Spatiotemporal Structure of Hα Emission from the Detached Plasma in GAMMA 10/PDX

Tanaka, Hirohiko; Sakamoto, M.; Ezumi, N.; Terakado, A.; Nojiri, Kunpei; Mikami, Tomohiro; Kinoshita, Yoshinori; Kobayashi, K.; Yoshikawa, Masayuki; Kohagura, J.; Ohno, Noriyasu

doi:10.1585/pfr.14.2402036

Cited by 3 publications

(9 citation statements)

References 10 publications

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“…Such a shoulder, which is often observed in the blob study [25], appears when spikes with a characteristic duration do not occur periodically in a fluctuation [26]. This feature is consistent with the previous study in GAMMA10/PDX [14],…”

Section: Ion Saturation Current Signal Inside the D-modulesupporting

confidence: 91%

“…1(a). The discharge conditions are similar to those in the previous study [14]. A massive H2 puffing into the D-module in a 400 ms long-pulse H2 discharge resulted in a transition from attached to detached state on the target.…”

Section: Experimental Setup and Discharge Conditionsupporting

confidence: 77%

“…In the previous study in a similar operational discharge [14], positive and negative skewness were clearly observed around probes #5 and probe #3, respectively. Particularly, amplitudes of absolute values of the skewness were reported to become larger in the transient state.…”

Section: Ion Saturation Current Signal Inside the D-modulementioning

confidence: 59%

“…In the tandem mirror device GAMMA 10/PDX, high-density and low-density isolated structures, which were detected as positive and negative spikes intermittently appearing in the ion saturation current fluctuations, were captured by Langmuir probes located near the outer edge of the V-shaped target inside the "divertor simulation experimental module (D-module)" [14]. Further, these structures were observed to be evident during the transient state from the attached to the detached states.…”

Section: Introductionmentioning

confidence: 99%

“…It is also unclear whether these intermittent structures originated inside the D-module or upstream. In addition, although the high-speed camera measurement was performed to obtain the two-dimensional behavior for the same discharge, 3 the set frame rate (20 kfps) was not sufficient to detect these structures [16].…”

Section: Introductionmentioning

confidence: 99%

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Study of the intermittent plasma structure around the divertor simulation experimental module in GAMMA 10/PDX

et al. 2023

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We have investigated the generation region of intermittent plasma structures, which could be due to the blob-like cross field transport around the divertor simulation experimental module (D-module) in the tandem mirror device GAMMA 10/PDX. A positive skewness of the ion saturation current was clearly seen when the electrode of the movable probe was located at the radial edge and just in front of the entrance limiter of the D-module. Fourier analysis and conditional averaging clarified that positive spikes intermittently appeared in the same region. This is the first indication that the phenomenon producing the high-density isolated plasma structures occurred in the upstream of the D-module. A negative skewness was also found, and large amplitude fluctuation was detected between regions showing positive and negative skewness. Furthermore, this and light emission fluctuations become stronger during the transient state from attached to detached state on the V-shaped target.

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Section: Ion Saturation Current Signal Inside the D-modulesupporting

confidence: 91%

Section: Experimental Setup and Discharge Conditionsupporting

confidence: 77%

Section: Ion Saturation Current Signal Inside the D-modulementioning

confidence: 59%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Study of the intermittent plasma structure around the divertor simulation experimental module in GAMMA 10/PDX

et al. 2023

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Four-dimensional conditional averaging tomography of rotating plasma ejection from cylindrical detached plasma

Tanaka,

Kajita,

Natsume

et al. 2024

Sci Rep

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Detached plasma formation is a way to reduce the heat load on the wall in magnetic fusion devices. This study proposes a novel analysis technique consisting of the conditional averaging, sliding window, and tomography to reveal the spatiotemporal behavior of the rotating radial ejection event of detached plasma, which further contributes to local heat load reduction. The used equipment is a high-speed camera and an electrostatic probe located at the periphery of the linear plasma device NAGDIS-II. By applying this method, four-dimensional (4D) behavior of the emission structure along time (1D) and space perpendicular and parallel to the magnetic field (3D) was clarified; a rotating distorted structure appears as a precursor, which is then scraped and transported radially and axially. The proposed method is widely applicable to short-term rigid-body rotating structures, especially in linear plasmas.

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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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Spatiotemporal Structure of Hα Emission from the Detached Plasma in GAMMA 10/PDX

Cited by 3 publications

References 10 publications

Study of the intermittent plasma structure around the divertor simulation experimental module in GAMMA 10/PDX

Study of the intermittent plasma structure around the divertor simulation experimental module in GAMMA 10/PDX

Four-dimensional conditional averaging tomography of rotating plasma ejection from cylindrical detached plasma

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

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