Distinct turbulence sources and confinement features in the spherical tokamak plasma regime

Wang, W. X.; Ethier, S.; Ren, Y.; Kaye, S.; Chen, J.; Startsev, E.; Lu, Z.

doi:10.1088/0029-5515/55/12/122001

Distinct turbulence sources and confinement features in the spherical tokamak plasma regime

Journal Article · Fri Oct 30 00:00:00 UTC 2015 · Nuclear Fusion

DOI:https://doi.org/10.1088/0029-5515/55/12/122001· OSTI ID:1256375

Wang, W. X. ^[1]; Ethier, S. ^[1]; ^[1]; Kaye, S. ^[1]; Chen, J. ^[1]; Startsev, E. ^[1]; Lu, Z. ^[2]

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.

View Accepted Manuscript (DOE)

Research Organization:: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Fusion Energy Sciences (FES); USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)

Grant/Contract Number:: AC02-09CH11466

OSTI ID:: 1256375

Alternate ID(s):: OSTI ID: 1238950

Report Number(s):: PPPL--5203

Journal Information:: Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 12 Vol. 55; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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