N." "Nishino

National Institute for Fusion Science (NIFS-Repository)

Supersonic molecular beam injection (SMBI) is oneof local gas fueling method, and it was quite successful inseveral machines. In this experimental campaign peripheralturbulence behavior due to 5MBI was investigated using afast camera, Langmuir probe and magnetic probes.Experimental setup is shown in Fig. 1. Two 5MBI wereinstalled at the toroidal opposite position (#3.5, #11.5) and aset of movable Langmuir/magnetic probes was installed inone 5MBI port (#3.5) to investigate peripheral turbulence.Figure 2 shows typical waveform of 5MBI (#3.5) shot andFigure 3 shows the power spectra of magnetic probe data.Before 5MBI low frequency turbulence of below 10kHzwas observed near 5MBI position, and after 5MBI thatturbulence of the same frequency range was suppressed. Inthe 5MBI (#11.5) shot the magnetic probe data was similar(not shown in the figure). Therefore, low frequencyturbulence was completely suppressed toroidally du,e to5MBI. Moreover moving the magnetic probe position shotby shot it was found near plasma surface (LCFS) that therewas the power spectra peak at 7 kHz, and this peak rapidlydecreased with the distance from LCFS. On the other handfast camera measurement always showed the fine structureturbulence was appeared after 5MBI. If peripheralturbulence is magnetic fluctuation, those data would becoincident, and it suggested that turbulence of the lowfrequency range was suppressed due to 5MBI.Therefore, using 5MBI better energy confinementplasma would be handled, and it is very important to resolvethe physics of 5MBI effect. At the next experimentalcampaign it should be resolved.Fig.3 Power spectra of movable magneticprobe signalFig.l Top view of Heliotron J and the locations of the fast camerasSA5 used the tangential port, and K-5 used the horizontal and vertical ports. lViAXused the horizontal port.495§17. A Study of Peripheral Plasma in Heliotron J by Fast CamerasNishino, N. (Graduate School of Engineering, Hiroshima Univ.)

A Study of Peripheral Plasma in Heliotron J by Fast Cameras

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