In a magnetized toroidal plasma, an antenna tunable in vertical wave number is used to excite density perturbations. Coherent detection is performed by means of Langmuir probes to directly determine both the wave vector and the plasma response induced by the antenna. Comparison between the theoretical density response predicted by the generalized Hasegawa-Wakatani model, and the experimentally determined density response enables us the identification of one peak of the plasma response as a drift wave.
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The distinction between drift and interchange modes cannot be clearly established using phase shift measurements between density and potential. Indeed, in Refs. 16 and 24, it has been shown this phase shift can vary over a wide range. Thus, relying on phase shift measurements between identity and potential can be misleading in characterizing the wave nature.
