Since 18 of December 2019 uses Nucleus credentials. Visit our help pages for information on how to Register and Sign-in using Nucleus.
Oct 13 – 18, 2014
Hotel Park Inn Pribaltiyskaya
Europe/Moscow timezone

Plasmoid Ejection Mechanism in Dynamic Divertor Experiment and Simulation

Oct 16, 2014, 8:30 AM
Green 8-9 (Hotel Park Inn Pribaltiyskaya)

Green 8-9

Hotel Park Inn Pribaltiyskaya

Saint Petersburg, Russian Federation
Poster ICC - Innovative Confinement Concepts Poster 5


Prof. Yasushi Ono (University of Tokyo)


We have been developing a new type of divertor concept: “dynamic divertor” composed of periodic ejection of plasmoid from a core-plasma and its gas-puff cooling, to reduce significantly heat flux to divertor plates. Our TS-4 experiment and PIC simulation consistently solved the plasmoid formation and pinch-off mechanisms essential to the dynamic divertor operation. We found the acceleration dV/dt of plasmoid promotes its pinch-off from the core-plasma through fast reconnection and also that the external inflow flux controlled by the external coil current increases with the plasmoid size. In TS-4, the X-point region between the ST plasma and the divertor plate are formed by induction of two poloidal field (PF) coils. The corresponding plasmoid ejection was observed in 2-1/2D Full PIC simulation (PASMO) with 2×10^10 particles in a domain of (x, y) = (512, 256) Debye length under uniform guide field ~ 4 reconnecting magnetic field. The maximum acceleration rate dV/dt of plasmoid occurs simultaneously with the maximum reconnection electric field E_t, indicating that the acceleration rate of plasmoid is directly connected with the reconnection time - the plasmoid pinch-off time like the coronal mass ejection in the solar flares. The plasmoid ejection from the current sheet reduces significantly its thermal/ magnetic pressures, causing further thinning of the current sheet. When the current sheet is compressed thinner than the ion meandering length (ion gyro-radius), its effective resistivity tends to increase significantly, causing its anomalous dissipation and thus faster reconnection rate, both in TS-4 experiment and the PIC simulation. They agree in the normalized plasmoid ejection time ~5 Alfven time but E_t and dV/dt in the former is 70% and 50% of those in the latter, probably due to low downstream magnetic pressure in the slab model simulation. The PIC simulation also indicates that the heat flux from the core-plasma is transported along the separatrix field line and confined in the plasmoid. The field-aligned velocity component is essential to the plasma transport from the core-plasma to the plasmoid, which indirectly connects them for the gas-puff cooling.
Country or International Organisation University of Tokyo, Japan
Paper Number PD/P5-5

Primary author

Prof. Yasushi Ono (University of Tokyo)


Prof. Chio Zong Cheng (University of Tokyo) Prof. Ritoku Horiuchi (National Institute for Fusion Science) Mr Shizuo Inoue (Univ. Tokyo) Dr Yoshinori Hayashi (University of Tokyo)

Presentation materials

There are no materials yet.