KR100921417B1 - Multi-sided thickness measuring device and measuring method using single point isotope radiation source - Google Patents

Abstract

The present invention relates to a method for non-destructively and non-contactly measuring the thickness of an object at several points using one isotope radiation source and a plurality of radiation detectors, and more particularly, having one isotope radiation source at a single point, The ion current detector for detecting radiation emitted from the radiation source and passing through the object is provided for each of a plurality of measurement points, and the minimum current value required for the radiation detection even in the ion chamber detector, which is located far from the radiation source and has a relatively low amount of incident radiation. By setting the type, volume or pressure of the filling gas differently according to the position of the ion-containing detector so that the above current signal is output, the amount of single radiation source required is improved to improve the safety of the use of the radiation and at the same time, the cost of maintenance and repair of the radiation source. To save money It relates to the measurement apparatus and method.

A multi-faceted thickness measuring apparatus according to the present invention includes a single radiation source for irradiating radiation to an object side; And a plurality of ion-box detectors disposed between a plurality of measurement points on opposite sides of the radiation source and detecting radiation passing from the radiation source and passing through the object, with the object interposed therebetween. The detector is set such that the volume or pressure of the gas filled in the interior of the ion chamber detector located at a relatively distance from the radiation source is greater than the volume or pressure of the gas filled in the interior of the ion chamber detector located at a close distance from the radiation source. It is characterized in that the configuration.

Isotope, Radiation Source, Ion Box Detector, Area, Thickness Measurement, Safety

Description

A device for measuring the thickness of a large area subject using one point radioactive isotope source and the measurement method}

The present invention relates to a method for non-destructively and non-contactly measuring the thickness of an object at several points using one isotope radiation source and a plurality of radiation detectors, and more particularly, having one isotope radiation source at a single point, The ion current detector for detecting radiation emitted from the radiation source and passing through the object is provided for each of a plurality of measurement points, and the minimum current value required for the radiation detection even in the ion chamber detector, which is located far from the radiation source and has a relatively low amount of incident radiation. By setting the type, volume or pressure of the filling gas differently according to the position of the ion-containing detector so that the above current signal is output, the amount of single radiation source required is improved to improve the safety of the use of the radiation and at the same time, the cost of maintenance and repair of the radiation source. To save money It relates to the measurement apparatus and method.

In order to measure the thickness of an object in a non-contact or non-destructive manner, a method of irradiating radiation from an isotope toward the object and then detecting and measuring the radiation transmitted through the object by a radiation detector has been widely used.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the structure of the thickness measuring apparatus using the conventional isotope radiation source.

As shown in FIG. 1, a conventional thickness measuring apparatus for measuring the thickness of an object by using an isotope radiation source installed at one point is provided with a radiation source 10 including a radioisotope, and a radiation source ( 10 is a radiation detector 20 which detects radiation passing through the inlet of the isotope container 10 and passes through the measuring object 5, and is conveyed through the roller 6 provided in the production line. The thickness of the object 5 can be measured continuously at a specific point. Here, the isotope is regarded as a radiation source that emits radiation at one point, that is, a point source, and the intensity of the radiation emitted from and transmitted through the object decreases at a predetermined rate according to the thickness of the object.

In general, X-rays or gamma rays are used when the object is thick, such as steel, and beta rays are used when the object is relatively thin, such as paper or fiber. The type and amount of suitable isotopes that can emit radiation should be selected.

As a radiation detector, various types of detectors capable of measuring the dose of radiation transmitted through an object may be used. A type of radiation detector mainly used in a thickness measuring device may be an ion-containing detector containing gas therein. have. When radiation is incident on the iontophore detector, the gas inside the detector is ionized, and the cations and electrons generated therefrom form a current by the applied voltage. Therefore, by measuring the amount of current output from the ion-containing detector it is possible to measure the radiation intensity proportional to it.

The gas used in the ion-containing detector is generally 1 atmosphere of air, and the radiation response current signal of the detector should be about 10 times or more than the leakage current, which is the noise signal of the detector, for accurate radiation measurement. Since the leakage current of a typical ion-box detector does not exceed several tens of femtoamps (fA), the current signal output from the detector should be at least 1 picoamp (pA), which requires the amount of radioisotope and the distance between the isotope and the detector. Must be set appropriately to ensure sufficient radiation dose to reach the iontophor detector.

In terms of safety and cost, it is desirable to minimize the amount of radioactive isotopes. Therefore, the distance between the isotope and the ion-containing detector is minimized as much as possible, and the current signal value of the desired size can be obtained from the ion-box detector filled with 1 atmosphere of air. Set the amount of radioactive isotopes to be obtained. In this way, when the amount of radioisotope and the distance between the isotope and the detector are set, the measured value change of the current value is recorded while transferring the thickness measurement object, and the thickness of the material being produced is used as the basic data. It can be measured at a fixed point.

When using a conventional thickness measuring device to measure the thickness of a wide area product such as paper, steel or fiber immediately in the production process, the thickness of the product is measured in the width direction instead of only one point. It is necessary to check at several points simultaneously to ensure that an even thickness distribution is maintained throughout.

2 is a view showing the configuration of a conventional thickness measuring apparatus for simultaneously measuring the thickness for each location using an isotope radiation source installed at several points.

Conventionally, as shown in FIG. 2, isotope radiation sources 11, 12, 13 and iontophor detectors of the same specification on the upper and lower portions of the respective points along the width direction of the product 5 to be measured. Using a thickness measuring device provided with (21, 22, 23), respectively, a method of analyzing the signals output from the radiation detectors (21, 22, 23) to obtain the thickness distribution for each point is mainly used.

However, since the number of isotope radiation sources increases according to the number of measuring points in the conventional measuring method, the cost of purchasing and replacing the radiation source increases, and it is difficult to efficiently manage the isotopes, thereby exposing workers to radiation. There is a problem that the risk of safety increases, such as the risk of becoming higher.

The present invention solves the problems of the prior art described above. That is, an object of the present invention is to include one isotope radiation source at a single point, and each ion point detector for detecting the radiation that has passed through an object, for each measurement point, and the radiation dose incident by being located far from the radiation source By setting the type, volume or pressure of the gas filled inside the detector according to the position of each ion chamber detector so that even the ion chamber detector that is insufficient is outputted the minimum current value required for the radiation detection, It is to minimize the amount, thereby further improving the safety and economics of using radiation.

The present invention as a technical idea for achieving the above object, and a single radiation source for irradiating radiation to the object side; And a plurality of ion-box detectors disposed between a plurality of measurement points on opposite sides of the radiation source and detecting radiation passing from the radiation source and passing through the object, with the object interposed therebetween. The detector is set such that the volume or pressure of the gas filled in the interior of the ion chamber detector located at a relatively distance from the radiation source is greater than the volume or pressure of the gas filled in the interior of the ion chamber detector located at a close distance from the radiation source. It provides a thickness measuring device using a single point isotope radiation source characterized in that the configuration.
The present invention is a single radiation source for irradiating radiation to the object side; And a plurality of ion-box detectors disposed between a plurality of measurement points on opposite sides of the radiation source and detecting radiation passing from the radiation source and passing through the object, with the object interposed therebetween. The detector is characterized in that a gas filled in the interior of an iontophor detector located relatively far from the radiation source has a higher density and less ionization energy than a gas filled in the interior of the iontophor detector located close to the radiation source. Provided is a multi-faceted thickness measurement apparatus using a single point isotope radiation source.

In the present invention, in setting the volume or pressure of a gas filled in a plurality of ion box detectors, the volume or pressure of a gas filled in an inside of an ion box detector located at a relatively long distance from the radiation source is determined by a distance close to the radiation source. It provides a multi-sided thickness measurement method using a single point isotope radiation source, characterized in that it is set larger than the volume or pressure of the gas filled in the inside of the ion box detector located at.
According to the present invention, in setting the type of gas filled inside a plurality of ion box detectors, the gas filled inside the ion box detector located relatively far from the radiation source is the It provides a multi-faceted thickness measurement method using a single point isotope radiation source, characterized in that the density is set higher than the gas filled therein and the ionization energy is smaller.

Thickness measuring apparatus and method using a single point isotope radiation source according to the present invention, by using only one radiation source with the minimum amount of isotope can be efficiently measured the thickness of the object at several points, thereby improving the safety of the use of radiation At the same time, the cost of purchasing, maintaining, and repairing a radiation source can be reduced.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a view showing the configuration of a large area thickness measuring apparatus according to an embodiment of the present invention, Figure 4 is a cross-sectional view showing the internal structure of the ion box detector shown in FIG.

The present invention is an apparatus for simultaneously measuring the thickness of the object at several points using an isotope radiation source provided at a single point, as shown in Figure 3, a single radiation source 110 for irradiating the radiation to the measurement object side, and the object And a plurality of ion box detectors 121, 122, 123 disposed at a plurality of measurement points opposite to the radiation source 110, respectively, for detecting radiation emitted from the radiation source 110 and passing through the object. It is composed.

Ion box detectors 121, 122, 123 correspond to a single radiation source 110 so that the thickness of the measurement object conveyed in the longitudinal direction along the production line can be measured along various points in the width direction at a specific position in the longitudinal direction. A plurality of products are installed in the width direction of the product. The radiation incident surfaces of the ion chamber detectors 121, 122, and 123 are perpendicular to the direction of the incident radiation, thereby increasing the amount of incident radiation as much as possible, thereby increasing the amount of incident radiation. It is desirable to increase the detection efficiency. Looking at the structure of the ion chamber detector (121, 122, 123), as shown in Figure 4, the upper opening is closed by the radiation incident window 130 made of mylar (mylar) to receive the gas therein ( 125 and an insulator 150 that insulates the signal electrode 140 and the signal electrode 140 provided inside the housing 125 from the housing 125. When the gas is filled in the ion chamber detectors 121, 122, and 123, and a voltage of about 500V is applied, gas and electrons ionized by the incident radiation are collected through the signal electrode and current flows. The thickness of the object through which radiation is transmitted can be measured.

As described above, since the present invention is configured to measure thickness at various positions in the width direction of the object by using only a single radiation source, the number of radiation sources can be reduced as compared with the case where a plurality of radiation sources are provided to correspond to each ion chamber detector. .

However, when using only a single radiation source 110 as in the present invention, the distance between the ion chamber detector 121, 122, 123 and the radiation source 110 is different from each other, to measure the thickness of the center of the measurement object The distance between the ion chamber detector 122 and the ion chamber detectors 121 and 123 for measuring the thickness of the edge portion of the measurement object with the radiation source 110 becomes larger as the width of the measurement object is wider.

Therefore, in order to output a current signal above the minimum current value capable of measuring radiation at each ion box detector 121, 122, and 123 without the influence of a noise signal, it is located farthest from the radiation source 110 and irradiated from a single radiation source. The amount of radiation source 110, i.e., the amount of radioactive isotopes, should be set so that the ion signal detectors 121 and 123 having the least amount of radiation can be outputted.

Since the radiation dose at a specific location is inversely proportional to the square of the distance from the radiation source 110, the distance between the radiation source 110 and the radiation source 110 is such that a current signal greater than or equal to the minimum current value is output from the ionization detector farthest from the radiation source 110. A larger amount of radiation source is required compared to the amount of radiation source for outputting the current signal of the minimum current value at the nearest ion-containing detector.

As such, in order to measure the thickness at several points in the width direction of the object, the amount of radioisotopes required is increased as compared to the case where the thickness is measured at only one point, thereby increasing the shielding facility for the increased radiation source 110. The need for more increases manufacturing and maintenance costs while reducing efficiency in terms of safety in management.

Thus, in the present invention, instead of increasing the amount of radioactive isotopes, the type, volume, or pressure of the packed gas contained in the ion-containing detectors 121, 122, 123 is ionized. By setting different distances according to the distance between the terminals, the amount of radioisotope required can be minimized by adjusting the current signal output from each detector to be above the minimum current value.

The magnitude of the current generated as the gas filled in the ion-containing detectors 121, 122, and 123 is ionized by the incident radiation depends on the type of gas, and in the case of the same gas, it is proportional to the volume and pressure of the gas. To increase. Therefore, the same type of filling gas is used for each of the ion box detectors 121, 122, and 123, and the volume or pressure of the gas filled as the position of the ion box detectors 121, 122, and 123 moves away from the radiation source 110. By further increasing, it is possible to satisfy the minimum current value required for each iontophor detector 121, 122, 123 without increasing the amount of isotopes.

On the other hand, if the volume and pressure of the filling gas are set to the same for each of the ionization detectors 121, 122, and 123, the magnitude of the output current signal is changed according to the type of the filling gas, which is the density and ionization of the filling gas. Energy, etc., the denser the filling gas and the smaller the ionization energy, the larger the current signal for the same amount of radiation. Gases that generate a larger current signal than air commonly used in the ion ion detector include xenon (Xe) and argon (Ar), and the density and ionization energy of air, argon and xenon are shown in Table 1 below.

Gas type Density (g / cm ³ ) Ionization energy (eV) air 0.001205 35.1 argon 0.001662 26.3 Xenon 0.005485 21.9

The magnitude of the current signal for each gas type has a larger value in the order of xeno, argon, and air, in the order of high density and low ionization energy, as shown in Table 1 above.

Therefore, as the positions of the iontophoresis detectors 121, 122, and 123 move away from the radiation source 110, ions placed farther from the radiation source 110 are filled with a gas of a higher density and smaller ionization energy to the detector. This can increase the magnitude of the current signal in the detector. For example, the detector closest to the radiation source can be filled with air used in a typical ionic box, argon for the farthest detector, and xenon for the farthest detector to minimize the amount of isotope required. Can be.

In addition, the current signal output from each detector may be equal to or greater than the minimum current value by changing the volume or pressure along with the type of filling gas.

FIG. 5 is a diagram illustrating an arrangement structure of the ion chamber detector illustrated in FIG. 3.

Hereinafter, a result of simulating the change of the current signal value according to the type and pressure change of the filling gas for the ion chamber detectors 121, 122, and 123 arranged as shown in FIG. 5 will be described.

Simulation was performed using a Monte Carlo code called MCNPX, the radiation source 110 was assumed to be 0.4 MeV beta-line, the measurement target material (5) was set to PVP (Poly Vinyl Pyrrolidone) having a constant thickness of 0.5 mm. In addition, the distance between the detector A 122 located at the center and the radiation source is set to 9 cm, and the distance between the detectors B 121 and 123 and the radiation source is set to 12.5 cm. The detectors A 122 and B (121, 123) The distance between the entrance window centers was set to 9 cm.

The simulation results assuming that the filling gas of the detector A 122 is 1 atm of air, and it can be seen that a radiation source of 71 μCi is required to generate a current signal of 1 pA, which is the minimum signal level of the detector. When the detectors B 121 and 123 are filled with 1 atm of air as in A 122, a current signal of 0.2 pA is generated when the radiation source is the same intensity. Since this does not reach the minimum current value of 1 pA, the gas type and pressure of the detector B can be changed to generate a current signal of 1 pA. As a result of the simulation, when the detector B (121, 123) is filled with 9 atm of air, 1 pA is filled with 6 atm of argon and 1.1 pA is filled with 2 atm of xenon. Satisfied.

As such, when the type and pressure of the gas filled in the detector are set appropriately according to the positions of the respective ion chamber detectors 121, 122, and 123, the current signal values output from all the ion chamber detectors 121, 122, and 123 are determined. The amount of radiation source 110 required can be minimized while satisfying to be equal to or greater than the minimum current value. In addition, the pressure of the packed gas remains the same, and the ion chamber detectors 121, 122, and 123 are changed as in the case where the pressure is changed even when the volume of the gas is changed by changing the sizes of the ion chamber detectors 121, 122, and 123. ) Could satisfy the minimum current value condition.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible in the art without departing from the technical spirit of the present invention. It will be clear to those of ordinary knowledge.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows the structure of the thickness measuring apparatus using the conventional isotope radiation source.

2 is a view showing the configuration of a conventional thickness measuring apparatus for simultaneously measuring the thickness of each location using an isotope radiation source installed at several points.

3 is a view showing the configuration of a large area thickness measuring apparatus according to an embodiment of the present invention.

4 is a cross-sectional view showing the internal structure of the ion chamber detector shown in FIG.

FIG. 5 is a view showing a layout structure of the ion box detector shown in FIG. 3. FIG.

<Explanation of symbols for the main parts of the drawings>

5: measuring object

10, 11, 12, 13, 110: radiation source

20, 21, 22, 23, 121, 122, 123: ion box detector

125: housing

130: radiation incident window

140: signal electrode

Claims (5)

A device that measures the thickness of an object simultaneously at several points using an isotope radiation source. A single radiation source for irradiating radiation to the object side; A plurality of ion-box detectors disposed at a plurality of measurement points on opposite sides of the radiation source with the object interposed therebetween, for detecting radiation emitted from the radiation source and passing through the object; Consists of including The plurality of ion box detector, The volume or pressure of the gas filled in the interior of the ion chamber detector located at a relatively long distance from the radiation source is set to be greater than the volume or the pressure of the gas filled in the interior of the ion chamber detector located at a distance from the radiation source measuring the thickness using a single multi-faceted point isotope radiation source, characterized in that. A device that measures the thickness of an object simultaneously at several points using an isotope radiation source. A single radiation source for irradiating radiation to the object side; A plurality of ion-box detectors disposed at a plurality of measurement points on opposite sides of the radiation source with the object interposed therebetween, for detecting radiation emitted from the radiation source and passing through the object; Consists of including The plurality of ion box detector, A gas filled in the interior of the ion chamber detector located relatively far from the radiation source has a higher density and less ionization energy than a gas filled in the interior of the ion chamber detector located close to the radiation source Multi-sided thickness measurement apparatus using a point isotope radiation source. The method according to claim 1 or 2, Each of the plurality of ion box detectors, And a radiation incident surface of the iontophor detector is installed so as to be perpendicular to the direction of radiation incident through the object from the radiation source. In a method for measuring the thickness of an object at the same time using a single radiation source provided at a single point and a plurality of ion-box detectors arranged for each measurement point, In setting the volume or pressure of the gas filled in the interior of the plurality of ion box detectors, the ion or the volume of the gas filled in the interior of the ion box detector located at a relatively long distance from the radiation source Method for measuring the multi-area thickness using a single point isotope radiation source, characterized in that it is set larger than the volume or pressure of the gas filled inside the detector. In a method for measuring the thickness of an object at the same time using a single radiation source provided at a single point and a plurality of ion-box detectors arranged for each measurement point, In setting the type of gas filled in the plurality of ion box detectors, the gas filled inside the ion box detector located relatively far from the radiation source is filled inside the ion box detector located close to the radiation source. A method for measuring thickness of a multifaceted area using a single point isotope radiation source, characterized in that it is set to have a higher density and smaller ionization energy than a gas to be used.

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