Method of testing a high-energy photon reference radiation field for contaminant radiation

Abstract

The application relates to a kind of contamination radiation test methods of high-energy photon reference radiation field, based on Monte Carlo method, the physical model of high-energy photon detector is constructed;The measurement spectrum at the calibration point of high-energy photon radiation quality is obtained by HpGe detector and matching electronics equipment;The measurement spectrum is calculated by G function, and the high-energy photon dose rate value is obtained;The HpGe detector detection efficiency curve within the energy range of 8MeV is simulated in the physical model of detector, and the low-energy photon dose rate value is obtained;Based on Co-60 isotope energy calibration, the electron dose rate value is determined by extrapolation ionization chamber;Set up neutron isotope, based on long counter, obtain the neutron dose rate value;Based on the above dose rate value, determine the dose proportion value.The application realizes the technical effect of obtaining high-energy photon dose rate value, the low-energy photon dose rate value, the electron dose rate value and the dose proportion value of the neutron dose rate value.

Description

Technical Field

[0001] This invention relates to the field of radiation pollution technology, and in particular to a method for testing pollution radiation in a high-energy photon reference radiation field. Background Technology

[0002] In the field of clinical radiation medicine, such as radical radiotherapy and palliative radiotherapy, it is unavoidable to use high-energy photon rays to deliver precise therapeutic doses to the patient's target area while minimizing the radiation dose to surrounding normal tissues. This requires high-energy photon ray monitoring devices to provide accurate dose rate calibration values ​​at the calibration point (target area), thus limiting the magnitude of the high-energy photon dose rate. However, the radiation energy of high-energy photons is far higher than that of photons produced by conventional X-ray machines and isotopes, reaching up to 10 MeV or more. When high-energy photons exceed the threshold, they can undergo photonuclear reactions with surrounding air or materials to produce positrons, accompanied by the photoelectric effect / Compton scattering, generating a large number of high-energy negative electrons. These electrons interact secondaryly with matter, forming radiation pollution, which includes three types of pollution radiation: low-energy photons, electrons, and neutrons.

[0003] Although the standard ISO 4037-1:2019 clearly states that other contaminating radiation may exist, it does not provide clear quantitative indicators for the types and quantities of contaminating radiation, nor does it provide measurement methods for contaminating radiation. This means that when a predetermined value for the high-energy photon dose rate is provided to the monitoring equipment, it will be affected by contaminating radiation from low-energy photons, electrons, neutrons, etc. This results in the actual reading of the monitoring equipment during the metrological calibration process being a superposition of the high-energy photon dose rate and one or more contaminating radiations. The lack of effective preliminary measurement and evaluation methods for the proportion of each type of contaminating radiation dose rate will lead to a large systematic error between the monitoring equipment and the predetermined true value, causing many difficulties for the later construction and operation of the accelerator-based high-energy photon standard reference radiation field and the accuracy of the measurement values.

[0004] The relevant technologies do not address the proportion of contamination from low-energy photons, electrons, and neutrons to high-energy photons, leading to errors in determining the high-energy photon dose rate.

[0005] The above problems urgently need to be addressed. Summary of the Invention

[0006] This invention discloses a method for testing contaminated radiation in a high-energy photon reference radiation field, aiming to solve the technical problems existing in the prior art.

[0007] The present invention adopts the following technical solution: On one hand, this invention provides a method for testing contaminated radiation in a high-energy photon reference radiation field, comprising: constructing a detector physical model for high-energy photons based on the Monte Carlo method; obtaining a measurement spectrum at a high-energy photon radiation quality calibration point using an HpGe detector and supporting electronic equipment; calculating the high-energy photon dose rate value using the G function; simulating the detection efficiency curve of an HpGe detector within an energy range of 8 MeV in the detector physical model to obtain a low-energy photon dose rate value; determining the electron dose rate value by extrapolation ionization chamber based on Co-60 isotope energy calibration; setting neutron isotopes and obtaining the neutron dose rate value based on a long counter; and determining the dose ratio value based on the high-energy photon dose rate value, the low-energy photon dose rate value, the electron dose rate value, and the neutron dose rate value.

[0008] Optionally, obtaining the low-energy photon dose rate value by simulating the detection efficiency curve of the HpGe detector within an energy range of 8 MeV in the detector physical model includes: simulating the detection efficiency curve of the HpGe detector within an energy range of 8 MeV in the detector physical model; fitting a high-energy photon emission spectrum based on the detection efficiency curve and the measured spectrum; determining a spectrum of photon energy and dose based on the high-energy photon emission spectrum, combined with photon fluence and dose conversion coefficients of different energies; and calculating the low-energy photon dose rate value by counting the total count of the low-energy photon energy range in the spectrum.

[0009] Optionally, the step of calculating the low-energy photon dose rate by counting the total count of the low-energy photon energy range in the spectrum includes: calibrating the energy response characteristics of the ionization chamber in the photon energy range of 65keV to 300keV using a narrow-spectrum series of X-ray reference radiation fields; fitting the response characteristic curve of the ionization chamber based on the energy response characteristics; performing integral processing on the characteristic curve of the ionization chamber to obtain the area integral result; obtaining the total dose rate value containing the proportion of low-energy photons based on the ratio of the total count of the low-energy photon energy range to the area integral result; and determining the low-energy photon dose rate value based on the total dose rate value and the high-energy photon dose rate value.

[0010] Optionally, the step of determining the electron dose rate value based on Co-60 isotope energy calibration and using an extrapolation ionization chamber includes: determining a calibration factor corresponding to the extrapolation ionization chamber based on the Co-60 isotope energy calibration; setting an electron blocking plate in front of the extrapolation ionization chamber; obtaining a fitted dose rate corresponding to the high-energy photons after electron blocking based on the extrapolation ionization chamber; determining an extrapolation curve based on the fitted dose rate; determining the photon dose rate value of the high-energy photons after electron blocking at the calibration point based on the extrapolation curve and the calibration factor; and obtaining the electron dose rate value by subtracting the high-energy photon dose rate from the photon dose rate value.

[0011] Optionally, the electron blocking plate is disposed 1 cm from the front window of the extrapolation ionization chamber; the area of ​​the electron blocking plate is greater than or equal to the area of ​​the front window of the extrapolation ionization chamber; and the thickness of the electron blocking plate is greater than or equal to 5 mm.

[0012] Optionally, the step of setting neutron isotopes and obtaining neutron dose rate values ​​based on a long counter includes: setting neutron isotopes and obtaining a first neutron dose rate based on a long counter, wherein the first neutron dose rate is used to indicate the neutron dose rate in the presence of neutron contamination; obtaining a calibration factor in the neutron radiation field by adjusting the pulse discrimination threshold of the long counter; and correcting the first neutron dose rate based on the calibration factor to obtain the neutron dose rate value.

[0013] Optionally, the step of correcting the first neutron dose rate based on the calibration factor to obtain the neutron dose rate value includes: determining a second neutron dose rate at a calibration point in the radiation field based on the calibration factor, combined with the reference radiation quality and the calibration radiation quality, wherein the second neutron dose rate is used to indicate the neutron dose rate of neutrons at the calibration point; determining the ratio of the first neutron dose rate to the second neutron dose rate; and correcting the first neutron dose rate based on the ratio to obtain the neutron dose rate value.

[0014] According to another aspect of the present invention, a contaminated radiation testing device for a high-energy photon reference radiation field is also provided, comprising: a construction module for constructing a detector physical model of high-energy photons based on the Monte Carlo method; a measurement spectrum module for obtaining the measurement spectrum at the high-energy photon radiation quality calibration point using an HpGe detector and supporting electronic equipment; a high-energy photon module for calculating the high-energy photon dose rate value by using the G function on the measurement spectrum; a low-energy photon module for obtaining the low-energy photon dose rate value by simulating the detection efficiency curve of an HpGe detector within an energy range of 8 MeV in the detector physical model; an electron module for determining the electron dose rate value by extrapolation ionization chamber based on Co-60 isotope energy calibration; a neutron module for setting neutron isotopes and obtaining the neutron dose rate value based on a long counter; and a proportioning module for determining a dose proportion value based on the high-energy photon dose rate value, the low-energy photon dose rate value, the electron dose rate value, and the neutron dose rate value.

[0015] According to another aspect of the present invention, a non-volatile storage medium is also provided, the non-volatile storage medium storing a plurality of instructions adapted for loading by a processor and executing any one of the methods for testing contamination radiation of a high-energy photon reference radiation field.

[0016] According to another aspect of the present invention, a computer program product is also provided, comprising a computer program that, when executed by a processor, implements the steps of a method for testing contaminated radiation in a high-energy photon reference radiation field as described in any one of the present invention.

[0017] The technical solution adopted in this invention can achieve at least one of the following beneficial effects: In this embodiment of the invention, a physical model of a high-energy photon detector is constructed using the Monte Carlo method; a measurement spectrum at the high-energy photon radiation quality calibration point is obtained using an HpGe detector and supporting electronic equipment; the high-energy photon dose rate is obtained by calculating the measurement spectrum using the G function; a low-energy photon dose rate is obtained by simulating the detection efficiency curve of the HpGe detector within an energy range of 8 MeV in the physical model of the detector; the electron dose rate is determined by extrapolation ionization chamber based on Co-60 isotope energy calibration; a neutron isotope is set, and the neutron dose rate is obtained based on a long counter; based on... The high-energy photon dose rate value, the low-energy photon dose rate value, the electron dose rate value, and the neutron dose rate value are used to determine the dose ratio value, thereby achieving the purpose of determining the low-energy photon dose rate value, the electron dose rate value, and the neutron dose rate value. This achieves the technical effect of obtaining the dose ratio value of the high-energy photon dose rate value, the low-energy photon dose rate value, the electron dose rate value, and the neutron dose rate value, and thus solves the technical problem in related technologies that do not propose the proportion of the contamination influence of low-energy photons, electrons, and neutrons on high-energy photons, resulting in errors in determining the high-energy photon dose rate. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below, forming part of the present invention. The illustrative embodiments of the present invention and their descriptions explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings: Figure 1 This is a flowchart of a method for testing contaminated radiation in a high-energy photon reference radiation field according to Embodiment 1 of the present invention; Figure 2 This is a flowchart of the low-energy photon contamination measurement process in a contamination radiation test method for a high-energy photon reference radiation field according to Embodiment 1 of the present invention. Figure 3 This is a flowchart of electron contamination measurement in a contamination radiation test method for a high-energy photon reference radiation field according to Embodiment 1 of the present invention; Figure 4 This is a flowchart of neutron contamination measurement in a contamination radiation testing method for a high-energy photon reference radiation field according to Embodiment 1 of the present invention. Figure 5This is a schematic diagram of the structure of a pollution radiation testing device for a high-energy photon reference radiation field according to Embodiment 2 of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. In the description of this invention, it should be noted that the term "or" is generally used to include the meaning of "and / or," unless otherwise expressly indicated.

[0020] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or a magnetic connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, in the description of this application, the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying relative importance. In the description of this invention, "a plurality of" means at least two, such as two, three, or more, unless otherwise explicitly specified.

[0021] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0022] First, to facilitate understanding of the embodiments of the present invention, some terms or nouns involved in the present invention will be explained below: High-energy photons are photons with higher frequencies and higher energies, and they belong to the basic particles of electromagnetic radiation.

[0023] The contamination radiation of the high-energy photon reference radiation field mainly comes from natural and anthropogenic factors, and its impact includes experimental interference, radiation protection challenges, and equipment wear and tear.

[0024] To address the problems existing in the prior art, this application provides a method for testing contaminated radiation in a high-energy photon reference radiation field.

[0025] Example 1 This embodiment provides a method for testing contamination radiation in a high-energy photon reference radiation field, such as... Figure 1 As shown, Figure 1 This is a flowchart of a method for testing contaminated radiation in a high-energy photon reference radiation field according to Embodiment 1 of the present invention. The method includes: Step S102: Construct a physical model for a high-energy photon detector based on the Monte Carlo method; Optionally, based on the Monte Carlo method and the MCNP simulation model (MCNP, Monte Carlo N-Particle Transport Code), the MCNP simulation model is a particle transport simulation tool that simulates the transport process of particles (such as neutrons, photons, electrons, etc.) in complex geometric structures through random sampling and probability statistics, and establishes the physical model of the HpGe detector, that is, the physical model of the high-energy photon detector.

[0026] Optionally, by setting a single-energy photon incident energy corresponding to the aforementioned radioactive isotope energy, and continuously modifying and optimizing the size and thickness of the HpGe detector physical model, a physical model with a deviation of less than 5% from the experimental calibration results is obtained. Subsequently, the detection efficiency curve of the HpGe detector within the energy range of 8 MeV is simulated. It should be noted that the energy range of single-energy photons within 300 keV should not exceed 30 keV, and the energy range from 300 keV to 8 MeV should not exceed 300 keV.

[0027] Optionally, since all volumes in the MCNP simulation model represent the effective detection area—for example, if a 1cm cube is established, the effective measurement area is also a 1cm cube—the initial size and thickness of the model are set based on the actual volume of the HpGe detector crystal. However, due to factors such as the age of the equipment, differences in manufacturing processes, and surface losses, actual HpGe detectors may have a volume of 1cm cube but an actual effective detection area of ​​only 0.8cm. This can lead to discrepancies between the simulated detection efficiency curve and the actual efficiency of the selected HpGe detector. Therefore, the size and thickness of the model are manually fine-tuned and compared with the actual situation to ensure that the error does not exceed 5%.

[0028] Step S104: Obtain the measurement spectrum at the high-energy photon radiation quality calibration point using an HpGe detector and supporting electronic equipment. Optionally, the measurement spectrum of high-energy photons at the RF and RC radiation quality calibration points can be obtained through experimental measurement using the physical model of the HpGe detector. Here, RF represents the Reference Radiation Quality and RC represents the Calibration Radiation Quality. Specifically, the calibration point is located 1.0 m away from the target point in the direction of the target plane normal in the physical model of the detector. The measurement duration should ensure that the cumulative count of the target energy point of the RF and RC radiation quality is more than 10,000 per channel.

[0029] Optionally, first, prepare a physical model of the HpGe detector and its supporting electronics (such as a preamplifier and multichannel analyzer); second, configure radiation sources for the HpGe detector physical model (such as using standard gamma sources like Co-60 or Cs-137); third, calibrate the detector's energy scale, specifically by measuring the energy spectra of each standard source (Cs-137, Co-60, Ba-133, Eu-152) at distances of 5 cm, 15 cm, and 25 cm. For each energy peak, calculate the net count rate n. net (Total count - background count) / liveness, combined with the source activity A0 (which needs to be corrected to the experimental date based on the half-life), calculate the detection efficiency: Based on the detection efficiency, a curve showing the relationship between efficiency and energy is fitted. Next, the energy spectrum is measured under different radiometric qualities. Finally, the data is analyzed to determine the measurement spectrum at the calibration point.

[0030] Step S106: Calculate the high-energy photon dose rate value by using the G function to measure the spectrum; Optionally, the high-energy photon dose rate can be directly calculated from the measured spectrum obtained based on the HpGe detector physical model using the G function. The G function (energy spectrum-dose conversion function) is a mathematical function used to convert the gamma-ray spectrum data measured by the HpGe detector into the air absorbed dose rate. It takes into account the contribution of gamma rays of different energies to the dose, because photons of different energies have different absorption coefficients in matter, and therefore contribute differently to the dose.

[0031] Specifically, high-energy photon dose rate value The count rate N of each energy channel in the energy spectrum can be used to determine this. i Multiply by the corresponding G function value G(E) i ), and sum them up to get: Where i represents the energy channel in the energy spectrum, and n is the total number of channels.

[0032] Optionally, measurements can also be performed using a graphite cavity ionization chamber. Specifically, a graphite cavity ionization chamber with an additional air-equivalent balancing cap is selected to ensure charged particle balance during the measurement phase. The balancing cap can be made of an air-equivalent organic material with a concentration of 4.0 g / cm². Considering that the photon yield of RF and RC radiation is typically below the mGy / h level, a 10L graphite cavity ionization chamber should be selected to improve the stability of dose rate measurements. Dose rate measurements should be taken at a calibration point 1.0 m away from the target in the direction normal to the target plane. The graphite cavity ionization chamber can directly measure and provide the high-energy photon dose rate value at the calibration point.

[0033] Step S108: Simulate the detection efficiency curve of the HpGe detector within the energy range of 8 MeV in the detector physical model to obtain the low-energy photon dose rate value; the specific measurement flowchart is as follows. Figure 2 As shown, where, Figure 2 This is a flowchart of the low-energy photon contamination measurement process in a contamination radiation test method for a high-energy photon reference radiation field according to Embodiment 1 of the present invention.

[0034] In some preferred embodiments, the low-energy photon dose rate value is obtained by simulating the detection efficiency curve of an HpGe detector within an energy range of 8 MeV in the detector physical model. This includes: simulating the detection efficiency curve of an HpGe detector within an energy range of 8 MeV in the detector physical model; fitting a high-energy photon emission spectrum based on the detection efficiency curve and the measured spectrum; determining the photon energy and dose spectrum based on the high-energy photon emission spectrum, combined with photon fluence and dose conversion coefficients at different energies; and calculating the low-energy photon dose rate value by counting the total count of the low-energy photon energy range in the spectrum.

[0035] Optionally, based on the anti-Compton HpGe semiconductor detector, a detector physical model can be selected. Using radioactive isotopes Am-241, Co-57, Co-60, Cs-137, Ba-133, and Eu-152, and referring to the test methods recommended in the calibration specification JJF 1850—2020 "Calibration Specification for Germanium Gamma-ray Spectrometer", the detection efficiency of the HpGe detector physical model can be experimentally calibrated to obtain accurate detection efficiency values ​​for each nuclide characteristic energy point within the energy range of 1.5 MeV. Based on these accurate detection efficiency values, a detector efficiency curve is determined, where the horizontal axis represents photon energy (keV) and the vertical axis represents photon detection efficiency (%).

[0036] Optionally, the detector efficiency curve represents the ratio of the number of photon radiation events recorded by the HpGe detector physical model to the total number of gamma rays incident on the HpGe detector physical model, which can intuitively demonstrate the detection capability of the HpGe detector physical model at different energies. By calculating using MATLAB functions, dividing the count rate of each channel in the measured spectrum by the accurate detection efficiency value of the corresponding channel address on the detection efficiency curve can eliminate the influence of the change in detection efficiency with high-energy photon energy, and the high-energy photon emission spectrum at the calibration point can be obtained by fitting.

[0037] Optionally, based on the fitted high-energy photon emission spectrum, and combined with the photon fluence-dose conversion coefficients for different energies, the count rate of each channel in the emission spectrum is multiplied by the conversion coefficient corresponding to that energy point to obtain a spectrum. The horizontal axis of the spectrum represents energy, and the vertical axis represents dose. Specifically, the photon fluence-dose conversion coefficients are referenced in the appendix to ICRP Report 74-1996, ANNXE 2.

[0038] Optionally, based on the energy and dose spectrum, and according to the specific requirements for low-energy contaminant photons needed for the calibration experiment (ISO 4037-1:2019 recommends considering photons with energies below 1.5 MeV as contaminant photons), the proportion of the total count in the low-energy photon energy range to the total count in the full spectrum is calculated, thus obtaining the dose ratio of contaminant photons. The specific calculation is as follows: Dosage percentage = N0 ÷ N1 × 100% Wherein, N0 is the total count corresponding to the range of energy from 0keV to 1.5MeV on the horizontal axis in the spectrum, which can be directly read by delineating this region in the spectrum; N1 is the total count corresponding to the range of energy from 0keV to Emax (the maximum energy of high-energy photons) on the horizontal axis in the spectrum, which can also be directly read by delineating this region in the spectrum.

[0039] In some preferred embodiments, the low-energy photon dose rate is calculated by statistically analyzing the total count of the low-energy photon energy range in the spectrum, including: calibrating the energy response characteristics of the ionization chamber in the photon energy range of 65keV to 300keV using a narrow-spectrum X-ray reference radiation field; fitting the response characteristic curve of the ionization chamber based on the energy response characteristics; performing integral processing on the ionization chamber characteristic curve to obtain the area integral result; obtaining the total dose rate value containing the proportion of low-energy photons based on the ratio of the total count of the low-energy photon energy range to the area integral result; and determining the low-energy photon dose rate value based on the total dose rate value and the high-energy photon dose rate value.

[0040] Optionally, considering the drastic change in the response curve of the ionization chamber with photon energy below 300 keV, a narrow-spectrum series of X-ray reference radiation fields should be used to calibrate the energy response characteristics of the ionization chamber in the photon energy range of 65 keV to 300 keV. For ionization chambers above 300 keV, the response tends to be uniform, and only Cs-137 and Co-60 are needed to calibrate their energy response characteristics. Finally, the response characteristic curve of the ionization chamber is fitted and normalized according to the Co-60 energy response point. Combined with the maximum high-energy photon energy Emax measured by the HpGe detector for RF and RC radiation quality, the integral area of ​​the response characteristic curve (65 keV to Emax range) is calculated as 1.0 × Emax × high-energy photon dose rate value ÷ response characteristic curve integral area (range of 65 keV to Emax). This eliminates the dependence of the ionization chamber on photon energy, yielding the total dose rate value containing the proportion of low-energy photons at the calibration point after energy response compensation correction.

[0041] Optionally, the total dose rate value can be multiplied by the dose ratio of contaminated photons (or determined by subtracting the high-energy photon dose rate value from the total dose rate value) to obtain the contribution of low-energy photons in the high-energy photon RF and RC radiation quality to the dose rate at the calibration point, i.e., the low-energy photon dose rate value.

[0042] Step S110: Based on the Co-60 isotope energy calibration, the electron dose rate value is determined by extrapolation ionization chamber; Optionally, in high-energy photon RF and RC radiation quality, electron contamination originates from the interaction of high-energy photons with air, target tube, ground, and surrounding matter. Its highest energy is close to that of high-energy photons, and in certain measurement scenarios (such as windowless or thin-window detector calibration), the contamination value may even be higher than the true value of high-energy photons. The electron contamination situation at the calibration point can be directly quantitatively described by the electron dose rate. The specific measurement flowchart is as follows. Figure 3 As shown, where, Figure 3 This is a flowchart of electron contamination measurement in a contamination radiation test method for a high-energy photon reference radiation field according to Embodiment 1 of the present invention.

[0043] In some preferred embodiments, the electron dose rate value is determined by extrapolation ionization chamber based on Co-60 isotope energy calibration, including: determining the calibration factor corresponding to the extrapolation ionization chamber based on the Co-60 isotope energy calibration; setting an electron blocking plate in front of the extrapolation ionization chamber; obtaining the fitted dose rate corresponding to the high-energy photons after electron blocking based on the extrapolation ionization chamber; determining the extrapolation curve based on the fitted dose rate; determining the photon dose rate value of the high-energy photons after electron blocking at the calibration point based on the extrapolation curve and the calibration factor; and obtaining the electron dose rate value by subtracting the high-energy photon dose rate from the photon dose rate value.

[0044] Optionally, the device for measuring the electron dose rate is an extrapolation ionization chamber for absolute measurement of β-absorbed dose rate. The dose rate is measured at the calibration point by fitting an extrapolation curve of the dose rate through changes in the electrode spacing (or the high-energy photon dose rate value obtained based on the detector physical model described above can be used as the dose rate value at that calibration point). Before measurement, the extrapolation ionization chamber is calibrated under a β-absorbed dose rate reference standard radiation field of Sr-90 or Y-90, and the corresponding calibration factor for the extrapolation ionization chamber is given.

[0045] Optionally, direct measurement under the Sr-90 / Y-90 calibration factor yields the sum of the contributions of electrons and high-energy photons to the dose rate at the calibration point. The energy response characteristics of the extrapolated ionization chamber to pure gamma radiation are calibrated using the Co-60 reference radiation field, and a corresponding calibration factor is assigned to the extrapolated ionization chamber.

[0046] Optionally, considering the energy and penetration depth of electrons in RF and RC radiation fields, as well as the difference in penetration ability between electrons and photons, an aluminum plate with a thickness of 5 mm or more, or an acrylic glass plate with a thickness of 2 cm or more, should be placed approximately 1 cm from the front window of the extrapolation ionization chamber. The area of ​​the aluminum plate or acrylic glass plate should completely cover the front window of the extrapolation ionization chamber. Combined with the aforementioned calibration factor of the extrapolation ionization chamber under the Co-60 reference radiation field, the measurement will realize the photon dose rate value at the calibration point, where the photon dose rate blocks electrons in the high-energy photon beam.

[0047] Optionally, by subtracting the photon dose rate value from the aforementioned high-energy photon dose rate, the dose rate value of electron contamination at the calibration point, i.e., the electron dose rate value, can be obtained.

[0048] In some preferred embodiments, the electron blocking plate is disposed 1 cm from the front window of the extrapolation ionization chamber; the area of ​​the electron blocking plate is greater than or equal to the area of ​​the front window of the extrapolation ionization chamber; and the thickness of the electron blocking plate is greater than or equal to 5 mm.

[0049] Step S112: Set the neutron isotope and obtain the neutron dose rate value based on the long counter; Optionally, in high-energy photon RF and RC radiation masses, neutron contamination originates from Ca atoms in the CaF2 target material of the RF radiation mass and C-13 impurity atoms in the C-12 target material of the RC radiation mass, which react with (p,n)-like nuclear reactions with incident protons at the accelerator. Typically, the contribution of contaminating neutrons to the dose rate at the calibration point does not exceed 5%. The specific measurement flowchart is as follows. Figure 4 As shown, where, Figure 4 This is a flowchart of neutron contamination measurement in a contamination radiation testing method for a high-energy photon reference radiation field according to Embodiment 1 of the present invention.

[0050] In some preferred embodiments, setting neutron isotopes and obtaining neutron dose rate values ​​based on a long counter includes: setting neutron isotopes and obtaining a first neutron dose rate based on a long counter, wherein the first neutron dose rate is used to indicate the neutron dose rate in the presence of neutron contamination; obtaining a calibration factor in the neutron radiation field by adjusting the pulse discrimination threshold of the long counter; and correcting the first neutron dose rate based on the calibration factor to obtain the neutron dose rate value.

[0051] Optionally, the equipment for measuring the neutron dose rate value is a long counter slowed down by polyethylene for absolute neutron dose rate measurement. After being calibrated by the neutron dose rate reference standard radiation field, the conversion coefficient of the long counter fluence rate to dose rate under Am-Be or Cf isotopes is given. The long counter needs to be equipped with a preamplifier, a main amplifier, a constant ratio timing discriminator and a calibrator.

[0052] Optionally, the amplitude spectrum of neutron-triggered pulses is much higher than that of photons, so the response of long counters to high-energy photons is usually extremely low. To further eliminate measurement errors caused by high-energy photons, a dose rate of approximately 1 mSv / h is provided to the long counter using Co-60 isotopes. The pulse amplitude discrimination threshold is adjusted by a constant-ratio timing discriminator (or calibrator) until the calibrator pulse amplitude count is zero. Then, the calibration factor of the long counter is given again by the neutron radiation field of Am-Be or Cf isotopes.

[0053] In some preferred embodiments, the first neutron dose rate is corrected based on a calibration factor to obtain a neutron dose rate value, including: determining a second neutron dose rate at a calibration point in the radiation field based on the calibration factor, in conjunction with a reference radiation quality and a calibration radiation quality, wherein the second neutron dose rate is used to indicate the neutron dose rate of neutrons at the calibration point; determining the ratio of the first neutron dose rate to the second neutron dose rate; and correcting the first neutron dose rate based on the ratio to obtain a neutron dose rate value.

[0054] Optionally, since adjusting the pulse amplitude discrimination threshold will cause a certain deviation in the measured neutron dose rate value, the second neutron dose rate value at the calibration point in the RF and RC radiation fields can be directly measured using a long counter in conjunction with the calibration factor. The long counter should be used in an Am-Be or Cf isotope neutron radiation field with a dose rate similar to that measured in the RF and RC radiation fields. The ratio of the dose rate change before and after the discrimination threshold adjustment (the ratio of the first neutron dose rate to the second neutron dose rate) should be calculated and directly multiplied by the first neutron dose rate value in the RF and RC radiation fields for correction, and finally the neutron dose rate value at the calibration point can be obtained.

[0055] The percentage of neutron contamination at the calibration point can be obtained by calculating the ratio of the corrected neutron dose rate to the corrected dose rate of the aforementioned graphite cavity ionization chamber.

[0056] Step S114: Determine the dose ratio based on the high-energy photon dose rate, low-energy photon dose rate, electron dose rate, and neutron dose rate.

[0057] Through the above steps S102 to S114, the purpose of determining the low-energy photon dose rate value, electron dose rate value, and neutron dose rate value is achieved. This realizes the technical effect of obtaining the dose ratio values ​​of high-energy photon dose rate value, low-energy photon dose rate value, electron dose rate value, and neutron dose rate value. In turn, it solves the technical problem in related technologies that do not propose the proportion of the contamination influence of low-energy photons, electrons, and neutrons on high-energy photons, which leads to the inability to determine the high-energy photon dose rate and the existence of errors.

[0058] Example 2 This embodiment also provides a contamination radiation testing device for a high-energy photon reference radiation field. This device is used to implement the above embodiments and preferred embodiments, and details already described will not be repeated. As used below, the terms "module" and "device" can refer to a combination of software and / or hardware that performs a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0059] According to an embodiment of the present invention, an apparatus embodiment for implementing the above-described method for testing contamination radiation in a high-energy photon reference radiation field is also provided. Figure 5 This is a schematic diagram of the structure of a contamination radiation testing device for a high-energy photon reference radiation field according to Embodiment 2 of the present invention, as shown below. Figure 5 As shown, the above-mentioned device includes: a construction module 201, a measurement spectrum module 202, a high-energy photon module 203, a low-energy photon module 204, an electron module 205, a neutron module 206, and a proportioning module 207, wherein: Module 201 is used to construct a physical model of a high-energy photon detector based on the Monte Carlo method; The measurement spectrum module 202, connected to the building module 201, is used to obtain the measurement spectrum at the high-energy photon radiation quality calibration point through the HpGe detector and supporting electronic equipment. The high-energy photon module 203 is connected to the measurement spectrum module 202 and is used to calculate the high-energy photon dose rate value by using the G function to calculate the measurement spectrum. The low-energy photon module 204 is connected to the high-energy photon module 203 and is used to simulate the detection efficiency curve of the HpGe detector within the energy range of 8MeV in the detector physical model to obtain the low-energy photon dose rate value. Electronic module 205, connected to low-energy photon module 204, is used to determine the electron dose rate value by extrapolation ionization chamber based on Co-60 isotope energy calibration. Neutron module 206, connected to electronic module 205, is used to set neutron isotopes and obtain neutron dose rate values ​​based on a long counter. The proportion module 207, connected to the neutron module 206, is used to determine the dose proportion value based on the high-energy photon dose rate value, the low-energy photon dose rate value, the electron dose rate value, and the neutron dose rate value.

[0060] It should be noted that the above modules can be implemented by software or hardware. For example, for the latter, it can be implemented in the following ways: the above modules can be located in the same processor; or the above modules can be located in different processors in any combination.

[0061] It should be noted that the aforementioned construction module 201, measurement spectrum module 202, high-energy photon module 203, low-energy photon module 204, electron module 205, neutron module 206, and proportioning module 207 correspond to steps S102 to S114 in the embodiments. The instances and application scenarios implemented by the above modules and corresponding steps are the same, but are not limited to the content disclosed in the above embodiments. It should be noted that the above modules, as part of the device, can run on a computer terminal.

[0062] It should be noted that the optional or preferred implementation methods of this embodiment can be found in the relevant descriptions in the embodiments, and will not be repeated here.

[0063] The aforementioned high-energy photon reference radiation field contamination radiation testing device may further include a processor and a memory. The aforementioned construction module 201, measurement spectrum module 202, high-energy photon module 203, low-energy photon module 204, electron module 205, neutron module 206, and proportion module 207 are all stored in the memory as program modules. The processor executes the aforementioned program modules stored in the memory to realize the corresponding functions.

[0064] The processor contains a core that retrieves the corresponding program modules from memory. One or more cores may be configured. Memory may include non-persistent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, like read-only memory (ROM) or flash RAM. Memory includes at least one memory chip.

[0065] According to an embodiment of this application, an embodiment of a non-volatile storage medium is also provided. Optionally, in this embodiment, the non-volatile storage medium includes a stored program, wherein, when the program is running, it controls the device containing the non-volatile storage medium to execute any of the above-mentioned methods for testing contamination radiation of a high-energy photon reference radiation field.

[0066] Optionally, in this embodiment, the non-volatile storage medium may be located in any computer terminal in a group of computer terminals in a computer network, or in any mobile terminal in a group of mobile terminals, and the non-volatile storage medium includes stored programs.

[0067] Optionally, during program execution, the device containing the non-volatile storage medium may perform the following functions: Construct a detector physical model for high-energy photons based on the Monte Carlo method; obtain the measurement spectrum at the high-energy photon radiation quality calibration point using the detector physical model; calculate the high-energy photon dose rate value using the G function; simulate the detection efficiency curve of an HpGe detector within an energy range of 8 MeV in the detector physical model to obtain the low-energy photon dose rate value; determine the electron dose rate value by extrapolating the ionization chamber based on Co-60 isotope energy calibration; set the neutron isotope and obtain the neutron dose rate value based on a long counter; determine the dose ratio value based on the high-energy photon dose rate value, low-energy photon dose rate value, electron dose rate value, and neutron dose rate value.

[0068] According to an embodiment of this application, an embodiment of a processor is also provided. Optionally, in this embodiment, the processor is used to run a program, wherein the program executes any of the above-described methods for testing contamination radiation in a high-energy photon reference radiation field.

[0069] According to an embodiment of this application, an embodiment of a computer program product is also provided. Optionally, in this embodiment, the computer program product includes a computer program that, when executed by a processor, implements the steps of any of the above-described methods for testing contaminated radiation in a high-energy photon reference radiation field.

[0070] Optionally, when the aforementioned computer program product is executed on a data processing device, it is suitable to execute an initialization program with the following steps: constructing a detector physical model for high-energy photons based on the Monte Carlo method; obtaining the measurement spectrum at the high-energy photon radiation quality calibration point through the detector physical model; calculating the high-energy photon dose rate value by using the G function to calculate the measurement spectrum; simulating the detection efficiency curve of an HpGe detector within an energy range of 8 MeV in the detector physical model to obtain the low-energy photon dose rate value; determining the electron dose rate value by extrapolating the ionization chamber based on Co-60 isotope energy calibration; setting neutron isotopes and obtaining the neutron dose rate value based on a long counter; determining the dose ratio value based on the high-energy photon dose rate value, low-energy photon dose rate value, electron dose rate value, and neutron dose rate value.

[0071] This invention provides an electronic device, which includes a processor, a memory, and a program stored in the memory and executable on the processor. When the processor executes the program, it performs the following steps: constructing a detector physical model for high-energy photons based on the Monte Carlo method; obtaining the measurement spectrum at the high-energy photon radiation quality calibration point using the detector physical model; calculating the high-energy photon dose rate value using the G function; simulating the detection efficiency curve of an HpGe detector within an energy range of 8 MeV in the detector physical model to obtain the low-energy photon dose rate value; determining the electron dose rate value by extrapolating the ionization chamber based on Co-60 isotope energy calibration; setting neutron isotopes and obtaining the neutron dose rate value based on a long counter; and determining the dose ratio value based on the high-energy photon dose rate value, low-energy photon dose rate value, electron dose rate value, and neutron dose rate value.

[0072] The order of the above embodiments of the present invention is merely for description and does not represent the superiority or inferiority of the embodiments.

[0073] In the above embodiments of the present invention, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0074] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. The device embodiments described above are merely illustrative; for example, the division of modules described above can be a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, or indirect coupling or communication connection between modules, and may be electrical or other forms.

[0075] The modules described above as separate components may or may not be physically separate. Similarly, the components shown as modules may or may not be physical modules; they may be located in one place or distributed across multiple modules. Some or all of the modules can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0076] Furthermore, the functional modules in the various embodiments of the present invention can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module. The integrated modules described above can be implemented in hardware or as software functional modules.

[0077] If the aforementioned integrated modules are implemented as software functional modules and sold or used as independent products, they can be stored in a computer-readable non-volatile storage medium. Based on this understanding, the technical solution of this invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a non-volatile storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned non-volatile storage medium includes various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0078] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for testing contamination radiation in a high-energy photon reference radiation field, characterized in that, include: A physical model for high-energy photon detectors is constructed based on the Monte Carlo method. The measurement spectrum at the high-energy photon radiation quality calibration point was obtained using an HpGe detector and supporting electronic equipment. The high-energy photon dose rate value is obtained by calculating the measured spectrum using the G function; By simulating the detection efficiency curve of the HpGe detector within the energy range of 8MeV in the physical model of the detector, the low-energy photon dose rate value is obtained. The detection efficiency curve of the HpGe detector within the energy range of 8 MeV is simulated in the physical model of the detector; based on the detection efficiency curve and the measured spectrum, a high-energy photon emission spectrum is obtained by fitting; based on the high-energy photon emission spectrum, combined with the photon fluence of different energies and the dose conversion coefficient, the spectrum of photon energy and dose is determined; the total count of the low-energy photon energy range in the spectrum is counted, and the low-energy photon dose rate value is calculated; Based on the Co-60 isotope energy calibration, the electron dose rate value was determined by extrapolation of the ionization chamber; Based on the energy calibration of the Co-60 isotope, a calibration factor corresponding to the extrapolation ionization chamber is determined; an electron blocking plate is placed in front of the extrapolation ionization chamber; a fitted dose rate corresponding to the high-energy photons after electron blocking is obtained based on the extrapolation ionization chamber; an extrapolation curve is determined based on the fitted dose rate; based on the extrapolation curve and the calibration factor, the photon dose rate value of the high-energy photons after electron blocking at the calibration point is determined; the electron dose rate value is obtained by subtracting the high-energy photon dose rate from the photon dose rate value. Set up neutron isotopes and obtain neutron dose rate values ​​based on long counters; A neutron isotope is set up, and a first neutron dose rate is obtained based on a long counter, wherein the first neutron dose rate is used to indicate the neutron dose rate in the presence of neutron contamination; a calibration factor in the neutron radiation field is obtained by adjusting the pulse discrimination threshold of the long counter; the first neutron dose rate is corrected based on the calibration factor to obtain the neutron dose rate value. The dose ratio is determined based on the high-energy photon dose rate value, the low-energy photon dose rate value, the electron dose rate value, and the neutron dose rate value.

2. The method for testing contamination radiation in a high-energy photon reference radiation field according to claim 1, characterized in that, The total count of low-energy photon energy ranges in the spectrum is statistically analyzed to calculate the low-energy photon dose rate, including: The energy response characteristics of the ionization chamber in the photon energy range of 65 keV to 300 keV were calibrated using a narrow-spectrum series of X-ray reference radiation fields. Based on the energy response characteristics, the response characteristic curve of the ionization chamber is fitted; The characteristic curve of the ionization chamber is integrated to obtain the area integral result; The total dose rate value containing the proportion of low-energy photons is obtained based on the ratio of the total count to the area integral result in the low-energy photon energy range. Based on the total dose rate value and the high-energy photon dose rate value, the low-energy photon dose rate value is determined.

3. The method for testing contamination radiation in a high-energy photon reference radiation field according to claim 1, characterized in that, The electron blocking plate is positioned 1 cm from the front window of the outward-pushing ionization chamber; The area of ​​the electron blocking plate is greater than or equal to the area of ​​the front window of the extrapolation ionization chamber; The thickness of the electron blocking sheet is greater than or equal to 5 mm.

4. The method for testing contamination radiation in a high-energy photon reference radiation field according to claim 1, characterized in that, The step of correcting the first neutron dose rate based on the calibration factor to obtain the neutron dose rate value includes: Based on the calibration factor, combined with the reference radiation quality and the calibration radiation quality, the second neutron dose rate at the calibration point in the radiation field is determined, wherein the second neutron dose rate is used to indicate the neutron dose rate of neutrons at the calibration point. Determine the ratio of the first neutron dose rate to the second neutron dose rate; Based on the ratio, the first neutron dose rate is corrected to obtain the neutron dose rate value.

5. A contamination radiation testing device for a high-energy photon reference radiation field, applied to the contamination radiation testing method for a high-energy photon reference radiation field as described in any one of claims 1 to 4, characterized in that, include: The building block is used to construct a physical model of a high-energy photon detector based on the Monte Carlo method. The measurement spectrum module is used to obtain the measurement spectrum at the high-energy photon radiation quality calibration point through an HpGe detector and supporting electronic equipment; The high-energy photon module is used to calculate the high-energy photon dose rate value by using the G function to calculate the measured spectrum; The low-energy photon module is used to simulate the detection efficiency curve of the HpGe detector within the energy range of 8MeV in the physical model of the detector to obtain the low-energy photon dose rate value. An electronic module is used to determine the electron dose rate value by extrapolating the ionization chamber based on Co-60 isotope energy calibration. The neutron module is used to set neutron isotopes and obtain neutron dose rate values ​​based on a long counter. The proportion module is used to determine the dose proportion value based on the high-energy photon dose rate value, the low-energy photon dose rate value, the electron dose rate value, and the neutron dose rate value.

6. A non-volatile storage medium, characterized in that, The non-volatile storage medium stores multiple instructions, which are adapted to be loaded by a processor and executed by a method for testing contaminated radiation of a high-energy photon reference radiation field as described in any one of claims 1 to 4.

7. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the pollution radiation testing method for a high-energy photon reference radiation field as described in any one of claims 1 to 4.

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