KR102062450B1 - A radiation detecting device usnig multi-photo-diode and a radiation detecting method usnig multi-photo-diode - Google Patents

Abstract

The present invention relates to a radiation measuring apparatus using multiple photodiodes and a radiation measuring method using multiple photodiodes, and more particularly, in a photodiode radiation detector using a point where a specific phosphor emits light in response to radiation, Combine large photodiodes that respond well to energy with small photoresists that respond well to low energy, set sensitivity individually for each photodiode to respond to specific energy, and read fluorescence measurements on each photodiode The present invention relates to a radiation measuring apparatus using multiple photodiodes and a radiation measuring method using multiple photodiodes to enable the detection of radiation components of various energies.
According to the present invention, various radiation energies such as alpha rays, beta rays, gamma rays, X-rays, neutrons, etc. existing in the natural world can be measured by a single semiconductor sensor, and nuclide analysis according to the energy of radiation is possible. Since the mass production of is possible, the production price is lowered, and the spread of the radiation detector is spread, and there is an effect that can contribute to creating a safe society.

Description

Radiation measuring apparatus using multiple photodiodes and radiation measuring method using multiple photodiodes {A RADIATION DETECTING DEVICE USNIG MULTI-PHOTO-DIODE AND A RADIATION DETECTING METHOD USNIG MULTI-PHOTO-DIODE}

The present invention relates to a radiation measuring apparatus using multiple photodiodes and a radiation measuring method using multiple photodiodes, and more particularly, in a photodiode radiation detector using a point where a specific phosphor emits light in response to radiation, Combine large photodiodes that respond well to energy with small photoresists that respond well to low energy, set sensitivity individually for each photodiode to respond to specific energy, and read fluorescence measurements on each photodiode The present invention relates to a radiation measuring apparatus using multiple photodiodes and a radiation measuring method using multiple photodiodes to enable the detection of radiation components of various energies.

Radiation sensors are classified into sensors using gas ionization, sensors using solid ionization, and sensors using excitation.

The gas ionization sensor is also divided into ion chabmer, proportional counter, and GM muller counter according to the ionization method, and the solid-state ionization semiconductor sensor is a PN junction and surface barrier. Are divided into types.

Gas-type detectors using gas ionization are the longest used and are still widely used radiation detection methods. This is based on the effect that occurs when charged particles pass through the gas. The gas detector configured in the form of a cylinder has an anode connected to the center and a cylinder wall connected to the cathode. When radiation enters the detection sensor, the gas is ionized to produce electrons and cations, ie ion pairs. At this time, the cation of the detector moves to the cathode, and the electron moves to the anode. As electrons and cations are collected on the electrode, current flows and the radiation is detected by measuring the current. The higher the level of radiation incident on the sensor, the more current flows.

The gas detector using the gas ionization is further divided according to the effect of voltage application and ion saturation. The ion chamber type, which measures only the charge of the first ion pair at a low voltage, is applied by applying a higher voltage. It is divided into proportional counter system using gas multiplication through ion saturation zone where pair recombination is suppressed, and finally GM counter using nonlinear effect by applying a higher voltage than proportional counter system.

Solid state ionization type semiconductor sensor has a high density of solids compared to gas density, so solid state detectors can be designed smaller than gas detectors having the same characteristics when measuring high energy electrons and gamma rays. However, since the semiconductor detector always has a small amount of current flowing through the semiconductor detector due to thermal excitation, it should be cooled with liquid nitrogen.

In semiconductor sensors, when electrons in the valence band move to the conduction band, vacancies called holes are created in the valence band, which produces a positron effect. The energy required to create electron and hole pairs in semiconductors is 2.9 eV to 3.6 eV, which is considerably smaller than gas 30 eV, so that many information carriers are generated for radiation with the same energy. Therefore, the energy resolution of incident radiation is excellent. In addition, because of the high density, radiation detection efficiency is also excellent.

The excitation sensor is a method of detecting radiation ionized by fluorescence generated from a specific kind of material. When the energy of the radiation is absorbed, the electrons in the valence band are excited to conduction bands, and then transition back to emit visible light. It is a sensor that uses a substance, or a scintillator. Depending on the fluorescent material used, it is divided into solid, liquid, gas or organic, inorganic and the like. This type of excitation sensor is required to amplify the output signal using a light multiplier tube because the amount of visible light emitted as the energy of the radiation absorbed by the fluorescent material is extremely small. Therefore, the energy resolution is lower than that of the semiconductor detector.

Each of the three existing technologies mentioned above has different advantages and disadvantages. First of all, sensors using gas ionization have the advantage of distinguishing nuclides due to their high energy decomposability except GM counter. There is a disadvantage in that the size increases. The semiconductor method, which is a solid ionization method, can be manufactured in a relatively small size, but has a disadvantage of cooling with liquid nitrogen due to heat excitation.

Lastly, sensors based on phosphors can be used for various applications depending on the type of phosphor. However, due to the effects of optical amplifiers, which are used because the fluorescence itself is too weak, resolution of energy is difficult to distinguish the nuclides.

There is a thermofluorescence dosimeter (TLD), which is widely used as a statutory personal dosimeter in hospitals. The thermofluorescence dosimeter uses light through a phosphor, similar to the excitation phosphor. In addition, the radiation type can be distinguished, the measurement range is wide, and the sealing is good, so that the degeneration phenomenon can be almost eliminated. However, it has to be sent to a separate facility to generate light to be detected while heating. The disadvantage is that such detection is possible only days or months after exposure to radiation.

Among such various types of radiation sensors, the radiation detector of the phosphor type will be described in detail.

1 is a conceptual diagram showing the structure of a radiation measuring apparatus using a photodiode, Figure 2 is a block diagram showing the internal structure of the radiation measuring apparatus of FIG.

Referring to FIG. 1, radiation having a specific energy strikes the phosphor 11 and emits light. The photodiode 12 measures this light to detect radiation. In this case, it is common to design and manufacture a material and a size of the photodiode 12 and the phosphor 11 to fit the energy of the radiation source to be measured and the purpose of the measurement. For example, it is suitable to use Nal (TI) (Thallium-doped sodium iodide) phosphor to detect gamma radiation of Cs-137 with energy of 662keV.

The size of the photodiode 12 depends on the amount and purpose of the radiation to be measured, which means that large diodes do not have a fast reaction time, but are advantageous for distinguishing nuclides, have a large energy, and are suitable for detecting low radiation doses. Because. And small diodes have a fast reaction time, low energy, and are suitable for detecting high radiation doses. This is because small diodes can be quickly charged and discharged, allowing for fast response, but are difficult to measure because they quickly saturate for high energy radiation. Therefore, in general, radiation sensors designed for the radiation energy band and the purpose of use to be measured are generally used only for the purpose. Therefore, radiation sensors of various sizes and materials suitable for various radiation energy bands and measurement purposes are required.

In the measuring device using the photodiode, when light generated from the phosphor 11 by radiation reaches the photodiode 12, the output signal of the photodiode 12 is changed to generate a fine waveform. When such a fine signal is amplified through the amplifier 13a inside the detector 13, the waveform is increased in a form that is easier to analyze.

The output waveform of the amplifier 13a is compared with the desired set value and digitized. For example, if the output waveform of the amplifier 13a and the value set to ref1, ref2, or ref3 are digitized through the comparators 13c-1, 13c-2, and 13c-3, a voltage smaller than ref1 is equal to the first comparator 13c-. In 1), a voltage greater than ref1 may be digitized to 1 in the first comparator 13c-1 (211).

In addition, the second comparator 13c-2 digitizes a voltage smaller than ref2 to 0 and a voltage greater than ref2 to 1, and the third comparator 13c-3 converts a voltage smaller than ref3 to 0 and a voltage greater than ref3. Digitize to 1

If the digital output is continuously measured for a certain period, it is possible to quantify how many times 1 occurs through the counters 13d-1 13d-2 and 13d-3.

Radiation often has secondary energy waveforms depending on the radiation source. To analyze these secondary waveforms, two or more comparators are required. For example, Co-60, a type of gamma ray, has a primary energy peak of 1173 keV and a secondary energy peak of 1332 keV. Therefore, two or more comparators are required to simultaneously detect and compare the energy of the primary and secondary. In the last step, the final digital sensing data may be generated by passing through the multiplexer 13e to sum the outputs of the counters 13d-1 13d-2 and 13d-3.

In order to implement such a semiconductor measuring device into a real product, some core technology is required. First, the photodiode 12 should be designed to be able to recognize at low light in order to accommodate light as much as possible, and it is also necessary to design the photodiode 12 to block ambient light to ensure detection of only a pure light signal. The detector 13 amplifies a very small signal to a level that is easy to handle. In this case, it is important to amplify only a pure signal as much as possible while eliminating noise, and also to linearly amplify constant in a low voltage band and a high voltage band. Linearity is also important.

Since the comparators 13c-1, 13c-2, 13c-3, the counters 13d-1, 13d-2, 13d-3, and the multiplexer 13e are digital circuits, the photodiode 12 and the amplifier (the analog circuit) It is important to design to minimize noise generation that affects 13a).

As described above, the conventional technique uses a circuit for detecting and comparing signals using one phosphor 11, a photodiode 12, and a detector 13 to detect radiation. This method has been used for a long time and is evaluated stably, but since it cannot be used for all radiation bands with various energies, it is used as a sensor specialized to respond only to a specific radiation band. Therefore, beta rays, gamma rays, medical X-rays, industrial X-rays, There is no sensor that can be commonly used in various energy bands such as Neutron.

In other words, it is difficult to use a radioactive sensor manufactured for the detection of strong X-ray radiation for medical use in the detection of low level radiation such as natural radiation. It is difficult.

In addition, a phenomenon in which the capacitance of the diode increases in proportion to the size of the photodiode 12, which causes a thermal noise to increase in proportion, resulting in a proportionally higher radiation detection energy band. do.

In addition, the time that the charge moves in proportion to the size of the photodiode 12 is increased proportionally, because the reaction delay time is increased proportionally, the problem that the detection of high-level radiation that requires a quick response as the diode increases Occurs.

Therefore, the use of a single size photodiode limits the energy band that can be detected, and it is impossible to make a general-purpose radiation sensor capable of detecting all the various radiations in nature.

KR 10-1648395 B1

In order to solve the above problems, the present invention combines a large number of large photodiodes and small photodiodes that respond well to high energy on a single silicon wafer, and for each diode, an amplifier, a comparator and a counter And a means for detecting radiation, and for setting the sensitivity individually to respond to a specific energy for each photodiode and integrating and analyzing the radiation values individually detected in each photodiode An object of the present invention is to provide a radiation measuring apparatus using a diode and a radiation measuring method using multiple photodiodes.

In addition, when analyzing the integrated signal of the photodiode, the radiation measuring device using multiple photodiodes and the radiation measurement using multiple photodiodes to detect more accurate radiation dose by judging the error and failure of individual photodiodes together It is an object to provide a method.

The present invention devised to solve the above problems is a radiation measuring device to improve the radiation detection efficiency by combining multiple sizes of photodiodes 120 of different sizes, the phosphor 110 that emits light according to the input of radiation Wow; A photodiode 120 for converting light generated from the phosphor 110 into an electrical signal; And a detector 130 that analyzes an electrical signal transmitted from the photodiode 120 and calculates information for identifying a radiation dose and a nuclide. The photodiode 120 includes a first relatively large size. It is characterized by consisting of a photodiode 121 and a second photodiode 122 having a relatively small size.

According to another embodiment of the present invention, there is provided a radiation measuring device for improving radiation detection efficiency by combining multiple sizes of photodiodes 120 of different sizes, comprising: a phosphor 110 emitting light according to an input of radiation; A photodiode 120 for converting light generated from the phosphor 110 into an electrical signal; And a detector 130 that analyzes an electrical signal transmitted from the photodiode 120 and calculates information for identifying a radiation dose and a nuclide. The photodiode 120 includes a first relatively large size. The photodiode 121, the second photodiode 122 having a smaller size than the first photodiode 121, and the third photodiode 123 having a smaller size than the second photodiode 122. It characterized by consisting of).

The detector 130 may include a first detector 131 that receives an electrical signal transmitted from the first photodiode 121, and a second receiver that receives an electrical signal transmitted from the second photodiode 122. The first detector 131 includes a first amplifier 131a, a first divider 131b, a 1-1 comparator 131c, a 1-2 comparator 131d, and a first detector 131a. It consists of a -1 counter (131e), 1-2 counter (131f), the first multiplexer (131g), the second detector 132 is a second amplifier 132a, a second divider (132b), a second And a -1 comparator 132c, a 2-2 comparator 132d, a 2-1 counter 132e, a 2-2 counter 132f, and a second multiplexer 132g.

The detector 130 may include a first detector 131 that receives an electrical signal transmitted from the first photodiode 121, and a second receiver that receives an electrical signal transmitted from the second photodiode 122. The detector 132 and the third detector 133 for receiving an electrical signal transmitted from the third photodiode 123, the first detector 131 is the first amplifier 131a, the first It consists of a dispenser 131b, a 1-1 comparator 131c, a 1-2 comparator 131d, a 1-1 counter 131e, a 1-2 counter 131f, and a first multiplexer 131g. The second detector 132 may include a second amplifier 132a, a second divider 132b, a 2-1 comparator 132c, a 2-2 comparator 132d, a 2-1 counter 132e, It consists of a 2-2 counter 132f, a second multiplexer (132g), the third detector 133 is a third amplifier 133a, a third divider 133b, a 3-1 comparator 133c, It consists of a 3-2 comparator 133d, a 3-1 counter 133e, a 3-2 counter 133f, and a third multiplexer 133g. It is characterized by losing.

The gain setting value of the first amplifier 131a included in the first detector 131 and the gain setting value of the second amplifier 132a included in the second detector 132 are different from each other. The comparator set values of the first-first comparator 131c and the first-second comparator 131d and the second-first detector 132 included in the second detector 132 are included in the first detector 131. The comparator 132c and the comparator set values of the second-comparator 132d are different from each other.

As a method of measuring radiation having a plurality of energies by using the above-described radiation measuring apparatus 100, light generated when radiation is input to the phosphor 110 included in the radiation measuring apparatus 100 includes a photodiode ( A first step detected by 120; A second step of the detector 130 classifying and measuring the intensity of light detected by the multiple photodiodes 120 having different sizes; A third step of generating, by the detector 130, a measurement value for each region detected by the multiple photodiode 120; A fourth step of the radiographic analysis device (150) calculating a deviation and a sum of the deviations of the measured values for each area transmitted from the detection unit (130); And a fifth step of the radiographic analysis device 150 determining the nuclide that emits the radiation from the deviation and the sum of the deviations.

The radiographic apparatus 150 compares the measured values for each of the plurality of nuclides with each other, calculates the deviation and the sum of the deviations for the measured values for the regions, and selects the nuclides having the smallest sum of the deviations. It is characterized by determining the radionuclide that emitted the radiation.

According to the present invention, various radiation energies such as alpha rays, beta rays, gamma rays, X-rays, neutrons, etc. existing in the natural world can be measured by a single semiconductor sensor, and nuclide analysis according to the energy of radiation is possible. Since the mass production of is possible, the production price is lowered, and the spread of the radiation detector is spread, and there is an effect that can contribute to creating a safe society.

1 is a conceptual diagram showing the structure of a radiation measuring apparatus using a photodiode.
2 is a block diagram showing the internal structure of the radiation measuring apparatus of FIG.
Figure 3 is a perspective view showing the structure of a radiation measuring apparatus according to an embodiment of the present invention.
4 is a plan view showing an example of the arrangement of multiple photodiodes;
5 is a block diagram showing the structure of a photodiode and a detector arranged in multiple.
6A to 6C are block diagrams illustrating the internal structure of the first to third detection units.
7 is a conceptual diagram illustrating a method of measuring radiation using a photodiode having the same gain setting value.
8 is a conceptual diagram illustrating a method of measuring radiation using a photodiode with two gain settings.
9 is a conceptual diagram illustrating a method of measuring radiation using a photodiode with four gain settings.
10 is a conceptual diagram illustrating a method of measuring radiation using a photodiode with two gain settings and two comparator settings.
FIG. 11 is a conceptual diagram illustrating a method of detecting a bad device using a photodiode having the same comparator set value. FIG.
12 is a conceptual diagram illustrating a method of detecting a bad device using a photodiode having different comparator settings.
Fig. 13 is a plan view showing a state in which serial numbers are attached to multiple photodiodes;
14 is a conceptual diagram illustrating a method of calculating the radiation dose measured in each photodiode.
Fig. 15 is a table showing the nuclide type energy and the set value.
FIG. 16 is a flowchart illustrating a process of finding radionuclides using multiple photodiodes. FIG.

Hereinafter, a "radiation measuring apparatus using multiple photodiodes and a radiation measuring method using multiple photodiodes" according to an embodiment of the present invention will be described with reference to the drawings.

3 is a perspective view showing the structure of a radiation measuring apparatus according to an embodiment of the present invention, Figure 4 is a plan view showing an example of the arrangement of multiple photodiodes, Figure 5 is a block showing the structure of the photodiode and the detection unit arranged in multiple 6A to 6C are block diagrams illustrating the internal structure of the first to third detection units.

Thermal Noise is an irregular movement according to the heat of electrons inside a conductor, that is, noise from inside due to heat disturbance. This noise is present in all types of electronic equipment, and its magnitude is proportional to the absolute temperature and has a uniform power spectrum for all ranges of frequencies.

Thermal noise is also called white noise (white noise) because it has a frequency spectrum like white light, and it is also called Johnson Noise after the person who identified this phenomenon.

Since this noise is called random noise because the pattern is random, it must be designed in consideration of the noise because it can not be removed from the electronic equipment. Silicon semiconductors must also consider this thermal noise. Diodes, which are silicon semiconductors, have a large capacitance in proportion to their area. Thermal noise also increases in proportion to the capacitance of the semiconductor, and the noise Q _n due to the capacitance of the semiconductor sensor is called reset noise and is represented by Equation 1 below.

Where k _B is Boltzmann's constant in joules per kelvin, T is absolute temperature and C is capacitance. Reset noise is sometimes referred to as kTC noise in the form of an equation.

In Equation 1, it can be seen that as the capacitance C of the semiconductor increases, kTC noise also increases. In general, semiconductors of silicon devices have a capacitance of 0.01 fF per 1 μm ² area. From Equation 2 below, it can be seen that a silicon semiconductor having an area of 1 cm 2 corresponds to a capacitance of 1 nF.

As described above, as the area of the silicon semiconductor increases, the capacitance increases, so that the diffusion time of the charge increases accordingly. For example, in silicon semiconductors, the charge diffusion time would be 50ms to 100ms at 10mm intervals.

In designing a semiconductor sensor, the capacitance increase and charge diffusion time change according to the size of the diode, and the characteristics of the radiation detection change accordingly.

Since the radiation detection characteristics vary depending on the size of the diodes, multiple diodes of different sizes can be placed on one sensor to create a semiconductor radiation measuring device with more stable characteristics that can compensate for the advantages and disadvantages of each diode. have.

As shown in FIG. 3, the "radiation measuring apparatus using multiple photodiodes" (hereinafter, referred to as "radiation measuring apparatus") according to an embodiment of the present invention is the same as the apparatus according to the prior art according to the input of radiation Phosphor 110 for emitting light, photodiode 120 for converting light generated from the phosphor 110 into an electrical signal, and analyzing the electrical signal transmitted from the photodiode 120 to determine the amount of radiation and nuclides, etc. Radiation analysis to analyze the radiation dose and nuclide using the detection unit 130, the communication cable 140 for transmitting data from the detection unit 130, the measured value transmitted through the communication cable 140 to calculate the information for Device 150.

In the present invention, the photodiode 120 for converting the light generated from the phosphor 110 into an electrical signal is configured not in one size but in multiples to enable detection of an optimized optical signal for each size. Photodiode 120 is composed of a combination of a plurality of diodes, it is possible to measure the radiation of various energy by varying the size and detection performance of the individual diodes.

More specifically, as shown in FIG. 4, the radiation measuring apparatus 100 is configured by combining the pixel having the largest area, the pixel of the middle size, and the pixel of the smallest size. What constitutes the largest pixel is called the first photodiode 121, the intermediate size is defined as the second photodiode 122, and the smallest size is defined as the third photodiode 123. In the present invention, the use of three sizes of diodes is described as a representative embodiment. However, in some cases, a combination of two or four or more diodes may be configured.

Each pixel is composed of a photodiode 120 for detecting radiation in one pixel and a leader-out circuit that is a signal processing circuit capable of amplifying and distinguishing a signal of the photodiode 120. The leader-out circuit is a signal processing circuit including all of the amplifier, the comparator, the counter, and the multiplexer shown in FIG. 2, and is a part designated as the detector 130 in the present invention.

The pixel composed of the first photodiode 121 having the largest area has excellent resolution with respect to radiation with high energy and responds well to low-level radiation having a small amount of radiation incident. The pixel consisting of the third photodiode 123 having the smallest area responds well to low energy radiation and rapidly entering large amounts of radiation. And the pixel consisting of the second photodiode 122 having a medium size area also responds well to the intermediate energy band.

The first photodiode 121 to the third photodiode 123 may be arranged in various forms. As shown in the first (a) of FIG. 4, the first photodiode 121 is installed in the center, and 16 second photodiodes 122 are arranged in total of 4 each in the top, bottom, left and right, and 16 in total are disposed therebetween. 64 third photodiodes 123 may be disposed.

More simply, as shown in (b), four second photodiodes 122 may be disposed on the side of the first photodiode 121, and sixteen third photodiodes 123 may be disposed on the side of the first photodiode 121. have. The arrangement of the photodiode 120 may vary depending on the size, use, and sensing performance of the device.

Each photodiode 120 is connected to an individual detector 130. In the present invention, a part connected to the first photodiode 121 and receiving a signal is referred to as a first detector 131, and a part connected to the second photodiode 122 and the third photodiode 123 is respectively made of a first part. It is referred to as a second detector 132 and a third detector 133. The circuits constituting the first detector 131 to the third detector 133 have the same configuration, as described in FIGS. 5 and 6A to 6C.

The first detector 131 includes a first amplifier 131a, a first divider 131b, a 1-1 comparator 131c, a 1-2 comparator 131d, a 1-1 counter 131e, and a first detector 131a. It consists of -2 counter 131f and the 1st multiplexer 131g.

In addition, the second detector 132 may include a second amplifier 132a, a second divider 132b, a 2-1 comparator 132c, a 2-2 comparator 132d, a 2-1 counter 132e, and a second detector 132a. It consists of a 2-2 counter 132f and the 2nd multiplexer 132g.

In addition, the third detector 133 may include a third amplifier 133a, a third divider 133b, a 3-1 comparator 133c, a 3-2 comparator 133d, a 3-1 counter 133e, and a third detector 133a. It consists of a 3-2 counter 133f and a 3rd multiplexer 133g.

In this way, the first photodiode 121, the second photodiode 122, and the third photodiode 123 are constituted in one silicon semiconductor, and the phosphor 110 is attached as necessary to provide high energy radiation. Can be detected. A communication port 134 may be added to collect each pixel signal, integrate it into one sensor data, and provide a single interface to the outside. The communication port 134 is connected to the communication cable 140 as an IO block for data communication, and uses a communication method widely used for communication between semiconductors, such as an SPI communication method, a serial communication method, and an I2C communication method.

Data on the radiation dose output from the first multiplexer 131g, the second multiplexer 132g, and the third multiplexer 133g is transmitted to the radiation analyzer 150 or a separate external system through the communication port 134. It is used to analyze radiation dose or to identify nuclides.

A method of reading radiation in the radiation measuring apparatus 100 made of pixels provided with multiple photodiodes 120 having different sizes will be described with reference to the drawings.

FIG. 7 is a conceptual diagram illustrating a method of measuring radiation by using a photodiode having the same gain setting value. The radiation measuring apparatus 100 including six horizontal pixels, six vertical pixels, and a total of 36 pixels will be described as an example.

When radiation collides with the radiation measuring apparatus 100, light is generated from the phosphor 110 attached to the upper portion, and the photodiode 120 below detects the light. When light is emitted from the phosphor 110, the pixel 201 belonging to the emission region reacts. If the light does not occur, the pixel 203 does not react. Pixel 202 does not react even when light is generated very weakly. The light intensity is proportional to the energy intensity of the radiation, and the size of the light emitting area is also proportional to the energy intensity of the radiation.

For example, the emission area of Co-60 gamma rays with an energy of 1.17 MeV is larger than that of Cs-137 gamma rays with an energy of 662 keV. The emission area of FIG. 7 shows that radiation is detected in 12 pixels (parts marked with X). Each pixel has the photodiode 120 and the detector 130 independently, and the detector 130 includes an amplifier, a comparator, and a counter. Each photodiode 120 and the detector 130 may be set to respond to light of different intensities, but in FIG. 7, it is assumed that all pixels have the same setting value. That is, the amplification degree of the amplifier included in the detector 130 is the same and has the same gain setting value.

Therefore, in the case of using the photodiode 120 and the detector 130 having the same gain setting value, whether or not light emission will be determined according to the size of the light emitting area.

8 is a conceptual diagram illustrating a method of measuring radiation by using a photodiode having two gain setting values.

Differentiating the setting of the detection unit 130 used for each pixel to design a combination of two pixels of high amplification pixels (303 and 304 as hatched squares) and low amplification pixels (301 and 302 as white squares) It will be as shown in FIG.

The amplification degree of the detector 130 is determined according to the gain setting value of the amplifier disposed in front of the circuit. That is, the gain setting values of the first amplifier 131a, the second amplifier 132a, and the third amplifier 133a correspond to the amplification degree of the first detector 131, the second detector 132, and the third detector 133, respectively. Determine. Increasing the gain setting of the amplifier results in pixels 303 and 304 having high amplification, and lowering them into pixels 301 and 302 having low amplification.

In this case, when the same energy is absorbed as in FIG. 7, light emitting regions having the same size will be formed. In this case, the pixel 304 with a high amplification degree amplifies the detection result to a larger width, thereby making the signal stronger. Thus, a signal is detected even when the light is in a weak periphery.

However, since the weak signal is not sufficiently amplified in the low-amplification pixel 301, the signal is not detected when the weak light is detected. The pixel 302 at the center of the light emitting area although the amplification degree is low can detect light because a signal of sufficient intensity is generated even without amplifying the signal.

In FIG. 8, a total of eight pixels are detected, which is small compared to 12 of FIG. 7. However, if the same area is filled with pixels, it can be seen that the radiation measuring apparatus 100 of FIG. 8 can detect radiation of high energy better than that of the radiation measuring apparatus 100 of FIG.

9 is a conceptual diagram illustrating a method of measuring radiation using a photodiode having four kinds of gain setting values.

If the amplifier settings of the pixel are further subdivided, the pixel with the lowest amplification (401 as white), the second lowest amplification pixel (402 and 403 as squares shaded down to the right), and the second highest amplification If the design is a combination of four pixels (a 404 and 405 as a left-hatched square) and a pixel having the highest amplification degree (406 and 407 as a diagonal lattice pattern), it is as shown in FIG.

Again, when the same energy is absorbed as in Fig. 7, the size of the light emitting area is formed the same. However, pixels 402 with the second lowest amplification will not be detected at the periphery where light is weak, while pixels 404 with the second highest amplification will be detected at the periphery. The pixel 406 with the highest amplification is the periphery but detects light. The total number of pixels detected is a total of eight, which is small compared to 12 of FIG. 8 and 9, the number of pixels detected is equal to eight, so the effect of subdividing the gain setting value of the amplifier may not be seen.

10 is a conceptual diagram illustrating a method of measuring radiation using a photodiode having two gain settings and two comparator settings.

The gain setting value of the amplifier of the pixel may be designed as shown in FIG. 10 by setting the gain setting value of the pixel in two stages as shown in FIG. 7 and setting the resolution (comparator set value) of the comparator in two stages. Pixels with low amplification and low comparator settings (501 as white), pixels with high amplification and low comparator settings (502 as squares shaded down to the right), pixels with low amplification and high comparator settings (white with thick borders) 503 and 504 as squares, a combination of four pixels of pixels with high amplification and high comparator settings (505 and 506 as squares shaded down to the right with a thick border). The comparator set point is for setting an energy detection reference and can be set in combination with the gain set point of the amplifier.

The high comparator setting value means that the detector 130 can detect a high intensity light or signal because a high ref value is input to the comparator.

When the phosphor 110 emits light while energy of the same size as in FIG. 7 is absorbed, the size of the emission area will be the same. However, pixels 502 with high gain settings and low comparator settings will be detected at the periphery where light is weak, whereas pixels 504 with low gain settings and high comparator settings will not be detected at the periphery. Pixel 505 with a high gain setting and a high comparator setting detects light at the periphery.

The total number of pixels for which light is detected is nine, which is small compared to the twelve in FIG. 7, but is larger than the eight detected in FIGS. 8 and 9. Even if the radiation is incident with the same energy, the number of detected signals may be set differently by setting the amplifier value and the comparator value of each pixel differently.

In this way, the amplifier value and the comparator value can be set to suit the energy band and radiation dose of the radiation to be detected. For example, assuming that a Co-60 gamma ray having an energy of 1.17 MeV is rapidly detected at 1 mSv, Since it is relatively large, it is better to set the amplifier value low to reduce the noise while ensuring the linearity of the amplifier, and to set the value of the comparator large. On the other hand, assuming that Cs-137 gamma rays with an energy of 662 keV are detected slowly as 20 μSv, it is recommended to set the amplifier value higher so that the signal can be detected more clearly and the comparator value lower to increase the sensitivity. .

FIG. 11 is a conceptual diagram illustrating a method of detecting a defective device using a photodiode having the same comparator set value.

The brightness of the light in the light emitting area is the strongest in the center and weakens toward the periphery. Looking at pixels 601, 602, 603, 604 having the same amplifier value and comparator values, peripheral pixels 601, 604 detect light and central pixel 603 detects light, which is the central pixel 602. If no silver light is detected, this pixel 602 can be determined to be bad. In this way, the neighboring pixels having the same set value can be compared to determine a failure.

12 is a conceptual diagram illustrating a method of detecting a bad device using a photodiode having different comparator settings.

If pixels 703 and 705 having a high comparator set value in the emission area and detectable at the periphery can be detected, pixels 702 and 704 that are more central and have a lower comparator set value should naturally be detected. However, since the center pixel 702 has failed to detect, it can be determined as defective.

If pixels with the same comparator settings are continuous, if a signal is detected on either left or right with respect to one pixel, but not at the center pixel, this is most likely a bad pixel. Therefore, in the present invention, such an area is set to be regarded as a bad pixel.

As such, bad pixels may occur during production, but may also occur at the end of their lifetime during operation. If a bad pixel occurs once, only the pixel can't be repaired, so it must be recognized to ensure correct operation of the measuring device. Most pixel defects in the current production process are grasped and classified as a measurement device. However, there is no radiation sensor that determines and compensates for pixel defects during operation.

Hereinafter, a method of obtaining a radiation dose and determining a nuclide using a radiation measuring apparatus 100 having such a structure and functional characteristics will be described.

FIG. 13 is a plan view illustrating a state in which serial numbers are attached to multiple photodiodes, and FIG. 14 is a conceptual diagram illustrating a method of calculating a radiation dose measured in each photodiode.

Figure 13 shows the area of the radiation measuring apparatus 100 used in the present invention in units of pixels. The structure of FIG. 13 is identical to the structure (b) presented second in FIG. 4.

One area occupied by the first photodiode 121 is called a1. Four regions occupied by the second photodiode 122 are referred to as b1, b2, b3, and b4. The sixteen areas occupied by the third photodiode 123 are called c1 to c16 in order. Each pixel includes a detector 130 for reading a signal of the photodiode.

A signal output from a total of 21 pixels shown in FIG. 13 has a format as shown in FIG. 14. Each pixel has a counter value according to a result of comparing ref1 and ref2 values as shown in FIG. 5. That is, one pixel outputs two comparators. One comparator stores a value in a 16-bit counter. The counter value corresponding to ref1 of a1 pixel is called a1.r1 and the counter value corresponding to ref2 of a1 pixel is called a1.r2.

Similarly, the counter value corresponding to ref1 of the b1 pixel is referred to as b1.r1, and the counter value corresponding to ref2 of the b1 pixel is referred to as b1.r2. You can specify a counter value up to the last pixel, c16 pixels.

The figure below the string in FIG. 14 shows an example. As an example of each counter value, since ref1 has a higher reference point than ref2, it can be seen that the counter value of each pixel also has more values of ref2. As this example shows, the larger the pixel, the smaller the counter value, because the larger the size of the pixel, the smaller the number of reactions per unit pixel, even if the same radiation comes in.

Radiation measuring device 100 is an important function of the radiation rate (dose rate) and nuclide (nuclide). That is, since the main purpose is to measure how much radiation is generated and how much radiation is generated, the process of obtaining the radiation dose will first be described. Each time the radiation is incident, each pixel reacts and the counter value increases. This action is proportional to the area occupied by the pixel per unit area, and the equation for obtaining the radiation dose by the radiation measuring apparatus 100 is expressed by Equation 3 below.

The counter values included in a1, which is the largest pixel region 121, are added together and multiplied by the correction value A. In addition, all the counter values included in b4 are added to b1, which is the middle pixel region 122, and multiplied by the correction value B. Finally, in the smallest pixel region 123 cl, all the counter values included in c16 are added, and the correction value C is multiplied. The sum of these values gives the radiation dose. In this case, correction values A, B, and C for each region may be obtained through Equation 4 below.

For example, the c region 123, which is a small pixel, needs to divide the total area from the unit area occupied by each pixel to know the specific gravity of the area of each pixel, and it is not proportional to the area. The weight of the c region 123 is multiplied by taking into account the response variation according to the dose intensity.

Next, the process for nuclide classification is explained.

FIG. 15 is a table showing nuclear energy and setting values, and a table used in the nuclear species classification process is described. The nuclide described in this example relates to 10 representative gamma ray emitting elements.

The second column of the table shows the energy of radiation for each nuclide, and since Sn-113 and Co-60 have secondary energy, two energy are indicated.

The calibration setting value represents a calibration value for the radiation measuring apparatus 100. Calibration refers to a process of presetting linearity and accuracy of a sensor according to each nuclide. In the present invention, specific gravity values for each region are set. . For example, when Am-241 emits radiation, if the measurement ratio of each area of the radiation measuring apparatus 100 is 5.2%, 24.6%, and 70.2%, respectively, it is inputted to the analyzer beforehand and used as a reference value for measurement later. use. In the same way, calculate the specific gravity for all remaining nuclides. In other words, the calibration setting value is a reference value known through experiments or measurements. The area specific gravity is the contribution ratio of each area, as shown in Equation 5.

That is, it can be seen that the specific gravity of each region is the ratio of the radiation dose measured in each region among the total radiation doses.

The deviation described in FIG. 15 is a value in which the contribution ratio for each region of the radiation dose of the specific nuclide measured is compared with all the nuclides.

FIG. 16 is a flowchart illustrating a process of finding a radionuclide using multiple photodiodes. The method for identifying a radionuclide that emits radiation based on a radiation dose of unknown radiation using the above-described radiation measuring apparatus 100 is described. It is described in detail.

Radiation is measured using the radiation measuring apparatus 100 of the present invention.

The photodiode 120 detects light generated from the phosphor 110, and the detector 130 generates a measurement value that varies according to the presence or absence of light and uses multiple photodiodes 120 having different sizes. Therefore, the measured values for each area are generated. (S102)

The multiplexer collects measurement data generated by an amplifier, a comparator, and a counter to generate an integrated data table (S104).

The generated data is transmitted to the radiation analysis apparatus 150 or an external system through the communication port 134 and the communication cable 140, and generates data by calculating the radiation dose for each region.

The specific gravity of each region is calculated, and the deviation and the sum of the deviations are calculated using the calculated values. (S108, S110)

To this end, the radiation analysis device 150 is provided with a means such as a CPU, a communication unit, a radionuclide database, a memory, a display, an input device, and the like. The CPU grasps accurate radionuclide information by using the radiation dose measurement value and the data table transmitted from the radiation measuring apparatus 100. However, in some cases, the radiation measuring apparatus 100 and the radiation analyzing apparatus 150 may be integrally formed.

The deviation for each region is determined as the absolute value of the difference between the calibration set value and the actual measured value of the radiation measuring apparatus 100.

Computation of deviation for each region a, b, c is given by Equation 6.

The deviation represents the difference between the two values, so the negative value needs to be removed, so take the absolute value.

For example, the measured values obtained by using the radiation measuring apparatus 100 of the present invention are a region 18.4%, b region 22.9%, and c region 58.7%. In order to determine what kind of radionuclide the radiation is emitted from this measured value, first, the deviation and the sum of the deviations are obtained for Am-241 shown in the table of FIG. Subtract the measurement value of area a, 18.4, from 5.2, the calibration setting for area a, and record its absolute value of 13.2 as the area a deviation.

Next, subtract 22.9, the measured value of b, from 24.6, the calibration setting of b, for Am-241, and record its absolute value, 1.7, as b.

Next, subtract 58.7, the measured value of c, from the calibration setting of 70.2, the c area of Am-241, and record its absolute value, 11.5, as the c area deviation.

In this way, the sum of the deviations of the three areas (13.2, 1.7, 11.5) is summed to obtain the sum of the deviations of each of the a, b, and c areas, and the combined value 26.4 is recorded for comparison.

After summating the deviations for Am-241, the first nuclide to be compared, Cd-109 is selected as the next nuclide to be compared. In the same way, calculate the deviation of a, b and c areas of Cd-109, add them together, and record the sum of the deviation of 25.1.

Repeat this process up to Y-88, the last nuclide to compare. The nuclide with the smallest sum of deviations is the one we are looking for. This is because the smallest difference between the calibration setpoint and each region means that the corresponding nuclide and energy band are the closest. This is because if the difference in energy bands in each of the regions a, b and c is large, the variation in each region will also be large. Therefore, in the present invention, the embodiment described in FIG. 15 shows the measured values of CS-137 (a-area weight ratio) of 18.4% of a-area ratio, 22.9% of b-area ratio, 58.7% of c-area ratio, and the lowest calibration setting value for each region. 18.9%, b. 23.1%, c. 58.0%) are the correct nuclides.

As such, the radiation analysis apparatus 150 searches for a suitable nuclide by finding a value having a smallest difference between the deviations using a table of the set value and the measured value.

On the other hand, in the process of finding a bad pixel, the light intensity detected by each pixel is compared with the average of the surrounding pixels to determine whether or not the bad.

If each pixel is in normal operation, the radiation dose detected will be similar to the neighboring pixels. If the pixel is in an abnormal state, the amount of radiation detected will be much different from neighboring pixels of the same size. A typical abnormality would be a case where a pixel does not operate at all due to a circuit failure, or the output value of a pixel is deviated due to some circuit failure of an amplifier and a comparator.

The radiation dose input to the radiation measuring apparatus 100 will reach all the pixels evenly, and the pixels of each of a, b, and c areas have the same size, so the individual pixel output values in each area will be similar to the average value. If a particular pixel differs significantly from the average, that portion can be determined to be a bad pixel.

For example, if the output value of pixel c12 of region c shows a large standard deviation relative to the surroundings, it can be expected that pixel c12 is defective.

In general, the term "average" is defined as the number of variables divided by the sum of the variables, and in the present invention, the sum of the measured values of each pixel divided by the number of pixels.

The subtraction of each pixel is obtained by subtracting the average value from the measured value of each pixel.

As shown in Equation 8, the standard deviation may be obtained by adding all the deviations of each pixel and dividing by the number of pixels.

How far the deviation of each pixel is from the standard deviation, the ratio can be found by calculating the ratio.

If the deviation rate of a particular pixel is excessively large compared to other pixels, the corresponding pixel may be determined as defective. For example, if most pixels have a deviation of less than 20%, and only a specific pixel has a deviation of 150% or more, the pixel is likely to be bad.

In general, pixel defects are convenient to compare pixels having the same size, but when the number of pixels to be compared is small, it may be compared with other sized pixels to increase the size of the comparison set. In this case, the deviation rate for the defect determination can be further increased. Since the radiation measuring apparatus 100 cannot replace or repair a defective pixel generated during use, once it is determined as a defective pixel, it should be excluded from all subsequent calculations.

Such a configuration and method can accurately determine the amount of radiation randomly generated from various nuclides and predict which radionuclides are emitted.

Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the above-described technical configuration of the present invention may be embodied by those skilled in the art to which the present invention pertains without changing the technical spirit or essential features of the present invention. It will be appreciated that the present invention may be practiced as. Therefore, the exemplary embodiments described above are to be understood as illustrative and not restrictive in all respects, and the scope of the present invention is indicated by the following claims rather than the detailed description, and the meaning and scope of the claims and All changes or modifications derived from the equivalent concept should be construed as being included in the scope of the present invention.

10, 100: radiation measuring apparatus 11, 110: phosphor
12, 120: photodiode 13, 130: detector
121: first photodiode 122: second photodiode
123: third photodiode 131: first detection unit
132: second detection unit 133: third detection unit
134: communication port 140: communication cable
150: radiation analysis device

Claims (7)

delete As a radiation measuring device to improve the radiation detection efficiency by multiple combinations of photodiodes 120 of different sizes,
Phosphor 110 which emits light according to the input of radiation;
A photodiode 120 for converting light generated from the phosphor 110 into an electrical signal;
And a plurality of detection units 130 that are connected to the plurality of photodiodes 120 to calculate information for analyzing radiation doses and nuclides by analyzing the electrical signals transmitted from the photodiodes 120. ,
The photodiode 120 may include a first photodiode 121 having a relatively large size, a second photodiode 122 having a relatively smaller size than the first photodiode 121, and the second photodiode ( And a third photodiode 123 having a smaller size than 122).
A total of sixteen second photodiodes 122 are arranged in the top, bottom, left, and right sides of the first photodiode 121 installed in the center, and a total of sixteen are arranged in the space between the second photodiodes 122. The third photodiode 123 is disposed,
The detector 130 may include a first detector 131 that receives an electrical signal transmitted from the first photodiode 121, and a second receiver that receives an electrical signal transmitted from the second photodiode 122. It consists of a detector 132, and a third detector 133 for receiving an electrical signal transmitted from the third photodiode 123,
The first detector 131 includes a first amplifier 131a, a first divider 131b, a 1-1 comparator 131c, a 1-2 comparator 131d, a 1-1 counter 131e, and a first detector 131a. It consists of 1-2 counter (131f), the first multiplexer (131g),
The second detector 132 includes a second amplifier 132a, a second divider 132b, a 2-1 comparator 132c, a 2-2 comparator 132d, a 2-1 counter 132e, and a second detector 132a. It consists of a 2-2 counter 132f, a second multiplexer (132g),
The third detector 133 may include a third amplifier 133a, a third divider 133b, a 3-1 comparator 133c, a 3-2 comparator 133d, a 3-1 counter 133e, and a third amplifier 133a. It consists of a 3-2 counter (133f), the third multiplexer (133g),
The gain setting value of the first amplifier 131a, the gain setting value of the second amplifier 132a, and the gain setting value of the third amplifier 133a are different from each other.
Comparator set values of the 1-1 comparator 131c and the 1-2 comparator 131d, comparator set values of the 2-1 comparator 132c and the 2-2 comparator 132d, and the first comparator Comparator set values of the 3-1 comparator 133c and the 3-2 comparator 133d are set differently from each other.
The gain setting value and the comparator setting value are variably set according to the type of radiation to be detected.
Although the pixels 703 and 705 in the periphery of the emission area detect light emission, the pixels 702 and 704 in the center and relatively low in the comparator set value do not detect light emission, or
In the case where pixels having the same comparator set value are consecutive, the pixel is regarded as a bad pixel when no emission is detected at the center pixel even though a signal is detected at the left and right sides based on any one pixel. Radiation measuring device using multiple photodiodes. delete delete delete A method of measuring radiation having a plurality of energies using the radiation measuring apparatus 100 of claim 2,
A first step in which the photodiode 120 senses light generated when radiation is input to the phosphor 110 included in the radiation measuring apparatus 100;
A second step of the detector 130 classifying and measuring the intensity of light detected by the multiple photodiodes 120 having different sizes;
A third step of generating, by the detector 130, a measurement value for each region detected by the multiple photodiode 120;
A fourth step of the radiographic analysis device (150) calculating a deviation and a sum of the deviations of the measured values for each area transmitted from the detection unit (130);
And a fifth step of the radiographic analysis device (150) determining the nuclide that emits the radiation from the deviation and the sum of the deviations. The method of claim 6,
The radiation analysis device 150 is
Comparing the measured values for each of the plurality of nuclides with each other, calculating the deviation and the sum of the deviations for the measured values for the regions, and determining the nuclide having the smallest sum of the deviations as the radionuclide that emits the radiation. Radiation measuring method using a multiple photodiode, characterized in that.

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