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Research Activities

High-Density Plasma Physics Research Division

Toward the early realization of fusion energy, the High-Density Plasma Physics Research Division promotes research aiming at a comprehensive and exact understanding, and at the performance improvement of plasmas with an emphasis on “high density.” In conjunction with physics, the division is charged in engineering development and operation of experimental facilities and devices, such as magnetic fields, wall conditioning, pumping, and fueling, for physics research.

The High-Density Plasma Physics Research Division promotes synergistic development of physics and engineering, software, and hardware. It conducts research related to confinement and stability physics of high-density high-pressure plasmas, heat and particle control, edge plasma physics, impurity transport, and discharge control to enable high performance steady state plasmas. In particular, the division dedicates intensive effort to the closed divertor, which opens a new stage of the LHD experiments. The closed divertor, which is installed in the plasma vacuum vessel, pumps impurities and fuel particles from the plasma edge very efficiently. While neutralized gas from the plasma returns to the hot plasma in the open divertor, neutralized gas can be compressed and maintained in a local area by means of the closed divertor. Efficient pumping of this compressed gas by a cryopump installed in the closed divertor enables significant improvement of the plasma performance.

Closed Divertor Construction

The closed helical divertor in the LHD consists of ten discrete modules. Baffles to close the divertor region are being installed. In the 16th experimental campaign, eight of ten modules will be completed and one cryopump will be installed. The photo below shows one of the closed helical divertor modules installed on the inboard side of the torus.