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Matsuoka, Seikichi*; Sugama, Hideo*; Idomura, Yasuhiro
Physics of Plasmas, 28(6), p.064501_1 - 064501_5, 2021/06
Times Cited Count：4 Percentile：41.65(Physics, Fluids & Plasmas)The improved model collision operator proposed by Sugama et al., which can recover the friction-flow relation of the linearized Landau collision operator, is newly implemented in a global full- f gyrokinetic simulation code, GT5D, and collisional transport simulations of a single ion species plasma in a tokamak are performed over the wide collisionality regime. The improved operator is verified to reproduce the theoretical collisional thermal diffusivity precisely in the high collisionality regime, where the friction-flow relation of higher accuracy is required than in the lower collisional regime. In addition, it is found in all collisionality regimes that the higher accuracy of the collisional thermal diffusivity and the parallel flow coefficient is obtained by the improved operator, demonstrating that collisional processes described by the linearized Landau collision operator is correctly retained.
Takizuka, Tomonori; Hojo, Hitoshi*; Hatori, Tadatsugu*
Purazuma, Kaku Yugo Gakkai-Shi, 78(9), p.857 - 912, 2002/09
Transport along field lines in magnetic confinement plasmas is reviewed. Collisionless and collisional-diffusive transports are discussed. Because of their fast transport, features of plasmas along field lines are apt to behave nonlocally. A nonlocal phenomenon of scrape-off layer (SOL) and divertor plasmas in a tokamak is introduced, whose asymmetry along field lines is induced by the thermoelectric instability related to the SOL current. A local phenomenon called MARFE can be brought by the strong radiation cooling. The "snake" with nonlocal feature along field lines but with local structure perpendicular to the field is observed in a tokamak core plasma. For mirror-confined plasmas, axial particle losses from the mirror ends, especially pitch-angle-sattering losses into the loss cone and nondiabatic losses due to the breakdown of adiabaticity of the magnetic moment, are also discussed in the relation to nonlocal axial transport.
Obrejan, K.; Idomura, Yasuhiro; Honda, Mitsuru*
no journal, ,
The use of tungsten to coat divertors or other plasma facing components inevitably leads to the pollution of the fusion plasma by high-Z tungsten impurities. Several tokamaks have reported accumulation and exhaust of tungsten depending on a heating condition. This kind of collisional and turbulent transport of high-Z impurities is not yet fully understood. To treat high-Z impurities, the gyrokinetic full-f Eulerian code GT5D was extended with an implicit collision solver based on a multi-species linear Fokker-Plank collision operator. A collisional transport benchmark of tungsten was conducted to verify the accuracy of GT5D.
Obrejan, K.; Idomura, Yasuhiro; Honda, Mitsuru*
no journal, ,
To analyze heavy impurity transport, the gyrokinetic full-f Eulerian code GT5D was extended with an implicit collision solver based on a multi-species linear Fokker-Plank collision operator. In the collision solver, a Krylov subspace method is applied to a collision operator, which is given as a convection diffusion operator in velocity space, and severe CFL conditions of heavy impurities are resolved. In addition, flux coordinates are newly applied to resolve magnetic field structures with less grids, and collisional transport simulations are dramatically accelerated. A collisional transport benchmark of tungsten was conducted to verify the accuracy of GT5D.
