CATEGORY #1: OBJECTIVE
Comparison between L-mode and H-mode discharge based on differenciating parameters (pinch velocity,
diffusion coefficients, etc) of confinement.
Determination of radial force balance between 1) Er, 2) VXB and 3) Pressure gradients in L-mode to Hmode transition
CATEGORY #2: PREVIOUS STUDIES
Previous studies on L-H transition suggests the following:
Radical change in radial electric field related as a cause for transition between confinement modes
(PLOT OF RADIAL ELECTRIC FIELD)
2.50E+04
1525 ms
Radial Electric Field (V/m)
2.00E+04
2140 ms
1.50E+04
1.00E+04
5.00E+03
0.00E+00
-5.00E+03
-1.00E+04
-1.50E+04
-2.00E+04
0.86
0.88
0.9
0.92
0.94
0.96
0.98
1
Normalized Radius, ρ
Large change in velocity indicates increase in the value of VXB from L-mode to H-mode
REFERENCE: R.J. Groebner, K. H. Burrell and R.P. Seraydarian, “Role of Edge Electric Field and Poloidal
Rotation in the L-H Transition”, Physical Review Letters. Vol. 64 – 25, American Physical Society
(1990).
Abrupt change in edge impurity ion poloidal rotation and edge radial electric field in L-H mode transition
REFERENCE: J.Kim et al, “Rotation Characteristic of Main Ions and Impurity Ions in H-Mode Tokamak
Plasma”, Physical Review Letters. Vol. 72-14, American Physical Society (1994)
Particle diffusion coefficient can be determined by fitting density profile from experimental data with a
diffusive particle flux model
REFERENCE: W. M. Stacey and R. J. Groebner, “Interpretation of particle pinches and diffusion
coefficients in the edge pedestal of DIII-D H-mode Plasmas”, Physics of Plasma. 16, 102504-1 (2009)
H-mode confinement is characterized by large increase in inward pinch velocity rather than decrease in
diffusion coefficient: Large inward pinch velocity observed over the outer most radii (ρ > 0.945) of Hmode plasma confinement
REFERENCE: W. M. Stacey and R. J. Groebner, “Force balance and ion particle transport differences in
high and low confinement tokamak edge pedestals”, Physics of Plasma. 17, 112512-7 (2010).
CATEGORY #3 & 4: SHOT & TIME SELECTION DESCRIPTION
DIII-D SHOT #118897:
Conventional L-mode to H-mode transition
Extended ELM-free H-mode discharge
Moderately high triangularity values of discharge provide edge MHD stability
REFERENCE: THERMAL TRANSPORT ANALYSIS OF THE EDGE REGION IN THE LOW AND HIGH
CONFINEMENT STAGES OF A DIII-D DISCHARGE (W.Stacey and R. Groebner) PHYSICS OF PLASMA
14.012501 (2007)
(PLOT OF PEDESTAL ELECTRON DENSITY VS TIME)
(PLOT OF TRIANGULARITY VALUES FOR SHOT)
0.4
0.35
TRIANGULARITY
0.3
0.25
0.2
0.15
Lower Triangularity
0.1
Upper Triangularity
0.05
0
1490 1540 1590 1640 1690 1740 1790 1840 1890 1940 1990 2040 2090 2140
Time (ms)
REFERENCES: TRIANGULARITY & DENSITY PLOTS TAKEN FROM DIII-D database
Time selected to cover the entire transition from L-mode (1490ms), Early stages of L-H transition (1525
and 155ms) and H-mode (2140ms) confinement before ELM-mode.
CATEGORY #5: PARAMETERS OF INTEREST
TOROIDAL AND RADIAL MOMENTUM BALANCE EQUATIONS
A
nj mj [(νjk + νdj )Vϕj − νjk Vϕk ] = nj ej Eϕ
+ nj ej Bθ Vrj + Mϕj
Vϕj =
1
1 ∂pj
[Er + Vθj Bϕ −
]
Bθ
nj ej ∂r
PINCH VELOCITY EQUATION
pinch
Vrj
=
A
+ nj mj (νjk + νdj )(fp−1 Vθj + Er ⁄Bθ ) − nj mj νjk Vϕk ]
[−Mϕj − nj ej Eϕ
nj ej Bθ
DIFFUSION COEFFICIENT EQUATION
Dj =
mj Tj νjk
2 (1 +
(ej Bθ )
νdj ej
− )
νjk ek
Edge pedestal simulation (GTEDGE) will be employed to determine and analyze above parameters
REFERENCES: FORCE BALANCE AND ION PARTICLE TRANSPORT DIFFERENCES IN HIGH AND LOW
CONFINEMENT TOKAMAK EDGE PEDESTALS (W.STACEY) PHYSICS OF PLASMAS 17.112512 (2010)
(DIFFUSION COEFFICIENT PLOT FOR 1525MS AND 2140MS)
Deuterium Diffusion Coefficient (m²/s)
8.00E-01
7.00E-01
6.00E-01
5.00E-01
4.00E-01
3.00E-01
2.00E-01
1525 ms
1.00E-01
2140 ms
0.00E+00
0.86
0.88
0.90
0.92
0.94
0.96
0.98
1.00
0.96
0.98
1.00
Normalized Radius, ρ
(PINCH VELOCiTY PLOT 1525MS AND 2140MS)
0.00E+00
-5.00E+01
Pinch Velocity (m/s)
-1.00E+02
1525 ms
-1.50E+02
2140 ms
-2.00E+02
-2.50E+02
-3.00E+02
-3.50E+02
-4.00E+02
-4.50E+02
0.86
0.88
0.90
0.92
0.94
Normalized Radius, ρ