Cross-field transport in detached helium plasmas in Magnum-PSI. (8th October 2020)

• Record Type: Journal Article
• Authors: Tanaka, H; Hayashi, Y; Kajita, S; van der Meiden, H J; Yoshikawa, M; Vernimmen, J W M; Scholten, J; Classen, I; Morgan, T W; Ohno, N
• Is Part Of: Plasma physics and controlled fusion. Volume 62:Number 11(2020)
• Publication Date: 2020-10-08
• Subjects: cross-field transport -- plasma detachment -- Langmuir probe -- fast framing camera -- Magnum-PSI -- recombination front; Plasma (Ionized gases) -- Periodicals; Controlled fusion -- Periodicals; 530.44
• DOI: 10.1088/1361-6587/abb88f
• Languages: English
• ISSNs: 0741-3335

Abstract

Abstract: 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.