Speaker
Description
Neoclassical ambipolar radial electric field Er could suppress the microturbulence to improve confinement in stellarators. It can also affect energetic particle transport and be modified by energetic particle neoclassical loss, which induces a radial current that changes the Er in the stellarators. The intrinsic 3D magnetic field in the stellarators provides a unique possibility of manipulating the Er by deliberately injecting the fast ions in the loss regions of the phase space. The goal is to maximize the effects of Er by losing a small amount of low energy fast ions in order to minimize thermal plasmas turbulent transport and alpha particle loss in a stellarator fusion reactor. Detailed study of phase space dependence of the fast ion loss may also help removal of helium ash after alpha particles deposit most of their birth energy to thermal plasmas but are still much more energetic (~100s keV) than thermal plasmas. Preliminary study on the LHD has shown that perpendicular beam injection modifies the Er and leads to significant density peaking as compared to the parallel beam injection.
In this work, global gyrokinetic code GTC has been applied to study neoclassical ambipolar electric field Er and its effects on plasma confinement in the stellarators. We will report recent progress on global GTC simulations of interactions between Er and fast ions loss, comprehensive studies of phase space structures of the fast ions loss in the LHD and W7-X, and self-consistent simulations of the Er and its suppression of microturbulence in the W7-X. GTC simulations of Alfven eigenmodes excited by fast ions in the W7-X and LHD will also be presented.
Work supported by US DOE SciDAC and INCITE.
| Presentation type | Oral |
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