Jungpyo Lee

Intrinsic Rotation Driven by Non-Maxwellian Equilibria in Tokamak Plasmas

The effect of small deviations from a Maxwellian equilibrium on turbulent momentum transport in tokamak plasmas is considered. These non-Maxwellian features, arising from diamagnetic effects, introduce a strong dependence of the radial flux of cocurrent toroidal angular momentum on collisionality: As the plasma goes from nearly collisionless to weakly collisional, the flux reverses direction from radially inward to outward. This indicates a collisionality-dependent transition from peaked to hollow rotation profiles, consistent with experimental observations of intrinsic rotation.

Turbulent momentum pinch of diamagnetic flows in a tokamak

The ion toroidal rotation in a tokamak consists of an

Effects of LHRF on toroidal rotation in Alcator C-Mod plasmas

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Perpendicular momentum injection by lower hybrid wave in a tokamak

flow due to the radial electric field and a diamagnetic flow due to the radial pressure gradient. The turbulent pinch of toroidal angular momentum due to the Coriolis force studied in previous work is only applicable to the

Production of internal transport barriers via self-generated mean flows in Alcator C-Mod

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Selective Nanopatterning of Protein via Ion-Induced Focusing and its Application to Metal-Enhanced Fluorescence

flow. In this Letter, the momentum pinch for the rotation generated by the radial pressure gradient is calculated and is compared with the Coriolis pinch. This distinction is important for subsonic flows or the flow in the pedestal where the two types of flows are similar in size and opposite in direction. In the edge, the different pinches due to the opposite rotations can result in intrinsic momentum transport that gives significant rotation peaking.

The effect of diamagnetic flows on turbulent driven ion toroidal rotationa)

Application of lower hybrid range of frequencies (LHRF) waves can induce both co- and counter-current directed changes in toroidal rotation in Alcator C-Mod plasmas, depending on the target plasma current, electron density, confinement regime and magnetic shear. For ohmic L-mode discharges with good core LH wave absorption, and significant current drive at a fixed LH power near 0.8 MW, the interior (r/a q95/11.5, and in the co-current direction if ne(1020 m−3) 1, indicating a good correlation with driven current fraction, unifying the results observed on various tokamaks. For high density (ne ≥ 1.2 × 1020 m−3) L-mode target discharges, where core LH wave absorption is low, the rotation change is in the co-current direction, but evolves on a shorter momentum transport time scale, and is seen across the entire spatial profile. For H-mode target plasmas, both co- and counter-current direction increments have been observed with LHRF. The H-mode co-rotation is correlated with the pedestal temperature gradient, which itself is enhanced by the LH waves absorbed in the plasma periphery. The H-mode counter-rotation increment, a flattening of the peaked velocity profile in the core, is consistent with a reduction in the momentum pinch correlated with a steepening of the core density profile. Most of these rotation changes must be due to indirect transport effects of LH waves on various parameters, which modify the momentum flux.

Turbulent momentum transport due to neoclassical flows

The injection of lower hybrid (LH) waves for current drive into a tokamak affects the profile of intrinsic rotation. In this paper, the momentum deposition by the LH wave on the electrons is studied. Due to the increase in the poloidal momentum of the wave as it propagates into the tokamak, the parallel momentum of the wave increases considerably. The change in the perpendicular momentum of the wave is such that the toroidal angular momentum of the wave is conserved. If the perpendicular momentum transfer via electron Landau damping is ignored, the transfer of the toroidal angular momentum to the plasma will be larger than the injected toroidal angular momentum. A proper quasilinear treatment proves that both perpendicular and parallel momentum are transferred to the electrons. The toroidal angular momentum of the electrons is then transferred to the ions via different mechanisms for the parallel and perpendicular momentum. The perpendicular momentum is transferred to ions through an outward radial electron pinch, while the parallel momentum is transferred through collisions.

Challenges in Self-Consistent Full-Wave Simulations of Lower Hybrid Waves

New results suggest that changes observed in the intrinsic toroidal rotation influence the internal transport barrier (ITB) formation in the Alcator C-Mod tokamak [E. S. Marmar and Alcator C-Mod group, Fusion Sci. Technol. 51, 261 (2007)]. These arise when the resonance for ion cyclotron range of frequencies (ICRF) minority heating is positioned off-axis at or outside of the plasma half-radius. These ITBs form in a reactor relevant regime, without particle or momentum injection, with Ti ≈ Te, and with monotonic q profiles (qmin 1.5 × 105 rad/s) in the regi...

Quasilinear diffusion coefficients in a finite Larmor radius expansion for ion cyclotron heated plasmas

Selective immobilization onto the designated sites is particularly important as well as maintaining high spatial resolution down to the nanoscale to prevent unwanted nonspecifi c protein interactions. [ 6 , 7 ] Most previous attempts to form protein nanoarrays were done based on dip-pen nanolithography, which has been demonstrated as able to ensure nanoscale resolution with high selectivity. [ 8–13 ] However, dip-pen lithography is inherently a serial process, even though a parallel approach was recently reported. [ 12 ] Previously developed parallel methods for patterning proteins include microcontact printing, [ 14 , 15 ] ink jet printing, [ 16 , 17 ] optical printing, [ 18 ]