KR102483516B1 - Radon detector using pulsified alpha particle - Google Patents

Abstract

The present invention relates to a radon measuring device through pulse detection of alpha particles, and more particularly, to detect ion charges generated by alpha particles generated during the alpha decay of radon by pulsed through a single probe rod, and to detect alpha particles finely in succession. It relates to a radon measuring device that improves measurement accuracy by measuring the number of particles without omission even when it occurs.

Description

Radon detector through pulse detection of alpha particles {RADON DETECTOR USING PULSIFIED ALPHA PARTICLE}

The present invention relates to a radon measuring device through pulse detection of alpha particles, and more particularly, to detect ion charges generated by alpha particles generated during the alpha decay of radon by pulsed through a single probe rod, and to detect alpha particles finely in succession. It relates to a radon measuring device that improves measurement accuracy by measuring the number of particles without omission even when it occurs.

Alpha particles are emitted during alpha decay of radioactive materials such as uranium and radium. In this process, sometimes the original atomic nucleus is 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 element's atomic mass is reduced by nearly 4 amu. This is because it loses four nucleons. An atom loses 2 protons and its atomic number decreases by 2, making it a new element. For example, radium becomes radon through alpha decay.

Because of their charge and heavy mass, alpha particles are easily absorbed by matter and can only travel a few centimeters in air. It is absorbed in a sheet of tissue paper, and in the outer layer of the human skin (about 40 micrometers, about the thickness of a few cells). For this reason, it is generally not dangerous unless eaten or inhaled. However, because of 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 symptoms of exposure. The damage to chromosomes caused by alpha particles is more than 100 times greater than that 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 instruments and various measurement 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 it is not reactive, and since the frequency of alpha particles generated when radon (Rn) decays is proportional to the radon concentration, the indoor radon concentration is measured by detecting alpha particles in the air. In other words, accurately detecting alpha particles is a method of accurately measuring indoor radon concentration.

For example, there is an alpha particle detection technique using a pulsed ionization chamber among the prior art. The pulsed ionization chamber has a structure in which a probe-shaped electrode is installed inside a metal box and an electric field is formed by applying a bias voltage between the metal cylinder and the internal probe. When alpha decay occurs inside the ion chamber and alpha particles are emitted, the alpha particles are annihilated by collision with air, but ion charges are generated, so the alpha particles can be detected by absorbing them through the central probe and amplifying the signal. However, in the case of an ionization chamber, it is difficult to design a measurement circuit because it is sensitive to electrical noise, and when a large number of fine charges with a short time interval are in contact with the probe due to the continuous generation of fine alpha particles, it is difficult to count the number of pulses. There was a problem with a large error.

Republic of Korea Patent Publication No. 10-2014-0023599

The present invention has been conceived to solve the above problems, and detects the ionic charge generated by alpha particles generated during the alpha decay of radon by pulsed through a single probe rod, and misses even when the alpha particles are finely generated consecutively. It is an object of the present invention to provide a radon measuring device through pulse detection of alpha particles with improved measurement accuracy by measuring the number of particles without

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

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

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

The probe unit may be electrically connected to the first terminal of the BNC connector so 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.

Also, the second terminal of the BNC connector may be grounded.

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

Furthermore, a voltage follower unit that amplifies the current of the electrical signal input from the preamplifier unit and generates a constant signal delay; It is preferable to further include; a differential amplifier for generating electrical pulses according to the radon ions.

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

Further, the pulse processing unit, when the potential of the electrical signal is lower than the pulse generation reference voltage after the first maximum voltage is generated, sets 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 at which the voltage lower than the threshold potential difference is detected, the voltage change amount per unit time of the electrical signal becomes negative again. The potential at the time of (-) change is set as the second maximum voltage, and when a voltage lower than a predetermined threshold potential difference is detected after the time at which the second maximum voltage occurs, a pulse is generated at the time when the second maximum voltage occurs. It can be determined that it has been detected.

Using the present invention, the ion charge generated by the alpha particles generated during the alpha decay of radon is pulsed and detected through a single probe rod, and the number of particles is measured without omission even when the alpha particles are finely generated in succession, resulting in measurement accuracy. There is an effect that can implement a radon meter through pulse detection of alpha particles with 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 view illustrating a case in which a BNC connector used as a probe unit shield is combined with an ionization chamber and a probe unit;
5 is a graph illustrating a waveform of a pulse output from the alpha particle detector of FIG. 2;
6 is a graph illustrated to explain a pulse processing algorithm of a pulse processing unit.

Hereinafter, a radon detector 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 the radon meter 1 through pulse detection of alpha particles includes an alpha particle detection unit 10, a pulse processing unit 20, a control unit 30, a power supply unit 40, and an input unit 50. and a display unit 60.

The alpha particle detector 10 further includes an ionization chamber and an ion detection probe, and generates a pulse corresponding to an 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 the 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's input for a specific operation of the radon meter 1. For example, the input unit 50 can be a sensor switch module including at least one touch-type sensor switch, and in addition, a keyboard, keypad, or any other input interface can be used as long as it can accept an input signal according to a user's operation. and a combination of two or more input interfaces is also possible.

The display unit 60 displays the radon concentration measured by the radon meter 1, the number of alpha particles, and other various information to be displayed by the radon meter 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 the embodiment of FIG. 1 in more detail.

As shown in FIG. 2, the alpha particle detection unit 10 includes an ionization chamber 100, a probe unit 200, a probe shield 300, a preamplifier unit 400, a preamplifier shield 450, a voltage A follower unit 500 and a differential amplifier unit 600 are included.

The ionization chamber 100 serves to trap part of the air in the space where the radon detector 1 is disposed in order to collect alpha particles to be detected. In general, the ionization chamber 100 has a shape in which at least a part of a metallic cylinder is open so that air can flow therethrough.

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 charged ions (hereinafter referred to as “radon ions” for convenience) by alpha particles generated by alpha decay in the air remaining inside the ionization chamber 100 .

The probe unit shield 300 physically surrounds the probe unit 200 and electrically shields it, thereby preventing external noise from entering the probe unit 200 .

The preamplifier unit 400 amplifies the electrical signal according to the radon ions detected by the probe unit 200 and transfers it to subsequent circuit components.

The pre-amplifier shield 450 physically surrounds the pre-amplifier 400 and electrically shields it, thereby preventing external noise from entering the pre-amplifier 400 .

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

The differential amplifier 600 receives electrical signals from the preamplifier 400 and the voltage follower unit 500, respectively, and differentially amplifies them to generate electrical pulses according to the detected radon ions, which are then transferred to the 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 denote like elements throughout the specification.

In order to charge the ionization chamber 100 with a constant voltage, a predetermined bias power supply 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 may further include a circuit for boosting the voltage of the secondary battery, and the output voltage from the power supply unit 40 may be a 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 must 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. Therefore, the bias power supply 110 may further include a boost circuit having a power supply voltage of about 12V supplied from the power supply unit 40 as an input voltage and a charging voltage of about 50V 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 supply having a 3.7V rated voltage.

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

The probe unit shield 300 physically surrounds the probe unit 200 and electrically shields it, thereby preventing external noise from entering the probe unit 200 .

For example, a metallic BNC connector may be used as the probe 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 a wire surrounded by an insulator inside the body of the BNC connector. can Since the probe 200 connected to one end of the BNC connector is disposed inside the ionization chamber 100, the other end of the wire of the BNC connector is disposed outside the ionization chamber 100.

Meanwhile, an insulator surrounding the wire inside the BNC connector may act as an insulating member to insulate the probe unit 200 from the ionization chamber 100 in advance.

In addition, by connecting the probe unit shield 300 to the ground (GND) of the circuit of the radon meter 1, external noise introduced into the probe unit 200 can be further reduced.

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

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

As shown in FIG. 4 , the ionization chamber 100 is formed by combining a side chamber 120 and an 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 portion 312 of the BNC connector 310 electrically insulates the probe portion 200 from the ionization chamber 100 as described above with reference to FIG. 3 .

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

The second terminal 316 of the BNC connector 310 is connected to a wire to be grounded to the ground (GND) of the printed circuit board (not shown).

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

The input terminal of the preamplifier unit 400 is connected to the terminal of the probe unit 200 exposed to the outside of the ionization chamber 100, and the output terminal of the preamplifier unit 400 is connected to the input terminal of the voltage follower unit 500 and the differential Each is connected to the input terminal of the amplifier 600. In addition, one end of the preamplifier 400 is grounded to the ground (GND) in the circuit of the radon meter (1).

The pre-amplifier shield 450 physically surrounds the pre-amplifier 400 and electrically shields it to prevent external noise from entering the pre-amplifier 400, such as a metallic foil such as copper foil or aluminum foil. It may be appropriately selected and used from various materials capable of electrical shielding.

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

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

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

In the differential amplifier 600, electrical pulses according to the detected radon ions are differentially amplified and generated, and the generated pulses are transmitted to the pulse processing unit 20.

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

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

As shown in FIG. 5, an electrical pulse is transmitted to the pulse processor 20 for each radon ion charged by alpha particles in the air.

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

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

The parts C1 and C2 circled in FIG. 5 represent cases in which two pulses are detected at an extremely short time interval.

In this case, since two pulses are combined, the radon analyzer according to the prior art often recognizes these pulses as one instead of two.

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

6 is a graph illustrated to explain a pulse processing algorithm of a pulse processing unit.

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

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

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

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

If the voltage rise occurs again in a situation where the voltage of the input signal is 1.5V or higher, the “second maximum voltage time” is searched.

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

Set the time F to “second 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, by determining whether the change in voltage per unit time has changed from positive (+) to negative (-), it is possible to detect a plurality of alpha particles generated at extremely close time intervals. This is a mathematical expression of a continuous and differentiable function in which a convex upward point (for example, a point at time B and a point at time F) must exist between a section where the change per unit time is positive (+) and a section where the change is negative (-). based on the principle

As such, the pulse processing unit 20 can count the number of generated pulses without missing pulses through a unique configuration and processing algorithm, so that measurement accuracy can be improved even when fine alpha particles are continuously generated.

The detailed description of the preferred embodiments of the present invention disclosed above is provided to enable any person skilled in the art to implement and practice the present invention. Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art will understand that the present invention can be variously modified and changed 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 manner of combining with each other. Thus, 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 limiting in all respects and should be considered as illustrative. The scope of the present invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the present invention are included in the scope of the present invention. The 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 do not have an explicit citation relationship in the claims may be combined to form an embodiment or may be included as new claims by amendment after filing.

One . . . . . . radon meter
10. . . . . . Alpha Particle Detector
20. . . . . . pulse processing unit
30. . . . . . control unit
40. . . . . . power supply
50. . . . . . input part
60. . . . . . display part
100. . . . . . ionization chamber
200. . . . . . probe
300. . . . . . probe shield
400. . . . . . preamplifier donation
450. . . . . . preamplifier shield
500. . . . . . voltage follower part
600. . . . . . differential amplifier section
110. . . . . . bias power supply
120. . . . . . side chamber
130. . . . . . top chamber
312. . . . . . insulation
314. . . . . . BNC connector 1st terminal
316. . . . . . BNC connector second terminal

Claims (11)

an alpha particle detection unit generating an electrical pulse corresponding to an alpha particle detected by an 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 controlling overall operations of the alpha particle detection unit and the pulse processing unit; and
A power supply unit supplying power to the alpha particle detection unit, the pulse processing unit, and the control unit;
The pulse processing unit,
determining whether the potential of the electrical signal input from the alpha particle detector 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 a voltage change amount 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 time at which this occurs, it is determined that a pulse is detected at the time when the first maximum voltage occurs.
Radon meter through pulse detection of alpha particles. According to claim 1,
The alpha particle detector,
Further comprising, a radon meter through pulse detection of alpha particles; a probe unit shield that physically surrounds the probe unit and electrically shields it. According to claim 2,
The probe unit shield,
A BNC connector coupled to a part of the ionization chamber and having an insulation part, a first terminal and a second terminal formed through the center, a radon meter through pulse detection of alpha particles. According to claim 3,
The insulation unit insulates the probe unit and the ionization chamber, a radon meter through pulse detection of alpha particles. According to claim 3,
Alpha particle pulse detection, wherein the probe is electrically connected to the first terminal of the BNC connector so that one end of the probe is located inside the ionization chamber and the other end of the probe is located outside the ionization chamber. Radon meter via. According to claim 3,
The second terminal of the BNC connector is grounded, a radon meter through pulse detection of alpha particles. According to claim 2,
A pre-amplifier for amplifying the electrical signal input from the probe; and
A pre-amplifier shield electrically shielding the pre-amplifier unit; further comprising a radon meter through pulse detection of alpha particles. According to claim 7,
A voltage follower unit amplifying the current of the electrical signal input from the pre-amplifier unit and generating a constant signal delay; and
A differential amplification unit that receives electrical signals from the preamplifier unit and the voltage follower unit and then differentially amplifies them to generate electrical pulses according to the detected radon ions; further comprising a radon detector through pulse detection of alpha particles . delete According to claim 1,
The pulse processing unit,
After the first maximum voltage occurs, if 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. According to claim 1,
The pulse processing unit,
When the voltage change amount of the electrical signal per unit time becomes positive (+) again after the time when the voltage lower than the threshold potential difference is detected, the time when the voltage change amount per unit time of the electrical signal changes to negative (-) again. Alpha sets the potential of to the second maximum voltage, and if a voltage lower than a predetermined threshold potential difference is detected after the time the second maximum voltage occurs, it is determined that a pulse is detected at the time the second maximum voltage occurs. Radon meter through pulse detection of particles.

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