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The role of zonal flows and predator–prey oscillations in triggering the formation of edge and core transport barriers

Journal Article · · Nuclear Fusion
 [1];  [2];  [2];  [3];  [2];  [4];  [4];  [5];  [5];  [6];  [7]; ;  [2];  [8];  [6];  [9];  [8];  [2]
  1. Univ. of California, Los Angeles, CA (United States); General Atomics
  2. Univ. of California, Los Angeles, CA (United States)
  3. EURATOM/CCFE Fusion Assoc., Oxon (United Kingdom)
  4. General Atomics, San Diego, CA (United States)
  5. Univ. of Wisconsin, Madison, WI (United States)
  6. Univ. of California San Diego, La Jolla, CA (United States)
  7. Univ. of California San Diego, La Jolla, CA (United States); WCI Center for Fusion Theory, Daejeon (Korea)
  8. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  9. Univ. of Texas, Austin, TX (United States)
+ Show Author Affiliations
Here, we present direct evidence of low frequency, radially sheared, turbulence-driven flows (zonal flows (ZFs)) triggering edge transport barrier formation preceding the L- to H-mode transition via periodic turbulence suppression in limit-cycle oscillations (LCOs), consistent with predator–prey dynamics. The final transition to edge-localized mode-free H-mode occurs after the equilibrium E × B flow shear increases due to ion pressure profile evolution. ZFs are also observed to initiate formation of an electron internal transport barrier (ITB) at the q = 2 rational surface via local suppression of electron-scale turbulence. Multi-channel Doppler backscattering (DBS) has revealed the radial structure of the ZF-induced shear layer and the E × B shearing rate, ωE×B, in both barrier types. During edge barrier formation, the shearing rate lags the turbulence envelope during the LCO by 90°, transitioning to anti-correlation (180°) when the equilibrium shear dominates the turbulence-driven flow shear due to the increasing edge pressure gradient. The time-dependent flow shear and the turbulence envelope are anti-correlated (180° out of phase) in the electron ITB. LCOs with time-reversed evolution dynamics (transitioning from an equilibrium-flow dominated to a ZF-dominated state) have also been observed during the H–L back-transition and are potentially of interest for controlled ramp-down of the plasma stored energy and pressure (normalized to the poloidal magnetic field) $$\beta_{\theta} =2\mu_{0} n{( {T_{{\rm e}} +T_{{\rm i}}})}/{B_{\theta}^{2}}$$ in ITER.
Research Organization:
General Atomics, San Diego, CA (United States)
Sponsoring Organization:
USDOE Office of Nuclear Energy (NE)
Grant/Contract Number:
FC02-04ER54698
OSTI ID:
1352935
Alternate ID(s):
OSTI ID: 22331318
Journal Information:
Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 7 Vol. 54; ISSN 0029-5515
Publisher:
IOP ScienceCopyright Statement
Country of Publication:
United States
Language:
English

References (33)

Core barrier formation near integer q surfaces in DIII-D journal August 2006
Edge radial electric field structure and its connections to H-mode confinement in Alcator C-Mod plasmas journal May 2009
A multichannel, frequency-modulated, tunable Doppler backscattering and reflectometry system journal August 2009
A novel, multichannel, comb-frequency Doppler backscatter system journal October 2010
New plasma measurements with a multichannel millimeter-wave fluctuation diagnostic system in the DIII-D tokamak (invited) journal October 2010
Quiet periods in edge turbulence preceding the L-H transition in the National Spherical Torus Experiment journal October 2010
Zonal flow triggers the L-H transition in the Experimental Advanced Superconducting Tokamak journal July 2012
Spatio-temporal evolution of the L → I → H transition journal September 2012
Spatio-temporal evolution of the H → L back transition journal June 2013
Influence of sheared poloidal rotation on edge turbulence journal January 1990
Effects of E×B velocity shear and magnetic shear on turbulence and transport in magnetic confinement devices journal May 1997
Dependence of the L- to H-mode power threshold on toroidal rotation and the link to edge turbulence dynamics journal September 2009
H-mode threshold and confinement in helium and deuterium in ASDEX Upgrade journal May 2009
L–H transition studies on DIII-D to determine H-mode access for operational scenarios in ITER journal August 2011
L- to H-mode transitions at low density in ASDEX Upgrade journal December 2011
High-accuracy characterization of the edge radial electric field at ASDEX Upgrade journal April 2013
Spatio-temporal evolution of the L → H and H → L transitions journal June 2013
Turbulent-driven low-frequency sheared E × B flows as the trigger for the H-mode transition journal July 2013
Doppler reflectometry for the investigation of propagating density perturbations journal October 2001
Edge radial electric field structure in quiescent H-mode plasmas in the DIII-D tokamak journal April 2004
Power requirement for accessing the H-mode in ITER journal July 2008
Localized Turbulence Suppression and Increased Flow Shear near the q = 2 Surface during Internal-Transport-Barrier Formation journal August 2009
Mean and Oscillating Plasma Flows and Turbulence Interactions across the L − H Confinement Transition journal February 2011
First Evidence of the Role of Zonal Flows for the L − H Transition at Marginal Input Power in the EAST Tokamak journal September 2011
Spatiotemporal Structure of the Interaction between Turbulence and Flows at the L-H Transition in a Toroidal Plasma journal December 2011
Role of Zonal Flow Predator-Prey Oscillations in Triggering the Transition to H-Mode Confinement journal April 2012
Dynamics of Low-Intermediate–High-Confinement Transitions in Toroidal Plasmas journal June 2013
Spatiotemporal Structures of Edge Limit-Cycle Oscillation before L-to-H Transition in the JFT-2M Tokamak journal July 2013
Experimental Evidence for the Intimate Interaction among Sheared Flows, Eddy Structures, Reynolds Stress, and Zonal Flows across a Transition to Improved Confinement journal August 2013
Internal transport barrier on q =3 surface and poloidal plasma spin up in JT-60U high- β p discharges journal June 1994
Radial Electric Field Measurements in Reversed Shear Plasmas journal June 1998
Quiescent Double Barrier Regime in the DIII-D Tokamak journal May 2001
Zonal Flows and Transient Dynamics of the L − H Transition journal May 2003

Cited By (2)

A theory of self-organized zonal flow with fine radial structure in tokamak journal December 2017
Poloidal asymmetries of flows in the Tore Supra tokamak journal February 2018

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Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
DIII-D
L-H transition
internal transport barriers
predator-prey oscillations
tokamak
zonal flows