Negative feedback dose rate measuring method

Abstract

The invention relates to the technical field of nuclear radiation detection, in particular to a negative feedback dose rate measurement method, which is based on a quasi-real-time dose rate measurement device adopting a pulsed light luminescence technology, and comprises the following steps: firstly, determining parameters such as photomultiplier dark count, inherent background, accumulated dose, counting conversion coefficient, dose loss factor and the like of the measurement device; and writing an inherent parameter serving as a measuring device into an equipment memory, and continuously measuring the dose rate subsequently to obtain the average dose rate between the current measurement and the last measurement. The accumulated dose loss caused by each dose rate measurement is effectively and accurately compensated, the negative feedback characteristic is achieved, continuous multiple measurement can be achieved after the measurement device is annealed, the measurement error of the measurement device cannot be degraded along with increase of the continuous measurement times, and frequent long-time annealing treatment is not needed; various dynamic and static backgrounds are considered, background deduction is comprehensive and accurate, and the dose rate measurement value is high in accuracy.

Description

Technical Field

[0001] The present application relates to the technical field of nuclear radiation detection, and in particular to a negative feedback dose rate measurement method. Background Art

[0002] Photoluminescent materials have the characteristics of high sensitivity, wide linear range, fast readout speed, repeatable reading, and annealing without heating. They have been maturely and widely used in fields such as personal dose monitoring. In recent years, quasi-real-time dose rate measurement methods using pulsed photoluminescence technology have also gradually been studied and applied.

[0003] The background composition of the quasi-real-time dose rate measurement device using pulsed photoluminescence technology is very complex. It includes dynamic backgrounds related to the dose rate, such as the radiation fluorescence of photoluminescence materials, the radiation fluorescence of optical fibers, and Cherenkov light, as well as static backgrounds unrelated to the dose rate, such as dark counts of photomultiplier tubes, reflected excitation light, and fluorescence emitted by optical devices. These backgrounds need to be effectively and accurately removed in the dose rate measurement method.

[0004] In the quasi-real-time dose rate measurement device using pulsed photoluminescence technology, the radiation dose accumulated by the photoluminescence material will be partially lost during each cumulative dose reading process. This partial loss needs to be effectively and accurately compensated in the dose rate measurement method to obtain an accurate dose rate measurement value. However, when the conventional compensation method (authorization announcement number "CN110376937B") is used to measure the dose rate, the error will rapidly deteriorate with the increase in the number of consecutive measurements after annealing. After only a few measurements, a long annealing process needs to be performed again, resulting in a significant decrease in the accuracy and real-time performance of the dose rate measurement. Summary of the invention

[0005] The present application provides a negative feedback dose rate measurement method, which accurately measures the average dose rate between the current measurement and the previous measurement based on parameters such as the dark count of the photomultiplier tube of the measuring device, the inherent background, the conversion coefficient of the accumulated dose and the count, and the dose loss factor.

[0006] In order to achieve the above object, the present application provides a negative feedback dose rate measurement method, comprising the following steps:

[0007] Step 1: Based on the quasi-real-time dose rate measurement device using pulsed optical luminescence technology, determine various parameters of the measurement device, including the dark count of the photomultiplier tube b pmt , inherent background b intrinsic , conversion coefficients A and B of cumulative dose D and count I, and dose loss factor R i ;

[0008] Step 2: Perform a dose rate measurement according to the timing control logic of the timing control unit, and record the count of the counter within 1s after the shutter is opened as I raw ;

[0009] Step 3: Record the count of the counter from the i-th second to the i+1-th second after the start of measurement as b di , use the following formula to calculate the dynamic background b of this measurement dynamic :

[0010]

[0011] Step 4: Use the following formula to calculate the net count I0 obtained from this measurement:

[0012]

[0013] Where r is the pulse pair resolution of the amplifier discriminator and counter;

[0014] Step 5: Use the following formula to calculate the net cumulative dose D0 obtained from this measurement:

[0015] D0=A′I0+B;

[0016] Step 6: Record the time of this dose rate measurement as t0, and record the time of the i-th measurement before this measurement as t -i The measured dose rate is recorded as The time interval between the i+1th measurement before this measurement is recorded as Δt -i , the number of measurements between the current measurement and the last annealing is recorded as n, and the average dose rate between the current measurement and the last measurement is calculated according to the following formula

[0017]

[0018] Furthermore, a quasi-real-time dose rate measurement device using pulsed light luminescence technology includes a detector, an electronics module and an optical module, wherein: the electronics module and the optical module are arranged inside a photoelectric control box, and the detector is arranged outside the photoelectric control box; the electronics module includes an amplifier discriminator, a counter and a timing control unit; the optical module includes a laser, a spectrometer, a fiber coupler and a photomultiplier tube, a filter is arranged between the laser and the spectrometer, and a fluorescence collection lens and a filter group are arranged between the spectrometer and the photomultiplier tube; the fiber coupler is connected to the detector through an optical fiber; the photomultiplier tube is connected to the amplifier discriminator; the timing control unit is respectively connected to the laser, the control shutter and the counter.

[0019] Furthermore, in step 1, when measuring the dark count of the photomultiplier tube, the measuring device is annealed and placed in a normal environment, the power of the laser is turned off, and the dose rate measurement is repeated multiple times. The average value of the counts measured multiple times is the dark count b of the photomultiplier tube. pmt .

[0020] Furthermore, in step 1, when performing inherent background measurement, the measuring device is annealed and placed in a daily environment, and the dose rate measurement is repeated multiple times. The average value of the counts of the multiple measurements is the inherent background b of the measuring device. intrinsic .

[0021] Furthermore, in step 1, when determining the conversion coefficient, 1 to 2 doses are selected for each order of magnitude of the cumulative dose measurement range of the measuring device, and are recorded as D i (i=1,2,3,…); for each dose D i After annealing, the measuring device is placed in the radiation field to irradiate the cumulative dose D i Then stop irradiation and measure the dose rate to get the corresponding count I i ; Draw D i Follow me i -b intrinsic The slope A and intercept B are obtained after linear fitting.

[0022] Furthermore, in step 1, when determining the dose loss factor, the measuring device is annealed and placed in the radiation field to irradiate a typical cumulative dose D t Then, the irradiation was stopped and multiple dose rate measurements were performed continuously. The counts obtained were recorded as I ti (i=1,2,3,…)), the dose loss factor R is calculated using the following formula i :

[0023]

[0024] Furthermore, in step 2, the timing control logic is as follows: the laser is turned on at the 0th second when the dose rate measurement starts, the counter is turned on at the 4th second for counting, the control shutter is opened at the 15th second, the laser starts to irradiate the photoluminescent material in the detector and induces its emitted photoluminescent fluorescence, the control shutter is closed at the 16th second, the laser is turned off at the same time, and the cumulative dose and dose rate are calculated based on the count of the counter within 1 second after the shutter is opened.

[0025] The negative feedback dose rate measurement method provided in this application has the following beneficial effects:

[0026] The present application effectively and accurately compensates for the cumulative dose loss caused by each dose rate measurement, and has a negative feedback characteristic. After annealing, the measuring device can not only perform multiple measurements in succession, but also its measurement error will not deteriorate with the increase in the number of consecutive measurements, and there is no need for frequent and long-term annealing treatment; various dynamic and static backgrounds are taken into consideration, the background deduction is comprehensive and accurate, and the dose rate measurement value is highly accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings constituting a part of this application are used to provide a further understanding of this application, so that other features, purposes and advantages of this application become more obvious. The schematic embodiment drawings and their descriptions of this application are used to explain this application and do not constitute an improper limitation on this application. In the drawings:

[0028] Figure 1 is a schematic diagram of a quasi-real-time dose rate measurement device using pulsed light luminescence technology provided according to an embodiment of the present application;

[0029] Figure 2 It is a schematic diagram of the timing control logic of the measuring device completing one dose rate measurement;

[0030] Figure 3 It is a schematic diagram of the change curve of the dose loss factor with the number of measurements during the measurement process of the measuring device;

[0031] Figure 4 It is a schematic diagram of a curve showing the change of the dose rate measurement value with the number of measurements when the dose rate measurement is continuously performed after the measuring device is annealed;

[0032] In the figure: 1-detector, 2-electronics module, 21-amplifier discriminator, 22-counter, 23-timing control unit, 3-optical module, 31-laser, 32-beam splitter, 33-fiber coupler, 34-photomultiplier tube, 35-control shutter, 36-filter, 37-fluorescence collection lens, 38-filter set. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0034] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0035] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0036] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in this application can be understood according to specific circumstances.

[0037] In addition, the term "plurality" shall mean two or more.

[0038] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0039] The present application provides a negative feedback dose rate measurement method, which is based on a quasi-real-time dose rate measurement device using pulsed optical luminescence technology. The parameters of the photomultiplier tube dark count, inherent background, cumulative dose and count conversion coefficient, dose loss factor and the like of the measuring device are first determined and written into the device memory as the inherent parameters of the measuring device. When the dose rate measurement is performed subsequently, steps 2-6 can be repeated to accurately measure the average dose rate between the current measurement and the previous measurement. The measurement error will not deteriorate with the increase of the number of consecutive measurements, and there is no need to frequently perform long-term annealing treatment. The method specifically includes the following steps:

[0040] Step 1: Based on the quasi-real-time dose rate measurement device using pulsed optical luminescence technology, determine various parameters of the measurement device, including the dark count of the photomultiplier tube bpmt , inherent background b intrinsic , conversion coefficients A and B of cumulative dose D and count I, and dose loss factor R i ;

[0041] When measuring the dark count of the photomultiplier tube, the measuring device is annealed and placed in a normal environment, the power of the laser 31 is turned off, and the dose rate measurement is repeated multiple times. The average value of the counts measured multiple times is the dark count b of the photomultiplier tube 34. pmt ;

[0042] When measuring the inherent background, the measuring device is annealed and placed in a daily environment. The dose rate measurement is repeated multiple times. The average value of the counts of the multiple measurements is the inherent background b of the measuring device. intrinsic ;

[0043] When determining the conversion coefficient, select 1 to 2 doses for each order of magnitude of the cumulative dose measurement range of the measuring device, denoted as D i (i=1,2,3,…)); for each dose D i After annealing, the measuring device is placed in the radiation field to irradiate the cumulative dose D i Then stop irradiation and measure the dose rate to get the corresponding count I i ; Draw D i Follow me i -b intrinsic The slope A and intercept B are obtained after linear fitting.

[0044] When determining the dose loss factor, the measuring device is annealed and placed in the radiation field to receive a typical cumulative dose D t Then, the irradiation was stopped and multiple dose rate measurements were performed continuously. The counts obtained were recorded as I ti (i=1,2,3,…)), the dose loss factor R is calculated using the following formula i ,like Figure 3 As shown:

[0045]

[0046] Step 2: Perform a dose rate measurement according to the timing control logic of the timing control unit, and record the count of the counter within 1s after the shutter is opened as I raw ;

[0047] like Figure 2As shown, the timing control logic is: the laser 31 is turned on at the 0th second when the dose rate measurement starts, the counter 22 is turned on at the 4th second to count, the control shutter 35 is opened at the 15th second, the laser starts to irradiate the photoluminescent material in the detector 1 and induces its emitted photoluminescent fluorescence, the control shutter 35 is closed at the 16th second, the laser 31 is turned off at the same time, and the cumulative dose and dose rate are calculated according to the count of the counter 22 within 1 second after the shutter is opened;

[0048] Step 3: Record the count of the counter from the i-th second to the i+1-th second after the start of measurement as b di , use the following formula to calculate the dynamic background b of this measurement dynamic :

[0049]

[0050] Step 4: Use the following formula to calculate the net count I0 obtained from this measurement:

[0051]

[0052] Wherein, r is the pulse pair resolution of the amplifier discriminator 21 and the counter 22;

[0053] Step 5: Use the following formula to calculate the net cumulative dose D0 obtained from this measurement:

[0054] D0=A′I0+B;

[0055] Step 6: Record the time of this dose rate measurement as t0, and record the time of the i-th measurement before this measurement as t -i The measured dose rate is recorded as The time interval between the i+1th measurement before this measurement is recorded as Δt -i , the number of measurements between the current measurement and the last annealing is recorded as n, and the average dose rate between the current measurement and the last measurement is calculated according to the following formula

[0056]

[0057] Further, such as Figure 1As shown, the quasi-real-time dose rate measurement device using pulsed light luminescence technology includes a detector 1, an electronics module 2 and an optical module 3, wherein: the electronics module 2 and the optical module 3 are arranged inside the photoelectric control box, and the detector 1 is arranged outside the photoelectric control box; the electronics module 2 includes an amplifier discriminator 21, a counter 22 and a timing control unit 23; the optical module 3 includes a laser 31, a beam splitter 32, a fiber coupler 33 and a photomultiplier tube 34, a filter 36 is arranged between the laser 31 and the beam splitter 32, and a fluorescence collection lens 37 and a filter group 38 are arranged between the beam splitter 32 and the photomultiplier tube 34; the fiber coupler 33 is connected to the detector 1 through an optical fiber; the photomultiplier tube 34 is connected to the amplifier discriminator 21; the timing control unit 23 is respectively connected to the laser 31, the control shutter 35 and the counter 22.

[0058] Specifically, the laser emitted by the laser 31 is coupled by the optical fiber coupler 33 and then enters the detector 1. The detector 1 is located in a radiation environment, and the photoluminescent material inside the detector emits photoluminescent fluorescence after being irradiated by the laser. The fluorescence is reflected by the spectrometer 32 and enters the photomultiplier tube 34, and then is counted. The count value is proportional to the cumulative radiation dose received by the photoluminescent material.

[0059] More specifically, compared with the conventional measurement method, the embodiment of the present application has different definitions and measurement calculation methods of the dose loss factor, as well as different calculation methods of the average dose rate. The embodiment of the present application not only takes into account various dynamic and static backgrounds, but also comprehensively and accurately deducts the background. In addition, by using the method determined in step 1, Figure 3 The dose rate loss factor shown in FIG. 1 and the negative feedback characteristic of the dose rate calculation formula described in step 6 effectively and accurately compensate for the cumulative dose loss caused by each dose rate measurement. The dose rate measurement value has high accuracy and can achieve continuous measurement. Figure 4 As shown, thanks to the negative feedback characteristics of the embodiment of the present application, the continuous measurement error of the dose rate after the measuring device is annealed will not deteriorate with the increase of the number of continuous measurements, and there is no need for frequent and long-term annealing treatment.

[0060] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A negative feedback dose rate measurement method, characterized in that: The steps include: Step 1: Based on the quasi-real-time dose rate measurement device using pulsed optical luminescence technology, determine various parameters of the measurement device, including the dark count of the photomultiplier tube b pmt , inherent background b intrinsic , conversion coefficients A and B of cumulative dose D and count I, and dose loss factor R i ; Step 2: Perform a dose rate measurement according to the timing control logic of the timing control unit, and record the count of the counter within 1s after the shutter is opened as I raw ; Step 3: Record the count of the counter from the i-th second to the i+1-th second after the start of measurement as b di , use the following formula to calculate the dynamic background b of this measurement dynamic : Step 4: Use the following formula to calculate the net count I0 obtained from this measurement: Where r is the pulse pair resolution of the amplifier discriminator and counter; Step 5: Use the following formula to calculate the net cumulative dose D0 obtained from this measurement: D0=A′I0+B; Step 6: Record the time of this dose rate measurement as t0, and record the time of the i-th measurement before this measurement as t -i The measured dose rate is recorded as The time interval between the i+1th measurement before this measurement is recorded as Δt -i , the number of measurements between the current measurement and the last annealing is recorded as n, and the average dose rate between the current measurement and the last measurement is calculated according to the following formula 2. The negative feedback dose rate measurement method according to claim 1, characterized in that: The quasi-real-time dose rate measurement device using pulsed optical luminescence technology includes a detector, an electronics module and an optical module, wherein: The electronics module and the optical module are arranged inside the photoelectric control box, and the detector is arranged outside the photoelectric control box; The electronics module includes an amplifier discriminator, a counter and a timing control unit; The optical module includes a laser, a beam splitter, a fiber coupler and a photomultiplier tube, a filter is arranged between the laser and the beam splitter, and a fluorescence collection lens and a filter group are arranged between the beam splitter and the photomultiplier tube; The optical fiber coupler is connected to the detector via an optical fiber; the photomultiplier tube is connected to the amplifying discriminator; The timing control unit is connected to the laser, the control shutter and the counter respectively.

3. The negative feedback dose rate measurement method according to claim 2, characterized in that: In step 1, when measuring the dark count of the photomultiplier tube, the measuring device is annealed and placed in a normal environment, the power of the laser is turned off, and the dose rate measurement is repeated multiple times. The average value of the counts measured multiple times is the dark count b of the photomultiplier tube. pmt .

4. The negative feedback dose rate measurement method according to claim 3, characterized in that: In step 1, when measuring the inherent background, the measuring device is annealed and placed in a daily environment, and the dose rate measurement is repeated multiple times. The average value of the counts of the multiple measurements is the inherent background b of the measuring device. intrinsic .

5. The negative feedback dose rate measurement method according to claim 4, characterized in that: In step 1, when determining the conversion coefficient, select 1 to 2 doses for each order of magnitude of the cumulative dose measurement range of the measuring device, denoted as D i (i=1,2,3,…); for each dose D i After annealing, the measuring device is placed in the radiation field to irradiate the cumulative dose D i Then stop irradiation and measure the dose rate to get the corresponding count I i ; Draw D i Follow me i -b intrinsic The slope A and intercept B are obtained after linear fitting.

6. The negative feedback dose rate measurement method according to claim 5, characterized in that: In step 1, when determining the dose loss factor, the measuring device is annealed and placed in the radiation field to irradiate the typical cumulative dose D t Then, the irradiation was stopped and multiple dose rate measurements were performed continuously. The counts obtained were recorded as I ti (i=1,2,3,…), the dose loss factor R is calculated using the following formula i :

7. The negative feedback dose rate measurement method according to claim 6, characterized in that: In step 2, the timing control logic is as follows: turn on the laser at the 0th second when the dose rate measurement starts, turn on the counter at the 4th second to start counting, open the control shutter at the 15th second, the laser starts to irradiate the photoluminescent material in the detector and induce its emitted photoluminescent fluorescence, close the control shutter at the 16th second, turn off the laser at the same time, and calculate the cumulative dose and dose rate based on the count of the counter within 1 second after the shutter is opened.

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