Presentation Magnetically-guided liquid metal plasma-facing components

嶋田, 道也

In a strong magnetic field, liquid metal is frozen in the magnetic field. This property enables liquid metal to flow along the field line. In a divertor configuration with a lower single-null, a second separatrix exists above the plasma. Toroidally-continuous liquid metal sheets, poured through toroidal slots located above the plasma and radially outside the 2nd separatrix flux surface, move along the field line, absorbing heat and particles, reach the divertor at a glancing angle, and give toroidal momentum to the divertor liquid metal. This makes the divertor liquid metal rotate in the toroidal direction, making the temperature and particle content toroidally uniform. At the current quench in a disruption, toroidal current is induced automatically in the liquid metal surrounding the core plasma. The resultant jxB force pushes the liquid metal toward the core plasma, significantly mitigating the heat load and force on the first wall and the divertor. Use of magnetically-guided liquid metal PFC would also eliminate the need of fine toroidal alignment of the first wall and the divertor. The wall conditioning is done automatically during the discharge. Use of lithium-containing liquid metal (e.g. LiSn) would facilitate tritium breeding. To avoid the complication due to the current induced in the liquid metal, the liquid metal sheets must be poured after the plasma current reaches a flat top and non-inductive current drive makes the one-turn voltage to a very low value. Current drive can be provided by ECW launched from above. Some diagnostics can be also installed on the upper port. Occasional interruption of the liquid metal flow would enable diagnosis from the midplane ports.

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