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

Journal Article · Mon Sep 18 00:00:00 EDT 2017 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.5000276· OSTI ID:1398392

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] ; Solomon, Wayne M. ^[2]; Turco, Francesca ^[8]; Yan, Z. ^[7]; Zeng, L. ^[12]

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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)

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.

• Research Organization: General Atomics, San Diego, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Fusion Energy Sciences (FES)
• Contributing Organization: DIII-D Team
• 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
• OSTI ID: 1398392
• Alternate ID(s): OSTI ID: 1392144; OSTI ID: 1839874
• Report Number(s): LLNL-JRNL-752165
• Journal Information: Physics of Plasmas, Vol. 24, Issue 10; ISSN 1070-664X
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

Related Subjects

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