Internal measurement of magnetic turbulence in ELMy H-mode tokamak plasmas

Magnetic turbulence is directly observed internally in the pedestal of ELMy H-mode tokamak plasmas using a newly developed Faraday-effect polarimetry measurement. Fluctuation amplitude is δ b r ≥ 15 G (150–500 kHz), with a ratio of magnetic to density fluctuation | δ b r / B | / | δ n / n | ≥ 0.15. Magnetic turbulence is identified as resulting from micro-tearing-instability and mode growth accompanied by degraded plasma confinement is observed.

[1]  L. Lao,et al.  First experimental tests of a new small angle slot divertor on DIII-D , 2019, Nuclear Fusion.

[2]  J. Contributors,et al.  Gyrokinetic analysis and simulation of pedestals to identify the culprits for energy losses using ‘fingerprints’ , 2019, Nuclear Fusion.

[3]  A. Diallo,et al.  Direct Observation of Nonlinear Coupling between Pedestal Modes Leading to the Onset of Edge Localized Modes. , 2018, Physical review letters.

[4]  D. Brower,et al.  A Faraday-effect polarimeter for fast magnetic dynamics measurement on DIII-D. , 2018, The Review of scientific instruments.

[5]  G. Staebler,et al.  Stationary QH-mode plasmas with high and wide pedestal at low rotation on DIII-D , 2017 .

[6]  E. Wolfrum,et al.  High frequency magnetic fluctuations correlated with the inter-ELM pedestal evolution in ASDEX Upgrade , 2016 .

[7]  Y. Liu,et al.  Excitation of edge plasma instabilities and their role in pedestal saturation in the HL-2A tokamak , 2016 .

[8]  F. Jenko,et al.  Microtearing turbulence limiting the JET-ILW pedestal , 2015 .

[9]  F. Jenko,et al.  Overview of gyrokinetic studies of finite-β microturbulence , 2015 .

[10]  David R. Smith,et al.  Correlations between quasi-coherent fluctuations and the pedestal evolution during the inter-edge localized modes phase on DIII-Da) , 2015 .

[11]  B. Wan,et al.  Observation of a quasi-coherent high-frequency electromagnetic mode at the pedestal region in EAST RF-dominant H-modes , 2014 .

[12]  Alcator C-Mod Team,et al.  Observation of edge instability limiting the pedestal growth in tokamak plasmas. , 2014, Physical review letters.

[13]  D. Brower,et al.  Role of nonlinear coupling and density fluctuations in magnetic-fluctuation-induced particle transport. , 2012, Physical review letters.

[14]  R. Groebner,et al.  Global gyrokinetic simulation of Tokamak edge pedestal instabilities. , 2012, Physical review letters.

[15]  C. Roach,et al.  Kinetic instabilities that limit β in the edge of a tokamak plasma: a picture of an H-mode pedestal. , 2011, Physical review letters.

[16]  T. Osborne,et al.  Pedestal density fluctuation dynamics during the inter-ELM cycle in DIII-D a) , 2011 .

[17]  F Jenko,et al.  Gyrokinetic microtearing turbulence. , 2011, Physical review letters.

[18]  R. Bell,et al.  Electromagnetic transport from microtearing mode turbulence. , 2011, Physical review letters.

[19]  D. Brower,et al.  Magnetic-fluctuation-induced particle transport and density relaxation in a high-temperature plasma. , 2009, Physical review letters.

[20]  R. J. Groebner,et al.  Development and validation of a predictive model for the pedestal height , 2008 .

[21]  A. Schekochihin,et al.  Turbulence, magnetic fields, and plasma physics in clusters of galaxies , 2006, astro-ph/0601246.

[22]  R. J. Fonck,et al.  Turbulence imaging and applications using beam emission spectroscopy on DIII-D (invited) , 2003 .

[23]  D. Brower,et al.  Measurement of internal magnetic field fluctuations in a reversed-field pinch by Faraday rotation. , 2003, Physical review letters.

[24]  F. Wagner,et al.  Development of an Edge Transport Barrier at the H-Mode Transition of ASDEX , 1984 .

[25]  N. T. Gladd,et al.  Microtearing modes and anomalous transport in tokamaks , 1980 .

[26]  J. Drake,et al.  Kinetic theory of tearing instabilities , 1977 .

[27]  R. Hazeltine,et al.  Kinetic theory of tearing instability , 1975 .

[28]  C. Roach,et al.  Intermediate-k density and magnetic field fluctuations during inter-ELM pedestal evolution in MAST , 2015 .

[29]  F. C. Schüller,et al.  Washboard modes as ELM-related events in JET , 2004 .