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Bootstrap current and parallel ion velocity in imperfectly optimized stellarators

Journal Article · · Journal of Plasma Physics
 [1];  [2]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); OSTI
  2. Max-Planck-Institut für Plasmaphysik (Germany)
Here, a novel derivation of the parallel ion velocity, and the bootstrap and Pfirsch–Schlüter currents in an imperfectly optimized (that is, almost omnigenous) stellarator magnetic field, B, is presented that somewhat more generally recovers expressions completely consistent with previous analytic results. However, it is also shown that, when the conventional radially local form of the drift kinetic equation is employed, the flow velocity and the bootstrap current acquire a spurious contribution proportional to ω/$$\textit{ν}$$, where ω denotes the E×B rotation frequency (due to the radial electric field E ) and $$\textit{ν}$$ the collision frequency. This contribution is particularly large in the $$\sqrt{v}$$ regime and at smaller collisionalities, where ω/ν≳1 , and is presumably present in most numerical calculations, but it disappears if a more accurate drift kinetic equation is used.
Research Organization:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
Sponsoring Organization:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
Grant/Contract Number:
FG02-91ER54109
OSTI ID:
1897052
Journal Information:
Journal of Plasma Physics, Journal Name: Journal of Plasma Physics Journal Issue: 1 Vol. 86; ISSN 0022-3778
Publisher:
Cambridge University PressCopyright Statement
Country of Publication:
United States
Language:
English

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