Plasma and Fusion Research

Volume 16, 1202014 (2021)

Rapid Communications

Application of Divertor Pumping to Long-Pulse Discharge for Particle Control in LHD
Gen MOTOJIMA1,2), Suguru MASUZAKI1,2), Tomohiro MORISAKI1,2), Masahiro KOBAYASHI1,2), Ryuichi SAKAMOTO1,2), Yasuyuki TSUCHIBUSHI1), Takanori MURASE1), Yasuhiko TAKEIRI1,2) and the LHD experiment group1)
1)
National Institute for Fusion Science, National Institutes of Natural Sciences, 322-6 Oroshi-cho, Toki, Gifu 509-5292, Japan
2)
SOKENDAI (The Graduate University for Advanced Studies), 322-6 Oroshi-cho, Toki, Gifu 509-5292, Japan
(Received 18 December 2020 / Accepted 5 January 2021 / Published 8 February 2021)

Abstract

Divertor pumping was applied to plasma discharges for superior fuel particle control in the Large Helical Device (LHD). The LHD is equipped with two different pumping systems. One is the main pumping system, in which the pumping speed is 260 m3/s in hydrogen. The other pumping system is the divertor pumping system in which the pumping speed is 70 m3/s in hydrogen. Divertor pumping was applied to 40-second long pulse Electron Cyclotron Heating (ECH) discharges to assess the improvement in particle control provided by divertor pumping. The results show that without divertor pumping, the electron density was not controlled by gas puffing using the feedback signal of line-averaged electron density. Then, the plasma confinement deteriorated, finally leading to radiation collapse. On the other hand, with divertor pumping, the density was well-controlled by gas puffing using the feedback signal. The results indicate that divertor pumping is one of the key tools for controlling the particles in fusion plasmas.

Keywords

LHD, Divertor pump, density control

DOI: 10.1585/pfr.16.1202014

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