JPH01100443A - Method and apparatus for manufacturing sample for gamma-rays transmission measurement - Google Patents

Abstract

PURPOSE:To obtain a sample for measurement with a better S/N of spectrum irrelevant to the size and unevenness of a powder sample to be measured, by repeating an operation of evacuating and returning the pressure to amt. within a circular frame. CONSTITUTION:A circular frame 12 into which a specified amount of a mixed liquid 11 flows as obtained by mixing a solution having a thermoplastic resin dissolved in an organic solvent with a powder sample to be measured is provided in a closed container 13, which is connected to a piping 17 and an air piping 16 to a vacuum pump 15 through a three-way changeover valve 14. The tree-way changeover value 14 is opened on the side of the vacuum pump 15 and the vacuum pump 15 is driven to evacuate inside the circular frame 12. Then, the vacuum pump 15 is stopped and the three-way changeover valve 14 switched to return the pressure in the cylindrical frame 12 to atm. By repeating the operation of evacuating and returning the pressure to atm., gas generated is reduced gradually thereby enabling the obtaining of a bubble-free dry sample being measured.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method and apparatus for producing a sample for measuring gamma ray transmission in methods such as Mössbauer spectroscopy.

"Conventional technology" Mössbauer spectroscopy uses the fact that the energy level of an atomic nucleus changes depending on the atomic arrangement and the position of the electron cloud around the nucleus, and measures the energy of gamma rays while slightly changing them due to the Doppler effect. It is a method that accurately detects changes in energy levels by irradiating a sample and causing resonance absorption in the atomic nuclei (Mössbauer effect), and determining ionization, crystalline state, magnetic properties, etc. It is used in the fields of
Particularly in the field of ferromagnets, it plays an important role in elucidating the magnitude of internal magnetic fields, the direction of magnetic moments, magnetic transitions, and relaxation phenomena.

There are several methods for spectrum measurement, including the transmission method, which measures the gamma rays that have passed through the sample with a detector placed behind the measurement sample after irradiation with gamma rays, and the secondary method, which uses a detector placed in front of the sample. It is broadly divided into two types: reflection methods, which measure electrons, X-rays, and re-emitted gamma rays caused by In particular, the transmission method can obtain information from the entire sample and is excellent for obtaining the average characteristics of the sample.

Most measurement samples are in the form of thin plates or powders, and powders are widely used because they are easy to prepare.
In the case of the transmission method, the powder must be consolidated and formed into a thin foil. There are two methods for producing such measurement samples: one is to sprinkle the powder sample to be measured on cellophane tape or an adhesive sheet, and the other is to mix the powder sample to be measured in a solution containing styrofoam. A well-known method is to pour the mixed liquid into a circular mold having a cylinder 2 attached to a pedestal 1 with a horizontal bottom wall as shown in FIGS. 8 and 9, and then air dry it.

"Problems to be Solved by the Invention" A sample for measuring gamma ray transmission must be (1) as thin as possible to minimize attenuation of gamma rays, ideally with a
μ- or less, (2) γ-rays should pass through the sample without causing the Mössbauer effect without creating gaps that would increase the background, (3) The thickness should be uniform, (4) ) be made in an area larger than the detector window;
(5) Many devices have a configuration in which the measurement sample is held vertically.
Moreover, since measurements are sometimes carried out over several days, it is important that the material does not change or collapse during that time.

By the way, the method of sprinkling it on the cellophane tape etc. mentioned above is as follows.
There are problems in that it is difficult to create a uniform thickness without any gaps. That is, in order to make the thickness uniform,
After sprinkling the powder sample to be measured, it is necessary to shake off the excess sample, but if the particles are fine, the required amount of sample may not adhere, and if the particles are coarse, gaps may be created.
If they are not aligned, both of these will occur, resulting in defects that cannot be addressed in either case.

In the above-mentioned method of natural drying, when the amount of powder sample to be measured is large, the amount of solution to be mixed will also be large, and the depth of the mixed solution will increase when poured into the circular mold, making it difficult to dry. There is a problem that a thin film is formed on the surface during drying, and the bubbles of the solvent newly generated from inside are trapped, resulting in different gamma ray attenuation in that part.For example, if the powder sample to be measured is 100 ml, When using a circular formwork with a cylindrical inner diameter of 50 m, if the mixed liquid does not exceed approximately 1 mJ, the thermoplastic support film will not be able to hold the powder sample and will collapse when it dries. To prevent this, the liquid volume should be reduced. If it increases, the depth will exceed 1■.

Furthermore, when large bubbles are generated, gaps are created in the measurement sample, resulting in a problem that the S/N of the Mössbauer spectrum is reduced.

Furthermore, if the amount of the mixed liquid is large, the mixture will remain along the cylinder 2 during air drying, making it impossible to prepare a measurement sample with a flat surface. A circular mold with a certain surface is also used, but in that case there is a problem in that it is difficult to control the size and thickness of the measurement sample.

An object of the present invention is to provide a method for manufacturing a sample for gamma-ray transmission measurement and an apparatus therefor, which eliminates the above-mentioned problems.

"Means for Solving the Problems" The first aspect of the present invention is to mix a solution obtained by dissolving a thermoplastic plastic in an organic solvent and a sample amount of powder to be measured, and to form a mixed solution in a circular shape. This is a method for producing a sample for gamma ray transmission measurement by pouring into a mold, and then repeating evacuation and return to atmospheric pressure multiple times in the circular mold.

Further, a second aspect of the present invention provides a closed container having piping to a vacuum suction means and atmospheric piping via a switching valve, and a solution dissolving a thermoplastic plastic in an organic solvent installed in the sealed container. The circular mold consists of a pedestal serving as a bottom wall, and two upper and lower parts fixed on the pedestal. A pillar with a horizontal surface or a cut u! ! This is an apparatus for producing a sample for gamma ray transmission measurement, which is formed by a core having the same shape and a cylinder that is attached to the outer peripheral edge of the upper surface of the core and serves as a peripheral wall with a clearance of one dragon or less.

The thermoplastic plastic used in the present invention is preferably one composed of a light element such as expanded polystyrene or vinyl chloride, and has a low density and low gamma ray attenuation.

The organic solvent used in the present invention is preferably one that has a large amount of dissolved carbon in the thermoplastic plastic and evaporates quickly, such as tetrahydrofuran, acetone, ethanol, methanol, and dichloroethylene.

The particle size of the powder sample to be measured is not particularly limited.

As the circular formwork used in the present invention, in addition to the one shown in FIG. 8, those shown in FIGS. 2 to 7, which will be described later, can be used.

Next, an example of the manufacturing method of the present invention will be explained with reference to FIG.

First, a mixed solution 1 obtained by mixing a solution of thermoplastic plastic dissolved in an organic solvent and a powder sample to be measured.
A circular mold 12 into which a predetermined amount of 1 is poured is placed in an airtight container 13.
For example, it is installed in a vacuum pelger, and the vacuum pelger is connected to a pipe to a vacuum pump 15 and an atmospheric pipe 16 via a three-way switching valve 14. 17 is a tube. Open the three-way switching valve 14 to the vacuum pump 15 side, and
is driven to evacuate the inside of the circular formwork 12. The degree of vacuum is not particularly limited.

Next, the vacuum pump 15 is stopped and the three-way switching valve 14 is switched to return the inside of the circular formwork 12 to atmospheric pressure. The time between evacuation and return to atmospheric pressure is not particularly limited.

By repeating the above evacuation and return to atmospheric pressure, the gas generated gradually decreases and the bulge of the membrane becomes smaller until it finally converges to a flat surface, making it possible to obtain a dry measurement sample free of bubbles. By the above method, a flat measurement sample with a uniform thickness can be obtained without using a watch glass-shaped pedestal.

In addition to the one shown in FIG. 8, the circular formwork 12 includes a pedestal serving as a bottom wall, and a columnar or M-cone-shaped core that is fixed on the pedestal and whose upper and lower surfaces are horizontal. A circular formwork 12 formed by a cylinder attached to the outer peripheral edge of the upper surface of the core with a clearance of less than l+ia and serving as a peripheral wall.
can be used.

FIGS. 2 to 7 are examples, and 18 is a core.

All of these may be made by processing the core and the pedestal as one unit.These circular forms prevent the mixed liquid from rising along the inner wall surface of the cylinder, especially when the amount of the mixed liquid is large. It is designed to prevent this. That is, the rising phenomenon is determined by the balance between the total weight of the rising part and the wetting force, so when the mixed liquid is poured into the circular form, the mixed liquid rises at the outer periphery of the upper surface of the core 18. protrudes outward from the outer periphery of the upper surface of the core 18 by the above-mentioned clearance, so the weight of the rising portion cannot be supported by the force of wetting, and the rising height becomes low and the weight of the rising portion decreases. When the rising height becomes lower, the wetting force becomes weaker and the height becomes further lower, and the height becomes lower until the total weight of the rising part and the wetting force are balanced, and the crown shape can be eliminated. However, if the above-mentioned clearance is made too large, the drop of the mixed liquid becomes significant, so it is preferable that the clearance is 1 crane or less, and a core of an appropriate shape can be selected depending on the viscosity of the mixed liquid.

``Operation'' By evacuating the inside of the circular mold before the surface layer of the liquid mixture hardens, the evaporation rate of the solvent gas is slowed and air bubbles are forcibly exhausted. Although a thin film still forms on the surface of the mixture,
By returning to atmospheric pressure, the thin film is ruptured by the pressure of the inflowing air. By repeating this evacuation and return to atmospheric pressure, drying and hazy air are gradually carried out.

Further, by providing the core in a circular mold and attaching a cylinder with a clearance at the outer periphery of the upper surface of the cough core, it is possible to prevent the liquid mixture from rising.

``Example - A solution of commercially available expanded polystyrene 400 mm dissolved in f4 in 4 ml of commercially available tetrahydrofuran, and a diameter of 1 to IO μm.
The mixed liquid obtained by mixing 150 cm of non-uniform magnetite powder was placed in a circular frame shown in FIG. The mixture was poured into a vacuum Pel jar and evacuated to approximately 0 and IT Torr using an aspirator, and the cock of the Pel jar was opened to return the pressure to atmospheric pressure. This evacuation and return to atmospheric pressure were repeated five times to obtain a flat measurement sample.

This sample was integrated for 3 hours using 1co of 18.4 mC1 as a gamma ray source to obtain a Mössbauer spectrum. The S/N of this spectrum was good.

"Effects of the Invention" As described above, according to the method of manufacturing a sample for T-ray transmission measurement of the present invention, the powder to be measured can be prepared by a simple method of repeatedly evacuation and return to atmospheric pressure in a circular mold. A measurement sample with a good spectrum S/N ratio can be obtained regardless of sample size or non-uniformity, and characteristics of ferrite particles, which are materials for magnets, magnetic tapes, etc., can be precisely evaluated. Furthermore, the characteristics of Mi particles, iron powder, etc., which have been recently developed, can be evaluated more precisely. Furthermore, in the chemical field, there is no need to make the particle sizes of powder samples for running parallel to each other, and samples for measurement can be prepared as they are, making it easy to measure highly reactive samples.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram showing an example of a manufacturing apparatus according to the present invention;
Figures 2 and 4 to 7 are longitudinal sectional views showing an example of a circular formwork having a core, Figure 3 is a plan view of the circular formwork shown in Figure 2, and Figure 8 is a conventional circular formwork. A vertical cross-sectional view of the formwork and FIG. 9 are plan views thereof.

Claims (2)

[Claims] (1) Pour the mixed solution obtained by mixing a solution of thermoplastic plastic in an organic solvent and a powder sample to be measured into a circular mold, and then vacuum the same in the circular mold. A method for producing a sample for gamma ray transmission measurement, characterized by repeating atmospheric pressure return multiple times. (2) A closed container that has piping to a vacuum suction means and atmospheric piping via a switching valve, and a solution containing a thermoplastic plastic dissolved in an organic solvent and a powder sample to be measured, which are installed inside the closed container. It consists of a circular formwork for pouring the mixed liquid obtained by mixing the above, and a pedestal serving as a bottom wall, and a columnar or cut-out shape fixed on the pedestal and having two horizontal sides, the top and the bottom. A cone-shaped core and a 1mm diameter at the outer periphery of the upper surface of the core.
1. An apparatus for manufacturing a sample for gamma-ray transmission measurement, characterized in that it is formed of a cylinder that is attached with the following clearance and serves as a peripheral wall.