Safety factor and turbulence dynamics dependence of the L-H power threshold on DIII-D

Yan, Z.; Mckee, G. R.; Gohil, P.; Schmitz, L.; Holland, C.; Haskey, S. R.; Grierson, B. A.; Ke, R.; Rhodes, T.; Petty, C.

doi:10.1063/1.5091701

Title: Safety factor and turbulence dynamics dependence of the L-H power threshold on DIII-D

Journal Article · Mon Jun 17 00:00:00 EDT 2019 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.5091701· OSTI ID:1561976

Yan, Z. ^[1]; Mckee, G. R. ^[1];

^[2]; Schmitz, L. ^[3]; Holland, C. ^[4];

^[5];

^[6]; Rhodes, T. ^[3]; Petty, C. ^[2]

Univ. of Wisconsin-Madison, Madison, WI (United States)
General Atomics, San Diego, CA (United States)
Univ. of California, Los Angeles, CA (United States)
Univ. of California, San Diego, CA (United States)
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Southwestern Inst.of Physics, Chengdu (China)

The L-H transition power threshold (PLH) is discovered to have a vital dependence on q₉₅, at n_e ~ 3.2 × 10¹⁹ m^-3 on DIII-D. Comprehensive 2D turbulence and flow measurements in the plasma edge reveal the co-existence of two frequency bands of broadband modes across the L-H transition with higher flow shear at higher q₉₅, which can help explain the linear decrease in PLH as q₉₅ is increased from 3.5 to 4.9. Density fluctuation measurements by beam emission spectroscopy at higher q₉₅ show that the lower frequency band (<20 kHz) of the broadband modes propagates in the ion diamagnetic direction in the lab frame (identified as an ion mode), whereas the higher frequency band (>20 kHz) propagates in the electron diamagnetic direction (identified as an electron mode). The turbulence amplitude at the plasma edge is higher at higher q₉₅, implying a higher drive for a Reynolds stress driven zonal flow. At lower density, n_e ~ 1.5 × 10¹⁹ m^-3, there is little dependence of PLH on q95. Linear CGYRO kinetic simulation has shown a switch from one mode to two modes at higher q₉₅ at n_e ~ 3.2 × 10¹⁹ m^-3 compared to lower q₉₅. The ion temperature profile has been shown to strongly impact the dual mode characteristics with the increasing growth rate of the ion mode at a higher edge Ti gradient. The observations imply that it may be possible to reduce the required input power to trigger the L-H transition for ITER if both the ion and electron modes are similarly driven in the plasma edge.

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

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

Grant/Contract Number:: AC02-09CH11466; FC02-04ER54698; FG02- 08ER54984; FG02-08ER54999; FG02-89ER53296; SC0018287

OSTI ID:: 1561976

Alternate ID(s):: OSTI ID: 1526657

Journal Information:: Physics of Plasmas, Vol. 26, Issue 6; Conference: 60. Annual Meeting of the APS Division of Plasma Physics., Portland, OR (United States), 5-9 Nov 2018; ISSN 1070-664X

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 3 works

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References (24)

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