## "Snowflake" H Mode in a Tokamak Plasma

An edge-localized mode (ELM) H-mode regime, supported by electron cyclotron heating, has been successfully established in a snowflake (second-order null) divertor configuration for the first time in the TCV tokamak. This regime exhibits 2 to 3 times lower ELM frequency and 20%30% increased normalized ELM energy ($Delta W_{ELM}/W_p$) compared to an identically shaped, conventional single-null diverted H mode. Enhanced stability of mid- to high-toroidal-mode-number ideal modes is consistent with the different snowflake ELM phenomenology. The capability of the snowflake to redistribute the edge power on the additional strike points has been confirmed experimentally.

Published in:
Physical Review Letters, 105, 155003
Year:
2010
Publisher:
The American Physical Society
Keywords:
Laboratories:
SPC
CRPP