Density, temperature and plasma potential are measured simultaneously at the same spatial point in the SOL plasma of FTU at a rate faster than the typical turbulence frequency. This is done through a harmonic analysis of the current drawn on a single Langmuir probe swept in voltage at high rate (≈0.9 MHz). The current signal is detected with a down frequency conversion by means of a homodyne technique. The fluctuation levels are around 30% for all three quantities, but the autocorrelation times of temperature and potential are shorter than that of density: <3 μm against ≈13 μs. The magnitude and mutual coherence of the fluctuations are affected by the connection length L c of the flux tube connected to the probe, offering a possible explanation of the variation of both the particle and the energy transport coefficient with L c found experimentally.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics
- Condensed Matter Physics
Pericoli-Ridolfini, V., Pietropaolo, A., Cesario, R., & Zonca, F. (1998). Density, temperature and potential fluctuations in the edge plasma of the FTU tokamak. Nuclear Fusion, 38(12), 1745 - 1755. https://doi.org/10.1088/0029-5515/38/12/301