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22-27 October 2018
Mahatma Mandir Conference Centre
Asia/Kolkata timezone

New approach to the control of particle recycling using divertor pumping in LHD

24 Oct 2018, 08:30
Mahatma Mandir Conference Centre

Mahatma Mandir Conference Centre

Gandhinagar (nearest Airport: Ahmedabad), India
Poster P3 Posters


Dr Gen Motojima (National Institute for Fusion Science)


Superior control of particle recycling and of plasma density has been established in the Large Helical Device (LHD) using greatly enhanced active pumping of the closed helical divertor (CHD). In-vessel cryo-sorption pumping systems inside the CHD in five out of ten inner toroidal divertor sections have been developed and installed step by step in LHD. The total effective pumping speed obtained was 67±5 m3/s in hydrogen, which is approximately seven times larger than previously obtained. As a result, a low recycling state was observed with the CHD pumping for the first time under the helical divertor configuration in LHD featuring excellent density control even under intense pellet fueling conditions. A global particle confinement time is used for comparison of operation with and without the CHD pumping. The global particle confinement time was evaluated from the density decay after the fueling of hydrogen pellet injection or gas puffing in NBI plasmas. A short global particle confinement time after the fueling was obtained during the CHD pumping, demonstrating the control of the particle balance with active pumping in CHD for the first time in LHD.
Country or International Organization Japan
Paper Number EX/P3-27

Primary author

Dr Gen Motojima (National Institute for Fusion Science)


Dr Hirohiko Tanaka (Nagoya University) Prof. Hiroshi Yamada (National Institute for Fusion Science) Dr Mamoru Shoji (National Institute for Fusion Science) Dr Masahiro Kobayashi (NIFS) Dr Masayuki TOKITANI (National Institute for Fusion Science) Dr Oliver Schmitz (University of Wisconsin - Madison, Department of Engineering Physics) Prof. Ryuichi Sakamoto (National Institute for Fusion Science) Prof. Suguru Masuzaki (National Institute for Fusion Science) Mr Takanori Murase (National Institute for Fusion Science) Dr Tomohiro Morisaki (National Institute for Fusion Science) Yasuhiko Takeiri (National Institute for Fusion Science) Mr Yasuyuki Tsuchibushi (National Institute for Fusion Science)

Presentation Materials