Neoclassical transport in stellarators

Abstract

DISCLAIMERThis report was prepared as an account of work sponsored by an agency of the United Slates Government. Neither the United Stales Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsi bility for the accuracy, completeness, or usefulness or any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Refer ence herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, rccomraeodalioo, or favoring by the United States Gov**nment or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States GwKtnacat or any agency thereof. + s^irs^.^rasr^5^r^L ab --* <* fisrasuTOij OF IBS mratiii is mmm >> 2 . ABSTRACTThe stellarator neoclassical transport due to particles trapped in local helical wells ig calculated in the low-collisionality regime using a systematic expansion. The behavior of electron transport is found to be the game over a wide range of energies, but the behavior of ion transport for low energy ions is found to be different than that for high energy ions.

The effect of tangential drifts on neoclassical transport in stellarators close to omnigeneity

“…The point that needs to be emphasized here is that the expansions (17) and (18) do not work when ν i * ρ i * because F i1 becomes as large as F E i0 and ϕ 1 becomes as large as ϕ 0 (see (20) and (26)). The regime ν i * ρ i * is the subject of this paper, and we start to analyze it in the next subsection.…”

“…The first layer (see subsection 4.1) gives the so-called √ ν regime, found in certain models of stellarator geometry [19,20] where the inverse aspect ratio and the helical ripple are employed as expansion parameters. The second layer (see subsection 4.2) gives the superbanana-plateau regime, derived in [21] for finite aspect ratio tokamaks with broken symmetry.…”

Stellarator and tokamak plasmas: a comparison

“…These have been reviewed in great detail elsewhere [25,26,27,28,29], and it has been established that the neoclassical heat flux is very significant in the plasma core of most experiments. At low collisionality, the electrons are usually in the 1/ν-regime, where the diffusivity is inversely proportional to the collision frequency ν,…”

Parallel impurity dynamics in the TJ-II stellarator

“…This part, often termed Φ 1 in the literature, arises to preserve local charge neutrality and its computation requires to solve kinetic equations for ions and electrons. We refer interested readers to the theory articles on the subject [10,27] as well as to the more recent work on kinetic simulations [11,9] (cite Landreman et al this issue). § More precisely, the inertia force of an incompressible stream line is stellarator anti-symmetric and its parallel derivative at the minimum-B center of symmetry (usually labeled θ = 0, φ = 0) is negative.…”