Title: Experimental evidence of edge intrinsic momentum source driven by kinetic ion loss and edge radial electric fields in tokamaks

Abstract

Here, bulk ion toroidal velocity profiles, V^D+_||, peaking at 40–60 km/s are observed with Mach probes in a narrow edge region of DIII-D discharges without external momentum input. This intrinsic rotation can be well reproduced by a first principle, collisionless kinetic loss model of thermal ion loss that predicts the existence of a loss-cone distribution in velocity space resulting in a co-Ip directed velocity. We consider two kinetic models, one of which includes turbulence-enhanced momentum transport, as well as the Pfirsch-Schluter (P-S) fluid mechanism. We measure a fine structure of the boundary radial electric field, Er, insofar ignored, featuring large (10–20 kV/m) positive peaks in the scrape off layer (SOL) at, or slightly inside, the last closed flux surface of these low power L- and H-mode discharges in DIII-D. The Er structure significantly affects the ion-loss model, extended to account for a non-uniform electric field. We also find that V^D+_|| is reduced when the magnetic topology is changed from lower single null to upper single null. The kinetic ion loss model containing turbulence-enhanced momentum transport can explain the reduction, as we find that the potential fluctuations decay with radius, while we need to invoke a topology-enhanced collisionality on the simplermore » kinetic model. The P-S mechanism fails to reproduce the damping. We show a clear correlation between the near core V^C6+_|| velocity and the peak edge V^D+_|| in discharges with no external torque, further supporting the hypothesis that ion loss is the source for intrinsic torque in the present tokamaks. However, we also show that when external torque is injected in the core, it can complete with, and eventually overwhelm, the edge source, thus determining the near SOL flows. Finally, we show some additional evidence that the ion/electron distribution in the SOL is non-Maxwellian.« less

Authors:

Boedo, J. A.  ^[1];

• Search DOE PAGES for author "Boedo, J. A."
• Search DOE PAGES for ORCID "0000-0003-2230-4112"

deGrassie, J. S.  ^[2];

• Search DOE PAGES for author "deGrassie, J. S."
• Search DOE PAGES for ORCID "0000-0002-6012-7404"

Grierson, B. ^[3]; Stoltzfus-Dueck, T. ^[3]; Battaglia, D. J. ^[3]; Rudakov, D. L. ^[1]; Belli, E. A.  ^[2];

• Search DOE PAGES for author "Belli, E. A."
• Search DOE PAGES for ORCID "0000-0001-7947-2841"

Groebner, R. J. ^[2]; Hollmann, E. ^[1]; Lasnier, C. ^[4]; Solomon, W. M. ^[3]; Unterberg, E. A.  ^[5];

• Search DOE PAGES for author "Unterberg, E. A."
• Search DOE PAGES for ORCID "0000-0003-1353-8865"

Watkins, J. ^[6]

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+ Show Author Affiliations

1. Univ. of California - San Diego, La Jolla, CA (United States)
2. General Atomics, San Diego, CA (United States)
3. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
4. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
6. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Publication Date:

Wed Sep 21 00:00:00 EDT 2016

Research Org.:

Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); General Atomics, San Diego, CA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Sponsoring Org.:

USDOE Office of Nuclear Energy (NE); USDOE Office of Science (SC); USDOE National Nuclear Security Administration (NNSA)

Contributing Org.:

DIII-D Team

OSTI Identifier:

1332295

Alternate Identifier(s):

OSTI ID: 1325841; OSTI ID: 1331213; OSTI ID: 1371911; OSTI ID: 1515662; OSTI ID: 1542111

Report Number(s):

DOE-GA-30200-1; LLNL-JRNL-736686
Journal ID: ISSN 1070-664X; TRN: US1701624

Grant/Contract Number:  

AC02-09CH11466; AC04-94AL85000; AC05-00OR22725; AC52-07NA27344; FC02- 04ER54698; FG02-07ER54917; FG02-95ER54309; FC02-04ER54698

Resource Type:

Accepted Manuscript

Journal Name:

Physics of Plasmas

Additional Journal Information:

Journal Volume: 23; Journal Issue: 9; 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; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; turbulence simulations; tokamaks; torque; collision theories; electric fields; Physics - Plasma physics