A method for generating an organizational equivalent proportional counter simulation spectrum and its application

Abstract

The present invention relates to a method for generating an analog spectrum of a tissue equivalent proportional counter and its application. By collecting the data measured by tissue equivalent proportional counters in the environments of the International Space Station, monoenergetic particles, γ fields, and neutron fields published at home and abroad, and processing the collected data to form a basic spectrum, an analog spectrum that satisfies the measurement distribution law of tissue equivalent proportional counters in the above different radiation fields is generated on the basis of the basic spectrum, and the quality factor Q, absorbed dose D, and dose equivalent H values are obtained from this spectrum, which can be applied to calibrating the hardware measurement system and signal processing module of the tissue equivalent proportional counter. The tissue equivalent proportional counter calibration method disclosed by the present invention has the advantages of high calibration efficiency, real-time calibration, and wide application range.

Description

Technical Field

[0001] The present invention belongs to the technical field of radiation measurement, and particularly relates to a method for generating a simulated spectrum of a tissue equivalent proportional counter and its application. Background Art

[0002] A tissue equivalent proportional counter is a detector for measuring microdosimetric quantities. By measuring the microdosimetric spectrum and absorbed dose of a radiation field, and performing conversion calculations, the quality factor Q and dose equivalent H can be obtained. The original output of a tissue equivalent proportional counter is the deposited energy spectrum in the detector, simply referred to as the measurement spectrum. The conversion process from the measurement spectrum to the absorbed dose D, quality factor Q, and dose equivalent H is highly professional. Not only is the process complex and cumbersome, and prone to errors, but also the calculation methods given by different international authoritative institutions are different, and the calculation standards are not unified.

[0003] When developing a TEPC measurement system, different radiation fields (neutron field, γ field, proton field, heavy charged particle field, etc.) are required to calibrate the measurement system. However, for the calibration of tissue equivalent proportional counters, there is still a blank in China at present. Internationally, tissue equivalent proportional counters are usually calibrated and tested under laboratory conditions using neutron, γ reference radiation fields, etc. However, due to the time-consuming and laborious disassembly and transfer of tissue equivalent proportional counters, and certain requirements for the application site, the current calibration method for tissue equivalent proportional counters is inefficient, cannot be calibrated in real time, and has limited application scope. Summary of the Invention

[0004] Aiming at the defects existing in the prior art, the purpose of the present invention is to provide a method for generating a simulated spectrum of a tissue equivalent proportional counter and its application. The method has the advantages of high calibration efficiency, being able to be calibrated in real time, and having a wide application scope.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a method for generating a simulated spectrum of a tissue equivalent proportional counter, the method comprising the following steps:

[0006] S1. According to the received input conditions, retrieve the pre-stored basic spectrum data;

[0007] S2. Generate a simulated spectrum that satisfies the measurement distribution law of the tissue equivalent proportional counter according to the input conditions based on the basic spectrum data;

[0008] S3. Calculate and convert the simulated spectrum using the pre-stored conversion formula to obtain the values of the quality factor Q, absorbed dose D, and dose equivalent H.

[0009] Further, the input conditions include: irradiation conditions, total number of channels, width of each channel, number of particles, dosimetric calculation mode, simulated cell diameter.

[0010] Further, the irradiation conditions are selected by the user and are one of "space station, quiet solar activity period, non-SAA area", "space station, quiet solar activity period, SAA area", "neutron, Am-Be source", "neutron, Cf-252", "γ, Cs-137", "γ, Co-60", "γ, Am-241", "monoenergetic proton", "monoenergetic C particle", "monoenergetic Fe particle".

[0011] Further, by processing the flux spectrum under specific irradiation conditions disclosed in existing materials into a probability density spectrum of the LET linear energy transfer differential flux, the pre-stored basic spectrum data is formed.

[0012] Further, the flux spectrum is mainly collected from the data measured by a tissue equivalent proportional counter in the international space station environment, monoenergetic particles, γ field, and neutron field published at home and abroad.

[0013] Further, step S2 includes the following sub-steps:

[0014] S201. Generate a simulation spectrum array N[i] representing the simulation spectrum, set all elements in the simulation spectrum array N[i] to 0, generate a probability array f[i] representing the counting probability of each channel in the simulation spectrum, the sum of the probability array f[i] is 1, set the initial value of the recorded number of particles m to 0, and set i to 1;

[0015] i max Represents the total number of channels of the simulation spectrum, and the range of i is from 1 to i max ;

[0016] S202. Generate a random number in the range of 0 - 1.0, and determine whether the random number is less than the probability f[i] of the i-th channel in the basic spectrum. If it is less than the probability, then N[i]=N[i]+1, m=m + 1, otherwise, N[i] remains unchanged. Repeat this step until i continuously takes values from 1 to i max to obtain the counts of the 1st channel to the i-th max channel;

[0017] S203. Repeat step S202 until the recorded number of particles m reaches the set number of particles M.

[0018] Further, the precision of the random number should reach at least 10 -9 .

[0019] Further, the pre-stored conversion formula in step S3 is based on the conversion method defined by the quality factor Q(L) defined by ICRP or the conversion method defined by the linear energy y of ICRU.

[0020] A method for calibrating a tissue equivalent proportional counter, the method comprising the steps:

[0021] S11. Irradiate a tissue equivalent proportional counter under the same conditions using a radiation source to obtain an actual measured spectrum, and calibrate the hardware measurement system of the tissue equivalent proportional counter in combination with the simulated spectrum obtained in step S2.

[0022] Furthermore, the method further includes the step

[0023] S12. Input the simulated spectrum data obtained in step S2 into the signal processing module of the tissue equivalent proportional counter to obtain simulated quality factor Q, absorbed dose D, and dose equivalent H values, and calibrate the signal processing module of the tissue equivalent proportional counter in combination with the quality factor Q, absorbed dose D, and dose equivalent H values obtained in step S3.

[0024] The effect of the present invention is that: by adopting a method for generating a simulated spectrum of a tissue equivalent proportional counter and its application disclosed in the present invention, the deposited energy spectrum of the TEPC under different irradiation conditions can be simulated and generated. By comparing the simulated spectrum with the actual measured spectrum, the hardware measurement system of the tissue equivalent proportional counter can be calibrated.

[0025] Furthermore, dosimetric quantities such as absorbed dose D, quality factor Q, and dose equivalent H can be calculated from the simulated spectrum according to a pre-stored conversion formula. During the calculation process, the user can select different standard calculation methods. The developers of the TEPC measurement system can input the simulated spectrum into the signal processing module of the tissue equivalent proportional counter to obtain simulated quality factor Q, absorbed dose D, and dose equivalent H values, and compare them with the dosimetric quantities such as absorbed dose D, quality factor Q, and dose equivalent H calculated according to the pre-stored conversion formula, thereby calibrating the signal processing module of the tissue equivalent proportional counter. Description of the Drawings

[0026] Figure 1 It is the LET integral flux spectrum diagram measured by the tissue equivalent proportional counter on the STS-89 International Space Station obtained by referring to materials in a method for generating a simulated spectrum of a tissue equivalent proportional counter according to Embodiment 1 of the present invention;

[0027] Figure 2 For Figure 1 The integral flux spectrum diagram is converted into a differential flux spectrum diagram by differential processing;

[0028] Figure 3 For Figure 2 The differential flux spectrum diagram in is processed and converted into a probability density spectrum diagram;

[0029] Figure 4 It is the method flow chart of step S2 in a method for generating a simulated spectrum of a tissue equivalent proportional counter according to Embodiment 1 of the present invention;

[0030] Figure 5 This is the method flowchart of a method for calibrating an tissue equivalent proportional counter according to Embodiment 2 of the present invention. Specific embodiments

[0031] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0032] Embodiment 1

[0033] A method for generating a simulated spectrum of an tissue equivalent proportional counter includes the following steps:

[0034] S1. According to the received input conditions, retrieve the pre-stored basic spectrum data.

[0035] The input conditions include: irradiation conditions, total number of channels, width of each channel, number of particles, dosimetry calculation mode, and simulated cell diameter.

[0036] The irradiation conditions are selected by the user and can be selected from several irradiation modes such as "space station, quiet solar activity period, non-SAA area", "space station, quiet solar activity period, SAA area", "neutron, Am-Be source", "neutron, Cf-252", "γ, Cs-137", "γ, Co-60", "γ, Am-241", "monoenergetic proton", "monoenergetic C particle", and "monoenergetic Fe particle".

[0037] If one of "monoenergetic proton", "monoenergetic C particle", and "monoenergetic Fe particle" is selected, the energy also needs to be selected. Since it is necessary to read the pre-calculated basic spectrum, the energy in "monoenergetic proton", "monoenergetic C particle", and "monoenergetic Fe particle" cannot be input arbitrarily and can only be selected from the limited energies.

[0038] By processing the flux spectrum under specific irradiation conditions disclosed in existing materials into a probability density spectrum of the LET linear energy transfer differential flux, the pre-stored basic spectrum data is formed.

[0039] The flux spectrum is mainly collected from the data measured by tissue equivalent proportional counters in the international space station environment, monoenergetic particles (protons, C ions, Fe ions), γ fields (137Cs, 60Co, 241Am), neutron fields (241Am, 252Cf) published at home and abroad.

[0040] S2. Based on the basic spectrum, generate a simulated spectrum that satisfies the measurement distribution law of the tissue equivalent proportional counter under the specific irradiation conditions.

[0041] S3. Use the pre-stored conversion formula to calculate and convert the simulated spectrum to obtain the quality factor Q, absorbed dose D, and dose equivalent H values.

[0042] The basic spectrum data pre-stored in step S1 is obtained in the following manner

[0043] For example, the flux spectrum published in the literature under specific irradiation conditions is processed into a probability density spectrum of the LET linear energy transfer differential flux as the basic spectrum. As Figure 1 shown, an example of the integral flux spectrum measured by the tissue equivalent proportional counter on the International Space Station during a period of stable solar activity can be found

[0044] As Figure 2 shown, the integral flux spectrum in Figure 1 is processed into a differential flux spectrum

[0045] The number of channels of the differential flux spectrum can be set according to user needs. Denote the number of channels of the differential flux as i max . In this embodiment, an example is given with the number of channels of the spectrum being 256 channels Figure 2 The count situation of each channel of the differential flux spectrum in

[0046] Table 1 LET differential flux spectrum data measured by TEPC (256 channels, each channel represents 4 keV / μm. The flux unit is (cm2·sr·day) -1 )

[0047]

[0048]

[0049] As Figure 3 shown, the differential flux spectrum in Figure 2 is converted into a probability density spectrum, and the LET differential flux probability density spectrum data in Table 2 is obtained

[0050] Table 2 LET differential flux probability density spectrum data (256 channels, each channel represents 4 keV / μm)

[0051]

[0052]

[0053] As Figure 4 shown, in step S2, the simulated spectrum is generated according to the following method

[0054] S201. Generate a simulated spectrum array N[i] representing the simulated spectrum, and set all elements in the simulated spectrum array to 0. Generate a probability array f[i] representing the counting probability of each channel in the simulated spectrum. The sum of the probability array f[i] is 1. Set the initial value of the recorded number of particles m to 0 and set i to 1

[0055] i maxDenoted as the total number of channels of the spectrum, the count of the i-th channel is represented by N[i], and the range of i is from 1 to i max 。

[0056] S202. When the tissue-equivalent proportional counter detects the i-th particle, generate a random number in the range of 0 to 1.0 (the precision should be at least 10 -9 ), determine whether the random number is less than the probability f[i] of the i-th channel in Table 2. If it is less than the probability, increment N[i] by 1 and increment the recorded number of particles m by 1. Otherwise, keep N[i] unchanged. Repeat this step until i continuously takes values from 1 to i max , to obtain the counts of the 1st channel to the i max -th channel.

[0057] In this embodiment, when the tissue-equivalent proportional counter detects the first particle, generate a random number in the range of 0 to 1.0 (the precision should be at least 10 -9 ), determine whether the random number is less than the probability f[1] of the 1st channel in Table 2 (in this embodiment, the value of f[1] is 0.9508). If it is less than the probability, increment N[1] by 1, m = 1, then keep N[1] unchanged.

[0058] The above method is used to determine whether the particle causes a count in the 1st channel when the tissue-equivalent proportional counter detects the first particle.

[0059] When the tissue-equivalent proportional counter detects the second particle, generate a random number in the range of 0 to 1.0 (the precision should be at least 10 -9 ), determine whether the random number is less than the probability f[2] of the 2nd channel in Table 2 (in this embodiment, the value of f[2] is 0.03725). If it is less than the probability, increment N[2] by 1, m = 2, then keep N[2] unchanged.

[0060] Using the same method, continue to determine whether the particle causes a count in the 3rd channel, the 4th channel... up to the 256th channel when the tissue-equivalent proportional counter detects the particle, and according to the judgment result, increment the count of that channel by 1 or keep it unchanged.

[0061] S203. Repeat step S202 until the recorded number of particles reaches the set simulated number of particles M.

[0062] The conversion formulas pre-stored in step S3 include the following two types, and one of the conversion formulas can be selected according to the user's choice.

[0063] The conversion from the original spectrum to dosimetric quantities is divided into a conversion method defined based on the quality factor Q(L) defined by ICRP (International Commission on Radiological Protection) and a conversion method defined based on the linear energy y of ICRU (International Commission on Radiation Units and Measurements). The measured spectrum obtained by simulation is a linear energy spectrum.

[0064] Conversion method based on the Q(L) definition of ICRP

[0065] The absorbed dose D is obtained using the following formula:

[0066]

[0067] ε i = i·W·l (2)

[0068] In the above two equations, Dd is the absorbed dose, md is the mass of the simulated cells, which can be calculated according to the cells being spherical, with a density of 1.0 g / cm 3 , and the diameter d is input by the user. εi is the deposited energy represented by a count in the i-th channel. i represents the channel number, W is the LET width (keV / μm) represented by one channel, l is the chord length of the spherical cell, and l = 2 / 3d.

[0069] The average quality factor is obtained using the following formula

[0070] First, calculate Q(yi). Take the linear energy transfer density L with the same value as yi, calculate Q(L) according to the following formula, and equate the calculated result to the value of Q(yi):

[0071]

[0072] Obtain the Q(yi) values for each channel

[0073]

[0074] ③ The dose equivalent H is obtained using the following formula:

[0075]

[0076] Conversion method based on the Q value definition of ICRU

[0077] The linear energy y corresponding to each channel i is obtained using the following formula i The frequency value f(y i )

[0078]

[0079] The frequency-averaged linear energy is obtained using the following formula

[0080]

[0081] The average dose energy is obtained using the following formula

[0082]

[0083] Quality factor

[0084] As can be seen from the above embodiments, a method for generating a simulated spectrum of a tissue equivalent proportional counter disclosed by the present invention collects data measured by a tissue equivalent proportional counter in the environments of the International Space Station, monoenergetic particles (protons, C ions, Fe ions), γ fields (137Cs, 60Co, 241Am), and neutron fields (241Am, 252Cf) published at home and abroad, processes the collected data to form a basic spectrum, generates a simulated spectrum that satisfies the measurement distribution law of the tissue equivalent proportional counter in the above different radiation fields based on the basic spectrum, and obtains the quality factor Q, absorbed dose D, and dose equivalent H values from this spectrum, which can calibrate the hardware measurement system and signal processing module of the tissue equivalent proportional counter

[0085] Embodiment 2

[0086] As Figure 5 shown, a method for calibrating a tissue equivalent proportional counter includes the following steps

[0087] S11. Irradiate the tissue equivalent proportional counter under the same conditions using a radiation source to obtain a measured spectrum, and calibrate the measured spectrum by combining with the simulated spectrum obtained in step S2

[0088] S12. Input the simulated spectrum data obtained in step S2 into the signal processing module of the tissue equivalent proportional counter to obtain simulated quality factor Q, absorbed dose D, and dose equivalent H values, and calibrate the signal processing module of the tissue equivalent proportional counter by combining with the quality factor Q, absorbed dose D, and dose equivalent H values obtained in step S3

[0089] As can be seen from the above embodiments, a method for calibrating a tissue equivalent proportional counter disclosed by the present invention can, through the comparison between the simulated spectrum and the actual measurement spectrum, enable developers of the TEPC measurement system to input the simulated spectrum into the signal processing module of the tissue equivalent proportional counter to obtain simulated quality factor Q, absorbed dose D, and dose equivalent H values, and compare them with the dosimetric quantities such as absorbed dose D, quality factor Q, and dose equivalent H calculated according to the pre-stored conversion formula, thereby calibrating the signal processing module of the tissue equivalent proportional counter, which has the advantages of high calibration efficiency, real-time calibration, and wide application range

[0090] The method described in the present invention is not limited to the embodiments described in the specific embodiments. Those skilled in the art can obtain other embodiments based on the technical solution of the present invention, which also belong to the scope of the technical innovation of the present invention.

Claims

1. A method for generating a simulated spectrum of an tissue equivalent proportional counter, the method comprising the following steps: S1. According to the received input conditions, retrieve the pre-stored basic spectrum data; S2. Generate a simulated spectrum that satisfies the measurement distribution law of the tissue equivalent proportional counter under the input conditions based on the basic spectrum data; S3. Calculate and convert the simulated spectrum using a pre-stored conversion formula to obtain the quality factor Q, absorbed dose D, and dose equivalent H values; The step S2 includes the following sub-steps: S201. Generate a simulated spectrum array N[i] representing the simulated spectrum, set all elements in the simulated spectrum array N[i] to 0, generate a probability array f[i] representing the counting probability of each channel in the simulated spectrum, the sum of the probability array f[i] is 1, set the initial value of the recorded particle number m to 0, and set i to 1; i max Denotes the total number of channels of the said simulated spectrum, and the range of i is from 1 to i max ; S202. Generate a random number within the range of 0 - 1.0, and determine whether the random number is less than the probability f[i] of the i-th channel in the base spectrum. If it is less than this probability, then N[i] = N[i] + 1, m = m + 1; otherwise, N[i] remains unchanged. Repeat this step until i continuously takes values from 1 to i max , obtaining the counts of the 1st channel to the i-th max channel; S203. Repeat step S202 until the recorded particle number m reaches the set particle number M.

2. A method for generating an analog spectrum of a tissue equivalent proportional counter according to claim 1, characterized in that: The input conditions include: irradiation conditions, total number of channels, width of each channel, number of particles, dosimetry calculation mode, simulated cell diameter.

3. A method for generating an analog spectrum of a tissue equivalent proportional counter as described in claim 2, characterized in that: The irradiation conditions are selected by the user and are one of "space station, quiet solar activity period, non-SAA area", "space station, quiet solar activity period, SAA area", "neutron, Am-Be source", "neutron, Cf-252", "γ, Cs-137", "γ, Co-60", "γ, Am-241", "monoenergetic proton", "monoenergetic C particle", "monoenergetic Fe particle".

4. A method for generating a simulated spectrum of an tissue equivalent proportional counter as described in claim 1, characterized in that: By processing the flux spectrum under specific irradiation conditions disclosed in existing materials into a probability density spectrum of the LET linear energy transfer differential flux, the pre-stored basic spectrum data is formed.

5. A method for generating an analog spectrum of a tissue equivalent proportional counter as described in claim 4, characterized in that: The flux spectrum is mainly collected from the data measured by tissue equivalent proportional counters in the international space station environment, monoenergetic particles, γ field, and neutron field published at home and abroad.

6. A method for generating a simulated spectrum of an tissue equivalent proportional counter as described in claim 1, characterized in that: The precision of the random number should be at least 10 -9 .

7. A method for generating an analog spectrum of an tissue equivalent proportional counter as described in claim 4, characterized in that: The pre-stored conversion formula in step S3 is based on the conversion method defined by the quality factor Q(L) defined by ICRP or the conversion method defined by the linear energy y of ICRU.

8. A method for calibrating an tissue equivalent proportional counter, the method uses a method for generating a simulated spectrum of an tissue equivalent proportional counter according to any one of claims 1-7 to generate a simulated spectrum, and the method includes the steps: S11. Irradiate the tissue equivalent proportional counter under the same conditions using a radiation source to obtain a measured measurement spectrum, and calibrate the hardware measurement system of the tissue equivalent proportional counter in combination with the simulated spectrum obtained in step S2.

9. A method for calibrating an tissue equivalent proportional counter as described in claim 8, characterized in that: The method further includes the step S12. Input the simulated spectrum data obtained in step S2 into the signal processing module of the tissue equivalent proportional counter to obtain the simulated quality factor Q, absorbed dose D, and dose equivalent H values, and calibrate the signal processing module of the tissue equivalent proportional counter in combination with the quality factor Q, absorbed dose D, and dose equivalent H values obtained in step S3.

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