Application of Divertor Pumping to Long-Pulse Discharge for Particle Control in LHD

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...

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Bibliographic Details
Published in:Plasma and Fusion Research 2021/02/08, Vol.16, pp.1202014-1202014
Main Authors: MOTOJIMA, Gen, MASUZAKI, Suguru, MORISAKI, Tomohiro, KOBAYASHI, Masahiro, SAKAMOTO, Ryuichi, TSUCHIBUSHI, Yasuyuki, MURASE, Takanori, TAKEIRI, Yasuhiko, group, the LHD experiment
Format: Article
Language:English
Subjects:
Cyclotrons
density control
Discharge
Divertor pump
Electron cyclotron heating
Electron density
Electrons
Feedback
Hydrogen
LHD
Plasma control
Pumping
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Summary: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.
ISSN:1880-6821
1880-6821
DOI:10.1585/pfr.16.1202014