Scaling studies of the high mode pedestal

The structure and scaling of the H-mode (high mode) pedestal are examined for discharges in the DIII-D tokamak [Plasma Physics and Controlled Fusion Research (International Atomic Energy Agency, Vienna, 1986), p. 159]. For typical conditions, the pedestal values of the ion and electron temperatures Ti and Te are comparable. Measurements of main ion and C6+ profiles indicate that the ion pressure gradient in the barrier is 50%–100% of the electron pressure gradient for deuterium plasmas. The magnitude of the pressure gradient in the barrier often exceeds the predictions of infinite-n ballooning mode theory by a factor of 2. Moreover, via the bootstrap current, the finite pressure gradient acts to entirely remove ballooning stability limits for typical discharges. For a large dataset, the width of the pressure barrier δ is best described by the dimensionless scaling δ/R∝(βpolped)0.4 where (βpolped) is the pedestal value of poloidal beta and R is the major radius. Scalings based on the poloidal ion gyroradiu...

[1]  F. Wagner,et al.  Regime of Improved Confinement and High Beta in Neutral-Beam-Heated Divertor Discharges of the ASDEX Tokamak , 1982 .

[2]  Olivier Sauter,et al.  Stable equilibria for bootstrap-current driven low aspect ratio tokamaks , 1996 .

[3]  K. H. Burrell,et al.  Effects of E×B velocity shear and magnetic shear on turbulence and transport in magnetic confinement devices , 1997 .

[4]  C. Bishop,et al.  Ideal MHD ballooning stability in the vicinity of a separatrix , 1984 .

[5]  G. L. Campbell,et al.  Design and operation of the multipulse Thomson scattering diagnostic on DIII‐D (invited) , 1992 .

[6]  V. Rozhansky,et al.  The effect of the radial electric field on the L–H transitions in tokamaks , 1992 .

[7]  V. Lebedev,et al.  Dynamics of spatiotemporally propagating transport barriers , 1995 .

[8]  R. J. Groebner,et al.  An emerging understanding of H-mode discharges in tokamaks , 1993 .

[9]  S. Wolfe,et al.  A new look at density limits in tokamaks , 1988 .

[10]  H. Zohm.  Edge localized modes (ELMs) , 1996 .

[11]  J. Manickam,et al.  Attainment of high confinement in neutral beam heated divertor discharges in the PDX tokamak , 1984 .

[12]  Lao,et al.  Study of giant edge-localized modes in DIII-D and comparison with ballooning theory. , 1988, Physical review letters.

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

[14]  K. Itoh.  Theoretical progress on H-mode physics , 1994 .

[15]  G. M. Staebler,et al.  Particle and energy confinement bifurcation in tokamaks , 1993 .

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

[17]  Douglass E. Post,et al.  Physics of Plasma-Wall Interactions in Controlled Fusion , 1986, Springer US.

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

[19]  Y. Wang,et al.  H mode confinement in Alcator C-Mod , 1997 .