Abstract Details
Abstracts
Author: Jungpyo Lee
Requested Type: Poster
Submitted: 2025-03-14 12:24:07
Co-authors: Felix I. Parra, Yunho Jeong, Hyojong Lee
Contact Info:
Hanyang University
222 Wangsimni-ro, Seongdong-gu
Seoul, Seoul 04763
South Korea
Abstract Text:
Since the transport time scale in a modern tokamak is longer than both the collision time and the microscale turbulence eddy turnover time, the distribution functions are very close to a Maxwellian. To determine the density, average velocity, and temperature in the Maxwellian, the poloidally and temporally averaged neoclassical and turbulent fluxes are balanced with several particle, momentum, and energy sources. In this poster, we will present two examples where this time scale separation breaks down. First, it is found that the high-Z impurities in the pedestal can experience 2D (radial and poloidal) transport on a similar time scale as both the parallel dynamics and the radial flux due to the steep density and temperature gradient and high friction. The kinetic equation representing the impurity compressible flow is derived, and it results in impurity density evolution that is simultaneously affected by radial and poloidal motion at first order. As a second example, we show that the radial and poloidal localization of heating source can lead to the breakdown of the conventional ordering. The quasilinear velocity diffusion coefficient, which describes RF wave energy and momentum deposition, can be included in the first-order drift kinetic equation when the source intensity is sufficiently large (>1MW/m3) due to radial and poloidal localization. The wave-particle interactions can directly modify the neoclassical bootstrap currents. We have found that ion cyclotron heating likely reduces the existing bootstrap current by interfering with pitch-angle scattering of the trapped particles. However, under certain conditions of radial temperature gradient and wave parallel refractive index, the wave can enhance the larger bootstrap current, offering a promising potential for the synergy between RF-driven current and bootstrap current.
Characterization: 1.0
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