Title: Main-ion intrinsic toroidal rotation across the ITG/TEM boundary in DIII-D discharges during ohmic and electron cyclotron heating

Abstract

Direct measurements of deuterium main-ion toroidal rotation spanning the linear ohmic to saturated ohmic confinement (LOC-SOC) regime are presented and compared to the more commonly measured impurity (carbon) ion rotation in DIII-D. Main ions carry the bulk of the plasma toroidal momentum, and hence the shape of the main-ion rotation is more relevant to the study of angular momentum transport in tokamaks. In the linear ohmic confinement (LOC) regime the main-ion toroidal rotation frequency is flat across the profile from the sawtooth region to the plasma separatrix. However, the impurity rotation profile possess a rotation gradient, with the rotation frequency being lower near the plasma edge, implying a momentum pinch or negative residual stress inferred from the impurity rotation that differs from the main-ion rotation. In the saturated ohmic confinement regime (SOC), both the main-ion and impurity rotation profiles develop a deeply hollow feature near mid-radius while maintaining the offset in the edge rotation, both implying a positive core residual stress. In the radial region where the rotation gradient changes the most dramatically, turbulence measurement show that density fluctuations near the TEM scale are higher when the rotation profile is flat, and drop significantly when the plasma density is raisedmore » and the rotation profile hollows, consistent with instabilities damped by collisions. Linear gyrokinetic simulations with GYRO indicate the transition from LOC-SOC in DIII-D occurs as trapped electron modes (TEMs) are replaced by ion temperature gradient driven modes (ITGs) from the outer radii inwards as the plasma collisionality increases, Zeff decreases, and the power flow through the ion channel progressively increases due to the electron-ion energy exchange. Gyrofluid modeling with TGLF successfully reproduces the plasma profiles at key times in the discharge, and in time dependent simulations with predictive TRANSP. TGLF indicates that during both the LOC and SOC regimes, subdominant modes are present and that the plasma is not in a pure TEM or ITG binary state, but rather a more subtle mixed state. Predictions of the main-ion rotation profiles are performed with global nonlinear gyrokinetic simulations using GTS and reveals that the flat rotation is due to oscillatory variation of the turbulent residual stress across the profile, whereas the deeply hollow rotation profile is due to a larger-scale, dipole-like stress profile. In both cases, the predicted and observed main-ion rotation profile is consistent with the balance of turbulent residual stress and momentum diffusion.« less

Authors:

Grierson, B. A.  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-5918-6506"

Chrystal, C.  ^[2];

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• Search DOE PAGES for ORCID "0000-0003-3049-8658"

Haskey, S. R.  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-9978-6597"

Wang, W. X.  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-9415-1560"

Rhodes, T. L. ^[3]; McKee, G. R. ^[4]; Barada, K.  ^[3];

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• Search DOE PAGES for ORCID "0000-0001-7724-8491"

Yuan, X.  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-6146-1260"

Nave, M. F. F. ^[5]; Ashourvan, A.  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-5107-8682"

Holland, C. ^[6]

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+ Show Author Affiliations

1. Princeton Univ., Princeton, NJ (United States). Princeton Plasma Physics Lab
2. General Atomics, San Diego, CA (United States)
3. Univ. of California, Los Angeles, CA (United States)
4. Univ. of Wisconsin-Madison, Madison, WI (United States)
5. Univ. de Lisboa, Lisbon (Portugal)
6. Univ. of California San Diego, La Jolla, CA (United States)

Publication Date:

Fri Apr 19 00:00:00 EDT 2019

Research Org.:

Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC); Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Univ. of Texas, Austin, TX (United States); General Atomics, San Diego, CA (United States); Univ. of Wisconsin, Madison, WI (United States); Univ. of California, San Diego, CA (United States)

Sponsoring Org.:

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

OSTI Identifier:

1542941

Alternate Identifier(s):

OSTI ID: 1507812; OSTI ID: 1508619; OSTI ID: 1565960

Grant/Contract Number:  

FG03-97ER54415; AC02-09CH11466; FC02-04ER54698; FG02-08ER54999; FG02- 08ER54984; FG02-04ER54235; FG02-07ER54917; FG02-08ER54984

Resource Type:

Accepted Manuscript

Journal Name:

Physics of Plasmas

Additional Journal Information:

Journal Volume: 26; Journal Issue: 4; 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