Multipoint measurements employing a microwave interferometer and a Langmuir probe in the detached linear plasma

Natsume, Hiroki; Tanaka, Hirohiko; Kajita, Shin; Yoshikawa, Masayuki; Seki, Mayuko; Ohshima, Hiroshi; Ohno, Noriyasu

doi:10.1063/1.5081929

Cited by 6 publications

(5 citation statements)

References 18 publications

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“…The negatively biased cathode in the cascaded arc discharge makes the V p radial profile of hollow shape, particularly in the ionizing plasma at P = 0.44 Pa. By promoting plasma detachment by increasing P, the V p profile becomes shallower, which is similar to the axial V p change in NAGDIS-II [8,9,18].…”

Section: Electrostatic-signal Statisticsmentioning

confidence: 81%

Cross-field transport in detached helium plasmas in Magnum-PSI

Tanaka

Hayashi

Kajita

et al. 2020

Plasma Phys. Control. Fusion

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In this study, enhanced radial transport in a volume-recombining region in detached helium plasmas in a linear device, Magnum-PSI, was investigated. By installing a reciprocating Langmuir probe, electrostatic fluctuations with high spatiotemporal resolutions were measured and analyzed. As a result, the ion-flux profile broadening in the detached state and the coherent plasma structure, which has an internal electric field in the azimuthal direction, were confirmed. By analyzing the emission intensities obtained with a fast framing camera viewing around the probe head, an enhanced fluctuation, which has an azimuthal mode number of m = 1, was found to be correlated with radial plasma ejection. This m = 1 mode rotates by the drift with the radial electric field and magnetic field and is correlated with the m = 0 mode. These two modes behave like a predator and prey; they quasi-periodically appear with about a quarter-period shift. Because the ion flux flowing into the target plate decreases when the radial transport is enhanced, this cross-field transport disperses the ion flux and decreases the maximum heat load applied to the target.

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Section: Electrostatic-signal Statisticsmentioning

confidence: 81%

Cross-field transport in detached helium plasmas in Magnum-PSI

Tanaka

Hayashi

Kajita

et al. 2020

Plasma Phys. Control. Fusion

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“…The frequency multiplier-containing microwave reflectometry system (Fig. 2), which was built as the interferometer system in 12], was situated 350 mm (Z = 0 mm) downstream from the target skimmer. It is a heterodyne reflectometry system equipped with a 17.5-GHz phase-locked dielectric resonator oscillator, a 37.5-MHz temperature-compensated crystal oscillator, and frequency multipliers for obtaining both 70-GHz probing beam and reference beam.…”

Section: Microwave Reflectometry Systemmentioning

confidence: 99%

“…The radiation zone, ionization region, recombination region, and momentum loss region are thought to make up the plasma conditions along the magnetic field to the diverter plate [1][2][3][4]. In addition, in some linear plasma simulators, including NAGDIS-II, Pilot-PSI, and Magnum-PSI [5][6][7][8][9][10][11][12][13][14][15], and the SOL of the tokamak plasma of ASDEX Upgrade [16], low-frequency fluctuations around the recombination front region have been observed in the detached plasma conditions. These fluctuations result in radial particle losses across the magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Effects from the Target Plate Geometry on Fluctuations of Helium Plasma in the Linear Divertor Simulator Magnum-PSI

Yoshikawa

Tanaka

Hayashi

et al. 2022

Plasma and Fusion Research

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With the help of the linear divertor simulation device Magnum-PSI, a fluctuation investigation of the impact of the target plate geometry was conducted. We simultaneously quantify coherent low-frequency fluctuations with a newly built 70-GHz microwave reflectometry system, a reciprocating probe, a light emission detector system, and a fast-framing camera system. The strong low-frequency fluctuations were observed at both the electron density and the plasma radiations by moving the target plate along the magnetic field line. Furthermore, a strong peak in fluctuation intensity and the influence of the target plate tilt angle on the fluctuation intensity were noted. c

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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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Multipoint measurements employing a microwave interferometer and a Langmuir probe in the detached linear plasma

Cited by 6 publications

References 18 publications

Cross-field transport in detached helium plasmas in Magnum-PSI

Cross-field transport in detached helium plasmas in Magnum-PSI

Effects from the Target Plate Geometry on Fluctuations of Helium Plasma in the Linear Divertor Simulator Magnum-PSI

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

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