Differential energy spectrum stabilizing method

Abstract

The invention discloses a differential energy spectrum stabilization method, which belongs to the field of nuclear instruments and meters and nuclear radiation detection, and specifically comprises the following steps: after an energy spectrum measurement system is started, a spectrum stabilization algorithm module firstly reads a background spectrum containing a characteristic peak; after the system collects energy spectrum data, energy spectrum conversion is carried out on the collected energy spectrum according to step gain to obtain a gain conversion spectrum, background spectrum measurement time is normalized, and then subtraction is carried out on the background spectrum measurement time and the gain conversion spectrum channel by channel to obtain a difference spectrum. The total area of the characteristic peak region of the difference spectrum is calculated, and the energy spectrum transformation gain corresponding to the difference spectrum with the minimum total area of the characteristic peak region is the gain amount needing spectrum stabilization adjustment. According to the method, the characteristic peak does not need to be found, and accurate spectrum stabilization can be achieved under the condition that the reference peak is weak and even more interference nuclides exist; the method can realize spectrum stabilization of the energy spectrum measurement system, and has the characteristics of simple algorithm, simple system implementation, low cost and the like.

Description

Technical Field

[0001] The invention relates to the field of nuclear instrumentation and nuclear radiation detection, and in particular to a differential energy spectrum stabilization method. Background Art

[0002] In the field of nuclear instrumentation and nuclear radiation detection, energy spectrum measurement systems usually use scintillators and semiconductor detectors. Since the detector itself, photoelectric conversion devices (photomultiplier tubes, SiPM, etc.), electronics and other parts are affected by temperature and electromagnetic environment, energy spectrum drift will occur, resulting in spectrum drift. Energy spectrum drift may cause problems such as misidentification of energy spectrum peaks, missed identification, and reduced identification rate in nuclide identification instruments; it may cause data fluctuations to increase and measurement values ​​to be inaccurate in activity measurement and dose rate measurement instruments. Therefore, in energy spectrum measurement systems, it is usually necessary to integrate some kind of spectrum stabilization method to stabilize the spectrum so that the system can work properly.

[0003] Common spectrum stabilization methods, such as spectrum stabilization based on the radioactive characteristic peak of the crystal itself, spectrum stabilization based on the characteristic peak of natural nuclides, spectrum stabilization based on artificial radioactive nuclides, and spectrum stabilization based on LED equivalent peaks, all calculate the spectrum drift value by identifying the peak position spectrum drift of the characteristic peak or the change in the count rate in the characteristic peak monitoring interval, and then perform gain adjustment. In practice, the above methods may cause the characteristic peak to be identified incorrectly or the count rate in the characteristic peak monitoring interval to be disturbed due to the presence of other nuclides in the measured sample or environment, resulting in spectrum stabilization failure. In order to reduce misidentification, the intensity of the stabilization peak must be increased, which will reduce the effective pulse rate of the energy spectrum measurement system and increase the system background. Summary of the invention

[0004] The purpose of the present invention is to provide a differential energy spectrum stabilization method to solve the above problems.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows: a differential energy spectrum stabilization method, comprising the following steps:

[0006] (1) After the energy spectrum measurement system is started, a background spectrum is read and recorded as background[n];

[0007] (2) The energy spectrum data collector collects the energy spectrum at a fixed frequency to form a cumulative energy spectrum, which is recorded as measureData[n];

[0008] (3) Entering the energy spectrum gain scanning process, the process continuously adjusts the energy spectrum gain Gain, uses the accumulated energy spectrum measureData[n] to generate a gain transformation spectrum newData[n] according to the gain Gain, and differentiates the background energy spectrum background[n] from the gain transformation spectrum newData[n] to obtain a differential spectrum diffData[n]. When the peak positions of the gain transformation spectrum newData[n] and the background energy spectrum background[n] are aligned, the characteristic peak area Area of ​​the differential spectrum diffData[n] is the smallest. The gain value Gain obtained at this time is the ratio that needs to be adjusted to stabilize the spectrum;

[0009] (4) Gain adjustment judgment process: If the gain value Gain>1.005 or Gain<0.995, adjust the hardware gain or software gain of the energy spectrum measurement system according to Gain; if the gain value is not satisfied, it means that the current energy spectrum measurement system has an appropriate gain value and no obvious spectrum drift, and there is no need to adjust the gain.

[0010] The method of the present invention does not require searching for characteristic peaks, and can achieve accurate spectrum stabilization under conditions of weaker reference peaks even in the presence of more interfering nuclides.

[0011] As a preferred technical solution, in step (1), the background energy spectrum includes characteristic peaks required for spectrum stabilization of the system.

[0012] As a further preferred technical solution, the characteristic peak required for spectrum stabilization of the system is one of the characteristic peak of the crystal's own radioactivity, the characteristic peak of a natural nuclide, the characteristic peak of an artificial radionuclide, and the LED equivalent peak.

[0013] As a preferred technical solution, in step (3), the gain Gain is scanned from 0.9 to 1.1, which is equivalent to a stable spectrum range of ±10%, and a step of 0.005 is equivalent to an accuracy of 0.5%.

[0014] As a preferred technical solution, in step (3), the specific process of the energy spectrum gain scanning process is as follows:

[0015] 1) The energy spectrum gain generator S105 generates the energy spectrum conversion gain Gain according to formula (1): k ,

[0016] Gain k is the energy spectrum conversion gain, used in the energy spectrum gain converter S106, with a value range of 0.9 to 1.1; K is the number of scanning cycles;

[0017] 2) Cumulative energy spectrum measureData[n], energy spectrum conversion gain Gaink Input to the energy spectrum gain converter S106, and transform according to equations (2) to (5) to obtain the gain transformation spectrum newData[n];

[0018] Among them, adjCh is a floating point number, which means the gain Gain of the energy spectrum conversion of the i-th channel k The new channel address of the transformation; i is the channel address, ranging from 1 to N (the maximum channel address of the energy spectrum); mapCh is an integer, which means the channel address rounded down by adjCh, that is, the largest integer less than adjCh; newData[n] is from i=1 to i=N, that is, the maximum channel address of the energy spectrum, calculated channel by channel;

[0019] 3) The gain transformation spectrum newData[n] and the background energy spectrum background[n] are input into the difference spectrum calculator and calculated according to formula (6) to obtain the difference spectrum diffData[n];

[0020] 4) The characteristic peak total area calculator will calculate the total area of ​​the characteristic peak area of ​​the difference spectrum diffData[n] k , K increases by 1, and then enters the next scan.

[0021] 5) After scanning, the gain recorder S109 records the total area of ​​the characteristic peak and the minimum area output by the computer S108 k The corresponding energy spectrum conversion gain Gain k .

[0022] As a further preferred technical solution, in step 3), note that the background energy spectrum background[n] needs to be normalized according to the measurement time of the cumulative energy spectrum measureData[n]; the difference spectrum diffData[n] is recorded as 0 if it is less than 0, and is retained normally if it is greater than 0; if the gain transformation spectrum is not aligned with the background energy spectrum peak, then the unaligned characteristic peak will form a "residual peak" on the difference spectrum; if the gain transformation spectrum is aligned with the background spectrum peak, then the "residual peak" formed on the difference spectrum has a very small area.

[0023] Compared with the prior art, the advantages of the present invention are: the method of the present invention does not need to find characteristic peaks, and can achieve accurate and stable spectra under weak reference peak conditions even in the presence of more interfering nuclides; and the implementation of the method has low requirements on hardware resources, and can be implemented on embedded software, computer host software, and cloud server software, with the advantages of simple algorithm, simple system implementation, and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1This is a flow chart for implementing the differential energy spectrum stabilization method of the present invention;

[0025] Figure 2 is the background spectrum containing characteristic peaks;

[0026] Figure 3 is the difference spectrum without spectral drift;

[0027] Figure 4 is the difference spectrum when drifting 15 traces to the right;

[0028] Figure 5 Taking the Th source as an example, the comparison of the measured spectrum (above) and the differential spectrum (below) when the gain is not adjusted;

[0029] Figure 6 For Figure 5 Comparison of the measured spectrum (upper figure) and the differential spectrum (lower figure) after the first stabilization;

[0030] Figure 7 For Figure 6 Comparison of the measured spectrum (upper figure) and the differential spectrum (lower figure) after the second spectrum stabilization. DETAILED DESCRIPTION

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0032] Embodiment 1:

[0033] A differential energy spectrum stabilization method, the flow chart of which is as follows Figure 1 As shown:

[0034] The energy spectrum measurement system S101 starts to read the background spectrum data S102; the background spectrum data includes characteristic peaks required for spectrum stabilization of the system, which may be characteristic peaks of the crystal's own radioactivity, characteristic peaks of natural nuclides, characteristic peaks of artificial radioactive nuclides, LED equivalent peaks, etc. The background spectrum measurement time is 3600 seconds, and the background spectrum is recorded as background[n];

[0035] The energy spectrum measurement system S101 periodically enters the energy spectrum data collector S103 to collect energy spectrum from the hardware system, and the collected data is saved as a cumulative energy spectrum, which is recorded as measureData[n];

[0036] When the total count of the accumulated energy spectrum data is greater than 5000, the energy spectrum gain scanning process S104 is entered. This loop continuously adjusts the energy spectrum gain Gain, uses the accumulated energy spectrum measureData[n] to generate the gain transformation spectrum newData[n] according to the gain Gain, and differentiates the background energy spectrum background[n] from the gain transformation spectrum newData[n] to obtain the differential spectrum diffData[n]. When the peak positions of the gain transformation spectrum newData[n] and the background energy spectrum background[n] are aligned, the characteristic peak area Area of ​​the differential spectrum diffData[n] is the smallest. The gain value Gain obtained at this time is the proportion that needs to be adjusted to stabilize the spectrum. The gain Gain is scanned from 0.9 to 1.1, which is equivalent to a stable spectrum range of ±10%, and a step of 0.005 is equivalent to an accuracy of 0.5%;

[0037] The energy spectrum gain scanning process S104 includes units such as an energy spectrum gain generator S105, an energy spectrum gain converter S106, a difference calculator S107, a characteristic peak total area calculator S108, and a gain value recorder S109. The specific workflow is as follows:

[0038] The energy spectrum gain generator S105 generates the energy spectrum conversion gain Gain according to formula (1): k .

[0039]

[0040] Gain k is the energy spectrum change gain, used in the energy spectrum gain converter S106, with a value range of 0.9~1.1; K is the number of scanning cycles.

[0041] Cumulative spectrum measureData[n], energy spectrum conversion gain Gain k It is input into the energy spectrum gain converter S106 and transformed according to equations (2) to (5) to obtain the gain transformation spectrum newData[n].

[0042]

[0043] Among them, adjCh is a floating point number, which means the gain Gain of the energy spectrum conversion of the i-th channel k The new channel address of the transformation; i is the channel address, ranging from 1 to N (the maximum channel address of the energy spectrum); mapCh is an integer, which means the channel address rounded down by adjCh, that is, the largest integer less than adjCh; newData[n] is from i=1 to i=N, that is, the maximum channel address of the energy spectrum, calculated channel by channel;

[0044] The gain transformation spectrum newData[n] and the background spectrum background[n] are input into the differential spectrum calculator according to formula (6) to calculate the differential spectrum diffData[n]; note that the background spectrum background[n] needs to be normalized according to the measurement time of the cumulative spectrum measureData[n]; diffData[n] is recorded as 0 if it is less than 0, and is retained if it is greater than 0. If the peak positions of the gain transformation spectrum and the background spectrum are not aligned, then the unaligned characteristic peaks will form a "residual peak" on the differential spectrum; if the peak positions of the gain transformation spectrum and the background spectrum are aligned, then the "residual peak" formed on the differential spectrum has a very small area;

[0045] The characteristic peak total area calculator will calculate the total area of ​​the characteristic peak area of ​​the difference spectrum diffData[n] k ; K increases by 1, and then enters the next scan;

[0046] After scanning, the gain recorder S109 records the minimum area Area output by the characteristic peak total area computer S108 k The corresponding energy spectrum conversion gain Gain k ;

[0047] In the gain adjustment judgement S110, if the energy spectrum conversion gain Gain k >1.005 or Gain k <0.995, then enter the energy spectrum measurement system gain adjuster S111, otherwise it means that the energy spectrum drift is very small, no gain adjustment is needed, and enter the data resetter S112;

[0048] Energy spectrum measurement system gain regulator S111 converts gain according to energy spectrum k Adjust the hardware gain or software gain of the spectrum measurement system and enter the data reset device S112;

[0049] The data resetter S112 clears the current accumulated energy spectrum measureData[n], sets K to zero, enters the next spectrum stabilization process, and returns to the energy spectrum data collector S103.

[0050] Figure 2 , Figure 3 and Figure 4 It is a comparison of the difference spectrum with and without spectral drift in the background environment; Figure 2 is the background energy spectrum containing characteristic peaks (radioactive characteristic peaks of LaBr3 crystal itself), Figure 3 is the difference spectrum without spectral drift, Figure 4 is the difference spectrum when drifting 15 channels to the right, from Figure 2 , Figure 3and Figure 4 It can be seen that the counts in the characteristic peak area of ​​the differential spectrum with spectral drift are significantly increased compared with the differential spectrum without spectral drift.

[0051] Figure 5 , Figure 6 and Figure 7 The system's spectrum stabilization capability is tested in a high-dose and complex radiation environment (the test uses a Th source with numerous daughter nuclides, a complex energy spectrum, a count rate of 6500cps, and a dose rate of >3uSv / h).

[0052] in, Figure 5 The initial state spectrum drifts -90 channels. At this time, the 32keV energy region is very low, the 1468keV energy region is occupied by other peaks, and the energy region above 2615keV has fewer counts due to the left shift of the energy spectrum. At this time, the differential spectrum and the counts in the high-energy region are significantly increased. It can be seen from the figure that the "residual peak" in the high-energy peak region is obvious;

[0053] By calculating the above method of this embodiment, the first spectrum stabilization is performed, and the gain adjustment ratio is 1.1 (reaching the upper limit of the adjustment), the energy spectrum after the gain is adjusted in this way is shown as Figure 6 , the measured spectrum drifts to the left by 13 channels, that is, the spectrum drift is -13. It can be seen from the figure that the "residual peak" in the high-energy peak area of ​​the differential spectrum decreases;

[0054] Then perform the second spectrum stabilization, and the recommended gain adjustment ratio is 1.015; the energy spectrum after adjusting the gain by 1.015 is shown in Figure 7 , the measured spectrum drifts to the left by 2 channels, that is, the spectrum drift is -2. It can be seen from the figure that the "residual peak" in the high-energy peak area of ​​the differential spectrum is further reduced;

[0055] Perform the third spectrum stabilization, and the recommended gain adjustment ratio is 1.005. This value is lower than the adjustment threshold, and the gain is no longer adjusted. The spectrum stabilization is completed.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A differential energy spectrum stabilization method, characterized in that: The following steps are involved: (1) After the energy spectrum measurement system is started, a background spectrum is read and recorded as background[n]; (2) The energy spectrum data collector collects the energy spectrum at a fixed frequency to form a cumulative energy spectrum, which is recorded as measureData[n]; (3) Entering the energy spectrum gain scanning process, the process continuously adjusts the energy spectrum gain Gain, uses the accumulated energy spectrum measureData[n] to generate a gain transformation spectrum newData[n] according to the gain Gain, and differentiates the background energy spectrum background[n] from the gain transformation spectrum newData[n] to obtain a differential spectrum diffData[n]. When the peak positions of the gain transformation spectrum newData[n] and the background energy spectrum background[n] are aligned, the characteristic peak area Area of ​​the differential spectrum diffData[n] is the smallest. The gain value Gain obtained at this time is the ratio that needs to be adjusted to stabilize the spectrum; (4) Gain adjustment judgment process: If the gain value Gain>1.005 or Gain<0.995, adjust the hardware gain or software gain of the energy spectrum measurement system according to Gain; if the gain value is not satisfied, it means that the current energy spectrum measurement system has an appropriate gain value and no obvious spectrum drift, and there is no need to adjust the gain.

2. A differential energy spectrum stabilization method according to claim 1, characterized in that: In step (1), the background energy spectrum includes characteristic peaks required for spectrum stabilization of the system.

3. A differential energy spectrum stabilization method according to claim 2, characterized in that: The characteristic peak required for spectrum stabilization of the system is one of the characteristic peak of the crystal's own radioactivity, the characteristic peak of a natural nuclide, the characteristic peak of an artificial radionuclide, and the LED equivalent peak.

4. A differential energy spectrum stabilization method according to claim 1, characterized in that: In step (3), the gain Gain is scanned from 0.9 to 1.1, which is equivalent to a stable spectrum range of ±10%, and a step of 0.005 is equivalent to an accuracy of 0.5%.

5. A differential energy spectrum stabilization method according to claim 1, characterized in that: In step (3), the specific process of the energy spectrum gain scanning process is as follows: 1) The energy spectrum gain generator S105 generates the energy spectrum conversion gain Gain according to formula (1): k , ； Gain k is the energy spectrum conversion gain, used in the energy spectrum gain converter S106, with a value range of 0.9 to 1.1; K is the number of scanning cycles; 2) Cumulative energy spectrum measureData[n], energy spectrum conversion gain Gain k Input to the energy spectrum gain converter S106, and transform according to equations (2) to (5) to obtain the gain transformation spectrum newData[n]; ； Among them, adjCh is a floating point number, which means the gain Gain of the energy spectrum conversion of the i-th channel k The new channel address of the transformation; i is the channel address, ranging from 1 to N (the maximum channel address of the energy spectrum); mapCh is an integer, which means the channel address rounded down by adjCh, that is, the largest integer less than adjCh; newData[n] is from i=1 to i=N, that is, the maximum channel address of the energy spectrum, calculated channel by channel; 3) The gain transformation spectrum newData[n] and the background energy spectrum background[n] are input into the difference spectrum calculator and calculated according to formula (6) to obtain the difference spectrum diffData[n]; ； 4) The characteristic peak total area calculator will calculate the total area of ​​the characteristic peak area of ​​the difference spectrum diffData[n] k , K increases by 1, and then enters the next scan; 5) After scanning, the gain recorder S109 records the minimum area of ​​the characteristic peak output by the computer S108. k The corresponding energy spectrum conversion gain Gain k .

6. A differential energy spectrum stabilization method according to claim 5, characterized in that: In step 3), note that the background spectrum background[n] needs to be normalized according to the measurement time of the cumulative spectrum measureData[n]; the difference spectrum diffData[n] less than 0 is recorded as 0, and greater than 0 is retained normally.

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