Comparison between fast-sweep Langmuir probe and triple probe for fluctuations measurements

Two techniques are applied and the results compared both in the plasma core and in the edge region of "Thorello" to estimate electron temperature fluctuations. The first method is a fast-sweep Langmuir probe: it is a new apparatus based on a dual channel circuit that compensates for stray capacitance and permits sweep speeds up to 400 kHz, so that we can investigate the electrostatic turbulence with good temporal resolution. The second technique is the conventional triple probe: this method allows us to measure density, temperature, and floating potential as a function of time. The fast-sweep Langmuir probe provides a more reliable electron temperature fluctuations and these measurements are essential for a correct interpretation of density and potential fluctuations.