A. Komori

M. Shoji

National Institute for Fusion Science (NIFS-Repository)

§ 29. Construction of Video On Demand(VOD) Systems for Real TimeMonitoring of a Local Island Divertor(LID) HeadShoji, M., Komori, A.Local Island Divertor (LID) experiments have beenstarted from the sixth experimental campaign. The LIDsystem has a limiter head for controlling neutral particlesand impurities in the plasma periphery. The limiter headmade of carbon plates and molybdenum is inserted into amagnetic island (poloidal mode number m= I) formed in theplasma periphery, which causes the concentration of the heatload from the main plasma at the edge of the limiter head. Areal time monitoring system for observing the limiter headby using Charge Coupled Device (CCD) cameras, therefore,is needed for optimization of the shape and position of thelimiter head in order to effective particle and impuritycontrol without serious mechanical damages.Video On Demand (VOD) server systems (Dell,PowerEdge2400) have been constructed for observation ofthe limiter head, plasma dynamic behavior and plasma-wallinteractions, etc. It can display the images observed withCCD cameras on a large screen in the LHD control room,and we can easily access image data via the Internet byusing Web browser software. Figure I indicates a schematicview of the VOD systems. The images taken with thecameras are combined a single image by a video multiplexer(For-A, MV-40E). The video signals are transferred to thecontrol room via electric/optical video signal converters(Melco Technorex, AL-233). The transferred video imagesare displayed on the large screen and captured in an MPEGencoder board (Canopus, MVR-D2000) installed in apersonal computer (Dell Dimension 8300, OS: WindowsXP). We customized the data acquisition software to startvideo capture by a TTL trigger signal using the softwaredeveloper's kit (SDK) with an I/O board (Interface,PCI-2753). Video capture is automatically stopped byanother TTL signal triggered after the termination of visibleemission from the main plasma detected by a tangentiallyviewing CCD camera (Sony, DXC-LSI) installed in 6-T port,which makes a moving picture compression format(MPEG-I) file after every plasma discharge. The capturedvideo data are temporary saved in the personal computers,then, the data are automatically transferred into a NetworkAttached Storage (NAS) RAID-5 disk (Logitec,LAS-RA500N/H). The video images taken by the otherCCD cameras are also stored in the RAID-5 disk. The VODserver system (http://cdpvodsl.lhd.nifs.ac.jp/) can retrieve arequired video data from the RAID disk via the MicrosoftInternet Information Service (IIS4.0) with Active ServerPages (ASP) technology.Figure 2 shows a snap shot of a video taken in the sixthexperimental campaign, which includes four images: theLID head observed from inner port (6-1) (upper right); amovable gas puff (7.5-D) (upper left); a back side view ofthe LID head (lower left); lower divertor plates observedfrom an outer port (3-0) (lower right). The camera installedin the inner port observed two bright spots at the edge of thelimiter head during the plasma discharge when the limiterhead was inserted into the plasma periphery. It indicates thatthe excessive thermal heat load is concentrated at the edge ofthe limiter head. The divertor plasma image shows nodivertor leg structures (which are clearly observed instandard plasma discharges without LID head), showing thatthe limiter head can almost scrape the peripheral plasmaforming the ergodic layer and the divertor leg structures.Images taken by the CCD cameras and the VOD serversystems show the useful information of the effect of the LIDhead on the plasma periphery. It also indicates the scope ofthe improvement of the shape and position of the LID headto avoid excessive thermal heat load concentration.&lGlJ l:CO e-r. (5onYDXCU')!! LHD Contral Raam! .NlselClient PCs (WIndows, .scintosh, L1nLll()lIIIith web brollllser Iinlernet Explorer. Netsc.pe Nswlllslorla.Wlndollllll Medis PlllJer (WIndows) or Quicklime PlllJer IWlndolllls. Mscintoshl ar MpeglVPllIJjlIr ILlnllll) etc.Fig.l. Schematic view of the VOD systems for archivingthe video image data observed by CCD cameras formonitoring the LID head.Fig.2. A video image including a LID head viewed frominner port (6-1) (upper right); a movable gas puff (7.5-V)(upper left); a back side view of the LID head (lowerleft); lower divertor plates (3-0) (lower right).33

Construction of Video On Demand (VOD) Systems for Real Time Monitoring of a Local Island Divertor (LID) Head

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