阅读说明：本技术 一种采用能谱法实现低能x射线能量补偿的方法 (Method for realizing low-energy X-ray energy compensation by adopting energy spectrum method ) 是由 刘冰 杨松 张晓泉 张艳婷 邓长明 马慧敏 于 2021-09-08 设计创作，主要内容包括：本发明公开了一种采用能谱法实现低能X射线能量补偿的方法,基于便携式γ能谱仪的能谱测量,通过测量探测器输出的脉冲幅度,(幅度信息代表射线能量),在低能X射线辐射场下,通过数字多道能谱法获取能谱数据；根据不同能量的低能X射线能谱峰值的不同,进行能量补偿,尤其适用于便携式γ能谱仪仪表中。发明提供的一种采用能谱法实现低能X射线能量补偿的方法,可以提高探测器对低能X射线测量结果的准确性。(The invention discloses a method for realizing low-energy X-ray energy compensation by adopting an energy spectrum method, which is based on the energy spectrum measurement of a portable gamma energy spectrometer, and obtains energy spectrum data by a digital multi-channel energy spectrum method under a low-energy X-ray radiation field by measuring the pulse amplitude output by a detector (the amplitude information represents the ray energy); the energy compensation is carried out according to the difference of the energy spectrum peak values of the low-energy X-ray with different energies, and the method is particularly suitable for a portable gamma energy spectrometer. The method for realizing the low-energy X-ray energy compensation by adopting the energy spectrum method can improve the accuracy of the detector to the low-energy X-ray measurement result.)

1. A method for realizing low-energy X-ray energy compensation by adopting an energy spectrum method is characterized by comprising the following steps: the method comprises the following steps:

the method comprises the following steps: identifying and determining characteristic peaks of low-energy X-rays through a LaBr3 detector, and setting corresponding energy compensation factors according to the characteristic peaks of different low-energy X-rays¹³⁷A Cs source 662keV is used as a standard to normalize the counting rate;

step two: and (3) calibrating a dose equivalent standard value under the condition of each energy section by using the standard radiation field in combination with the energy characteristic value of the standard radiation field, wherein each energy section specifically comprises: seven energy sections including low-energy X-rays of 48keV, 60keV, 87keV, 149keV and 211keV and gamma-rays of 662keV and 1173keV are obtained, and conversion factors of counting-dose equivalent of the detector under the conditions of the energy sections are obtained;

step three: of count-dose equivalentsMultiplying the conversion factor by the counting rate in the measuring process to obtain the dose equivalent measured value at the moment, and normalizing the dose equivalent measured value to the dose equivalent standard value¹³⁷The reference value at the position of the Cs source 662keV completes corresponding correction of energy;

step four: the ratio of dose equivalent measurement to dose equivalent standard at each set of energy points is divided by¹³⁷The ratio of the dose equivalent measured value at the energy point of the Cs source 662keV to the dose equivalent standard value is obtained to obtain the reference value at each group of energy points¹³⁷And the energy response value at the position of the Cs source 662keV is substituted into the corresponding energy section according to the energy response value at different energy points, so that the energy compensation can be realized.

2. The method of claim 1, wherein the energy compensation of the low energy X-ray is achieved by energy spectroscopy, and the method comprises the following steps: the LaBr3 detector in the first step, the LaBr3 detector is a front-end detection part of a portable gamma energy spectrometer, the LaBr3 detector comprises a 1.5-inch LaBr3 crystal and a photomultiplier PMT (photomultiplier tube), the portable gamma energy spectrometer is connected to digital multichannel through a special tube seat and a voltage division assembly, a core board communicates with the digital multichannel through a high-speed USB (universal serial bus) interface to complete energy spectrum data processing and transmission, the core board is input to a Micro Control Unit (MCU) processor in a TTL (transistor-transistor logic) serial port mode, and finally the MCU realizes a low-energy X-ray energy compensation algorithm.

3. The method of claim 1, wherein the energy compensation of the low energy X-ray is achieved by energy spectroscopy, and the method comprises the following steps: the conversion factor of the count-dose equivalent in the second step is specifically solved as follows: under the radiation field environment with the dose rate of 30uSv/h, the net count under each energy segment is respectively acquired through digital multi-channel, and the conversion factor of the count-dose equivalent can be obtained by dividing the net count by the dose rate.

Technical Field

The invention relates to the technical field of radioactivity measurement, in particular to a method for realizing low-energy X-ray energy compensation by adopting an energy spectrum method

Background

In the development of nuclear radiation detection instruments, the energy response problem of the detector has been one of the important influencing factors influencing the measurement accuracy. The portable gamma energy spectrometer can detect, position and quantify radioactive materials, and can be applied to nuclear power station pollution measurement, nuclear facility decommissioning, radioactive laboratory measurement, hospital radioactive sites, radioactive metering stations, radioactive laboratories of colleges and scientific research units, and the like. When a LaBr3 detector is used as a detection unit of a portable gamma energy spectrometer, the energy response of the detector is inconsistent within the energy range of 50keV to 1.25MeV, particularly the response value is larger near low energy (less than 200keV), and the energy compensation of the detector is particularly important because the accuracy of the measurement result is influenced during measurement due to the different energy responses of the detector. The commonly used energy compensation method is physical compensation, namely, an energy compensation layer with proper thickness is added on the front end face and the side face of a packaged Labr3(Ce) scintillator, but the related parameters of the traditional energy compensation material can be realized through numerical calculation or Monte Carlo simulation, and the core of the energy compensation method is to design a material combination which is complementary with the energy response of the Labr3 detector, so as to achieve the purpose of offsetting the larger low-energy response of the Labr3 detector. However, the difficulty of this method is that it is not easy to produce a lot of compensation materials meeting the conditions, and the measurement error is relatively large.

Disclosure of Invention

In order to overcome the defects and shortcomings of the prior art, the method for realizing the low-energy X-ray energy compensation by adopting the energy spectrum method is provided, so that the accuracy of the detector on the low-energy X-ray measurement result is improved.

The invention provides a method for realizing low-energy X-ray energy compensation by adopting an energy spectrum method, which comprises the following steps:

the method comprises the following steps: identifying and determining a characteristic peak of low-energy X-rays through a LaBr3 detector, and setting corresponding energy compensation factors according to the characteristic peaks of different low-energy X-rays, wherein the energy compensation factors normalize the counting rate by taking a 137Cs source 662keV as a standard;

step two: and (3) calibrating a dose equivalent standard value under the condition of each energy section by using the standard radiation field in combination with the energy characteristic value of the standard radiation field, wherein each energy section specifically comprises: seven energy sections including low-energy X-rays of 48keV, 60keV, 87keV, 149keV and 211keV and gamma-rays of 662keV and 1173keV are obtained, and conversion factors of counting-dose equivalent of the detector under the conditions of the energy sections are obtained;

step three: multiplying the counting-dose equivalent conversion factor by the counting rate in the measuring process to obtain a dose equivalent measured value at the moment, and normalizing the dose equivalent measured value to a reference value at the 662keV position of the 137Cs source according to the dose equivalent standard value to finish corresponding energy correction;

step four: under each group of energy points, the ratio of the dose equivalent measured value to the dose equivalent standard value is divided by the ratio of the dose equivalent measured value to the dose equivalent standard value under the energy point at the position of the 137Cs source 662keV to obtain an energy response value under the reference 137Cs source 662keV under each group of energy points, and the energy response values under different energy points are substituted into corresponding energy sections, so that the energy compensation can be realized.

As a further improvement of the above scheme, the LaBr3 detector in the first step, the LaBr3 detector is a front-end detection part of the portable gamma energy spectrometer, the LaBr3 detector is a detection unit consisting of a 1.5-inch LaBr3 crystal and a photomultiplier PMT, the portable gamma energy spectrometer is connected to a digital multichannel through a special tube seat and a voltage division assembly, the core board communicates with the digital multichannel through a high-speed USB interface to complete energy spectrum data processing and transmission, the core board is input to the MCU processor in the form of a TTL serial port, and finally the MCU realizes a low-energy X-ray energy compensation algorithm.

As a further improvement of the above scheme, the conversion factor of count-dose equivalent in the second step is specifically solved as follows: under the radiation field environment with the dose rate of 30uSv/h, the net count under each energy segment is respectively acquired through digital multi-channel, and the conversion factor of the count-dose equivalent can be obtained by dividing the net count by the dose rate.

Compared with the prior art, the method for realizing low-energy X-ray energy compensation by adopting the energy spectrum method, provided by the invention, is based on the energy spectrum measurement of a portable gamma energy spectrometer, and can be used for acquiring energy spectrum data by a digital multi-channel energy spectrum method under a low-energy X-ray radiation field by measuring the pulse amplitude (amplitude information represents ray energy) output by a detector; the energy compensation is carried out according to the difference of the energy spectrum peak values of the low-energy X-ray with different energies, and the method is particularly suitable for a portable gamma energy spectrometer.

The resolution of the LaBr3 detector adopted in the invention is better than 3.5%, and the energy spectrum information of the energy interval of 30 keV-200 keV can be well identified; the voltage division component provides power supply voltages of all stages of the PMT; the digital multichannel comprises an analog part and a digital processing part, wherein the analog part mainly realizes signal pre-amplification and shaping amplification, and the digital processing part adopts an FPGA to realize the functions of analog-to-digital conversion, digital signal processing, energy spectrum data transmission and the like; the core board adopts NanoPi NEOCore to realize the functions of energy spectrum data acquisition, energy spectrum peak stabilization, radiation field characteristic energy identification and the like. The method for realizing the low-energy X-ray energy compensation by adopting the energy spectrum method can improve the accuracy of the detector on the low-energy X-ray measurement result.

Drawings

The following detailed description of embodiments of the invention is provided in conjunction with the appended drawings, in which:

FIG. 1 is a schematic diagram of the present invention;

FIG. 2 is a graph of the relative energy response of the detector of the present invention before correction;

FIG. 3 is a modified energy response curve of the present invention;

FIG. 4 shows the present invention¹³⁷Spectrum test pattern of 30uSv/h radiation field under Cs source.

Detailed Description

As shown in FIG. 1, the method for realizing low-energy X-ray energy compensation by using energy spectrometry provided by the invention is realized by the following steps:

1. firstly, an energy spectrum under an environment background is obtained through a portable gamma energy spectrometer, multi-channel gains are automatically adjusted through a built-in software algorithm (an algorithm of an Autack identification spectrum software built in Autack Gamma Vision spectrum analysis software) by identifying the environment background, and energy spectrum peak stabilization is realized. Respectively adopting standard radiation fields of low-energy X rays with characteristic energy of 48keV, 60keV, 87keV, 149keV and 211keV and gamma rays with characteristic energy of 662keV and 1173keV to obtain respective energy spectrograms, and respectively finding out seven characteristic peaks under the standard radiation fields through the high-resolution characteristic of a LaBr3 detector. The low energy region of the energy spectrum data can be divided into a plurality of sections according to the characteristic peak information, and each section corresponds to an energy compensation factor.

2. Then, the energy characteristic value of the standard radiation field is combined, the dose equivalent standard value under each energy section condition is calibrated by using the standard radiation field, and the conversion factor of the counting-dose equivalent of the detector under each energy section condition is obtained;

3. then, the dose equivalent measurement value at the moment is obtained by multiplying the conversion factor of the count-dose equivalent by the counting rate in the measurement process, so as to obtain the dose equivalent measurement value¹³⁷The Cs source 662keV is used as a standard to normalize different radiation doses¹³⁷The Cs source 662keV is used for carrying out an energy response experiment, the radiation field is 30uSv/h, and under the radiation, the radiation can be obtained¹³⁷The count rate X at the Cs source 662keV spectrum is used as a reference. For five low-energy X-rays and gamma rays of 1173keV, under the same radiation field of 30uSv/h, the respective counting rates X1, X2, X3, X4, X5 and X6 are obtained, so that the energy compensation factor K1-X1/X, K2-X2/X, K3-X3/X, K4-X4/X, K5-X5/X of the low-energy segment can be obtained.

4. And according to the intervals of different energy sections obtained in the step, bringing the energy compensation factors into the counting rates corresponding to the energy sections respectively, and finishing the correction of the counting rates under different energies.

5. And under a standard radiation field, carrying out dose rate calibration on the corrected counting rate to obtain the relation between the counting rate and the dose rate.

As shown in FIG. 2, according to the relative energy response of the LaBr3 detector, the relative response in low-energy X/gamma rays is high, generally 4-9 times, far exceeding the national standard requirement. The invention adopts an energy spectrum method to finish low-energy X-ray energy correction and realizes accurate measurement in the energy range of 50keV to 1.25 MeV.

As shown in FIG. 3, compared with an uncompensated LaBr3 detector, the energy response of the LaBr3 detector with the energy compensation is greatly improved, and the national standard requirement is met.

In a national defense science and technology industry ionizing radiation first-level metering station, a portable gamma energy spectrometer for low-energy X-ray energy compensation by adopting an energy spectrum method is tested and verified. The specific data are shown in the table below, and it can be seen that energy compensation of low-energy X-rays is realized by the energy spectrometry, and the energy response is about +/-15%.

FIG. 4 shows the present invention¹³⁷Spectrum test pattern of 30uSv/h radiation field under Cs source.

The above embodiments are not limited to the technical solutions of the embodiments themselves, and the embodiments may be combined with each other into a new embodiment. The above embodiments are only for illustrating the technical solutions of the present invention and are not limited thereto, and any modification or equivalent replacement without departing from the spirit and scope of the present invention should be covered within the technical solutions of the present invention.