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Two-dimensional turbulence analysis using high-speed visible imaging in SLPM plasmas

Abstract:

Combined measurements of high-speed camera images and reciprocating Langmuir probes have been used to characterize coherent structures in SLPM plasmas. It is common to find two intermittent structures in Argon plasmas separated approximately 10 mm one from each other, with a rotation angle of about 150°, radially opposite from the plasma centre. Neither poloidal nor radial motion have been appreciated. Further studies are in progress to induce that kind of motion during biasing experiments in Helium, Neon and Argon plasmas. In the other hand, coherence between light emissions near to the probe tips and the ion saturation current of the Langmuir probes is almost maximum at different frequencies, which suggests that light intensity fluctuations are related to electron density fluctuations at those frequencies. Statistical analysis of the temporary images will be done due to the huge volume of frames recorded at 250 kfps (up to 1 106 per shot). Preliminary results show a gaussian behaviour of the light intensity fluctuations around the probes radial position.