JP2544431B2 - Method and device for measuring the density of objects - Google Patents

Description

The present invention relates to a method and apparatus for non-destructively measuring the density and density distribution in an object using radiation, and in particular, there is a density difference in the thickness direction. The present invention relates to a density and density distribution measuring method suitable for measuring the density inside a plate-like object.

[Conventional technology]

To measure the density distribution in a plate-like object in which there is a density difference only in the thickness direction, IEE, Transaction on New Clear Science, NS-30, 2 (1983) p. 1680 To page 1684 (IEEE, Tran
s.Nucl.Sci., NS-30, No.2 (1983) pp 1680-1684), the application of a method for detecting defects in concrete structures using scattered gamma rays is considered. To be

[Problems to be Solved by the Invention]

However, the above-mentioned conventional technique does not consider the point of quantitatively evaluating the density in the object, which is simply detecting the presence or absence of a defect, and the inside of a plate-like object having a density difference only in the thickness direction. When the above-mentioned conventional technique is applied to the method of quantitatively measuring the density distribution of, the data processing becomes complicated, and the measurement error of the density becomes larger at a deeper position.

Incidentally, as a density distribution measuring device using scattered radiation, there is one described in JP-A-56-74644.

In view of the above problems, an object of the present invention is to provide a method and a device for easily and accurately measuring the density and the density distribution in a plate-shaped object having a density difference only in the thickness direction.

[Means for solving the problem]

The above-mentioned purpose is to detect the detection angle when the primary γ-rays incident on the object collimated from the γ-ray source and emitted to the object are detected by the collimated radiation detector, which is the primary γ-ray scattered in the object. This is accomplished by measuring in a system such that the ratio of the object's linear absorption coefficient to γ-rays and the scattered γ-ray's object linear absorption coefficient equals the ratio of the cosine of the incident angle to the cosine of the detected angle.

That is, the present invention irradiates a plate-shaped object to be measured with γ-rays (primary γ-rays) collimated from a γ-ray source, and provides the object to be measured on the side opposite to the side where the γ-ray source is located. With at least one radiation detector, the scattered γ-rays that are Compton scattered in the measurement region of the measured object and the primary γ-rays that have been transmitted through the measured object are detected to measure the density inside the object. , The effective absorption coefficient of γ-rays, which is defined by the ratio of the linear absorption coefficient of γ-rays to the cosine of the angle formed by the γ-ray transmission path with the thickness direction of the plate-shaped object to be measured,
The above object is achieved by defining the irradiation direction of γ-rays and the detection direction of scattered γ-rays so that the rays and the scattered γ-rays are equal.

In addition, the direction of incidence of primary γ-rays on the object and the direction of detection of scattered γ-rays are made constant, and the γ-ray source and the radiation detector are moved up and down at a fixed interval to form a plate shape. It is possible to measure the density distribution in the thickness direction of the object.

Another method for measuring the density distribution in the thickness direction of a plate-like object is to detect the incident direction of primary γ-rays to the object and scattered γ-rays according to the position change of the measurement area in the thickness direction of the plate-like object. There is a method of changing the direction and the direction.

Further, the temperature distribution of a plate-like object having a metal in a molten state inside can also be obtained by using the density measuring method.

In addition, the above-mentioned object can be achieved by the density measuring device having the following configuration.

That is, the device of the present invention is a γ-ray source with a collimator arranged on one surface side of the plate-shaped object to be measured, and arranged on the other surface side of the object to be measured, and γ in the measurement area of the object to be measured. Object density measuring device provided with scattered γ-rays generated by γ-rays (primary γ-rays) emitted from a radiation source and at least one radiation detector with a collimator for detecting primary γ-rays transmitted through an object to be measured Therefore, the direction in which γ-rays (primary γ-rays) are incident on the γ-ray source or the object to be measured and the direction in which scattered γ-rays generated in the measurement area of the radiation detector are detected are defined by the absorption coefficient of γ-rays. And the effective absorption coefficient of γ-ray defined by the ratio of the angle of the γ-ray transmission path to the thickness direction of the plate-shaped object to be measured, and the scattering obtained by Compton scattering with the primary γ-ray irradiating the object to be measured. Set to be the same for γ-rays,
Attenuation of the primary γ-ray in the object, which is obtained from the intensity of scattered γ-ray detected by the radiation detector and the intensity of transmitted primary γ-ray detected by the radiation detector (attenuation of the primary γ-ray to the measurement area of the object And a device for calculating the density of the object based on the attenuation of the scattered γ-rays from the measurement region of the object (attenuation of the primary γ-rays within the object), and a device for outputting the calculated density. .

As the γ-ray detecting means, a scattered γ-ray and a transmitted primary γ-ray are detected by the same radiation detector with a collimator, and a wave height analyzer for distinguishing the scattered γ-ray and the transmitted primary γ-ray is provided. Conceivable. Further, scattered γ-rays and transmitted primary γ-rays may be detected by separate radiation detectors with a collimator.

Further, it is effective to configure the collimator of the γ-ray source and the collimator of the radiation detector as follows. That is, the collimator of the γ-ray source is configured so as to have a portion in which the primary γ-rays are radiated in a cone shape and a portion in which the primary γ-rays are radiated through the central portion of the cone to detect radiation. The collimator of the instrument transmits the object from the cone center of the γ-ray source collimator and the part that detects the scattered γ-ray generated in the measurement area by the cone-shaped primary γ-ray from the γ-ray source. It is configured to have a portion for detecting the above-mentioned primary γ ray. In this case, the scattered γ-rays and the transmitted primary γ-rays are detected by the same radiation detector, and the scattered γ-rays are detected.
A wave height analyzer for discriminating between the transmitted primary γ-ray and the primary ray, and means for determining the attenuation of the primary γ-ray radiated in a cone shape and transmitted through the object based on the detected value of the transmitted primary γ-ray are provided.

Further, the collimator of the above-mentioned γ-ray source may be provided with a shield at the portion where the primary γ-rays pass through the central portion of the cone shape.

Further, instead of detecting the scattered γ-rays and the transmitted primary γ-rays with the same radiation detector, a circular radiation detector for detecting the scattered γ-rays collimated in a cone shape, and the circular radiation detector You may make it detect separately with the cylindrical radiation detector which detects the transmitted primary γ ray provided inside the radiation detector through the shield.

In order to obtain the density distribution, it is effective to provide a device that holds the γ-ray source and the radiation detector at a constant interval and moves the γ-ray source and the radiation detector in the thickness direction of the object. is there.

[Action]

 The principle of the present invention will be described below with reference to FIG.

The sample (object) 10 is a plate having a density difference only in the thickness direction (x). The primary γ-rays 22 of energy E ₀ emitted from the γ-ray source 20 enter the sample 10 at an incident angle 23 (θ ₀ ). The radiation detector 30a shows that the primary γ ray 22 is scattered γ of energy E ₁ scattered at the Compton scattering angle 34 () in the measurement region 11 at the depth x.
The line 32 is detected at the detection angle 33 (θ ₁ ). At this time, the intensity I of the scattered γ-ray 32 of the energy E ₁ detected by the radiation detector 30a
₁ (E ₁ , x) can be expressed by the following equation.

_{Here, I 0 (E 0, x} ): Primary energy E ₀ in the measurement region 11 gamma
Line intensity μ (E, x): Line absorption coefficient of the sample 10 at the depth x with respect to the γ-ray of the energy E f (E ₀ ,, x): The primary γ-ray of the energy E ₀ is the measurement region 11
Collide with one electron inside and undergo Compton scattering at the scattering angle,
Probability of being emitted within a solid angle that looks into the radiation detector 30a ρ _e (x): electron density in the measurement region 11 L: thickness of the sample 10 Here, over the entire region of the sample 10, When is established (note that Is defined as the effective line absorption coefficient), and the equation (1) is as follows.

In equation (3), Is the attenuation of the primary γ-ray in the sample 10,
It can be obtained by detecting the primary γ-rays 22 of energy E ₀ with another radiation detector 30b shown in FIG. Therefore, equation (3) can be summarized as follows.

here, In the equation (4), I ₀ (E ₀ , x) and f (E ₀ ,, x) do not depend on the type of the sample 10, and can be evaluated by calculation if the measurement system is determined. The electron density ρ _e (x) is closely related to the density distribution ρ (x) of the sample 10, and, for example, when the sample 10 is made of the same substance and has different densities in the thickness direction. Can be obtained by multiplying ρ _e (x) by a coefficient according to the atomic number. That is, the density distribution of the sample 10 in the thickness direction can be obtained from the equation (4).

Also, since J ₁ (E ₀ ) in the equation (4) does not depend on the depth x, the measurement error of the density is simply the measurement value I _{1 of the} radiation detector 30a.
It does not depend on the statistical error of (E ₁ , x) but directly on the depth x.

Next, the condition expressed by the equation (2) will be described. The linear absorption coefficient can be approximately expressed by the following equation for γ-rays having a certain energy or more.

μ (E, x) ≈σ _T (E) ρ _e (x) (5) where σ _T (E) is the Compton scattering cross-section per unit electron density for γ-rays of energy E, It does not depend on the type. Therefore, using the relation of the equation (5), the equation (2) can be rewritten as follows.

Also, from Compton scattering law and geometrical conditions, θ ₀ = + θ ₁ (8) holds. Where m ₀ is the rest mass of the electron.
Since the expression (6) does not depend on the depth x, θ ₀ and θ ₁ that satisfy the expression (6) can be easily obtained from the expressions (7) and (8). FIG. 2 shows, as an example, the relationship between θ ₀ and the case where the 1.33 MeV γ-rays emitted by ⁶⁰ C ₀ are primary γ-rays (that is, θ ₁ ).

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to FIG.

Reference numerals 20 and 21 denote a γ-ray source (for example, ⁶⁰ C ₀ ) and its collimator (for example, lead), and energy E ₀ emitted from the γ-ray source 20.
The incident angle 23 of the primary γ-rays 22 on the sample 10 (a plate having a density difference only in the thickness direction, and the thickness is L)
It is installed so as to be incident at (θ ₀ ). Reference numerals 30a and 31a are a radiation detector (for example, a NaI (Tl) scintillator and a photomultiplier tube (not shown)) and its collimator, and the primary γ-ray 22 has a specific depth in the sample 10 to be measured. It is installed so that only the scattered γ-rays 32 of energy E ₁ that are Compton scattered at the scattering angle 34 () in the measurement region 11 of x can be detected. 33 is the detection angle θ ₁ of scattered γ rays 32
Is. At this time, the incident angle 23 (θ ₀ ) of the primary γ-ray 22 and the detection angle 33 (θ ₁ ) of the scattered γ-ray are set so as to satisfy the relationship of the expression (6). Further, 30b and 31b are radiation detectors and collimators similar to 30a and 31b, and are installed so that only primary γ-rays of energy E ₀ emitted from the γ-ray source 20 and transmitted through the sample 10 can be detected. .

The output of the scattered γ-ray radiation detector 30a is the scattered γ of energy E ₁ set in advance by the scattered γ-ray counter 40a.
The lines are counted and stored in the storage device 50 as the intensity at the position x of the measurement region 11 (I ₁ (E ₁ , x) shown in the equation (4)). On the other hand, the output of the primary γ-ray radiation detector is the time when the scattered γ-rays are measured by the radiation detector 30a in the primary γ-ray counter 40b, the primary γ-rays of energy E ₀ are counted, and the equation (4) is used. As the value of J ₁ (E ₀ ) shown in
Sent to In the density calculation device 60, the scattered γ-ray intensity I ₁ (E ₁ , x) stored in the storage device 50 and the transmission intensity J of the primary γ-ray are stored.
_The density is calculated from the value of ₁ (E ₀ ) based on the equation (4). I ₀ (E ₀ , x) and f (E ₀ ,, x) in the equation (4) are evaluated in advance and incorporated in the density calculation device 60. 70 is an output device for outputting the result of the density calculation device 60, for example,
CRT or printer.

The sample 10 was assumed to have a density distribution only in the thickness direction, but in the present example, it is sufficient if this assumption holds in the transmission region of the primary γ-rays and scattered γ-rays in the sample 10, and a relatively narrow plane. It is possible to measure the density at any one point in the region in the thickness direction.

Next, another embodiment of the present invention will be described below with reference to FIG.

Reference numeral 25 denotes a collimator of the γ-ray source 20, which is made to radiate the primary γ-ray 22 of energy E _{0 to} the sample 10 in a cone shape. Reference numeral 35 is a collimator for measuring scattered γ rays 32 in which the primary γ rays are Compton scattered in the annular measurement region 11 of the sample 10. The collimator opening is a collimator.
Like the 25, it is cone-shaped. In addition, collimator 25,35
Is the primary γ emitted from the γ-ray source 20 and passing through the sample 10.
It has an opening through which the line 22 can be measured. Reference numeral 30 is a radiation detector, and 41 is a wave height analyzer, which distinguishes the primary γ-rays 22 of energy E ₀ and the scattered γ-rays 32 of energy E from each other, and the primary γ-ray counters 43 and 42 and the scattered γ-ray counters respectively. Send a signal to. Other reference numerals are the same as those in FIG. Also in this case, similarly to the embodiment shown in FIG. 1, the incident angle 23 (θ ₀ ) of the primary γ rays 22 and the detection angle 33 (θ ₁ ) of the scattered γ rays 32, that is, the Compton scattering angle () are It is installed so as to satisfy the relationship of equation (6).

The method of obtaining the density from the radiation measurement value is the same as that of the embodiment shown in FIG. 1, but the evaluation method of J ₁ (E ₀ ) of the equation (4) showing the attenuation of the primary γ rays in the sample 10 is shown. Is different. (4)
The relational expression of J ₁ (E ₀ ) in the equation is Therefore, the direct requirement in this embodiment is Is. Therefore, As a result, J ₁ (E ₀ ) is obtained.

In this embodiment, the measurement region 11 has an annular shape, and the intensity of scattered γ-rays incident on the radiation detector becomes large, so that the measurement time can be shortened.

FIG. 4 shows another embodiment of the collimator on the γ-ray source side among the embodiments shown in FIG.

Reference numeral 100 is a shield provided in the opening for measuring the attenuation of the primary γ ray in the sample 10 shown in FIG. In this embodiment, the intensity of the primary γ-rays incident on the radiation detector 30 shown in FIG.
The measurement error of the scattered γ-ray intensity at 1 is reduced, and the density measurement accuracy is improved. The effect of this embodiment is the same even when the shield 100 is attached to the collimator on the radiation detector side.

FIG. 5 shows another embodiment of the detector in the embodiment shown in FIG.

30b 'is a cylindrical radiation detector for detecting the primary γ-rays 22 shown in FIG. 3, 30a' is an annular radiation detector for similarly detecting scattered γ-rays 32, and 30c is a primary γ-ray 22 for radiation detection. Bowl 3
0a 'is a shield for preventing scattered γ rays 32 from being detected by the radiation detector 30b', and has a ring shape. The radiation detectors 30a 'and 30b' can be made of, for example, NaI (Tl) scintillator.

The data processing of the outputs of the radiation detectors 30a 'and 30b' is the same as in FIG.

In the present embodiment, since the primary γ-rays and the scattered γ-rays are detected by different radiation detectors, there is no interaction between the primary γ-rays and the scattered γ-rays in the detector. Therefore, both can be measured with a high count rate and high accuracy, the density measurement accuracy can be improved, and the measurement time can be shortened.

 FIG. 6 is a diagram showing another embodiment of the present invention.

Reference numeral 200 designates an external radiation source section composed of a γ-ray source and a collimator, which is composed of 20 and 21 in the embodiment of FIG. 1 and 20 and 25 in the embodiment of FIG. Reference numeral 300 denotes a radiation detecting section including a radiation detector and a collimator, which is composed of 30a, 31a, 30b and 31b in the embodiment of FIG. 1 and 30 and 35 in the embodiment of FIG. 210 is the external radiation source unit 200
And 220, a support, which integrally supports the radiation detection unit 300 and the radiation detection unit 300, and 230 is an electric motor. 240 is a distance detector, 25
0 is a depth calculator. Other reference numerals are the same as those in FIGS. 1 and 3.

The operation of this embodiment will be described below. Measurement area in sample 10
The position x of 11 changes as the external radiation source unit 200 and the radiation detection unit 300 become integrated with each other via the electric motor 230 and the support 220 and move up and down with respect to the sample 10. At this time, the measurement area 11
The position x can be determined by the depth calculator 250 by receiving the signal of the distance y measured by the distance detector 240. That is, x = a−y, where a is the distance between the external line deep portion 200 and the measurement region 11, and is a quantity uniquely determined by the geometrical arrangement. The output of the depth calculator 250 is input to the storage device shown in FIG. At this time, in the storage device 50, as the intensity of the depth x,
Memorize the intensity of scattered γ rays.

The calculation of the density with respect to the depth x is the same as that of the embodiment shown in FIG.

According to this example, the density at an arbitrary depth in the sample, that is, the density distribution can be measured. Further, it can be applied to a plate-shaped sample whose thickness is unknown.

FIG. 7 is a diagram showing an embodiment of the present invention when another radiation detector is used.

Reference numeral 310 is a radiation detector having a very high energy resolution, the effect of scattered γ-rays in the detector is negligible, and the shape is small. Other reference numerals are the same as those in FIGS. 1 and 3. Also in this example, the method of calculating the density from the intensity measurement values of the primary γ-rays and the scattered γ-rays is the same as that shown in FIGS. 1 and 3. Therefore, the method for measuring the intensity of primary γ-rays and scattered γ-rays will be described below.

The output of the radiation detector 310 has a high energy resolution and the influence of scattered γ-rays within the detector is very small, so that it becomes as shown in FIG. E ₀ is the energy of the primary γ-ray 22, E ₁ is the energy of the Compton scattering angle 34
It is the energy of scattered γ rays 32 after being scattered by (). Here, since the primary γ-rays 22 are radiated in the cone shape by the cone-shaped collimator 25 on the γ-ray source side, if the measurement system is determined, the energy E ₁ is uniquely the measurement area.
Corresponds to a depth x of 11. Therefore, (6),
Compton scattering angle 34 () that satisfies Eqs. (7) and (8)
If you measure only the energy E ₁ corresponding to
The intensity of scattered γ-rays corresponds to the depth x. On the other hand, the primary γ
The intensity of the line is the primary γ if the energy E ₀ is measured.
It becomes the strength of the line.

In this embodiment, since the collimator on the side of the radiation detector is unnecessary, the radiation detector can be brought close to the sample, so that the counting rate of scattered γ rays can be increased. Therefore, the measurement time can be shortened.

The above-mentioned density and density distribution measuring method is effective as a temperature distribution measuring method.

When a molten metal is present inside the plate-shaped object, the density is low when the metal is in the molten state and high when the metal is in a solid state. That is, the density is proportional to the temperature. Therefore, the temperature in the plate-like object can be measured by using the above-mentioned density measuring method.

〔The invention's effect〕

According to the invention, the scattering γ scattered at a position in the object
Since the measured value of the line strength uniquely corresponds to the density at that position, it is possible to measure the density and the density distribution in the plate-shaped object having a density difference only in the thickness direction with simple data processing and with high accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing an example of the relationship between the Compton scattering angle and the incident angle of primary γ rays in the present invention, and FIG. 3 is The figure which shows another Example of this invention, 4th
FIG. 5 is a diagram showing another embodiment of the gamma ray source collimator of the embodiment shown in FIG. 3, and FIG. 5 is a diagram showing another embodiment of the radiation detector of the embodiment shown in FIG. FIG. 6 is a diagram showing another embodiment of the present invention in which the depth of the measurement region can be arbitrarily changed, FIG. 7 is a diagram showing another embodiment of the radiation detector, and FIG. 8 is shown in FIG. It is a figure which shows the example of a detection of the (gamma) ray by the radiation detector shown. 10 …… Sample, 11 …… Measurement area, 20 …… γ-ray source, 21,25…
… Collimator, 22 …… Primary γ-ray, 23 …… Primary γ-ray incident angle, 30,30a, 30b …… Radiation detector, 31a, 31b, 35 …… Collimator, 33 …… Scattered γ-ray detection angle, 34 …… Compton scattering angle, 40a, 42 …… Scattering γ-ray counter, 40b, 43 …… Primary γ
Line counting device, 50 ... Storage device, 60 ... Density calculation device, 70
...... Display device, 240 …… Distance detector, 250 …… Depth calculator, 230 …… Electric motor.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shigeru Izumi 1168 Moriyama-cho, Hitachi-shi, Ibaraki Energy Research Laboratory, Hitachi, Ltd. (72) Inventor Takashi Yaagi 3-1-1, Saicho-cho, Hitachi, Ibaraki Stock Hitachi, Ltd. Hitachi factory

Claims (7)

(57) [Claims] 1. A γ-ray source which irradiates a plate-shaped object to be measured with primary γ-rays collimated from a γ-ray source, the objects being made of the same substance and having different densities only in the thickness direction. By at least one radiation detector provided on the side opposite to the side where is located, scattered γ-rays that are Compton scattered in the measurement region of the measured object and the primary γ transmitted by the measured object.
There is a method of measuring the density of the above-mentioned measurement region inside the object by detecting a line, and the linear absorption coefficient of γ-rays, and the cosine of the angle that the γ-ray transmission path makes with the thickness direction of the plate-shaped object to be measured. Γ defined as the ratio with
The irradiation direction of the γ-ray and the scattering γ so that the effective absorption coefficient of the ray becomes equal between the primary γ-ray and the scattered γ-ray.
A method for measuring the density of an object, comprising setting a detection direction of rays and measuring the scattered γ-rays and the primary γ-rays. 2. A plate-shaped object composed of the same substance and having different densities only in the thickness direction is irradiated with primary γ-rays collimated from the γ-ray source, and a side on which the γ-ray source is located with respect to the object. Is a method of measuring the density inside the object by detecting the scattered γ-rays that have been Compton scattered in the measurement region of the object and the primary γ-rays that have passed through the object, with the radiation detector provided on the opposite side. hand, A density measuring method for an object, in which the electron density is obtained based on the following equation and the electron density is multiplied by a coefficient according to the substance constituting the substance to measure the density of the substance in a measurement region. 3. The method according to claim 2, And when Instead of A method for measuring the density so as to satisfy the condition. 4. A primary radiation collimated from a radiation source is applied to a plate-shaped object made of the same substance and having a different density only in the thickness direction, and the scattered radiation generated by the primary radiation is collimated and detected. In the method for measuring the density in an object, the scattered radiation is detected on the side opposite to the side where the radiation source is located with respect to the object, and the linear absorption coefficient of radiation and the radiation transmission path are The effective line absorption coefficient of the radiation defined by the ratio of the cosine to the thickness direction of the plate-shaped object, the irradiation direction of the radiation and the scattered radiation so that the primary radiation and the scattered radiation are equal. Is set, the attenuation of the primary radiation in the object obtained from the intensity of the primary radiation transmitted through the object is reduced to the measurement area of the object of the primary radiation. And density measurement method of an object and obtaining a density of the measurement region of the object therefore be regarded as an attenuation from the object measuring region of the scattered radiation. 5. A γ-ray source with a collimator, which is made of the same substance and has a different density only in the thickness direction and is arranged on one surface side of an object to be measured, and on the other surface side of the object to be measured. The primary γ irradiated from the γ-ray source in the measurement area of the measured object.
A density measuring device for an object, comprising: scattered γ-rays generated by X-rays, and at least one radiation detector with a collimator for detecting primary γ-rays transmitted through the object to be measured. Direction of incidence of γ rays on the object and scattering γ generated in the measurement area of the radiation detector
The effective absorption of γ-rays is defined by the ratio of the γ-ray absorption coefficient and the cosine of the angle formed by the γ-ray transmission bus with the thickness direction of the plate-shaped object to be measured. The incident angle of the γ-ray source-side collimator and the detection angle of the detector-side collimator are set so that the coefficient becomes equal between the primary γ-rays irradiating the object to be measured and the scattered γ-rays that are Compton scattered, and the radiation detector Intensity of scattered γ-rays detected by, the attenuation of the incident γ-rays from the primary γ-rays obtained by the transmitted primary γ-ray intensity detected by the radiation detector to the measurement region of the object and the scattered γ-rays Object density measuring apparatus provided with a device for calculating the density of the object based on the attenuation in the object of the primary γ ray grasped as the attenuation from the measurement region of the object to the emission part, and a device for outputting the calculated density . 6. A γ-ray source with a collimator, which is made of the same substance and has a different density only in the thickness direction, arranged on one surface side of a plate-shaped object to be measured, and on the other surface side of the object to be measured. The primary γ irradiated from the γ-ray source in the measurement area of the measured object.
A density measuring device for an object, comprising: scattered γ-rays generated by X-rays, and at least one radiation detector with a collimator for detecting primary γ-rays transmitted through the object to be measured. The direction in which the primary γ-rays are incident on the object and the direction in which scattered γ-rays generated in the measurement region of the radiation detector are detected are defined as the total Compton scattering cross-section per unit electron density for the primary γ-rays and the primary γ-ray transmission. The ratio of the cosine of the angle that the path makes with the thickness direction of the object, the total Compton scattering cross-section per unit electron density for scattered γ-rays, and the cosine of the angle that the scattered γ-ray transmission path makes with the thickness direction of the object. The incident angle of the γ-ray side collimator and the detection angle of the detection base side collimator are set so that the ratio becomes equal, the intensity of the scattered γ-ray detected by the radiation detector and the transmission detected by the radiation detector. Primary γ Attenuation of the primary γ ray to the measurement area of the object and the scattering γ, which are obtained by the line intensity.
The first order γ as the attenuation of the line from the measurement area of the object
An apparatus for measuring a density of an object, comprising: a device for calculating the density of the object based on the attenuation of a line in the object; and a device for outputting the calculated density. 7. The wave height analysis according to claim 5, wherein the scattered γ-rays and the transmitted primary γ-rays are detected by the same radiation detector with a collimator, and the scattered γ-rays and the transmitted primary γ-rays are distinguished from each other. An object density measuring device equipped with a device.