A study on fast digital discrimination of neutron and gamma-ray for improvement neutron emission profile measurement

Uchida, Yuki; Takada, Eiji; Fujisaki, A.; Isobe, M.; Ogawa, K.; Shinohara, K.; Tomita, Hideki; Kawarabayashi, Jun; Iguchi, Tetsuo

doi:10.1063/1.4891711

Cited by 10 publications

(5 citation statements)

References 13 publications

(23 reference statements)

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“…Recently, the performance of stellarators and helical devices increased dramatically. For example, the 3 achievement of 10 keV ion temperature in LHD [3] and the stored plasma energy exceeds 6×10 26 Celsius m -3 s in Wendelstein 7-X [4]. In stellarators and helical systems, the energetic particle confinement study has been led by the Large Helical Device (LHD) using intensive neutral beam (NB) injection [5][6][7].…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, the advanced study of EPs performed in the large tokamaks is expected in stellarators and helical systems using the LHD. To conduct the EP study, development and prior evaluations of the neutron flux monitor [21][22][23][24], the neutron camera based on a scintillation detector [25][26][27][28] and on nuclear emulsion [29][30][31][32], and the neutron energy spectrometer [33,34] have been performed. Furthermore, the simulation of 3.5 MeV alpha particle confinement using 1 MeV tritons created by deuterium-deuterium (DD) reactions is possible for the first time in the stellarator/heliotron devices.…”

Section: Introductionmentioning

confidence: 99%

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Energetic ion confinement studies using comprehensive neutron diagnostics in the Large Helical Device

et al. 2019

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Understanding of energetic particle (EP) confinement is one of the critical issues in realizing fusion reactor. In stellarator/helical devices, the research on EP confinement is one of the key topics to obtain better confinement by utilizing the flexibility of three-dimensional magnetic field. Study of EP transport in the Large Helical Device (LHD) has been performed by means of escaping EP diagnostics in hydrogen plasma operation. By starting deuterium operation of the LHD, confinement study of EPs has progressed remarkably by using newly developed comprehensive neutron diagnostics providing the information of EPs confined in the core region. The total neutron emission rate (Sn) increases due to the relatively low deviation of beam ion orbit from the flux surface with the inward shift of the magnetic axis. Sn has the peak around the electron density of 2×10 19 m -3 to 3×10 19 m -3 , as predicted. It is found that the fraction of beam-beam components in Sn is evaluated to be approximately 20% by the Fokker-Planck models TASK/FP in the plasma with both co-and counter-neutral beam injections. The equivalent fusion gain in DT plasma achieved 0.11 in a negative-ion-based neutral beam heated 2 plasma. Time evolution of Sn following the short pulse neutral beam injection into the electroncyclotron-heated low-beta plasma is reproduced by drift kinetic simulation, indicating that transport of beam ion injected by short pulse neutral beam can be described with neoclassical models in magnetohydrodynamic quiescent low-beta plasmas. The vertical neutron camera works successfully, demonstrating that in the co-neutral beam injected plasma, neutron emission profile shifts according to magnetic axis position. The shift of the neutron emission profile is reproduced by orbit-following models. The triton burnup study is performed for the first time in stellarator/heliotron so as to understand the alpha particle confinement. It is found that the triton burnup ratio, which largely increases at inward shifted configurations due to the better triton orbit and better plasma performance in inward shifted configuration is similar to that measured in tokamak having a similar minor radius with the LHD. We study the confinement capability of EPs toward a helical reactor in magnetohydrodynamic -quiescent region and expansion of the energetic-ion physics study in toroidal fusion plasmas.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Energetic ion confinement studies using comprehensive neutron diagnostics in the Large Helical Device

et al. 2019

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“…The iterative approach used is an example of an expectationmaximization algorithm for Gaussian mixtures [15] with fixed means and standard deviations. Iterations terminate when the convergence criteria is satisfied.…”

Section: Inferring the Photon-to-neutron Ratiomentioning

confidence: 99%

Application of Bayes׳ theorem for pulse shape discrimination

Monterial

Marleau

Clarke

et al. 2015

Nuclear Instruments and Methods in Physics Research Section A:

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a b s t r a c tA Bayesian approach is proposed for pulse shape discrimination of photons and neutrons in liquid organic scinitillators. Instead of drawing a decision boundary, each pulse is assigned a photon or neutron confidence probability. This allows for photon and neutron classification on an event-by-event basis. The sum of those confidence probabilities is used to estimate the number of photon and neutron instances in the data. An iterative scheme, similar to an expectation-maximization algorithm for Gaussian mixtures, is used to infer the ratio of photons-to-neutrons in each measurement. Therefore, the probability space adapts to data with varying photon-to-neutron ratios. A time-correlated measurement of Am-Be and separate measurements of 137 Cs, 60 Co and 232 Th photon sources were used to construct libraries of neutrons and photons. These libraries were then used to produce synthetic data sets with varying ratios of photons-to-neutrons. Probability weighted method that we implemented was found to maintain neutron acceptance rate of up to 90% up to photon-to-neutron ratio of 2000, and performed 9% better than the decision boundary approach. Furthermore, the iterative approach appropriately changed the probability space with an increasing number of photons which kept the neutron population estimate from unrealistically increasing.

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“…A scintillation detector with pulse shape discrimination ability has been commonly utilized in fusion research, especially as the neutron energy spectrum measurement [23][24][25][26][27] or neutron emission profile measurement [28][29][30][31][32]. To obtain better performance of neutron and gammaray discrimination, data acquisition with a high sampling rate is required [33][34][35]. Then, a high sampling rate data acquisition system working in the high pulse count rate region has been developed.…”

Section: Introductionmentioning

confidence: 99%

Development of a High Sampling Rate Data Acquisition System Working in a High Pulse Count Rate Region for Radiation Diagnostics in Nuclear Fusion Plasma Research

Ogawa,

Sangaroon,

Liao

et al. 2023

Electronics

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In this study, a high sampling rate data acquisition system with the ability to provide timestamp, pulse shape information, and waveform simultaneously under a sub megahertz pulse counting rate was developed for radiation diagnostics for magnetic confinement nuclear fusion plasma research. The testing of the data acquisition system under the high pulse counting rate condition using real signals was performed in an accelerator-based deuterium-deuterium fusion neutron source (Fast Neutron Source) at the Japan Atomic Energy Agency. We found that the pulse counts acquired by the system linearly increased up to 6 × 105 cps, and the count loss at 106 cps was estimated to be ~10%. The data acquisition system was applied to deuterium-deuterium neutron profile diagnostics in the deuterium gas operation of a helical-type magnetic confinement plasma device, called the Large Helical Device, to observe the radial profile of neutron emissivity for the first time in a three-dimensional magnetic confinement fusion device. Time-resolved measurements of the deuterium-deuterium fusion emission profile were performed. The experimentally observed radial neutron emission profile was consistent with numerical predictions based on the orbit-following models using experimental data. The data acquisition system was shown to have the desired performance.

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A study on fast digital discrimination of neutron and gamma-ray for improvement neutron emission profile measurement

Cited by 10 publications

References 13 publications

Energetic ion confinement studies using comprehensive neutron diagnostics in the Large Helical Device

Energetic ion confinement studies using comprehensive neutron diagnostics in the Large Helical Device

Application of Bayes׳ theorem for pulse shape discrimination

Development of a High Sampling Rate Data Acquisition System Working in a High Pulse Count Rate Region for Radiation Diagnostics in Nuclear Fusion Plasma Research

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