Journal article
Nonlinear decay of high-power microwaves into trapped modes in inhomogeneous plasma
We present novel experimental evidence of parametric decay instability of microwave beams in the plasma edge of the Wendelstein 7-X stellarator. We propose that the instability is sustained by trapping of only one daughter wave in the non-monotonic density profile measured with high spatial resolution within a stationary magnetic island.
The power levels and spectral shapes of the detected microwave signal are reproduced by numerical modelling and a theoretical power threshold is predicted around 300 kW, comparable with observations. We predict a fraction of power drained by daughter waves around 4% in the experiments, potentially increasing above 50% for more hollow edge density profiles.
Such absorption levels could significantly reduce the efficiency of the microwave heating and current-drive system in tokamaks and stellarators.
Language: | English |
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Publisher: | IOP Publishing |
Year: | 2022 |
Pages: | 074003 |
ISSN: | 17414326 , 00295515 and 10185577 |
Types: | Journal article |
DOI: | 10.1088/1741-4326/ac5d61 |
ORCIDs: | Tancetti, A. , Nielsen, S. K. , Rasmussen, J. , 0000-0003-0574-516X , Senstius, M. G. , 0000-0001-7747-3066 , 0000-0003-4596-1211 , 0000-0002-8717-1106 , 0000-0002-7324-2647 , Jensen, T. and Stejner, M. |