Description
The Quasi-Continuous Exhaust (QCE) regime [1] is free of type-I ELMs while maintaining the high normalized energy confinement typical for H-mode operation, making it one candidate for an integrated reactor scenario. Instead of large-scale ELMs, high-frequency, low-amplitude filaments are observed. The Quasi-Coherent Mode (QCM) is a characteristic edge fluctuation observed in the QCE regime and is believed to play an important role in regulating edge transport. To better understand the properties of QCM and filaments, we use the W-band tunable, 7-channel, frequency comb Doppler Backscattering (DBS) diagnostic [2] on the ASDEX Upgrade tokamak. With its capability for simultaneous multi-point measurements and frequency stepping, the DBS system enables QCM localization, observation of filament propagation, and measurement of the Er profile with a single diagnostic. We find that the QCM is localized within the Er well. In addition, a possible filament birth location is identified and compared with the QCM location.
[1] Faitsch M et al, Nucl. Mater. Energy 42 101904
[2] Molina Cabrera P A et al., Rev. Sci. Instrum. 94 083504
Acknowledgments
This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200 - EUROfusion). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them.