WO2022092708A1

WO2022092708A1 - Device for measuring radon through pulse detection of alpha particles

Info

Publication number: WO2022092708A1
Application number: PCT/KR2021/014870
Authority: WO
Inventors: 김경환; 신상원
Original assignee: 한일원자력(주)
Priority date: 2020-10-28
Filing date: 2021-10-22
Publication date: 2022-05-05
Also published as: KR102483516B1; KR20220056408A

Abstract

The present invention relates to a device for measuring radon through pulse detection of alpha particles and, more particularly, to a device for measuring radon wherein ion charges generated due to alpha particles generated during alpha decay of radon are pulsed and detected through a single probe rod, and the number of particles is counted without omission, even when alpha particles are generated in microscopic succession, thereby improving measurement accuracy of radon.

Description

Radon Meter with Pulse Detection of Alpha Particles

The present invention relates to a radon measuring instrument through pulse detection of alpha particles, and more particularly, by pulsing the ion charge generated due to alpha particles generated during the alpha decay of radon through a single probe rod and detecting the alpha particles minutely in succession. It relates to a radon meter that improves the measurement accuracy by measuring the number of particles without omission even when they occur.

Alpha particles are emitted during alpha decay of radioactive materials such as uranium and radium. In this process, the original nucleus is sometimes placed in an excited state, and the excess energy is released through gamma-ray emission. Unlike beta decay, alpha decay is driven by strong interactions.

When an alpha particle is emitted, the atomic mass of the element is reduced by almost 4 amu. This is because it loses 4 nucleons. The atom loses its atomic number by 2 due to the loss of two protons and becomes a new element. For example, radium becomes radon through alpha decay.

Because of their electric charge and heavy mass, alpha particles are easily absorbed by matter and can only travel a few centimeters in air. It is absorbed even in a sheet of tissue paper, and it is also absorbed into the human outer skin layer (about 40 micrometers, the thickness of a few cells). For this reason, it is generally not dangerous if not eaten or inhaled. However, due to its heavy mass and strong absorption, it is also the most dangerous ionizing radiation once it enters the body. It is the most strongly ionized, and if exposed to a certain amount, it may show various exposure symptoms. The damage to chromosomes caused by alpha particles is more than 100 times greater than the damage caused by the same amount of other types of radiation.

In order to accurately evaluate the indoor concentration of radon (Rn), which has a huge impact on human health, various types of measuring instruments and various measuring methods and devices have been widely developed and used. Radon (Rn) is a colorless, odorless inert gas. Therefore, it is difficult to measure directly because there is no reactivity, and since the frequency of alpha particles generated during alpha (α) decay of radon (Rn) is proportional to the radon concentration, the indoor radon concentration is measured by detecting alpha particles in the atmosphere. In other words, accurate detection of alpha particles is a method of accurately measuring indoor radon concentration.

For example, among the prior art, there is an alpha particle detection technique using a pulsed ionization chamber. The pulsed ionization chamber has a structure in which an electric field is formed by installing a probe-shaped electrode inside a metal box and applying a bias voltage between the metal cylinder and the inner probe. When alpha decay occurs inside this ion chamber and alpha particles are released, alpha particles are destroyed by collision with air, but ionic charges are generated. However, in the case of the ionization chamber, it is difficult to decorate the measurement circuit because it is sensitive to electrical noise, and when a large number of microcharges with short time intervals are in contact with the probe due to alpha particles being generated minutely in succession, it is difficult to count the number of pulses. There was a problem in which a large error occurred.

The present invention was conceived to solve the above problems, and the ion charge generated due to the alpha particles generated during the alpha decay of radon is detected by pulsing through a single probe, and the alpha particles are omitted even when they are generated minutely in succession. An object of the present invention is to provide a radon meter through pulse detection of alpha particles, which improves measurement accuracy by measuring the number of particles without

A radon measuring device through pulse detection of alpha particles according to an example of the present invention includes: an alpha particle detection unit generating an electrical pulse corresponding to the alpha particles detected by the ion detection probe constituting the probe unit in the ionization chamber; a pulse processing unit that processes the electrical pulse and counts the number of alpha particles detected by the alpha particle detection unit; a control unit for controlling overall operations of the alpha particle detection unit and the pulse processing unit; and a power supply unit for supplying power to the alpha particle detection unit, the pulse processing unit, and the control unit.

In addition, the alpha particle detection unit may further include a probe unit shield that physically surrounds the probe unit and electrically shields the probe unit.

In addition, the shield of the probe unit may be a BNC connector coupled to a part of the ionization chamber and having an insulating unit, a first terminal, and a second terminal formed through a center thereof.

In addition, the insulating part may insulate the probe part from the ionization chamber.

In addition, the probe unit may be electrically connected to the first terminal of the BNC connector such that one end of the probe unit is located inside the ionization chamber and the other end of the probe unit is located outside the ionization chamber.

In addition, the second terminal of the BNC connector may be grounded.

In addition, it is preferable to further include a pre-amplification unit for amplifying the electrical signal input from the probe unit; and a pre-amplification unit shield for electrically shielding the pre-amplifier unit.

Furthermore, a voltage follower unit amplifies the current of the electrical signal inputted from the preamplifier unit and generates a constant signal delay; and after receiving the electrical signals from the preamplifier unit and the voltage follower unit, respectively, it is detected by differentially amplifying it It is preferable to further include; a differential amplifier for generating an electrical pulse according to the radon ions.

In addition, the pulse processing unit determines whether a potential of the electrical signal input from the alpha particle detection unit is greater than a predetermined pulse generation reference voltage, and when the electrical signal potential is higher than the pulse generation reference voltage, per unit time The potential at the time when the voltage change amount changes from positive (+) to negative (-) is set as the first maximum voltage, and when a voltage lower than a predetermined threshold potential difference is detected after the time when the first maximum voltage is generated, the second 1 It can be determined that the pulse is detected at the time when the maximum voltage is generated.

In addition, the pulse processing unit, after the first maximum voltage is generated, when the potential of the electrical signal is lower than the pulse generation reference voltage, the number of pulses until the potential of the electrical signal becomes higher than the pulse generation reference voltage again may not count.

In addition, when the voltage change amount of the electrical signal per unit time becomes positive again after the time when a voltage lower than the threshold potential difference is detected, the pulse processing unit, the voltage change amount per unit time of the electrical signal is negative again The potential at the time of changing to (-) is set as the second maximum voltage, and when a voltage lower than a predetermined threshold potential difference is detected after the time when the second maximum voltage is generated, a pulse is generated at the time when the second maximum voltage is generated can be judged to have been detected.

Using the present invention, the ion charge generated by the alpha particles generated during the alpha decay of radon is detected by pulsing through a single probe, and the number of particles is measured without omission even when the alpha particles are generated minutely in succession. It has the effect of realizing a radon meter through the pulse detection of alpha particles, which has improved

1 is a block diagram showing an example of a radon meter through pulse detection of alpha particles;

2 is a block diagram showing the alpha particle detection unit in more detail in the embodiment of FIG. 1;

3 is a circuit diagram according to an example of the alpha particle detection unit of FIG. 2;

4 is a diagram illustrating a case in which a BNC connector used as a probe part shield is combined with an ionization chamber and a probe part;

5 is a graph illustrating a waveform of a pulse output from the alpha particle detection unit of FIG. 2;

6 is a graph illustrating a pulse processing algorithm of the pulse processing unit.

Hereinafter, a radon meter through pulse detection of alpha particles according to an embodiment of the present invention will be described in detail with reference to the drawings.

1 is a block diagram showing an example of a radon meter through pulse detection of alpha particles.

As shown in FIG. 1 , an example of a radon measuring instrument 1 through pulse detection of alpha particles is an alpha particle detection unit 10 , a pulse processing unit 20 , a control unit 30 , a power supply unit 40 , an input unit 50 . and a display unit 60 .

The alpha particle detection unit 10 further includes an ionization chamber and an ion detection probe, and generates a pulse corresponding to the alpha particle detected by the ion detection probe. The generated pulse is transmitted to the pulse processing unit 20 .

The pulse processing unit 20 processes a pulse input from the alpha particle detection unit 10 and counts the number of alpha particles detected by the alpha particle detection unit 10 .

The control unit 30 controls the overall operation of the radon meter (1).

The power supply unit 40 supplies power to each component of the radon meter 1 so that the radon meter 1 can operate normally.

The input unit 50 receives a user input for a specific operation of the radon meter 1 . For example, the input unit 50 may be a sensor switch module including at least one touch-type sensor switch, and in addition, as long as it can receive an input signal according to a user's operation, a keyboard, keypad, or any other input interface is possible. and a combination of two or more input interfaces is also possible.

The display unit 60 displays the radon concentration measured by the radon measuring device 1 , the number of alpha particles, and other various information to be displayed by the radon measuring device 1 . The display unit 60 may be an LCD display, an LED display, an LED lamp array, or any other display device as long as it can visually display information and provide it to the user, and a combination of two or more display devices is also possible.

FIG. 2 is a block diagram showing the alpha particle detection unit in more detail in the embodiment of FIG. 1 .

As shown in FIG. 2 , the alpha particle detection unit 10 includes an ionization chamber 100 , a probe unit 200 , a probe unit shield 300 , a preamplifier unit 400 , a preamplifier shield 450 , and a voltage It is made to include a follower unit 500 and a differential amplification unit (600).

The ionization chamber 100 serves to confine a part of air in the space in which the radon meter 1 is disposed in order to collect the alpha particles to be detected. The ionization chamber 100 generally has a shape in which at least a portion of the metallic cylinder is opened so that air can flow.

The probe unit 200 is disposed inside the ionization chamber 100 so as not to contact the ionization chamber 100 . The probe unit 200 detects ions (hereinafter, referred to as “radon ions” for convenience) charged by alpha particles generated due to alpha decay in the air staying inside the ionization chamber 100 .

The probe part shield 300 physically surrounds the probe part 200 to electrically shield it, so that external noise is not introduced into the probe part 200 .

The preamplifier 400 amplifies an electrical signal according to the radon ion detected by the probe unit 200 and transmits it to a subsequent circuit component.

The pre-amplifier shield 450 physically surrounds the pre-amplifier 400 and electrically shields it to prevent external noise from being introduced into the pre-amplifier 400 .

The voltage follower unit 500 amplifies the current of the electric signal input from the preamplifier unit 400 and generates a constant signal delay.

The differential amplifier 600 receives electrical signals from the pre-amplifier 400 and the voltage follower 500, respectively, and then differentially amplifies them to generate an electric pulse according to the detected radon ions, and it is a pulse processing unit 20 forward to

3 is a circuit diagram according to an example of the alpha particle detection unit of FIG. 2 .

Like reference numerals refer to like elements throughout the specification.

In order to charge the ionization chamber 100 at a constant voltage, a predetermined bias power source 110 having a positive (+) value is applied. The bias power supply 110 may be provided from the power supply unit 40 .

Meanwhile, the power supply unit 40 may receive power from a secondary battery such as a lithium polymer battery having a rated voltage of 3.7V. In this case, the power supply unit 40 is further equipped with a circuit for boosting the voltage of the secondary battery, and the output voltage from the power supply unit 40 can be the power supply voltage supplied to the circuit of the radon meter 1, for example, 12V. .

However, in the case of the ionization chamber 100, the air in the chamber needs to be charged with a voltage of about 50V. In this case, the output voltage of the power supply unit 40, for example, 12V, becomes an excessively low voltage. Accordingly, the bias power supply 110 may further include a boosting circuit in which a power supply voltage of about 12V supplied from the power supply unit 40 is used as an input voltage and a charging voltage of about 50V is used as an output voltage.

Through this, it is possible to use both the power supply voltage (12V) and the charging voltage (50V), which are different voltages, from a secondary battery power source having a 3.7V rated voltage.

The probe unit 200 is disposed inside the ionization chamber 100 , and is disposed so as not to contact the ionization chamber 100 . To this end, an insulating member (not shown) for insulating the probe unit 200 from the ionization chamber 100 may be further disposed between the probe unit 200 and the ionization chamber 100 .

For example, a metallic BNC connector may be used as the probe unit shield 300 . That is, the body of the BNC connector is physically fixed to one surface of the ionization chamber 100 through a bolt-nut structure, and the probe unit 200 is connected to one end of the conducting wire surrounded by an insulator inside the body of the BNC connector. can Since the probe unit 200 connected to one end of the BNC connector is disposed inside the ionization chamber 100 , the other end of the lead wire of the BNC connector is disposed outside the ionization chamber 100 .

Meanwhile, the insulator surrounding the conductive wire inside the BNC connector may act as an insulating member for insulating the probe unit 200 from the ionization chamber 100 .

In addition, by connecting the probe unit shield 300 to the ground (GND) of the circuit of the radon meter 1 , it is possible to further reduce external noise flowing into the probe unit 200 .

For example, a terminal to which a probe is not connected among two terminals existing in the BNC connector may be connected to the ground (GND) of the circuit.

4 is a diagram illustrating a case in which the BNC connector used as the probe shield is coupled to the ionization chamber and the probe.

As shown in FIG. 4 , the ionization chamber 100 is formed by combining the side chamber 120 and the upper chamber 130 .

The BNC connector 310 is coupled to the central portion of the upper chamber 130 , and an insulating portion 312 , a first terminal 314 , and a second terminal 316 are formed through the center of the BNC connector 310 . .

The insulating part 312 of the BNC connector 310 allows the probe part 200 to be electrically insulated from the ionization chamber 100 as described above with reference to FIG. 3 .

A probe constituting the probe unit 200 is electrically connected to the first terminal 314 of the BNC connector 310 as shown in FIG. 4 , and one end is inside the ionization chamber 100 and the other end is the ionization chamber 100 . ) are located outside the

The second terminal 316 of the BNC connector 310 connects the conductive wire to the ground GND of the printed circuit board (not shown).

Returning to FIG. 3 again, the preamplifier 400 amplifies an electrical signal according to the radon ion detected by the probe unit 200 to a certain extent and transmits it to subsequent circuit components. The preamplifier 400 may use a variety of known techniques within the range for performing appropriate signal amplification in order to amplify the radon ion detection signal.

The input terminal of the preamplifier 400 is connected to the exposed side of the ionization chamber 100 among the terminals of the probe 200 , and the output terminal of the preamplifier 400 is the input terminal and the differential of the voltage follower part 500 . They are respectively connected to input terminals of the amplifier 600 . In addition, one end of the preamplifier 400 is grounded to the ground (GND) in the circuit of the radon measuring instrument (1).

The preamplifier shield 450 is to prevent external noise from entering the preamplifier 400 by physically enclosing the preamplifier 400 and electrically shielding it, like a metallic foil such as copper foil or aluminum foil. It may be appropriately selected from a variety of materials capable of electrical shielding.

The voltage follower unit 500 amplifies the current of the electric signal input from the preamplifier unit 400 and generates a constant signal delay. Therefore, the electrical signal input from the preamplifier 400 is delayed by a predetermined time interval at the output terminal of the voltage follower unit 500 and output, which is a positive (+) input terminal among the input terminals of the differential amplifier 600 . connected

The differential amplifier 600 receives electrical signals from the pre-amplifier 400 and the voltage follower 500, respectively, and then differentially amplifies them.

Among the input terminals of the differential amplifier 600 , a positive (+) input terminal is connected to an output terminal of the voltage follower unit 500 , and a negative (−) input terminal is connected to an output terminal of the pre-amplifier 400 .

In the differential amplification unit 600 , an electric pulse according to the detected radon ion is differentially amplified and generated, and the generated pulse is transmitted to the pulse processing unit 20 .

5 is a graph illustrating a waveform of a pulse output from the alpha particle detection unit of FIG. 2 .

The graph shown in FIG. 5 is a graph illustrating a waveform of a pulse input from the differential amplifier 600 to the pulse processing unit 20 .

As shown in FIG. 5 , an electric pulse is transmitted to the pulse processing unit 20 for each radon ion charged by alpha particles in the atmosphere.

In order to observe the pulse shape in the pulse processing unit 20, an analog input method is applied instead of using the GPIO interrupt method used in the prior art.

For example, in the example of FIG. 5 , the pulse processing unit 20 may count only pulses having a voltage of 1.5V or more among electrical pulses input from the differential amplifier 600 of the alpha particle detection unit 10 .

Portions C1 and C2 indicated by circles in FIG. 5 show a case in which two pulses are detected with an extremely short time interval.

In this case, two pulses are combined, and the radon measuring device according to the prior art recognizes these pulses as one instead of two in many cases.

However, in the present invention, accurate pulse counting is possible without missing pulses through the unique configuration and processing algorithm of the pulse processing unit 20 .

In the examples of FIGS. 5 and 6 , when the reference voltage for determining whether a pulse is generated (“pulse generation reference voltage”) is 1.5V, when the voltage of the input signal exceeds 1.5V (time A), the pulse The processing unit 20 finds a time (time B) at which the maximum voltage is detected after time A. At the time at which the maximum voltage is detected, the amount of change in voltage per unit time up to the time (eg, time B) is positive (+), and the amount of change in voltage per unit time after the time (eg, time B) is negative (-) ) can be detected by finding the time at which In other words, the time at which the voltage continues to rise and then starts to fall becomes the maximum voltage time.

Set time B as “1st maximum voltage time”.

Then, if the voltage at the first maximum voltage time (time B), that is, a voltage lower than a predetermined “threshold potential difference” compared to the first maximum voltage, for example, a voltage lower by 0.025 V is detected (time C), one pulse is detected treated as being If the potential difference with the primary maximum voltage is less than 0.025V, it is judged as noise and no special processing is performed.

If the voltage of the input signal falls below the pulse generation reference voltage of 1.5V (time D), the pulse counting operation is not performed until an input signal of 1.5V or more is detected again.

If the voltage rises again when the voltage of the input signal is 1.5V or higher, find the “second maximum voltage time”.

That is, at time E, since the amount of change in voltage per unit time changes to positive (+) again, the time at which the secondary maximum voltage appears immediately before the amount of change in voltage per unit time changes to negative (-) again after time E (Time F) appears.

Set time F as “secondary maximum voltage time”.

As before, when a voltage 0.025V lower than the second maximum voltage time is detected (time G), it is determined that one additional pulse has occurred.

In this way, it is possible to detect a large number of alpha particles generated at extremely adjacent time intervals by determining whether the amount of change in voltage per unit time has changed from positive (+) to negative (-). This is mathematically related to a continuous and differentiable function that states that there must be an upward convex point (for example, a point at time B and a point at time F) between the section in which the amount of change per unit time is positive (+) and the section in which the amount of change per unit time is positive (-). based on the principle.

As such, by allowing the pulse processing unit 20 to count the number of generated pulses without missing pulses through a unique configuration and processing algorithm, it is possible to improve measurement accuracy even when alpha particles are generated minutely in succession.

The detailed description of the preferred embodiments of the present invention disclosed above is provided to enable any person skilled in the art to make and practice the present invention. Although the above has been described with reference to preferred embodiments of the present invention, it will be understood by those skilled in the art that various modifications and changes can be made to the present invention without departing from the scope of the present invention. For example, those skilled in the art can use each configuration described in the above-described embodiments in a way in combination with each other. Accordingly, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

The present invention may be embodied in other specific forms without departing from the spirit and essential characteristics of the present invention. Accordingly, the above detailed description should not be construed as restrictive in all respects but as exemplary. The scope of the present invention should be determined by a reasonable interpretation of the appended claims, and all modifications within the equivalent scope of the present invention are included in the scope of the present invention. The present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. In addition, claims that are not explicitly cited in the claims may be combined to form an embodiment, or may be included as new claims by amendment after filing.

[Explanation of code]

One . . . . . . radon meter

10 . . . . . . Alpha particle detector

20 . . . . . . pulse processing unit

30 . . . . . . control

40 . . . . . . power supply

50 . . . . . . input

60 . . . . . . display

100 . . . . . . ionization chamber

200 . . . . . . probe

300 . . . . . . probe shield

400 . . . . . . Preamplifier Donation

450 . . . . . . preamplifier shield

500 . . . . . . voltage follower

600 . . . . . . differential amplifier

110 . . . . . . bias power supply

120 . . . . . . side chamber

130 . . . . . . upper chamber

312 . . . . . . insulation

314 . . . . . . BNC connector 1st terminal

316 . . . . . . BNC connector 2nd terminal

Claims

an alpha particle detection unit generating an electrical pulse corresponding to the alpha particle detected by the ion detection probe constituting the probe unit in the ionization chamber;

a pulse processing unit that processes the electrical pulse and counts the number of alpha particles detected by the alpha particle detection unit;

a control unit for controlling overall operations of the alpha particle detection unit and the pulse processing unit; and

A radon measuring device through pulse detection of alpha particles, including; a power supply unit for supplying power to the alpha particle detection unit, the pulse processing unit, and the control unit.
According to claim 1,

The alpha particle detection unit,

A radon measuring instrument through pulse detection of alpha particles further comprising; a shield shield that physically surrounds the probe and electrically shields the probe.
3. The method of claim 2,

The probe part shield,

A radon meter through pulse detection of alpha particles, which is a BNC connector coupled to a part of the ionization chamber and having an insulating part, a first terminal, and a second terminal formed through the center.
4. The method of claim 3,

The insulator insulates the probe and the ionization chamber, a radon meter through pulse detection of alpha particles.
4. The method of claim 3,

The probe part is electrically connected to the first terminal of the BNC connector so that one end of the probe part is located inside the ionization chamber and the other end of the probe part is located outside the ionization chamber, respectively. Pulse detection of alpha particles With a radon meter.
4. The method of claim 3,

The second terminal of the BNC connector is grounded, a radon meter through pulse detection of alpha particles.
3. The method of claim 2,

A preamplifier for amplifying an electrical signal input from the probe unit; And

A radon measuring device through pulse detection of alpha particles further comprising; a preamplifier shield for electrically shielding the preamplifier.
3. The method of claim 2,

A voltage follower unit for amplifying a current of an electrical signal input from the preamplifier unit and generating a constant signal delay; and

Radon measuring device through pulse detection of alpha particles further comprising; a differential amplifying unit that receives electrical signals from the preamplifier and the voltage follower, respectively, and differentially amplifies them to generate an electrical pulse according to the detected radon ions .
According to claim 1,

The pulse processing unit,

It is determined whether the potential of the electrical signal input from the alpha particle detection unit is greater than a predetermined pulse generation reference voltage,

When the potential of the electrical signal is higher than the pulse generation reference voltage, a potential at a time when the amount of voltage change per unit time changes from positive (+) to negative (-) is set as a first maximum voltage, and the first maximum voltage When a voltage lower than a predetermined threshold potential difference is detected after the occurrence time, it is determined that a pulse is detected at the time when the first maximum voltage is generated.
10. The method of claim 9,

The pulse processing unit,

After the first maximum voltage is generated, when the potential of the electrical signal is lower than the pulse generation reference voltage, the number of pulses is not counted until the potential of the electrical signal becomes higher than the pulse generation reference voltage again. Radon meter with pulse detection.
10. The method of claim 9,

The pulse processing unit,

When the voltage change amount of the electrical signal per unit time becomes positive (+) again after the time when a voltage lower than the threshold potential difference is detected, the time at which the voltage change amount per unit time of the electrical signal changes to negative (-) again is set as the second maximum voltage, and when a voltage lower than a predetermined threshold potential difference is detected after the time when the second maximum voltage is generated, it is determined that a pulse is detected at the time when the second maximum voltage is generated, alpha A radon meter with pulse detection of particles.