JP3101005B2 - Surface scattering density meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention transmits a signal line such as a transmission line such as gamma rays or an ultrasonic wave into a sample and scatters the sample inside the sample.
The present invention relates to a surface scattering type densitometer for measuring the density of a sample by utilizing the fact that a change in a signal pulse obtained is correlated with the density of the sample.

[0002]

2. Description of the Related Art Conventionally, as a measurement of a physical quantity of a sample using radiation such as gamma rays or ultrasonic waves, various measurements such as a densitometer measurement using gamma rays and an elastic coefficient measurement using ultrasonic waves have been used. Are known. Taking the density meter measurement using γ-rays as an example, there is a surface scattering type density meter as shown in FIG. In this surface scattering type densitometer, the radiation source 1 and the detection sensor 2 are installed at a predetermined distance from the surface of the sample 3,
The γ-ray pulse emitted from the radiation source 1 is detected by the detection sensor 2 and output to the measuring device 4, and the measuring device 4 counts the number N of detected pulses per unit time. There is a correlation between the number N of detection pulses and the density ρ of the sample, and a data table based on the correlation is prepared in advance, or the value of the density ρ with respect to the number N of pulses is obtained and displayed by calculation. I do.

[0003] In such a conventional physical quantity measuring device, there are a device in which a signal source and a detection sensor are independently moved and installed, and a device in which a signal source and a detection sensor are integrated.

[0004]

However, when the signal source and the detection sensor can be moved independently and independently, there is an advantage that the relative distance between the signal source and the detection sensor can be freely changed. However, there is a problem that it is difficult to set the distance accurately. For example, in the above-described density meter, the relative distance between the radiation source and the detection sensor is also a parameter of the density ρ, so that it is necessary to arrange the radiation source and the detection sensor at an accurate distance. Therefore, when it is desired to measure a plurality of data at a plurality of sample positions, there is an inconvenience that attention must be paid to each measurement so that a constant relative distance is obtained.

Further, when the signal source and the detection sensor are integrated, there is an advantage that the distance between the two does not have to be paid for every measurement, but it is difficult to make the distance variable. Is disadvantageous. The present invention has been made in view of such a conventional problem, and simply and stably changes the relative distance between a signal source and a detection sensor to determine the density of a sample from the measurement results of the detection values of a plurality of signal pulses. an object of the present invention and Turkey be measured.

[0006]

According to the present invention, a signal pulse is transmitted from a signal source into a sample, and a detection sensor detects a signal pulse scattered inside the sample. In a surface scattering type densitometer that measures the density of the sample by utilizing the fact that the change in the signal pulse is related to the physical properties of the sample, the signal source and the detection sensor are placed on the same surface of the sample. And a mechanism for changing the relative distance between the signal source and the detection sensor is provided in the housing of the surface scattering type densitometer, and a mechanism for changing the relative distance between the signal source and the detection sensor is provided. From the measurement result of the detected value of the pulse, the signal pulse diffuses radially around the relative interval.
The density of the sample was measured after correcting by the equivalent average distance caused by the measurement.

Further, the mechanism is rotatable about an axis perpendicular to the sample surface of the sample has a rotary member provided at a predetermined distance from the signal source, the signal source Is provided at an eccentric position of the rotator and opposed to the sample, and by rotating the rotator, the relative distance between the signal source and the detection sensor is changed to measure a plurality of signal pulse detection values. From the results, the density of the sample was measured.

The mechanism has a mechanism for linearly moving the signal source in an appropriate direction at a position distant from the detection sensor while facing the sample surface of the sample, and linearly moving the signal source. in, it was decided to measure the density of the sample from the measurement result of the detection values of the plurality of signal pulses by changing the relative spacing of the signal source and the sensor. Also, before dangerous exits provided a plurality of sensors, and to measure the density of the sample from the change of the respective signal pulse number measured by the detection sensor.

Further, a plurality of the signal sources are provided, and the density of the sample is measured from a change in the number of detection pulses measured by the detection sensor. Also, the relationship between the detection sensor and the signal source is determined.
The clerk provided two detection sensors, and from each of the detection sensors
Two signal sources are installed at predetermined intervals facing the sample surface
Realized by a signal pulse from each source to the sample
To provide a shutter to shield and release
Therefore, the relative distance between the signal source and the detection sensor is changed.
Realized that mechanism, the transmission of signal pulses to the sample sequentially performed by the opening of the shutter according to any one of the signal source, to measure the density of the sample from the measurement results of the detection value of the signal pulse from each source It was to be.

[0010]

According to the apparatus having such a configuration, since the relative distance between the radiation source and the detection sensor can be changed with high accuracy, highly accurate measurement can be realized.
In addition, since measurement is performed at a plurality of relative intervals, there is no need to change the position of the measurement device itself, and measurement can be performed at the once installed position, so that errors in measured values due to the surface shape of the sample do not occur. The accuracy can be improved.

Further, by providing a plurality of detection sensors, the measurement time can be reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a density measuring apparatus according to one embodiment of the present invention will be described with reference to the drawings. First, FIG. 1 and FIG.
The structure will be described with reference to the drawings. A turntable 8 is housed in a housing 6 composed of a platform 6a and side walls 6a which are fixedly attached to the platform and hang down.

The turntable 8 includes a platform 6a
Bearings 12 and 14 are attached to a supporting shaft 10 which is fixed to
A radiation source 16 that emits gamma rays at an eccentric position of the rotation center of the turntable 8 is attached. Further, a tower-shaped support portion 18 is fixed to the platform 6a at a location away from the mounting position of the turntable 8, and the support portion 18 has a pair of penetrating through the platform 6a and hanging down to the inside of the housing 6. The detection sensors 20, 22 are fixed. Then, the detection signals of the respective detection sensors 20 and 22 are transferred to a measuring device (not shown) via signal lines 24 and 26.

As shown in the longitudinal sectional view of FIG. 2, the support shaft 10 and the detection sensors 20 and 22 are arranged in parallel, and the radiation source 1 is always in contact with the rotation of the turntable 8.
6 and the bottom surfaces of the detection sensors 20 and 22 are configured to be located on the same plane. Also, the distance from the rotation center of the turntable 8 to the detection sensor 20 and the turntable 8
The distance from the rotation center to the detection sensor 22 is configured to be equal.

Next, the operation of the embodiment having such a structure will be described. First, in use, the radiation source 16 and the detection sensors 20 and 22 are installed so as to face the sample surface. Next, as shown in FIG. 3, the distance L1 from the detection sensor 20 to the radiation source 16 and the detection sensor Radiation source 16 from 22
The turntable 8 is rotated (the position of Ao) so that the distances L2 to the distance L2 are equal to each other.
The gain of a measuring device (not shown) is adjusted so that the detection results of 0 and 22 become substantially equal.

After completing the adjustment for initialization, the radiation source 16 is moved to an appropriate position (for example, the position of A) by rotating the turntable 8 and emitted from the radiation source 16 at the position A. γ-ray pulse detection sensors 20 and 22
Measure with Accordingly, the detection sensor 20 counts the number of γ-ray pulses that have passed through the sample from the radiation source 16 separated by the distance L1 shown in FIG.
The number of γ-ray pulses that have passed through the sample from the radiation source 16 that is farther away is counted.

Next, the turntable 8 is rotated again,
The radiation source 16 is moved to the position A 'where the distance from the detection sensor 20 to the radiation source 16 is L2 and the distance from the detection sensor 22 to the radiation source 16 is L1, and γ emitted from the radiation source 16 at the position A' The number of line pulses is detected by sensors 20 and 2
Count at 2. By this operation, a plurality of measurement results can be obtained for a plurality of distances.

Then, the measuring device calculates the density of the sample by arithmetically processing these measurement results. next,
The principle of measuring a sample will be described. First, when γ-rays pass through a substance, they are absorbed by the interaction of the photoelectric effect, backscattering, and electron pair generation, and the intensity of γ-rays decreases logarithmically with the passage distance. That is, when a radiation source emits gamma rays having a uniform energy and a constant energy at a direction Io from a radiation source and passes through a sample having a thickness of x, the intensity I after passing is represented by

[0019]

(Equation 1)

## EQU1 ## Where B is the built-up count, μ
Is the γ-ray absorption coefficient. Further, the γ-ray absorption coefficient μ for the sample is given as a function of the density ρ of the sample, and according to the experiments of the present inventor, there is no significant difference in the composition between the γ-ray absorption coefficient μ and the density ρ. For example, it was confirmed that the following equation (2) was satisfied.

[0021]

(Equation 2)

Here, P and Q are constants. Therefore, the third
Assuming that the intensity of the γ-ray pulse emitted from the radiation source 16 set at the position A in the drawing is Io, the intensity I1 of the γ-ray obtained by the detection sensor 20 at a position separated by the distance L1 is given by considering the scattering cross section and the like. ,

[0023]

(Equation 3)

Similarly, the intensity I2 of the γ-ray obtained by the detection sensor 22 at a position separated by the distance L2 is

[0025]

(Equation 4)

## EQU1 ## B1 in the above equations (3) and (4)
B2 is a built-up coefficient including a coefficient efficiency due to the intensity of the radiation source, a detection efficiency specific to the detection sensor, a gap between the detection sensor and the sample surface, and the like. Further, when the natural logarithm of the ratio of the results of the above equations (3) and (4) is obtained,

[0027]

(Equation 5)

The first term on the right side of the above equation (5) is a constant unique to the detection sensor. In the actual density measurement, the intensity I of the γ-ray detected by each of the detection sensors 20 and 22
Since 1,12 are the count values N1, N2 of the γ-ray pulses received per unit time,

[0029]

(Equation 6)

The following relationship is established. Therefore, while substituting equation (5) into equation (6), the radiation source 16
When L1 is replaced with an equivalent average distance K1 · L1 and L2 is replaced with an equivalent average distance K2 · L2 in consideration of that the γ-rays generated from are diffused radially, the following equation (7) is obtained.

[0031]

(Equation 7)

As described above, the pulse numbers N1 and N2 of γ-rays for different distances L1 and L2 are detected, and the above equation (7) is obtained.
Is calculated to calculate the density of the sample. Thus, according to this embodiment, when the rotating body rotates,
Since the relative distance between the radiation source and the detection sensor can be changed while the distance between the radiation source and the detection sensor with respect to the sample surface is always kept constant, high-precision density measurement using the above relational expression can be realized. it can. Further, in order to perform measurement at a plurality of relative distances, it is not necessary to change the direction of the density measurement device itself, and the measurement can be performed at the once installed position, so that there is no error in the measurement value due to the surface shape of the sample. And accuracy can be improved.

Further, there is an effect that a change in the detection efficiency of the detection sensor can be canceled. The detection efficiency of a detection sensor is generally sensitive to external changes such as temperature, and the sensitivity is usually different for each detection sensor. In addition, there is a high possibility that an irreversible change in detection efficiency will occur even with aging. Assume that the rate of change in the counting efficiency of the detection sensor 20 is E1, and the rate of the counting efficiency of the detection sensor 22 is E2. Then, the count values N11 'and N21' of the detection sensor 20 and the detection sensor 22 when the radiation source 16 moves to the position A are set as the count values N11 'and N21', respectively.
And N22 'and N22', respectively, when moving to

[0034]

(Equation 8)

[0035]

(Equation 9)

Can be represented by Applying these equations to equation (7) above gives

[0037]

(Equation 10)

Thus, the effects of E1 and E2 can be canceled. Therefore, the measurement can be stably performed without being affected by the change in the detection efficiency of the detection sensor. Next, another embodiment will be described with reference to FIG. This is because a rotatable turntable 30 is mounted on the housing 28 of the device.
And a detection sensor 32 are provided in parallel with each other, and a radiation source (not shown) is provided at a position eccentric from the rotation center of the turntable 30. The turntable 30 and the detection sensor 32 are provided so as to face the sample on the same plane as shown in FIG.

Then, the turntable 30 is rotated so that the distance between the radiation source and the detection sensor 32 becomes an appropriate distance L1, and the number N1 of γ-ray pulses from the radiation source is counted. The turntable 30 is rotated so that the number N2 of γ-ray pulses from the radiation source is counted,
By applying the count values N1 and N2 to the above equation (7), the density of the sample is calculated.

According to this embodiment, since the configuration is simple, it is possible to reduce the size and weight. Next, still another embodiment will be described with reference to FIG. This is the case 34 of the device,
While providing one rotatable turntable 36,
A pair of detection sensors 38 and 40 are provided in parallel at a target position equidistant from the rotation center of the turntable 36, and a radiation source (not shown) is provided at a position eccentric from the rotation center of the turntable 36. I have. The turntable 36 and the detection sensors 38 and 40 are provided so as to face the sample on the same plane, as shown in FIG.

The distance L1 from the radiation source to the detection sensor 38 and the distance L from the radiation source to the detection sensor 40
By rotating the turntable 36 so that 2 differs, the number N1 of γ-ray pulses from the radiation source is counted by the detection sensor 38, and at the same time, the number N2 of γ-ray pulses from the radiation source is counted by the detection sensor 40. The density of the sample is calculated by applying the count values N1 and N2 to the equation (7).

According to this embodiment, the pair of detection sensors 3
Since the measurement can be performed simultaneously at 8, 40, the measurement result can be obtained quickly. Next, still another embodiment will be described with reference to FIG. That is, one rotatable turntable 44 is provided in the housing 42 of the apparatus, and three detection sensors 46 and 4 are separated from the turntable 44.
8 and 50 are provided in parallel with each other,
A radiation source (not shown) is provided at a position eccentric from the center of rotation of.

The turntable 44 and the detection sensor 4
As shown in FIG. 2, 6, 48 and 50 are provided so as to face the sample on the same plane. Then, the turntable 44 is rotated so that the distances L1, L2, and L3 from the radiation source to the respective detection sensors 46, 48, and 50 are different, and γ-ray pulses from the radiation source are detected by the respective detection sensors 46, 48, and 50. Count values N1, N counted at 50
By applying two combinations of 2, 2 and N3 to the above equation (7), a maximum of three calculation results are calculated. Then, the average value of these calculation results is calculated as the density of the sample.

According to this embodiment, a plurality of count values are obtained simultaneously by a plurality of detection sensors, and an average value thereof is calculated, whereby more reliable measurement can be performed quickly. Next, still another embodiment will be described with reference to FIG. In FIG. 7, the same or corresponding parts as those in FIG. 1 are indicated by the same reference numerals.

The platform is configured so that the storage section 52 storing the radiation source 16 facing the sample surface can be moved linearly in parallel to the detection sensors 20 and 22 and in the direction of arrow Z in the figure. 6a. First, by linearly moving the storage section 52, the same positional relationship as that shown in FIG. 3, that is, the distance between the radiation source 16 and the detection sensor 20 is L1, and the distance between the radiation source 16 and the detection sensor 22 is L1. L2, each detection sensor 20,
At 22, the count value of the γ-ray pulse is measured.
6 is set to L2, and the interval between the radiation source 16 and the detection sensor 22 is set to L1, and each of the detection sensors 2 is set to L2.
The density of the sample is calculated by measuring the count value of the γ-ray pulse at 0 and 22 and applying each measurement result to the above equation (7).

According to this embodiment, the detection sensors 20 and 2
Since the positional relationship of the radiation source 16 with respect to 2 can be changed with high accuracy, accurate density measurement can be performed. FIG. 7 shows a typical example of a configuration in which the radiation source is moved linearly with respect to the detection sensors. As shown in FIGS. 4 to 6, one or more detection sensors are provided, and these detections are performed. The radiation source may be moved linearly with respect to the sensor.

Next, still another embodiment will be described with reference to FIG. In FIG. 8, the same or corresponding parts as those in FIG. 1 are indicated by the same reference numerals. This is the radiation source 5 facing the sample surface.
And a radiation source 58 (radiation source 5).
4 is fixed to the platform 6a and installed.
0, that is, the end at which the γ-ray pulse is emitted, is covered with shutter members 62 and 64 made of lead, and the shutter members 62 and 64 are separately removed from the bottom ends of the storage portions 56 and 60. By doing so, a gamma-ray pulse can be separately transmitted toward the sample. A well-known link mechanism or the like can be used for attaching and detaching the shutter members 62 and 64.

When performing the measurement, first, by removing only the shutter member 62, γ
A line pulse is transmitted, the transmission from the other radiation source 58 is shielded by a shutter member 64, the count value is measured by each of the detection sensors 20 and 22, and then the sample is removed from the radiation source 58 by removing only the shutter member 64. Γ-ray pulse is transmitted to the shutter member 6
2 and the count value is measured by each of the detection sensors 20 and 22. Accordingly, the distance between the radiation sources with respect to the detection sensors 20 and 22 can be set to substantially the same relationship as shown in FIG. 3 without moving the radiation sources. ) Can realize accurate density measurement.

In the embodiment shown in FIG. 8, the radiation sources 54 and 58 are opened or shielded by separate shutter members 62 and 64, respectively. However, the present invention is not limited to such a configuration. As shown in FIG. 9, one shutter member 66 is rotatably supported at an intermediate position between the radiation sources 54 and 58, and by rotating the shutter member 66, one of the radiation sources 54 and 58 is shut off. You may make it. The point is that a configuration in which one of the pair of radiation sources can be shielded by a shutter made of lead or the like to change the radiation position of the radiation is included in this embodiment.

According to this embodiment, since the detection sensor and the radiation source are fixed in advance, the accuracy of density measurement can be improved. The present invention is not limited to the configuration of the embodiment described above, but has a structure in which one or more signal sources are provided so that the distance to the detection sensor can be changed. Alternatively, two or more signal pulses may be counted.

Also, by using an ultrasonic transmission sensor as a signal source and an ultrasonic reception sensor as a detection sensor, the above-described configuration enables the measurement by ultrasonic waves in the same manner.

[0052]

As described above, according to the present invention, the relative distance between the signal source and the detection sensor, that is, the geometrical positional relationship can be changed, and high-precision measurement can be realized. In addition, in order to perform measurement at a plurality of relative distances, it is not necessary to change the position of the measurement device itself, and the measurement can be performed at the once installed position, so that there is no error in the measurement value due to the surface shape of the sample. And accuracy can be improved.

By providing a plurality of detection sensors,
The measurement time can be shortened, and more accurate measurement results can be obtained by comprehensively judging the respective detection results. In addition, since the distance between the radiation source and the detection sensor with respect to the sample surface is always constant, and this can be realized with a simple structure, a small and high-precision density measuring device can be applied.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a partial cross section of a structure according to an embodiment of the present invention along a broken line.

FIG. 2 is a longitudinal sectional view of a main part of FIG.

FIG. 3 is an explanatory diagram showing a positional relationship between a signal source and a detection sensor.

FIG. 4 is a perspective view showing the structure of another embodiment.

FIG. 5 is a perspective view showing the structure of still another embodiment.

FIG. 6 is a perspective view showing a structure of still another embodiment.

FIG. 7 is a perspective view showing a structure of still another embodiment.

FIG. 8 is a perspective view showing the structure of still another embodiment.

FIG. 9 is an explanatory diagram showing a modification of the embodiment shown in FIG. 8;

FIG. 10 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 6a: Platform 6b: Side plate 6: Housing 8, 30, 36, 44: Turntable 10: Support shaft 12, 14: Bearing 16, 54, 58: Radiation source 18: Supporting part 20, 22, 32, 38: Detection sensor 40, 46, 48, 50: Detection sensor 62, 64, 66: Shutter member

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Tatsuo Oyama 2-16-46 Minami Kamata, Ota-ku, Tokyo Inside Tokimec Co., Ltd. (56) References JP-A-63-247623 (JP, A) 3-181840 (JP, A) JP-A-50-6364 (JP, A) Jpn. Meeting Summary Part 5 (issued September 1, 1991) 66-67 (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 9/00-9/36 G01F 23/28 JICST file (JOIS)

Claims (6)

(57) [Claims] A signal pulse is transmitted from a signal source into a sample,
A surface scattering type densitometer that measures the density of the sample by utilizing that the change of the signal pulse when detecting the signal pulse scattered inside the sample by the detection sensor is related to the physical property of the sample. In the above, the signal source and the detection sensor are arranged on the same surface on the sample, and a mechanism for changing a relative distance between the signal source and the detection sensor is provided in a housing of the surface scattering type densitometer; From the measurement results of the detection values of the plurality of signal pulses when the relative distance between the source and the detection sensor is changed, the relative distance
Due to the signal pulse spreading radially around
A surface scattering type density meter, wherein the density of the sample is measured after being corrected by an equivalent average distance. 2. A surface scattering densitometer of claim 1, wherein the mechanism is rotatable about an axis perpendicular to the sample surface of the sample, provided at a predetermined distance from the signal source The signal source is provided at an eccentric position of the rotator and opposed to the sample, and the relative distance between the signal source and the detection sensor is changed by rotating the rotator. surface that by the measurement result of the detection values of the plurality of signal pulses, characterized in that for measuring the density of the sample
Scattering densitometer . 3. The surface scattering densitometer according to claim 1, wherein the mechanism linearly moves the signal source in an appropriate direction at a position distant from the detection sensor while facing the sample surface of the sample. It has, by linearly moving the signal source, characterized by measuring the density of the sample from the measurement result of the detection values of the plurality of signal pulses by changing the relative spacing of the signal source and the sensor Surface scattering density meter . 4. A surface scattering type densitometer according to claim 1, wherein the relationship between said detection sensor and said signal source is determined by said detection sensor.
Are provided at predetermined intervals from each of the detection sensors.
Realized by placing two signal sources facing the sample surface
And, shielding and releasing the transmission of signal pulses from the signal source to the sample
Signal source and detection by providing a shutter
A mechanism that changes the relative distance to the sensor is realized, and signal pulses are sequentially transmitted to the sample by one of the signal sources by opening the shutter, and the measurement result of the detected value of the signal pulse from each signal source A surface scattering type densitometer characterized in that a sample density is measured from the sample. 5. The method of claim 1 or any one of surface scattering densitometer according to claim 4, before dangerous exits provided a plurality of sensors, from a change of the signal pulse number measured by the sensor of each of the samples Table for measuring density
Surface scattering density meter . 6. The method of claim 1 or any one of surface scattering densitometer of claim 3, provided a plurality of pre-SL signal source, the density of the sample from the change in the detected number of pulses measured by the sensor Surface scattering type dense to measure
Degree meter .