A global resonance phenomenon at the TJ-II stellarator

A new phenomenon at the TJ-II stellarator is reported. The line-integrated density measured by a microwave interferometer systematically shows bursts of fluctuations at regularly spaced values of the mean density across a very large number of discharges. Related modes are also observed with other diagnostics, such as the magnetic pickup coils and the heavy ion beam probe. The mode is tentatively identified with an acoustic mode, and its relation to confinement transitions at TJ-II is discussed.

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