CN103969677A - Wide dynamic range neutron flux measuring system and method based on Pulse-Current mode - Google Patents
Wide dynamic range neutron flux measuring system and method based on Pulse-Current mode Download PDFInfo
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- CN103969677A CN103969677A CN201310030086.8A CN201310030086A CN103969677A CN 103969677 A CN103969677 A CN 103969677A CN 201310030086 A CN201310030086 A CN 201310030086A CN 103969677 A CN103969677 A CN 103969677A
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Abstract
The invention discloses a wide dynamic range neutron flux measuring system and method based on a Pulse-Current mode. The system comprises a fission chamber, a reference chamber, a Pulse module, a Current module, a postprocessing module and a mode selection mode. The invention further discloses a wide dynamic range neutron flux measuring method based on the Pulse-Current mode. According to the system and method, the contradiction between background radial inhibition capacity and the requirement for the signal to noise ratio in a traditional wide dynamic range neutron flux measuring process is eliminated.
Description
Technical field
The present invention relates to nuclear detection field, especially a kind of wide dynamic range neutron flux measurement system and method based on Pulse-Current pattern.
Background technology
Fission chamber detector is widely used in neutron flux monitoring field because it has good γ inhibition ability.Fissioner in neutron and fission chamber (as
235u) while interaction, can produce fission fragment, thereby fragment causes gas ionization output pulse signal in indoor Drift Process.In the time that neutron flux is lower, it is very little that the pulse signal of fission chamber output is piled up probability, counts the flux that can obtain neutron by paired pulses, and this mode of operation is called Pulse pattern; Along with the increase of neutron flux, detector output pulse starts to pile up, and Pulse pattern cannot obtain correct amount of flux, now can adopt Campbell pattern, pile up the counter flux of releasing incident neutron of mean square value of afterpulse signal by measurement; And continue to increase so that detector output signal while becoming the approximate direct current signal of slow variation when neutron flux, adopt Current pattern more, solve incoming neutron flux by the mean value of measuring this approximate direct current signal.
Adopt the sharpest edges of Campbell pattern to be that it has optimum inhibition ability to background ray (as γ etc.).For fission chamber, because of the difference of the mechanism of action, the amplitude of neutron signal is generally far longer than background ray, and after signal is carried out square, both amplitude difference will further increase, thereby background ray is reduced greatly to the contribution of mean square value.Current pattern is owing to only averaging, although dynamic range increases to some extent with respect to the Campbell pattern of getting mean square value, but its inhibition ability to background ray is nothing like Campbell pattern, therefore this pattern is only used in the very large situation that consequently can ignore the impact of background ray of neutron flux.Therefore, the measurement of wide dynamic range neutron flux in most cases is all carried out based on Pulse-Campbell pattern.
But, because the mean square value of signal is very responsive to signal noise, therefore Campbell pattern is in obtaining excellent background ray inhibition ability, the requirement of signal to noise ratio (S/N ratio) is also improved greatly.The technology of development all concentrates on the system signal noise ratio how reducing under Campbell pattern at present, although also obtained certain effect, all fails fundamentally to solve this contradiction.
Summary of the invention
In order to solve in traditional wide dynamic range neutron flux measurement process, background ray is suppressed to the contradiction between ability and signal to noise ratio (S/N ratio) requirement.The present invention proposes a kind of wide dynamic range neutron flux measurement system and method based on Pulse-Current pattern.
According to an aspect of the present invention, a kind of wide dynamic range neutron flux measurement system based on Pulse-Current pattern is proposed, this system comprises: fission chamber, reference chamber, Pulse module, Current module, post-processing module and mode selection module, wherein:
Described fission chamber is used for detected neutron, the particle that the background ray in radiation environment and fissioner spontaneous fission produce, and export respectively neutron signal, background signal and other undesired signals to described Pulse module and described Current module;
Described reference chamber is used for surveying background ray, and to described Current module output background signal;
Described Pulse module is connected with described fission chamber, it is operated under Pulse pattern, deduct described background signal and other undesired signals for the mode by amplitude discriminator from received signal, and described neutron signal is counted, complete the measurement under low neutron flux;
Described Current module is connected with described fission chamber and described reference chamber, and it is operated under Current pattern, for the pulse signal receiving is carried out to integration, and asks its mean value; Corresponding to the output of described fission chamber, the mean value that described Current module obtains is designated as V
1, corresponding to the output of described reference chamber, the mean value that described Current module obtains is designated as V
2;
Described post-processing module is connected with described Current module, and it is by processing two mean value V
1and V
2solve the flux that obtains pure neutron;
Described mode selection module is connected with described Pulse module and described post-processing module, for the output based on described Pulse module and described post-processing module, between Pulse and two kinds of mode of operations of Current, select a pattern also by corresponding this pattern result, be the output of described Pulse module or the output of described post-processing module, as final neutron flux output, complete the measurement of wide dynamic range neutron flux.
According to a further aspect in the invention, propose a kind of wide dynamic range neutron flux measurement method based on Pulse-Current pattern, the method comprises the following steps:
Step 1, fission chamber detected neutron, the particle that background ray and fissioner spontaneous fission produce, and export respectively neutron signal, background signal and other undesired signals to Pulse module and Current module; Meanwhile, reference chamber is surveyed background ray and is exported background signal to described Current module;
Step 2, the Pulse module being operated under Pulse pattern is deducted described background signal and other undesired signals by the mode of amplitude discriminator from received signal, and described neutron signal is counted, and completes the measurement under low neutron flux; Meanwhile, the Current module being operated under Current pattern is carried out integration to the pulse signal of described fission chamber output, asks its mean value, and is designated as V
1; Pulse signal to described reference chamber output carries out integration, asks its mean value, is designated as V
2;
Step 3, post-processing module is processed two obtained mean values, obtains characterizing the mean value of pure neutron signal, then can instead solve the flux of incident neutron by this mean value;
Step 4, based on the flux of described incident neutron, utilize sluggish relative method, between Pulse and two kinds of mode of operations of Current, select a pattern and using corresponding this pattern result as final neutron flux output, complete the measurement of wide dynamic range neutron flux.
Advantage of the present invention is: the first, because the present invention uses Current pattern, and the mean value of noise is 0, thus greatly reduce the requirement of system to signal to noise ratio (S/N ratio), and dynamic range is also higher than Campbell pattern; The second, owing to having adopted reference chamber, thereby background ray also can be subtracted each other and thoroughly be eliminated by mean value the contribution of mean value.Therefore, the present invention has fundamentally solved in traditional wide dynamic range neutron flux measurement process background ray has been suppressed to the contradiction between ability and signal to noise ratio (S/N ratio) requirement.
Brief description of the drawings
Fig. 1 is the theory diagram that the present invention is based on the wide dynamic range neutron flux measurement system of Pulse-Current pattern;
Fig. 2 is the wide dynamic range neutron flux measurement method flow diagram that the present invention is based on Pulse-Current pattern;
Fig. 3 is the neutron flux monitoring system pictorial diagram in ITER international cooperative project.
Embodiment
For making the object, technical solutions and advantages of the present invention clearer, below in conjunction with specific embodiment, and with reference to accompanying drawing, the present invention is described in more detail.
Fig. 1 is the theory diagram that the present invention is based on the wide dynamic range neutron flux measurement system of Pulse-Current pattern, as shown in Figure 1, according to an aspect of the present invention, the described wide dynamic range neutron flux measurement system based on Pulse-Current pattern that the present invention proposes comprises: fission chamber, reference chamber, Pulse module, Current module, post-processing module and mode selection module, wherein:
Described fission chamber is used for surveying following three kinds of particles: neutron, background ray (as α, β, the gamma-rays etc. of institute's association in neutron irradiation process) in radiation environment, and the particle that produces of fissioner spontaneous fission, remember that the pulse signal that described three kinds of particles produce in fission chamber is respectively: neutron signal, background signal and other undesired signals, these three kinds of pulse signals will be sent to described Pulse module and described Current module simultaneously;
Described reference chamber is identical with the structure of described fission chamber, both difference are only that the top layer of described reference chamber does not scribble fissioner, therefore it cannot detected neutron, and only, for surveying background ray, the background signal of its output also only sends to described Current module;
Described Pulse module is connected with described fission chamber, it is operated under Pulse pattern, deduct described background signal and other undesired signals for the mode by amplitude discriminator from received signal, and described neutron signal is counted, complete the measurement under low neutron flux;
Described Current module is connected with described fission chamber and described reference chamber, and it is operated under Current pattern, for the pulse signal receiving is carried out to integration, and asks its mean value; Corresponding to the output of described fission chamber, the mean value that described Current module obtains is designated as V
1, corresponding to the output of described reference chamber, the mean value that described Current module obtains is designated as V
2, wherein, V
1mainly comprise the contribution of following three kinds of particles: the particle that neutron, background ray and fissioner spontaneous fission produce, and V
2in only comprise the contribution of background ray;
Described post-processing module is connected with described Current module, and it is by processing two mean value V
1and V
2: V=V
1-V
2-K, the anti-flux that solves pure neutron.Due to reference chamber and fission chamber structure basic identical, therefore the interaction process of background ray in fission chamber and reference chamber is also basic identical, therefore background signal also can be considered identical to the contribution of mean value, so, if from V
1in deduct V
2, can eliminate the contribution of background ray for mean value; The particle (as α) producing for fissioner spontaneous fission, because it is to V
2not contribution, therefore cannot be by deducting V
2and eliminate, but only relevant with the characteristic of fission chamber itself due to the contribution of this part of particle, do not change with the change of measurement environment, therefore can be considered as a constant, be designated as K, obviously, K can be by once demarcating and record.Therefore,
If again from V
1-V
2in to deduct K be the contribution of particle that deductible spontaneous fission produces for mean value, that is, V
1-V
2-K has just characterized the mean value of pure neutron signal, can instead solve the flux of incident neutron by this mean value.
Described mode selection module is connected with described Pulse module and described post-processing module, for the flux based on described incident neutron, between Pulse and two kinds of mode of operations of Current, select a suitable pattern also by corresponding this pattern result, be the output of described Pulse module or the output of described post-processing module, as final neutron flux output, complete the measurement of wide dynamic range neutron flux.Wherein, the method for model selection adopts sluggish relative method, sets respectively a upper and lower threshold value, in the time that incoming neutron flux exceedes upper threshold value, selects Current mode of operation; When incoming neutron flux is during lower than lower threshold value, select Pulse pattern.Described sluggish relative method has adopted two threshold values, and than a threshold value, it can not cause because of the impact of noise the frequent switching of mode of operation.The value of concrete upper and lower threshold value need be by considering the environment of neutron irradiation to be measured, the practical factor such as shape, the probability of signal pile-up of neutron signal is set.
Fig. 2 is the wide dynamic range neutron flux measurement method flow diagram that the present invention is based on Pulse-Current pattern, as shown in Figure 2, according to a further aspect in the invention, the described wide dynamic range neutron flux measurement method based on Pulse-Current pattern that the present invention proposes comprises the following steps:
Step 1, fission chamber detected neutron, the particle that background ray and fissioner spontaneous fission produce, and export respectively neutron signal, background signal and other undesired signals to Pulse module and Current module; Meanwhile, reference chamber is surveyed background ray and is exported background signal to described Current module;
Step 2, the Pulse module being operated under Pulse pattern is deducted described background signal and other undesired signals by the mode of amplitude discriminator from received signal, and described neutron signal is counted, and completes the measurement under low neutron flux; Meanwhile, the Current module being operated under Current pattern is carried out integration to the pulse signal of described fission chamber output, asks its mean value, and is designated as V
1, this mean value mainly comprises the contribution of following three kinds of particles: the particle that neutron, background ray and fissioner spontaneous fission produce; Pulse signal to described reference chamber output carries out integration, asks its mean value, is designated as V
2, this mean value only comprises the contribution of background ray;
Step 3, post-processing module is processed two obtained mean values, obtains characterizing the mean value of pure neutron signal: V=V
1-V
2-K, then can instead solve the flux of incident neutron by this mean value.In formula, K is a constant, only relevant with the characteristic of fission chamber itself, the contribution of the particle that the spontaneous fission of expression fissioner produces to mean value;
Step 4, based on the flux of described incident neutron, utilize sluggish relative method, between Pulse and two kinds of mode of operations of Current, select a pattern and corresponding this pattern result is exported as final neutron flux, complete the measurement of wide dynamic range neutron flux, particularly, adopt sluggish relative method to select mode of operation: to set respectively upper and lower threshold value, in the time that the flux of described incident neutron exceedes upper threshold value, select Current mode of operation; When the flux of described incident neutron is during lower than lower threshold value, select Pulse pattern.
Successfully the inventive method is applied at present to the neutron flux monitoring (NFM in ITER international cooperative project, Neutron Flux Monitor) system, this system mainly utilizes totally digitilized technology to carry out step-by-step counting and digital integration to neutron signal, and adopt described Pulse-Current mode of operation, complete the neutron flux monitoring of wide dynamic range.Fig. 3 is the neutron flux monitoring system pictorial diagram in ITER international cooperative project.
Above-described specific embodiment; object of the present invention, technical scheme and beneficial effect are further described; institute is understood that; the foregoing is only specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any amendment of making, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.
Claims (9)
1. the wide dynamic range neutron flux measurement system based on Pulse-Current pattern, is characterized in that, this system comprises: fission chamber, reference chamber, Pulse module, Current module, post-processing module and mode selection module, wherein:
Described fission chamber is used for detected neutron, the particle that the background ray in radiation environment and fissioner spontaneous fission produce, and export respectively neutron signal, background signal and other undesired signals to described Pulse module and described Current module;
Described reference chamber is used for surveying background ray, and to described Current module output background signal;
Described Pulse module is connected with described fission chamber, it is operated under Pulse pattern, deduct described background signal and other undesired signals for the mode by amplitude discriminator from received signal, and described neutron signal is counted, complete the measurement under low neutron flux;
Described Current module is connected with described fission chamber and described reference chamber, and it is operated under Current pattern, for the pulse signal receiving is carried out to integration, and asks its mean value; Corresponding to the output of described fission chamber, the mean value that described Current module obtains is designated as V
1, corresponding to the output of described reference chamber, the mean value that described Current module obtains is designated as V
2;
Described post-processing module is connected with described Current module, and it is by processing two mean value V
1and V
2solve the flux that obtains pure neutron;
Described mode selection module is connected with described Pulse module and described post-processing module, for the output based on described Pulse module and described post-processing module, between Pulse and two kinds of mode of operations of Current, select a pattern also by corresponding this pattern result, be the output of described Pulse module or the output of described post-processing module, as final neutron flux output, complete the measurement of wide dynamic range neutron flux.
2. system according to claim 1, is characterized in that, described reference chamber is identical with the structure of described fission chamber, and its difference is only that the top layer of described reference chamber does not scribble fissioner.
3. system according to claim 1, is characterized in that, described mean value V
1comprise the contribution of following three kinds of particles: the particle that neutron, background ray and fissioner spontaneous fission produce, and described mean value V
2only comprise the contribution of background ray.
4. system according to claim 1, is characterized in that, processes two mean value V
1and V
2solving the flux that obtains pure neutron is further:
Process according to the following formula two mean value V
1and V
2obtain characterizing the mean value of pure neutron signal:
V＝V
1-V
2-K，
Wherein, K is a constant, the contribution of the particle that the spontaneous fission of expression fissioner produces to mean value;
Can instead solve the flux of incident neutron by this mean value.
5. system according to claim 1, is characterized in that, described mode selection module adopts sluggish relative method to select pattern: set respectively upper and lower threshold value, in the time that the flux of described incident neutron exceedes upper threshold value, select Current mode of operation; When the flux of described incident neutron is during lower than lower threshold value, be switched to Pulse pattern.
6. the wide dynamic range neutron flux measurement method based on Pulse-Current pattern, is characterized in that, the method comprises the following steps:
Step 1, fission chamber detected neutron, the particle that background ray and fissioner spontaneous fission produce, and export respectively neutron signal, background signal and other undesired signals to Pulse module and Current module; Meanwhile, reference chamber is surveyed background ray and is exported background signal to described Current module;
Step 2, the Pulse module being operated under Pulse pattern is deducted described background signal and other undesired signals by the mode of amplitude discriminator from received signal, and described neutron signal is counted, and completes the measurement under low neutron flux; Meanwhile, the Current module being operated under Current pattern is carried out integration to the pulse signal of described fission chamber output, asks its mean value, and is designated as V
1; Pulse signal to described reference chamber output carries out integration, asks its mean value, is designated as V
2;
Step 3, post-processing module is processed two obtained mean values, obtains characterizing the mean value of pure neutron signal, then can instead solve the flux of incident neutron by this mean value;
Step 4, based on the flux of described incident neutron, utilize sluggish relative method, between Pulse and two kinds of mode of operations of Current, select a pattern and using corresponding this pattern result as final neutron flux output, complete the measurement of wide dynamic range neutron flux.
7. method according to claim 6, is characterized in that, described mean value V
1comprise the contribution of following three kinds of particles: the particle that neutron, background ray and fissioner spontaneous fission produce, described mean value V
2only comprise the contribution of background ray.
8. method according to claim 6, is characterized in that, the mean value of the pure neutron signal of described sign is expressed as:
V＝V
1-V
2-K，
Wherein, K is a constant, the contribution of the particle that the spontaneous fission of expression fissioner produces to mean value.
9. method according to claim 6, is characterized in that, in described step 4, adopts sluggish relative method to select mode of operation: set respectively upper and lower threshold value, in the time that the flux of described incident neutron exceedes upper threshold value, select Current mode of operation; When the flux of described incident neutron is during lower than lower threshold value, select Pulse pattern.
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Citations (4)
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| JP2011002301A (en) * | 2009-06-17 | 2011-01-06 | Toshiba Corp | Neutron instrumentation system and neutron instrumentation method |
-
2013
- 2013-01-25 CN CN201310030086.8A patent/CN103969677B/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4086490A (en) * | 1976-07-07 | 1978-04-25 | Westinghouse Electric Corporation | Wide range neutron detection system |
| CN1677127A (en) * | 2004-03-31 | 2005-10-05 | 热电集团 | Method and apparatus for detecting high-energy radiation using a pulse mode ion chamber |
| JP2011002301A (en) * | 2009-06-17 | 2011-01-06 | Toshiba Corp | Neutron instrumentation system and neutron instrumentation method |
| CN101937093A (en) * | 2009-06-30 | 2011-01-05 | 同方威视技术股份有限公司 | Method for correcting afterglow of scintillation detector |
Non-Patent Citations (2)
| Title |
|---|
| CAO HONGRUI等: "A High-Speed Baseline Restorer for Neutron Flux Detection in ITER", 《PLASMA SCIENCE AND TECHNOLOGY》 * |
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