Integrated real-time control of MHD instabilities using multi-beam ECRH/ECCD systems on TCV

Simultaneous real-time control of multiple MHD instabilities is experimentally demonstrated in the TCV tokamak. Multiple sources of EC heating and current drive, injected through real-time controlled launchers, are used to stabilize 3/2 and 2/1 neoclassical tearing modes (NTMs) rapidly after their appearance. Control of the sawtooth instability using a new sawtooth-pacing technique is demonstrated, providing precise control of the time of appearance of the sawtooth crash. Efficient NTM preemption can then be performed by applying pulsed power on the mode rational surface at the time of the seed-island generating sawtooth crash. These three elements are combined into one integrated control system which can simultaneously control the sawtooth period, preempt the formation of NTMs and suppress these if they appear.

[1]  A Bottino,et al.  Inductive current density perturbations to probe electron internal transport barriers in tokamaks. , 2005, Physical review letters.

[2]  B. P. Duval,et al.  Creation and control of variably shaped plasmas in TCV , 1994 .

[3]  F. Felici,et al.  Architecture and commissioning of the TCV distributed feedback control system , 2010, 2010 17th IEEE-NPSS Real Time Conference.

[4]  R. J. La Haye,et al.  Neoclassical tearing modes and their controla) , 2005 .

[5]  F. Leuterer,et al.  Enhancement of the stabilization efficiency of a neoclassical magnetic island by modulated electron cyclotron current drive in the ASDEX upgrade tokamak. , 2007, Physical review letters.

[6]  O. Sauter,et al.  Control of neoclassical tearing modes by sawtooth control. , 2002, Physical review letters.

[7]  M Maarten Steinbuch,et al.  Real-time control of tearing modes using a line-of-sight electron cyclotron emission diagnostic , 2010 .

[8]  M Maarten Steinbuch,et al.  Systematic design of a sawtooth period feedback controller using a Kadomtsev–Porcelli sawtooth model , 2011 .

[9]  K. Matsuda,et al.  Ray tracing study of the electron cyclotron current drive in DIII-D using 60 GHz , 1989 .

[10]  M. Rosenbluth,et al.  Model for the sawtooth period and amplitude , 1996 .

[11]  O. Sauter,et al.  Sawtooth pacing by real-time auxiliary power control in a tokamak plasma. , 2011, Physical review letters.

[12]  Olivier Sauter,et al.  Effects of localized electron heating and current drive on the sawtooth period , 2003 .

[13]  Akihiko Isayama,et al.  Stabilization effect of early ECCD on a neoclassical tearing mode in the JT-60U tokamak , 2003 .

[14]  Gerhard Raupp,et al.  Development of a feedback system to control MHD instabilities in ASDEX Upgrade , 2007 .

[15]  S. Coda,et al.  Progress and scientific results in the TCV tokamak , 2011 .

[16]  O. Sauter,et al.  Individual Sawtooth pacing by synchronized ECCD in TCV , 2011 .

[17]  O. Sauter,et al.  Neoclassical conductivity and bootstrap current formulas for general axisymmetric equilibria and arbitrary collisionality regime , 1999 .

[18]  A. Collazos,et al.  Progress on the ITER H&CD EC Upper Launcher Steering-Mirror Control System , 2010, IEEE Transactions on Plasma Science.

[19]  D. Ryutov,et al.  Current and potential distribution in a divertor with toroidally-asymmetric biasing of the divertor plate , 2006 .

[20]  E. Westerhof,et al.  On the merits of heating and current drive for tearing mode stabilization , 2009 .

[21]  L. L. Lao,et al.  Beta limits in long-pulse tokamak discharges , 1997 .

[22]  Olivier Sauter,et al.  On the requirements to control neoclassical tearing modes in burning plasmas , 2010 .

[23]  Olivier Sauter,et al.  Marginal β-limit for neoclassical tearing modes in JET H-mode discharges , 2002 .

[24]  Stefano Coda,et al.  Real time control of the plasma current and elongation in tokamaks using ECRH actuators , 2007 .

[25]  F Turco,et al.  Demonstration of effective control of fast-ion-stabilized sawteeth by electron-cyclotron current drive. , 2009, Physical review letters.

[26]  Costanza Zucca.  Modeling and control of the current density profile in tokamaks and its relation to electron transport , 2009 .

[27]  Gerd Vandersteen,et al.  Demonstration of sawtooth period locking with power modulation in TCV plasmas , 2012 .

[28]  F. Felici,et al.  Real-time physics-model-based simulation of the current density profile in tokamak plasmas , 2011 .

[29]  J. B. Lister,et al.  Steady-state fully noninductive operation with electron cyclotron current drive and current profile control in the tokamak à configuration variable (TCV) , 2001 .

[30]  J. B. Lister,et al.  The Control of Tokamak Configuration Variable Plasmas , 1997 .

[31]  R. J. La Haye,et al.  Prospects for stabilization of neoclassical tearing modes by electron cyclotron current drive in ITER , 2009 .

[32]  D. A. Humphreys,et al.  Higher stable beta by use of pre-emptive electron cyclotron current drive on DIII-D , 2005 .

[33]  G. Granucci,et al.  Avoidance of disruptions at high βN in ASDEX Upgrade with off-axis ECRH , 2011 .

[34]  J. B. Lister,et al.  Safety factor profile requirements for electron ITB formation in TCV , 2005 .

[35]  Y. R. Martin,et al.  Plasma dynamics with second and third-harmonic ECRH and access to quasi-stationary ELM-free H-mode on TCV , 2007 .

[36]  K. Kajiwara,et al.  Complete stabilization of a tearing mode in steady state high-βp H-mode discharges by the first harmonic electron cyclotron heating/current drive on JT-60U , 2000 .

[37]  Giovanni Ramponi,et al.  Overview of the ITER EC upper launcher , 2008 .

[38]  D. A. Humphreys,et al.  Active control for stabilization of neoclassical tearing modes , 2005 .

[39]  T. P. Goodman,et al.  Experience in integrated control of the multi-megawatt electron cyclotron heating system on the TCV tokamak: the first decade , 2008 .

[40]  Y. Camenen,et al.  High-resolution multiwire proportional soft x-ray diagnostic measurements on TCV. , 2008, The Review of scientific instruments.

[41]  R. H. Bulmer,et al.  Sustained Spheromak Physics Experiment (SSPX): design and physics results , 2012 .

[42]  Modulation of electron transport during Swing ECCD discharges in TCV , 2009 .

[43]  O. Sauter,et al.  Rapid and localized electron internal-transport-barrier formation during shear inversion in fully noninductive TCV discharges. , 2004, Physical review letters.

[44]  Ambrogio Fasoli,et al.  Generation of suprathermal electrons during sawtooth crashes in a tokamak plasma , 2007 .

[45]  D. A. Humphreys,et al.  Stabilization and prevention of the 2/1 neoclassical tearing mode for improved performance in DIII-D , 2007 .

[46]  G. Tonetti,et al.  Tokamak equilibrium reconstruction using Faraday rotation measurements , 1988 .

[47]  Faa Federico Felici,et al.  From profile to sawtooth control: developing feedback control using ECRH/ECCD systems on the TCV tokamak , 2009 .

[48]  W. A. Cooper,et al.  Magnetic reconnection triggering magnetohydrodynamic instabilities during a sawtooth crash in a Tokamak plasma. , 2010, Physical review letters.