Very high confinement discharges in DIII‐D after boronization

A regime of very high confinement (VH mode) has recently been observed in DIII‐D with global energy confinement times up to a factor of 3.5 above the ITER89‐P L‐mode scaling [Nucl. Fusion 30, 1999 (1990)] and 1.5 to 2 times greater than the DIII‐D/JET edge‐localized‐mode‐free H‐mode scaling relation [Nucl. Fusion 31, 73 (1991)]. These discharges were obtained after boronization in DIII‐D and are characterized by low radiated power and Zeff, increasing confinement time during the VH phase of the discharge and low Ohmic target density. The low radiated power and Zeff are a consequence of the boronization. During the VH phase these discharges exhibit an inward shift in the region of highest electric field shear and a large calculated edge bootstrap current. The outer region (ρ≳0.85) is calculated to be in the second stable regime to ideal ballooning modes.

[1]  W. A. Peebles,et al.  Modifications in turbulence and edge electric fields at the L–H transition in the DIII‐D tokamak , 1991 .

[2]  G. Jackson,et al.  Particle control in DIII-D with helium glow discharge conditioning , 1990 .

[3]  Paul W. Terry,et al.  Influence of sheared poloidal rotation on edge turbulence , 1990 .

[4]  K. Burrell,et al.  Changes in local confinement after an L-H transition in DIII-D , 1992 .

[5]  T. W. Petrie,et al.  Giant sawtooth oscillations in the Doublet III tokamak , 1985 .

[6]  P. Stott,et al.  H-mode energy confinement scaling from the DIII-D and JET tokamaks , 1991 .

[7]  E. Doyle,et al.  Physics of the L to H transition in the DIII-D tokamak , 1990 .

[8]  Lao,et al.  Regime of very high confinement in the boronized DIII-D tokamak. , 1991, Physical review letters.

[9]  H. Reimer,et al.  Boronization in textor , 1989 .

[10]  K. Burrell,et al.  High spatial and temporal resolution visible spectroscopy of the plasma edge in DIII‐D , 1990 .

[11]  J. T. Scoville,et al.  Critical error fields for locked mode instability in tokamaks , 1992 .

[12]  Tadashi Sekiguchi,et al.  Plasma Physics and Controlled Nuclear Fusion Research , 1987 .

[13]  E. Doyle,et al.  Far‐infrared heterodyne scattering to study density fluctuations on the DIII‐D tokamak , 1990 .

[14]  E. C. Crume,et al.  Bifurcation theory of poloidal rotation in tokamaks: A model for L-H transition. , 1989, Physical review letters.

[15]  Yu.A. Sokolov,et al.  ITER conceptual design , 1991 .