title: "Snowflake" H mode in a tokamak plasma.
abstract: 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 (ΔWELM/Wp) 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.
authors.affiliation: Ecole Polytechnique Fédérale de Lausanne, Centre de Recherches en Physique des Plasmas, Association Euratom-Confédération Suisse, Station 13, CH-1015 Lausanne, Switzerland. francesco.piras@epfl.ch
authors.forename: F
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authors.lastname: Piras
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authors.lastname: Duval
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authors.lastname: Medvedev
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authors.lastname: Moret
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authors.lastname: Pitzschke
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authors.lastname: Sauter