Method and device for measuring intrinsic characteristics of thorium

Abstract

The invention provides an intrinsic measurement method and device for thorium. The intrinsic measurement method comprises the following steps: recording detection time of alpha particles released by decay of to-be-measured < 220 > Rn gas and daughter < 216 > Po in a measurement chamber; performing Bayesian analysis according to the detection time, and calculating a 220Rn-216Po true coincidence count; and according to the < 220 > Rn count, the < 216 > Po count and the < 20 > Rn-< 216 > Po true coincidence count, calculating the activity concentration of the thorium. According to the intrinsic measurement method and device, two alpha particles emitted by successive decay of 220Rn and 216Po are utilized to form an intrinsic characteristic conforming to a signal, so that the detection efficiency is reduced; the detection efficiency is reduced, so that the method and the device do not need to measure the detection efficiency of the standard scale from the outside, and have self-traceability; meanwhile, the influence of the change of the detection efficiency on the measurement accuracy is avoided, and the measurement accuracy is improved.

Description

Technical Field

[0001] This invention belongs to the field of radiometric measurement technology, and in particular relates to a method and apparatus for intrinsic measurement of thorium gas. Background Technology

[0002] Thorium gas ( 220 Radon (Rn) is one of the isotopes of the radioactive element radon (Rn), a naturally occurring radioactive inert gas. Radon is recognized by the World Health Organization as the second leading cause of lung cancer after smoking. Radon exposure is a major source of natural radiation dose for the public. Among the natural ionizing radiation received by humans, radon has two radioactive isotopes (Rn, Rn, and Rn). 222 Rn and 220 The radiation dose contributed by Rn and its short-lived daughter particles exceeds half of the total natural radiation dose. Therefore, accurate measurement of Rn in the air is crucial. 222 Rn and 220 Rn is of great significance for assessing public health risks.

[0003] for 220 Isotopes of Rn 222 For Rn, my country has established corresponding measurement standards, making 222 Rn measuring instruments are traceable to a unified standard, ensuring the accuracy of measurement results. However, for 220 Rn, my country has not yet established corresponding measurement standards, resulting in 220 The Rn measuring instruments are not traceable in the country, their values ​​cannot be standardized, and their accuracy cannot be guaranteed.

[0004] Internationally, the German Federal Institute of Physics (PTB) and the French Henri Becquerel National Laboratory (LNE-LNHB) have established [relationships / institutions]. 220 Primary measurement standard for Rn activity concentration. (Germany) 220 Rn primary measurement standard is not directly measured 220 Rn, but by measuring its parent source 228 Th activity and ejection coefficient (i.e. 228 Th decay 220 The proportion of Rn extracted from the maternal source is used to indirectly estimate its standard. 220 Rn indoor 220 Rn concentration. The accuracy of this method is highly dependent on standards. 220 The uniformity and stability of indoor gases, Rn, thus limiting 220 The dimensions and practical applications of the Rn chamber. (France) 220 A set of Rn primary measurement standards was developed. 20 The Rn measuring device was used to calculate the device's performance using a Monte Carlo simulation method. 220 The detection efficiency of Rn and its daughter bodies is to achieve 220Accurate measurement of Rn activity concentration. The accuracy of this method heavily depends on the accuracy of the detection efficiency, which is affected by factors such as temperature, humidity, and detector condition. Therefore, its accuracy is relatively lower than that of the German method. 220 The primary measurement standard for Rn is poor.

[0005] In summary, this study aims to develop a method that does not rely on external measurement standards and avoids the limitations of the German and French approaches. 220 Accurate Rn measurement methods are helpful. 220 The development of Rn measurement capabilities will help ensure public radiation safety. Summary of the Invention

[0006] This invention provides a method and apparatus for measuring the intrinsic properties of thorium-injected gas. The method and apparatus utilize... 220 Rn and 216 The intrinsic property that the two alpha particles emitted by the successive decay of Po constitute a coincidence signal eliminates the detection efficiency. Since the detection efficiency is eliminated, the method and device do not need to be calibrated by an external measurement standard, thus possessing self-traceability. At the same time, it also avoids the influence of changes in detection efficiency on measurement accuracy, thereby improving measurement accuracy.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: One objective of this invention is to provide an intrinsic method for measuring the activity concentration of thorium-injected gas, the intrinsic measurement method comprising the following steps: Record the measurement chamber to be measured 220 Rn gas and its products 216 Detection time of alpha particles released by Po decay; Bayesian analysis is performed based on the detection time to calculate... 220 Rn- 216 Po truly matches the count; according to 220 Rn count, 216 Po count and the aforementioned 20 Rn- 216 Po true coincidence counts are used to calculate the activity concentration of the thorium ejection gas.

[0008] As a preferred technical solution of the present invention, the formula for calculating the thorium injection gas activity concentration is shown in Equation 1: Formula 1 in, C For measuring the chamber 220 The activity concentration of Rn for 220 Rn counts, for 216 Po count, for220 Rn- 216 Po truly matches the count. V To measure the chamber volume, T For measuring duration; λ for 216 The decay constant of Po τ To match the window duration, the expression To conform to the decay coefficient, it means 216 The probability of Po decaying within the specified window.

[0009] As a preferred embodiment of the present invention, the time accuracy of the detection time is not less than 500 ms, and preferably not less than 10 ms.

[0010] As a preferred technical solution of the present invention, the measurement chamber can also record the data to be measured. 220 Rn gas and its products 216 The energy of the alpha particles released by the decay of Po.

[0011] As a preferred technical solution of the present invention, the detection time difference of the two α particles is compared with the coincidence window to determine whether the two α particles constitute a coincidence signal, and then each coincidence signal is accumulated according to Equation 2. 220 Rn- 216 The probability that Po truly matches the signal is obtained. 220 Rn- 216 Po truly matches the count: Formula 2 in, i Indicates the first i A matching signal, w i Indicates the first i The time difference between the α signal and the α signal of a given signal. This indicates that the time difference between the α signal and the α signal is 0. w i In this case, the coincidence signal is 220 Rn- 216 The probability that Po truly matches the signal.

[0012] As a preferred technical solution of the present invention, when performing the Bayesian analysis, the coincidence signal is calculated according to Equation 3. 220 Rn- 216 The probability that Po truly matches the signal: Formula 3 in, , These represent, respectively, a coincidence signal without posterior information. 220Rn- 216 Po's prior probabilities of true coincidence signals and random coincidence signals; , Each represents a coincident signal. 220 Rn- 216 Under the premise of true coincidence and random coincidence of Po signal, the time difference of its α signal is: w The probability of.

[0013] As a preferred technical solution of the present invention, when the measurement chamber records the measurement to be performed... 220 When determining the energy of the alpha particles released by the decay of Rn gas, the method not only compares the detection time difference of the two alpha particles with the coincidence window, but also uses the energy of the two alpha particles to determine whether they constitute a coincidence signal, and calculates the energy of the two alpha particles. 220 Rn- 216 Po truly matches the count.

[0014] A second objective of this invention is to provide an intrinsic thorium gas measurement device, wherein the intrinsic thorium gas activity concentration measurement device can operate the intrinsic thorium gas measurement method provided in the first objective.

[0015] As a preferred technical solution of the present invention, the intrinsic measuring device includes a measuring chamber, a counting module, and a data analysis module; The counting module is used to record the test results. 220 The detection time of alpha particles released by the decay of Rn gas is also used to record the analyte. 220 The energy of alpha particles released by the decay of Rn gas; The data analysis module is used to perform Bayesian analysis and calculate the activity concentration of thorium gas.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: (1) This invention provides an intrinsic measurement method for thorium-injected gas, which conforms to the principle that the window width can be arbitrarily adjusted during the analysis process, while traditional methods... 220 Rn- 216 Po conforms to the counting method, which does not have such requirements.

[0017] (2) This invention provides an intrinsic measurement method for thorium-injected gas, which proposes to estimate the true coincidence signal count by accumulating the probability of each coincidence signal being a true coincidence signal, while the traditional method... 220 Rn- 216 The Po coincidence counting method estimates the true coincidence count by subtracting the random coincidence count from the total coincidence count. The method proposed in this invention can estimate the true coincidence count more accurately.

[0018] (3) This invention provides an intrinsic measurement method for thorium-injected gas. This intrinsic measurement method proposes to use Bayesian analysis to calculate the probability that a coincidence signal is a true coincidence signal, while the traditional method... 220 Rn- 216 The Po coincidence counting method does not involve probability calculations and is therefore unsuitable for Bayesian analysis methods that rely on probability calculations. Meanwhile, this invention utilizes the time difference between the two α signals within a coincidence signal, providing an informatics basis for more accurate estimation of true coincidence techniques using Bayesian analysis methods. This approach is also a traditional... 220 Rn- 216 Po meets the conditions that the counting method does not possess.

[0019] (4) The present invention provides an intrinsic measurement method for thorium-injected gas, which will... 220 Rn and 216 Po's product of each count divided by 220 Rn- 216 Po coincides with the counting, and the detection efficiency is reduced, so that the present invention does not require external measurement standard scale to calibrate its detection efficiency, and has self-traceability. Attached Figure Description

[0020] Figure 1 for 220 Schematic diagram of the Rn decay chain.

[0021] Figure 2 for 220 Schematic diagram of Rn measurement energy spectrum.

[0022] Figure 3 A schematic diagram of the thorium-ejected gas intrinsic measurement device provided for a specific embodiment of the present invention.

[0023] In the diagram: 1-Measuring chamber, 2-Counting module, 3-Data analysis module.

[0024] Figure 4 The intrinsic measurement method of thorium-injected gas and the flow-type scintillation chamber provided in the embodiments of the present invention 220 Comparison chart of test results for the Rn measurement method. Detailed Implementation

[0025] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0026] This invention provides an intrinsic measurement method for thorium gas activity concentration, which includes the following steps: Record the measurement chamber to be measured 220 Rn gas and its products 216 Detection time of alpha particles released by Po decay; Bayesian analysis was performed based on the detection time to calculate... 220 Rn-216 Po truly matches the count; according to 220 Rn count, 216 Po count and 20 Rn- 216 Po true coincidence counts are used to calculate the activity concentration of thorium gas.

[0027] Figure 1 Showing 220 Rn decay chain, including 220 The decay relationships, half-lives, decay types (α or β), and α-particle energies between Rn and its daughters. Figure 1 As shown, 220 Rn decay releases an alpha particle with an energy of 6.29 MeV, and its subsequent daughter particles... 216 Po、 212 Bi、 212 Po may also undergo alpha decay, releasing alpha particles with energies of 6.78, 6.05, and 8.78 MeV, respectively. 212 Bi has two decay branches, α and β, with the α decay branch accounting for 35.9%. Because α particles have high energy and are easy to detect and distinguish, they are usually measured... 220 The alpha particles emitted by Rn and its daughters are realized. 220 Measurement of Rn.

[0028] In this decay chain, 220 Rn's first child 216 The half-life of Po is very short (0.144 s), therefore 216 Po generally and 220 Rn remains in equilibrium, with their activities approximately equal; while the second daughter body... 212 Pb has a long half-life (10.6 h). 212 Pb after 212 Bi、 212 Po is difficult to understand 220 Rn reaches an equilibrium state, and its activity is related to 220 The activities of Rn exhibit complex dynamic relationships. Therefore, existing... 220 Rn measurement generally only includes 220 Rn and 216 The alpha particle count of Po was used as an effective measurement signal, and exclusion was performed using energy spectrum differentiation or time series analysis methods. 212 Bi and 212 Alpha particle interference of Po.

[0029] existing 220 Rn measurement typically utilizes 220 Rn and (or) 216 Po count (hereinafter referred to as "Po count") 220Rn / 216 Po count (represented by "Po count"), will 220 Rn / 216 Po count divided by detector pair 220 Rn / 216 The detection efficiency of Po α particles, combined with other parameters, was estimated. 220 Rn activity concentration can be referred to as " 220 Rn / 216 Po counting method, France 220 The primary measurement standard for Rn and almost all current standards 220 Commercial Rn measuring instruments all use this type of measurement method.

[0030] remove 220 Rn / 216 Besides the Po counting method, there is another type of existing technology... 220 Rn- 216 "Po coincidence counting method": This method utilizes... 220 Rn- 216 The coincidence signal, consisting of two consecutive alpha particles generated by the continuous decay of Po, is measured. 220 Rn- 216 Po coincides with signal counting, satisfying equation 4: Formula 4 As can be seen from equation 4 220 Rn- 216 Po conforms to the count and 220 Rn activity concentration is directly proportional to Rn activity concentration, therefore it can be derived from Rn activity concentration. 220 Rn- 216 Po conforms to the multiplication (or division) of the count by a fixed conversion factor, and estimates 220 Rn activity concentration. The fixed conversion coefficient is mainly composed of... 220 Rn detection efficiency and 216 The Po detection efficiency (with other coefficients easily and accurately determined) can be calculated theoretically or obtained from standard source calibration. This method was proposed as early as the 1960s by Giffin et al., and several improvements have been proposed since. Unlike the method proposed in this invention, this type of measurement method involves calculation... 220 When calculating Rn activity concentration, the detection efficiency still needs to be included in the calculation. The detection efficiency needs to be calibrated by an external standard measurement. The measurement result will deviate from the true value due to fluctuations in the detection efficiency.

[0031] 220 Rn- 216 In the Po coincidence counting method, there is a problem of distinguishing between true coincidence signals and accidental coincidence signals. When the time interval between two alpha particles is shorter than the coincidence window length, a coincidence signal is formed, which may originate from...220 Rn- 216 The two consecutive alpha particles produced by the continuous decay of Po may also originate from two unrelated alpha particles, only their detection times happen to be close. The former is called a true coincidence signal, and the latter is called a random coincidence signal. Formula (1) requires the counting of true coincidence signals for calculation, so true coincidence signals need to be selected from all the measured coincidence signals. Theoretically, considering that all alpha counts are randomly and uniformly distributed throughout the measurement time, the random coincidence count is proportional to the square of the total alpha count and proportional to the coincidence window length, so the expected value of the random coincidence count can be calculated. Then, the expected value of the random coincidence is subtracted from the total coincidence count to estimate the true coincidence count. However, this method has a large error when the proportion of random coincidences is high due to the random fluctuations of the random coincidence count. For traditional coincidence measurement methods, such as β-γ coincidence, the coincidence signal composed of two rays emitted by the decay of a single nuclide is used. Its coincidence window width is generally very short (microsecond level), so the proportion of random coincidences is generally very low. This method is sufficient to accurately estimate the true coincidence count. 220 The Rn coincidence counting method utilizes 220 Rn- 216 Po decays continuously and requires waiting. 216 Po decay, with coincidence window widths typically lasting hundreds of milliseconds, generally results in a high proportion of accidental coincidences, leading to significant errors in estimating true coincidence counts using this method. Furthermore, with... 220 An increase in Rn activity concentration leads to an increase in the total α count, and a significant increase in the random coincidence count. Therefore, random coincidences can also lead to... 220 Rn- 216 The measurement range of the Po coincidence counting method is limited.

[0032] In conclusion, 220 Rn- 216 The Po coincidence counting method has disadvantages such as complex implementation, difficulty in handling accidental coincidences, and a limited effective measurement range. Therefore, compared to 220 Rn / 216 Po counting method, 220 Rn- 216 The Po coincidence counting method lacks practical applications in both academia and business.

[0033] This invention proposes to estimate the true coincidence signal count using the cumulative probability of each coincidence signal being a true coincidence signal, whereas the traditional method... 220 Rn- 216 The Po coincidence counting method estimates the true coincidence count by subtracting the random coincidence count from the total coincidence count. The method proposed in this invention can theoretically estimate the true coincidence count more accurately.

[0034] This invention proposes using Bayesian analysis to calculate the probability that a coincidence signal is a true coincidence signal. Traditional...220 Rn- 216 This method is not found in the Po coincidence counting method. This is because traditional 220 Rn- 216 The Po coincidence counting method does not involve probability calculations and is therefore unsuitable for Bayesian analysis methods that calculate probabilities. Furthermore, this invention utilizes the time difference between the two α signals within the coincidence signal, providing an informatics basis for more accurate estimation of true coincidence techniques using Bayesian analysis methods. This is also a traditional approach. 220 Rn- 216 Po meets the conditions that the counting method does not possess.

[0035] In this invention, 220 Rn and 216 Po's product of each count divided by 220 Rn- 216 Po coincident counting, by reducing the detection efficiency, eliminates the need for external measurement standards to calibrate its detection efficiency, thus possessing self-traceability. Traditional 220 Rn- 216 Po coincidence counting method requires external measurement of standard scales to determine its detection efficiency.

[0036] In one specific embodiment of the present invention, the time accuracy of the detection time is not less than 500 ms, preferably not less than 10 ms.

[0037] In one specific embodiment of the present invention, before performing the Bayesian analysis, it is determined whether the two alpha particles constitute a coincidence signal by comparing the detection time difference between the two alpha particles with the coincidence window. The detection time can be absolute or relative. A coincidence signal is constituted if the detection time difference between the two alpha particles is not greater than the coincidence window. This design allows the width of the coincidence window to be arbitrarily adjustable, enabling the use of different coincidence window widths, which is beneficial for more accurate estimation. 220 Rn concentration, and is beneficial for expansion 220 Rn measurement range. Specifically, for low concentrations... 220 Rn, using a longer conformance window, can increase 220 Rn- 216 Po coincident counting reduces statistical error; for high concentrations 220 Using a shorter coincidence window (Rn) can reduce the proportion of accidental coincidences and thus reduce the error caused by accidental coincidences. Therefore, by adjusting the width of the coincidence window, a wider range of coincidences can be achieved. 220 The Rn concentration meets the measurement accuracy requirements, and the expansion... 220 Rn activity concentration measurement range.

[0038] In one specific embodiment of the present invention, the measurement chamber can also record the data to be measured. 220 Rn gas and its products 216The energy of the alpha particles released by the decay of Po.

[0039] In one specific embodiment of the present invention, Bayesian analysis includes: The parameters required to calculate Bayes' theorem include the random coincidence count, the prior probability of the true coincidence signal, the prior probability of the random signal, and the time difference between the two α signals. w The probability and the time difference between the two α signals are: w The probability of; Substituting the parameter values ​​into Bayes' theorem, we obtain the time difference between the two α signals as follows: w The posterior probability of the signal that matches the given signal; Iterate through all coincident signals, calculate the probability of a true coincident signal, and sum them to obtain the given result. 20 Rn- 216 Po truly matches the count.

[0040] When the measurement chamber does not record the test result 220 When calculating the energy of alpha particles released by the decay of Rn gas, the coincidence count is obtained from the total alpha count, measurement duration, and coincidence window width.

[0041] In one specific embodiment of the present invention, the Bayesian analysis method is as follows: The prior probability that a coincident signal is true. Satisfying Equation 5: Formula 5 A coincident signal is a random coincident signal. The prior probability satisfies equation 6: Formula 6 in, For coincident coincidence counting, equation 7 is satisfied: Formula 7 in, This is the total α count.

[0042] For a true coincidence signal, the time difference between its two α signals is: w probability Satisfying Equation 8: Formula 8 For a coincident signal, the time difference between its two α signals is: w probability Satisfying Equation 9: Formula 9 in, It is an infinitesimal time element, which can be canceled out in subsequent calculations.

[0043] According to Bayes' theorem, the time difference between the two α signals is: w The posterior probability that a signal is a true coincident signal is given by the given information. Satisfying Equation 3: Formula 3 Iterate through all coincident signals, calculate the probability of each signal being a true coincident signal according to Equation 3, and accumulate the probabilities to obtain the true coincident count. As shown in Equation 2; Formula 2 in, i Indicates the first i One conformity count, Indicates the first i Each coincides with the time difference of its α signal.

[0044] In one specific embodiment of the present invention, during the calculation of the true coincidence count using the Bayesian analysis method, the true coincidence count itself needs to be input into Equations 5 and 6. The true coincidence count can be estimated using iterative methods or maximum likelihood estimation, etc.

[0045] In one specific embodiment of the present invention, as an example, estimation is based on an iterative method. 220 Rn- 216 Methods for counting true Poisson coincidences include: (a) Calculation using Monte Carlo simulation method 220 Rn detection efficiency and 216 Po detection efficiency, combined with 220 Rn / 216 Po counting, using traditional 220 Rn / 216 Po counting method calculation 220 Rn activity concentration; (b) Using the calculation results 220 Rn detection efficiency and 216 Po detection efficiency and 220 Rn activity concentration, calculated according to Equation 2 220 Rn- 216 Po coincidence count, i.e., true coincidence count; (c) Substitute the calculated true coincidence counts into the Bayesian analysis method to calculate new true coincidence counts; (d) Update using the new coincident count according to Equation 3. 220 Rn activity concentration, and updated according to Equation 10. 220 Rn detection efficiency and216 Po detection efficiency.

[0046] Formula 10 Repeat steps (b)-(d) until convergence.

[0047] In one specific embodiment of the present invention, when the measurement chamber records the data to be measured... 220 When considering the energy of the α particles released by the decay of Rn gas, the prior probability formulas for true coincidence counts and random coincidence counts remain as shown in Equations 5 and 6. However, due to the introduction of energy distinction, the expected value of the random coincidence count rate is calculated according to Equation 11: Formula 11 in, The energy is located in the range of 3.2~6.3 MeV ( Figure 2 α count in region A) The energy is located at 6.3~6.8 MeV ( Figure 2 α count in region B.

[0048] In this invention, since alpha particles may lose some energy in the air and on the surface of the detector before entering the sensitive area of ​​the detector, the recorded energy of the alpha particle is not equal to its emitted energy, but rather exhibits a certain degree of broadening and tailing in the energy spectrum. Figure 2 This demonstrates a typical 220 The Rn energy spectrum, based on its energy counting peaks, can be mainly divided into three regions: A, B, and C. Region A covers 3.2–6.3 MeV and is mainly composed of… 220 Rn (6.29 MeV) and 212 The Bi (6.05 MeV) contribution also includes a certain amount of 216 The Po region (6.78 MeV) exhibits a tail; region B covers 6.3–6.8 MeV, primarily composed of… 216 Po (6.78 MeV) contributes, and the C region covers 8.0~9.0 MeV, mainly due to 212 Po (8.78 MeV) contribution. In summary, when selecting coincidence counts, the preceding α count should be located in region A, and the following α count should be located in region B.

[0049] In one specific embodiment of the present invention, except for Equation 11, the calculation formula of the Bayesian analysis method incorporating energy information is no different from that of the Bayesian analysis method without incorporating energy information. However, note that the meanings of some physical symbols in the formula have changed. The most important change is in the determination of the conformity signal, which requires combining energy information for judgment. Only when two time intervals are shorter than... τOnly α counts whose preceding α count is in energy region A and whose subsequent α count is in energy region B are considered coincident counts, and only then do they require iterative calculation of their probability of being true coincident counts in Equation 9. Furthermore, 220 Rn and 216 The detection efficiency of Po is no longer the probability that the two nuclides emit alpha particles and are detected, but rather the probability that they are detected and recorded in the A and B energy regions.

[0050] In this invention, the activity concentration of the thorium-injected gas is calculated according to Equations 12 and 13: Formula 12 Formula 13 in, for 220 Rn- 216 Po conforms to the count, C For measuring the chamber 220 The activity concentration of Rn V To measure the chamber volume, T For measuring duration; For the detector to 220 Detection efficiency of Rn-released alpha particles For the detector to 216 Detection efficiency of alpha particles released by Po. λ for 216 The decay constant of Po (4.81 s) -1 ), τ To match the window duration, the expression To conform to the decay coefficient, it means 216 The probability of Po decaying within a window is... for 220 Rn counts, for 216 Po count; Equation 1 can be obtained from Equations 12 and 13, that is... 220 Methods for calculating Rn activity concentration, i.e. 220 Rn counting and 216 The product of Po counts, divided by 220 Rn- 216 The Po coincidence count is then divided by the measured chamber volume and the total measurement time, and then multiplied by the coincidence decay coefficient to obtain the result. 220 Rn activity concentration.

[0051] Formula 1.

[0052] The present invention provides an intrinsic measurement device for thorium gas activity concentration, which can operate any of the intrinsic measurement methods for thorium gas activity concentration provided in the specific embodiments.

[0053] In one specific embodiment of the present invention, the structure of the intrinsic measuring device for thorium injection gas activity concentration is as follows: Figure 3 As shown, the intrinsic measurement device includes a measurement chamber 1, a counting module 2, and a data analysis module 3; The measuring chamber 1, the counting module 2, and the data analysis module 3 can be connected by means of data cable, wireless data transmission, integrated circuit coupling, or optocoupler, but are not limited to the above connection methods. The specific connection method can be selected according to the product production requirements. Counting module 2 is used to record the test results. 220 The detection time of alpha particles released by the decay of Rn gas is also used to record the analyte. 220 The energy of alpha particles released by the decay of Rn gas; Data analysis module 3 is used for Bayesian analysis calculations. 220 Rn- 216 Po true coincidence count, and calculation of thorium gas activity concentration.

[0054] In one specific embodiment of the present invention, the measuring chamber 1 has an alpha particle measuring function, which may include a scintillator detector, a semiconductor detector, or a gas detector, etc.

[0055] In one specific embodiment of the present invention, the scintillator detector may be a ZnS(Ag) scintillation chamber, the semiconductor detector may be a PIPS detector, and the gas detector may be an ionization chamber or a proportional counter.

[0056] In one specific embodiment of the present invention, the counting module 2 includes a high-voltage power supply module, a preamplifier, a comparator, and a multichannel analyzer, etc.

[0057] In one specific embodiment of the present invention, the data analysis module 3 may include a computer, which performs Bayesian analysis calculations using data analysis software built into the computer. 220 Rn- 216 Po true coincidence counting, realizing the conversion of alpha particle records into... 220 The function of Rn activity concentration.

[0058] Example This embodiment applies the intrinsic measurement method for thorium gas activity concentration provided in the specific implementation method, including Bayesian analysis calculations involving Equations 4-10. 220 Rn- 216 Po is the true coincidence count; the true coincidence count itself is input into Equations 4 and 5, and estimated using an iterative method involving Equation 11; from Equations 1-3, i.e.220 Rn counting and 216 The product of Po counts, divided by 220 Rn- 216 The Po coincidence count is calculated by dividing by the measured chamber volume and the total measurement time, and then multiplying by the coincidence decay coefficient. 220 Rn activity concentration.

[0059] Using the intrinsic measurement method for thorium gas activity concentration described above, at the Shanghai Institute of Metrology and Testing Technology Co., Ltd. 220 Measurements were performed inside the chamber, measuring its volume. V It is 31.9 mL. 216 The decay constant of Po λ It is 4.81 s -1 The default window width is 300 ms, which will be dynamically adjusted according to the measured count rate during the calculation process to ensure that the product of the window width and the measured count rate does not exceed 6.0.

[0060] The intrinsic measurement method of thorium gas activity concentration provided by this invention is applied to a gas-flow scintillation chamber. 220 Rn measurement method ( 220 Rn / 216 A comparison was made using one of the Po counting methods, and the results are as follows: Figure 4 As shown. Figure 4 In the middle, in two different 220 Under Rn concentration conditions, the measurement results of the two methods were basically consistent, with no statistically significant difference. Among them, the gas flow scintillation chamber... 220 The detection efficiency of the Rn measurement method (blue measurement results) is attributed to Germany. 220 The Rn primary measurement standard is obtained and has undergone international comparison to ensure the accuracy of its measurement results. The invention proposes... 220 The Rn measurement method (orange measurement results) does not require other measurement standards to calibrate its detection efficiency; accurate results can be obtained directly. 220 Rn concentration. This result proves the validity of the invention. 220 The effectiveness of intrinsic measurement methods for Rn activity concentration.

[0061] It is worth noting that, such as Figure 4 As shown, the method proposed in this invention, compared to the gas flow scintillation chamber... 220 The Rn measurement method exhibits greater fluctuations and error bars in its measurement results because the sensitivity coefficient (a factor that integrates detection efficiency and measurement chamber volume) of the method proposed in this invention is much lower than that of the gas flow scintillation chamber. 220The Rn measurement method leads to significant statistical fluctuations. However, measurement errors include both systematic and random errors. This invention eliminates the need for detection efficiency, thus avoiding systematic errors caused by deviations between the estimated and true values ​​of the detection efficiency. This is in contrast to gas flow scintillation chambers that rely on external measurement standards. 220 The Rn measurement method has an advantage in terms of systematic errors. However, in terms of random errors, the gas-flow scintillation chamber... 220 The Rn measurement method has advantages. However, random errors can be infinitely reduced by increasing the number of measurements. Therefore, in scenarios where the concentration is stable and can be measured for a long time, the method proposed in this invention will have a greater advantage in terms of measurement accuracy. In addition, the self-traceability of the method proposed in this invention is also a unique advantage.

[0062] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0063] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0064] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0065] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for measuring the intrinsic properties of thorium-injected gas, characterized in that, The intrinsic measurement method includes the following steps: Record the measurement chamber to be measured 220 Rn gas and its products 216 Detection time of alpha particles released by Po decay; Bayesian analysis is performed based on the detection time to calculate... 220 Rn- 216 Po truly matches the count; according to 220 Rn count, 216 Po count and the aforementioned 20 Rn- 216 Po true coincidence counts are used to calculate the activity concentration of the thorium ejection gas.

2. The intrinsic measurement method for thorium-injected gas according to claim 1, characterized in that, The formula for calculating the activity concentration of the thorium-injected gas is shown in Equation 1: Formula 1 in, C For measuring the chamber 220 The activity concentration of Rn, for 220 Rn counts, for 216 Po count, for 220 Rn- 216 Po truly matches the count. V To measure the chamber volume, T For measuring duration; λ for 216 The decay constant of Po τ To match the window duration, the expression To conform to the decay coefficient, it means 216 The probability of Po decaying within the specified window.

3. The intrinsic measurement method for thorium-injected gas according to claim 1, characterized in that, The time accuracy of the detection time is not less than 500 ms, preferably not less than 10 ms.

4. The intrinsic measurement method for thorium gas activity concentration according to claim 1, characterized in that, The measurement chamber can also record the data to be measured. 220 Rn gas and its products 216 The energy released by the decay of Po (alpha particles).

5. The method for measuring the intrinsic properties of thorium-injected gas according to claim 1, characterized in that, Based on the comparison between the detection time difference of the two alpha particles and the coincidence window, it is determined whether the two alpha particles constitute a coincidence signal. Then, each coincidence signal is accumulated according to Equation 2. 220 Rn- 216 The probability that Po truly matches the signal is obtained. 220 Rn- 216 Po truly matches the count: Formula 2 in, i Indicates the first i A matching signal, w i Indicates the first i The time difference between the α signal and the α signal of a given signal. This indicates that the time difference between the α signal and the α signal is 0. w i In this case, the coincidence signal is 220 Rn- 216 The probability that Po truly matches the signal.

6. The method for measuring the intrinsic properties of thorium-injected gas according to claim 1, characterized in that, When performing the Bayesian analysis, the coincidence signal is calculated according to Equation 3. 220 Rn- 216 The probability that Po truly matches the signal: Formula 3 in, , These represent, respectively, a coincidence signal without posterior information. 220 Rn- 216 Po's prior probabilities of true coincidence signals and random coincidence signals; , Each represents a coincident signal. 220 Rn- 216 Under the premise of true coincidence and random coincidence of Po signal, the time difference of its α signal is: w The probability of.

7. The method for measuring the intrinsic properties of thorium-injected gas according to claim 4, characterized in that, When the measurement chamber records the test result 220 When determining the energy of the alpha particles released by the decay of Rn gas, the method not only compares the detection time difference of the two alpha particles with the coincidence window, but also uses the energy of the two alpha particles to determine whether they constitute a coincidence signal, and calculates the energy of the two alpha particles. 220 Rn- 216 Po truly matches the count.

8. A thorium-injected gas intrinsic measurement device, characterized in that, The intrinsic thorium gas activity concentration measuring device can operate the intrinsic thorium gas measurement method according to any one of claims 1-7.

9. The intrinsic thorium gas measuring device according to claim 8, characterized in that, The intrinsic measurement device includes a measurement chamber, a counting module, and a data analysis module; The counting module is used to record the test results. 220 The detection time of alpha particles released by the decay of Rn gas is also used to record the analyte. 220 The energy of alpha particles released by the decay of Rn gas; The data analysis module is used to perform Bayesian analysis and calculate the activity concentration of thorium gas.

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