Campbelling-type theory of fission chamber signals generated by neutron chains in a multiplying medium

Пал, Л.; Pázsit, Imre

doi:10.1016/j.nima.2015.05.006

Cited by 14 publications

(8 citation statements)

References 7 publications

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“…The main objective of the present work is to determine the stochastic properties of the detector signal for detections in a multiplying system driven by a Poisson-like neutron source with constant intensity, where the individual detection events are not independent. In the previous work [1] it was already shown that the Campbell theorem becomes invalid when the detected neutrons lose their independence. In the present work, the theory will be extended for the case when the effect of the delayed neutrons in the neutron multiplication process is taken into account.…”

Section: Basic Considerationsmentioning

confidence: 99%

“…The statistical theory of the fission detector signal due to independent detection events, based on the backward master equation approach, was introduced in [7]. Then the theory was extended to the case of detecting neutrons in a subcritical medium driven with an extraneous neutron source with Poisson statistics [1]. All fission neutrons were considered as prompt in this latter work.…”

Section: Basic Considerationsmentioning

confidence: 99%

“…However, in the present work, like in its predecessors, we will only account for the fluctuations of the detector current due to the randomness of the arrival times of the neutrons. Therefore, similarly to Refs [7] and [1], we will choose a constant value α e instead of the random variable ξ, defined by (2), i.e. we will use the density function w(x) = δ(x−α e ) in the formula (6).…”

Section: A Concrete Example For the Expectationmentioning

confidence: 99%

“…A first step to achieve these goals was made recently by the present authors by setting up a formalism which unites the stochastic description of the branching process with that of the statistical theory of the detector signal [1]. In that work, delayed neutrons were not accounted for.…”

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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Theory of fission detector signals in reactor measurements - detailed calculations

Pál,

Pázsit

2015

Preprint

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The Campbell theorem, relating the variance of the current of a fission chamber (a "filtered Poisson process") to the intensity of the detection events and to the detector pulse shape, becomes invalid when the neutrons generating the fission chamber current are not independent. Recently a formalism was developed [1] by which the variance of the detector current could be calculated for detecting neutrons in a subcritical multiplying system, where the detection events are obviously not independent. In the present paper, the previous formalism, which only accounted for prompt neutrons, is generalised to account also for delayed neutrons. A rigorous probabilistic analysis of the detector current was performed by using the same simple, but realistic detector model as in the previous work. The results of the present analysis made it possible to determine the bias of the traditional Campbelling techniques both qualitatively and quantitatively. The results show that the variance still remains proportional to the detection intensity, and is thus suitable for the monitoring of the mean flux, but the calibration factor between the variance and the detection intensity is an involved function of the detector pulse shape and the subcritical reactivity of the system, which diverges for critical systems.

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Section: Basic Considerationsmentioning

confidence: 99%

Section: Basic Considerationsmentioning

confidence: 99%

Section: A Concrete Example For the Expectationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…

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confidence: 99%

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Theory of fission detector signals in reactor measurements - detailed calculations

Pál,

Pázsit

2015

Preprint

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Development of a wide-range and fast-response digitizing pulse signal acquisition and processing system for neutron flux monitoring on EAST

Cao

Zhao

et al. 2022

NUCL SCI TECH

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The neutron count rate fluctuation reaches six orders of magnitude between the ohmic plasma scenario and high power of auxiliary heating on an experimental advanced superconducting tokamak (EAST). The measurement result of neutron flux monitoring (NFM) is a significant feedback parameter related to the acquisition of radiation protection-related information and rapid fluctuations in neutron emission induced by plasma magnetohydrodynamic activity. Therefore, a wide range and high time resolution are required for the NFM system on EAST. To satisfy these requirements, a digital pulse signal acquisition and processing system with a wide dynamic range and fast response time was developed. The present study was conducted using a field-programmable gate array (FPGA) and peripheral component interconnect extension for instrument express (PXIe) platform. The digital dual measurement modes, which are composed of the pulse-counting mode and AC coupled square integral’s Campbelling mode, were designed to expand the measurement range of the signal acquisition and processing system. The time resolution of the signal acquisition and processing system was improved from 10 to 1 ms owing to utilizing high-speed analog-to-digital converters (ADCs), a high-speed PXIe communication with a direct memory access (DMA) mode, and online data preprocessing technology of FPGA. The signal acquisition and processing system was tested experimentally in the EAST radiation field. The test results showed that the time resolution of NFM was improved to 1 ms, and the dynamic range of the neutron counts rate was expanded to more than $$10^{6}$$ 10 6 counts per second. The Campbelling mode was calibrated using a multipoint average linear fitting method; subsequently, the fitting coefficient reached 0.9911. Therefore, the newly developed pulse signal acquisition and processing system ensures that the NFM system meets the requirements of high-parameter experiments conducted on EAST more effectively.

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Measurement of fast neutrons with 238U-coated fission chamber

Guan

Yang

Duan

et al. 2019

Radiat Detect Technol Methods

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Campbelling-type theory of fission chamber signals generated by neutron chains in a multiplying medium

Cited by 14 publications

References 7 publications

Theory of fission detector signals in reactor measurements - detailed calculations

Theory of fission detector signals in reactor measurements - detailed calculations

Development of a wide-range and fast-response digitizing pulse signal acquisition and processing system for neutron flux monitoring on EAST

Measurement of fast neutrons with 238U-coated fission chamber

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