JPH04369460A - Density measuring apparatus - Google Patents

Abstract

PURPOSE:To measure density distribution of an object to be inspected by means of calculation based on X-ray intensity by applying X-rays to the object which is baked to be a product such as soft ferrite or ceramic and measuring X-ray intensities before and after the rays transmit through the object. CONSTITUTION:In measuring density of an object A to be inspected wherein (n) components are mixed, a target 2 for generating fluorescent X-rays containing (m) kinds of Kalpha rays is provided. Every time the fluorescent X-rays are transmitted through the object A, an X-ray detector 3 is used to detect and count with respective energy of the (m) kinds of Kalpha rays, and the following m-order relational expression for X-ray absorption is solved for each measurement region: (In(N<0>m/Nm))/t=SIGMAmumn (rhoWn). A ratio in components of materials of the object A is obtained and whether or not the materials have been uniformly mixed is measured to obtain correct density.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a density measuring device.
In particular, by irradiating X-rays onto an inspected object such as soft ferrite or ceramics, which becomes a product by firing, the X-ray intensity before and after passing through the inspected object is measured in a desired minute area,
The present invention relates to an apparatus that obtains a density distribution of an object to be inspected by calculation using a relational expression of X-ray absorption during X-ray transmission based on the X-ray intensity.

0002

2. Description of the Related Art Materials such as soft ferrite or ceramics that are made into products by firing shrink in size by about 20% of the size before firing after firing. For this amount of shrinkage, the required accuracy of product dimensions is strict, within ±0.5%. However, for materials that are uniformly mixed, there is a correlation between the amount of shrinkage and the rate of change in density before and after firing, so in order to obtain highly accurate product dimensions, it is necessary to increase the density distribution of the molded body material before firing. It is necessary to measure accurately.

Conventionally, in a non-destructive method of measuring partial density, density ρ×
A method is used in which the density ρ is calculated by determining the thickness t and dividing it by a separately measured thickness t. In addition, as a method for measuring the weight component ratio of constituent substances, Japanese Patent Application Laid-Open No. 57-11624
As shown in Publication No. 0, m (m≧n−
1) A method is also used in which the weight component ratio is determined by irradiating gamma rays with different energies and measuring the transmitted intensities of m types of gamma rays.

0004

[Problem to be solved by the invention] By the way, monochromatic X-rays,
The principle formula for the attenuation of X-ray intensity when transmitting single-energy radiation such as γ-rays is
N=Noexp(-ρμt)
(1) However, N: Number of transmitted radiation detection (numbers) t: Thickness of the object to be inspected (cm) μ: Mass absorption coefficient of the object to be inspected for radiation (cm2
/g) No: Number of transmitted X-rays detected at t=0 (number) ρ: Density of the object to be inspected (g/cm3) When No., μ, and t are each known, N
The density ρ can be calculated by measuring ρ.

However, as in the past, single energy γ
In the method using radiation, if the mixture of the materials of the object to be inspected is not uniform, the mass absorption coefficient μ of the object to be inspected will differ from measurement point to measurement point, and the value of the X-ray detection coefficient N will change. There is a problem in that even though the density distribution has not changed, it is measured as if the density distribution has changed according to equation (1). Also, γ of multiple energies
In the method of determining the weight component ratio of a mixture of an object to be inspected using radiation, for example, indium-114 is used as a gamma ray source that requires three types of energy, while indium-114 is used as a gamma ray source that requires n types of energy. Radium-226 is used for this purpose, but since the energy of the emitted gamma rays is very high, several MeV, when the object to be inspected is soft ferrite or ceramics, the radiation is hardly attenuated or absorbed, and the radiation is not absorbed. No change in detection count can be obtained. That is, there has been a problem in that it is not easy to obtain a radiation source in the energy range from which density distribution or weight component ratio change rate can be measured. Furthermore, there are also problems in that a gamma ray source with sufficient gamma ray intensity is not easy to handle.

[0006] The present device has been developed based on the above circumstances, and provides a density measuring device that measures whether a mixture of materials such as soft ferrite and ceramics is homogeneous or not and determines the density distribution using a simple means. The purpose is to

[0007]

[Means for Solving the Problems] In order to achieve the above object, a density measuring device according to the present invention irradiates a target with X-rays emitted from an X-ray tube, emits fluorescent X-rays,
After collimating the emitted fluorescent X-rays, the fluorescent X-rays are detected by an X-ray detector capable of energy analysis by transmitting them through an object to be inspected, which is a mixture of n types of component materials at a predetermined weight component ratio Won. In the density measuring apparatus, a means for providing a target composed of m types of elements that generate m types of Kα rays, and a means for collimating the generated fluorescent X-rays containing the m types of Kα rays, Each time the X-ray passes through each measurement area, the energy is analyzed by the X-ray detector, and the energies of the m types of Kα rays are detected and counted, and the following m-order simultaneous equations are calculated for each measurement area.

[0008]

[Equation 1] Where, Wn: Weight component ratio (%) of the nth component in the measurement area of the object to be inspected No m: m types of Kα rays emitted from the target and detected in the absence of the object to be inspected Detection count Nm: Detection count of m types of Kα rays emitted from the target and detected after passing through the inspection object ρ: Density in the measurement area of the inspection object (g/cm3)
μmn: Mass absorption coefficient of the n-th component of the object to be inspected for m types of Kα rays (cm2/g) t: Thickness of the object to be inspected (cm), and the n-th component in each measurement region of the object to be inspected Find each ρWn and calculate the relative weight component ratio Wn of Wn in n same measurement areas based on W1 for each measurement point.
/W1 is determined, and the predetermined weight component ratio Wo of the object to be inspected is determined.
A means was provided to compare the relative weight component ratio Won/Wo1 determined in advance from n, and if they were equal, it was determined that the material to be inspected was uniformly mixed, and to calculate the density from the determined ρWn. It is something.

[0009]

[Operation] The density measuring device according to the present invention has the above-mentioned structure, and by means of providing a target composed of m types of elements, the generated m types of Kα rays are detected by X-ray detection after passing through the object to be inspected. It is possible to arbitrarily select an energy region in which the amount of change becomes significant when detected by the instrument.

[0010] The m types of Kα rays emitted from the target are collimated and transmitted through a desired minute range of the object to be inspected, which is composed of a mixture of n types of components at a predetermined weight component ratio, and then become X-rays. The energy of each of the m types of Kα rays is detected and counted by the detector. At this time, the type of mixture of the object to be inspected, the mass absorption number μmn of the nth component of the object to m types of Kα rays, and the m types of Kα emitted from the target when there is no object to be inspected.
Since the line detection count No m has been evaluated in advance and is known, it becomes possible to solve the m-th order simultaneous equations in (2) above, and calculate n types of ρW at each measurement point of the object to be inspected.
n is obtained. This operation is performed for the number of measurement points set in advance.

Next, the relative value of Wn of the n-th component with respect to component 1 in the same measurement area is determined. Here, the relative value of n types of ρWn in the same measurement area is based on ρW1, and the following formula is obtained, ρWn /ρW1 = Wn /W1

(3) is obtained, and as a result, the relative weight component ratio Wn/W1 of Wn of the n-th component is obtained.

On the other hand, the predetermined weight component ratio Won of the object to be inspected
The relative weight component ratio Won/Wo1 determined in advance from Won/Wo1 is the same in all measured measurement areas if the materials of the object to be inspected are uniformly mixed. That is, when the relative weight component ratio Wn/W1 obtained from the measurement and the relative weight component ratio Won/Wo1 constituting the object to be inspected are equal, the materials to be inspected are uniformly mixed. The value of ρWn obtained is ρWn = ρWon

(4), and since Won has been determined in advance, the density ρ can be calculated immediately.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing the arrangement of the main components of a density measuring device according to an embodiment of the present invention. In the figure, the inspected object A is a mixture of m-component materials at a predetermined weight component ratio, and has a density of ρ and a thickness of t. 1 and 10
is an X-ray generator and its collimator (e.g. lead),
It is installed so that an X-ray beam 20 generated from an X-ray generator 1 irradiates a target 2 . When the target 2 is irradiated with the X-ray beam 20 generated by the X-ray generator 1, the target 2 emits fluorescent X-rays 30. According to the present invention, the target is desirably composed of m types of elements so as to generate m types of Kα rays. For example, when m=3, W (tungsten), Pt (
It is preferable to use an alloy of (platinum) and Bi (bismuth). At this time, the Kα ray energy generated is 58.
They are 8keV, 66.3keV, and 76.5keV. Here, the Kα rays are referred to as WKα rays and PtKα rays. 11 and 12
is a collimator (for example, made of lead), and a filter 13 is provided in a desired measurement area 40 (for example, a cylindrical shape with a diameter of 1 mm and a length of t) of the object A to remove scattered X-rays.
Fluorescent X transmitted through (for example, 2 mm thick aluminum)
It is installed in advance so that the line 30 is irradiated. Reference numeral 15 denotes a test object stage on which the test object A is fixed and moves in the x and y directions in the figure to scan the measurement area 40 of the test object defined by the collimators 11 and 12 with the fluorescent X-rays 30. , and this test object stage 1
5 is moved by a drive mechanism 6, and this drive mechanism 6
The control is performed by the computer 7. 3 and 4 and 5
is an X-ray detector capable of energy analysis (for example, consisting of a Ge semiconductor detector and an amplifier (not shown)), an energy analyzer, and an X-ray counter; The X-ray detector 3 is installed so as to detect the fluorescent X-rays 30 that have passed through the desired microregion 40 of A. 8 is an output device for outputting the results, such as a CRT or a printing device.

The output of the X-ray detector 3 is calculated by the energy analyzer 4 and the X-ray counter 5 each time for the measurement area 40 determined by the movement of the inspection object stage 15.
The energy of each type of Kα ray is counted for a certain period of time, and this is transferred to the computer 7 as a detection count and transmitted X-ray detection count (Nm shown in equation (2)) of m types of Kα rays. This operation is performed in synchronization with the scanning of the inspection object stage 15 according to the number of measurements and the measurement position set in the computer 7 in advance. On the other hand, the mass absorption coefficient μmn for m types of Kα rays of a mixture of n types of the test object in equation (2)
, and the detection count No m of m types of Kα rays emitted from the target when the object to be inspected is not combined, are evaluated in advance and incorporated into the computer. Therefore, n types of ρWn in the inspection area can be obtained from equation (2). For example, if the object to be inspected is soft ferrite, Fe2O3
, Zn0, and Mn, with predetermined weight component ratios of 80%, 10%, and 10%, respectively, and an alloy target of W (tungsten), Pt (platinum), and Bi (bismuth). , for each measurement point, WKα ray detection count transmitted X-ray detection count N1, PtKα ray detection count transmitted X-ray detection count N2, BiKα ray detection count transmitted X-ray detection count N3 are measured, and equation (2) is as follows. becomes the formula, (l
n(No 1/N1))/t=
μ11(ρW1)+μ12(ρW2)+μ13(ρ
W3 )(ln(No 2/N2 ))/t =
μ21(ρW1)+μ22(ρW2)+μ23(ρ
W3)(ln(No3/N3))/t=
μ31(ρW1)+μ32(ρW2)+μ33(ρ
W3) Therefore, ρW1, ρW2 for each measurement point
, ρW3 are obtained as unknowns, and the computer 7 calculates ρW1 , ρW2 for each measurement point.
, ρW3 are calculated and stored. Next, in order to determine whether the materials of inspection object A are mixed uniformly,
The obtained ρW1, ρW2, and ρW3 are calculated from three types of relative weight component ratios, W1/W1, W2, based on the ρW1 of the component Fe2O3 in the measurement area, using equation (3).
/W1 and W3 /W1 are calculated.

On the other hand, the predetermined weight component ratio of the test object A is Fe.
80% each for the three components of 2O3, Zn0, and Mn,
Since the values 10% and 10% are determined in advance, the component F
The relative weight component ratios based on e2O3 are respectively 1.
The calculated values 000, 0.125, and 0.125 are stored in the computer 7. Therefore, in the measurement area 40 measured by this device, all W1 /W
1, W2 /W1 and W3 /W1 are each 1.00
0, 0.125, and 0.125, and if they are not equal, it is determined that the inspected object A is a defective material in which the materials are not evenly mixed, and this is displayed on the output device 8. If they are equal, it is determined that the materials to be inspected A are uniformly mixed, and the density ρ of the measurement area 40 is calculated using equation (4). The density distribution is measured by performing this series of operations according to the number of measurements and the measurement position set in advance in the computer 7, and the results are displayed on the output device 8.

[0016]

[Effects of the Invention] As explained above, according to the present invention, when measuring the density of materials such as soft ferrite or ceramics that are fired into products, it is possible to non-destructively check whether the materials are mixed uniformly or not. If the material is uniform, it is possible to provide a density measuring device that can measure the density distribution by measuring the partial density, which greatly contributes to the development and production of the material.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the arrangement of main components of a density measuring device that is an embodiment of the present invention.

[Explanation of symbols]

1 X-ray generator 2 Target 3 X-ray detector 4 Energy analyzer 5 X-ray counter 6 Drive mechanism 7 Computer 8 Output devices 10, 11, 12, collimator 13 Filter 15 Inspection object stage 20 Radiation from the X-ray generator X-rays emitted 30 Fluorescent X-rays 40 emitted from the target Measurement area A Object to be inspected

Claims (1)

[Claims] Claim 1: After irradiating a target with X-rays emitted from an X-ray generator to emit fluorescent X-rays and collimating the emitted fluorescent In a density measurement device that detects fluorescent X-rays with an X-ray detector that can transmit energy through an object mixed with Won and perform energy analysis, m types of elements that generate m types of Kα rays (m≧n) are used. The fluorescent X-rays containing the m types of Kα rays generated are collimated, and each time the fluorescent X-rays pass through each measurement area of the object to be inspected, the energy is analyzed by the X-ray detector.
The energy of each type of Kα ray is detected and counted, and for each measurement area, the m-th order simultaneous equation of the formula 1 is given.where Wn: weight component ratio of the n-th component in the measurement area of the object to be inspected (% ) No m: Detection count of m types of Kα rays emitted from the target and detected when there is no object to be inspected Nm: Detection count of m types of Kα rays emitted from the target and detected after passing through the object to be inspected Detection count ρ: Density in the measurement area of the object to be inspected (g/cm3)
μmn: Mass absorption coefficient of the n-th component of the object to be inspected for m types of Kα rays (cm2/g) t: Thickness of the object to be inspected (cm), and the n-th component in each measurement region of the object to be inspected Determine each ρWn, and calculate the first
Relative weight component ratio W of the weight component ratio Wn of the n-th component in n same measurement areas based on the weight component ratio W1 of the component
n/W1 is determined and compared with the relative weight component ratio Won/Wo1 determined in advance from the predetermined weight component ratio Won of the object to be inspected. If they are equal, it is determined that the materials to be inspected are uniformly mixed. A density measuring device characterized in that the density is calculated from the value of ρWn.