JP2501819Y2 - Radiation applied measurement device - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is a radiation detector of a radiation applied measuring device for measuring physical quantities (grammage, moisture, etc.) of paper, plastic, rubber, etc. using a semiconductor radiation detector. It is about.

<Prior art> When radiation (eg, β-rays) passes through a material layer, it gradually loses energy due to ionization and excitation, and is attenuated. Further, it undergoes such inelastic scattering many times and the traveling direction changes. . Therefore, as the physical quantity (for example, thickness) of the measurement object increases, the number of β rays transmitted decreases. By applying such a principle, a device for measuring physical quantities of various sheet-like substances is known.

As shown in FIG. 5, such a radiation applied measuring device has a radiation source (hereinafter, simply referred to as a radiation source) 1 and a radiation detector (hereinafter, simply referred to as a detector) 2 which are arranged to face each other and to be measured. It is configured to measure by sandwiching the body 3.
As shown in FIG. 6, the spatial intensity distribution of radiation from this radiation source has a strongest Gaussian distribution in the front and a weaker Gaussian distribution as it moves away from the front. Therefore, when the radiation source 1 and the detector 2 move relative to each other in the X, Y or Z directions, there is a problem that the amount of radiation incident on the detector 2 changes and the output fluctuates.

Conventionally, as shown in FIGS. 7 (a), 7 (b) and 7 (c), there has been proposed a device for removing this type of output fluctuation. That is, the absorption plate 6 is arranged at a portion 2a of the detector that receives radiation (hereinafter, simply referred to as a light receiving portion) at a right angle to the radiation irradiation direction and the X direction, and the positional relationship between the radiation source 1 and the light receiving portion 2a. The output fluctuation caused by the change of is reduced.

FIG. 7 (a) is a plan view showing the relationship between the radiation source 1, the light receiving portion 2a, and the absorbing plate 6. The absorbing plate 6 is located at the center of the light receiving portion of the detector at a right angle to the X direction. The source is located in the center of the light receiver. The absorption plate 6 has a length l that is longer than the diameter of the light receiving portion and a width W that is wider than the radiation source and smaller than the diameter of the light receiving window.
It consists of a plate and is attached to the center of the front surface of the light receiving part 2a.
A part of the strongest part of the radiation beam of the radiation source 1 is blocked to reduce the amount of radiation incident on the light receiving part 2a. The radiation source 1 is usually wrapped in a metal box or the like as a safety measure, and since the exit of the radiation source box is covered with a thin metal plate or the like, the radiation emitted from the radiation source 1 is hard to go straight and is scattered. Become. Therefore, the intensity of the radiation beam is strongest at the front of the radiation source 1 and becomes weaker as it goes away from the front.

In Fig. 7 (b), the detector 2 is in the X direction (to the left).
In the side view showing the state shifted by X ₁ , R represents the equivalent dose of radiation. When such a shift occurs, the output is weakened because the left side moves away from the radiation source, but the strongest part of the radiation blocked by the absorption plate 6 irradiates the light receiving surface on the right side. Therefore, the output becomes stronger. Therefore, the total amount of radiation received by the light receiving unit does not change, and output fluctuations due to deviation do not occur.

In Fig. 7 (c), the detector is Z _{1 in the} Z direction (upward in the figure).
In the side view showing the shifted state, in this example, the light receiving surface approaches the radiation source, so that the portion not covered with the absorption plate 6 acts to increase the output, and at the same time, the portion with strong radiation spreads wider. Therefore, the total amount of radiation does not change and the output fluctuation due to the deviation does not occur.

According to the above configuration, even if the relationship between the radiation source and the detector moves in the X and Z directions, the total amount of radiation can be made almost the same. It should be noted that the illustrated absorbing plate cannot deal with the deviation in the Y direction.

<Problems to be solved by the device> However, in the above-mentioned conventional radiation applied measurement device, since the radiation sensitivity is adjusted by using the absorption plate in front of the detector, the sensitivity of the detector is 1/2 to 1 /. There was a problem that it would drop to 5. In addition, when an absorbing plate is used, its location must be determined by trial and error according to the properties of the object to be measured.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to realize a radiation applied measuring apparatus that does not vary in output with respect to deviations in the X and Z directions without lowering detection sensitivity.

<Means for Solving the Problems> The configuration of the present invention for solving the above problems is that a semiconductor radiation detector emits radiation that is emitted from a radiation source whose spatial intensity has a Gaussian distribution and that passes through an object to be measured. In a radiation applied measuring device for detecting and measuring the physical quantity of the object to be measured, a distance detector for detecting the distance from the radiation source to the semiconductor radiation detector, and a plurality of strip-shaped detecting elements having the same sensitivity. Each of the blocks corresponding to the distance signal based on the distance signal detected by the distance detector. It is composed of detection element selection means for selecting one of the detection elements, and outputs the sum of the outputs from each of the detection elements as a signal corresponding to the physical quantity. Things.

<Operation> Each output of each detection element is monitored by the detection device. Then, the detection device selects the same number of blocks as the detector centering on the block with the maximum output among the blocks, selects one of the elements of each block, collects the outputs from those elements, and Output.

When a shift occurs in the X direction, the block that outputs the maximum output shifts, but the same number of blocks on the left and right selected centering on the block with the new maximum output is selected as the detector.

When a shift occurs in the Z direction, one of the elements forming the steps of each block is selected based on the output of the distance detector.

<Example> FIG. 1 (a), 2 shown in (b) ^- a detector showing a main portion of an embodiment of the present invention (a) is a front view (b) is a plan view. Although not in the figure this detector similar to Figure 5, the detector 2 across the object to be measured 3 ^- shall the radiation source 1 is arranged to face. In Figure 1, 20, 21, ~ 221
Is made of navy blue cormorant with a plurality of strip-shaped semiconductor detectors.
For example, in the detection block 20, the detection elements 20 _{1 to} 20 _n are formed in a step shape. The detection element of each of these blocks is, for example, 40
Wafers of × 0.1 × 0.1 mm are arranged in a staircase pattern with a pitch of 0.1 mm. Therefore, in this embodiment, 201 stair-like detection blocks having a height of 1 mm and a width of 1 mm are arranged in parallel.

The output from each element is output to a detection device (not shown) and added, and the output for each block is monitored.

Figure 2 is a detector 2 of the structure ^- show a state where the center was allowed to face the radiation source (not shown) of, curve a shows the intensity distribution of the radiation. In the figure, for easy understanding, the block facing the center of the radiation source is set to 0, and 100 blocks are arranged on both sides of the block.

If there is no deviation between the detector 2 ^- and the radiation source, the total output from the 0 block becomes strong, so the detector selects, for example, 90 left and right blocks centering on this 0 block, and selects one element of each block. (In the embodiment, one block is composed of 10 elements, and the sixth element from the bottom in the figure) is summed up and output.

Next, as shown in FIG. 3, when the detector position is relatively deviated in the X direction by Δa and the total output of one block becomes maximum, 90 blocks on the left and right of the one block are centered. The respective outputs from one element (the sixth element from the bottom in the figure) of each selected block are summed and output. Therefore, if the performance of each element is the same, the output fluctuation due to the deviation in the X direction does not occur.

FIG. 4 illustrates the case where the radiation source and the detector 2 ⁻ are displaced in the Z direction. In this case, the deviation itself is measured by a distance measuring means (not shown) provided separately. As a result, if the radiation source and the detector 2 ⁻ are separated by 0.3 mm, the detecting device is an element that makes the distance substantially 0, that is, 9 from the lower end of each block.
Output the sum of the signals from the th element. Therefore, also in this case, if the performance of each element is the same, the output fluctuation due to the deviation in the Z direction does not occur.

In this embodiment, the number of blocks and the number of elements forming the block are described by giving numerical values, but this number can be appropriately increased or decreased according to the expected deviation amount or the like.

Further, here, the error with respect to the deviation of the radiation source and the detector in the Y direction will not be discussed, but the deviation in the Y direction will be corrected by another method.

<Advantage of Device> As described above in detail with the embodiments, according to the present invention, since the absorption plate is not used, the sensitivity does not decrease, the output fluctuation due to the deviation in the X and Z directions is small, and the ratio of the sensitivity decrease. It is possible to realize a radiation application measuring device with less waste.

[Brief description of drawings]

FIG. 1 is an explanatory view of an essential part showing an embodiment of a detector of the radiation detecting apparatus of the present invention, FIG. 2 is an explanatory view when the center of the detector is located at the center of the radiation source, and FIG. 3 is a line. Fig. 4 is an explanatory view showing a case where the source and the detector are displaced in the X direction, Fig. 4 is an explanatory view showing a case where the source and the detector are displaced in the Z direction, and Fig. 5 is a radiation source and the detector. FIG. 6 is an explanatory view of the general positional relationship of FIG. 6, FIG. 6 is a view showing the intensity distribution of radiation, and FIG. 7 is an explanatory view of a conventional example. 1 ... radiation source, 2,2 ^- ... radiation detector, 3 ... object to be measured, 20, 21,
To 221 ... detection block, 20 ₁ to 20 _n ... detecting element.

Claims (1)

(57) [Scope of utility model registration request] 1. A radiation applied measuring device for detecting a radiation emitted from a radiation source whose spatial intensity has a Gaussian distribution and passing through an object to be measured by a semiconductor radiation detector to measure a physical quantity of the object to be measured. In, a distance detector for detecting the distance from the radiation source to the semiconductor radiation detector and a plurality of strip-shaped detection elements having similar sensitivity are arranged in a stepwise manner and the blocks are arranged in parallel. A semiconductor radiation detector fixed side by side, and a detection element selecting means for selecting one of the detection elements of the block corresponding to the distance signal based on the distance signal detected by the distance detector, A radiation applied measurement apparatus, wherein the total output from the detection elements is output as a signal corresponding to the physical quantity.