Distinct turbulence sources and confinement features in the spherical tokamak plasma regime
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- Univ. of California, San Diego, CA (United States). La Jolla, CA
New turbulence contributions to plasma transport and confinement in the spherical tokamak (ST) regime are identified through nonlinear gyrokinetic simulations. The drift wave Kelvin-Helmholtz (KH) mode characterized by intrinsic mode asymmetry is shown to drive significant ion thermal transport in strongly rotating national spherical torus experiment (NSTX) L-modes. The long wavelength, quasi-coherent dissipative trapped electron mode (TEM) is destabilized in NSTX H-modes despite the presence of strong E x B shear, providing a robust turbulence source dominant over collisionless TEM. Dissipative trapped electron mode (DTEM)-driven transport in the NSTX parametric regime is shown to increase with electron collision frequency, offering one possible source for the confinement scaling observed in experiments. There exists a turbulence-free regime in the collision-induced collisionless trapped electron mode to DTEM transition for ST plasmas. In conclusion, this predicts a natural access to a minimum transport state in the low collisionality regime that future advanced STs may cover.
- Research Organization:
- Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Fusion Energy Sciences (FES)
- Grant/Contract Number:
- AC02-09CH11466; Contract No. DE-AC02-09CH11466
- OSTI ID:
- 1256375
- Alternate ID(s):
- OSTI ID: 1238950
- Report Number(s):
- PPPL-5203
- Journal Information:
- Nuclear Fusion, Vol. 55, Issue 12; ISSN 0029-5515
- Publisher:
- IOP ScienceCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Development and testing of an unstructured mesh method for whole plasma gyrokinetic simulations in realistic tokamak geometry
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journal | December 2019 |
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