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Stationary QH-mode plasmas with high and wide pedestal at low rotation on DIII-D

Journal Article · · Nuclear Fusion
 [1];  [2];  [2];  [3];  [4];  [2];  [2];  [5];  [6];  [2];  [7];  [2];  [8];  [4];  [8];  [2];  [2];  [3];  [6]
  1. General Atomics, San Diego, CA (United States); General Atomics
  2. General Atomics, San Diego, CA (United States)
  3. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  4. Univ. of California, Los Angeles, CA (United States)
  5. Univ. of California, Davis, CA (United States)
  6. Univ. of Wisconsin, Madison, WI (United States)
  7. Graduate Univ. for Advanced Studies (SOKENDAI), Kanagawa (Japan)
  8. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
+ Show Author Affiliations
A stationary, quiescent H-mode (QH-mode) regime with a wide pedestal and improved confinement at low rotation has been discovered on DIII-D with reactor relevant edge parameters and no ELMs. As the injected neutral beam torque is ramped down and the edge ExB rotation shear reduces, the transition from standard QH to the wide pedestal QH-mode occurs. And at the transition, the coherent edge harmonic oscillations (EHO) that usually regulate the standard QH edge cease and broadband edge MHD modes appear along with a rapid increase in the pedestal pressure height (by ≤60%) and width (by ≤50%). We posit that the enhanced edge turbulence-driven transport, enabled by the lower edge ExB flow shear due to lower torque reduces the pedestal gradient and, combined with the high edge instability limit provided by the balanced double-null plasma shape, permits the development of a broader and thus higher pedestal that is turbulence-transport-limited. Even with the significantly enhanced pedestal pressure, the edge operating point is below the peeling ballooning mode stability boundary and thus without ELMs. Improved transport in the outer core region (0.8≤ρ≤0.9) owing to increased ExB flow shear in that region and the enhanced pedestal boost the overall confinement by up to 45%. Our findings advance the physics basis for developing stationary ELM-free high-confinement operation at low rotation for future burning plasma where similar collisionality and rotation levels are expected.
Research Organization:
General Atomics, San Diego, CA (United States); Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
Sponsoring Organization:
USDOE; USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
Contributing Organization:
the DIII-D Team
Grant/Contract Number:
AC02-09CH11466; FC02-04ER54698; FC02-06ER54873; FG02-08ER54984; FG02-08ER54999; FG02-94ER54235; FG02-99ER54531; FG03-95ER54309
OSTI ID:
1372267
Alternate ID(s):
OSTI ID: 1327560
OSTI ID: 22925605
Journal Information:
Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 2 Vol. 57; ISSN 0029-5515
Publisher:
IOP ScienceCopyright Statement
Country of Publication:
United States
Language:
English

References (33)

The beam emission spectroscopy diagnostic on the DIII-D tokamak journal January 1999
Quiescent double barrier high-confinement mode plasmas in the DIII-D tokamak journal May 2001
Edge localized modes and the pedestal: A model based on coupled peeling–ballooning modes journal May 2002
Numerical studies of edge localized instabilities in tokamaks journal April 2002
Advances in understanding quiescent H-mode plasmas in DIII-D journal May 2005
Magnetic diagnostic system of the DIII-D tokamak journal February 2006
A theory-based transport model with comprehensive physics journal May 2007
Localized measurement of short wavelength plasma fluctuations with the DIII-D phase contrast imaging diagnostic journal February 2009
Development and validation of a predictive model for the pedestal height journal May 2009
A novel, multichannel, comb-frequency Doppler backscatter system journal October 2010
Reactor-relevant quiescent H-mode operation using torque from non-axisymmetric, non-resonant magnetic fields journal May 2012
Short wavelength turbulence generated by shear in the quiescent H-mode edge on DIII–D journal June 2014
Technical overview of the millimeter-wave imaging reflectometer on the DIII-D tokamak (invited) journal November 2014
Edge-localized-modes in tokamaks journal September 2014
Impurity confinement and transport in high confinement regimes without edge localized modes on DIII-Da) journal May 2015
Discovery of stationary operation of quiescent H-mode plasmas with net-zero neutral beam injection torque and high energy confinement on DIII-D journal March 2016
Effects of E×B velocity shear and magnetic shear on turbulence and transport in magnetic confinement devices journal May 1997
Chapter 2: Plasma confinement and transport journal December 1999
Progress in quantifying the edge physics of the H mode regime in DIII-D journal December 2001
Edge stability of the ELM-free quiescent H-mode on DIII-D journal November 2005
Studies of the ‘Quiescent H-mode’ regime in ASDEX Upgrade and JET journal July 2005
Energy loss for grassy ELMs and effects of plasma rotation on the ELM characteristics in JT-60U journal July 2005
Edge pedestal control in quiescent H-mode discharges in DIII-D using co-plus counter-neutral beam injection journal July 2009
A first-principles predictive model of the pedestal height and width: development, testing and ITER optimization with the EPED model journal August 2011
ITER predictions using the GYRO verified and experimentally validated trapped gyro-Landau fluid transport model journal June 2011
Advances towards QH-mode viability for ELM-stable operation in ITER journal July 2011
Access to high beta advanced inductive plasmas at low injected torque journal September 2013
Enhanced H-mode pedestals with lithium injection in DIII-D journal May 2015
Integrated modeling applications for tokamak experiments with OMFIT journal July 2015
ELM-free stationary H-mode plasmas in the ASDEX Upgrade tokamak journal June 2003
Impact of toroidal rotation on ELM behaviour in the H-mode on JT-60U journal April 2004
Edge stability of stationary ELM-suppressed regimes on DIII-D journal July 2008
Role of edge electric field and poloidal rotation in the L - H transition journal June 1990

Cited By (4)

A Riccati solution for the ideal MHD plasma response with applications to real-time stability control journal March 2018
Physics of increased edge electron temperature and density turbulence during ELM-free QH-mode operation on DIII-D journal May 2018
Edge state selection by modulating E  ×  B shearing profile in toroidally confined plasmas journal May 2019
Long-lived predator-prey dynamics in the pedestal of near-zero torque high performance DIII-D plasmas journal September 2019

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Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
E x B shear
ELM-free
QH-mode
low rotation
pedestal transport
turbulence