Feedback control of the safety factor profile evolution during formation of an advanced tokamak discharge

Active feedback control for regulation of the safety factor (q) profile at the start of the high stored energy phase of an advanced tokamak discharge has been demonstrated in the DIII-D tokamak. The time evolution of the on-axis or minimum value of q is controlled during and just following the period of ramp-up of the plasma current using electron heating to modify the rate of relaxation of the current profile. In L-mode and H-mode discharges, feedback control of q is effective with the appropriate choice of either off-axis electron cyclotron heating or neutral beam heating as the actuator. The q profile is calculated in real time from a complete equilibrium reconstruction fitted to external magnetic field and flux measurements and internal poloidal field measurements from the motional Stark effect diagnostic.

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

[2]  O. Sauter,et al.  Erratum: “Neoclassical conductivity and bootstrap current formulas for general axisymmetric equilibria and arbitrary collisionality regime” [Phys. Plasmas 6, 2834 (1999)] , 2002 .

[3]  L. L. Lao,et al.  Direct Measurement of the Radial Electric Field in Tokamak Plasmas using the Stark Effect , 1997 .

[4]  Olivier Sauter,et al.  Integrated scenario in JET using real-time profile control , 2003 .

[5]  L. Lao,et al.  MHD Equilibrium Reconstruction in the DIII-D Tokamak , 2005 .

[6]  A. Murari,et al.  LETTER TO THE EDITOR: Active control of the current density profile in JET , 2003 .

[7]  P. C. de Vries,et al.  Real-time control of the q-profile in JET for steady state advanced tokamak operation , 2003 .

[8]  David Mikkelsen,et al.  Current relaxation time scales in toroidal plasmas , 1989 .

[9]  R. J. Groebner,et al.  Scaling studies of the high mode pedestal , 1998 .

[10]  X. Litaudon,et al.  Feedback control of the current profile on Tore Supra , 1997 .

[11]  E. Joffrin,et al.  A versatile method for the real time determination of the safety factor and density profiles in JET , 2002 .

[12]  Alfredo Pironti,et al.  A model-based technique for integrated real-time profile control in the JET tokamak , 2004 .

[13]  T. S. Taylor,et al.  Physics of advanced tokamaks , 1997 .

[14]  L. L. Lao,et al.  Real time equilibrium reconstruction for tokamak discharge control , 1998 .

[15]  M. Mauel,et al.  The formation and evolution of negative central magnetic shear current profiles on DIII-D , 1996 .

[16]  T. Fujita.  Steady state operation research in JT-60U with extended pulse length , 2006 .

[17]  L. L. Lao,et al.  Progress toward fully noninductive, high beta conditions in DIII-D , 2005 .

[18]  L. Lao,et al.  Reconstruction of current profile parameters and plasma shapes in tokamaks , 1985 .

[19]  T. C. Luce,et al.  Electron cyclotron current drive efficiency in general tokamak geometry , 2003 .