Mode Structure Analysis of Detached Plasmas with 2D Images

Kajita, Shin; Tanaka, Hirohiko; Ohno, Noriyasu; Onda, T

doi:10.1585/pfr.13.1402033

Cited by 3 publications

(3 citation statements)

References 16 publications

(24 reference statements)

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“…The profile broadening was likely because of an enhancement of radial transport by forming radially elongated spiral plasma structures [17]; similar behavior was demonstrated using three-dimensional global drift fluid simulations [18]. Fast framing camera observation [19], a segmented electrode target, and a microwave interferometer [20] have been used to investigate the instabilities of the recombining plasmas in the NAGDIS-II. It was found that m=0, 1 instability, where m is the mode number in the azimuthal direction, likely deeply related to the formation of the spiral shaped structures.…”

Section: Introductionmentioning

confidence: 72%

Spatial and temporal measurement of recombining detached plasmas by laser Thomson scattering

Kajita

Ohshima

Tanaka

et al. 2019

Plasma Sources Sci. Technol.

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Elucidation and control of the low temperature recombining plasmas under fusion relevant conditions are crucial issues. In this study, we applied a conditional average for laser Thomson scattering technique to measure the temporal evolution of the plasma instability in detached recombining plasmas in the divertor simulator NAGDIS-II. In recombining plasmas, it is shown that the electron energy distribution function has a non-Maxwellian component, and the fraction of the low electron temperature component increases with the gas pressure. It is found that one of the major reasons to cause the non-Maxwellian distribution function is in the temporal variations of the electron temperature. By using the conditional averaging method, the temporal evolutions of the spatial (vertical and radial) profiles of the electron density and temperature are revealed for different frequency ranges.

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Section: Introductionmentioning

confidence: 72%

Spatial and temporal measurement of recombining detached plasmas by laser Thomson scattering

Kajita

Ohshima

Tanaka

et al. 2019

Plasma Sources Sci. Technol.

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“…Such a correlation is expected to expand the width of the heat flux to the divertor target, i.e., λ q . Thus, the observation and analysis regarding the correlation phenomena have been actively performed in linear devices, e.g., the NAGDIS-II [5,6,7,8,13,14,15,16,17,18,19,20]. However, the physical dynamics of the correlation has not been revealed sufficiently.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, the observation and analysis regarding the correlation phenomena have been actively performed in linear devices, e.g. the NAGDIS-II [5][6][7][8][13][14][15][16][17][18][19][20]. However, the physical dynamics of the correlation has not been * Author to whom any correspondence should be addressed.…”

Section: Introductionmentioning

confidence: 99%

Linear analysis of cross-field dynamics with feedback instability on detached divertor plasmas

Hasegawa¹,

Tanaka²,

Ishiguro³

2021

Nucl. Fusion

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The theoretical model of the feedback instability is proposed to explain the mechanism of the correlation between the detachment and the cross-field plasma transport. It is shown that the feedback instability on the detached divertor plasma can be induced in a certain condition in which the volume recombination frequency is larger than the ion cyclotron frequency in the recombination region. Further, the density gradient and the electric field in the direction perpendicular to the magnetic flux surface are not zero in the condition. The feedback instability can provide the cross-field plasma transport in the boundary layer of magnetic fusion torus devices. Furthermore, the properties of the radial transport observed in the NAGDIS-II linear device experiment are compared with the estimation by the feedback instability model. The dependence of the feedback instability mode on the total collision frequency and the recombination coefficient and the density gradient has been also investigated. Although the dependency on the total collision frequency and the recombination coefficient for the typical fusion torus device case is opposite to that for the NAGDIS-II case, the represented dependencies show the reasonable tendency in each case.

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Application of dynamic mode decomposition to rotating structures in detached linear plasmas

et al. 2020

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Dynamic mode decomposition (DMD) was applied to time-series snapshots of dynamic behavior in detached plasmas with a fast framing camera in the linear plasma device NAGDIS-II. The DMD extracted radial plasma ejection and Er×B rotation structures, which are associated with blob-like plasma structures. Besides, we investigated the influences from neutral gas pressure on the growth rates of the DMD modes. By increasing the neutral gas flow rate in the detached plasma, the growth rate of rotation mode became larger while the frequency decreased. The results indicated that the ejected plasma existed for a longer time in the periphery region. It is likely due to the fact that the ratio of the radial velocity to the rotation velocity of the ejected plasma decreased.

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Mode Structure Analysis of Detached Plasmas with 2D Images

Cited by 3 publications

References 16 publications

Spatial and temporal measurement of recombining detached plasmas by laser Thomson scattering

Spatial and temporal measurement of recombining detached plasmas by laser Thomson scattering

Linear analysis of cross-field dynamics with feedback instability on detached divertor plasmas

Application of dynamic mode decomposition to rotating structures in detached linear plasmas

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