Time: Wednesday, Dec. 11, 2:00 pm
Venue: Rm. 413, Bld. 11#, Yuquan Campus
Speaker 1: Guodong Yu
Title: Particle Confinement in Stellarators
Abstract:
There are two kinds of trapped particles in stellarators, the toroidal trapped particles and the helical trapped particles. Due to lack of toroidal symmetry, the trapped particles’ first orbit loss in stellarator is the first problem for us to deal with. Helically trapped particles' confinement for low collisionality is in 1/nu regime. In order to reduce the neoclassical transport in low-collision regime, the concept of quasi-symmetry is introduced to improve trapped particle confinement. Axisymmetry and helical-symmetry are included in Omnigenous which is the most general condition for symmetry. The goal of our work is to design a moderate size stellarator with simple coils and good neoclassical confinement. Towards this goal we have developed a code suite for calculating vacuum flux surfaces directly from 3D magnetic coils, evaluating single particle confinement as well as calculating neoclassical transport. In contract with the traditional method of optimizing from plasma boundary shape, our code suite has been used to design simple stellarators by direct optimization from coils. Finally, We found a new configuration which has a much lower 1/nu neoclassical transport than that of CNT(Columbia Non-neutral Torus).
Speaker 2: Yu Zhang
Title: SOME HIGH ENERGY DISCHARGE PHENONMENON IN LIGHTNING AND ITS SIMULATION METHOD
Abstract:
We’ll introduce some remarkable high energy discharge phenomenon in lightning, and its simulation method – analytic high energy Monte Carlo Collision method. The dispersion characteristics in plasma with THz collision frequency (typical collision frequency of atmospheric plasma) would also be discussed.