JPH06258450A - Radiation measuring equipment - Google Patents

Abstract

PURPOSE:To provide a downsized radiation measuring equipment for measuring radon and thoron existing in a gas with high sensitivity. CONSTITUTION:A container 32 for an ionization chamber 30 is composed of an alpha-ray transmitting material and an ionization gas is encapsulated therein. The container 32 is made of an organic film, for example, and a frame 44 is provided in order to hold the container 32. A conductive coating material 46 is applied to the inner face of the container 32 and a voltage is applied between the coating material 46 and a current collecting electrode 34. Since the container 32 is entirely composed of an alpha-ray transmitting material, radon existing around the container can be measured efficiently.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
It relates to a line measuring device.

[0002]

2. Description of the Related Art Radon and thoron are daughter nuclei of uranium and radium, which can exist as gases and are released from the earth to the atmosphere, and also from structures to indoor air.

Radon and thoron existing as gases (hereinafter referred to as radon) emit α rays of about 5 MeV.

Radon concentration in the air is usually 1 Bq / m.
It is said to be about ³ . However, the concentration of radon varies greatly depending on the weather and location, and in some cases, it may exceed the limit concentration. For example, in a room close to a closed state, radon released from the wall accumulates in the indoor space. Radon (also thoron) has a relatively short half-life, and after a certain period of time (for example, 3 days), a saturated state is formed in the indoor space.

As described above, radon is present in the air we breathe and causes internal exposure to the body. Therefore, continuous monitoring of its concentration is significant. Although the range of α-rays is smaller than that of other β-rays, the ionization density is high, so it is necessary to be careful when ingesting radon from excessive breath.

FIG. 3 shows the configuration of a conventional radon measuring device. The gas (air) containing radon is dusted by the dust filter 10 and then ionized by the ion precipitator 12 to be introduced into the ionization chamber 14. The pump 16 is sucking gas, and the air passing through the ionization chamber 14 is discharged into the atmosphere.

Here, the ionization chamber 14 is composed of a metal electrode container 18 forming one electrode and a collector electrode 20 arranged at the center of the electrode container. A high voltage is applied between the electrode container 18 and the collecting electrode 20 by a DC power source 22, and various radioactive substances emit radiation, so that part of the gas is ionized and ions and electrons are carried to the electrodes by the electric field. , Is taken out as a signal. Specifically, after being amplified by the vibration capacitance electrometer head 24, a signal is measured by, for example, the vibration capacitance electrometer 26, and the radon concentration and the like are recorded in the recorder 28.

[0008]

However, the above-mentioned conventional apparatus has a relatively good detection sensitivity because it is a gas flow type, but the ionization chamber becomes large and other equipment for gas flow is installed. There is a problem of needing it. Therefore,
Radon concentration cannot be easily measured. An ionization chamber provided with a window that allows α rays to pass through has also been proposed, but it measures the α rays by bringing the radiation source close to the window, and measures the amount of radon in the room air. Is not suitable for, and is not sufficient in terms of sensitivity.

The present invention has been made in view of the above conventional problems, and an object thereof is to provide an improved radiation measuring apparatus capable of sensitively measuring a radioactive substance (especially radon) existing in a gas. is there.

[0010]

In order to achieve the above object, the present invention is an ionization box including a container containing an ionization gas and a collector electrode provided inside the container,
The entire container is made of an α-ray transparent material,
A line is detected in the container.

[0011]

According to the above construction, since the entire container of the ionization chamber is made of the α-ray transparent material, α
It is possible to efficiently introduce the wire inside the container. Therefore, the detection sensitivity can be increased. When the container is made of an insulating material, for example, an electrode is provided inside the container and a voltage is applied between the electrode and the collecting electrode.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a preferred embodiment of the radiation measuring apparatus according to the present invention. The device shown in FIG. 1 is for measuring the concentration of radon (and thoron) contained in air.

In FIG. 1, the container 32 of the ionization chamber 30 is
It is composed of a thin film α-ray transparent material. As is well known, since the range of α rays in the substance is relatively short (about 5 cm in air), the thickness of the container 32 is, for example, 1 μm, and the substance is, for example, an organic film [Myra: Trademark)] is used. Generally, the thickness of the container is α
The line also needs to be 1/3 or less of the range of about 5 mg / cm ² .

A gas for ionization (for example, air or argon) is hermetically sealed in the container 32, and there is no inflow of gas from the outside. Therefore, radon cannot enter the container, and only α rays can enter the container 32.

Of course, there is a possibility that α-rays will be absorbed by the container 32 itself and will not enter the ionization chamber. However, as described above, by making the container 32 extremely thin and using a substance having small energy absorption, Such a probability can be lowered. Since the entire container 32 is made of an α-ray transparent substance, the α-rays coming from around the ionization chamber can be efficiently detected.

When α rays enter the container 32, the α
The kinetic energy of the line is converted into the ionization energy of gas atoms, and the generated electrons are captured by the collecting electrode 34. The current generated thereby is amplified by the oscillating capacitance electrometer head 38, further amplified by the current amplifier 40 composed of a charge type amplifier, and then the current is integrated and recorded in the recorder 42. Other signal processing methods can also be applied.

The DC power source 36 is for applying a high DC voltage between the collecting electrode 34 which is one electrode and the other electrode.

FIG. 2 shows the structure of the ionization chamber 30.

In FIG. 2, in the present embodiment, since the container 32 is made of an insulating material, it is necessary to provide an electrode on the other side. Therefore, the conductive resin coating 46 is formed on the entire inner surface of the container 32. It has been subjected. That is, a DC voltage is applied between the conductive resin coating 46 and the collector electrode. In the figure, 48 is a lead therefor, and 50 and 52 are insulating members.

FIG. 4 shows a modified example. In this modified example, a guard ring 70 is provided on the support portion of the collector electrode 34. Specifically, the ring-shaped insulating member 72,
74 is disposed between the container and the collecting electrode 34. Then, the guard ring 70 is grounded.

As a result, the collector electrode 34 and the guard ring 7 are
Since 0 has the same potential, a potential gradient is generated between the guard ring 70 and the container, while there is no potential gradient between the guard ring 70 and the collecting electrode 34, and as a result, leakage between them occurs. It is possible to prevent current and the like and improve the measurement accuracy. Therefore, the current type measurement can be performed in addition to the pulse type measurement.

As described above with reference to FIG. 2, since the container 32 is formed into a thin film, the frame 4 is used for maintaining the structure.
4 is provided outside the container 32. In the present embodiment, the frame 44, which is the skeletal structure, is formed of a net-like metal in a cage shape to avoid the blocking of α rays as much as possible. The diameter of the container is, for example, 10 cm, and the length is, for example, 20 cm.

[0024]

As described above, according to the present invention,
Since the container of the ionization chamber is made of an α-ray transparent substance, it is possible to efficiently detect the α-rays flying around the container. Further, there is an effect that the device can be downsized.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an overall configuration of a radiation measuring apparatus according to the present invention.

FIG. 2 is a sectional view showing a configuration of an ionization chamber.

FIG. 3 is an explanatory diagram showing a configuration of a conventional radiation measuring apparatus.

FIG. 4 is a sectional view showing a guard ring 70.

[Explanation of symbols]

 30 Ionization box 32 α-ray transparent container 34 Collection electrode 44 Frame 46 Conductive coating material

Claims (1)

[Claims] 1. An ionization chamber comprising: a container for containing an ionizing gas; and a collector electrode provided inside the container, wherein the container is entirely made of an α-ray permeable substance, A radiation measuring apparatus, which detects α rays in the container.