CN117724147A - Rapid calibration method for large-batch gamma detectors - Google Patents

Abstract

The invention belongs to the field of nuclear instruments and meters, and provides a rapid calibration method for a large quantity of gamma detectors. The calibration method is a rapid and efficient automatic metering calibration method.

Description

Rapid calibration method for large-batch gamma detectors

Technical Field

The invention belongs to the field of nuclear instruments and meters, and particularly relates to a rapid calibration method for a large quantity of gamma detectors.

Background

The nuclear radiation detector is used as a relatively wide device in the nuclear instrument, and along with the continuous development of nuclear energy engineering construction, the development and the demand of the nuclear radiation detector are increased. The portable radiation instrument is used as a nuclear radiation monitoring instrument which is convenient to carry and operate and can feed back radiation dose in real time, and the demand of the portable radiation instrument is also increasing. The main components of the nuclear radiation detector are nuclear radiation detectors, and the types of the nuclear radiation detectors commonly used at present are as follows: ionization chamber, GM count tube, scintillator detector, semiconductor detector, etc. Among them, GM counting tubes are widely used because of their high sensitivity, large pulse amplitude, good stability, convenient observation, convenient use, low price, low process requirements, etc. The main object of the present invention is also a GM tube based gamma detector.

Calibration is the basis of quantitative radiometric measurement, whose purpose is to convert the detector response value (output value) into a corresponding radiometric unit value, for gamma detectors the device response value is the count rate (CPS), the corresponding radiometric unit is Sv/h. In the past, the metering calibration method for the equipment is to select proper measuring points in the range of the equipment design through a standard field for calibration, and establish the corresponding relation between the counting rate of the detector and the radiation quantity through a fitting function, so as to ensure that the error of the instrument in the range meets the requirement. The method is time-consuming and labor-consuming, and cannot be used in large-scale and large-batch production and debugging.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, and provides a rapid calibration method for a large number of gamma detectors according to the calibration and metering process of a large number of portable gamma radiation measuring devices in actual production. In the batch equipment production debugging calibration link, a set of fitting parameter table with universality is established by utilizing a sampling analysis method, and a proper radiation response fitting curve is rapidly matched for equipment to be tested in a characteristic point screening mode. The calibration method is a rapid and efficient automatic metering calibration method.

In the calibration link of a large number of gamma detectors of the same type, the consistency degree of the detectors is relatively good, and the detectors are generally fitted by adopting a similar fitting curve, so that the output CPS of the detectors is converted into a detected dose rate result. In this regard, a feature screening method may be adopted, that is, only a part of the detectors (recorded as a sample set) are calibrated in a complete and full-range, and the calibration result is calculated and fitted to obtain a fitted curve. For gamma detectors, the fitted curve is typically composed of piecewise functions. And then selecting a measuring point as a characteristic point in the range of each section according to the fitted segmentation condition. When a new detector is calibrated later, only the feature point is needed to be measured, then the new measurement result is compared with the feature point measurement result in the sample group, and the result is selected to be similar, and at the moment, the method can be approximately considered as follows: the gamma detector has the same fitted curve as the gamma detector in the sample set in the range segment where the feature point is located. The selection of the sample group is performed during the aging screening of the detector. And selecting a calibration measuring point closest to the middle point in each measuring range according to the segmentation condition as a characteristic point by the characteristic point selection.

Further, the object of the present invention is achieved by the following technical measures.

A rapid calibration method for a large quantity of gamma detectors comprises the following steps:

(1) Establishing a fitting curve between a control group and a control group:

performing preliminary screening on all detectors in a large-dose field aging screening mode, removing defective products with unqualified detection efficiency of the detectors, and dividing gamma detectors with similar CPS output results into a group according to CPS output results of the gamma detectors under large dose;

according to grouping conditions, respectively selecting a plurality of detectors from each group as sample groups to enter a full-range calibration environment;

calibrating the whole measuring range of the selected sample group;

performing curve fitting according to the calibration result;

according to the obtained segmented fitting curve and fitting coefficient, a comparison relation table of the fitting coefficient and characteristic points is manufactured, wherein the characteristic points are selected from the radiation field calibration points to be closest to the middle of the segment;

(2) According to the obtained comparison relation table of the fitting coefficient and the characteristic point, the gamma detector to be measured is rapidly calibrated through the following steps:

according to a comparison relation table of the fitting coefficient and the characteristic points, placing the gamma detector to be measured under a radiation field corresponding to the characteristic points for measurement;

and respectively carrying the measured results into a comparison relation table, determining a fitting coefficient of the detector in the range according to the CPS interval condition of the measured results, and obtaining a segmented fitting curve of the gamma detector in the full range after all characteristic points are compared.

Compared with the existing gamma detector calibration method, the method saves the time cost of a large amount of equipment in the calibration process by reducing the measurement points in the standard radiation field, and the fitting curve of the detector can be obtained by only measuring one point in each section.

Drawings

FIG. 1 is a flow chart of the invention for establishing a control group and a fitted curve thereof during gamma detector calibration.

FIG. 2 is a flow chart of the present invention for rapid calibration of a gamma detector under test during calibration.

Fig. 3 is a graph of a partial sample set fit established for a gamma detector in accordance with an embodiment of the present invention.

Fig. 4 is a retest error histogram for a portion of a gamma detector sample set apparatus in accordance with an embodiment of the present invention.

Fig. 5 is a pie chart of retest error results after the fast calibration is completed for a gamma detector non-sample group device in an embodiment of the present invention.

Detailed Description

The embodiment is based on the case that in a certain project, the near 4000 sets of gamma detectors are required to be calibrated in a short time, and the case is found and used in actual production. The following describes the technical scheme in the invention in detail through practical operation flow with reference to the attached drawings and the embodiments. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which can be made by a person skilled in the art without any inventive effort, are intended to be within the scope of the present patent.

In the preferred embodiment of the invention, as shown in fig. 1, when the near 4000 sets of gamma detectors to be tested are faced, a fitting curve between a control group and a control group is established by the following steps:

firstly, all detectors are initially screened in a large-dose field aging screening mode, defective products with unqualified detection efficiency of the detectors can be removed, and gamma detectors with similar CPS output results are grouped according to CPS output results of the gamma detectors under large dose.

And secondly, according to the grouping condition of the first step, respectively selecting a plurality of detectors from each group as sample groups to enter a full-range calibration environment, wherein the selection number suggestion is optimal for 5% -10% of the total number of the current groups, so that the universality of the selected sample detectors is ensured to be higher, and the situation that sample data need to be repeatedly updated in the later period due to insufficient selection of the sample groups can be avoided to the greatest extent.

And thirdly, calibrating the whole measuring range of the selected sample group.

And fourthly, performing curve fitting according to the calibration result of the third step.

And fifthly, according to the segmented fitting curve obtained in the fourth step, a comparison relation table of the fitting coefficient and the characteristic point is manufactured with the fitting coefficient, wherein the characteristic point is selected from the radiation field calibration points to be closest to the middle of the segment.

In the preferred embodiment of the invention, as shown in fig. 2, according to the comparison relation table of the fitting coefficient and the characteristic point obtained by the flow of fig. 1, the gamma detector to be measured is calibrated rapidly by the following steps:

firstly, according to a comparison relation table of fitting coefficients and characteristic points, a gamma detector to be measured is placed under a radiation field corresponding to the characteristic points for measurement.

And secondly, respectively carrying the results obtained by the measurement in the first step into a comparison relation table, determining a fitting coefficient of the detector in the range according to the CPS interval condition where the measurement results fall, and obtaining a segmented fitting curve of the gamma detector in the full range after all the characteristic points are compared.

When a curve is fitted by a traditional calibration method, at least two points need to be measured to calculate and obtain the fitted curve. As can be seen from the flow of FIG. 1 and FIG. 2, compared with the traditional method, the rapid calibration method can obtain the fitting curve of the detector by measuring only one point in each section, thereby greatly saving the time cost spent in calibration.

In the above embodiment, when the sample group and the non-sample group are calibrated, the method of matching the common acrylic plate with the stepping motor can realize one-time testing of 12 gamma detectors, and further improve the calibration efficiency. Other methods may be employed in the embodiments to increase the number of detectors calibrated at a time, thereby saving time, as would be apparent to one of ordinary skill in the art.

In the above embodiment, as shown in fig. 3, the calibration data is part of the calibration data of the sample group at the time of calibration. The following table is a comparison relation table of fitting coefficients and characteristic points formed after the fitting is completed.

All sample group fitting curve fitting coefficient comparison relation table

In the above embodiment, as shown in fig. 4 and 5, the retest error distribution diagrams of the sample group and the non-sample group are shown, it can be seen from fig. 5 that the gamma detector after full-range calibration has small relative error, while as can be seen from fig. 5, the gamma detector after calibration by the fast calibration method of the present invention has a relative error larger than that of the gamma detector after full-range calibration, but the error of the gamma detector is not more than ±10%, and the actual use requirement of the detection device is completely satisfied. In addition, according to the actual use condition, the quick calibration method can compress the time cost into one third of the original time cost, and the time cost can be further compressed along with the increase of the number of gamma detectors to be calibrated.

What is not described in detail in this specification is prior art known to those skilled in the art.

The above describes the method for rapidly calibrating a large number of gamma detectors in detail, and specific examples are applied to illustrate the principles and embodiments of the present invention, and the above examples are only used to help understand the method and core ideas of the present invention; meanwhile, as for the person skilled in the art, according to the idea of the present invention, there are changes in the specific embodiments and the application scope, so that the content of the present specification is only the embodiments of the present invention, and therefore, the present invention is not limited to the patent scope of the present invention, and all equivalent structures or equivalent processes using the content of the present specification and the accompanying drawings are included in the patent protection scope of the present invention, or are directly or indirectly applied to other related technical fields. And should not be construed as limiting the invention.

Claims (2)

1. A rapid calibration method for a large quantity of gamma detectors is characterized by comprising the following steps:

(1) Establishing a fitting curve between a control group and a control group:

performing preliminary screening on all detectors in a large-dose field aging screening mode, removing defective products with unqualified detection efficiency of the detectors, and dividing gamma detectors with similar CPS output results into a group according to CPS output results of the gamma detectors under large dose;

according to grouping conditions, respectively selecting a plurality of detectors from each group as sample groups to enter a full-range calibration environment;

calibrating the whole measuring range of the selected sample group;

performing curve fitting according to the calibration result;

according to the obtained segmented fitting curve and fitting coefficient, a comparison relation table of the fitting coefficient and characteristic points is manufactured, wherein the characteristic points are selected from the radiation field calibration points to be closest to the middle of the segment;

(2) According to the obtained comparison relation table of the fitting coefficient and the characteristic point, the gamma detector to be measured is rapidly calibrated through the following steps:

according to a comparison relation table of the fitting coefficient and the characteristic points, placing the gamma detector to be measured under a radiation field corresponding to the characteristic points for measurement;

and respectively carrying the measured results into a comparison relation table, determining a fitting coefficient of the detector in the range according to the CPS interval condition of the measured results, and obtaining a segmented fitting curve of the gamma detector in the full range after all characteristic points are compared.

2. The method for rapidly calibrating a large batch of gamma detectors according to claim 1, wherein: in the step (1), a plurality of detectors are selected as sample groups, and the number of the selected detectors is 5% -10% of the total number of the current groups.