title: Coaxial pellets for metallic impurity injection on the large helical device.
abstract: Two coaxial pellets with tungsten inserted into graphite carbon and polyethylene (PE) tubes are compared for tungsten spectroscopic study in the Large Helical Device. The tungsten pellet with carbon tube causes plasma collapse, while that with PE tube smoothly ablates without collapse. The deposition profile of the pellets is analyzed with a help of pellet ablation spectroscopy. It is found that the tungsten pellet with carbon tube can significantly penetrate into the core plasma and leads to the plasma collapse. A tungsten spectrum with radial profile is successfully observed when the tungsten pellet with PE tube is used.
authors.affiliation: Department of Fusion Science, Graduate University for Advanced Studies, Toki 509-5292, Gifu, Japan.
authors.forename: X L
authors.initials: XL
authors.lastname: Huang
authors.affiliation: Department of Fusion Science, Graduate University for Advanced Studies, Toki 509-5292, Gifu, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Morita
authors.affiliation: Department of Fusion Science, Graduate University for Advanced Studies, Toki 509-5292, Gifu, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Oishi
authors.affiliation: Department of Fusion Science, Graduate University for Advanced Studies, Toki 509-5292, Gifu, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Goto
authors.affiliation: Department of Fusion Science, Graduate University for Advanced Studies, Toki 509-5292, Gifu, Japan.
authors.forename: H M
authors.initials: HM
authors.lastname: Zhang