1. 연사: 채길병 박사 (Nuclear Data Center, Korea Atomic Energy Research Institute)
2. 일시: 2018. 9. 19(수), 오후 2시
3. 장소: 공학3동 201호 (세미나실)
4. 제목: Laboratory experiments to study physics of dusty plasmas and magnetized plasma flows
An RF discharge with liquid nitrogen cooled electrodes and injected water vapor has been used to study nucleation, growth, and dynamics of water-ice dust particles formed in a plasma environment. Examples of water-ice dusty plasma include polar mesospheric clouds, Saturn’s diffusive rings, and protoplanetary disks. We found that nonspherical dust particles are typically formed in a plasma having external parameters similar to actual space plasmas (low pressure and light background gas) and have fractal nature with the fractal dimension of 1.7. Nonspherical particles align in the direction perpendicular to the dust cloud edge line and rotate about their alignment axis owing to the interaction between the dipole moment and the surrounding electric field. In addition, axisymmetric dust vortex motion which results from the non-conservative ion drag force is observed.
The MHD-driven jet experiment at Caltech produces plasma jets having low plasma beta and large Lundquist number similar to astrophysical jets, solar corona loops, and tokamaks. We have studied various phenomena associated with magnetic reconnection induced by a kink-driven Rayleigh-Taylor instability occurring in the experiment. It is found that a spatially localized, transient EUV burst appears at the presumed position of magnetic reconnection and is associated with electron heating. Circularly polarized whistler waves are simultaneously observed indicating that Hall dynamics likely governs the reconnection process. Spectroscopic measurement shows fast ion heating when there is magnetic reconnection. We propose that the electron heating is consistent with Ohmic dissipation while the ion heating is consistent with ion trajectories becoming stochastic.
Recently, a new experiment has been developed using a magnetoplasmadynamic thruster similar to the MHD-driven jet to simulate heat and particle fluxes in the fusion divertor region; this facility will be used to address future divertor design issues. In addition, several divertor plasma diagnostics such as Langmuir probe array, EUV camera, and optical emission spectroscopy have been developed for both laboratory experiment and KSTAR and will be used to study plasma dynamics and kinetics in the divertor region.