Stationary, high bootstrap fraction plasmas in DIII-D without inductive current control

We have initiated an experimental programme to address some of the questions associated with the operation of a tokamak with high bootstrap current fraction under high performance conditions, without assistance from a transformer. In these discharges, stationary (or slowly improving) conditions are maintained for up to 3.7 s at βN ≈ βp approaching 3.3. The achievable current and pressure are limited by a relaxation oscillation, involving growth and collapse of an internal transport barrier at ρ ≥ 0.6. The pressure gradually increases and the current profile broadens throughout the discharge. Eventually the plasma reaches a more stable, high confinement (H89P ~ 3) state. Characteristically these plasmas have 65–85% bootstrap current, 15–30% neutral-beam-driven current and 0–10% driven by electron cyclotron frequency electromagnetic waves.

[1]  O. Naito,et al.  Combined non-inductive current drive in a high confinement reversed magnetic shear plasma at high normalized density in JT-60U , 2002 .

[2]  O. Naito,et al.  Heating and non-inductive current drive by negative ion based NBI in JT-60U , 2000 .

[3]  Y. Kamada,et al.  Extended JT-60U plasma regimes for high integrated performance , 2001 .

[4]  Magnin,et al.  Steady-state fully noninductive current driven by electron cyclotron waves in a magnetically confined plasma , 2000, Physical review letters.

[5]  H Kubo,et al.  Quasisteady high-confinement reversed shear plasma with large bootstrap current fraction under full noninductive current drive condition in JT-60U. , 2001, Physical review letters.

[6]  J. W. Connor,et al.  Diffusion Driven Plasma Currents and Bootstrap Tokamak , 1971 .

[7]  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 .

[8]  F. Imbeaux,et al.  New tokamak plasma regime with stationary temperature oscillations. , 2003, Physical review letters.

[9]  C. Giroud,et al.  Progress towards steady-state operation and real-time control of internal transport barriers in JET , 2003 .

[10]  W. Treutterer,et al.  Performance, heating and current drive scenarios of ASDEX Upgrade advanced tokamak discharges , 2001 .

[11]  P J McCarthy,et al.  Reaching high poloidal beta at Greenwald density with internal transport barrier close to full noninductive current drive. , 2001, Physical review letters.

[12]  D. Moreau.  Lower‐hybrid current drive experiments in TORE SUPRA , 1992 .

[13]  S. Kawasaki,et al.  Overview of steady state tokamak plasma experiments in TRIAM-1M , 2003 .

[14]  C. Gil,et al.  Particle pinch with fully noninductive lower hybrid current drive in Tore Supra. , 2003, Physical review letters.

[15]  ASDEX-Upgrade team,et al.  The H-Mode of ASDEX , 1989 .

[16]  J. L. Luxon,et al.  A design retrospective of the DIII-D tokamak , 2002 .

[17]  L. L. Lao,et al.  Equilibrium analysis of current profiles in tokamaks , 1990 .

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

[19]  Y Miura,et al.  Formation of advanced tokamak plasmas without the use of an ohmic-heating solenoid. , 2004, Physical review letters.

[20]  J. B. Lister,et al.  Recent results from the electron cyclotron heated plasmas in Tokamak à Configuration Variable (TCV) , 2003 .