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[PAST EVENT] Physics Colloquium
Abstract:
Plasma is a state of matter composed of mobile charged particles, electrons and ions, globally keeping electrical charge neutrality. The state of plasma prevails in universe; sun, fixed stars, their surroundings, and interstellar space. The sun is a high-temperature plasma sustained by nuclear fusion reaction as an energy source. It is emitting a broad range of radiation and also energetic charged particles called a solar wind, which produces auroras in the polar regions of the earth. In addition to natural plasmas including lightening, man-made plasmas have been widely used for lighting, welding, and micro processing. The most intensive plasma research, however, has been made for the quest of a nuclear fusion reactor as a sustainable energy source. Nuclear fusion is a nuclear reaction in which light atomic nuclei are combined to form a heavier nucleus and a lighter nucleus or a neutron. Though the reaction requires a collision of nuclei with large relative kinetic energy, it produces much more energy due to the difference of total mass, in other words, binding energy. The most easily accessible fusion reaction on the earth is considered to be that of a dueteron (D) and a triton (T) which are the nuclei of the isotopes of hydrogen, dueterium and tritium. This reaction generates a 3.5 MeV helium nuclei, alpha particle, and a 14.1 MeV neutron. DT fusion reactor requires a high-temperature fuel plasma, above 10 keV, and good confinement of plasma in order to sustain the fusion reaction. The confinement performance is usually evaluated by the product of fuel ion density and energy confinement time. For realizing good confinement of charged particles, various kinds of magnetic confinement devices have been developed. The best confinement results have been obtained in tokamak devices which contain axi-symmetric doughnut-shaped plasmas. In order to analyze various physics phenomena in tokamak plasmas and predict the performance of future fusion reactors, reliable computational tool which self-consistently describes whole plasma over whole discharge is required. Integrated modeling of fusion plasmas is in progress for this purpose including the analyses of dynamical equilibrium, global stability, transport, heating, fueling, and so on. We are developing an integrated tokamak modeling code TASK with advanced features, and have applied for the analysis of various tokamaks. Some results of kinetic transport modeling and kinetic full wave analyses will be presented.