JPS6135655B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Geiga-Muller counting device used for detecting radiation doses and the like.

Gaiga-Muller counter tubes (hereinafter referred to as GM tubes) detect radiation in the plateau region by inserting a metal core into a small metal cylinder and filling the inside with helium, neon gas, and halogen gas for ion erasure. Widely used in counting devices (hereinafter referred to as GM counting devices).

The sensitivity of such a GM tube depends on the absorption efficiency of the filled gas, and is low and constant in the high energy region of 200 KeV or more, but is high in the low energy region of 200 KeV or less, and the sensitivity increases depending on the energy of the radiation. There is a problem that it changes depending on the situation.

In FIG. 1, the energy characteristic of the GM tube is shown by curve a, with the horizontal axis representing the energy of the radiation (KeV) and the vertical axis representing the sensitivity (counts/roentgen) of the GM tube.

To solve this problem, we surrounded the outer periphery of the GM tube with a metal tube that absorbs radiation in the low-energy region, reducing the sensitivity below 200 KeV.
There is a GM counting device. FIG. 2 is a diagram showing a conventional example in which such a countermeasure is taken.

The GM tube 1 is inserted inside a tin tubular jacket 2 and 4 with a plastic window 3 and absorbs a significant portion of the relatively low-energy radiation in the tin tubular jacket 2 and 4, thereby generating energy. It has improved characteristics. In FIG. 1, the transmittance (%) of a 2 mm thick tin with respect to radiation energy (KeV) is plotted as a curve c on the vertical axis. From the figure, the transmittance is extremely small below around 100KeV.
It can be understood that there is virtually no transmission around 60KeV.

That is, the plastic window 3 in the conventional GM counting device is provided for the purpose of allowing some of the radiation to pass through, since if it were not provided, all radiation around 60 KeV would be blocked.

Such a configuration is undesirable because a sharp directivity appears for low-energy X-rays in the direction facing the plastic window 3, which can improve the energy characteristics as a whole.

An object of the present invention is to provide an omnidirectional GM counting device that solves the above-mentioned problems.

In order to achieve the above object, the omnidirectional GM counting device according to the present invention fixes a tubular GM tube within a spherical shell of a material that blocks relatively low-energy radiation;
The spherical shell has a large number of holes evenly distributed in it.

According to the above configuration, an omnidirectional GM counting device with good energy characteristics can be realized, and the object of the present invention can be completely achieved.

The GM counting device according to the present invention will be explained in more detail below with reference to the drawings and the like.

FIG. 3 is a diagram showing an embodiment of the GM counting device according to the present invention, and is partially cut away to show the internal structure. The lead wire 1b from the outer circumferential wall of the GM tube 1 and the core wire 1a stretched at the center are pulled out in one direction all at once. A spherical shell 5 made of a tin plate with a thickness of 2 mm is provided with a large number of through holes 6 toward the center of the spherical shell.

The holes 6 are uniformly distributed over the entire surface, and in this embodiment, 24 holes 6 with a diameter of 2 mm are provided in a spherical shell with a diameter of 40 mm.

The energy sensitivity characteristics of the GM counting device having the above configuration are extremely flat, as shown in b in FIG. The unit of sensitivity is (counts/roentgen).

The curve a described above corresponds to the characteristics of only the GM tube 1 with the configuration shown in FIG. 3 from which the spherical shell 5 is removed.

FIG. 4 shows a comparison of the directivity of the conventional device shown in FIG. 2 and the device of the embodiment.

In the figure, lines A, B, and C represent the conventional GM counting device.
Directional characteristics for 60KeV, 122KeV and 660KeV radiation, lines D, E and F are of the embodiment of the present invention.
This shows the directivity of the GM counter for 60KeV, 122KeV, and 660KeV radiation. each
The direction of the central axis of the GM counter is set at 0°, and the radiation directions are irradiated at 0°, 30°, 45°, 60°, and 90°, and the sensitivity at 90° is set as 100 for each, and the comparison is made.

The conventional GM counting device shown in Figure 2 shows lines A and B.
As shown in FIGS. and C, the sensitivity is in the 90° (direction of the plastic window 3) 0° direction, and the sensitivity at 45° is significantly reduced. On the other hand, the GM counting device according to the embodiment of the present invention has the same sensitivity in the 0° and 90° directions, as shown by lines D, E, and F;
It can be said that the sensitivity increases only slightly at the angles of 60° and 60°, but remains essentially unchanged.

As described above in detail, according to the present invention, it is possible to realize an omnidirectional GM counting device with excellent energy characteristics.

[Brief explanation of the drawing]

Figure 1 is a graph showing the energy characteristics a and b of the GM tube and GM counting device and the transmittance characteristic c of the tin plate.
Figure 2 is a diagram showing an example of the configuration of a conventional GM counting device.
FIG. 3 is a partially cutaway view of an embodiment of the GM counting device according to the present invention, and FIG. 4 is a graph showing the directivity of the embodiment device in comparison with a conventional device. 1... GM pipe, 2, 4... tin mantle, 3... plastic window, 5... tin spherical shell, 6... through hole.

Claims (1)

[Claims] 1. An omnidirectional system in which a tubular GM tube is fixed within a spherical shell made of a material that blocks relatively low-energy radiation, and a large number of through holes are uniformly distributed in the spherical shell.
GM counting device. 2. Claim 1, wherein the spherical shell material is tin.
Omnidirectional GM counting device as described in section.