A method for measuring radon decay times based on pulsed ionization chamber radon measurement method

Abstract

The present invention relates to a method for measuring the number of radon decays based on a pulsed ionization chamber radon measurement method, and belongs to the technical field of marine radon concentration measurement. The method comprises the following steps: using a radon probe to periodically collect the voltage value of the waveform signal generated by radon decay to obtain a measured waveform diagram; calculating the total waveform area; S , and obtain the maximum waveform area of ​​a single waveform signal corresponding to a single radon decay S max ,right S Divide by S max The result is rounded up to get the minimum theoretical number of waveforms N 0; Calculate the waveform slope based on the measured waveform, and count the peaks according to the slope change N 1. When N 1 < N 0, it is determined that there is peak overlap, and the N 0 as the number of radon decays N On the contrary, it is determined that the peak is separated and the N 1 as the number of radon decays N The radon decay number measurement method realizes the correction of radon decay number when waveform overlap and peak overlap exist under high radon concentration.

Description

Technical Field

[0001] The invention belongs to the technical field of ocean radon concentration measurement, and in particular relates to a radon decay number measurement method based on a pulse ionization chamber radon measurement method. Background Art

[0002] Marine radon isotope tracing technology is an ideal tool for studying ocean processes from a chemical perspective. Natural radon isotopes are classic tracers for studying ocean dynamics. Currently, the measurement of radon concentration in seawater primarily uses a water-gas separation device to separate the dissolved radon from the seawater, allowing the radon to enter the measuring instrument in gaseous form for measurement.

[0003] The pulsed ionization chamber (PIC) method for radon measurement has emerged in recent years as a method for measuring radon in seawater. Its radon concentration measurement principle is as follows: when radon and its daughters decay within the ionization chamber to produce alpha particles, these alpha particles ionize the air, forming electron-ion pairs. These electron-ion pairs drift under the influence of the chamber's electric field, generating weak electrical signals. These signals undergo multiple stages of amplification, filtering, and comparison screening, and the number of signals counted corresponds to the number of radon decays. Because the vast majority of alpha particles are fully or largely deposited in the pulsed ionization chamber and identified, the absolute detection efficiency of the PIC method is far greater than that of semiconductor and scintillator detectors. Furthermore, because it counts the number of electrical signals generated by radon decay, the detection efficiency is virtually unaffected by air humidity.

[0004] When using the pulsed ionization chamber (PIC) method to measure radon, when the radon concentration is low, the number of α particles decaying per unit time is small, the corresponding ionization signal is relatively sparse, and there is a certain time interval between the two waveforms. Each α particle decay can generate an effective pulse, such as Figure 1 However, as the radon concentration increases, the number of waveforms generated per unit time increases, and the probability of multiple waveforms overlapping each other increases. As a result, although multiple α particles decay, the voltage value is always higher than the comparison threshold due to the waveform superposition, and only one high-level signal is generated, as shown in Figure 1. Figure 1As shown in (b), this leads to the phenomenon of missed counting. Moreover, the higher the radon concentration, the more serious the phenomenon of missed counting of radon decay times due to waveform superposition, which will eventually lead to a decrease in the efficiency of radon concentration measurement. At the same time, the pulse ionization chamber is essentially a capacitor. Any external vibration will produce a small change in the original capacitance value. This change will generate interference current, resulting in the generation of noise signals, affecting the true statistics of the number of radon decay times. In summary, the existing pulse ionization chamber radon measurement method still has the following shortcomings: (1) Under high radon concentration conditions, there is a phenomenon of missed counting of radon decay times due to waveform superposition, which cannot be applied to high radon concentration environments such as nearshore and groundwater monitoring wells, restricting its use scenarios; (2) In complex marine environments such as swaying vibration, it is easily disturbed by vibration, which seriously affects the measurement accuracy and limits its application on unmanned observation platforms such as buoys and submerged buoys. Summary of the Invention

[0005] The present invention provides a method for measuring the number of radon decays based on a pulsed ionization chamber radon measurement method, which at least solves the technical problem of inaccurate measurement of the number of radon decays in the case of high radon concentration in the existing pulsed ionization chamber radon measurement method.

[0006] The present invention provides a method for measuring the number of radon decays based on a pulsed ionization chamber radon measurement method, comprising the following steps:

[0007] Acquisition signal: Measure radon concentration according to the pulse ionization chamber radon measurement method. Use the timer and analog-to-digital converter of the radon probe microprocessor to periodically acquire the voltage value of the waveform signal generated by radon decay until the waveform signal ends, and obtain the measured waveform graph;

[0008] Calculate the minimum theoretical number of waveforms based on waveform area: Calculate the total waveform area of ​​the waveforms within the total acquisition time period based on the measured waveform graph S ; Get the maximum waveform area of ​​a single waveform signal corresponding to a single radon decay S max ,right S Divide by S max The result is rounded up to get the minimum theoretical number of waveforms in the total acquisition time period. N 0;

[0009] Determine the number of peaks based on the change in waveform slope: Based on the measured waveform, calculate the slope of the waveform in each acquisition cycle; when the slope changes from positive to negative, it is recorded as a peak, and when the slope changes from negative to positive, it is recorded as a trough. Count the number of peaks in the total acquisition time period N 1;

[0010] Determine the number of radon decays: N 1< N 0, it is determined that there is peak overlap, and the N 0 as the number of radon decaysN On the contrary, it is determined that the peak is separated and the N 1 as the number of radon decays N .

[0011] In some embodiments, in the step of calculating the minimum theoretical number of waveforms based on the waveform area, the total waveform area S The calculation formula is as follows:

[0012] ;

[0013] in, T is the acquisition period corresponding to the measured waveform; is the initial voltage value in the measured waveform, It is the voltage value collected for the first time in the measured waveform. This is the voltage value collected for the second time in the measured waveform, and so on. is the voltage value collected for the n-1th time in the measured waveform diagram, is the voltage value collected for the nth time in the measured waveform; n is the number of collections in the total collection time period.

[0014] In some embodiments, in the step of calculating the minimum theoretical waveform number based on the waveform area, the maximum waveform area of ​​a single waveform signal corresponding to a single radon decay is obtained. S max The specific steps are as follows: Under a measurement environment where the radon concentration is 300 Bq / m³ or less, the radon concentration is measured using the pulse ionization chamber radon measurement method; the voltage value of the waveform signal generated by radon decay is collected using the timer and analog-to-digital converter of the radon probe microprocessor to obtain a low-concentration waveform graph composed of several non-overlapping waveform signals; the waveform area of ​​the single waveform signal corresponding to each radon decay in the low-concentration waveform graph is calculated; and the maximum value among them is taken as the maximum waveform area of ​​the single waveform signal corresponding to a single radon decay. S max .

[0015] In some embodiments, the waveform area of ​​the i-th single waveform signal in the low-concentration waveform graph is S i The calculation formula is as follows:

[0016] ;

[0017] in, T’ is the acquisition period corresponding to the low-concentration waveform; is the initial voltage value of the i-th single waveform signal, The voltage value collected for the first time in the i-th single waveform signal, is the voltage value collected for the second time in the i-th single waveform signal, and so on. is the voltage value collected at the m-1th time in the ith single waveform signal, is the voltage value collected for the mth time in the ith single waveform signal; m is the number of collections within the collection time period of the ith single waveform signal.

[0018] In some embodiments, in the step of determining the number of peaks based on the change in the waveform slope, the slope of the waveform in the first acquisition cycle is K The calculation formula for 1 is , the slope of the waveform in the second acquisition cycle K The calculation formula for 2 is , and so on, the slope of the waveform in the nth acquisition cycle is K n The calculation formula is ;in, T is the acquisition period corresponding to the measured waveform; is the initial voltage value in the measured waveform, It is the voltage value collected for the first time in the measured waveform. This is the voltage value collected for the second time in the measured waveform, and so on. is the voltage value collected for the n-1th time in the measured waveform diagram, is the voltage value collected for the nth time in the measured waveform; n is the number of collections in the total collection time period.

[0019] In some embodiments, in the signal acquisition step, the acquisition period for periodic acquisition is 10 ms.

[0020] In some embodiments, the signal acquisition step also includes a noise signal removal step, which is specifically as follows: using a three-axis acceleration sensor provided on the radon probe to collect accelerations in the X-axis, Y-axis and Z-axis directions in real time, and calculating the real-time total acceleration of the radon probe. ; Compare the real-time total acceleration of the radon probe The minimum acceleration that generates vibration noise signal is set The size of > When the waveform signal currently generated is determined to be noise, the waveform signal currently generated is removed; otherwise, the waveform signal currently generated is determined to be a valid signal and is collected.

[0021] In some embodiments, the minimum acceleration The setting steps are as follows: seal the radon probe into a sealed cabin, use activated carbon to remove radon gas in the air, and use the air after radon gas is removed to purge the sealed cabin until the radon gas in the sealed cabin is completely removed; place the sealed cabin after radon gas is removed on a vibration table for vibration testing, and during the test, use the three-axis acceleration sensor set on the radon probe to collect the acceleration in the X-axis, Y-axis and Z-axis directions in real time to calculate the total acceleration of the radon probe under the vibration test, and during the test, adjust the vibration parameters to change the total acceleration of the radon probe under the vibration test, and set the total acceleration of the radon probe under the vibration test when the radon probe starts to detect the waveform signal to the minimum acceleration. .

[0022] In some embodiments, the vibration test is specifically performed with a frequency ranging from 2 Hz to 100 Hz, an amplitude of 3 mm, and an acceleration of 10 m / s. 2 Frequency sweep experiment.

[0023] In some embodiments, the step of removing the noise signal further comprises: > When the device is turned on, a vibration prompt signal is issued.

[0024] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0025] 1. The radon decay number measurement method based on the pulse ionization chamber radon measurement method provided by some embodiments of the present invention calculates the minimum theoretical waveform number based on the waveform area for the measured waveform diagram obtained. N 0, on the other hand, the number of peaks is determined based on the change in waveform slope N 1, and then by comparison N 0 and N 1, and judge whether there is peak overlap, thus realizing the correction of radon decay times when there is waveform overlap and peak overlap under high radon concentration, which is beneficial for application in high radon concentration environments such as nearshore and groundwater monitoring wells;

[0026] 2. Some embodiments of the present invention provide a method for measuring the number of radon decays based on the pulsed ionization chamber radon measurement method, which obtains the real-time total acceleration of the radon probe by setting a three-axis acceleration sensor on the radon probe. , to generate the minimum acceleration of the vibration noise signal is the threshold, by comparing and The size of the waveform signal can be used to determine whether it is a vibration noise signal, thereby eliminating the interference of the vibration noise signal and ensuring the measurement accuracy. It can ensure the accuracy of radon measurement in complex marine environments such as swaying vibration, and is conducive to its application on unmanned observation platforms such as buoys and submerged buoys. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0028] Figure 1 Schematic diagram of signal measurement obtained using the existing pulsed ionization chamber radon measurement method, where (a) is the signal measurement diagram at a radon concentration of 150 Bq / m³, and (b) is the signal measurement diagram at a radon concentration of 1200 Bq / m³;

[0029] Figure 2 A flowchart of a method for measuring radon decay times based on a pulsed ionization chamber radon measurement method provided in one embodiment of the present invention;

[0030] Figure 3 A flowchart of the step of eliminating noise signals in a method for measuring the number of radon decays based on a pulsed ionization chamber radon measurement method provided in one embodiment of the present invention;

[0031] Figure 4 This is a measured waveform diagram obtained in specific embodiment 1 of the present invention;

[0032] Figure 5 A single waveform diagram corresponding to a single waveform signal with the largest waveform area obtained in specific embodiment 1 of the present invention;

[0033] Figure 6 This is the measured waveform diagram obtained in specific embodiment 2 of the present invention. DETAILED DESCRIPTION

[0034] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0035] like Figure 2 As shown, an embodiment of the present invention provides a method for measuring the number of radon decays based on a pulsed ionization chamber radon measurement method, comprising the following steps:

[0036] S1 Signal Acquisition: Measure radon concentration using the pulsed ionization chamber radon measurement method. Use the timer and analog-to-digital converter of the radon probe microprocessor to periodically acquire the voltage value of the waveform signal generated by radon decay until the waveform signal ends, and obtain the measured waveform graph.

[0037] S2 calculates the minimum theoretical number of waveforms based on waveform area: Based on the measured waveform graph, calculates the total waveform area of ​​the waveform within the total acquisition time period S; Get the maximum waveform area of ​​a single waveform signal corresponding to a single radon decay S max ,right S Divide by S max The result is rounded up to get the minimum theoretical number of waveforms in the total acquisition time period. N 0;

[0038] S3 determines the number of peaks based on the change in waveform slope: Based on the measured waveform, calculate the slope of the waveform in each acquisition cycle; when the slope changes from positive to negative, it is recorded as a peak, and when the slope changes from negative to positive, it is recorded as a trough, and the number of peaks in the total acquisition time period is calculated. N 1;

[0039] S4 determines the number of radon decays: N 1< N 0, it is determined that there is peak overlap, and the N 0 as the number of radon decays N On the contrary, it is determined that the peak is separated and the N 1 as the number of radon decays N .

[0040] In the above-mentioned method for measuring the number of radon decays based on the pulsed ionization chamber radon measurement method, it should be noted that steps S2 and S3 can be reversed.

[0041] The above-mentioned radon decay number measurement method based on the pulse ionization chamber radon measurement method calculates the minimum theoretical waveform number based on the waveform area for the obtained measured waveform. N 0, on the other hand, the number of peaks is determined based on the change in waveform slope N 1, and then by comparison N 0 and N 1, and determine whether there is a peak overlap, thereby realizing the correction of the radon decay times when there is waveform overlap and peak overlap under high radon concentration, which is beneficial for application in high radon concentration environments such as nearshore and groundwater monitoring wells.

[0042] In some embodiments, in the step S2 of calculating the minimum theoretical number of waveforms based on the waveform area, the total waveform area S The calculation formula is as follows:

[0043] (1);

[0044] In formula (1), T is the acquisition period corresponding to the measured waveform; is the initial voltage value in the measured waveform, It is the voltage value collected for the first time in the measured waveform. This is the voltage value collected for the second time in the measured waveform, and so on. is the voltage value collected for the n-1th time in the measured waveform diagram, is the voltage value collected for the nth time in the measured waveform; n is the number of collections in the total collection time period.

[0045] In this embodiment, the waveform area of ​​the waveform signal is simplified to the sum of the areas of multiple adjacent trapezoids divided by the acquisition period, thereby simplifying the total waveform area. S The calculation method can quickly realize the total waveform area S calculation, which is conducive to improving efficiency.

[0046] In some embodiments, in the step of calculating the minimum theoretical waveform number based on the waveform area, the maximum waveform area of ​​a single waveform signal corresponding to a single radon decay is obtained. S max The specific steps are as follows: Under a measurement environment where the radon concentration is 300 Bq / m³ or less, the radon concentration is measured using the pulse ionization chamber radon measurement method; the voltage value of the waveform signal generated by radon decay is collected using the timer and analog-to-digital converter of the radon probe microprocessor to obtain a low-concentration waveform graph composed of several non-overlapping waveform signals; the waveform area of ​​the single waveform signal corresponding to each radon decay in the low-concentration waveform graph is calculated; and the maximum value among them is taken as the maximum waveform area of ​​the single waveform signal corresponding to a single radon decay. S max .

[0047] This embodiment obtains a number of non-overlapping waveform signals at low radon concentrations and selects the waveform area of ​​the single waveform signal with the largest area as the maximum waveform area. S max , so that the maximum waveform area obtained S max More representative, which is beneficial to improve the minimum theoretical waveform number of subsequent calculations N 0 accuracy.

[0048] Among them, the waveform area of ​​the i-th single waveform signal in the low-concentration waveform diagram is S i The calculation formula is as follows:

[0049] (2);

[0050] In formula (2), T’ is the acquisition period corresponding to the low-concentration waveform; is the initial voltage value of the i-th single waveform signal, The voltage value collected for the first time in the i-th single waveform signal, is the voltage value collected for the second time in the i-th single waveform signal, and so on. is the voltage value collected at the m-1th time in the ith single waveform signal, is the voltage value collected for the mth time in the ith single waveform signal; m is the number of collections within the collection time period of the ith single waveform signal.

[0051] In this embodiment, the calculation method for the waveform area of ​​a single waveform signal corresponding to each radon decay in the low concentration waveform diagram adopts the same method as that for calculating the maximum waveform area. S max The same simplified calculation method is used, which greatly reduces the calculation workload of the waveform area of ​​each single waveform signal and improves the calculation efficiency.

[0052] In some embodiments, in the step of determining the number of peaks based on the change in the slope of the waveform in S3, the slope of the waveform in the first acquisition cycle is K The calculation formula for 1 is , the slope of the waveform in the second acquisition cycle K The calculation formula for 2 is , and so on, the slope of the waveform in the nth acquisition cycle is K n The calculation formula is ;in, T is the acquisition period corresponding to the measured waveform; is the initial voltage value in the measured waveform, It is the voltage value collected for the first time in the measured waveform. This is the voltage value collected for the second time in the measured waveform, and so on. is the voltage value collected for the n-1th time in the measured waveform diagram, is the voltage value collected for the nth time in the measured waveform; n is the number of collections in the total collection time period.

[0053] This embodiment calculates the slope of the waveform in each acquisition cycle in the measured waveform diagram based on the voltage values ​​acquired twice adjacently. The calculation method is simple and the calculation efficiency is high.

[0054] In some embodiments, in the step S1 of collecting signals, the periodic collection cycle is preferably 10 ms. It should be noted that when obtaining a low-concentration waveform, 10 ms can also be used as a collection cycle.

[0055] In this embodiment, 10ms is used as an acquisition period, which can ensure the integrity of the waveform signal in the measured waveform diagram; at the same time, when the waveform area is calculated using the above-mentioned simplified method, a shorter acquisition period is beneficial to reducing the error caused by simplified calculation; in addition, when the number of peaks is determined based on the waveform slope of each acquisition period, a shorter acquisition period is more conducive to accurately determining the peaks and troughs.

[0056] In some embodiments, in order to eliminate noise signals generated by vibration, the signal acquisition step S1 further includes a noise signal elimination step, such as Figure 3 As shown in the figure, the specific steps of removing noise signals are as follows: using the three-axis acceleration sensor set on the radon probe to collect the acceleration in the X-axis, Y-axis and Z-axis directions in real time, and calculating the real-time total acceleration of the radon probe ; Compare the real-time total acceleration of the radon probe The minimum acceleration that generates vibration noise signal is set The size of > When the waveform signal currently generated is determined to be noise, the waveform signal currently generated is eliminated. Otherwise, the waveform signal currently generated is determined to be a valid signal and is collected. It should be noted that the three-axis acceleration sensor is integrated on the circuit board of the radon probe microprocessor. It should also be noted that the acceleration in the X-axis, Y-axis and Z-axis directions collected by the three-axis acceleration sensor is used to calculate the total acceleration. The calculation formula is as follows:

[0057] (3);

[0058] In formula (3), is the total acceleration, is the acceleration in the X-axis direction, is the acceleration in the Y-axis direction, is the acceleration in the Z-axis direction.

[0059] This embodiment sets a three-axis acceleration sensor on the radon probe to obtain the real-time total acceleration of the radon probe. , to generate the minimum acceleration of the vibration noise signal is the threshold, by comparing and The size of the waveform signal can be used to determine whether it is a vibration noise signal, thereby eliminating the interference of the vibration noise signal and ensuring the measurement accuracy. It can ensure the accuracy of radon measurement in complex marine environments such as swaying vibration, and is conducive to its application on unmanned observation platforms such as buoys and submerged buoys.

[0060] In some embodiments, the minimum acceleration The setting steps are as follows: seal the radon probe into a sealed cabin, use activated carbon to remove radon gas in the air, and use the air after radon gas is removed to purge the sealed cabin until the radon gas in the sealed cabin is completely removed; place the sealed cabin after radon gas is removed on a vibration table for vibration testing, and during the test, use the three-axis acceleration sensor set on the radon probe to collect the acceleration in the X-axis, Y-axis and Z-axis directions in real time to calculate the total acceleration of the radon probe under the vibration test, and during the test, adjust the vibration parameters to change the total acceleration of the radon probe under the vibration test, and set the total acceleration of the radon probe under the vibration test when the radon probe starts to detect the waveform signal to the minimum acceleration. .

[0061] In this embodiment, the radon probe is sealed in a sealed cabin, and the radon gas in the sealed cabin is completely exhausted. Then, the minimum acceleration of the pure vibration noise signal in the absence of radon decay signal is obtained through vibration testing. , the minimum acceleration obtained in this way It is representative and can ensure the accuracy of subsequent noise signal removal.

[0062] Among them, regarding the vibration test, it should be noted that the vibration test is carried out in accordance with the vibration test standard in the "Environmental Test Methods for Marine Instruments" (GB / T 32065.14-2019), and the test is simulated with reference to the most severe use environment when it is integrated into the ship platform. Specifically, the frequency changes from 2Hz to 100Hz, the amplitude is 3mm, and the acceleration is 10m / s 2 Frequency sweep experiment.

[0063] In some embodiments, the step of removing the noise signal further comprises: > When the vibration signal is sent, it will prompt that the vibration is currently generated. Figure 3 As shown, when > If no waveform signal is currently generated, a vibration prompt signal is also issued to prompt that vibration is currently generated.

[0064] In order to more clearly and in detail introduce the radon decay number measurement method based on the pulsed ionization chamber radon measurement method provided by the embodiment of the present invention, it will be described below in conjunction with specific embodiments.

[0065] Example 1

[0066] A method for measuring the number of radon decays based on a pulsed ionization chamber radon measurement method comprises the following steps:

[0067] (1) Signal acquisition

[0068] The radon concentration is measured according to the pulse ionization chamber radon measurement method. The voltage value of the waveform signal generated by radon decay is periodically collected using the timer and analog-to-digital converter of the radon probe microprocessor. The collection period is T The time period is 10ms, and the waveform signal ends. A total of 26 cycles are collected. The collected data are shown in Table 1. The measured waveform is shown in Figure 4 shown.

[0069] Table 1 Voltage values ​​corresponding to the measured waveforms

[0070]

[0071] In this step, it should be noted that noise signals are eliminated during the acquisition process. The specific steps are: using the three-axis acceleration sensor set on the radon probe to collect the acceleration in the X-axis, Y-axis and Z-axis directions in real time, and calculate the real-time total acceleration of the radon probe ; Set the minimum acceleration to generate vibration noise signal 6.207m / s 2 ,Compare and The size of > When the current waveform signal is determined to be noise, the current waveform signal is removed; otherwise, the current waveform signal is determined to be a valid signal and is collected; at the same time, when > During this acquisition, no noise signals were generated and all the signals were valid.

[0072] Among them, the minimum acceleration The acquisition steps are as follows: seal the radon probe into a sealed cabin, use activated carbon to remove radon gas in the air, and use the air after radon gas removal to purge the sealed cabin until the radon gas in the sealed cabin is completely removed; place the sealed cabin after radon gas removal on a vibration table for vibration testing. During the test, the three-axis acceleration sensor installed on the radon probe is used to collect the acceleration in the X-axis, Y-axis and Z-axis directions in real time to calculate the total acceleration of the radon probe under the vibration test; the vibration test is carried out according to the vibration test standard in the "Environmental Test Method for Marine Instruments" (GB / T 32065.14-2019), and a simulation test is carried out with reference to the most stringent use environment when it is integrated into the ship platform, specifically the frequency changes from 2Hz to 100Hz, the amplitude is 3mm, and the acceleration is 10m / s 2 Frequency sweep experiment. Due to the large amount of vibration test data, we will not list all the data here. We will only take part of the data as an example. The vibration test data is shown in Table 2, where the total acceleration It is calculated according to the above formula (3).

[0073] Table 2 Vibration test data

[0074]

[0075] During the vibration test, as the vibration parameters were adjusted, the total acceleration of the radon probe changed. In the 15,400th test, the radon probe began to detect a waveform signal. The total acceleration of the radon probe at this time was set to the minimum acceleration. ,Right now Take 6.207m / s 2 .

[0076] (2) Calculate the minimum theoretical number of waveforms based on the waveform area

[0077] based on Figure 4 The total waveform area of ​​the waveform in the total acquisition time period is calculated using the above formula (1) and the data in Table 1. S 355500mV•ms; the maximum waveform area of ​​a single waveform signal corresponding to a single radon decay S max is 125550mV•ms, S Divide by S max The result is rounded up to get the minimum theoretical number of waveforms in the total acquisition time period. N 0 is 3.

[0078] In this step, it should be noted that the maximum waveform area of ​​a single waveform signal corresponding to a single radon decay is obtained. S max The specific steps are as follows: under a measurement environment with a radon concentration of 150 Bq / m³, the radon concentration is measured according to the pulse ionization chamber radon measurement method; the voltage value of the waveform signal generated by radon decay is collected using the timer and analog-to-digital converter of the radon probe microprocessor to obtain a low-concentration waveform diagram composed of several non-overlapping waveform signals; the waveform area of ​​the single waveform signal corresponding to each radon decay in the low-concentration waveform diagram is calculated according to formula (2); the maximum value among them is taken as the maximum waveform area of ​​the single waveform signal corresponding to a single radon decay S max Due to the large amount of voltage data collected, we will not list all the data here. We will only take the collected data of a single waveform signal with the largest waveform area as an example. The collected data is shown in Table 3, and the corresponding single waveform diagram is shown in Figure 5 As shown, according to formula (2), the waveform area is calculated to be 125550mV•ms, which is the maximum waveform area. S max .

[0079] Table 3. The collected voltage values ​​corresponding to a single waveform signal

[0080]

[0081] (3) Determine the number of peaks based on the change in waveform slope

[0082] based on Figure 4 The slope of the waveform in each acquisition period is calculated using the above formula for calculating the slope of the waveform in each acquisition period as shown in Table 4; when the slope changes from positive to negative, it is recorded as a peak, and when the slope changes from negative to positive, it is recorded as a trough. The number of peaks in the total acquisition period is obtained by counting N 1 is 3;

[0083] Table 4 Calculation results of waveform slopes for each acquisition period in the measured waveform

[0084]

[0085] (4) Determine the number of radon decays

[0086] because N 1 =N 0, determine peak separation, take N 1 as the number of radon decays N , determine the number of radon decays N is 3.

[0087] The waveform signal collected in this embodiment is Figure 4 It can be seen that there is waveform overlap. If the existing pulse ionization chamber radon measurement method is used to determine the number of radon decays based on the number of high levels, since the waveform signal is always at a high level, only one radon decay is recorded. However, the radon decay number measurement method based on the pulse ionization chamber radon measurement method provided by this embodiment obtains three radon decays, avoiding the problem of missed counting caused by waveform overlap.

[0088] Since no noise signal appears during the signal acquisition process of this embodiment, in order to verify the effectiveness of the noise signal removal step in the signal acquisition step S1, a supplementary noise signal removal effect verification experiment is performed as follows:

[0089] The sealed cabin after radon removal was placed on a vibration table, and lateral vibration and / or vertical vibration were applied according to Table 5 (vibration parameters: frequency range 2-100 Hz, amplitude 3 mm, frequency sweep number 2). The waveform signal acquisition results of the radon probe when the above-mentioned noise signal removal step was used and when the noise signal removal step was not performed are shown in Table 5.

[0090] Table 5 Experimental results for verifying the effect of noise signal removal

[0091]

[0092] Table 5 shows that without the noise signal removal step, the radon probe collected waveform signals under the lateral and / or vertical vibrations applied during the five frequency sweep experiments. However, after the noise signal removal step was performed, no noise signals generated by vibration were collected. This demonstrates that the noise signal removal step can effectively address signal interference caused by vibration.

[0093] Example 2

[0094] A method for measuring the number of radon decays based on a pulsed ionization chamber radon measurement method comprises the following steps:

[0095] (1) Signal acquisition

[0096] The radon concentration is measured according to the pulse ionization chamber radon measurement method. The voltage value of the waveform signal generated by radon decay is periodically collected using the timer and analog-to-digital converter of the radon probe microprocessor. The collection period is T The sampling period is 10ms, and the waveform signal is collected until it ends. A total of 22 cycles are collected. The collected data are shown in Table 6. The measured waveform is shown in Table 6. Figure 6 shown.

[0097] Table 6 Voltage values ​​corresponding to the measured waveforms

[0098]

[0099] In this step, it should be noted that noise signals are removed during the acquisition process, and the noise signal removal steps are the same as in Example 1. In this acquisition, no noise signals are generated, and all signals are valid.

[0100] (2) Calculate the minimum theoretical number of waveforms based on the waveform area

[0101] based on Figure 6 The total waveform area of ​​the waveform in the total acquisition time period is calculated using the above formula (1) and the data in Table 6. S The maximum waveform area of ​​a single waveform signal corresponding to a single radon decay obtained in Example 1 is 291550mV·ms. S max ( S max = 125550 mV•ms) S Divide by S max The result is rounded up to get the minimum theoretical number of waveforms in the total acquisition time period. N 0 is 3.

[0102] (3) Determine the number of peaks based on the change in waveform slope

[0103] based on Figure 6The slope of the waveform in each acquisition period is calculated using the above formula for calculating the slope of the waveform in each acquisition period as shown in Table 7; when the slope changes from positive to negative, it is recorded as a peak, and when the slope changes from negative to positive, it is recorded as a trough. The number of peaks in the total acquisition period is obtained by counting. N 1 is 2;

[0104] Table 7 Calculation results of waveform slopes for each acquisition period in the measured waveform diagram

[0105]

[0106] (4) Determine the number of radon decays

[0107] because N 1< N 0, determine if there is peak overlap, take N 0 as the number of radon decays N , determine the number of radon decays N is 3.

[0108] The waveform signal collected in this embodiment is Figure 6 It can be seen that there is waveform overlap. If the existing pulse ionization chamber radon measurement method is used to determine the number of radon decays based on the number of high levels, since the waveform signal is always at a high level, only one radon decay is recorded; if the number of peaks is determined only based on the change in the waveform slope, the number of radon decays is 2, and it is impossible to know whether there is peak overlap; however, the radon decay number measurement method based on the pulse ionization chamber radon measurement method provided in this embodiment obtains 3 radon decays, while avoiding the problem of missed counting caused by waveform overlap and peak overlap.

Claims

1. A method for measuring the number of radon decays based on a pulsed ionization chamber radon measurement method, characterized in that: The steps include: Acquisition signal: Measure radon concentration according to the pulse ionization chamber radon measurement method. Use the timer and analog-to-digital converter of the radon probe microprocessor to periodically acquire the voltage value of the waveform signal generated by radon decay until the waveform signal ends, and obtain the measured waveform graph; Calculate the minimum theoretical number of waveforms based on waveform area: Calculate the total waveform area of ​​the waveforms within the total acquisition time period based on the measured waveform graph S ; Get the maximum waveform area of ​​a single waveform signal corresponding to a single radon decay S max ,right S Divide by S max The result is rounded up to get the minimum theoretical number of waveforms in the total acquisition time period. N 0; Determine the number of peaks based on the change in waveform slope: Based on the measured waveform, calculate the slope of the waveform within each acquisition cycle; When the slope changes from positive to negative, it is recorded as a peak; when the slope changes from negative to positive, it is recorded as a trough. The number of peaks in the total acquisition time period is counted. N 1; Determine the number of radon decays: N 1< N 0, it is determined that there is peak overlap, and the N 0 as the number of radon decays N On the contrary, it is determined that the peak is separated and the N 1 as the number of radon decays N .

2. The method for measuring the number of radon decays based on the pulsed ionization chamber radon measurement method according to claim 1, wherein: In the step of calculating the minimum theoretical number of waveforms based on the waveform area, the total waveform area S The calculation formula is as follows: ； in, T is the acquisition period corresponding to the measured waveform; is the initial voltage value in the measured waveform, It is the voltage value collected for the first time in the measured waveform. This is the voltage value collected for the second time in the measured waveform, and so on. is the voltage value collected for the n-1th time in the measured waveform diagram, is the voltage value collected for the nth time in the measured waveform; n is the number of collections in the total collection time period.

3. The method for measuring the number of radon decays based on the pulsed ionization chamber radon measurement method according to claim 1, wherein: In the step of calculating the minimum theoretical number of waveforms based on the waveform area, the maximum waveform area of ​​a single waveform signal corresponding to a single radon decay is obtained. S max The specific steps are as follows: Under a measurement environment where the radon concentration is 300 Bq / m³ or less, the radon concentration is measured using the pulse ionization chamber radon measurement method; the voltage value of the waveform signal generated by radon decay is collected using the timer and analog-to-digital converter of the radon probe microprocessor to obtain a low-concentration waveform graph composed of several non-overlapping waveform signals; the waveform area of ​​the single waveform signal corresponding to each radon decay in the low-concentration waveform graph is calculated; and the maximum value among them is taken as the maximum waveform area of ​​the single waveform signal corresponding to a single radon decay. S max .

4. The method for measuring the number of radon decays based on the pulsed ionization chamber radon measurement method according to claim 3, wherein: The waveform area of ​​the i-th single waveform signal in the low-concentration waveform graph S i The calculation formula is as follows: ； in, T’ is the acquisition period corresponding to the low-concentration waveform; is the initial voltage value of the i-th single waveform signal, The voltage value collected for the first time in the i-th single waveform signal, is the voltage value collected for the second time in the i-th single waveform signal, and so on. is the voltage value collected at the m-1th time in the ith single waveform signal, is the voltage value collected for the mth time in the ith single waveform signal; m is the number of collections within the collection time period of the ith single waveform signal.

5. The method for measuring the number of radon decays based on the pulsed ionization chamber radon measurement method according to claim 1, wherein: In the step of determining the number of peaks based on the change in waveform slope, the slope of the waveform in the first acquisition cycle is K The calculation formula for 1 is , the slope of the waveform in the second acquisition cycle K The calculation formula for 2 is , and so on, the slope of the waveform in the nth acquisition cycle is K n The calculation formula is ;in, T is the acquisition period corresponding to the measured waveform; is the initial voltage value in the measured waveform, It is the voltage value collected for the first time in the measured waveform. This is the voltage value collected for the second time in the measured waveform, and so on. is the voltage value collected for the n-1th time in the measured waveform diagram, is the voltage value collected for the nth time in the measured waveform; n is the number of collections in the total collection time period.

6. The method for measuring the number of radon decays based on the pulsed ionization chamber radon measurement method according to claim 1, 2 or 5, characterized in that: In the signal acquisition step, the acquisition period for periodic acquisition is 10ms.

7. The method for measuring radon decay times based on pulsed ionization chamber radon measurement according to claim 1, wherein: The signal acquisition step also includes a noise signal removal step, which specifically comprises: using a three-axis acceleration sensor provided on the radon probe to collect accelerations in the X-axis, Y-axis and Z-axis directions in real time, and calculating the real-time total acceleration of the radon probe. ; Compare the real-time total acceleration of the radon probe The minimum acceleration that generates vibration noise signal is set The size of > When the waveform signal currently generated is determined to be noise, the waveform signal currently generated is removed; otherwise, the waveform signal currently generated is determined to be a valid signal and is collected.

8. The method for measuring the number of radon decays based on the pulsed ionization chamber radon measurement method according to claim 7, characterized in that: minimum acceleration The setting steps are as follows: sealing the radon probe into a sealed cabin, removing radon gas from the air with activated carbon, and purging the sealed cabin with the radon-removed air until the radon gas in the sealed cabin is completely removed; The sealed cabin after radon gas removal is placed on a vibration table for vibration testing. During the test, the three-axis acceleration sensor provided on the radon probe is used to collect accelerations in the X-axis, Y-axis and Z-axis directions in real time to calculate the total acceleration of the radon probe under the vibration test. During the test, the vibration parameters are adjusted to change the total acceleration of the radon probe under the vibration test. The total acceleration of the radon probe under the vibration test when the radon probe begins to detect the waveform signal is set as the minimum acceleration. .

9. The method for measuring the number of radon decays based on the pulsed ionization chamber radon measurement method according to claim 8, characterized in that: The vibration test is specifically performed with a frequency ranging from 2 Hz to 100 Hz, an amplitude of 3 mm, and an acceleration of 10 m / s. 2 Frequency sweep experiment.

10. The method for measuring radon decay times based on the pulsed ionization chamber radon measurement method according to claim 7, wherein: The step of removing the noise signal also includes: > When the device is turned on, a vibration prompt signal is issued.

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