Title: Validation of the model for ELM suppression with 3D magnetic fields using low torque ITER baseline scenario discharges in DIII-D

Abstract

Experiments have been executed in the DIII-D tokamak to extend suppression of Edge Localized Modes (ELMs) with Resonant Magnetic Perturbations (RMPs) to ITER-relevant levels of beam torque. Additionally, the results support the hypothesis for RMP ELM suppression based on transition from an ideal screened response to a tearing response at a resonant surface that prevents expansion of the pedestal to an unstable width [Snyder et al., Nucl. Fusion 51, 103016 (2011) and Wade et al., Nucl. Fusion 55, 023002 (2015)]. In ITER baseline plasmas with I/aB = 1.4 and pedestal ${\nu }^{*}$ ~ 0.15, ELMs are readily suppressed with co- $I_p$ neutral beam injection. However, reducing the beam torque from 5 Nm to ≤ 3.5 Nm results in loss of ELM suppression and a shift in the zero-crossing of the electron perpendicular rotation ${\omega }_{\perp e}$ ~ 0 deeper into the plasma. The change in radius of ${\omega }_{\perp e}$ ~ 0 is due primarily to changes to the electron diamagnetic rotation frequency ${\omega }_e^{*}$. Linear plasma response modeling with the resistive MHD code m3d-c1 indicates that the tearing response location tracks the inward shift in ${\omega }_{\perp e}$ ~ 0. At pedestal ${\nu }^{*}$~ 1, ELM suppression is also lost when the beam torque is reduced, but the ${\omega }_{\perp e}$ change is dominated by collapse of the toroidal rotation $v_T$. The hypothesis predicts that it should be possible to obtain ELM suppression at reduced beam torque by also reducing the height and width of the ${\omega }_e^{*}$ profile. This prediction has been confirmed experimentally with RMP ELM suppression at 0 Nm of beam torque and plasma normalized pressure ${\beta }_N$ ~ 0.7. This opens the possibility of accessing ELM suppression in low torque ITER baseline plasmas by establishing suppression at low beta and then increasing beta while relying on the strong RMP-island coupling to maintain suppression.

Authors:

Moyer, Richard A. ^[1]; Paz-Soldan, Carlos ^[2]; Nazikian, Raffi ^[3]; Orlov, Dmitry M. ^[1]; Ferraro, N. M. ^[4]; Grierson, Brian A. ^[3]; Knolker, M. ^[5]; Lyons, B. C. ^[6]; McKee, George R. ^[7]; Osborne, Thomas H. ^[2]; Rhodes, T. L. ^[8]; Meneghini, Orso ^[2]; Smith, Sterling ^[2]; Evans, Todd E. ^[2]; Fenstermacher, Max E. ^[9]; Groebner, Richard J. ^[2]; Hanson, Jeremy M. ^[10]; La Haye, Robert J. ^[2]; Luce, Timothy C. ^[2]; Mordijck, Saskia ^[11] more »; Solomon, Wayne M. ^[2]; Turco, Francesca ^[8]; Yan, Z. ^[7]; Zeng, L. ^[12] « less

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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. General Atomics, San Diego, CA (United States); Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
5. Ludwigs Maximilians Univ., Munchen (Germany)
6. Oak Ridge Inst. for Science and Education (ORISE), Oak Ridge, TN (United States); General Atomics, San Diego, CA (United States)
7. Univ. of Wisconsin-Madison, Madison, WI (United States)
8. Univ. of California, Los Angeles, CA (United States)
9. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
10. Columbia Univ., New York, NY (United States)
11. The College of William and Mary, Williamsburg, VA (United States)
12. Oak Ridge Inst. for Science and Education (ORISE), Oak Ridge, TN (United States); Univ. of California, Los Angeles, CA (United States)

Publication Date:

Mon Sep 18 00:00:00 EDT 2017

Research Org.:

General Atomics, San Diego, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Sponsoring Org.:

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

Contributing Org.:

DIII-D Team

OSTI Identifier:

1398392

Alternate Identifier(s):

OSTI ID: 1392144; OSTI ID: 1839874

Report Number(s):

LLNL-JRNL-752165
Journal ID: ISSN 1070-664X

Grant/Contract Number:  

FC02-04ER54698; AC02-76CH03073; AC05-06OR23100; AC52-07NA27344; FG02-04ER54761; FG02-07ER54917; FG02-08ER54984; FG02-08ER54999; FG02ER54809; SC0007880; FG02- 07ER54917; FG02-05ER54809

Resource Type:

Accepted Manuscript

Journal Name:

Physics of Plasmas

Additional Journal Information:

Journal Volume: 24; Journal Issue: 10; 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; Plasma confinement; Nuclear energy; Statistical analysis; Electron density; Diamagnetic materials; Chemical elements; Magnetic fields; Plasma properties and parameters; Plasma instabilities; Tokamaks