JPS6118887A - Chopper - Google Patents

Abstract

PURPOSE:To obtain a plurality of frequencies from one chopper, by arranging at least two kinds of radiation adjusting parts at a fixed interval in a disc near the circumference thereof to increase or decrease the transmissivity of radiation. CONSTITUTION:Discs in which at least two kinds of radiation adjusting parts are arranged at a fixed interval near the circumference thereof to increase or decrease the transmissivity of radiation are laminated aligning a plurality of center lines. Here, the radiation adjusting parts of the discs are varied in the shape. Then, the use of the discs thus laminated as chopper 2 enables the generation of electrical signals in a detector 3 corresponding to radiation varied in the intensity.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is a chopper suitable for use in a device for measuring the response characteristics of a radiation m (light, X, α, β, γ fine particle beam) detector. Regarding.

<Prior Art> The response characteristic of a radiation detector is expressed by the frequency at which the output drops by 3 dB when the frequency is sequentially increased from low to high for a step input with a constant amplitude in the form of a sine wave. As a response characteristic measuring device for measuring these characteristics, there is a conventional device having a configuration shown in FIG. In the response characteristic measuring device shown in FIG. 6, 1 is, for example, a radiation source, 2 is a chopper that chops the radiation from the radiation source 1, 3 is a radiation detector (hereinafter referred to as a detector), and 4 is a chopper that chops the radiation from the radiation source 1.
is an amplifier that amplifies the output from detector 3, and 5 is a high-speed amplifier 7.
- A FFT spectrum analyzer (hereinafter referred to as FFT). 6 is a reference signal source that generates the same phase as the chopped radiation, which is input to the FFT, and is input to the amplifier 47il.
- It is used as a reference signal to average and remove the noise component of the output signal of the detector 5 which is inputted through the input signal.

With the above-mentioned configuration, the frequency response characteristics at a constant frequency caused by the pain rolling are measured, but in this case, it is desirable to be able to change the types of frequencies as many as possible. Figure 7 plots the frequency characteristics on the horizontal axis and the frequency characteristics on the vertical axis.The more frequency sampling points that can be obtained from low to high frequencies, the more accurate the characteristics of the detector will be. You can get a ton of data.

The first method is to change the sampling frequency by changing the number of rotations of the chopper, but it is difficult to obtain a wide range of rotation speeds with one motor while satisfying frequency reproducibility and stability.

Another option is to change the bar to one with a different number of blades, but having multiple choppers has the disadvantage of not only being expensive but also requiring a lot of time to replace the choppers. .

<Object of the invention> The present invention has been made in view of the drawbacks of the above-mentioned prior art.
It is possible to obtain multiple frequencies from a single piece of paper, and the measurement time is shortened.

<Configuration of the Invention> The configuration of the present invention that achieves this object is to provide at least two types of radiation increasing/decreasing portions that increase or decrease the transmittance near the outer periphery of a disk having a constant transmittance to radiation. The feature of this structure is that they are arranged at intervals of .

<Example> When a certain type of radiation passes through a substance, the intensity of the radiation decreases exponentially depending on the thickness of the substance through which it passes, and the intensity of the transmitted radiation that passes through the substance is I = I.

It is expressed in e-μt.

Here, the incident radiation intensity is μ = attenuation coefficient t=transmission distance It is.

The present invention utilizes these properties of radiation to
One example is shown in Fig. 1 and Fig. 2.

Figure 1 shows, for example, medical X-rays (effective energy 6DKeV)
This figure shows an example in which the chopper 10 of the present invention used in the present invention is formed by laminating a plurality of discs.
) and (c) show the state in which the laminated chopper 10 of FIG. 1 is disassembled. In this example, a brass plate is used as the material of the disc (attenuation coefficient P of the brass plate at 60 KeV K is 1
3.7cm-'').The disk in Figure 2 (8) is 0,
The thickness is s'mm, and the center line x-x', y-y'
A divided into four.

Of the areas B, C, and D, area A has 18 concave radiation increase/decrease areas arranged at equal intervals (in this example, every 3 areas from the convex part A of the 6 areas on the circumference in the direction of the official seal). It has a shape with 5 measurements and 9 removed of the convex parts, and in area B, of the 18 concave and convex parts provided at equal intervals, 3 of the concave parts are filled in from the mouth part, and the 3 frozen parts are filled in by 3 WA, and then It is said to have a shape of 3 flying and 3 buried, and A
The part and the 0 part, and the B part and the D part are formed in the same shape. Figure 2 (
The disk in b) has a thickness of 0.3 mm, and the center line X-X'
+, fill 3 in the direction of the mark divided into 4 by y-y', 5
It is assumed that the area F starts from the second part, skips three convex parts, creates a concave part for two, and then skips three WA and fills in 3 WA. E
The part and G part, and the second part and Hs are formed in the same shape. Figure 2 (
The disk in c) has a thickness of 0.5 mm, and the center line
-X/.

■ Of the areas I, J, and L divided into four by Y-Y'
The regions J and K are formed in a convex state throughout, and the regions J and H are formed in a concave state throughout.

When the three plates mentioned above are stacked with their center lines xx' and y-y' aligned as shown in the chopper 10 of FIG. 1, the thickness level of each uneven portion becomes as shown in FIG. 3. In FIG. 3, the horizontal axis indicates the rotation direction of the chopper 10, and the vertical axis indicates the change in the thickness of the uneven portion.
) plate (plate thickness a, 5 mm) where only the convex portion exists,
The level of b is as shown in Figure 2 (a) or Figure 2 (c).
, 5mm) where the convex portion exists, level C is the second level.
Figure (a) or 2nd IN ((1) and the part where the convex part of Figure 2 LbJ exists, - level is Figure 2 (ML (b
), (e) shows the part where all the convex parts are present, and when this is used for the conventional example of the Chig7 bar, the detector 5 has four types of strength as shown in Fig. 4. Electrical signals corresponding to different radiations are generated. In Figure 4,
In the horizontal axis direction, the rotation direction of the chopper 10 is 9 levels, the level B is <0.5 mm, and the level C is 0.
The level of 8 mm and D indicates the level of the intensity of radiation transmitted through a portion of thickness L3 mm and attenuated.

When an electric signal generated according to the above-mentioned attenuation degree is input to the FFT K shown in FIG. 6 via an amplifier, three types of frequencies having equal amplitudes as shown in FIG. 5 can be obtained from the FFT. In Fig. 5, the range of the arrow W shows the waveform every time the chopper 10 makes a half rotation, the waveform ``■'' is one cycle every time the chopper 10 makes a half rotation, ``■'' is the same 6 cycles, and ``■'' is the same <36 cycles. It shows that. The three frequencies obtained by rotating the chopper consisting of these three periods are called fundamental frequencies, and if you analyze the third, fifth, etc. harmonics using FFT, you can obtain even more types of frequencies. can.

In addition, in the above embodiment, an uneven portion was provided near the outer periphery of most of the disks, and the radiation transmittance increasing/decreasing portion was formed by stacking these three disks, but the present invention is not limited to the above embodiment. A single disc may be processed to have multiple parts with different thicknesses arranged at regular intervals, or plates of the same thickness but with different radiation transmittances may be arranged near the outer periphery of the disc. It may be arranged by embedding it in the interval or by pasting it. In this example, we have focused on X-rays, but α-rays, β-rays, γ-rays, and light radiation can also be applied to particle beams.

<Effects of the Invention> As specifically explained above in conjunction with the embodiments, the present invention allows a single chopper to generate a plurality of fundamental frequencies. Measurement time can be shortened.

[Brief explanation of the drawing]

Figures 1 and 2 (a), '(b), ((1) shows the chopper of the present invention, Figure 1 is a diagram in which three plates are stacked, Figure 2 (a), (b) ), (e) is an exploded view of the laminated chopper shown in Fig. 1, and Fig. 6 shows the portions where the radiation transmittance increases and decreases (uneven portions) when the chopper of the present invention rotates.
Figure 4 is a diagram showing the degree of attenuation of radiation when the chopper of the present invention rotates, and Figure 5 is a diagram showing the frequency at which the radiation transmitted through the chopper of the present invention irradiates the detector. FIG. 6 is a diagram illustrating a configuration example and a conventional chopper for measuring radiation characteristics, and FIG. 7 is an explanatory diagram showing the output of a detector with respect to frequency. 1...Radiation source, 2.10...Chopper, 3...
- Radiation F-ray detector, 4... Amplifier, 5... Fast Fourier transform Schiveter analyzer, 6... Reference signal source. 1M1 figure n! Rashishi Atsushi 2 (a) (c) (b)

Claims (1)

[Claims] 1. At least two types of radiation transmittance increasing/decreasing portions that increase or decrease the transmittance are arranged at regular intervals near the outer periphery of a disk having a constant transmittance to radiation. Chopper featuring. 2. The thickness or material of the chopper is selected so that the proportion of the transmittance increase/decrease is always equal, and the radiation transmitted through the chopper is modulated into waves having multiple fundamental periods with equal power or amplitude. A chopper according to claim 1, characterized in that: