, and calculates a current at a specific location of the sample from the difference. . A solid polymer electrolyte membrane containing a protic solvent; a fuel electrode disposed on one side of the solid polymer electrolyte membrane; and an oxidant electrode disposed on the other side of the solid polymer electrolyte membrane. A fuel cell having
A fuel cell system including a measuring device,
The fuel cell system wherein the measuring device is a measuring device according to any one of claims 1 to 10.