1. N. Oyama, H. Urano, Y. Sakamoto
14th meeting of the ITPA-TG on Pedestal&Edge Physics Group,
General Atomics, April 29-May 2, 2008
Effect of edge plasma rotation on pedestal and ELMs ~ preparation for DIII-D/JT-60U exp. ~
N. Oyama, H. Urano, Y. Sakamoto
and the JT-60 Team
JAEA Naka

2. Background for PEP-17/18
Pedestal pressure and type I ELM characteristics vary with edge plasma rotation. These rotation effects can be separated from effects of TF ripple.
(Urano IAEA 2006, NF 47(2007)706)
Grassy ELM frequency varies with edge plasma rotation.
(Oyama, PPCF 49(2007)249)
Small plasma rotation in ITER is expected. To obtain better prediction of ITER pedestal parameters (especially ELM size), it is important to understand the physical mechanism of rotation effects.
=> Inter-machine experiments between DIII-D and JT-60U (PEP-17/18) will provide new information, making use of good capability of toroidal torque input in both devices.

3. Configurations for rotation effects
for type I ELM
~1% ripple
for grassy ELM
Ferritic
Steel Tile
for type I ELM
~0.5% ripple
for QH-mode

4. Rotation effect on type I ELMs
At fixed Pnet, pped gradually decreases with increasing ctr-VT
At fixed Psep (Pnet~1.5xPLH), fELM increases with increasing ctr-VT 2 4 6
pped [kPa] -1 1
VTPED [105m/s]
co-NBI with FST
bal-NBI with FST
ctr-NBI with FST
Pnet~6.5MW
Fixed Pnet 20 40 60 80
100 -1 1
VTped [105m/s]
fELM [Hz]
co-NBI with FST
co-NBI w/o FST
bal-NBI with FST
bal-NBI w/o FST
ctr-NBI with FST
ctr-NBI w/o FST
Psep = 5MW,
ne = 2x1019m-3
Fixed Psep

5. Rotation effect on type I ELMs
At fixed Pnet, pped gradually decreases with increasing ctr-VT
At fixed Psep (Pnet~1.5xPLH), fELM increases with increasing ctr-VT
Degradation of pped in ctr-rotating plasma is smaller than reduction of DWELM at higher fELM => smaller DWELM/Wped
These results are obtained at 1% ripple case in large VP config. 2 4 6
pped [kPa] -1 1
VTPED [105m/s]
co-NBI with FST
bal-NBI with FST
ctr-NBI with FST
Pnet~6.5MW
Fixed Pnet
Fixed Psep 2 4 6 8 10 -1 1
VTPED [105m/s]
DWELM / Wped [%]
Psep = 5MW,
ne = 2x1019m-3
co-NBI with FST
co-NBI w/o FST
bal-NBI with FST
bal-NBI w/o FST
ctr-NBI with FST
ctr-NBI w/o FST

6. Moderate TF ripple case (~0.5%)
pped can increase with heating power (bp)
At fixed Pnet, pped decreases with increasing ctr-rotation
DWELM/Wped decreases with increasing ctr-rotation
Similar changes in 1% ripple case were observed.
co-NBI with FST
bal-NBI with FST
ctr-NBI with FST
5.7-6MW
10MW
co-NBI with FST
bal-NBI with FST
ctr-NBI with FST

7. Rotation effect on grassy ELMs
Grassy ELMs can be obtained at zero rotation & rotation shear
Not only high q95 (>6), rotation effect can be observed in moderate q95 (≤5)
Sign of rotation seems to be important, similar to type I ELM

8. Rotation effect on grassy ELMs
Grassy ELMs can be obtained at zero rotation & rotation shear
Not only high q95 (>6), rotation effect can be observed in moderate q95 (≤5)
Sign of rotation seems to be important, similar to type I ELM
In high d configuration, no degradation of pped was observed

9. Difference between grassy ELM&QH
Grassy ELM: Localized collapse near pedestal top
QH-mode: No collapse. EHO seen in Te, ne, Is
~18%

10. Proposal for DIII-D as PEP-17/18
For the comparison of pedestal & H-mode performance,
and ELM characteristics,
Rotation/beta scan at different plasma configuration
(low d, high d, DN)
(Similar q95 and ne* regime to JT-60U database)
Discussions
Possibility to get similar plasma shape for each target
example type I ELM: d~0.35, k~1.4
grassy ELM: d~0.6, k~1.4
Possibility for reversed Ip/Bt for larger CTR torque
If yes, may be suitable to perform QH-mode comparison experiments in DIII-D (PEP-14)