JPS5919411B2 - gas flow counter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves insulating and stretching an anode wire in a metal container having a radiation entrance window, allowing a counting gas to flow through the container, and using the container as a cathode to connect the container and the anode wire. The present invention relates to a gas flow counter that counts radiation incident into a container through an entrance window by applying a high voltage between the two.

In this type of conventional gas flow counter, the container is made of aluminum, and the anode wire is made of gold-plated tungsten wire.The container is used as a cathode, and a voltage of, for example, 1000 to 2000 V is applied between the cathode and the anode wire. High voltage is applied.

In this case, a counting gas is passed through the container, and the radiation incident on the container through the radiation entrance window is detected in the form of pulses by the anode beam.

As the counting gas, for example, PR gas (argon gas + methane gas), Q gas (helium gas + isophytane gas), propane gas, methane gas, etc. are used.

By the way, in this type of gas flow counter, when setting the high voltage to be applied between the cathode container and the anode wire, a plateau characteristic indicating the relationship between the applied voltage and the counting rate is investigated.

This plateau characteristic depicts the counter output (count rate) obtained when a radiation source with a constant count rate N is kept close to the emission window and the applied voltage is gradually increased. The characteristic line will be as shown in Figure 1.

In FIG. 1, the applied voltage a is referred to as the discharge starting voltage.

The set voltage is set to a voltage in a section where the counter output is almost flat with respect to the applied voltage.

However, in the conventional gas flow counter having the above-mentioned configuration, that is, a gas flow counter whose cathode is made of a container with an aluminum surface, as a result of various experiments, it was found that PR gas, methane gas, and propane gas were allowed to flow as counting gases. In this case, a plateau characteristic as shown in FIG. 1 can be obtained, but it has been found that when Q gas is passed as a counting gas, continuous discharge occurs and the device becomes unusable.

In other words, Figure 4 shows the experimental results of plateau characteristics.
A conventional gas flow counter has a plateau characteristic as shown by characteristic line a, and there is no flat section.

By the way, when Q gas is used as a counting gas, the applied voltage can be set lower than with other gases, and the amplification degree of the gas is large. Therefore, it is not necessary to connect a scaler to the counter output side. It has the advantage of being good.

Therefore, it is often required to use Q gas as a counting gas.

The present invention has been made in view of these points, and an object of the present invention is to provide a gas flow counter that can obtain good plateau characteristics even when Q gas is used as a counting gas.

In order to achieve this objective, the present inventor has conducted numerous studies and various experiments, and has found that good plateau characteristics can be obtained by applying a chromium film to the inner wall surface of the cathode container. I found it.

In a preferred embodiment of the invention, the chromium film comprises a vapor deposited film of chromium.

In another preferred embodiment of the present invention, the chromium film is a chromium plated film.

Next, one embodiment of the present invention will be described in detail based on the drawings.

FIG. 2 is a longitudinal cross-sectional view of one embodiment of the present invention, and FIG. 3 is a cross-sectional view thereof.

A plurality of anode wires 1 are insulated and stretched around the container 2.

This container 2 is made of aluminum and is used as a cathode.

At this time, this container 2 is grounded.

The anode wire 1 is made of gold-plated Tasksten wire, and a high voltage H (V) is applied between the anode wire 1 and the container 2.

The container 2 is provided with a radiation entrance window 3 made of a thin film.

4 is an electric field correction tube, and 5 is an insulator that insulates between the anode wire 1 and the container 2.

6 is a protection plate for the entrance window 3, and 7 is an O-ring.

Counting gas is introduced into this container 2 from a gas port 8 and is led out via a gas outlet 9.

In the present invention, a chromium film 10 is applied on the inner wall surface of the container 2, and this chromium film 10 is made of a chromium vapor deposited film or a chromium plating film.

The radiation that enters the container 2 through the entrance window 3 thus causes a discharge within the container 2 and is extracted from the anode wire in the form of electrical pulses.

FIG. 4 shows the beta ray plateau characteristic experimental results when Q gas is used as the counting gas, and the characteristic line is the plateau characteristic line of one embodiment of the present invention.

According to the experimental results shown in FIG. 4, it was found that good plateau characteristics could be obtained simply by applying a chromium film to the inner wall surface of the container 2.

At present, it is unclear why the good plateau characteristics shown by the characteristic line in Figure 4 can be obtained by simply applying a chromium film to the inner wall surface of the container 2. It is.

FIG. 5 shows experimental results of plateau characteristics when PR gas was used as the counting gas in one embodiment of the present invention.

As is clear from the experimental results shown in FIG. 5, in the present invention, not only Q gas but also other gases such as PR gas can be used as the counting gas.

As explained above, according to the present invention, by simply applying a chromium film on the inner wall surface of the cathode container, Q
Even when gas is used, good plateau characteristics can be obtained as shown by the characteristic line in FIG.

[Brief explanation of the drawing]

Fig. 1 is a general plateau characteristic diagram of a gas flow counter, Fig. 2 is a longitudinal cross-sectional view of an embodiment of the present invention, Fig. 3 is a cross-sectional view thereof, and Fig. 4 shows Q gas as a counting gas. A characteristic diagram showing the experimental results for explaining the difference in plateau characteristics between a conventional gas flow counter and an embodiment of the present invention when used. Figure 5 shows a case where PR gas is used as the counting gas. FIG. 3 is a plateau characteristic diagram of an embodiment of the present invention. 1: anode wire, 2: container, 3: radiation entrance window, 5: insulator, 8: gas inlet, 9: gas outlet, 10 nichrome film.

Claims (1)

[Claims] 1. An anode wire is insulated and stretched in a metal container having a radiation entrance window, a counting gas is passed through the container, and the container is used as a cathode between the container and the anode wire. 1. A gas flow counter that counts radiation incident into the container through the entrance window by applying a high voltage to the container, wherein a chromium film is applied to the inner wall surface of the container. 2. A gas flow counter according to claim 1, wherein the chromium film is a vapor-deposited chromium film. 3. A gas flow counter according to claim 1, wherein the chromium film is a chromium plating film. 4. A gas flow counter according to any one of claims 1 to 3, characterized in that the counting gas is Q gas. 5. A gas flow counter according to any one of claims 1 to 4, wherein the container is made of aluminum. 6. A gas flow counter according to any one of claims 1 to 5, wherein the anode wire is a gold-plated tungsten wire.