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

Abstract

The L-H transition power threshold (PLH) is discovered to have a vital dependence on q 95, at n e ~ 3.2 × 10 19 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 q 95, which can help explain the linear decrease in PLH as q 95 is increased from 3.5 to 4.9. Density fluctuation measurements by beam emission spectroscopy at higher q 95 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 q 95, implying a higher drive for a Reynolds stress driven zonal flow. At lower density, n e ~ 1.5 × 10 19 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 q 95 at n e ~more » 3.2 × 10 19 m -3 compared to lower q 95. 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.« less

Authors:
 [1];  [1]; ORCiD logo [2];  [3];  [4]; ORCiD logo [5]; ORCiD logo [5]; ORCiD logo [6];  [3];  [2]
  1. Univ. of Wisconsin-Madison, Madison, WI (United States)
  2. General Atomics, San Diego, CA (United States)
  3. Univ. of California, Los Angeles, CA (United States)
  4. Univ. of California, San Diego, CA (United States)
  5. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  6. Southwestern Inst.of Physics, Chengdu (China)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
OSTI Identifier:
1561976
Alternate Identifier(s):
OSTI ID: 1526657
Grant/Contract Number:  
AC02-09CH11466; FC02-04ER54698; FG02- 08ER54984; FG02-08ER54999; FG02-89ER53296; SC0018287
Resource Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 26; Journal Issue: 6; Conference: 60. Annual Meeting of the APS Division of Plasma Physics., Portland, OR (United States), 5-9 Nov 2018; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Yan, Z., Mckee, G. R., Gohil, P., Schmitz, L., Holland, C., Haskey, S. R., Grierson, B. A., Ke, R., Rhodes, T., and Petty, C. Safety factor and turbulence dynamics dependence of the L-H power threshold on DIII-D. United States: N. p., 2019. Web. doi:10.1063/1.5091701.
Yan, Z., Mckee, G. R., Gohil, P., Schmitz, L., Holland, C., Haskey, S. R., Grierson, B. A., Ke, R., Rhodes, T., & Petty, C. Safety factor and turbulence dynamics dependence of the L-H power threshold on DIII-D. United States. doi:10.1063/1.5091701.
Yan, Z., Mckee, G. R., Gohil, P., Schmitz, L., Holland, C., Haskey, S. R., Grierson, B. A., Ke, R., Rhodes, T., and Petty, C. Mon . "Safety factor and turbulence dynamics dependence of the L-H power threshold on DIII-D". United States. doi:10.1063/1.5091701.
@article{osti_1561976,
title = {Safety factor and turbulence dynamics dependence of the L-H power threshold on DIII-D},
author = {Yan, Z. and Mckee, G. R. and Gohil, P. and Schmitz, L. and Holland, C. and Haskey, S. R. and Grierson, B. A. and Ke, R. and Rhodes, T. and Petty, C.},
abstractNote = {The L-H transition power threshold (PLH) is discovered to have a vital dependence on q95, at ne ~ 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, ne ~ 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 ne ~ 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.},
doi = {10.1063/1.5091701},
journal = {Physics of Plasmas},
number = 6,
volume = 26,
place = {United States},
year = {2019},
month = {6}
}

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